MC68HC912DT128A
MC68HC912DG128A
MC68HC912DT128C
MC68HC912DG128C
MC68HC912DT128P
MC68HC912DG128P
Technical Data
M68HC12
Microcontrollers
MC912DT128A/D
Rev. 4, 10/2003
MOTOROLA.COM/SEMICONDUCTORS
MC68HC912DT128A
MC68HC912DG128A
MC68HC912DT128C
MC68HC912DG128C
MC68HC912DT128P
MC68HC912DG128P
Technical Data Rev 4.0
Motorola reserves the right to make changes without further notice to any products
herein. Motorola makes no warranty, representation or guarantee regarding the
suitability of its products for any particular purpose, nor does Motorola assume any
liability arising out of the application or use of any product or circuit, and specifically
disclaims any and all liability, including without limitation consequential or incidental
damages. "Typical" parameters which may be provided in Motorola data sheets and/or
specifications can and do vary in different applications and actual performance may
vary over time. All operating parameters, including "Typicals" must be validated for
each customer application by customer's technical experts. Motorola does not convey
any license under its patent rights nor the rights of others. Motorola products are not
designed, intended, or authorized for use as components in systems intended for
surgical implant into the body, or other applications intended to support or sustain life,
or for any other application in which the failure of the Motorola product could create a
situation where personal injury or death may occur. Should Buyer purchase or use
Motorola products for any such unintended or unauthorized application, Buyer shall
indemnify and hold Motorola and its officers, employees, subsidiaries, affiliates, and
distributors harmless against all claims, costs, damages, and expenses, and
reasonable attorney fees arising out of, directly or indirectly, any claim of personal
injury or death associated with such unintended or unauthorized use, even if such claim
alleges that Motorola was negligent regarding the design or manufacture of the part.
Motorola, Inc. is an Equal Opportunity/Affirmative Action Employer.
Motorola and
are registered trademarks of Motorola, Inc.
DigitalDNA is a trademark of Motorola, Inc.
MC68HC912DT128A — Rev 4.0
MOTOROLA
© Motorola, Inc., 2003
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Technical Data — MC68HC912DT128A
List of Paragraphs
Technical Data — List of Paragraphs . . . . . . . . . . . . . . . . 5
Technical Data — Table of Contents. . . . . . . . . . . . . . . . . 7
Technical Data — List of Figures . . . . . . . . . . . . . . . . . . 17
Technical Data — List of Tables . . . . . . . . . . . . . . . . . . . 21
Section 1. General Description . . . . . . . . . . . . . . . . . . . . 25
Section 2. Central Processing Unit . . . . . . . . . . . . . . . . . 35
Section 3. Pinout and Signal Descriptions . . . . . . . . . . . 41
Section 4. Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Section 5. Operating Modes. . . . . . . . . . . . . . . . . . . . . . . 79
Section 6. Resource Mapping . . . . . . . . . . . . . . . . . . . . . 87
Section 7. Bus Control and Input/Output . . . . . . . . . . . 103
Section 8. Flash Memory . . . . . . . . . . . . . . . . . . . . . . . . 115
Section 9. EEPROM Memory . . . . . . . . . . . . . . . . . . . . . 123
Section 10. Resets and Interrupts . . . . . . . . . . . . . . . . . 137
Section 11. I/O Ports with Key Wake-up . . . . . . . . . . . . 149
Section 12. Clock Functions . . . . . . . . . . . . . . . . . . . . . 157
Section 13. Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
Section 14. Pulse Width Modulator . . . . . . . . . . . . . . . . 225
Section 15. Enhanced Capture Timer . . . . . . . . . . . . . . 241
Section 16. Multiple Serial Interface . . . . . . . . . . . . . . . 277
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Section 17. Inter IC Bus . . . . . . . . . . . . . . . . . . . . . . . . . 301
Section 18. MSCAN Controller . . . . . . . . . . . . . . . . . . . . 325
Section 19. Analog-to-Digital Converter . . . . . . . . . . . . 367
Section 20. Development Support. . . . . . . . . . . . . . . . . 395
Section 21. Electrical Specifications. . . . . . . . . . . . . . . 421
Section 22. Appendix: Changes from
MC68HC912DG128 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 441
Section 23. Appendix: CGM Practical Aspects . . . . . . 447
Section 24. Appendix: Information on
MC68HC912DT128A Mask Set Changes . . . . . . . . . . . . 457
Technical Data — Glossary . . . . . . . . . . . . . . . . . . . . . . 461
Technical Data — Revision History . . . . . . . . . . . . . . . . 473
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Table of Contents
List of Paragraphs
Table of Contents
List of Figures
List of Tables
Section 1. General Description
1.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
1.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.3
Devices Covered in this Document. . . . . . . . . . . . . . . . . . . . . .26
1.4
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.5
MC68HC912DT128A Block Diagram . . . . . . . . . . . . . . . . . . . . 30
1.6
MC68HC912DG128A Block Diagram. . . . . . . . . . . . . . . . . . . . 31
1.7
Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Section 2. Central Processing Unit
2.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
2.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3
Programming Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.4
Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.5
Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
2.6
Indexed Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . .39
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2.7
Opcodes and Operands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Section 3. Pinout and Signal Descriptions
3.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
3.2
MC68HC912DT128A Pin Assignments in 112-pin QFP. . . . . . 41
3.3
Power Supply Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
3.4
Signal Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.5
Port Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
Section 4. Registers
4.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
4.2
Register Block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
Section 5. Operating Modes
5.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
5.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.3
Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.4
Background Debug Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
Section 6. Resource Mapping
6.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .87
6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
6.3
Internal Resource Mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . .87
6.4
Flash EEPROM mapping through internal Memory Expansion 92
6.5
Miscellaneous System Control Register . . . . . . . . . . . . . . . . . . 96
6.6
Mapping test registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
6.7
Memory Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
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Section 7. Bus Control and Input/Output
7.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7.3
Detecting Access Type from External Signals . . . . . . . . . . . .103
7.4
Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
Section 8. Flash Memory
8.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
8.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
8.3
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
8.4
Flash EEPROM Control Block . . . . . . . . . . . . . . . . . . . . . . . .116
8.5
Flash EEPROM Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
8.6
Flash EEPROM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
8.7
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
8.8
Programming the Flash EEPROM . . . . . . . . . . . . . . . . . . . . . 120
8.9
Erasing the Flash EEPROM . . . . . . . . . . . . . . . . . . . . . . . . . . 121
8.10
Stop or Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121
8.11
Flash protection bit FPOPEN . . . . . . . . . . . . . . . . . . . . . . . . .122
Section 9. EEPROM Memory
9.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
9.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
9.3
EEPROM Selective Write More Zeros . . . . . . . . . . . . . . . . . .124
9.4
EEPROM Programmer’s Model . . . . . . . . . . . . . . . . . . . . . . .125
9.5
EEPROM Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 126
9.6
Program/Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . .133
9.7
Shadow Word Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
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9.8
Programming EEDIVH and EEDIVL Registers. . . . . . . . . . . . 135
Section 10. Resets and Interrupts
10.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .137
10.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
10.3
Exception Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
10.4
Maskable interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138
10.5
Latching of Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
10.6
Interrupt Control and Priority Registers . . . . . . . . . . . . . . . . .141
10.7
Interrupt test registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
10.8
Resets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
10.9
Effects of Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
10.10 Register Stacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Section 11. I/O Ports with Key Wake-up
11.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .149
11.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
11.3
Key Wake-up and port Registers . . . . . . . . . . . . . . . . . . . . . . 150
11.4
Key Wake-Up Input Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
Section 12. Clock Functions
12.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
12.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
12.3
Clock Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
12.4
Phase-Locked Loop (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
12.5
Acquisition and Tracking Modes. . . . . . . . . . . . . . . . . . . . . . .161
12.6
Limp-Home and Fast STOP Recovery modes . . . . . . . . . . . . 163
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12.7
System Clock Frequency Formulae . . . . . . . . . . . . . . . . . . . . 181
12.8
Clock Divider Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
12.9
Computer Operating Properly (COP) . . . . . . . . . . . . . . . . . . .185
12.10 Real-Time Interrupt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
12.11 Clock Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186
12.12 Clock Function Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
Section 13. Oscillator
13.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
13.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
13.3
MC68HC912DT128A Oscillator Specification . . . . . . . . . . . .194
13.4
MC68HC912Dx128C Colpitts Oscillator Specification . . . . . . 197
13.5
MC68HC912Dx128P Pierce Oscillator Specification . . . . . . . 212
Section 14. Pulse Width Modulator
14.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .225
14.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
14.3
PWM Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . .229
14.4
PWM Boundary Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .240
Section 15. Enhanced Capture Timer
15.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .241
15.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
15.3
Enhanced Capture Timer Modes of Operation . . . . . . . . . . . . 247
15.4
Timer Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . 251
15.5
Timer and Modulus Counter Operation in Different Modes . . 275
Section 16. Multiple Serial Interface
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16.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .277
16.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
16.3
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278
16.4
Serial Communication Interface (SCI) . . . . . . . . . . . . . . . . . .278
16.5
Serial Peripheral Interface (SPI) . . . . . . . . . . . . . . . . . . . . . . .289
16.6
Port S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
Section 17. Inter IC Bus
17.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .301
17.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
17.3
IIC Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
17.4
IIC System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
17.5
IIC Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
17.6
IIC Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
17.7
IIC Programming Examples . . . . . . . . . . . . . . . . . . . . . . . . . .318
Section 18. MSCAN Controller
18.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .325
18.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
18.3
External Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
18.4
Message Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
18.5
Identifier Acceptance Filter . . . . . . . . . . . . . . . . . . . . . . . . . . .332
18.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335
18.7
Protocol Violation Protection. . . . . . . . . . . . . . . . . . . . . . . . . . 337
18.8
Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338
18.9
Timer Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
18.10 Clock System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343
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18.11 Memory Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
18.12 Programmer’s Model of Message Storage . . . . . . . . . . . . . . .346
18.13 Programmer’s Model of Control Registers . . . . . . . . . . . . . . . 351
Section 19. Analog-to-Digital Converter
19.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .367
19.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
19.3
Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369
19.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370
19.5
ATD Operational Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372
19.6
ATD Operation In Different MCU Modes . . . . . . . . . . . . . . . . 373
19.7
General Purpose Digital Input Port Operation . . . . . . . . . . . .375
19.8
Application Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . .376
19.9
ATD Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
Section 20. Development Support
20.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395
20.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
20.3
Instruction Queue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395
20.4
Background Debug Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .397
20.5
Breakpoints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
20.6
Instruction Tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
Section 21. Electrical Specifications
21.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .421
21.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
21.3
Tables of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
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Section 22. Appendix: Changes from MC68HC912DG128
22.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441
22.2
Significant changes from the MC68HC912DG128 (non-suffix device)441
Section 23. Appendix: CGM Practical Aspects
23.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .447
23.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447
23.3
Practical Aspects For The PLL Usage . . . . . . . . . . . . . . . . . .447
23.4
Printed Circuit Board Guidelines. . . . . . . . . . . . . . . . . . . . . . .453
Section 24. Appendix: Information on
MC68HC912DT128A Mask Set Changes
24.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .457
24.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457
24.3
Oscillator – Major Changes . . . . . . . . . . . . . . . . . . . . . . . . . .457
24.4
Flash Protection Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
24.5
Clock Circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .458
24.6
Pseudo Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
24.7
Oscillator – Minor Changes . . . . . . . . . . . . . . . . . . . . . . . . . .459
24.8
PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459
Technical Data — Glossary
Technical Data — Revision History
24.9
Changes in Rev. 3.1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 473
24.10 Changes from Rev 2.0 to Rev 3.0 . . . . . . . . . . . . . . . . . . . . . 473
24.11 Changes from Rev 1.0 to Rev 2.0 . . . . . . . . . . . . . . . . . . . . . 475
Technical Data
14
MC68HC912DT128A — Rev 4.0
Table of Contents
MOTOROLA
Table of Contents
24.12 Changes from first version (internal release, no
revision number) to Rev 1.0 . . . . . . . . . . . . . . . . . . . . . . . . . .475
MC68HC912DT128A — Rev 4.0
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Table of Contents
Technical Data
16
MC68HC912DT128A — Rev 4.0
Table of Contents
MOTOROLA
Technical Data — MC68HC912DT128A
List of Figures
Figure
1-1
1-2
2-1
3-1
3-2
3-3
3-4
3-5
6-1
6-2
11-1
12-1
12-2
12-3
12-4
12-5
12-6
12-7
12-8
12-9
13-1
13-2
13-3
13-4
14-1
14-2
14-3
15-1
15-2
Title
MC68HC912DT128A Block Diagram . . . . . . . . . . . . . . . . . . . . 30
MC68HC912DG128A Block Diagram. . . . . . . . . . . . . . . . . . . . 31
Programming Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Pin Assignments in 112-pin QFP for MC68HC912DT128A . . . 42
Pin Assignments in 112-pin QFP for MC68HC912DG128A . . .43
112-pin QFP Mechanical Dimensions (case no. 987) . . . . . . . 44
PLL Loop FIlter Connections . . . . . . . . . . . . . . . . . . . . . . . . . .46
External Oscillator Connections . . . . . . . . . . . . . . . . . . . . . . . .48
MC68HC912DT128A Memory Map after reset. . . . . . . . . . . . 100
MC68HC912DT128A Memory Paging . . . . . . . . . . . . . . . . . .101
STOP Key Wake-up Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Internal Clock Relationships . . . . . . . . . . . . . . . . . . . . . . . . . . 159
PLL Functional Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
Clock Loss during Normal Operation . . . . . . . . . . . . . . . . . . .164
No Clock at Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . .166
STOP Exit and Fast STOP Recovery . . . . . . . . . . . . . . . . . . . 168
Clock Generation Chain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
Clock Chain for SCI0, SCI1, RTI, COP. . . . . . . . . . . . . . . . . . 183
Clock Chain for ECT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
Clock Chain for MSCAN, SPI, ATD0, ATD1 and BDM . . . . . . 185
MC68HC912DT128A Colpitts Oscillator Architecture. . . . . . .195
MC68HC912Dx128C Colpitts Oscillator Architecture. . . . . . .198
MC68HC912Dx128C Crystal with DC Blocking Capacitor . . . 210
MC68HC912Dx128P Pierce Oscillator Architecture. . . . . . . .213
Block Diagram of PWM Left-Aligned Output Channel . . . . . . 226
Block Diagram of PWM Center-Aligned Output Channel . . . . 227
PWM Clock Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
Timer Block Diagram in Latch Mode. . . . . . . . . . . . . . . . . . . .243
Timer Block Diagram in Queue Mode. . . . . . . . . . . . . . . . . . . 244
MC68HC912DT128A — Rev 4.0
MOTOROLA
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Technical Data
List of Figures
17
List of Figures
15-3 8-Bit Pulse Accumulators Block Diagram . . . . . . . . . . . . . . . .245
15-4 16-Bit Pulse Accumulators Block Diagram . . . . . . . . . . . . . . .246
15-5 Block Diagram for Port7 with Output compare / Pulse
Accumulator A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
15-6 C3F-C0F Interrupt Flag Setting . . . . . . . . . . . . . . . . . . . . . . .247
16-1 Multiple Serial Interface Block Diagram . . . . . . . . . . . . . . . . .278
16-2 Serial Communications Interface Block Diagram . . . . . . . . . . 279
16-3 Serial Peripheral Interface Block Diagram . . . . . . . . . . . . . . . 291
16-4 SPI Clock Format 0 (CPHA = 0) . . . . . . . . . . . . . . . . . . . . . . .292
16-5 SPI Clock Format 1 (CPHA = 1) . . . . . . . . . . . . . . . . . . . . . . .293
16-6 Normal Mode and Bidirectional Mode. . . . . . . . . . . . . . . . . . . 294
17-1 IIC Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .303
17-2 IIC Transmission Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
17-3 IIC Clock Synchronization. . . . . . . . . . . . . . . . . . . . . . . . . . . .308
17-4 Flow-Chart of Typical IIC Interrupt Routine . . . . . . . . . . . . . . 323
18-1 The CAN System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
18-2 User Model for Message Buffer Organization. . . . . . . . . . . . . 330
18-3 32-bit Maskable Identifier Acceptance Filters . . . . . . . . . . . . . 333
18-4 16-bit Maskable Acceptance Filters . . . . . . . . . . . . . . . . . . . . 333
18-5 8-bit Maskable Acceptance Filters . . . . . . . . . . . . . . . . . . . . . 334
18-6 SLEEP Request / Acknowledge Cycle . . . . . . . . . . . . . . . . . . 340
18-7 Clocking Scheme . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
18-8 Segments within the Bit Time . . . . . . . . . . . . . . . . . . . . . . . . . 344
18-9 CAN Standard Compliant Bit Time Segment Settings . . . . . . 345
18-10 msCAN12 Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345
18-11 Message Buffer Organization . . . . . . . . . . . . . . . . . . . . . . . . . 346
18-12 Receive/Transmit Message Buffer Extended Identifier. . . . . . 347
18-13 Standard Identifier Mapping . . . . . . . . . . . . . . . . . . . . . . . . . .348
18-14 Identifier Acceptance Registers (1st bank) . . . . . . . . . . . . . . .364
18-15 Identifier Acceptance Registers (2nd bank) . . . . . . . . . . . . . . 364
18-16 Identifier Mask Registers (1st bank) . . . . . . . . . . . . . . . . . . . .365
18-17 Identifier Mask Registers (2nd bank) . . . . . . . . . . . . . . . . . . .365
19-1 Analog-to-Digital Converter Block Diagram . . . . . . . . . . . . . . 368
20-1 BDM Host to Target Serial Bit Timing. . . . . . . . . . . . . . . . . . . 399
20-2 BDM Target to Host Serial Bit Timing (Logic 1) . . . . . . . . . . .399
20-3 BDM Target to Host Serial Bit Timing (Logic 0) . . . . . . . . . . .400
21-1 Timer Inputs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .429
21-2 POR and External Reset Timing Diagram . . . . . . . . . . . . . . . 430
Technical Data
18
MC68HC912DT128A — Rev 4.0
List of Figures
MOTOROLA
List of Figures
21-3
21-4
21-5
21-6
21-7
21-8
21-9
21-9
21-9
21-10
STOP Recovery Timing Diagram . . . . . . . . . . . . . . . . . . . . . .431
WAIT Recovery Timing Diagram . . . . . . . . . . . . . . . . . . . . . . 432
Interrupt Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
Port Read Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .434
Port Write Timing Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .434
Multiplexed Expansion Bus Timing Diagram . . . . . . . . . . . . . 436
A) SPI Master Timing (CPHA = 0) . . . . . . . . . . . . . . . . . . . . . 438
B) SPI Master Timing (CPHA = 1) . . . . . . . . . . . . . . . . . . . . . 438
SPI Timing Diagram (1 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . 438
A) SPI Slave Timing (CPHA = 0) . . . . . . . . . . . . . . . . . . . . . . 439
B) SPI Slave Timing (CPHA = 1) . . . . . . . . . . . . . . . . . . . . . . 439
SPI Timing Diagram (2 of 2) . . . . . . . . . . . . . . . . . . . . . . . . . . 439
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
List of Figures
19
List of Figures
Technical Data
20
MC68HC912DT128A — Rev 4.0
List of Figures
MOTOROLA
Technical Data — MC68HC912DT128A
List of Tables
Table
1-1
1-2
2-1
2-2
3-1
3-2
3-3
3-4
4-1
5-1
6-1
6-2
6-3
6-4
6-5
6-6
7-1
9-1
9-2
9-3
9-4
10-1
10-2
12-1
12-2
12-3
12-4
12-5
Title
Device Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . 32
Development Tools Ordering Information. . . . . . . . . . . . . . . . .33
M68HC12 Addressing Mode Summary . . . . . . . . . . . . . . . . . .38
Summary of Indexed Operations . . . . . . . . . . . . . . . . . . . . . . . 39
MC68HC912DT128A Power and Ground Connection
Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
MC68HC912DT128A Signal Description Summary . . . . . . . . .54
MC68HC912DT128A Port Description Summary. . . . . . . . . . . 64
Port Pull-Up, Pull-Down and Reduced Drive Summary . . . . . .65
Register Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
Mode Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
Mapping Precedence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .88
Program space Page Index . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Flash Register space Page Index. . . . . . . . . . . . . . . . . . . . . . .93
Test mode program space Page Index. . . . . . . . . . . . . . . . . . . 94
RFSTR Stretch Bit Definition . . . . . . . . . . . . . . . . . . . . . . . . . .97
EXSTR Stretch Bit Definition . . . . . . . . . . . . . . . . . . . . . . . . . .98
Access Type vs. Bus Control Pins . . . . . . . . . . . . . . . . . . . . . 104
EEDIV Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .127
2K byte EEPROM Block Protection . . . . . . . . . . . . . . . . . . . . 130
Erase Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131
Shadow word mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .134
Interrupt Vector Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
Stacking Order on Entry to Interrupts . . . . . . . . . . . . . . . . . . . 147
Summary of STOP Mode Exit Conditions. . . . . . . . . . . . . . . .174
Summary of Pseudo STOP Mode Exit Conditions . . . . . . . . .174
Clock Monitor Time-Outs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
Real Time Interrupt Rates. . . . . . . . . . . . . . . . . . . . . . . . . . . .188
COP Watchdog Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
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Technical Data
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21
List of Tables
14-1
14-2
14-3
15-1
15-2
15-3
16-1
16-2
16-3
16-4
17-1
17-2
18-1
18-2
18-3
18-4
18-5
18-6
18-7
18-8
18-9
19-1
19-2
19-3
19-4
19-5
19-6
19-7
19-8
19-9
19-10
20-1
20-2
20-3
20-4
20-5
20-6
Clock A and Clock B Prescaler. . . . . . . . . . . . . . . . . . . . . . . . 230
PWM Left-Aligned Boundary Conditions . . . . . . . . . . . . . . . . 240
PWM Center-Aligned Boundary Conditions . . . . . . . . . . . . . . 240
Compare Result Output Action . . . . . . . . . . . . . . . . . . . . . . . . 255
Edge Detector Circuit Configuration . . . . . . . . . . . . . . . . . . . .256
Prescaler Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
Baud Rate Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .280
Loop Mode Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
SS Output Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
SPI Clock Rate Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
IIC Tap and Prescale Values . . . . . . . . . . . . . . . . . . . . . . . . .310
IIC Divider and SDA Hold values . . . . . . . . . . . . . . . . . . . . . . 311
msCAN12 Interrupt Vectors . . . . . . . . . . . . . . . . . . . . . . . . . .337
msCAN12 vs. CPU operating modes . . . . . . . . . . . . . . . . . . . 338
Data length codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .349
Synchronization jump width . . . . . . . . . . . . . . . . . . . . . . . . . .354
Baud rate prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .354
Time segment syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
Time segment values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
Identifier Acceptance Mode Settings . . . . . . . . . . . . . . . . . . .362
Identifier Acceptance Hit Indication . . . . . . . . . . . . . . . . . . . . 362
Result Data Formats Available . . . . . . . . . . . . . . . . . . . . . . . . 379
Left Justified ATD Output Codes . . . . . . . . . . . . . . . . . . . . . . 380
ATD Response to Background Debug Enable . . . . . . . . . . . . 382
Final Sample Time Selection . . . . . . . . . . . . . . . . . . . . . . . . .383
Clock Prescaler Values. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .384
Conversion Sequence Length Coding . . . . . . . . . . . . . . . . . .385
Result Register Assignment for Different Conversion
Sequences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .385
Special Channel Conversion Select Coding . . . . . . . . . . . . . .386
Analog Input Channel Select Coding . . . . . . . . . . . . . . . . . . .387
Multichannel Mode Result Register Assignment (MULT=1) . .388
IPIPE Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
Hardware Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 402
BDM Firmware Commands . . . . . . . . . . . . . . . . . . . . . . . . . .403
BDM registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405
TTAGO Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .410
REGN Decoding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .410
Technical Data
22
MC68HC912DT128A — Rev 4.0
List of Tables
MOTOROLA
List of Tables
20-7
20-8
20-9
20-10
21-1
21-2
21-3
21-4
21-5
21-6
21-7
21-8
21-9
21-10
21-11
21-12
21-13
21-14
21-15
21-16
21-17
21-18
23-1
Breakpoint Mode Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
Breakpoint Address Range Control . . . . . . . . . . . . . . . . . . . . 416
Breakpoint Read/Write Control . . . . . . . . . . . . . . . . . . . . . . . . 418
Tag Pin Function. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .420
Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .422
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 423
DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . .424
Supply Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 425
ATD DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . 425
Analog Converter Characteristics (Operating) . . . . . . . . . . . .426
ATD AC Characteristics (Operating). . . . . . . . . . . . . . . . . . . .426
ATD Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .427
EEPROM Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .427
Flash EEPROM Characteristics . . . . . . . . . . . . . . . . . . . . . . .428
Pulse Width Modulator Characteristics. . . . . . . . . . . . . . . . . . 428
Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
Peripheral Port Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .434
Multiplexed Expansion Bus Timing. . . . . . . . . . . . . . . . . . . . .435
SPI Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .437
CGM Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440
Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . 440
STOP Key Wake-up Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . 440
Suggested 8MHz Synthesis PLL Filter Elements
(Tracking Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 451
23-2 Suggested 8MHz Synthesis PLL Filter Elements
(Acquisition Mode) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .452
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
List of Tables
23
List of Tables
Technical Data
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MC68HC912DT128A — Rev 4.0
List of Tables
MOTOROLA
Technical Data — MC68HC912DT128A
Section 1. General Description
1.1 Contents
1.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.3
Devices Covered in this Document. . . . . . . . . . . . . . . . . . . . . .26
1.4
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
1.5
MC68HC912DT128A Block Diagram . . . . . . . . . . . . . . . . . . . . 30
1.6
MC68HC912DG128A Block Diagram. . . . . . . . . . . . . . . . . . . . 31
1.7
Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
1.2 Introduction
The MC68HC912DT128A microcontroller unit (MCU) is a 16-bit device
composed of standard on-chip peripherals including a 16-bit central
processing unit (CPU12), 128K bytes of flash EEPROM, 8K bytes of
RAM, 2K bytes of EEPROM, two asynchronous serial communications
interfaces (SCI), a serial peripheral interface (SPI), an inter-IC interface
(I2C), an enhanced capture timer (ECT), two 8-channel, 10-bit analogto-digital converters (ADC), a four-channel pulse-width modulator
(PWM), and three CAN 2.0 A, B software compatible modules
(MSCAN12). System resource mapping, clock generation, interrupt
control and bus interfacing are managed by the lite integration module
(LIM). The MC68HC912DT128A has full 16-bit data paths throughout,
however, the external bus can operate in an 8-bit narrow mode so single
8-bit wide memory can be interfaced for lower cost systems. The
inclusion of a PLL circuit allows power consumption and performance to
be adjusted to suit operational requirements. In addition to the I/O ports
available in each module, 16 I/O ports are available with Key-Wake-Up
capability from STOP or WAIT mode.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
General Description
25
General Description
1.3 Devices Covered in this Document
The MC68HC912DG128A device is similar to the MC68HC912DT128A,
but it has only two MSCAN12 modules. The entire databook applies to
both devices, except where differences are noted.
The MC68HC912DT128C and MC68HC912DT128P are devices similar
to the MC68HC912DT128A, but with different oscillator configurations.
Sections of this book applicable to the MC68HC912DT128A also apply
to the MC68HC912DT128C and MC68HC912DT128P, except for the
differences highlighted in Section 13. Oscillator.
The MC68HC912DG128C and MC68HC912DG128P are devices
similar to the MC68HC912DG128A, but with different oscillator
configurations. Sections of this book applicable to the
MC68HC912DG128A also apply to the MC68HC912DG128C and
MC68HC912DG128P, except for the differences highlighted in Section
13. Oscillator.
NOTE:
The generic term MC68HC912DT128A is used throughout the
document to mean all derivatives mentioned above, except in Section
13. Oscillator, where it refers only to the MC68HC912DT128A and
MC68HC912DG128A devices.
1.4 Features
•
16-bit CPU12
– Upward compatible with M68HC11 instruction set
– Interrupt stacking and programmer’s model identical to
M68HC11
– 20-bit ALU
– Instruction queue
– Enhanced indexed addressing
•
Multiplexed bus
– Single chip or expanded
– 16 address/16 data wide or 16 address/8 data narrow modes
Technical Data
26
MC68HC912DT128A — Rev 4.0
General Description
MOTOROLA
General Description
Features
•
Memory
– 128K byte flash EEPROM, made of four 32K byte modules
with 8K bytes protected BOOT section in each module
– 2K byte EEPROM
– 8K byte RAM with Vstby, made of two 4K byte modules.
•
Two Analog-to-digital converters
– 2 times 8-channels, 10-bit resolution
•
Three 1M bit per second, CAN 2.0 A, B software compatible
modules on the MC68HC912DT128A (two on the
MC68HC912DG128A)
– Two receive and three transmit buffers per CAN
– Flexible identifier filter programmable as 2 x 32 bit, 4 x 16 bit or
8 x 8 bit
– Four separate interrupt channels for Rx, Tx, error and wake-up
per CAN
– Low-pass filter wake-up function
– Loop-back for self test operation
– Programmable link to a timer input capture channel, for timestamping and network synchronization.
•
Enhanced capture timer (ECT)
– 16-bit main counter with 7-bit prescaler
– 8 programmable input capture or output compare channels; 4
of the 8 input captures with buffer
– Input capture filters and buffers, three successive captures on
four channels, or two captures on four channels with a
capture/compare selectable on the remaining four
– Four 8-bit or two 16-bit pulse accumulators
– 16-bit modulus down-counter with 4-bit prescaler
– Four user-selectable delay counters for signal filtering
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
General Description
27
General Description
•
4 PWM channels with programmable period and duty cycle
– 8-bit 4-channel or 16-bit 2-channel
– Separate control for each pulse width and duty cycle
– Center- or left-aligned outputs
– Programmable clock select logic with a wide range of
frequencies
•
Serial interfaces
– Two asynchronous serial communications interfaces (SCI)
– Inter IC bus interface (I2C)
– Synchronous serial peripheral interface (SPI)
•
LIM (lite integration module)
– WCR (windowed COP watchdog, real time interrupt, clock
monitor)
– ROC (reset and clocks)
– MEBI (multiplexed external bus interface)
– MMI (memory map and interface)
– INT (interrupt control)
– BKP (breakpoints)
– BDM (background debug mode)
•
Two 8-bit ports with key wake-up interrupt
•
Clock generation
– Phase-locked loop clock frequency multiplier
– Limp home mode in absence of external clock
– Slow mode divider
– Low power 0.5 to 16 MHz crystal oscillator reference clock
– Option of a Pierce or Colpitts oscillator
Technical Data
28
MC68HC912DT128A — Rev 4.0
General Description
MOTOROLA
General Description
Features
•
112-Pin TQFP package
– Up to 67 general-purpose I/O lines on the
MC68HC912DT128A (up to 69 on the MC68HC912DG128A),
plus up to 18 input-only lines
– 5.0V operation at 8 MHz
•
Development support
– Single-wire background debug™ mode (BDM)
– On-chip hardware breakpoints
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
General Description
29
General Description
1.5 MC68HC912DT128A Block Diagram
VRH0
RxD0
TxD0
RxD1
TxD1
SCI0
EXTAL
XTAL
RESET
SCI1
SDI/MISO
SDO/MOSI
SCK
SS
SPI
PORT E
PE0
PE1
PE2
PE3
PE4
PE5
PE6
PE7
XIRQ
IRQ
R/W
LSTRB
ECLK
MODA
MODB
DBE/CAL
Lite
integration
module
(LIM)
PW0
PW1
PW2
PW3
PWM
PIX0
PIX1
PIX2
PPAGE
I/O
SCL
SDA
IIC
DDRH
PORTH
CAN0
KWH7
KWH6
KWH5
KWH4
KWH3
KWH2
KWH1
KWH0
PH7
PH6
PH5
PH4
PH3
PH2
PH1
PH0
KWU
KWJ7
KWJ6
KWJ5
KWJ4
KWJ3
KWJ2
KWJ1
KWJ0
DDRJ
PB7
PB6
PB5
PB4
PB3
PB2
PB1
PB0
ADDR7
ADDR6
ADDR5
ADDR4
ADDR3
ADDR2
ADDR1
ADDR0
DATA7
DATA6
DATA5
DATA4
DATA3
DATA2
DATA1
DATA0
Narrow bus
CAN1
PORTJ
PA7
PA6
PA5
PA4
PA3
PA2
PA1
PA0
PORT B
ADDR15
ADDR14
ADDR13
ADDR12
ADDR11
ADDR10
ADDR9
ADDR8
PORT A
DATA7 DATA15
DATA6 DATA14
DATA5 DATA13
DATA4 DATA12
DATA3 DATA11
DATA2 DATA10
DATA1 DATA9
DATA0 DATA8
Wide
bus
DDRB
PORT AD1
PORT T
PK0
PK1
PK2
PK3
PK7
PIB7
PIB6
TxCAN2
RxCAN2
TxCAN1
RxCAN1
TxCAN0
RxCAN0
CAN2
DDRA
PS4
PS5
PS6
PS7
PP0
PP1
PP2
PP3
ECS
Multiplexed Address/Data Bus
PS0
PS1
PS2
PS3
PORT P
Clock
Generation
module
Enhanced
capture
timer
PAD10
PAD11
PAD12
PAD13
PAD14
PAD15
PAD16
PAD17
PT0
PT1
PT2
PT3
PT4
PT5
PT6
PT7
PORT K
PLL
IOC0
IOC1
IOC2
IOC3
IOC4
IOC5
IOC6
IOC7
PORT IB
XFC
VDDPLL
VSSPLL
Periodic interrupt
COP watchdog
Clock monitor
Breakpoints
DDRT
BKGD
Single-wire
background
debug module
DDRS
CPU12
AN10
AN11
AN12
AN13
AN14
AN15
AN16
AN17
DDRP
2K byte EEPROM
PAD00
PAD01
PAD02
PAD03
PAD04
PAD05
PAD06
PAD07
PORT S
AN00
AN01
AN02
AN03
AN04
AN05
AN06
AN07
VDDA
VSSA
DDRK
8K byte RAM
VRH1
VRL1
VDDA
VSSA
VRH1
ATD1 VRL1
VDDA
VSSA
PORT AD0
VSTBY
VRH0
VRL0
ATD0 VRL0
DDRIB
128K byte flash EEPROM
PJ7
PJ6
PJ5
PJ4
PJ3
PJ2
PJ1
PJ0
VDD ×2
VSS ×2
Power for internal circuitry
VDDX ×2
VSSX ×2
Power for I/O drivers
Figure 1-1. MC68HC912DT128A Block Diagram
Technical Data
30
MC68HC912DT128A — Rev 4.0
General Description
MOTOROLA
General Description
MC68HC912DG128A Block Diagram
1.6 MC68HC912DG128A Block Diagram
VRH0
RxD0
TxD0
RxD1
TxD1
SCI0
EXTAL
XTAL
RESET
SCI1
SDI/MISO
SDO/MOSI
SCK
SS
SPI
PORT E
PE0
PE1
PE2
PE3
PE4
PE5
PE6
PE7
XIRQ
IRQ
R/W
LSTRB
ECLK
MODA
MODB
DBE/CAL
Lite
integration
module
(LIM)
PW0
PW1
PW2
PW3
PWM
PIX0
PIX1
PIX2
PPAGE
I/O
ECS
Multiplexed Address/Data Bus
I/O
PORTH
DDRH
DDRJ
Narrow bus
KWJ7
KWJ6
KWJ5
KWJ4
KWJ3
KWJ2
KWJ1
KWJ0
PORTJ
PB7
PB6
PB5
PB4
PB3
PB2
PB1
PB0
TxCAN1
RxCAN1
ADDR7
ADDR6
ADDR5
ADDR4
ADDR3
ADDR2
ADDR1
ADDR0
CAN1
DATA7
DATA6
DATA5
DATA4
DATA3
DATA2
DATA1
DATA0
PORT B
PA7
PA6
PA5
PA4
PA3
PA2
PA1
PA0
PORT A
ADDR15
ADDR14
ADDR13
ADDR12
ADDR11
ADDR10
ADDR9
ADDR8
TxCAN0
RxCAN0
KWU
PJ7
PJ6
PJ5
PJ4
PJ3
PJ2
PJ1
PJ0
PORT AD1
PIB7
PIB6
PIB5
PIB4
CAN0
PH7
PH6
PH5
PH4
PH3
PH2
PH1
PH0
PS4
PS5
PS6
PS7
PK0
PK1
PK2
PK3
PK7
DDRB
KWH7
KWH6
KWH5
KWH4
KWH3
KWH2
KWH1
KWH0
PS0
PS1
PS2
PS3
PP0
PP1
PP2
PP3
DDRA
DATA7 DATA15
DATA6 DATA14
DATA5 DATA13
DATA4 DATA12
DATA3 DATA11
DATA2 DATA10
DATA1 DATA9
DATA0 DATA8
Wide
bus
DDRIB
SCL
SDA
IIC
PORT T
Clock
Generation
module
Enhanced
capture
timer
PAD10
PAD11
PAD12
PAD13
PAD14
PAD15
PAD16
PAD17
PT0
PT1
PT2
PT3
PT4
PT5
PT6
PT7
PORT S
PLL
IOC0
IOC1
IOC2
IOC3
IOC4
IOC5
IOC6
IOC7
PORT P
XFC
VDDPLL
VSSPLL
Periodic interrupt
COP watchdog
Clock monitor
Breakpoints
PORT K
BKGD
Single-wire
background
debug module
PORTIB
CPU12
AN10
AN11
AN12
AN13
AN14
AN15
AN16
AN17
DDRS
2K byte EEPROM
PAD00
PAD01
PAD02
PAD03
PAD04
PAD05
PAD06
PAD07
DDRT
AN00
AN01
AN02
AN03
AN04
AN05
AN06
AN07
VDDA
VSSA
DDRP
8K byte RAM
VRH1
VRL1
VDDA
VSSA
VRH1
ATD1 VRL1
VDDA
VSSA
PORT AD0
VSTBY
VRH0
VRL0
ATD0 VRL0
DDRK
128K byte flash EEPROM
VDD ×2
VSS ×2
Power for internal circuitry
VDDX ×2
VSSX ×2
Power for I/O drivers
Figure 1-2. MC68HC912DG128A Block Diagram
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
General Description
31
General Description
1.7 Ordering Information
Table 1-1. Device Ordering Information
Ambient Temperature
Package
Order Number
Range
Designator
–40 to +85°C
C
MC912DG128ACPV
–40 to +105°C
V
MC912DG128AVPV
–40 to +125°C
M
MC912DG128AMPV
–40 to +85°C
C
MC912DT128ACPV
–40 to +105°C
V
MC912DT128AVPV
–40 to +125°C
M
MC912DT128AMPV
–40 to +85°C
C
MC912DG128CCPV
–40 to +105°C
V
MC912DG128CVPV
–40 to +125°C
M
MC912DG128CMPV
–40 to +85°C
C
MC912DT128CCPV
–40 to +105°C
V
MC912DT128CVPV
–40 to +125°C
M
MC912DT128CMPV
–40 to +85°C
C
MC912DG128PCPV
–40 to +105°C
V
MC912DG128PVPV
–40 to +125°C
M
MC912DG128PMPV
–40 to +85°C
C
MC912DT128PCPV
–40 to +105°C
V
MC912DT128PVPV
–40 to +125°C
M
MC912DT128PMPV
112-Pin TQFP
Technical Data
32
MC68HC912DT128A — Rev 4.0
General Description
MOTOROLA
General Description
Ordering Information
Table 1-2. Development Tools Ordering Information
Description
Details
Order Number
Evaluation board kit
EVB and user's manual only
M68EVB912DG128
Serial Debug Interface
Low voltage serial debug interface cable can be
ordered separately
M68SDIL12
Complete evaluation
board kit
EVB, MCUez debug software, SDIL low voltage serial
debug interface cable
M68KIT912DG128
Adapter
112 pin TQFP adapter is also available.
M68ADP912DG128PV
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
General Description
33
General Description
Technical Data
34
MC68HC912DT128A — Rev 4.0
General Description
MOTOROLA
Technical Data — MC68HC912DT128A
Section 2. Central Processing Unit
2.1 Contents
2.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.3
Programming Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
2.4
Data Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.5
Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
2.6
Indexed Addressing Modes . . . . . . . . . . . . . . . . . . . . . . . . . . .39
2.7
Opcodes and Operands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2.2 Introduction
The CPU12 is a high-speed, 16-bit processing unit. It has full 16-bit data
paths and wider internal registers (up to 20 bits) for high-speed extended
math instructions. The instruction set is a proper superset of the
M68HC11instruction set. The CPU12 allows instructions with odd byte
counts, including many single-byte instructions. This provides efficient
use of ROM space. An instruction queue buffers program information so
the CPU always has immediate access to at least three bytes of machine
code at the start of every instruction. The CPU12 also offers an
extensive set of indexed addressing capabilities.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Central Processing Unit
35
Central Processing Unit
2.3 Programming Model
CPU12 registers are an integral part of the CPU and are not addressed
as if they were memory locations.
7
A
0 7
B
0
8-BIT ACCUMULATORS A & B
OR
15
D
0
16-BIT DOUBLE ACCUMULATOR D
15
IX
0
INDEX REGISTER X
15
IY
0
INDEX REGISTER Y
15
SP
0
STACK POINTER
15
PC
0
PROGRAM COUNTER
S X H I N Z V C
CONDITION CODE REGISTER
Figure 2-1. Programming Model
Accumulators A and B are general-purpose 8-bit accumulators used to
hold operands and results of arithmetic calculations or data
manipulations. Some instructions treat the combination of these two 8bit accumulators as a 16-bit double accumulator (accumulator D).
Index registers X and Y are used for indexed addressing mode. In the
indexed addressing mode, the contents of a 16-bit index register are
added to 5-bit, 9-bit, or 16-bit constants or the content of an accumulator
to form the effective address of the operand to be used in the instruction.
Technical Data
36
MC68HC912DT128A — Rev 4.0
Central Processing Unit
MOTOROLA
Central Processing Unit
Data Types
Stack pointer (SP) points to the last stack location used. The CPU12
supports an automatic program stack that is used to save system
context during subroutine calls and interrupts, and can also be used for
temporary storage of data. The stack pointer can also be used in all
indexed addressing modes.
Program counter is a 16-bit register that holds the address of the next
instruction to be executed. The program counter can be used in all
indexed addressing modes except autoincrement/decrement.
Condition Code Register (CCR) contains five status indicators, two
interrupt masking bits, and a STOP disable bit. The five flags are half
carry (H), negative (N), zero (Z), overflow (V), and carry/borrow (C). The
half-carry flag is used only for BCD arithmetic operations. The N, Z, V,
and C status bits allow for branching based on the results of a previous
operation.
2.4 Data Types
The CPU12 supports the following data types:
•
Bit data
•
8-bit and 16-bit signed and unsigned integers
•
16-bit unsigned fractions
•
16-bit addresses
A byte is eight bits wide and can be accessed at any byte location. A
word is composed of two consecutive bytes with the most significant
byte at the lower value address. There are no special requirements for
alignment of instructions or operands.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Central Processing Unit
37
Central Processing Unit
2.5 Addressing Modes
Addressing modes determine how the CPU accesses memory locations
to be operated upon. The CPU12 includes all of the addressing modes
of the M68HC11 CPU as well as several new forms of indexed
addressing. Table 2-1 is a summary of the available addressing modes.
Table 2-1. M68HC12 Addressing Mode Summary
Addressing Mode
Source Format
INST
(no externally supplied
operands)
INST #opr8i
or
INST #opr16i
Abbreviation
Description
INH
Operands (if any) are in CPU registers
IMM
Operand is included in instruction stream
8- or 16-bit size implied by context
Direct
INST opr8a
DIR
Extended
INST opr16a
INST rel8
or
INST rel16
EXT
REL
An 8-bit or 16-bit relative offset from the current
pc is supplied in the instruction
INST oprx5,xysp
IDX
5-bit signed constant offset from x, y, sp, or pc
INST oprx3,–xys
IDX
Auto pre-decrement x, y, or sp by 1 ~ 8
INST oprx3,+xys
IDX
Auto pre-increment x, y, or sp by 1 ~ 8
INST oprx3,xys–
IDX
Auto post-decrement x, y, or sp by 1 ~ 8
INST oprx3,xys+
IDX
Auto post-increment x, y, or sp by 1 ~ 8
INST abd,xysp
IDX
INST oprx9,xysp
IDX1
INST oprx16,xysp
IDX2
Indexed-Indirect
(16-bit offset)
INST [oprx16,xysp]
[IDX2]
Indexed-Indirect
(D accumulator
offset)
INST [D,xysp]
[D,IDX]
Inherent
Immediate
Relative
Indexed
(5-bit offset)
Indexed
(auto pre-decrement)
Indexed
(auto pre-increment)
Indexed
(auto postdecrement)
Indexed
(auto post-increment)
Indexed
(accumulator offset)
Indexed
(9-bit offset)
Indexed
(16-bit offset)
Operand is the lower 8-bits of an address in the
range $0000 – $00FF
Operand is a 16-bit address
Indexed with 8-bit (A or B) or 16-bit (D)
accumulator offset from x, y, sp, or pc
9-bit signed constant offset from x, y, sp, or pc
(lower 8-bits of offset in one extension byte)
16-bit constant offset from x, y, sp, or pc
(16-bit offset in two extension bytes)
Pointer to operand is found at...
16-bit constant offset from x, y, sp, or pc
(16-bit offset in two extension bytes)
Technical Data
38
Pointer to operand is found at...
x, y, sp, or pc plus the value in D
MC68HC912DT128A — Rev 4.0
Central Processing Unit
MOTOROLA
Central Processing Unit
Indexed Addressing Modes
2.6 Indexed Addressing Modes
The CPU12 indexed modes reduce execution time and eliminate code
size penalties for using the Y index register. CPU12 indexed addressing
uses a postbyte plus zero, one, or two extension bytes after the
instruction opcode. The postbyte and extensions do the following tasks:
•
Specify which index register is used.
•
Determine whether a value in an accumulator is used as an offset.
•
Enable automatic pre- or post-increment or decrement
•
Specify use of 5-bit, 9-bit, or 16-bit signed offsets.
Table 2-2. Summary of Indexed Operations
Postbyte
Code (xb)
rr0nnnnn
111rr0zs
111rr011
rr1pnnnn
111rr1aa
111rr111
Source Code
Comments
Syntax
,r
5-bit constant offset n = –16 to +15
n,r
rr can specify X, Y, SP, or PC
–n,r
Constant offset (9- or 16-bit signed)
z-0 = 9-bit with sign in LSB of postbyte(s)
n,r
1 = 16-bit
–n,r
if z = s = 1, 16-bit offset indexed-indirect (see below)
rr can specify X, Y, SP, or PC
16-bit offset indexed-indirect
[n,r]
rr can specify X, Y, SP, or PC
Auto pre-decrement/increment or Auto post-decrement/increment;
n,–r n,+r
p = pre-(0) or post-(1), n = –8 to –1, +1 to +8
n,r– n,r+
rr can specify X, Y, or SP (PC not a valid choice)
Accumulator offset (unsigned 8-bit or 16-bit)
aa-00 = A
A,r
01 = B
B,r
10 = D (16-bit)
D,r
11 = see accumulator D offset indexed-indirect
rr can specify X, Y, SP, or PC
Accumulator D offset indexed-indirect
[D,r]
rr can specify X, Y, SP, or PC
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Central Processing Unit
39
Central Processing Unit
2.7 Opcodes and Operands
The CPU12 uses 8-bit opcodes. Each opcode identifies a particular
instruction and associated addressing mode to the CPU. Several
opcodes are required to provide each instruction with a range of
addressing capabilities.
Only 256 opcodes would be available if the range of values were
restricted to the number that can be represented by 8-bit binary
numbers. To expand the number of opcodes, a second page is added to
the opcode map. Opcodes on the second page are preceded by an
additional byte with the value $18.
To provide additional addressing flexibility, opcodes can also be
followed by a postbyte or extension bytes. Postbytes implement certain
forms of indexed addressing, transfers, exchanges, and loop primitives.
Extension bytes contain additional program information such as
addresses, offsets, and immediate data.
Technical Data
40
MC68HC912DT128A — Rev 4.0
Central Processing Unit
MOTOROLA
Technical Data — MC68HC912DT128A
Section 3. Pinout and Signal Descriptions
3.1 Contents
3.2
MC68HC912DT128A Pin Assignments in 112-pin QFP. . . . . . 41
3.3
Power Supply Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .45
3.4
Signal Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47
3.5
Port Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
3.2 MC68HC912DT128A Pin Assignments in 112-pin QFP
The MC68HC912DT128A is available in a 112-pin thin quad flat pack
(TQFP). Most pins perform two or more functions, as described in the
Signal Descriptions. Figure 3-1 shows pin assignments. In expanded
narrow modes the lower byte data is multiplexed with higher byte data
through pins 57-64.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
41
84
83
82
81
80
79
78
77
76
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
MC68HC912DT128A
112TQFP
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
PAD17/AN17
PAD07/AN07
PAD16/AN16
PAD06/AN06
PAD15/AN15
PAD05/AN05
PAD14/AN14
PAD04/AN04
PAD13/AN13
PAD03/AN03
PAD12/AN12
PAD02/AN02
PAD11/AN11
PAD01/AN01
PAD10/AN10
PAD00/AN00
VRL0
VRH0
VSS
VDD
PA7/ADDR15/DATA15/DATA7
PA6/ADDR14/DATA14/DATA6
PA5/ADDR13/DATA13/DATA5
PA4/ADDR12/DATA12/DATA4
PA3/ADDR11/DATA11/DATA3
PA2/ADDR10/DATA10/DATA2
PA1/ADDR9/DATA9/DATA1
PA0/ADDR8/DATA8/DATA0
ADDR5/DATA5/PB5
ADDR6/DATA6/PB6
ADDR7/DATA7/PB7
KWH7/PH7
KWH6/PH6
KWH5/PH5
KWH4/PH4
DBE/CAL/PE7
MODB/IPIPE1/PE6
MODA/IPIPE0/PE5
ECLK/PE4
VSSX
VSTBY
VDDX
VDDPLL
XFC
VSSPLL
RESET
EXTAL
XTAL
KWH3/PH3
KWH2/PH2
KWH1/PH1
KWH0/PH0
LSTRB/TAGLO/PE3
R/W/PE2
IRQ/PE1
XIRQ/PE0
PW2/PP2
PW1/PP1
PW0/PP0
IOC0/PT0
IOC1/PT1
IOC2/PT2
IOC3/PT3
KWJ7/PJ7
KWJ6/PJ6
KWJ5/PJ5
KWJ4/PJ4
VDD
PK3
VSS
IOC4/PT4
IOC5/PT5
IOC6/PT6
IOC7/PT7
KWJ3/PJ3
KWJ2/PJ2
KWJ1/PJ1
KWJ0/PJ0
SMODN/TAGHI/BKGD
ADDR0/DATA0/PB0
ADDR1/DATA1/PB1
ADDR2/DATA2/PB2
ADDR3/DATA3/PB3
ADDR4/DATA4/PB4
112
111
110
109
108
107
106
105
104
103
102
101
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
PP3/PW3
PK0/PIX0
PK1/PIX1
PK2/PIX2
PK7/ECS
VDDX
VSSX
RxCAN0
TxCAN0
RxCAN1
TxCAN1
RxCAN2
TxCAN2
PIB6/SDA
PIB7/SCL
TEST
PS7/SS
PS6/SCK
PS5/SDO/MOSI
PS4/SDI/MISO
PS3/TxD1
PS2/RxD1
PS1/TxD0
PS0/RxD0
VSSA
VRL1
VRH1
VDDA
Pinout and Signal Descriptions
Note: TEST = This pin is used for factory test purposes. It is recommended that this pin is not connected in the
application, but it may be bonded to 5.5 V max without issue.
Never apply voltage higher than 5.5 V to this pin.
Figure 3-1. Pin Assignments in 112-pin QFP for MC68HC912DT128A
Technical Data
42
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
MC68HC912DG128A
112TQFP
84
83
82
81
80
79
78
77
76
75
74
73
72
71
70
69
68
67
66
65
64
63
62
61
60
59
58
57
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
PAD17/AN17
PAD07/AN07
PAD16/AN16
PAD06/AN06
PAD15/AN15
PAD05/AN05
PAD14/AN14
PAD04/AN04
PAD13/AN13
PAD03/AN03
PAD12/AN12
PAD02/AN02
PAD11/AN11
PAD01/AN01
PAD10/AN10
PAD00/AN00
VRL0
VRH0
VSS
VDD
PA7/ADDR15/DATA15/DATA7
PA6/ADDR14/DATA14/DATA6
PA5/ADDR13/DATA13/DATA5
PA4/ADDR12/DATA12/DATA4
PA3/ADDR11/DATA11/DATA3
PA2/ADDR10/DATA10/DATA2
PA1/ADDR9/DATA9/DATA1
PA0/ADDR8/DATA8/DATA0
ADDR5/DATA5/PB5
ADDR6/DATA6/PB6
ADDR7/DATA7/PB7
KWH7/PH7
KWH6/PH6
KWH5/PH5
KWH4/PH4
ECLK/DBE/CAL/PE7
CGMTST/MODB/IPIPE1/PE6
MODA/IPIPE0/PE5
ECLK/PE4
VSSX
VSTBY
VDDX
VDDPLL
XFC
VSSPLL
RESET
EXTAL
XTAL
KWH3/PH3
KWH2/PH2
KWH1/PH1
KWH0/PH0
LSTRB/TAGLO/PE3
R/W/PE2
IRQ/PE1
XIRQ/PE0
PW2/PP2
PW1/PP1
PW0/PP0
IOC0/PT0
IOC1/PT1
IOC2/PT2
IOC3/PT3
KWJ7/PJ7
KWJ6/PJ6
KWJ5/PJ5
KWJ4/PJ4
VDD
PK3
VSS
IOC4/PT4
IOC5/PT5
IOC6/PT6
IOC7/PT7
KWJ3/PJ3
KWJ2/PJ2
KWJ1/PJ1
KWJ0/PJ0
SMODN/TAGHI/BKGD
ADDR0/DATA0/PB0
ADDR1/DATA1/PB1
ADDR2/DATA2/PB2
ADDR3/DATA3/PB3
ADDR4/DATA4/PB4
112
111
110
109
108
107
106
105
104
103
102
101
100
99
98
97
96
95
94
93
92
91
90
89
88
87
86
85
PP3/PW3
PK0/PIX0
PK1/PIX1
PK2/PIX2
PK7/ECS
VDDX
VSSX
RxCAN0
TxCAN0
RxCAN1
TxCAN1
PIB4
PIB5
PIB6/SDA
PIB7/SCL
TEST
PS7/SS
PS6/SCK
PS5/SDO/MOSI
PS4/SDI/MISO
PS3/TxD1
PS2/RxD1
PS1/TxD0
PS0/RxD0
VSSA
VRL1
VRH1
VDDA
Pinout and Signal Descriptions
MC68HC912DT128A Pin Assignments in 112-pin QFP
Note: TEST = This pin is used for factory test purposes. It is recommended that this pin is not connected in the
application, but it may be bonded to 5.5 V max without issue.
Never apply voltage higher than 5.5 V to this pin.
Figure 3-2. Pin Assignments in 112-pin QFP for MC68HC912DG128A
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
43
Pinout and Signal Descriptions
0.20 T L-M N
4X
PIN 1
IDENT
0.20 T L-M N
4X 28 TIPS
112
J1
85
4X
P
J1
1
CL
84
VIEW Y
108X
X
X=L, M OR N
G
VIEW Y
B
L
V
M
B1
28
AA
J
V1
57
29
F
D
56
0.13
N
M
T
BASE
METAL
L-M N
SECTION J1-J1
ROTATED 90 ° COUNTERCLOCKWISE
A1
S1
A
S
C2
C
VIEW AB
θ2
0.050
0.10 T
112X
SEATING
PLANE
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ASME Y14.5M, 1994.
2. DIMENSIONS IN MILLIMETERS.
3. DATUMS L, M AND N TO BE DETERMINED AT
SEATING PLANE, DATUM T.
4. DIMENSIONS S AND V TO BE DETERMINED AT
SEATING PLANE, DATUM T.
5. DIMENSIONS A AND B DO NOT INCLUDE
MOLD PROTRUSION. ALLOWABLE
PROTRUSION IS 0.25 PER SIDE. DIMENSIONS
A AND B INCLUDE MOLD MISMATCH.
6. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR
PROTRUSION SHALL NOT CAUSE THE D
DIMENSION TO EXCEED 0.46.
θ3
T
θ
R
R2
R
0.25
R1
GAGE PLANE
(K)
C1
θ1
E
(Y)
(Z)
VIEW AB
DIM
A
A1
B
B1
C
C1
C2
D
E
F
G
J
K
P
R1
R2
S
S1
V
V1
Y
Z
AA
θ
θ1
θ2
θ3
MILLIMETERS
MAX
MIN
20.000 BSC
10.000 BSC
20.000 BSC
10.000 BSC
--1.600
0.050
0.150
1.350
1.450
0.270
0.370
0.450
0.750
0.270
0.330
0.650 BSC
0.090
0.170
0.500 REF
0.325 BSC
0.100
0.200
0.100
0.200
22.000 BSC
11.000 BSC
22.000 BSC
11.000 BSC
0.250 REF
1.000 REF
0.090
0.160
8 °
0°
7 °
3 °
13 °
11 °
11 °
13 °
Figure 3-3. 112-pin QFP Mechanical Dimensions (case no. 987)
Technical Data
44
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Power Supply Pins
3.3 Power Supply Pins
MC68HC912DT128A power and ground pins are described below and
summarized in Table 3-1.
All power supply pins must be connected to appropriate supplies.
On no account must any pins be left floating.
3.3.1 Internal Power (VDD) and Ground (VSS)
Power is supplied to the MCU through VDD and VSS. Because fast signal
transitions place high, short-duration current demands on the power
supply, use bypass capacitors with high-frequency characteristics and
place them as close to the MCU as possible.
3.3.2 External Power (VDDX) and Ground (VSSX)
External power and ground for I/O drivers. Because fast signal
transitions place high, short-duration current demands on the power
supply, use bypass capacitors with high-frequency characteristics and
place them as close to the MCU as possible. Bypass requirements
depend on how heavily the MCU pins are loaded.
3.3.3 VDDA, VSSA
Provides operating voltage and ground for the analog-to-digital
converter. This allows the supply voltage to the A/D to be bypassed
independently.
3.3.4 Analog to Digital Reference Voltages (VRH, VRL)
VRH0, VRL0: reference voltage high and low for ATD converter 0.
VRH1, VRL1: reference voltage high and low for ATD converter 1.
If the ATD modules are not used, leaving VRH connected to VDD will not
result in an increase of power consumption.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
45
Pinout and Signal Descriptions
3.3.5 VDDPLL, VSSPLL
Provides operating voltage and ground for the Phase-Locked Loop. This
allows the supply voltage to the PLL to be bypassed independently.
NOTE:
The VSSPLL pin should always be grounded even if the PLL is not used.
The VDDPLL pin should not be left floating. It is recommended to
connect the VDDPLL pin to ground if the PLL is not used.
3.3.6 XFC
PLL loop filter. Please see Appendix: CGM Practical Aspects for
information on how to calculate PLL loop filter elements. Any current
leakage on this pin must be avoided.
VDDPLL
C0
MCU
R0
Ca
XFC
Figure 3-4. PLL Loop FIlter Connections
Technical Data
46
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Signal Descriptions
3.3.7 VSTBY
Stand-by voltage supply to static RAM. Used to maintain the contents of
RAM with minimal power when the rest of the chip is powered down.
Table 3-1. MC68HC912DT128A Power and Ground Connection Summary
VDD
Pin Number
112-pin QFP
12, 65
VSS
14, 66
VDDX
42, 107
VSSX
40, 106
VDDA
85
VSSA
88
VRH1
86
VRL1
87
VRH0
67
VRL0
68
VDDPLL
43
VSSPLL
45
VSTBY
41
Mnemonic
Description
Internal power and ground.
External power and ground, supply to pin drivers.
Operating voltage and ground for the analog-to-digital converter, allows the
supply voltage to the A/D to be bypassed independently.
Reference voltages for the analog-to-digital converter 1
Reference voltages for the analog-to-digital converter 0.
Provides operating voltage and ground for the Phase-Locked Loop. This allows
the supply voltage to the PLL to be bypassed independently.
Stand-by voltage supply to maintain the contents of RAM with minimal power
when the rest of the chip is powered down.
3.4 Signal Descriptions
3.4.1 Crystal Driver and External Clock Input (XTAL, EXTAL)
These pins provide the interface for either a crystal or a CMOS
compatible clock to control the internal clock generator circuitry. Out of
reset the frequency applied to EXTAL is twice the desired E–clock rate.
All the device clocks are derived from the EXTAL input frequency.
3.4.1.1 Crystal Connections
Refer to Section 13. Oscillator for details of crystal connections.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
47
Pinout and Signal Descriptions
NOTE:
When selecting a crystal, it is recommended to use one with the lowest
possible frequency in order to minimise EMC emissions.
3.4.1.2 External Oscillator Connections
XTAL is the crystal output. The XTAL pin must be left unterminated when
an external CMOS compatible clock input is connected to the EXTAL
pin. The XTAL output is normally intended to drive only a crystal. The
XTAL output can be buffered with a high-impedance buffer to drive the
EXTAL input of another device.
2 xE
CMOS-COMPATIBLE
EXTERNAL OSCILLATOR
EXTAL
MCU
XTAL
NC
Figure 3-5. External Oscillator Connections
3.4.2 E-Clock Output (ECLK)
ECLK is the output connection for the internal bus clock. It is used to
demultiplex the address and data in expanded modes and is used as a
timing reference. ECLK frequency is equal to 1/2 the crystal frequency
out of reset. The E-clock output is turned off in single chip user mode to
reduce the effects of RFI. It can be turned on if necessary. In special
single-chip mode, the E-clock is turned ON at reset and can be turned
OFF. In special peripheral mode the E-clock is an input to the MCU. All
clocks, including the E clock, are halted when the MCU is in STOP
mode. It is possible to configure the MCU to interface to slow external
memory. ECLK can be stretched for such accesses.
3.4.3 Reset (RESET)
An active low bidirectional control signal, RESET, acts as an input to
initialize the MCU to a known start-up state. It also acts as an open-drain
Technical Data
48
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Signal Descriptions
output to indicate that an internal failure has been detected in either the
clock monitor or COP watchdog circuit. The MCU goes into reset
asynchronously and comes out of reset synchronously. This allows the
part to reach a proper reset state even if the clocks have failed, while
allowing synchronized operation when starting out of reset.
It is important to use an external low-voltage reset circuit (such as
MC34064 or MC34164) to prevent corruption of RAM or EEPROM due
to power transitions.
The reset sequence is initiated by any of the following events:
•
Power-on-reset (POR)
•
COP watchdog enabled and watchdog timer times out
•
Clock monitor enabled and Clock monitor detects slow or stopped
clock
•
User applies a low level to the reset pin
External circuitry connected to the reset pin should not include a large
capacitance that would interfere with the ability of this signal to rise to a
valid logic one within nine bus cycles after the low drive is released.
Upon detection of any reset, an internal circuit drives the reset pin low
and a clocked reset sequence controls when the MCU can begin normal
processing. In the case of POR or a clock monitor error, a 4096 cycle
oscillator startup delay is imposed before the reset recovery sequence
starts (reset is driven low throughout this 4096 cycle delay). The internal
reset recovery sequence then drives reset low for 16 to 17 cycles and
releases the drive to allow reset to rise. Nine cycles later this circuit
samples the reset pin to see if it has risen to a logic one level. If reset is
low at this point, the reset is assumed to be coming from an external
request and the internally latched states of the COP timeout and clock
monitor failure are cleared so the normal reset vector ($FFFE:FFFF) is
taken when reset is finally released. If reset is high after this nine cycle
delay, the reset source is tentatively assumed to be either a COP failure
or a clock monitor fail. If the internally latched state of the clock monitor
fail circuit is true, processing begins by fetching the clock monitor vector
($FFFC:FFFD). If no clock monitor failure is indicated, and the latched
state of the COP timeout is true, processing begins by fetching the COP
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
49
Pinout and Signal Descriptions
vector ($FFFA:FFFB). If neither clock monitor fail nor COP timeout are
pending, processing begins by fetching the normal reset vector
($FFFE:FFFF).
3.4.4 Maskable Interrupt Request (IRQ)
The IRQ input provides a means of applying asynchronous interrupt
requests to the MCU. Either falling edge-sensitive triggering or levelsensitive triggering is program selectable (INTCR register). IRQ is
always enabled and configured to level-sensitive triggering at reset. It
can be disabled by clearing IRQEN bit (INTCR register). When the MCU
is reset the IRQ function is masked in the condition code register. This
pin is always an input and can always be read. There is an active pull-up
on this pin while in reset and immediately out of reset. The pullup can be
turned off by clearing PUPE in the PUCR register.
Technical Data
50
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Signal Descriptions
3.4.5 Nonmaskable Interrupt (XIRQ)
The XIRQ input provides a means of requesting a nonmaskable interrupt
after reset initialization. During reset, the X bit in the condition code
register (CCR) is set and any interrupt is masked until MCU software
enables it. Because the XIRQ input is level sensitive, it can be connected
to a multiple-source wired-OR network. This pin is always an input and
can always be read. There is an active pull-up on this pin while in reset
and immediately out of reset. The pullup can be turned off by clearing
PUPE in the PUCR register. XIRQ is often used as a power loss detect
interrupt.
Whenever XIRQ or IRQ are used with multiple interrupt sources (IRQ
must be configured for level-sensitive operation if there is more than one
source of IRQ interrupt), each source must drive the interrupt input with
an open-drain type of driver to avoid contention between outputs. There
must also be an interlock mechanism at each interrupt source so that the
source holds the interrupt line low until the MCU recognizes and
acknowledges the interrupt request. If the interrupt line is held low, the
MCU will recognize another interrupt as soon as the interrupt mask bit in
the MCU is cleared (normally upon return from an interrupt).
3.4.6 Mode Select (SMODN, MODA, and MODB)
The state of these pins during reset determine the MCU operating mode.
After reset, MODA and MODB can be configured as instruction queue
tracking signals IPIPE0 and IPIPE1 in expanded modes. MODA and
MODB have active pulldowns during reset.
The SMODN pin has an active pullup when configured as an input. The
pin can be used as BKGD or TAGHI after reset.
3.4.7 Single-Wire Background Mode Pin (BKGD)
The BKGD pin receives and transmits serial background debugging
commands. A special self-timing protocol is used. The BKGD pin has an
active pullup when configured as an input; BKGD has no pullup control.
Refer to Development Support.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
51
Pinout and Signal Descriptions
3.4.8 External Address and Data Buses (ADDR[15:0] and DATA[15:0])
External bus pins share functions with general-purpose I/O ports A and
B. In single-chip operating modes, the pins can be used for I/O; in
expanded modes, the pins are used for the external buses.
In expanded wide mode, ports A and B are used for multiplexed 16-bit
data and address buses. PA[7:0] correspond to
ADDR[15:8]/DATA[15:8]; PB[7:0] correspond to ADDR[7:0]/DATA[7:0].
In expanded narrow mode, ports A and B are used for the16-bit address
bus, and an 8-bit data bus is multiplexed with the most significant half of
the address bus on port A. In this mode, 16-bit data is handled as two
back-to-back bus cycles, one for the high byte followed by one for the
low byte. PA[7:0] correspond to ADDR[15:8] and to DATA[15:8] or
DATA[7:0], depending on the bus cycle. The state of the address pins
should be latched at the rising edge of E. To allow for maximum address
setup time at external devices, a transparent latch should be used.
3.4.9 Read/Write (R/W)
In all modes this pin can be used as a general-purpose I/O and is an
input with an active pull-up out of reset. If the read/write function is
required it should be enabled by setting the RDWE bit in the PEAR
register. External writes will not be possible until enabled.
3.4.10 Low-Byte Strobe (LSTRB)
In all modes this pin can be used as a general-purpose I/O and is an
input with an active pull-up out of reset. If the strobe function is required,
it should be enabled by setting the LSTRE bit in the PEAR register. This
signal is used in write operations. Therefore external low byte writes will
not be possible until this function is enabled. This pin is also used as
TAGLO in Special Expanded modes and is multiplexed with the LSTRB
function.
Technical Data
52
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Signal Descriptions
3.4.11 Instruction Queue Tracking Signals (IPIPE1 and IPIPE0)
IPIPE1 (PE6) and IPIPE0 (PE5) signals are used to track the state of the
internal instruction queue. Data movement and execution state
information is time-multiplexed on the two signals. Refer to Development
Support.
3.4.12 Data Bus Enable (DBE)
The DBE pin (PE7) is an active low signal that will be asserted low during
E-clock high time. DBE provides separation between output of a
multiplexed address and the input of data. When an external address is
stretched, DBE is asserted during what would be the last quarter cycle
of the last E-clock cycle of stretch. In expanded modes this pin is used
to enable the drive control of external buses during external reads. Use
of the DBE is controlled by the NDBE bit in the PEAR register. DBE is
enabled out of reset in expanded modes.
3.4.13 Inverted E clock (ECLK)
The ECLK pin (PE7) can be used to latch the address for demultiplexing. It has the same behavior as the ECLK, except is inverted.
In expanded modes this pin is used to enable the drive control of external
buses during external reads. Use of the ECLK is controlled by the NDBE
and DBENE bits in the PEAR register.
3.4.14 Calibration reference (CAL)
The CAL pin (PE7) is the output of the Slow Mode programmable clock
divider, SLWCLK, and is used as a calibration reference. The SLWCLK
frequency is equal to the crystal frequency out of reset and always has
a 50% duty. If the DBE function is enabled it will override the enabled
CAL output. The CAL pin output is disabled by clearing CALE bit in the
PEAR register.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
53
Pinout and Signal Descriptions
3.4.15 Clock generation module test (CGMTST)
The CGMTST pin (PE6) is the output of the clocks tested when CGMTE
bit is set in PEAR register. The PIPOE bit must be cleared for the clocks
to be tested.
3.4.16 TEST
This pin is used for factory test purposes. It is recommended that this
pin is not connected in the application, but it may be bonded to 5.5 V max
without issue. Never apply voltage higher than 5.5 V to this pin
Table 3-2. MC68HC912DT128A Signal Description Summary
Pin Name
Shared
port
EXTAL
XTAL
-
RESET
-
ADDR[7:0]
DATA[7:0]
ADDR[15:8]
DATA[15:8]
Pin
Number
Description
112-pin
47
Crystal driver and external clock input pins. On reset all the device clocks are
derived from the EXTAL input frequency. XTAL is the crystal output.
48
An active low bidirectional control signal, RESET acts as an input to initialize the
46
MCU to a known start-up state, and an output when COP or clock monitor
causes a reset.
PB[7:0]
31–24
PA[7:0]
64–57
DBE
PE7
36
ECLK
PE7
36
CAL
PE7
36
CGMTST
PE6
MODB/IPIP
E1,
PE6, PE5
MODA/IPIP
E0
37
37, 38
ECLK
PE4
39
LSTRB/TA
GLO
PE3
53
R/W
PE2
54
External bus pins share function with general-purpose I/O ports A and B. In
single chip modes, the pins can be used for I/O. In expanded modes, the pins
are used for the external buses.
Data bus control and, in expanded mode, enables the drive control of external
buses during external reads.
Inverted E clock used to latch the address.
CAL is the output of the Slow Mode programmable clock divider, SLWCLK, and
is used as a calibration reference for functions such as time of day. It is
overridden when DBE function is enabled. It always has a 50% duty.
Clock generation module test output.
State of mode select pins during reset determine the initial operating mode of
the MCU. After reset, MODB and MODA can be configured as instruction
queue tracking signals IPIPE1 and IPIPE0 or as general-purpose I/O pins.
E Clock is the output connection for the external bus clock. ECLK is used as a
timing reference and for address demultiplexing.
Low byte strobe (0 = low byte valid), in all modes this pin can be used as I/O.
The low strobe function is the exclusive-NOR of A0 and the internal SZ8
signal. (The SZ8 internal signal indicates the size 16/8 access.) Pin function
TAGLO used in instruction tagging. See Development Support.
Indicates direction of data on expansion bus. Shares function with generalpurpose I/O. Read/write in expanded modes.
Technical Data
54
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Signal Descriptions
Table 3-2. MC68HC912DT128A Signal Description Summary
Pin Name
Shared
port
Pin
Number
112-pin
Description
Maskable interrupt request input provides a means of applying asynchronous
interrupt requests to the MCU. Either falling edge-sensitive triggering or levelsensitive triggering is program selectable (INTCR register).
Provides a means of requesting asynchronous nonmaskable interrupt requests
XIRQ
PE0
56
after reset initialization
During reset, this pin determines special or normal operating mode. After reset,
SMODN/
single-wire background interface pin is dedicated to the background debug
BKGD/
23
function. Pin function TAGHI used in instruction tagging. See Development
TAGHI
Support.
IX[2:0]
PK[2:0] 109-111 Page Index register emulation outputs.
ECS
PK7
108
Emulation Chip select.
PW[3:0]
PP[3:0] 112, 1–3 Pulse Width Modulator channel outputs.
SS
PS7
96
Slave select output for SPI master mode, input for slave mode or master mode.
SCK
PS6
95
Serial clock for SPI system.
SDO/MOSI
PS5
94
Master out/slave in pin for serial peripheral interface
SDI/MISO
PS4
93
Master in/slave out pin for serial peripheral interface
TxD1
PS3
92
SCI1 transmit pin
RxD1
PS2
91
SCI1 receive pin
TxD0
PS1
90
SCI0 transmit pin
RxD0
PS0
89
SCI0 receive pin
18–15, Pins used for input capture and output compare in the timer and pulse
IOC[7:0]
PT[7:0]
7–4
accumulator subsystem.
84/82/80/
AN1[7:0] PAD1[7:0] 78/76/74/ Analog inputs for the analog-to-digital conversion module 1
72/70
83/81/79/
AN0[7:0] PAD0[7:0] 77/75/73/ Analog inputs for the analog-to-digital conversion module 0
71/69
Used for factory test purposes. Do not connect in the application; may be
TEST
97
bonded to 5.5 V max.
IRQ
PE1
55
TxCAN2(1)
-
100
RxCAN2(1)
-
101
TxCAN1
-
102
RxCAN1
-
103
TxCAN0
-
104
RxCAN0
-
105
SCL
PIB7
98
MSCAN2 transmit pin (MC68HC912DT128A only). Leave unconnected if
MSCAN2 is not used.
MSCAN2 receive pin (MC68HC912DT128A only). Pin has internal pull-up;
where msCAN module is not used, do not tie to VSS.
MSCAN1 transmit pin. Leave unconnected if MSCAN1 is not used.
MSCAN1 receive pin. Pin has internal pull-up; where msCAN module is not
used, do not tie to VSS.
MSCAN0 transmit pin. Leave unconnected if MSCAN0 is not used.
MSCAN0 receive pin. Pin has internal pull-up; where msCAN module is not
used, do not tie to VSS.
I2C bus serial clock line pin
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
55
Pinout and Signal Descriptions
Table 3-2. MC68HC912DT128A Signal Description Summary
Pin Name
Shared
port
SDA
PIB6
KWJ[7:0]
PJ[7:0]
KWH[7:0]
PH[7:0]
Pin
Number
112-pin
Description
I2C bus serial data line pin
8–11, Key wake-up and general purpose I/O; can cause an interrupt when an input
19–22
transitions from high to low or from low to high (KWPJ).
32–35, Key wake-up and general purpose I/O; can cause an interrupt when an input
49–52
transitions from high to low or from low to high (KWPH).
99
1. MC68HC912DT128A only
3.5 Port Signals
The MC68HC912DT128A incorporates eleven ports which are used to
control and access the various device subsystems. When not used for
these purposes, port pins may be used for general-purpose I/O. In
addition to the pins described below, each port consists of a data register
which can be read and written at any time, and, with the exception of port
AD0, port AD1, PE[1:0], RxCAN and TxCAN, a data direction register
which controls the direction of each pin. After reset all general purpose
I/O pins are configured as input.
3.5.1 Port A
Port A pins are used for address and data in expanded modes. When
this port is not used for external access such as in single-chip mode,
these pins can be used as general purpose I/O. The port data register is
not in the address map during expanded and peripheral mode operation.
When it is in the map, port A can be read or written at anytime.
Register DDRA determines whether each port A pin is an input or output.
DDRA is not in the address map during expanded and peripheral mode
operation. Setting a bit in DDRA makes the corresponding bit in port A
an output; clearing a bit in DDRA makes the corresponding bit in port A
an input. The default reset state of DDRA is all zeroes.
When the PUPA bit in the PUCR register is set, all port A input pins are
pulled-up internally by an active pull-up device. PUCR is not in the
address map in peripheral mode.
Technical Data
56
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Port Signals
Setting the RDPA bit in register RDRIV causes all port A outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
in the address map in peripheral mode. Refer to Bus Control and
Input/Output.
3.5.2 Port B
Port B pins are used for address and data in expanded modes. When
this port is not used for external access such as in single-chip mode,
these pins can be used as general purpose I/O. The port data register is
not in the address map during expanded and peripheral mode operation.
When it is in the map, port B can be read or written at anytime.
Register DDRB determines whether each port B pin is an input or output.
DDRB is not in the address map during expanded and peripheral mode
operation. Setting a bit in DDRB makes the corresponding bit in port B
an output; clearing a bit in DDRB makes the corresponding bit in port B
an input. The default reset state of DDRB is all zeroes.
When the PUPB bit in the PUCR register is set, all port B input pins are
pulled-up internally by an active pull-up device. PUCR is not in the
address map in peripheral mode.
Setting the RDPB bit in register RDRIV causes all port B outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
in the address map in peripheral mode. Refer to Bus Control and
Input/Output.
3.5.3 Port E
Port E pins operate differently from port A and B pins. Port E pins are
used for bus control signals and interrupt service request signals. When
a pin is not used for one of these specific functions, it can be used as
general-purpose I/O. However, two of the pins (PE[1:0]) can only be
used for input, and the states of these pins can be read in the port data
register even when they are used for IRQ and XIRQ.
The PEAR register determines pin function, and register DDRE
determines whether each pin is an input or output when it is used for
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
57
Pinout and Signal Descriptions
general-purpose I/O. PEAR settings override DDRE settings. Because
PE[1:0] are input-only pins, only DDRE[7:2] have effect. Setting a bit in
the DDRE register makes the corresponding bit in port E an output;
clearing a bit in the DDRE register makes the corresponding bit in port E
an input. The default reset state of DDRE is all zeroes.
When the PUPE bit in the PUCR register is set, PE[7,3,2,1,0] are pulled
up. PE[7,3,2,0] are active pull-up devices. PUPCR is not in the address
map in peripheral mode.
Neither port E nor DDRE is in the map in peripheral mode or in the
internal map in expanded modes with EME set.
Setting the RDPE bit in register RDRIV causes all port E outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
in the address map in peripheral mode. Refer to Bus Control and
Input/Output.
3.5.4 Port H
Port H pins are used for key wake-ups that can be used with the pins
configured as inputs or outputs. The key wake-ups are triggered with
either a rising or falling edge signal (KWPH). An interrupt is generated if
the corresponding bit is enabled (KWIEH). If any of the interrupts is not
enabled, the corresponding pin can be used as a general purpose I/O
pin. Refer to I/O Ports with Key Wake-up.
Register DDRH determines whether each port H pin is an input or output.
Setting a bit in DDRH makes the corresponding bit in port H an output;
clearing a bit in DDRH makes the corresponding bit in port H an input.
The default reset state of DDRH is all zeroes.
Register KWPH not only determines what type of edge the key wake ups
are triggered, but it also determines what type of resistive load is used
for port H input pins when PUPH bit is set in the PUCR register. Setting
a bit in KWPH makes the corresponding key wake up input pin trigger at
rising edges and loads a pull down in the corresponding port H input pin.
Clearing a bit in KWPH makes the corresponding key wake up input pin
trigger at falling edges and loads a pull up in the corresponding port H
input pin. The default state of KWPH is all zeroes.
Technical Data
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MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Port Signals
Setting the RDPH bit in register RDRIV causes all port H outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
in the address map in peripheral mode. Refer to Bus Control and
Input/Output.
3.5.5 Port J
Port J pins are used for key wake-ups that can be used with the pins
configured as inputs or outputs. The key wake-ups are triggered with
either a rising or falling edge signal (KWPJ). An interrupt is generated if
the corresponding bit is enabled (KWIEJ). If any of the interrupts is not
enabled, the corresponding pin can be used as a general purpose I/O
pin. Refer to I/O Ports with Key Wake-up.
Register DDRJ determines whether each port J pin is an input or output.
Setting a bit in DDRJ makes the corresponding bit in port J an output;
clearing a bit in DDRJ makes the corresponding bit in port J an input. The
default reset state of DDRJ is all zeroes.
Register KWPJ not only determines what type of edge the key wake ups
are triggered, but it also determines what type of resistive load is used
for port J input pins when PUPJ bit is set in the PUCR register. Setting a
bit in KWPJ makes the corresponding key wake up input pin trigger at
rising edges and loads a pull down in the corresponding port J input pin.
Clearing a bit in KWPJ makes the corresponding key wake up input pin
trigger at falling edges and loads a pull up in the corresponding port J
input pin. The default state of KWPJ is all zeroes.
Setting the RDPJ bit in register RDRIV causes all port J outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
in the address map in peripheral mode. Refer to Bus Control and
Input/Output.
3.5.6 Port K
Port K pins are used for page index emulation in expanded or peripheral
modes. When page index emulation is not enabled, EMK is not set in
MODE register, or the part is in single chip mode, these pins can be used
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
59
Pinout and Signal Descriptions
for general purpose I/O. Port K bit 3 is used as a general purpose I/O pin
only. The port data register is not in the address map during expanded
and peripheral mode operation with EMK set. When it is in the map, port
K can be read or written at anytime.
Register DDRK determines whether each port K pin is an input or output.
DDRK is not in the address map during expanded and peripheral mode
operation with EMK set. Setting a bit in DDRK makes the corresponding
bit in port K an output; clearing a bit in DDRK makes the corresponding
bit in port K an input. The default reset state of DDRK is all zeroes.
When the PUPK bit in the PUCR register is set, all port K input pins are
pulled-up internally by an active pull-up device. PUCR is not in the
address map in peripheral mode.
Setting the RDPK bit in register RDRIV causes all port K outputs to have
reduced drive level. RDRIV can be written once after reset. RDRIV is not
in the address map in peripheral mode. Refer to Bus Control and
Input/Output.
3.5.7 Port CAN2
(MC68HC912DT128A only)
The MSCAN2 uses two external pins, one input (RxCAN2) and one
output (TxCAN2). The TxCAN2 output pin represents the logic level on
the CAN: ‘0’ is for a dominant state, and ‘1’ is for a recessive state.
RxCAN2 is on bit 0 of Port CAN2, TxCAN2 is on bit 1. If the MSCAN2 is
not used, TxCAN2 should be left unconnected and, due to an internal
pull-up, the RxCAN2 pin should not be tied to VSS.
3.5.8 Port CAN1
The MSCAN1 uses two external pins, one input (RxCAN1) and one
output (TxCAN1). The TxCAN1 output pin represents the logic level on
the CAN: ‘0’ is for a dominant state, and ‘1’ is for a recessive state.
RxCAN1 is on bit 0 of Port CAN1, TxCAN1 is on bit 1. If the MSCAN1 is
not used, TxCAN1 should be left unconnected and, due to an internal
pull-up, the RxCAN1 pin should not be tied to VSS.
Technical Data
60
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Port Signals
3.5.9 Port CAN0
The MSCAN0 uses two external pins, one input (RxCAN0) and one
output (TxCAN0). The TxCAN0 output pin represents the logic level on
the CAN: ‘0’ is for a dominant state, and ‘1’ is for a recessive state.
RxCAN0 is on bit 0 of Port CAN0, TxCAN0 is on bit 1. If the MSCAN0 is
not used, TxCAN0 should be left unconnected and, due to an internal
pull-up, the RxCAN0 pin should not be tied to VSS.
3.5.10 Port IB
Bidirectional pins to IIC bus interface subsystem. The IIC bus interface
uses a Serial Data line (SDA) and Serial Clock line (SCL) for data
transfer. The pins are connected to a positive voltage supply via a pull
up resistor. The pull ups can be enabled internally or connected
externally. The output stages have open drain outputs in order to
perform the wired-AND function. When the IIC is disabled the pins can
be used as general purpose I/O pins. SCL is on bit 7 of Port IB and SDA
is on bit 6. On the MC68HC912DG128A, the remaining two pins of Port
IB (PIB5 and PIB4) are controlled by registers in the IIC address space.
Register DDRIB determines pin direction of port IB when used for
general-purpose I/O. When DDRIB bits are set, the corresponding pin is
configured for output. On reset the DDRIB bits are cleared and the
corresponding pin is configured for input.
When the PUPIB bit in the IBPURD register is set, all input pins are
pulled up internally by an active pull-up device. Pullups are disabled after
reset, except for input ports 0 through 5, which are always on regardless
of PUPIB bit.
Setting the RDPIB bit in the IBPURD register configures all port IB
outputs to have reduced drive levels. Levels are at normal drive
capability after reset. The IBPURD register can be read or written
anytime after reset. Refer to section Inter IC Bus.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
61
Pinout and Signal Descriptions
3.5.11 Port AD1
This port is an analog input interface to the analog-to-digital subsystem
and used for general-purpose input. When analog-to-digital functions
are not enabled, the port has eight general-purpose input pins,
PAD1[7:0]. The ADPU bit in the ATD1CTL2 register enables the A/D
function.
Port AD1 pins are inputs; no data direction register is associated with this
port. The port has no resistive input loads and no reduced drive controls.
Refer to Analog-to-Digital Converter.
3.5.12 Port AD0
This port is an analog input interface to the analog-to-digital subsystem
and used for general-purpose input. When analog-to-digital functions
are not enabled, the port has eight general-purpose input pins,
PAD0[7:0]. The ADPU bit in the ATD0CTL2 register enables the A/D
function.
Port AD0 pins are inputs; no data direction register is associated with this
port. The port has no resistive input loads and no reduced drive controls.
Refer to Analog-to-Digital Converter.
3.5.13 Port P
The four pulse-width modulation channel outputs share general-purpose
port P pins. The PWM function is enabled with the PWEN register.
Enabling PWM pins takes precedence over the general-purpose port.
When pulse-width modulation is not in use, the port pins may be used for
general-purpose I/O.
Register DDRP determines pin direction of port P when used for
general-purpose I/O. When DDRP bits are set, the corresponding pin is
configured for output. On reset the DDRP bits are cleared and the
corresponding pin is configured for input.
When the PUPP bit in the PWCTL register is set, all input pins are pulled
up internally by an active pull-up device. Pullups are disabled after reset.
Technical Data
62
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Port Signals
Setting the RDPP bit in the PWCTL register configures all port P outputs
to have reduced drive levels. Levels are at normal drive capability after
reset. The PWCTL register can be read or written anytime after reset.
Refer to Pulse Width Modulator.
3.5.14 Port S
Port S is the 8-bit interface to the standard serial interface consisting of
the two serial communications interfaces (SCI1 and SCI0) and the serial
peripheral interface (SPI) subsystems. Port S pins are available for
general-purpose I/O when standard serial functions are not enabled.
Port S pins serve several functions depending on the various internal
control registers. If WOMS bit in the SC0CR1register is set, the Pchannel drivers of the output buffers are disabled (wire-or mode) for pins
0 through 3. If SWOM bit in the SP0CR1 register is set, the P-channel
drivers of the output buffers are disabled (wire-or mode) for pins 4
through 7. The open drain control affects both the serial and the generalpurpose outputs. If the RDPS bit in the SP0CR2 register is set, Port S
pin drive capabilities are reduced. If PUPS bit in the SP0CR2 register is
set, a pull-up device is activated for each port S pin programmed as a
general purpose input. If the pin is programmed as a general-purpose
output, the pull-up is disconnected from the pin regardless of the state of
PUPS bit. See Multiple Serial Interface.
3.5.15 Port T
This port provides eight general-purpose I/O pins when not enabled for
input capture and output compare in the timer and pulse accumulator
subsystem. The TEN bit in the TSCR register enables the timer function.
The pulse accumulator subsystem is enabled with the PAEN bit in the
PACTL register.
Register DDRT determines pin direction of port T when used for generalpurpose I/O. When DDRT bits are set, the corresponding pin is
configured for output. On reset the DDRT bits are cleared and the
corresponding pin is configured for input.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pinout and Signal Descriptions
63
Pinout and Signal Descriptions
When the PUPT bit in the TMSK2 register is set, all input pins are pulled
up internally by an active pull-up device. Pullups are disabled after reset.
Setting the RDPT bit in the TMSK2 register configures all port T outputs
to have reduced drive levels. Levels are at normal drive capability after
reset. The TMSK2 register can be read or written anytime after reset.
Refer to Enhanced Capture Timer.
Table 3-3. MC68HC912DT128A Port Description Summary
Port Name
Pin
Numbers
112-pin
Data Direction
Register (Address)
Port A
PA[7:0]
64-57
In/Out
DDRA ($0002)
Port B
PB[7:0]
31–24
In/Out
DDRB ($0003)
Port AD1
PAD1[7:0]
Port AD0
PAD0[7:0]
84/82/80/7
8/76/74/72
/70
83/81/79/7
7/75/73/71
/69
Port CAN2
PCAN2[1:0]
100–101
(1)
Port CAN1
PCAN1[1:0]
Port CAN0
PCAN0[1:0]
102–103
104–105
Description
Port A and port B pins are used for address and data in
expanded modes. The port data registers are not in the
address map during expanded and peripheral mode
operation. When in the map, port A and port B can be read or
written any time.
DDRA and DDRB are not in the address map in expanded or
peripheral modes.
In
Analog-to-digital converter 1 and general-purpose I/O.
In
Analog-to-digital converter 0 and general-purpose I/O.
PCAN2[1] Out
PCAN2[0] In
PCAN2[1:0] are used with the MSCAN2 module and cannot be
used as general purpose I/O (MC68HC912DT128A only).
PCAN1[1] Out
PCAN1[0] In
PCAN0[1] Out
PCAN0[0] In
PCAN1[1:0] are used with the MSCAN1 module and cannot be
used as general purpose I/O.
PCAN0[1:0] are used with the MSCAN0 module and cannot be
used as general purpose I/O.
Port IB
PIB[7:6]
98–99
In/Out
DDRIB ($00E7)
General purpose I/O. PIB[7:6] are used with the I-Bus module
when enabled.
Port IB
PIB[5:4](2)
100–101
In/Out
DDRIB ($00E7)
General purpose I/O (MC68HC912DG128A only).
Port E
PE[7:0]
36–39,
53–56
Port K
PK[7,3:0]
Port P
PP[3:0]
13,
108-111
112,
1–3
PE[1:0] In
PE[7:2] In/Out
DDRE ($0009)
In/Out
DDRK ($00FD)
In/Out
DDRP ($0057)
Mode selection, bus control signals and interrupt service
request signals; or general-purpose I/O.
Page index emulation signals in expanded or peripheral mode
or general-purpose I/O.
General-purpose I/O. PP[3:0] are used with the pulse-width
modulator when enabled.
Technical Data
64
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Table 3-3. MC68HC912DT128A Port Description Summary
Port Name
Pin
Numbers
112-pin
Data Direction
Register (Address)
Port S
PS[7:0]
96–89
In/Out
DDRS ($00D7)
Port T
PT[7:0]
18–15,
7–4
In/Out
DDRT ($00AF)
Description
Serial communications interfaces 1 and 0 and serial peripheral
interface subsystems; or general-purpose I/O.
General-purpose I/O when not enabled for input capture and
output compare in the timer and pulse accumulator
subsystem.
1. MC68HC912DT128A only
2. MC68HC912DG128A only
3.5.16 Port Pull-Up Pull-Down and Reduced Drive
MCU ports can be configured for internal pull-up. To reduce power
consumption and RFI, the pin output drivers can be configured to
operate at a reduced drive level. Reduced drive causes a slight increase
in transition time depending on loading and should be used only for ports
which have a light loading. Table 3-4 summarizes the port pull-up default
status and controls.
Table 3-4. Port Pull-Up, Pull-Down and Reduced Drive Summary
Port
Resistive
Name
Input Loads
Port A
Pull-up
Port B
Pull-up
Port E:
PE7, PE[3:2]
Pull-up
PE[1:0]
Pull-up
PE[6:4]
None
Pull-up or
Port H
Pull-down
Pull-up or
Port J
Pull-down
Port K
Pull-up
Port P
Pull-up
Port S
Pull-up
Port T
Pull-up
Port IB[7:6]
Pull-up
Enable Bit
Register
Reset
Bit Name
(Address)
State
PUCR ($000C)
PUPA
Disabled
PUCR ($000C)
PUPB
Disabled
Reduced Drive Control Bit
Register
Reset
Bit Name
(Address)
State
RDRIV ($000D)
RDPA
Full drive
RDRIV ($000D)
RDPB
Full drive
PUCR ($000C)
PUCR ($000C)
RDRIV ($000D)
PUPE
PUPE
Enabled
Enabled
—
Full drive
PUCR ($000C)
PUPH
Disabled
RDRIV ($000D)
RDPH
Full drive
PUCR ($000C)
PUPJ
Disabled
RDRIV ($000D)
RDPJ
Full drive
PUCR ($000C)
PWCTL ($0054)
SP0CR2 ($00D1)
TMSK2 ($008D)
IBPURD ($00E5)
PUPK
PUPP
PUPS
TPU
PUPIB
Disabled
Disabled
Enabled
Disabled
Disabled
RDRIV ($000D)
PWCTL ($0054)
SP0CR2 ($00D1)
TMSK2 ($008D)
IBPURD ($00E5)
RDPK
RDPP
RDPS
TDRB
RDPIB
Full drive
Full drive
Full drive
Full drive
Full drive
Technical Data
65
Full drive
RDRIV ($000D)
RDPE
—
RDPE
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Pinout and Signal Descriptions
Table 3-4. Port Pull-Up, Pull-Down and Reduced Drive Summary
Enable Bit
Port
Name
Resistive
Input Loads
Register
(Address)
Bit Name
Port IB[5:4](1)
Port AD0
Port AD1
Port
CAN2[1](2)
Port
CAN2[0](2)
Port CAN1[1]
Port CAN1[0]
Port CAN0[1]
Port CAN0[0]
Pull-up
IBPURD ($00E5)
PUPIB
Reset
State
Reduced Drive Control Bit
Register
Reset
Bit Name
(Address)
State
Disabled IBPURD ($00E5)
RDPIB
None
None
—
—
—
—
None
—
—
Pull-up
Always enabled
—
None
Pull-up
None
Pull-up
—
Always enabled
—
Always enabled
—
—
—
—
Full drive
1. MC68HC912DG128A only
2. MC68HC912DT128A only
Technical Data
66
MC68HC912DT128A — Rev 4.0
Pinout and Signal Descriptions
MOTOROLA
Technical Data — MC68HC912DT128A
Section 4. Registers
4.1 Contents
4.2
Register Block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
4.2 Register Block
The register block can be mapped to any 2K byte boundary within the
standard 64K byte address space by manipulating bits REG[15:11] in
the INITRG register. INITRG establishes the upper five bits of the
register block’s 16-bit address. The register block occupies the first 1K
byte of the 2K byte block. Default addressing (after reset) is indicated in
the table below. For additional information refer to Operating Modes.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Registers
67
Registers
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$0000
PA7
PA6
PA5
PA4
PA3
PA2
PA1
PA0
PORTA(1)
$0001
PB7
PB6
PB5
PB4
PB3
PB2
PB1
PB0
PORTB(1)
$0002
DDA7
DDA6
DDA5
DDA4
DDA3
DDA2
DDA1
DDA0
DDRA(1)
$0003
DDB7
DDB6
DDB5
DDB4
DDB3
DDB2
DDB1
DDB0
DDRB(1)
$0004$0007
0
0
0
0
0
0
0
0
Reserved(3)
$0008
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
PORTE(2)
$0009
DDE7
DDE6
DDE5
DDE4
DDE3
DDE2
0
0
DDRE(2)
$000A
NDBE
CGMTE
PIPOE
NECLK
LSTRE
RDWE
CALE
DBENE
PEAR(3)
$000B
SMODN
MODB
MODA
ESTR
IVIS
EBSWAI
EMK
EME
MODE(3)
$000C
PUPK
PUPJ
PUPH
PUPE
0
0
PUPB
PUPA
PUCR(3)
$000D
RDPK
RDPJ
RDPH
RDPE
0
0
RDPB
RDPA
RDRIV(3)
$000E
0
0
0
0
0
0
0
0
Reserved(3)
$000F
0
0
0
0
0
0
0
0
Reserved(3)
$0010
RAM15
RAM14
RAM13
0
0
0
0
0
INITRM
$0011
REG15
REG14
REG13
REG12
REG11
0
0
MMSWAI
INITRG
$0012
EE15
EE14
EE13
EE12
0
0
0
EEON
INITEE
$0013
ROMTST
NDRF
RFSTR1
RFSTR0
EXSTR1
EXSTR0
ROMHM
ROMON
MISC
$0014
RTIE
RSWAI
RSBCK
Reserved
RTBYP
RTR2
RTR1
RTR0
RTICTL
$0015
RTIF
0
0
0
0
0
0
0
RTIFLG
$0016
CME
FCME
FCMCOP
WCOP
DISR
CR2
CR1
CR0
COPCTL
$0017
Bit 7
6
5
4
3
2
1
Bit 0
COPRST
$0018
ITE6
ITE8
ITEA
ITEC
ITEE
ITF0
ITF2
ITF4
ITST0
$0019
ITD6
ITD8
ITDA
ITDC
ITDE
ITE0
ITE2
ITE4
ITST1
$001A
ITC6
ITC8
ITCA
ITCC
ITCE
ITD0
ITD2
ITD4
ITST2
$001B
ITB6
ITB8
ITBA
ITBC
ITBE
ITC0
ITC2
ITC4
ITST3
$001C
ITA6
ITA8
ITAA
ITAC
ITAE
ITB0
ITB2
ITB4
ITST4
$001D
0
0
0
0
0
0
0
0
Reserved
$001E
IRQE
IRQEN
DLY
0
0
0
0
0
INTCR
$001F
1
PSEL6
PSEL5
PSEL4
PSEL3
PSEL2
PSEL1
0
HPRIO
$0020
BKEN1
BKEN0
BKPM
0
BK1ALE
BK0ALE
0
0
BRKCT0
$0021
0
BKDBE
BKMBH
BKMBL
BK1RWE
BK1RW
BK0RWE
BK0RW
BRKCT1
$0022
Bit 15
14
13
12
11
10
9
Bit 8
BRKAH
$0023
Bit 7
6
5
4
3
2
1
Bit 0
BRKAL
Table 4-1. Register Map (Sheet 1 of 11)
Technical Data
68
MC68HC912DT128A — Rev 4.0
Registers
MOTOROLA
Registers
Register Block
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$0024
Bit 15
14
13
12
11
10
9
Bit 8
BRKDH
$0025
Bit 7
6
5
4
3
2
1
Bit 0
BRKDL
$0026
0
0
0
0
0
0
0
0
Reserved
$0027
0
0
0
0
0
0
0
0
Reserved
$0028
PJ7
PJ6
PJ5
PJ4
PJ3
PJ2
PJ1
PJ0
PORTJ
$0029
PH7
PH6
PH5
PH4
PH3
PH2
PH1
PH0
PORTH
$002A
DDJ7
DDJ6
DDJ5
DDJ4
DDJ3
DDJ2
DDJ1
DDJ0
DDRJ
$002B
DDH7
DDH6
DDH5
DDH4
DDH3
DDH2
DDH1
DDH0
DDRH
$002C
KWIEJ7
KWIEJ6
KWIEJ5
KWIEJ4
KWIEJ3
KWIEJ2
KWIEJ1
KWIEJ0
KWIEJ
$002D
KWIEH7
KWIEH6
KWIEH5
KWIEH4
KWIEH3
KWIEH2
KWIEH1
KWIEH0
KWIEH
$002E
KWIFJ7
KWIFJ6
KWIFJ5
KWIFJ4
KWIFJ3
KWIFJ2
KWIFJ1
KWIFJ0
KWIFJ
$002F
KWIFH7
KWIFH6
KWIFH5
KWIFH4
KWIFH3
KWIFH2
KWIFH1
KWIFH0
KWIFH
$0030
KWPJ7
KWPJ6
KWPJ5
KWPJ4
KWPJ3
KWPJ2
KWPJ1
KWPJ0
KWPJ
$0031
KWPH7
KWPH6
KWPH5
KWPH4
KWPH3
KWPH2
KWPH1
KWPH0
KWPH
$0032
0
0
0
0
0
0
0
0
Reserved
$0033
0
0
0
0
0
0
0
0
Reserved
$0034–
$0037
Unimplemented(4)
Reserved
$0038
0
0
SYN5
SYN4
SYN3
SYN2
SYN1
SYN0
SYNR
$0039
0
0
0
0
0
REFDV2
REFDV1
REFDV0
REFDV
$003A
TSTOUT7 TSTOUT6 TSTOUT5 TSTOUT4 TSTOUT3 TSTOUT2 TSTOUT1 TSTOUT0
CGTFLG
$003B
LOCKIF
LOCK
0
0
0
0
LHIF
LHOME
PLLFLG
$003C
LOCKIE
PLLON
AUTO
ACQ
0
PSTP
LHIE
NOLHM
PLLCR
$003D
0
BCSP
BCSS
0
0
MCS
0
0
CLKSEL
$003E
0
0
SLDV5
SLDV4
SLDV3
SLDV2
SLDV1
SLDV0
SLOW
$003F
OPNLE
TRK
TSTCLKE
TST4
TST3
TST2
TST1
TST0
CGTCTL
$0040
CON23
CON01
PCKA2
PCKA1
PCKA0
PCKB2
PCKB1
PCKB0
PWCLK
$0041
PCLK3
PCLK2
PCLK1
PCLK0
PPOL3
PPOL2
PPOL1
PPOL0
PWPOL
$0042
0
0
0
0
PWEN3
PWEN2
PWEN1
PWEN0
PWEN
$0043
0
Bit 6
5
4
3
2
1
Bit 0
PWPRES
$0044
Bit 7
6
5
4
3
2
1
Bit 0
PWSCAL0
$0045
Bit 7
6
5
4
3
2
1
Bit 0
PWSCNT0
$0046
Bit 7
6
5
4
3
2
1
Bit 0
PWSCAL1
$0047
Bit 7
6
5
4
3
2
1
Bit 0
PWSCNT1
$0048
Bit 7
6
5
4
3
2
1
Bit 0
PWCNT0
$0049
Bit 7
6
5
4
3
2
1
Bit 0
PWCNT1
$004A
Bit 7
6
5
4
3
2
1
Bit 0
PWCNT2
$004B
Bit 7
6
5
4
3
2
1
Bit 0
PWCNT3
Table 4-1. Register Map (Sheet 2 of 11)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Registers
69
Registers
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$004C
Bit 7
6
5
4
3
2
1
Bit 0
PWPER0
$004D
Bit 7
6
5
4
3
2
1
Bit 0
PWPER1
$004E
Bit 7
6
5
4
3
2
1
Bit 0
PWPER2
$004F
Bit 7
6
5
4
3
2
1
Bit 0
PWPER3
$0050
Bit 7
6
5
4
3
2
1
Bit 0
PWDTY0
$0051
Bit 7
6
5
4
3
2
1
Bit 0
PWDTY1
$0052
Bit 7
6
5
4
3
2
1
Bit 0
PWDTY2
$0053
Bit 7
6
5
4
3
2
1
Bit 0
PWDTY3
$0054
0
0
0
PSWAI
CENTR
RDPP
PUPP
PSBCK
PWCTL
$0055
DISCR
DISCP
DISCAL
0
0
0
0
0
PWTST
$0056
PP7
PP6
PP5
PP4
PP3
PP2
PP1
PP0
PORTP
$0057
DDP7
DDP6
DDP5
DDP4
DDP3
DDP2
DDP1
DDP0
DDRP
$0058$005F
0
0
0
0
0
0
0
0
Reserved
$0060
Reserved
ATD0CTL0
$0061
Reserved
ATD0CTL1
$0062
ADPU
AFFC
ASWAI
DJM
DSGN
Reserved
ASCIE
ASCIF
ATD0CTL2
$0063
0
0
0
0
S1C
FIFO
FRZ1
FRZ0
ATD0CTL3
$0064
RES10
SMP1
SMP0
PRS4
PRS3
PRS2
PRS1
PRS0
ATD0CTL4
$0065
0
S8C
SCAN
MULT
CD
CC
CB
CA
ATD0CTL5
$0066
SCF
0
0
0
0
CC2
CC1
CC0
ATD0STAT0
$0067
CCF7
CCF6
CCF5
CCF4
CCF3
CCF2
CCF1
CCF0
ATD0STAT1
$0068
SAR9
SAR8
SAR7
SAR6
SAR5
SAR4
SAR3
SAR2
ATD0TESTH
$0069
SAR1
SAR0
RST
TSTOUT
TST3
TST2
TST1
TST0
ATD0TESTL
$006A–$
006E
0
0
0
0
0
0
0
0
Reserved
$006F
PAD07
PAD06
PAD05
PAD04
PAD03
PAD02
PAD01
PAD00
PORTAD0
$0070
Bit 15
14
13
12
11
10
9
Bit 8
ADR00H
$0071
Bit 7
Bit 6
0
0
0
0
0
0
ADR00L
$0072
Bit 15
14
13
12
11
10
9
Bit 8
ADR01H
$0073
Bit 7
Bit 6
0
0
0
0
0
0
ADR01L
$0074
Bit 15
14
13
12
11
10
9
Bit 8
ADR02H
$0075
Bit 7
Bit 6
0
0
0
0
0
0
ADR02L
$0076
Bit 15
14
13
12
11
10
9
Bit 8
ADR03H
$0077
Bit 7
Bit 6
0
0
0
0
0
0
ADR03L
$0078
Bit 15
14
13
12
11
10
9
Bit 8
ADR04H
$0079
Bit 7
Bit 6
0
0
0
0
0
0
ADR04L
$007A
Bit 15
14
13
12
11
10
9
Bit 8
ADR05H
$007B
Bit 7
Bit 6
0
0
0
0
0
0
ADR05L
Table 4-1. Register Map (Sheet 3 of 11)
Technical Data
70
MC68HC912DT128A — Rev 4.0
Registers
MOTOROLA
Registers
Register Block
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$007C
Bit 15
14
13
12
11
10
9
Bit 8
ADR06H
$007D
Bit 7
Bit 6
0
0
0
0
0
0
ADR06L
$007E
Bit 15
14
13
12
11
10
9
Bit 8
ADR07H
$007F
Bit 7
Bit 6
0
0
0
0
0
0
ADR07L
$0080
IOS7
IOS6
IOS5
IOS4
IOS3
IOS2
IOS1
IOS0
TIOS
$0081
FOC7
FOC6
FOC5
FOC4
FOC3
FOC2
FOC1
FOC0
CFORC
$0082
OC7M7
OC7M6
OC7M5
OC7M4
OC7M3
OC7M2
OC7M1
OC7M0
OC7M
$0083
OC7D7
OC7D6
OC7D5
OC7D4
OC7D3
OC7D2
OC7D1
OC7D0
OC7D
$0084
Bit 15
14
13
12
11
10
9
Bit 8
TCNT
$0085
Bit 7
6
5
4
3
2
1
Bit 0
$0086
TEN
TSWAI
TSBCK
TFFCA
$0087
Reserved
Reserved
$0088
OM7
OL7
OM6
OL6
TCNT
TSCR
TQCR
OM5
OL5
OM4
OL4
TCTL1
$0089
OM3
OL3
OM2
OL2
OM1
OL1
OM0
OL0
TCTL2
$008A
EDG7B
EDG7A
EDG6B
EDG6A
EDG5B
EDG5A
EDG4B
EDG4A
TCTL3
$008B
EDG3B
EDG3A
EDG2B
EDG2A
EDG1B
EDG1A
EDG0B
EDG0A
TCTL4
$008C
C7I
C6I
C5I
C4I
C3I
C2I
C1I
C0I
TMSK1
$008D
TOI
0
PUPT
RDPT
TCRE
PR2
PR1
PR0
TMSK2
$008E
C7F
C6F
C5F
C4F
C3F
C2F
C1F
C0F
TFLG1
$008F
TOF
0
0
0
0
0
0
0
TFLG2
$0090
Bit 15
14
13
12
11
10
9
Bit 8
TC0
$0091
Bit 7
6
5
4
3
2
1
Bit 0
TC0
$0092
Bit 15
14
13
12
11
10
9
Bit 8
TC1
$0093
Bit 7
6
5
4
3
2
1
Bit 0
TC1
$0094
Bit 15
14
13
12
11
10
9
Bit 8
TC2
$0095
Bit 7
6
5
4
3
2
1
Bit 0
TC2
$0096
Bit 15
14
13
12
11
10
9
Bit 8
TC3
$0097
Bit 7
6
5
4
3
2
1
Bit 0
TC3
$0098
Bit 15
14
13
12
11
10
9
Bit 8
TC4
$0099
Bit 7
6
5
4
3
2
1
Bit 0
TC4
$009A
Bit 15
14
13
12
11
10
9
Bit 8
TC5
$009B
Bit 7
6
5
4
3
2
1
Bit 0
TC5
$009C
Bit 15
14
13
12
11
10
9
Bit 8
TC6
$009D
Bit 7
6
5
4
3
2
1
Bit 0
TC6
$009E
Bit 15
14
13
12
11
10
9
Bit 8
TC7
$009F
Bit 7
6
5
4
3
2
1
Bit 0
TC7
$00A0
0
PAEN
PAMOD
PEDGE
CLK1
CLK0
PAOVI
PAI
PACTL
$00A1
0
0
0
0
0
0
PAOVF
PAIF
PAFLG
Table 4-1. Register Map (Sheet 4 of 11)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Registers
71
Registers
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$00A2
Bit 7
6
5
4
3
2
1
Bit 0
PACN3
$00A3
Bit 7
6
5
4
3
2
1
Bit 0
PACN2
$00A4
Bit 7
6
5
4
3
2
1
Bit 0
PACN1
$00A5
Bit 7
6
5
4
3
2
1
Bit 0
PACN0
$00A6
MCZI
MODMC
RDMCL
ICLAT
FLMC
MCEN
MCPR1
MCPR0
MCCTL
$00A7
MCZF
0
0
0
POLF3
POLF2
POLF1
POLF0
MCFLG
$00A8
0
0
0
0
PA3EN
PA2EN
PA1EN
PA0EN
ICPAR
$00A9
0
0
0
0
0
0
DLY1
DLY0
DLYCT
$00AA
NOVW7
NOVW6
NOVW5
NOVW4
NOVW3
NOVW2
NOVW1
NOVW0
ICOVW
$00AB
SH37
SH26
SH15
SH04
TFMOD
PACMX
BUFEN
LATQ
ICSYS
$00AC
0
0
0
0
0
0
0
0
Reserved
$00AD
0
0
0
0
0
0
TCBYP
0
TIMTST
$00AE
PT7
PT6
PT5
PT4
PT3
PT2
PT1
PT0
PORTT
$00AF
DDT7
DDT6
DDT5
DDT4
DDT3
DDT2
DDT1
DDT0
DDRT
$00B0
0
PBEN
0
0
0
0
PBOVI
0
PBCTL
$00B1
0
0
0
0
0
0
PBOVF
0
PBFLG
$00B2
Bit 7
6
5
4
3
2
1
Bit 0
PA3H
$00B3
Bit 7
6
5
4
3
2
1
Bit 0
PA2H
$00B4
Bit 7
6
5
4
3
2
1
Bit 0
PA1H
$00B5
Bit 7
6
5
4
3
2
1
Bit 0
PA0H
$00B6
Bit 15
14
13
12
11
10
9
Bit 8
MCCNTH
$00B7
Bit 7
6
5
4
3
2
1
Bit 0
MCCNTL
$00B8
Bit 15
14
13
12
11
10
9
Bit 8
TC0H
$00B9
Bit 7
6
5
4
3
2
1
Bit 0
TC0H
$00BA
Bit 15
14
13
12
11
10
9
Bit 8
TC1H
$00BB
Bit 7
6
5
4
3
2
1
Bit 0
TC1H
$00BC
Bit 15
14
13
12
11
10
9
Bit 8
TC2H
$00BD
Bit 7
6
5
4
3
2
1
Bit 0
TC2H
$00BE
Bit 15
14
13
12
11
10
9
Bit 8
TC3H
$00BF
Bit 7
6
5
4
3
2
1
Bit 0
TC3H
$00C0
BTST
BSPL
BRLD
SBR12
SBR11
SBR10
SBR9
SBR8
SC0BDH
$00C1
SBR7
SBR6
SBR5
SBR4
SBR3
SBR2
SBR1
SBR0
SC0BDL
$00C2
LOOPS
WOMS
RSRC
M
WAKE
ILT
PE
PT
SC0CR1
$00C3
TIE
TCIE
RIE
ILIE
TE
RE
RWU
SBK
SC0CR2
$00C4
TDRE
TC
RDRF
IDLE
OR
NF
FE
PF
SC0SR1
$00C5
0
0
0
0
0
0
0
RAF
SC0SR2
$00C6
R8
T8
0
0
0
0
0
0
SC0DRH
$00C7
R7/T7
R6/T6
R5/T5
R4/T4
R3/T3
R2/T2
R1/T1
R0/T0
SC0DRL
Table 4-1. Register Map (Sheet 5 of 11)
Technical Data
72
MC68HC912DT128A — Rev 4.0
Registers
MOTOROLA
Registers
Register Block
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$00C8
BTST
BSPL
BRLD
SBR12
SBR11
SBR10
SBR9
SBR8
SC1BDH
$00C9
SBR7
SBR6
SBR5
SBR4
SBR3
SBR2
SBR1
SBR0
SC1BDL
$00CA
LOOPS
WOMS
RSRC
M
WAKE
ILT
PE
PT
SC1CR1
$00CB
TIE
TCIE
RIE
ILIE
TE
RE
RWU
SBK
SC1CR2
$00CC
TDRE
TC
RDRF
IDLE
OR
NF
FE
PF
SC1SR1
$00CD
0
0
0
0
0
0
0
RAF
SC1SR2
$00CE
R8
T8
0
0
0
0
0
0
SC1DRH
$00CF
R7/T7
R6/T6
R5/T5
R4/T4
R3/T3
R2/T2
R1/T1
R0/T0
SC1DRL
$00D0
SPIE
SPE
SWOM
MSTR
CPOL
CPHA
SSOE
LSBF
SP0CR1
$00D1
0
0
0
0
PUPS
RDPS
SSWAI
SPC0
SP0CR2
$00D2
0
0
0
0
0
SPR2
SPR1
SPR0
SP0BR
$00D3
SPIF
WCOL
0
MODF
0
0
0
0
SP0SR
$00D4
0
0
0
0
0
0
0
0
Reserved
$00D5
Bit 7
6
5
4
3
2
1
Bit 0
SP0DR
$00D6
PS7
PS6
PS5
PS4
PS3
PS2
PS1
PS0
PORTS
$00D7
DDS7
DDS6
DDS5
DDS4
DDS3
DDS2
DDS1
DDS0
DDRS
$00D8–$
00DF
0
0
0
0
0
0
0
0
Reserved
$00E0
ADR7
ADR6
ADR5
ADR4
ADR3
ADR2
ADR1
0
IBAD
$00E1
0
0
IBC5
IBC4
IBC3
IBC2
IBC1
IBC0
IBFD
$00E2
IBEN
IBIE
MS/SL
Tx/Rx
TXAK
RSTA
0
IBSWAI
IBCR
$00E3
TCF
IAAS
IBB
IBAL
0
SRW
IBIF
RXAK
IBSR
$00E4
D7
D6
D5
D4
D3
D2
D1
D0
IBDR
$00E5
0
0
0
RDPIB
0
0
0
PUPIB
IBPURD
$00E6
PIB7
PIB6
PIB5
PIB4
PIB3
PIB2
PIB1
PIB0
PORTIB
$00E7
DDRIB7
DDRIB6
DDRIB5
DDRIB4
DDRIB3
DDRIB2
DDRIB1
DDRIB0
DDRIB
$00E8–
$00EB
Unimplemented(4)
$00EC–$
00ED
0
0
0
0
0
Reserved
0
0
0
Reserved
$00EE
0
0
0
0
0
0
EEDIV9
EEDIV8
EEDIVH
$00EF
EEDIV7
EEDIV6
EEDIV5
EEDIV4
EEDIV3
EEDIV2
EEDIV1
EEDIV0
EEDIVL
FPOPEN(5)
1
EERC
EEMCR
BPROT4
BPROT3
BPROT2
BPROT0
EEPROT
$00F0
NOBDML NOSHW Reserved
$00F1
SHPROT
1
$00F2
0
EREVTN
0
0
0
ETMSD
ETMR
ETMSE
EETST
$00F3
BULKP
0
AUTO
BYTE
ROW
ERASE
EELAT
EEPGM
EEPROG
$00F4
0
0
0
0
0
0
0
LOCK
FEELCK
$00F5
0
0
0
0
0
0
0
BOOTP
FEEMCR
$00F6
STRE
REVTUN
0
0
0
TMSD
TMR
TMSE
FEETST
BPROT5
EESWAI PROTLCK
BPROT1
Table 4-1. Register Map (Sheet 6 of 11)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Registers
73
Registers
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$00F7
0
0
0
FEESWAI
HVEN
0
ERAS
PGM
FEECTL
$00F8
MT07
MT06
MT05
MT04
MT03
MT02
MT01
MT00
MTST0
$00F9
MT0F
MT0E
MT0D
MT0C
MT0B
MT0A
MT09
MT08
MTST1
$00FA
MT17
MT16
MT15
MT14
MT13
MT12
MT11
MT10
MTST2
$00FB
MT1F
MT1E
MT1D
MT1C
MT1B
MT1A
MT19
MT18
MTST3
$00FC
PK7
0
0
0
PK3
PK2
PK1
PK0
PORTK(6)
$00FD
DDK7
0
0
0
DDK3
DDK2
DDK1
DDK0
DDRK(6)
$00FE
0
0
0
0
0
0
0
0
Reserved
$00FF
0
0
0
0
0
PIX2
PIX1
PIX0
PPAGE
$0100
0
0
CSWAI
SYNCH
TLNKEN
SLPAK
SLPRQ
SFTRES
C0MCR0
$0101
0
0
0
0
0
LOOPB
WUPM
CLKSRC
C0MCR1
$0102
SJW1
SJW0
BRP5
BRP4
BRP3
BRP2
BRP1
BRP0
C0BTR0
$0103
SAMP
TSEG22
TSEG21
TSEG20
TSEG13
TSEG12
TSEG11
TSEG10
C0BTR1
$0104
WUPIF
RWRNIF
TWRNIF
RERRIF
TERRIF
BOFFIF
OVRIF
RXF
C0RFLG
$0105
WUPIE
RWRNIE
TWRNIE
RERRIE
TERRIE
BOFFIE
OVRIE
RXFIE
C0RIER
$0106
0
ABTAK2
ABTAK1
ABTAK0
0
TXE2
TXE1
TXE0
C0TFLG
$0107
0
ABTRQ2 ABTRQ1 ABTRQ0
0
TXEIE2
TXEIE1
TXEIE0
C0TCR
$0108
0
0
IDHIT2
IDHIT1
IDHIT0
C0IDAC
0
IDAM1
IDAM0
$0109–
$010D
Unimplemented(4)
Reserved
$010E
RXERR7 RXERR6 RXERR5 RXERR4 RXERR3 RXERR2 RXERR1 RXERR0
C0RXERR
$010F
TXERR7
TXERR6
TXERR5
TXERR4
TXERR3
TXERR2
TXERR1
TXERR0
C0TXERR
$0110
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR0
$0111
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR1
$0112
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR2
$0113
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR3
$0114
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR0
$0115
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR1
$0116
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR2
$0117
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR3
$0118
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR4
$0119
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR5
$011A
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR6
$011B
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C0IDAR7
$011C
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR4
$011D
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR5
$011E
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR6
$011F
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C0IDMR7
Table 4-1. Register Map (Sheet 7 of 11)
Technical Data
74
MC68HC912DT128A — Rev 4.0
Registers
MOTOROLA
Registers
Register Block
Address
Bit 7
6
5
$0120–
$013C
4
3
2
Bit 0
Unimplemented(4)
Name
Reserved
$013D
0
0
0
0
0
0
$013E
PCAN7
PCAN6
PCAN5
PCAN4
PCAN3
PCAN2
$013F
1
PUPCAN RDPCAN PCTLCAN0
TxCAN
RxCAN
PORTCAN0
0
0
DDRCAN0
DDCAN7 DDCAN6 DDCAN5 DDCAN4 DDCAN3 DDCAN2
$0140–
$014F
FOREGROUND RECEIVE BUFFER 0
RxFG0
$0150–
$015F
TRANSMIT BUFFER 00
Tx00
$0160–
$016F
TRANSMIT BUFFER 01
Tx01
$0170–
$017F
TRANSMIT BUFFER 02
Tx02
$0180–
$01DF
Unimplemented(4)
Reserved
$01E0
Reserved
ATD1CTL0
$01E1
Reserved
ATD1CTL1
$01E2
ADPU
AFFC
ASWAI
DJM
DSGN
Reserved
ASCIE
ASCIF
ATD1CTL2
$01E3
0
0
0
0
S1C
FIFO
FRZ1
FRZ0
ATD1CTL3
$01E4
RES10
SMP1
SMP0
PRS4
PRS3
PRS2
PRS1
PRS0
ATD1CTL4
$01E5
0
S8C
SCAN
MULT
CD
CC
CB
CA
ATD1CTL5
$01E6
SCF
0
0
0
0
CC2
CC1
CC0
ATD1STAT0
$01E7
CCF7
CCF6
CCF5
CCF4
CCF3
CCF2
CCF1
CCF0
ATD1STAT1
$01E8
SAR9
SAR8
SAR7
SAR6
SAR5
SAR4
SAR3
SAR2
ATD1TESTH
$01E9
SAR1
SAR0
RST
TSTOUT
TST3
TST2
TST1
TST0
ATD1TESTL
$01EA–$
01EE
0
0
0
0
0
0
0
0
Reserved
$01EF
PAD17
PAD16
PAD15
PAD14
PAD13
PAD12
PAD11
PAD10
PORTAD1
$01F0
Bit 15
14
13
12
11
10
9
Bit 8
ADR10H
$01F1
Bit 7
Bit 6
0
0
0
0
0
0
ADR10L
$01F2
Bit 15
14
13
12
11
10
9
Bit 8
ADR11H
$01F3
Bit 7
Bit 6
0
0
0
0
0
0
ADR11L
$01F4
Bit 15
14
13
12
11
10
9
Bit 8
ADR12H
$01F5
Bit 7
Bit 6
0
0
0
0
0
0
ADR12L
$01F6
Bit 15
14
13
12
11
10
9
Bit 8
ADR13H
$01F7
Bit 7
Bit 6
0
0
0
0
0
0
ADR13L
$01F8
Bit 15
14
13
12
11
10
9
Bit 8
ADR14H
$01F9
Bit 7
Bit 6
0
0
0
0
0
0
ADR14L
$01FA
Bit 15
14
13
12
11
10
9
Bit 8
ADR15H
$01FB
Bit 7
Bit 6
0
0
0
0
0
0
ADR15L
Table 4-1. Register Map (Sheet 8 of 11)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Registers
75
Registers
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$01FC
Bit 15
14
13
12
11
10
9
Bit 8
ADR16H
$01FD
Bit 7
Bit 6
0
0
0
0
0
0
ADR16L
$01FE
Bit 15
14
13
12
11
10
9
Bit 8
ADR17H
$01FF
Bit 7
Bit 6
0
0
0
0
0
0
ADR17L
(7)
$0200
0
0
CSWAI
SYNCH
TLNKEN
SLPAK
SLPRQ
SFTRES
C2MCR0
(7)$0201
0
0
0
0
0
LOOPB
WUPM
CLKSRC
C2MCR1
(7)
$0202
SJW1
SJW0
BRP5
BRP4
BRP3
BRP2
BRP1
BRP0
C2BTR0
(7)$0203
SAMP
TSEG22
TSEG21
TSEG20
TSEG13
TSEG12
TSEG11
TSEG10
C2BTR1
(7)
$0204
WUPIF
RWRNIF
TWRNIF
RERRIF
TERRIF
BOFFIF
OVRIF
RXF
C2RFLG
(7)$0205
WUPIE
RWRNIE
TWRNIE
RERRIE
TERRIE
BOFFIE
OVRIE
RXFIE
C2RIER
ABTAK1
(7)
$0206
0
ABTAK2
ABTAK0
0
TXE2
TXE1
TXE0
C2TFLG
(7)
$0207
0
ABTRQ2 ABTRQ1 ABTRQ0
0
TXEIE2
TXEIE1
TXEIE0
C2TCR
(7)
$0208
0
0
IDHIT2
IDHIT1
IDHIT0
C2IDAC
0
IDAM1
$0209–
$020D
(7)
IDAM0
Unimplemented(4)
Reserved
$020E RXERR7 RXERR6 RXERR5 RXERR4 RXERR3 RXERR2 RXERR1 RXERR0
(7)$020F
C2RXERR
TXERR7
TXERR6
TXERR5
TXERR4
TXERR3
TXERR2
TXERR1
TXERR0
C2TXERR
$0210
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR0
(7)$0211
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR1
(7)
$0212
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR2
(7)$0213
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR3
(7)
$0214
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR0
(7)$0215
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR1
(7)
$0216
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR2
(7)
$0217
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR3
(7)
$0218
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR4
(7)
$0219
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR5
(7)$021A
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR6
(7)
(7)
$021B
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C2IDAR7
(7)$021C
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR4
(7)
$021D
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR5
(7)$021E
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR6
(7)
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C2IDMR7
$021F
Table 4-1. Register Map (Sheet 9 of 11)
Technical Data
76
MC68HC912DT128A — Rev 4.0
Registers
MOTOROLA
Registers
Register Block
Address
Bit 7
6
5
$0220–
$023C
3
2
1
Bit 0
Name
Unimplemented(4)
(7)
Reserved
0
0
0
0
0
0
PCAN7
PCAN6
PCAN5
PCAN4
PCAN3
PCAN2
$023D
(7)$023E
4
PUPCAN RDPCAN PCTLCAN2
TxCAN
RxCAN
PORTCAN2
0
0
DDRCAN2
(7)
$023F DDCAN7 DDCAN6 DDCAN5 DDCAN4 DDCAN3 DDCAN2
(7)$0240
FOREGROUND RECEIVE BUFFER 2
RxFG2
TRANSMIT BUFFER 20
Tx20
TRANSMIT BUFFER 21
Tx21
$0270
– $027F
TRANSMIT BUFFER 22
Tx22
$0280$02FF
Unimplemented(4)
Reserved
– $024F
(7)
$0250
– $025F
(7)
$0260
– $026F
(7)
$0300
0
0
CSWAI
SYNCH
TLNKEN
SLPAK
SLPRQ
SFTRES
C1MCR0
$0301
0
0
0
0
0
LOOPB
WUPM
CLKSRC
C1MCR1
$0302
SJW1
SJW0
BRP5
BRP4
BRP3
BRP2
BRP1
BRP0
C1BTR0
$0303
SAMP
TSEG22
TSEG21
TSEG20
TSEG13
TSEG12
TSEG11
TSEG10
C1BTR1
$0304
WUPIF
RWRNIF
TWRNIF
RERRIF
TERRIF
BOFFIF
OVRIF
RXF
C1RFLG
$0305
WUPIE
RWRNIE
TWRNIE
RERRIE
TERRIE
BOFFIE
OVRIE
RXFIE
C1RIER
$0306
0
ABTAK2
ABTAK1
ABTAK0
0
TXE2
TXE1
TXE0
C1TFLG
$0307
0
ABTRQ2 ABTRQ1 ABTRQ0
0
TXEIE2
TXEIE1
TXEIE0
C1TCR
$0308
0
0
IDHIT2
IDHIT1
IDHIT0
C1IDAC
0
IDAM1
IDAM0
$0309–
$030D
Unimplemented(4)
Reserved
$030E
RXERR7 RXERR6 RXERR5 RXERR4 RXERR3 RXERR2 RXERR1 RXERR0
C1RXERR
$030F
TXERR7
TXERR6
TXERR5
TXERR4
TXERR3
TXERR2
TXERR1
TXERR0
C1TXERR
$0310
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR0
$0311
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR1
$0312
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR2
$0313
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR3
$0314
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR0
$0315
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR1
$0316
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR2
$0317
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR3
$0318
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR4
$0319
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR5
Table 4-1. Register Map (Sheet 10 of 11)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Registers
77
Registers
Address
Bit 7
6
5
4
3
2
1
Bit 0
Name
$031A
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR6
$031B
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
C1IDAR7
$031C
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR4
$031D
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR5
$031E
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR6
$031F
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
C1IDMR7
$0320–
$033C
Unimplemented(4)
Reserved
$033D
0
0
0
0
0
0
$033E
PCAN7
PCAN6
PCAN5
PCAN4
PCAN3
PCAN2
$033F
PUPCAN RDPCAN PCTLCAN1
TxCAN
RxCAN
PORTCAN1
0
0
DDRCAN1
DDCAN7 DDCAN6 DDCAN5 DDCAN4 DDCAN3 DDCAN2
$0340–
$034F
FOREGROUND RECEIVE BUFFER 1
RxFG1
$0350–
$035F
TRANSMIT BUFFER 10
Tx10
$0360–
$036F
TRANSMIT BUFFER 11
Tx11
$0370–
$037F
TRANSMIT BUFFER 12
Tx12
$0380$03FF
Unimplemented(4)
Reserved
= Reserved or unimplemented bits.
Table 4-1. Register Map (Sheet 11 of 11)
1. Port A, port B and data direction registers DDRA, DDRB are not in map in expanded and peripheral modes.
2. Port E and DDRE not in the map in peripheral and expanded modes with EME set.
3. Registers also not in map in peripheral mode.
4. Data read at these locations is undefined.
5. The FPOPEN bit is available only on the 0L05H and later mask sets. For previous masks, this bit is reserved.
6. Port K and DDRK not in the map in peripheral and expanded modes with EMK set.
7. MC68HC912DT128A only. Locations are unimplemented on the MC68HC912DG128A.
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Technical Data — MC68HC912DT128A
Section 5. Operating Modes
5.1 Contents
5.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.3
Operating Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.4
Background Debug Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .84
5.2 Introduction
Eight possible operating modes determine the operating configuration of
the MC68HC912DT128A. Each mode has an associated default
memory map and external bus configuration.
5.3 Operating Modes
The operating mode out of reset is determined by the states of the
BKGD, MODB, and MODA pins during reset.
The SMODN, MODB, and MODA bits in the MODE register show current
operating mode and provide limited mode switching during operation.
The states of the BKGD, MODB, and MODA pins are latched into these
bits on the rising edge of the reset signal.
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Operating Modes
Table 5-1. Mode Selection
BKGD
1
1
1
1
0
0
0
0
MODB
0
0
1
1
0
0
1
1
MODA
0
1
0
1
0
1
0
1
Mode
Normal Single Chip
Normal Expanded Narrow
Reserved (Forced to Peripheral)
Normal Expanded Wide
Special Single Chip
Special Expanded Narrow
Special Peripheral
Special Expanded Wide
Port A
G.P. I/O
ADDR/DATA
—
ADDR/DATA
G.P. I/O
ADDR/DATA
ADDR/DATA
ADDR/DATA
Port B
G.P. I/O
ADDR
—
ADDR/DATA
G.P. I/O
ADDR
ADDR/DATA
ADDR/DATA
There are two basic types of operating modes:
Normal modes — some registers and bits are protected
against accidental changes.
Special modes — allow greater access to protected control
registers and bits for special purposes such as testing and
emulation.
A system development and debug feature, background debug mode
(BDM), is available in all modes. In special single-chip mode, BDM is
active immediately after reset.
5.3.1 Normal Operating Modes
These modes provide three operating configurations. Background
debug is available in all three modes, but must first be enabled for some
operations by means of a BDM background command, then activated.
Normal Single-Chip Mode — There are no external address and
data buses in this mode. The MCU operates as a stand-alone
device and all program and data resources are on-chip. External
port pins normally associated with address and data buses can be
used for general-purpose I/O.
Normal Expanded Wide Mode — This is a normal mode of
operation in which the expanded bus is present with a 16-bit data
bus. Ports A and B are used for the 16-bit multiplexed
address/data bus.
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Operating Modes
Operating Modes
Normal Expanded Narrow Mode — This is a normal mode of
operation in which the expanded bus is present with an 8-bit data
bus. Ports A and B are used for the16-bit address bus. Port A is
used as the data bus, multiplexed with addresses. In this mode,
16-bit data is presented one byte at a time, the high byte followed
by the low byte. The address is automatically incremented on the
second cycle.
5.3.2 Special Operating Modes
There are three special operating modes that correspond to normal
operating modes. These operating modes are commonly used in factory
testing and system development. In addition, there is a special
peripheral mode, in which an external master, such as an I.C. tester, can
control the on-chip peripherals.
Special Single-Chip Mode — This mode can be used to force the
MCU to active BDM mode to allow system debug through the
BKGD pin. There are no external address and data buses in this
mode. The MCU operates as a stand-alone device and all
program and data space are on-chip. External port pins can be
used for general-purpose I/O.
Special Expanded Wide Mode — This mode can be used for
emulation of normal expanded wide mode and emulation of
normal single-chip mode. Ports A and B are used for the 16-bit
multiplexed address/data bus.
Special Expanded Narrow Mode — This mode can be used for
emulation of normal expanded narrow mode. Ports A and B are
used for the16-bit address bus. Port A is used as the data bus,
multiplexed with addresses. In this mode, 16-bit data is presented
one byte at a time, the high byte followed by the low byte. The
address is automatically incremented on the second cycle.
Special Peripheral Mode — The CPU is not active in this mode.
An external master can control on-chip peripherals for testing
purposes. It is not possible to change to or from this mode without
going through reset. Background debugging should not be used
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Operating Modes
while the MCU is in special peripheral mode as internal bus
conflicts between BDM and the external master can cause
improper operation of both functions.
Bit 7
6
5
4
3
2
1
Bit 0
SMODN
MODB
MODA
ESTR
IVIS
EBSWAI
EMK
EME
RESET:
0
0
0
1
1
0
1
1
Special Single Chip
RESET:
0
0
1
1
1
0
1
1
Special Exp Nar
RESET:
0
1
0
1
1
0
1
1
Peripheral
RESET:
0
1
1
1
1
0
1
1
Special Exp Wide
RESET:
1
0
0
1
0
0
0
0
Normal Single Chip
RESET:
1
0
1
1
0
0
0
0
Normal Exp Nar
RESET:
1
1
1
1
0
0
0
0
Normal Exp Wide
MODE — Mode Register
$000B
The MODE register controls the MCU operating mode and various
configuration options. This register is not in the map in peripheral mode
SMODN, MODB, MODA — Mode Select Special, B and A
These bits show the current operating mode and reflect the status of
the BKGD, MODB and MODA input pins at the rising edge of reset.
Read anytime.
SMODN may only be written if SMODN = 0 (in special modes) but the
first write is ignored.
MODB, MODA may be written once if SMODN = 1; anytime if SMODN
= 0 but the first write is ignored and in special peripheral and reserved
modes cannot be selected.
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Operating Modes
ESTR — E Clock Stretch Enable
Determines if the E Clock behaves as a simple free-running clock or
as a bus control signal that is active only for external bus cycles.
ESTR is always one in expanded modes since it is required for
address and data de-multiplexing and must follow stretched cycles.
0 = E never stretches (always free running).
1 = E stretches high during external access cycles and low during
non-visible internal accesses (IVIS = 0).
Normal modes: write once; Special modes: write anytime, read
anytime.
IVIS — Internal Visibility
This bit determines whether internal ADDR, DATA, R/W and LSTRB
signals can be seen on the external bus during accesses to internal
locations. In Special Narrow Mode if this bit is set and an internal
access occurs the data will appear wide on Ports A and B. This serves
the same function as the EMD bit of the non-multiplexed versions of
the HC12 and allows for emulation. Visibility is not available when the
part is operating in a single-chip mode.
0 = No visibility of internal bus operations on external bus.
1 = Internal bus operations are visible on external bus.
Normal modes: write once; Special modes: write anytime EXCEPT
the first time. Read anytime.
EBSWAI — Multiplexed External Bus Interface Module Stops in Wait
Mode
This bit controls access to the multiplexed external bus interface
module during wait mode. The module will delay before shutting down
in wait mode to allow for final bus activity to complete.
0 = MEBI continues functioning during wait mode.
1 = MEBI is shut down during wait mode.
Normal modes: write anytime; special modes: write never. Read
anytime.
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Operating Modes
EMK — Emulate Port K
In single-chip mode PORTK and DDRK are always in the map
regardless of the state of this bit.
0 = Port K and DDRK registers are in the memory map. Memory
expansion emulation is disabled and all pins are general
purpose I/O.
1 = In expanded or peripheral mode, PORTK and DDRK are
removed from the internal memory map. Removing the
registers from the map allows the user to emulate the function
of these registers externally.
Normal modes: write once; special modes: write anytime EXCEPT
the first time. Read anytime.
EME — Emulate Port E
In single-chip mode PORTE and DDRE are always in the map
regardless of the state of this bit.
0 = PORTE and DDRE are in the memory map.
1 = If in an expanded mode, PORTE and DDRE are removed from
the internal memory map. Removing the registers from the
map allows the user to emulate the function of these registers
externally.
Normal modes: write once; special modes: write anytime EXCEPT
the first time. Read anytime.
5.4 Background Debug Mode
Background debug mode (BDM) is an auxiliary operating mode that is
used for system development. BDM is implemented in on-chip hardware
and provides a full set of debug operations. Some BDM commands can
be executed while the CPU is operating normally. Other BDM
commands are firmware based, and require the BDM firmware to be
enabled and active for execution.
In special single-chip mode, BDM is enabled and active immediately out
of reset. BDM is available in all other operating modes, but must be
enabled before it can be activated. BDM should not be used in special
peripheral mode because of potential bus conflicts.
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Operating Modes
Background Debug Mode
Once enabled, background mode can be made active by a serial
command sent via the BKGD pin or execution of a CPU12 BGND
instruction. While background mode is active, the CPU can interpret
special debugging commands, and read and write CPU registers,
peripheral registers, and locations in memory.
While BDM is active, the CPU executes code located in a small on-chip
ROM mapped to addresses $FF20 to $FFFF, and BDM control registers
are accessible at addresses $FF00 to $FF06. The BDM ROM replaces
the regular system vectors while BDM is active. While BDM is active, the
user memory from $FF00 to $FFFF is not in the map except through
serial BDM commands.
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Operating Modes
Technical Data
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Technical Data — MC68HC912DT128A
Section 6. Resource Mapping
6.1 Contents
6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
6.3
Internal Resource Mapping. . . . . . . . . . . . . . . . . . . . . . . . . . . .87
6.4
Flash EEPROM mapping through internal Memory Expansion 92
6.5
Miscellaneous System Control Register . . . . . . . . . . . . . . . . . . 96
6.6
Mapping test registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
6.7
Memory Maps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
6.2 Introduction
After reset, most system resources can be mapped to other addresses
by writing to the appropriate control registers.
6.3 Internal Resource Mapping
The internal register block, RAM, and EEPROM have default locations
within the 64K byte standard address space but may be reassigned to
other locations during program execution by setting bits in mapping
registers INITRG, INITRM, and INITEE. During normal operating modes
these registers can be written once. It is advisable to explicitly establish
these resource locations during the initialization phase of program
execution, even if default values are chosen, in order to protect the
registers from inadvertent modification later.
Writes to the mapping registers go into effect between the cycle that
follows the write and the cycle after that. To assure that there are no
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Resource Mapping
unintended operations, a write to one of these registers should be
followed with a NOP instruction.
If conflicts occur when mapping resources, the register block will take
precedence over the other resources; RAM or EEPROM addresses
occupied by the register block will not be available for storage. When
active, BDM ROM takes precedence over other resources, although a
conflict between BDM ROM and register space is not possible. The
following table shows resource mapping precedence.
Table 6-1. Mapping Precedence
Precedence
1
2
3
4
5
6
Resource
BDM ROM (if active)
Register Space
RAM
EEPROM
On-Chip Flash EEPROM
External Memory
In expanded modes, all address space not used by internal resources is
by default external memory.
The MC68HC912DT128A contains 128K bytes of Flash EEPROM
nonvolatile memory which can be used to store program code or static
data. This physical memory is composed of four 32k byte array modules,
00FEE32K, 01FEE32K, 10FEE32K and 11FEE32K. The 32K byte array
11FEE32K has a fixed location from $4000 to $7FFF and $C000 to
$FFFF. The three 32K byte arrays 00FEE32K, 01FEE32K and
10FEE32K are accessible through a 16K byte program page window
mapped from $8000 to $BFFF. The fixed 32K byte array 11FEE32K can
also be accessed through the program page window.
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Resource Mapping
Internal Resource Mapping
6.3.1 Register Block Mapping
After reset the 1K byte register block resides at location $0000 but can
be reassigned to any 2K byte boundary within the standard 64K byte
address space. Mapping of internal registers is controlled by five bits in
the INITRG register. The register block occupies the first 1K byte of the
2K byte block.
INITRG — Initialization of Internal Register Position Register
RESET:
$0011
Bit 7
6
5
4
3
2
1
Bit 0
REG15
REG14
REG13
REG12
REG11
0
0
MMSWAI
0
0
0
0
0
0
0
0
REG[15:11] — Internal register map position
These bits specify the upper five bits of the 16-bit registers address.
Normal modes: write once; special modes: write anytime. Read
anytime.
MMSWAI — Memory Mapping Interface Stop in Wait Control
This bit controls access to the memory mapping interface when in
Wait mode.
Normal modes: write anytime; special modes: write never. Read
anytime.
0 = Memory mapping interface continues to function during Wait
mode.
1 = Memory mapping interface access is shut down during Wait
mode.
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Resource Mapping
6.3.2 RAM Mapping
The MC68HC912DT128A has 8K bytes of fully static RAM that is used
for storing instructions, variables, and temporary data during program
execution. Since the RAM is actually implemented with two 4K RAM
arrays, any misaligned word access between last address of first 4K
RAM and first address of second 4K RAM will take two cycles instead of
one. After reset, RAM addressing begins at location $2000 but can be
assigned to any 8K byte boundary within the standard 64K byte address
space. Mapping of internal RAM is controlled by three bits in the INITRM
register.
INITRM — Initialization of Internal RAM Position Register
$0010
Bit 7
6
5
4
3
2
1
Bit 0
RAM15
RAM14
RAM13
0
0
0
0
0
0
0
1
0
0
0
0
0
RESET:
RAM[15:13] — Internal RAM map position
These bits specify the upper three bits of the 16-bit RAM address.
Normal modes: write once; special modes: write anytime. Read
anytime.
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Resource Mapping
Internal Resource Mapping
6.3.3 EEPROM Mapping
The MC68HC912DT128A has 2K bytes of EEPROM which is activated
by the EEON bit in the INITEE register. Mapping of internal EEPROM is
controlled by four bits in the INITEE register. After reset EEPROM
address space begins at location $0800 but can be mapped to any 4K
byte boundary within the standard 64K byte address space. The
EEPROM block occupies the last 2K bytes of the 4K byte block.
INITEE— Initialization of Internal EEPROM Position Register
RESET:
$0012
Bit 7
6
5
4
3
2
1
Bit 0
EE15
EE14
EE13
EE12
0
0
0
EEON
0
0
0
0
0
0
0
1
EE[15:12] — Internal EEPROM map position
These bits specify the upper four bits of the 16-bit EEPROM address.
Normal modes: write once; special modes: write anytime. Read
anytime.
EEON — internal EEPROM On (Enabled)
Read or write anytime.
0 = Removes the EEPROM from the map.
1 = Places the on-chip EEPROM in the memory map at the
address selected by EE[15:12].
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Resource Mapping
6.4 Flash EEPROM mapping through internal Memory Expansion
The Page Index register or PPAGE provides memory management for
the MC68HC912DT128A. PPAGE consists of three bits to indicate
which physical location is active within the windows of the
MC68HC912DT128A. The MC68HC912DT128A has a user’s program
space window, a register space window for Flash module registers, and
a test program space window.
The user’s program page window consists of 16K Flash EEPROM bytes.
One of eight pages is viewed through this window for a total of 128K
accessible Flash EEPROM bytes.
The register space window consists of a 4-byte register block. One of
four pages is viewed through this window for each of the 32K flash
module register blocks of MC68HC912DT128A.
The test mode program page window consists of 32K Flash EEPROM
bytes. One of the four 32K byte arrays is viewed through this window for
a total 128K accessible Flash EEPROM bytes. This window is only
available in special mode for test purposes and replaces the user’s
program page window.
MC68HC912DT128A has a five pin port, port K, for emulation and for
general purpose I/O. Three pins are used to emulate the three page
indices (PPAGE bits) and one pin is used as an emulation chip select.
When these four pins are not used for emulation they serve as general
purpose I/O pins. The fifth port K pin is used as a general purpose I/O
pin.
6.4.1 Program space expansion
There are 128K bytes of Flash EEPROM for MC68HC912DT128A. With
a 64K byte address space, the PPAGE register is needed to perform on
chip memory expansion. A program space window of 16K byte pages is
located from $8000 to $BFFF. Three page indices are used to point to
one of eight different 16K byte pages.
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Resource Mapping
Flash EEPROM mapping through internal Memory Expansion
Table 6-2. Program space Page Index
Page Index 2 Page Index 1 Page Index 0
(PPAGE bit 2) (PPAGE bit 1) (PPAGE bit 0)
0
0
0
0
0
1
0
1
0
0
1
1
1
0
0
1
0
1
1
1
0
1
1
1
16K Program space Page
Flash array
16K byte Page 0
16K byte Page 1
16K byte Page 2
16K byte Page 3
16K byte Page 4
16K byte Page 5
16K byte Page 6*
16K byte Page 7*
00FEE32K
00FEE32K
01FEE32K
01FEE32K
10FEE32K
10FEE32K
11FEE32K
11FEE32K
* The 16K byte flash in program space page 6 can also be accessed at
a fixed location from $4000 to $7FFF. The 16K byte flash in program
space page 7 can also be accessed at a fixed location from $C000 to
$FFFF.
6.4.2 Flash register space expansion
There are four 32K Flash arrays for MC68HC912DT128A and each
requires a 4-byte register block. A register space window is used to
access one of the four 4-byte blocks and the PPAGE register to map
each one into the window. The register space window is located from
$00F4 to $00F7 after reset. Only two page indices are used to point to
one of the four pages of the register space.
Table 6-3. Flash Register space Page Index
Page Index 2
Page Index 1 Page Index 0
(PPAGE bit
(PPAGE bit 1) (PPAGE bit 0)
2)
0
0
X
0
1
X
1
0
X
1
1
X
Flash register space Page
Flash array
$00F4-$00F7 Page 0
$00F4-$00F7 Page 1
$00F4-$00F7 Page 2
$00F4-$00F7 Page 3
00FEE32K
01FEE32K
10FEE32K
11FEE32K
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Resource Mapping
6.4.3 Test mode Program space expansion
In special mode and for test purposes only, the 128K bytes of Flash
EEPROM for MC68HC912DT128A can be accessed through a test
program space window of 32K bytes. This window replaces the user’s
program space window to be able to access an entire array. In special
mode and with ROMTST bit set in MISC register, a program space is
located from $8000 to $FFFF. Only two page indices are used to point
to one of the four 32K byte arrays. These indices can be viewed as
expanded addresses X16 and X15.
Table 6-4. Test mode program space Page Index
Page Index 2 Page Index 1 Page Index 0
(PPAGE bit 2) (PPAGE bit 1) (PPAGE bit 0)
0
0
X
0
1
X
1
0
X
1
1
X
Flash register space Page
Flash array
32K byte array Page 0
32K byte array Page 1
32K byte array Page 2
32K byte array Page 3
00FEE32K
01FEE32K
10FEE32K
11FEE32K
6.4.4 Page Index register descriptions
PORTK — Port K Data Register
$00FC
Bit 7
6
5
4
3
2
1
Bit 0
PORT
PK7
0
0
0
PK3
PK2
PK1
PK0
Emulation
ECS
0
0
0
-
PIX2
PIX1
PIX0
RESET:
-
0
0
0
-
-
-
-
Read and write anytime
Writes do not change pin state when pin configured for page index
emulation output.
This port is associated with page index emulation pins. When the port is
not enabled to emulate page index, the port pins are used as generalpurpose I/O. Port K bit 3 is used as a general purpose I/O pin only. This
register is not in the map in peripheral or expanded modes while the
EMK control bit in MODE register is set.
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Resource Mapping
Flash EEPROM mapping through internal Memory Expansion
When inputs, these pins can be selected to be high impedance or pulled
up.
ECS — Emulation Chip Select of selected program space
When this signal is active low it indicates that the program space is
accessed. This also applies to test mode program space. An access
is made if address is at the program space window and either the
Flash or external memory is accessed. The ECS timing is E clock high
and can be stretched when accessing external memory depending on
the EXTR0 and EXTR1 bits in the MISC register. The ECS signal is
only active when the EMK bit is set.
PIX[2:0] — The content of the PPAGE register emulated externally.
This content indicates which Flash module register space is in the
memory map and which 16K byte Flash memory is in the program
space. In special mode and with ROMTST bit set, the content of the
Page Index register indicates which 32K byte Flash array is in the test
program space.
I
DDRK — Port K Data Direction Register
RESET:
$00FD
Bit 7
6
5
4
3
2
1
Bit 0
DDK7
0
0
0
DDK3
DDK2
DDK1
DDK0
0
0
0
0
0
0
0
0
Read and write: anytime.
This register determines the primary direction for each port K pin
configured as general-purpose I/O.
0 = Associated pin is a high-impedance input.
1 = Associated pin is an output.
This register is not in the map in peripheral or expanded modes while the
EMK control bit is set.
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Resource Mapping
PPAGE — (Program) Page Index Register
$00FF
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
PIX2
PIX1
PIX0
0
0
0
0
0
0
0
0
RESET:
Read and write: anytime.
This register determines the active page viewed through
MC68HC912DT128A windows.
CALL and RTC instructions have a special single wire mechanism to
read and write this register without using an address bus.
6.5 Miscellaneous System Control Register
Additional mapping and external resource controls are available. To use
external resources the part must be operated in one of the expanded
modes.
MISC — Miscellaneous Mapping Control Register
$0013
RESET:
Bit 7
ROMTST
0
6
NDRF
0
5
RFSTR1
0
4
RFSTR0
0
3
EXSTR1
1
2
EXSTR0
1
1
ROMHM
0
Bit 0
ROMON
0
RESET:
0
0
0
0
1
1
0
1
Mode
Exp mode
peripheral or
SC mode
Normal modes: write once; Special modes: write anytime. Read
anytime.
ROMTST — FLASH EEPROM Test mode
In normal modes, this bit is forced to zero.
0 = 16K window for Flash memory is located from $8000-$BFFF
1 = 32K window for Flash memory is located from $8000-$FFFF
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Resource Mapping
Miscellaneous System Control Register
NDRF — Narrow Data Bus for Register-Following Map Space
This bit enables a narrow bus feature for the 1K byte RegisterFollowing Map. This is useful for accessing 8-bit peripherals and
allows 8-bit and 16-bit external memory devices to be mixed in a
system. In Expanded Narrow (eight bit) modes, Single Chip Modes,
and Peripheral mode, this bit has no effect.
0 = Makes Register-Following MAP space act as a full 16 bit data
bus.
1 = Makes the Register-Following MAP space act the same as an
8 bit only external data bus (data only goes through port A
externally).
The Register-Following space is mapped from $0400 to $07FF after
reset, which is next to the register map. If the registers are moved this
space follows.
RFSTR1, RFSTR0 — Register Following Stretch
This two bit field determines the amount of clock stretch on accesses
to the 1K byte Register Following Map. It is valid regardless of the
state of the NDRF bit. In Single Chip and Peripheral Modes this bit
has no meaning or effect.
Table 6-5. RFSTR Stretch Bit Definition
RFSTR1
RFSTR0
0
0
1
1
0
1
0
1
Number of E Clocks
Stretched
0
1
2
3
EXSTR1, EXSTR0 — External Access Stretch
This two bit field determines the amount of clock stretch on accesses
to an external address space. In Single Chip and Peripheral Modes
this bit has no meaning or effect.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Resource Mapping
97
Resource Mapping
Table 6-6. EXSTR Stretch Bit Definition
EXSTR1
EXSTR0
0
0
1
1
0
1
0
1
Number of E Clocks
Stretched
0
1
2
3
ROMHM — Flash EEPROM only in second Half of Map
This bit has no meaning if ROMON bit is clear.
0 = The 16K byte of fixed Flash EEPROM in location $4000-$7FFF
can be accessed.
1 = Disables direct access to 16K byte Flash EEPROM from
$4000-$7FFF in the memory map. The physical location of
this16K byte Flash can still be accessed through the Program
Page window.
In special mode and with ROMTST bit set, this bit will allow overlap of
the four 32K Flash arrays and overlap the four 4-byte Flash register
space in the same map space to be able to program all arrays at the
same time.
0 = The four 32K Flash arrays are accessed with four pages for
each.
1 = The four 32K Flash arrays coincide in the same space and are
selected at the same time for programming.
CAUTION:
Bit must be cleared before reading any of the arrays or registers.
ROMON — Enable Flash EEPROM
These bits are used to enable the Flash EEPROM arrays.
0 = Disables Flash EEPROM in the memory map.
1 = Enables Flash EEPROM in the memory map.
Technical Data
98
MC68HC912DT128A — Rev 4.0
Resource Mapping
MOTOROLA
Resource Mapping
Mapping test registers
6.6 Mapping test registers
These registers are used in for testing the mapping logic. They can only
be read and after each read they get cleared. A write to each register will
have no effect.
MTST0 — Mapping Test Register 0
RESET:
Bit 7
MT07
0
6
MT06
0
$00F8
5
MT05
0
4
MT04
0
3
MT03
0
2
MT02
0
1
MT01
0
Bit 0
MT00
0
MTST1 — Mapping Test Register 1
RESET:
Bit 7
MT0F
0
6
MT0E
0
$00F9
5
MT0D
0
4
MT0C
0
3
MT0B
0
2
MT0A
0
1
MT09
0
Bit 0
MT08
0
MTST2 — Mapping Test Register 2
RESET:
Bit 7
MT17
0
6
MT16
0
$00FA
5
MT15
0
4
MT14
0
3
MT13
0
2
MT12
0
1
MT11
0
Bit 0
MT10
0
MTST3 — Mapping Test Register 3
RESET:
Bit 7
MT1F
0
6
MT1E
0
$00FB
5
MT1D
0
4
MT1C
0
3
MT1B
0
MC68HC912DT128A — Rev 4.0
MOTOROLA
2
MT1A
0
1
MT19
0
Bit 0
MT18
0
Technical Data
Resource Mapping
99
Resource Mapping
6.7 Memory Maps
The following diagrams illustrate the memory map for each mode of
operation immediately after reset.
$0000
$03FF
$0000
$0400
$0800
$0FFF
$0800
$1000
$2000
$2000
$3FFF
$4000
$4000
$8000
$8000
EXT
$BFFF
$C000
$C000
REGISTERS
(MAPPABLE TO ANY 2K SPACE)
2K bytes EEPROM
(MAPPABLE TO ANY 4K SPACE)
8K bytes RAM
(MAPPABLE TO ANY 8K SPACE)
16K Fixed Flash EEPROM
16K Page Window
Eight 16K Flash EEPROM pages
$A000 - $BFFF Protected BOOT
at odd programing pages
16K Fixed Flash EEPROM
$E000 - $FFFF Protected BOOT
$FFFF
$FF00
$FF00
$FFFF
VECTORS
VECTORS
VECTORS
NORMAL
SINGLE CHIP
EXPANDED
SPECIAL
SINGLE CHIP
$FFFF
BDM
(if active)
Figure 6-1. MC68HC912DT128A Memory Map after reset
The following diagram illustrates the memory paging scheme.
Technical Data
100
MC68HC912DT128A — Rev 4.0
Resource Mapping
MOTOROLA
Resource Mapping
Memory Maps
$0000
$0400
$0800
$1000
$2000
$4000
6
16K Flash
(Unpaged)
One 16K Page accessible at a time (selected by PPAGE value = 0 to 7)
00 Flash 32K
$8000
0
01 Flash 32K
1
2
10 Flash 32K
3
4
11 Flash 32K *
5
6
7
16K Flash
(Paged)
(8K Boot)
$C000
(8K Boot)
(8K Boot)
7
* This 32K Flash
accessible as
pages 6 & 7 and
as unpaged
$4000 - $7FFF &
$C000 - $FFFF
16K Flash
(Unpaged)
$E000
(8K Boot)
$FF00
$FFFF
(8K Boot)
VECTORS
NORMAL
SINGLE CHIP
Figure 6-2. MC68HC912DT128A Memory Paging
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Resource Mapping
101
Resource Mapping
Technical Data
102
MC68HC912DT128A — Rev 4.0
Resource Mapping
MOTOROLA
Technical Data — MC68HC912DT128A
Section 7. Bus Control and Input/Output
7.1 Contents
7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7.3
Detecting Access Type from External Signals . . . . . . . . . . . .103
7.4
Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
7.2 Introduction
Internally the MC68HC912DT128A has full 16-bit data paths, but
depending upon the operating mode and control registers, the external
multiplexed bus may be 8 or 16 bits. There are cases where 8-bit and
16-bit accesses can appear on adjacent cycles using the LSTRB signal
to indicate 8- or 16-bit data.
It is possible to have a mix of 8 and 16 bit peripherals attached to the
external multiplexed bus, using the NDRF bit in the MISC register while
in expanded wide modes.
7.3 Detecting Access Type from External Signals
The external signals LSTRB, R/W, and A0 can be used to determine the
type of bus access that is taking place. Accesses to the internal RAM
module are the only type of access that produce LSTRB = A0 = 1,
because the internal RAM is specifically designed to allow misaligned
16-bit accesses in a single cycle. In these cases the data for the address
that was accessed is on the low half of the data bus and the data for
address + 1 is on the high half of the data bus.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Bus Control and Input/Output
103
Bus Control and Input/Output
Table 7-1. Access Type vs. Bus Control Pins
LSTRB
1
0
1
0
0
A0
0
1
0
1
0
R/W
1
1
0
0
1
1
1
1
0
0
0
1
1
0
Type of Access
8-bit read of an even address
8-bit read of an odd address
8-bit write of an even address
8-bit write of an odd address
16-bit read of an even address
16-bit read of an odd address
(low/high data swapped)
16-bit write to an even address
16-bit write to an odd address
(low/high data swapped)
7.4 Registers
Not all registers are visible in the MC68HC912DT128A memory map
under certain conditions. In special peripheral mode the first 16 registers
associated with bus expansion are removed from the memory map.
In expanded modes, some or all of port A, port B, and port E are used
for expansion buses and control signals. In order to allow emulation of
the single-chip functions of these ports, some of these registers must be
rebuilt in an external port replacement unit. In any expanded mode, port
A, and port B, are used for address and data lines so registers for these
ports, as well as the data direction registers for these ports, are removed
from the on-chip memory map and become external accesses.
In any expanded mode, port E pins may be needed for bus control (e.g.,
ECLK, R/W). To regain the single-chip functions of port E, the emulate
port E (EME) control bit in the MODE register may be set. In this special
case of expanded mode and EME set, PORTE and DDRE registers are
removed from the on-chip memory map and become external accesses
so port E may be rebuilt externally.
Technical Data
104
MC68HC912DT128A — Rev 4.0
Bus Control and Input/Output
MOTOROLA
Bus Control and Input/Output
Registers
PORTA — Port A Register
Single Chip
RESET:
Expanded
& Periph:
Expanded
narrow
Bit 7
PA7
—
ADDR15/
DATA15
ADDR15/
DATA15/
DATA7
$0000
6
PA6
—
ADDR14/
DATA14
ADDR14/
DATA14/
DATA6
5
PA5
—
ADDR13/
DATA13
ADDR13/
DATA13/
DATA5
4
PA4
—
ADDR12/
DATA12
ADDR12/
DATA12/
DATA4
3
PA3
—
ADDR11/
DATA11
ADDR11/
DATA11/
DATA3
2
PA2
—
ADDR10/
DATA10
ADDR10/
DATA10/
DATA2
1
PA1
—
ADDR9/
DATA9
ADDR9/
DATA9/
DATA1
Bit 0
PA0
—
ADDR8/
DATA8
ADDR8/
DATA8/
DATA0
Bits PA[7:0] are associated respectively with addresses ADDR[15:8],
DATA[15:8] and DATA[7:0], in narrow mode. When this port is not
used for external addresses such as in single-chip mode, these pins
can be used as general-purpose I/O. DDRA determines the primary
direction of each pin. This register is not in the on-chip map in
expanded and peripheral modes. Read and write anytime.
DDRA — Port A Data Direction Register
RESET:
Bit 7
DDA7
0
6
DDA6
0
$0002
5
DDA5
0
4
DDA4
0
3
DDA3
0
2
DDA2
0
1
DDA1
0
Bit 0
DDA0
0
This register determines the primary direction for each port A pin
when functioning as a general-purpose I/O port. DDRA is not in the
on-chip map in expanded and peripheral modes. Read and write
anytime.
0 = Associated pin is a high-impedance input
1 = Associated pin is an output
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Bus Control and Input/Output
105
Bus Control and Input/Output
PORTB — Port B Register
Single Chip
RESET:
Expanded
& Periph:
Expanded
narrow
Bit 7
PB7
—
ADDR7/
DATA7
ADDR7
$0001
6
PB6
—
ADDR6/
DATA6
ADDR6
5
PB5
—
ADDR5/
DATA5
ADDR5
4
PB4
—
ADDR4/
DATA4
ADDR4
3
PB3
—
ADDR3/
DATA3
ADDR3
2
PB2
—
ADDR2/
DATA2
ADDR2
1
PB1
—
ADDR1/
DATA1
ADDR1
Bit 0
PB0
—
ADDR0/
DATA0
ADDR0
Bits PB[7:0] are associated with addresses ADDR[7:0] and DATA[7:0]
(except in narrow mode) respectively. When this port is not used for
external addresses such as in single-chip mode, these pins can be
used as general-purpose I/O. DDRB determines the primary direction
of each pin. This register is not in the on-chip map in expanded and
peripheral modes. Read and write anytime.
DDRB — Port B Data Direction Register
RESET:
Bit 7
DDB7
0
6
DDB6
0
$0003
5
DDB5
0
4
DDB4
0
3
DDB3
0
2
DDB2
0
1
DDB1
0
Bit 0
DDB0
0
This register determines the primary direction for each port B pin
when functioning as a general-purpose I/O port. DDRB is not in the
on-chip map in expanded and peripheral modes. Read and write
anytime.
0 = Associated pin is a high-impedance input
1 = Associated pin is an output
PORTE — Port E Register
RESET:
Alt. Pin
Function
BIT 7
PE7
—
DBE or
ECLK or
CAL
$0008
6
PE6
—
MODB or
IPIPE1 or
CGMTST
5
PE5
—
4
PE4
—
3
PE3
—
2
PE2
—
1
PE1
—
BIT 0
PE0
—
MODA or
IPIPE0
ECLK
LSTRB or
TAGLO
R/W
IRQ
XIRQ
This register is associated with external bus control signals and
interrupt inputs, including data bus enable (DBE), mode select
(MODB/IPIPE1, MODA/IPIPE0), E clock, size (LSTRB), read/write
Technical Data
106
MC68HC912DT128A — Rev 4.0
Bus Control and Input/Output
MOTOROLA
Bus Control and Input/Output
Registers
(R/W), IRQ, and XIRQ. When the associated pin is not used for one
of these specific functions, the pin can be used as general-purpose
I/O. The port E assignment register (PEAR) selects the function of
each pin. DDRE determines the primary direction of each port E pin
when configured to be general-purpose I/O.
Some of these pins have software selectable pull-ups (DBE, LSTRB,
R/W, IRQ and XIRQ). A single control bit enables the pull-ups for all
these pins which are configured as inputs.
This register is not in the map in peripheral mode or expanded modes
when the EME bit is set.
Read and write anytime.
DDRE — Port E Data Direction Register
RESET:
Bit 7
DDE7
0
6
DDE6
0
5
DDE5
0
$0009
4
DDE4
0
3
DDE3
0
2
DDE2
0
1
0
0
Bit 0
0
0
This register determines the primary direction for each port E pin
configured as general-purpose I/O.
0 = Associated pin is a high-impedance input
1 = Associated pin is an output
PE[1:0] are associated with XIRQ and IRQ and cannot be configured
as outputs. These pins can be read regardless of whether the
alternate interrupt functions are enabled.
This register is not in the map in peripheral mode and expanded
modes while the EME control bit is set.
Read and write anytime.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Bus Control and Input/Output
107
Bus Control and Input/Output
PEAR — Port E Assignment Register
$000A
BIT 7
NDBE
6
CGMTE
5
PIPOE
4
NECLK
3
LSTRE
2
RDWE
1
CALE
BIT 0
DBENE
RESET:
0
0
0
0
0
0
0
0
RESET:
0
0
1
0
1
1
0
0
RESET:
1
1
0
1
0
0
0
0
RESET:
1
0
0
1
0
0
0
0
RESET:
0
0
1
0
1
1
0
0
Normal Expanded
Special Expanded
Peripheral
Normal single chip
Special single chip
Port E serves as general purpose I/O lines or as system and bus
control signals. The PEAR register is used to choose between the
general-purpose I/O functions and the alternate bus control functions.
When an alternate control function is selected, the associated DDRE
bits are overridden.
The reset condition of this register depends on the mode of operation
because bus control signals are needed immediately after reset in
some modes.
In normal single-chip mode, no external bus control signals are
needed so all of port E is configured for general-purpose I/O.
In normal expanded modes, the reset vector is located in external
memory. The DBE and E clock are required for de-multiplexing
address and data but LSTRB and R/W are only needed by the system
when there are external writable resources. Therefore in normal
expanded modes, the DBE and the E clock are configured for their
alternate bus control functions and the other bits of port E are
configured for general-purpose I/O. If the normal expanded system
needs any other bus control signals, PEAR would need to be written
before any access that needed the additional signals.
In special expanded modes, DBE, IPIPE1, IPIPE0, E, LSTRB, and
R/W are configured as bus-control signals.
In special single chip modes, DBE, IPIPE1, IPIPE0, E, LSTRB, R/W,
and CALE are configured as bus-control signals.
Technical Data
108
MC68HC912DT128A — Rev 4.0
Bus Control and Input/Output
MOTOROLA
Bus Control and Input/Output
Registers
In peripheral mode, the PEAR register is not accessible for reads or
writes. However, the CGMTE control bit is reset to one to configure
PE6 as a test output for the CGM module.
NDBE — No Data Bus Enable
Normal: write once; Special: write anytime EXCEPT the first. Read
anytime.
0 = PE7 is used for DBE, external control of data enable on
memories, or inverted E clock.
1 = PE7 is CAL function if CALE bit is set in PEAR register or
general-purpose I/O otherwise.
The NDBE bit has no effect in Single Chip or Peripheral Modes and
PE7 is defaulted to the CAL function if CALE bit is set in PEAR
register or to an I/O otherwise.
CGMTE — Clock Generator Module Testing Enable
Normal: write never; Special: write anytime EXCEPT the first time.
Read anytime.
0 = PE6 is general-purpose I/O or pipe output.
1 = PE6 is a test signal output from the CGM module (no effect in
single chip or normal expanded modes). PIPOE = 1 overrides
this function and forces PE6 to be a pipe status output signal.
PIPOE — Pipe Status Signal Output Enable
Normal: write once; Special: write anytime EXCEPT the first time.
Read anytime.
0 = PE[6:5] are general-purpose I/O (if CGMTE = 1, PE6 is a test
output signal from the CGM module).
1 = PE[6:5] are outputs and indicate the state of the instruction
queue (only effective in expanded modes).
NECLK — No External E Clock
Normal single chip: write once; special single chip: write anytime; all
other modes: write never.
Read anytime. In peripheral mode, E is an input and in all other
modes, E is an output.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Bus Control and Input/Output
109
Bus Control and Input/Output
0 = PE4 is the external E-clock pin subject to the following
limitation: In single-chip modes, to get an E clock output signal,
it is necessary to have ESTR = 0 in addition to NECLK = 0. A
16-bit write to PEAR and MODE registers can configure all
three bits in one operation.
1 = PE4 is a general-purpose I/O pin.
LSTRE — Low Strobe (LSTRB) Enable
Normal: write once; Special: write anytime EXCEPT the first time.
Read anytime. This bit has no effect in single-chip modes or normal
expanded narrow mode.
0 = PE3 is a general-purpose I/O pin.
1 = PE3 is configured as the LSTRB bus-control output, provided
the MCU is not in single chip or normal expanded narrow
modes.
LSTRB is used during external writes. After reset in normal expanded
mode, LSTRB is disabled. If needed, it should be enabled before
external writes. External reads do not normally need LSTRB because
all 16 data bits can be driven even if the MCU only needs 8 bits of
data.
TAGLO is a shared function of the PE3/LSTRB pin. In special
expanded modes with LSTRE set and the BDM tagging on, a zero at
the falling edge of E tags the instruction word low byte being read into
the instruction queue.
RDWE — Read/Write Enable
Normal: write once; Special: write anytime EXCEPT the first time.
Read anytime. This bit has no effect in single-chip modes.
0 = PE2 is a general-purpose I/O pin.
1 = PE2 is configured as the R/W pin. In single chip modes, RDWE
has no effect and PE2 is a general-purpose I/O pin.
R/W is used for external writes. After reset in normal expanded mode,
it is disabled. If needed it should be enabled before any external
writes.
Technical Data
110
MC68HC912DT128A — Rev 4.0
Bus Control and Input/Output
MOTOROLA
Bus Control and Input/Output
Registers
CALE — Calibration Reference Enable
Read and write anytime.
0 = Calibration reference is disabled and PE7 is general purpose
I/O in single chip or peripheral modes or if NDBE bit is set.
1 = Calibration reference is enabled on PE7 in single chip and
peripheral modes or if NDBE bit is set.
DBENE — DBE or Inverted E Clock on PE7
Normal modes: write once. Special modes: write anytime EXCEPT
the first time. Read anytime.
DBENE controls which signal is output on PE7 when NDBE control bit
is cleared. The inverted E clock output can be used to latch the
address for de-multiplexing. It has the same behavior as the E clock,
except it is inverted. Please note that in the case of idle expansion
bus, the ‘not E clock’ signal could stay high for many cycles.
The DBENE bit has no effect in Single Chip or Peripheral Modes and
PE7 is defaulted to the CAL function if CALE bit is set in PEAR
register or to an I/O otherwise.
0 = PE7 pin used for DBE external control of data enable on
memories in expanded modes when NDBE = 0
1 = PE7 pin used for inverted E clock output in expanded modes
when NDBE = 0
PUCR — Pull-Up Control Register
RESET:
Bit 7
PUPK
0
6
PUPJ
0
$000C
5
PUPH
0
4
PUPE
1
3
0
0
2
0
0
1
PUPB
0
Bit 0
PUPA
0
These bits select pull-up resistors for any pin in the corresponding
port that is currently configured as an input. This register is not in the
map in peripheral mode.
Read and write anytime.
PUPK — Pull-Up Port K Enable
0 = Port K pull-ups are disabled.
1 = Enable pull-up devices for all port K input pins.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Bus Control and Input/Output
111
Bus Control and Input/Output
PUPJ — Pull-Up or Pull-Down Port J Enable
0 = Port J resistive loads (pull-ups or pull-downs) are disabled.
1 = Enable resistive load devices (pull-ups or pull-downs) for all
port J input pins.
PUPH — Pull-Up or Pull-Down Port H Enable
0 = Port H resistive loads (pull-ups or pull-downs) are disabled.
1 = Enable resistive load devices (pull-ups or pull-downs) for all
port H input pins.
PUPE — Pull-Up Port E Enable
0 = Port E pull-ups on PE7, PE3, PE2, PE1 and PE0 are disabled.
1 = Enable pull-up devices for port E input pins PE7, PE3, PE2,
PE1 and PE0.
When this bit is set port E input pins 7, 3, 2, 1 & 0 have an active pullup device.
PUPB — Pull-Up Port B Enable
0 = Port B pull-ups are disabled.
1 = Enable pull-up devices for all port B input pins.
PUPA — Pull-Up Port A Enable
0 = Port A pull-ups are disabled.
1 = Enable pull-up devices for all port A input pins.
Technical Data
112
MC68HC912DT128A — Rev 4.0
Bus Control and Input/Output
MOTOROLA
Bus Control and Input/Output
Registers
RDRIV — Reduced Drive of I/O Lines
RESET:
Bit 7
RDPK
0
6
RDPJ
0
$000D
5
RDPH
0
4
RDPE
0
3
0
0
2
0
0
1
RDPB
0
Bit 0
RDPA
0
These bits select reduced drive for the associated port pins. This
gives reduced power consumption and reduced RFI with a slight
increase in transition time (depending on loading). The reduced drive
function is independent of which function is being used on a particular
port.
This register is not in the map in peripheral mode.
Normal: write once; Special: write anytime EXCEPT the first time.
Read anytime.
RDPK — Reduced Drive of Port K
0 = All port K output pins have full drive enabled.
1 = All port K output pins have reduced drive capability.
RDPJ — Reduced Drive of Port J
0 = All port J output pins have full drive enabled.
1 = All port J output pins have reduced drive capability.
RDPH — Reduced Drive of Port H
0 = All port H output pins have full drive enabled.
1 = All port H output pins have reduced drive capability.
RDPE — Reduced Drive of Port E
0 = All port E output pins have full drive enabled.
1 = All port E output pins have reduced drive capability.
RDPB — Reduced Drive of Port B
0 = All port B output pins have full drive enabled.
1 = All port B output pins have reduced drive capability.
RDPA — Reduced Drive of Port A
0 = All port A output pins have full drive enabled.
1 = All port A output pins have reduced drive capability.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Bus Control and Input/Output
113
Bus Control and Input/Output
Technical Data
114
MC68HC912DT128A — Rev 4.0
Bus Control and Input/Output
MOTOROLA
Technical Data — MC68HC912DT128A
Section 8. Flash Memory
8.1 Contents
8.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
8.3
Overview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
8.4
Flash EEPROM Control Block . . . . . . . . . . . . . . . . . . . . . . . .116
8.5
Flash EEPROM Arrays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .116
8.6
Flash EEPROM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
8.7
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .119
8.8
Programming the Flash EEPROM . . . . . . . . . . . . . . . . . . . . . 120
8.9
Erasing the Flash EEPROM . . . . . . . . . . . . . . . . . . . . . . . . . . 121
8.10
Stop or Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .121
8.11
Flash protection bit FPOPEN . . . . . . . . . . . . . . . . . . . . . . . . .122
8.2 Introduction
The four Flash EEPROM array modules 00FEE32K, 01FEE32K,
10FEE32K and 11FEE32K for the MC68HC912DT128A serve as
electrically erasable and programmable, non-volatile ROM emulation
memory. The modules can be used for program code that must either
execute at high speed or is frequently executed, such as operating
system kernels and standard subroutines, or they can be used for static
data which is read frequently. The Flash EEPROM module is ideal for
program storage for single-chip applications allowing for field
reprogramming.
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Flash Memory
8.3 Overview
Each 32K Flash EEPROM array is arranged in a 16-bit configuration and
may be read as either bytes, aligned words or misaligned words. Access
time is one bus cycle for byte and aligned word access and two bus
cycles for misaligned word operations.
The Flash EEPROM module supports bulk erase only.
Each Flash EEPROM module has hardware interlocks which protect
stored data from accidental corruption. An erase- and programprotected 8-Kbyte block for boot routines is located at the top of each 32Kbyte array. Since boot programs must be available at all times, the only
useful boot block is at $E000–$FFFF location. All paged boot blocks can
be used as protected program space if desired.
On 0L05H and later mask sets, an optional protection scheme is
supported to protect all four 32-Kbyte Flash EEPROM modules against
accident program or erase. This is achieved using the protection bit
FPOPEN in EEPROM EEMCR (see 8.11 Flash protection bit FPOPEN).
8.4 Flash EEPROM Control Block
A 4-byte register block for each module controls the Flash EEPROM
operation. Configuration information is specified and programmed
independently from the contents of the Flash EEPROM array. At reset,
the 4-byte register section starts at address $00F4 and points to the
00FEE32K register block.
8.5 Flash EEPROM Arrays
After reset, a fixed 32K Flash EEPROM array, 11FEE32K, is located
from addresses $4000 to $7FFF and from $C000 to $FFFF. The other
three 32K Flash EEPROM arrays 00FEE32K, 01FEE32K and
10FEE32K, are mapped through a 16K byte program page window
located from addresses $8000 to $BFFF. The page window has eight
16K byte pages. The last two pages also map the physical location of the
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Flash EEPROM Registers
fixed 32K Flash EEPROM array 11FEE32K. In expanded modes, the
Flash EEPROM arrays are turned off. See Operating Modes.
8.6 Flash EEPROM Registers
Each 32K byte Flash EEPROM module has a set of registers. The
register space $00F4-$00F7 is in a register space window of four pages.
Each register page of four bytes maps the register space for each Flash
module and each page is selected by the PPAGE register. See
Resource Mapping
FEELCK — Flash EEPROM Lock Control Register
RESET:
$00F4
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
LOCK
0
0
0
0
0
0
0
0
In normal modes the LOCK bit can only be written once after reset.
LOCK — Lock Register Bit
0 = Enable write to FEEMCR register
1 = Disable write to FEEMCR register
FEEMCR — Flash EEPROM Module Configuration Register
RESET:
$00F5
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
BOOTP
0
0
0
0
0
0
0
1
This register controls the operation of the Flash EEPROM array.
BOOTP cannot be changed when the LOCK control bit in the
FEELCK register is set or if HVEN or PGM or ERAS in the FEECTL
register is set.
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Flash Memory
BOOTP — Boot Protect
The boot blocks are located at $E000–$FFFF and $A000–$BFFF for
odd program pages for each Flash EEPROM module. Since boot
programs must be available at all times, the only useful boot block is
at $E000–$FFFF location. All paged boot blocks can be used as
protected program space if desired.
0 = Enable erase and program of 8K byte boot block
1 = Disable erase and program of 8K byte boot block
FEECTL — Flash EEPROM Control Register
$00F7
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
FEESWAI
HVEN
0
ERAS
PGM
0
0
0
0
0
0
0
0
RESET:
This register controls the programming and erasure of the Flash
EEPROM.
FEESWAI — Flash EEPROM Stop in Wait Control
0 = Do not halt Flash EEPROM clock when the part is in wait
mode.
1 = Halt Flash EEPROM clock when the part is in wait mode.
HVEN — High-Voltage Enable
This bit enables the charge pump to supply high voltages for program
and erase operations in the array. HVEN can only be set if either PGM
or ERAS are set and the proper sequence for program or erase is
followed.
0 = Disables high voltage to array and charge pump off
1 = Enables high voltage to array and charge pump on
ERAS — Erase Control
This bit configures the memory for erase operation. ERAS is
interlocked with the PGM bit such that both bits cannot be equal to 1
or set to1 at the same time.
0 = Erase operation is not selected.
1 = Erase operation selected.
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Operation
PGM — Program Control
This bit configures the memory for program operation. PGM is
interlocked with the ERAS bit such that both bits cannot be equal to 1
or set to1 at the same time.
0 = Program operation is not selected.
1 = Program operation selected.
8.7 Operation
The Flash EEPROM can contain program and data. On reset, it can
operate as a bootstrap memory to provide the CPU with internal
initialization information during the reset sequence.
8.7.1 Bootstrap Operation Single-Chip Mode
After reset, the CPU controlling the system will begin booting up by
fetching the first program address from address $FFFE.
8.7.2 Normal Operation
The Flash EEPROM allows a byte or aligned word read in one bus cycle.
Misaligned word read require an additional bus cycle. The Flash
EEPROM array responds to read operations only. Write operations are
ignored.
8.7.3 Program/Erase Operation
An unprogrammed Flash EEPROM bit has a logic state of one. A bit
must be programmed to change its state from one to zero. Erasing a bit
returns it to a logic one. The Flash EEPROM has a minimum
program/erase life of 100 cycles. Programming or erasing the Flash
EEPROM is accomplished by a series of control register writes.
The Flash EEPROM must be completely erased prior to programming
final data values.
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Flash Memory
Programming and erasing of Flash locations cannot be performed by
code being executed from the Flash memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps. Do not exceed tFPGM maximum (40µs).
8.8 Programming the Flash EEPROM
Programming the Flash EEPROM is done on a row basis. A row consists
of 32 consecutive words (64 bytes) with rows starting from addresses
$XX00, $XX40, $XX80 and $XXC0. When writing a row care should be
taken not to write data to addresses outside of the row. Programming is
restricted to aligned word i.e. data writes to select rows/blocks for
programming/erase should be to even adresses and writes to any row
for programming should be to aligned words.
Use this step-by-step procedure to program a row of Flash memory.
1. Set the PGM bit. This configures the memory for program
operation and enables the latching of address and data for
programming.
2. Write to any aligned word Flash address within the row address
range desired (with any data) to select the row.
3. Wait for a time, tNVS (min. 10µs).
4. Set the HVEN bit.
5. Wait for a time, tPGS (min. 5µs).
6. Write one data word (two bytes) to the next aligned word Flash
address to be programmed. If BOOTP is asserted, an attempt to
program an address in the boot block will be ignored.
7. Wait for a time, tFPGM (min. 30µs).
8. Repeat step 6 and 7 until all the words within the row are
programmed.
9. Clear the PGM bit.
10. Wait for a time, tNVH (min. 5µs).
11. Clear the HVEN bit.
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Erasing the Flash EEPROM
12. After time, tRCV (min 1µs), the memory can be accessed in read
mode again.
This program sequence is repeated throughout the memory until all data
is programmed. For minimum overall programming time and least
program disturb effect, the sequence should be part of an intelligent
operation which iterates per row.
8.9 Erasing the Flash EEPROM
The following sequence demonstrates the recommended procedure for
erasing any of the Flash EEPROM array.
1. Set the ERAS bit.
2. Write to any valid address in the Flash array. The data written and
the address written are not important. The boot block will be
erased only if the control bit BOOTP is negated.
3. Wait for a time, tNVS.
4. Set the HVEN bit.
5. Wait for a time, tERAS.
6. Clear the ERAS bit.
7. Wait for a time, tNVHL.
8. Clear the HVEN bit.
9. After time, tRCV, the memory can be accessed in read mode again.
8.10 Stop or Wait Mode
When stop or wait commands are executed, the MCU puts the Flash
EEPROM in stop or wait mode. In these modes the Flash module will
cease erasure or programming immediately.
CAUTION:
It is advised not to enter stop or wait modes when program or erase
operation of the Flash array is in progress.
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Flash Memory
8.11 Flash protection bit FPOPEN
The FPOPEN bit is located in EEMCR – EEPROM Module Configuration
Register, bit 4.
FPOPEN – Opens the Flash array for program or erase
0 = The whole Flash array is protected.
1 = The whole Flash array is enabled for program or erase
FPOPEN can be read at anytime.
FPOPEN can be written only to ’0’ for protection but not to ’1’ for unprotect in normal mode.
FPOPEN can be written ’0’ and ’1’ in special mode only.
FPOPEN is loaded at reset from EEPROM SHADOW word bit 4.
When FPOPEN is cleared to ’0’, the Flash array cannot be
reprogrammed in normal modes.
CAUTION:
Programming the NVM FPOPEN bit in the SHADOW word ($_FC0, bit
4) means that the FPOPEN bit in the EEMCR register will always be ’0’
in normal modes. The flash array can no longer be modified in normal
modes.
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Technical Data — MC68HC912DT128A
Section 9. EEPROM Memory
9.1 Contents
9.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
9.3
EEPROM Selective Write More Zeros . . . . . . . . . . . . . . . . . .124
9.4
EEPROM Programmer’s Model . . . . . . . . . . . . . . . . . . . . . . .125
9.5
EEPROM Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 126
9.6
Program/Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . .133
9.7
Shadow Word Mapping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
9.8
Programming EEDIVH and EEDIVL Registers. . . . . . . . . . . . 135
9.2 Introduction
The MC68HC912DT128A EEPROM nonvolatile memory is arranged in
a 16-bit configuration. The EEPROM array may be read as either bytes,
aligned words or misaligned words. Access times are one bus cycle for
byte and aligned word access and two bus cycles for misaligned word
operations.
Programming is by byte or aligned word. Attempts to program or erase
misaligned words will fail. Only the lower byte will be latched and
programmed or erased. Programming and erasing of the user EEPROM
can be done in normal modes.
Each EEPROM byte or aligned word must be erased before
programming. The EEPROM module supports byte, aligned word, row
(32 bytes) or bulk erase, all using the internal charge pump. The erased
state is $FF. The EEPROM module has hardware interlocks which
protect stored data from corruption by accidentally enabling the
program/erase voltage. Programming voltage is derived from the
internal VDD supply with an internal charge pump.
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EEPROM Memory
9.3 EEPROM Selective Write More Zeros
The EEPROM can be programmed such that one or multiple bits are
programmed (written to a logic “0”) at a time. However, the user should
never program any bit more than once before erasing the entire byte. In
other words, the user is not allowed to over write a logic “0” with another
“0’.
For some applications it may be advantageous to track more than 10k
events with a single byte of EEPROM by programming one bit at a time.
For that purpose, a special selective bit programming technique is
available. An example is shown here.
Original state of byte = binary 1111:1111 (erased)
First event is recorded by programming bit position 0
Program write = binary 1111:1110;
Result = binary 1111:1110
Second event is recorded by programming bit position 1
Program write = binary 1111:1101;
Result = binary 1111:1100
Third event is recorded by programming bit position 2
Program write = binary 1111:1011;
Result = binary 1111:1000
Fourth event is recorded by programming bit position 3
Program write = binary 1111:0111;
Result = binary 1111:0000
Events five through eight are recorded in a similar fashion.
Note that none of the bit locations are actually programmed more than
once although the byte was programmed eight times.
When this technique is utilized, a program / erase cycle is defined as
multiple writes (up to eight) to a unique location followed by a single
erase sequence.
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EEPROM Memory
EEPROM Programmer’s Model
9.4 EEPROM Programmer’s Model
The EEPROM module consists of two separately addressable sections.
The first is an eight-byte memory mapped control register block used for
control, testing and configuration of the EEPROM array. The second
section is the EEPROM array itself.
At reset, the eight-byte register section starts at address $00EC and the
EEPROM array is located from addresses $0800 to $0FFF. Registers
$00EC-$00ED are reserved.
Read/write access to the memory array section can be enabled or
disabled by the EEON control bit in the INITEE register ($0012). This
feature allows the access of memory mapped resources that have lower
priority than the EEPROM memory array. EEPROM control registers can
be accessed regardless of the state of EEON. Any EEPROM erase or
program operation already in progress will not be affected by the change
of EEON state. For information on re-mapping the register block and
EEPROM address space, refer to Operating Modes.
CAUTION:
It is strongly recommended to discontinue program/erase operations
during WAIT (when EESWAI=1) or STOP modes since all
program/erase activities will be terminated abruptly and considered
unsuccessful.
For lowest power consumption during WAIT mode, it is advised to turn
off EEPGM.
The EEPROM module contains an extra word called SHADOW word
which is loaded at reset into the EEMCR, EEDIVH and EEDIVL
registers. To program the SHADOW word, when in special modes
(SMODN=0), the NOSHW bit in EEMCR register must be cleared.
Normal programming routines are used to program the SHADOW word
which becomes accessible at address $0FC0-$0FC1 when NOSHW is
cleared. At the next reset the SHADOW word data is loaded into the
EEMCR, EEDIVH and EEDIVL registers. The SHADOW word can be
protected from being programmed or erased by setting the SHPROT bit
of EEPROT register.
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125
EEPROM Memory
A steady internal self-time clock is required to provide accurate counts
to meet EEPROM program/erase requirements. This clock is generated
via by a programmable 10-bit prescaler register. Automatic
program/erase termination is also provided.
In ordinary situations, with crystal operating properly, the steady internal
self-time clock is derived from the input clock source (EXTALi). The
divider value is as in EEDIVH:EEDIVL. In limp-home mode, where the
oscillator clock has malfunctioned or is unavailable, the self-time clock is
derived from the PLL at a nominal fVCOMIN using a predefined divider
value of $0023. Program/erase operation is not guaranteed in limphome mode.
CAUTION:
It is strongly recommended that program/erase operation is terminated
in the event of loss of crystal, either by the application software (clearing
EEPGM & EELAT bits) when entering limp home mode or by enabling
the clock monitor to generate a clock monitor reset. This will prevent
unnecessary stress on the emulated EEPROM during oscillator failure.
9.5 EEPROM Control Registers
EEDIVH — EEPROM Modulus Divider
RESET:
Bit 7
0
0
6
0
0
$00EE
5
0
0
4
0
0
3
0
0
2
0
0
1
EEDIV9
—(1)
Bit 0
EEDIV8
—(1)
1. Loaded from SHADOW word.
EEDIVL — EEPROM Modulus Divider
RESET:
Bit 7
EEDIV7
—(1)
6
EEDIV6
—(1)
5
EEDIV5
—(1)
$00EF
4
EEDIV4
—(1)
3
EEDIV3
—(1)
2
EEDIV2
—(1)
1
EEDIV1
—(1)
Bit 0
EEDIV0
—(1)
1. Loaded from SHADOW word.
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EEPROM Memory
EEPROM Control Registers
EEDIV[9:0] — Prescaler divider
Loaded from SHADOW word at reset.
Read anytime. Write once in normal modes (SMODN =1) if EELAT =
0 and anytime in special modes (SMODN =0) if EELAT = 0.
The prescaler divider is required to produce a self-time clock with a
fixed frequency around 28.6 Khz for the range of oscillator
frequencies. The divider is set so that the oscillator frequency can be
divided by a divide factor that can produce a 35 µs ± 2µs timebase.
CAUTION:
An incorrect or uninitialized value on EEDIV can result in overstress of
EEPROM array during program/erase operation. It is also strongly
recommend not to program EEPROM with oscillator frequencies less
than 250 Khz.
The EEDIV value is determined by the following formula:
EEDIV = INT [ EXTALi (hz) x 35 ×10
NOTE:
–6
+ 0.5 ]
INT[A] denotes the round down integer value of A. Program/erase cycles
will not be activated when EEDIV = 0.
Table 9-1. EEDIV Selection
Osc Freq.
16 Mhz
8 Mhz
4 Mhz
2 Mhz
1 Mhz
500 Khz
250 Khz
Osc Period
62.5ns
125ns
250ns
500ns
1µs
2µs
4µs
MC68HC912DT128A — Rev 4.0
MOTOROLA
Divide Factor
560
280
140
70
35
18
9
EEDIV
$0230
$0118
$008C
$0046
$0023
$0012
$0009
Technical Data
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127
EEPROM Memory
EEMCR — EEPROM Module Configuration
RESET:
Bit 7
6
NOBDML
NOSHW
—(3)
—(3)
$00F0
5
Reserved
—(3)
4
(1)
(2)
FPOPEN
—(3)
3
2
1
Bit 0
1
EESWAI
PROTLCK
DMY
1
1
0
0
1. Bit 5 has a test function and should not be programmed.
2. The FPOPEN bit is available only on the 0L05H and later mask sets. For previous masks, this bit is reserved.
3. Loaded from SHADOW word.
Bits[7:4] are loaded at reset from the EEPROM SHADOW word.
NOTE:
The bits 5 and 4 are reserved for test purposes. These locations in
SHADOW word should not be programmed otherwise some locations of
regular EEPROM array will not be more visible.
NOBDML — Background Debug Mode Lockout Disable
0 = The BDM lockout is enabled.
1 = The BDM lockout is disabled.
Loaded from SHADOW word at reset.
Read anytime. Write anytime in special modes (SMODN=0).
NOSHW — SHADOW Word Disable
0 = The SHADOW word is enabled and accessible at address
$0FC0-$0FC1.
1 = Regular EEPROM array at address $0FC0-$0FC1.
Loaded from SHADOW word at reset.
Read anytime. Write anytime in special modes (SMODN=0).
When NOSHW cleared, the regular EEPROM array bytes at address
$0FC0 and $0FC1 are not visible. The SHADOW word is accessed
instead for both read and program/erase operations. Bits[7:4] from
the high byte of the SHADOW word, $0FC0, are loaded to
EEMCR[7:4]. Bits[1:0] from the high byte of the SHADOW word,
$0FC0,are loaded to EEDIVH[1:0]. Bits[7:0] from the low byte of the
SHADOW word, $0FC1,are loaded to EEDIVL[7:0]. BULK
program/erase only applies if SHADOW word is enabled.
NOTE:
Bit 6 from high byte of SHADOW word should not be programmed in
order to have the full EEPROM array visible.
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MOTOROLA
EEPROM Memory
EEPROM Control Registers
FPOPEN — Opens the Flash Block for Program or Erase
0 = The whole Flash array is protected.
1 = The whole Flash array is enable for program or erase.
Loaded from SHADOW word at reset. Read anytime. Write anytime
in special modes (SMODN=0). Write once ’0’ is allowed in normal
mode.
EESWAI — EEPROM Stops in Wait Mode
0 = The module is not affected during WAIT mode
1 = The module ceases to be clocked during WAIT mode
Read and write anytime.
NOTE:
The EESWAI bit should be cleared if the WAIT mode vectors are
mapped in the EEPROM array.
PROTLCK — Block Protect Write Lock
0 = Block protect bits and bulk erase protection bit can be written
1 = Block protect bits are locked
Read anytime. Write once in normal modes (SMODN = 1), set and
clear any time in special modes (SMODN = 0).
DMY— Dummy bit
Read and write anytime.
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EEPROM Memory
EEPROT — EEPROM Block Protect
RESET:
Bit 7
SHPROT
1
6
1
1
$00F1
5
BPROT5
1
4
BPROT4
1
3
BPROT3
1
2
BPROT2
1
1
BPROT1
1
Bit 0
BPROT0
1
Prevents accidental writes to EEPROM. Read anytime. Write anytime if
EEPGM = 0 and PROTLCK = 0.
SHPROT — SHADOW Word Protection
0 = The SHADOW word can be programmed and erased.
1 = The SHADOW word is protected from being programmed and
erased.
BPROT[5:0] — EEPROM Block Protection
0 = Associated EEPROM block can be programmed and erased.
1 = Associated EEPROM block is protected from being
programmed and erased.
Table 9-2. 2K byte EEPROM Block Protection
Bit Name
BPROT5
BPROT4
BPROT3
BPROT2
BPROT1
BPROT0
Block Protected
$0800 to $0BFF
$0C00 to $0DFF
$0E00 to $0EFF
$0F00 to $0F7F
$0F80 to $0FBF
$0FC0 to $0FFF
Block Size
1024 Bytes
512 Bytes
256 Bytes
128 Bytes
64 Bytes
64 Bytes
EETST — EEPROM Test
RESET:
Bit 7
0
0
$00F2
6
EREVTN
0
5
0
0
4
0
0
3
0
0
2
ETMSD
0
1
ETMR
0
Bit 0
ETMSE
0
In normal mode, writes to EETST control bits have no effect and
always read zero. The EEPROM module cannot be placed in test
mode inadvertently during normal operation
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MOTOROLA
EEPROM Memory
EEPROM Control Registers
.
EEPROG — EEPROM Control
RESET:
Bit 7
BULKP
1
6
0
0
$00F3
5
AUTO
0
4
BYTE
0
3
ROW
0
2
ERASE
0
1
EELAT
0
Bit 0
EEPGM
0
BULKP — Bulk Erase Protection
0 = EEPROM can be bulk erased.
1 = EEPROM is protected from being bulk or row erased.
Read anytime. Write anytime if EEPGM = 0 and PROTLCK = 0.
AUTO — Automatic shutdown of program/erase operation.
EEPGM is cleared automatically after the program/erase cycles are
finished when AUTO is set.
0 = Automatic clear of EEPGM is disabled.
1 = Automatic clear of EEPGM is enabled.
Read anytime. Write anytime if EEPGM = 0.
BYTE — Byte and Aligned Word Erase
0 = Bulk or row erase is enabled.
1 = One byte or one aligned word erase only.
Read anytime. Write anytime if EEPGM = 0.
ROW — Row or Bulk Erase (when BYTE = 0)
0 = Erase entire EEPROM array.
1 = Erase only one 32-byte row.
Read anytime. Write anytime if EEPGM = 0.
BYTE and ROW have no effect when ERASE = 0
Table 9-3. Erase Selection
BYTE
0
0
1
1
ROW
0
1
0
1
Block size
Bulk erase entire EEPROM array
Row erase 32 bytes
Byte or aligned word erase
Byte or aligned word erase
If BYTE = 1 only the location specified by the address written to the
programming latches will be erased. The operation will be a byte or
an aligned word erase depending on the size of written data.
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EEPROM Memory
ERASE — Erase Control
0 = EEPROM configuration for programming.
1 = EEPROM configuration for erasure.
Read anytime. Write anytime if EEPGM = 0.
Configures the EEPROM for erasure or programming.
Unless BULKP is set, erasure is by byte, aligned word, row or bulk.
EELAT — EEPROM Latch Control
0 = EEPROM set up for normal reads.
1 = EEPROM address and data bus latches set up for
programming or erasing.
Read anytime.
Write anytime except when EEPGM = 1 or EEDIV = 0.
BYTE, ROW, ERASE and EELAT bits can be written simultaneously
or in any sequence.
EEPGM — Program and Erase Enable
0 = Disables program/erase voltage to EEPROM.
1 = Applies program/erase voltage to EEPROM.
The EEPGM bit can be set only after EELAT has been set. When
EELAT and EEPGM are set simultaneously, EEPGM remains clear
but EELAT is set.
The BULKP, AUTO, BYTE, ROW, ERASE and EELAT bits cannot be
changed when EEPGM is set. To complete a program or erase cycle
when AUTO bit is clear, two successive writes to clear EEPGM and
EELAT bits are required before reading the programmed data.
When the AUTO bit is set, EEPGM is automatically cleared after the
program or erase cycle completes. Note that if an attempt is made to
modify a protected block location the modify cycle does not start and
the EEPGM bit isn’t automatically cleared.
A write to an EEPROM location has no effect when EEPGM is set.
Latched address and data cannot be modified during program or
erase.
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Program/Erase Operation
9.6 Program/Erase Operation
A program or erase operation should follow the sequence below if AUTO
bit is clear:
1. Write BYTE, ROW and ERASE to desired value, write EELAT = 1
2. Write a byte or an aligned word to an EEPROM address
3. Write EEPGM = 1
4. Wait for programming, tPROG or erase, tERASE delay time
5. Write EEPGM = 0
6. Write EELAT = 0
If the AUTO bit is set, steps 4 and 5 can be replaced by a step to poll the
EEPGM bit until it is cleared.
CAUTION:
The state machine will not start if an attempt is made to program or erase
a protected location and therefore the EEPGM bit will never clear on that
EEPROM operation. Check for protected status or use a software
timeout to avoid a continuous loop whilst polling the EEPGM bit. If using
a timeout, ensure steps 5 and 6 are still executed.
It is possible to program/erase more bytes or words without intermediate
EEPROM reads, by jumping from step 5 to step 2.
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9.7 Shadow Word Mapping
The shadow word is mapped to location $_FC0 and $_FC1 when the
NOSHW bit in EEMCR register is zero. The value in the shadow word is
loaded to the EEMCR, EEDIVH and EEDIVL after reset. Table 9-4
shows the mapping of each bit from shadow word to the registers.
Table 9-4. Shadow word mapping
Shadow word location
Register / Bit
$_FC0 bit 7
EEMCR / NOBDML
$_FC0, bit 6
EEMCR / NOSHW
$_FC0, bit 5
EEMCR / bit 5(1)
$_FC0, bit 4
EEMCR / bit 4(1)
$_FC0, bit 3:2
not mapped(2))
$_FC0, bit 1:0
EEDIVH / bit 1:0
$_FC1, bit 7:0
EEDIVCLK / bit 7:0
1. Reserved for testing. Must be set to one in user application.
2. Reserved. Must be set to one in user application for future compatibility.
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Programming EEDIVH and EEDIVL Registers
9.8 Programming EEDIVH and EEDIVL Registers
The EEDIVH and EEDIVL registers must be correctly set according to
the oscillator frequency before any EEPROM location can be
programmed or erased.
9.8.1 Normal mode
The EEDIVH and EEDIVL registers are write once in normal mode.
Upon system reset, the application program is required to write the
correct divider value to EEDIVH and EEDIVL registers based on the
oscillator frequency. After the first write, the value in the EEDIVH and
EEDIVL registers is locked from being overwritten until the next reset.
The EEPROM is then ready for standard program/erase routines.
CAUTION:
Runaway code can possibly corrupt the EEDIVH and EEDIVL registers
if they are not initialized (write once registers).
9.8.2 Special mode
If an existing application code with EEPROM program/erase routines is
fixed and the system is already operating at a known oscillator
frequency, it is recommended to initialize the shadow word with the
corresponding EEDIVH and EEDIVL values in special mode. The
shadow word initializes EEDIVH and EEDIVL registers upon system
reset to ensure software compatibility with existing code. Initializing the
EEDIVH and EEDIVL registers in special modes (SMODN=0) is
accomplished by the following steps.
1. Write correct divider value to EEDIVH and EEDIVL registers
based on the oscillator frequency as per Table 9-1.
2. Remove the SHADOW word protection by clearing SHPROT bit in
EEPROT register.
3. Clear NOSHW bit in EEMCR register to make the SHADOW word
visible at $0FC0-$0FC1.
4. Write NOSHW bit in EEMCR register to make the SHADOW word
visible at $0FC0-$0FC1.
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EEPROM Memory
5. Program bits 1 and 0 of the high byte of the SHADOW word and
bits 7 to 0 of the low byte of the SHADOW word like a regular
EEPROM location at address $0FC0 and $0FC1. Do not program
other bits of the high byte of the SHADOW word (location $0FC0);
otherwise some regular EEPROM array locations will not be
visible. At the next reset, the SHADOW values are loaded into the
EEDIVH and EEDIVL registers. They do not require further
initialization as long as the oscillator frequency of the target
application is not changed.
6. Protect the SHADOW word by setting SHPROT bit in EEPROT
register.
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Technical Data — MC68HC912DT128A
Section 10. Resets and Interrupts
10.1 Contents
10.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
10.3
Exception Priority . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
10.4
Maskable interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .138
10.5
Latching of Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
10.6
Interrupt Control and Priority Registers . . . . . . . . . . . . . . . . .141
10.7
Interrupt test registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
10.8
Resets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .143
10.9
Effects of Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
10.10 Register Stacking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
10.2 Introduction
CPU12 exceptions include resets and interrupts. Each exception has an
associated 16-bit vector, which points to the memory location where the
routine that handles the exception is located. Vectors are stored in the
upper 128 bytes of the standard 64K byte address map.
The six highest vector addresses are used for resets and non-maskable
interrupt sources. The remainder of the vectors are used for maskable
interrupts, and all must be initialized to point to the address of the
appropriate service routine.
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10.3 Exception Priority
A hardware priority hierarchy determines which reset or interrupt is
serviced first when simultaneous requests are made. Six sources are not
maskable. The remaining sources are maskable, and any one of them
can be given priority over other maskable interrupts.
The priorities of the non-maskable sources are:
1. POR or RESET pin
2. Clock monitor reset
3. COP watchdog reset
4. Unimplemented instruction trap
5. Software interrupt instruction (SWI)
6. XIRQ signal (if X bit in CCR = 0)
10.4 Maskable interrupts
Maskable interrupt sources include on-chip peripheral systems and
external interrupt service requests. Interrupts from these sources are
recognized when the global interrupt mask bit (I) in the CCR is cleared. The
default state of the I bit out of reset is one, but it can be written at any time.
Interrupt sources are prioritized by default but any one maskable interrupt
source may be assigned the highest priority by means of the HPRIO
register. The relative priorities of the other sources remain the same.
An interrupt that is assigned highest priority is still subject to global
masking by the I bit in the CCR, or by any associated local bits. Interrupt
vectors are not affected by priority assignment. HPRIO can only be
written while the I bit is set (interrupts inhibited). Table 10-1 lists interrupt
sources and vectors in default order of priority. Before masking an
interrupt by clearing the corresponding local enable bit, it is required to
set the I-bit to avoid an SWI.
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Latching of Interrupts
10.5 Latching of Interrupts
XIRQ is always level triggered and IRQ can be selected as a level
triggered interrupt. These level triggered interrupt pins should only be
released during the appropriate interrupt service routine. Generally the
interrupt service routine will handshake with the interrupting logic to
release the pin. In this way, the MCU will never start the interrupt service
sequence only to determine that there is no longer an interrupt source.
In event that this does occur the trap vector will be taken.
If IRQ is selected as an edge triggered interrupt, the hold time of the level
after the active edge is independent of when the interrupt is serviced. As
long as the minimum hold time is met, the interrupt will be latched inside
the MCU. In this case the IRQ edge interrupt latch is cleared
automatically when the interrupt is serviced.
All of the remaining interrupts are latched by the MCU with a flag bit.
These interrupt flags should be cleared during an interrupt service
routine or when interrupts are masked by the I bit. By doing this, the
MCU will never get an unknown interrupt source and take the trap vector.
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Table 10-1. Interrupt Vector Map
Vector Address
Interrupt Source
CCR
Mask
None
None
None
None
None
X bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
I bit
$FFFE, $FFFF
$FFFC, $FFFD
$FFFA, $FFFB
$FFF8, $FFF9
$FFF6, $FFF7
$FFF4, $FFF5
$FFF2, $FFF3
$FFF0, $FFF1
$FFEE, $FFEF
$FFEC, $FFED
$FFEA, $FFEB
$FFE8, $FFE9
$FFE6, $FFE7
$FFE4, $FFE5
$FFE2, $FFE3
$FFE0, $FFE1
$FFDE, $FFDF
$FFDC, $FFDD
$FFDA, $FFDB
$FFD8, $FFD9
Reset
Clock monitor fail reset
COP failure reset
Unimplemented instruction trap
SWI
XIRQ
IRQ
Real time interrupt
Timer channel 0
Timer channel 1
Timer channel 2
Timer channel 3
Timer channel 4
Timer channel 5
Timer channel 6
Timer channel 7
Timer overflow
Pulse accumulator overflow
Pulse accumulator input edge
SPI serial transfer complete
$FFD6, $FFD7
SCI 0
I bit
$FFD4, $FFD5
SCI 1
I bit
$FFD2, $FFD3
$FFD0, $FFD1
ATD0 or ATD1
MSCAN 0 wake-up
I bit
I bit
$FFCE, $FFCF
Key wake-up J or H
I bit
$FFCC, $FFCD
$FFCA, $FFCB
Modulus down counter underflow
Pulse Accumulator B Overflow
I bit
I bit
$FFC8, $FFC9
MSCAN 0 errors
I bit
$FFC6, $FFC7
$FFC4, $FFC5
$FFC2, $FFC3
$FFC0, $FFC1
$FFBE, $FFBF
MSCAN 0 receive
MSCAN 0 transmit
CGM lock and limp home
IIC Bus
MSCAN 1 wake-up
I bit
I bit
I bit
I bit
I bit
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Local Enable
None
COPCTL (CME, FCME)
COP rate selected
None
None
None
INTCR (IRQEN)
RTICTL (RTIE)
TMSK1 (C0I)
TMSK1 (C1I)
TMSK1 (C2I)
TMSK1 (C3I)
TMSK1 (C4I)
TMSK1 (C5I)
TMSK1 (C6I)
TMSK1 (C7I)
TMSK2 (TOI)
PACTL (PAOVI)
PACTL (PAI)
SP0CR1 (SPIE)
SC0CR2
(TIE, TCIE, RIE, ILIE)
SC1CR2
(TIE, TCIE, RIE, ILIE)
ATDxCTL2 (ASCIE)
C0RIER (WUPIE)
KWIEJ[7:0] and
KWIEH[7:0]
MCCTL (MCZI)
PBCTL (PBOVI)
C0RIER (RWRNIE,
TWRNIE,
RERRIE, TERRIE,
BOFFIE, OVRIE)
C0RIER (RXFIE)
C0TCR (TXEIE[2:0])
PLLCR (LOCKIE, LHIE)
IBCR (IBIE)
C1RIER (WUPIE)
HPRIO Value to
Elevate
–
–
–
–
–
–
$F2
$F0
$EE
$EC
$EA
$E8
$E6
$E4
$E2
$E0
$DE
$DC
$DA
$D8
$D6
$D4
$D2
$D0
$CE
$CC
$CA
$C8
$C6
$C4
$C2
$C0
$BE
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Interrupt Control and Priority Registers
Table 10-1. Interrupt Vector Map
Vector Address
CCR
Mask
Interrupt Source
Local Enable
HPRIO Value to
Elevate
$FFBC, $FFBD
MSCAN 1 errors
I bit
$FFBA, $FFBB
$FFB8, $FFB9
MSCAN 1 receive
MSCAN 1 transmit
I bit
I bit
C1RIER (RWRNIE,
TWRNIE,
RERRIE, TERRIE,
BOFFIE, OVRIE)
C1RIER (RXFIE)
C1TCR (TXEIE[2:0])
$FFB6, $FFB7(1)
MSCAN 2 wake-up
I bit
C2RIER (WUPIE)
$B6
$B4
$B2
$FFB4, $FFB5
MSCAN 2 errors
I bit
C2RIER (RWRNIE,
TWRNIE,
RERRIE, TERRIE,
BOFFIE, OVRIE)
$FFB2, $FFB3(1)
MSCAN 2 receive
I bit
C2RIER (RXFIE)
$FFB0, $FFB1(1)
$FF80–$FFAF
MSCAN 2 transmit
I bit
C2TCR (TXEIE[2:0])
Reserved
I bit
(1)
$BC
$BA
$B8
$B0
$80–$AE
1. MC68HC912DT128A only
10.6 Interrupt Control and Priority Registers
INTCR — Interrupt Control Register
RESET:
Bit 7
IRQE
0
6
IRQEN
1
$001E
5
DLY
1
4
0
0
3
0
0
2
0
0
1
0
0
Bit 0
0
0
IRQE — IRQ Select Edge Sensitive Only
0 = IRQ configured for low-level recognition.
1 = IRQ configured to respond only to falling edges (on pin
PE1/IRQ).
IRQE can be read anytime and written once in normal modes. In
special modes, IRQE can be read anytime and written anytime,
except the first write is ignored.
IRQEN — External IRQ Enable
The IRQ pin has an internal pull-up.
0 = External IRQ pin is disconnected from interrupt logic.
1 = External IRQ pin is connected to interrupt logic.
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IRQEN can be read and written anytime in all modes.
DLY — Enable Oscillator Start-up Delay on Exit from STOP
The delay time of about 4096 cycles is based on the XCLK rate
chosen.
0 = No stabilization delay imposed on exit from STOP mode. A
stable external oscillator must be supplied.
1 = Stabilization delay is imposed before processing resumes after
STOP.
DLY can be read anytime and written once in normal modes. In
special modes, DLY can be read and written anytime.
HPRIO — Highest Priority I Interrupt
RESET:
Bit 7
1
1
6
PSEL6
1
$001F
5
PSEL5
1
4
PSEL4
1
3
PSEL3
0
2
PSEL2
0
1
PSEL1
1
Bit 0
0
0
Write only if I mask in CCR = 1 (interrupts inhibited). Read anytime.
To give a maskable interrupt source highest priority, write the low byte of
the vector address to the HPRIO register. For example, writing $F0 to
HPRIO would assign highest maskable interrupt priority to the real-time
interrupt timer ($FFF0). If an un-implemented vector address or a non-Imasked vector address (value higher than $F2) is written, then IRQ will
be the default highest priority interrupt.
10.7 Interrupt test registers
These registers are used in special modes for testing the interrupt logic
and priority without needing to know which modules and what functions
are used to generate the interrupts.Each bit is used to force a specific
interrupt vector by writing it to 1.Bits are named with B6 through F4 to
indicate vectors $FFB6 through $FFF4. These bits are also used in
special modes to view that an interrupt caused by a module has reached
the interrupt module.
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Resets
These registers can only be read in special modes (read in normal mode
will return $00). Reading these registers at the same time as the interrupt
is changing will cause an indeterminate value to be read. These
registers can only be written in special mode.
ITST0 — Interrupt Test Register 0
RESET:
Bit 7
ITE6
0
6
ITE8
0
$0018
5
ITEA
0
4
ITEC
0
3
ITEE
0
2
ITF0
0
1
ITF2
0
Bit 0
ITF4
0
ITST1 — Interrupt Test Register 1
RESET:
Bit 7
ITD6
0
6
ITD8
0
$0019
5
ITDA
0
4
ITDC
0
3
ITDE
0
2
ITE0
0
1
ITE2
0
Bit 0
ITE4
0
ITST2 — Interrupt Test Register 2
RESET:
Bit 7
ITC6
0
6
ITC8
0
$001A
5
ITCA
0
4
ITCC
0
3
ITCE
0
2
ITD0
0
1
ITD2
0
Bit 0
ITD4
0
ITST3 — Interrupt Test Register 3
RESET:
Bit 7
ITB6
0
6
ITB8
0
$001B
5
ITBA
0
4
ITBC
0
3
ITBE
0
2
ITC0
0
1
ITC2
0
Bit 0
ITC4
0
10.8 Resets
There are four possible sources of reset. Power-on reset (POR), and
external reset on the RESET pin share the normal reset vector. The
computer operating properly (COP) reset and the clock monitor reset
each has a vector. Entry into reset is asynchronous and does not require
a clock but the MCU cannot sequence out of reset without a system
clock.
10.8.1 Power-On Reset
A positive transition on VDD causes a power-on reset (POR). An external
voltage level detector, or other external reset circuits, are the usual
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source of reset in a system. The POR circuit only initializes internal
circuitry during cold starts and cannot be used to force a reset as system
voltage drops.
It is important to use an external low voltage reset circuit (for example:
MC34064 or MC33464) to prevent power transitions or corruption of
RAM or EEPROM.
10.8.2 External Reset
The CPU distinguishes between internal and external reset conditions
by sensing whether the reset pin rises to a logic one in less than nine Eclock cycles after an internal device releases reset. When a reset
condition is sensed, an internal circuit drives the RESET pin low and a
clocked reset sequence controls when the MCU can begin normal
processing. In the case of a clock monitor error, a 4096 cycle oscillator
start-up delay is imposed before the reset recovery sequence starts
(reset is driven low throughout this 4096 cycle delay). The internal reset
recovery sequence then drives reset low for 16 to 17 cycles and releases
the drive to allow reset to rise. Nine E-clock cycles later the reset pin is
sampled. If the pin is still held low, the CPU assumes that an external
reset has occurred. If the pin is high, it indicates that the reset was
initiated internally by either the COP system or the clock monitor.
To prevent a COP reset from being detected during an external reset,
hold the reset pin low for at least 32 cycles. To prevent a clock monitor
reset from being detected during an external reset, hold the reset pin low
for at least 4096 + 32 cycles. An external RC power-up delay circuit on
the reset pin is not recommended — circuit charge time can cause the
MCU to misinterpret the type of reset that has occurred.
10.8.3 COP Reset
The MCU includes a computer operating properly (COP) system to help
protect against software failures. When COP is enabled, software must
write $55 and $AA (in this order) to the COPRST register in order to keep
a watchdog timer from timing out. Other instructions may be executed
between these writes. A write of any value other than $55 or $AA or
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Effects of Reset
software failing to execute the sequence properly causes a COP reset to
occur. In addition, windowed COP operation can be selected. In this
mode, a write to the COPRST register must occur in the last 25% of the
selected period. A premature write will also reset the part.
10.8.4 Clock Monitor Reset
If clock frequency falls below a predetermined limit when the clock
monitor is enabled, a reset occurs.
10.9 Effects of Reset
When a reset occurs, MCU registers and control bits are changed to
known start-up states, as follows.
10.9.1 Operating Mode and Memory Map
Operating mode and default memory mapping are determined by the
states of the BKGD, MODA, and MODB pins during reset. The SMODN,
MODA, and MODB bits in the MODE register reflect the status of the
mode-select inputs at the rising edge of reset. Operating mode and
default maps can subsequently be changed according to strictly defined
rules.
10.9.2 Clock and Watchdog Control Logic
The COP watchdog system is enabled, with the CR[2:0] bits set for the
longest duration time-out. The clock monitor is disabled. The RTIF flag
is cleared and automatic hardware interrupts are masked. The rate
control bits are cleared, and must be initialized before the RTI system is
used. The DLY control bit is set to specify an oscillator start-up delay
upon recovery from STOP mode.
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10.9.3 Interrupts
PSEL is initialized in the HPRIO register with the value $F2, causing the
external IRQ pin to have the highest I-bit interrupt priority. The IRQ pin
is configured for level-sensitive operation (for wired-OR systems).
However, the interrupt mask bits in the CPU12 CCR are set to mask Xand I-related interrupt requests.
10.9.4 Parallel I/O
If the MCU comes out of reset in a single-chip mode, all ports are
configured as general-purpose high-impedance inputs.
If the MCU comes out of reset in an expanded mode, port A and port B
are used for the address/data bus, and port E pins are normally used to
control the external bus (operation of port E pins can be affected by the
PEAR register). Out of reset, port J, port H, port K, port IB, port P, port
S, port T, port AD0 and port AD1 are all configured as general-purpose
inputs.
10.9.5 Central Processing Unit
After reset, the CPU fetches a vector from the appropriate address, then
begins executing instructions. The stack pointer and other CPU registers
are indeterminate immediately after reset. The CCR X and I interrupt
mask bits are set to mask any interrupt requests. The S bit is also set to
inhibit the STOP instruction.
10.9.6 Memory
After reset, the internal register block is located from $0000 to $03FF,
RAM is at $2000 to $3FFF, and EEPROM is located at $0800 to $0FFF.
In single chip mode one 32-Kbyte FLASH EEPROM module is located
from $4000 to $7FFF and $C000 to $FFFF, and the other three 32-Kbyte
FLASH EEPROM modules are accessible through the program page
window located from $8000 to $BFFF. The first 32-Kbyte FLASH
EEPROM is also accessible through the program page window.
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Register Stacking
10.9.7 Other Resources
The enhanced capture timer (ECT), pulse width modulation timer
(PWM), serial communications interfaces (SCI0 and SCI1), serial
peripheral interface (SPI), inter-IC bus (IIC), Motorola Scalable CANs
(MSCAN0 and MSCAN1) and analog-to-digital converters (ATD0 and
ATD1) are off after reset.
10.10 Register Stacking
Once enabled, an interrupt request can be recognized at any time after
the I bit in the CCR is cleared. When an interrupt service request is
recognized, the CPU responds at the completion of the instruction being
executed. Interrupt latency varies according to the number of cycles
required to complete the instruction. Some of the longer instructions can
be interrupted and will resume normally after servicing the interrupt.
When the CPU begins to service an interrupt, the instruction queue is
cleared, the return address is calculated, and then it and the contents of
the CPU registers are stacked as shown in Table 10-2.
Table 10-2. Stacking Order on Entry to Interrupts
Memory Location
SP – 2
CPU Registers
RTNH : RTNL
SP – 4
YH : YL
SP – 6
XH : XL
SP – 8
SP – 9
B:A
CCR
After the CCR is stacked, the I bit (and the X bit, if an XIRQ interrupt
service request is pending) is set to prevent other interrupts from
disrupting the interrupt service routine. The interrupt vector for the
highest priority source that was pending at the beginning of the interrupt
sequence is fetched, and execution continues at the referenced location.
At the end of the interrupt service routine, an RTI instruction restores the
content of all registers from information on the stack, and normal
program execution resumes.
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If another interrupt is pending at the end of an interrupt service routine,
the register unstacking and restacking is bypassed and the vector of the
interrupt is fetched.
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Technical Data — MC68HC912DT128A
Section 11. I/O Ports with Key Wake-up
11.1 Contents
11.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
11.3
Key Wake-up and port Registers . . . . . . . . . . . . . . . . . . . . . . 150
11.4
Key Wake-Up Input Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
11.2 Introduction
The offers 16 additional I/O ports with key wake-up capability.
The key wake-up feature of the MC68HC912DT128A issues an interrupt
that will wake up the CPU when it is in the STOP or WAIT mode. Two
ports are associated with the key wake-up function: port H and port J.
Port H and port J wake-ups are triggered with either a rising or falling
signal edge. For each pin which has an interrupt enabled, there is a path
to the interrupt request signal which has no clocked devices when the
part is in stop mode. This allows an active edge to bring the part out of
stop.
Digital filtering is included to prevent pulses shorter than a specified
value from waking the part from STOP.
An interrupt is generated when a bit in the KWIFH or KWIFJ register and
its corresponding KWIEH or KWIEJ bit are both set. All 16 bits/pins share
the same interrupt vector. Key wake-ups can be used with the pins
configured as inputs or outputs.
Default register addresses, as established after reset, are indicated in
the following descriptions. For information on re-mapping the register
block, refer to Operating Modes.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
I/O Ports with Key Wake-up
149
I/O Ports with Key Wake-up
11.3 Key Wake-up and port Registers
PORTJ — Port J Register
$0028
Bit 7
6
5
4
3
2
1
Bit 0
PORT
PJ7
PJ6
PJ5
PJ4
PJ3
PJ2
PJ1
PJ0
KWU
KWJ7
KWJ6
KWJ5
KWJ4
KWJ3
KWJ2
KWJ1
KWJ0
RESET:
-
-
-
-
-
-
-
-
Read and write anytime.
PORTH — Port H Register
$0029
Bit 7
6
5
4
3
2
1
Bit 0
PH7
PH6
PH5
PH4
PH3
PH2
PH1
PH0
KWU
KWH7
KWH6
KWH5
KWH4
KWH3
KWH2
KWH1
KWH0
RESET:
-
-
-
-
-
-
-
-
Read and write anytime.
DDRJ — Port J Data Direction Register
$002A
Bit 7
6
5
4
3
2
1
Bit 0
DDJ7
DDJ6
DDJ5
DDJ4
DDJ3
DDJ2
DDJ1
DDJ0
0
0
0
0
0
0
0
0
RESET:
Data direction register J is associated with port J and designates each
pin as an input or output.
Read and write anytime
DDRJ[7:0] — Data Direction Port J
0 = Associated pin is an input
1 = Associated pin is an output
Technical Data
150
MC68HC912DT128A — Rev 4.0
I/O Ports with Key Wake-up
MOTOROLA
I/O Ports with Key Wake-up
Key Wake-up and port Registers
DDRH — Port H Data Direction Register
RESET:
$002B
Bit 7
6
5
4
3
2
1
Bit 0
DDH7
DDH6
DDH5
DDH4
DDH3
DDH2
DDH1
DDH0
0
0
0
0
0
0
0
0
Data direction register H is associated with port H and designates each
pin as an input or output. Read and write anytime.
DDRH[7:0] — Data Direction Port H
0 = Associated pin is an input
1 = Associated pin is an output
KWIEJ — Key Wake-up Port J Interrupt Enable Register
RESET:
$002C
Bit 7
6
5
4
3
2
1
Bit 0
KWIEJ7
KWIEJ6
KWIEJ5
KWIEJ4
KWIEJ3
KWIEJ2
KWIEJ1
KWIEJ0
0
0
0
0
0
0
0
0
Read and write anytime.
KWIEJ[7:0] — Key Wake-up Port J Interrupt Enables
0 = Interrupt for the associated bit is disabled
1 = Interrupt for the associated bit is enabled
KWIEH — Key Wake-up Port H Interrupt Enable Register
$002D
Bit 7
6
5
4
3
2
1
Bit 0
KWIEH7
KWIEH6
KWIEH5
KWIEH4
KWIEH3
KWIEH2
KWIEH1
KWIEH0
0
0
0
0
0
0
0
0
RESET:
Read and write anytime.
KWIEH[7:0] — Key Wake-up Port H Interrupt Enables
0 = Interrupt for the associated bit is disabled
1 = Interrupt for the associated bit is enabled
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
I/O Ports with Key Wake-up
151
I/O Ports with Key Wake-up
KWIFJ — Key Wake-up Port J Flag Register
$002E
Bit 7
6
5
4
3
2
1
Bit 0
KWIFJ7
KWIFJ6
KWIFJ5
KWIFJ4
KWIFJ3
KWIFJ2
KWIFJ1
KWIFJ0
0
0
0
0
0
0
0
0
RESET:
Read and write anytime.
Each flag is set by an active edge on its associated input pin. This could
be a rising or falling edge based on the state of the KWPJ register. To
clear the flag, write one to the corresponding bit in KWIFJ.
Initialize this register after initializing KWPJ so that illegal flags can be
cleared.
KWIFJ[7:0] — Key Wake-up Port J Flags
0 = Active edge on the associated bit has not occurred
1 = Active edge on the associated bit has occurred (an interrupt will
occur if the associated enable bit is set).
KWIFH — Key Wake-up Port H Flag Register
$002F
Bit 7
6
5
4
3
2
1
Bit 0
KWIFH7
KWIFH6
KWIFH5
KWIFH4
KWIFH3
KWIFH2
KWIFH1
KWIFH0
0
0
0
0
0
0
0
0
RESET:
Read and write anytime.
Each flag is set by an active edge on its associated input pin. This could
be a rising or falling edge based on the state of the KWPH register. To
clear the flag, write one to the corresponding bit in KWIFH.
Initialize this register after initializing KWPH so that illegal flags can be
cleared.
KWIFH[7:0] — Key Wake-up Port H Flags
0 = Active edge on the associated bit has not occurred
1 = Active edge on the associated bit has occurred (an interrupt will
occur if the associated enable bit is set)
Technical Data
152
MC68HC912DT128A — Rev 4.0
I/O Ports with Key Wake-up
MOTOROLA
I/O Ports with Key Wake-up
Key Wake-up and port Registers
KWPJ — Key Wake-up Port J Polarity Register
RESET:
$0030
Bit 7
6
5
4
3
2
1
Bit 0
KWPJ7
KWPJ6
KWPJ5
KWPJ4
KWPJ3
KWPJ2
KWPJ1
KWPJ0
0
0
0
0
0
0
0
0
Read and write anytime. It is best to clear the flags after initializing this
register because changing the polarity of a bit can cause the associated
flag to become set.
KWPJ[7:0] — Key Wake-up Port J Polarity Selects
0 = Falling edge on the associated port J pin sets the associated
flag bit in the KWIFJ register and a resistive pull-up device is
connected to associated port J input pin.
1 = Rising edge on the associated port J pin sets the associated
flag bit in the KWIFJ register and a resistive pull-down device
is connected to associated port J input pin.
KWPH — Key Wake-up Port H Polarity Register
$0031
Bit 7
6
5
4
3
2
1
Bit 0
KWPH7
KWPH6
KWPH5
KWPH4
KWPH3
KWPH2
KWPH1
KWPH0
0
0
0
0
0
0
0
0
RESET:
Read and write anytime. It is best to clear the flags after initializing this
register because changing the polarity of a bit can cause the associated
flag to become set.
KWPH[7:0] — Key Wake-up Port H Polarity Selects
0 = Falling edge on the associated port H pin sets the associated
flag bit in the KWIFH register and a resistive pull-up device is
connected to associated port H input pin.
1 = Rising edge on the associated port H pin sets the associated
flag bit in the KWIFH register and a resistive pull-down device
is connected to associated port H input pin.
MC68HC912DT128A — Rev 4.0
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Technical Data
I/O Ports with Key Wake-up
153
I/O Ports with Key Wake-up
11.4 Key Wake-Up Input Filter
The KWU input signals are filtered by a digital filter which is active only
during STOP mode.
The purpose of the filter is to prevent single pulses shorter than a
specified value from waking the part from STOP.
The filter is composed of an internal oscillator and a majority voting logic.
The filter oscillator starts the oscillation by detecting a triggering edge on
an input if the corresponding interrupt enable bit is set.
The majority voting logic takes three samples of an asserted input pin at
each filter oscillator period and if two samples are taken at the triggering
level, the filter recognizes a valid triggering level and sets the
corresponding interrupt flag. In this way the majority voting logic rejects
the short non-triggering state between two incoming triggering pulses.
As the filter is shared with all KWU inputs, the filter considers any pulse
coming from any input pin for which the corresponding interrupt enable
bit is set.
The timing specification is given for a single pulse. The time interval
between the triggering edges of two following pulses should be greater
than the tKWSP in order to be considered as a single pulse by the filter. If
this time interval is shorter than tKWSP, the majority voting logic may treat
the two consecutive pulses as a single valid pulse.
The filter is shared by all the KWU pins. Hence any valid triggering level
on any KWU pin is seen by the filter. The timing specification applies to
the input of the filter.
Technical Data
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MC68HC912DT128A — Rev 4.0
I/O Ports with Key Wake-up
MOTOROLA
I/O Ports with Key Wake-up
Key Wake-Up Input Filter
Glitch, filtered out, no STOP wake-up
Valid STOP Wake-Up pulse
tKWSTP min.
tKWSTP max.
Minimum time interval between pulses to be recognized as single pulses
tKWSP
Figure 11-1. STOP Key Wake-up Filter
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
I/O Ports with Key Wake-up
155
I/O Ports with Key Wake-up
Technical Data
156
MC68HC912DT128A — Rev 4.0
I/O Ports with Key Wake-up
MOTOROLA
Technical Data — MC68HC912DT128A
Section 12. Clock Functions
12.1 Contents
12.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
12.3
Clock Sources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
12.4
Phase-Locked Loop (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
12.5
Acquisition and Tracking Modes. . . . . . . . . . . . . . . . . . . . . . .161
12.6
Limp-Home and Fast STOP Recovery modes . . . . . . . . . . . . 163
12.7
System Clock Frequency Formulae . . . . . . . . . . . . . . . . . . . . 181
12.8
Clock Divider Chains . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
12.9
Computer Operating Properly (COP) . . . . . . . . . . . . . . . . . . .185
12.10 Real-Time Interrupt. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
12.11 Clock Monitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .186
12.12 Clock Function Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
12.2 Introduction
Clock generation circuitry generates the internal and external E-clock
signals as well as internal clock signals used by the CPU and on-chip
peripherals. A clock monitor circuit, a computer operating properly
(COP) watchdog circuit, and a periodic interrupt circuit are also
incorporated into the MC68HC912DT128A.
MC68HC912DT128A — Rev 4.0
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Technical Data
Clock Functions
157
Clock Functions
12.3 Clock Sources
A compatible external clock signal can be applied to the EXTAL pin or
the MCU can generate a clock signal using an on-chip oscillator circuit
and an external crystal or ceramic resonator. The MCU uses several
types of internal clock signals derived from the primary clock signal:
TxCLK clocks are used by the CPU.
ECLK and PCLK are used by the bus interfaces, SPI, PWM, ATD0 and
ATD1.
MCLK is either PCLK or XCLK, and drives on-chip modules such as
SCI0, SCI1 and ECT.
XCLK drives on-chip modules such as RTI, COP and restart-from-stop
delay time.
SLWCLK is used as a calibration output signal.
The MSCAN module is clocked by EXTALi or SYSCLK, under control of
an MSCAN bit.
The clock monitor is clocked by EXTALi.
The BDM system is clocked by BCLK or ECLK, under control of a BDM
bit.
A slow mode clock divider is included to deliver a lower clock frequency
for the SCI baud rate generators, the ECT timer module, and the RTI and
COP clocks. The slow clock bus frequencies divide the crystal frequency
in a programmable range of 4 to 252, with steps of 4. This is very useful
for low power operation.
See the Clock Divider Chains section for further details. Figure 12-1
shows some of the timing relationships.
Technical Data
158
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Phase-Locked Loop (PLL)
T1CLK
T2CLK
T3CLK
T4CLK
INT ECLK
PCLK
XCLK
CANCLK
Figure 12-1. Internal Clock Relationships
12.4 Phase-Locked Loop (PLL)
The phase-locked loop (PLL) of the MC68HC912DT128A is designed for
robust operation in an Automotive environment. The allowed PLL crystal
or ceramic resonator reference of 0.5 to 8MHz is selected for the wide
availability of components with good stability over the automotive
temperature range. Please refer to Figure 12-6 in section Clock Divider
Chains for an overview of system clocks.
NOTE:
When selecting a crystal, it is recommended to use one with the lowest
possible frequency in order to minimise EMC emissions.
An oscillator design with reduced power consumption allows for slow
wait operation with a typical power supply current less than a milliampere. The PLL circuitry can be bypassed when the VDDPLL supply is
at VSS level. In this case, the PLL module is powered down and the
oscillator output transistor has a stronger transconductance for improved
drive of higher frequency resonators (as the crystal frequency needs to
be twice the maximum bus frequency). Refer to Figure 3-4 in Pinout and
Signal Descriptions.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
159
Clock Functions
EXTAL
REDUCED
CONSUMPTION
OSCILLATOR
LOCK
LOCK
DETECTOR
REFDV <2:0>
REFERENCE
PROGRAMMABLE
DIVIDER
REFCLK
XTAL
EXTALi
DIVCLK
PDET
PHASE
DETECTOR
UP
DOWN
CPUMP
VCO
VDDPLL
SLOW MODE
PROGRAMMABLE
CLOCK DIVIDER
SLWCLK
LOOP
PROGRAMMABLE
DIVIDER
LOOP
FILTER
÷2
SLDV <5:0>
EXTALi
SYN <5:0>
XFC
PAD
×2
PLLCLK
XCLK
Figure 12-2. PLL Functional Diagram
The PLL may be used to run the MCU from a different time base than the
incoming crystal value. It creates an integer multiple of a reference
frequency. For increased flexibility, the crystal clock can be divided by
values in a range of 1 – 8 (in unit steps) to generate the reference
frequency. The PLL can multiply this reference clock in a range of 1 to
64. Although it is possible to set the divider to command a very high clock
frequency, do not exceed the specified bus frequency limit for the MCU.
If the PLL is selected, it will continue to run when in WAIT mode resulting
in more power consumption than normal. To take full advantage of the
reduced power consumption of WAIT mode, turn off the PLL before
going into WAIT. Please note that in this case the PLL stabilization time
applies.
The PLL operation is suspended in STOP mode. After STOP exit
followed by the stabilization time, it resumes operation at the same
frequency, provided the AUTO bit is set.
A passive external loop filter must be placed on the control line (XFC
pad). The filter is a second-order, low-pass filter to eliminate the VCO
input ripple. Values of components in the diagram are dependent upon
the desired VCO operation. See XFC description.
Technical Data
160
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Acquisition and Tracking Modes
12.5 Acquisition and Tracking Modes
The lock detector compares the frequencies of the VCO feedback clock,
DIVCLK, and the final reference clock, REFCLK. Therefore, the speed
of the lock detector is directly proportional to the final reference
frequency. The circuit determines the mode of the PLL and the lock
condition based on this comparison.
The PLL filter is manually or automatically configurable into one of two
operating modes:
•
Acquisition mode — In acquisition mode, the filter can make large
frequency corrections to the VCO. This mode is used at PLL startup or when the PLL has suffered a severe noise hit and the VCO
frequency is far off the desired frequency. This mode can also be
desired in harsh environments when the leakage levels on the
filter pin (XFC) can overcome the tracking currents of the PLL
charge pump. When in acquisition mode, the ACQ bit in the PLL
control register is clear.
•
Tracking mode — In tracking mode, the filter makes only small
corrections to the frequency of the VCO. The PLL enters tracking
mode when the VCO frequency is nearly correct. The PLL is
automatically in tracking mode when not in acquisition mode or
when the ACQ bit is set.
The PLL can change the bandwidth or operational mode of the loop filter
manually or automatically. With an identical filtering time constant, the
PLL bandwidth is larger in acquisition mode than in tracking by a ratio of
about 3.
In automatic bandwidth control mode (AUTO = 1), the lock detector
automatically switches between acquisition and tracking modes.
Automatic bandwidth control mode also is used to determine when the
VCO clock, PLLCLK, is safe to use as the source for the base clock,
SYSCLK. If PLL LOCK interrupt requests are enabled, the software can
wait for an interrupt request and then check the LOCK bit. If CPU
interrupts are disabled, software can poll the LOCK bit continuously
(during PLL start-up, usually) or at periodic intervals. In either case,
when the LOCK bit is set, the PLLCLK clock is safe to use as the source
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
161
Clock Functions
for the base clock. See Clock Divider Chains. If the VCO is selected as
the source for the base clock and the LOCK bit is clear, the PLL has
suffered a severe noise hit and the software must take appropriate
action, depending on the application.
The following conditions apply when the PLL is in automatic bandwidth
control mode:
•
The ACQ bit is a read-only indicator of the mode of the filter.
•
The ACQ bit is set when the VCO frequency is within a certain
tolerance, ∆trk, and is cleared when the VCO frequency is out of a
certain tolerance, ∆unt. See 19 Electrical Characteristics.
•
The LOCK bit is a read-only indicator of the locked state of the PLL.
•
The LOCK bit is set when the VCO frequency is within a certain
tolerance, ∆Lock, and is cleared when the VCO frequency is out of
a certain tolerance, ∆unl. See 19 Electrical Characteristics.
•
CPU interrupts can occur if enabled (LOCKIE = 1) when the lock
condition changes, toggling the LOCK bit.
The PLL also can operate in manual mode (AUTO = 0). All LOCK
features described above are active in this mode, only the bandwidth
control is disabled. Manual mode is used mainly for systems operating
under harsh conditions (e.g.uncoated PCBs in automotive
environments). When this is the case, the PLL is likely to remain in
acquisition mode. The following conditions apply when in manual mode:
•
ACQ is a writable control bit that controls the mode of the filter.
Before turning on the PLL in manual mode, the ACQ bit must be
clear.
•
In case tracking is desired (ACQ = 1), the software must wait a
given time, tacq, after turning on the PLL by setting PLLON in the
PLL control register. This is to avoid switching to tracking mode
too early while the XFC voltage level is still too far away from its
quiescent value corresponding to the target frequency. This
operation would be very detrimental to the stabilization time.
Technical Data
162
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
12.6 Limp-Home and Fast STOP Recovery modes
If the crystal frequency is not available due to a crystal failure or a long
crystal start-up time, the MCU system clock can be supplied by the VCO
at its minimum operating frequency, f VCOMIN. This mode of operation is
called Limp-Home Mode and is only available when the VDDPLL supply
voltage is at VDD level (i.e. power supply for the PLL module is present).
Upon power-up, the ability of the system to start in Limp-Home Mode is
restricted to normal MCU modes only.
The Clock Monitor circuit (see section Clock Monitor) can detect the loss
of EXTALi, the external clock input signal, regardless of whether this
signal is used as the source for MCU clocks or as the PLL reference
clock. The clock monitor control bits, CME and FCME, are used to
enable or disable external clock detection.
A missing external clock may occur in the three following instances:
•
During normal clock operation.
•
At Power-On Reset.
•
In the STOP exit sequence
12.6.1 Clock Loss during Normal Operation
The ‘no limp-home mode’ bit, NOLHM, determines how the MCU
responds to an external clock loss in this case.
With limp home mode disabled (NOLHM bit set) and the clock monitor
enabled (CME or FCME bits set), on a loss of clock the MCU is reset via
the clock monitor reset vector. A latch in the PLL control section prevents
the chip exiting reset in Limp Home Mode (this is required as the NOLHM
bit gets cleared bu reset). Only external clock activity can bring the MCU
out from this reset state. Once reset has been exited, the latch is cleared
and another session, with or without Limp Home Mode enabled, can
take place. This is the same behavior as standard M68HC12 circuits
without PLL or operation with VDDPLL at VSS level.
With limp home mode enabled (NOLHM bit cleared) and the clock
monitor enabled (CME or FCME bits set), on a loss of clock, the PLL
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
163
Clock Functions
VCO clock at its minimum frequency, f VCOMIN, is provided as the system
clock, allowing the MCU to continue operating.
The MCU is said to be operating in “limp-home” mode with the forced
VCO clock as the system clock. PLLON and BCSP (‘bus clock select
PLL’) signals are forced high and the MCS (‘module clock select’) signal
is forced low. The LHOME flag in the PLLFLG register is set to indicate
that the MCU is running in limp-home mode. A change of this flag sets
the limp-home interrupt flag, LHIF, and if enabled by the LHIE bit, the
limp-home mode interrupt is requested. The Clock Monitor is enabled
irrespective of CME and FCME bit settings. Module clocks to the RTI &
COP (XCLK), BDM (BCLK) and ECT & SCI (MCLK) are forced to be
PCLK (at f VCOMIN) and ECLK is also equal to f VCOMIN. MSCAN clock
select is unaffected.
EXTALi
A
B
Clock Monitor Fail
0 --> 4096
0 --> 4096
13-stage counter
(Clocked by XCLK)
Limp-Home
BCSP
SYSCLK
Restore BCSP
PLLCLK (Limp-Home)
Restore PLLCLK or EXTALi
Figure 12-3. Clock Loss during Normal Operation
The clock monitor is polled each time the 13-stage free running counter
reaches a count of 4096 XCLK cycles i.e. mid-count, hence the clock
status gets checked once every 8192 XCLK cycles. When the presence
of an external clock is detected, the MCU exits limp-home mode,
clearing the LHOME flag and setting the limp-home interrupt flag. Upon
leaving limp-home mode, BCSP and MCS signals are restored to their
Technical Data
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MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
values before the clock loss. All clocks return to their normal settings and
Clock Monitor control is returned to the CME & FCME bits. If AUTO and
BCSP bits were set before the clock loss (selecting the PLL to provide a
system clock) the SYSCLK ramps-up and the PLL locks at the previously
selected frequency. To prevent PLL operation when the external clock
frequency comes back, software should clear the BCSP bit while running
in limp-home mode.
The two shaded regions A and B in Figure 12-3 present a of code run
away due to incorrect clocks on SYSCLK if the MCU is clocked by
EXTALi and the PLL is not used.
In region A, there is a delay between the loss of clock and its detection
by the clock monitor. When the EXTALi clock signal is disturbed, the
clock generation circuitry may receive an out of spec signal and drive the
CPU with irregular clocks. This may lead to code runaway.
In region B, as the 13-stage counter is free running, the count of 4096
may be reached when the amplitude of the EXTALi clock has not
stabilized. In this case, an improper EXTALi is sent to the clock
generation circuitry when limp-home mode is exited. This may also
cause code runaway.
If the MCU is clocked by the PLL, the risk of code runaway is very
low, but it can still occur under certain conditions due to irregular
clocks from the clock source appearing on the SYSCLK.
CAUTION:
NOTE:
The COP watch dog should always be enabled in order to reset the MCU
in case of a code runaway situation.
It is always advisable to take additional precautions within the
application software to trap such situations.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
165
Clock Functions
12.6.2 No Clock at Power-On Reset
The voltage level on VDDPLL determines how the MCU responds to an
external clock loss in this case.
With the VDDPLL supply voltage at VDD level, any reset sets the Clock
Monitor Enable bit (CME) and the PLLON bit and clears the NOLHM bit.
Therefore, if the MCU is powered up without an external clock, limphome mode is entered provided the MCU is in a normal mode of
operation.
VDD
Power-On Detector
EXTALi
(Slow EXTALi)
Clock Monitor Fail
Limp-Home
13-stage counter
(Clocked by XCLK)
0 --> 4096
0 --> 4096
BCSP
Reset: BCSP = 0
Internal reset
SYSCLK
SYSCLK
(Slow EXTALi)
PLLCLK (L.H.)
EXTALi
PLLCLK (Software check of Limp-Home Flag)
EXTALi
Figure 12-4. No Clock at Power-On Reset
Technical Data
166
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
During this power up sequence, after the POR pulse falling edge, the
VCO supplies the limp-home clock frequency to the 13-stage counter, as
the BCSP output is forced high and MCS is forced low. XCLK, BCLK and
MCLK are forced to be PCLK, which is supplied by the VCO at fVCOMIN.
The initial period taken for the 13-stage counter to reach 4096 defines
the internal reset period.
If the clock monitor indicates the presence of an external clock during the
internal reset period, limp-home mode is de-asserted and the 13-stage
counter is then driven by EXTALi clock. After the 13-stage counter
reaches a count of 4096 XCLK cycles, the internal reset is released, the
13-stage counter is reset and the MCU exits reset normally using
EXTALi clock.
However, if the crystal start-up time is longer than the initial count of
4096 XCLK cycles, or in the absence of an external clock, the MCU will
leave the reset state in limp-home mode. The LHOME flag is set and
LHIF limp-home interrupt request is set, to indicate it is not operating at
the desired frequency. Then after yet another 4096 XCLK cycles
followed regularly by 8192 XCLK cycles (corresponding to the 13-stage
counter timing out), a check of the clock monitor status is performed.
When the presence of an external clock is detected limp-home mode is
exited generating a limp-home interrupt if enabled.
CAUTION:
The clock monitor circuit can be misled by the EXTALi clock into
reporting a good signal before it has fully stabilised. Under these
conditions improper EXTALi clock cycles can occur on SYSCLK. This
may lead to a code runaway. To ensure that this situation does not
occur, the external Reset period should be longer than the oscillator
stabilisation time - this is an application dependent parameter.
With the VDDPLL supply voltage at VSS level, the PLL module and
hence limp-home mode are disabled, the device will remain effectively
in a static state whilst there is no activity on EXTALi. The internal reset
period and MCU operation will execute only on EXTALi clock.
NOTE:
The external clock signal must stabilise within the initial 4096 reset
counter cycles.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
167
Clock Functions
12.6.3 STOP Exit and Fast STOP Recovery
Stop mode is entered when a STOP instruction is executed. Recovery
from STOP depends primarily on the state of the three status bits
NOLHM, CME & DLY.
The DLY bit controls the duration of the waiting period between the
actual exit for some key blocks (e.g. clock monitor, clock generators) and
the effective exit from stop for all the rest of the MCU. DLY=1 enables
the 13-stage counter to generate a 4096 count delay. DLY=0 selects no
delay. As the XCLK is derived from the slow mode divider, the value in
the SLOW register modifies the actual delay time.
NOTE:
DLY=0 is only recommended when there is a good signal available
at the EXTAL pin (e.g. an external square wave source).
STOP mode is exited with an external reset, an external interrupt from
IRQ or XIRQ, a Key Wake-Up interrupt from port J or port H, or an
MSCAN Wake-Up interrupt.
EXTALi
Clock Monitor Fail
Limp-Home
13-stage counter
(Clocked by XCLK)
0 --> 4096
BCSP
Restore BCSP
STOP (DLY = 1)
STOP (DLY = 0)
SYSCLK
PLLCLK (L.H.)
Restore PLLCLK or EXTALi
Figure 12-5. STOP Exit and Fast STOP Recovery
Technical Data
168
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
12.6.4 STOP exit without Limp Home mode, clock monitor disabled
(NOLHM=1, CME=0, DLY=X)
If Limp home mode is disabled (VDDPLL=VSS or NOLHM bit set) and the
CME (or FCME) bit is cleared, the MCU goes into STOP mode when a
STOP instruction is executed.
If EXTALi clock is present then exit from STOP will occur normally using
this clock. Under this condition, DLY should always be set to allow the
crystal to stabilise and minimise the risk of code runaway. With DLY=1
execution resumes after a delay of 4096 XCLK cycles.
NOTE:
The external clock signal should stabilise within the 4096 reset counter
cycles. Use of DLY=0 is not recommended due to this requirement.
12.6.5 Executing the STOP instruction without Limp Home mode, clock monitor enabled
(NOLHM=1, CME=1, DLY=X)
If the NOLHM bit and the CME (or FCME) bits are set, a clock monitor
failure is detected when a STOP instruction is executed and the MCU
resets via the clock monitor reset vector.
12.6.6 STOP exit in Limp Home mode with Delay
(NOLHM=0, CME=X, DLY=1)
If the NOLHM bit is cleared, then the CME (or FCME) bit is masked when
a STOP instruction is executed to prevent a clock monitor failure. When
coming out of STOP mode, the MCU goes into limp-home mode where
CME and FCME signals are asserted.
When using a crystal oscillator, a normal STOP exit sequence requires
the DLY bit to be set to allow for the crystal stabilization period.
With the 13-stage counter clocked by the VCO (at fVCOMIN), following a
delay of 4096 XCLK cycles at the limp-home frequency, if the clock
monitor indicates the presence of an external clock, the limp-home mode
is de-asserted and the MCU exits STOP normally using EXTALi clock.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
169
Clock Functions
Where the crystal start-up time is longer than the initial count of 4096
XCLK cycles, or in the absence of an external clock, the MCU recovers
from STOP following the 4096 count in limp-home mode with both the
LHOME flag set and the LHIF limp-home interrupt request set to indicate
it is not operating at the desired frequency. Each time the 13-stage
counter reaches a count of 4096 XCLK cycles, a check of the clock
monitor status is performed.
When the presence of an external clock is detected, limp-home mode is
exited and the LHOME flag is cleared. This sets the limp-home interrupt
flag and if enabled by the LHIE bit, the limp-home mode interrupt is
requested.
CAUTION:
The clock monitor circuit can be misled by EXTALi clock into reporting a
good signal before it has fully stabilised. Under these conditions,
improper EXTALi clock cycles can occur on SYSCLK. This may lead to
a code runaway.
12.6.7 STOP exit in Limp Home mode without Delay (Fast Stop Recovery)
(NOLHM=0, CME=X, DLY=0)
Fast STOP recovery refers to any exit from STOP using DLY=0.
If the NOLHM bit is cleared, then the CME (or FCME) bit is masked when
a STOP instruction is executed to prevent a clock monitor failure. When
coming out of STOP mode, the MCU goes into limp-home mode where
CME and FCME signals are asserted.
When using a crystal oscillator, it is possible to exit STOP with the DLY
bit cleared. In this case, STOP is de-asserted without delay and the MCU
will execute software in limp-home mode, giving the crystal oscillator
time to stablise.
CAUTION:
This mode is not recommended since the risk of the clock monitor
detecting incorrect clocks is high.
Technical Data
170
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
Each time the 13-stage counter reaches a count of 4096 XCLK cycles
(every 8192 cycles), a check of the clock monitor status is performed. If
the clock monitor indicates the presence of an external clock limp-home
mode is de-asserted, the LHOME flag is cleared and the limp-home
interrupt flag is set. Upon leaving limp-home mode, BCSP and MCS are
restored to their values before the loss of clock, and all clocks return to
their previous frequencies. If AUTO and BCSP were set before the clock
loss, the SYSCLK ramps-up and the PLL locks at the previously selected
frequency.
To prevent PLL operation when the external clock frequency comes
back, the software should clear the BCSP bit while running in limp-home
mode.
When using an external clock, i.e. a square wave source, it is possible
to exit STOP with the DLY bit cleared. In this case the LHOME flag is
never set and STOP is de-asserted without delay.
12.6.8 Pseudo-STOP
Pseudo-STOP is a low power mode similar to STOP where the external
oscillator is allowed to run (at reduced amplitude) whilst the rest of the
part is in STOP. This increases the current consumption over STOP
mode by the amount of current in the oscillator, but reduces wear and
mechanical stress on the crystal.
If the PSTP bit in the PLLCR register is set, the MCU goes into PseudoSTOP mode when a STOP instruction is executed.
Pseudo-STOP mode is exited the same as STOP with an external reset,
an external interrupt from IRQ or XIRQ, a Key Wake-Up interrupt from
port J or port H, or an MSCAN Wake-Up interrupt.
The effect of the DLY bit is the same as noted above in STOP Exit and
Fast STOP Recovery.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
171
Clock Functions
12.6.9 Pseudo-STOP exit in Limp Home mode with Delay
(NOLHM=0, CME=X, DLY=1)
When coming out of Pseudo-STOP mode with the NOLHM bit cleared
and the DLY bit set, the MCU goes into limp-home mode (regardless of
the state of the CME or FCME bits).
The VCO supplies the limp-home clock frequency to the 13-stage
counter (XCLK). The BCSP output is forced high and MCS is forced low.
After the 13-stage counter reaches a count of 4096 XCLK cycles, a
check of the clock monitor is performed and as the crystal oscillator was
kept running due to the Pseudo-stop mode, the MCU exits STOP
normally, using the EXTALi clock. In the case where a crystal failure
occurred during pseudo-stop, then the MCU exits STOP using the limp
home clock (fVCOMIN) with both the LHOME flag set and the LHIF limphome interrupt request set to indicate it is not operating at the desired
frequency. Each time the 13-stage counter reaches a count of 4096
XCLK cycles, a check of the clock monitor is performed. If the clock
monitor indicates the presence of an external clock, limp-home mode is
de-asserted, the LHOME flag is cleared and the LHIF limp-home
interrupt request is set to indicate a return to normal operation using
EXTALi clock.
12.6.10 Pseudo-STOP exit in Limp Home mode without Delay (Fast Stop Recovery)
(NOLHM=0, CME=X, DLY=0)
If Pseudo-STOP is exited with the NOLHM bit set to 0 and the DLY bit is
cleared then the exit from Pseudo-STOP is accomplished without delay
as in Fast STOP recovery.
CAUTION:
Where Pseudo-STOP recovers using the Limp Home Clock the VCO which has been held in STOP - must be restarted in order to supply the
limp home frequency. This restart, which occurs at a high frequency and
ramps toward the limp home frequency, is almost immediately supplied
to the CPU before it may have reached the steady state frequency. It is
possible that the initial clock frequency may be high enough to cause the
CPU to function incorrectly with a resultant risk of code runaway.
Technical Data
172
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
12.6.11 Pseudo-STOP exit without Limp Home mode, clock monitor enabled
(NOLHM=1, CME=1, DLY=X)
If the NOLHM bit is set and the CME (or FCME) bits are set, a clock
monitor failure is detected when a STOP instruction is executed and the
MCU resets via the clock monitor reset vector.
12.6.12 Pseudo-STOP exit without Limp Home mode, clock monitor disabled
(NOLHM=1, CME=0, DLY=1)
If NOLHM is set to 1 and the CME and FCME bits are cleared, the limp
home clock is not used. In this mode, crystal activity is the only method
by which the device may recover from Pseudo-STOP. The device will
start execution with the EXTALi clock following 4096 XCLK cycles.
(NOLHM=1, CME=0, DLY=0)
If NOLHM is set to 1 and the CME and FCME bits are cleared, the limp
home clock is not used. In this mode, crystal activity is the only method
by which the device may recover from Pseudo-STOP. The device will
start execution with the EXTALi clock following 16 XCLK cycles.
CAUTION:
Due to switching of the clock this configuration is not recommended.
12.6.13 Summary of STOP and pseudo-STOP Mode Exit Conditions
Table 12-1 and Table 12-2 summarise the exit conditions from STOP
and pseudo-STOP modes using Interrupt, Key-interrupt and XIRQ.
A short RESET pulse should not be used to exit stop or pseudo-STOP
mode because Limp Home mode is automatically entered after RESET
(when VDDPLL=VDD). The RESET wakeup pulse must be longer than the
oscillator startup time (as in power on reset) in order to remove the risk
of code runaway.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
173
Clock Functions
. .
Table 12-1. Summary of STOP Mode Exit Conditions
Mode
Conditions
Summary
STOP exit without Limp Home
mode,
clock monitor disabled
NOLHM=1
CME=0
DLY=X
Oscillator must be stable within 4096 XCLK cycles. XCLK
can be modified by SLOW divider register.
Use of DLY=0 only recommended with external clock.
Executing the STOP instruction
without Limp Home mode,
clock monitor enabled
NOLHM=1
CME=1
DLY=X
When a STOP instruction is executed the MCU resets via
the clock monitor reset vector.
STOP exit in Limp Home mode
with Delay
NOLHM=0
CME=X
DLY=1
Oscillator must be stable within 4096
fVCOMIN cycles or there is a possibility of code runaway as
the clock monitor circuit can be misled by EXTALi clock
into reporting a good signal before it has fully stabilised
STOP exit in Limp Home mode
without Delay (Fast Stop
Recovery)
NOLHM=0
CME=X
DLY=0
This mode is only recommended for use with an external
clock source.
Table 12-2. Summary of Pseudo STOP Mode Exit Conditions
Mode
Conditions
Summary
Pseudo-STOP exit in Limp Home
mode with Delay
NOLHM=0
CME=X
DLY=1
CPU exits stop in limp home mode and oscillator running. If
the oscillator fails during pseudo-STOP and then recovers
there is a possibility of code runaway as the clock monitor
circuit can be misled by EXTALi clock into reporting a
good signal before it has fully stabilised
Pseudo-STOP exit
in Limp Home mode without
Delay (Fast Stop Recovery)
NOLHM=0
CME=X
DLY=0
This mode is not recommended as it is possible that the
initial VCO clock frequency may be high enough to cause
code runaway.
Pseudo-STOP exit without Limp
Home mode, clock monitor
enabled
NOLHM=1
CME=1
DLY=X
When a STOP instruction is executed the MCU resets via
the clock monitor reset vector.
Pseudo-STOP exit without Limp
Home mode, clock monitor
disabled, with Delay
NOLHM=1
CME=0
DLY=1
Oscillator starts operation following 4096 XCLK cycles
(actual controlled by SLOW mode divider).
Pseudo-STOP exit without Limp
Home mode, clock monitor
disabled, without Delay
NOLHM=1
CME=0
DLY=0
This mode is only recommended for use with an external
clock source.
Technical Data
174
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
12.6.14 PLL Register Descriptions
RESET:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
SYN5
SYN4
SYN3
SYN2
SYN1
SYN0
0
0
0
0
0
0
0
0
SYNR — Synthesizer Register
$0038
Read anytime, write anytime, except when BCSP = 1 (PLL selected as
bus clock).
If the PLL is on, the count in the loop divider (SYNR) register effectively
multiplies up the bus frequency from the PLL reference frequency by
SYNR + 1. Internally, SYSCLK runs at twice the bus frequency. Caution
should be used not to exceed the maximum rated operating frequency
for the CPU.
RESET:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
REFDV2
REFDV1
REFDV0
0
0
0
0
0
0
0
0
REFDV — Reference Divider Register
$0039
Read anytime, write anytime, except when BCSP = 1.
The reference divider bits provides a finer granularity for the PLL
multiplier steps. The reference frequency is divided by REFDV + 1.
Bit 7
6
5
4
3
2
1
Bit 0
TSTOUT7
TSTOUT6
TSTOUT5
TSTOUT4
TSTOUT3
TSTOUT2
TSTOUT1
TSTOUT0
0
0
0
0
0
0
0
0
RESET:
CGTFLG — Clock Generator Test Register
$003A
Always reads zero, except in test modes.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
175
Clock Functions
Bit 7
6
5
4
3
2
1
Bit 0
LOCKIF
LOCK
0
0
0
0
LHIF
LHOME
0
0
0
0
0
0
0
0
RESET:
PLLFLG — PLL Flags
$003B
Read anytime, refer to each bit for write conditions.
LOCKIF — PLL Lock Interrupt Flag
0 = No change in LOCK bit.
1 = LOCK condition has changed, either from a locked state to an
unlocked state or vice versa.
To clear the flag, write one to this bit in PLLFLG. Cleared in limp-home
mode.
LOCK — Locked Phase Lock Loop Circuit
Regardless of the bandwidth control mode (automatic or manual):
0 = PLL VCO is not within the desired tolerance of the target
frequency.
1 = After the phase lock loop circuit is turned on, indicates the PLL
VCO is within the desired tolerance of the target frequency.
Write has no effect on LOCK bit. This bit is cleared in limp-home mode as
the lock detector cannot operate without the reference frequency.
LHIF — Limp-Home Interrupt Flag
0 = No change in LHOME bit.
1 = LHOME condition has changed, either entered or exited limphome mode.
To clear the flag, write one to this bit in PLLFLG.
LHOME — Limp-Home Mode Status
0 = MCU is operating normally, with EXTALi clock available for
generating clocks or as PLL reference.
1 = Loss of reference clock. CGM delivers PLL VCO limp-home
frequency to the MCU.
For Limp-Home mode, see Limp-Home and Fast STOP Recovery
modes.
Technical Data
176
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
Bit 7
6
5
4
3
2
1
Bit 0
LOCKIE
PLLON
AUTO
ACQ
0
PSTP
LHIE
NOLHM
0
—(1)
1
0
0
0
0
—(2)
RESET:
PLLCR — PLL Control Register
$003C
1. Set when VDDPLL power supply is high. Forced to 0 when VDDPLL is low.
2. Cleared when VDDPLL power supply is high. Forced to 1 when VDDPLL is low.
Read and write anytime. Exceptions are listed below for each bit.
LOCKIE — PLL LOCK Interrupt Enable
0 = PLL LOCK interrupt is disabled
1 = PLL LOCK interrupt is enabled
Forced to 0 when VDDPLL=0.
PLLON — Phase Lock Loop On
0 = Turns the PLL off.
1 = Turns on the phase lock loop circuit. If AUTO is set, the PLL will
lock automatically.
Cannot be cleared when BCSP = 1 (PLL selected as bus clock). Forced
to 0 when VDDPLL is at VSS level. In limp-home mode, the output of
PLLON is forced to 1, but the PLLON bit reads the latched value.
AUTO — Automatic Bandwidth Control
0 = Automatic Mode Control is disabled and the PLL is under
software control, using ACQ bit.
1 = Automatic Mode Control is enabled. ACQ bit is read only.
Automatic bandwidth control selects either the high bandwidth
(acquisition) mode or the low bandwidth (tracking) mode depending
on how close to the desired frequency the VCO is running. See
Electrical Specifications.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
177
Clock Functions
ACQ — Not in Acquisition
If AUTO = 1 (ACQ is Read Only)
0 = PLL VCO is not within the desired tolerance of the target
frequency. The loop filter is in high bandwidth, acquisition
mode.
1 = After the phase lock loop circuit is turned on, indicates the PLL
VCO is within the desired tolerance of the target frequency.
The loop filter is in low bandwidth, tracking mode.
If AUTO = 0
0 = High bandwidth PLL loop selected
1 = Low bandwidth PLL loop selected
PSTP — Pseudo-STOP Enable
0 = Pseudo-STOP oscillator mode is disabled
1 = Pseudo-STOP oscillator mode is enabled
In Pseudo-STOP mode, the oscillator is still running while the MCU is
maintained in STOP mode. This allows for a faster STOP recovery
and reduces the mechanical stress and aging of the resonator in case
frequent STOP conditions at the expense of a slightly increased
power consumption.
LHIE — Limp-Home Interrupt Enable
0 = Limp-Home interrupt is disabled
1 = Limp-Home interrupt is enabled
Forced to 0 when VDDPLL is at VSS level.
NOLHM —No Limp-Home Mode
0 = Loss of reference clock forces the MCU in limp-home mode.
1 = Loss of reference clock causes standard Clock Monitor reset.
Read anytime; Normal modes: write once; Special modes: write
anytime. Forced to 1 when VDDPLL is at VSS level.
Technical Data
178
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Limp-Home and Fast STOP Recovery modes
RESET:
Bit 7
6
5
4
3
2
1
Bit 0
0
BCSP
BCSS
0
0
MCS
0
0
0
0
0
0
0
0
0
0
CLKSEL — Clock Generator Clock select Register
$003D
Read and write anytime. Exceptions are listed below for each bit.
BCSP and BCSS bits determine the clock used by the main system
including the CPU and buses.
BCSP — Bus Clock Select PLL
0 = SYSCLK is derived from the crystal clock or from SLWCLK.
1 = SYSCLK source is the PLL.
Cannot be set when PLLON = 0. In limp-home mode, the output of
BCSP is forced to 1, but the BCSP bit reads the latched value.
BCSS — Bus Clock Select Slow
0 = SYSCLK is derived from the crystal clock EXTALi.
1 = SYSCLK source is the Slow clock SLWCLK.
This bit has no effect when BCSP is set.
MCS — Module Clock Select
0 = M clock is the same as PCLK.
1 = M clock is derived from Slow clock SLWCLK.
This bit determines the clock used by the ECT module and the baud
rate generators of the SCIs. In limp-home mode, the output of MCS is
forced to 0, but the MCS bit reads the latched value.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
179
Clock Functions
Bit 7
6
5
4
3
2
1
Bit 0
0
0
SLDV5
SLDV4
SLDV3
SLDV2
SLDV1
SLDV0
0
0
0
0
0
0
0
0
RESET:
SLOW — Slow mode Divider Register
$003E
Read and write anytime.
A write to this register changes the SLWCLK frequency with minimum
delay (less than one SLWCLK cycle), thus allowing immediate tuneup of the performance versus power consumption for the modules
using this clock. The frequency divide ratio is 2 times (SLOW), hence
the divide range is 2 to 126 (not on first pass products). When
SLOW = 0, the divider is bypassed. The generation of E, P and
M clocks further divides SLWCLK by 2. Hence, the final ratio of Bus
to EXTALi Frequency is programmable to 2, 4, 8, 12, 16, 20, ..., 252,
by steps of 4. SLWCLK is a 50% duty cycle signal.
Technical Data
180
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
System Clock Frequency Formulae
12.7 System Clock Frequency Formulae
See Figure 12-6:
SLWCLK = EXTALi / ( 2 x SLOW )
SLOW = 1,2,..63
SLWCLK = EXTALi
SLOW = 0
PLLCLK = 2 x EXTALi x (SYNR + 1) / (REFDV + 1)
ECLK = SYSCLK / 2
XCLK = SLWCLK / 2
PCLK = SYSCLK / 2
BCLK(1) = EXTALi / 2
Boolean equations:
SYSCLK = (BCSP & PLLCLK) | (BCSP & BCSS & EXTALi) | (BCSP &
BCSS & SLWCLK)
MCLK = (PCLK & MCS) | (XCLK & MCS)
MSCAN system = (EXTALi & CLKSRC) | (SYSCLK & CLKSRC)
BDM system = (BCLK & CLKSW) | (ECLK & CLKSW)
NOTE:
During limp-home mode PCLK, ECLK, BCLK, MCLK and XCLK are
supplied by VCO (PLLCLK).
1. If SYSCLK is slower than EXTALi (BCSS=1, BCSP=0, SLOW>0), BCLK becomes ECLK.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
181
Clock Functions
12.8 Clock Divider Chains
Figure 12-6, Figure 12-7, Figure 12-8, and Figure 12-9 summarize the
clock divider chains for the various peripherals on the
MC68HC912DT128A.
BCSP BCSS
1:x
PHASE
LOCK
LOOP
SYSCLK
PLLCLK
÷2
EXTALi
EXTAL
BCSP BCSS
0:0
REDUCED
CONSUMPTION
OSCILLATOR
T CLOCK
GENERATOR
TCLKs
E AND P
CLOCK
GENERATOR
ECLK
PCLK
EXTALi
TO CPU
TO
BUSES,
SPI,
PWM,
ATD0, ATD1
CLKSRC = 1
BCSP BCSS
0:1
XTAL
EXTALi
TO
MSCAN
CLKSRC = 0
MCS = 0
MCLK
MCS = 1
SLOW MODE
CLOCK
DIVIDER
SLWCLK
÷2
TO
SCI0, SCI1,
ECT
SYNC
XCLK
TO
RTI, COP
TO CAL
CLKSW = 0
÷2
SYNC
CLKSW = 1
TO BDM
TO CLOCK
MONITOR
Figure 12-6. Clock Generation Chain
Technical Data
182
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Clock Divider Chains
Bus clock select bits BCSP and BCSS in the clock select register
(CLKSEL) determine which clock drives SYSCLK for the main system
including the CPU and buses. BCSS has no effect if BCSP is set. During
the transition, the clock select output will be held low and all CPU activity
will cease until the transition is complete.
The Module Clock Select bit MCS determines the clock used by the ECT
module and the baud rate generators of the SCIs. In limp-home mode,
the output of MCS is forced to 0, but the MCS bit reads the latched value.
It allows normal operation of the serial and timer subsystems at a fixed
reference frequency while allowing the CPU to operate at a higher,
variable frequency.
XCLK
÷ 2048
÷4
REGISTER: RTICTL
BITS: RTR2, RTR1, RTR0
REGISTER: RTICTL
BIT:RTBYP
0:0:0
REGISTER: COPCTL
BITS: CR2, CR1, CR0
0:0:1
MCLK
SC0BD
MODULUS DIVIDER:
÷ 1, 2, 3, 4, 5, 6,...,8190, 8191
SCI0
RECEIVE
BAUD RATE (16x)
÷ 16
SCI0
TRANSMIT
BAUD RATE (1x)
SC1BD
MODULUS DIVIDER:
÷ 1, 2, 3, 4, 5, 6,...,8190, 8191
SCI1
RECEIVE
BAUD RATE (16x)
÷ 16
SCI1
TRANSMIT
BAUD RATE (1x)
0:0:0
0:0:1
÷2
0:1:0
÷4
0:1:0
÷2
0:1:1
÷4
0:1:1
÷2
1:0:0
÷4
1:0:0
÷2
1:0:1
÷4
1:0:1
÷2
1:1:0
÷2
1:1:0
÷2
1:1:1
÷2
1:1:1
TO RTI
TO COP
Figure 12-7. Clock Chain for SCI0, SCI1, RTI, COP
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
183
Clock Functions
MCLK
REGISTER: TMSK2
BITS: PR2, PR1, PR0
0:0:0
TEN
REGISTER: MCCTL
BITS: MCPR1, MCPR0
0:0
MCEN
÷2
0:0:1
÷4
0:1
÷2
0:1:0
÷2
1:0
÷2
0:1:1
÷2
1:1
MODULUS
DOWN
COUNTER
REGISTER: PACTL
BITS: PAEN, CLK1, CLK0
0:x:x
1:0:0
÷2
1:0:0
Prescaled MCLK
1:0:1
÷2
1:0:1
÷2
1:1:0
1:1:0
÷2
PULSE ACC
LOW BYTE
PACLK/256
1:1:1
PACLK/65536
(PAOV)
1:1:1
PACLK
GATE
LOGIC
PORT T7
PULSE ACC
HIGH BYTE
PAMOD
TO TIMER
MAIN
COUNTER
(TCNT)
PAEN
Figure 12-8. Clock Chain for ECT
Technical Data
184
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Computer Operating Properly (COP)
PCLK
5-BIT MODULUS
COUNTER (PR0-PR4)
÷2
÷2
TO ATD0
and ATD1
÷2
REGISTER: SP0BR
BITS: SPR2, SPR1, SPR0
0:0:0
SPI
BIT RATE
0:0:1
MSCAN
CLOCK
EXTALi
÷2
0:1:0
÷2
0:1:1
÷2
1:0:0
÷2
1:0:1
÷2
÷2
CLKSRC
SYSCLK
ECLK
CLKSW
1:1:0
BDM BIT CLOCK:
BCLK
BKGD IN
SYNCHRONIZER
1:1:1
BKGD DIRECTION
BKGD
PIN
LOGIC
BKGD OUT
Receive: Detect falling edge,
count 12 E clocks, Sample input
Transmit 1: Detect falling edge,
count 6 E clocks while output is
high impedance, Drive out 1 E
cycle pulse high, high impedance output again
Transmit 0: Detect falling edge,
Drive out low, count 9 E clocks,
Drive out 1 E cycle pulse high,
high impedance output
Figure 12-9. Clock Chain for MSCAN, SPI, ATD0, ATD1 and BDM
12.9 Computer Operating Properly (COP)
The COP or watchdog timer is an added check that a program is running
and sequencing properly. When the COP is being used, software is
responsible for keeping a free running watchdog timer from timing out. If
the watchdog timer times out it is an indication that the software is no
longer being executed in the intended sequence; thus a system reset is
initiated. Three control bits allow selection of seven COP time-out
periods. When COP is enabled, sometime during the selected period the
program must write $55 and $AA (in this order) to the COPRST register.
If the program fails to do this the part will reset. If any value other than
$55 or $AA is written, the part is reset.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
185
Clock Functions
In addition, windowed COP operation can be selected. In this mode,
writes to the COPRST register must occur in the last 25% of the selected
period. A premature write will also reset the part.
12.10 Real-Time Interrupt
There is a real time (periodic) interrupt available to the user. This
interrupt will occur at one of seven selected rates. An interrupt flag and
an interrupt enable bit are associated with this function. There are three
bits for the rate select.
12.11 Clock Monitor
The clock monitor circuit is based on an internal resistor-capacitor (RC)
time delay. If no EXTALi clock edges are detected within this RC time
delay, the clock monitor can optionally generate a system reset. The
clock monitor function is enabled/disabled by the CME control bit in the
COPCTL register. This time-out is based on an RC delay so that the
clock monitor can operate without any EXTALi clock.
Clock monitor time-outs are shown in Table 12-3. The corresponding
EXTALi clock period with an ideal 50% duty cycle is twice this time-out
value.
Table 12-3. Clock Monitor Time-Outs
Supply
5 V +/– 10%
Technical Data
186
Range
2–20 µS
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Clock Function Registers
12.12 Clock Function Registers
All register addresses shown reflect the reset state. Registers may be
mapped to any 2K byte space.
RESET:
Bit 7
6
5
4
3
2
1
Bit 0
RTIE
RSWAI
RSBCK
Reserved
RTBYP
RTR2
RTR1
RTR0
0
0
0
0
0
0
0
0
RTICTL — Real-Time Interrupt Control Register
$0014
RTIE — Real Time Interrupt Enable
Read and write anytime.
0 = Interrupt requests from RTI are disabled.
1 = Interrupt will be requested whenever RTIF is set.
RSWAI — RTI and COP Stop While in Wait
Write once in normal modes, anytime in special modes. Read
anytime.
0 = Allows the RTI and COP to continue running in wait.
1 = Disables both the RTI and COP whenever the part goes into
Wait.
RSBCK — RTI and COP Stop While in Background Debug Mode
Write once in normal modes, anytime in special modes. Read
anytime.
0 = Allows the RTI and COP to continue running while in
background mode.
1 = Disables both the RTI and COP when the part is in background
mode. This is useful for emulation.
RTBYP — Real Time Interrupt Divider Chain Bypass
Write not allowed in normal modes, anytime in special modes. Read
anytime.
0 = Divider chain functions normally.
1 = Divider chain is bypassed, allows faster testing (the divider
chain is normally XCLK divided by 213, when bypassed
becomes XCLK divided by 4).
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
187
Clock Functions
RTR2, RTR1, RTR0 — Real-Time Interrupt Rate Select
Read and write anytime.
Rate select for real-time interrupt. The clock used for this module is
the XCLK.
Table 12-4. Real Time Interrupt Rates
RTR2 RTR1 RTR0 Divide X By:
Time-Out Period Time-Out Period Time-Out Period Time-Out Period
X = 125 KHz
X = 500 KHz
X = 2.0 MHz
X = 8.0 MHz
OFF
OFF
OFF
OFF
0
0
0
OFF
0
0
1
213
65.536 ms
16.384 ms
4.096 ms
1.024 ms
131.72 ms
32.768 ms
8.196 ms
2.048 ms
0
1
0
214
0
1
1
215
263.44 ms
65.536 ms
16.384 ms
4.096 ms
1
0
0
216
526.88 ms
131.72 ms
32.768 ms
8.196 ms
1
0
1
217
1.05 s
263.44 ms
65.536 ms
16.384 ms
0
2
18
2.11 s
526.88 ms
131.72 ms
32.768 ms
1
219
4.22 s
1.05 s
263.44 ms
65.536 ms
1
1
1
1
Bit 7
6
5
4
3
2
1
Bit 0
RTIF
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
RESET:
RTIFLG — Real Time Interrupt Flag Register
$0015
RTIF — Real Time Interrupt Flag
This bit is cleared automatically by a write to this register with this bit
set.
0 = Time-out has not yet occurred.
1 = Set when the time-out period is met.
Technical Data
188
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Clock Function Registers
Bit 7
6
5
4
3
2
1
Bit 0
CME
FCME
FCMCOP
WCOP
DISR
CR2
CR1
CR0
RESET:
0/1
0
0
0
0
1
1
1
Normal
RESET:
0/1
0
0
0
1
1
1
1
Special
COPCTL — COP Control Register
$0016
CME — Clock Monitor Enable
Read and write anytime.
If FCME is set, this bit has no meaning nor effect.
0 = Clock monitor is disabled. Slow clocks and stop instruction may
be used.
1 = Slow or stopped clocks (including the stop instruction) will
cause a clock reset sequence or limp-home mode. See LimpHome and Fast STOP Recovery modes.
On reset
CME is 1 if VDDPLL is high
CME is 0 if VDDPLL is low.
NOTE:
The VDDPLL-dependent reset operation is not implemented on first
pass products.
In this case the state of CME on reset is 0.
FCME — Force Clock Monitor Enable
Write once in normal modes, anytime in special modes. Read
anytime.
In normal modes, when this bit is set, the clock monitor function
cannot be disabled until a reset occurs.
0 = Clock monitor follows the state of the CME bit.
1 = Slow or stopped clocks will cause a clock reset sequence or
limp-home mode.
See Limp-Home and Fast STOP Recovery modes.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
189
Clock Functions
FCMCOP — Force Clock Monitor Reset or COP Watchdog Reset
Writes are not allowed in normal modes, anytime in special modes.
Read anytime.
If DISR is set, this bit has no effect.
0 = Normal operation.
1 = A clock monitor failure reset or a COP failure reset is forced
depending on the state of CME and if COP is enabled.
CME
COP enabled
Forced reset
0
0
none
0
1
COP failure
1
0
Clock monitor failure
1
1
Both(1)
1. Highest priority interrupt vector is serviced.
WCOP — Window COP mode
Write once in normal modes, anytime in special modes. Read
anytime.
0 = Normal COP operation
1 = Window COP operation
When set, a write to the COPRST register must occur in the last 25%
of the selected period. A premature write will also reset the part. As
long as all writes occur during this window, $55 can be written as often
as desired. Once $AA is written the time-out logic restarts and the
user must wait until the next window before writing to COPRST.
Please note, there is a fixed time uncertainty about the exact COP
counter state when reset, as the initial prescale clock divider in the
RTI section is not cleared when the COP counter is cleared. This
means the effective window is reduced by this uncertainty. Table 125 below shows the exact duration of this window for the seven
available COP rates.
Technical Data
190
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Clock Functions
Clock Function Registers
Table 12-5. COP Watchdog Rates
CR2
CR1
CR0
Window COP enabled:
Divide
XCLK
by
8.0 MHz XCLK
Time-out
Window start
(1)
Window end
Effective
Window (2)
0
0
0
OFF
OFF
OFF
OFF
OFF
0
0
1
2 13
1.024 ms -0/+0.256 ms
0.768 ms
0.768 ms
0 % (3)
0
1
0
2 15
4.096 ms -0/+0.256 ms
3.072 ms
3.840 ms
18.8 %
0
1
1
2 17
16.384 ms -0/+0.256 ms
12.288 ms
16.128 ms
23.4 %
1
0
0
2 19
65.536 ms -0/+1.024 ms
49.152 ms
64.512 ms
23.4 %
1
0
1
2 21
262.144 ms -0/+1.024 ms
196.608 ms
261.120 ms
24.6 %
1
1
0
2 22
524.288 ms -0/+1.024 ms
393.216 ms
523.264 ms
24.8 %
1
1
1
2 23
1.048576 ms -0/+1.024 ms
786.432 ms
1.047552 s
24.9 %
1. Time for writing $55 following previous COP restart of time-out logic due to writing $AA.
2. Please refer to WCOP bit description above.
3. Window COP cannot be used at this rate.
DISR — Disable Resets from COP Watchdog and Clock Monitor
Writes are not allowed in normal modes, anytime in special modes.
Read anytime.
0 = Normal operation.
1 = Regardless of other control bit states, COP and clock monitor
will not generate a system reset.
CR2, CR1, CR0 — COP Watchdog Timer Rate select bits
These bits select the COP time-out rate. The clock used for this
module is the XCLK.
Write once in normal modes, anytime in special modes. Read
anytime.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Clock Functions
191
Clock Functions
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
RESET:
COPRST — Arm/Reset COP Timer Register
$0017
Always reads $00.
Writing $55 to this address is the first step of the COP watchdog
sequence.
Writing $AA to this address is the second step of the COP watchdog
sequence. Other instructions may be executed between these writes
but both must be completed in the correct order prior to time-out to
avoid a watchdog reset. Writing anything other than $55 or $AA
causes a COP reset to occur.
Technical Data
192
MC68HC912DT128A — Rev 4.0
Clock Functions
MOTOROLA
Oscillator
Contents
Technical Data — MC68HC912DT128A
Section 13. Oscillator
13.1 Contents
13.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
13.3
MC68HC912DT128A Oscillator Specification . . . . . . . . . . . .194
13.4
MC68HC912Dx128C Colpitts Oscillator Specification . . . . . . 197
13.5
MC68HC912Dx128P Pierce Oscillator Specification . . . . . . . 212
13.2 Introduction
The oscillator implementation on the original 0.65µ (non-suffix) HC12 Dfamily is a ‘Colpitts Oscillator with Translated Ground’. This design was
carried over to the first 0.5µ devices (A-suffix), up to the 0L05H mask set,
and is described in Section 13.3 MC68HC912DT128A Oscillator
Specification. In this section of the document, the term
MC68HC912DT128A refers only to the MC68HC912DT128A and
MC68HC912DG128A devices.
On mask set 1L05H, the Colpitts oscillator was updated, primarily to
improve its performance. To maximise the benefit of this change,
different external component values are required. However, the
oscillator will perform at least as well as the MC68HC912DT128A
version with the same components. This implementation and the
changes are described in section 13.4 MC68HC912Dx128C Colpitts
Oscillator Specification. In this section of the document, the term
MC68HC912Dx128C refers only to the MC68HC912DT128C and
MC68HC912DG128C devices.
In order to make the HC12 D-family oscillator options more flexible, a
Pierce oscillator configuration has been implemented on the 2L05H
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
193
Oscillator
mask set. This implementation, described in section 13.5
MC68HC912Dx128P Pierce Oscillator Specification, utilises the
Automatic Level Control circuit to provide a lower power oscillator than
traditional Pierce oscillators based on simple inverter circuits. In this
section of the document, the term MC68HC912Dx128P refers only to the
MC68HC912DT128P and MC68HC912DG128P devices.
In the following sections, each particular oscillator implementation is
described in detail. Refer to the appropriate sections for the mask set
being used and optimum external component selection.
13.3 MC68HC912DT128A Oscillator Specification
This section applies to the 0L05H mask set and all previous
MC68HC912DT128A versions.
13.3.1 MC68HC912DT128A Oscillator Design Architecture
The Colpitts oscillator architecture is shown in Figure 13-1. The
component configuration for this oscillator is the same as all previous
MC68HC912DT128A configurations.
Technical Data
194
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912DT128A Oscillator Specification
BUF
-
CFLT
2
OTA
+
RFLT
ALC
+
BIAS
EN
RFLT
CFLT
GM
RESD
EXTAL
XTAL
CX-EX
Resonator
CX-VSS
Figure 13-1. MC68HC912DT128A Colpitts Oscillator Architecture
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
195
Oscillator
13.3.2 MC68HC912DT128A Oscillator Design Guidelines
Proper and robust operation of the oscillator circuit requires excellent
board layout design practice. Poor layout of the application board can
contribute to EMC susceptibility, noise generation, slow starting
oscillators, and reaction to noise on the clock input buffer. In addition to
published errata for the MC68HC912DT128A, the following guidelines
must be followed or failure in operation may occur.
•
Minimize Capacitance to VSS on EXTAL pin — The Colpitts
oscillator architecture is sensitive to capacitance in parallel with
the resonator (from EXTAL to VSS). Follow these techniques:
i. Remove ground plane from all layers around resonator
and EXTAL route
ii. Observe a minimum spacing from the EXTAL trace to
all other traces of at least three times the design rule
minimum (until the microcontroller’s pin pitch prohibits
this guideline)
iii. Where possible, use XTAL as a shield between EXTAL
and VSS
iv. Keep EXTAL capacitance to less than 1pF (2pF
absolute maximum)
NOTE:
•
Shield all oscillator components from all noisy traces (while
observing above guideline).
•
Keep the VSSPLL pin and the VSS reference to the oscillator
as identical as possible. Impedance between these signals must
be minimum.
•
Observe best practice supply bypassing on all MCU power
pins. The oscillator’s supply reference is VDD, not VDPLL.
•
Account for XTAL–VSS and EXTAL–XTAL parasitics in
component values.
An increase in the EXTAL–XTAL parasitic as a result of reducing
EXTAL–VSS parasitic is acceptable provided component value is
reduced by the appropriate value.
•
Minimize XTAL and EXTAL routing lengths to reduce EMC
issues.
Technical Data
196
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
NOTE:
EXTAL and XTAL routing resistances are less important than
capacitances. Using minimum width traces is an acceptable trade-off to
reduce capacitance.
13.4 MC68HC912Dx128C Colpitts Oscillator Specification
This section applies to the 1L05H mask set, which refers to the newest
set of CGM improvements (to the MC68HC912DT128A) with the Colpitts
oscillator configuration enabled. The name for these devices is
MC68HC912Dx128C.
13.4.1 MC68HC912Dx128C Oscillator Design Architecture
The Colpitts oscillator architecture is shown in Figure 13-2. The
component configuration for this oscillator is the same as all previous
MC68HC912DT128A configurations, although the recommended
component values may be different.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
197
Oscillator
BUF
-
CFLT
2
OTA
+
RFLT
ALC
+
BIAS
EN
RFLT
CFLT
GM
RESD
EXTAL
XTAL
CX-EX
Resonator
CX-VSS
Figure 13-2. MC68HC912Dx128C Colpitts Oscillator Architecture
There are the following primary differences between the previous (’A’)
and new (’C’) Colpitts oscillator configurations:
•
Hysteresis was added to the clock input buffer to reduce sensitivity
to noise
•
Internal parasitics were reduced from EXTAL to VSS to increase
oscillator gain margin.
Technical Data
198
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
•
The bias current to the amplifier was optimized for less variation
over process.
•
The input ESD resistor from EXTAL to the gate of the oscillator
amplifier was changed to provide a parallel path, reducing
parasitic phase shift in the oscillator.
13.4.1.1 Clock Buffer Hysteresis
The input clock buffer uses an Operational Transconductance Amplifier
(labeled ‘OTA’ in the figure above) followed by a digital buffer to amplify
the input signal on the EXTAL pin into a full-swing clock for use by the
clock generation section of the microcontroller. There is an internal R-C
filter (composed of components RFLT2 and CFLT2 in the figure above),
which creates the DC value to which the EXTAL signal is compared. In
this manner, the clock input buffer can track changes in the EXTAL bias
voltage due to process variation as well as external factors such as
leakage.
Because the purpose of the clock input buffer is to amplify relatively lowswing signals into a full-rail output, the gain of the OTA is very high. In
the configuration shown, this means that very small levels of noise can
be coupled onto the input of the clock buffer resulting in noise
amplification.
To remedy this issue, hysteresis was added to the OTA so that the circuit
could still provide the tolerance to leakage and the high gain required
without the noise sensitivity. Approximately 150mV of hysteresis was
added with a maximum hysteresis over process variation of 350mV. As
such, the clock input buffer will not respond to input signals until they
exceed the hysteresis level. At this point, the input signal due to
oscillation will dominate the total input waveform and narrow clock
pulses due to noise will be eliminated.
This circuit will limit the overall performance of the oscillator block only
in cases where the amplitude of oscillation is less than the level of
hysteresis. The minimum amplitude of oscillation is expected to be in
excess of 750mV and the maximum hysteresis is expected to be less
than 350mV, providing a factor of safety in excess of two.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
199
Oscillator
13.4.1.2 Internal Parasitic Reduction
Any oscillator circuit’s gain margin is reduced when a low AC-impedance
(low resistance or high capacitance) is placed in parallel with the
resonator. In the Colpitts oscillator configuration, this impedance is
dominated by the parasitic capacitance from the EXTAL pin to VSS.
Since this capacitance is large compared to the shunt capacitance of the
resonator, the gain margin in a Colpitts configuration is less than in other
configurations.
To remedy this issue, the internal circuits were optimized for lower
capacitance. This should increase the gain margin and allow more
robust operation over process, temperature and voltage variation. To
maximize the benefit of this change, different external component values
are required. However, the oscillator will function at least as well as the
MC68HC912DT128A version with the same components.
13.4.1.3 Bias Current Process Optimization
For proper oscillation, the gain margin of the oscillator must exceed one
or the circuit will not oscillate. Due to the sensitive gain margin of the
Colpitts configuration, process variance in the bias current (which
controls the gain of the amplifier) can cause the gain margin to be much
lower than typical. This can be as a result of either too much or too little
current.
To reduce the process sensitivity of the gain, the material of the device
that sets the bias current was changed to a material with tighter process
and temperature control. As a result, the transconductance and Ibias
variances are more limited than in the previous design.
Technical Data
200
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
13.4.1.4 Input ESD Resistor Path Modification
To satisfy the condition of oscillation, the oscillator circuit must not only
provide the correct amount of gain but also the correct amount of phase
shift. In the Colpitts configuration, the phase shift due to parasitics in the
input path to the gate of the transconductance amplifier must be as low
as possible. In the original configuration, the parasitic capacitance of the
clock input buffer (OTA), automatic Loop Control circuit (ALC), and input
resistors (RFLT and RFLT2) reacted with the input resistance to cause
a large phase shift.
To reduce the phase shift, the input ESD resistor (marked RESD in the
figure above) was changed from a single path to the input circuitry (the
ALC and the OTA) and oscillator transconductance amplifier (marked
GM in the figure above) to a parallel path. In this configuration, the only
capacitance causing a phase shift on the input to the transconductance
device is due to the transconductance device itself.
13.4.2 MC68HC912Dx128C Oscillator Circuit Specifications
13.4.2.1 Negative Resistance Margin
Negative Resistance Margin (NRM) is a figure of merit commonly used
to qualify an oscillator circuit with a given resonator. NRM is an indicator
of how much additional resistance in series with the resonator is
tolerable while still maintaining oscillation. This figure is usually expected
to be a multiple of the nominal "maximum" rated ESR of the resonator to
allow for variation and degradation of the resonator.
Currently, many systems are optimized for NRM by adjusting the load
capacitors until NRM is maximized. This method may not achieve the
best overall NRM because the optimization method is empirical and not
analytical. That is, the method only achieves the best NRM for the
particular sample set of microcontrollers, resonators, and board values
tested. The figure below shows the anticipated NRM for a nominal 4MHz
resonator given the expected process variance of the microcontroller
(D60A), board, and crystal (excluding ESR). In this case, the value of
load capacitors providing the optimum NRM for a best-case situation
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
201
Oscillator
yield an unacceptable NRM for a worst-case situation (the slope of the
NRM vs. capacitance curve is very steep, indicating severe sensitivity to
small variations). If the NRM optimization happened to be performed on
a best-case sample set, there could be unexpected sensitivity at worstcase.
Negative Resistance Margin vs. Capacitance
100
Negative Resistance Margin
1000
WCS
TYP
TYP
BCS
10
8
10 13 15 18 22 27 33 39 47 56 68
Capacitance
NRM measurement techniques can also generate misleading results
when applied to Automatic Level Control (ALC) style oscillator circuits
such as the D60x/Dx128x. Many NRM methods slowly increase series
resistance until oscillation stops. ALC-style oscillators reduce the gain of
the oscillator circuit after start-up to reduce current, so if the oscillator
tends to have more gain than optimum it will be more tolerant of
additional resistance after start-up than it will during the start-up process.
This means that NRM figures may be optimistic unless the method
verifies the NRM value by attempting to start the oscillator with the
additional resistance in-place. Worse, this phenomenon exaggerates
the difference between best- and worst-case NRM curves.
Technical Data
202
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
13.4.2.2 Gain Margin
The Gain Margin of the oscillator indicates the amount the gain of the
oscillator can vary while maintaining oscillation. Specifically, Gain
Margin is:
Gain Margin = MIN(gain/minimum required gain, maximum allowed
gain/gain)
Just like NRM, Gain Margin may be dominated by either too much or too
little oscillator gain and an increase in gain may not increase Gain
Margin. Gain Margin is theoretically related to NRM since the maximum
allowed gain is (approximately) inversely proportional to ESR, and the
minimum required gain is (approximately) proportional to ESR, leaving
Gain Margin (approximately) inversely proportional to ESR.
The preferred method for specifying the oscillator, given a set of load
capacitor values, is to determine the maximum allowed while
maintaining a worst-case Gain Margin of 2. Since Gain Margin is
proportional to ESR, this means the empirically measured NRM at the
worst-case point would be approximately twice the maximum allowed
ESR. However, since typical NRM is likely to be higher and most
measurement techniques do not account for ALC effects, actual NRM
measurements are likely to be much higher.
13.4.2.3 Optimizing Component Values
The maximum ESR possible (given a worst-case Gain Margin of 2) is not
the optimum operating point. In some cases, the frequency accuracy of
the oscillator is important and in other cases satisfying the traditional
NRM measurement technique is important.
If frequency accuracy is important, the total load capacitance (the
combination of the load capacitors and their associated parasitics)
should be equal (or close to equal) to the rated load capacitance of the
resonator. Provided the resultant load capacitors yield a maximum
allowed ESR greater than the maximum ESR of the crystal (while
maintaining the worst case Gain Margin of 2), this is an acceptable
operating point. If the maximum allowed ESR is not high enough, the
closest possible components with high enough ESR should be chosen.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
203
Oscillator
Similarly, if meeting a traditional NRM optimization criteria is important,
then the components determined by this method are acceptable if the
same components yield a maximum allowed ESR greater than the
maximum ESR of the crystal while maintaining the worst case Gain
Margin of 2. There is no guarantee that components chosen through
traditional NRM optimization techniques will yield acceptable results
across all expected variations.
13.4.2.4 Key Parameters
The following items are of critical importance to the operation of the
oscillator:
•
EXTAL–XTAL capacitor value — The value of the component
plus external (board) parasitic in excess of 0.1pF between EXTAL
and XTAL.
•
XTAL–VSS capacitor value — The value of the component plus
external (board) parasitic in excess of 1.0pF between XTAL and
VSS.
•
Maximum Shunt Capacitance — The maximum value of the
resonator’s shunt capacitance (C0) plus the external (board)
parasitics in excess of 1pF from EXTAL to VSS.
•
VDDPLL Setting — The Voltage applied to the VDDPLL pin
(Logic 1 means VDDPLL is tied to the same potential as VDD).
•
Resonator Frequency — The frequency of oscillation of the
resonator.
•
Maximum ESR — The maximum effective series resistance
(ESR) of the resonator. This figure must include any increases
due to ageing, power dissipation, temperature, process variation
or particle contamination.
Technical Data
204
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
13.4.3 Important Information For Calculating Component Values
Before attempting to apply the information in section 13.4.2.4 Key
Parameters, the following data from the resonator vendor is required:
•
Resonator Frequency (f)
•
Maximum ESR (R, ESR, or R1)
•
Maximum Shunt Capacitance (C0)
•
Load Capacitance (CL) — this is not the external component
values but rather the capacitance applied in parallel with the
resonator during the tuning procedure.
13.4.3.1 How to Use This Information
The following tables provide Maximum ESR vs. component value for
various frequencies. This table should be used in the following manner:
1. Choose the set of component values corresponding to the correct
maximum shunt capacitance (equal to the sum of EXTAL–VSS
parasitics in excess of 1pF, plus the C0 of the resonator) and
VDDPLL setting.
2. Determine the range of components for which the Maximum ESR
is greater than the absolute maximum ESR of the resonator
(including ageing, power dissipation, temperature, process
variation or particle contamination).
3. Within this range, choose the EXTAL–XTAL capacitance closest
to (CEXTAL–XTAL = 2*CL – 1pF).
4. If the ideal component is between two valid component values (the
maximum ESR is sufficient for both component values), then
choose the component with the highest maximum ESR or choose
an available component between the two listed values.
5. Choose the size of the XTAL–VSS capacitance equal to the
closest available size to (CXTAL–VSS = 0.82*CEXTAL–XTAL).
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
205
Oscillator
6. If the frequency of the crystal falls between listed values,
determine the appropriate component for the listed frequency
values on either side and extrapolate.
7. The maximum allowed capacitor is the highest listed component,
and the minimum allowed capacitor is the lowest listed
component. ‘NA’ or ‘Not Allowed’ means the listed component is
not valid or allowed for the given frequency, Shunt Capacitance,
and VDDPLL setting.
13.4.3.2 General Specifications
The following limitations apply to every system:
•
Ceramic resonators with integrated components should not be
used, as they are designed for Pierce-configured oscillators.
•
Series cut resonators should not be used. Use parallel cut instead.
•
The Load Capacitance should be 12pF or higher, preferably
greater than 15pF.
Technical Data
206
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
Table 13-1. MC68HC912Dx128C EXTAL–XTAL Capacitor Values vs. Maximum ESR, Shunt
Capacitance, and VDDPLL setting
Maximum ESR vs. EXTAL–XTAL capacitor value, 1MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=VDD)
3
1570
2080
2620
2700
1870
1140
630
170
5
1460
1890
2340
2010
1370
830
460
120
7
1350
1730
2100
1550
1050
630
350
90
10
1210
1520
1600
1100
740
440
240
60
100pF
82pF
68pF
56pF
47pF
39pF
33pF
27pF
CEXTAL-XTAL (pF)
22pF
18pF
Maximum ESR vs. EXTAL–XTAL capacitor value, 2MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=VDD)
3
360
480
620
780
940
1100
1080
730
440
240
5
340
450
570
700
830
950
800
530
320
170
7
320
410
520
630
740
830
620
410
250
130
10
290
370
450
550
620
600
440
290
170
90
100pF
82pF
68pF
56pF
47pF
39pF
33pF
27pF
22pF
18pF
CEXTAL-XTAL (pF)
Maximum ESR vs. EXTAL–XTAL capacitor value, 4MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=VDD)
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
210
255
290
335
370
340
175
80
5
190
225
254
290
310
255
130
60
7
170
200
227
250
270
200
100
45
10
145
170
190
205
205
140
70
25
3
250
300
350
400
440
325
165
75
5
225
265
305
340
345
245
120
55
7
200
235
265
295
270
190
90
40
10
175
200
220
240
195
135
65
20
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
CEXTAL-XTAL (pF)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
207
Oscillator
Maximum ESR vs. EXTAL–XTAL capacitor value, 8MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=VDD)
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
40
50
60
70
80
90
95
90
5
35
45
50
60
70
75
80
70
7
30
40
45
50
60
65
65
10
25
30
35
40
45
50
3
50
60
70
85
95
105
115
104
5
40
50
60
70
80
90
95
75
7
35
45
55
60
70
75
80
60
10
35
40
45
50
55
60
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
CEXTAL-XTAL (pF)
Maximum ESR vs. EXTAL–XTAL capacitor value, 10MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
25
35
40
50
55
65
70
5
25
30
35
40
50
55
60
7
20
25
30
35
40
45
10
15
20
25
30
35
47pF
39pF
33pF
27pF
22pF
CEXTAL-XTAL (pF)
18pF
70
13pF
10pF
Maximum ESR vs. EXTAL–XTAL capacitor value, 16MHz resonators
3
Shunt
Capacitance
(pF) (1)
(VDDPLL=0)
5
7
10
CEXTAL-XTAL (pF)
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
= Not allowed
1. Please refer to point 1 in 13.4.3.1 How to Use This Information for important information regarding shunt capacitance.
Technical Data
208
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
13.4.4 MC68HC912Dx128C DC Blocking Capacitor Guidelines
Due to the placement of the resonator from EXTAL to VSS and the
nature of the microcontroller’s inputs, there will be a DC bias voltage of
approximately (VDD–2V) across the pins of the resonator. For some
resonators, this can have long-term reliability issues. To remedy this
situation, a DC-blocking capacitor can be placed in series with the
crystal, as shown in Figure 13-3.
The value of the DC-blocking capacitor should be between 0.1 and
10nF, with a preferred value of 1nF. This capacitor must be connected
as shown in Figure 13-3. If connected thus, all other oscillator
specifications and guidelines continue to apply.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
209
Oscillator
BUF
-
CFLT
2
OTA
+
RFLT
ALC
+
BIAS
EN
RFLT
CFLT
GM
RESD
EXTAL
XTAL
CX-EX
1nF
DC-blocking
capacitor
Resonator
CX-VSS
CDC
Figure 13-3. MC68HC912Dx128C Crystal with DC Blocking
Capacitor
Technical Data
210
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128C Colpitts Oscillator Specification
13.4.5 MC68HC912Dx128C Oscillator Design Guidelines
Proper and robust operation of the oscillator circuit requires excellent
board layout design practice. Poor layout of the application board can
contribute to EMC susceptibility, noise generation, slow starting
oscillators, and reaction to noise on the clock input buffer. In addition to
published errata for the MC68HC912DT128A, the following guidelines
must be followed or failure in operation may occur.
•
Minimize Capacitance to VSS on EXTAL pin — The Colpitts
oscillator architecture is sensitive to capacitance in parallel with
the resonator (from EXTAL to VSS). Follow these techniques:
i. Remove ground plane from all layers around resonator
and EXTAL route
ii. Observe a minimum spacing from the EXTAL trace to
all other traces of at least three times the design rule
minimum (until the microcontroller’s pin pitch prohibits
this guideline)
iii. Where possible, use XTAL as a shield between EXTAL
and VSS
iv. Keep EXTAL capacitance to less than 1pF (2pF
absolute maximum)
NOTE:
•
Shield all oscillator components from all noisy traces (while
observing above guideline).
•
Keep the VSSPLL pin and the VSS reference to the oscillator
as identical as possible. Impedance between these signals must
be minimum.
•
Observe best practice supply bypassing on all MCU power
pins. The oscillator’s supply reference is VDD, not VDDPLL.
•
Account for XTAL–VSS and EXTAL–XTAL parasitics in
component values. The specified component values assume a
maximum parasitic capacitance of 1pF and 0.1pF, respectively.
An increase in the EXTAL–XTAL parasitic as a result of reducing
EXTAL–VSS parasitic is acceptable provided component value is
reduced by the appropriate value.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
211
Oscillator
•
NOTE:
Minimize XTAL and EXTAL routing lengths to reduce EMC
issues.
EXTAL and XTAL routing resistances are less important than
capacitances. Using minimum width traces is an acceptable trade-off to
reduce capacitance.
13.5 MC68HC912Dx128P Pierce Oscillator Specification
This section applies to the 2L05H mask set, which refers to the newest
set of CGM fixes (to the MC68HC912DT128A) with the Pierce oscillator
configuration enabled. The name for these devices is
MC68HC912Dx128P.
13.5.1 MC68HC912Dx128P Oscillator Design Architecture
The Pierce oscillator architecture is shown in Figure 13-4. The
component configuration for this oscillator is different to all previous
MC68HC912DT128A configurations and the recommended
components may be different.
Please note carefully the connection of external capacitors and the
resonator in this diagram.
Technical Data
212
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128P Pierce Oscillator Specification
BUF
-
CFLT
2
OTA
+
RFLT
ALC
+
BIAS
RFEEDBACK
EN
GM
RESD
EXTAL
XTAL
Resonator
CEX-VSS
CX-VSS
Figure 13-4. MC68HC912Dx128P Pierce Oscillator Architecture
There are the following primary differences between the previous
Colpitts (‘A’) and new Pierce (‘P’) oscillator configurations:
•
Oscillator architecture was changed from Colpitts to Pierce.
•
Hysteresis was added to the clock input buffer to reduce sensitivity
to noise.
•
The bias current to the amplifier was optimized for less process
variation.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
213
Oscillator
•
The input ESD resistor from EXTAL to the gate of the oscillator
amplifier was changed to provide a parallel path, reducing
parasitic phase shift in the oscillator.
13.5.1.1 Oscillator Architecture Change from Colpitts to Pierce
The primary difference from the ‘A’ to the ‘P’ versions of the
MC68HC912Dx128 is the architecture, or configuration, of the oscillator.
The previous version (‘A’) is connected in Colpitts configuration, where
the resonator is connected between the EXTAL pin and VSS. This
configuration causes the relatively large parasitics from EXTAL to VSS
react in parallel with the resonator, decreasing gain margin in some
corners. The Pierce configuration places the much-lower EXTAL to
XTAL parasitic capacitances in parallel with the resonator, providing a
much larger gain margin across process, temperature and voltage
variance.
Implementation of the Pierce architecture required the replacement of
the previous P-type, non-inverting source-follower amplifier with an Ntype, inverting, traditional amplifier. Additionally, the EXTAL biasing
circuit on the Colpitts configurations was replaced with a feedback
resistor from XTAL to EXTAL to achieve self-bias. Parametric
differences from the ‘A’ to the ‘P’ versions of the oscillator include:
•
Phase shift from EXTAL to XTAL — The phase shift on the ‘P’
version will be approximately 180 degrees (vs. approximately 0
degrees on the ‘A’ version) due to the requirement of an inverting
amplifier in the Pierce configuration).
•
DC offset of oscillation on EXTAL and XTAL — The DC offset of
the EXTAL and XTAL nodes on the ‘P’ version will be
approximately 0.7–1.0V (vs. approximately VDD–2V and
VDD–1V, respectively, on the ‘A’ version) due to the different bias
requirements of the N-type inverting amplifier.
•
Amplitude of oscillation — The amplitude of oscillation may be
slightly lower on the ‘P’ version than the ‘A’ version due to using
the same Amplitude Level Control (ALC) circuit for both
architectures. The circuit responds slightly differently to the
different DC offsets in the two architectures, resulting in slightly
Technical Data
214
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128P Pierce Oscillator Specification
lower amplitude for the Pierce. The amplitude will still be sufficient
for robust operation across process, temperature, and voltage
variance.
13.5.1.2 Clock Buffer Hysteresis
The input clock buffer uses an Operational Transconductance Amplifier
(labeled ‘OTA’ in the figure above) followed by a digital buffer to amplify
the input signal on the EXTAL pin into a full-swing clock for use by the
clock generation section of the microcontroller. There is an internal R-C
filter (composed of components RFLT2 and CFLT2 in the figure above),
which creates the DC value to which the EXTAL signal is compared. In
this manner, the clock input buffer can track changes in the EXTAL DC
offset voltage due to process variation as well as external factors such
as leakage.
Because the purpose of the clock input buffer is to amplify relatively lowswing signals into a full-rail output, the gain of the OTA is very high. In
the configuration shown, this means that very small levels of noise can
be coupled onto the input of the clock buffer resulting in noise
amplification.
To remedy this issue, hysteresis was added to the OTA so that the circuit
could still provide the tolerance to leakage and the high gain required
without the noise sensitivity. Approximately 150mV of hysteresis was
added with a maximum hysteresis over process variation of 350mV. As
such, the clock input buffer will not respond to input signals until they
exceed the hysteresis level. At this point, the input signal due to
oscillation will dominate the total input waveform and narrow clock
pulses due to noise will be eliminated.
This circuit will limit the overall performance of the oscillator block only
in cases where the amplitude of oscillation is less than the level of
hysteresis. The minimum amplitude of oscillation is expected to be in
excess of 750mV and the maximum hysteresis is expected to be less
than 350mV, providing a factor of safety in excess of two.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
215
Oscillator
13.5.1.3 Bias Current Process Optimization
For proper oscillation, the gain margin of the oscillator must exceed one
or the circuit will not oscillate. Process variance in the bias current (which
controls the gain of the amplifier) can cause the gain margin to be much
lower than typical. This can be as a result of either too much or too little
current.
To reduce the process sensitivity of the gain, the material of the device
that sets the bias current was changed to a material with tighter process
and temperature control. As a result, the transconductance and Ibias
variances are more limited than in the previous design.
13.5.1.4 Input ESD Resistor Path Modification
To satisfy the condition of oscillation, the oscillator circuit must not only
provide the correct amount of gain but also the correct amount of phase
shift. In the Pierce configuration, the phase shift due to parasitics in the
input path to the gate of the transconductance amplifier must be as low
as possible. In the original configuration, the parasitic capacitance of the
clock input buffer (OTA), automatic Loop Control circuit (ALC), and input
resistor (RFLT) reacted with the input resistance to cause a large phase
shift.
To reduce the phase shift, the input ESD resistor (marked RESD in the
figure above) was changed from a single path to the input circuitry (the
ALC and the OTA) and oscillator transconductance amplifier (marked
GM in the figure above) to a parallel path. In this configuration, the only
capacitance causing a phase shift on the input to the transconductance
device is due to the transconductance device itself.
Technical Data
216
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128P Pierce Oscillator Specification
13.5.2 MC68HC912Dx128P Oscillator Circuit Specifications
13.5.2.1 Negative Resistance Margin
Negative Resistance Margin (NRM) is a figure of merit commonly used
to qualify an oscillator circuit with a given resonator. NRM is an indicator
of how much additional resistance in series with the resonator is
tolerable while still maintaining oscillation. This figure is usually expected
to be a multiple of the nominal "maximum" rated ESR of the resonator to
allow for variation and degradation of the resonator.
Currently, many systems are optimized for NRM by adjusting the load
capacitors until NRM is maximized. This method may not achieve the
best overall NRM because the optimization method is empirical and not
analytical. That is, the method only achieves the best NRM for the
particular sample set of microcontrollers, resonators, and board values
tested. The figure below shows the anticipated NRM for a nominal 4MHz
resonator given the expected process variance of the microcontroller
(D60A), board, and crystal (excluding ESR). In this case, the value of
load capacitors providing the optimum NRM for a best-case situation
yield an unacceptable NRM for a worst-case situation (the slope of the
NRM vs. capacitance curve is very steep, indicating severe sensitivity to
small variations). If the NRM optimization happened to be performed on
a best-case sample set, there could be unexpected sensitivity at worstcase.
Negative Resistance Margin vs. Capacitance
100
Negative Resistance Margin
1000
WCS
TYP
TYP
BCS
10
8
10 13 15 18 22 27 33 39 47 56 68
Capacitance
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
217
Oscillator
NRM measurement techniques can also generate misleading results
when applied to Automatic Level Control (ALC) style oscillator circuits
such as the D60x/Dx128x. Many NRM methods slowly increase series
resistance until oscillation stops. ALC-style oscillators reduce the gain of
the oscillator circuit after start-up to reduce current, so if the oscillator
tends to have more gain than optimum it will be more tolerant of
additional resistance after start-up than it will during the start-up process.
This means that NRM figures may be optimistic unless the method
verifies the NRM value by attempting to start the oscillator with the
additional resistance in-place. Worse, this phenomenon exaggerates
the difference between best- and worst-case NRM curves.
13.5.2.2 Gain Margin
The Gain Margin of the oscillator indicates the amount the gain of the
oscillator can vary while maintaining oscillation. Specifically, Gain
Margin is:
Gain Margin = MIN(gain/minimum required gain, maximum allowed
gain/gain)
Just like NRM, Gain Margin may be dominated by either too much or too
little oscillator gain and an increase in gain may not increase Gain
Margin. Gain Margin is theoretically related to NRM since the maximum
allowed gain is (approximately) inversely proportional to ESR, and the
minimum required gain is (approximately) proportional to ESR, leaving
Gain Margin (approximately) inversely proportional to ESR.
The preferred method for specifying the oscillator, given a set of load
capacitor values, is to determine the maximum allowed ESR while
maintaining a worst-case Gain Margin of 2. Since Gain Margin is
proportional to ESR, this means the empirically measured NRM at the
worst-case point would be approximately twice the maximum allowed
ESR. However, since typical NRM is likely to be higher and most
measurement techniques do not account for ALC effects, actual NRM
measurements are likely to be much higher.
Technical Data
218
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128P Pierce Oscillator Specification
13.5.2.3 Optimizing Component Values
The maximum ESR possible (given a worst-case Gain Margin of 2) is not
the optimum operating point. In some cases, the frequency accuracy of
the oscillator is important and in other cases satisfying the traditional
NRM measurement technique is important.
If frequency accuracy is important, the total load capacitance (the
combination of the load capacitors and their associated parasitics)
should be equal (or close to equal) to the rated load capacitance of the
resonator. Provided the resultant load capacitors yield a maximum
allowed ESR greater than the maximum ESR of the crystal (while
maintaining the worst case Gain Margin of 2), this is an acceptable
operating point. If the maximum allowed ESR is not high enough, the
closest possible components with high enough ESR should be chosen.
Similarly, if meeting a traditional NRM optimization criteria is important,
then the components determined by this method are acceptable if the
same components yield a maximum allowed ESR greater than the
maximum ESR of the crystal while maintaining the worst case Gain
Margin of 2. There is no guarantee that components chosen through
traditional NRM optimization techniques will yield acceptable results
across all expected variations.
13.5.2.4 Key Parameters
The following items are of critical importance to the operation of the
oscillator:
•
EXTAL–VSS capacitor value — The value of the component
plus external (board) parasitic in excess of 1.0pF between EXTAL
and VSS.
•
XTAL–VSS capacitor value — The value of the component plus
external (board) parasitic in excess of 1.0pF between XTAL and
VSS.
•
Maximum Shunt Capacitance — The maximum value of the
resonator’s shunt capacitance (C0) plus the external (board)
parasitics in excess of 0.1pF from EXTAL to XTAL.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
219
Oscillator
•
VDDPLL Setting — The Voltage applied to the VDDPLL pin
(Logic 1 means VDDPLL is tied to the same potential as VDD).
•
Resonator Frequency — The frequency of oscillation of the
resonator.
•
Maximum ESR — The maximum effective series resistance
(ESR) of the resonator. This figure must include any increases
due to ageing, power dissipation, temperature, process variation
or particle contamination.
13.5.3 Important Information For Calculating Component Values
Before attempting to apply the information in section 13.5.2.4 Key
Parameters, the following data from the resonator vendor is required:
•
Resonator Frequency (f)
•
Maximum ESR (R, ESR, or R1)
•
Maximum Shunt Capacitance (C0)
•
Load Capacitance (CL) — this is not the external component
values but rather the capacitance applied in parallel with the
resonator during the tuning procedure.
13.5.3.1 How to Use This Information
The following tables provide Maximum ESR vs. component value for
various frequencies. This table should be used in the following manner:
1. Choose the set of component values corresponding to the correct
maximum shunt capacitance (equal to the sum of EXTAL–XTAL
parasitics in excess of 0.1pF, plus the C0 of the resonator) and
VDDPLL setting.
2. Determine the range of components for which the Maximum ESR
is greater than the absolute maximum ESR of the resonator
(including ageing, power dissipation, temperature, process
Technical Data
220
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128P Pierce Oscillator Specification
variation or particle contamination).
3. Within this range, choose the EXTAL–VSS capacitance closest to
(CEXTAL–VSS = 2*CL – 10pF).
4. If the ideal component is between two valid component values (the
maximum ESR is sufficient for both component values), then
choose the component with the highest maximum ESR or choose
an available component between the two listed values.
5. Choose the size of the XTAL–VSS capacitance equal to
EXTAL–VSS capacitance.
6. If the frequency of the crystal falls between listed values,
determine the appropriate component for the listed frequency
values on either side and extrapolate.
7. The maximum allowed capacitor is the highest listed component,
and the minimum allowed capacitor is the lowest listed
component. ‘NA’ or ‘Not Allowed’ means the listed component is
not valid or allowed for the given frequency, Shunt Capacitance,
and VDDPLL setting.
13.5.3.2 General Specifications
The following limitations apply to every system:
•
Ceramic resonators with integrated components must have the
integrated components accounted for in the total component
value.
•
Series cut resonators should not be used. Use parallel cut instead.
•
The Load Capacitance should be 12pF or higher, preferably
greater than 15pF.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
221
Oscillator
Table 13-2. MC68HC912Dx128P EXTAL–VSS, XTAL–VSS Capacitor Values vs. Maximum
ESR, Shunt Capacitance, and VDDPLL setting
Maximum ESR vs. EXTAL–VSS or XTAL–VSS capacitor value, 1MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
4400
5500
6700
8100
8500
6350
3700
2250
5
3800
4650
5400
5350
4000
2900
1650
1000
7
3300
3950
4150
3100
2300
1650
950
550
10
2700
2900
2300
1700
1200
850
500
300
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
CEXTAL-VSS (pF)
Maximum ESR vs. EXTAL–VSS or XTAL–VSS capacitor value, 2MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
1100
1425
1750
2200
2700
3200
3975
3925
5
975
1225
1500
1825
2150
2475
2350
1825
7
850
1050
1275
1525
1750
1925
1375
1050
10
725
875
1025
1175
1325
1050
725
550
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
CEXTAL-VSS (pF)
Maximum ESR vs. EXTAL–VSS or XTAL–VSS capacitor value, 4MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=VDD)
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
270
350
440
560
700
850
1100
1310
5
240
310
380
470
570
680
850
970
7
210
270
320
400
480
550
670
740
10
180
220
260
320
370
420
490
520
3
250
330
410
520
660
800
1040
1230
5
230
290
350
440
540
640
800
910
7
200
250
300
370
450
520
630
700
10
170
210
250
300
350
400
450
500
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
CEXTAL-VSS (pF)
Technical Data
222
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Oscillator
MC68HC912Dx128P Pierce Oscillator Specification
Maximum ESR vs. EXTAL–VSS or XTAL–VSS capacitor value, 8MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=VDD)
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
60
80
100
130
165
200
270
325
5
55
70
85
110
135
165
210
250
7
50
60
75
95
115
135
170
195
10
40
50
60
75
90
105
125
145
3
60
75
95
125
155
190
255
305
5
50
65
80
105
130
155
200
235
7
45
55
70
90
105
125
160
185
10
40
45
55
70
85
95
120
130
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
CEXTAL-VSS (pF)
Maximum ESR vs. EXTAL–VSS or XTAL–VSS capacitor value,10MHz resonators
Shunt
Capacitance
(pF)
(VDDPLL=0)
3
35
45
60
80
100
120
165
200
5
30
40
50
65
80
100
125
150
7
25
35
45
55
65
80
100
120
10
20
30
35
40
50
60
70
80
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
CEXTAL-VSS (pF)
Maximum ESR vs. EXTAL–VSS or XTAL–VSS capacitor value,16MHz resonators
10
3
Shunt
Capacitance
(pF) (1)
(VDDPLL=0)
5
15
20
30
35
50
60
10
15
20
25
30
45
10
15
20
30
35
7
10
CEXTAL-VSS (pF)
20
47pF
39pF
33pF
27pF
22pF
18pF
13pF
10pF
1. Please refer to point 1 in 13.5.3.1 How to Use This Information for important information regarding shunt capacitance.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Oscillator
223
Oscillator
13.5.4 MC68HC912Dx128P Guidelines
Proper and robust operation of the oscillator circuit requires excellent
board layout design practice. Poor layout of the application board can
contribute to EMC susceptibility, noise generation, slow starting
oscillators, and reaction to noise on the clock input buffer. In addition to
published errata for the MC68HC912DT128A, the following guidelines
must be followed or failure in operation may occur.
NOTE:
•
Minimize Capacitance between EXTAL and XTAL traces —
The Pierce oscillator architecture is sensitive to capacitance in
parallel with the resonator (from EXTAL to XTAL). To reduce this
capacitance, run a shield trace (connected to VSS) between
EXTAL and XTAL as far as possible.
•
Shield all oscillator components from all noisy traces. If the
VSS used for shielding is not identical to the oscillator reference,
it must be considered a noisy signal.
•
Keep the VSSPLL pin and the VSS reference to the oscillator
as identical as possible. Impedance between these signals must
be minimum.
•
Observe best practice supply bypassing on all MCU power
pins. The oscillator’s supply reference is VDD, not VDDPLL.
•
Account for XTAL–VSS and EXTAL–VSS parasitics in
component values. The specified component values assume a
maximum parasitic capacitance of 1pF for these pins.
An increase in the EXTAL–VSS or XTAL–VSS parasitic as a result of
reducing EXTAL–XTAL parasitic is acceptable provided the component
values are reduced by the appropriate value.
•
NOTE:
Minimize XTAL and EXTAL routing lengths to reduce EMC
issues.
EXTAL and XTAL routing resistances are less important than
capacitances. Using minimum width traces is an acceptable trade-off to
reduce capacitance.
Technical Data
224
MC68HC912DT128A — Rev 4.0
Oscillator
MOTOROLA
Technical Data — MC68HC912DT128A
Section 14. Pulse Width Modulator
14.1 Contents
14.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
14.3
PWM Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . .229
14.4
PWM Boundary Cases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .240
14.2 Introduction
The pulse-width modulator (PWM) subsystem provides four
independent 8-bit PWM waveforms or two 16-bit PWM waveforms or a
combination of one 16-bit and two 8-bit PWM waveforms. Each
waveform channel has a programmable period and a programmable
duty-cycle as well as a dedicated counter. A flexible clock select scheme
allows four different clock sources to be used with the counters. Each of
the modulators can create independent, continuous waveforms with
software-selectable duty rates from 0 percent to 100 percent. The PWM
outputs can be programmed as left-aligned outputs or center-aligned
outputs.
The period and duty registers are double buffered so that if they change
while the channel is enabled, the change will not take effect until the
counter rolls over or the channel is disabled. If the channel is not
enabled, then writes to the period and/or duty register will go directly to
the latches as well as the buffer, thus ensuring that the PWM output will
always be either the old waveform or the new waveform, not some
variation in between.
A change in duty or period can be forced into immediate effect by writing
the new value to the duty and/or period registers and then writing to the
counter. This causes the counter to reset and the new duty and/or period
values to be latched. In addition, since the counter is readable it is
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
225
Pulse Width Modulator
possible to know where the count is with respect to the duty value and
software can be used to make adjustments by turning the enable bit off
and on.
The four PWM channel outputs share general-purpose port P pins.
Enabling PWM pins takes precedence over the general-purpose port.
When PWM are not in use, the port pins may be used for discrete
input/output.
CLOCK SOURCE
(ECLK or Scaled ECLK)
CENTR = 0
FROM PORT P
DATA REGISTER
UP/DOWN
PWCNTx
GATE
(CLOCK EDGE SYNC)
RESET
8-BIT COMPARE =
PWDTYx
S
Q
MUX
MUX
Q
8-BIT COMPARE =
PWPERx
PWENx
TO PIN
DRIVER
R
PPOLx
SYNC
PPOL = 0
PPOL = 1
PWDTY
PWPER
Figure 14-1. Block Diagram of PWM Left-Aligned Output Channel
Technical Data
226
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Pulse Width Modulator
Introduction
CLOCK SOURCE
(ECLK or Scaled ECLK)
CENTR = 1
FROM PORT P
DATA REGISTER
RESET
PWCNTx
GATE
(CLOCK EDGE SYNC)
UP/DOWN
(DUTY CYCLE)
8-BIT COMPARE =
PWDTYx
T
Q
(PERIOD)
MUX
MUX
Q
TO PIN
DRIVER
8-BIT COMPARE =
PWPERx
PPOLx
PWENx
SYNC
PPOL = 1
PPOL = 0
PWDTY
(PWPER − PWDTY) × 2
PWPER × 2
PWDTY
Figure 14-2. Block Diagram of PWM Center-Aligned Output Channel
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
227
Pulse Width Modulator
PSBCK
PSBCK IS BIT 0 OF PWCTL REGISTER.
INTERNAL SIGNAL LIMBDM IS ONE IF THE MCU IS IN BACKGROUND DEBUG MODE.
LIMBDM
CLOCK A
MUX
ECLK
0:0:0
8-BIT DOWN COUNTER
0:1:0
÷2
÷2
0:0:1
PWSCNT0
0:1:0
8-BIT SCALE REGISTER
0:1:1
÷2
0:1:1
1:0:0
÷2
1:0:0
PCLK0
MUX
0:0:1
=0
CLOCK S0*
0:0:0
PCLK1
1:0:1
1:1:0
÷2
1:1:0
1:1:1
÷2
1:1:1
MUX
÷2
8-BIT DOWN COUNTER
BITS:
PCKA2,
PCKA1,
PCKA0
CLOCK S1**
8-BIT SCALE REGISTER
PWSCAL1
PCLK2
MUX
REGISTER:
PWPRES
CLOCK TO PWM
CHANNEL 2
=0
PWSCNT1
BITS:
PCKB2,
PCKB1,
PCKB0
CLOCK TO PWM
CHANNEL 1
÷2
PWSCAL0
CLOCK B
1:0:1
CLOCK TO PWM
CHANNEL 0
CLOCK TO PWM
CHANNEL 3
÷2
*CLOCK S0 = (CLOCK A)/2, (CLOCK A)/4, (CLOCK A)/6,... (CLOCK A)/512
**CLOCK S1 = (CLOCK B)/2, (CLOCK B)/4, (CLOCK B)/6,... (CLOCK B)/512
PCLK3
Figure 14-3. PWM Clock Sources
Technical Data
228
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Pulse Width Modulator
PWM Register Descriptions
14.3 PWM Register Descriptions
PWCLK — PWM Clocks and Concatenate
RESET:
$0040
Bit 7
6
5
4
3
2
1
Bit 0
CON23
CON01
PCKA2
PCKA1
PCKA0
PCKB2
PCKB1
PCKB0
0
0
0
0
0
0
0
0
Read and write anytime.
CON23 — Concatenate PWM Channels 2 and 3
When concatenated, channel 2 becomes the high-order byte and
channel 3 becomes the low-order byte. Channel 2 output pin is used
as the output for this 16-bit PWM (bit 2 of port P). Channel 3 clockselect control bits determines the clock source. Channel 3 output pin
becomes a general purpose I/O.
0 = Channels 2 and 3 are separate 8-bit PWMs.
1 = Channels 2 and 3 are concatenated to create one 16-bit PWM
channel.
CON01 — Concatenate PWM Channels 0 and 1
When concatenated, channel 0 becomes the high-order byte and
channel 1 becomes the low-order byte. Channel 0 output pin is used
as the output for this 16-bit PWM (bit 0 of port P). Channel 1 clockselect control bits determine the clock source. Channel 1 output pin
becomes a general purpose I/O.
0 = Channels 0 and 1 are separate 8-bit PWMs.
1 = Channels 0 and 1 are concatenated to create one 16-bit PWM
channel.
PCKA2 – PCKA0 — Prescaler for Clock A
Clock A is one of two clock sources which may be used for channels
0 and 1. These three bits determine the rate of clock A, as shown in
Table 14-1.
PCKB2 – PCKB0 — Prescaler for Clock B
Clock B is one of two clock sources which may be used for channels
2 and 3. These three bits determine the rate of clock B, as shown in
Table 14-1.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
229
Pulse Width Modulator
Table 14-1. Clock A and Clock B Prescaler
PCKA2
(PCKB2)
0
0
0
0
1
1
1
1
PCKA1
(PCKB1)
0
0
1
1
0
0
1
1
PCKA0
(PCKB0)
0
1
0
1
0
1
0
1
Value of
Clock A (B)
P
P÷2
P÷4
P÷8
P ÷ 16
P ÷ 32
P ÷ 64
P ÷ 128
PWPOL — PWM Clock Select and Polarity
$0041
Bit 7
6
5
4
3
2
1
Bit 0
PCLK3
PCLK2
PCLK1
PCLK0
PPOL3
PPOL2
PPOL1
PPOL0
0
0
0
0
0
0
0
0
RESET:
Read and write anytime.
PCLK3 — PWM Channel 3 Clock Select
0 = Clock B is the clock source for channel 3.
1 = Clock S1 is the clock source for channel 3.
PCLK2 — PWM Channel 2 Clock Select
0 = Clock B is the clock source for channel 2.
1 = Clock S1 is the clock source for channel 2.
PCLK1 — PWM Channel 1 Clock Select
0 = Clock A is the clock source for channel 1.
1 = Clock S0 is the clock source for channel 1.
PCLK0 — PWM Channel 0 Clock Select
0 = Clock A is the clock source for channel 0.
1 = Clock S0 is the clock source for channel 0.
If a clock select is changed while a PWM signal is being generated, a
truncated or stretched pulse may occur during the transition.
The following four bits apply in left-aligned mode only:
Technical Data
230
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Pulse Width Modulator
PWM Register Descriptions
PPOL3 — PWM Channel 3 Polarity
0 = Channel 3 output is low at the beginning of the period; high
when the duty count is reached.
1 = Channel 3 output is high at the beginning of the period; low
when the duty count is reached.
PPOL2 — PWM Channel 2 Polarity
0 = Channel 2 output is low at the beginning of the period; high
when the duty count is reached.
1 = Channel 2 output is high at the beginning of the period; low
when the duty count is reached.
PPOL1 — PWM Channel 1 Polarity
0 = Channel 1 output is low at the beginning of the period; high
when the duty count is reached.
1 = Channel 1 output is high at the beginning of the period; low
when the duty count is reached.
PPOL0 — PWM Channel 0 Polarity
0 = Channel 0 output is low at the beginning of the period; high
when the duty count is reached.
1 = Channel 0 output is high at the beginning of the period; low
when the duty count is reached.
Depending on the polarity bit, the duty registers may contain the count
of either the high time or the low time. If the polarity bit is zero and left
alignment is selected, the duty registers contain a count of the low
time. If the polarity bit is one, the duty registers contain a count of the
high time.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
231
Pulse Width Modulator
PWEN — PWM Enable
$0042
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
PWEN3
PWEN2
PWEN1
PWEN0
0
0
0
0
0
0
0
0
RESET:
Setting any of the PWENx bits causes the associated port P line to
become an output regardless of the state of the associated data
direction register (DDRP) bit. This does not change the state of the data
direction bit. When PWENx returns to zero, the data direction bit controls
I/O direction. On the front end of the PWM channel, the scaler clock is
enabled to the PWM circuit by the PWENx enable bit being high. When
all four PWM channels are disabled, the prescaler counter shuts off to
save power. There is an edge-synchronizing gate circuit to guarantee
that the clock will only be enabled or disabled at an edge.
Read and write anytime.
PWEN3 — PWM Channel 3 Enable
The pulse modulated signal will be available at port P, bit 3 when its
clock source begins its next cycle.
0 = Channel 3 is disabled.
1 = Channel 3 is enabled.
PWEN2 — PWM Channel 2 Enable
The pulse modulated signal will be available at port P, bit 2 when its
clock source begins its next cycle.
0 = Channel 2 is disabled.
1 = Channel 2 is enabled.
PWEN1 — PWM Channel 1 Enable
The pulse modulated signal will be available at port P, bit 1 when its
clock source begins its next cycle.
0 = Channel 1 is disabled.
1 = Channel 1 is enabled.
PWEN0 — PWM Channel 0 Enable
The pulse modulated signal will be available at port P, bit 0 when its
clock source begins its next cycle.
0 = Channel 0 is disabled.
1 = Channel 0 is enabled.
Technical Data
232
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Pulse Width Modulator
PWM Register Descriptions
PWPRES — PWM Prescale Counter
RESET:
$0043
Bit 7
6
5
4
3
2
1
Bit 0
0
Bit 6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
PWPRES is a free-running 7-bit counter. Read anytime. Write only in
special mode (SMOD = 1).
PWSCAL0 — PWM Scale Register 0
RESET:
$0044
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Read and write anytime. A write will cause the scaler counter PWSCNT0
to load the PWSCAL0 value unless in special mode with DISCAL = 1 in
the PWTST register.
PWM channels 0 and 1 can select clock S0 (scaled) as its input clock by
setting the control bit PCLK0 and PCLK1 respectively. Clock S0 is
generated by dividing clock A by the value in the PWSCAL0 register + 1
and dividing again by two. When PWSCAL0 = $FF, clock A is divided by
256 then divided by two to generate clock S0.
PWSCNT0 — PWM Scale Counter 0 Value
RESET:
$0045
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
PWSCNT0 is a down-counter that, upon reaching $00, loads the value
of PWSCAL0. Read any time.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
233
Pulse Width Modulator
PWSCAL1 — PWM Scale Register 1
$0046
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
RESET:
Read and write anytime. A write will cause the scaler counter PWSCNT1
to load the PWSCAL1 value unless in special mode with DISCAL = 1 in
the PWTST register.
PWM channels 2 and 3 can select clock S1 (scaled) as its input clock by
setting the control bit PCLK2 and PCLK3 respectively. Clock S1 is
generated by dividing clock B by the value in the PWSCAL1 register + 1
and dividing again by two. When PWSCAL1 = $FF, clock B is divided by
256 then divided by two to generate clock S1.
PWSCNT1 — PWM Scale Counter 1 Value
$0047
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
RESET:
PWSCNT1 is a down-counter that, upon reaching $00, loads the value
of PWSCAL1. Read any time.
PWCNTx — PWM Channel Counters
Bit 7
6
5
4
3
2
1
Bit 0
PWCNT0
Bit 7
6
5
4
3
2
1
Bit 0
$0048
PWCNT1
Bit 7
6
5
4
3
2
1
Bit 0
$0049
PWCNT2
Bit 7
6
5
4
3
2
1
Bit 0
$004A
PWCNT3
Bit 7
6
5
4
3
2
1
Bit 0
$004B
RESET:
0
0
0
0
0
0
0
0
Read and write anytime. A write will cause the PWM counter to reset to
$00.
In special mode, if DISCR = 1, a write does not reset the PWM counter.
Technical Data
234
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Pulse Width Modulator
PWM Register Descriptions
The PWM counters are not reset when PWM channels are disabled. The
counters must be reset prior to a new enable.
Each counter may be read any time without affecting the count or the
operation of the corresponding PWM channel. Writes to a counter cause
the counter to be reset to $00 and force an immediate load of both duty
and period registers with new values. To avoid a truncated PWM period,
write to a counter while the counter is disabled. In left-aligned output
mode, resetting the counter and starting the waveform output is
controlled by a match between the period register and the value in the
counter. In center-aligned output mode the counters operate as up/down
counters, where a match in period changes the counter direction. The
duty register changes the state of the output during the period to
determine the duty.
When a channel is enabled, the associated PWM counter starts at the
count in the PWCNTx register using the clock selected for that channel.
In special mode, when DISCP = 1 and configured for left-aligned output,
a match of period does not reset the associated PWM counter.
PWPERx — PWM Channel Period Registers
Bit 7
6
5
4
3
2
1
Bit 0
PWPER0
Bit 7
6
5
4
3
2
1
Bit 0
$004C
PWPER1
Bit 7
6
5
4
3
2
1
Bit 0
$004D
PWPER2
Bit 7
6
5
4
3
2
1
Bit 0
$004E
PWPER3
Bit 7
6
5
4
3
2
1
Bit 0
$004F
RESET:
1
1
1
1
1
1
1
1
Read and write anytime.
The value in the period register determines the period of the associated
PWM channel. If written while the channel is enabled, the new value will
not take effect until the existing period terminates, forcing the counter to
reset. The new period is then latched and is used until a new period
value is written. Reading this register returns the most recent value
written. To start a new period immediately, write the new period value
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
235
Pulse Width Modulator
and then write the counter forcing a new period to start with the new
period value.
Period = Channel-Clock-Period × (PWPER + 1)
Period = Channel-Clock-Period × (2 × PWPER)
(CENTR = 0)
(CENTR = 1)
PWDTYx — PWM Channel Duty Registers
Bit 7
6
5
4
3
2
1
Bit 0
PWDTY0
Bit 7
6
5
4
3
2
1
Bit 0
$0050
PWDTY1
Bit 7
6
5
4
3
2
1
Bit 0
$0051
PWDTY2
Bit 7
6
5
4
3
2
1
Bit 0
$0052
PWDTY3
Bit 7
6
5
4
3
2
1
Bit 0
$0053
RESET:
1
1
1
1
1
1
1
1
Read and write anytime.
The value in each duty register determines the duty of the associated
PWM channel. When the duty value is equal to the counter value, the
output changes state. If the register is written while the channel is
enabled, the new value is held in a buffer until the counter rolls over
or the channel is disabled. Reading this register returns the most
recent value written.
If the duty register is greater than or equal to the value in the period
register, there will be no duty change in state. If the duty register is set
to $FF the output will always be in the state which would normally be
the state opposite the PPOLx value.
Left-Aligned-Output Mode (CENTR = 0):
Duty cycle = [(PWDTYx+1)/(PWPERx+1)] × 100%
Duty cycle = [(PWPERx−PWDTYx)/(PWPERx+1)] × 100%
(PPOLx = 1)
(PPOLx = 0)
Center-Aligned-Output Mode (CENTR = 1):
Duty cycle = [(PWPERx−PWDTYx)/PWPERx] × 100%
Duty cycle = [PWDTYx/PWPERx] × 100%
(PPOLx = 0)
(PPOLx = 1)
Technical Data
236
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Pulse Width Modulator
PWM Register Descriptions
PWCTL — PWM Control Register
RESET:
$0054
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
PSWAI
CENTR
RDPP
PUPP
PSBCK
0
0
0
0
0
0
0
0
Read and write anytime.
PSWAI — PWM Halts while in Wait Mode
0 = Allows PWM main clock generator to continue while in wait
mode.
1 = Halt PWM main clock generator when the part is in wait mode.
CENTR — Center-Aligned Output Mode
To avoid irregularities in the PWM output mode, write the CENTR bit
only when PWM channels are disabled.
0 = PWM channels operate in left-aligned output mode
1 = PWM channels operate in center-aligned output mode
RDPP — Reduced Drive of Port P
0 = All port P output pins have normal drive capability.
1 = All port P output pins have reduced drive capability.
PUPP — Pull-Up Port P Enable
0 = All port P pins have an active pull-up device disabled.
1 = All port P pins have an active pull-up device enabled.
PSBCK — PWM Stops while in Background Mode
0 = Allows PWM to continue while in background mode.
1 = Disable PWM input clock when the part is in background mode.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
237
Pulse Width Modulator
PWTST — PWM Special Mode Register (“Test”)
$0055
Bit 7
6
5
4
3
2
1
Bit 0
DISCR
DISCP
DISCAL
0
0
0
0
0
0
0
0
0
0
0
0
0
RESET:
Read anytime but write only in special mode (SMODN = 0). These bits
are available only in special mode and are reset in normal mode.
DISCR — Disable Reset of Channel Counter on Write to Channel
Counter
0 = Normal operation. Write to PWM channel counter will reset
channel counter.
1 = Write to PWM channel counter does not reset channel counter.
DISCP — Disable Compare Count Period
0 = Normal operation
1 = In left-aligned output mode, match of period does not reset the
associated PWM counter register.
DISCAL — Disable Load of Scale-Counters on Write to the Associated
Scale-Registers
0 = Normal operation
1 = Write to PWSCAL0 and PWSCAL1 does not load scale
counters
Technical Data
238
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Pulse Width Modulator
PWM Register Descriptions
PORTP — Port P Data Register
$0056
Bit 7
6
5
4
3
2
1
Bit 0
PP7
PP6
PP5
PP4
PP3
PP2
PP1
PP0
PWM
–
–
–
–
PWM3
PWM2
PWM1
PWM0
RESET:
–
–
–
–
–
–
–
–
PORTP can be read anytime.
PWM functions share port P pins 3 to 0 and take precedence over the
general-purpose port when enabled.
When configured as input, a read will return the pin level. For port bits 7
to 4 it will read zero because there are no available external pins.
When configured as output, a read will return the latched output data.
For port bits 7 to 4 it will read the last value written. A write will drive
associated pins only if configured for output and the corresponding PWM
channel is not enabled.
After reset, all pins are general-purpose, high-impedance inputs.
DDRP — Port P Data Direction Register
RESET:
$0057
Bit 7
6
5
4
3
2
1
Bit 0
DDP7
DDP6
DDP5
DDP4
DDP3
DDP2
DDP1
DDP0
0
0
0
0
0
0
0
0
DDRP determines pin direction of port P when used for general-purpose
I/O.
DDRP[7:4] — This bits served as memory locations since there are no
corresponding port pins.
DDRP[3:0] — Data Direction Port P pin 0-3
0 = I/O pin configured as high impedance input
1 = I/O pin configured for output.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Pulse Width Modulator
239
Pulse Width Modulator
14.4 PWM Boundary Cases
The boundary conditions for the PWM channel duty registers and the
PWM channel period registers cause these results:
Table 14-2. PWM Left-Aligned Boundary Conditions
PWDTYx
$FF
$FF
≥PWPERx
≥PWPERx
–
–
PWPERx
>$00
>$00
–
–
$00
$00
PPOLx
1
0
1
0
1
0
Output
Low
High
High
Low
High
Low
Table 14-3. PWM Center-Aligned Boundary Conditions
PWDTYx
$00
$00
≥PWPERx
≥PWPERx
–
–
PWPERx
>$00
>$00
–
–
$00
$00
Technical Data
240
PPOLx
1
0
1
0
1
0
Output
Low
High
High
Low
High
Low
MC68HC912DT128A — Rev 4.0
Pulse Width Modulator
MOTOROLA
Technical Data — MC68HC912DT128A
Section 15. Enhanced Capture Timer
15.1 Contents
15.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 241
15.3
Enhanced Capture Timer Modes of Operation . . . . . . . . . . . . 247
15.4
Timer Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . 251
15.5
Timer and Modulus Counter Operation in Different Modes . . 275
15.2 Introduction
The HC12 Enhanced Capture Timer module has the features of the
HC12 Standard Timer module enhanced by additional features in order
to enlarge the field of applications, in particular for automotive ABS
applications.
The additional features permit the operation of this timer module in a
mode similar to the Input Control Timer implemented on
MC68HC11NB4.
These additional features are:
•
16-Bit Buffer Register for four Input Capture (IC) channels.
•
Four 8-Bit Pulse Accumulators with 8-bit buffer registers
associated with the four buffered IC channels. Configurable also
as two 16-Bit Pulse Accumulators.
•
16-Bit Modulus Down-Counter with 4-bit Prescaler.
•
Four user selectable Delay Counters for input noise immunity
increase.
•
Main Timer Prescaler extended to 7-bit.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
241
Enhanced Capture Timer
This design specification describes the standard timer as well as the
additional features.
The basic timer consists of a 16-bit, software-programmable counter
driven by a prescaler. This timer can be used for many purposes,
including input waveform measurements while simultaneously
generating an output waveform. Pulse widths can vary from
microseconds to many seconds.
A full access for the counter registers or the input capture/output
compare registers should take place in one clock cycle. Accessing high
byte and low byte separately for all of these registers may not yield the
same result as accessing them in one word.
Technical Data
242
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Introduction
÷ 1, 2, ..., 128
M clock
16-bit Free-running
16 BIT MAIN
mainTIMER
timer
Prescaler
÷ 1, 4, 8, 16
M clock
Prescaler
16-bit load register
16-bit modulus
down counter
RESET
0
PT0
Pin logic
Delay counter
EDG0
TC0 capture/compare register
TC0H hold register
Underflow
Comparator
PAC0
PA0H hold register
RESET
0
Comparator
PT1
Pin logic
Delay counter
EDG1
TC1 capture/compare register
TC1H hold register
PAC1
PA1H hold register
RESET
0
Comparator
PT2
Pin logic
Delay counter
EDG2
TC2 capture/compare register
TC2H hold register
PAC2
PA2H hold register
RESET
0
Comparator
Pin logic
Delay counter
EDG3
TC3 capture/compare register
TC3H hold register
PAC3
PA3H hold register
LATCH
PT3
Comparator
PT4
Pin logic
EDG4
EDG0
TC4 capture/compare register
MUX
ICLAT, LATQ, BUFEN
(force latch)
Comparator
PT5
Pin logic
EDG5
EDG1
TC5 capture/compare register
MUX
Comparator
PT6
Pin logic
EDG6
EDG2
Write $0000
to modulus counter
LATQ
(MDC latch enable)
TC6 capture/compare register
MUX
Comparator
PT7
Pin logic
EDG7
EDG3
TC7 capture/compare register
MUX
Figure 15-1. Timer Block Diagram in Latch Mode
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
243
Enhanced Capture Timer
÷1, 2, ..., 128
M clock
16-bit Free-running
16 BIT MAIN
mainTIMER
timer
Prescaler
16-bit load register
÷ 1, 4, 8, 16
M clock
Prescaler
16-bit modulus
down counter
0
RESET
Comparator
Pin logic
Delay counter
EDG0
TC0 capture/compare register
TC0H hold register
PAC0
LATCH0
PT0
PA0H hold register
0
RESET
Comparator
Pin logic
Delay counter
EDG1
TC1 capture/compare register
TC1H hold register
PAC1
LATCH1
PT1
PA1H hold register
0
RESET
Comparator
Pin logic
Delay counter
EDG2
TC2 capture/compare register
TC2H hold register
PAC2
PA2H hold register
0
RESET
LATCH2
PT2
Comparator
Pin logic
Delay counter
EDG3
TC3 capture/compare register
TC3H hold register
PAC3
PA3H hold register
LATCH3
PT3
Comparator
PT4
Pin logic
EDG4
EDG0
TC4 capture/compare register
MUX
Comparator
PT5
Pin logic
EDG5
EDG1
LATQ, BUFEN
(queue mode)
Read TC3H
hold register
TC5 capture/compare register
MUX
Read TC2H
hold register
Comparator
PT6
Pin logic
EDG6
EDG2
TC6 capture/compare register
MUX
Read TC1H
hold register
Comparator
PT7
Pin logic
EDG7
EDG3
TC7 capture/compare register
Read TC0H
hold register
MUX
Figure 15-2. Timer Block Diagram in Queue Mode
Technical Data
244
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Introduction
Load holding register and reset pulse accumulator
0
EDG0
PT0
Edge detector
8-bit PAC0 (PACN0)
Delay counter
PA0H holding register
Interrupt
0
EDG1
Edge detector
8-bit PAC1 (PACN1)
Delay counter
Host CPU data bus
PT1
PA1H holding register
0
EDG2
PT2
Edge detector
8-bit PAC2 (PACN2)
Delay counter
PA2H holding register
Interrupt
0
EDG3
PT3
Edge detector
8-bit PAC3 (PACN3)
Delay counter
PA3H holding register
Figure 15-3. 8-Bit Pulse Accumulators Block Diagram
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
245
Enhanced Capture Timer
To TCNT Counter
CLK1
CLK0
Clock select
(PAMOD)
Edge detector
PT7
PACLK
PACLK / 256
PACLK / 65536
Prescaled MCLK
(TMSK2 bits PR2-PR0)
4:1 MUX
Interrupt
8-bit PAC3 (PACN3)
8-bit PAC2 (PACN2)
MUX
PACA
M clock
Intermodule Bus
Divide by 64
Interrupt
8-bit PAC1 (PACN1)
8-bit PAC0 (PACN0)
Delay counter
PACB
Edge detector
PT0
Figure 15-4. 16-Bit Pulse Accumulators Block Diagram
Technical Data
246
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Enhanced Capture Timer Modes of Operation
Pulse accumulator A
PAD
OC7
(OM7=1 or OL7=1) or (OC7M7 = 1)
Figure 15-5. Block Diagram for Port7 with Output compare / Pulse Accumulator A
16-bit Main Timer
PTn
Delay counter
Edge detector
Set CnF Interrupt
TCn Input Capture Reg.
TCnH I.C. Holding Reg.
BUFEN • LATQ • TFMOD
Figure 15-6. C3F-C0F Interrupt Flag Setting
15.3 Enhanced Capture Timer Modes of Operation
The Enhanced Capture Timer has 8 Input Capture, Output Compare
(IC/OC) channels same as on the HC12 standard timer (timer channels
TC0 to TC7). When channels are selected as input capture by selecting
the IOSx bit in TIOS register, they are called Input Capture (IC)
channels.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
247
Enhanced Capture Timer
Four IC channels are the same as on the standard timer with one capture
register which memorizes the timer value captured by an action on the
associated input pin.
Four other IC channels, in addition to the capture register, have also one
buffer called holding register. This permits to memorize two different
timer values without generation of any interrupt.
Four 8-bit pulse accumulators are associated with the four buffered IC
channels. Each pulse accumulator has a holding register to memorize
their value by an action on its external input. Each pair of pulse
accumulators can be used as a 16-bit pulse accumulator.
The 16-bit modulus down-counter can control the transfer of the IC
registers contents and the pulse accumulators to the respective holding
registers for a given period, every time the count reaches zero.
The modulus down-counter can also be used as a stand-alone time base
with periodic interrupt capability.
15.3.1 IC Channels
The IC channels are composed of four standard IC registers and four
buffered IC channels.
An IC register is empty when it has been read or latched into the
holding register.
A holding register is empty when it has been read.
15.3.1.1 Non-Buffered IC Channels
The main timer value is memorized in the IC register by a valid input pin
transition. If the corresponding NOVWx bit of the ICOVW register is
cleared, with a new occurrence of a capture, the contents of IC register
are overwritten by the new value.
If the corresponding NOVWx bit of the ICOVW register is set, the
capture register cannot be written unless it is empty.
This will prevent the captured value to be overwritten until it is read.
Technical Data
248
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Enhanced Capture Timer Modes of Operation
15.3.1.2 Buffered IC Channels
There are two modes of operations for the buffered IC channels.
•
IC Latch Mode:
When enabled (LATQ=1), the main timer value is memorized in the IC
register by a valid input pin transition.
The value of the buffered IC register is latched to its holding register by
the Modulus counter for a given period when the count reaches zero, by
a write $0000 to the modulus counter or by a write to ICLAT in the
MCCTL register.
If the corresponding NOVWx bit of the ICOVW register is cleared, with a
new occurrence of a capture, the contents of IC register are overwritten
by the new value. In case of latching, the contents of its holding register
are overwritten.
If the corresponding NOVWx bit of the ICOVW register is set, the capture
register or its holding register cannot be written by an event unless they
are empty (see IC Channels). This will prevent the captured value to be
overwritten until it is read or latched in the holding register.
•
IC queue mode:
When enabled (LATQ=0), the main timer value is memorized in the IC
register by a valid input pin transition.
If the corresponding NOVWx bit of the ICOVW register is cleared, with a
new occurrence of a capture, the value of the IC register will be transferred
to its holding register and the IC register memorizes the new timer value.
If the corresponding NOVWx bit of the ICOVW register is set, the capture
register or its holding register cannot be written by an event unless they
are empty (see IC Channels).
In queue mode, reads of holding register will latch the corresponding
pulse accumulator value to its holding register.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
249
Enhanced Capture Timer
15.3.2 Pulse Accumulators
There are four 8-bit pulse accumulators with four 8-bit holding registers
associated with the four IC buffered channels. A pulse accumulator
counts the number of active edges at the input of its channel.
The user can prevent 8-bit pulse accumulators counting further than $FF
by PACMX control bit in ICSYS ($AB). In this case a value of $FF means
that 255 counts or more have occurred.
Each pair of pulse accumulators can be used as a 16-bit pulse
accumulator.
There are two modes of operation for the pulse accumulators.
15.3.2.1 Pulse Accumulator latch mode
The value of the pulse accumulator is transferred to its holding register
when the modulus down-counter reaches zero, a write $0000 to the
modulus counter or when the force latch control bit ICLAT is written.
At the same time the pulse accumulator is cleared.
15.3.2.2 Pulse Accumulator queue mode
When queue mode is enabled, reads of an input capture holding register
will transfer the contents of the associated pulse accumulator to its
holding register.
At the same time the pulse accumulator is cleared.
15.3.3 Modulus Down-Counter
The modulus down-counter can be used as a time base to generate a
periodic interrupt. It can also be used to latch the values of the IC
registers and the pulse accumulators to their holding registers.
The action of latching can be programmed to be periodic or only once.
Technical Data
250
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
15.4 Timer Register Descriptions
Input/output pins default to general-purpose I/O lines until an internal
function which uses that pin is specifically enabled. The timer overrides
the state of the DDR to force the I/O state of each associated port line
when an output compare using a port line is enabled. In these cases the
data direction bits will have no affect on these lines.
When a pin is assigned to output an on-chip peripheral function, writing
to this PORTT bit does not affect the pin but the data is stored in an
internal latch such that if the pin becomes available for general-purpose
output the driven level will be the last value written to the PORTT bit.
TIOS — Timer Input Capture/Output Compare Select
RESET:
$0080
Bit 7
6
5
4
3
2
1
Bit 0
IOS7
IOS6
IOS5
IOS4
IOS3
IOS2
IOS1
IOS0
0
0
0
0
0
0
0
0
Read or write anytime.
IOS[7:0] — Input Capture or Output Compare Channel Configuration
0 = The corresponding channel acts as an input capture
1 = The corresponding channel acts as an output compare.
CFORC — Timer Compare Force Register
RESET:
$0081
Bit 7
6
5
4
3
2
1
Bit 0
FOC7
FOC6
FOC5
FOC4
FOC3
FOC2
FOC1
FOC0
0
0
0
0
0
0
0
0
Read anytime but will always return $00 (1 state is transient). Write
anytime.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
251
Enhanced Capture Timer
FOC[7:0] — Force Output Compare Action for Channel 7-0
A write to this register with the corresponding data bit(s) set causes
the action which is programmed for output compare “n” to occur
immediately. The action taken is the same as if a successful
comparison had just taken place with the TCn register except the
interrupt flag does not get set.
OC7M — Output Compare 7 Mask Register
$0082
Bit 7
6
5
4
3
2
1
Bit 0
OC7M7
OC7M6
OC7M5
OC7M4
OC7M3
OC7M2
OC7M1
OC7M0
0
0
0
0
0
0
0
0
RESET:
Read or write anytime.
The bits of OC7M correspond bit-for-bit with the bits of timer port
(PORTT). Setting the OC7Mn will set the corresponding port to be an
output port regardless of the state of the DDRTn bit when the
corresponding TIOSn bit is set to be an output compare. This does not
change the state of the DDRT bits. At successful OC7, for eachbit that is
set in OC7M, the corresponding data bit in OC7D is stored to the
corresponding bit of the timer port.
NOTE:
OC7M has priority over output action on timer port enabled by OMn and
OLn bits in TCTL1 and TCTL2. If an OC7M bit is set, it prevents the
action of corresponding OM and OL bits on the selected timer port.
OC7D — Output Compare 7 Data Register
$0083
Bit 7
6
5
4
3
2
1
Bit 0
OC7D7
OC7D6
OC7D5
OC7D4
OC7D3
OC7D2
OC7D1
OC7D0
0
0
0
0
0
0
0
0
RESET:
Read or write anytime.
The bits of OC7D correspond bit-for-bit with the bits of timer port
(PORTT). When a successful OC7 compare occurs, for each bit that is
set in OC7M, the corresponding data bit in OC7D is stored to the
corresponding bit of the timer port.
Technical Data
252
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
When the OC7Mn bit is set, a successful OC7 action will override a
successful OC[6:0] compare action during the same cycle; therefore, the
OCn action taken will depend on the corresponding OC7D bit.
TCNT — Timer Count Register
RESET:
$0084–$0085
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
The 16-bit main timer is an up counter.
A full access for the counter register should take place in one clock cycle.
A separate read/write for high byte and low byte will give a different result
than accessing them as a word.
Read anytime.
Write has no meaning or effect in the normal mode; only writable in
special modes (SMODN = 0).
The period of the first count after a write to the TCNT registers may be a
different size because the write is not synchronized with the prescaler
clock.
TSCR — Timer System Control Register
RESET:
$0086
Bit 7
6
5
4
TEN
TSWAI
TSBCK
TFFCA
0
0
0
0
3
2
1
Bit 0
0
0
0
0
Read or write anytime.
TEN — Timer Enable
0 = Disables the main timer, including the counter. Can be used for
reducing power consumption.
1 = Allows the timer to function normally.
If for any reason the timer is not active, there is no ÷64 clock for the
pulse accumulator since the E÷64 is generated by the timer prescaler.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
253
Enhanced Capture Timer
TSWAI — Timer Module Stops While in Wait
0 = Allows the timer module to continue running during wait.
1 = Disables the timer module when the MCU is in the wait mode.
Timer interrupts cannot be used to get the MCU out of wait.
TSWAI also affects pulse accumulators and modulus down counters.
TSBCK — Timer and Modulus Counter Stop While in Background Mode
0 = Allows the timer and modulus counter to continue running while
in background mode.
1 = Disables the timer and modulus counter whenever the MCU is
in background mode. This is useful for emulation.
TBSCK does not stop the pulse accumulator.
TFFCA — Timer Fast Flag Clear All
0 = Allows the timer flag clearing to function normally.
1 = For TFLG1($8E), a read from an input capture or a write to the
output compare channel ($90–$9F) causes the corresponding
channel flag, CnF, to be cleared. For TFLG2 ($8F), any access
to the TCNT register ($84, $85) clears the TOF flag. Any
access to the PACN3 and PACN2 registers ($A2, $A3) clears
the PAOVF and PAIF flags in the PAFLG register ($A1). Any
access to the PACN1 and PACN0 registers ($A4, $A5) clears
the PBOVF flag in the PBFLG register ($B1). Any access to the
MCCNT register ($B6, $B7) clears the MCZF flag in the
MCFLG register ($A7). This has the advantage of eliminating
software overhead in a separate clear sequence. Extra care is
required to avoid accidental flag clearing due to unintended
accesses.
Technical Data
254
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
TQCR — Reserved
RESET:
$0087
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
TCTL1 — Timer Control Register 1
RESET:
$0088
Bit 7
6
5
4
3
2
1
Bit 0
OM7
OL7
OM6
OL6
OM5
OL5
OM4
OL4
0
0
0
0
0
0
0
0
TCTL2 — Timer Control Register 2
RESET:
$0089
Bit 7
6
5
4
3
2
1
Bit 0
OM3
OL3
OM2
OL2
OM1
OL1
OM0
OL0
0
0
0
0
0
0
0
0
Read or write anytime.
OMn — Output Mode
OLn — Output Level
These eight pairs of control bits are encoded to specify the output
action to be taken as a result of a successful OCn compare. When
either OMn or OLn is one, the pin associated with OCn becomes an
output tied to OCn regardless of the state of the associated DDRT bit.
NOTE:
To enable output action by OMn and OLn bits on timer port, the
corresponding bit in OC7M should be cleared.
Table 15-1. Compare Result Output Action
OMn
0
0
1
1
OLn
0
1
0
1
Action
Timer disconnected from output pin logic
Toggle OCn output line
Clear OCn output line to zero
Set OCn output line to one
To operate the 16-bit pulse accumulators A and B (PACA and PACB)
independently of input capture or output compare 7 and 0 respectively
the user must set the corresponding bits IOSn = 1, OMn = 0 and OLn
= 0. OC7M7 or OC7M0 in the OC7M register must also be cleared.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
255
Enhanced Capture Timer
TCTL3 — Timer Control Register 3
$008A
Bit 7
6
5
4
3
2
1
Bit 0
EDG7B
EDG7A
EDG6B
EDG6A
EDG5B
EDG5A
EDG4B
EDG4A
0
0
0
0
0
0
0
0
RESET:
TCTL4 — Timer Control Register 4
$008B
Bit 7
6
5
4
3
2
1
Bit 0
EDG3B
EDG3A
EDG2B
EDG2A
EDG1B
EDG1A
EDG0B
EDG0A
0
0
0
0
0
0
0
0
RESET:
Read or write anytime.
EDGnB, EDGnA — Input Capture Edge Control
These eight pairs of control bits configure the input capture edge
detector circuits.
Table 15-2. Edge Detector Circuit Configuration
EDGnB
0
0
1
1
EDGnA
0
1
0
1
Configuration
Capture disabled
Capture on rising edges only
Capture on falling edges only
Capture on any edge (rising or falling)
TMSK1 — Timer Interrupt Mask 1
$008C
Bit 7
6
5
4
3
2
1
Bit 0
C7I
C6I
C5I
C4I
C3I
C2I
C1I
C0I
0
0
0
0
0
0
0
0
RESET:
Read or write anytime.
The bits in TMSK1 correspond bit-for-bit with the bits in the TFLG1 status
register. If cleared, the corresponding flag is disabled from causing a
hardware interrupt. If set, the corresponding flag is enabled to cause a
hardware interrupt.
Read or write anytime.
C7I–C0I — Input Capture/Output Compare “x” Interrupt Enable.
Technical Data
256
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
TMSK2 — Timer Interrupt Mask 2
RESET:
$008D
Bit 7
6
5
4
3
2
1
Bit 0
TOI
0
PUPT
RDPT
TCRE
PR2
PR1
PR0
0
0
0
0
0
0
0
0
Read or write anytime.
TOI — Timer Overflow Interrupt Enable
0 = Interrupt inhibited
1 = Hardware interrupt requested when TOF flag set
PUPT — Timer Port Pull-Up Resistor Enable
This enable bit controls pull-up resistors on the timer port pins when
the pins are configured as inputs.
0 = Disable pull-up resistor function
1 = Enable pull-up resistor function
RDPT — Timer Port Drive Reduction
This bit reduces the effective output driver size which can reduce
power supply current and generated noise depending upon pin
loading.
0 = Normal output drive capability
1 = Enable output drive reduction function
TCRE — Timer Counter Reset Enable
This bit allows the timer counter to be reset by a successful output
compare 7 event. This mode of operation is similar to an up-counting
modulus counter.
0 = Counter reset inhibited and counter free runs
1 = Counter reset by a successful output compare 7
If TC7 = $0000 and TCRE = 1, TCNT will stay at $0000 continuously.
If TC7 = $FFFF and TCRE = 1, TOF will never be set when TCNT is
reset from $FFFF to $0000.
PR2, PR1, PR0 — Timer Prescaler Select
These three bits specify the number of ÷2 stages that are to be
inserted between the module clock and the main timer counter.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
257
Enhanced Capture Timer
Table 15-3. Prescaler Selection
PR2
0
0
0
0
1
1
1
1
PR1
0
0
1
1
0
0
1
1
PR0
0
1
0
1
0
1
0
1
Prescale Factor
1
2
4
8
16
32
64
128
The newly selected prescale factor will not take effect until the next
synchronized edge where all prescale counter stages equal zero.
TFLG1 — Main Timer Interrupt Flag 1
$008E
Bit 7
6
5
4
3
2
1
Bit 0
C7F
C6F
C5F
C4F
C3F
C2F
C1F
C0F
0
0
0
0
0
0
0
0
RESET:
TFLG1 indicates when interrupt conditions have occurred. To clear a bit
in the flag register, write a one to the bit.
Use of the TFMOD bit in the ICSYS register ($AB) in conjunction with the
use of the ICOVW register ($AA) allows a timer interrupt to be generated
after capturing two values in the capture and holding registers instead of
generating an interrupt for every capture.
Read anytime. Write used in the clearing mechanism (set bits cause
corresponding bits to be cleared). Writing a zero will not affect current
status of the bit.
When TFFCA bit in TSCR register is set, a read from an input capture or
a write into an output compare channel ($90–$9F) will cause the
corresponding channel flag CnF to be cleared.
C7F–C0F — Input Capture/Output Compare Channel “n” Flag.
Technical Data
258
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
TFLG2 — Main Timer Interrupt Flag 2
RESET:
$008F
Bit 7
6
5
4
3
2
1
Bit 0
TOF
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
TFLG2 indicates when interrupt conditions have occurred. To clear a bit
in the flag register, set the bit to one.
Read anytime. Write used in clearing mechanism (set bits cause
corresponding bits to be cleared).
Any access to TCNT will clear TFLG2 register if the TFFCA bit in TSCR
register is set.
TOF — Timer Overflow Flag
Set when 16-bit free-running timer overflows from $FFFF to $0000.
This bit is cleared automatically by a write to the TFLG2 register with
bit 7 set. (See also TCRE control bit explanation.)
TC0 — Timer Input Capture/Output Compare Register 0
$0090–$0091
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC1 — Timer Input Capture/Output Compare Register 1
$0092–$0093
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC2 — Timer Input Capture/Output Compare Register 2
$0094–$0095
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC3 — Timer Input Capture/Output Compare Register 3
$0096–$0097
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
259
Enhanced Capture Timer
TC4 — Timer Input Capture/Output Compare Register 4
$0098–$0099
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC5 — Timer Input Capture/Output Compare Register 5
$009A–$009B
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC6 — Timer Input Capture/Output Compare Register 6
$009C–$009D
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC7 — Timer Input Capture/Output Compare Register 7
$009E–$009F
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
Depending on the TIOS bit for the corresponding channel, these
registers are used to latch the value of the free-running counter when a
defined transition is sensed by the corresponding input capture edge
detector or to trigger an output action for output compare.
Read anytime. Write anytime for output compare function. Writes to
these registers have no meaning or effect during input capture. All timer
input capture/output compare registers are reset to $0000.
PACTL — 16-Bit Pulse Accumulator A Control Register
$00A0
BIT 7
6
5
4
3
2
1
BIT 0
0
PAEN
PAMOD
PEDGE
CLK1
CLK0
PAOVI
PAI
0
0
0
0
0
0
0
0
RESET:
16-Bit Pulse Accumulator A (PACA) is formed by cascading the 8-bit
pulse accumulators PAC3 and PAC2.
When PAEN is set, the PACA is enabled. The PACA shares the input pin
with IC7.
Read: any time
Write: any time
Technical Data
260
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
PAEN — Pulse Accumulator A System Enable
0 = 16-Bit Pulse Accumulator A system disabled. 8-bit PAC3 and
PAC2 can be enabled when their related enable bits in ICPACR
($A8) are set.
Pulse Accumulator Input Edge Flag (PAIF) function is disabled.
1 = Pulse Accumulator A system enabled. The two 8-bit pulse
accumulators PAC3 and PAC2 are cascaded to form the PACA
16-bit pulse accumulator. When PACA in enabled, the PACN3
and PACN2 registers contents are respectively the high and low
byte of the PACA.
PA3EN and PA2EN control bits in ICPACR ($A8) have no effect.
Pulse Accumulator Input Edge Flag (PAIF) function is enabled.
PAEN is independent from TEN. With timer disabled, the pulse
accumulator can still function unless pulse accumulator is disabled.
PAMOD — Pulse Accumulator Mode
0 = event counter mode
1 = gated time accumulation mode
PEDGE — Pulse Accumulator Edge Control
For PAMOD bit = 0 (event counter mode).
0 = falling edges on PT7 pin cause the count to be incremented
1 = rising edges on PT7 pin cause the count to be incremented
For PAMOD bit = 1 (gated time accumulation mode).
0 = PT7 input pin high enables M divided by 64 clock to Pulse
Accumulator and the trailing falling edge on PT7 sets the PAIF
flag.
1 = PT7 input pin low enables M divided by 64 clock to Pulse
Accumulator and the trailing rising edge on PT7 sets the PAIF
flag.
PAMOD
PEDGE
0
0
Falling edge
Pin Action
0
1
Rising edge
1
0
Div. by 64 clock enabled with pin high level
1
1
Div. by 64 clock enabled with pin low level
If the timer is not active (TEN = 0 in TSCR), there is no divide-by-64
since the E÷64 clock is generated by the timer prescaler.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
261
Enhanced Capture Timer
CLK1, CLK0 — Clock Select Bits
CLK1
CLK0
0
0
Use timer prescaler clock as timer counter clock
Clock Source
0
1
Use PACLK as input to timer counter clock
1
0
Use PACLK/256 as timer counter clock frequency
1
1
Use PACLK/65536 as timer counter clock
frequency
If the pulse accumulator is disabled (PAEN = 0), the prescaler clock
from the timer is always used as an input clock to the timer counter.
The change from one selected clock to the other happens
immediately after these bits are written.
PAOVI — Pulse Accumulator A Overflow Interrupt enable
0 = interrupt inhibited
1 = interrupt requested if PAOVF is set
PAI — Pulse Accumulator Input Interrupt enable
0 = interrupt inhibited
1 = interrupt requested if PAIF is set
PAFLG — Pulse Accumulator A Flag Register
$00A1
BIT 7
6
5
4
3
2
1
BIT 0
0
0
0
0
0
0
PAOVF
PAIF
0
0
0
0
0
0
0
0
RESET:
Read or write anytime. When the TFFCA bit in the TSCR register is set,
any access to the PACNT register will clear all the flags in the PAFLG
register.
PAOVF — Pulse Accumulator A Overflow Flag
Set when the 16-bit pulse accumulator A overflows from $FFFF to
$0000,or when 8-bit pulse accumulator 3 (PAC3) overflows from $FF
to $00.
This bit is cleared automatically by a write to the PAFLG register with
bit 1 set.
Technical Data
262
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
PAIF — Pulse Accumulator Input edge Flag
Set when the selected edge is detected at the PT7 input pin. In event
mode the event edge triggers PAIF and in gated time accumulation
mode the trailing edge of the gate signal at the PT7 input pin triggers
PAIF.
This bit is cleared by a write to the PAFLG register with bit 0 set.
Any access to the PACN3, PACN2 registers will clear all the flags in
this register when TFFCA bit in register TSCR($86) is set.
PACN3, PACN2 — Pulse Accumulators Count Registers
$00A2, $00A3
BIT 7
6
5
4
3
2
1
BIT 0
$00A2
BIt 7
6
5
4
3
2
1
Bit 0
PACN3 (hi)
$00A3
Bit 7
6
5
4
3
2
1
Bit 0
PACN2 (lo)
RESET:
0
0
0
0
0
0
0
0
Read or write any time.
The two 8-bit pulse accumulators PAC3 and PAC2 are cascaded to form
the PACA 16-bit pulse accumulator. When PACA in enabled (PAEN=1
in PACTL, $A0) the PACN3 and PACN2 registers contents are
respectively the high and low byte of the PACA.
When PACN3 overflows from $FF to $00, the Interrupt flag PAOVF in
PAFLG ($A1) is set.
Full count register access should take place in one clock cycle. A
separate read/write for high byte and low byte will give a different result
than accessing them as a word.
PACN1, PACN0 — Pulse Accumulators Count Registers
$00A4, $00A5
BIT 7
6
5
4
3
2
1
BIT 0
$00A4
BIt 7
6
5
4
3
2
1
Bit 0
PACN1 (hi)
$00A5
Bit 7
6
5
4
3
2
1
Bit 0
PACN0 (lo)
RESET:
0
0
0
0
0
0
0
0
Read or write any time.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
263
Enhanced Capture Timer
The two 8-bit pulse accumulators PAC1 and PAC0 are cascaded to form
the PACB 16-bit pulse accumulator. When PACB in enabled, (PBEN=1
in PBCTL, $B0) the PACN1 and PACN0 registers contents are
respectively the high and low byte of the PACB.
When PACN1 overflows from $FF to $00, the Interrupt flag PBOVF in
PBFLG ($B1) is set.
Full count register access should take place in one clock cycle. A
separate read/write for high byte and low byte will give a different result
than accessing them as a word.
MCCTL — 16-Bit Modulus Down-Counter Control Register
$00A6
BIT 7
6
5
4
3
2
1
BIT 0
MCZI
MODMC
RDMCL
ICLAT
FLMC
MCEN
MCPR1
MCPR0
0
0
0
0
0
0
0
0
RESET:
Read or write any time.
MCZI — Modulus Counter Underflow Interrupt Enable
0 = Modulus counter interrupt is disabled.
1 = Modulus counter interrupt is enabled.
MODMC — Modulus Mode Enable
0 = The counter counts once from the value written to it and will
stop at $0000.
1 = Modulus mode is enabled. When the counter reaches $0000,
the counter is loaded with the latest value written to the
modulus count register.
NOTE:
For proper operation, the MCEN bit should be cleared before modifying
the MODMC bit in order to reset the modulus counter to $FF.
RDMCL — Read Modulus Down-Counter Load
0 = Reads of the modulus count register will return the present
value of the count register.
1 = Reads of the modulus count register will return the contents of
the load register.
Technical Data
264
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
ICLAT — Input Capture Force Latch Action
When input capture latch mode is enabled (LATQ and BUFEN bit in
ICSYS ($AB) are set), a write one to this bit immediately forces the
contents of the input capture registers TC0 to TC3 and their
corresponding 8-bit pulse accumulators to be latched into the
associated holding registers. The pulse accumulators will be
automatically cleared when the latch action occurs.
Writing zero to this bit has no effect. Read of this bit will return always
zero.
FLMC — Force Load Register into the Modulus Counter Count Register
This bit is active only when the modulus down-counter is enabled
(MCEN=1).
A write one into this bit loads the load register into the modulus
counter count register. This also resets the modulus counter
prescaler. Write zero to this bit has no effect.
When MODMC=0, counter starts counting and stops at $0000.
Read of this bit will return always zero.
MCEN — Modulus Down-Counter Enable
0 = Modulus counter disabled.
1 = Modulus counter is enabled.
When MCEN=0, the counter is preset to $FFFF. This will prevent an
early interrupt flag when the modulus down-counter is enabled.
MCPR1, MCPR0 — Modulus Counter Prescaler select
These two bits specify the division rate of the modulus counter
prescaler.
The newly selected prescaler division rate will not be effective until a
load of the load register into the modulus counter count register
occurs.
MCPR1
MCPR0
Prescaler division rate
0
0
1
0
1
4
1
0
8
1
1
16
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
265
Enhanced Capture Timer
MCFLG — 16-Bit Modulus Down-Counter FLAG Register
$00A7
BIT 7
6
5
4
3
2
1
BIT 0
MCZF
0
0
0
POLF3
POLF2
POLF1
POLF0
0
0
0
0
0
0
0
0
RESET:
Read: any time
Write: Only for clearing bit 7
MCZF — Modulus Counter Underflow Interrupt Flag
The flag is set when the modulus down-counter reaches $0000.
A write one to this bit clears the flag. Write zero has no effect.
Any access to the MCCNT register will clear the MCZF flag in this
register when TFFCA bit in register TSCR($86) is set.
POLF3 – POLF0 — First Input Capture Polarity Status
This are read only bits. Write to these bits has no effect.
Each status bit gives the polarity of the first edge which has caused
an input capture to occur after capture latch has been read.
Each POLFx corresponds to a timer PORTx input.
0 = The first input capture has been caused by a falling edge.
1 = The first input capture has been caused by a rising edge.
ICPAR — Input Control Pulse Accumulators Register
$00A8
BIT 7
6
5
4
3
2
1
BIT 0
0
0
0
0
PA3EN
PA2EN
PA1EN
PA0EN
0
0
0
0
0
0
0
0
RESET:
The 8-bit pulse accumulators PAC3 and PAC2 can be enabled only if
PAEN in PATCL ($A0) is cleared. If PAEN is set, PA3EN and PA2EN
have no effect.
The 8-bit pulse accumulators PAC1 and PAC0 can be enabled only if
PBEN in PBTCL ($B0) is cleared. If PBEN is set, PA1EN and PA0EN
have no effect.
Read or write any time.
Technical Data
266
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
PAxEN — 8-Bit Pulse Accumulator ‘x’ Enable
0 = 8-Bit Pulse Accumulator is disabled.
1 = 8-Bit Pulse Accumulator is enabled.
DLYCT — Delay Counter Control Register
RESET:
$00A9
BIT 7
6
5
4
3
2
1
BIT 0
0
0
0
0
0
0
DLY1
DLY0
0
0
0
0
0
0
0
0
Read or write any time.
If enabled, after detection of a valid edge on input capture pin, the delay
counter counts the pre-selected number of M clock (module clock)
cycles, then it will generate a pulse on its output. The pulse is generated
only if the level of input signal, after the preset delay, is the opposite of
the level before the transition.This will avoid reaction to narrow input
pulses.
After counting, the counter will be cleared automatically.
Delay between two active edges of the input signal period should be
longer than the selected counter delay.
DLYx — Delay Counter Select
DLY1
DLY0
0
0
Disabled (bypassed)
Delay
0
1
256M clock cycles
1
0
512M clock cycles
1
1
1024 M clock cycles
ICOVW — Input Control Overwrite Register
RESET:
$00AA
BIT 7
6
5
4
3
2
1
BIT 0
NOVW7
NOVW6
NOVW5
NOVW4
NOVW3
NOVW2
NOVW1
NOVW0
0
0
0
0
0
0
0
0
Read or write any time.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
267
Enhanced Capture Timer
An IC register is empty when it has been read or latched into the holding
register.
A holding register is empty when it has been read.
NOVWx — No Input Capture Overwrite
0 = The contents of the related capture register or holding register
can be overwritten when a new input capture or latch occurs.
1 = The related capture register or holding register cannot be
written by an event unless they are empty (see IC Channels).
This will prevent the captured value to be overwritten until it is
read or latched in the holding register.
ICSYS — Input Control System Control Register
$00AB
BIT 7
6
5
4
3
2
1
BIT 0
SH37
SH26
SH15
SH04
TFMOD
PACMX
BUFEN
LATQ
0
0
0
0
0
0
0
0
RESET:
Read: any time
Write: May be written once (SMODN=1). Writes are always permitted
when SMODN=0.
SHxy — Share Input action of Input Capture Channels x and y
0 = Normal operation
1 = The channel input ‘x’ causes the same action on the channel
‘y’. The port pin ‘x’ and the corresponding edge detector is
used to be active on the channel ‘y’.
TFMOD — Timer Flag-setting Mode
Use of the TFMOD bit in the ICSYS register ($AB) in conjunction with
the use of the ICOVW register ($AA) allows a timer interrupt to be
generated after capturing two values in the capture and holding
registers instead of generating an interrupt for every capture.
By setting TFMOD in queue mode, when NOVW bit is set and the
corresponding capture and holding registers are emptied, an input
capture event will first update the related input capture register with
Technical Data
268
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
the main timer contents. At the next event the TCn data is transferred
to the TCnH register, The TCn is updated and the CnF interrupt flag
is set. See Figure 15-6.
In all other input capture cases the interrupt flag is set by a valid
external event on PTn.
0 = The timer flags C3F–C0F in TFLG1 ($8E) are set when a valid
input capture transition on the corresponding port pin occurs.
1 = If in queue mode (BUFEN=1 and LATQ=0), the timer flags
C3F–C0F in TFLG1 ($8E) are set only when a latch on the
corresponding holding register occurs.
If the queue mode is not engaged, the timer flags C3F–C0F are
set the same way as for TFMOD=0.
PACMX — 8-Bit Pulse Accumulators Maximum Count
0 = Normal operation. When the 8-bit pulse accumulator has
reached the value $FF, with the next active edge, it will be
incremented to $00.
1 = When the 8-bit pulse accumulator has reached the value $FF,
it will not be incremented further. The value $FF indicates a
count of 255 or more.
BUFEN — IC Buffer Enable
0 = Input Capture and pulse accumulator holding registers are
disabled.
1 = Input Capture and pulse accumulator holding registers are
enabled. The latching mode is defined by LATQ control bit.
Write one into ICLAT bit in MCCTL ($A6), when LATQ is set
will produce latching of input capture and pulse accumulators
registers into their holding registers.
LATQ — Input Control Latch or Queue Mode Enable
The BUFEN control bit should be set in order to enable the IC and
pulse accumulators holding registers. Otherwise LATQ latching
modes are disabled.
Write one into ICLAT bit in MCCTL ($A6), when LATQ and BUFEN
are set will produce latching of input capture and pulse accumulators
registers into their holding registers.
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269
Enhanced Capture Timer
0 = Queue Mode of Input Capture is enabled.
The main timer value is memorized in the IC register by a valid
input pin transition.
With a new occurrence of a capture, the value of the IC register
will be transferred to its holding register and the IC register
memorizes the new timer value.
1 = Latch Mode is enabled. Latching function occurs when
modulus down-counter reaches zero or a zero is written into
the count register MCCNT (see Buffered IC Channels).
With a latching event the contents of IC registers and 8-bit
pulse accumulators are transferred to their holding registers.
8-bit pulse accumulators are cleared.
TIMTST — Timer Test Register
$00AD
BIT 7
6
5
4
3
2
1
BIT 0
0
0
0
0
0
0
TCBYP
0
0
0
0
0
0
0
0
0
RESET:
Read: any time
Write: only in special mode (SMOD = 1).
TCBYP — Main Timer Divider Chain Bypass
0 = Normal operation
1 = For testing only. The 16-bit free-running timer counter is divided
into two 8-bit halves and the prescaler is bypassed. The clock
drives both halves directly.
When the high byte of timer counter TCNT ($84) overflows
from $FF to $00, the TOF flag in TFLG2 ($8F) will be set.
PORTT — Timer Port Data Register
$00AE
BIT 7
6
5
4
3
2
1
BIT 0
PORT
PT7
PT6
PT5
PT4
PT3
PT2
PT1
PT0
TIMER
I/OC7
I/OC6
I/OC5
I/OC4
I/OC3
I/OC2
I/OC1
I/OC0
RESET:
-
-
-
-
-
-
-
-
Read: any time (inputs return pin level; outputs return data register
contents)
Technical Data
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MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
Write: data stored in an internal latch (drives pins only if configured for
output)
Since the Output Compare 7 shares the pin with Pulse Accumulator
input, the only way for Pulse accumulator to receive an independent
input from Output Compare 7 is setting both OM7 & OL7 to be zero, and
also OC7M7 in OC7M register to be zero.
OC7 is still able to reset the counter if enabled while PT7 is used as input
to Pulse Accumulator.
PORTT can be read anytime. When configured as an input, a read will
return the pin level. When configured as an output, a read will return the
latched output data.
NOTE:
Writes do not change pin state when the pin is configured for timer
output. The minimum pulse width for pulse accumulator input should
always be greater than the width of two module clocks due to input
synchronizer circuitry. The minimum pulse width for the input capture
should always be greater than the width of two module clocks due to
input synchronizer circuitry.
DDRT — Data Direction Register for Timer Port
RESET:
$00AF
BIT 7
6
5
4
3
2
1
BIT 0
DDT7
DDT6
DDT5
DDT4
DDT3
DDT2
DDT1
DDT0
0
0
0
0
0
0
0
0
Read or write any time.
0 = Configures the corresponding I/O pin for input only
1 = Configures the corresponding I/O pin for output.
The timer forces the I/O state to be an output for each timer port line
associated with an enabled output compare. In these cases the data
direction bits will not be changed, but have no effect on the direction
of these pins. The DDRT will revert to controlling the I/O direction of
a pin when the associated timer output compare is disabled. Input
captures do not override the DDRT settings.
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Technical Data
Enhanced Capture Timer
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Enhanced Capture Timer
PBCTL — 16-Bit Pulse Accumulator B Control Register
$00B0
BIT 7
6
5
4
3
2
1
BIT 0
0
PBEN
0
0
0
0
PBOVI
0
0
0
0
0
0
0
0
0
RESET:
Read or write any time.
16-Bit Pulse Accumulator B (PACB) is formed by cascading the 8-bit
pulse accumulators PAC1 and PAC0.
When PBEN is set, the PACB is enabled. The PACB shares the input pin
with IC0.
PBEN — Pulse Accumulator B System Enable
0 = 16-bit Pulse Accumulator system disabled. 8-bit PAC1 and
PAC0 can be enabled when their related enable bits in
ICPACR ($A8) are set.
1 = Pulse Accumulator B system enabled. The two 8-bit pulse
accumulators PAC1 and PAC0 are cascaded to form the
PACB 16-bit pulse accumulator. When PACB in enabled, the
PACN1 and PACN0 registers contents are respectively the
high and low byte of the PACB.
PA1EN and PA0EN control bits in ICPACR ($A8) have no
effect.
PBEN is independent from TEN. With timer disabled, the pulse
accumulator can still function unless pulse accumulator is disabled.
PBOVI — Pulse Accumulator B Overflow Interrupt enable
0 = interrupt inhibited
1 = interrupt requested if PBOVF is set
PBFLG — Pulse Accumulator B Flag Register
$00B1
BIT 7
6
5
4
3
2
1
BIT 0
0
0
0
0
0
0
PBOVF
0
0
0
0
0
0
0
0
0
RESET:
Read or write any time.
Technical Data
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MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer Register Descriptions
PBOVF — Pulse Accumulator B Overflow Flag
This bit is set when the 16-bit pulse accumulator B overflows from
$FFFF to $0000, or when 8-bit pulse accumulator 1 (PAC1) overflows
from $FF to $00.
This bit is cleared by a write to the PBFLG register with bit 1 set.
Any access to the PACN1 and PACN0 registers will clear the PBOVF
flag in this register when TFFCA bit in register TSCR($86) is set.
PA3H–PA0H — 8-Bit Pulse Accumulators Holding Registers
$00B2–$00B5
BIT 7
6
5
4
3
2
1
BIT 0
$00B2
BIt 7
6
5
4
3
2
1
Bit 0
PA3H
$00B3
Bit 7
6
5
4
3
2
1
Bit 0
PA2H
$00B4
BIt 7
6
5
4
3
2
1
Bit 0
PA1H
$00B5
Bit 7
6
5
4
3
2
1
Bit 0
PA0H
RESET:
0
0
0
0
0
0
0
0
Read: any time
Write: has no effect.
These registers are used to latch the value of the corresponding pulse
accumulator when the related bits in register ICPAR ($A8) are enabled
(see Pulse Accumulators).
MCCNT — Modulus Down-Counter Count Register
$00B6, $00B7
BIT 7
6
5
4
3
2
1
BIT 0
$00B6
BIt 15
14
13
12
11
10
9
Bit 8
MCCNTH
$00B7
Bit 7
6
5
4
3
2
1
Bit 0
MCCNTL
RESET:
1
1
1
1
1
1
1
1
Read or write any time.
A full access for the counter register should take place in one clock cycle.
A separate read/write for high byte and low byte will give different result
than accessing them as a word.
If the RDMCL bit in MCCTL register is cleared, reads of the MCCNT
register will return the present value of the count register. If the RDMCL
MC68HC912DT128A — Rev 4.0
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Technical Data
Enhanced Capture Timer
273
Enhanced Capture Timer
bit is set, reads of the MCCNT will return the contents of the load
register.
If a $0000 is written into MCCNT and modulus counter while LATQ and
BUFEN in ICSYS ($AB) register are set, the input capture and pulse
accumulator registers will be latched.
With a $0000 write to the MCCNT, the modulus counter will stay at zero
and does not set the MCZF flag in MCFLG register.
If modulus mode is enabled (MODMC=1), a write to this address will
update the load register with the value written to it. The count register will
not be updated with the new value until the next counter underflow.
The FLMC bit in MCCTL ($A6) can be used to immediately update the
count register with the new value if an immediate load is desired.
If modulus mode is not enabled (MODMC=0), a write to this address will
clear the prescaler and will immediately update the counter register with
the value written to it and down-counts once to $0000.
TC0H — Timer Input Capture Holding Register 0
$00B8–$00B9
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC1H — Timer Input Capture Holding Register 1
$00BA–$00BB
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC2H — Timer Input Capture Holding Register 2
$00BC–$00BD
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
TC3H — Timer Input Capture Holding Register 3
$00BE–$00BF
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Bit 7
6
5
4
3
2
1
Bit 0
Technical Data
274
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Enhanced Capture Timer
Timer and Modulus Counter Operation in Different Modes
Read: any time
Write: has no effect.
These registers are used to latch the value of the input capture registers
TC0 – TC3. The corresponding IOSx bits in TIOS ($80) should be
cleared (see IC Channels).
15.5 Timer and Modulus Counter Operation in Different Modes
STOP:
Timer and modulus counter are off since clocks are
stopped.
BGDM:
Timer and modulus counter keep on running, unless
TSBCK (REG$86, bit5) is set to one.
WAIT:
Counters keep on running, unless TSWAI in TSCR ($86)
is set to one.
NORMAL:
Timer and modulus counter keep on running, unless TEN
in TSCR($86) respectively MCEN in MCCTL ($A6) are
cleared.
TEN=0:
All 16-bit timer operations are stopped, can only access
the registers.
MCEN=0:
Modulus counter is stopped.
PAEN=1:
16-bit Pulse Accumulator A is active.
PAEN=0:
8-Bit Pulse Accumulators 3 and 2 can be enabled. (see
ICPAR)
PBEN=1:
16-bit Pulse Accumulator B is active.
PBEN=0:
8-Bit Pulse Accumulators 1 and 0 can be enabled. (see
ICPAR)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Enhanced Capture Timer
275
Enhanced Capture Timer
Technical Data
276
MC68HC912DT128A — Rev 4.0
Enhanced Capture Timer
MOTOROLA
Technical Data — MC68HC912DT128A
Section 16. Multiple Serial Interface
16.1 Contents
16.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
16.3
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .278
16.4
Serial Communication Interface (SCI) . . . . . . . . . . . . . . . . . .278
16.5
Serial Peripheral Interface (SPI) . . . . . . . . . . . . . . . . . . . . . . .289
16.6
Port S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
16.2 Introduction
The multiple serial interface (MSI) module consists of three independent
serial I/O sub-systems: two serial communication interfaces (SCI0 and
SCI1) and the serial peripheral interface (SPI). Each serial pin shares
function with the general-purpose port pins of port S. The SCI
subsystems are NRZ type systems that are compatible with standard
RS-232 systems. These SCI systems have a new single wire operation
mode which allows the unused pin to be available as general-purpose
I/O. The SPI subsystem, which is compatible with the M68HC11 SPI,
includes new features such as SS output and bidirectional mode.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
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Multiple Serial Interface
16.3 Block diagram
SCI1
RxD0
PS0
TxD0
PS1
RxD1
TxD1
MISO/SISO
SPI
MOSI/MOMI
PORT S I/O DRIVERS
SCI0
DDRS/IOCTLR
MSI
PS2
PS3
PS4
PS5
SCK
PS6
CS/SS
PS7
HC12A4 MSI BLOCK
Figure 16-1. Multiple Serial Interface Block Diagram
16.4 Serial Communication Interface (SCI)
Two serial communication interfaces are available on the
MC68HC912DT128A. These are NRZ format (one start, eight or nine
data, and one stop bit) asynchronous communication systems with
independent internal baud rate generation circuitry and SCI transmitters
and receivers. They can be configured for eight or nine data bits (one of
which may be designated as a parity bit, odd or even). If enabled, parity
is generated in hardware for transmitted and received data. Receiver
parity errors are flagged in hardware. The baud rate generator is based
on a modulus counter, allowing flexibility in choosing baud rates. There
is a receiver wake-up feature, an idle line detect feature, a loop-back
mode, and various error detection features. Two port pins for each SCI
provide the external interface for the transmitted data (TXD) and the
received data (RXD).
For a faster wake-up out of WAIT mode by a received SCI message,
both SCI have the capability of sending a receiver interrupt, if enabled,
when RAF (receiver active flag) is set. For compatibility with other
M68HC12 products, this feature is active only in WAIT mode and is
disabled when VDDPLL supply is at VSS level.
Technical Data
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MC68HC912DT128A — Rev 4.0
Multiple Serial Interface
MOTOROLA
Multiple Serial Interface
Serial Communication Interface (SCI)
MCLK
BAUD RATE
CLOCK
SCI TRANSMITTER
MSB
DIVIDER
Rx Baud Rate
PARITY
GENERATOR
LSB
10-11 Bit SHIFT REG
TxD BUFFER/SCxDRL
PIN CONTROL / DDRS / PORT S
SCxBD/SELECT
Tx Baud Rate
SCxCR1/SCI CTL 1
TxMTR CONTROL
DATA BUS
SCxCR2/SCI CTL 2
TxD
SCxSR1/INT STATUS
RxD
INT REQUEST LOGIC
TO
INTERNAL
LOGIC
PARITY
DETECT
DATA RECOVERY
SCI RECEIVER
MSB
LSB
10-11 BIT SHIFT REG
TxD BUFFER/SCxDRL
SCxCR1/SCI CTL 1
WAKE-UP LOGIC
SCxSR1/INT STATUS
SCxCR2/SCI CTL 2
INT REQUEST LOGIC
HC12A4 SCI BLOCK
Figure 16-2. Serial Communications Interface Block Diagram
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
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279
Multiple Serial Interface
16.4.1 Data Format
The serial data format requires the following conditions:
•
An idle-line in the high state before transmission or reception of a
message.
•
A start bit (logic zero), transmitted or received, that indicates the
start of each character.
•
Data that is transmitted or received least significant bit (LSB) first.
•
A stop bit (logic one), used to indicate the end of a frame. (A frame
consists of a start bit, a character of eight or nine data bits and a
stop bit.)
•
A BREAK is defined as the transmission or reception of a logic
zero for one frame or more.
•
This SCI supports hardware parity for transmit and receive.
16.4.2 SCI Baud Rate Generation
The basis of the SCI baud rate generator is a 13-bit modulus counter.
This counter gives the generator the flexibility necessary to achieve a
reasonable level of independence from the CPU operating frequency
and still be able to produce standard baud rates with a minimal amount
of error. The clock source for the generator comes from the M Clock.
Table 16-1. Baud Rate Generation
Desired
SCI Baud Rate
110
300
600
1200
2400
4800
9600
14400
19200
38400
BR Divisor for
M = 4.0 MHz
2273
833
417
208
104
52
26
17
13
—
Technical Data
280
BR Divisor for
M = 8.0 MHz
4545
2273
833
417
208
104
52
35
26
13
MC68HC912DT128A — Rev 4.0
Multiple Serial Interface
MOTOROLA
Multiple Serial Interface
Serial Communication Interface (SCI)
16.4.3 SCI Register Descriptions
Control and data registers for the SCI subsystem are described below.
The memory address indicated for each register is the default address
that is in use after reset. Both SCI have identical control registers
mapped in two blocks of eight bytes.
SC0BDH/SC1BDH — SCI Baud Rate Control Register
RESET:
Bit 7
BTST
0
6
BSPL
0
5
BRLD
0
4
SBR12
0
$00C0/$00C8
3
SBR11
0
2
SBR10
0
1
SBR9
0
SC0BDL/SC1BDL — SCI Baud Rate Control Register
RESET:
Bit 7
SBR7
0
6
SBR6
0
5
SBR5
0
4
SBR4
0
Bit 0
SBR8
0
High
$00C1/$00C9
3
SBR3
0
2
SBR2
1
1
SBR1
0
Bit 0
SBR0
0
Low
SCxBDH and SCxBDL are considered together as a 16-bit baud rate
control register.
Read any time. Write SBR[12:0] anytime. Low order byte must be written
for change to take effect. Write SBR[15:13] only in special modes. The
value in SBR[12:0] determines the baud rate of the SCI. The desired
baud rate is determined by the following formula:
MCLKSCI Baud Rate = ------------------16 × BR
which is equivalent to:
MCLK
BR = -----------------------------------------------16 × SCI Baud Rate
BR is the value written to bits SBR[12:0] to establish baud rate.
NOTE:
The baud rate generator is disabled until TE or RE bit in SCxCR2
register is set for the first time after reset, and/or the baud rate generator
is disabled when SBR[12:0] = 0.
BTST — Reserved for test function
BSPL — Reserved for test function
BRLD — Reserved for test function
MC68HC912DT128A — Rev 4.0
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Technical Data
Multiple Serial Interface
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Multiple Serial Interface
SC0CR1/SC1CR1 — SCI Control Register 1
RESET:
Bit 7
LOOPS
0
6
WOMS
0
5
RSRC
0
$00C2/$00CA
4
M
0
3
WAKE
0
2
ILT
0
1
PE
0
Bit 0
PT
0
Read or write anytime.
LOOPS — SCI LOOP Mode/Single Wire Mode Enable
0 = SCI transmit and receive sections operate normally.
1 = SCI receive section is disconnected from the RXD pin and the
RXD pin is available as general purpose I/O. The receiver input
is determined by the RSRC bit. The transmitter output is
controlled by the associated DDRS bit. Both the transmitter
and the receiver must be enabled to use the LOOP or the
single wire mode.
If the DDRS bit associated with the TXD pin is set during the LOOPS
= 1, the TXD pin outputs the SCI waveform. If the DDRS bit
associated with the TXD pin is clear during the LOOPS = 1, the TXD
pin becomes high (IDLE line state) for RSRC = 0 and high impedance
for RSRC = 1. Refer to Table 16-2.
WOMS — Wired-Or Mode for Serial Pins
This bit controls the two pins (TXD and RXD) associated with the SCIx
section.
0 = Pins operate in a normal mode with both high and low drive
capability. To affect the RXD bit, that bit would have to be
configured as an output (via DDRS0/2) which is the single wire
case when using the SCI. WOMS bit still affects generalpurpose output on TXD and RXD pins when SCIx is not using
these pins.
1 = Each pin operates in an open drain fashion if that pin is
declared as an output.
Technical Data
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Multiple Serial Interface
MOTOROLA
Multiple Serial Interface
Serial Communication Interface (SCI)
RSRC — Receiver Source
When LOOPS = 1, the RSRC bit determines the internal feedback
path for the receiver.
0 = Receiver input is connected to the transmitter internally (not
TXD pin)
1 = Receiver input is connected to the TXD pin
Table 16-2. Loop Mode Functions
LOOPS RSRC DDRS1(3) WOMS
Function of Port S Bit 1/3
0
x
x
x
Normal Operations
1
0
0
0/1
LOOP mode without TXD output(TXD = High Impedance)
1
0
1
1
LOOP mode with TXD output (CMOS)
1
0
1
1
LOOP mode with TXD output (open-drain)
Single wire mode without TXD output
1
1
0
x
(the pin is used as receiver input only, TXD = High Impedance)
Single wire mode with TXD output
1
1
1
0
(the output is also fed back to receiver input, CMOS)
1
1
1
1
Single wire mode for the receiving and transmitting(open-drain)
M — Mode (select character format)
0 = One start, eight data, one stop bit
1 = One start, eight data, ninth data, one stop bit
WAKE — Wake-up by Address Mark/Idle
0 = Wake up by IDLE line recognition
1 = Wake up by address mark (last data bit set)
ILT — Idle Line Type
Determines which of two types of idle line detection will be used by
the SCI receiver.
0 = Short idle line mode is enabled.
1 = Long idle line mode is detected.
In the short mode, the SCI circuitry begins counting ones in the search
for the idle line condition immediately after the start bit. This means
that the stop bit and any bits that were ones before the stop bit could
be counted in that string of ones, resulting in earlier recognition of an
idle line.
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Technical Data
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Multiple Serial Interface
In the long mode, the SCI circuitry does not begin counting ones in the
search for the idle line condition until a stop bit is received. Therefore,
the last byte’s stop bit and preceding “1” bits do not affect how quickly
an idle line condition can be detected.
PE — Parity Enable
0 = Parity is disabled.
1 = Parity is enabled.
PT — Parity Type
If parity is enabled, this bit determines even or odd parity for both the
receiver and the transmitter.
0 = Even parity is selected. An even number of ones in the data
character causes the parity bit to be zero and an odd number
of ones causes the parity bit to be one.
1 = Odd parity is selected. An odd number of ones in the data
character causes the parity bit to be zero and an even number
of ones causes the parity bit to be one.
SC0CR2/SC1CR2 — SCI Control Register 2
RESET:
Bit 7
TIE
0
6
TCIE
0
5
RIE
0
$00C3/$00CB
4
ILIE
0
3
TE
0
2
RE
0
1
RWU
0
Bit 0
SBK
0
Read or write anytime.
TIE — Transmit Interrupt Enable
0 = TDRE interrupts disabled
1 = SCI interrupt will be requested whenever the TDRE status flag
is set.
TCIE — Transmit Complete Interrupt Enable
0 = TC interrupts disabled
1 = SCI interrupt will be requested whenever the TC status flag is
set.
Technical Data
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Multiple Serial Interface
MOTOROLA
Multiple Serial Interface
Serial Communication Interface (SCI)
RIE — Receiver Interrupt Enable
0 = RDRF and OR interrupts disabled, RAF interrupt in WAIT mode
disabled
1 = SCI interrupt will be requested whenever the RDRF or OR
status flag is set, or when RAF is set while in WAIT mode with
VDDPLL high.
ILIE — Idle Line Interrupt Enable
0 = IDLE interrupts disabled
1 = SCI interrupt will be requested whenever the IDLE status flag
is set.
TE — Transmitter Enable
0 = Transmitter disabled
1 = SCI transmit logic is enabled and the TXD pin (Port S bit 1/bit
3) is dedicated to the transmitter. The TE bit can be used to
queue an idle preamble.
RE — Receiver Enable
0 = Receiver disabled
1 = Enables the SCI receive circuitry.
RWU — Receiver Wake-Up Control
0 = Normal SCI Receiver
1 = Enables the wake-up function and inhibits further receiver
interrupts. Normally hardware wakes the receiver by
automatically clearing this bit.
SBK — Send Break
0 = Break generator off
1 = Generate a break code (at least 10 or 11 contiguous zeros).
As long as SBK remains set the transmitter will send zeros. When
SBK is changed to zero, the current frame of all zeros is finished
before the TxD line goes to the idle state. If SBK is toggled on and off,
the transmitter will send only 10 (or 11) zeros and then revert to mark
idle or sending data.
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SC0SR1/SC1SR1 — SCI Status Register 1
RESET:
Bit 7
TDRE
1
6
TC
1
5
RDRF
0
$00C4/$00CC
4
IDLE
0
3
OR
0
2
NF
0
1
FE
0
Bit 0
PF
0
The bits in these registers are set by various conditions in the SCI
hardware and are automatically cleared by special acknowledge
sequences. The receive related flag bits in SCxSR1 (RDRF, IDLE,
OR, NF, FE, and PF) are all cleared by a read of the SCxSR1 register
followed by a read of the transmit/receive data register low byte.
However, only those bits which were set when SCxSR1 was read will
be cleared by the subsequent read of the transmit/receive data
register low byte. The transmit related bits in SCxSR1 (TDRE and TC)
are cleared by a read of the SCxSR1 register followed by a write to
the transmit/receive data register low byte.
Read anytime (used in auto clearing mechanism). Write has no
meaning or effect.
TDRE — Transmit Data Register Empty Flag
New data will not be transmitted unless SCxSR1 is read before writing
to the transmit data register. Reset sets this bit.
0 = SCxDR busy
1 = Any byte in the transmit data register is transferred to the serial
shift register so new data may now be written to the transmit
data register.
TC — Transmit Complete Flag
Flag is set when the transmitter is idle (no data, preamble, or break
transmission in progress). Clear by reading SCxSR1 with TC set and
then writing to SCxDR.
0 = Transmitter busy
1 = Transmitter is idle
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Serial Communication Interface (SCI)
RDRF — Receive Data Register Full Flag
Once cleared, IDLE is not set again until the RxD line has been active
and becomes idle again. RDRF is set if a received character is ready
to be read from SCxDR. Clear the RDRF flag by reading SCxSR1 with
RDRF set and then reading SCxDR.
0 = SCxDR empty
1 = SCxDR full
IDLE — Idle Line Detected Flag
Receiver idle line is detected (the receipt of a minimum of 10/11
consecutive ones). This bit will not be set by the idle line condition
when the RWU bit is set. Once cleared, IDLE will not be set again until
after RDRF has been set (after the line has been active and becomes
idle again).
0 = RxD line is idle
1 = RxD line is active
OR — Overrun Error Flag
New byte is ready to be transferred from the receive shift register to
the receive data register and the receive data register is already full
(RDRF bit is set). Data transfer is inhibited until this bit is cleared.
0 = No overrun
1 = Overrun detected
NF — Noise Error Flag
Set during the same cycle as the RDRF bit but not set in the case of
an overrun (OR).
0 = Unanimous decision
1 = Noise on a valid start bit, any of the data bits, or on the stop bit
FE — Framing Error Flag
Set when a zero is detected where a stop bit was expected. Clear the
FE flag by reading SCxSR1 with FE set and then reading SCxDR.
0 = Stop bit detected
1 = Zero detected rather than a stop bit
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PF — Parity Error Flag
Indicates if received data’s parity matches parity bit. This feature is
active only when parity is enabled. The type of parity tested for is
determined by the PT (parity type) bit in SCxCR1.
0 = Parity correct
1 = Incorrect parity detected
SC0SR2/SC1SR2 — SCI Status Register 2
RESET:
Bit 7
0
0
6
0
0
$00C5/$00CD
5
0
0
4
0
0
3
0
0
2
0
0
1
0
0
Bit 0
RAF
0
Read anytime. Write has no meaning or effect.
RAF — Receiver Active Flag
This bit is controlled by the receiver front end. It is set during the RT1
time period of the start bit search. It is cleared when an idle state is
detected or when the receiver circuitry detects a false start bit
(generally due to noise or baud rate mismatch).
0 = A character is not being received
1 = A character is being received
If enabled with RIE = 1, RAF set generates an interrupt when
VDDPLL is high while in WAIT mode.
SC0DRH/SC1DRH — SCI Data Register High
RESET:
Bit 7
R8
—
6
T8
—
5
0
—
$00C6/$00CE
4
0
—
3
0
—
2
0
—
1
0
—
SC0DRL/SC1DRL — SCI Data Register Low
RESET:
Bit 7
R7/T7
—
6
R6/T6
—
5
R5/T5
—
$00C7/$00CF
4
R4/T4
—
3
R3/T3
—
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288
Bit 0
0
—
2
R2/T2
—
1
R1/T1
—
Bit 0
R0/T0
—
MC68HC912DT128A — Rev 4.0
Multiple Serial Interface
MOTOROLA
Multiple Serial Interface
Serial Peripheral Interface (SPI)
R8 — Receive Bit 8
Read anytime. Write has no meaning or affect.
This bit is the ninth serial data bit received when the SCI system is
configured for nine-data-bit operation.
T8 — Transmit Bit 8
Read or write anytime.
This bit is the ninth serial data bit transmitted when the SCI system is
configured for nine-data-bit operation. When using 9-bit data format
this bit does not have to be written for each data word. The same
value will be transmitted as the ninth bit until this bit is rewritten.
R7/T7–R0/T0 — Receive/Transmit Data Bits 7 to 0
Reads access the eight bits of the read-only SCI receive data register
(RDR). Writes access the eight bits of the write-only SCI transmit data
register (TDR). SCxDRL:SCxDRH form the 9-bit data word for the
SCI. If the SCI is being used with a 7- or 8-bit data word, only SCxDRL
needs to be accessed. If a 9-bit format is used, the upper register
should be written first to ensure that it is transferred to the transmitter
shift register with the lower register.
16.5 Serial Peripheral Interface (SPI)
The serial peripheral interface allows the MC68HC912DT128A to
communicate synchronously with peripheral devices and other
microprocessors. The SPI system in the MC68HC912DT128A can
operate as a master or as a slave. The SPI is also capable of
interprocessor communications in a multiple master system.
When the SPI is enabled, all pins that are defined by the configuration
as inputs will be inputs regardless of the state of the DDRS bits for those
pins. All pins that are defined as SPI outputs will be outputs only if the
DDRS bits for those pins are set. Any SPI output whose corresponding
DDRS bit is cleared can be used as a general-purpose input.
A bidirectional serial pin is possible using the DDRS as the direction
control.
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Multiple Serial Interface
16.5.1 SPI Baud Rate Generation
The E Clock is input to a divider series and the resulting SPI clock rate
may be selected to be E divided by 2, 4, 8, 16, 32, 64, 128 or 256. Three
bits in the SP0BR register control the SPI clock rate. This baud rate
generator is activated only when SPI is in the master mode and serial
transfer is taking place. Otherwise this divider is disabled to save power.
16.5.2 SPI Operation
In the SPI system the 8-bit data register in the master and the 8-bit data
register in the slave are linked to form a distributed 16-bit register. When
a data transfer operation is performed, this 16-bit register is serially
shifted eight bit positions by the SCK clock from the master so the data
is effectively exchanged between the master and the slave. Data written
to the SP0DR register of the master becomes the output data for the
slave and data read from the SP0DR register of the master after a
transfer operation is the input data from the slave.
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Serial Peripheral Interface (SPI)
MCU P CLOCK
(SAME AS E RATE)
DIVIDER
÷2 ÷4 ÷8 ÷16 ÷32 ÷64 ÷128 ÷256
8-BIT SHIFT REGISTER
S
M
MISO
PS4
M
S
MOSI
PS5
READ DATA BUFFER
SP0DR SPI DATA REGISTER
SELECT
LSBF
PIN
CONTROL
LOGIC
SPR0
SPR1
SPR2
SHIFT CONTROL LOGIC
CLOCK
SPI CONTROL
SCK
PS6
S
CLOCK
LOGIC
SP0BR SPI BAUD RATE REGISTER
M
SS
PS7
MSTR
SPE
SPI
INTERRUPT
REQUEST
SP0SR SPI STATUS REGISTER
SP0CR1 SPI CONTROL REGISTER 1
SPC0
RDS
PUPS
LSBF
SSOE
CPHA
CPOL
SWOM
MSTR
SPE
SPIE
MODF
WCOL
SPIF
SWOM
SP0CR2 SPI CONTROL REGISTER 2
INTERNAL BUS
HC12 SPI BLOCK
Figure 16-3. Serial Peripheral Interface Block Diagram
A clock phase control bit (CPHA) and a clock polarity control bit (CPOL)
in the SP0CR1 register select one of four possible clock formats to be
used by the SPI system. The CPOL bit simply selects non-inverted or
inverted clock. The CPHA bit is used to accommodate two
fundamentally different protocols by shifting the clock by one half cycle
or no phase shift.
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Begin
Transfer
End
SCK (CPOL=0)
SCK (CPOL=1)
If next transfer begins here
SAMPLE I
(MOSI/MISO)
CHANGE O
(MOSI pin)
CHANGE O
(MISO pin)
SEL SS (O)
(Master only)
SEL SS (I)
MSB first (LSBF=0):
LSB first (LSBF=1):
tL
MSB
LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
Bit 1
Bit 6
LSB
MSB
tI
tT
tL
Minimum 1/2 SCK
for tT, tl, tL
HC12 SPI CLOCK FORM 0
Figure 16-4. SPI Clock Format 0 (CPHA = 0)
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Serial Peripheral Interface (SPI)
Transfer
Begin
End
SCK (CPOL=0)
SCK (CPOL=1)
If next transfer begins here
SAMPLE I
(MOSI/MISO)
CHANGE O
(MOSI pin)
CHANGE O
(MISO pin)
SEL SS (O)
(Master only)
SEL SS (I)
tL
MSB first (LSBF=0):
LSB first (LSBF=1):
MSB
LSB
Bit 6
Bit 1
Bit 5
Bit 2
Bit 4
Bit 3
Bit 3
Bit 4
Bit 2
Bit 5
Bit 1
Bit 6
tI
tT
tL
LSB Minimum 1/2 SCK
for tT, tl, tL
MSB
HC12 SPI CLOCK FORM 1
Figure 16-5. SPI Clock Format 1 (CPHA = 1)
16.5.3 SS Output
Available in master mode only, SS output is enabled with the SSOE bit
in the SP0CR1 register if the corresponding DDRS is set. The SS output
pin will be connected to the SS input pin of the external slave device. The
SS output automatically goes low for each transmission to select the
external device and it goes high during each idling state to deselect
external devices.
Table 16-3. SS Output Selection
DDRS7
0
0
1
1
SSOE
0
1
0
1
Master Mode
SS Input with MODF Feature
Reserved
General-Purpose Output
SS Output
MC68HC912DT128A — Rev 4.0
MOTOROLA
Slave Mode
SS Input
SS Input
SS Input
SS Input
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16.5.4 Bidirectional Mode (MOMI or SISO)
In bidirectional mode, the SPI uses only one serial data pin for external
device interface. The MSTR bit decides which pin to be used. The MOSI
pin becomes serial data I/O (MOMI) pin for the master mode, and the
MISO pin becomes serial data I/O (SISO) pin for the slave mode. The
direction of each serial I/O pin depends on the corresponding DDRS bit.
Figure 16-6. Normal Mode and Bidirectional Mode
When SPE=1
Master Mode
MSTR=1
Slave Mode
MSTR=0
MO
Serial Out
Normal
Mode
SPC0=0
SPI
SPI
DDRS5
MI
Serial In
SPI
SPI
PS4
SWOM enables open drain output. PS4 becomes GPIO.
PS5
Serial In
DDRS5
Serial In
SO
SWOM enables open drain output.
MOMI
Serial Out
DDRS4
Serial Out
SWOM enables open drain output.
Bidirectional
Mode
SPC0=1
SI
Serial In
DDRS4
SISO
Serial Out
SWOM enables open drain output. PS5 becomes GPIO.
16.5.5 Register Descriptions
Control and data registers for the SPI subsystem are described below.
The memory address indicated for each register is the default address
that is in use after reset. For more information refer to Operating Modes.
SP0CR1 — SPI Control Register 1
RESET:
Bit 7
SPIE
0
6
SPE
0
$00D0
5
SWOM
0
4
MSTR
0
3
CPOL
0
2
CPHA
1
1
SSOE
0
Bit 0
LSBF
0
Read or write anytime.
SPIE — SPI Interrupt Enable
0 = SPI interrupts are inhibited
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Serial Peripheral Interface (SPI)
1 = Hardware interrupt sequence is requested each time the SPIF
or MODF status flag is set
SPE — SPI System Enable
0 = SPI internal hardware is initialized and SPI system is in a lowpower disabled state.
1 = PS[4:7] are dedicated to the SPI function
When MODF is set, SPE always reads zero. SP0CR1 must be written
as part of a mode fault recovery sequence.
SWOM — Port S Wired-OR Mode
Controls not only SPI output pins but also the general-purpose output
pins (PS[4:7]) which are not used by SPI.
0 = SPI and/or PS[4:7] output buffers operate normally
1 = SPI and/or PS[4:7] output buffers behave as open-drain
outputs
MSTR — SPI Master/Slave Mode Select
0 = Slave mode
1 = Master mode
When MODF is set, MSTR always reads zero. SP0CR1 must be
written as part of a mode fault recovery sequence.
CPOL, CPHA — SPI Clock Polarity, Clock Phase
These two bits are used to specify the clock format to be used in SPI
operations. When the clock polarity bit is cleared and data is not being
transferred, the SCK pin of the master device is low. When CPOL is
set, SCK idles high. See Figure 16-4 and Figure 16-5.
SSOE — Slave Select Output Enable
The SS output feature is enabled only in the master mode by
asserting the SSOE and DDRS7.
LSBF — SPI LSB First enable
0 = Data is transferred most significant bit first
1 = Data is transferred least significant bit first
Normally data is transferred most significant bit first.This bit does not
affect the position of the MSB and LSB in the data register. Reads and
writes of the data register will always have MSB in bit 7.
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SP0CR2 — SPI Control Register 2
RESET:
Bit 7
0
0
6
0
0
$00D1
5
0
0
4
0
0
3
PUPS
1
2
RDPS
0
1
SSWAI
0
Bit 0
SPC0
0
Read or write anytime.
PUPS — Pull-Up Port S Enable
0 = No internal pull-ups on port S
1 = All port S input pins have an active pull-up device. If a pin is
programmed as output, the pull-up device becomes inactive
RDPS — Reduce Drive of Port S
0 = Port S output drivers operate normally
1 = All port S output pins have reduced drive capability for lower
power and less noise
SSWAI — Serial Interface Stop in WAIT mode
0 = Serial interface clock operates normally
1 = Halt serial interface clock generation in WAIT mode
SPC0 — Serial Pin Control 0
This bit decides serial pin configurations with MSTR control bit.
SPC0(1)
Pin Mode
#1
#2
#3
#4
Normal
0
Bidirectional
1
MSTR
MISO(2)
MOSI(3)
SCK(4)
SS(5)
0
Slave Out
Slave In
SCK In
SS In
1
Master In
Master
Out
SCK Out
SS I/O
0
Slave I/O
GPI/O
SCK In
SS In
1
GPI/O
Master I/O
SCK Out
SS I/O
1. The serial pin control 0 bit enables bidirectional configurations.
2. Slave output is enabled if DDRS4 = 1, SS = 0 and MSTR = 0. (#1, #3)
3. Master output is enabled if DDRS5 = 1 and MSTR = 1. (#2, #4)
4. SCK output is enabled if DDRS6 = 1 and MSTR = 1. (#2, #4)
5. SS output is enabled if DDRS7 = 1, SSOE = 1 and MSTR = 1. (#2, #4)
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Serial Peripheral Interface (SPI)
SP0BR — SPI Baud Rate Register
RESET:
Bit 7
0
0
6
0
0
$00D2
5
0
0
4
0
0
3
0
0
2
SPR2
0
1
SPR1
0
Bit 0
SPR0
0
Read anytime. Write anytime.
At reset, E Clock divided by 2 is selected.
SPR[2:0] — SPI Clock (SCK) Rate Select Bits
These bits are used to specify the SPI clock rate.
Table 16-4. SPI Clock Rate Selection
SPR2
SPR1
SPR0
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
E Clock
Divisor
2
4
8
16
32
64
128
256
Frequency at
E Clock = 4 MHz
2.0 MHz
1.0 MHz
500 kHz
250 kHz
125 kHz
62.5 kHz
31.3 kHz
15.6 kHz
Frequency at
E Clock = 8 MHz
4.0 MHz
2.0 MHz
1.0 MHz
500 KHz
250 KHz
125 KHz
62.5 KHz
31.3 KHz
SP0SR — SPI Status Register
RESET:
Bit 7
SPIF
0
$00D3
6
WCOL
0
5
0
0
4
MODF
0
3
0
0
2
0
0
1
0
0
Bit 0
0
0
Read anytime. Write has no meaning or effect.
SPIF — SPI Interrupt Request
SPIF is set after the eighth SCK cycle in a data transfer and it is
cleared by reading the SP0SR register (with SPIF set) followed by an
access (read or write) to the SPI data register.
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WCOL — Write Collision Status Flag
The MCU write is disabled to avoid writing over the data being
transferred. No interrupt is generated because the error status flag
can be read upon completion of the transfer that was in progress at
the time of the error. Automatically cleared by a read of the SP0SR
(with WCOL set) followed by an access (read or write) to the SP0DR
register.
0 = No write collision
1 = Indicates that a serial transfer was in progress when the MCU
tried to write new data into the SP0DR data register.
MODF — SPI Mode Error Interrupt Status Flag
This bit is set automatically by SPI hardware if the MSTR control bit is
set and the slave select input pin becomes zero. This condition is not
permitted in normal operation. In the case where DDRS bit 7 is set,
the PS7 pin is a general-purpose output pin or SS output pin rather
than being dedicated as the SS input for the SPI system. In this
special case the mode fault function is inhibited and MODF remains
cleared. This flag is automatically cleared by a read of the SP0SR
(with MODF set) followed by a write to the SP0CR1 register.
SP0DR — SPI Data Register
Bit 7
Bit 7
6
6
$00D5
5
5
4
4
3
3
2
2
1
1
Bit 0
Bit 0
Read anytime (normally only after SPIF flag set). Write anytime (see
WCOL write collision flag).
Reset does not affect this address.
This 8-bit register is both the input and output register for SPI data.
Reads of this register are double buffered but writes cause data to
written directly into the serial shifter. In the SPI system the 8-bit data
register in the master and the 8-bit data register in the slave are linked
by the MOSI and MISO wires to form a distributed 16-bit register. When
a data transfer operation is performed, this 16-bit register is serially
shifted eight bit positions by the SCK clock from the master so the data
is effectively exchanged between the master and the slave. Note that
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Port S
some slave devices are very simple and either accept data from the
master without returning data to the master or pass data to the master
without requiring data from the master.
16.6 Port S
In all modes, port S bits PS[7:0] can be used for either general-purpose
I/O, or with the SCI and SPI subsystems. During reset, port S pins are
configured as high-impedance inputs (DDRS is cleared).
PORTS — Port S Data Register
Bit 7
6
$00D6
5
4
3
2
1
Bit 0
PS7
PS6
PS5
PS4
PS3
PS2
PS1
PS0
MSI
SS
CS
SCK
MOSI
MOMI
MISO
SISO
TXD1
RXD1
TXD0
RXD0
RESET:
-
-
-
-
-
-
-
-
Read anytime (inputs return pin level; outputs return pin driver input
level). Write data stored in internal latch (drives pins only if configured for
output). Writes do not change pin state when pin configured for SPI or
SCI output.
After reset all bits are configured as general-purpose inputs.
Port S shares function with the on-chip serial systems (SPI and SCI0/1).
DDRS — Data Direction Register for Port S
RESET:
Bit 7
DDS7
0
6
DDS6
0
5
DDS5
0
$00D7
4
DDS4
0
3
DDS3
0
2
DDS2
0
1
DDS1
0
Bit 0
DDS0
0
Read or write anytime.
After reset, all general-purpose I/O are configured for input only.
0 = Configure the corresponding I/O pin for input only
1 = Configure the corresponding I/O pin for output
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DDS2, DDS0 — Data Direction for Port S Bit 2 and Bit 0
If the SCI receiver is configured for two-wire SCI operation,
corresponding port S pins will be input regardless of the state of these
bits.
DDS3, DDS1 — Data Direction for Port S Bit 3 and Bit 1
If the SCI transmitter is configured for two-wire SCI operation,
corresponding port S pins will be output regardless of the state of
these bits.
DDS[6:4] — Data Direction for Port S Bits 6 through 4
If the SPI is enabled and expects the corresponding port S pin to be
an input, it will be an input regardless of the state of the DDRS bit. If
the SPI is enabled and expects the bit to be an output, it will be an
output ONLY if the DDRS bit is set.
DDS7 — Data Direction for Port S Bit 7
In SPI slave mode, DDRS7 has no meaning or effect; the PS7 pin is
dedicated as the SS input. In SPI master mode, DDRS7 determines
whether PS7 is an error detect input to the SPI or a general-purpose
or slave select output line.
NOTE:
If mode fault error occurs bits 5, 6 and 7 are forced to zero.
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Technical Data — MC68HC912DT128A
Section 17. Inter IC Bus
17.1 Contents
17.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
17.3
IIC Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .302
17.4
IIC System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
17.5
IIC Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
17.6
IIC Register Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
17.7
IIC Programming Examples . . . . . . . . . . . . . . . . . . . . . . . . . .318
17.2 Introduction
The Inter-IC Bus (IIC or I2C) is a two-wire, bidirectional serial bus that
provides a simple, efficient method of data exchange between devices.
Being a two-wire device, the IIC minimizes the need for large numbers
of connections between devices, and eliminates the need for an address
decoder.
This bus is suitable for applications requiring occasional
communications over a short distance between a number of devices. It
also provides flexibility, allowing additional devices to be connected to
the bus for further expansion and system development.
The interface is designed to operate up to 100kbps with maximum bus
loading and timing. The device is capable of operating at higher baud
rates, up to a maximum of clock/20, with reduced bus loading. The
maximum communication length and the number of devices that can be
connected are limited by a maximum bus capacitance of 400pF.
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301
Inter IC Bus
17.3 IIC Features
The IIC module has the following key features:
•
Compatible with I2C Bus standard
•
Multi-master operation
•
Software programmable for one of 64 different serial clock
frequencies
•
Software selectable acknowledge bit
•
Interrupt driven byte-by-byte data transfer
•
Arbitration lost interrupt with automatic mode switching from
master to slave
•
Calling address identification interrupt
•
Start and stop signal generation/detection
•
Repeated start signal generation
•
Acknowledge bit generation/detection
•
Bus busy detection
•
Eight-bit general purpose I/O port
A block diagram of the IIC module is shown in Figure 17-1.
Technical Data
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MOTOROLA
Inter IC Bus
IIC Features
ADDR & CONTROL
DATA
INTERRUPT
ADDR_DECODE
CTRL_REG
DATA_MUX
FREQ_REG
ADDR_REG
STATUS_REG
DATA_REG
In/Out
Input
Data
Sync
Shift
Start,
Register
Stop &
Arbitration
Control
Clock
Control
Address
Compare
SCL
SDA
Figure 17-1. IIC Block Diagram
MC68HC912DT128A — Rev 4.0
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Technical Data
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303
Inter IC Bus
17.4 IIC System Configuration
The IIC system uses a Serial Data line (SDA) and a Serial Clock Line
(SCL) for data transfer. All devices connected to it must have open drain
or open collector outputs. Logic “and” function is exercised on both lines
with external pull-up resistors, the value of these resistors is system
dependent.
17.5 IIC Protocol
Normally, a standard communication is composed of four parts: START
signal, slave address transmission, data transfer and STOP signal. They
are described briefly in the following sections and illustrated in Figure 172.
MSB
SCL
SDA
1
LSB
2
3
4
5
6
7
Calling Address
Read/
Write
MSB
SDA
Start
Signal
9
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
Start
Signal
SCL
8
MSB
1
XXX
3
4
5
6
7
8
Read/
Write
2
3
4
5
6
7
8
D7
D6
D5
D4
D3
D2
D1
D0
Data Byte
1
XX
Ack
Bit
9
No
Ack
Bit
MSB
9
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
Calling Address
1
Ack
Bit
LSB
2
LSB
Stop
Signal
LSB
2
3
4
5
6
7
8
9
AD7 AD6 AD5 AD4 AD3 AD2 AD1 R/W
Repeated
Start
Signal
New Calling Address
Read/
Write
No
Ack
Bit
Stop
Signal
Figure 17-2. IIC Transmission Signals
Technical Data
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MC68HC912DT128A — Rev 4.0
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MOTOROLA
Inter IC Bus
IIC Protocol
17.5.1 START Signal
When the bus is free, i.e. no master device is engaging the bus (both
SCL and SDA lines are at logical high), a master may initiate
communication by sending a START signal. As shown in Figure 17-2, a
START signal is defined as a high-to-low transition of SDA while SCL is
high. This signal denotes the beginning of a new data transfer (each data
transfer may contain several bytes of data) and wakes up all slaves.
17.5.2 Slave Address Transmission
The first byte of data transfer immediately after the START signal is the
slave address transmitted by the master. This is a seven-bit calling
address followed by a R/W bit. The R/W bit tells the slave the desired
direction of data transfer.
1 = Read transfer, the slave transmits data to the master.
0 = Write transfer, the master transmits data to the slave.
Only the slave with a calling address that matches the one transmitted
by the master will respond by sending back an acknowledge bit. This is
done by pulling the SDA low at the 9th clock (see Figure 17-2).
Slave address - No two slaves in the system may have the same
address. If the IIC is master, it must not transmit an address that
is equal to its own slave address. The IIC cannot be master and
slave at the same time. If however arbitration is lost during an
address cycle the IIC will revert to slave mode and operate
correctly even if it is being addressed by another master.
17.5.3 Data Transfer
Once successful slave addressing is achieved, the data transfer can
proceed byte-by-byte in a direction specified by the R/W bit sent by the
calling master.
NOTE:
All transfers that come after an address cycle are referred to as data
transfers, even if they carry sub-address information for the slave
device.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Inter IC Bus
305
Inter IC Bus
Each data byte is 8 bits long. Data may be changed only while SCL is
low and must be held stable while SCL is high as shown in Figure 17-2.
There is one clock pulse on SCL for each data bit, the MSB being
transferred first. Each data byte has to be followed by an acknowledge
bit, which is signalled from the receiving device by pulling the SDA low
at the ninth clock. So one complete data byte transfer needs nine clock
pulses.
If the slave receiver does not acknowledge the master, the SDA line
must be left high by the slave. The master can then generate a stop
signal to abort the data transfer or a start signal (repeated start) to
commence a new calling.
If the master receiver does not acknowledge the slave transmitter after
a byte transmission, it means 'end of data' to the slave, so the slave
releases the SDA line for the master to generate STOP or START signal.
17.5.4 STOP Signal
The master can terminate the communication by generating a STOP
signal to free the bus. However, the master may generate a START
signal followed by a calling command without generating a STOP signal
first. This is called repeated START. A STOP signal is defined as a lowto-high transition of SDA while SCL at logical “1” (see Figure 17-2).
The master can generate a STOP even if the slave has generated an
acknowledge at which point the slave must release the bus.
17.5.5 Repeated START Signal
As shown in Figure 17-2, a repeated START signal is a START signal
generated without first generating a STOP signal to terminate the
communication. This is used by the master to communicate with another
slave or with the same slave in different mode (transmit/receive mode)
without releasing the bus.
Technical Data
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MOTOROLA
Inter IC Bus
IIC Protocol
17.5.6 Arbitration Procedure
IIC is a true multi-master bus that allows more than one master to be
connected on it. If two or more masters try to control the bus at the same
time, a clock synchronization procedure determines the bus clock, for
which the low period is equal to the longest clock low period and the high
is equal to the shortest one among the masters. The relative priority of
the contending masters is determined by a data arbitration procedure, a
bus master loses arbitration if it transmits logic “1” while another master
transmits logic “0”. The losing masters immediately switch over to slave
receive mode and stop driving SDA output. In this case the transition
from master to slave mode does not generate a STOP condition.
Meanwhile, a status bit is set by hardware to indicate loss of arbitration.
17.5.7 Clock Synchronization
Since wire-AND logic is performed on SCL line, a high-to-low transition
on SCL line affects all the devices connected on the bus. The devices
start counting their low period and once a device's clock has gone low,
it holds the SCL line low until the clock high state is reached. However,
the change of low to high in this device clock may not change the state
of the SCL line if another device clock is still within its low period.
Therefore, synchronized clock SCL is held low by the device with the
longest low period. Devices with shorter low periods enter a high wait
state during this time (see Figure 17-3). When all devices concerned
have counted off their low period, the synchronized clock SCL line is
released and pulled high. There is then no difference between the device
clocks and the state of the SCL line and all the devices start counting
their high periods. The first device to complete its high period pulls the
SCL line low again.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Inter IC Bus
307
Inter IC Bus
WAIT
Start Counting High Period
SCL1
SCL2
SCL
Internal Counter Reset
Figure 17-3. IIC Clock Synchronization
17.5.8 Handshaking
The clock synchronization mechanism can be used as a handshake in
data transfer. Slave devices may hold the SCL low after completion of
one byte transfer (9 bits). In such case, it halts the bus clock and forces
the master clock into wait states until the slave releases the SCL line.
17.5.9 Clock Stretching
The clock synchronization mechanism can be used by slaves to slow
down the bit rate of a transfer. After the master has driven SCL low the
slave can drive SCL low for the required period and then release it. If the
slave SCL low period is greater than the master SCL low period then the
resulting SCL bus signal low period is stretched.
Technical Data
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MOTOROLA
Inter IC Bus
IIC Register Descriptions
17.6 IIC Register Descriptions
.
IBAD — IIC Bus Address Register
RESET:
Bit 7
ADR7
0
6
ADR6
0
$00E0
5
ADR5
0
4
ADR4
0
3
ADR3
0
2
ADR2
0
1
ADR1
0
Bit 0
0
0
Read and write anytime
This register contains the address the IIC will respond to when
addressed as a slave; note that it is not the address sent on the bus
during the address transfer
ADR7–ADR1 — Slave Address
Bit 1 to bit 7 contain the specific slave address to be used by the IIC
module.
The default mode of IIC is slave mode for an address match on the
bus.
IBFD — IIC Bus Frequency Divider Register
RESET:
Bit 7
0
0
6
0
0
5
IBC5
0
$00E1
4
IBC4
0
3
IBC3
0
2
IBC2
0
1
IBC1
0
Bit 0
IBC0
0
Read and write anytime
IBC5–IBC0 — IIC Bus Clock Rate 5–0
This field is used to prescale the clock for bit rate selection. The bit
clock generator is implemented as a prescaled shift register - IBC5-3
select the prescaler divider and IBC2-0 select the shift register tap
point. The IBC bits are decoded to give the Tap and Prescale values
as shown in Table 17-1.
NOTE:
At 8 MHz system bus frequency, the IIC bus frequency will slow down by
as much as 5%. However, the communications rate of the IIC system will
be automatically adjusted to a slower rate.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Inter IC Bus
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Inter IC Bus
Table 17-1. IIC Tap and Prescale Values
IBC2-0
(bin)
SCL Tap
(clocks)
SDA Tap
(clocks)
IBC5-3
(bin)
scl2tap
(clocks)
tap2tap
(clocks)
000
5
1
000
4
1
001
6
1
001
4
2
010
7
2
010
6
4
011
8
2
011
6
8
100
9
3
100
14
16
101
10
3
101
30
32
110
12
4
110
62
64
111
15
4
111
126
128
The number of clocks from the falling edge of SCL to the first tap
(Tap[1]) is defined by the values shown in the scl2tap column of Table
17-1, all subsequent tap points are separated by 2IBC5-3 as shown in
the tap2tap column in Table 17-1. The SCL Tap is used to generated
the SCL period and the SDA Tap is used to determine the delay from
the falling edge of SCL to SDA changing, the SDA hold time.
The serial bit clock frequency is equal to the CPU clock frequency
divided by the divider shown in Table 17-2. The equation used to
generate the divider values from the IBFD bits is:
SCL Divider = 2 x ( scl2tap + [ ( SCL_Tap -1 ) x tap2tap ] + 2 )
The SDA hold delay is equal to the CPU clock period multiplied by the
SDA Hold value shown in Figure 17-2. The equation used to generate
the SDA Hold value from the IBFD bits is:
SDA Hold = scl2tap + [ ( SDA_Tap - 1 ) x tap2tap ] + 3
Technical Data
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Inter IC Bus
MOTOROLA
Inter IC Bus
IIC Register Descriptions
Table 17-2. IIC Divider and SDA Hold values
IBC5-0
(hex)
SCL Divider
(clocks)
SDA Hold
(clocks)
IBC5-0
(hex)
SCL Divider
(clocks)
SDA Hold
(clocks)
00
20
7
20
160
17
01
22
7
21
192
17
02
24
8
22
224
33
03
26
8
23
256
33
04
28
9
24
288
49
05
30
9
25
320
49
06
34
10
26
384
65
07
40
10
27
480
65
08
28
7
28
320
33
09
32
7
29
384
33
0A
36
9
2A
448
65
0B
40
9
2B
512
65
0C
44
11
2C
576
97
0D
48
11
2D
640
97
0E
56
13
2E
768
129
0F
68
13
2F
960
129
10
48
9
30
640
65
11
56
9
31
768
65
12
64
13
32
896
129
13
72
13
33
1024
129
14
80
17
34
1152
193
15
88
17
35
1280
193
16
104
21
36
1536
257
17
128
21
37
1920
257
18
80
9
38
1280
129
19
96
9
39
1536
129
1A
112
17
3A
1792
257
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Inter IC Bus
311
Inter IC Bus
Table 17-2. IIC Divider and SDA Hold values
IBC5-0
(hex)
SCL Divider
(clocks)
SDA Hold
(clocks)
IBC5-0
(hex)
SCL Divider
(clocks)
SDA Hold
(clocks)
1B
128
17
3B
2048
257
1C
144
25
3C
2304
385
1D
160
25
3D
2560
385
1E
192
33
3E
3072
513
1F
240
33
3F
3840
513
IBCR — IIC Bus Control Register
RESET:
Bit 7
IBEN
0
6
IBIE
0
$00E2
5
MS/SL
0
4
Tx/Rx
0
3
TXAK
0
2
RSTA
0
1
0
0
Bit 0
IBSWAI
0
Read and write anytime
IBEN — IIC Bus Enable
This bit controls the software reset of the entire IIC module.
0 = The module is reset and disabled. This is the power-on reset
situation. When low the IIC system is held in reset but registers
can still be accessed.
1 = The IIC system is enabled. This bit must be set before any other
IBCR bits have any effect.
If the IIC module is enabled in the middle of a byte transfer the
interface behaves as follows: slave mode ignores the current transfer
on the bus and starts operating whenever a subsequent start
condition is detected. Master mode will not be aware that the bus is
busy, hence if a start cycle is initiated then the current bus cycle may
become corrupt. This would ultimately result in either the current bus
master or the IIC module losing arbitration, after which bus operation
would return to normal.
NOTE:
To prevent glitches from appearing on the SDA & SCL lines during reset
of the IIC module, set PORTIB bit 6 & 7 to 1 before clearing the IBEN bit.
Technical Data
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Inter IC Bus
MOTOROLA
Inter IC Bus
IIC Register Descriptions
IBIE — IIC Bus Interrupt Enable
0 = Interrupts from the IIC module are disabled. Note that this does
not clear any currently pending interrupt condition.
1 = Interrupts from the IIC module are enabled. An IIC interrupt
occurs provided the IBIF bit in the status register is also set.
MS/SL — Master/Slave mode select bit
Upon reset, this bit is cleared. When this bit is changed from 0 to 1, a
START signal is generated on the bus, and the master mode is
selected. When this bit is changed from 1 to 0, a STOP signal is
generated and the operation mode changes from master to slave.
MS/SL is cleared without generating a STOP signal when the master
loses arbitration.
0 = Slave Mode
1 = Master Mode
Tx/Rx — Transmit/Receive mode select bit
This bit selects the direction of master and slave transfers. When
addressed as a slave this bit should be set by software according to
the SRW bit in the status register. In master mode this bit should be
set according to the type of transfer required. Therefore, for address
cycles, this bit will always be high.
0 = Receive
1 = Transmit
TXAK — Transmit Acknowledge enable
This bit specifies the value driven onto SDA during acknowledge
cycles for both master and slave receivers. Note that values written to
this bit are only used when the IIC is a receiver, not a transmitter.
0 = An acknowledge signal will be sent out to the bus at the 9th
clock bit after receiving one byte data
1 = No acknowledge signal response is sent (i.e. acknowledge bit
= 1)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Inter IC Bus
313
Inter IC Bus
RSTA — Repeat Start
Writing a 1 to this bit will generate a repeated START condition on the
bus, provided it is the current bus master. This bit will always be read
as a low. Attempting a repeated start at the wrong time, if the bus is
owned by another master, will result in loss of arbitration.
1 = Generate repeat start cycle
IBSWAI — IIC Stop in WAIT mode
0 = IIC module operates normally
1 = Halt clock generation of IIC module in WAIT mode
IBSR — IIC Bus Status Register
RESET:
Bit 7
TCF
1
6
IAAS
0
$00E3
5
IBB
0
4
IBAL
0
3
0
0
2
SRW
0
1
IBIF
0
Bit 0
RXAK
0
This status register is read-only with exception of bit 1 (IBIF) and bit 4
(IBAL), which are software clearable
TCF — Data transferring bit
While one byte of data is being transferred, this bit is cleared. It is set
by the falling edge of the 9th clock of a byte transfer.
0 = Transfer in progress
1 = Transfer complete
IAAS — Addressed as a slave bit
When its own specific address (IIC Bus Address Register) is matched
with the calling address, this bit is set. The CPU is interrupted
provided the IBIE is set. Then the CPU needs to check the SRW bit
and set its Tx/Rx mode accordingly. Writing to the IIC Bus Control
Register clears this bit.
0 = Not addressed
1 = Addressed as a slave
IBB — IIC Bus busy bit
This bit indicates the status of the bus. When a START signal is
detected, the IBB is set. If a STOP signal is detected, it is cleared.
0 = Bus is idle
1 = Bus is busy
Technical Data
314
MC68HC912DT128A — Rev 4.0
Inter IC Bus
MOTOROLA
Inter IC Bus
IIC Register Descriptions
NOTE:
If, after trying to generate a START signal and neither the IBB nor IBAL
bits are set after several cycles, the IIC should be disabled and reenabled with IBEN bit.
IBAL — Arbitration Lost
The arbitration lost bit (IBAL) is set by hardware when the arbitration
procedure is lost. Arbitration is lost in the following circumstances:
1. SDA sampled as low when the master drives a high during an
address or data transmit cycle.
2. SDA sampled as a low when the master drives a high during the
acknowledge bit of a data receive cycle.
3. A start cycle is attempted when the bus is busy.
4. A repeated start cycle is requested in slave mode.
5. A stop condition is detected when the master did not request it.
This bit must be cleared by software, by writing a one to it.
NOTE:
If, after trying to generate a START signal and neither the IBB nor IBAL
bits are set after several cycles, the IIC should be disabled and reenabled with IBEN bit.
SRW — Slave Read/Write
When IAAS is set this bit indicates the value of the R/W command bit
of the calling address sent from the master.
CAUTION:
This bit is only valid when the IIC is in slave mode, a complete address
transfer has occurred with an address match and no other transfers have
been initiated.
Checking this bit, the CPU can select slave transmit/receive mode
according to the command of the master.
0 = Slave receive, master writing to slave
1 = Slave transmit, master reading from slave
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Inter IC Bus
315
Inter IC Bus
IBIF — IIC Bus Interrupt Flag
The IBIF bit is set when an interrupt is pending, which will cause a
processor interrupt request provided IBIE is set. IBIF is set when one
of the following events occurs:
1. Complete one byte transfer (set at the falling edge of the 9th
clock).
2. Receive a calling address that matches its own specific address in
slave receive mode.
3. Arbitration lost.
This bit must be cleared by software, writing a one to it, in the interrupt
routine.
RXAK — Received Acknowledge
The value of SDA during the acknowledge bit of a bus cycle. If the
received acknowledge bit (RXAK) is low, it indicates an acknowledge
signal has been received after the completion of 8 bits data
transmission on the bus. If RXAK is high, it means no acknowledge
signal is detected at the 9th clock.
0 = Acknowledge received
1 = No acknowledge received
.
IBDR — IIC Bus Data I/O Register
RESET:
Bit 7
D7
0
6
D6
0
$00E4
5
D5
0
4
D4
0
3
D3
0
2
D2
0
1
D1
0
Bit 0
D0
0
High
Read and write anytime
In master transmit mode, when data is written to the IBDR a data transfer
is initiated. The most significant bit is sent first. In master receive mode,
reading this register initiates next byte data receiving. In slave mode, the
same functions are available after an address match has occurred.
NOTE:
In master transmit mode, the first byte of data written to IBDR following
assertion of MS/SL is used for the address transfer and should comprise
of the calling address (in position D7-D1) concatenated with the required
R/W bit (in position D0).
Technical Data
316
MC68HC912DT128A — Rev 4.0
Inter IC Bus
MOTOROLA
Inter IC Bus
IIC Register Descriptions
IBPURD — Pull-Up and Reduced Drive for Port IB
RESET:
Bit 7
0
0
6
0
0
5
0
0
$00E5
4
RDPIB
0
3
0
0
2
0
0
1
0
0
Bit 0
PUPIB
0
Read and write anytime
RDPIB - Reduced Drive of Port IB
0 = All port IB output pins have full drive enabled.
1 = All port IB output pins have reduced drive capability.
PUPIB - Pull-Up Port IB Enable
0 = Port IB pull-ups are disabled.
1 = Enable pull-up devices for port IB input pins [7:6]. Pull-ups for
port IB input pins [5:0] are always enabled.
PORTIB — Port Data IB Register
IIC
RESET:
Bit 7
PIB7
SCL
-
6
PIB6
SDA
-
$00E6
5
PIB5
-
4
PIB4
-
3
PIB3
-
2
PIB2
-
1
PIB1
-
Bit 0
PIB0
-
Read and write anytime.
IIC functions SCL and SDA share port IB pins 7 and 6 and take
precedence over the general-purpose port when IIC is enabled. The
SCL and SDA output buffers behave as open-drain outputs.
When port is configured as input, a read will return the pin level. Port bits
5 through 0 have internal pull ups when configured as inputs so they will
read ones.
When configured as output, a read will return the latched output data.
Port bits 5 through 0 will read the last value written. A write will drive
associated pins only if configured for output and IIC is not enabled.
Port bits 5 through 0 do not have available external pins for
MC68HC912DT128A.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Inter IC Bus
317
Inter IC Bus
DDRIB — Data Direction for Port IB Register
RESET:
Bit 7
DDRIB7
0
6
DDRIB6
0
5
DDRIB5
0
$00E7
4
DDRIB4
0
3
DDRIB3
0
2
DDRIB2
0
1
DDRIB1
0
Bit 0
DDRIB0
0
Read and write anytime
DDRIB[7:2]— Port IB [7:2] Data direction
Each bit determines the primary direction for each pin configured as
general-purpose I/O.
0 = Associated pin is a high-impedance input.
1 = Associated pin is an output.
DDRIB[5:0] — These bits served as memory locations since there are
no corresponding external port pins for MC68HC912DT128A.
17.7 IIC Programming Examples
17.7.1 Initialization Sequence
Reset will put the IIC Bus Control Register to its default status. Before
the interface can be used to transfer serial data, an initialization
procedure must be carried out, as follows:
1. Update the Frequency Divider Register (IBFD) and select the
required division ratio to obtain SCL frequency from system clock.
2. Update the IIC Bus Address Register (IBAD) to define its slave
address.
3. Set the IBEN bit of the IIC Bus Control Register (IBCR) to enable
the IIC interface system.
4. Modify the bits of the IIC Bus Control Register (IBCR) to select
Master/Slave mode, Transmit/Receive mode and interrupt enable
or not.
Technical Data
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Inter IC Bus
MOTOROLA
Inter IC Bus
IIC Programming Examples
17.7.2 Generation of START
After completion of the initialization procedure, serial data can be
transmitted by selecting the 'master transmitter' mode. If the device is
connected to a multi-master bus system, the state of the IIC Bus Busy
bit (IBB) must be tested to check whether the serial bus is free.
If the bus is free (IBB=0), the start condition and the first byte (the slave
address) can be sent. The data written to the data register comprises the
slave calling address and the LSB set to indicate the direction of transfer
required from the slave.
The bus free time (i.e., the time between a STOP condition and the
following START condition) is built into the hardware that generates the
START cycle. Depending on the relative frequencies of the system clock
and the SCL period it may be necessary to wait until the IIC is busy after
writing the calling address to the IBDR before proceeding with the
following instructions. This is illustrated in the following example.
An example of a program which generates the START signal and
transmits the first byte of data (slave address) is shown below:
CHFLAG
TXSTART
IBFREE
BRSET
BSET
IBSR,#$20,*
IBCR,#$30
MOVB
CALLING,IBDR
BRCLR
IBSR,#$20,*
;WAIT FOR IBB FLAG TO CLEAR
;SET TRANSMIT AND MASTER MODE
;i.e. GENERATE START CONDITION
;TRANSMIT THE CALLING
;ADDRESS, D0=R/W
;WAIT FOR IBB FLAG TO SET
17.7.3 Post-Transfer Software Response
Transmission or reception of a byte will set the data transferring bit (TCF)
to 1, which indicates one byte communication is finished. The IIC Bus
interrupt bit (IBIF) is set also; an interrupt will be generated if the interrupt
function is enabled during initialization by setting the IBIE bit. Software
must clear the IBIF bit in the interrupt routine first. The TCF bit will be
cleared by reading from the IIC Bus Data I/O Register (IBDR) in receive
mode or writing to IBDR in transmit mode.
Software may service the IIC I/O in the main program by monitoring the
IBIF bit if the interrupt function is disabled. Note that polling should
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monitor the IBIF bit rather than the TCF bit since their operation is
different when arbitration is lost.
Note that when an interrupt occurs at the end of the address cycle the
master will always be in transmit mode, i.e. the address is transmitted. If
master receive mode is required, indicated by R/W bit in IBDR, then the
Tx/Rx bit should be toggled at this stage.
During slave mode address cycles (IAAS=1) the SRW bit in the status
register is read to determine the direction of the subsequent transfer and
the Tx/Rx bit is programmed accordingly. For slave mode data cycles
(IAAS=0) the SRW bit is not valid, the Tx/Rx bit in the control register
should be read to determine the direction of the current transfer.
The following is an example of a software response by a 'master
transmitter' in the interrupt routine (see Figure 17-4).
ISR
TRANSMIT
BCLR
BRCLR
BRCLR
BRSET
MOVB
IBSR,#$02
IBCR,#$20,SLAVE
IBCR,#$10,RECEIVE
IBSR,#$01,END
DATABUF,IBDR
;CLEAR THE IBIF FLAG
;BRANCH IF IN SLAVE MODE
;BRANCH IF IN RECEIVE MODE
;IF NO ACK, END OF TRANSMISSION
;TRANSMIT NEXT BYTE OF DATA
17.7.4 Generation of STOP
A data transfer ends with a STOP signal generated by the 'master'
device. A master transmitter can simply generate a STOP signal after all
the data has been transmitted. The following is an example showing how
a stop condition is generated by a master transmitter.
MASTX
TST
TXCNT
END
EMASTX
BEQ
BRSET
MOVB
DEC
BRA
BCLR
RTI
END
IBSR,#$01,END
DATABUF,IBDR
TXCNT
EMASTX
IBCR,#$20
;GET VALUE FROM THE
;TRANSMITING COUNTER
;END IF NO MORE DATA
;END IF NO ACK
;TRANSMIT NEXT BYTE OF DATA
;DECREASE THE TXCNT
;EXIT
;GENERATE A STOP CONDITION
;RETURN FROM INTERRUPT
If a master receiver wants to terminate a data transfer, it must inform the
slave transmitter by not acknowledging the last byte of data which can
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be done by setting the transmit acknowledge bit (TXAK) before reading
the 2nd last byte of data. Before reading the last byte of data, a STOP
signal must be generated first. The following is an example showing how
a STOP signal is generated by a master receiver.
MASR
LAMAR
ENMASR
NXMAR
DEC
BEQ
MOVB
DEC
BNE
BSET
RXCNT
ENMASR
RXCNT,D1
D1
NXMAR
IBCR,#$08
BRA
BCLR
MOVB
RTI
NXMAR
IBCR,#$20
IBDR,RXBUF
;DECREASE THE RXCNT
;LAST BYTE TO BE READ
;CHECK SECOND LAST BYTE
;TO BE READ
;NOT LAST OR SECOND LAST
;SECOND LAST, DISABLE ACK
;TRANSMITTING
;LAST ONE, GENERATE ‘STOP’ SIGNAL
;READ DATA AND STORE
17.7.5 Generation of Repeated START
At the end of data transfer, if the master still wants to communicate on
the bus, it can generate another START signal followed by another slave
address without first generating a STOP signal. A program example is
as shown.
RESTART
BSET
MOVB
IBCR,#$04
CALLING,IBDR
ANOTHER START (RESTART)
;TRANSMIT THE CALLING ADDRESS
;D0=R/W
17.7.6 Slave Mode
In the slave interrupt service routine, the module addressed as slave bit
(IAAS) should be tested to check if a calling of its own address has just
been received (see Figure 17-4). If IAAS is set, software should set the
transmit/receive mode select bit (Tx/Rx bit of IBCR) according to the
R/W command bit (SRW). Writing to the IBCR clears the IAAS
automatically. Note that the only time IAAS is read as set is from the
interrupt at the end of the address cycle where an address match
occurred, interrupts resulting from subsequent data transfers will have
IAAS cleared. A data transfer may now be initiated by writing information
to IBDR, for slave transmits, or dummy reading from IBDR, in slave
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receive mode. The slave will drive SCL low in-between byte transfers,
SCL is released when the IBDR is accessed in the required mode.
In slave transmitter routine, the received acknowledge bit (RXAK) must
be tested before transmitting the next byte of data. Setting RXAK means
an 'end of data' signal from the master receiver, after which it must be
switched from transmitter mode to receiver mode by software. A dummy
read then releases the SCL line so that the master can generate a STOP
signal.
17.7.7 Arbitration Lost
If several masters try to engage the bus simultaneously, only one master
wins and the others lose arbitration. The devices which lost arbitration
are immediately switched to slave receive mode by the hardware. Their
data output to the SDA line is stopped, but SCL is still generated until the
end of the byte during which arbitration was lost. An interrupt occurs at
the falling edge of the ninth clock of this transfer with IBAL=1 and
MS/SL=0. If one master attempts to start transmission while the bus is
being engaged by another master, the hardware will inhibit the
transmission; switch the MS/SL bit from 1 to 0 without generating STOP
condition; generate an interrupt to CPU and set the IBAL to indicate that
the attempt to engage the bus is failed. When considering these cases,
the slave service routine should test the IBAL first and the software
should clear the IBAL bit if it is set.
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Clear
IBIF
Master
Mode
?
Y
TX
N
Y
RX
Tx/Rx
?
Arbitration
Lost
?
N
Last Byte
Transmitted
?
Clear IBAL
Y
N
RXAK=0
?
Last
Byte To Be Read
?
N
N
Y
N
Y
Y
IAAS=1
?
IAAS=1
?
Y
N
Data Transfer
Address Transfer
End Of
Addr Cycle
(Master Rx)
?
N
Y
Y
Y
(Read)
2nd Last
Byte To Be Read
?
SRW=1
?
Write Next
Byte To IBDR
Set TXAK =1
Generate
Stop Signal
Y
Set TX
Mode
Switch To
Rx Mode
Generate
Stop Signal
Read Data
From IBDR
And Store
ACK From
Receiver
?
N
Read Data
From IBDR
And Store
Tx Next
Byte
Write Data
To IBDR
Dummy Read
From IBDR
TX
N (Write)
N
RX
TX/RX
?
Set RX
Mode
Switch To
Rx Mode
Dummy Read
From IBDR
Dummy Read
From IBDR
RTI
Figure 17-4. Flow-Chart of Typical IIC Interrupt Routine
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Section 18. MSCAN Controller
18.1 Contents
18.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
18.3
External Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
18.4
Message Storage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
18.5
Identifier Acceptance Filter . . . . . . . . . . . . . . . . . . . . . . . . . . .332
18.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .335
18.7
Protocol Violation Protection. . . . . . . . . . . . . . . . . . . . . . . . . . 337
18.8
Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .338
18.9
Timer Link . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
18.10 Clock System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .343
18.11 Memory Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
18.12 Programmer’s Model of Message Storage . . . . . . . . . . . . . . .346
18.13 Programmer’s Model of Control Registers . . . . . . . . . . . . . . . 351
18.2 Introduction
The MC68HC912DT128A has three identical msCAN12 modules,
identified as CAN0, CAN1 and CAN2. The MC68HC912DG128A has
two: CAN0 and CAN1. The information to follow describes one msCAN
unless specifically noted and register locations specifically relate to
CAN0. CAN1 registers are located 512 bytes from CAN0, and on the
MC68HC912DT128A, CAN2 registers are located 256 bytes from
CAN0.
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The msCAN12 is the specific implementation of the Motorola scalable
CAN (msCAN) concept targeted for the Motorola M68HC12
microcontroller family.
The module is a communication controller implementing the CAN 2.0
A/B protocol as defined in the BOSCH specification dated September
1991.
The CAN protocol was primarily, but not only, designed to be used as a
vehicle serial data bus, meeting the specific requirements of this field:
real-time processing, reliable operation in the EMI environment of a
vehicle, cost-effectiveness and required bandwidth.
msCAN12 utilizes an advanced buffer arrangement resulting in a
predictable real-time behavior and simplifies the application software.
18.3 External Pins
The msCAN12 uses 2 external pins, 1 input (RxCAN) and 1 output
(TxCAN). The TxCAN output pin represents the logic level on the CAN:
0 is for a dominant state, and 1 is for a recessive state.
RxCAN is on bit 0 of Port CAN, TxCAN is on bit 1. The remaining six pins
of Port CAN are controlled by registers in the msCAN12 address space
(see msCAN12 Port CAN Control Register (PCTLCAN) and msCAN12
Port CAN Data Direction Register (DDRCAN)).
A typical CAN system with msCAN12 is shown in Figure 18-1 below.
Each CAN station is connected physically to the CAN bus lines through
a transceiver chip. The transceiver is capable of driving the large current
needed for the CAN and has current protection, against defected CAN
or defected stations.
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CAN station 1
CAN station 2
.....
CAN station n
CAN system
msCAN12
Controller
TxCAN
RxCAN
Transceiver
CAN
Figure 18-1. The CAN System
18.4 Message Storage
msCAN12 facilitates a sophisticated message storage system which
addresses the requirements of a broad range of network applications.
18.4.1 Background
Modern application layer software is built upon two fundamental
assumptions:
1. Any CAN node is able to send out a stream of scheduled
messages without releasing the bus between two messages.
Such nodes will arbitrate for the bus right after sending the
previous message and will only release the bus in case of lost
arbitration.
2. The internal message queue within any CAN node is organized
such that if more than one message is ready to be sent, the
highest priority message will be sent out first.
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Above behavior can not be achieved with a single transmit buffer. That
buffer must be reloaded right after the previous message has been sent.
This loading process lasts a definite amount of time and has to be
completed within the inter-frame sequence (IFS) in order to be able to
send an uninterrupted stream of messages. Even if this is feasible for
limited CAN bus speeds it requires that the CPU reacts with short
latencies to the transmit interrupt.
A double buffer scheme would de-couple the re-loading of the transmit
buffers from the actual message sending and as such reduces the
reactiveness requirements on the CPU. Problems may arise if the
sending of a message would be finished just while the CPU re-loads the
second buffer, no buffer would then be ready for transmission and the
bus would be released.
At least three transmit buffers are required to meet the first of above
requirements under all circumstances. The msCAN12 has three transmit
buffers.
The second requirement calls for some sort of internal prioritizing which
the msCAN12 implements with the local priority concept described
below.
18.4.2 Receive Structures
The received messages are stored in a two stage input FIFO. The two
message buffers are mapped using a ping-pong arrangement into a
single memory area (see Figure 18-2). While the background receive
buffer (RxBG) is exclusively associated to the msCAN12, the foreground
receive buffer (RxFG) is addressed by the CPU12. This scheme
simplifies the handler software as only one address area is applicable for
the receive process.
Both buffers have a size of 13 bytes to store the CAN control bits, the
identifier (standard or extended) and the data contents (for details see
Programmer’s Model of Message Storage).
The receiver full flag (RXF) in the msCAN12 receiver flag register
(CRFLG) (see msCAN12 Receiver Flag Register (CRFLG)) signals the
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status of the foreground receive buffer. When the buffer contains a
correctly received message with matching identifier this flag is set.
After the msCAN12 successfully received a message into the
background buffer and if the message passes the filter, it copies the
content of RxBG into RxFG(1), sets the RXF flag, and emits a receive
interrupt to the CPU(2). A new message (which may follow immediately
after the IFS field of the CAN frame) will be received into RxBG. The
over-writing of the background buffer is independent of the identifier filter
function.
The user’s receive handler has to read the received message from
RxFG and to reset the RXF flag in order to acknowledge the interrupt
and to release the foreground buffer.
An overrun condition occurs when both the foreground and the
background receive message buffers are filled with correctly received
messages with accepted identifiers and a further correctly received
message with accepted identifier is received from the bus. The latter
message will be discarded and an error interrupt with overrun indication
will occur if enabled. As long as both buffers remain filled, the msCAN12
is able to transmit messages but it will discard all incoming messages.
NOTE:
The msCAN12 will receive its own messages into the background
receive buffer RxBG but will not overwrite RxFG and will not emit a
receive interrupt nor will it acknowledge (ACK) its own messages on the
CAN bus. The exception to this rule is that when in loop-back mode
msCAN12 will treat its own messages exactly like all other incoming
messages.
1. Only if the RXF flag is not set.
2. The receive interrupt will occur only if not masked. A polling scheme can be applied on RXF
also.
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msCAN12
CPU bus
RxBG
RxFG
RXF
Tx0
TXE
PRIO
Tx1
TXE
PRIO
Tx2
TXE
PRIO
Figure 18-2. User Model for Message Buffer Organization
18.4.3 Transmit Structures
The msCAN12 has a triple transmit buffer scheme in order to allow
multiple messages to be set up in advance and to achieve an optimized
real-time performance. The three buffers are arranged as shown in
Figure 18-2.
All three buffers have a 13 byte data structure similar to the outline of the
receive buffers (see Programmer’s Model of Message Storage). An
additional transmit buffer priority register (TBPR) contains an 8-bit so
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called local priority field (PRIO) (see Transmit Buffer Priority Registers
(TBPR)).
In order to transmit a message, the CPU12 has to identify an available
transmit buffer which is indicated by a set transmit buffer empty (TXE)
flag in the msCAN12 transmitter flag register (CTFLG) (see msCAN12
Transmitter Flag Register (CTFLG)).
The CPU12 then stores the identifier, the control bits and the data
content into one of the transmit buffers. Finally, the buffer has to be
flagged as being ready for transmission by clearing the TXE flag.
The msCAN12 will then schedule the message for transmission and will
signal the successful transmission of the buffer by setting the TXE flag.
A transmit interrupt will be emitted(1) when TXE is set and this can be
used to drive the application software to re-load the buffer.
In case more than one buffer is scheduled for transmission when the
CAN bus becomes available for arbitration, the msCAN12 uses the local
priority setting of the three buffers for prioritizing. For this purpose every
transmit buffer has an 8-bit local priority field (PRIO). The application
software sets this field when the message is set up. The local priority
reflects the priority of this particular message relative to the set of
messages being emitted from this node. The lowest binary value of the
PRIO field is defined to be the highest priority.
The internal scheduling process takes places whenever the msCAN12
arbitrates for the bus. This is also the case after the occurrence of a
transmission error.
When a high priority message is scheduled by the application software
it may become necessary to abort a lower priority message being set up
in one of the three transmit buffers. As messages that are already under
transmission can not be aborted, the user has to request the abort by
setting the corresponding abort request flag (ABTRQ) in the
transmission control register (CTCR). The msCAN12 grants the request,
if possible, by setting the corresponding abort request acknowledge
(ABTAK) and the TXE flag in order to release the buffer and by emitting
1. The transmit interrupt will occur only if not masked. A polling scheme can be applied on TXE
also.
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a transmit interrupt. The transmit interrupt handler software can tell from
the setting of the ABTAK flag whether the message was actually aborted
(ABTAK=1) or sent in the meantime (ABTAK=0).
18.5 Identifier Acceptance Filter
A very flexible programmable generic identifier acceptance filter has
been introduced in order to reduce the CPU interrupt loading. The filter
is programmable to operate in four different modes:
•
Two identifier acceptance filters, each to be applied to the full 29
bits of the identifier and to the following bits of the CAN frame:
RTR, IDE, SRR. This mode implements a two filters for a full
length CAN 2.0B compliant extended identifier. Figure 18-3 shows
how the first 32-bit filter bank (CIDAR0–3, CIDMR0–3) produces a
filter 0 hit. Similarly, the second filter bank (CIDAR4–7,
CIDMR4–7) produces a filter 1 hit.
•
Four identifier acceptance filters, each to be applied to a) the 11
bits of the identifier and the RTR bit of CAN 2.0A messages or b)
the 14 most significant bits of the identifier of CAN 2.0B messages.
Figure 18-4 shows how the first 32-bit filter bank (CIDAR0–3,
CIDMR0–3) produces filter 0 and 1 hits. Similarly, the second filter
bank (CIDAR4–7, CIDMR4–7) produces filter 2 and 3 hits.
•
Eight identifier acceptance filters, each to be applied to the first 8
bits of the identifier. This mode implements eight independent
filters for the first 8 bit of a CAN 2.0A compliant standard identifier
or of a CAN 2.0B compliant extended identifier. Figure 18-5 shows
how the first 32-bit filter bank (CIDAR0–3, CIDMR0–3) produces
filter 0 to 3 hits. Similarly, the second filter bank (CIDAR4–7,
CIDMR4–7) produces filter 4 to 7 hits.
•
Closed filter. No CAN message will be copied into the foreground
buffer RxFG, and the RXF flag will never be set.
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Identifier Acceptance Filter
ID28 IDR0
ID10 IDR0
ID21 ID20 IDR1
ID3 ID2
ID15
ID14 IDR2
ID7
ID6
IDR3 RTR
IDR1 IDE
AM7 CIDMRO AM0 AM7 CIDMR1 AM0
AM7 CIDMR2 AM0
AM7 CIDMR3 AM0
AC7 CIDARO AC0 AC7 CIDAR1 AC0
AC7 CIDAR2 AC0
AC7 CIDAR3 AC0
ID accepted (Filter 0 hit)
Figure 18-3. 32-bit Maskable Identifier Acceptance Filters
ID28 IDR0
ID10 IDR0
ID21 ID20 IDR1
ID3 ID2
ID15
ID14 IDR2
ID7
ID6
IDR3 RTR
IDR1 IDE
AM7 CIDMRO AM0 AM7 CIDMR1 AM0
AC7 CIDARO AC0 AC7 CIDAR1 AC0
ID accepted (Filter 0 hit)
AM7 CIDMR2 AM0 AM7 CIDMR3 AM0
AC7 CIDAR2 AC0 AC7 CIDAR3 AC0
ID accepted (Filter 1 hit)
Figure 18-4. 16-bit Maskable Acceptance Filters
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ID28
IDR0
ID21 ID20
ID10
IDR0
ID3 ID2
IDR1
ID15
ID14 IDR2
ID7
ID6
IDR3
RTR
IDR1 IDE
AM7 CIDMRO AM0
AC7 CIDARO AC0
ID accepted (Filter 0 hit)
AM7 CIDMR1 AM0
AC7 CIDAR1 AC0
ID accepted (Filter 1 hit)
AM7 CIDMR2 AM0
AC7 CIDAR2 AC0
ID accepted (Filter 2 hit)
AM7 CIDMR3 AM0
AC7 CIDAR3 AC0
Figure 18-5. 8-bit Maskable Acceptance Filters
The identifier acceptance registers (CIDAR0–7) define the acceptable
patterns of the standard or extended identifier (ID10–ID0 or ID28–ID0).
Any of these bits can be marked don’t care in the identifier mask
registers (CIDMR0–7).
A filter hit is indicated to the application software by a set RXF (receive
buffer full flag, see msCAN12 Receiver Flag Register (CRFLG)) and
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three bits in the identifier acceptance control register (see msCAN12
Identifier Acceptance Control Register (CIDAC)). These identifier hit
flags (IDHIT2–0) clearly identify the filter section that caused the
acceptance. They simplify the application software’s task to identify the
cause of the receiver interrupt. In case that more than one hit occurs (two
or more filters match) the lower hit has priority.
A hit will also cause a receiver interrupt if enabled.
18.6 Interrupts
The msCAN12 supports four interrupt vectors mapped onto eleven
different interrupt sources, any of which can be individually masked (for
details see msCAN12 Receiver Flag Register (CRFLG) to msCAN12
Transmitter Control Register (CTCR)):
•
Transmit interrupt: At least one of the three transmit buffers is
empty (not scheduled) and can be loaded to schedule a message
for transmission. The TXE flags of the empty message buffers are
set.
•
Receive interrupt: A message has been successfully received and
loaded into the foreground receive buffer. This interrupt will be
emitted immediately after receiving the EOF symbol. The RXF flag
is set.
•
Wake-up interrupt: An activity on the CAN bus occurred during
msCAN12 internal SLEEP mode.
•
Error interrupt: An overrun, error or warning condition occurred.
The receiver flag register (CRFLG) will indicate one of the
following conditions:
– Overrun: an overrun condition as described in Receive
Structures has occurred.
– Receiver warning: the receive error counter has reached the
CPU warning limit of 96.
– Transmitter warning: the transmit error counter has reached
the CPU warning limit of 96.
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– Receiver error passive: the receive error counter has
exceeded the error passive limit of 127 and msCAN12 has
gone to error passive state.
– Transmitter error passive: the transmit error counter has
exceeded the error passive limit of 127 and msCAN12 has
gone to error passive state.
– Bus off: the transmit error counter has exceeded 255 and
msCAN12 has gone to BUSOFF state.
18.6.1 Interrupt Acknowledge
Interrupts are directly associated with one or more status flags in either
the msCAN12 receiver flag register (CRFLG) or the msCAN12
transmitter flag register (CTFLG). Interrupts are pending as long as one
of the corresponding flags is set. The flags in above registers must be
reset within the interrupt handler in order to handshake the interrupt. The
flags are reset through writing a 1 to the corresponding bit position. A flag
can not be cleared if the respective condition still prevails.
NOTE:
Bit manipulation instructions (BSET) shall not be used to clear interrupt
flags.
18.6.2 Interrupt Vectors
The msCAN12 supports four interrupt vectors as shown in Table 18-1.
The vector addresses and the relative interrupt priority are dependent on
the chip integration and to be defined.
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Protocol Violation Protection
Table 18-1. msCAN12 Interrupt Vectors
Function
Wake-Up
Source
WUPIF
RWRNIF
TWRNIF
RERRIF
TERRIF
BOFFIF
OVRIF
RXF
TXE0
TXE1
TXE2
Error
Interrupts
Receive
Transmit
Local Mask
WUPIE
RWRNIE
TWRNIE
RERRIE
TERRIE
BOFFIE
OVRIE
RXFIE
TXEIE0
TXEIE1
TXEIE2
Global Mask
I Bit
18.7 Protocol Violation Protection
The msCAN12 will protect the user from accidentally violating the CAN
protocol through programming errors. The protection logic implements
the following features:
•
The receive and transmit error counters cannot be written or
otherwise manipulated.
•
All registers which control the configuration of the msCAN12 can
not be modified while the msCAN12 is on-line. The SFTRES bit in
CMCR0 (see msCAN12 Module Control Register (CMCR0))
serves as a lock to protect the following registers:
– msCAN12 module control register 1 (CMCR1)
– msCAN12 bus timing register 0 and 1 (CBTR0, CBTR1)
– msCAN12 identifier acceptance control register (CIDAC)
– msCAN12 identifier acceptance registers (CIDAR0–7)
– msCAN12 identifier mask registers (CIDMR0–7)
•
The TxCAN pin is forced to recessive when the msCAN12 is in any
of the low power modes.
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18.8 Low Power Modes
The msCAN12 has three modes with reduced power consumption
compared to normal mode. In SLEEP and SOFT_RESET mode, power
consumption is reduced by stopping all clocks except those to access
the registers. In POWER_DOWN mode, all clocks are stopped and no
power is consumed.
The WAI and STOP instructions put the MCU in low power consumption
stand-by modes. Table 18-2 summarizes the combinations of msCAN12
and CPU modes. A particular combination of modes is entered for the
given settings of the bits CSWAI, SLPAK, and SFTRES. For all modes,
an msCAN wake-up interrupt can occur only if SLPAK=WUPIE=1. While
the CPU is in Wait Mode, the msCAN12 can be operated in Normal
Mode and emit interrupts (registers can be accessed via background
debug mode).
Table 18-2. msCAN12 vs. CPU operating modes
STOP
CPU Mode
WAIT
CSWAI = X(1)
SLPAK = X
SFTRES = X
CSWAI = 1
SLPAK = X
SFTRES = X
msCAN Mode
POWER_DOWN
SLEEP
SOFT_RESET
Normal
CSWAI = 0
SLPAK = 1
SFTRES = 0
CSWAI = 0
SLPAK = 0
SFTRES = 1
CSWAI = 0
SLPAK = 0
SFTRES = 0
RUN
CSWAI = X
SLPAK = 1
SFTRES = 0
CSWAI = X
SLPAK = 0
SFTRES = 1
CSWAI = X
SLPAK = 0
SFTRES = 0
1. X means don’t care.
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Low Power Modes
18.8.1 msCAN12 SLEEP Mode
The CPU can request the msCAN12 to enter this low-power mode by
asserting the SLPRQ bit in the module configuration register (see Figure
18-6). The time when the msCAN12 will then enter SLEEP mode
depends on its current activity:
•
If there are one or more message buffers are scheduled for
transmission (TXEx = 0), the msCAN will continue to transmit until
all transmit message buffers are empty (TXEx = 1, transmitted
successfully or aborted) and then goes into Sleep Mode
•
If it is receiving, it continues to receive and goes into Sleep Mode
as soon as the CAN bus next becomes idle
•
If it is neither transmitting nor receiving, it will immediately go into
SLEEP mode
The application software must avoid setting up a transmission (by
clearing one or more TXE flag(s)) and immediately request SLEEP
mode (by setting SLPRQ). It will then depend on the exact sequence of
operations whether the msCAN12 will start transmitting or go into
SLEEP mode directly.
During SLEEP mode, the SLPAK flag is set. The application software
should use SLPAK as a handshake indication for the request (SLPRQ) to
go into SLEEP mode. When in SLEEP mode, the msCAN12 stops its
internal clocks. Clocks to allow register accesses will still run. The TxCAN
pin will stay in recessive state. If RXF=1, the message can be read and
RXF can be cleared. However, if the msCAN12 is in bus-off state, it stops
counting 128*11 consecutive recessive bits due to the stopped clocks.
Likewise, copying of RxBG into RxFG will not take place while in sleep
mode. It is possible to access the transmit buffers and to clear the TXE
flags. No message abort will take place while in sleep mode.
The msCAN12 will leave SLEEP mode (wake-up) when
•
bus activity occurs or
•
the MCU clears the SLPRQ bit or
•
the MCU sets SFTRES.
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NOTE:
The MCU cannot clear the SLPRQ bit before the msCAN12 is in SLEEP
mode (SLPAK = 1).
After wake-up, the msCAN12 waits for 11 consecutive recessive bits to
synchronize to the bus. As a consequence, if the msCAN12 is woken-up
by a CAN frame, this frame will not be received. The receive message
buffers (RxBG and RxFG) will contain messages if they were received
before sleep mode was entered. Pending copying of RxBG and RxFG,
as well as pending message aborts and pending message
transmissions, will now be executed. If the msCAN12 is still in bus-off
state after sleep mode was left, it continues counting the 128*11
consecutive recessive bits.
msCAN12 Running
SLPRQ = 0
SLPAK = 0
MCU
MCU
or msCAN12
msCAN12 Sleeping
SLEEP Request
SLPRQ = 1
SLPAK = 1
SLPRQ = 1
SLPAK = 0
msCAN12
Figure 18-6. SLEEP Request / Acknowledge Cycle
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Low Power Modes
18.8.2 msCAN12 SOFT_RESET Mode
In SOFT_RESET mode, the msCAN12 is stopped. Registers can still be
accessed. This mode is used to initialize the module configuration, bit
timing, and the CAN message filter. See msCAN12 Module Control
Register (CMCR0) for a complete description of the SOFT_RESET
mode.
When setting the SFTRES bit, the msCAN12 immediately stops all
ongoing transmissions and receptions, potentially causing the CAN
protocol violations. The user is responsible to take care that the
msCAN12 is not active when SOFT_RESET mode is entered. The
recommended procedure is to bring the msCAN12 into SLEEP mode
before the SFTRES bit is set.
18.8.3 msCAN12 POWER_DOWN Mode
The msCAN12 is in POWER_DOWN mode when
•
the CPU is in STOP mode or
•
the CPU is in WAIT mode and the CSWAI bit is set (see msCAN12
Module Control Register (CMCR0)).
When entering the POWER_DOWN mode, the msCAN12 immediately
stops all ongoing transmissions and receptions, potentially causing CAN
protocol violations. The user is responsible to take care that the
msCAN12 is not active when POWER_DOWN mode is entered. The
recommended procedure is to bring the msCAN12 into SLEEP mode
before the STOP instruction (or the WAI instruction, if CSWAI is set) is
executed.
To protect the CAN bus system from fatal consequences of violations to
above rule, the msCAN12 will drive the TxCAN pin into recessive state.
In POWER_DOWN mode, no registers can be accessed.
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18.8.4 Programmable Wake-Up Function
The msCAN12 can be programmed to apply a low-pass filter function to
the RxCAN input line while in SLEEP mode (see control bit WUPM in the
module control register, msCAN12 Module Control Register (CMCR0)).
This feature can be used to protect the msCAN12 from wake-up due to
short glitches on the CAN bus lines. Such glitches can result from
electromagnetic inference within noisy environments.
18.9 Timer Link
The msCAN12 will generate a timer signal whenever a valid frame has
been received. Because the CAN specification defines a frame to be
valid if no errors occurred before the EOF field has been transmitted
successfully, the timer signal will be generated right after the EOF. A
pulse of one bit time is generated. As the msCAN12 receiver engine
receives also the frames being sent by itself, a timer signal will also be
generated after a successful transmission.
The previously described timer signal can be routed into the on-chip
timer module (ECT). Under the control of the timer link enable (TLNKEN)
bit in the CMCR0, this signal will be connected to the ECT timer channel
m input(1).
After ECT timer has been programmed to capture rising edge events, it
can be used under software control to generate 16-bit time stamps which
can be stored with the received message.
1. The timer channel being used for the timer link for CAN0 is channel 4 and for CAN1 is channel
5.
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Clock System
18.10 Clock System
Figure 18-7 shows the structure of the msCAN12 clock generation
circuitry. With this flexible clocking scheme the msCAN12 is able to
handle CAN bus rates ranging from 10 kbps up to 1 Mbps.
CGM
msCAN12
SYSCLK
CGMCANCLK
CLKSRC
EXTALi
Prescaler
(1...64)
Time quanta
clock
CLKSRC
Figure 18-7. Clocking Scheme
The clock source bit (CLKSRC) in the msCAN12 module control register
(CMCR1) (see msCAN12 Bus Timing Register 0 (CBTR0)) defines
whether the msCAN12 is connected to the output of the crystal oscillator
(EXTALi) or to the system clock (SYSCLK).
The clock source has to be chosen such that the tight oscillator tolerance
requirements (up to 0.4%) of the CAN protocol are met. Additionally, for
high CAN bus rates (1 Mbps), a 50% duty cycle of the clock is required.
For microcontrollers without the CGM module, CGMCANCLK is driven
from the crystal oscillator (EXTALi).
A programmable prescaler is used to generate out of msCANCLK the
time quanta (Tq) clock. A time quantum is the atomic unit of time handled
by the msCAN12. A bit time is subdivided into three segments(1):
•
SYNC_SEG: This segment has a fixed length of one time
quantum. Signal edges are expected to happen within this section.
1. For further explanation of the under-lying concepts please refer to ISO/DIS 11519-1, Section
10.3.
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•
Time segment 1: This segment includes the PROP_SEG and the
PHASE_SEG1 of the CAN standard. It can be programmed by
setting the parameter TSEG1 to consist of 4 to 16 time quanta.
•
Time segment 2: This segment represents the PHASE_SEG2 of
the CAN standard. It can be programmed by setting the TSEG2
parameter to be 2 to 8 time quanta long.
The synchronization jump width can be programmed in a range of 1 to 4
time quanta by setting the SJW parameter.
Above parameters can be set by programming the bus timing registers
(CBTR0–1, see msCAN12 Bus Timing Register 0 (CBTR0) and
msCAN12 Bus Timing Register 1 (CBTR1)).
It is the user’s responsibility to make sure that his bit time settings are in
compliance with the CAN standard. Figure 18-9 gives an overview on
the CAN conforming segment settings and the related parameter values.
NRZ Signal
SYNC
_SEG
Time segment 1
(PROP_SEG + PHASE_SEG1)
Time Seg. 2
(PHASE_SEG2)
1
4 ... 16
2 ... 8
8... 25 Time Quanta
= 1 Bit Time
Transmit point
Sample point
(single or triple sampling)
Figure 18-8. Segments within the Bit Time
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Memory Map
Figure 18-9. CAN Standard Compliant Bit Time Segment Settings
Time Segment 1
TSEG1
Time Segment 2
TSEG2
5 .. 10
4 .. 11
5 .. 12
6 .. 13
7 .. 14
8 .. 15
9 .. 16
4 .. 9
3 .. 10
4 .. 11
5 .. 12
6 .. 13
7 .. 14
8 .. 15
2
3
4
5
6
7
8
1
2
3
4
5
6
7
Synchron.
Jump Width
1 .. 2
1 .. 3
1 .. 4
1 .. 4
1 .. 4
1 .. 4
1 .. 4
SJW
0 .. 1
0 .. 2
0 .. 3
0 .. 3
0 .. 3
0 .. 3
0 .. 3
18.11 Memory Map
The msCAN12 occupies 128 bytes in the CPU12 memory space. The
background receive buffer can only be read in test mode.
Figure 18-10. msCAN12 Memory Map
$0100
$0108
$0109
$010D
$010E
$010F
$0110
$011F
$0120
$013C
$013D
$013F
$0140
$014F
$0150
$015F
$0160
$016F
$0170
$017F
Control registers
9 bytes
Reserved
5 bytes
Error counters
2 bytes
Identifier filter
16 bytes
Reserved
29 bytes
Port CAN registers
3 bytes
Foreground Receive buffer
MC68HC912DT128A — Rev 4.0
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Transmit buffer 0
Transmit buffer 1
Transmit buffer 2
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18.12 Programmer’s Model of Message Storage
The following section details the organization of the receive and transmit
message buffers and the associated control registers. For reasons of
programmer interface simplification the receive and transmit message
buffers have the same outline. Each message buffer allocates 16 bytes
in the memory map containing a 13 byte data structure. An additional
transmit buffer priority register (TBPR) is defined for the transmit buffers.
Figure 18-11. Message Buffer Organization
Address
(1)
Register name
01x0
Identifier register 0
01x1
01x2
01x3
01x4
01x5
01x6
01x7
01x8
01x9
01xA
01xB
01xC
Identifier register 1
Identifier register 2
Identifier register 3
Data segment register 0
Data segment register 1
Data segment register 2
Data segment register 3
Data segment register 4
Data segment register 5
Data segment register 6
Data segment register 7
Data length register
01xD
Transmit buffer priority register(2)
Unused
Unused
01xE
01xF
1. x is 4, 5, 6, or 7 depending on which buffer RxFG,
Tx0, Tx1, or Tx2 respectively.
2. Not applicable for receive buffers
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Programmer’s Model of Message Storage
18.12.1 Message Buffer Outline
Figure 18-12 shows the common 13 byte data structure of receive and
transmit buffers for extended identifiers. The mapping of standard
identifiers into the IDR registers is shown in Figure 18-13. All bits of the
13 byte data structure are undefined out of reset.
NOTE:
The foreground receive buffer can be read anytime but can not be
written. The transmit buffers can be read or written anytime.
Figure 18-12. Receive/Transmit Message Buffer Extended Identifier
ADDR(1)
REGISTER
$01x0
IDR0
$01x1
IDR1
$01x2
IDR2
$01x3
IDR3
$01x4
DSR0
$01x5
DSR1
$01x6
DSR2
$01x7
DSR3
$01x8
DSR4
$01x9
DSR5
$01xA
DSR6
$01xB
DSR7
$01xC
DLR
R/W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
R
W
BIT 7
6
5
4
3
2
1
BIT 0
ID28
ID27
ID26
ID25
ID24
ID23
ID22
ID21
ID20
ID19
ID18
ID17
ID16
ID15
ID14
ID13
ID12
ID11
ID10
ID9
ID8
ID7
ID6
ID5
ID4
ID3
ID2
ID1
ID0
RTR
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DB7
DB6
DB5
DB4
DB3
DB2
DB1
DB0
DLC3
DLC2
DLC1
DLC0
SRR (1) IDE (1)
1. x is 4, 5, 6, or 7 depending on which buffer RxFG, Tx0, Tx1, or Tx2 respectively.
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Figure 18-13. Standard Identifier Mapping
ADDR(1)
REGISTER
$01x0
IDR0
$01x1
IDR1
$01x2
IDR2
$01x3
IDR3
R/W
R
W
R
W
R
W
R
W
BIT 7
6
5
4
3
2
1
BIT 0
ID10
ID9
ID8
ID7
ID6
ID5
ID4
ID3
ID2
ID1
ID0
RTR
IDE(0)
1. x is 4, 5, 6, or 7 depending on which buffer RxFG, Tx0, Tx1, or Tx2 respectively.
18.12.2 Identifier Registers (IDRn)
The identifiers consist of either 11 bits (ID10–ID0) for the standard, or 29
bits (ID28–ID0) for the extended format. ID10/28 is the most significant
bit and is transmitted first on the bus during the arbitration procedure.
The priority of an identifier is defined to be highest for the smallest binary
number.
SRR — Substitute Remote Request
This fixed recessive bit is used only in extended format. It must be set
to 1 by the user for transmission buffers and will be stored as received
on the CAN bus for receive buffers.
IDE — ID Extended
This flag indicates whether the extended or standard identifier format
is applied in this buffer. In case of a receive buffer the flag is set as
being received and indicates to the CPU how to process the buffer
identifier registers. In case of a transmit buffer the flag indicates to the
msCAN12 what type of identifier to send.
0 = Standard format (11-bit)
1 = Extended format (29-bit)
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Programmer’s Model of Message Storage
RTR — Remote transmission request
This flag reflects the status of the Remote Transmission Request bit
in the CAN frame. In case of a receive buffer it indicates the status of
the received frame and allows to support the transmission of an
answering frame in software. In case of a transmit buffer this flag
defines the setting of the RTR bit to be sent.
0 = Data frame
1 = Remote frame
18.12.3 Data Length Register (DLR)
This register keeps the data length field of the CAN frame.
DLC3 – DLC0 — Data length code bits
The data length code contains the number of bytes (data byte count)
of the respective message. At transmission of a remote frame, the
data length code is transmitted as programmed while the number of
transmitted bytes is always 0. The data byte count ranges from 0 to 8
for a data frame. Table 18-3 shows the effect of setting the DLC bits.
Table 18-3. Data length codes
Data length code
DLC3
DLC2
DLC1
DLC0
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
1
1
0
0
0
1
1
0
0
1
1
0
0
1
0
1
0
1
0
1
0
MC68HC912DT128A — Rev 4.0
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Data
byte
count
0
1
2
3
4
5
6
7
8
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18.12.4 Data Segment Registers (DSRn)
The eight data segment registers contain the data to be transmitted or
being received. The number of bytes to be transmitted or being received
is determined by the data length code in the corresponding DLR.
18.12.5 Transmit Buffer Priority Registers (TBPR)
TBPR(1)
R
$01xD
W
RESET
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
PRIO7
PRIO6
PRIO5
PRIO4
PRIO3
PRIO2
PRIO1
PRIO0
-
-
-
-
-
-
-
-
1. x is 5, 6, or 7 depending on which buffer Tx0, Tx1, or Tx2 respectively.
PRIO7 – PRIO0 — Local Priority
This field defines the local priority of the associated message buffer.
The local priority is used for the internal prioritizing process of the
msCAN12 and is defined to be highest for the smallest binary number.
The msCAN12 implements the following internal priorization
mechanism:
NOTE:
•
All transmission buffers with a cleared TXE flag participate in the
priorisation right before the SOF (Start of Frame) is sent.
•
The transmission buffer with the lowest local priority field wins the
priorisation.
•
In case of more than one buffer having the same lowest priority the
message buffer with the lower index number wins.
To ensure data integrity, no registers of the transmit buffers shall be
written while the associated TXE flag is cleared.
To ensure data integrity, no registers of the receive buffer shall be read
while the RXF flag is cleared.
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Programmer’s Model of Control Registers
18.13 Programmer’s Model of Control Registers
18.13.1 Overview
The programmer’s model has been laid out for maximum simplicity and
efficiency.
18.13.2 msCAN12 Module Control Register (CMCR0)
CMCR0
R
$0100
W
RESET
Bit 7
0
6
0
0
0
5
CSWAI
1
4
SYNCH
3
TLNKEN
0
0
2
SLPAK
0
1
Bit 0
SLPRQ
SFTRES
0
1
CSWAI — CAN Stops in Wait Mode
0 = The module is not affected during WAIT mode.
1 = The module ceases to be clocked during WAIT mode.
SYNCH — Synchronized Status
This bit indicates whether the msCAN12 is synchronized to the CAN
bus and as such can participate in the communication process.
0 = msCAN12 is not synchronized to the CAN bus
1 = msCAN12 is synchronized to the CAN bus
TLNKEN — Timer Enable
This flag is used to establish a link between the msCAN12 and the onchip timer (see Timer Link).
0 = The port is connected to the timer input.
1 = The msCAN12 timer signal output is connected to the timer
input.
SLPAK — SLEEP Mode Acknowledge
This flag indicates whether the msCAN12 is in module internal
SLEEP Mode. It shall be used as a handshake for the SLEEP Mode
request (see msCAN12 SLEEP Mode).
0 = Wake-up – The msCAN12 is not in SLEEP Mode.
1 = SLEEP – The msCAN12 is in SLEEP Mode.
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SLPRQ — SLEEP request
This flag allows to request the msCAN12 to go into an internal powersaving mode (see msCAN12 SLEEP Mode).
0 = Wake-up – The msCAN12 will function normally.
1 = SLEEP request – The msCAN12 will go into SLEEP Mode
when the CAN bus is idle, i.e. the module is not receiving a
message and all transmit buffers are empty.
SFTRES— SOFT_RESET
When this bit is set by the CPU, the msCAN12 immediately enters the
SOFT_RESET state. Any ongoing transmission or reception is
aborted and synchronization to the bus is lost.
The following registers will go into and stay in the same state as out
of hard reset: CMCR0, CRFLG, CRIER, CTFLG, CTCR.
The registers CMCR1, CBTR0, CBTR1, CIDAC, CIDAR0–3,
CIDMR0–3 can only be written by the CPU when the msCAN12 is in
SOFT_RESET state. The values of the error counters are not affected
by SOFT_RESET.
When this bit is cleared by the CPU, the msCAN12 will try to
synchronize to the CAN bus: If the msCAN12 is not in BUSOFF state
it will be synchronized after 11 recessive bits on the bus; if the
msCAN12 is in BUSOFF state it continues to wait for 128 occurrences
of 11 recessive bits.
Clearing SFTRES and writing to other bits in CMCR0 must be in
separate instructions.
0 = Normal operation
1 = msCAN12 in SOFT_RESET state.
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Programmer’s Model of Control Registers
18.13.3 msCAN12 Module Control Register (CMCR1)
CMCR1
R
$0101
W
RESET
Bit 7
0
6
0
5
0
4
0
3
0
0
0
0
0
0
2
1
Bit 0
LOOPB
WUPM
CLKSRC
0
0
0
LOOPB — Loop Back Self Test Mode
When this bit is set the msCAN12 performs an internal loop back
which can be used for self test operation: the bit stream output of the
transmitter is fed back to the receiver. The RxCAN input pin is ignored
and the TxCAN output goes to the recessive state (1). Note that in this
state the msCAN12 ignores the bit sent during the ACK slot of the
CAN frame Acknowledge field to insure proper reception of its own
message and will treat messages being received while in
transmission as received messages from remote nodes.
0 = Normal operation
1 = Activate loop back self test mode
WUPM — Wake-Up Mode
This flag defines whether the integrated low-pass filter is applied to
protect the msCAN12 from spurious wake-ups (see Programmable
Wake-Up Function).
0 = msCAN12 will wake up the CPU after any recessive to
dominant edge on the CAN bus.
1 = msCAN12 will wake up the CPU only in case of dominant pulse
on the bus which has a length of at least approximately Twup.
CLKSRC — msCAN12 Clock Source
This flag defines which clock source the msCAN12 module is driven
from (only for system with CGM module; see Clock System, Figure
18-7).
0 = The msCAN12 clock source is EXTALi.
1 = The msCAN12 clock source is SYSCLK, twice the frequency of
ECLK.
NOTE:
The CMCR1 register can only be written if the SFTRES bit in CMCR0 is
set.
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18.13.4 msCAN12 Bus Timing Register 0 (CBTR0)
CBTR0
R
$0102
W
RESET
Bit 7
6
5
4
3
2
1
Bit 0
SJW1
SJW0
BRP5
BRP4
BRP3
BRP2
BRP1
BRP0
0
0
0
0
0
0
0
0
SJW1, SJW0 — Synchronization Jump Width
The synchronization jump width defines the maximum number of time
quanta (Tq) clock cycles by which a bit may be shortened, or
lengthened, to achieve resynchronization on data transitions on the
bus (see Table 18-4).
Table 18-4. Synchronization jump width
SJW1
0
0
1
1
SJW0
0
1
0
1
Synchronization jump width
1 Tq clock cycle
2 Tq clock cycles
3 Tq clock cycles
4 Tq clock cycles
BRP5 – BRP0 — Baud Rate Prescaler
These bits determine the time quanta (Tq) clock, which is used to
build up the individual bit timing, according to Table 18-5.
Table 18-5. Baud rate prescaler
BRP5
0
0
0
0
:
:
1
NOTE:
BRP4
0
0
0
0
:
:
1
BRP3
0
0
0
0
:
:
1
BRP2
0
0
0
0
:
:
1
BRP0
0
1
0
1
:
:
1
Prescaler value (P)
1
2
3
4
:
:
64
The CBTR0 register can only be written if the SFTRES bit in CMCR0 is
set.
Technical Data
354
BRP1
0
0
1
1
:
:
1
MC68HC912DT128A — Rev 4.0
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MSCAN Controller
Programmer’s Model of Control Registers
18.13.5 msCAN12 Bus Timing Register 1 (CBTR1)
CBTR1
R
$0103
W
RESET
Bit 7
6
5
4
3
2
1
Bit 0
SAMP
TSEG22
TSEG21
TSEG20
TSEG13
TSEG12
TSEG11
TSEG10
0
0
0
0
0
0
0
0
SAMP — Sampling
This bit determines the number of samples of the serial bus to be
taken per bit time. If set three samples per bit are taken, the regular
one (sample point) and two preceding samples, using a majority rule.
For higher bit rates SAMP should be cleared, which means that only
one sample will be taken per bit.
0 = One sample per bit.
1 = Three samples per bit(1).
TSEG22 – TSEG10 — Time Segment
Time segments within the bit time fix the number of clock cycles per
bit time, and the location of the sample point.
Table 18-6. Time segment syntax
SYNC_SEG
System expects transitions to occur on the bus during this period.
A node in transmit mode will transfer a new value to the CAN bus at
Transmit point
this point.
A node in receive mode will sample the bus at this point. If the three
Sample point
samples per bit option is selected then this point marks the position
of the third sample.
Time segment 1 (TSEG1) and time segment 2 (TSEG2) are
programmable as shown in Table 18-7.
Table 18-7. Time segment values
TSEG13 TSEG12 TSEG11 TSEG10 Time segment 1
0
0
0
0
1 Tq clock cycle
0
0
0
1
2 Tq clock cycles
0
0
1
0
3 Tq clock cycles
0
0
1
1
4 Tq clock cycles
.
.
.
.
.
.
.
.
.
.
1
1
1
1
16 Tq clock cycles
TSEG22 TSEG21 TSEG20 Time segment 2
0
0
0
1 Tq clock cycle
0
0
1
2 Tq clock cycles
.
.
.
.
.
.
.
.
1
1
1
8 Tq clock cycles
1. In this case PHASE_SEG1 must be at least 2 TimeQuanta.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
MSCAN Controller
355
MSCAN Controller
The bit time is determined by the oscillator frequency, the baud rate
prescaler, and the number of time quanta (Tq) clock cycles per bit (as
shown above).
NOTE:
The CBTR1 register can only be written if the SFTRES bit in CMCR0 is
set.
18.13.6 msCAN12 Receiver Flag Register (CRFLG)
All bits of this register are read and clear only. A flag can be cleared by
writing a 1 to the corresponding bit position. A flag can only be cleared
when the condition which caused the setting is no more valid. Writing a
0 has no effect on the flag setting. Every flag has an associated interrupt
enable flag in the CRIER register. A hard or soft reset will clear the
register.
CRFLG
R
$0104
W
RESET
Bit 7
6
5
4
3
2
1
Bit 0
WUPIF
RWRNIF
TWRNIF
RERRIF
TERRIF
BOFFIF
OVRIF
RXF
0
0
0
0
0
0
0
0
WUPIF — Wake-up Interrupt Flag
If the msCAN12 detects bus activity while it is in SLEEP Mode, it
clears the SLPAK bit in the CMCR0 register; the WUPIF bit will then
be set. If not masked, a Wake-Up interrupt is pending while this flag
is set.
0 = No wake-up activity has been observed while in SLEEP Mode.
1 = msCAN12 has detected activity on the bus and requested
wake-up.
RWRNIF — Receiver Warning Interrupt Flag
This bit will be set when the msCAN12 goes into warning status due
to the Receive Error counter (REC) exceeding 96 and neither one of
the Error interrupt flags or the Bus-Off interrupt flag is set(1). If not
masked, an Error interrupt is pending while this flag is set.
0 = No receiver warning status has been reached.
1 = msCAN12 went into receiver warning status.
1. RWRNIF = (96 < REC) & RERRIF& TERRIF & BOFFIF
Technical Data
356
MC68HC912DT128A — Rev 4.0
MSCAN Controller
MOTOROLA
MSCAN Controller
Programmer’s Model of Control Registers
TWRNIF — Transmitter Warning Interrupt Flag
This bit will be set when the msCAN12 goes into warning status due
to the Transmit Error counter (TEC) exceeding 96 and neither one of
the Error interrupt flags or the Bus-Off interrupt flag is set(1). If not
masked, an Error interrupt is pending while this flag is set.
0 = No transmitter warning status has been reached.
1 = msCAN12 went into transmitter warning status.
RERRIF — Receiver Error Passive Interrupt Flag
This bit will be set when the msCAN12 goes into error passive status
due to the Receive Error counter (REC) exceeding 127 and the BusOff interrupt flag is not set(2). If not masked, an Error interrupt is
pending while this flag is set.
0 = No receiver error passive status has been reached.
1 = msCAN12 went into receiver error passive status.
TERRIF — Transmitter Error Passive Interrupt Flag
This bit will be set when the msCAN12 goes into error passive status
due to the Transmit Error counter (TEC) exceeding 127 and the BusOff interrupt flag is not set(3). If not masked, an Error interrupt is
pending while this flag is set.
0 = No transmitter error passive status has been reached.
1 = msCAN12 went into transmitter error passive status.
BOFFIF — BUSOFF Interrupt Flag
This bit will be set when the msCAN12 goes into BUSOFF status, due
to the Transmit Error counter exceeding 255. It cannot be cleared
before the msCAN12 has monitored 128*11 consecutive recessive
bits on the bus. If not masked, an Error interrupt is pending while this
flag is set.
0 = No BUSOFF status has been reached.
1 = msCAN12 went into BUSOFF status.
1. TWRNIF = (96 < TEC) & RERRIF& TERRIF & BOFFIF
2. RERRIF = (128 < REC < 255) & BOFFIF
3. TERRIF = (128 < TEC < 255) & BOFFIF
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
MSCAN Controller
357
MSCAN Controller
OVRIF — Overrun Interrupt Flag
This bit will be set when a data overrun condition occurred. If not
masked, an Error interrupt is pending while this flag is set.
0 = No data overrun has occurred.
1 = A data overrun has been detected.
RXF — Receive Buffer Full
The RXF flag is set by the msCAN12 when a new message is
available in the foreground receive buffer. This flag indicates whether
the buffer is loaded with a correctly received message. After the CPU
has read that message from the receive buffer the RXF flag must be
handshaked (cleared) in order to release the buffer. A set RXF flag
prohibits the exchange of the background receive buffer into the
foreground buffer. If not masked, a Receive interrupt is pending while
this flag is set.
0 = The receive buffer is released (not full).
1 = The receive buffer is full. A new message is available.
NOTE:
The CRFLG register is held in the reset state if the SFTRES bit in
CMCR0 is set.
18.13.7 msCAN12 Receiver Interrupt Enable Register (CRIER)
CRIER
R
$0105
W
RESET
Bit 7
6
5
4
3
2
1
Bit 0
WUPIE
RWRNIE
TWRNIE
RERRIE
TERRIE
BOFFIE
OVRIE
RXFIE
0
0
0
0
0
0
0
0
WUPIE — Wake-up Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A wake-up event will result in a wake-up interrupt.
RWRNIE — Receiver Warning Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A receiver warning status event will result in an error interrupt.
TWRNIE — Transmitter Warning Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A transmitter warning status event will result in an error
interrupt.
Technical Data
358
MC68HC912DT128A — Rev 4.0
MSCAN Controller
MOTOROLA
MSCAN Controller
Programmer’s Model of Control Registers
RERRIE — Receiver Error Passive Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A receiver error passive status event will result in an error
interrupt.
TERRIE — Transmitter Error Passive Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A transmitter error passive status event will result in an error
interrupt.
BOFFIE — BUSOFF Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A BUSOFF event will result in an error interrupt.
OVRIE — Overrun Interrupt Enable
0 = No interrupt will be generated from this event.
1 = An overrun event will result in an error interrupt.
RXFIE — Receiver Full Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A receive buffer full (successful message reception) event will
result in a receive interrupt.
NOTE:
The CRIER register is held in the reset state if the SFTRES bit in CMCR0
is set.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
MSCAN Controller
359
MSCAN Controller
18.13.8 msCAN12 Transmitter Flag Register (CTFLG)
The Abort Acknowledge flags are read only. The Transmitter Buffer
Empty flags are read and clear only. A flag can be cleared by writing a1
to the corresponding bit position. Writing a zero has no effect on the flag
setting. The Transmitter Buffer Empty flags each have an associated
interrupt enable flag in the CTCR register. A hard or soft reset will reset
the register.
CTFLG
R
$0106
W
RESET
Bit 7
0
6
ABTAK2
5
ABTAK1
4
ABTAK0
3
0
0
0
0
0
0
2
1
Bit 0
TXE2
TXE1
TXE0
1
1
1
ABTAK2 – ABTAK0 — Abort Acknowledge
This flag acknowledges that a message has been aborted due to a
pending abort request from the CPU. After a particular message
buffer has been flagged empty, this flag can be used by the
application software to identify whether the message has been
aborted successfully or has been sent in the meantime. The flag is
reset implicitly whenever the associated TXE flag is set to 0.
0 = The massage has not been aborted, thus has been sent out.
1 = The message has been aborted.
TXE2 – TXE0 —Transmitter Buffer Empty
This flag indicates that the associated transmit message buffer is
empty, thus not scheduled for transmission. The CPU must
handshake (clear) the flag after a message has been set up in the
transmit buffer and is due for transmission. The msCAN12 will set the
flag after the message has been sent successfully. The flag will also
be set by the msCAN12 when the transmission request was
successfully aborted due to a pending abort request (msCAN12
Transmitter Control Register (CTCR)). If not masked, a transmit
interrupt is pending while this flag is set.
Clearing this flag will also clear the corresponding Abort Acknowledge
flag (ABTAK, see above). Setting this flag will clear the corresponding
Abort Request flag (ABTRQ, msCAN12 Transmitter Control Register
(CTCR)).
Technical Data
360
MC68HC912DT128A — Rev 4.0
MSCAN Controller
MOTOROLA
MSCAN Controller
Programmer’s Model of Control Registers
0 = The associated message buffer is full (loaded with a message
due for transmission).
1 = The associated message buffer is empty (not scheduled).
NOTE:
The CTFLG register is held in the reset state if the SFTRES bit in
CMCR0 is set.
18.13.9 msCAN12 Transmitter Control Register (CTCR)
CTCR
R
$0107
W
RESET
Bit 7
0
6
5
4
ABTRQ2
ABTRQ1
ABTRQ0
0
0
0
0
3
0
0
2
1
Bit 0
TXEIE2
TXEIE1
TXEIE0
0
0
0
ABTRQ2 – ABTRQ0 — Abort Request
The CPU sets this bit to request that an already scheduled message
buffer (TXE = 0) shall be aborted. The msCAN12 will grant the
request when the message is not already under transmission. When
a message is aborted the associated TXE and the abort acknowledge
flag (ABTAK, see msCAN12 Transmitter Flag Register (CTFLG)) will
be set and an TXE interrupt will occur if enabled. The CPU can not
reset ABTRQx. ABTRQx is reset implicitly whenever the associated
TXE flag is set.
0 = No abort request.
1 = Abort request pending.
NOTE:
The software must not clear one or more of the TXE flags in CTFGL and
simultaneously set the respective ABTRQ bit(s).
TXEIE2 – TXEIE0 — Transmitter Empty Interrupt Enable
0 = No interrupt will be generated from this event.
1 = A transmitter empty (transmit buffer available for transmission)
event will result in a transmitter empty interrupt.
NOTE:
The CTCR register is held in the reset state if the SFTRES bit in CMCR0
is set.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
MSCAN Controller
361
MSCAN Controller
18.13.10 msCAN12 Identifier Acceptance Control Register (CIDAC)
CIDAC
R
$0108
W
RESET
Bit 7
0
6
0
0
0
5
4
IDAM1
IDAM0
0
0
3
0
2
IDHIT2
1
IDHIT1
Bit 0
IDHIT0
0
0
0
0
IDAM1 – IDAM0 — Identifier Acceptance Mode
The CPU sets these flags to define the identifier acceptance filter
organization (see Identifier Acceptance Filter). Table 18-7
summarizes the different settings. In Filter Closed mode no
messages will be accepted such that the foreground buffer will never
be reloaded.
Table 18-8. Identifier Acceptance Mode Settings
IDAM1
0
0
1
1
IDAM0
0
1
0
1
Identifier Acceptance Mode
Two 32 bit Acceptance Filters
Four 16 bit Acceptance Filters
Eight 8 bit Acceptance Filters
Filter Closed
IDHIT2 – IDHIT0 — Identifier Acceptance Hit Indicator
The msCAN12 sets these flags to indicate an identifier acceptance hit
(see Identifier Acceptance Filter). Table 18-7 summarizes the
different settings.
Table 18-9. Identifier Acceptance Hit Indication
IDHIT2
0
0
0
0
1
1
1
1
IDHIT1
0
0
1
1
0
0
1
1
IDHIT0
0
1
0
1
0
1
0
1
Identifier Acceptance Hit
Filter 0 Hit
Filter 1 Hit
Filter 2 Hit
Filter 3 Hit
Filter 4 Hit
Filter 5 Hit
Filter 6 Hit
Filter 7 Hit
The IDHIT indicators are always related to the message in the
foreground buffer. When a message gets copied from the background to
the foreground buffer the indicators are updated as well.
NOTE:
The CIDAC register can only be written if the SFTRES bit in CMCR0 is
set.
Technical Data
362
MC68HC912DT128A — Rev 4.0
MSCAN Controller
MOTOROLA
MSCAN Controller
Programmer’s Model of Control Registers
18.13.11 msCAN12 Receive Error Counter (CRXERR)
CRXERR R
$010E
W
RESET
Bit 7
RXERR7
6
RXERR6
5
RXERR5
4
RXERR4
3
RXERR3
2
RXERR2
1
RXERR1
Bit 0
RXERR0
0
0
0
0
0
0
0
0
This register reflects the status of the msCAN12 receive error counter.
The register is read only.
18.13.12 msCAN12 Transmit Error Counter (CTXERR)
CTXERR R
$010F
W
RESET
Bit 7
TXERR7
6
TXERR6
5
TXERR5
4
TXERR4
3
TXERR3
2
TXERR2
1
TXERR1
Bit 0
TXERR0
0
0
0
0
0
0
0
0
This register reflects the status of the msCAN12 transmit error counter.
The register is read only.
NOTE:
Both error counters must only be read when in SLEEP or SOFT_RESET
mode.
18.13.13 msCAN12 Identifier Acceptance Registers (CIDAR0–7)
On reception each message is written into the background receive
buffer. The CPU is only signalled to read the message however, if it
passes the criteria in the identifier acceptance and identifier mask
registers (accepted); otherwise, the message will be overwritten by the
next message (dropped).
The acceptance registers of the msCAN12 are applied on the IDR0 to
IDR3 registers of incoming messages in a bit by bit manner.
For extended identifiers all four acceptance and mask registers are
applied. For standard identifiers only the first two (CIDMR0/1 and
CIDAR0/1) are applied. In the latter case it is required to program the
three last bits (AM2 – AM0) in the mask register CIDMR1 to ‘don’t care’.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
MSCAN Controller
363
MSCAN Controller
Figure 18-14. Identifier Acceptance Registers (1st bank)
CIDAR0
$0110
CIDAR1
$0111
CIDAR2
$0112
CIDAR3
$0113
RESET
R
W
R
W
R
W
R
W
Bit 7
6
5
4
3
2
1
Bit 0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
-
-
-
-
-
-
-
-
Figure 18-15. Identifier Acceptance Registers (2nd bank)
CIDAR4
$0118
CIDAR5
$0119
CIDAR6
$011A
CIDAR7
$011B
RESET
R
W
R
W
R
W
R
W
Bit 7
6
5
4
3
2
1
Bit 0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
AC7
AC6
AC5
AC4
AC3
AC2
AC1
AC0
-
-
-
-
-
-
-
-
AC7 – AC0 — Acceptance Code Bits
AC7 – AC0 comprise a user defined sequence of bits with which the
corresponding bits of the related identifier register (IDRn) of the
receive message buffer are compared. The result of this comparison
is then masked with the corresponding identifier mask register.
NOTE:
The CIDAR0–7 registers can only be written if the SFTRES bit in
CMCR0 is set.
Technical Data
364
MC68HC912DT128A — Rev 4.0
MSCAN Controller
MOTOROLA
MSCAN Controller
Programmer’s Model of Control Registers
18.13.14 msCAN12 Identifier Mask Registers (CIDMR0–7)
The identifier mask register specifies which of the corresponding bits in
the identifier acceptance register are relevant for acceptance filtering.
Figure 18-16. Identifier Mask Registers (1st bank)
CIDMR0
$0114
CIDMR1
$0115
CIDMR2
$0116
CIDMR3
$0117
RESET
R
W
R
W
R
W
R
W
Bit 7
6
5
4
3
2
1
Bit 0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
-
-
-
-
-
-
-
-
Figure 18-17. Identifier Mask Registers (2nd bank)
CIDMR4
$011C
CIDMR5
$011D
CIDMR6
$011E
CIDMR7
$011F
RESET
R
W
R
W
R
W
R
W
Bit 7
6
5
4
3
2
1
Bit 0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
AM7
AM6
AM5
AM4
AM3
AM2
AM1
AM0
-
-
-
-
-
-
-
-
AM7 – AM0 — Acceptance Mask Bits
If a particular bit in this register is cleared this indicates that the
corresponding bit in the identifier acceptance register must be the
same as its identifier bit, before a match will be detected. The
message will be accepted if all such bits match. If a bit is set, it
indicates that the state of the corresponding bit in the identifier
acceptance register will not affect whether or not the message is
accepted.
0 = Match corresponding acceptance code register and identifier bits.
1 = Ignore corresponding acceptance code register bit.
NOTE:
The CIDMR0–7 registers can only be written if the SFTRES bit in
CMCR0 is set.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
MSCAN Controller
365
MSCAN Controller
18.13.15 msCAN12 Port CAN Control Register (PCTLCAN)
PCTLCAN R
$013D
W
RESET
Bit 7
0
6
0
5
0
4
0
3
0
2
0
0
0
0
0
0
0
1
Bit 0
PUPCAN
RDPCAN
0
0
The following bits control pins 7 through 2 of Port CAN when they are
implemented externally.
PUPCAN — Pull-Up Enable Port CAN
0 = Pull mode disabled for Port CAN.
1 = Pull mode enabled for Port CAN.
RDPCAN — Reduced Drive Port CAN
0 = Reduced drive disabled for Port CAN.
1 = Reduced drive enabled for Port CAN.
18.13.16 msCAN12 Port CAN Data Register (PORTCAN)
PORTCAN
$013E
RESET
R
W
Bit 7
6
5
4
3
2
PCAN7
PCAN6
PCAN5
PCAN4
PCAN3
PCAN2
-
-
-
1
TxCAN
Bit 0
RxCAN
-
-
Port bits 7 to 2 will read zero when configured as inputs because they
are not implemented externally.
When configured as output, port bits 7 to 2 will read the last value
written.
Reading bits 1 and 0 returns the value of the TxCan and RxCan pins,
respectively.
18.13.17 msCAN12 Port CAN Data Direction Register (DDRCAN)
DDRCAN R
$013F
W
RESET
Bit 7
6
5
4
3
2
DDCAN7
DDCAN6
DDCAN5
DDCAN4
DDCAN3
DDCAN2
0
0
0
0
0
0
1
0
Bit 0
0
0
0
DDCAN7 – DDCAN2 — This bits served as memory locations since
there are no corresponding external port pins.
Technical Data
366
MC68HC912DT128A — Rev 4.0
MSCAN Controller
MOTOROLA
Technical Data — MC68HC912DT128A
Section 19. Analog-to-Digital Converter
19.1 Contents
19.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 367
19.3
Modes of Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369
19.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .370
19.5
ATD Operational Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . .372
19.6
ATD Operation In Different MCU Modes . . . . . . . . . . . . . . . . 373
19.7
General Purpose Digital Input Port Operation . . . . . . . . . . . .375
19.8
Application Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . .376
19.9
ATD Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
19.2 Introduction
The MC68HC912DT128A has two identical ATD modules identified as
ATD0 and ATD1. Except for the VDDA and VSSA Analog supply voltage,
all pins are duplicated and indexed with ‘0’ or ‘1’ in the following
description. An ‘x’ indicates either ‘0’ or ‘1’.
The ATD module is an 8-channel, 10-bit or 8-bit, multiplexed-input,
successive-approximation analog-to-digital converter. It does not
require external sample and hold circuits because of the type of charge
redistribution technique used. The ATD converter timing can be
synchronized to the system PCLK. The ATD module consists of a 16word (32-byte) memory-mapped control register block used for control,
testing and configuration.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Analog-to-Digital Converter
367
Analog-to-Digital Converter
19.2.1 Features
•
8/10 Bit Resolution
•
10 µs, 10-Bit Single Conversion Time
•
Sample and Transfer Buffer Amplifier
•
Programmable Sample Time
•
Left/Right Justified Result Data
•
Conversion Completion Interrupt
•
Analog Input Multiplexer for 8 Analog Input Channels
•
Analog/Digital Input Pin Multiplexing
•
1, 4, 8 Conversion Sequence Lengths
•
Continuous Conversion Mode
•
Multiple Channel Scans
VRHx
RC DAC ARRAY
AND COMPARATOR
VRLx
REFERENCE
MODE AND TIMING CONTROLS
VDDA
SUPPLY
VSSA
SAR
ATD 0
ANALOG MUX
AND
SAMPLE BUFFER AMP
ATD 1
ATD 2
ATD 3
ATD 4
ANx7/PADx7
ANx6/PADx6
ANx5/PADx5
ANx4/PADx4
ANx3/PADx3
ANx2/PADx2
ANx1/PADx1
ANx0/PADx0
PORT AD
DATA INPUT REGISTER
ATD 5
ATD 6
ATD 7
CLOCK
SELECT/PRESCALE
INTERNAL BUS
HC12 ATD BLOCK
Figure 19-1. Analog-to-Digital Converter Block Diagram
Technical Data
368
MC68HC912DT128A — Rev 4.0
Analog-to-Digital Converter
MOTOROLA
Analog-to-Digital Converter
Modes of Operation
19.3 Modes of Operation
Analog to digital conversions are performed in a variety of different
programmable sequences referred to as conversion modes. Each
conversion mode is defined by:
•
How many A/D conversions (one, four or eight) are performed in
a sequence
•
Which analog input channels are examined during a sequence
•
The sample time length
•
Whether sequences are performed continuously or not
•
Result register assignments
The modes are defined by the settings of three control bits (in ATDCTL5)
•
MULT controls whether the sequence examines a single analog
input channel or scans a number of different channels
•
SCAN determines if sequences are performed continuously
•
SC determines if we are performing a special conversion i.e.
converting VRL, VRH, (VRL+VRH)/2 (usually used for test purposes).
and three control values
•
CC/CB/CA (in ATDCTL5) define the input channel(s) to be
examined
•
S8C/S1C (in ATDCTL3/5) define the number of conversions in a
sequence
•
SMP0/SMP1 (in ATDCTL4) define the length of the sample time.
Sequences are initiated or halted by writing to control registers
ATDCTL4 and ATDCTL5.
For the continuous sequence modes, conversions will not stop until
•
Another non-continuous conversion sequence is initiated and
finishes
•
The ATD is powered down (ADPU control bit)
•
The ATD is reset
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•
WAIT is executed (if the ASWAI bit is activated)
•
STOP is executed.
The MCU can discover when result data is available in the result
registers with an interrupt on sequence complete or by polling the
conversion complete flags
NOTE:
•
The SCF bit is set after the completion of each sequence.
•
The CCF bit associated with each result register is set when that
register is loaded with result data.
ATD conversion modes should not be confused with MCU operating
modes such as STOP, WAIT, IDLE, RUN, DEBUG, and SPECIAL (test)
modes or with module defined operating modes such as power down,
fast flag clear, 8-bit resolution, 10-bit resolution, interrupt enable, clock
prescaler setting, and freeze modes; and finally do not confuse with
module result data formats such as right justify mode and left justify
mode.
19.4 Functional Description
19.4.1 Analog Input Multiplexer
The analog input multiplexer selects one of the 8 external analog input
channels to generate an analog sample. The input analog signals are
unipolar and must fall within the potential range of VSSA to VDDA
(analog electronics supply potentials).
19.4.2 Sample Buffer Amplifier
A sample amplifier is used to buffer the input analog signal so that a
storage node can be quickly charged to the sample potential.
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Functional Description
19.4.3 Sample and Hold Stage
A Sample and Hold (S/H) stage accepts the analog signal from the input
multiplexer and stores it as a capacitor charge on a storage node in the
module. The sample process uses a three stage approach:
1. The input signal is sampled onto a sample capacitor (for 2 module
clocks).
2. The sample amplifier quickly charges the storage node with a
copy of the sample capacitor potential (for 4 module clocks).
3. The input signal is connected directly to the storage node to
complete the sample for high accuracy (for 2, 4, 8 or 16 module
clocks). Longer sample times allow accurate measurement of
higher impedance sources.
This charge redistribution method eliminates the need for external
sample-and-hold circuitry.
19.4.4 Analog-to-Digital Converter Submodule
The Analog-to-Digital (A/D) Machine uses a successive approximation
A/D architecture to perform analog to digital conversions. The resolution
of the A/D converter is selectable at either 8 or 10 bits. It functions by
comparing the stored analog sample potential with a series of digitally
generated analog potentials (using CDAC & RDAC arrays). By following
a binary search algorithm, the converter quickly locates the
approximating potential that is nearest to the sampled potential. At the
end of the conversion process (10 module clocks for 8-bit, 12 module
clocks for 10-bit), the Successive Approximation Register (SAR)
contains the nearest approximation to the sampled signal, given the
resolution of the A/D converter, and is transferred to the appropriate
results register in the selected format.
19.4.5 Clock Prescaler Function
To keep the ATD module clock within the specified frequency range
(note: there is a minimum and maximum frequency), a clock prescaler
function is available. This function divides the system PCLK by a
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programmable constant in order to generate the ATD module’s internal
clock. One additional benefit of the prescaled clock feature is that it
allows the user further control over the sample period (note that
changing the module clock also affects conversion time).
The prescaler is based on a 5 bit modulus counter and divides the PCLK
by an integer value between 1 and 32. The final clock frequency is
obtained with a further division by 2.
The internal ATD module clock and the system PCLK have a direct
phase relationship, however the ATD module operates as if it is
effectively asynchronous to MCU bus clock cycles.
19.5 ATD Operational Modes
19.5.1 Power Down Mode
The ATD module can be powered down under program control. This is
done by turning the clock signals off to the digital electronics of the
module and eliminating the quiescent current draw of the analog
electronics.
Power down control is implemented in one of three ways.
1. Using the ADPU bit in control register ATDCTL2.
2. When STOP instruction is executed, the module will power down
for the duration of the STOP function.
3. If the module WAIT enable bit (ASWAI) is set and a WAIT
instruction is executed, the module will power down for the
duration of the WAIT function.
Note that the reset default for the ADPU bit is zero. Therefore, when this
module is reset, it is reset into the power down state.
Once the command to power down has been received, the ATD module
aborts any conversion sequence in progress and enters lower power
mode. When the module is powered up again, the bias settings in the
analog electronics must be given time to stabilize before conversions
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ATD Operation In Different MCU Modes
can be performed. Note that powering up the module does not reset the
module since the register file is not initialized.
In power down mode, the control and result registers are still accessible.
19.5.2 IDLE Mode
IDLE mode for the ATD module is defined as the state where the ATD
module is powered up and ready to perform an A/D conversion, but not
actually performing a conversion at the present time. Access to all
control, status, and result registers is available. The module is
consuming near maximum power.
NOTE:
When not active, the sample-and-hold and analog-to-digital submodules disable the clocks at their inputs to conserve power. The analog
electronics still draw quiescent current.
19.5.3 RUN Mode
RUN mode for the ATD module is defined as the state where the ATD
module is powered up and currently performing an A/D conversion.
Complete assess to all control, status and result registers is available.
The module is consuming maximum power.
19.6 ATD Operation In Different MCU Modes
19.6.1 STOP Mode
Asserting Stop causes the ATD module to power down. The digital clocks
are disabled and the analog quiescent current draw is turned off; this
places the module into its power down state and is equivalent to clearing
the ADPU control bit in ATDCTL2.
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19.6.2 WAIT Mode
If the ASWAI control bit in ATDCTL2 is set, then the ATD responds to
WAIT mode. If the ASWAI control bit is clear, then the ATD ignores the
WAIT signal. The ATD response to the wait mode is to power down the
module. In this mode, the MCU does not have access to the control,
status or result registers.
19.6.3 Background Debug (ATD FREEZE) Mode
When debugging an application, it is useful to have the ATD pause when
a breakpoint is encountered. To accommodate this, there are two
FREEZE bits in the ATDCTL3 register used to select one of three
responses:
1. The ATD module may ignore the freeze request.
2. It may respond to the freeze request by finishing the current
conversion and ‘freezing’ before starting the next sample period.
3. It may respond by immediately ‘freezing’.
Control and timing logic is static allowing the register contents and timing
position to be remembered indefinitely. The analog electronics remains
powered up; however, internal leakage may compromise the accuracy
of a frozen conversion depending on the length of the freeze period.
When the BDM signal is negated clock activity resumes.
Access to the ATD register file is possible during the ‘frozen’ period.
19.6.4 Module Reset
The ATD module is reset on two different events.
1. In the case of a system reset.
2. If the RST bit in the ATDTEST register is activated.
The single difference between the two events is that the RST bit event
does not reset the ADPU bit to its reset state value - i.e. the module is
not reset into a powered down state and will be returned to an idle state.
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General Purpose Digital Input Port Operation
The ATD module reset function places the module back into an
initialized state. If the module is performing a conversion sequence, both
the current conversion and the sequence are terminated. The
conversion complete flags are cleared and any pending interrupts are
cancelled. Note that the control, test, and status registers are initialized
on reset; the initialized register state is defined in the register description
section of this specification.
Note that when the module powers up via a WAIT signal that the ATD is
not reset; ATD operation proceeds as it was prior to entering the wait.
Freezing the module does not cause it to be reset. If a freeze mode is
entered and defines that the current conversion be terminated, then this
is done and the module will be idle after exiting the freeze state, but the
module is not initialized.
Powering the module up (using the ADPU bit) does not cause the
module to reset since the register file is not initialized. Finally, writing to
control register ATDCTL4/5 does not cause the module to be reset; the
current conversion and sequence will be terminated and new ones
started; the conversion complete flags and pending interrupts will be
cleared. This is a restart operation rather than a reset operation because
the register file is not reinitialized.
19.7 General Purpose Digital Input Port Operation
There is one digital, 8-bit, input-only port associated with the ATD
module. It is accessed through the 8-bit Port Data Register (PORTADx).
Since the port pins are used only as inputs, in normal operating modes,
no data direction register is available for this port.
The input channel pins can be used to read analog and digital data. As
analog inputs, they are multiplexed and sampled to supply signals to the
A/D converter. As digital inputs, they supply input data buffers that can
be accessed through the digital port registers. Analog signals present on
the input pins at the digital sampling time that don’t meet the VIL or VIH
specification will return unknown digital values.
A read of PORTADx may affect the accuracy of an in progress sample
period but will not affect an in progress A/D conversion.
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19.8 Application Considerations
Note that the A/D converter’s accuracy is limited by the accuracy of the
reference potentials. Noise on the reference potentials will result in noise
on the digital output data stream: the reference potential lines do not
reject reference noise.
The reference potential pins must have a low AC impedance path back
to the source. A large bypass capacitor (100nF or larger) will suffice in
most cases. In extreme cases, inductors and/or ferrite beads may be
necessary if high frequency noise is present. Series resistance is not
advisable since the ATD module draws current from the reference. A
potential drop across any series resistance would result in gain and
offset errors in the digital data output stream unless the reference
potential was sensed at the reference input pin and any potential drop
compensated for.
For best performance, the analog inputs should have a low AC
impedance at the input pins to shunt noise current coupled onto the input
node away from the A/D input. This can be accomplished by placing a
capacitor with good high frequency characteristics between the input pin
and VSSA. The size of this capacitor is application dependent; larger
capacitors will lower the AC impedance and be more effective at
shunting away noise current. However, the input analog signal has its
own dynamic characteristics which the A/D converter is being used to
track. These, along with the source impedance of the signal driver, must
also be considered when choosing the capacitor size to avoid rolling off
any high frequency components of interest.
If the input signal contains excessive high frequency conducted noise,
then a series resistance may be used with the capacitor to generate a
one pole, low pass anti-aliasing filter.
19.9 ATD Registers
Control and data registers for the ATD modules are described below.
Both ATDs have identical control registers mapped in two blocks of 16
bytes.
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ATD Registers
19.9.1 ATD Control Registers 0 &1 (ATDCTL0, ATDCTL1)
ATD0CTL0/ATD1CTL0 — Reserved
RESET:
$0060/$01E0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Writes to this register will abort current conversion sequence.
Read or write any time.
ATD0CTL1/ATD1CTL1 — Reserved
RESET:
$0061/$01E1
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
WRITE: Write to this register has no meaning.
READ: Special Mode only.
19.9.2 ATD Control Registers 2 & 3 (ATDCTL2, ATDCTL3)
The ATD control registers 2 & 3 are used to select the power up mode,
fast flag clear mode, wait mode, 16 channel mode, interrupt control, and
freeze control. Writes to these registers will not abort the current
conversion sequence nor start a new sequence.
ATD0CTL2/ATD1CTL2 — ATD Control Register 2
RESET:
Bit 7
ADPU
0
6
AFFC
0
5
ASWAI
0
4
DJM
0
$0062/$01E2
3
Reserved
0
2
Reserved
0
1
ASCIE
0
Bit 0
ASCIF
0
READ: any time
WRITE: any time
(except for Bit 0 – ASCIF, READ: any time, WRITE: not allowed)
ADPU — ATD Disable / Power Down
0 = Disable and power down the ATD
1 = Normal ATD functionality
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This bit provides program on/off control over the ATD module allowing
reduced MCU power consumption when the ATD is not being used.
When reset to zero, the ADPU bit aborts any conversion sequence in
progress. Because the analog electronics is turned off when powered
down, the ATD requires a recovery time period when ADPU bit is
enabled.
AFFC — ATD Fast Conversion Complete Flag Clear
0 = ATD flag clearing operates normally (read the status register
before reading the result register to clear the associated CCF
bit).
1 = Changes all ATD conversion complete flags to a fast clear
sequence. Any access to a result register (ATD0–7) will cause
the associated CCF flag to clear automatically if it was set at
the time.
Operating normally means that the status register must be read after
the conversion complete flag has been set before that flag can be
reset. After the status register read, a read to the associated result
register causes its conversion complete flag in the status register to be
cleared. The SCF flag is cleared when a new conversion sequence is
begun by writing to control register ATDCTL4/5. In applications where
the ATD module is polled to determine if an ATD conversion is
complete, this feature provides a convenient way of clearing the status
register conversion complete flag.
In applications where ATD interrupts are used to signal conversion
completion, the precondition of reading the status register can be
eliminated using fast conversion complete flag clear mode. In this
mode, any access to a result register will cause its associated
conversion complete flag in the status register to be cleared. The SCF
flag is cleared after the first (any) result register is read.
ASWAI — ATD Stop In Wait Mode
0 = ATD continues to run when the MCU is in wait mode
1 = ATD stops to save power when the MCU is in wait mode
The wait function allows the MCU to selectively halt and power down
the ATD module. If the ASWAI bit is set and the MCU, then the ATD
module immediately halts operation and powers down. When WAIT is
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ATD Registers
exited, the ATD module powers up and continues operation. The
module is not reset; the register file is not reinitialized; the conversion
sequence is not restarted.
When the module comes out of wait, it is recommended that a
stabilization delay ( tSR) is allowed before new conversions are
started.
DJM — Result Register Data Justification Mode
0 = Left justified mode
1 = Right justified mode
For 10-bit resolution, left justified mode maps a result register into
data bus bits 6 through 15; bit 15 is the MSB. In right justified mode,
the result registers maps onto data bus bits 0 through 9; bit 9 is the
MSB.
For 8-bit resolution, left justified mode maps a result into the high byte
(bits 8 though 15; bit 15 is the MSB). Right justified maps a result into
the low byte (bits 0 through 7; bit 7 is the MSB).
Table 19-1 summarizes the result data formats available and how
they are set up using the control bits.
Table 19-2 illustrates left justified output codes for an input signal
range between 0 and 5.1 Volts.
RES10
DJM
0
0
1
1
0
1
0
1
Result Data Formats
Description and Bus Bit Mapping
8-bit/left justified - bits 8-15
8-bit/right justified - bits 0-7
10-bit/left justified - bits 6-15
10-bit/right justified - bits 0-9
Table 19-1. Result Data Formats Available
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Input Signal
Vrl = 0 Volts
Vrh = 5.12 Volts
5.120 Volts
5.100
5.080
8-Bit
Codes
10-Bit
Codes
FF
FF
FE
FFC0
FF00
FE00
2.580
2.560
2.540
81
80
7F
8100
8000
7F00
0.020
0.000
01
00
0100
0000
Table 19-2. Left Justified ATD Output Codes
ASCIE — ATD Sequence Complete Interrupt Enable
0 = Disables ATD interrupt
1 = Enables ATD interrupt on Sequence Complete
The sequence complete interrupt function signals the MCU when a
conversion sequence is complete. At this time, the result registers
contain the result data generated by the conversion sequence. If this
interrupt function is disabled, then the conversion complete flags must
be polled to determine when a conversion or a conversion sequence
is complete. Note that reset clears pending interrupts.
ASCIF — ATD Sequence Complete Interrupt Flag
0 = No ATD sequence complete interrupt occurred
1 = ATD sequence complete interrupt occurred
The sequence complete interrupt flag. This flag is not cleared until the
interrupt is serviced (by reading the result data in such a way that the
conversion complete flag is cleared), a new conversion sequence is
initiated, or the module is reset. This bit is not writable in any mode.
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ATD Registers
ATD0CTL3/ATD1CTL3 — ATD Control Register 3
RESET:
Bit 7
0
0
6
0
0
5
0
0
$0063/$01E3
4
0
0
3
S1C
0
2
FIFO
0
1
FRZ1
0
Bit 0
FRZ0
0
READ: any time
WRITE: any time
S1C — Conversion Sequence Length (Least Significant Bit)
This control bit works with control bit S8C in ATDCTL5 in determining
how many conversion are performed per sequence.
When the S1C bit is set, a sequence length of 1 is defined. However,
if the S8C bit is also set, the S8C bit takes precedence. For sequence
length coding information see the description for S8C bit in ATDCTL5.
FIFO — Result Register FIFO Mode
0 = Result registers maps to the conversion sequence
1 = Result registers do not map to the conversion sequence
In normal operation, the A/D conversion results map into the result
registers based on the conversion sequence; the result of the first
conversion appears in the first result register, the second result in the
second result register, and so on. In FIFO mode the result register
counter is not reset at the beginning or ending of a conversion
sequence; conversion results are placed in consecutive result
registers between sequences. The result register counter wraps
around when it reaches the end of the result register file. The
conversion counter value in ATDSTAT0 can be used to determine
where in the result register file, the next conversion result will be
placed.
The results register counter is initialized to zero on three events: on
reset, the beginning of a normal (non-FIFO) conversion sequence,
and the end of a normal (non-FIFO) conversion sequence. Therefore,
the reset bit in register ATDTEST1 can be toggled to zero the result
register counter; any sequence allowed to complete normally will zero
the result register counter; a new sequence (non-FIFO) initiated with
a write to ATDCTL4/5 followed by a write to ATDCTL3 to set the FIFO
bit will start a FIFO sequence with the result register initialized.
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Finally, which result registers hold valid data can be tracked using the
conversion complete flags. Fast flag clear mode may or may not be
useful in a particular application to track valid data.
FRZ1, FRZ0 — Background Debug Freeze Enable
Background debug freeze function allows the ATD module to pause
when a breakpoint is encountered. Table 19-3 shows how FRZ1 and
FRZ0 determine the ATD’s response to a breakpoint. When BDM is
deasserted, the ATD module continues operating as it was before the
breakpoint occurred.
Table 19-3. ATD Response to Background Debug Enable
FRZ1
0
0
1
1
FRZ0
0
1
0
1
ATD Response
Continue conversions in active background mode
Reserved
Finish current conversion, then freeze
Freeze when BDM is active
19.9.3 ATDCTL4 ATD Control Register 4
ATD control register 4 is used to select the internal ATD clock frequency
(based on the system clock), select the length of the third phase of the
sample period, and set the resolution of the A/D conversion (i.e. 8-bits or
10-bits). All writes to this register have an immediate effect. If a
conversion is in progress, the entire conversion sequence is aborted. A
write to this register (or ATDCTL5) initiates a new conversion sequence.
ATD0CTL4/ATD1CTL4 — ATD Control Register 4
RESET:
Bit 7
RES10
0
6
SMP1
0
5
SMP0
0
4
PRS4
0
$0064/$01E4
3
PRS3
0
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PRS2
0
1
PRS1
0
Bit 0
PRS0
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ATD Registers
RES10 — A/D Resolution Select
0 = 8-bit resolution selected
1 = 10-bit resolution selected
This bit determines the resolution of the A/D converter: 8-bits or 10bits. The A/D converter has the accuracy of a 10-bit converter.
However, if low resolution is adequate, the conversion can be
speeded up by selecting 8-bit resolution.
SMP[1:0] — Sample Time Select
These two bits select the length of the third phase of the sample
period (in internal ATD clock cycles) which occurs after the buffered
sample and transfer. During this phase, the external analog signal is
connected directly to the storage node for final charging and improved
accuracy. Note that the ATD clock period is itself a function of the
prescaler value (bits PRS0–4). Table 19-4 lists the lengths available
for the third sample phase.
Table 19-4. Final Sample Time Selection
SMP1
0
0
1
1
SMP0
0
1
0
1
Final Sample Time
2 A/D clock periods
4 A/D clock periods
8 A/D clock periods
16 A/D clock periods
PRS[4:0] — ATD Clock Prescaler
The binary prescaler value (0 to 31) plus one (1 to 32) becomes the
divide-by-factor for a modulus counter used to prescale the system
PCLK frequency. The resulting scaled clock is further divided by 2
before the ATD internal clock is generated. This clock is used to drive
the S/H and A/D machines.
Note that the maximum ATD clock frequency is half of the system
clock. The default prescaler value is 00001 which results in a default
ATD clock frequency that is quarter of the system clock i.e. with 8MHz
bus the ATD module clock is 2MHz. Table 19-5 illustrates the divideby operation and the appropriate range of system clock frequencies.
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Table 19-5. Clock Prescaler Values
Prescale
Value
00000
00001
00010
00011
00100
00101
00110
00111
01xxx
1xxxx
Total Divisor
Max PCLK(1)
Min PCLK(2)
÷2
÷4
÷6
÷8
÷10
÷12
÷14
÷16
4 MHz
8 MHz
8 MHz
8 MHz
8 MHz
8 MHz
8 MHz
8 MHz
1 MHz
2 MHz
3 MHz
4 MHz
5 MHz
6 MHz
7 MHz
8 MHz
Do Not Use
1. Maximum conversion frequency is 2 MHz. Maximum PCLK divisor value will become
maximum conversion rate that can be used on this ATD module.
2. Minimum conversion frequency is 500 kHz. Minimum PCLK divisor value will become
minimum conversion rate that this ATD can perform.
19.9.4 ATDCTL5 ATD Control Register 5
ATD control register 5 determines the type of conversion sequence and
the analog input channels sampled. All writes to this register have an
immediate effect. If a conversion is in progress, the entire conversion
sequence is aborted. A write to this register (or ATDCTL4) initiates a new
conversion sequence (SCF and CCF bits are reset).
ATD0CTL5/ATD1CTL5 — ATD Control Register 5
RESET:
Bit 7
0
0
6
S8C
0
5
SCAN
0
4
MULT
0
$0065/$01E5
3
SC
0
2
CC
0
1
CB
0
Bit 0
CA
0
S8C / S1C — Conversion Sequence Length
S8C: Bit Position: 6, ATDCTL5
S1C: Bit Position: 3, ATDCTL3
The S8C/S1C bits define the length of a conversion sequence. Table
19-6 lists the coding combinations.
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ATD Registers
S8C
S1C
0
0
1
0
1
X
Number of Conversions per
Sequence
4
1
8
Table 19-6. Conversion Sequence Length Coding
The result register assignments made to a conversion sequence follow
a few simple rules. Normally, the first result is placed in the first register;
the second result is placed in the second register, and so on. Table 197 presents the result register assignments for the various conversion
lengths that are normally made. If FIFO mode is used, the result
register assignments differ. The results are placed in consecutive
registers between conversion sequences; the result register mapping
wraps around when the end of the register file is reached.
Number of Conversions per Sequence
1
4
8
Result Register Assignment
ADR0
ADR0 through ADR3
ADR0 through ADR7
Table 19-7. Result Register Assignment for Different Conversion
Sequences
SCAN — Continuous Conversion Sequence Mode
0 = Perform a conversion sequence and return to idle mode
1 = Perform conversion sequences continuously (scan mode)
The scan mode bit controls whether or not conversion sequences are
performed continuously or not. If this control bit is 0, a write to control
register 4 or 5 will initiate a conversion sequence; the conversion
sequence will be executed; the sequence complete flag (SCF) will be
set, and the module will return to idle mode. In this mode, the module
remains powered up but no conversions are performed; the module
waits for the next conversion sequence to be initiated.
If this control bit is 1, a single conversion sequence initiation will result
in a continuously executed conversion sequence. When a conversion
sequence completes, the sequence complete flag (SCF) is set and a
new sequence is immediately begun. The conversion mode
characteristics of each sequence are identical. If a new conversion
MC68HC912DT128A — Rev 4.0
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Analog-to-Digital Converter
mode is required, the existing continuous sequence must be
interrupted, the control registers modified, and a new conversion
sequence initiated.
MULT — Multi-Channel Sample Mode
0 = Sample only the specified channel
1 = Sample across many channels
When MULT is 0, the ATD sequence controller samples only from the
specified analog input channel for an entire conversion sequence.
The analog channel is selected by channel selection code (control
bits CC/CB/CA located in ATDCTL5).
When MULT is 1, the ATD sequence controller samples across
channels. The number of channels sampled is determined by the
sequence length value (S8C, S1C control bits). The first analog
channel examined is determined by channel selection code (CC, CB,
CA control bits); subsequent channels sampled in the sequence are
determined by incrementing the channel selection code.
SC — Special Channel Conversion Mode
0 = Perform A/D conversion on an analog input channel
1 = Perform special channel A/D conversion
SC determines if the ATD module performs A/D conversions on any
of the analog input channels (normal operation) or whether it performs
a conversion on one of the defined, special channels. The special
channels are normally used to test the A/D machine and include
converting the high and low reference potentials for the module. The
control bits CC/CB/CA are used to indicate which special channel is
to be converted.
Table 19-8. Special Channel Conversion Select Coding
CC
CB
CA
0
1
1
1
1
X
0
0
1
1
X
0
1
0
1
Special
Channel
reserved
VRH
VRL
(VRH + VRL)/2
reserved
Technical Data
386
Expected
Digital Result Code
–
$FF
$00
$7F
–
MC68HC912DT128A — Rev 4.0
Analog-to-Digital Converter
MOTOROLA
Analog-to-Digital Converter
ATD Registers
Table 19-8 lists the special channels. The last column in the table
denote the expected digital code that should be generated by the
special conversion for 8-bit resolution.
CC, CB, CA — Analog Input Channel Select Code
These bits select the analog input channel(s). Table 19-9 lists the
coding used to select the various analog input channels. In the case
of single channel scans (MULT=0), this selection code specifies the
channel for conversion. In the case of multi-channel scans (MULT=1),
this selection code represents the first channel to be examined in the
conversion sequence. Subsequent channels are determined by
incrementing the channel selection code; selection codes that reach
the maximum value wrap around to the minimum value.
Note that for special conversion mode, bits CC/CB/CA have a
different function. Instead of specifying the analog input channel, they
identify which special channel conversion is to take place. (See Table
19-8.) A summart of the channels converted and the associated result
locations for multiple channel scans can be found in Table 19-10.
Table 19-9. Analog Input Channel Select Coding
CC
CB
CA
0
0
0
0
1
1
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
MC68HC912DT128A — Rev 4.0
MOTOROLA
Analog Input
Channel
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
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Analog-to-Digital Converter
Table 19-10. Multichannel Mode Result Register Assignment (MULT=1)
4 channel conversion, External channels (S8C = 0, SC = 0)
CC
0
0
0
0
CB
0
0
1
1
CA
0
1
0
1
ADR0
AN0
AN1
AN2
AN3
ADR1
AN1
AN2
AN3
AN4
ADR2
AN2
AN3
AN4
AN5
ADR3
AN3
AN4
AN5
AN6
1
0
0
AN4
AN5
AN6
AN7
1
0
1
AN5
AN6
AN7
AN0
1
1
0
AN6
AN7
AN0
AN1
1
1
1
AN7
AN0
AN1
AN2
1
0
0
VRH
VRL
MID
1
0
1
VRL
MID
1
1
0
MID
1
1
1
S1C bit must be clear.
4 channel conversion, Internal sources (S8C = 0, SC = 1)
CC
0
0
0
0
CB
0
0
1
1
CA
0
1
0
1
ADR0
ADR1
VRH
ADR2
VRH
VRL
ADR3
VRH
VRL
MID
Shaded cells are reserved
MID = (VRH + VRL) / 2
S1C bit must be clear.
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ATD Registers
Table 19-10. Multichannel Mode Result Register Assignment (MULT=1) (Continued)
8 channel conversion, External channels (S8C = 1, SC = 0)
CC
0
0
0
0
CB
0
0
1
1
CA
0
1
0
1
ADR0
AN0
AN1
AN2
AN3
ADR1
AN1
AN2
AN3
AN4
ADR2
AN2
AN3
AN4
AN5
ADR3
AN3
AN4
AN5
AN6
ADR4
AN4
AN5
AN6
AN7
ADR5
AN5
AN6
AN7
AN0
ADR6
AN6
AN7
AN0
AN1
ADR7
AN7
AN0
AN1
AN2
8 channel conversion, Internal Sources (S8C = 1, SC = 1)
CC
0
0
0
0
CB
0
0
1
1
CA
0
1
0
1
ADR0
ADR1
VRH
ADR2
VRH
VRL
ADR3
VRH
VRL
MID
ADR4
VRH
VRL
MID
ADR5
VRL
MID
ADR6
MID
ADR7
1
0
0
AN4
AN5
AN6
AN7
AN0
AN1
AN2
AN3
1
0
1
AN5
AN6
AN7
AN0
AN1
AN2
AN3
AN4
1
1
0
AN6
AN7
AN0
AN1
AN2
AN3
AN4
AN5
1
1
1
AN7
AN0
AN1
AN2
AN3
AN4
AN5
AN6
1
0
0
VRH
VRL
MID
1
0
1
VRL
MID
1
1
0
MID
1
1
1
VRH
VRH
VRL
VRH
VRL
MID
Shaded cells are reserved
MID = (VRH + VRL) / 2
NOTES:
1) For compatibility with the MC68HC912DG128, CA, CB, CC bits must be ‘0’ where masked on the
MC68HC912DG128. This is shown above in bold text.
2) When MULT = 0, all four bits (SC, CC, CB, and CA) must be specified and a conversion sequence consists of four
or eight consecutive conversions of the single specified channel.
3) When S8C = 0 and S1C = 1, all four bits (SC, CC, CB, and CA) must be specified and a conversion sequence consists
of one conversion of the single specified channel.
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19.9.5 ATDSTAT A/D Status Register
The ATD Status registers contain the conversion complete flags and the
conversion sequence counter. The status registers are read-only.
ATD0STAT0/ATD1STAT0 — ATD Status Register
RESET:
Bit 7
SCF
0
6
0
0
5
0
0
$0066/$01E6
4
0
0
3
0
0
2
CC2
0
1
CC1
0
Bit 0
CC0
0
ATD0STAT1/ATD1STAT1 — ATD Status Register
RESET:
Bit 7
CCF7
0
6
CCF6
0
5
CCF5
0
4
CCF4
0
$0067/$01E7
3
CCF3
0
2
CCF2
0
1
CCF1
0
Bit 0
CCF0
0
SCF — Sequence Complete Flag
This flag is set upon completion of a conversion sequence. If
conversion sequences are continuously performed (SCAN=1), the
flag is set after each one is completed. How this flag is cleared
depends on the setting of the fast flag clear bit. When AFFC=0, SCF
is cleared when a new conversion sequence is initiated (write to
register ATDCTL4/5). When AFFC=1, SCF is cleared after reading
the first (any) result register.
CC[2:0] — Conversion Counter
This 3-bit value represents the contents of the result register counter;
the result register counter points to the result register that will receive
the result of the current conversion. If not in FIFO mode, the register
counter is initialized to zero when a new conversion sequence is
begun.
If in FIFO mode, the register counter is not initialized. The result
register count wraps around when its maximum value is reached.
CCF[7:0] — Conversion Complete Flags
A conversion complete flag is set at the end of each conversion in a
conversion sequence. The flags are associated with the conversion
position in a sequence and the result register number. Therefore,
CCF0 is set when the first conversion in a sequence is complete and
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Analog-to-Digital Converter
ATD Registers
the result is available in result register ADR0; CCF1 is set when the
second conversion in a sequence is complete and the result is
available in ADR1, and so forth.
The conversion complete flags are cleared depending on the setting
of the fast flag clear bit (AFFC in ATDCTL2). When AFFC=0, the
status register containing the conversion complete flag must be read
as a precondition before the flag can be cleared. The flag is actually
cleared during a subsequent access to the result register. This
provides a convenient method for clearing the conversion complete
flag when the user is polling the ATD module; it ensures the user is
signaled as to the availability of new data and avoids having to have
the user clear the flag explicitly.
When AFFC=1, the conversion complete flags are cleared when their
associated result registers are read; reading the status register is not
a necessary condition in order to clear them. This is the easiest
method for clearing the conversion complete flags which is useful
when the ATD module signals conversion completion with an
interrupt.
The conversion complete flags are normally read only; in special (test)
mode they can be written.
NOTE:
When ATDCTL4/5 register is written, the SCF flags and all CCFx flags
are cleared; any pending interrupt request is canceled.
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19.9.6 ATDTEST Module Test Register (ATDTEST)
The test registers implement various special (test) modes used to test
the ATD module. The reset bit in ATDTEST1 is always read/write. The
SAR (successive approximation register) can always be read but only
written in special (test) mode.
The functions implemented by the test registers are reserved for factory
test.
ATD0TESTH/ATD1TESTH — ATD Test Register
RESET:
Bit 7
SAR9
0
6
SAR8
0
5
SAR7
0
$0068/$01E8
4
SAR6
0
3
SAR5
0
2
SAR4
0
1
SAR3
0
Bit 0
SAR2
0
ATD0TESTL/ATD1TESTL — ATD Test Register
RESET:
Bit 7
SAR1
0
6
SAR0
0
5
RST
0
$0069/$01E9
4
0
0
3
0
0
2
0
0
1
0
0
Bit 0
0
0
SAR[9:0] — Successive Approximation Register
This ten bit value represents the contents of the AD machine’s
successive approximation register. This value can always be read. It
can only be written in special (test) mode. Note that ATDTEST0 acts
as a ten bit register since the entire SAR is read/written when
accessing this address.
RST — Test Mode Reset Bit
0 = No reset
1 = Reset the ATD module
When set, this bit causes the ATD module to reset itself. This sets all
registers to their reset state (note the reset state of the reset bit is
zero), the current conversion and conversion sequence are aborted,
pending interrupts are cleared, and the module is placed in an idle
mode.
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ATD Registers
Resetting to idle mode defines the only exception of the reset control
bit condition to the system reset condition. The reset control bit does
not initialize the ADPU bit to its reset condition and therefore does not
power down the module. This except allows the module to remain
active for other test operations.
19.9.7 PORTAD Port Data Register
The input data port associated with the ATD module is input-only. The
port pins are shared with the analog A/D inputs.
PORTAD0/PORTAD1 — Port AD Data Input Register
RESET:
Bit 7
PADx7
-
6
PADx6
-
5
PADx5
-
4
PADx4
-
$006F/$01EF
3
PADx3
-
2
PADx2
-
1
PADx1
-
Bit 0
PADx0
-
PADx[7:0] — Port AD Data Input Bits
Reset: These pins reflect the state of the input pins.
The ATD input ports may be used for general purpose digital input.
When the port data registers are read, they contain the digital levels
appearing on the input pins at the time of the read. Input pins with signal
potentials not meeting V IL or V IH specifications will have an
indeterminate value.
Use of any Port pin for digital input does not preclude the use of any
other Port pin for analog input.
Writes to this register have no meaning at any time.
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19.9.8 ADRx A/D Conversion Result Registers (ADR0-15)
ADRx0H — A/D Converter Result Register 0
ADRx0L — A/D Converter Result Register 0
ADRx1H — A/D Converter Result Register 1
ADRx1L — A/D Converter Result Register 1
ADRx2H — A/D Converter Result Register 2
ADRx2L — A/D Converter Result Register 2
ADRx3H — A/D Converter Result Register 3
ADRx3L — A/D Converter Result Register 3
ADRx4H — A/D Converter Result Register 4
ADRx4L — A/D Converter Result Register 4
ADRx5H — A/D Converter Result Register 5
ADRx5L — A/D Converter Result Register 5
ADRx6H — A/D Converter Result Register 6
ADRx6L — A/D Converter Result Register 6
ADRx7H — A/D Converter Result Register 7
ADRx7L — A/D Converter Result Register 7
ADRxxH
ADRxxL
RESET:
$0070/$01F0
$0071/$01F1
$0072/$01F2
$0073/$01F3
$0074/$01F4
$0075/$01F5
$0076/$01F6
$0077/$01F7
$0078/$01F8
$0079/$01F9
$007A/$01FA
$007B/$01FB
$007C/$01FC
$007D/$01FD
$007E/$01FE
$007F/$01FF
Bit 15
6
5
4
3
2
1
Bit 8
Bit 7
0
Bit 6
0
0
0
0
0
0
0
0
0
0
0
0
0
The A/D conversion results are stored in 8 result registers. These
registers are designated ADR0 through ADR7.
The result data is formatted using the DJM control bit in ATDCTL2. For
8-bit result data, the result data maps between the high (left justified) and
low (right justified) order bytes of the result register. For 10-bit result
data, the result data maps between bits 6-15 (left justified) and bits 0-9
(right justified) of the result register.
These registers are normally read-only.
Technical Data
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MOTOROLA
Technical Data — MC68HC912DT128A
Section 20. Development Support
20.1 Contents
20.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
20.3
Instruction Queue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395
20.4
Background Debug Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . .397
20.5
Breakpoints. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 412
20.6
Instruction Tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 419
20.2 Introduction
Development support involves complex interactions between
MC68HC912DT128A resources and external development systems.
The following section concerns instruction queue and queue tracking
signals, background debug mode, and instruction tagging.
20.3 Instruction Queue
The CPU12 instruction queue provides at least three bytes of program
information to the CPU when instruction execution begins. The CPU12
always completely finishes executing an instruction before beginning to
execute the next instruction. Status signals IPIPE[1:0] provide
information about data movement in the queue and indicate when the
CPU begins to execute instructions. This makes it possible to monitor
CPU activity on a cycle-by-cycle basis for debugging. Information
available on the IPIPE[1:0] pins is time multiplexed. External circuitry
can latch data movement information on rising edges of the E-clock
signal; execution start information can be latched on falling edges. Table
20-1 shows the meaning of data on the pins.
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Table 20-1. IPIPE Decoding
Data Movement — IPIPE[1:0] Captured at Rising Edge of E Clock(1)
IPIPE[1:0]
Mnemonic
Meaning
0:0
—
No Movement
0:1
LAT
Latch Data From Bus
1:0
ALD
Advance Queue and Load From Bus
1:1
ALL
Advance Queue and Load From Latch
Execution Start — IPIPE[1:0] Captured at Falling Edge of E Clock(2)
IPIPE[1:0]
Mnemonic
Meaning
0:0
—
No Start
0:1
INT
Start Interrupt Sequence
1:0
SEV
Start Even Instruction
1:1
SOD
Start Odd Instruction
1. Refers to data that was on the bus at the previous E falling edge.
2. Refers to bus cycle starting at this E falling edge.
Program information is fetched a few cycles before it is used by the CPU.
In order to monitor cycle-by-cycle CPU activity, it is necessary to
externally reconstruct what is happening in the instruction queue.
Internally the MCU only needs to buffer the data from program fetches.
For system debug it is necessary to keep the data and its associated
address in the reconstructed instruction queue. The raw signals required
for reconstruction of the queue are ADDR, DATA, R/W, ECLK, and
status signals IPIPE[1:0].
The instruction queue consists of two 16-bit queue stages and a holding
latch on the input of the first stage. To advance the queue means to
move the word in the first stage to the second stage and move the word
from either the holding latch or the data bus input buffer into the first
stage. To start even (or odd) instruction means to execute the opcode in
the high-order (or low-order) byte of the second stage of the instruction
queue.
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Background Debug Mode
20.4 Background Debug Mode
Background debug mode (BDM) is used for system development, incircuit testing, field testing, and programming. BDM is implemented in
on-chip hardware and provides a full set of debug options.
Because BDM control logic does not reside in the CPU, BDM hardware
commands can be executed while the CPU is operating normally. The
control logic generally uses CPU dead cycles to execute these
commands, but can steal cycles from the CPU when necessary. Other
BDM commands are firmware based, and require the CPU to be in active
background mode for execution. While BDM is active, the CPU executes
a firmware program located in a small on-chip ROM that is available in
the standard 64-Kbyte memory map only while BDM is active.
The BDM control logic communicates with an external host development
system serially, via the BKGD pin. This single-wire approach minimizes
the number of pins needed for development support.
20.4.1 Enabling BDM Firmware Commands
BDM is available in all operating modes, but must be made active before
firmware commands can be executed. BDM is enabled by setting the
ENBDM bit in the BDM STATUS register via the single wire interface
(using a hardware command; WRITE_BD_BYTE at $FF01). BDM must
then be activated to map BDM registers and ROM to addresses $FF00
to $FFFF and to put the MCU in active background mode.
After the firmware is enabled, BDM can be activated by the hardware
BACKGROUND command, by the BDM tagging mechanism, or by the
CPU BGND instruction. An attempt to activate BDM before firmware has
been enabled causes the MCU to resume normal instruction execution
after a brief delay.
BDM becomes active at the next instruction boundary following
execution of the BDM BACKGROUND command, but tags activate BDM
before a tagged instruction is executed.
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In special single-chip mode, background operation is enabled and active
immediately out of reset. This active case replaces the M68HC11 boot
function, and allows programming a system with blank memory.
While BDM is active, a set of BDM control registers are mapped to
addresses $FF00 to $FF06. The BDM control logic uses these registers
which can be read anytime by BDM logic, not user programs. Refer to
BDM Registers for detailed descriptions.
Some on-chip peripherals have a BDM control bit which allows
suspending the peripheral function during BDM. For example, if the timer
control is enabled, the timer counter is stopped while in BDM. Once
normal program flow is continued, the timer counter is re-enabled to
simulate real-time operations.
20.4.2 BDM Serial Interface
The BDM serial interface requires the external controller to generate a
falling edge on the BKGD pin to indicate the start of each bit time. The
external controller provides this falling edge whether data is transmitted
or received.
BKGD is a pseudo-open-drain pin that can be driven either by an
external controller or by the MCU. Data is transferred MSB first at 16
BDMCLK cycles per bit (nominal speed). The interface times out if 512
BDMCLK cycles occur between falling edges from the host. The
hardware clears the command register when a time-out occurs.
The BKGD pin can receive a high or low level or transmit a high or low
level. The following diagrams show timing for each of these cases.
Interface timing is synchronous to MCU clocks but asynchronous to the
external host. The internal clock signal is shown for reference in counting
cycles.
Figure 20-1 shows an external host transmitting a logic one or zero to the
BKGD pin of a target MC68HC912DT128A MCU. The host is
asynchronous to the target so there is a 0-to-1 cycle delay from the hostgenerated falling edge to where the target perceives the beginning of the
bit time. Ten target B cycles later, the target senses the bit level on the
BKGD pin. Typically the host actively drives the pseudo-open-drain
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Background Debug Mode
BKGD pin during host-to-target transmissions to speed up rising edges.
Since the target does not drive the BKGD pin during this period, there is
no need to treat the line as an open-drain signal during host-to-target
transmissions.
BDMCLK
(TARGET MCU)
HOST
TRANSMIT 1
HOST
TRANSMIT 0
PERCEIVED
START
OF BIT TIME
TARGET SENSES BIT
EARLIEST
START OF
NEXT BIT
10 CYCLES
SYNCHRONIZATION
UNCERTAINTY
HC12A4 BDM HOST TO TARGET TIM
Figure 20-1. BDM Host to Target Serial Bit Timing
BDMCLK
(TARGET
MCU)
HOST
DRIVE TO
BKGD PIN
HIGH-IMPEDANCE
TARGET MCU
SPEEDUP PULSE
HIGH-IMPEDANCE
PERCEIVED
START OF BIT
TIME
HIGH-IMPEDANCE
R-C RISE
BKGD PIN
10 CYCLES
10 CYCLES
HOST SAMPLES
BKGD PIN
EARLIEST
START OF
NEXT BIT
HC12A4 BDM TARGET TO HOST TIM 1
Figure 20-2. BDM Target to Host Serial Bit Timing (Logic 1)
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Development Support
Figure 20-2 shows the host receiving a logic one from the target
MC68HC912DT128A MCU. Since the host is asynchronous to the target
MCU, there is a 0-to-1 cycle delay from the host-generated falling edge
on BKGD to the perceived start of the bit time in the target MCU. The
host holds the BKGD pin low long enough for the target to recognize it
(at least two target B cycles). The host must release the low drive before
the target MCU drives a brief active-high speed-up pulse seven cycles
after the perceived start of the bit time. The host should sample the bit
level about ten cycles after it started the bit time.
BDMCLK
(TARGET
MCU)
HOST
DRIVE TO
BKGD PIN
HIGH-IMPEDANCE
SPEEDUP PULSE
TARGET MCU
DRIVE AND
SPEEDUP PULSE
PERCEIVED
START OF BIT TIME
BKGD PIN
10 CYCLES
10 CYCLES
HOST SAMPLES
BKGD PIN
EARLIEST
START OF
NEXT BIT
HC12A4 BDM TARGET TO HOST TIM 0
Figure 20-3. BDM Target to Host Serial Bit Timing (Logic 0)
Technical Data
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Background Debug Mode
Figure 20-3 shows the host receiving a logic zero from the target
MC68HC912DT128A MCU. Since the host is asynchronous to the target
MCU, there is a 0-to-1 cycle delay from the host-generated falling edge
on BKGD to the start of the bit time as perceived by the target MCU. The
host initiates the bit time but the target MC68HC912DT128A finishes it.
Since the target wants the host to receive a logic zero, it drives the
BKGD pin low for 13 BDMCLK cycles, then briefly drives it high to speed
up the rising edge. The host samples the bit level about ten cycles after
starting the bit time.
20.4.3 BDM Commands
The BDM command set consists of two types: hardware and firmware.
Hardware commands allow target system memory to be read or
written.Target system memory includes all memory that is accessible by
the CPU12 including EEPROM, on-chip I/O and control registers, and
external memory that is connected to the target HC12 MCU.Hardware
commands are implemented in hardware logic and do not require the
HC12 MCU to be in BDM mode for execution.The control logic watches
the CPU12 buses to find a free bus cycle to execute the command so the
background access does not disturb the running application programs. If
a free cycle is not found within 128 BDMCLK cycles, the CPU12 is
momentarily frozen so the control logic can steal a cycle.Commands
implemented in BDM control logic are listed in Table 20-2.
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Table 20-2. Hardware Commands(1)
Command
BACKGROUND
Opcode (Hex)
90
Data
None
READ_BD_BYTE(1)
E4
16-bit address
16-bit data out
READ_BD_WORD(1)
EC
16-bit address
16-bit data out
READ_BYTE
E0
16-bit address
16-bit data out
READ_WORD
E8
16-bit address
16-bit data out
WRITE_BD_BYTE(1)
C4
16-bit address
16-bit data in
WRITE_BD_WORD(1)
CC
16-bit address
16-bit data in
WRITE_BYTE
C0
16-bit address
16-bit data in
WRITE_WORD
C8
16-bit address
16-bit data in
Description
Enter background mode if firmware enabled.
Read from memory with BDM in map (may steal cycles
if external access) data for odd address on low byte,
data for even address on high byte.
Read from memory with BDM in map (may steal cycles
if external access). Must be aligned access.
Read from memory with BDM out of map (may steal
cycles if external access) data for odd address on low
byte, data for even address on high byte.
Read from memory with BDM out of map (may steal
cycles if external access). Must be aligned access.
Write to memory with BDM in map (may steal cycles if
external access) data for odd address on low byte,
data for even address on high byte.
Write to memory with BDM in map (may steal cycles if
external access). Must be aligned access.
Write to memory with BDM out of map (may steal cycles
if external access) data for odd address on low byte,
data for even address on high byte.
Write to memory with BDM out of map (may steal cycles
if external access). Must be aligned access.
1. Use these commands only for reading/writing to BDM locations.The BDM firmware ROM and BDM registers are not normally in the HC12 MCU memory map.Since these locations have the same addresses as some of the normal application
memory map, there needs to be a way to decide which physical locations are being accessed by the hardware BDM commands.This gives rise to needing separate memory access commands for the BDM locations as opposed to the normal
application locations.In logic, this is accomplished by momentarily enabling the BDM memory resources, just for the access
cycles of the READ_BD and WRITE_BD commands.This logic allows the debugging system to unobtrusively access the
BDM locations even if the application program is running out of the same memory area in the normal application memory
map.
The second type of BDM commands are called firmware commands
implemented in a small ROM within the HC12 MCU.The CPU must be in
background mode to execute firmware commands. The usual way to get
to background mode is by the hardware command BACKGROUND. The
BDM ROM is located at $FF20 to $FFFF while BDM is active. There are
also seven bytes of BDM registers located at $FF00 to $FF06 while BDM
is active. The CPU executes code in the BDM firmware to perform the
requested operation. The BDM firmware watches for serial commands
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Background Debug Mode
and executes them as they are received. The firmware commands are
shown in Table 20-3.
Table 20-3. BDM Firmware Commands
Command
READ_NEXT
READ_PC
READ_D
READ_X
READ_Y
READ_SP
WRITE_NEXT
WRITE_PC
WRITE_D
WRITE_X
WRITE_Y
WRITE_SP
GO
TRACE1
TAGGO
Opcode (Hex)
62
63
64
65
66
67
42
43
44
45
46
47
08
10
18
Data
16-bit data out
16-bit data out
16-bit data out
16-bit data out
16-bit data out
16-bit data out
16-bit data in
16-bit data in
16-bit data in
16-bit data in
16-bit data in
16-bit data in
None
None
None
Description
X = X + 2; Read next word pointed to by X
Read program counter
Read D accumulator
Read X index register
Read Y index register
Read stack pointer
X = X + 2; Write next word pointed to by X
Write program counter
Write D accumulator
Write X index register
Write Y index register
Write stack pointer
Go to user program
Execute one user instruction then return to BDM
Enable tagging and go to user program
Each of the hardware and firmware BDM commands start with an 8-bit
command code (opcode). Depending upon the commands, a 16-bit
address and/or a 16-bit data word is required as indicated in the tables
by the command. All the read commands output 16-bits of data despite
the byte/word implication in the command name.
The external host should wait 150 BDMCLK cycles for a non-intrusive
BDM command to execute before another command is sent. This delay
includes 128 BDMCLK cycles for the maximum delay for a free cycle.For
data read commands, the host must insert this delay between sending
the address and attempting to read the data.In the case of a write
command, the host must delay after the data portion, before sending a
new command, to be sure the write has finished.
The external host should delay about 32 target BDMCLK cycles between
a firmware read command and the data portion of these commands. This
allows the BDM firmware to execute the instructions needed to get the
requested data into the BDM SHIFTER register.
The external host should delay about 32 target BDMCLK cycles after the
data portion of firmware write commands to allow BDM firmware to
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complete the requested write operation before a new serial command
disturbs the BDM SHIFTER register.
The external host should delay about 64 target BDMCLK cycles after a
TRACE1 or GO command before starting any new serial command. This
delay is needed because the BDM SHIFTER register is used as a
temporary data holding register during the exit sequence to user code.
BDM logic retains control of the internal buses until a read or write is
completed.If an operation can be completed in a single cycle, it does not
intrude on normal CPU12 operation.However, if an operation requires
multiple cycles, CPU12 clocks are frozen until the operation is complete.
20.4.4 BDM Lockout
The access to the MCU resources by BDM may be prevented by
enabling the BDM lockout feature. When enabled, the BDM lockout
mechanism prevents the BDM from being active. In this case the BDM
ROM is disabled and does not appear in the MCU memory map.
The BDM lockout is enabled by clearing NOBDML bit of EEMCR
register. The NOBDML bit is loaded at reset from the SHADOW word of
EEPROM module. Modifying the state of the NOBDML and
corresponding EEPROM SHADOW bit is only possible in special modes.
Please refer to EEPROM Memory for NOBDML information.
20.4.4.1 Enabling the BDM lockout
Enabling the BDM lockout feature is only possible in special modes
(SMODN=0) and is accomplished by the following steps.
1. Remove the SHADOW word protection by clearing SHPROT bit in
EEPROT register.
2. Clear NOSHW bit in EEMCR register to make the SHADOW word
visible at $0FC0-$0FC1.
3. Program bit 7 of the high byte of the SHADOW word like a regular
EEPROM location at address $0FC0 (write $7F into address
$0FC0). Do not program other bits of the high byte of the
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SHADOW word (location $0FC0); otherwise some regular
EEPROM array locations will not be visible. At the next reset, the
high byte of the SHADOW word is loaded into the EEMCR
register. NOBDML bit in EEMCR will be cleared and BDM will not
be operational.
4. Protect the SHADOW word by setting SHPROT bit in EEPROT
register.
20.4.4.2 Disabling the BDM lockout
Disabling the BDM lockout is only possible in special modes
(SMODN=0) except in special single chip. Follow the same steps as for
enabling the BDM lockout, but erase the SHADOW word.
At the next reset, the high byte of SHADOW word is loaded into the
EEMCR register. NOBDML bit in EEMCR will be set and BDM becomes
operational.
NOTE:
When the BDM lockout is enabled it is not possible to run code from the
reset vector in special single chip mode.
20.4.5 BDM Registers
Seven BDM registers are mapped into the standard 64-Kbyte address
space when BDM is active. Mapping is shown in Table 20-4.
Table 20-4. BDM registers
Address
Register
$FF00
BDM Instruction Register
$FF01
BDM Status Register
$FF02 – $FF03
BDM Shift Register
$FF04 – $FF05
BDM Address Register
$FF06
BDM CCR Holding Register
The content of the INSTRUCTION register is determined by the type of
background command being executed.The STATUS register indicates
BDM operating conditions.The SHIFT register contains data being
received or transmitted via the serial interface. The ADDRESS register
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is temporary storage for BDM commands.The CCRSAV register
preserves the content of the CPU12 CCR while BDM is active.
The only registers of interest to users are the STATUS register and the
CCRSAV register.The other BDM registers are only used by the BDM
firmware to execute commands.The registers are accessed by means of
the hardware READ_BD and WRITE_BD commands, but should not be
written during BDM operation (except the CCRSAV register which could
be written to modify the CCR value).
20.4.5.1 STATUS
The STATUS register is read and written by the BDM hardware as a
result of serial data shifted in on the BKGD pin.
Read: all modes.
Write: Bits 3 through 5, and bit 7 are writable in all modes. Bit 6,
BDMACT, can only be written if bit 7 H/F in the INSTRUCTION register
is a zero. Bit 2, CLKSW, can only be written if bit 7 H/F in the
INSTRUCTION register is a one. A user would never write ones to bits
3 through 5 because these bits are only used by BDM firmware.
STATUS— BDM Status Register(1)
RESET:
RESET:
$FF01
BIT 7
ENBDM
6
BDMACT
5
ENTAG
4
SDV
3
TRACE
2
CLKSW
1
-
BIT 0
-
0
(NOTE 1)
0
1
0
0
0
0
0
0
Special Single
Chip & Periph
0
0
0
0
0
0
0
All other modes
1. ENBDM is set to 1 by the firmware in Special Single Chip mode.
ENBDM — Enable BDM (permit active background debug mode)
0 = BDM cannot be made active (hardware commands still
allowed).
1 = BDM can be made active to allow firmware commands.
BDMACT — Background Mode Active Status
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BDMACT becomes set as active BDM mode is entered so that the
BDM firmware ROM is enabled and put into the map. BDMACT is
cleared by a carefully timed store instruction in the BDM firmware as
part of the exit sequence to return to user code and remove the BDM
memory from the map. This bit has 4 clock cycles write delay.
0 = BDM is not active. BDM ROM and registers are not in map.
1 = BDM is active and waiting for serial commands. BDM ROM and
registers are in map
The user should be careful that the state of the BDMACT bit is not
unintentionally changed with the WRITE_NEXT firmware command. If it
is unintentionally changed from 1 to 0, it will cause a system runaway
because it would disable the BDM firmware ROM while the CPU12 was
executing BDM firmware. The following two commands show how
BDMACT may unintentionally get changed from 1 to 0.
WRITE_X with data $FEFE
WRITE_NEXT with data $C400
The first command writes the data $FEFE to the X index register. The
second command writes the data $C4 to the $FF00 INSTRUCTION
register and also writes the data $00 to the $FF01 STATUS register.
ENTAG — Tagging Enable
Set by the TAGGO command and cleared when BDM mode is
entered. The serial system is disabled and the tag function enabled
16 cycles after this bit is written.
0 = Tagging not enabled, or BDM active.
1 = Tagging active. BDM cannot process serial commands while
tagging is active.
SDV — Shifter Data Valid
Shows that valid data is in the serial interface shift register. Used by
the BDM firmware.
0 = No valid data. Shift operation is not complete.
1 = Valid Data. Shift operation is complete.
TRACE — Asserted by the TRACE1 command
CLKSW — BDMCLK Clock Switch
0 = BDM system operates with BCLK.
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1 = BDM system operates with ECLK.
The WRITE_BD_BYTE@FF01 command that changes CLKSW
including 150 cycles after the data portion of the command should be
timed at the old speed. Beginning with the start of the next BDM
command, the new clock can be used for timing BDM
communications.
If ECLK rate is slower than BDMCLK rate, CLKSW is ignored and
BDM system is forced to operate with ECLK.
20.4.5.2 INSTRUCTION - Hardware Instruction Decode
The INSTRUCTION register is written by the BDM hardware as a result
of serial data shifted in on the BKGD pin. It is readable and writable in
Special Peripheral mode on the parallel bus. It is discussed here for two
conditions: when a hardware command is executed and when a
firmware command is executed.
Read and write: all modes
. The hardware clears the INSTRUCTION register if 512 BDMCLK
cycles occur between falling edges from the host.
INSTRUCTION— BDM Instruction Register (hardware command explanation)
RESET:
BIT 7
H/F
0
6
DATA
0
5
R/W
0
4
BKGND
0
3
W/B
0
2
BD/U
0
$FF00
1
0
0
BIT 0
0
0
The bits in the BDM instruction register have the following meanings
when a hardware command is executed.
H/F — Hardware/Firmware Flag
0 = Firmware command
1 = Hardware command
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DATA — Data Flag - Shows that data accompanies the command.
0 = No data
1 = Data follows the command
R/W — Read/Write Flag
0 = Write
1 = Read
BKGND — Hardware request to enter active background mode
0 = Not a hardware background command
1 = Hardware background command (INSTRUCTION = $90)
W/B — Word/Byte Transfer Flag
0 = Byte transfer
1 = Word transfer
BD/U — BDM Map/User Map Flag
Indicates whether BDM registers and ROM are mapped to addresses
$FF00 to $FFFF in the standard 64-Kbyte address space. Used only
by hardware read/write commands.
0 = BDM resources not in map
1 = BDM ROM and registers in map
INSTRUCTION — BDM Instruction Register (firmware command bit explanation)
Bit 7
H/F
6
DATA
5
R/W
4
3
TTAGO
2
1
REGN
$FF00
Bit 0
The bits in the BDM instruction register have the following meanings
when a firmware command is executed.
H/F — Hardware/Firmware Flag
0 = Firmware command
1 = Hardware command
DATA — Data Flag – Shows that data accompanies the command.
0 = No data
1 = Data follows the command
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R/W — Read/Write Flag
0 = Write
1 = Read
TTAGO — Trace, Tag, Go Field
Table 20-5. TTAGO Decoding
TTAGO Value
Instruction
00
—
01
GO
10
TRACE1
11
TAGGO
REGN — Register/Next Field
Indicates which register is being affected by a command. In the case of
a READ_NEXT or WRITE_NEXT command, index register X is preincriminated by 2 and the word pointed to by X is then read or written.
Table 20-6. REGN Decoding
REGN Value
Instruction
000
—
001
—
010
READ/WRITE NEXT
011
PC
100
D
101
X
110
Y
111
SP
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20.4.5.3 SHIFTER
This 16-bit shift register contains data being received or transmitted via
the serial interface. It is also used by the BDM firmware for temporary
storage.
Read: all modes (but not normally accessed by users)
Write: all modes (but not normally accessed by users)
SHIFTER — BDM Shift Register – High Byte
RESET:
$FF02
BIT 15
S15
14
S14
13
S13
12
S12
11
S11
10
S10
9
S9
BIT 8
S8
X
X
X
X
X
X
X
X
SHIFTER — BDM Shift Register – Low Byte
RESET:
$FF03
BIT 7
S7
6
S6
5
S5
4
S4
3
S3
2
S2
1
S1
BIT 0
S0
X
X
X
X
X
X
X
X
20.4.5.4 ADDRESS
This 16-bit address register is temporary storage for BDM hardware and
firmware commands.
Read: all modes (but not normally accessed by users)
Write: only by BDM hardware (state machine)
ADDRESS — BDM Address Register – High Byte
RESET:
$FF04
BIT 15
A15
14
A14
13
A13
12
A12
11
A11
10
A10
9
A9
BIT 8
A8
X
X
X
X
X
X
X
X
ADDRESS — BDM Address Register – High Byte
RESET:
$FF05
BIT 7
A7
6
A6
5
A5
4
A4
3
A3
2
A2
1
A1
BIT 0
A0
X
X
X
X
X
X
X
X
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20.4.5.5 CCRSAV
The CCRSAV register is used to save the CCR of the users program
when entering BDM. It is also used for temporary storage in the BDM
firmware.
Read and write: all modes
CCRSAV— BDM CCR Holding Register
$FF06
BIT 7
CCR7
6
CCR6
5
CCR5
4
CCR4
3
CCR3
2
CCR2
1
CCR1
BIT 0
CCR0
X
X
X
X
X
X
X
X
RESET:
NOTE 1 (1)
1. Initialized to equal the CPU12 CCR register by the firmware.
20.5 Breakpoints
Hardware breakpoints are used to debug software on the
MC68HC912DT128A by comparing actual address and data values to
predetermined data in setup registers. A successful comparison will
place the CPU in background debug mode (BDM) or initiate a software
interrupt (SWI). Breakpoint features designed into the
MC68HC912DT128A include:
•
Mode selection for BDM or SWI generation
•
Program fetch tagging for cycle of execution breakpoint
•
Second address compare in dual address modes
•
Range compare by disable of low byte address
•
Data compare in full feature mode for non-tagged breakpoint
•
Byte masking for high/low byte data compares
•
R/W compare for non-tagged compares
•
Tag inhibit on BDM TRACE
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Breakpoints
20.5.1 Breakpoint Modes
Three modes of operation determine the type of breakpoint in effect.
•
Dual address-only breakpoints, each of which will cause a
software interrupt (SWI)
•
Single full-feature breakpoint which will cause the part to enter
background debug mode (BDM)
•
Dual address-only breakpoints, each of which will cause the part
to enter BDM
Breakpoints will not occur when BDM is active.
20.5.1.1 SWI Dual Address Mode
In this mode, dual address-only breakpoints can be set, each of which
cause a software interrupt. This is the only breakpoint mode which can
force the CPU to execute a SWI. Program fetch tagging is the default in
this mode; data breakpoints are not possible. In the dual mode each
address breakpoint is affected by the BKPM bit and the BKALE bit. The
BKxRW and BKxRWE bits are ignored. In dual address mode the
BKDBE becomes an enable for the second address breakpoint. The
BKSZ8 bit will have no effect when in a dual address mode.
20.5.1.2 BDM Full Breakpoint Mode
A single full feature breakpoint which causes the part to enter
background debug mode. BDM mode may be entered by a breakpoint
only if an internal signal from the BDM indicates background debug
mode is enabled.
•
Breakpoints are not allowed if the BDM mode is already active.
Active mode means the CPU is executing out of the BDM ROM.
•
BDM should not be entered from a breakpoint unless the ENABLE
bit is set in the BDM. This is important because even if the
ENABLE bit in the BDM is negated the CPU actually does execute
the BDM ROM code. It checks the ENABLE and returns if not set.
If the BDM is not serviced by the monitor then the breakpoint
would be re-asserted when the BDM returns to normal CPU flow.
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•
There is no hardware to enforce restriction of breakpoint operation
if the BDM is not enabled.
20.5.1.3 BDM Dual Address Mode
Dual address-only breakpoints, each of which cause the part to enter
background debug mode. In the dual mode each address breakpoint is
affected, consistent across modes, by the BKPM bit, the BKALE bit, and
the BKxRW and BKxRWE bits. In dual address mode the BKDBE
becomes an enable for the second address breakpoint. The BKSZ8 bit
will have no effect when in a dual address mode. BDM mode may be
entered by a breakpoint only if an internal signal from the BDM indicates
background debug mode is enabled.
•
BKDBE will be used as an enable for the second address only
breakpoint.
•
Breakpoints are not allowed if the BDM mode is already active.
Active mode means the CPU is executing out of the BDM ROM.
•
BDM should not be entered from a breakpoint unless the ENABLE
bit is set in the BDM. This is important because even if the
ENABLE bit in the BDM is negated the CPU actually does execute
the BDM ROM code. It checks the ENABLE and returns if not set.
If the BDM is not serviced by the monitor then the breakpoint
would be re-asserted when the BDM returns to normal CPU flow.
There is no hardware to enforce restriction of breakpoint operation
if the BDM is not enabled.
20.5.2 Breakpoint Registers
Breakpoint operation consists of comparing data in the breakpoint
address registers (BRKAH/BRKAL) to the address bus and comparing
data in the breakpoint data registers (BRKDH/BRKDL) to the data bus.
The breakpoint data registers can also be compared to the address bus.
The scope of comparison can be expanded by ignoring the least
significant byte of address or data matches.
The scope of comparison can be limited to program data only by setting
the BKPM bit in breakpoint control register 0.
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Breakpoints
To trace program flow, setting the BKPM bit causes address comparison
of program data only. Control bits are also available that allow checking
read/write matches.
BRKCT0 — Breakpoint Control Register 0
RESET:
$0020
Bit 7
6
5
4
3
2
1
Bit 0
BKEN1
BKEN0
BKPM
0
BK1ALE
BK0ALE
0
0
0
0
0
0
0
0
0
0
Read and write anytime.
This register is used to control the breakpoint logic.
BKEN1, BKEN0 — Breakpoint Mode Enable
Table 20-7. Breakpoint Mode Control
BKEN1 BKEN0
Mode Selected
0
0
Breakpoints Off
0
1
SWI — Dual Address Mode
1
0
BDM — Full Breakpoint Mode
1
1
BDM — Dual Address Mode
BRKAH/L Usage BRKDH/L Usage
—
—
Address Match
Address Match
Address Match
Data Match
Address Match
Address Match
R/W
—
No
Yes
Yes
Range
—
Yes
Yes
Yes
BKPM — Break on Program Addresses
This bit controls whether the breakpoint will cause a break on a match
(next instruction boundary) or on a match that will be an executable
opcode. Data and non-executed opcodes cannot cause a break if this
bit is set. This bit has no meaning in SWI dual address mode. The
SWI mode only performs program breakpoints.
0 = On match, break at the next instruction boundary
1 = On match, break if the match is an instruction that will be
executed. This uses tagging as its breakpoint mechanism.
BK1ALE — Breakpoint 1 Range Control
Only valid in dual address mode.
0 = BRKDL will not be used to compare to the address bus.
1 = BRKDL will be used to compare to the address bus.
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BK0ALE — Breakpoint 0 Range Control
Valid in all modes.
0 = BRKAL will not be used to compare to the address bus.
1 = BRKAL will be used to compare to the address bus.
Table 20-8. Breakpoint Address Range Control
BK1ALE BK0ALE
Address Range Selected
–
0
Upper 8-bit address only for full mode or dual mode BKP0
–
1
Full 16-bit address for full mode or dual mode BKP0
0
–
Upper 8-bit address only for dual mode BKP1
1
–
Full 16-bit address for dual mode BKP1
BRKCT1 — Breakpoint Control Register 1
$0021
Bit 7
6
5
4
3
2
1
Bit 0
0
BKDBE
BKMBH
BKMBL
BK1RWE
BK1RW
BK0RWE
BK0RW
0
0
0
0
0
0
0
0
RESET:
This register is read/write in all modes.
BKDBE — Enable Data Bus
Enables comparing of address or data bus values using the BRKDH/L
registers.
0 = The BRKDH/L registers are not used in any comparison
1 = The BRKDH/L registers are used to compare address or data
(depending upon the mode selections BKEN1,0)
BKMBH — Breakpoint Mask High
Disables the comparing of the high byte of data when in full breakpoint
mode. Used in conjunction with the BKDBE bit (which should be set)
0 = High byte of data bus (bits 15:8) are compared to BRKDH
1 = High byte is not used to in comparisons
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BKMBL — Breakpoint Mask Low
Disables the matching of the low byte of data when in full breakpoint
mode. Used in conjunction with the BKDBE bit (which should be set)
0 = Low byte of data bus (bits 7:0) are compared to BRKDL
1 = Low byte is not used to in comparisons.
BK1RWE — R/W Compare Enable
Enables the comparison of the R/W signal to further specify what
causes a match. This bit is NOT useful in program breakpoints or in
full breakpoint mode. This bit is used in conjunction with a second
address in dual address mode when BKDBE=1.
0 = R/W is not used in comparisons
1 = R/W is used in comparisons
BK1RW — R/W Compare Value
When BK1RWE = 1, this bit determines the type of bus cycle to
match.
0 = A write cycle will be matched
1 = A read cycle will be matched
BK0RWE — R/W Compare Enable
Enables the comparison of the R/W signal to further specify what
causes a match. This bit is not useful in program breakpoints.
0 = R/W is not used in the comparisons
1 = R/W is used in comparisons
BK0RW — R/W Compare Value
When BK0RWE = 1, this bit determines the type of bus cycle to match
on.
0 = Write cycle will be matched
1 = Read cycle will be matched
MC68HC912DT128A — Rev 4.0
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Technical Data
Development Support
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Development Support
Table 20-9. Breakpoint Read/Write Control
BK1RWE
BK1RW
BK0RWE
BK0RW
–
–
0
X
–
–
0
1
1
–
–
X
0
1
1
1
–
–
–
0
1
–
–
–
Read/Write Selected
R/W is don’t care for full mode or dual mode
BKP0
R/W is write for full mode or dual mode BKP0
R/W is read for full mode or dual mode BKP0
R/W is don’t care for dual mode BKP1
R/W is write for dual mode BKP1
R/W is read for dual mode BKP1
BRKAH — Breakpoint Address Register, High Byte
$0022
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
RESET:
These bits are used to compare against the most significant byte of the
address bus.
BRKAL — Breakpoint Address Register, Low Byte
$0023
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
RESET:
These bits are used to compare against the least significant byte of the
address bus. These bits may be excluded from being used in the match
if BK0ALE = 0.
BRKDH — Breakpoint Data Register, High Byte
$0024
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
RESET:
These bits are compared to the most significant byte of the data bus or
the most significant byte of the address bus in dual address modes.
BKEN[1:0], BKDBE, and BKMBH control how this byte will be used in the
breakpoint comparison.
Technical Data
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MC68HC912DT128A — Rev 4.0
Development Support
MOTOROLA
Development Support
BRKDL — Breakpoint Data Register, Low Byte
$0025
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
RESET:
These bits are compared to the least significant byte of the data bus or
the least significant byte of the address bus in dual address modes.
BKEN[1:0], BKDBE, BK1ALE, and BKMBL control how this byte will be
used in the breakpoint comparison.
20.6 Instruction Tagging
The instruction queue and cycle-by-cycle CPU activity can be
reconstructed in real time or from trace history that was captured by a
logic analyzer. However, the reconstructed queue cannot be used to
stop the CPU at a specific instruction, because execution has already
begun by the time an operation is visible outside the MCU. A separate
instruction tagging mechanism is provided for this purpose.
Executing the BDM TAGGO command configures two MCU pins for
tagging. The TAGLO signal shares a pin with the LSTRB signal, and the
TAGHI signal shares a pin with the BKGD signal. Tagging information is
latched on the falling edge of ECLK.
Table 20-10 shows the functions of the two tagging pins. The pins
operate independently - the state of one pin does not affect the function
of the other. The presence of logic level zero on either pin at the fall of
ECLK performs the indicated function. Tagging is allowed in all modes.
Tagging is disabled when BDM becomes active and BDM serial
commands are not processed while tagging is active.
Technical Data
419
MC68HC912DT128A — Rev 4.0
Development Support
MOTOROLA
Development Support
Table 20-10. Tag Pin Function
TAGHI
TAGLO
Tag
1
1
no tag
1
0
low byte
0
1
high byte
0
0
both bytes
The tag follows program information as it advances through the queue.
When a tagged instruction reaches the head of the queue, the CPU
enters active background debugging mode rather than execute the
instruction.
Technical Data
420
MC68HC912DT128A — Rev 4.0
Development Support
MOTOROLA
Technical Data — MC68HC912DT128A
Section 21. Electrical Specifications
21.1 Contents
21.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 421
21.3
Tables of Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 422
21.2 Introduction
The MC68HC912DT128A microcontroller unit (MCU) is a16-bit device
composed of standard on-chip peripherals including a 16-bit central
processing unit (CPU12), 128-Kbyte flash EEPROM, 8K byte RAM, 2K
byte EEPROM, two asynchronous serial communications interfaces
(SCI), a serial peripheral interface (SPI), an 8-channel, 16-bit timer,
two16-bit pulse accumulators and 16-bit down counter (ECT), two 10-bit
analog-to-digital converter (ADC), a four-channel pulse-width modulator
(PWM), an IIC interface module, and three MSCAN modules. The chip
is the first 16-bit microcontroller to include both byte-erasable EEPROM
and flash EEPROM on the same device. System resource mapping,
clock generation, interrupt control and bus interfacing are managed by
the Lite integration module (LIM). The MC68HC912DT128A has full 16bit data paths throughout, however, the multiplexed external bus can
operate in an 8-bit narrow mode so single 8-bit wide memory can be
interfaced for lower cost systems.
MC68HC912DT128A — Rev 4.0
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Electrical Specifications
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Electrical Specifications
21.3 Tables of Data
Table 21-1. Maximum Ratings(1)
Rating
Symbol
Value
Unit
VDD, VDDA,
VDDX
−0.3 to +6.5
V
Input voltage
VIN
−0.3 to +6.5
V
Operating temperature range
TA(2)
TL to TH
−40 to +85
−40 to +105
−40 to +125
°C
Storage temperature range
Tstg
−55 to +150
°C
IIN
±25
mA
VDD−VDDX
6.5
V
Supply voltage
Current drain per pin(3)
Excluding VDD and VSS
VDD differential voltage
1. Permanent damage can occur if maximum ratings are exceeded. Exposures to voltages or currents in excess of recommended values affects device reliability. Device modules may not operate normally while being exposed to electrical extremes.
2. Please refer to Table 1-1 to identify part numbers associated with each temperature range.
3. One pin at a time, observing maximum power dissipation limits. Internal circuitry protects the inputs against damage caused
by high static voltages or electric fields; however, normal precautions are necessary to avoid application of any voltage higher than maximum-rated voltages to this high-impedance circuit. Extended operation at the maximum ratings can adversely
affect device reliability. Tying unused inputs to an appropriate logic voltage level (either GND or VDD) enhances reliability
of operation.
NOTE:
Four pins (VRL0, VRH0, VRL1, and VRH1) show ESD susceptibility
below the Motorola standards. Care should be exercised in handling
these pins.
Technical Data
422
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Electrical Specifications
Tables of Data
Table 21-2. Thermal Characteristics
Characteristic
Symbol
Value
Unit
Average junction temperature
TJ
TA + (PD × ΘJA)
°C
Ambient temperature
TA
User-determined
°C
ΘJA
40
°C/W
Package thermal resistance (junction-to-ambient)
112-pin quad flat pack (QFP)
PINT + PI/O or
(1)
PD
K
-------------------------T J + 273°C
W
Device internal power dissipation
PINT
IDD × VDD
W
I/O pin power dissipation(2)
PI/O
User-determined
W
K
PD × (TA + 273°C) + ΘJA × PD2
W · °C
Total power dissipation
A constant(3)
1. This is an approximate value, neglecting PI/O.
2. For most applications PI/O « PINT and can be neglected.
3. K is a constant pertaining to the device. Solve for K with a known TA and a measured PD (at equilibrium). Use this value of
K to solve for PD and TJ iteratively for any value of TA.
MC68HC912DT128A — Rev 4.0
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Technical Data
Electrical Specifications
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Electrical Specifications
Table 21-3. DC Electrical Characteristics
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
Characteristic
Symbol
Min
Max
Unit
Input high voltage, all inputs
VIH
0.7 × VDD
VDD + 0.3
V
Input low voltage, all inputs
VIL
VSS−0.3
0.2 × VDD
V
VOH
VDD − 0.2
VDD − 0.8
—
—
V
V
VDD − 0.2
VDD − 0.8
—
—
V
V
—
—
VSS+0.2
VSS+0.4
V
V
—
—
VSS+0.2
VSS+0.4
V
V
Output high voltage, all I/O and output pins except XTAL
Normal drive strength
IOH = −10.0 µA
IOH = −0.8 mA
Reduced drive strength
IOH = −4.0 µA
IOH = −0.3 mA
Output low voltage, all I/O and output pins except XTAL
Normal drive strength
IOL = 10.0 µA
IOL = 1.6 mA
Reduced drive strength
IOL = 3.6 µA
IOL = 0.6 mA
VOL
Input leakage current(1)
Vin = VDD or VSSAll input only pins except IRQ, ATD(2)
and VFP
Vin = VDD or VSSIRQ
Iin
—
—
±2.5
±10
µA
µA
Three-state leakage, I/O ports, BKGD, and RESET
IOZ
—
±2.5
µA
Input capacitance
All input pins and ATD pins (non-sampling)
ATD pins (sampling)
All I/O pins
Cin
—
—
—
10
15
20
pF
pF
pF
Output load capacitance
All outputs except PS[7:4]
PS[7:4] when configured as SPI
CL
—
—
90
200
pF
pF
Programmable active pull-up/pull-down current
IRQ, XIRQ, DBE, LSTRB, R/W. ports A, B, H, J, K, P, S, T
MODA, MODB active pull down during reset
BKGD passive pull up
IAPU
50
50
50
500
500
500
µA
µA
µA
RAM standby voltage, power down
VSB
1.5
—
V
RAM standby current
ISB
—
50
µA
1. Specification is for parts in the -40 to +85°C range. Higher temperature ranges will result in increased
current leakage.
2. See Table 21-5.
Technical Data
424
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Electrical Specifications
Tables of Data
Table 21-4. Supply Current
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
Frequency of Operation (E-clock)
Characteristic
Symbol
Maximum total supply current
RUN:
Single-chip mode
Expanded mode
4 MHz(1)
8 MHz
20
30
30
50
55
90
mA
mA
3
4
5
6.5
10
15
mA
mA
150
150
150
µA
IDD
WAIT: (All peripheral functions shut down)
Single-chip mode
Expanded mode
Unit
2 MHz(1)
WIDD
SIDD
STOP:
Single-chip mode, no clocks
1. Devices only tested at 8MHz (worst case conditions)
Table 21-5. ATD DC Electrical Characteristics
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, ATD Clock = 2 MHz, unless otherwise noted
Characteristic
Symbol
Min
Max
Unit
Analog supply voltage
VDDA
4.5
5.5
V
Analog supply currentNormal operation
STOP
IDDA
1.0
10
mA
µA
Reference voltage, low
VRL
VSSA
VDDA/2
V
Reference voltage, high
VRH
VDDA/2
VDDA
V
VRH−VRL
4.5
5.5
V
VINDC
VSSA
VDDA
V
VREF differential reference voltage(1)
Input voltage(2)
Input current, off channel(3)
IOFF
100
nA
Reference supply current
IREF
250
µA
Input capacitanceNot Sampling
Sampling
CINN
CINS
10
15
pF
pF
1. Accuracy is guaranteed at VRH − VRL = 5.0V ±10%.
2. To obtain full-scale, full-range results, VSSA ≤ VRL ≤ VINDC ≤ VRH ≤ VDDA.
3. Maximum leakage occurs at maximum operating temperature. Current decreases by approximately one-half for each 10°C
decrease from maximum temperature.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Electrical Specifications
425
Electrical Specifications
Table 21-6. Analog Converter Characteristics (Operating)
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, ATD Clock = 2 MHz, unless otherwise noted
Characteristic
Symbol
8-bit resolution(1)
Min
Typical
1 count
8-bit absolute error,(2)2, 4, 8, and 16 ATD sample clocks
10-bit resolution(1)
20
−1
AE
5
AE
–2.5
Unit
mV
+1
1 count
10-bit absolute error(2) 2, 4, 8, and 16 ATD sample clocks
Max
count
mV
2.5
count
1. At VRH – VRL = 5.12V, one 8-bit count = 20 mV, and one 10-bit count = 5mV.
2. These values include quantization error which is inherently 1/2 count for any A/D converter.
Absolute errors only guaranteed when VRL=VSS, VRH=VDD and when external source impedence is close to zero.
Table 21-7. ATD AC Characteristics (Operating)
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, ATD Clock = 2 MHz, unless otherwise noted
Characteristic
ATD operating clock frequency
Conversion time per channel
0.5 MHz ≤ fATDCLK ≤ 2 MHz
16 ATD clocks
30 ATD clocks
Symbol
Min
Max
Unit
fATDCLK
0.5
2.0
MHz
8.0
15.0
32.0
60.0
µs
µs
10
µs
tCONV
Stop and ATD power up recovery time(1)VDDA = 5.0V
tSR
1. From the time ADPU is asserted until the time an ATD conversion can begin.
Technical Data
426
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Electrical Specifications
Tables of Data
Table 21-8. ATD Maximum Ratings
Characteristic
Symbol
Value
Units
ATD reference voltage
VRH ≤ VDDA
VRL ≥ VSSA
VRH
VRL
−0.3 to +6.5
−0.3 to +6.5
V
V
VSS differential voltage
|VSS−VSSA|
0.1
V
VDD differential voltage
VDD−VDDA
VDDA−VDD
6.5
0.3
V
V
Reference to supply differential voltage
VDDA−VRH
VRH−VDDA
VDDA−VRL
VRL−VDDA
6.5
0.3
6.5
0.3
V
VDDA−VINDC
VINDC−VDDA
6.5
0.3
V
Analog input differential voltage
Table 21-9. EEPROM Characteristics
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
Characteristic
Symbol
Min
Minimum programming clock frequency
fPROG
250K
Programming time
tPROG
10
ms
Clock recovery time, following STOP, to continue programming
tCRSTOP
tPROG+ 1
ms
Erase time
tERASE
10
ms
Write/erase endurance
Data retention
Max
Unit
hz
10,000
cycles
10(1)
years
EEPROM Programming Maximum Time to ‘AUTO’ Bit Set
—
—
500
µs
EEPROM Erasing Maximum Time to ‘AUTO’ Bit Set
—
—
10
ms
1. Based on the average life time operating temperature of 70°C.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Electrical Specifications
427
Electrical Specifications
Table 21-10. Flash EEPROM Characteristics
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
Characteristic
Symbol
Min
Max
Units
—
64
64
Bytes
Read bus clock frequency
fREAD
32K
8M
hz
Erase time
tERAS
8
—
ms
PGM/ERAS to HVEN set up time
tNVS
10
—
µs
High-voltage hold time
tNVH
5
—
µs
High-voltage hold time (erase)
tNVHL
100
—
µs
Program hold time
tPGS
5
—
µs
tFPGM
30
40
µs
Return to read time
tRCV
1
—
µs
Cumulative program hv period
tHV
—
8
ms
Row program/erase endurance
—
100
cycles
Data retention
—
10(1)
years
Bytes per row
Program time
1. Based on the average life time operating temperature of 70°C.
Table 21-11. Pulse Width Modulator Characteristics
VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
Characteristic
Symbol
Min
Max
Unit
E-clock frequency
feclk
0.004
8.0
MHz
A-clock frequency
Selectable
faclk
feclk
Hz
BCLK frequency
Selectable
fbclk
feclk
Hz
Left-aligned PWM frequency
8-bit
16-bit
flpwm
feclk/1M
feclk/256M
feclk/2
feclk/2
Hz
Hz
Left-aligned PWM resolution
rlpwm
feclk/4K
feclk
Hz
Center-aligned PWM frequency
8-bit
16-bit
fcpwm
feclk/2M
feclk/512M
feclk
feclk
Hz
Hz
Center-aligned PWM resolution
rcpwm
feclk/4K
feclk
Hz
Technical Data
428
feclk/128
feclk/128
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Electrical Specifications
Tables of Data
Table 21-12. Control Timing
Characteristic
Symbol
8.0 MHz
Unit
Min
Max
fo
0.004
8.0
MHz
E-clock period
tcyc
0.125
250
µs
External oscillator frequency
feo
0.5
16.0(1)
MHz
Processor control setup time
tPCSU = tcyc/2+ 30
tPCSU
92
—
PWRSTL
32
2
—
—
tcyc
tcyc
Mode programming setup time
tMPS
4
—
tcyc
Mode programming hold time
tMPH
20
—
ns
PWIRQ
270
—
ns
tWRS
—
4
cycles
PWTIM
270
—
ns
Frequency of operation
Reset input pulse width
To guarantee external reset vector
Minimum input time (can be preempted by internal reset)
Interrupt pulse width, IRQ edge-sensitive mode
PWIRQ = 2tcyc + 20
Wait recovery startup time
Timer input capture pulse width
ns
1. When using a resonator (quartz or ceramic), see Table 21-17 for allowable values.
NOTE:
RESET is recognized during the first clock cycle it is held low. Internal
circuitry then drives the pin low for 16 clock cycles, releases the pin, and
samples the pin level 9 cycles later to determine the source of the
interrupt.
PT[7:0]1
PWTIM
PT[7:0]2
PT71
PWPA
PT72
NOTES:
1. Rising edge sensitive input
2. Falling edge sensitive input
Figure 21-1. Timer Inputs
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Electrical Specifications
429
430
Technical Data
Electrical Specifications
FFFE
4098 tcyc
NOTE: Reset timing is subject to change.
INTERNAL
ADDRESS
MODA, MODB
RESET
ECLK
EXTAL
VDD
FFFE
FREE
1ST
PIPE
2ND
PIPE
3RD
PIPE
tPCSU
1ST
EXEC
FFFE
FFFE
tMPS
PWRSTL
FFFE
FREE
tMPH
1ST
PIPE
2ND
PIPE
3RD
PIPE
1ST
EXEC
Electrical Specifications
Figure 21-2. POR and External Reset Timing Diagram
MC68HC912DT128A — Rev 4.0
MOTOROLA
MOTOROLA
MC68HC912DT128A — Rev 4.0
Electrical Specifications
SP-6
SP-6
SP-8
SP-8
SP-9
SP-9
PWIRQ
NOTES:
1. Edge Sensitive IRQ pin (IRQE bit = 1)
2. Level sensitive IRQ pin (IRQE bit = 0)
3. tSTOPDELAY = 4098 tcyc if DLY bit = 1 or 2 tcyc if DLY = 0.
4. XIRQ with X bit in CCR = 1.
5. IRQ or (XIRQ with X bit in CCR = 0).
ADDRESS5
ADDRESS4
ECLK
IRQ
or XIRQ
IRQ1
INTERNAL
CLOCKS
tSTOPDELAY3
FREE
FREE
OPT
FETCH
1ST
EXEC
FREE
1ST
PIPE
2ND
PIPE
3RD
PIPE
1ST
EXEC
Resume program with instruction which follows the STOP instruction.
VECTOR
FREE
Electrical Specifications
Tables of Data
Figure 21-3. STOP Recovery Timing Diagram
Technical Data
431
432
Technical Data
Electrical Specifications
SP – 2
NOTE: RESET also causes recovery from WAIT.
R/W
ADDRESS
IRQ, XIRQ,
OR INTERNAL
INTERRUPTS
ECLK
SP – 6 . . . SP – 9
PC, IY, IX, B:A, , CCR
STACK REGISTERS
SP – 4
SP – 9
SP – 9 . . . SP – 9
SP – 9
tPCSU
VECTOR
ADDRESS
tWRS
FREE
1ST
PIPE
2ND
PIPE
3RD
PIPE
1ST
EXEC
Electrical Specifications
Figure 21-4. WAIT Recovery Timing Diagram
MC68HC912DT128A — Rev 4.0
MOTOROLA
MOTOROLA
MC68HC912DT128A — Rev 4.0
Electrical Specifications
VECT
DATA
NOTES:
1. Edge sensitive IRQ pin (IRQE bit = 1)
2. Level sensitive IRQ pin (IRQE bit = 0)
R/W
VECTOR
ADDR
PWIRQ
tPCSU
ADDRESS
OR INTERNAL
INTERRUPT
IRQ2, XIRQ,
IRQ
1
ECLK
PC
SP – 2
PROG
FETCH
1ST
PIPE
IY
SP – 4
IX
SP – 6
PROG
FETCH
2ND
PIPE
B:A
SP – 8
CCR
SP – 9
PROG
FETCH
3RD
PIPE
1ST
EXEC
Electrical Specifications
Tables of Data
Figure 21-5. Interrupt Timing Diagram
Technical Data
433
Electrical Specifications
Table 21-13. Peripheral Port Timing
8.0 MHz
Characteristic
Symbol
Unit
Min
Max
fo
0.004
8.0
MHz
tcyc
0.125
250
µs
Peripheral data setup time
MCU read of ports
tPDSU
81
—
ns
Peripheral data hold time
MCU read of ports
tPDH
0
—
ns
Delay time, peripheral data write
MCU write to ports except Port CAN
tPWD
—
40
ns
Delay time, peripheral data write
MCU write to Port CAN
tPWD
—
71
ns
Frequency of operation (E-clock frequency)
E-clock period
MCU READ OF PORT
ECLK
tPDSU
tPDH
PORTS
PORT RD TIM
Figure 21-6. Port Read Timing Diagram
MCU WRITE TO PORT
ECLK
tPWD
PORT A
PREVIOUS PORT DATA
NEW DATA VALID
PORT WR TIM
Figure 21-7. Port Write Timing Diagram
Technical Data
434
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Electrical Specifications
Tables of Data
Table 21-14. Multiplexed Expansion Bus Timing
VDD = 5.0 Vdc ± 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
Characteristic(1), (2), (3), (4)
Num
Delay
Frequency of operation (E-clock frequency)
Symbol
8 MHz
Unit
Min
Max
fo
0.004
8.0
MHz
250
µs
1
Cycle timetcyc = 1/fo
—
tcyc
0.125
2
Pulse width, E lowPWEL = tcyc/2 + delay
−2
PWEL
60
ns
3
Pulse width, E high(5)PWEH = tcyc/2 + delay
−2
PWEH
60
ns
5
Address delay timetAD = tcyc/4 + delay
14
tAD
7
Address valid time to ECLK risetAV = PWEL − tAD
—
tAV
15
ns
8
Multiplexed address hold timetMAH = tcyc/4 + delay
−16
tMAH
15
ns
9
Address Hold to Data Valid
—
tAHDS
5
ns
10
Data Hold to High ZtDHZ = tAD − 20
—
tDHZ
11
Read data setup time
—
tDSR
38
ns
12
Read data hold time
—
tDHR
0
ns
13
Write data delay timetDDW = tcyc/4 + delay
14
tDDW
14
Write data hold timetDHW = tcyc/4 + delay
−11
tDHW
20
ns
15
Write data setup time(5)tDSW = PWEH − tDDW
—
tDSW
15
ns
16
Read/write delay timetRWD = tcyc/4 + delay
19
tRWD
17
Read/write valid time to E risetRWV = PWEL − tRWD
—
tRWV
10
ns
18
Read/write hold timetRWH = tcyc/4 + delay
−26
tRWH
5
ns
19
Low strobe(6) delay timetLSD = tcyc/4 + delay
26
tLSD
20
Low strobe(6) valid time to E risetLSV = PWEL − tLSD
—
tLSV
3
ns
21
Low strobe(6) hold timetLSH = tcyc/4 + delay
−26
tLSH
5
ns
22
Address access time(5)tACCA = tcyc − tAD − tDSR
—
tACCA
26
ns
23
Access time from E rise(5)tACCE = PWEH − tDSR
—
tACCE
22
ns
24
DBE delay from ECLK rise(5)tDBED = tcyc/4 + delay
20
tDBED
51
ns
25
DBE valid timetDBE = PWEH − tDBED
—
tDBE
9
26
DBE hold time from ECLK fall
tDBEH
0
45
20
45
50
57
ns
ns
ns
ns
ns
ns
10
ns
1. All timings are calculated for normal port drives.
2. Crystal input is required to be within 45% to 55% duty.
3. Reduced drive must be off to meet these timings.
4. Unequalled loading of pins will affect relative timing numbers.
5. This characteristic is affected by clock stretch.
Add N × tcyc where N = 0, 1, 2, or 3, depending on the number of clock stretches.
6. Without TAG enabled.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Electrical Specifications
435
Electrical Specifications
1
2
3
ECLK
16
17
18
19
20
21
R/W
LSTRB
(W/O TAG ENABLED)
5
23
7
11
22
10
READ
12
ADDRESS
ADDRESS/DATA
MULTIPLEXED
DATA
9
8
13
WRITE
ADDRESS
15
14
DATA
24
25
26
DBE
NOTE: Measurement points shown are 20% and 70% of VDD
Figure 21-8. Multiplexed Expansion Bus Timing Diagram
Technical Data
436
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Electrical Specifications
Tables of Data
Table 21-15. SPI Timing
(VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH , 200 pF load on all SPI pins)(1)
Function
Symbol
Min
Max
Unit
Operating Frequency
Master
Slave
fop
1/256
1/256
1/2
1/2
feclk
SCK Period
Master
Slave
tsck
2
2
256
—
tcyc
tcyc
Enable Lead Time
Master
Slave
tlead
1/2
1
—
—
tsck
tcyc
Enable Lag Time
Master
Slave
tlag
1/2
1
—
—
tsck
tcyc
twsck
tcyc − 30
tcyc − 30
128 tcyc
—
ns
ns
Sequential Transfer Delay
Master
Slave
ttd
1/2
1
—
—
tsck
tcyc
Data Setup Time (Inputs)
Master
Slave
tsu
30
30
—
—
ns
ns
Data Hold Time (Inputs)
Master
Slave
thi
0
30
—
—
ns
ns
Slave Access Time
ta
—
1
tcyc
Slave MISO Disable Time
tdis
—
1
tcyc
Data Valid (after SCK Edge)
Master
Slave
tv
—
—
50
50
ns
ns
Data Hold Time (Outputs)
Master
Slave
tho
0
0
—
—
ns
ns
Rise Time
Input
Output
tri
tro
—
—
tcyc − 30
30
ns
ns
Fall Time
Input
Output
tfi
tfo
—
—
tcyc − 30
30
ns
ns
Num
Clock (SCK) High or Low Time
Master
Slave
1. All AC timing is shown with respect to 20% VDD and 70% VDD levels unless otherwise noted.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Electrical Specifications
437
Electrical Specifications
SS1
(OUTPUT)
5
2
1
SCK
(CPOL = 0)
(OUTPUT)
3
12
4
4
13
SCK
(CPOL = 1)
(OUTPUT)
6
7
MISO
(INPUT)
MSB IN2
BIT 6 .
10
. .
1
LSB IN
10
MOSI
(OUTPUT)
MSB OUT2
11
BIT 6 .
. .
1
LSB OUT
1.
SS output mode (DDS7 = 1, SSOE = 1).
2. LSBF = 0. For LSBF = 1, bit order is LSB, bit 1, ..., bit 6, MSB.
A) SPI Master Timing (CPHA = 0)
SS1
(OUTPUT)
5
1
2
13
12
12
13
3
SCK
(CPOL = 0)
(OUTPUT)
4
4
SCK
(CPOL = 1)
(OUTPUT)
6
MISO
(INPUT)
7
MSB IN2
. .
1
LSB IN
11
10
MOSI
(OUTPUT) PORT DATA
BIT 6 .
MASTER MSB OUT2
BIT 6 .
. .
1
MASTER LSB OUT
PORT DATA
1.
SS output mode (DDS7 = 1, SSOE = 1).
2. LSBF = 0. For LSBF = 1, bit order is LSB, bit 1, ..., bit 6, MSB.
B) SPI Master Timing (CPHA = 1)
Figure 21-9. SPI Timing Diagram (1 of 2)
Technical Data
438
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Electrical Specifications
Tables of Data
SS
(INPUT)
5
1
13
12
12
13
3
SCK
(CPOL = 0)
(INPUT)
4
2
4
SCK
(CPOL = 1)
(INPUT)
9
8
MISO
(OUTPUT)
10
MSB OUT
SLAVE
6
MOSI
(INPUT)
11
11
BIT 6 .
. .
BIT 6 .
. .
1
SLAVE LSB OUT
SEE
NOTE
7
MSB IN
1
LSB IN
NOTE: Not defined but normally MSB of character just received.
A) SPI Slave Timing (CPHA = 0)
SS
(INPUT)
5
3
1
2
13
12
12
13
SCK
(CPOL = 0)
(INPUT)
4
4
SCK
(CPOL = 1)
(INPUT)
MISO
(OUTPUT)
SEE
NOTE
8
MOSI
(INPUT)
SLAVE
6
9
11
10
MSB OUT
BIT 6 .
. .
1
SLAVE LSB OUT
7
MSB IN
BIT 6 .
. .
1
LSB IN
NOTE: Not defined but normally LSB of character just received.
SPI SLAVE CPHA1
B) SPI Slave Timing (CPHA = 1)
Figure 21-10. SPI Timing Diagram (2 of 2)
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Electrical Specifications
439
Electrical Specifications
Table 21-16. CGM Characteristics
5.0 Volts +/- 10%
Characteristic
Symbol
Min.
Max.
Unit
PLL reference frequency
fREF
0.5
8
MHz
Bus frequency
fBUS
0.004
8
MHz
VCO range
fVCO
2.5
8
MHz
fVCOMIN
0.5
2.5
MHz
∆trk
3%
4%
—
∆Lock
0%
1.5%
—
Un-Lock Detection
∆unl
0.5%
2.5%
—
Lock Detector transition from Tracking to Acquisition mode
∆unt
6%
8%
—
VCO Limp-Home frequency
Lock Detector transition from Acquisition to Tracking mode
Lock Detection
PLLON Stabilization delay(1)
PLLON Total Stabilization delay(2)
tstab
3
ms
PLLON Acquisition mode stabilization delay(3)
tacq
1
ms
tal
2
ms
PLLON Tracking mode stabilization delay(3)
1. PLL stabilization delay is highly dependent on operational requirement and external component values (e.e. crystal, XFC
filter component values). Note (2) shows typical delay values for a typical configuration. Appropriate XFC filter values
should be chosen based on operational requirement of system.
2. fREF = 4MHz, fSYS = 8MHz (REFDV = #$00, SYNR = #$01), XFC: Cs = 33nF, Cp - 3.3nF, Rs = 2.7KΩ.
Table 21-17. Oscillator Characteristics
MC68HC912DT128A
MC68HC912Dx128C
MC68HC912Dx128P
Unit
Input buffer hysteresis(1)
Min
Max
0
50
75
350
75
350
mV
Resonator Frequency(2)
(VDDPLL=VDD)
Min
Max
0.5
8
0.5
8
0.5
8
MHz
Resonator Frequency(2)
(VDDPLL=0V)
Min
Max
4
10
4
10
0.5
16
MHz
1. These values are dervied from design simulation and are not tested
2. Specifications apply to quartz or ceramic resonators only
Table 21-18. STOP Key Wake-up Filter
Characteristic
Symbol
Min.
Max.
STOP Key Wake-Up Filter time
STOP Key Wake-Up Filter pulse interval
tKWSTP
2
10
µs
tKWSP
20
-
µs
Technical Data
440
Unit
MC68HC912DT128A — Rev 4.0
Electrical Specifications
MOTOROLA
Technical Data — MC68HC912DT128A
Section 22. Appendix: Changes from MC68HC912DG128
22.1 Contents
22.2
22.2.1
22.2.2
22.2.3
22.2.4
22.2.5
22.2.6
22.2.7
Significant changes from the MC68HC912DG128 (non-suffix
device) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441
Flash. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .441
EEPROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .442
STOP mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 443
WAIT mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444
KWU Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .444
Port ADx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444
ATD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 444
22.2 Significant changes from the MC68HC912DG128 (non-suffix device)
22.2.1 Flash
22.2.1.1 Flash Architecture
The flash arrays are made from a new non-volatile memory (NVM)
technology. An external VFP is no longer used. Programming is now
carried out on a whole row (64 bytes) at a time. Erasing is still a bulk
erase of the entire array.
22.2.1.2 Flash Control Register
The Flash Control Register (FEECTL) is in the same location. However,
the individual bit functions have changed significantly to support the new
technology.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Appendix: Changes from MC68HC912DG128
441
Appendix: Changes from MC68HC912DG128
22.2.1.3 Flash Programming Procedure
Programming of the flash is greatly simplified over previous HC12s. The
read / verify / re-pulse programming algorithm is replaced by a much
simpler method.
22.2.1.4 Flash Programming Time
The most significant change resulting from the new flash technology is
that the bulk erase and program times are now fixed. The erase time is
at least twice as fast while the word programming time is at least 20%
faster.
22.2.1.5 Flash External Programming Voltage
The new flash does not require an external high voltage supply. All
voltages required for programming and erase are now generated
internally. Pin 97 that was the VFP pin on the 68HC912DG128 is now a
factory TEST pin. On ealy production devices it is recommended that
this pin is not connected within the application, but it may be connected
to VSS or 5.5V max without issue.
22.2.2 EEPROM
22.2.2.1 EEPROM Architecture
Like the flash, the EEPROM is also made from this new NVM
technology. The architecture and basic programming and erase
operations are unchanged. However, there is a new optional
programming method that allows faster programming of the EEPROM.
22.2.2.2 EEPROM Clock Source and Pre-scaler
The first major difference on the new EEPROM is that it requires a
constant time base source to ensure secure programming and erase
operations. The clock source that is going to drive the clock divider input
is the external clock input, EXTALi. The divide ratio from this source has
Technical Data
442
MC68HC912DT128A — Rev 4.0
Appendix: Changes from MC68HC912DG128
MOTOROLA
Appendix: Changes from MC68HC912DG128
Significant changes from the MC68HC912DG128 (non-suffix device)
to be set by programming an 10-bit time base pre-scalar into bits spread
over two new registers, EEDIVH and EEDIVL.
The EEDIVH and EEDIVL registers are volatile. However, they are
loaded upon reset by the contents of the non-volatile SHADOW word
much in the same way as the EEPROM module control register
(EEMCR) bits interact with the SHADOW word for configuration control
on the existing revision.
22.2.2.3 EEPROM AUTO programming & erasing
The second major change to the EEPROM is the inclusion in the
EEPROM control register (EEPROG) of an AUTO function using the
previously unused bit 5 of this register.
The AUTO function enables the logic of the MCU to automatically use
the optimum programming or erasing time for the EEPROM. If using
AUTO, the user does not need to wait for the normal minimum specified
programming or erasing time. After setting the EEPGM bit as normal the
user just has to poll that bit again, waiting for the MCU to clear it
indicating that programming or erasing is complete.
22.2.2.4 EEPROM Selective Write More Zeros
For some applications it may be advantageous to track more than 10k
events with a single byte of EEPROM by programming one bit at a time.
For that purpose, a special selective bit programming technique is
available.
When this technique is utilized, a program / erase cycle is defined as
multiple writes (up to eight) to a unique location followed by a single
erase sequence.
22.2.3 STOP mode
This new version will correctly exit STOP mode without having to
synchronize the start of STOP with the RTI clock.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Appendix: Changes from MC68HC912DG128
443
Appendix: Changes from MC68HC912DG128
22.2.4 WAIT mode
This new version will correctly exit WAIT mode using short XIRQ or IRQ
inputs.
22.2.5 KWU Filter
The KWU filter will now ignore pulses shorter than 2 microseconds.
22.2.6 Port ADx
Power must be applied to VDDA at all times even if the ADC is not being
used. This is necessary for port AD0 and port AD1 to function correctly
as digital inputs.
22.2.7 ATD
22.2.7.1 Channel Selection
Any channel can be selected for the first conversion of a multiple channel
conversion. Bits CA, CB & CC in ATDxCTL5 do not get masked but are
used to select which channel is used to start the sequential conversion
sequence. For compatibilty, ensure that the appropriate bits are
cleared in the software. See Table 19-8.
Bit CC of ATDxCTL5 is not masked when bit S8CM = 1.
22.2.7.2 CD bit
Bit CD in ATDxCTL5 is renamed SC to differentiate it from extended
functionality of bits CA, CB & CC. Functionality is unchanged as it still
selects conversion from the internal reference sources but when doing a
multiple channel scan, bits CA, CB & CC must be cleared as appropriate
for compatible reference selection.
Technical Data
444
MC68HC912DT128A — Rev 4.0
Appendix: Changes from MC68HC912DG128
MOTOROLA
Appendix: Changes from MC68HC912DG128
Significant changes from the MC68HC912DG128 (non-suffix device)
22.2.7.3 Additional Features
ATD flexibility has been increased with additional signed result, data
justification, single conversion selection and results location FIFO
features.
DJM & DSGN bits have been added to ATDxCTL2 register. Default
values are compatible with MC68HC912DG128 functionality.
FIFO & S1C bits have been added to ATDxCTL3 register. Default values
are compatible with MC68HC912DG128 functionality.
22.2.7.4 S8CM bit
Bit S8CM in ATDxCTL5 is renamed S8C. Functionality is compatible
with S8CM but can now be modified by the new S1C bit in ATDxCTL3.
The default is compatible with MC68HC912DG128 functionality.
22.2.7.5 Writing to ATDxCTL4
Writing to ATDxCTL4 aborts any ongoing conversion sequence and
initiates a new conversion sequence. Previously it only aborted ongoing
sequences leaving the ATD in idle mode (no conversion sequences
being processed). Writing to ATDxCTL2 or ADTxCTL3 also does not
abort an ongoing conversion sequence. Previously writing these
registers also aborted any ongoing sequence leaving the ATD in idle
mode .
This is unlikely to be a compatibility issue as applications mostly write
these registers to configure the ATD, closely followed by a write to
ATDxCTL5 to initiate a new conversion sequence which does abort any
ongoing conversion sequence and resets the appropriate flags.
To ensure compatibility, the application should not rely on ongoing
conversions being aborted. Also any interrupts from the completion of an
ongoing sequence should be masked and/or handled correctly.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Appendix: Changes from MC68HC912DG128
445
Appendix: Changes from MC68HC912DG128
22.2.7.6 SCF bit
In SCAN mode (SCAN bit = 1 in ATDxCTL5) the Sequence Complete
Flag (SCF bit in ATDSTATx) is set after completion of each conversion
sequence. Previously it was only set at the end of the first conversion
sequence.
To ensure compatibility the application should not rely on this flag being
set only once per SCAN mode.
22.2.7.7 ATDTESTx
Reading the ATDTESTx register in nornal modes returns the value of the
Successive Approximation Register (SAR). Previously it always read as
zero.
The RST bit in the ATDTESTx register can be written in normal modes
(in order to reset the ATD). Previously it was read only.
To ensure compatibility this register should not be read or written to.
Technical Data
446
MC68HC912DT128A — Rev 4.0
Appendix: Changes from MC68HC912DG128
MOTOROLA
Technical Data — MC68HC912DT128A
Section 23. Appendix: CGM Practical Aspects
23.1 Contents
23.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 447
23.3
Practical Aspects For The PLL Usage . . . . . . . . . . . . . . . . . .447
23.4
Printed Circuit Board Guidelines. . . . . . . . . . . . . . . . . . . . . . .453
23.2 Introduction
This sections provides useful and practical pieces of information
concerning the implementation of the CGM module.
23.3 Practical Aspects For The PLL Usage
23.3.1 Synthesized Bus Frequency
Starting from a ceramic resonator or quartz crystal frequency FXTAL, if
‘refdv’ and ‘synr’ are the decimal content of the REFDV and SYNR
registers respectively, then the MCU bus frequency will simply be:
F XTAL ⋅ ( synr + 1 )
F BUS = F VCO = ----------------------------------------------( refdv + 1 )
synr ∈ { 0,1,2,3...63}
refdv ∈ { 0,1,2,3...7}
NOTE:
It is not allowed to synthesize a bus frequency that is lower than the
crystal frequency, as the correct functioning of some internal
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Appendix: CGM Practical Aspects
447
Appendix: CGM Practical Aspects
synchronizers would be jeopardized (e.g. the MCLK and XCLK clock
generators).
23.3.2 Operation Under Adverse Environmental Conditions
The normal operation for the PLL is the so-called ‘automatic bandwidth
selection mode’ which is obtained by having the AUTO bit set in the
PLLCR register. When this mode is selected and as the VCO frequency
approaches its target, the charge pump current level will automatically
switch from a relatively high value of around 40 µA to a lower value of
about 3 µA. It can happen that this low level of charge pump current is
not enough to overcome leakages present at the XFC pin due to adverse
environmental conditions. These conditions are frequently encountered
for uncoated PCBs in automotive applications. The main symptom for
this failure is an unstable characteristic of the PLL which in fact ‘hunts’
between acquisition and tracking modes. It is then advised for the
running software to place the PLL in manual, forced acquisition mode by
clearing both the AUTO and the ACQ bits in the PLLCR register. Doing
so will maintain the high current level in the charge pump constantly and
will permit to sustain higher levels of leakages at the XFC pin. This latest
revision of the Clock Generator Module maintains the lock detection
feature even in manual bandwidth control, offering then to the
application software the same flexibility for the clocking control as the
automatic mode.
23.3.3 Filter Components Selection Guide
23.3.3.1 Equations Set
These equations can be used to select a set of filter components. Two
cases are considered:
1. The ‘tracking’ mode. This situation is reached normally when the
PLL operates in automatic bandwidth selection mode (AUTO=1 in
the PLLCR register).
2. The ‘acquisition’ mode. This situation is reached when the PLL
operates in manual bandwidth selection mode and forced
Technical Data
448
MC68HC912DT128A — Rev 4.0
Appendix: CGM Practical Aspects
MOTOROLA
Appendix: CGM Practical Aspects
Practical Aspects For The PLL Usage
acquisition (AUTO=0, ACQ=0 in the PLLCR register).
In both equations, the power supply should be 5V. Start with the target
loop bandwidth as a function of the other parameters, but obviously,
nothing prevents the user from starting with the capacitor value for
example. Also, remember that the smoothing capacitor is always
assumed to be one tenth of the series capacitance value.
So with:
m:
R:
C:
Fbus:
ζ:
Fc:
the multiplying factor for the reference frequency (i.e. (synr+1))
the series resistance of the low pass filter in Ω
the series capacitance of the low pass filter in nF
the target bus frequency expressed in MHz
the desired damping factor
the desired loop bandwidth expressed in Hz
for the ‘tracking’ mode:
9
2
– F bus⎞
⎛ 1.675
---------------------------⎝ 10.795 ⎠
2 ⋅ 10 ⋅ ζ
37.78 ⋅ e
⋅R
F c = ------------------------- = -----------------------------------------------------π⋅R⋅C
2⋅π⋅m
and for the ‘acquisition’ mode:
9
2
– F bus⎞
⎛ 1.675
---------------------------⎝ 10.795 ⎠
415.61 ⋅ e
2 ⋅ 10 ⋅ ζ
⋅R
F c = ------------------------- = --------------------------------------------------------π⋅R⋅C
2⋅π⋅m
23.3.3.2 Particular Case of an 8MHz Synthesis
Assume that a desired value for the damping factor of the second order
system is close to 0.9 as this leads to a satisfactory transient response.
Then, derived from the equations above, Table 23-1 and Table 23-2
suggest sets of values corresponding to several loop bandwidth
possibilities in the case of an 8MHz synthesis for the two cases
mentioned above.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Appendix: CGM Practical Aspects
449
Appendix: CGM Practical Aspects
The filter components values are chosen from standard series (e.g. E12
for resistors). The operating voltage is assumed to be 5V (although there
is only a minor difference between 3V and 5V operation). The smoothing
capacitor Cp in parallel with R and C is set to be 1/10 of the value of C.
The reference frequencies mentioned in this table correspond to the
output of the fine granularity divider controlled by the REFDV register.
This means that the calculations are irrespective of the way the
reference frequency is generated (directly for the crystal oscillator or
after division). The target frequency value also has an influence on the
calculations of the filter components because the VCO gain is NOT
constant over its operating range.
The bandwidth limit corresponds to the so-called Gardner’s criteria. It
corresponds to the maximum value that can be chosen before the
continuous time approximation ceases to be justified. It is of course
advisable to stay far away from this limit.
Technical Data
450
MC68HC912DT128A — Rev 4.0
Appendix: CGM Practical Aspects
MOTOROLA
Appendix: CGM Practical Aspects
Practical Aspects For The PLL Usage
Table 23-1. Suggested 8MHz Synthesis PLL Filter Elements (Tracking Mode)
Reference [MHz]
SYNR
Fbus [MHz]
C [nF]
R [kΩ]
Loop Bandwidth
[kHz]
Bandwidth
Limit [kHz]
0.614
$0C
7.98
100
4.3
1.1
157
0.614
$0C
7.98
4.7
20
5.3
157
0.614
$0C
7.98
1
43
11.5
157
0.614
$0C
7.98
0.33
75
20
157
0.8
$09
8.00
220
2.7
0.9
201
0.8
$09
8.00
10
12
4.2
201
0.8
$09
8.00
2.2
27
8.6
201
0.8
$09
8.00
0.47
56
19.2
201
1
$07
8.00
220
2.4
1
251
1
$07
8.00
10
11
4.7
251
1
$07
8.00
2.2
24
9.9
251
1
$07
8.00
0.47
51
21.4
251
1.6
$05
8.00
330
1.5
1
402
1.6
$05
8.00
10
9.1
5.9
402
1.6
$05
8.00
3.3
15
10.2
402
1.6
$05
8.00
1
27
18.6
402
2
$03
8.00
470
1.1
0.96
502
2
$03
8.00
22
5.1
4.4
502
2
$03
8.00
4.7
11
9.6
502
2
$03
8.00
1
24
20.8
502
2.66
$02
8.00
220
1.5
1.6
668
2.66
$02
8.00
22
4.7
5.1
668
2.66
$02
8.00
4.7
10
11
668
2.66
$02
8.00
1
22
24
668
4
$01
8.00
220
1.2
1.98
1005
4
$01
8.00
33
3
5.1
1005
4
$01
8.00
10
5.6
9.3
1005
4
$01
8.00
2.2
12
19.8
1005
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Appendix: CGM Practical Aspects
451
Appendix: CGM Practical Aspects
Table 23-2. Suggested 8MHz Synthesis PLL Filter Elements (Acquisition Mode)
Reference [MHz]
SYNR
Fbus [MHz]
C [nF]
R [kΩ]
Loop Bandwidth
[kHz]
Bandwidth
Limit [kHz]
0.614
$0C
7.98
1000
0.43
1.2
157
0.614
$0C
7.98
47
2
5.5
157
0.614
$0C
7.98
10
4.3
12
157
0.614
$0C
7.98
3.3
7.5
21
157
0.8
$09
8.00
2200
0.27
0.9
201
0.8
$09
8.00
100
1.2
4.4
201
0.8
$09
8.00
22
2.4
9.3
201
0.8
$09
8.00
4.7
5.6
20.1
201
1
$07
8.00
2200
0.22
1
251
1
$07
8.00
100
1
4.8
251
1
$07
8.00
2.
2.2
10.4
251
1
$07
8.00
4.7
4.7
22.5
251
1.6
$05
8.00
3300
0.15
1.1
402
1.6
$05
8.00
100
0.82
6.2
402
1.6
$05
8.00
33
1.5
10.7
402
1.6
$05
8.00
10
2.7
19.5
402
2
$03
8.00
4700
0.1
1
502
2
$03
8.00
220
0.51
4.6
502
2
$03
8.00
47
1
10
502
2
$03
8.00
10
2.4
21.8
502
2.66
$02
8.00
2200
0.12
1.7
668
2.66
$02
8.00
220
0.43
5.3
668
2.66
$02
8.00
47
1
11.6
668
2.66
$02
8.00
10
2
25.1
668
4
$01
8.00
2200
0.1
2.1
1005
4
$01
8.00
330
0.27
5.4
1005
4
$01
8.00
100
0.51
9.7
1005
4
$01
8.00
22
1
20.8
1005
Technical Data
452
MC68HC912DT128A — Rev 4.0
Appendix: CGM Practical Aspects
MOTOROLA
Appendix: CGM Practical Aspects
Printed Circuit Board Guidelines
23.4 Printed Circuit Board Guidelines
Printed Circuit Boards (PCBs) are the board of choice for volume
applications. If designed correctly, a very low noise system can be built
on a PCB with consequently good EMI/EMC performances. If designed
incorrectly, PCBs can be extremely noisy and sensitive modules, and
the CGM could be disrupted. Some common sense rules can be used to
prevent such problems.
•
Use a ‘star’ style power routing plan as opposed to a ‘daisy chain’.
Route power and ground from a central location to each chip
individually, and use the widest trace practical (the more the chip
draws current, the wider the trace). NEVER place the MCU at the
end of a long string of serially connected chips.
•
When using PCB layout software, first direct the routing of the
power supply lines as well as the CGM wires (crystal oscillator and
PLL). Layout constraints must be then reported on the other
signals and not on these ‘hot’ nodes. Optimizing the ‘hot’ nodes at
the end of the routing process usually gives bad results.
•
Avoid notches in power traces. These notches not only add
resistance (and are not usually accounted for in simulations), but
they can also add unnecessary transmission line effects.
•
Avoid ground and power loops. This has been one of the most
violated guidelines of PCB layout. Loops are excellent noise
transmitters and can be easily avoided. When using multiple layer
PCBs, the power and ground plane concept works well but only
when strictly adhered to (do not compromise the ground plane by
cutting a hole in it and running signals on the ground plane layer).
Keep the spacing around via holes to a minimum (but not so small
as to add capacitive effects).
•
Be aware of the three dimensional capacitive effects of multilayered PCBs.
•
Bypass (decouple) the power supplies of all chips as close to the
chip as possible. Use one decoupling capacitor per power supply
pair (VDD/VSS, VDDX/VSSX...). Two capacitors with a ratio of
about 100 sometimes offer better performances over a broader
MC68HC912DT128A — Rev 4.0
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Technical Data
Appendix: CGM Practical Aspects
453
Appendix: CGM Practical Aspects
spectrum. This is especially the case for the power supply pins
close to the E port, when the E clock and/or the calibration clock
are used.
•
On the general VDD power supply input, a ‘T’ low pass filter LCL
can be used (e.g. 10µH-47µF-10µH). The ‘T’ is preferable to the
‘Π’ version as the exhibited impedance is more constant with
respect to the VDD current. Like many modular micro controllers,
HC12 devices have a power consumption which not only varies
with clock edges but also with the functioning modes.
•
Keep high speed clock and bus trace length to a minimum. The
higher the clock speed, the shorter the trace length. If noisy
signals are sent over long tracks, impedance adjustments should
be considered at both ends of the line (generally, simple resistors
suffice).
•
Bus drivers like the CAN physical interface should be installed
close to their connector, with dedicated filtering on their power
supply.
•
Mount components as close to the board as possible. Snip excess
lead length as close to the board as possible. Preferably use
Surface Mount Devices (SMDs).
•
Mount discrete components as close to the chip that uses them as
possible.
•
Do not cross sensitive signals ON ANY LAYER. If a sensitive
signal must be crossed by another signal, do it as many layers
away as possible and at right angles.
•
Always keep PCBs clean. Solder flux, oils from fingerprints,
humidity and general dirt can conduct electricity. Sensitive circuits
can easily be disrupted by small amounts of leakage.
•
Choose PCB coatings with care. Certain epoxies, paints, gelatins,
plastics and waxes can conduct electricity. If the manufacturer
cannot provide the electrical characteristics of the substance, do
not use it.
Technical Data
454
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Appendix: CGM Practical Aspects
MOTOROLA
Appendix: CGM Practical Aspects
Printed Circuit Board Guidelines
In addition to the above general pieces of advice, the following
guidelines should be followed for the CGM pins (but also more generally
for any sensitive analog circuitry):
•
Parasitic capacitance on EXTAL is absolutely critical – probably
the most critical layout consideration. The XTAL pin is not as
sensitive. All routing from the EXTAL pin through the resonator
and the blocking cap to the actual connection to VSS must be
considered.
•
For minimum capacitance there should ideally be no ground /
power plane around the EXTAL pin and associated routing.
However, practical EMC considerations obviously should be taken
into consideration for each application.
•
The clock input circuitry is sensitive to noise so excellent supply
routing and decoupling is mandatory. Connect the ground point of
the oscillator circuit directly to the VSSPLL pin.
•
Good isolation of PLL / Oscillator Power supply is critical. Use
1nF+ 100nF and keep tracks as low impedance as possible
•
Load capacitors should be low leakage and stable across
temperature – use NPO or C0G types.
•
The load capacitors may ‘pull’ the target frequency by a few ppm.
Crystal manufacturer specs show symmetrical values but the
series device capacitance on EXTAL and XTAL are not
symmetrical. It may be possible to adjust this by changing the
values of the load capacitors – start-up conditions should be
evaluated.
•
Keep the adjacent Port H / Port E and RESET signals noise free.
Don’t connect these to external signals and / or add series filtering
– a series resistor is probably adequate.
•
Any DC-blocking capacitor should be as low ESR as possible – for
the range of crystals we are looking at anything over 1 Ohm is too
much.
•
Mount oscillator components on MCU side of board – avoid using
vias in the oscillator circuitry.
MC68HC912DT128A — Rev 4.0
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Technical Data
Appendix: CGM Practical Aspects
455
Appendix: CGM Practical Aspects
•
Mount the PLL filter and oscillator components as close to the
MCU as possible.
•
Do not allow the EXTAL and XTAL signals to interfere with the
XFC node. Keep these tracks as short as possible.
•
Do not cross the CGM signals with any other signal on any level.
•
Remember that the reference voltage for the XFC filter is
VDDPLL.
•
As the return path for the oscillator circuitry is VSSPLL, it is
extremely important to CONNECT VSSPLL to VSS even if the
PLL is not to be powered. Surface mount components reduce the
susceptibility of signal contamination.
Technical Data
456
MC68HC912DT128A — Rev 4.0
Appendix: CGM Practical Aspects
MOTOROLA
Technical Data — MC68HC912DT128A
Section 24. Appendix: Information on MC68HC912DT128A
Mask Set Changes
24.1 Contents
24.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 457
24.3
Oscillator – Major Changes . . . . . . . . . . . . . . . . . . . . . . . . . .457
24.4
Flash Protection Feature . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
24.5
Clock Circuitry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .458
24.6
Pseudo Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 458
24.7
Oscillator – Minor Changes . . . . . . . . . . . . . . . . . . . . . . . . . .459
24.8
PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 459
24.2 Introduction
The following improvements were made to create the 1L05H mask set
(MC68HC912Dx128C) and the 2L05H mask set (MC68HC912Dx128P).
Previous MC68HC912DT128A mask sets 3K91D (TSMC wafer fab.)
and 0L05H (Motorola TSC6 wafer fab.) are equivalent with the only
change being the wafer fab location.
24.3 Oscillator – Major Changes
The following are the primary differences between the previous Colpitts
("A") and the new Colpitts ("C") oscillator configurations.
1. Optimisation of the bias current to the amplifier for less process
variation.
2. Addition of hysteresis to the clock input buffer to reduce sensitivity
to noise.
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Appendix: Information on MC68HC912DT128A Mask Set Changes
Technical Data
457
Appendix: Information on MC68HC912DT128A
3. Change to the input ESD resistor from EXTAL to the gate of the
oscillator amplifier to provide a parallel path, reducing parasitic
phase shift in the oscillator.
Additionally a new Pierce ("P") oscillator configurations has been added.
See Section 13. Oscillator for full details.
24.4 Flash Protection Feature
A flash protection bit has been added to the EEMCR register to protect
the Flash memory from accidental program or erasure. This bit is loaded
from the EEPROM Shadow word at reset, so that the flash can be
protected before any software is executed.
See EEPROM and Flash sections for more details.
24.5 Clock Circuitry
The crystal oscillator output is now frozen when Limp Home (LH) mode
is entered to prevent rapid switching between crystal and LH clocks.
Improvements have been made to the bus clock switching circuitry to
eliminate the potential for glitches to appear on the internal clock line.
The duration of the clock monitor pulses was increased to reduce
sensitivity of the clock monitor circuit to short clock pulses.
24.6 Pseudo Stop Mode
Oscillator amplifier drive is now not reduced in Pseudo Stop mode.
When exiting Pseudo Stop mode, the device will now not go into Limp
Home Mode since the crystal is already running.
Technical Data
458
MC68HC912DT128A — Rev 4.0
Appendix: Information on MC68HC912DT128A Mask Set Changes
MOTOROLA
Appendix: Information on MC68HC912DT128A Mask Set Changes
Oscillator – Minor Changes
24.7 Oscillator – Minor Changes
The Automatic Level Control (ALC) capacitor reference was changed
from VDD to VSS in the crystal oscillator circuit to improve noise
immunity.
Parasitic capacitance on internal signal lines has been decreased, thus
decreasing sensitivity to external capacitance changes.
NOTE:
For best oscillator performance, it is recommended that the load
capacitor selection is verified on changing to the new mask.
A reduction was made to the gain of the Operational Transconductance
Amplifier (OTA) to reduce the amplification of any noise on the EXTAL
pin.
24.8 PLL
The limp Home clock frequency has been re-alligned to the specification
values to reduce sensitivity to system noise and hence reduce PLL jitter.
Note: It is advisable to verify the XFC filter components and PLL lock
time due to the above changes.
VCO start-up will now be at the minimum frequency whilst the power up
sequence of the current controlled oscillator has been improved.
The XFC pin is now preconditioned to VDDPLL when PLL is deselected
so XFC doesn’t float. This ensures the PLL starts up at low frequency
and ramps up to the desired frequency.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Appendix: Information on MC68HC912DT128A Mask Set Changes
Technical Data
459
Appendix: Information on MC68HC912DT128A
Technical Data
460
MC68HC912DT128A — Rev 4.0
Appendix: Information on MC68HC912DT128A Mask Set Changes
MOTOROLA
Technical Data — MC68HC912DT128A
Glossary
A — See “accumulators (A and B or D).”
accumulators (A and B or D) — Two 8-bit (A and B) or one 16-bit (D) general-purpose registers
in the CPU. The CPU uses the accumulators to hold operands and results of arithmetic
and logic operations.
acquisition mode — A mode of PLL operation with large loop bandwidth. Also see ’tracking
mode’.
address bus — The set of wires that the CPU or DMA uses to read and write memory locations.
addressing mode — The way that the CPU determines the operand address for an instruction.
The M68HC12 CPU has 15 addressing modes.
ALU — See “arithmetic logic unit (ALU).”
analogue-to-digital converter (ATD) — The ATD module is an 8-channel, multiplexed-input
successive-approximation analog-to-digital converter.
arithmetic logic unit (ALU) — The portion of the CPU that contains the logic circuitry to perform
arithmetic, logic, and manipulation operations on operands.
asynchronous — Refers to logic circuits and operations that are not synchronized by a common
reference signal.
ATD — See “analogue-to-digital converter”.
B — See “accumulators (A and B or D).”
baud rate — The total number of bits transmitted per unit of time.
BCD — See “binary-coded decimal (BCD).”
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Glossary
461
Glossary
binary — Relating to the base 2 number system.
binary number system — The base 2 number system, having two digits, 0 and 1. Binary
arithmetic is convenient in digital circuit design because digital circuits have two
permissible voltage levels, low and high. The binary digits 0 and 1 can be interpreted to
correspond to the two digital voltage levels.
binary-coded decimal (BCD) — A notation that uses 4-bit binary numbers to represent the 10
decimal digits and that retains the same positional structure of a decimal number. For
example,
234 (decimal) = 0010 0011 0100 (BCD)
bit — A binary digit. A bit has a value of either logic 0 or logic 1.
branch instruction — An instruction that causes the CPU to continue processing at a memory
location other than the next sequential address.
break module — The break module allows software to halt program execution at a
programmable point in order to enter a background routine.
breakpoint — A number written into the break address registers of the break module. When a
number appears on the internal address bus that is the same as the number in the break
address registers, the CPU executes the software interrupt instruction (SWI).
break interrupt — A software interrupt caused by the appearance on the internal address bus
of the same value that is written in the break address registers.
bus — A set of wires that transfers logic signals.
bus clock — See "CPU clock".
byte — A set of eight bits.
CAN — See "Motorola scalable CAN."
CCR — See “condition code register.”
central processor unit (CPU) — The primary functioning unit of any computer system. The
CPU controls the execution of instructions.
Technical Data
462
MC68HC912DT128A — Rev 4.0
Glossary
MOTOROLA
Glossary
CGM — See “clock generator module (CGM).”
clear — To change a bit from logic 1 to logic 0; the opposite of set.
clock — A square wave signal used to synchronize events in a computer.
clock generator module (CGM) — The CGM module generates a base clock signal from which
the system clocks are derived. The CGM may include a crystal oscillator circuit and/or
phase-locked loop (PLL) circuit.
comparator — A device that compares the magnitude of two inputs. A digital comparator defines
the equality or relative differences between two binary numbers.
computer operating properly module (COP) — A counter module that resets the MCU if
allowed to overflow.
condition code register (CCR) — An 8-bit register in the CPU that contains the interrupt mask
bit and five bits that indicate the results of the instruction just executed.
control bit — One bit of a register manipulated by software to control the operation of the
module.
control unit — One of two major units of the CPU. The control unit contains logic functions that
synchronize the machine and direct various operations. The control unit decodes
instructions and generates the internal control signals that perform the requested
operations. The outputs of the control unit drive the execution unit, which contains the
arithmetic logic unit (ALU), CPU registers, and bus interface.
COP — See "computer operating properly module (COP)."
CPU — See “central processor unit (CPU).”
CPU12 — The CPU of the MC68HC12 Family.
CPU clock — Bus clock select bits BCSP and BCSS in the clock select register (CLKSEL)
determine which clock drives SYSCLK for the main system, including the CPU and buses.
When EXTALi drives the SYSCLK, the CPU or bus clock frequency (fo) is equal to the
EXTALi frequency divided by 2.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Glossary
463
Glossary
CPU cycles — A CPU cycle is one period of the internal bus clock, normally derived by dividing
a crystal oscillator source by two or more so the high and low times will be equal. The
length of time required to execute an instruction is measured in CPU clock cycles.
CPU registers — Memory locations that are wired directly into the CPU logic instead of being
part of the addressable memory map. The CPU always has direct access to the
information in these registers. The CPU registers in an M68HC12 are:
•
A (8-bit accumulator)
•
B (8-bit accumulator)
–
D (16-bit accumulator formed by concatenation of accumulators A and B)
•
IX (16-bit index register)
•
IY (16-bit index register)
•
SP (16-bit stack pointer)
•
PC (16-bit program counter)
• CCR (8-bit condition code register)
cycle time — The period of the operating frequency: tCYC = 1/fOP.
D — See “accumulators (A and B or D).”
decimal number system — Base 10 numbering system that uses the digits zero through nine.
duty cycle — A ratio of the amount of time the signal is on versus the time it is off. Duty cycle is
usually represented by a percentage.
ECT — See “enhanced capture timer.”
EEPROM — Electrically erasable, programmable, read-only memory. A nonvolatile type of
memory that can be electrically erased and reprogrammed.
EPROM — Erasable, programmable, read-only memory. A nonvolatile type of memory that can
be erased by exposure to an ultraviolet light source and then reprogrammed.
enhanced capture timer (ECT) — The HC12 Enhanced Capture Timer module has the features
of the HC12 Standard Timer module enhanced by additional features in order to enlarge
the field of applications.
exception — An event such as an interrupt or a reset that stops the sequential execution of the
instructions in the main program.
Technical Data
464
MC68HC912DT128A — Rev 4.0
Glossary
MOTOROLA
Glossary
fetch — To copy data from a memory location into the accumulator.
firmware — Instructions and data programmed into nonvolatile memory.
free-running counter — A device that counts from zero to a predetermined number, then rolls
over to zero and begins counting again.
full-duplex transmission — Communication on a channel in which data can be sent and
received simultaneously.
hexadecimal — Base 16 numbering system that uses the digits 0 through 9 and the letters A
through F.
high byte — The most significant eight bits of a word.
illegal address — An address not within the memory map
illegal opcode — A nonexistent opcode.
index registers (IX and IY) — Two 16-bit registers in the CPU. In the indexed addressing
modes, the CPU uses the contents of IX or IY to determine the effective address of the
operand. IX and IY can also serve as a temporary data storage locations.
input/output (I/O) — Input/output interfaces between a computer system and the external world.
A CPU reads an input to sense the level of an external signal and writes to an output to
change the level on an external signal.
instructions — Operations that a CPU can perform. Instructions are expressed by programmers
as assembly language mnemonics. A CPU interprets an opcode and its associated
operand(s) and instruction.
inter-IC bus (I2C) — A two-wire, bidirectional serial bus that provides a simple, efficient method
of data exchange between devices.
interrupt — A temporary break in the sequential execution of a program to respond to signals
from peripheral devices by executing a subroutine.
interrupt request — A signal from a peripheral to the CPU intended to cause the CPU to
execute a subroutine.
I/O — See “input/output (I/0).”
jitter — Short-term signal instability.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Glossary
465
Glossary
latch — A circuit that retains the voltage level (logic 1 or logic 0) written to it for as long as power
is applied to the circuit.
latency — The time lag between instruction completion and data movement.
least significant bit (LSB) — The rightmost digit of a binary number.
logic 1 — A voltage level approximately equal to the input power voltage (VDD).
logic 0 — A voltage level approximately equal to the ground voltage (VSS).
low byte — The least significant eight bits of a word.
M68HC12 — A Motorola family of 16-bit MCUs.
mark/space — The logic 1/logic 0 convention used in formatting data in serial communication.
mask — 1. A logic circuit that forces a bit or group of bits to a desired state. 2. A photomask used
in integrated circuit fabrication to transfer an image onto silicon.
MCU — Microcontroller unit. See “microcontroller.”
memory location — Each M68HC12 memory location holds one byte of data and has a unique
address. To store information in a memory location, the CPU places the address of the
location on the address bus, the data information on the data bus, and asserts the write
signal. To read information from a memory location, the CPU places the address of the
location on the address bus and asserts the read signal. In response to the read signal,
the selected memory location places its data onto the data bus.
memory map — A pictorial representation of all memory locations in a computer system.
MI-Bus — See "Motorola interconnect bus".
microcontroller — Microcontroller unit (MCU). A complete computer system, including a CPU,
memory, a clock oscillator, and input/output (I/O) on a single integrated circuit.
modulo counter — A counter that can be programmed to count to any number from zero to its
maximum possible modulus.
most significant bit (MSB) — The leftmost digit of a binary number.
Technical Data
466
MC68HC912DT128A — Rev 4.0
Glossary
MOTOROLA
Glossary
Motorola interconnect bus (MI-Bus) — The Motorola Interconnect Bus (MI Bus) is a serial
communications protocol which supports distributed real-time control efficiently and with
a high degree of noise immunity.
Motorola scalable CAN (msCAN) — The Motorola scalable controller area network is a serial
communications protocol that efficiently supports distributed real-time control with a very
high level of data integrity.
msCAN — See "Motorola scalable CAN".
MSI — See "multiple serial interface".
multiple serial interface — A module consisting of multiple independent serial I/O sub-systems,
e.g. two SCI and one SPI.
multiplexer — A device that can select one of a number of inputs and pass the logic level of that
input on to the output.
nibble — A set of four bits (half of a byte).
object code — The output from an assembler or compiler that is itself executable machine code,
or is suitable for processing to produce executable machine code.
opcode — A binary code that instructs the CPU to perform an operation.
open-drain — An output that has no pullup transistor. An external pullup device can be
connected to the power supply to provide the logic 1 output voltage.
operand — Data on which an operation is performed. Usually a statement consists of an
operator and an operand. For example, the operator may be an add instruction, and the
operand may be the quantity to be added.
oscillator — A circuit that produces a constant frequency square wave that is used by the
computer as a timing and sequencing reference.
OTPROM — One-time programmable read-only memory. A nonvolatile type of memory that
cannot be reprogrammed.
overflow — A quantity that is too large to be contained in one byte or one word.
page zero — The first 256 bytes of memory (addresses $0000–$00FF).
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Glossary
467
Glossary
parity — An error-checking scheme that counts the number of logic 1s in each byte transmitted.
In a system that uses odd parity, every byte is expected to have an odd number of logic
1s. In an even parity system, every byte should have an even number of logic 1s. In the
transmitter, a parity generator appends an extra bit to each byte to make the number of
logic 1s odd for odd parity or even for even parity. A parity checker in the receiver counts
the number of logic 1s in each byte. The parity checker generates an error signal if it finds
a byte with an incorrect number of logic 1s.
PC — See “program counter (PC).”
peripheral — A circuit not under direct CPU control.
phase-locked loop (PLL) — A clock generator circuit in which a voltage controlled oscillator
produces an oscillation which is synchronized to a reference signal.
PLL — See "phase-locked loop (PLL)."
pointer — Pointer register. An index register is sometimes called a pointer register because its
contents are used in the calculation of the address of an operand, and therefore points to
the operand.
polarity — The two opposite logic levels, logic 1 and logic 0, which correspond to two different
voltage levels, VDD and VSS.
polling — Periodically reading a status bit to monitor the condition of a peripheral device.
port — A set of wires for communicating with off-chip devices.
prescaler — A circuit that generates an output signal related to the input signal by a fractional
scale factor such as 1/2, 1/8, 1/10 etc.
program — A set of computer instructions that cause a computer to perform a desired operation
or operations.
program counter (PC) — A 16-bit register in the CPU. The PC register holds the address of the
next instruction or operand that the CPU will use.
pull — An instruction that copies into the accumulator the contents of a stack RAM location. The
stack RAM address is in the stack pointer.
Technical Data
468
MC68HC912DT128A — Rev 4.0
Glossary
MOTOROLA
Glossary
pullup — A transistor in the output of a logic gate that connects the output to the logic 1 voltage
of the power supply.
pulse-width — The amount of time a signal is on as opposed to being in its off state.
pulse-width modulation (PWM) — Controlled variation (modulation) of the pulse width of a
signal with a constant frequency.
push — An instruction that copies the contents of the accumulator to the stack RAM. The stack
RAM address is in the stack pointer.
PWM period — The time required for one complete cycle of a PWM waveform.
RAM — Random access memory. All RAM locations can be read or written by the CPU. The
contents of a RAM memory location remain valid until the CPU writes a different value or
until power is turned off.
RC circuit — A circuit consisting of capacitors and resistors having a defined time constant.
read — To copy the contents of a memory location to the accumulator.
register — A circuit that stores a group of bits.
reserved memory location — A memory location that is used only in special factory test modes.
Writing to a reserved location has no effect. Reading a reserved location returns an
unpredictable value.
reset — To force a device to a known condition.
SCI — See "serial communication interface module (SCI)."
serial — Pertaining to sequential transmission over a single line.
serial communications interface module (SCI) — A module that supports asynchronous
communication.
serial peripheral interface module (SPI) — A module that supports synchronous
communication.
set — To change a bit from logic 0 to logic 1; opposite of clear.
shift register — A chain of circuits that can retain the logic levels (logic 1 or logic 0) written to
them and that can shift the logic levels to the right or left through adjacent circuits in the
chain.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Glossary
469
Glossary
signed — A binary number notation that accommodates both positive and negative numbers.
The most significant bit is used to indicate whether the number is positive or negative,
normally logic 0 for positive and logic 1 for negative. The other seven bits indicate the
magnitude of the number.
software — Instructions and data that control the operation of a microcontroller.
software interrupt (SWI) — An instruction that causes an interrupt and its associated vector
fetch.
SPI — See "serial peripheral interface module (SPI)."
stack — A portion of RAM reserved for storage of CPU register contents and subroutine return
addresses.
stack pointer (SP) — A 16-bit register in the CPU containing the address of the next available
storage location on the stack.
start bit — A bit that signals the beginning of an asynchronous serial transmission.
status bit — A register bit that indicates the condition of a device.
stop bit — A bit that signals the end of an asynchronous serial transmission.
subroutine — A sequence of instructions to be used more than once in the course of a program.
The last instruction in a subroutine is a return from subroutine (RTS) instruction. At each
place in the main program where the subroutine instructions are needed, a jump or branch
to subroutine (JSR or BSR) instruction is used to call the subroutine. The CPU leaves the
flow of the main program to execute the instructions in the subroutine. When the RTS
instruction is executed, the CPU returns to the main program where it left off.
synchronous — Refers to logic circuits and operations that are synchronized by a common
reference signal.
timer — A module used to relate events in a system to a point in time.
toggle — To change the state of an output from a logic 0 to a logic 1 or from a logic 1 to a logic 0.
tracking mode — A mode of PLL operation with narrow loop bandwidth. Also see ‘acquisition
mode.’
two’s complement — A means of performing binary subtraction using addition techniques. The
most significant bit of a two’s complement number indicates the sign of the number (1
indicates negative). The two’s complement negative of a number is obtained by inverting
each bit in the number and then adding 1 to the result.
Technical Data
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MC68HC912DT128A — Rev 4.0
Glossary
MOTOROLA
Glossary
unbuffered — Utilizes only one register for data; new data overwrites current data.
unimplemented memory location — A memory location that is not used. Writing to an
unimplemented location has no effect. Reading an unimplemented location returns an
unpredictable value.
variable — A value that changes during the course of program execution.
VCO — See "voltage-controlled oscillator."
vector — A memory location that contains the address of the beginning of a subroutine written
to service an interrupt or reset.
voltage-controlled oscillator (VCO) — A circuit that produces an oscillating output signal of a
frequency that is controlled by a dc voltage applied to a control input.
waveform — A graphical representation in which the amplitude of a wave is plotted against time.
wired-OR — Connection of circuit outputs so that if any output is high, the connection point is
high.
word — A set of two bytes (16 bits).
write — The transfer of a byte of data from the CPU to a memory location.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Glossary
471
Glossary
Technical Data
472
MC68HC912DT128A — Rev 4.0
Glossary
MOTOROLA
Technical Data — MC68HC912DT128A
Revision History
This section lists the revision history of the document since the first
release. Data for previous internal drafts is unavailable.
24.9 Changes in Rev. 4.0
Section
Page (in Rev 3.0)
Electrical
Specifications
437
Description of change
Clock (SCK) High or Low Time, Master, twsck changed from
tcyc − 60 to tcyc − 30.
24.10 Changes from Rev 2.0 to Rev 3.0
Section
Page (in Rev 3.0)
42, 43
Pinout and Signal
Descriptions
Note about TEST pin updated
46
PLL loop filter connections diagram (Figure 3-4) updated
48
Note added about consideration of crystal selection due to EMC
emissions
54
Description of TEST pin added as new section and to Table 3-2
55, 60
Registers
Description of change
Text added in Table 3-2 and Port CAN pin descriptions about nonconnection of RxCAN pins when MSCAN modules are not used.
68
FPOPEN bit added to EEMCR register
116
New paragraph added to overview about flash protection via
FPOPEN bit
117
Last part of FEEMCR opening paragraph changed to ‘if HVEN or
PGM or ERAS in the FEECTL register is set’
120
Changes made to the Flash programming description for
clarification of aligned words
122
New section 7.11 Flash protection bit FPOPEN added
Flash Memory
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Revision History
473
Revision History
Section
Page (in Rev 3.0)
128, 129
EEPROM Memory
Description of change
FPOPEN bit added to EEMCR register
132
Paragraph added to the EEPGM description to clarify block
protection
159
Note added about consideration of crystal selection due to EMC
emissions
159
Opening paragraphs of PLL description changed for clarification
163
In the section on clock loss during normal operation, description of
operation in limp home mode has been expanded for clarification
182
In Figure 12-6, MSCAN clock source selection via CLKSRC bit
corrected
339
First two bullets of sleep mode description updated
352
SLPRQ = 1 description updated
Clock Functions
MSCAN Controller
Analog-to-Digital
Converter
Major rewrite of entire section for clarification
Clock for the BDM has been renamed as BDMCLK, to
differentiaite it from another internal signal, BCLK
Development Support
Electrical
Specifications
Appendix: Changes
from
MC68HC912DG128
Appendix: CGM
Practical Aspects
Appendix: Information
on
MC68HC912DT128A
Mask Set Changes
425
Units for IOFF corrected to nA
427
Reference to supply differential voltage values updated.
VREF differential voltage row removed
Analog input differential voltage row added
429
fXTAL removed
429
Footnote added restricting external oscillator operating frequency
to 8MHz when using a quartz crystal
440
Table footnote removed from Table 21-16 regarding VDDPLL
444
Additional paragraphs added describing ATD differences from the
non A suffix device
447
Section 23.3 A Few Hints For The CGM Crystal Oscillator
Application removed. All points are covered in new Oscillator
section
455
Extra bullets added
New Section
Technical Data
474
MC68HC912DT128A — Rev 4.0
Revision History
MOTOROLA
Revision History
Changes from Rev 1.0 to Rev 2.0
24.11 Changes from Rev 1.0 to Rev 2.0
Section
Page (in Rev 2.0)
30, 31
Description of change
Figures 4 and 5, pin 97 changed to TEST and note added.
33
Note added about connection of power supplies.
35
Note about non-standard oscillator circuit expanded.
35
Additional paragraphs added covering DC bias.
Registers
55
CD bit name corrected in ATD0CTL5.
EEPROM
104
New section added ‘EEPROM Selective Write More Zeros’
Pinout and Signal
Descriptions
143 to 153
Major rewrite of Limp Home and Fast STOP Recovery section.
160
System Clock Frequency Formulae updated for clarification.
161
Figure 18 modified for clarification.
164
Figure 21 modified for clarification.
ECT
194
Figure 28 modified for clarification.
ATD
321
Shading removed from CC bit in table 52. CD bit name corrected.
Clock Functions
353, 354
Preliminary notes removed.
361
EEPROM Programming Maximum Time to ‘AUTO’ Bit Set and
EEPROM Erasing Maximum Time to ‘AUTO’ Bit Set added to
table 71.
369
Several values in table 76 updated.
Appendix A
377
New section added ‘2d. EEPROM Selective Write More Zeros’.
New section added ‘6. Port ADx’.
New section added ‘7. ATD’.
Appendix B
380
New section added ‘DC Bias’.
Electrical
Characteristics
24.12 Changes from first version (internal release, no revision number) to
Rev 1.0
Section
Page (in Rev 1.0)
Description of change
General Description
21
Ordering Information updated.
EEPROM
109
Addition of Caution regarding attempts to erase or program
protected locations.
MC68HC912DT128A — Rev 4.0
MOTOROLA
Technical Data
Revision History
475
Revision History
Section
Page (in Rev 1.0)
MSI
236
Description of change
Clarification of SP0DR register state on reset.
Technical Data
476
MC68HC912DT128A — Rev 4.0
Revision History
MOTOROLA
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MC912DT128A/D