Freescale MC68HC908MR8MP M68hc08 microcontroller Datasheet

MC68HC908MR8
Technical Data
M68HC08
Microcontrollers
Rev. 4.1
MC68HC908MR8/D
August 16, 2005
freescale.com
MC68HC908MR8
Technical Data — Rev 4.0
Freescale reserves the right to make changes without further notice to any products
herein. Freescale makes no warranty, representation or guarantee regarding the
suitability of its products for any particular purpose, nor does Freescale 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 Freescale 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. Freescale does not
convey any license under its patent rights nor the rights of others. Freescale 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 Freescale product could
create a situation where personal injury or death may occur. Should Buyer purchase or
use Freescale products for any such unintended or unauthorized application, Buyer
shall indemnify and hold Freescale 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 Freescale was negligent regarding the design or manufacture of the part.
Freescale, Inc. is an Equal Opportunity/Affirmative Action Employer.
© Freescale, Inc., 2005
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List of Paragraphs
Section 1. General Description . . . . . . . . . . . . . . . . . . . . 29
Section 2. Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . 37
Section 3. Random-Access Memory (RAM) . . . . . . . . . . 53
Section 4. FLASH Memory . . . . . . . . . . . . . . . . . . . . . . . . 55
Section 5. Configuration Register (CONFIG) . . . . . . . . . 67
Section 6. Central Processor Unit (CPU) . . . . . . . . . . . . 71
Section 7. System Integration Module (SIM) . . . . . . . . . 89
Section 8. Clock Generator Module (CGM) . . . . . . . . . . 111
Section 9. Pulse-Width Modulator for Motor Control
(PWMMC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
Section 10. Monitor ROM (MON) . . . . . . . . . . . . . . . . . . 187
Section 11. Timer Interface A (TIMA). . . . . . . . . . . . . . . 199
Section 12. Timer Interface B (TIMB). . . . . . . . . . . . . . . 223
Section 13. Serial Communications Interface (SCI) . . . 247
Section 14. Input/Output (I/O) Ports . . . . . . . . . . . . . . . 279
Section 15. Computer Operating Properly (COP) . . . . 291
Section 16. External Interrupt (IRQ) . . . . . . . . . . . . . . . 297
Section 17. Low-Voltage Inhibit (LVI) . . . . . . . . . . . . . . 305
Section 18. Analog-to-Digital Converter (ADC) . . . . . . 311
Section 19. Power-On Reset (POR) . . . . . . . . . . . . . . . 327
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Section 20. Break (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . 329
Section 21. Electrical Specifications. . . . . . . . . . . . . . . 339
Section 22. Mechanical Specifications . . . . . . . . . . . . . 351
Section 23. Ordering Information . . . . . . . . . . . . . . . . . 355
Technical Data — Revision History . . . . . . . . . . . . . . . . 357
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Table of Contents
Section 1. General Description
1.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
1.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
1.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.4
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
1.5
Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1.5.1
Power Supply Pins (VDD and VSS) . . . . . . . . . . . . . . . . . . . . 34
1.5.2
Oscillator Pins (OSC1 and OSC2) . . . . . . . . . . . . . . . . . . . . 34
1.5.3
External Reset Pin (RST) . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
1.5.4
External Interrupt Pin (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.5.5
CGM Power Supply Pins (VDDA and VSSA) . . . . . . . . . . . . . 35
1.5.6
ADC Reference Voltage Input Pin (VREFH) . . . . . . . . . . . . . 35
1.5.7
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . 35
1.5.8
Port A Input/Output (I/O) Pins (PTA6/ATD6–PTA0/ATD0). . 35
1.5.9
Port B I/O Pins (PTB6/TCHB1–PTB0/RxD) . . . . . . . . . . . . . 36
1.5.10 Port C I/O Pins (PTC1/FAULT1–PTC0/FAULT4). . . . . . . . . 36
1.5.11 PWM Pins (PWM6–PWM1) . . . . . . . . . . . . . . . . . . . . . . . . . 36
Section 2. Memory Map
2.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
2.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
2.3
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . 38
2.4
Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . 38
2.5
I/O Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
2.6
Monitor ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
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Section 3. Random-Access Memory (RAM)
3.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
3.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Section 4. FLASH Memory
4.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
4.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.2.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
4.2.2
FLASH Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . .57
4.2.3
FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . 58
4.2.4
FLASH Mass Erase Operation . . . . . . . . . . . . . . . . . . . . . . . 59
4.2.5
FLASH Program/Read Operation. . . . . . . . . . . . . . . . . . . . .59
4.3
FLASH Programming Algorithm . . . . . . . . . . . . . . . . . . . . . . . . 60
4.3.1
FLASH Block Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . .62
4.3.2
FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . 63
4.3.3
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.3.3.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.3.3.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Section 5. Configuration Register (CONFIG)
5.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
5.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
5.3
CONFIG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
5.4
CONFIG Bits. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
Section 6. Central Processor Unit (CPU)
6.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
6.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
6.4
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
6.4.1
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.4.2
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.4.3
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
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6.4.4
6.4.5
6.5
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.6
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
6.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
6.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
6.7
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.8
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
Section 7. System Integration Module (SIM)
7.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
7.3
SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . 93
7.3.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.3.2
Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . . . . 93
7.3.3
Clocks in Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.4
Reset and System Initialization. . . . . . . . . . . . . . . . . . . . . . . . . 94
7.4.1
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.4.2
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . 95
7.4.2.1
Power-On Reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.4.2.2
Computer Operating Properly (COP) Reset. . . . . . . . . . . 97
7.4.2.3
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
7.4.2.4
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . .98
7.4.2.5
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . 98
7.5
SIM Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
7.5.1
SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . 99
7.5.2
SIM Counter and Reset States. . . . . . . . . . . . . . . . . . . . . . . 99
7.6
Exception Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
7.6.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
7.6.1.1
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
7.6.1.2
SWI Instruction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7.6.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
7.6.3
Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . 103
7.7
Low-Power Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
7.7.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
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7.7.2
7.7.3
7.7.4
7.7.5
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 106
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . 108
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . .109
Section 8. Clock Generator Module (CGM)
8.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .111
8.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
8.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
8.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
8.4.1
Crystal Oscillator Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . .113
8.4.2
Phase-Locked Loop Circuit (PLL) . . . . . . . . . . . . . . . . . . . 115
8.4.2.1
PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
8.4.2.2
Acquisition and Tracking Modes . . . . . . . . . . . . . . . . . . 118
8.4.2.3
Manual and Automatic PLL Bandwidth Modes . . . . . . . 118
8.4.2.4
Programming the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . 120
8.4.2.5
Special Programming Exceptions . . . . . . . . . . . . . . . . . 121
8.4.3
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . 121
8.4.4
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . 122
8.5
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
8.5.1
Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . 123
8.5.2
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . 123
8.5.3
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . 123
8.5.4
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . 124
8.5.5
Oscillator Enable Signal (SIMOSCEN). . . . . . . . . . . . . . . . 124
8.5.6
Crystal Output Frequency Signal (CGMXCLK) . . . . . . . . . 124
8.5.7
CGM Base Clock Output (CGMOUT). . . . . . . . . . . . . . . . . 124
8.5.8
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . 124
8.6
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
8.6.1
PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
8.6.2
PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . . 129
8.6.3
PLL Programming Register . . . . . . . . . . . . . . . . . . . . . . . . 131
8.7
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132
8.8
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
8.9
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
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8.10
CGM During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
8.11 Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . . . . . 134
8.11.1 Acquisition/Lock Time Definitions. . . . . . . . . . . . . . . . . . . .134
8.11.2 Parametric Influences on Reaction Time . . . . . . . . . . . . . . 135
8.11.3 Choosing a Filter Capacitor . . . . . . . . . . . . . . . . . . . . . . . . 136
8.11.4 Reaction Time Calculation . . . . . . . . . . . . . . . . . . . . . . . . . 137
Section 9. Pulse-Width Modulator for Motor Control
(PWMMC)
9.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
9.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
9.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
9.4
Timebase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
9.4.1
Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .146
9.4.2
Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
9.5
PWM Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
9.5.1
Load Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
9.5.2
PWM Data Overflow and Underflow Conditions. . . . . . . . . 152
9.6
Output Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.6.1
Selecting Six Independent PWMs or Three Complementary
PWM Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152
9.6.2
Dead-Time Insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
9.6.3
Output Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
9.6.4
Output Port Control Register . . . . . . . . . . . . . . . . . . . . . . .159
9.7
Fault Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
9.7.1
Fault Condition Input Pins . . . . . . . . . . . . . . . . . . . . . . . . . 164
9.7.1.1
Fault Pin Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
9.7.1.2
Automatic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
9.7.1.3
Manual Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
9.7.2
Software Output Disable . . . . . . . . . . . . . . . . . . . . . . . . . . 168
9.7.3
Output Port Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
9.8
Initialization and the PWMEN Bit . . . . . . . . . . . . . . . . . . . . . . 169
9.9
PWM Operation in Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . 170
9.10
PWM Operation in Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . 170
9.11
PWM Operation in Break Mode . . . . . . . . . . . . . . . . . . . . . . .171
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9.12 Control Logic Block. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
9.12.1 PWM Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .172
9.12.2 PWM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . 173
9.12.3 PWMx Value Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
9.12.4 PWM Control Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . .175
9.12.5 PWM Control Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . .177
9.12.6 Dead-Time Write-Once Register . . . . . . . . . . . . . . . . . . . . 179
9.12.7 PWM Disable Mapping Write-Once Register . . . . . . . . . . . 179
9.12.8 Fault Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
9.12.9 Fault Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
9.12.10 Fault Acknowledge Register. . . . . . . . . . . . . . . . . . . . . . . . 182
9.12.11 PWM Output Control Register . . . . . . . . . . . . . . . . . . . . . . 184
9.13
PWM Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Section 10. Monitor ROM (MON)
10.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
10.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
10.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
10.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
10.4.1 Entering Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
10.4.2 Forced Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
10.4.3 Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
10.4.4 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
10.4.5 Echoing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
10.4.6 Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
10.4.7 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193
10.5
Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
Section 11. Timer Interface A (TIMA)
11.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .199
11.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
11.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
11.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
11.4.1 TIMA Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . .204
11.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
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11.4.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
11.4.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . 206
11.4.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . .206
11.4.4 Pulse-Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . 207
11.4.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . 208
11.4.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . 209
11.4.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
11.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211
11.6
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
11.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
11.8
TIMA During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 212
11.9 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
11.9.1 TIMA Clock Pin (PTB2/TCLKA) . . . . . . . . . . . . . . . . . . . . . 213
11.9.2 TIMA Channel I/O Pins (PTB3/TCH0A–PTB4/TCH1A) . . . 213
11.10 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
11.10.1 TIMA Status and Control Register . . . . . . . . . . . . . . . . . . . 214
11.10.2 TIMA Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .216
11.10.3 TIMA Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . 217
11.10.4 TIMA Channel Status and Control Registers . . . . . . . . . . . 218
11.10.5 TIMA Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 222
Section 12. Timer Interface B (TIMB)
12.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .223
12.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
12.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
12.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .227
12.4.1 TIMB Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . .228
12.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
12.4.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
12.4.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . 230
12.4.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . .231
12.4.4 Pulse-Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . 231
12.4.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . 232
12.4.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . 233
12.4.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
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12.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .235
12.6
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
12.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
12.8
TIMB During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 236
12.9
TIMB Channel I/O Pins (PTB5/TCH0B–PTB6/TCH1B) . . . . . 237
12.10 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
12.10.1 TIMB Status and Control Register . . . . . . . . . . . . . . . . . . . 237
12.10.2 TIMB Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .240
12.10.3 TIMB Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . 241
12.10.4 TIMB Channel Status and Control Registers . . . . . . . . . . . 242
12.10.5 TIMB Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 245
Section 13. Serial Communications Interface (SCI)
13.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .247
13.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
13.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
13.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .249
13.4.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
13.4.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
13.4.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
13.4.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . 252
13.4.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
13.4.2.4
Idle Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
13.4.2.5
Inversion of Transmitted Output. . . . . . . . . . . . . . . . . . . 255
13.4.2.6
Transmitter Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . .255
13.4.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
13.4.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
13.4.3.2
Character Reception . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
13.4.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
13.4.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
13.4.3.5
Receiver Wakeup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
13.4.3.6
Receiver Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
13.4.3.7
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
13.5
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
13.6
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
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13.7
SCI During Break Module Interrupts. . . . . . . . . . . . . . . . . . . .262
13.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
13.8.1 PTE2/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . 263
13.8.2 PTB0/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . 263
13.9 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
13.9.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
13.9.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
13.9.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
13.9.4 SCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
13.9.5 SCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
13.9.6 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
13.9.7 SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . 276
Section 14. Input/Output (I/O) Ports
14.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
14.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
14.3 Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
14.3.1 Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
14.3.2 Data Direction Register A . . . . . . . . . . . . . . . . . . . . . . . . . 282
14.4 Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
14.4.1 Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
14.4.2 Data Direction Register B. . . . . . . . . . . . . . . . . . . . . . . . . . 285
14.5 Port C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
14.5.1 Port C Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
14.5.2 Data Direction Register C . . . . . . . . . . . . . . . . . . . . . . . . . 288
Section 15. Computer Operating Properly (COP)
15.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
15.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
15.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
15.4 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
15.4.1 CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
15.4.2 COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
15.4.3 Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
15.4.4 Internal Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
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15.4.5
15.4.6
Reset Vector Fetch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
COP Disable. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
15.5
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
15.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
15.7
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
15.8
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
15.9
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
15.10 COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . 295
Section 16. External Interrupt (IRQ)
16.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297
16.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
16.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
16.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .298
16.5
IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
16.6
IRQ Module During Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . 302
16.7
IRQ Module During Stop Mode. . . . . . . . . . . . . . . . . . . . . . . . 302
16.8
IRQ Module During Break Mode. . . . . . . . . . . . . . . . . . . . . . . 302
16.9
IRQ Status and Control Register . . . . . . . . . . . . . . . . . . . . . . 303
Section 17. Low-Voltage Inhibit (LVI)
17.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
17.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
17.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 305
17.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .306
17.4.1 Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
17.4.2 Forced Reset Operation . . . . . . . . . . . . . . . . . . . . . . . . . . .307
17.4.3 False Reset Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
17.4.4 LVI Trip Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
17.5
LVI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . 308
17.6
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309
17.7
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
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Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
Section 18. Analog-to-Digital Converter (ADC)
18.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .311
18.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
18.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
18.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .312
18.4.1 ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
18.4.2 Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314
18.4.3 Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 314
18.4.4 Continuous Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
18.4.5 Result Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 315
18.4.6 Monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
18.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .316
18.6
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
18.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
18.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
18.8.1 ADC Voltage Reference Pin (VREFH) . . . . . . . . . . . . . . . . . 317
18.8.2 ADC Voltage In (ADVIN) . . . . . . . . . . . . . . . . . . . . . . . . . . 318
18.8.3 ADC External Connection . . . . . . . . . . . . . . . . . . . . . . . . . 318
18.8.3.1
VREFH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .318
18.8.3.2
ANx . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
18.8.3.3
Grounding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
18.9 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
18.9.1 ADC Status and Control Register. . . . . . . . . . . . . . . . . . . .319
18.9.2 ADC Data Register High . . . . . . . . . . . . . . . . . . . . . . . . . . 322
18.9.3 ADC Data Register Low . . . . . . . . . . . . . . . . . . . . . . . . . . .323
18.9.4 ADC Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
Section 19. Power-On Reset (POR)
19.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327
19.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 327
19.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327
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Table of Contents
Section 20. Break (BRK)
20.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329
20.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
20.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
20.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .330
20.4.1 Flag Protection During Break Interrupts . . . . . . . . . . . . . . . 330
20.4.2 CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . .332
20.4.3 TIM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . 332
20.4.4 COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . 332
20.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
20.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333
20.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333
20.6 Break Module Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
20.6.1 Break Status and Control Register. . . . . . . . . . . . . . . . . . . 333
20.6.2 Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 334
20.6.3 SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 336
20.6.4 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . 337
Section 21. Electrical Specifications
21.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .339
21.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
21.3
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . 340
21.4
Functional Operating Range. . . . . . . . . . . . . . . . . . . . . . . . . . 341
21.5
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
21.6
DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 343
21.7
Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
21.8
Control Timing
21.9
TImer Interface Module Characteristics . . . . . . . . . . . . . . . . . 346
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
21.10 Clock Generation Module Component Specifications . . . . . . 347
21.11 CGM Operating Conditions. . . . . . . . . . . . . . . . . . . . . . . . . . .347
21.12 CGM Acquisition/Lock Time Specifications
. . . . . . . . . . . . 348
21.13 Analog-to-Digital Converter (ADC) Characteristics. . . . . . . . . 349
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Section 22. Mechanical Specifications
22.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .351
22.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
22.3
32-Pin LQFP (Case #873A) . . . . . . . . . . . . . . . . . . . . . . . . . . 352
22.4
28-Pin PDIP (Case #710) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
22.5
28-Pin SOIC (Case #751F). . . . . . . . . . . . . . . . . . . . . . . . . . .353
Section 23. Ordering Information
23.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
23.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
23.3
MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
Technical Data — Revision History
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
Changes from Rev 3.0 published in April 2002 to Rev 4.0 published in July 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
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Technical Data — MC68HC908MR8
List of Figures
Figure
1-1
1-2
1-3
2-1
2-2
4-1
4-2
4-3
4-4
5-1
6-1
6-2
6-3
6-4
6-5
6-6
7-1
7-2
7-3
7-4
7-5
7-6
7-7
7-8
7-9
7-10
7-11
Title
MCU Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
QFP and DIP/SOIC Pin Assignments . . . . . . . . . . . . . . . . . 33
Power Supply Bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Control, Status, and Data Registers. . . . . . . . . . . . . . . . . . . 41
FLASH Control Register (FLCR) . . . . . . . . . . . . . . . . . . . . . 57
FLASH Programming Algorithm . . . . . . . . . . . . . . . . . . . . . . 61
FLASH Block Protect Register (FLBPR) . . . . . . . . . . . . . . . 63
FLASH Block Protect Address . . . . . . . . . . . . . . . . . . . . . . . 64
CONFIG Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Accumulator (A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Index Register (H:X). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Stack Pointer (SP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Program Counter (PC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Condition Code Register (CCR) . . . . . . . . . . . . . . . . . . . . . . 76
SIM Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
SIM I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . 92
CGM Clock Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
External Reset Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Internal Reset Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Sources of Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . 96
POR Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
Interrupt Entry. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
Interrupt Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Interrupt Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Interrupt Recognition Example . . . . . . . . . . . . . . . . . . . . . . 103
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List of Figures
7-12
7-13
7-14
7-15
7-16
7-17
8-1
8-2
8-3
8-4
8-5
8-6
8-7
9-1
9-2
9-3
9-4
9-5
9-6
9-7
9-8
9-9
9-10
9-11
9-12
9-13
9-14
9-15
9-16
9-17
9-18
9-19
9-20
9-21
9-22
Wait Mode Entry Timing . . . . . . . . . . . . . . . . . . . . . . . . . . .104
Wait Recovery from Interrupt or Break. . . . . . . . . . . . . . . . 105
Wait Recovery from Internal Reset . . . . . . . . . . . . . . . . . . 105
SIM Break Status Register (SBSR) . . . . . . . . . . . . . . . . . . 106
SIM Reset Status Register (SRSR) . . . . . . . . . . . . . . . . . . 108
SIM Break Flag Control Register (SBFCR) . . . . . . . . . . . . 109
CGM Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
CGM I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . .115
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . 123
CGM I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . .125
PLL Control Register (PCTL) . . . . . . . . . . . . . . . . . . . . . . . 126
PLL Bandwidth Control Register (PBWC) . . . . . . . . . . . . . 129
PLL Programming Register (PPG) . . . . . . . . . . . . . . . . . . . 131
PWM Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . 141
Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
Center-Aligned PWM (Positive Polarity). . . . . . . . . . . . . . . 147
Edge-Aligned PWM (Positive Polarity) . . . . . . . . . . . . . . . . 147
Reload Frequency Change . . . . . . . . . . . . . . . . . . . . . . . . 149
PWM Interrupt Requests . . . . . . . . . . . . . . . . . . . . . . . . . . 150
Center-Aligned PWM Value Loading . . . . . . . . . . . . . . . . . 150
Center-Aligned Loading of Modulus . . . . . . . . . . . . . . . . . . 151
Edge-Aligned PWM Value Loading . . . . . . . . . . . . . . . . . . 151
Edge-Aligned Modulus Loading . . . . . . . . . . . . . . . . . . . . . 151
Complementary Pairing . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Typical AC Motor Drive . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
Dead-Time Generators. . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Effects of Dead-Time Insertion. . . . . . . . . . . . . . . . . . . . . . 156
Dead-Time at Duty Cycle Boundaries . . . . . . . . . . . . . . . . 156
Dead-Time and Small Pulse Widths. . . . . . . . . . . . . . . . . . 157
PWM Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
PWM Output Control Register (PWMOUT) . . . . . . . . . . . . 159
Dead-Time Insertion During OUTCTL = 1 . . . . . . . . . . . . . 160
Dead-Time Insertion During OUTCTL = 1 . . . . . . . . . . . . . 161
PWM Disabling Scheme. . . . . . . . . . . . . . . . . . . . . . . . . . .162
PWM Disable Mapping Write-Once Register (DISMAP) . . 163
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9-23
9-24
9-25
9-26
9-27
9-28
9-29
9-30
9-31
9-32
9-33
9-34
9-35
9-36
9-37
9-38
9-39
9-40
9-41
9-42
9-43
9-44
10-1
10-2
10-3
10-4
10-5
10-6
11-1
11-2
11-3
11-4
11-5
11-6
PWM Disabling Decode Scheme . . . . . . . . . . . . . . . . . . . .164
PWM Disabling in Automatic Mode . . . . . . . . . . . . . . . . . . 166
PWM Disabling in Manual Mode (Example 1) . . . . . . . . . . 167
PWM Disabling in Manual Mode (Example 2) . . . . . . . . . . 167
PWM Software Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
PWMEN and PWM Pins. . . . . . . . . . . . . . . . . . . . . . . . . . .169
PWM Counter Register High (PCNTH) . . . . . . . . . . . . . . . 172
PWM Counter Register Low (PCNTH) . . . . . . . . . . . . . . . . 172
PWM Counter Modulo Register High (PDMODH) . . . . . . . 173
PWM Counter Modulo Register Low (PDMODL) . . . . . . . . 173
PWMx Value Registers High (PVALxH) . . . . . . . . . . . . . . . 174
PWMx Value Registers Low (PVALxL) . . . . . . . . . . . . . . . 174
PWM Control Register 1 (PCTL1) . . . . . . . . . . . . . . . . . . . 175
PWM Control Register 2 (PCTL2) . . . . . . . . . . . . . . . . . . . 177
Dead-Time Write-Once Register (DEADTM) . . . . . . . . . . . 179
PWM Disable Mapping Write-Once Register (DISMAP) . . 179
Fault Control Register (FCR) . . . . . . . . . . . . . . . . . . . . . . .180
Fault Status Register (FSR) . . . . . . . . . . . . . . . . . . . . . . . . 181
Fault Acknowledge Register (FTACK) . . . . . . . . . . . . . . . . 182
PWM Output Control Register (PWMOUT) . . . . . . . . . . . . 184
PWM Clock Cycle and PWM Cycle Definitions . . . . . . . . . 186
PWM Load Cycle/Frequency Definition . . . . . . . . . . . . . . . 186
Monitor Mode Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 189
Monitor Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
Sample Monitor Waveforms . . . . . . . . . . . . . . . . . . . . . . . . 191
Read Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Break Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
Monitor Mode Entry Timing . . . . . . . . . . . . . . . . . . . . . . . . 196
TIMA Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
TIMA I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . .201
PWM Period and Pulse Width . . . . . . . . . . . . . . . . . . . . . . 208
TIMA Status and Control Register (TASC). . . . . . . . . . . . . 214
TIMA Counter Registers (TACNTH and TACNTL). . . . . . . 216
TIMA Counter Modulo Registers (TMODH and TMODL). . 217
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23
List of Figures
11-7
218
11-8
11-9
12-1
12-2
12-3
12-4
12-5
12-6
12-7
TIMA Channel Status and Control Registers (TASC0–TASC1)
12-8
12-9
13-1
13-2
13-3
13-4
13-5
13-6
13-7
13-8
13-9
13-10
13-11
13-12
13-13
13-14
14-1
14-2
14-3
14-4
CHxMAX Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
TIMA Channel Registers (TACH0H/L–TACH1H/L) . . . . . . 222
TIMB Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
TIMB I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . .225
PWM Period and Pulse Width . . . . . . . . . . . . . . . . . . . . . . 232
TIMB Status and Control Register (TBSC). . . . . . . . . . . . . 238
TIMB Counter Registers (TBCNTH and TBCNTL). . . . . . . 240
TIMB Counter Modulo Registers (TMODH and TMODL). . 241
TIMB Channel Status and Control Registers (TBSC0–TBSC1)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
CHxMAX Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
TIMB Channel Registers (TBCH0H/L–TBCH1H/L) . . . . . . 246
SCI Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . 250
SCI I/O Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . 251
SCI Data Formats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
SCI Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
SCI Receiver Block Diagram . . . . . . . . . . . . . . . . . . . . . . .256
Receiver Data Sampling. . . . . . . . . . . . . . . . . . . . . . . . . . .258
SCI Control Register 1 (SCC1) . . . . . . . . . . . . . . . . . . . . . 264
SCI Control Register 2 (SCC2) . . . . . . . . . . . . . . . . . . . . . 267
SCI Control Register 3 (SCC3) . . . . . . . . . . . . . . . . . . . . . 270
SCI Status Register 1 (SCS1) . . . . . . . . . . . . . . . . . . . . . . 271
Flag Clearing Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . .274
SCI Status Register 2 (SCS2) . . . . . . . . . . . . . . . . . . . . . . 275
SCI Data Register (SCDR). . . . . . . . . . . . . . . . . . . . . . . . . 276
SCI Baud Rate Register (SCBR) . . . . . . . . . . . . . . . . . . . . 276
I/O Port Register Summary . . . . . . . . . . . . . . . . . . . . . . . . 280
Port A Data Register (PTA) . . . . . . . . . . . . . . . . . . . . . . . . 281
Data Direction Register A (DDRA) . . . . . . . . . . . . . . . . . . . 282
Port A I/O Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
14-5
14-6
14-7
Port B Data Register (PTB) . . . . . . . . . . . . . . . . . . . . . . . . 284
Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . . 285
Port B I/O Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
Technical Data
24
MC68HC908MR8 — Rev 4.1
List of Figures
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List of Figures
14-8
14-9
14-10
15-1
15-2
15-3
16-1
16-2
16-3
16-4
17-1
17-2
17-3
18-1
18-2
18-3
18-4
18-5
18-6
18-7
18-8
18-9
20-1
20-2
20-3
20-4
20-5
20-6
20-7
20-8
Port C Data Register (PTC) . . . . . . . . . . . . . . . . . . . . . . . . 287
Data Direction Register C (DDRC). . . . . . . . . . . . . . . . . . . 288
Port C I/O Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
COP Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
COP I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . 292
COP Control Register (COPCTL). . . . . . . . . . . . . . . . . . . .294
IRQ Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . 298
IRQ I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . 298
IRQ Interrupt Flowchart . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
IRQ Status and Control Register (ISCR) . . . . . . . . . . . . . . 303
LVI Module Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . 306
LVI I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . 307
LVI Status and Control Register (LVISCR) . . . . . . . . . . . . 308
ADC Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
8-Bit Truncation Mode Error . . . . . . . . . . . . . . . . . . . . . . . . 316
ADC Status and Control Register (ADSCR). . . . . . . . . . . . 319
ADC Data Register High (ADRH) Left Justified Mode . . . . 322
ADC Data Register High (ADRH) Right Justified Mode . . . 322
ADC Data Register Low (ADRL) Left Justified Mode . . . . . 323
ADC Data Register Low (ADRL) Right Justified Mode. . . . 323
ADC Data Register Low (ADRL) 8-Bit Mode . . . . . . . . . . . 324
ADC Clock Register (ADCLK) . . . . . . . . . . . . . . . . . . . . . . 324
Break Module Block Diagram. . . . . . . . . . . . . . . . . . . . . . . 331
I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
Break Status and Control Register (BRKSCR) . . . . . . . . . 333
Break Address Register High (BRKH) . . . . . . . . . . . . . . . . 334
Break Address Register Low (BRKL) . . . . . . . . . . . . . . . . . 335
SIM Break Status Register (SBSR) . . . . . . . . . . . . . . . . . . 336
Example Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
SIM Break Flag Control Register (SBFCR) . . . . . . . . . . . . 337
MC68HC908MR8 — Rev 4.1
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Technical Data
List of Figures
25
List of Figures
Technical Data
26
MC68HC908MR8 — Rev 4.1
List of Figures
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Technical Data — MC68HC908MR8
List of Tables
Table
2-1
6-1
6-2
7-1
7-2
8-1
9-1
9-2
9-3
9-4
9-5
9-6
9-7
10-1
10-2
10-3
10-4
10-5
10-6
10-7
10-8
11-1
11-2
12-1
12-2
13-1
13-2
13-3
13-4
Title
Vector Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Signal Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
PIN Bit Set Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
VCO Frequency Multiplier (N) Selection. . . . . . . . . . . . . . . . 131
PWM Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
PWM Reload Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
PWM Data Overflow and Underflow Conditions. . . . . . . . . . 152
OUTx Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
PWM Reload Frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . 177
PWM Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
OUTx Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
Mode Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188
Mode Differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 190
READ (Read Memory) Command . . . . . . . . . . . . . . . . . . . . 193
WRITE (Write Memory) Command. . . . . . . . . . . . . . . . . . . .193
IREAD (Indexed Read) Command . . . . . . . . . . . . . . . . . . . .194
IWRITE (Indexed Write) Command . . . . . . . . . . . . . . . . . . . 194
READSP (Read Stack Pointer) Command. . . . . . . . . . . . . . 195
RUN (Run User Program) Command. . . . . . . . . . . . . . . . . . 195
Prescaler Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Mode, Edge, and Level Selection. . . . . . . . . . . . . . . . . . . . . 220
Prescaler Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Mode, Edge, and Level Selection. . . . . . . . . . . . . . . . . . . . . 244
Start Bit Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
Data Bit Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Stop Bit Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
Character Format Selection . . . . . . . . . . . . . . . . . . . . . . . . . 266
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Page
Technical Data
List of Tables
27
List of Tables
13-5
13-6
13-7
14-1
14-2
14-3
17-1
18-1
18-2
23-1
SCI Baud Rate Prescaling . . . . . . . . . . . . . . . . . . . . . . . . . . 277
SCI Baud Rate Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . 277
SCI Baud Rate Selection Examples . . . . . . . . . . . . . . . . . . . 278
Port A Pin Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
Port B Pin Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 286
Port C Pin Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
LVIOUT Bit Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
Mux Channel Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
ADC Clock Divide Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
Technical Data
28
MC68HC908MR8 — Rev 4.1
List of Tables
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 1. General Description
1.1 Contents
1.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
1.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.4
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
1.5
Pin Assignments. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
1.5.1
Power Supply Pins (VDD and VSS) . . . . . . . . . . . . . . . . . .34
1.5.2
Oscillator Pins (OSC1 and OSC2). . . . . . . . . . . . . . . . . . .34
1.5.3
External Reset Pin (RST) . . . . . . . . . . . . . . . . . . . . . . . . . .34
1.5.4
External Interrupt Pin (IRQ) . . . . . . . . . . . . . . . . . . . . . . . .35
1.5.5
CGM Power Supply Pins (VDDA and VSSA) . . . . . . . . . . . .35
1.5.6
ADC Reference Voltage Input Pin (VREFH) . . . . . . . . . . . .35
1.5.7
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . .35
1.5.8
Port A Input/Output (I/O) Pins (PTA6/ATD6–PTA0/ATD0)
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
1.5.9
Port B I/O Pins (PTB6/TCHB1–PTB0/RxD) . . . . . . . . . . . .36
1.5.10 Port C I/O Pins (PTC1/FAULT1–PTC0/FAULT4). . . . . . . .36
1.5.11 PWM Pins (PWM6–PWM1) . . . . . . . . . . . . . . . . . . . . . . . . .36
1.2 Introduction
The MC68HC908MR8 is a member of the low-cost, high-performance
M68HC08 Family of 8-bit microcontroller units (MCU). The M68HC08
Family is based on the customer-specified integrated circuit (CSIC)
design strategy. All MCUs in the family use the enhanced M68HC08
central processor unit (CPU08) and are available with a variety of
modules, memory sizes and types, and package types.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
General Description
29
General Description
1.3 Features
Features of the MC68HC908MR8 include:
•
High-performance M68HC08 architecture
•
Fully upward-compatible object code with M6805, M146805, and
M68HC05 Families
•
8-MHz internal bus frequency
•
8 Kbytes of on-chip FLASH
•
On-chip programming firmware for use with host personal
computer
•
256 bytes of on-chip random-access memory (RAM):
•
12-bit, 6-channel center-aligned or edge-aligned pulse-width
modulator (PWMMC)
•
Serial communications interface module (SCI)
•
Two 16-bit, 2-channel timer interface modules (TIMA and TIMB)
•
Eight high current sink and source pins (PTA1/ATD1, PTA0/ATD0,
PTB6/TCH1B, PTB5/TCH0B, PTB4/TCH1A, PTB3/TCH0A,
PTB2/TCLKA, and PTB1/TxD)
•
Clock generator module (CGM)
•
Digitally filtered low-voltage inhibit (LVI), software selectable for
±5 percent or ±10 percent tolerance
•
10-bit, 4 to 7-channel analog-to-digital converter (ADC)
•
System protection features:
– Optional computer operating properly (COP) reset
– Low-voltage detection with optional reset
– Illegal opcode detection with optional reset
– Illegal address detection with optional reset
– Fault detection with optional PWM disabling
Technical Data
30
MC68HC908MR8 — Rev 4.1
General Description
Freescale Semiconductor
General Description
MCU Block Diagram
•
Available packages:
– 32-pin low-profile quad flat pack (LQFP)
– 28-pin dual in-line package (PDIP)
– 28-pin small outline package (SOIC)
•
Low-power design, fully static with stop and wait modes
•
Break (BRK) module allows single breakpoint setting during
in-circuit debugging
•
Master reset pin and power-on reset (POR)
Features of the CPU08 include:
•
Enhanced HC05 programming model
•
Extensive loop control functions
•
16 addressing modes (eight more than the M68HC05)
•
16-bit index register and stack pointer
•
Memory-to-memory data transfers
•
Fast 8 × 8 multiply instruction
•
Fast 16 ÷ 8 divide instruction
•
Binary-coded decimal (BCD) instructions
•
Optimization for controller applications
•
C language support
1.4 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908MR8.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
General Description
31
PTB6/TCH1B
PTB5/TCH0B
PTB4/TCH1A
PTB3/TCH0A
PTB2/TCLKA
PTB1/TxD
PTB0/RxD
PWM6
PWM5
PWM4
PWM3
PWM2
PWM1
PTC1/FAULT4
PTC0/FAULT1
DDRA
PTA
USER FLASH — 7680 BYTES
PTA6/ATD6
PTA5/ATD5
PTA4/ATD4
PTA3/ATD3
PTA2/ATD2
PTA1/ATD1
PTA0/ATD0
PTB
CONTROL AND STATUS REGISTERS — 112 BYTES
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
BREAK
MODULE
USER RAM — 256 BYTES
TIMER A AND TIMER B INTERFACE
MODULES
DDRB
ARITHMETIC/LOGIC
UNIT (ALU)
PULSE-WIDTH
MODULATOR
CPU
REGISTERS
MONITOR ROM — 313 BYTES
General Description
USER VECTOR SPACE — 46 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VREFH
SERIAL COMMUNICATIONS INTERFACE
MODULE
POWER-ON RESET
MODULE
Freescale Semiconductor
MC68HC908MR8 — Rev 4.1
ANALOG-TO-DIGITAL CONVERTER
MODULE
PULSE-WIDTH MODULATOR
MODULE
VDD
VDDA
VSSA
POWER
VSS
Figure 1-1. MCU Block Diagram
General Description
Technical Data
32
INTERNAL BUS
M68HC08 CPU
General Description
Pin Assignments
1.5 Pin Assignments
2
23
PTA0/ATD0
OSC1
3
22
PTB6/TCH1B
CGMXFC
4
21
IRQ
5
20
PTB5/TCH0B
VSS
PWM1
6
19
VDD
PWM2
7
18
PTB4/TCH1A
11
12
13
14
15
PTC0/FAULT1
** PTC1/FAULT4
PTB0/RxD
PTB1/TxD
1O
RST
VDDA
2
VSSA
3
4
OSC2
5
PTB2/TCLKA 16
10
PWM6
VREFH
OSC1
CGMXFC
IRQ
17 PTB3/TCH0A
PWM5
PWM4 9
PWM3 8
32-PIN QFP
*
PTA4/ATD4 **
27
24 PTA1/ATD1
OSC2
*
PTA5/ATD5 **
28
PTA3/ATD3
25 PTA2/ATD2
PTA6/ATD6 **
29
26
RST
VREFH
O
30
VSSA 1
31
32 VDDA
Figure 1-2 shows 32-pin QFP and 28-pin DIP/SOIC pin assignments.
*
28
27
26
PTA3/ATD3
PTA2/ATD2
25
PTA1/ATD1
PTA0/ATD0
24
PTB6/TCH1B
VSS
VDD
28-PIN
6 DIP/SOIC 23
22
7
*
PTB5/TCH0B
8
21
PWM1
9
PTB4/TCH1A
PWM2
PWM3
10
11
20
19
18
PTB2/TCLKA
PWM4
12
17
PTB1/TxD
PWM5
13
16
PTB0/RxD
PWM6
14
15
PTC0/FAULT1
PTB3/TCH0A
*
* High current pins
** These pins are not bonded on the 28-pin package.
Figure 1-2. QFP and DIP/SOIC Pin Assignments
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
General Description
33
General Description
1.5.1 Power Supply Pins (VDD and VSS)
VDD and VSS are the power supply and ground pins. The MCU operates
from a single power supply.
Fast signal transitions on MCU pins place high, short-duration current
demands on the power supply. To prevent noise problems, take special
care to provide power supply bypassing at the MCU as Figure 1-3
shows. Place the C1 bypass capacitor as close to the MCU as possible.
Use a high-frequency-response ceramic capacitor for C1. C2 is an
optional bulk current bypass capacitor for use in applications that require
the port pins to source high current levels.
MCU
VSS
VDD
C1
0.1 µF
+
C2
VDD
Note: Component values shown represent typical applications.
Figure 1-3. Power Supply Bypassing
1.5.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscillator
circuit. See Section 8. Clock Generator Module (CGM).
1.5.3 External Reset Pin (RST)
A logic 0 on the RST pin forces the MCU to a known startup state. RST
is bidirectional, allowing a reset of the entire system. It is driven low when
any internal reset source is asserted. See Section 7. System
Integration Module (SIM).
Technical Data
34
MC68HC908MR8 — Rev 4.1
General Description
Freescale Semiconductor
General Description
Pin Assignments
1.5.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. See Section 16. External
Interrupt (IRQ).
1.5.5 CGM Power Supply Pins (VDDA and VSSA)
VDDA and VSSA are the power supply pins for the analog portion of the
clock generator module (CGM) and the analog-to-digital converter
(ADC). Decoupling of these pins should be per the digital supply. See
Section 8. Clock Generator Module (CGM) and Section 18.
Analog-to-Digital Converter (ADC).
1.5.6 ADC Reference Voltage Input Pin (VREFH)
VREFH is the power supply input for setting the reference voltage. See
Section 18. Analog-to-Digital Converter (ADC).
1.5.7 External Filter Capacitor Pin (CGMXFC)
CGMXFC is an external filter capacitor connection for the CGM. See
Section 8. Clock Generator Module (CGM).
1.5.8 Port A Input/Output (I/O) Pins (PTA6/ATD6–PTA0/ATD0)
Port A is a 7-bit special function port, sharing all of its pins with the
analog-to-digital converter (ADC). On the 32-pin QFP package, all seven
bits (PTA6/ATD6–PTA0/ATD0) of the port are available. On the 28-pin
package, four bits (PTA3/ATD3–PTA0/ATD0) are available.
PTA3–PTA0 have high current source and sink capability. See
Section 14. Input/Output (I/O) Ports.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
General Description
35
General Description
1.5.9 Port B I/O Pins (PTB6/TCHB1–PTB0/RxD)
Port B is a 7-bit special function port, sharing five of its pins with the timer
interface modules (TIMA and TIMB) and two of its pins with the serial
communications interface (SCI). See Section 11. Timer Interface A
(TIMA), Section 12. Timer Interface B (TIMB), Section 14.
Input/Output (I/O) Ports, and Section 13. Serial Communications
Interface (SCI).
1.5.10 Port C I/O Pins (PTC1/FAULT1–PTC0/FAULT4)
Port C is a 2-bit special function port, sharing its pins with pulse-width
modulator fault inputs. See Section 9. Pulse-Width Modulator for
Motor Control (PWMMC) and Section 14. Input/Output (I/O) Ports.
1.5.11 PWM Pins (PWM6–PWM1)
PWM6–PWM1 are dedicated pins used for the outputs of the pulsewidth modulator module (PWMMC). See Section 9. Pulse-Width
Modulator for Motor Control (PWMMC).
Technical Data
36
MC68HC908MR8 — Rev 4.1
General Description
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 2. Memory Map
2.1 Contents
2.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
2.3
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . .38
2.4
Reserved Memory Locations. . . . . . . . . . . . . . . . . . . . . . . . .38
2.5
I/O Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39
2.6
Monitor ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .52
2.2 Introduction
The central processor unit (CPU08) can address 64 Kbytes of memory
space.
The memory map, shown in Figure 2-1, includes these features:
•
8 Kbytes of FLASH
•
256 bytes of RAM
•
313 bytes of monitor ROM
•
46 bytes of user-defined vectors
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Memory Map
37
Memory Map
2.3 Unimplemented Memory Locations
Some addresses are unimplemented. Accessing an unimplemented
address will cause an illegal address reset. In the memory map and in
the input/output (I/O) register summary, unimplemented addresses are
shaded.
Some I/O bits are read-only; the write function is unimplemented. Writing
to a read-only I/O bit has no effect on MCU operation. In register figures,
the write function of read-only bits is shaded. Similarly, some I/O bits are
write-only; the read function is unimplemented. Reading of write-only I/O
bits has no effect on microcontroller unit (MCU) operation. In register
figures, the read function of write-only bits is shaded.
2.4 Reserved Memory Locations
Some addresses are reserved. Writing to a reserved address can have
unpredictable effects on MCU operation. In the memory map and in the
I/O register summary, reserved addresses are marked with the word
reserved.
Some I/O bits are reserved. Writing to a reserved bit can have
unpredictable effects on MCU operation. In register figures, reserved
bits are marked with the letter R.
Technical Data
38
MC68HC908MR8 — Rev 4.1
Memory Map
Freescale Semiconductor
Memory Map
I/O Section
2.5 I/O Section
Addresses $0000–$005F, shown in Figure 2-2, contain most of the
control, status, and data registers. Additional I/O registers have these
addresses:
•
$FE00, system integration module (SIM) break status register
(SBSR)
•
$FE01, SIM reset status register (SRSR)
•
$FE03, SIM break flag control register (SBFCR)
•
$FE08, FLASH control register (FLCR)
•
$FF57, FLASH test control register (FLTCR)
•
$FE0C, break address register high (BRKH)
•
$FE0D, break flag control register low (BRKL)
•
$FE0E, break status and control register (BRKSCR)
•
$FE0F, low-voltage inhibit (LVI) status and control register
(LVISCR)
•
$FF7E, FLASH block protect register (FLBPR)
•
$FFFF, computer operating properly (COP) control register
(COPCTL)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Memory Map
39
Memory Map
MC68HC908MR8
$0000
↓
$005F
$0060
↓
$011F
$0120
↓
$EDFF
$EE00
↓
$FDFF
$FE00
$FE01
$FE02
$FE03
$FE04
$FE05
$FE06
$FE07
$FE07
$FE09
$FE0A
$FE0B
$FE0C
$FE0D
$FE0E
$FE0F
$FE10
↓
$FF48
$FF49
↓
$FF7D
$0000
↓
$005F
$0060
I/O REGISTERS — 96 BYTES
RAM — 256 BYTES
↓
UNIMPLEMENTED — 56,992 BYTES
$015F
$0160
↓
$DFFF
$E000
FLASH MEMORY — 7,680 BYTES
↓
SIM BREAK STATUS REGISTER (SBSR)
SIM RESET STATUS REGISTER (SRSR)
RESERVED
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
RESERVED
RESERVED
RESERVED
RESERVED
FLASH CONTROL REGISTER (FLCR)
UNIMPLEMENTED
RESERVED
UNIMPLEMENTED
BREAK ADDRESS REGISTER HIGH (BRKH)
BREAK ADDRESS REGISTER LOW (BRKL)
BREAK STATUS AND CONTROL REGISTER (BRKSCR)
LVI STATUS AND CONTROL REGISTER (LVISCR)
$FDFF
$FE00
$FE01
$FE02
$FE03
$FE04
$FE05
$FE06
$FE07
$FE08
$FE09
$FE0A
$FE0B
$FE0C
$FE0D
$FE0E
$FE0F
$FE10
MONITOR ROM — 313 BYTES
↓
UNIMPLEMENTED — 53 BYTES
$FF48
$FF49
↓
$FF7D
Figure 2-1. Memory Map
Technical Data
40
MC68HC908MR8 — Rev 4.1
Memory Map
Freescale Semiconductor
Memory Map
I/O Section
$FF7E
$FF7F
↓
$FFD1
$FFD2
↓
$FFFE
FLASH BLOCK PROTECT REGISTER (FLBPR)
$FF7E
$FF7F
↓
$FFD1
$FFD2
↓
$FFFE
UNIMPLEMENTED — 83 BYTES
VECTORS — 45 BYTES (46 including $FFFF)
Low byte of reset vector when read
COP Control Register (COPCTL)
$FFFF
$FFFF
Figure 2-1. Memory Map
Addr.
$0000
Register Name
Read
Port A Data Register
(PTA) Write:
See page 281.
Reset
Bit 7
6
5
4
3
2
1
Bit 0
U
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
U
PTC1
PTC0
Unaffected by reset
Read:
$0001
Port B Data Register
(PTB) Write:
See page 284.
Reset:
U
PTB6
PTB5
PTB4
PTB3
Unaffected by reset
Read:
$0002
Port C Data Register
(PTC) Write:
See page 287.
Reset:
U
U
U
U
Unaffected by reset
$0003
$0004
U
Unimplemented
Read:
Data Direction Register
A
Write:
(DDRA)
See page 282. Reset:
U = Unaffected
nate
X = Indetermi-
U
U
R
DDRA6 DDRA5
0
0
= Reserved
DDRA4
DDRA3
DDRA2
0
0
0
Bold
= Buffered
DDRA1 DDRA0
0
0
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 10)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Memory Map
41
Memory Map
Addr.
$0005
$0006
Register Name
Read:
Data Direction Register
B
Write:
(DDRB)
See page 284. Reset:
Read:
Data Direction Register
C
Write:
(DDRC)
See page 288. Reset:
Bit 7
U
U
6
5
DDRB6 DDRB5
0
0
4
3
2
DDRB4
DDRB3
DDRB2
0
0
0
1
Bit 0
DDRB1 DDRB0
0
0
DDRC1 DDRC0
U
U
U
$0007
U
U
U
0
0
PS2
PS1
PS0
Unimplemented
↓
$000D
$000E
$000F
$0010
$0011
Unimplemented
Read:
TIMA Status/Control
Register (TASC) Write:
See page 214.
Reset:
0
0
TRST
R
1
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
14
13
12
11
10
9
Bit 8
1
1
1
1
1
1
1
Bit 7
6
5
4
3
2
1
Bit 0
1
1
1
1
1
1
1
1
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MA
X
0
0
0
0
0
0
0
TOIE
TSTOP
0
TIMA Counter Register Read: Bit 15
High
Write:
R
(TACNTH)
See page 216. Reset:
0
TIMA Counter Register Read:
Low
Write:
(TACNTL)
See page 216. Reset:
0
0
TIMA Counter Modulo Read:
Bit 15
Register High
Write:
(TAMODH)
See page 217. Reset:
1
Read:
TIMA Counter Modulo
$0012 Register Low (TAMODL) Write:
See page 217.
Reset:
$0013
TOF
TIMA Channel 0 Sta- Read: CH0F
tus/Control Register
Write:
0
(TASC0)
See page 218. Reset:
0
U = Unaffected
nate
X = Indetermi-
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 10)
Technical Data
42
MC68HC908MR8 — Rev 4.1
Memory Map
Freescale Semiconductor
Memory Map
I/O Section
Addr.
$0014
$0015
$0016
$0017
$0018
Register Name
Bit 7
Read:
TIMA Channel 0 RegisBit 15
ter High (TACH0H) Write:
See page 222.
Reset:
Read:
TIMA Channel 0 Register Low (TACH0L) Write:
See page 218.
Reset:
Bit 7
5
4
3
2
1
Bit 0
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
6
5
4
3
Indeterminate after reset
TIMA Channel 1 Sta- Read: CH1F
tus/Control
Write:
0
Register (TASC1)
See page 222. Reset:
0
Read:
TIMA Channel 1 RegisBit 15
ter High (TACH1H) Write:
See page 222.
Reset:
Read:
TIMA Channel 1 Register Low (TACH1L) Write:
See page 222.
Reset:
6
Bit 7
0
CH1IE
R
MS1A
ELS1B
ELS1A
TOV1
CH1MA
X
0
0
0
0
0
0
0
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
6
5
4
3
Indeterminate after reset
$0019
Unimplemented
↓
$001E
$001F
Unimplemented
Read:
Configuration Register
EDGE
(CONFIG) Write:
See page 68.
Reset:
0
Read:
PWM Control Register 1
DISX
$0020
(PCTL1) Write:
See page 175.
Reset:
0
BOTNEG
TOPNEG
INDEP
LVIRST
0
0
0
1
DISY
PWMINT
PWMF
0
0
0
0
SEL12
SEL34
0
0
Read:
PWM Control Register 2
LDFQ1 LDFQ0
$0021
(PCTL2) Write:
See page 177.
Reset:
0
0
U = Unaffected
nate
X = Indetermi-
R
0
0
= Reserved
Bold
= Buffered
LVIPWR STOPE
1
0
COPD
0
0
LDOK
PWMEN
0
0
SEL56 PRSC1 PRSC0
0
0
0
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 10)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Memory Map
43
Memory Map
Addr.
$0022
Register Name
Bit 7
6
5
Read:
FMODE
Fault Control Register
FINT4
4
(FCR) Write:
See page 180.
Reset:
0
0
4
3
2
1
Bit 0
FINT1
FMODE
1
0
0
0
0
0
0
FFLAG
4
0
0
0
0
FPIN1
FFLAG
1
U
0
U
0
U
0
U
0
Read:
Fault Acknowledge Reg$0024
ister (FTACK) Write:
See page 182.
Reset:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Read:
PWM Output Control
(PWMOUT) Write:
See page 159.
Reset:
0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
0
0
0
0
0
0
0
Read:
PWM Counter Register
High (PCNTH) Write:
See page 172.
Reset:
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
Read:
PWM Counter Register
Low (PCNTL) Write:
See page 172.
Reset:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
X
X
X
X
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Read: FPIN4
$0023
$0025
$0026
$0027
Fault Status Register
(FSR)
Write:
See page 181.
Reset:
Read:
PWM Counter Modulo
$0028 Register High (PMODH) Write:
See page 173.
Reset:
$0029
$002A
Read:
PWM Counter Modulo
Register Low (PMODL) Write:
See page 173.
Reset:
FTACK
4
Read:
PWM 1 Value Register
Bit 15
High (PVAL1H) Write:
See page 174.
Reset:
0
U = Unaffected
nate
X = Indetermi-
R
FTACK
1
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 10)
Technical Data
44
MC68HC908MR8 — Rev 4.1
Memory Map
Freescale Semiconductor
Memory Map
I/O Section
Addr.
$002B
$002C
$002D
$002E
$002F
$0030
$0031
$0032
$0033
$0034
Register Name
Read:
PWM 1 Value Register
Low (PVAL1L) Write:
See page 174.
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Read:
PWM 2 Value Register
Bit 15
High (PVAL2H) Write:
See page 174.
Reset:
0
Read:
PWM 2 Value Register
Low (PVAL2L) Write:
See page 174.
Reset:
Read:
PWM 3 Value Register
Bit 15
High (PVAL3H) Write:
See page 174.
Reset:
0
Read:
PWM 3 Value Register
Low (PVAL3L) Write:
See page 174.
Reset:
Read:
PWM 4 Value Register
Bit 15
High (PVAL4H) Write:
See page 174.
Reset:
0
Read:
PWM 4 Value Register
Low (PVAL4L) Write:
See page 174.
Reset:
Read:
PWM 5 Value Register
Bit 15
High (PMVAL5H) Write:
See page 174.
Reset:
0
Read:
PWM 5 Value Register
Low (PVAL5L) Write:
See page 174.
Reset:
Read:
PWM 6 Value Register
Bit 15
High (PVAL6H) Write:
See page 174.
Reset:
0
U = Unaffected
nate
X = Indetermi-
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 10)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Memory Map
45
Memory Map
Addr.
$0035
$0036
$0037
$0038
$0039
$003A
$003B
$003C
$003D
Register Name
Read:
PWM 6 Value Register
Low (PMVAL6L) Write:
See page 174.
Reset:
Read:
Dead-Time Write-Once
Register (DEADTM) Write:
See page 179.
Reset:
PWM Disable Mapping Read:
Write-Once Register
Write:
(DISMAP)
See page 179. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
0
R
R
ORIE
NEIE
FEIE
PEIE
U
0
0
0
0
0
0
TC
SCRF
IDLE
OR
NF
FE
PE
R
R
R
R
R
R
R
1
0
0
0
0
0
0
0
0
0
0
0
0
BKF
RPF
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
SCR2
SCR1
SCR0
0
0
0
Read: LOOP
SCI Control Register 1
S
(SCC1) Write:
See page 264.
Reset:
0
Read:
SCI Control Register 2
SCTIE
(SCC2) Write:
See page 267.
Reset:
0
Read:
SCI Control Register 3
(SCC3) Write:
See page 270.
Reset:
R8
R
U
Read: SCTE
SCI Status Register 1
(SCS1) Write:
R
See page 271.
Reset:
1
Read:
SCI Status Register 2
(SCS2) Write:
See page 275.
Reset:
Read:
SCI Data Register
(SCDR) Write:
See page 276.
Reset:
T8
Unaffected by reset
Read:
SCI Baud Rate Register
$003E
(SCBR) Write:
See page 276.
Reset:
0
0
R
R
0
0
U = Unaffected
nate
R
X = Indetermi-
SCP1
SCP0
0
0
= Reserved
Bold
0
R
0
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 6 of 10)
Technical Data
46
MC68HC908MR8 — Rev 4.1
Memory Map
Freescale Semiconductor
Memory Map
I/O Section
Addr.
Register Name
IRQ Status/Control Reg- Read:
ister
$003F
Write:
(ISCR)
See page 303. Reset:
Bit 7
6
5
4
0
0
0
0
R
R
R
R
0
0
0
0
0
0
AIEN
ADCO
ADCH4
ADCH3
ADCH2
0
0
1
1
1
1
1
0
0
0
0
0
0
AD9
AD8
R
R
R
R
R
R
R
R
Read:
ADC Status and Control
COCO
$0040
Register (ADSCR) Write:
See page 319.
Reset:
0
Read:
ADC Data Register High
$0041
(ADRH) Write:
See page 322.
Reset:
Read:
ADC Data Register Low
$0042
(ADRL) Write:
See page 323.
Reset:
$0043
3
IRQF
2
1
0
Bit 0
IMASK1 MODE1
ACK1
0
0
ADCH1 ADCH0
Unaffected by reset
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
R
R
R
R
R
R
R
R
Unaffected by reset
Read:
ADC Clock Register
ADIV2
(ADCLK) Write:
See page 324.
Reset:
0
0
ADIV1
ADIV0
ADICLK
MODE1
MODE0
0
0
0
0
0
1
0
0
PS2
PS1
PS0
$0044
R
Unimplemented
↓
$0050
$0051
$0052
$0053
$0054
Unimplemented
Read:
TIMB Status/Control
Register (TBSC) Write:
See page 238.
Reset:
TOF
0
0
TRST
R
1
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
TOIE
TSTOP
0
TIMB Counter Register Read: Bit 15
High
Write:
R
(TBCNTH)
See page 240. Reset:
0
TIMB Counter Register Read;
Low
Write:
(TBCNTL)
See page 240. Reset:
0
0
TIMB Counter Modulo Read:
Bit 15
Register High (TBWrite:
MODH)
See page 241. Reset:
1
U = Unaffected
nate
X = Indetermi-
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 7 of 10)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Memory Map
47
Memory Map
Addr.
Register Name
Read:
TIMB Counter Modulo
$0055 Register Low (TBMODL) Write:
See page 241.
Reset:
$0056
$0057
$0058
$0059
$005A
$005B
$005C
$005D
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MA
X
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
TIMB Channel 0 Sta- Read: CH0F
tus/Control Register
Write:
0
(TBSC0)
See page 242. Reset:
0
Read:
TIMB Channel 0 RegisBit 15
ter High (TBCH0H) Write:
See page 246.
Reset:
Read:
TIMB Channel 0 Register Low (TBCH0L) Write:
See page 246.
Reset:
Bit 7
Bit 6
Read:
TIMB Channel 1 RegisBit 15
ter High (TBCH1H) Write:
See page 246.
Reset:
Bit 7
Bit 4
Bit 3
R
MS1A
ELS1B
ELS1A
TOV1
CH1MA
X
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
1
1
1
1
R
R
R
R
1
1
1
1
0
0
0
0
R
R
R
R
Indeterminate after reset
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
PLLF
Read:
PLL Bandwidth Control
AUTO
Register (PBWC) Write:
See page 129.
Reset:
0
LOCK
PLL Programming Reg- Read:
MUL7
ister
$005E
Write:
(PPG)
See page 131. Reset:
0
X = Indetermi-
0
CH1IE
Read:
PLL Control Register
PLLIE
(PCTL) Write:
See page 126.
Reset:
0
U = Unaffected
nate
Bit 5
Indeterminate after reset
TIMB Channel 1 Sta- Read: CH1F
tus/Control Register
Write:
0
(TBSC1)
See page 242. Reset:
0
Read:
TIMB Channel 1 Register Low (TBCH1L) Write:
See page 246.
Reset:
Indeterminate after reset
R
PLLON
BCS
1
0
ACQ
XLD
0
0
0
0
0
0
0
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
1
1
0
0
1
1
0
R
0
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 8 of 10)
Technical Data
48
MC68HC908MR8 — Rev 4.1
Memory Map
Freescale Semiconductor
Memory Map
I/O Section
Addr.
Register Name
$005F
Reserved
SIM Break Status Regis- Read:
ter
$FE00
Write:
(SBSR)
See page 336. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
R
R
R
R
R
R
R
R
R
R
R
R
R
R
SBSW
Note(1)
R
0
Note 1. Writing a logic 0 clears SBSW.
SIM Reset Status Regis- Read:
ter
$FE01
Write:
(SRSR)
See page 108. Reset:
$FE03
POR
PIN
COP
ILOP
ILAD
0
LVI
0
R
R
R
R
R
R
R
R
1
0
0
0
0
0
0
0
R
R
R
R
R
R
R
HVEN
MASS
ERASE
PGM
Read:
SIM Break Flag Control
BCFE
Register (SBFCR) Write:
See page 109.
Reset:
0
Read:
FLASH Control Register
$FE08
(FLCR) Write:
See page 57.
Reset:
0
0
0
0
0
0
0
0
0
0
0
0
$FE0A
R
R
R
R
R
R
R
R
Reserved
$FE0B
Unimplemented
Read:
Break Address Register
Bit 15
$FE0C
High (BRKH) Write:
See page 334.
Reset:
0
Read:
Break Address Register
$FE0D
Low (BRKL) Write:
See page 334.
Reset:
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Read:
Break Status and ConBRKE
$FE0E trol Register (BRKSCR) Write:
See page 333.
Reset:
0
U = Unaffected
nate
X = Indetermi-
R
BRKA
0
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 9 of 10)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Memory Map
49
Memory Map
Addr.
$FE0F
$FF7E
$FFFF
Register Name
Read:
LVI Status and Control
Register (LVISCR)
Write:
See page 308.
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
LVIOUT
0
0
0
0
0
0
R
R
TRPSEL
R
R
R
R
R
0
0
0
0
0
0
0
0
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
Read:
FLASH Block Protect
BPR7
Register (FLBPR) Write:
See page 63.
Reset:
Unaffected by reset
Read:
COP Control Register
(COPCTL) Write:
See page 294.
Reset:
U = Unaffected
nate
X = Indetermi-
Low byte of reset vector
Clear COP counter
Unaffected by reset
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers (Sheet 10 of 10)
Technical Data
50
MC68HC908MR8 — Rev 4.1
Memory Map
Freescale Semiconductor
Memory Map
I/O Section
Table 2-1 is a list of vector locations.
Table 2-1. Vector Addresses
Priority
Low
Address
$FFD2
SCI transmit vector (high)
$FFD3
SCI transmit vector (low)
$FFD4
SCI receive vector (high)
$FFD5
SCI receive vector (low)
$FFD6
SCI error vector (high)
$FFD7
SCI error vector (low)
$FFD8
Reserved
$FFD9
Reserved
$FFDA
Reserved
$FFDB
Reserved
$FFDC
A/D vector (high)
$FFDD
A/D vector (low)
$FFDE
TIMB overflow vector (high)
$FFDF
TIMB overflow vector (low)
$FFE0
TIMB channel 1 vector (high)
$FFE1
TIMB channel 1 vector (low)
$FFE2
TIMB channel 0 vector (high)
$FFE3
TIMB channel 0 vector (low)
$FFE4
TIMA overflow vector (high)
$FFE5
TIMA overflow vector (low)
$FFE6
Reserved
$FFE7
Reserved
$FFE8
Reserved
$FFE9
Reserved
$FFEA
TIMA channel 1 vector (high)
$FFEB
TIMA channel 1 vector (low)
$FFEC
TIMA channel 0 vector (high)
$FFED
TIMA channel 0 vector (low)
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Memory Map
Table 2-1. Vector Addresses (Continued)
High
Priority
Address
Vector
$FFEE
PWMMC vector (high)
$FFEF
PWMMC vector (low)
$FFF0
FAULT 4 (high)
$FFF1
FAULT 4 (low)
$FFF2
Reserved
$FFF3
Reserved
$FFF4
Reserved
$FFF5
Reserved
$FFF6
FAULT 1 (high)
$FFF7
FAULT 1 (low)
$FFF8
PLL vector (high)
$FFF9
PLL vector (low)
$FFFA
IRQ vector (high)
$FFFB
IRQ vector (low)
$FFFC
SWI vector (high)
$FFFD
SWI vector (low)
$FFFE
Reset vector (high)
$FFFF
Reset vector (low)
2.6 Monitor ROM
313 bytes at addresses $FE10–$FF48 are reserved ROM addresses
that contain the instructions for the monitor functions.
See Section 10. Monitor ROM (MON).
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Technical Data — MC68HC908MR8
Section 3. Random-Access Memory (RAM)
3.1 Contents
3.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
3.3
Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
3.2 Introduction
This section describes the 256 bytes of random-access memory (RAM)
on the MC68HC908MR8.
3.3 Functional Description
Addresses $0060–$015F are RAM locations. The location of the stack
RAM is programmable. The 16-bit stack pointer allows the stack to be
anywhere in the 64-Kbyte memory space.
NOTE:
For correct operation, the stack pointer must point only to RAM
locations.
Within page zero are 160 bytes of RAM. Because the location of the
stack RAM is programmable, all page zero RAM locations can be used
for input/output (I/O) control and user data or code. When the stack
pointer is moved from its reset location at $00FF, direct addressing
mode instructions can access efficiently all page zero RAM locations.
Page zero RAM, therefore, provides ideal locations for frequently
accessed global variables.
Before processing an interrupt, the CPU uses five bytes of the stack to
save the contents of the central processor unit (CPU) registers.
NOTE:
For M6805 compatibility, the H register is not stacked.
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Random-Access Memory (RAM)
During a subroutine call, the CPU uses two bytes of the stack to store
the return address. The stack pointer decrements during pushes and
increments during pulls.
NOTE:
Be careful when using nested subroutines. The CPU may overwrite data
in the RAM during a subroutine or during the interrupt stacking
operation.
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Section 4. FLASH Memory
4.1 Contents
4.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .55
4.2.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . .56
4.2.2
FLASH Control Register . . . . . . . . . . . . . . . . . . . . . . . . . .57
4.2.3
FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . .58
4.2.4
FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . .59
4.2.5
FLASH Program/Read Operation . . . . . . . . . . . . . . . . . . .59
4.3
FLASH Programming Algorithm . . . . . . . . . . . . . . . . . . . . . .60
4.3.1
FLASH Block Protection . . . . . . . . . . . . . . . . . . . . . . . . . .62
4.3.2
FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . .63
4.3.3
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .64
4.2 Introduction
This section describes the operation of the MC68HC908MR8 embedded
FLASH memory. This memory can be read, programmed, and erased
from a single external supply. The program and erase operations are
enabled through the use of an internal charge pump.
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FLASH Memory
4.2.1 Functional Description
The FLASH memory physically consists of an array of 7680 bytes with
an additional 46 bytes of user vectors and one byte of block protection.
An erased bit reads as a logic 1 and a programmed bit reads as a logic 0.
Program and erase operations are facilitated through control bits in a
memory mapped register. Details for these operations appear later in
this section.
Memory in the FLASH array is organized into two rows per page base.
For the 8-K word by 8-bit embedded FLASH memory, the page size is
64 bytes per page. The minimum erase page size is 64 bytes. Program
and erase operations are performed through control bits in the FLASH
control register (FLCR).
The address ranges for the user memory, control register, and vectors
are:
•
$E000–$FDFF, user memory
•
$FF7E, block protect register (FLBPR)
•
$FE08, FLASH control register (FLCR)
•
$FFD2–$FFFF, locations reserved for user-defined interrupt and
reset vectors
Programming tools are available from Freescale. Contact a local
Freescale representative for more information.
NOTE:
A security feature1 prevents viewing of the FLASH contents.
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
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Introduction
4.2.2 FLASH Control Register
The FLASH control register (FLCR) controls the FLASH program, erase,
and read operations.
Ad- $FE08
dress:
Read:
Bit 7
6
5
4
0
0
0
0
0
0
0
0
Write:
Reset:
3
2
1
Bit 0
HVEN
MASS
ERASE
PGM
0
0
0
0
= Unimplemented
Figure 4-1. FLASH Control Register (FLCR)
HVEN — High-Voltage Enable Bit
This read/write bit enables the charge pump to drive high voltages for
program and erase operations in the array. HVEN can be set only if
either PGM = 1 or ERASE = 1 and the proper sequence for
program/margin read or erase is followed.
1 = High voltage enabled to array and charge pump on
0 = High voltage disabled to array and charge pump off
MASS — Mass Erase Control Bit
This read/write bit configures the memory for mass erase operation.
1 = Mass erase operation selected
0 = Mass erase operation unselected
ERASE — Erase Control Bit
This read/write bit configures the memory for erase operation.
ERASE is interlocked with the PGM bit such that both bits cannot be
set at the same time.
1 = Erase operation selected
0 = Erase operation unselected
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FLASH Memory
PGM — Program Control Bit
This read/write bit configures the memory for program operation.
PGM is interlocked with the ERASE bit such that both bits cannot be
set at the same time.
1 = Program operation selected
0 = Program operation unselected
4.2.3 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (64 bytes) of FLASH
memory to read as logic 1:
1. Set the ERASE bit and clear the MASS bit in the FLASH control
register.
2. Read the FLASH block protect register.
3. Write to any FLASH address with any data within the page
address range desired.
4. Wait for a time, tNVS (minimum of 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tErase (minimum of 1 ms).
7. Clear the ERASE bit.
8. Wait for a time, tNVH (minimum of 5 µs).
9. Clear the HVEN bit.
10. After a time, tRCV (typically 1 µs), the memory can be accessed in
read mode again.
NOTE:
While these operations must be performed in the order shown, other
unrelated operations may occur between the steps. Do not exceed tNVH
maximum. See 21.7 Memory Characteristics.
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Introduction
4.2.4 FLASH Mass Erase Operation
Use this step-by-step procedure to erase the entire FLASH memory to
read as logic 1:
1. Set the ERASE bit and the MASS bit in the FLASH control register.
2. Read the block protect register.
3. Write to any FLASH address with any data within the page
address range desired.
4. Wait for a time, tNVS (minimum of 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tErase (minimum of 4 ms).
7. Clear the ERASE bit.
8. Wait for a time, tNVHL (minimum of 100 µs).
9. Clear the HVEN bit.
10. After a time, tRCV (typically 1 µs), the memory can be accessed in
read mode again.
NOTE:
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 tNVH maximum. See 21.7
Memory Characteristics.
4.2.5 FLASH Program/Read Operation
Programming of the FLASH memory is done on a row basis. A row
consists of 32 consecutive bytes starting from address $XX00, $XX20,
$XX40, and $XX80.
Use this step-by-step procedure to program a row of FLASH memory:
1. Set the PGM bit in the FLASH control register. This configures the
memory for program operation and enables the latching of
address and data programming.
2. Read the block protect register.
3. Write to any FLASH address with any data within the page
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FLASH Memory
address range desired.
4. Wait for a time, tNVS (minimum of 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tPGS (minimum of 5 µs).
7. Write data to the FLASH address to be programmed.
8. Wait for a time, tPROG (minimum of 30 µs).
9. Repeat step 7 and step 8 until all the bytes within the row are
programmed.
10. Clear the PGM bit.
11. Wait for a time, tNVH (minimum of 5 µs).
12. Clear the HVEN bit.
13. After a time, tRCV (typically 1 µs), the memory can be accessed in
read mode again.
NOTE:
The time between each FLASH address change, or the time between
the last FLASH address programmed to clear the PGM bit, must not
exceed the maximum programming time, tPROG.
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 tPROG maximum. See 21.7
Memory Characteristics.
4.3 FLASH Programming Algorithm
Refer to Figure 4-2 for an algorithm for programming a row (32 bytes) of
FLASH memory.
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FLASH Programming Algorithm
Note:
This page program algorithm assumes the rows to be
programmed are initially erased.
PROGRAM FLASH
SET PGM BIT
READ FLASH BLOCK
PROTECT REGISTER
WRITE ANY DATA TO
SELECTED PAGE
WAIT FOR A TIME, tNVS
SET HVEN BIT
WAIT FOR A TIME, tPGS
WRITE DATA TO THE FLASH
ADDRESS TO BE PROGRAMMED
WAIT FOR A TIME, tPROG
NO
COMPLETED
PROGRAMMING
THIS ROW?
YES
CLEAR PGM BIT
WAIT FOR A TIME, tPROG
CLEAR HVEN BIT
Note:
The time between each address change, or the time
between the last FLASH address programmed to clear
the PGM bit, must not exceed the maximum
programming time, tPROG.
WAIT FOR A TIME, TPROG
PROGRAMMING OPERATION
COMPLETE
Figure 4-2. FLASH Programming Algorithm
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FLASH Memory
4.3.1 FLASH Block Protection
Due to the ability of the on-board charge pump to erase and program the
FLASH memory in the target application, provision is made for protecting
blocks of memory from unintentional erase or program operations due to
system malfunction. This protection is done by using a FLASH protection
register (FLBPR).
The FLBPR determines the range of the FLASH memory which is to be
protected. The range of the protected area starts from a location defined
by FLBPR and ends at the bottom of the FLASH memory ($FFFF). When
the memory is protected, the HVEN bit cannot be set in either erase or
program operations.
NOTE:
In performing a program erase operation, the FLASH block protect
register must be read after setting the PGM or ERASE bit and before
asserting the HVEN bit.
When the block protect register is erased (all 1s), the entire memory is
accessible for program and erase. When bits within the register are
programmed (set to 0), they lock blocks of memory address ranges as
shown in 4.3.2 FLASH Block Protect Register. Once the block protect
register is programmed with value other than $FF, any erase or program
of the block protect register or the protected pages will be prohibited. The
block protect register itself can be erased or programmed only with an
external voltage VHI present on the IRQ pin. The presence of VHI on the
IRQ pin also allows entry into monitor mode out of reset. Therefore, the
ability to change the block protect register is voltage dependent and can
occur in either user or monitor modes.
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FLASH Programming Algorithm
4.3.2 FLASH Block Protect Register
The block protect register (FLBPR) is implemented as a byte within the
FLASH memory, and therefore can only be written during a
programming sequence of the FLASH memory. The value in this register
determines the starting location of the protected range within the FLASH
memory.
Ad- $FF7E
dress:
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
U
U
U
U
U
U
U
U
U= Unaffected by reset. Initial value from factory is 1.
Write to this register by a programming sequence to the FLASH memory.
Figure 4-3. FLASH Block Protect Register (FLBPR)
BPR[7:0] — Block Protect Register Bits
These eight bits represent bits [13:6] of a 16-bit memory address.
Bits[15:14] are logical 1s and bits [5:0] are logic 0s.
The resultant 16-bit address is used for specifying the start address
of the FLASH memory for block protection. The FLASH is protected
from this start address to the end of FLASH memory at $FFFF. With
this mechanism, the protect start address can be $XX00, $XX40,
$XX80, and $XXC0 (64-byte page boundaries) within the FLASH
memory.
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FLASH Memory
16-BIT MEMORY ADDRESS
START ADDRESS OF
FLASH 1
BLOCK PROTECT
1
FLBPR VALUE
0
0
0
0
0
0
Figure 4-4. FLASH Block Protect Address
$80 = The entire FLASH memory is protected.
$81 = Protected range: $E040–$FFFF
$82 = Protected range: $E080–$FFFF
↓
↓
↓
$FE = Protected range: $FF80–$FFFF
$FF = Entire FLASH memory is not protected.
If all bits are erased, then all of the memory is available for erase and
program. The presence of a voltage VHI on the IRQ pin will bypass the
block protection so that all of the memory, including the block protect
register, is open for program and erase operations.
4.3.3 Low-Power Modes
The WAIT and STOP instructions will place the MCU in a low powerconsumption standby mode.
4.3.3.1 Wait Mode
Putting the MCU into wait mode while the FLASH is in read mode does
not affect the operation of the FLASH memory directly, but there will not
be any memory activity since the CPU is inactive.
The WAIT instruction should never be executed while performing a
program or erase operation on the FLASH. When the MCU is put into
wait mode, the charge pump for the FLASH is disabled so that either a
program or erase operation will not continue. If the memory is in either
program mode (PGM = 1, HVEN = 1) or erase mode (ERASE = 1,
HVEN = 1), then it will remain in that mode during wait.
NOTE:
Exiting from wait must now be done with a reset rather than an interrupt
because if exiting wait with an interrupt, the memory will not be in read
mode and the interrupt vector cannot be read from the memory.
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FLASH Programming Algorithm
4.3.3.2 Stop Mode
If the FLASH is in read mode, when the MCU is put into stop mode, the
FLASH will be put into low-power standby mode.
The STOP instruction should never be executed while performing a
program or erase operation on the FLASH. Otherwise the operation will
be discontinued and the FLASH will be in standby mode.
NOTE:
Standby mode is the power-saving mode of the FLASH module, in which
all internal control signals to the FLASH are inactive and the current
consumption of the FLASH is minimum.
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FLASH Memory
Technical Data
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Technical Data — MC68HC908MR8
Section 5. Configuration Register (CONFIG)
5.1 Contents
5.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .67
5.3
CONFIG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
5.4
CONFIG Bits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .68
5.2 Introduction
This section describes the configuration register (CONFIG).
The CONFIG registers contain bits that configure these options:
•
Resets caused by the low-voltage inhibit (LVI) module
•
Power to the LVI module
•
Computer operating properly (COP) module
•
Top-side pulse-width modulator (PWM) polarity
•
Bottom-side PWM polarity
•
Edge-aligned versus center-aligned PWMs
•
Six independent PWMs versus three complementary PWM pairs
•
STOP instruction enable
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Configuration Register (CONFIG)
5.3 CONFIG
The configuration register (CONFIG) is a write-once register. Once the
register is written, further writes will have no effect until a reset occurs.
5.4 CONFIG Bits
NOTE:
If the LVI module and the LVI reset signal are enabled, a reset occurs
when VDD falls to a voltage, LVITRIPF, and remains at or below that level
for at least nine consecutive central processor unit (CPU) cycles. Once
an LVI reset occurs, the microcontroller unit (MCU) remains in reset until
VDD rises to a voltage, LVITRIPR.
Address: $001F
Read:
Write:
Bit 7
6
5
4
3
2
1
Bit 0
EDGE
BOTNEG
TOPNEG
INDEP
LVIRST
LVIPWR
STOPE
COPD
0
0
0
0
1
1
0
0
Reset
states:
CONFIG
Figure 5-1. CONFIG Register
EDGE — Edge-Align Enable Bit
EDGE determines if the motor control PWM will operate in
edge-aligned mode or center-aligned mode. See Section 9.
Pulse-Width Modulator for Motor Control (PWMMC).
1 = Edge-aligned mode enabled
0 = Center-aligned mode enabled
BOTNEG — Bottom-Side PWM Polarity Bit
BOTNEG determines if the bottom-side PWMs will have positive or
negative polarity. See Section 9. Pulse-Width Modulator for Motor
Control (PWMMC).
1 = Negative polarity
0 = Positive polarity
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Configuration Register (CONFIG)
CONFIG Bits
TOPNEG — Top-Side PWM Polarity Bit
TOPNEG determines if the top-side PWMs will have positive or
negative polarity. See Section 9. Pulse-Width Modulator for Motor
Control (PWMMC).
1 = Negative polarity
0 = Positive polarity
INDEP — Independent Mode Enable Bit
INDEP determines if the motor control PWMs will be six independent
PWMs or three complementary PWM pairs. See Section 9.
Pulse-Width Modulator for Motor Control (PWMMC).
1 = Six independent PWMs
0 = Three complementary PWM pairs
LVIPWR — LVI Power Enable Bit
LVIPWR enables the LVI module. See Section 17. Low-Voltage
Inhibit (LVI).
1 = LVI module power enabled
0 = LVI module power disabled
LVIRST — LVI Reset Enable Bit
LVIRST enables the reset signal from the LVI module. See
Section 17. Low-Voltage Inhibit (LVI).
1 = LVI module resets enabled
0 = LVI module resets disabled
STOPE — STOP Enable Bit
STOPE enables the STOP instruction. See Section 6. Central
Processor Unit (CPU).
1 = STOP instruction is enabled.
0 = STOP instruction is disabled and executes as an illegal
instruction.
COPD — COP Disable Bit
COPD disables the COP module. See Section 15. Computer
Operating Properly (COP).
1 = COP module disabled
0 = COP module enabled
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Configuration Register (CONFIG)
Technical Data
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Technical Data — MC68HC908MR8
Section 6. Central Processor Unit (CPU)
6.1 Contents
6.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
6.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
6.4
CPU Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
6.4.1
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
6.4.2
Index Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
6.4.3
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
6.4.4
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .75
6.4.5
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . .76
6.5
Arithmetic/Logic Unit (ALU). . . . . . . . . . . . . . . . . . . . . . . . . .78
6.6
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
6.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
6.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .78
6.7
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
6.8
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .86
6.2 Introduction
This section describes the central processor unit (CPU08, version A).
The M68HC08 CPU is an enhanced and fully object-code-compatible
version of the M68HC05 CPU. The CPU08 Reference Manual,
Freescale document number CPU08RM/AD, contains a description of
the CPU instruction set, addressing modes, and architecture.
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Central Processor Unit (CPU)
6.3 Features
Features of the CPU include:
•
Fully upward, object-code compatibility with M68HC05 family
•
16-bit stack pointer with stack manipulation instructions
•
16-bit index register with X-register manipulation instructions
•
8-MHz CPU internal bus frequency
•
64-Kbyte program/data memory space
•
Sixteen addressing modes
•
Memory-to-memory data moves without using the accumulator
•
Fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions
•
Enhanced binary-coded decimal (BCD) data handling
•
Modular architecture with expandable internal bus definition for
extension of addressing range beyond 64 Kbytes
•
Low-power stop and wait modes
6.4 CPU Registers
Figure 6-1 shows the five CPU registers. CPU registers are not part of
the memory map.
0
7
ACCUMULATOR (A)
0
15
H
X
15
INDEX REGISTER (H:X)
0
STACK POINTER (SP)
15
0
PROGRAM COUNTER (PC)
7
0
V 1 1 H I N Z C
CONDITION CODE REGISTER (CCR)
CARRY/BORROW FLAG
ZERO FLAG
NEGATIVE FLAG
INTERRUPT MASK
HALF-CARRY FLAG
TWO’S COMPLEMENT OVERFLOW FLAG
Figure 6-1. CPU Registers
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Central Processor Unit (CPU)
CPU Registers
6.4.1 Accumulator
The accumulator is a general-purpose 8-bit register. The CPU uses the
accumulator to hold operands and the results of arithmetic/logic
operations.
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Unaffected by reset
Figure 6-2. Accumulator (A)
6.4.2 Index Register
The 16-bit index register allows indexed addressing of a 64-Kbyte
memory space. H is the upper byte of the index register, and X is the
lower byte. H:X is the concatenated 16-bit index register.
In the indexed addressing modes, the CPU uses the contents of the
index register to determine the conditional address of the operand.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
0
0
0
0
0
0
0
0
X
X
X
X
X
X
X
X
Read:
Write:
Reset:
X = Indeterminate
Figure 6-3. Index Register (H:X)
The index register can serve also as a temporary data storage location.
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Central Processor Unit (CPU)
73
Central Processor Unit (CPU)
6.4.3 Stack Pointer
The stack pointer (SP) is a 16-bit register that contains the address of
the next location on the stack. During a reset, the stack pointer is preset
to $00FF. The reset stack pointer (RSP) instruction sets the least
significant byte to $FF and does not affect the most significant byte. The
stack pointer decrements as data is pushed onto the stack and
increments as data is pulled from the stack.
In the stack pointer 8-bit offset and 16-bit offset addressing modes, the
stack pointer can function as an index register to access data on the
stack. The CPU uses the contents of the stack pointer to determine the
conditional address of the operand.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Read:
Write:
Reset:
Figure 6-4. Stack Pointer (SP)
NOTE:
The location of the stack is arbitrary and may be relocated anywhere in
RAM. Moving the SP out of page zero ($0000 to $00FF) frees direct
address (page zero) space. For correct operation, the stack pointer must
point only to RAM locations.
Technical Data
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Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
CPU Registers
6.4.4 Program Counter
The program counter (PC) is a 16-bit register that contains the address
of the next instruction or operand to be fetched.
Normally, the program counter automatically increments to the next
sequential memory location every time an instruction or operand is
fetched. Jump, branch, and interrupt operations load the program
counter with an address other than that of the next sequential location.
During reset, the program counter is loaded with the reset vector
address located at $FFFE and $FFFF. The vector address is the
address of the first instruction to be executed after exiting the reset state.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
Read:
Write:
Reset:
Loaded with vector from $FFFE and $FFFF
Figure 6-5. Program Counter (PC)
MC68HC908MR8 — Rev 4.1
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Technical Data
Central Processor Unit (CPU)
75
Central Processor Unit (CPU)
6.4.5 Condition Code Register
The 8-bit condition code register (CCR) contains the interrupt mask and
five flags that indicate the results of the instruction just executed. Bit 6
and bit 5 are set permanently to logic 1. The functions of the condition
code register are described here.
Read
:
Bit 7
6
5
4
3
2
1
Bit 0
V
1
1
H
I
N
Z
C
X
1
1
X
1
X
X
X
Write:
Reset:
X = Indeterminate
Figure 6-6. Condition Code Register (CCR)
V — Overflow Flag
The CPU sets the overflow flag when a two's complement overflow
occurs. The signed branch instructions BGT, BGE, BLE, and BLT use
the overflow flag.
1 = Overflow
0 = No overflow
H — Half-Carry Flag
The CPU sets the half-carry flag when a carry occurs between
accumulator bits 3 and 4 during an add without carry (ADD) or add
with carry (ADC) operation. The half-carry flag is required for
binary-coded decimal (BCD) arithmetic operations. The DAA
instruction uses the states of the H and C flags to determine the
appropriate correction factor.
1 = Carry between bits 3 and 4
0 = No carry between bits 3 and 4
I — Interrupt Mask
When the interrupt mask is set, all maskable CPU interrupts are
disabled. CPU interrupts are enabled when the interrupt mask is
cleared. When a CPU interrupt occurs, the interrupt mask is set
automatically after the CPU registers are saved on the stack, but
before the interrupt vector is fetched.
Technical Data
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Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
CPU Registers
1 = Interrupts disabled
0 = Interrupts enabled
NOTE:
To maintain M6805 compatibility, the upper byte of the index register (H)
is not stacked automatically. If the interrupt service routine modifies H,
then the user must stack and unstack H using the PSHH and PULH
instructions.
After the I bit is cleared, the highest-priority interrupt request is
serviced first.
A return-from-interrupt (RTI) instruction pulls the CPU registers from
the stack and restores the interrupt mask from the stack. After any
reset, the interrupt mask is set and can be cleared only by the clear
interrupt mask software instruction (CLI).
N — Negative Flag
The CPU sets the negative flag when an arithmetic operation, logic
operation, or data manipulation produces a negative result, setting
bit 7 of the result.
1 = Negative result
0 = Non-negative result
Z — Zero Flag
The CPU sets the zero flag when an arithmetic operation, logic
operation, or data manipulation produces a result of $00.
1 = Zero result
0 = Non-zero result
C — Carry/Borrow Flag
The CPU sets the carry/borrow flag when an addition operation
produces a carry out of bit 7 of the accumulator or when a subtraction
operation requires a borrow. Some instructions — such as bit test and
branch, shift, and rotate — also clear or set the carry/borrow flag.
1 = Carry out of bit 7
0 = No carry out of bit 7
MC68HC908MR8 — Rev 4.1
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Technical Data
Central Processor Unit (CPU)
77
Central Processor Unit (CPU)
6.5 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the
instruction set.
Refer to the CPU08 Reference Manual, Freescale document number
CPU08RM/AD, for a description of the instructions and addressing
modes and more detail about CPU architecture.
6.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption
standby modes.
6.6.1 Wait Mode
The WAIT instruction:
•
Clears the interrupt mask (I bit) in the condition code register,
enabling interrupts. After exit from wait mode by interrupt, the I bit
remains clear. After exit by reset, the I bit is set.
•
Disables the CPU clock
6.6.2 Stop Mode
The STOP instruction:
•
Clears the interrupt mask (I bit) in the condition code register,
enabling external interrupts. After exit from stop mode by external
interrupt, the I bit remains clear. After exit by reset, the I bit is set.
•
Disables the CPU clock
After exiting stop mode, the CPU clock begins running after the oscillator
stabilization delay.
Technical Data
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Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
Instruction Set Summary
6.7 Instruction Set Summary
Table 6-1 provides a summary of the M68HC08 instruction set.
IMM
DIR
EXT
↕ ↕ – ↕ ↕ ↕ IX2
IX1
IX
SP1
SP2
A9
B9
C9
D9
E9
F9
9EE9
9ED9
ii
dd
hh ll
ee ff
ff
IMM
DIR
EXT
↕ ↕ – ↕ ↕ ↕ IX2
IX1
IX
SP1
SP2
AB
BB
CB
DB
EB
FB
9EEB
9EDB
ii
dd
hh ll
ee ff
ff
V H I N Z C
A ← (A) + (M) + (C)
Add with Carry
Operand
Effect on CCR
Description
Opcode
ADC #opr
ADC opr
ADC opr
ADC opr,X
ADC opr,X
ADC ,X
ADC opr,SP
ADC opr,SP
Operation
Address
Mode
Source
Form
ADD #opr
ADD opr
ADD opr
ADD opr,X
ADD opr,X
ADD ,X
ADD opr,SP
ADD opr,SP
Add without Carry
AIS #opr
Add Immediate Value (Signed) to SP
SP ← (SP) + (16 « M)
– – – – – – IMM
AIX #opr
Add Immediate Value (Signed) to H:X
H:X ← (H:X) + (16 « M)
A ← (A) & (M)
AND #opr
AND opr
AND opr
AND opr,X
AND opr,X
AND ,X
AND opr,SP
AND opr,SP
ASL opr
ASLA
ASLX
ASL opr,X
ASL ,X
ASL opr,SP
Arithmetic Shift Left
(Same as LSL)
ASR opr
ASRA
ASRX
ASR opr,X
ASR opr,X
ASR opr,SP
Arithmetic Shift Right
BCC rel
Branch if Carry Bit Clear
C
b7
b7
ff
ee ff
A7
ii
2
– – – – – – IMM
AF
ii
2
IMM
DIR
EXT
0 – – ↕ ↕ – IX2
IX1
IX
SP1
SP2
A4
B4
C4
D4
E4
F4
9EE4
9ED4
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
0
DIR
INH
↕ – – ↕ ↕ ↕ INH
IX1
IX
SP1
38 dd
48
58
68 ff
78
9E68 ff
4
1
1
4
3
5
C
DIR
INH
↕ – – ↕ ↕ ↕ INH
IX1
IX
SP1
37 dd
47
57
67 ff
77
9E67 ff
4
1
1
4
3
5
b0
b0
PC ← (PC) + 2 + rel ? (C) = 0
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
2
3
4
4
3
2
4
5
2
3
4
4
3
2
4
5
A ← (A) + (M)
Logical AND
ff
ee ff
Cycles
Table 6-1. Instruction Set Summary (Sheet 1 of 8)
– – – – – – REL
24
ff
ee ff
rr
3
Technical Data
Central Processor Unit (CPU)
79
Central Processor Unit (CPU)
Mn ← 0
Effect on CCR
DIR (b0)
DIR (b1)
DIR (b2)
(b3)
– – – – – – DIR
DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
11
13
15
17
19
1B
1D
1F
dd
dd
dd
dd
dd
dd
dd
dd
4
4
4
4
4
4
4
4
V H I N Z C
Cycles
Description
Opcode
Operation
Address
Mode
Source
Form
Operand
Table 6-1. Instruction Set Summary (Sheet 2 of 8)
BCLR n, opr
Clear Bit n in M
BCS rel
Branch if Carry Bit Set (Same as BLO)
PC ← (PC) + 2 + rel ? (C) = 1
– – – – – – REL
25
rr
3
BEQ rel
Branch if Equal
PC ← (PC) + 2 + rel ? (Z) = 1
– – – – – – REL
27
rr
3
BGE opr
Branch if Greater Than or Equal To
(Signed Operands)
PC ← (PC) + 2 + rel ? (N Ý V) = 0
– – – – – – REL
90
rr
3
BGT opr
Branch if Greater Than
(Signed Operands)
PC ← (PC) + 2 + rel ? (Z) | (N Ý V) = 0
– – – – – – REL
92
rr
3
BHCC rel
Branch if Half Carry Bit Clear
PC ← (PC) + 2 + rel ? (H) = 0
– – – – – – REL
28
rr
3
BHCS rel
Branch if Half Carry Bit Set
PC ← (PC) + 2 + rel ? (H) = 1
– – – – – – REL
29
rr
BHI rel
Branch if Higher
PC ← (PC) + 2 + rel ? (C) | (Z) = 0
– – – – – – REL
22
rr
3
BHS rel
Branch if Higher or Same
(Same as BCC)
PC ← (PC) + 2 + rel ? (C) = 0
– – – – – – REL
24
rr
3
BIH rel
Branch if IRQ Pin High
PC ← (PC) + 2 + rel ? IRQ = 1
– – – – – – REL
2F
rr
3
BIL rel
Branch if IRQ Pin Low
PC ← (PC) + 2 + rel ? IRQ = 0
– – – – – – REL
2E
rr
3
(A) & (M)
IMM
DIR
EXT
0 – – ↕ ↕ – IX2
IX1
IX
SP1
SP2
A5
B5
C5
D5
E5
F5
9EE5
9ED5
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
3
BIT #opr
BIT opr
BIT opr
BIT opr,X
BIT opr,X
BIT ,X
BIT opr,SP
BIT opr,SP
Bit Test
BLE opr
Branch if Less Than or Equal To
(Signed Operands)
PC ← (PC) + 2 + rel ? (Z) | (N Ý V) = 1
– – – – – – REL
93
rr
3
BLO rel
Branch if Lower (Same as BCS)
PC ← (PC) + 2 + rel ? (C) = 1
– – – – – – REL
25
rr
3
BLS rel
Branch if Lower or Same
PC ← (PC) + 2 + rel ? (C) | (Z) = 1
– – – – – – REL
23
rr
3
BLT opr
Branch if Less Than (Signed Operands)
PC ← (PC) + 2 + rel ? (N Ý V) =1
– – – – – – REL
91
rr
3
BMC rel
Branch if Interrupt Mask Clear
PC ← (PC) + 2 + rel ? (I) = 0
– – – – – – REL
2C
rr
3
BMI rel
Branch if Minus
PC ← (PC) + 2 + rel ? (N) = 1
– – – – – – REL
2B
rr
3
BMS rel
Branch if Interrupt Mask Set
PC ← (PC) + 2 + rel ? (I) = 1
– – – – – – REL
2D
rr
3
Technical Data
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MC68HC908MR8 — Rev 4.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
Instruction Set Summary
Effect on CCR
V H I N Z C
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 3 of 8)
BNE rel
Branch if Not Equal
PC ← (PC) + 2 + rel ? (Z) = 0
– – – – – – REL
26
rr
3
BPL rel
Branch if Plus
PC ← (PC) + 2 + rel ? (N) = 0
– – – – – – REL
2A
rr
3
BRA rel
Branch Always
PC ¨ (PC) + 2 + rel
– – – – – – REL
20
rr
3
DIR (b0)
DIR (b1)
DIR (b2)
(b3)
– – – – – ↕ DIR
DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
01
03
05
07
09
0B
0D
0F
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
5
5
5
5
5
5
5
5
– – – – – – REL
21
rr
3
PC ← (PC) + 3 + rel ? (Mn) = 1
DIR (b0)
DIR (b1)
DIR (b2)
(b3)
– – – – – ↕ DIR
DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
00
02
04
06
08
0A
0C
0E
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
dd rr
5
5
5
5
5
5
5
5
Mn ← 1
DIR (b0)
DIR (b1)
DIR (b2)
(b3)
– – – – – – DIR
DIR (b4)
DIR (b5)
DIR (b6)
DIR (b7)
10
12
14
16
18
1A
1C
1E
dd
dd
dd
dd
dd
dd
dd
dd
4
4
4
4
4
4
4
4
PC ← (PC) + 2; push (PCL)
SP ← (SP) – 1; push (PCH)
SP ← (SP) – 1
PC ← (PC) + rel
– – – – – – REL
AD
rr
4
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (X) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 2 + rel ? (A) – (M) = $00
PC ← (PC) + 4 + rel ? (A) – (M) = $00
DIR
IMM
– – – – – – IMM
IX1+
IX+
SP1
31
41
51
61
71
9E61
dd rr
ii rr
ii rr
ff rr
rr
ff rr
5
4
4
5
4
6
BRCLR n,opr,rel
Branch if Bit n in M Clear
BRN rel
Branch Never
BRSET n,opr,rel
Branch if Bit n in M Set
BSET n,opr
Set Bit n in M
BSR rel
Branch to Subroutine
PC ← (PC) + 3 + rel ? (Mn) = 0
PC ← (PC) + 2
CBEQ opr,rel
CBEQA #opr,rel
CBEQX #opr,rel
CBEQ opr,X+,rel
CBEQ X+,rel
CBEQ opr,SP,rel
Compare and Branch if Equal
CLC
Clear Carry Bit
C←0
– – – – – 0 INH
98
1
CLI
Clear Interrupt Mask
I←0
– – 0 – – – INH
9A
2
M ← $00
A ← $00
X ← $00
H ← $00
M ← $00
M ← $00
M ← $00
DIR
INH
INH
0 – – 0 1 – INH
IX1
IX
SP1
CLR opr
CLRA
CLRX
CLRH
CLR opr,X
CLR ,X
CLR opr,SP
Clear
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
3F dd
4F
5F
8C
6F ff
7F
9E6F ff
3
1
1
1
3
2
4
Technical Data
Central Processor Unit (CPU)
81
Central Processor Unit (CPU)
Table 6-1. Instruction Set Summary (Sheet 4 of 8)
COM opr
COMA
COMX
COM opr,X
COM ,X
COM opr,SP
Complement (One’s Complement)
CPHX #opr
CPHX opr
Compare H:X with M
CPX #opr
CPX opr
CPX opr
CPX ,X
CPX opr,X
CPX opr,X
CPX opr,SP
CPX opr,SP
Compare X with M
DAA
Decimal Adjust A
DBNZ opr,rel
DBNZA rel
DBNZX rel
DBNZ opr,X,rel
DBNZ X,rel
DBNZ opr,SP,rel
Decrement and Branch if Not Zero
DEC opr
DECA
DECX
DEC opr,X
DEC ,X
DEC opr,SP
Decrement
DIV
Divide
EOR #opr
EOR opr
EOR opr
EOR opr,X
EOR opr,X
EOR ,X
EOR opr,SP
EOR opr,SP
Exclusive OR M with A
IMM
DIR
EXT
↕ – – ↕ ↕ ↕ IX2
IX1
IX
SP1
SP2
A1
B1
C1
D1
E1
F1
9EE1
9ED1
ii
dd
hh ll
ee ff
ff
M ← (M) = $FF – (M)
A ← (A) = $FF – (M)
X ← (X) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
DIR
INH
0 – – ↕ ↕ 1 INH
IX1
IX
SP1
33 dd
43
53
63 ff
73
9E63 ff
(H:X) – (M:M + 1)
↕ – – ↕ ↕ ↕ IMM
DIR
65
75
ii ii+1
dd
3
4
(X) – (M)
IMM
DIR
EXT
↕ – – ↕ ↕ ↕ IX2
IX1
IX
SP1
SP2
A3
B3
C3
D3
E3
F3
9EE3
9ED3
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
(A)10
U – – ↕ ↕ ↕ INH
72
A ← (A) – 1 or M ← (M) – 1 or X ←(X) – 1
PC ← (PC) + 3 + rel ? (result) ¼ 0
PC ← (PC) + 2 + rel ? (result) ¼ 0
PC ← (PC) + 2 + rel ? (result) ¼ 0
PC ← (PC) + 3 + rel ? (result) ¼ 0
PC ← (PC) + 2 + rel ? (result) ¼ 0
PC ← (PC) + 4 + rel ? (result) ¼ 0
DIR
INH
– – – – – – INH
IX1
IX
SP1
3B
4B
5B
6B
7B
9E6B
M ← M) – 1
A ← A) – 1
X ← (X) – 1
M ← (M) – 1
M ← (M) – 1
M ← (M) – 1
DIR
INH
↕ – – ↕ ↕ – INH
IX1
IX
SP1
3A dd
4A
5A
6A ff
7A
9E6A ff
A ← (H:A)/(X)
H ← Remainder
– – – – ↕ ↕ INH
52
A ← (A Ý M)
IMM
DIR
EXT
0 – – ↕ ↕ – IX2
IX1
IX
SP1
SP2
A8
B8
C8
D8
E8
F8
9EE8
9ED8
Description
(A) – (M)
Technical Data
82
V H I N Z C
ff
ee ff
ff
ee ff
Cycles
Operand
Compare A with M
Effect on CCR
Opcode
CMP #opr
CMP opr
CMP opr
CMP opr,X
CMP opr,X
CMP ,X
CMP opr,SP
CMP opr,SP
Operation
Address
Mode
Source
Form
2
3
4
4
3
2
4
5
4
1
1
4
3
5
2
dd rr
rr
rr
ff rr
rr
ff rr
5
3
3
5
4
6
4
1
1
4
3
5
7
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
MC68HC908MR8 — Rev 4.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
Instruction Set Summary
INC opr
INCA
INCX
INC opr,X
INC ,X
INC opr,SP
JMP opr
JMP opr
JMP opr,X
JMP opr,X
JMP ,X
JSR opr
JSR opr
JSR opr,X
JSR opr,X
JSR ,X
Load A from M
LDHX #opr
LDHX opr
Load H:X from M
LDX #opr
LDX opr
LDX opr
LDX opr,X
LDX opr,X
LDX ,X
LDX opr,SP
LDX opr,SP
LSL opr
LSLA
LSLX
LSL opr,X
LSL ,X
LSL opr,SP
PC ← Jump Address
DIR
EXT
– – – – – – IX2
IX1
IX
BC
CC
DC
EC
FC
dd
hh ll
ee ff
ff
2
3
4
3
2
PC ← (PC) + n (n = 1, 2, or 3)
Push (PCL); SP ← (SP) – 1
Push (PCH); SP ← (SP) – 1
PC ← Unconditional Address
DIR
EXT
– – – – – – IX2
IX1
IX
BD
CD
DD
ED
FD
dd
hh ll
ee ff
ff
4
5
6
5
4
A ← (M)
IMM
DIR
EXT
0 – – ↕ ↕ – IX2
IX1
IX
SP1
SP2
A6
B6
C6
D6
E6
F6
9EE6
9ED6
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
H:X ← (M:M + 1)
0 – – ↕ ↕ – IMM
DIR
45
55
ii jj
dd
3
4
X ← (M)
IMM
DIR
EXT
0 – – ↕ ↕ – IX2
IX1
IX
SP1
SP2
AE
BE
CE
DE
EE
FE
9EEE
9EDE
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
0
DIR
INH
↕ – – ↕ ↕ ↕ INH
IX1
IX
SP1
38 dd
48
58
68 ff
78
9E68 ff
4
1
1
4
3
5
C
DIR
INH
↕ – – 0 ↕ ↕ INH
IX1
IX
SP1
34 dd
44
54
64 ff
74
9E64 ff
4
1
1
4
3
5
Load X from M
Logical Shift Left
(Same as ASL)
LSR opr
LSRA
LSRX
LSR opr,X
LSR ,X
LSR opr,SP
Logical Shift Right
MOV opr,opr
MOV opr,X+
MOV #opr,opr
MOV X+,opr
Move
MUL
Unsigned multiply
C
b7
b0
0
b7
b0
3C dd
4C
5C
6C ff
7C
9E6C ff
H:X ← (H:X) + 1 (IX+D, DIX+)
DD
0 – – ↕ ↕ – DIX+
IMD
IX+D
4E
5E
6E
7E
X:A ¨ (X) ¥ (A)
– 0 – – – 0 INH
42
(M)Destination ← (M)Source
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Cycles
DIR
INH
↕ – – ↕ ↕ – INH
IX1
IX
SP1
Jump
LDA #opr
LDA opr
LDA opr
LDA opr,X
LDA opr,X
LDA ,X
LDA opr,SP
LDA opr,SP
V H I N Z C
M ← M) + 1
A ← (A) + 1
X ← X) + 1
M ← (M) + 1
M ← (M) + 1
M ← (M) + 1
Increment
Jump to Subroutine
Effect on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 5 of 8)
ff
ee ff
dd dd
dd
ii dd
dd
4
1
1
4
3
5
5
4
4
4
5
Technical Data
Central Processor Unit (CPU)
83
Central Processor Unit (CPU)
NEG opr
NEGA
NEGX
NEG opr,X
NEG ,X
NEG opr,SP
Negate (Two’s Complement)
NOP
NSA
V H I N Z C
30 dd
40
50
60 ff
70
9E60 ff
Cycles
Effect on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 6 of 8)
M ← –(M) = $00 – (M)
A ← –(A) = $00 – (A)
X ← –(X) = $00 – (X)
M ← –(M) = $00 – (M)
M ← –(M) = $00 – (M)
DIR
INH
↕ – – ↕ ↕ ↕ INH
IX1
IX
SP1
No Operation
None
– – – – – – INH
9D
1
Nibble Swap A
A ← (A[3:0]:A[7:4])
– – – – – – INH
62
3
A ← (A) | (M)
IMM
DIR
EXT
0 – – ↕ ↕ – IX2
IX1
IX
SP1
SP2
AA
BA
CA
DA
EA
FA
9EEA
9EDA
ii
dd
hh ll
ee ff
ff
4
1
1
4
3
5
2
3
4
4
3
2
4
5
ORA #opr
ORA opr
ORA opr
ORA opr,X
ORA opr,X
ORA ,X
ORA opr,SP
ORA opr,SP
Inclusive OR A and M
PSHA
Push A onto Stack
Push (A); SP ← (SP) – 1
– – – – – – INH
87
2
PSHH
Push H onto Stack
Push (H); SP ← (SP) – 1
– – – – – – INH
8B
2
PSHX
Push X onto Stack
Push (X); SP ← (SP) – 1
– – – – – – INH
89
2
PULA
Pull A from Stack
SP ← (SP + 1); Pull (A)
– – – – – – INH
86
2
PULH
Pull H from Stack
SP ← (SP + 1); Pull (H)
– – – – – – INH
8A
2
PULX
Pull X from Stack
SP ← (SP + 1); Pull (X)
– – – – – – INH
88
2
C
DIR
INH
↕ – – ↕ ↕ ↕ INH
IX1
IX
SP1
39 dd
49
59
69 ff
79
9E69 ff
4
1
1
4
3
5
DIR
INH
↕ – – ↕ ↕ ↕ INH
IX1
IX
SP1
36 dd
46
56
66 ff
76
9E66 ff
4
1
1
4
3
5
ROL opr
ROLA
ROLX
ROL opr,X
ROL ,X
ROL opr,SP
Rotate Left through Carry
b7
b0
ff
ee ff
ROR opr
RORA
RORX
ROR opr,X
ROR ,X
ROR opr,SP
Rotate Right through Carry
RSP
Reset Stack Pointer
SP ← $FF
– – – – – – INH
9C
1
RTI
Return from Interrupt
SP ← SP) + 1; Pull (CCR)
SP ← (SP) + 1; Pull (A)
SP ← (SP) + 1; Pull (X)
SP ← (SP) + 1; Pull (PCH)
SP ← (SP) + 1; Pull (PCL)
↕ ↕ ↕ ↕ ↕ ↕ INH
80
7
RTS
Return from Subroutine
SP ← SP + 1; Pull (PCH)
SP ← SP + 1; Pull (PCL)
– – – – – – INH
81
4
C
b7
b0
Technical Data
84
MC68HC908MR8 — Rev 4.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
Instruction Set Summary
Table 6-1. Instruction Set Summary (Sheet 7 of 8)
Subtract with Carry
SEC
Set Carry Bit
SEI
Set Interrupt Mask
STA opr
STA opr
STA opr,X
STA opr,X
STA ,X
STA opr,SP
STA opr,SP
Store A in M
STHX opr
Store H:X in M
STOP
Enable IRQ Pin; Stop Oscillator
STX opr
STX opr
STX opr,X
STX opr,X
STX ,X
STX opr,SP
STX opr,SP
SUB #opr
SUB opr
SUB opr
SUB opr,X
SUB opr,X
SUB ,X
SUB opr,SP
SUB opr,SP
Store X in M
Subtract
IMM
DIR
EXT
↕ – – ↕ ↕ ↕ IX2
IX1
IX
SP1
SP2
A2
B2
C2
D2
E2
F2
9EE2
9ED2
ii
dd
hh ll
ee ff
ff
C←1
– – – – – 1 INH
99
1
I←1
– – 1 – – – INH
9B
2
M ← (A)
DIR
EXT
IX2
0 – – ↕ ↕ – IX1
IX
SP1
SP2
B7
C7
D7
E7
F7
9EE7
9ED7
(M:M + 1) ← (H:X)
0 – – ↕ ↕ – DIR
35
I ← 0; Stop Oscillator
– – 0 – – – INH
8E
M ← (X)
DIR
EXT
IX2
0 – – ↕ ↕ – IX1
IX
SP1
SP2
BF
CF
DF
EF
FF
9EEF
9EDF
dd
hh ll
ee ff
ff
IMM
DIR
EXT
↕ – – ↕ ↕ ↕ IX2
IX1
IX
SP1
SP2
A0
B0
C0
D0
E0
F0
9EE0
9ED0
ii
dd
hh ll
ee ff
ff
– – 1 – – – INH
83
9
Description
A ← (A) – (M) – (C)
A ← (A) – (M)
V H I N Z C
ff
ee ff
dd
hh ll
ee ff
ff
Cycles
Operand
SBC #opr
SBC opr
SBC opr
SBC opr,X
SBC opr,X
SBC ,X
SBC opr,SP
SBC opr,SP
Effect on CCR
Opcode
Operation
Address
Mode
Source
Form
2
3
4
4
3
2
4
5
ff
ee ff
3
4
4
3
2
4
5
dd
4
1
ff
ee ff
ff
ee ff
3
4
4
3
2
4
5
2
3
4
4
3
2
4
5
SWI
Software Interrupt
PC ← (PC) + 1; Push (PCL)
SP ← (SP) – 1; Push (PCH)
SP ← (SP) – 1; Push (X)
SP ← (SP) – 1; Push (A)
SP ← (SP) – 1; Push (CCR)
SP ¨ (SP) – 1; I ¨ 1
PCH ← Interrupt Vector High Byte
PCL ← Interrupt Vector Low Byte
TAP
Transfer A to CCR
CCR ← (A)
↕ ↕ ↕ ↕ ↕ ↕ INH
84
2
TAX
Transfer A to X
X ← (A)
– – – – – – INH
97
1
TPA
Transfer CCR to A
A ← (CCR)
– – – – – – INH
85
1
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Central Processor Unit (CPU)
85
Central Processor Unit (CPU)
TST opr
TSTA
TSTX
TST opr,X
TST ,X
TST opr,SP
Test for Negative or Zero
TSX
Transfer SP to H:X
TXA
Transfer X to A
TXS
Transfer H:X to SP
WAIT
Enable Interrupts; Stop Processor
A
C
CCR
dd
dd rr
DD
DIR
DIX+
ee ff
EXT
ff
H
H
hh ll
I
ii
IMD
IMM
INH
IX
IX+
IX+D
IX1
IX1+
IX2
M
N
V H I N Z C
(A) – $00 or (X) – $00 or (M) – $00
DIR
INH
0 – – ↕ ↕ – INH
IX1
IX
SP1
H:X ← (SP) + 1
– – – – – – INH
95
2
A ← (X)
– – – – – – INH
9F
1
(SP) ← (H:X) – 1
– – – – – – INH
94
2
I bit ← 0
– – 0 – – – INH
8F
1
Accumulator
Carry/borrow bit
Condition code register
Direct address of operand
Direct address of operand and relative offset of branch instruction
Direct to direct addressing mode
Direct addressing mode
Direct to indexed with post increment addressing mode
High and low bytes of offset in indexed, 16-bit offset addressing
Extended addressing mode
Offset byte in indexed, 8-bit offset addressing
Half-carry bit
Index register high byte
High and low bytes of operand address in extended addressing
Interrupt mask
Immediate operand byte
Immediate source to direct destination addressing mode
Immediate addressing mode
Inherent addressing mode
Indexed, no offset addressing mode
Indexed, no offset, post increment addressing mode
Indexed with post increment to direct addressing mode
Indexed, 8-bit offset addressing mode
Indexed, 8-bit offset, post increment addressing mode
Indexed, 16-bit offset addressing mode
Memory location
Negative bit
n
opr
PC
PCH
PCL
REL
rel
rr
SP1
SP2
SP
U
V
X
Z
&
|
⊕
()
–( )
#
«
←
?
:
↕
—
3D dd
4D
5D
6D ff
7D
9E6D ff
Cycles
Effect on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 8 of 8)
3
1
1
3
2
4
Any bit
Operand (one or two bytes)
Program counter
Program counter high byte
Program counter low byte
Relative addressing mode
Relative program counter offset byte
Relative program counter offset byte
Stack pointer, 8-bit offset addressing mode
Stack pointer 16-bit offset addressing mode
Stack pointer
Undefined
Overflow bit
Index register low byte
Zero bit
Logical AND
Logical OR
Logical EXCLUSIVE OR
Contents of
Negation (two’s complement)
Immediate value
Sign extend
Loaded with
If
Concatenated with
Set or cleared
Not affected
6.8 Opcode Map
See Table 6-2.
Technical Data
86
MC68HC908MR8 — Rev 4.1
Central Processor Unit (CPU)
Freescale Semiconductor
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Table 6-2. Opcode Map
Bit Manipulation
DIR
DIR
MSB
Branch
REL
DIR
INH
Read-Modify-Write
INH
IX1
1
2
3
4
5
5
BRSET0
3
DIR
5
BRCLR0
3
DIR
5
BRSET1
3
DIR
5
BRCLR1
3
DIR
5
BRSET2
3
DIR
5
BRCLR2
3
DIR
5
BRSET3
3
DIR
5
BRCLR3
3
DIR
5
BRSET4
3
DIR
5
BRCLR4
3
DIR
5
BRSET5
3
DIR
5
BRCLR5
3
DIR
5
BRSET6
3
DIR
5
BRCLR6
3
DIR
5
BRSET7
3
DIR
5
BRCLR7
3
DIR
4
BSET0
2
DIR
4
BCLR0
2
DIR
4
BSET1
2
DIR
4
BCLR1
2
DIR
4
BSET2
2
DIR
4
BCLR2
2
DIR
4
BSET3
2
DIR
4
BCLR3
2
DIR
4
BSET4
2
DIR
4
BCLR4
2
DIR
4
BSET5
2
DIR
4
BCLR5
2
DIR
4
BSET6
2
DIR
4
BCLR6
2
DIR
4
BSET7
2
DIR
4
BCLR7
2
DIR
3
BRA
REL
3
BRN
REL
3
BHI
REL
3
BLS
REL
3
BCC
REL
3
BCS
REL
3
BNE
REL
3
BEQ
REL
3
BHCC
REL
3
BHCS
REL
3
BPL
REL
3
BMI
REL
3
BMC
REL
3
BMS
REL
3
BIL
REL
3
BIH
REL
4
NEG
2
DIR
5
CBEQ
3
DIR
1
NEGA
1
INH
4
CBEQA
3
IMM
5
MUL
1
INH
1
COMA
1
INH
1
LSRA
1
INH
3
LDHX
3
IMM
1
RORA
1
INH
1
ASRA
1
INH
1
LSLA
1
INH
1
ROLA
1
INH
1
DECA
1
INH
3
DBNZA
2
INH
1
INCA
1
INH
1
TSTA
1
INH
5
MOV
3
DD
1
CLRA
1
INH
1
NEGX
1
INH
4
CBEQX
3
IMM
7
DIV
1
INH
1
COMX
1
INH
1
LSRX
1
INH
4
LDHX
2
DIR
1
RORX
1
INH
1
ASRX
1
INH
1
LSLX
1
INH
1
ROLX
1
INH
1
DECX
1
INH
3
DBNZX
2
INH
1
INCX
1
INH
1
TSTX
1
INH
4
MOV
2 DIX+
1
CLRX
1
INH
IX
INH
INH
IMM
DIR
EXT
9E6
7
8
9
A
B
C
5
NEG
3
SP1
6
CBEQ
4
SP1
3
NEG
IX
4
CBEQ
IX+
2
DAA
INH
3
COM
IX
3
LSR
IX
4
CPHX
DIR
3
ROR
IX
3
ASR
IX
3
LSL
IX
3
ROL
IX
3
DEC
IX
4
DBNZ
IX
3
INC
IX
2
TST
IX
4
MOV
IX+D
2
CLR
IX
7
RTI
1
INH
4
RTS
1
INH
6
Register/Memory
IX2
SP2
D
9ED
IX1
SP1
IX
E
9EE
F
LSB
0
1
2
3
4
5
Central Processor Unit (CPU)
0
Control
SP1
6
7
8
9
A
B
C
E
F
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
3
2
2
4
COM
DIR
4
LSR
DIR
4
STHX
DIR
4
ROR
DIR
4
ASR
DIR
4
LSL
DIR
4
ROL
DIR
4
DEC
DIR
5
DBNZ
DIR
4
INC
DIR
3
TST
DIR
3
CLR
2
DIR
Technical Data
87
INH Inherent
REL Relative
IMM Immediate
IX
Indexed, No Offset
DIR Direct
IX1 Indexed, 8-Bit Offset
EXT Extended
IX2 Indexed, 16-Bit Offset
DD Direct-Direct
IMD Immediate-Direct
IX+D Indexed-Direct
DIX+ Direct-Indexed
*Pre-byte for stack pointer indexed instructions
2
3
1
2
2
3
2
2
2
2
2
3
2
2
3
2
Stack Pointer, 8-Bit Offset
Stack Pointer, 16-Bit Offset
Indexed, No Offset with
Post Increment
IX1+ Indexed, 1-Byte Offset with
Post Increment
1
2
1
5
COM
3
SP1
5
LSR
3
SP1
1
1
2
5
3
3
3
3
3
4
3
3
ROR
SP1
5
ASR
SP1
5
LSL
SP1
5
ROL
SP1
5
DEC
SP1
6
DBNZ
SP1
5
INC
SP1
4
TST
SP1
1
1
1
1
1
2
1
1
2
4
CLR
3
SP1
1
2
2
2
1
1
1
1
1
1
1
1
1
1
9
SWI
INH
2
TAP
INH
1
TPA
INH
2
PULA
INH
2
PSHA
INH
2
PULX
INH
2
PSHX
INH
2
PULH
INH
2
PSHH
INH
1
CLRH
INH
2
1
1
2
2
2
2
2
2
2
1
1
1
1
1
1
1
1
STOP
1
INH
1
WAIT
1
INH
3
BGE
REL
3
BLT
REL
3
BGT
REL
3
BLE
REL
2
TXS
INH
2
TSX
INH
1
TAX
INH
1
CLC
INH
1
SEC
INH
2
CLI
INH
2
SEI
INH
1
RSP
INH
1
NOP
INH
*
1
TXA
1
INH
2
2
2
2
2
2
SUB
IMM
2
CMP
IMM
2
SBC
IMM
2
CPX
IMM
2
AND
IMM
2
BIT
IMM
2
LDA
IMM
2
AIS
IMM
2
EOR
IMM
2
ADC
IMM
2
ORA
IMM
2
ADD
IMM
2
2
2
2
2
2
2
2
2
2
2
2
2
4
BSR
2
REL 2
2
LDX
2
IMM 2
2
AIX
2
IMM 2
SP1
SP2
IX+
3
SUB
DIR
3
CMP
DIR
3
SBC
DIR
3
CPX
DIR
3
AND
DIR
3
BIT
DIR
3
LDA
DIR
3
STA
DIR
3
EOR
DIR
3
ADC
DIR
3
ORA
DIR
3
ADD
DIR
2
JMP
DIR
4
JSR
DIR
3
LDX
DIR
3
STX
DIR
MSB
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
SUB
EXT
4
CMP
EXT
4
SBC
EXT
4
CPX
EXT
4
AND
EXT
4
BIT
EXT
4
LDA
EXT
4
STA
EXT
4
EOR
EXT
4
ADC
EXT
4
ORA
EXT
4
ADD
EXT
3
JMP
EXT
5
JSR
EXT
4
LDX
EXT
4
STX
EXT
0
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
3
4
SUB
IX2
4
CMP
IX2
4
SBC
IX2
4
CPX
IX2
4
AND
IX2
4
BIT
IX2
4
LDA
IX2
4
STA
IX2
4
EOR
IX2
4
ADC
IX2
4
ORA
IX2
4
ADD
IX2
4
JMP
IX2
6
JSR
IX2
4
LDX
IX2
4
STX
IX2
4
4
4
4
4
4
4
4
4
4
4
4
5
SUB
SP2
5
CMP
SP2
5
SBC
SP2
5
CPX
SP2
5
AND
SP2
5
BIT
SP2
5
LDA
SP2
5
STA
SP2
5
EOR
SP2
5
ADC
SP2
5
ORA
SP2
5
ADD
SP2
2
2
2
2
2
2
2
2
2
2
2
2
2
2
5
LDX
4
SP2
5
STX
4
SP2
2
2
3
SUB
IX1
3
CMP
IX1
3
SBC
IX1
3
CPX
IX1
3
AND
IX1
3
BIT
IX1
3
LDA
IX1
3
STA
IX1
3
EOR
IX1
3
ADC
IX1
3
ORA
IX1
3
ADD
IX1
3
JMP
IX1
5
JSR
IX1
3
LDX
IX1
3
STX
IX1
High Byte of Opcode in Hexadecimal
LSB
Low Byte of Opcode in Hexadecimal
0
5
Cycles
BRSET0 Opcode Mnemonic
3
DIR Number of Bytes / Addressing Mode
3
3
3
3
3
3
3
3
3
3
3
3
4
SUB
SP1
4
CMP
SP1
4
SBC
SP1
4
CPX
SP1
4
AND
SP1
4
BIT
SP1
4
LDA
SP1
4
STA
SP1
4
EOR
SP1
4
ADC
SP1
4
ORA
SP1
4
ADD
SP1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
4
LDX
3
SP1
4
STX
3
SP1
1
1
2
SUB
IX
2
CMP
IX
2
SBC
IX
2
CPX
IX
2
AND
IX
2
BIT
IX
2
LDA
IX
2
STA
IX
2
EOR
IX
2
ADC
IX
2
ORA
IX
2
ADD
IX
2
JMP
IX
4
JSR
IX
2
LDX
IX
2
STX
IX
Central Processor Unit (CPU)
Opcode Map
D
2
4
NEG
IX1
5
CBEQ
IX1+
3
NSA
INH
4
COM
IX1
4
LSR
IX1
3
CPHX
IMM
4
ROR
IX1
4
ASR
IX1
4
LSL
IX1
4
ROL
IX1
4
DEC
IX1
5
DBNZ
IX1
4
INC
IX1
3
TST
IX1
4
MOV
IMD
3
CLR
IX1
Central Processor Unit (CPU)
Technical Data
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Central Processor Unit (CPU)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 7. System Integration Module (SIM)
7.1 Contents
7.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .90
7.3
SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . .93
7.3.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
7.3.2
Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . .93
7.3.3
Clocks in Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94
7.4
Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . .94
7.4.1
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .94
7.4.2
Active Resets from Internal Sources . . . . . . . . . . . . . . . .95
7.5
SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
7.5.1
SIM Counter During Power-On Reset. . . . . . . . . . . . . . . .99
7.5.2
SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . .99
7.6
Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
7.6.1
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .100
7.6.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103
7.6.3
Status Flag Protection in Break Mode . . . . . . . . . . . . . .103
7.7
Low-Power Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .104
7.7.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
7.7.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .106
7.7.3
SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . .106
7.7.4
SIM Reset Status Register. . . . . . . . . . . . . . . . . . . . . . . .108
7.7.5
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . .109
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Technical Data
System Integration Module (SIM)
89
System Integration Module (SIM)
7.2 Introduction
This section describes the system integration module (SIM). Together
with the central processor unit (CPU), the SIM controls all
microcontroller unit (MCU) activities. A block diagram of the SIM is
shown in Figure 7-1. Figure 7-2 is a summary of the SIM inout/output
(I/O) registers.
The SIM is a system state controller that coordinates CPU and exception
timing. The SIM is responsible for:
•
Bus clock generation and control for CPU and peripherals:
– Stop, wait, reset, break entry, and recovery
– Internal clock control
•
Master reset control, including power-on reset (POR) and
computer operating properly (COP) timeout
•
Interrupt control:
– Acknowledge timing
– Arbitration control timing
– Vector address generation
•
CPU enable/disable timing
•
Modular architecture expandable to 128 interrupt sources
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Freescale Semiconductor
System Integration Module (SIM)
Introduction
MODULE WAIT
MODULE STOP
CPU WAIT (FROM CPU)
CPU STOP (FROM CPU)
SIMOSCEN (TO CGM)
STOP/WAIT
CONTROL
SIM
COUNTER
COP CLOCK
CGMXCLK (FROM CGM)
CGMOUT (FROM CGM)
÷2
CLOCK
CONTROL
RESET
PIN LOGIC
CLOCK GENERATORS
INTERNAL CLOCKS
LVI (FROM LVI MODULE)
POR CONTROL
MASTER
RESET
CONTROL
RESET PIN CONTROL
SIM RESET STATUS REGISTER
ILLEGAL OPCODE (FROM CPU)
ILLEGAL ADDRESS (FROM ADDRESS
MAP DECODERS)
COP (FROM COP MODULE)
RESET
INTERRUPT CONTROL
AND PRIORITY DECODE
INTERRUPT SOURCES
CPU INTERFACE
Figure 7-1. SIM Block Diagram
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Technical Data
System Integration Module (SIM)
91
System Integration Module (SIM)
Addr.
Register Name
Read:
SIM Break Status Register
Write:
$FE00
(SBSR)
See page 106.
Reset:
Read:
$FE01
Bit 7
6
5
4
3
2
R
R
R
R
R
R
SBSW
Note 1
Bit 0
R
0
POR
PIN
COP
ILOP
ILAD
0
LVI
0
R
R
R
R
R
R
R
R
1
0
0
0
0
0
0
0
R
R
R
R
R
R
R
SIM Reset Status Register
Write:
(SRSR)
See page 108.
Reset:
Read:
$FE03
1
BCFE
SIM Break Flag Control
Write:
Register (SBFCR)
See page 109.
Re0
set:
Note 1. Writing a logic 0 clears SBSW.
R
= Reserved
Figure 7-2. SIM I/O Register Summary
Table 7-1 shows the internal signal names used in this section.
Table 7-1. Signal Name Conventions
Signal Name
Description
CGMXCLK
Buffered version of OSC1 from clock generator module (CGM)
CGMVCLK
PLL output
CGMOUT
PLL-based or OSC1-based clock output from CGM module
(bus clock = CGMOUT divided by two)
IAB
Internal address bus
IDB
Internal data bus
PORRST
Signal from the power-on reset module to the SIM
IRST
Internal reset signal
R/W
Read/write signal
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Freescale Semiconductor
System Integration Module (SIM)
SIM Bus Clock Control and Generation
7.3 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and
peripherals on the MCU. The system clocks are generated from an
incoming clock, CGMOUT, as shown in Figure 7-3. This clock can come
from either an external oscillator or from the on-chip phase-locked loop
(PLL). See Section 8. Clock Generator Module (CGM).
CGMXCLK
OSC1
CLOCK
SELECT
CIRCUIT
CGMVCLK
÷2
A
CGMOUT
B S*
*When S = 1,
CGMOUT = B
BUS CLOCK
GENERATORS
÷2
SIM
BCS
PLL
SIM COUNTER
MONITOR MODE
USER MODE
CGM
Figure 7-3. CGM Clock Signals
7.3.1 Bus Timing
In user mode, the internal bus frequency is either the crystal oscillator
output (CGMXCLK) divided by four or the PLL output (CGMVCLK)
divided by four. See Section 8. Clock Generator Module (CGM).
7.3.2 Clock Startup from POR or LVI Reset
When the power-on reset (POR) module or the low-voltage inhibit (LVI)
module generates a reset, the clocks to the CPU and peripherals are
inactive and held in an inactive phase until after the 4096 CGMXCLK
cycle POR timeout has completed. The RST pin is driven low by the SIM
during this entire period. The IBUS clocks start upon completion of the
timeout.
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Technical Data
System Integration Module (SIM)
93
System Integration Module (SIM)
7.3.3 Clocks in Wait Mode
In wait mode, the CPU clocks are inactive. The SIM also produces two
sets of clocks for other modules. Refer to the wait mode subsection of
each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
7.4 Reset and System Initialization
The MCU has these reset sources:
•
Power-on reset module (POR)
•
External reset pin (RST)
•
Computer operating properly module (COP)
•
Low-voltage inhibit module (LVI)
•
Illegal opcode
•
Illegal address
All of these resets produce the vector $FFFE–FFFF ($FEFE–FEFF in
monitor mode) and assert the internal reset signal (IRST). IRST causes
all registers to be returned to their default values and all modules to be
returned to their reset states.
An internal reset clears the SIM counter (see 7.5 SIM Counter), but an
external reset does not. Each of the resets sets a corresponding bit in
the SIM reset status register (SRSR). See 7.7.4 SIM Reset Status
Register.
7.4.1 External Pin Reset
Pulling the asynchronous RST pin low halts all processing. The PIN bit
of the SIM reset status register (SRSR) is set as long as RST is held low
for a minimum of 67 CGMXCLK cycles, assuming that neither the POR
nor the LVI was the source of the reset. See Table 7-2 for details.
Figure 7-4 shows the relative timing.
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Freescale Semiconductor
System Integration Module (SIM)
Reset and System Initialization
Table 7-2. PIN Bit Set Timing
Reset Type
Number of Cycles Required to set PIN
POR/LVI
4163 (4096 + 64 + 3)
All Others
67 (64 + 3)
CGMOUT
RST
IAB
VECT H
PC
VECT L
Figure 7-4. External Reset Timing
7.4.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 CGMXCLK
cycles to allow resetting of external peripherals. The internal reset signal
(IRST) continues to be asserted for an additional 32 cycles (see
Figure 7-5). An internal reset can be caused by an illegal address, illegal
opcode, COP timeout, LVI, or POR (see Figure 7-6).
NOTE:
For LVI or POR resets, the SIM cycles through 4096 CGMXCLK cycles
during which the SIM forces the RST pin low. The internal reset signal
then follows the sequence from the falling edge of RST as shown in
Figure 7-5.
IRST
RST
RST PULLED LOW BY MCU
32 CYCLES
32 CYCLES
CGMXCLK
IAB
VECTOR HIGH
Figure 7-5. Internal Reset Timing
MC68HC908MR8 — Rev 4.1
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Technical Data
System Integration Module (SIM)
95
System Integration Module (SIM)
The COP reset is asynchronous to the bus clock.
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
POR
INTERNAL RESET
Figure 7-6. Sources of Internal Reset
The active reset feature allows the part to issue a reset to peripherals
and other chips within a system built around the MCU.
7.4.2.1 Power-On Reset (POR)
When power is first applied to the MCU, the power-on reset (POR)
module generates a pulse to indicate that power-on has occurred. The
external reset pin (RST) is held low while the SIM counter counts out
4096 CGMXCLK cycles. Sixty-four CGMXCLK cycles later, the CPU and
memories are released from reset to allow the reset vector sequence to
occur.
At power-on, these events occur:
•
A POR pulse is generated.
•
The internal reset signal is asserted.
•
The SIM enables CGMOUT.
•
Internal clocks to the CPU and modules are held inactive for 4096
CGMXCLK cycles to allow stabilization of the oscillator.
•
The RST pin is driven low during the oscillator stabilization time.
•
The POR bit of the SIM reset status register (SRSR) is set and all
other bits in the register are cleared.
Technical Data
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System Integration Module (SIM)
Freescale Semiconductor
System Integration Module (SIM)
Reset and System Initialization
OSC1
PORRST
4096
CYCLES
32
CYCLES
32
CYCLES
CGMXCLK
CGMOUT
RST
IAB
$FFFE
$FFFF
Figure 7-7. POR Recovery
7.4.2.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of
the COP counter causes an internal reset and sets the COP bit in the
SIM reset status register (SRSR). The SIM actively pulls down the RST
pin for all internal reset sources.
To prevent a COP module timeout, write any value to location $FFFF.
Writing to location $FFFF clears the COP counter and bits 12–4 of the
SIM counter. The SIM counter output, which occurs at least every
213–24 CGMXCLK cycles, drives the COP counter. The COP should be
serviced as soon as possible out of reset to guarantee the maximum
amount of time before the first timeout.
The COP module is disabled if the RST pin or the IRQ pin is held at
VDD + VHI while the MCU is in monitor mode. The COP module can be
disabled only through combinational logic conditioned with the high
voltage signal on the RST or the IRQ pin. This prevents the COP from
becoming disabled as a result of external noise. During a break state,
VDD + VHI on the RST pin disables the COP module.
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Technical Data
System Integration Module (SIM)
97
System Integration Module (SIM)
7.4.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An
illegal instruction sets the ILOP bit in the SIM reset status register
(SRSR) and causes a reset.
Because the MC68HC08MR8 has stop mode disabled by bit 1 in the
CONFIG register, execution of the STOP instruction will cause an illegal
opcode reset if stop mode has not been enabled by setting CONFIG
register bit 1.
7.4.2.4 Illegal Address Reset
An opcode fetch from addresses other than FLASH, I/O, or RAM
addresses generates an illegal address reset (unimplemented locations
within memory map). The SIM verifies that the CPU is fetching an
opcode prior to asserting the ILAD bit in the SIM reset status register
(SRSR) and resetting the MCU. A data fetch from an unmapped address
does not generate a reset.
7.4.2.5 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when
the VDD voltage falls to the LVILVRX voltage and remains at or below that
level for at least nine consecutive CPU cycles. The LVI bit in the SIM
reset status register (SRSR) is set, and the external reset pin (RST) is
held low while the SIM counter counts out 4096 CGMXCLK cycles.
Sixty-four CGMXCLK cycles later, the CPU is released from reset to
allow the reset vector sequence to occur. The SIM actively pulls down
the RST pin for all internal reset sources.
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Freescale Semiconductor
System Integration Module (SIM)
SIM Counter
7.5 SIM Counter
The SIM counter is used by the POR module to allow the oscillator time
to stabilize before enabling the internal bus (IBUS) clocks. The SIM
counter also serves as a prescaler for the COP module. The SIM counter
overflow supplies the clock for the COP module. The SIM counter is 13
bits long and is clocked by the falling edge of CGMXCLK.
7.5.1 SIM Counter During Power-On Reset
The POR detects power applied to the MCU. At power-on, the POR
circuit asserts the signal PORRST. Once the SIM is initialized, it enables
the clock generation module (CGM) to drive the bus clock state machine.
7.5.2 SIM Counter and Reset States
External reset has no effect on the SIM counter. The SIM counter is
free-running after all reset states. See 7.4.2 Active Resets from
Internal Sources for counter control and internal reset recovery
sequences.
7.6 Exception Control
Normal, sequential program execution can be changed in three different
ways:
1. Interrupts:
a. Maskable hardware CPU interrupts
b. Non-maskable software interrupt instruction (SWI)
2. Reset
3. Break interrupts
MC68HC908MR8 — Rev 4.1
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Technical Data
System Integration Module (SIM)
99
System Integration Module (SIM)
7.6.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register
contents on the stack and sets the interrupt mask (I bit) to prevent
additional interrupts. At the end of an interrupt, the return from interrupt
(RTI) instruction recovers the CPU register contents from the stack so
that normal processing can resume. Figure 7-8 shows interrupt entry
timing. Figure 7-10 shows interrupt recovery timing.
Interrupts are latched, and arbitration is performed in the SIM at the start
of interrupt processing. The arbitration result is a constant that the CPU
uses to determine which vector to fetch. Once an interrupt is latched by
the SIM, no other interrupt can take precedence, regardless of priority,
until the latched interrupt is serviced (or the I bit is cleared). See
Figure 7-9.
MODULE
INTERRUPT
I BIT
IAB
IDB
DUMMY
DUMMY
SP
SP – 1
SP – 2
PC – 1[7:0] PC – 1[15:8]
SP – 3
X
SP – 4
A
VECT H
CCR
VECT L START ADDR
V DATA H
V DATA L
OPCODE
R/W
Figure 7-8. Interrupt Entry
Technical Data
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System Integration Module (SIM)
Freescale Semiconductor
System Integration Module (SIM)
Exception Control
FROM RESET
BREAK
INTERRUPT?
I BIT
SET?
YES
NO
YES
I BIT SET?
NO
INT0
INTERRUPT?
YES
NO
INT1
INTERRUPT?
YES
NO
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
AS MANY INTERRUPTS AS EXIST ON CHIP
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION?
YES
NO
RTI
INSTRUCTION?
YES
UNSTACK CPU REGISTERS
NO
EXECUTE INSTRUCTION
Figure 7-9. Interrupt Processing
MC68HC908MR8 — Rev 4.1
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Technical Data
System Integration Module (SIM)
101
System Integration Module (SIM)
MODULE
INTERRUPT
I BIT
IAB
SP – 4
IDB
SP – 3
CCR
SP – 2
A
SP – 1
X
SP
PC
PC + 1
PC – 1[7:0] PC – 1[15:8] OPCODE
OPERAND
R/W
Figure 7-10. Interrupt Recovery
7.6.1.1 Hardware Interrupts
A hardware interrupt does not stop the current instruction. Processing of
a hardware interrupt begins after completion of the current instruction.
When the current instruction is complete, the SIM checks all pending
hardware interrupts. If interrupts are not masked (I bit clear in the
condition code register), and if the corresponding interrupt enable bit is
set, the SIM proceeds with interrupt processing; otherwise, the next
instruction is fetched and executed.
If more than one interrupt is pending at the end of an instruction
execution, the highest priority interrupt is serviced first. Figure 7-11
demonstrates what happens when two interrupts are pending. If an
interrupt is pending upon exit from the original interrupt service routine,
the pending interrupt is serviced before the LDA instruction is executed.
The LDA opcode is prefetched by both the INT1 and INT2 RTI
instructions. However, in the case of the INT1 RTI prefetch, this is a
redundant operation.
NOTE:
To maintain compatibility with the M6805 Family, the H register is not
pushed on the stack during interrupt entry. If the interrupt service routine
modifies the H register or uses the indexed addressing mode, software
should save the H register and then restore it prior to exiting the routine.
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Freescale Semiconductor
System Integration Module (SIM)
Exception Control
CLI
LDA #$FF
INT1
BACKGROUND ROUTINE
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 7-11. Interrupt Recognition Example
7.6.1.2 SWI Instruction
The SWI instruction is a non-maskable instruction that causes an
interrupt regardless of the state of the interrupt mask (I bit) in the
condition code register.
NOTE:
A software interrupt pushes PC onto the stack. A software interrupt does
not push PC – 1, as a hardware interrupt does.
7.6.2 Reset
All reset sources always have equal and highest priority and cannot be
arbitrated.
7.6.3 Status Flag Protection in Break Mode
The SIM controls whether status flags contained in other modules can
be cleared during break mode. The user can select whether flags are
protected from being cleared by properly initializing the break clear flag
enable bit (BCFE) in the SIM break flag control register (SBFCR).
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Technical Data
System Integration Module (SIM)
103
System Integration Module (SIM)
Protecting flags in break mode ensures that set flags will not be cleared
while in break mode. This protection allows registers to be freely read
and written during break mode without losing status flag information.
Setting the BCFE bit enables the clearing mechanisms. Once cleared in
break mode, a flag remains cleared even when break mode is exited.
Status flags with a 2-step clearing mechanism — for example, a read of
one register followed by the read or write of another — are protected,
even when the first step is accomplished prior to entering break mode.
Upon leaving break mode, execution of the second step will clear the flag
as normal.
7.7 Low-Power Mode
Executing the WAIT or STOP instruction puts the MCU in a low
power-consumption mode for standby situations. The SIM holds the
CPU in a non-clocked state. Both STOP and WAIT clear the interrupt
mask (I) in the condition code register, allowing interrupts to occur.
7.7.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks
continue to run. Figure 7-12 shows the timing for wait mode entry.
IAB
IDB
WAIT ADDR
WAIT ADDR + 1
PREVIOUS DATA
NEXT OPCODE
SAME
SAME
SAME
SAME
R/W
Note: Previous data can be operand data or the WAIT opcode, depending on the
last instruction.
Figure 7-12. Wait Mode Entry Timing
A module that is active during wait mode can wake up the CPU with an
interrupt if the interrupt is enabled. Stacking for the interrupt begins one
cycle after the WAIT instruction during which the interrupt occurred.
Refer to the wait mode subsection of each module to see if the module
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Freescale Semiconductor
System Integration Module (SIM)
Low-Power Mode
is active or inactive in wait mode. Some modules can be programmed to
be active in wait mode.
Wait mode can also be exited by a reset or break. A break interrupt
during wait mode sets the SIM break stop/wait bit, SBSW, in the SIM
break status register (SBSR). If the COP disable bit, COPD, in the
configuration register is logic 0, then the computer operating properly
module (COP) is enabled and remains active in wait mode.
Figure 7-13 and Figure 7-14 show the timing for wait recovery.
IAB
$6E0B
IDB
$A6
$A6
$6E0C
$A6
$00FF
$01
$0B
$00FE
$00FD
$00FC
$6E
EXITSTOPWAIT
Note: EXITSTOPWAIT = RST pin or CPU interrupt or break interrupt
Figure 7-13. Wait Recovery from Interrupt or Break
32
CYCLES
IAB
IDB
RST VCT H RST VCT L
$6E0B
$A6
$A6
32
CYCLES
$A6
RST
CGMXCLK
Figure 7-14. Wait Recovery from Internal Reset
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Technical Data
System Integration Module (SIM)
105
System Integration Module (SIM)
7.7.2 Stop Mode
In stop mode, the SIM counter is reset and the system clock is disabled.
An external interrupt request will cause an exit from stop mode. Stacking
for interrupts begins after the stop recovery delay time of 4096
CGMXCLK cycles has elapsed. Reset or break also cause an exit from
stop mode.
The SIM disables the clock generator module outputs in stop mode,
stopping the CPU and all peripherals.
NOTE:
It is important to note that when using the PWM generator Its outputs will
stop toggling when stop mode is entered. The PWM module must be
disabled before entering stop mode to prevent external inverter failure.
7.7.3 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a
break caused an exit from wait mode.
Ad- $FE00
dress:
Read:
Write:
BIt 7
6
5
4
3
2
R
R
R
R
R
R
Reset:
1
SBSW
Note(1)
Bit 0
R
0
R
= Reserved
1. Writing a logic 0 clears SBSW.
Figure 7-15. SIM Break Status Register (SBSR)
SBSW — SIM Break Stop/Wait Bit
This status bit is useful in applications requiring a return to wait mode
after exiting from a break interrupt. Clear SBSW by writing a logic 0 to
it. Reset clears SBSW.
1 = Wait mode was exited by break interrupt.
0 = Wait mode was not exited by break interrupt.
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Freescale Semiconductor
System Integration Module (SIM)
Low-Power Mode
SBSW can be read within the break state SWI routine. The user can
modify the return address on the stack by subtracting one from it. The
following code is an example of this. Writing 0 to the SBSW bit
clears it.
; This code works if the H register has been pushed onto the stack in the break
; service routine software. This code should be executed at the end of the break
; service routine software.
HIBYTE
EQU
5
LOBYTE
EQU
6
;
If not SBSW, do RTI
BRCLR
SBSW,SBSR, RETURN
; See if wait mode was exited by break.
;
TST
LOBYTE,SP
; If RETURNLO is not zero,
BNE
DOLO
; then just decrement low byte.
DEC
HIBYTE,SP
; Else deal with high byte, too.
DOLO
DEC
LOBYTE,SP
; Point to WAIT opcode.
RETURN
PULH
RTI
; Restore H register.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
System Integration Module (SIM)
107
System Integration Module (SIM)
7.7.4 SIM Reset Status Register
The SIM reset status register (SRSR) contains six flags that show the
source of the last reset. Clear the SRSR by reading it. A power-on reset
sets the POR bit and clears all other bits in the register.
Ad- $FE01
dress:
BIt 7
6
5
4
3
2
1
Bit 0
Read:
POR
PIN
COP
ILOP
ILAD
0
LVI
0
Write:
R
R
R
R
R
R
R
R
Reset:
1
0
0
0
0
0
0
0
R
= Reserved
Figure 7-16. SIM Reset Status Register (SRSR)
POR — Power-On Reset Bit
1 = Last reset caused by POR circuit
0 = Read of SRSR
PIN — External Reset Bit
1 = Last reset caused by external reset pin (RST)
0 = POR or read of SRSR
COP — Computer Operating Properly Reset Bit
1 = Last reset caused by COP counter
0 = POR or read of SRSR
ILOP — Illegal Opcode Reset Bit
1 = Last reset caused by an illegal opcode
0 = POR or read of SRSR
ILAD — Illegal Address Reset Bit (opcode fetches only)
1 = Last reset caused by an opcode fetch from an illegal address
0 = POR or read of SRSR
LVI — Low-Voltage Inhibit Reset Bit
1 = Last reset was caused by the LVI circuit
0 = POR or read of SRSR
Technical Data
108
MC68HC908MR8 — Rev 4.1
System Integration Module (SIM)
Freescale Semiconductor
System Integration Module (SIM)
Low-Power Mode
7.7.5 SIM Break Flag Control Register
The SIM break control register (SBFCR) contains a bit that enables
software to clear status bits while the MCU is in a break state.
Ad- $FE03
dress:
Read:
Write:
Reset:
BIt 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
0
R
= Reserved
Figure 7-17. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing
status registers while the MCU is in a break state. To clear status bits
during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
System Integration Module (SIM)
109
System Integration Module (SIM)
Technical Data
110
MC68HC908MR8 — Rev 4.1
System Integration Module (SIM)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 8. Clock Generator Module (CGM)
8.1 Contents
8.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
8.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .112
8.4
Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .113
8.4.1
Crystal Oscillator Circuit . . . . . . . . . . . . . . . . . . . . . . . . .113
8.4.2
Phase-Locked Loop Circuit (PLL). . . . . . . . . . . . . . . . . .115
8.4.3
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . .121
8.4.4
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . .122
8.5
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .123
8.5.1
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . .122
8.5.2
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . .123
8.5.3
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . .123
8.5.4
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . .124
8.5.5
Oscillator Enable Signal (SIMOSCEN) . . . . . . . . . . . . . .124
8.5.6
Crystal Output Frequency Signal (CGMXCLK) . . . . . . . 124
8.5.7
CGM Base Clock Output (CGMOUT) . . . . . . . . . . . . . . .124
8.5.8
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . .124
8.6
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
8.6.1
PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . .126
8.6.2
PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . .129
8.6.3
PLL Programming Register. . . . . . . . . . . . . . . . . . . . . . .131
8.7
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .132
8.8
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
8.9
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
8.10
CGM During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . .133
8.11 Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . .134
8.11.1 Acquisition/Lock Time Definitions . . . . . . . . . . . . . . . . .134
8.11.2 Parametric Influences on Reaction Time . . . . . . . . . . . .135
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
111
Clock Generator Module (CGM)
8.11.3
8.11.4
Choosing a Filter Capacitor . . . . . . . . . . . . . . . . . . . . . .136
Reaction Time Calculation . . . . . . . . . . . . . . . . . . . . . . .137
8.2 Introduction
This section describes the clock generator module (CGM, version A).
The CGM generates the crystal clock signal, CGMXCLK, which operates
at the frequency of the crystal. The CGM also generates the base clock
signal, CGMOUT, from which the system integration module (SIM)
derives the system clocks.
CGMOUT is based on either the crystal clock divided by two or the
phase-locked loop (PLL) clock, CGMVCLK, divided by two. The PLL is
a frequency generator designed for use with crystals or ceramic
resonators. The PLL can generate an 8-MHz bus frequency without
using a 32-MHz crystal.
8.3 Features
Features of the CGM include:
•
Phase-locked loop with output frequency in integer multiples of the
crystal reference
•
Programmable hardware voltage-controlled oscillator (VCO) for
low-jitter operation
•
Automatic bandwidth control mode for low-jitter operation
•
Automatic frequency lock detector
•
Central processor unit (CPU) interrupt on entry or exit from locked
condition
Technical Data
112
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Functional Description
8.4 Functional Description
The CGM consists of three major submodules:
1. Crystal oscillator circuit — The crystal oscillator circuit generates
the constant crystal frequency clock, CGMXCLK.
2. Phase-locked loop (PLL) — The PLL generates the
programmable VCO frequency clock, CGMVCLK.
3. Base clock selector circuit — This software-controlled circuit
selects either CGMXCLK divided by two or the VCO clock,
CGMVCLK, divided by two as the base clock, CGMOUT. The SIM
derives the system clocks from CGMOUT.
Figure 8-1 shows the structure of the CGM.
8.4.1 Crystal Oscillator Circuit
The crystal oscillator circuit consists of an inverting amplifier and an
external crystal. The OSC1 pin is the input to the amplifier and the OSC2
pin is the output. The SIMOSCEN signal from the system integration
module (SIM) enables the crystal oscillator circuit.
The CGMXCLK signal is the output of the crystal oscillator circuit and
runs at a rate equal to the crystal frequency. CGMXCLK is then buffered
to produce CGMRCLK, the PLL reference clock.
CGMXCLK can be used by other modules which require precise timing
for operation. The duty cycle of CGMXCLK is not guaranteed to be
50 percent and depends on external factors, including the crystal and
related external components.
An externally generated clock also can feed the OSC1 pin of the crystal
oscillator circuit. Connect the external clock to the OSC1 pin and let the
OSC2 pin float.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
113
Clock Generator Module (CGM)
CRYSTAL OSCILLATOR
OSC2
CGMXCLK
CLOCK
SELECT
CIRCUIT
OSC1
÷2
A
CGMOUT
B S*
TO SIM
TO SIM
*WHEN S = 1, CGMOUT = B
SIMOSCEN
CGMRDV
CGMRCLK
VDDA
BCS
CGMXFC
USER MODE
VSS
VRS[7:4]
PHASE
DETECTOR
MONITOR MODE
VOLTAGE
CONTROLLED
OSCILLATOR
LOOP
FILTER
PLL ANALOG
LOCK
DETECTOR
LOCK
BANDWIDTH
CONTROL
AUTO
ACQ
INTERRUPT
CONTROL
PLLIE
CGMINT
PLLF
MUL[7:4]
CGMVDV
FREQUENCY
DIVIDER
CGMVCLK
Figure 8-1. CGM Block Diagram
Technical Data
114
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Functional Description
Addr.
Register Name
Bit 7
Read
:
$005C
5
4
PLLF
PLLIE
PLL Control Register
Write
(PCTL)
:
See page 126.
Re0
set:
Read
:
PLLON
R
0
Read
:
MUL7
PLL Programming Register
Write
(PPG)
:
See page 131.
Re0
set:
R
3
2
1
Bit 0
1
1
1
1
R
R
R
R
1
1
1
1
0
0
0
0
R
R
R
R
BCS
1
0
LOCK
AUTO
PLL Bandwidth Control RegWrite
$005D
ister (PBWC)
:
See page 129.
Re0
set:
$005E
6
ACQ
XLD
R
0
0
0
0
0
0
0
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
1
1
0
0
1
1
0
= Reserved
Figure 8-2. CGM I/O Register Summary
8.4.2 Phase-Locked Loop Circuit (PLL)
The PLL is a frequency generator that can operate in either acquisition
mode or tracking mode, depending on the accuracy of the output
frequency. The PLL can change between acquisition and tracking
modes either automatically or manually.
8.4.2.1 PLL Circuits
The PLL consists of these circuits:
•
Voltage-controlled oscillator (VCO)
•
Modulo VCO frequency divider
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
115
Clock Generator Module (CGM)
•
Phase detector
•
Loop filter
•
Lock detector
Technical Data
116
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Functional Description
The operating range of the VCO is programmable for a wide range of
frequencies and for maximum immunity to external noise, including
supply and CGMXFC noise. The VCO frequency is bound to a range
from roughly one-half to twice the center-of-range frequency, fVRS.
Modulating the voltage on the CGMXFC pin changes the frequency
within this range. By design, fVRS is equal to the nominal center-of-range
frequency, fNOM, (4.9152 MHz) times a linear factor L, or (L) fNOM.
CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK.
CGMRCLK runs at a frequency, fRCLK, and is fed to the PLL through a
buffer. The buffer output is the final reference clock, CGMRDV, running
at a frequency, fRDV = fRCLK.
The VCO’s output clock, CGMVCLK, running at a frequency fVCLK, is fed
back through a programmable modulo divider. The modulo divider
reduces the VCO clock by a factor, N. The divider’s output is the VCO
feedback clock, CGMVDV, running at a frequency, fVDV = fVCLK/N. See
8.4.2.4 Programming the PLL for more information.
The phase detector then compares the VCO feedback clock, CGMVDV,
with the final reference clock, CGMRDV. A correction pulse is generated
based on the phase difference between the two signals. The loop filter
then slightly alters the dc voltage on the external capacitor connected to
CGMXFC based on the width and direction of the correction pulse. The
filter can make fast or slow corrections depending on its mode,
described in 8.4.2.2 Acquisition and Tracking Modes. The value of the
external capacitor and the reference frequency determines the speed of
the corrections and the stability of the PLL.
The lock detector compares the frequencies of the VCO feedback clock,
CGMVDV, and the final reference clock, CGMRDV. Therefore, the
speed of the lock detector is directly proportional to the final reference
frequency, fRDV. The circuit determines the mode of the PLL and the lock
condition based on this comparison.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
117
Clock Generator Module (CGM)
8.4.2.2 Acquisition and Tracking Modes
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. When in
acquisition mode, the ACQ bit is clear in the PLL bandwidth control
register. See 8.6.2 PLL Bandwidth Control Register.
•
Tracking mode — In tracking mode, the filter makes only small
corrections to the frequency of the VCO. PLL jitter is much lower
in tracking mode, but the response to noise is also slower. The
PLL enters tracking mode when the VCO frequency is nearly
correct, such as when the PLL is selected as the base clock
source. The PLL is automatically in tracking mode when not in
acquisition mode or when the ACQ bit is set. See 8.4.3 Base
Clock Selector Circuit.
8.4.2.3 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter
manually or automatically.
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, CGMVCLK, is safe to use as the source for the base clock,
CGMOUT (8.6.2 PLL Bandwidth Control Register). If PLL interrupts
are enabled, the software can wait for a PLL interrupt request and then
check the LOCK bit. If interrupts are disabled, software can poll the
LOCK bit continuously (during PLL startup, usually) or at periodic
intervals. In either case, when the LOCK bit is set, the VCO clock is safe
to use as the source for the base clock (see 8.4.3 Base Clock Selector
Circuit). 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.
See 8.7 Interrupts for information and precautions on using interrupts.
Technical Data
118
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Functional Description
These conditions apply when the PLL is in automatic bandwidth control
mode:
•
The ACQ bit (see 8.6.2 PLL Bandwidth Control Register) is a
read-only indicator of the mode of the filter. See 8.4.2.2
Acquisition and Tracking Modes.
•
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 8.11 Acquisition/Lock Time
Specifications for more information.
•
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 8.11 Acquisition/Lock Time
Specifications for more information.
•
CPU interrupts can occur if enabled (PLLIE = 1) when the PLL’s
lock condition changes, toggling the LOCK bit. See 8.6.1 PLL
Control Register.
The PLL also may operate in manual mode (AUTO = 0). Manual mode
is used by systems that do not require an indicator of the lock condition
for proper operation. Such systems typically operate well below fBUSMAX
and require fast startup.
These 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.
•
Before entering tracking mode (ACQ = 1), software must wait a
given time, tACQ (see 8.11 Acquisition/Lock Time
Specifications), after turning on the PLL by setting PLLON in the
PLL control register (PCTL).
•
Software must wait a given time, tAL, after entering tracking mode
before selecting the PLL as the clock source to CGMOUT
(BCS = 1).
•
The LOCK bit is disabled.
•
CPU interrupts from the CGM are disabled.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
119
Clock Generator Module (CGM)
8.4.2.4 Programming the PLL
This procedure shows how to program the PLL.
NOTE:
The round function in the following equations means that the real
number should be rounded to the nearest integer number.
1. Choose the desired bus frequency, fBUSDES.
2. Calculate the desired VCO frequency (four times the desired bus
frequency).
f
VCLKDES
= 4×f
BUSDES
3. Choose a practical PLL reference frequency, fRCLK.
4. Select a VCO frequency multiplier, N.
5. Calculate and verify the adequacy of the VCO and bus
frequencies fVCLK and fBUS.
f
VCLK
f
BUS
= N×f
= (f
RCLK
VCLK
)⁄4
6. Select a VCO linear range multiplier, L.
where fNOM = 4.9152 MHz
7. Calculate and verify the adequacy of the VCO programmed
center-of-range frequency, fVRS.
fVRS = (L) fNOM
8. Verify the choice of N and L by comparing fVCLK to fVRS and
fVCLKDES. For proper operation, fVCLK must be within the
application’s tolerance of fVCLKDES, and fVRS must be as close as
possible to fVCLK.
CAUTION:
Exceeding the recommended maximum bus frequency or VCO
frequency can crash the MCU.
9. Program the PLL registers accordingly:
a. In the upper four bits of the PLL programming register (PPG),
program the binary equivalent of N.
b. In the lower four bits of the PLL programming register (PPG),
program the binary equivalent of L.
Technical Data
120
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Functional Description
8.4.2.5 Special Programming Exceptions
The programming method described in 8.4.2.4 Programming the PLL
does not account for possible exceptions. A value of 0 for N or L is
meaningless when used in the equations given. To account for these
exceptions:
•
A 0 value for N is interpreted exactly the same as a value of 1.
•
A 0 value for L disables the PLL and prevents its selection as the
source for the base clock. See 8.4.3 Base Clock Selector
Circuit.
8.4.3 Base Clock Selector Circuit
This circuit is used to select either the crystal clock, CGMXCLK, or the
VCO clock, CGMVCLK, as the source of the base clock, CGMOUT. The
two input clocks go through a transition control circuit that waits up to
three CGMXCLK cycles and three CGMVCLK cycles to change from
one clock source to the other. During this time, CGMOUT is held in state.
The output of the transition control circuit is then divided by two to correct
the duty cycle. Therefore, the bus clock frequency, which is one-half of
the base clock frequency, is one-fourth the frequency of the selected
clock (CGMXCLK or CGMVCLK).
The BCS bit in the PLL control register (PCTL) selects which clock drives
CGMOUT. The VCO clock cannot be selected as the base clock source
if the PLL is not turned on. The PLL cannot be turned off if the VCO clock
is selected. The PLL cannot be turned on or off simultaneously with the
selection or deselection of the VCO clock. The VCO clock also cannot
be selected as the base clock source if the factor L is programmed to a 0.
This value would set up a condition inconsistent with the operation of the
PLL, so that the PLL would be disabled and the crystal clock would be
forced as the source of the base clock.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
121
Clock Generator Module (CGM)
8.4.4 CGM External Connections
In its typical configuration, the CGM requires seven external
components. Five of these are for the crystal oscillator and two are for
the PLL.
The crystal oscillator is normally connected in a Pierce oscillator
configuration, as shown in Figure 8-3. Figure 8-3 shows only the logical
representation of the internal components and may not represent actual
circuitry.
The oscillator configuration uses five components:
1. Crystal, X1
2. Fixed capacitor, C1
3. Tuning capacitor, C2 (can also be a fixed capacitor)
4. Feedback resistor, RB
5. Series resistor, RS (optional)
The series resistor (RS) is included in the diagram to follow strict Pierce
oscillator guidelines and may not be required for all ranges of operation,
especially with high frequency crystals. Refer to the crystal
manufacturer’s data for more information.
Figure 8-3 also shows the external components for the PLL:
•
Bypass capacitor, CBYP
•
Filter capacitor, CF
Routing should be done with great care to minimize signal cross talk and
noise. See 8.11 Acquisition/Lock Time Specifications for routing
information and more information on the filter capacitor’s value and its
effects on PLL performance.
Technical Data
122
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
I/O Signals
SIMOSCEN
CGMXCLK
OSC1
OSC2
VSS
RS *
CGMXFC
VDDA
VDD
CF
RB
CBYP
X1
C1
C2
*RS can be 0 (shorted) when used with higher-frequency crystals.
Refer to manufacturer’s data.
Figure 8-3. CGM External Connections
8.5 I/O Signals
The following paragraphs describe the CGM input/output (I/O) signals.
8.5.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
8.5.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
8.5.3 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase
corrections. A small external capacitor is connected to this pin.
NOTE:
To prevent noise problems, CF should be placed as close to the
CGMXFC pin as possible, with minimum routing distances and no
routing of other signals across the CF connection.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
123
Clock Generator Module (CGM)
8.5.4 PLL Analog Power Pin (VDDA)
VDDA is a power pin used by the analog portions of the PLL. Connect the
VDDA pin to the same voltage potential as the VDD pin.
NOTE:
Route VDDA carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
8.5.5 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM)
and enables the oscillator and PLL.
8.5.6 Crystal Output Frequency Signal (CGMXCLK)
CGMXCLK is the crystal oscillator output signal. It runs at the full speed
of the crystal (fXCLK) and comes directly from the crystal oscillator circuit.
Figure 8-3 shows only the logical relation of CGMXCLK to OSC1 and
OSC2 and may not represent the actual circuitry. The duty cycle of
CGMXCLK is unknown and may depend on the crystal and other
external factors. Also, the frequency and amplitude of CGMXCLK can be
unstable at startup.
8.5.7 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM,
which generates the MCU clocks. CGMOUT is a 50 percent duty cycle
clock running at twice the bus frequency. CGMOUT is software
programmable to be either the oscillator output, CGMXCLK, divided by
two or the VCO clock, CGMVCLK, divided by two.
8.5.8 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
Technical Data
124
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
CGM Registers
8.6 CGM Registers
These registers control and monitor operation of the CGM:
•
PLL control register (PCTL), see 8.6.1 PLL Control Register
•
PLL bandwidth control register (PBWC), see 8.6.2 PLL
Bandwidth Control Register
•
PLL programming register (PPG), see 8.6.3 PLL Programming
Register
Figure 8-4 is a summary of the CGM registers.
Addr.
Register Name
Bit 7
Read
:
$005C
PLLIE
PLL Control Register
Write
(PCTL)
:
See page 126.
Re0
set:
Read
:
AUTO
PLL Bandwidth Control RegWrite
$005D
ister (PBWC)
:
See page 129.
Re0
set:
6
5
4
PLLF
PLLON
1
0
LOCK
ACQ
1
Bit 0
1
1
1
1
R
R
R
R
1
1
1
1
0
0
0
0
R
R
R
R
0
0
0
0
XLD
R
0
2
BCS
R
0
3
0
0
Figure 8-4. CGM I/O Register Summary
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
125
Clock Generator Module (CGM)
Addr.
Register Name
Bit 7
Read
:
$005E
MUL7
PLL Programming Register
Write
(PPG)
:
See page 131.
Re0
set:
R
6
5
4
3
2
1
Bit 0
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
1
1
0
0
1
1
0
= Reserved
Notes:
1. When AUTO = 0, PLLIE is forced to logic 0 and is read-only.
2. When AUTO = 0, PLLF and LOCK read as logic 0.
3. When AUTO = 1, ACQ is read-only.
4. When PLLON = 0 or VRS[7:4] = $0, BCS is forced to logic 0 and is read-only.
5. When PLLON = 1, the PLL programming register is read-only.
6. When BCS = 1, PLLON is forced set and is read-only.
Figure 8-4. CGM I/O Register Summary
8.6.1 PLL Control Register
The PLL control register (PCTL) contains the interrupt enable and flag
bits, the on/off switch, and the base clock selector bit.
Ad- $005C
dress:
Bit 7
Read:
Write:
Reset:
PLLIE
0
R
6
PLLF
R
5
4
PLLON
BCS
1
0
0
3
2
1
Bit 0
1
1
1
1
R
R
R
R
1
1
1
1
= Reserved
Figure 8-5. PLL Control Register (PCTL)
Technical Data
126
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
CGM Registers
PLLIE — PLL Interrupt Enable Bit
This read/write bit enables the PLL to generate an interrupt request
when the LOCK bit toggles, setting the PLL flag, PLLF. When the
AUTO bit in the PLL bandwidth control register (PBWC) is clear,
PLLIE cannot be written and reads as logic 0. Reset clears the PLLIE
bit.
1 = PLL interrupts enabled
0 = PLL interrupts disabled
PLLF — PLL Interrupt Flag Bit
This read-only bit is set whenever the LOCK bit toggles. PLLF
generates an interrupt request if the PLLIE bit also is set. PLLF
always reads as logic 0 when the AUTO bit in the PLL bandwidth
control register (PBWC) is clear. Clear the PLLF bit by reading the
PLL control register. Reset clears the PLLF bit.
1 = Change in lock condition
0 = No change in lock condition
NOTE:
Do not inadvertently clear the PLLF bit. Any read or read-modify-write
operation on the PLL control register clears the PLLF bit.
PLLON — PLL On Bit
This read/write bit activates the PLL and enables the VCO clock,
CGMVCLK. PLLON cannot be cleared if the VCO clock is driving the
base clock, CGMOUT (BCS = 1). Reset sets this bit so that the loop
can stabilize as the MCU is powering up. See 8.4.3 Base Clock
Selector Circuit.
1 = PLL on
0 = PLL off
BCS — Base Clock Select Bit
This read/write bit selects either the crystal oscillator output,
CGMXCLK, or the VCO clock, CGMVCLK, as the source of the CGM
output, CGMOUT. CGMOUT frequency is one-half the frequency of
the selected clock. BCS cannot be set while the PLLON bit is clear.
After toggling BCS, it may take up to three CGMXCLK and three
CGMVCLK cycles to complete the transition from one source clock to
the other. During the transition, CGMOUT is held in stasis. Reset
clears the BCS bit. See 8.4.3 Base Clock Selector Circuit.
1 = CGMVCLK divided by two drives CGMOUT
0 = CGMXCLK divided by two drives CGMOUT
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
127
Clock Generator Module (CGM)
NOTE:
PLLON and BCS have built-in protection that prevents the base clock
selector circuit from selecting the VCO clock as the source of the base
clock if the PLL is off. Therefore, PLLON cannot be cleared when BCS
is set, and BCS cannot be set when PLLON is clear. If the PLL is off
(PLLON = 0), selecting CGMVCLK requires two writes to the PLL control
register. See 8.4.3 Base Clock Selector Circuit.
PCTL Bits 3–0 — Unimplemented Bits
These bits provide no function and always read as logic 1s.
Technical Data
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MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
CGM Registers
8.6.2 PLL Bandwidth Control Register
The PLL bandwidth control register:
•
Selects automatic or manual (software-controlled) bandwidth
control mode
•
Indicates when the PLL is locked
•
In automatic bandwidth control mode, indicates when the PLL is in
acquisition or tracking mode
•
In manual operation, forces the PLL into acquisition or tracking
mode
Ad- $005D
dress:
Bit 7
Read:
Write:
Reset:
AUTO
0
R
6
LOCK
R
5
4
ACQ
XLD
0
0
0
3
2
1
Bit 0
0
0
0
0
R
R
R
R
0
0
0
0
= Reserved
Figure 8-6. PLL Bandwidth Control Register (PBWC)
AUTO — Automatic Bandwidth Control Bit
This read/write bit selects automatic or manual bandwidth control.
When initializing the PLL for manual operation (AUTO = 0), clear the
ACQ bit before turning on the PLL. Reset clears the AUTO bit.
1 = Automatic bandwidth control
0 = Manual bandwidth control
LOCK — Lock Indicator Bit
When the AUTO bit is set, LOCK is a read-only bit that becomes set
when the VCO clock, CGMVCLK, is locked (running at the
programmed frequency). When the AUTO bit is clear, LOCK reads as
logic 0 and has no meaning. Reset clears the LOCK bit.
1 = VCO frequency correct or locked
0 = VCO frequency incorrect or unlocked
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
129
Clock Generator Module (CGM)
ACQ — Acquisition Mode Bit
When the AUTO bit is set, ACQ is a read-only bit that indicates
whether the PLL is in acquisition mode or tracking mode. When the
AUTO bit is clear, ACQ is a read/write bit that controls whether the
PLL is in acquisition or tracking mode.
In automatic bandwidth control mode (AUTO = 1), the last-written
value from manual operation is stored in a temporary location and is
recovered when manual operation resumes. Reset clears this bit,
enabling acquisition mode.
1 = Tracking mode
0 = Acquisition mode
XLD — Crystal Loss Detect Bit
When the VCO output, CGMVCLK, is driving CGMOUT, this
read/write bit can indicate whether the crystal reference frequency is
active or not. To check the status of the crystal reference, follow these
steps:
1. Write a logic 1 to XLD.
2. Wait N × 4 cycles. (N is the VCO frequency multiplier.)
3. Read XLD.
1 = Crystal reference is not active.
0 = Crystal reference is active.
The crystal loss detect function works only when the BCS bit is set,
selecting CGMVCLK to drive CGMOUT. When BCS is clear, XLD
always reads as logic 0.
PBWC Bits 3–0 — Reserved for Test
These bits enable test functions not available in user mode. To ensure
software portability from development systems to user applications,
software should write 0s to PBWC[3:0] whenever writing to PBWC.
Technical Data
130
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
CGM Registers
8.6.3 PLL Programming Register
The PLL programming register (PPG) contains the programming
information for the modulo feedback divider and the programming
information for the hardware configuration of the VCO.
Ad- $005E
dress:
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
Figure 8-7. PLL Programming Register (PPG)
MUL[7:4] — Multiplier Select Bits
These read/write bits control the modulo feedback divider that selects
the VCO frequency multiplier, N. See 8.4.2.1 PLL Circuits and
8.4.2.4 Programming the PLL. A value of $0 in the multiplier select
bits configures the modulo feedback divider the same as a value of
$1. Reset initializes these bits to $6 to give a default multiply value
of 6.
Table 8-1. VCO Frequency Multiplier (N) Selection
NOTE:
MUL7:MUL6:MUL5:MUL4
VCO Frequency Multiplier (N)
0000
1
0001
1
0010
2
0011
3
1101
13
1110
14
1111
15
The multiplier select bits have built-in protection that prevents them from
being written when the PLL is on (PLLON = 1).
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
131
Clock Generator Module (CGM)
VRS[7:4] — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear
multiplier L, which controls the hardware center-of-range frequency
fVRS. See 8.4.2.1 PLL Circuits, 8.4.2.4 Programming the PLL, and
8.6.1 PLL Control Register. VRS[7:4] cannot be written when the
PLLON bit in the PLL control register (PCTL) is set. See 8.4.2.5
Special Programming Exceptions. A value of $0 in the VCO range
select bits disables the PLL and clears the BCS bit in the PCTL. See
8.4.3 Base Clock Selector Circuit and 8.4.2.5 Special
Programming Exceptions for more information.
Reset initializes the bits to $6 to give a default range multiply
value of 6.
NOTE:
The VCO range select bits have built-in protection that prevents them
from being written when the PLL is on (PLLON = 1) and prevents
selection of the VCO clock as the source of the base clock (BCS = 1) if
the VCO range select bits are all clear.
The VCO range select bits must be programmed correctly. Incorrect
programming may result in failure of the PLL to achieve lock.
8.7 Interrupts
When the AUTO bit is set in the PLL bandwidth control register (PBWC),
the PLL can generate a CPU interrupt request every time the LOCK bit
changes state. The PLLIE bit in the PLL control register (PCTL) enables
CPU interrupts from the PLL. PLLF, the interrupt flag in the PCTL,
becomes set whether interrupts are enabled or not. When the AUTO bit
is clear, CPU interrupts from the PLL are disabled and PLLF reads as
logic 0.
Software should read the LOCK bit after a PLL interrupt request to see
if the request was due to an entry into lock or an exit from lock. When the
PLL enters lock, the VCO clock, CGMVCLK, divided by two can be
selected as the CGMOUT source by setting BCS in the PCTL. When the
PLL exits lock, the VCO clock frequency is corrupt, and appropriate
precautions should be taken. If the application is not
Technical Data
132
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Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Wait Mode
frequency-sensitive, interrupts should be disabled to prevent PLL
interrupt service routines from impeding software performance or from
exceeding stack limitations.
NOTE:
Software can select the CGMVCLK divided by two as the CGMOUT
source even if the PLL is not locked (LOCK = 0). Therefore, software
should make sure the PLL is locked before setting the BCS bit.
8.8 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby
mode.
The WAIT instruction does not affect the CGM. Before entering wait
mode, software can disengage and turn off the PLL by clearing the BCS
and PLLON bits in the PLL control register (PCTL). Less power-sensitive
applications can disengage the PLL without turning it off. Applications
that require the PLL to wake the MCU from wait mode also can deselect
the PLL output without turning off the PLL.
8.9 Stop Mode
The STOP instruction puts the MCU in low power-consumption standby
mode.
The STOP instruction disables the CGMC (oscillator and phase-lock
loop) and holds the CGM outputs low.
8.10 CGM During Break Mode
The system integration module (SIM) controls whether status bits in
other modules can be cleared during the break state. The BCFE bit in
the SIM break flag control register (SBFCR) enables software to clear
status bits during the break state. See 7.7.5 SIM Break Flag Control
Register.
To allow software to clear status bits during a break interrupt, write a
logic 1 to the BCFE bit. If a status bit is cleared during the break state, it
remains cleared when the MCU exits the break state.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
133
Clock Generator Module (CGM)
To protect the PLLF bit during the break state, write a logic 0 to the
BCFE bit. With BCFE at logic 0 (its default state), software can read and
write the PLL control register during the break state without affecting the
PLLF bit.
8.11 Acquisition/Lock Time Specifications
The acquisition and lock times of the PLL are, in many applications, the
most critical PLL design parameters. Proper design and use of the PLL
ensures the highest stability and lowest acquisition/lock times.
8.11.1 Acquisition/Lock Time Definitions
Typical control systems refer to the acquisition time or lock time as the
reaction time, within specified tolerances, of the system to a step input.
In a PLL, the step input occurs when the PLL is turned on or when it
suffers a noise hit. The tolerance is usually specified as a percent of the
step input or when the output settles to the desired value plus or minus
a percent of the frequency change. Therefore, the reaction time is
constant in this definition, regardless of the size of the step input. For
example, consider a system with a 5 percent acquisition time tolerance.
If a command instructs the system to change from 0 Hz to 1 MHz, the
acquisition time is the time taken for the frequency to reach
1 MHz ± 50 kHz. Fifty kHz = 5 percent of the 1-MHz step input. If the
system is operating at 1 MHz and suffers a –100-kHz noise hit, the
acquisition time is the time taken to return from 900 kHz to
1 MHz ± 5 kHz. Five kHz = 5 percent of the 100-kHz step input.
Other systems refer to acquisition and lock times as the time the system
takes to reduce the error between the actual output and the desired
output to within specified tolerances. Therefore, the acquisition or lock
time varies according to the original error in the output. Minor errors may
not even be registered. Typical PLL applications prefer to use this
definition because the system requires the output frequency to be within
a certain tolerance of the desired frequency regardless of the size of the
initial error.
Technical Data
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Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Acquisition/Lock Time Specifications
The discrepancy in these definitions makes it difficult to specify an
acquisition or lock time for a typical PLL. Therefore, the definitions for
acquisition and lock times for this module are:
•
Acquisition time, tACQ, is the time the PLL takes to reduce the error
between the actual output frequency and the desired output
frequency to less than the tracking mode entry tolerance, ∆TRK.
Acquisition time is based on an initial frequency error,
(fDES– fORIG)/fDES, of not more than ±100 percent. In automatic
bandwidth control mode (see 8.4.2.3 Manual and Automatic PLL
Bandwidth Modes), acquisition time expires when the ACQ bit
becomes set in the PLL bandwidth control register (PBWC).
•
Lock time, tLock, is the time the PLL takes to reduce the error
between the actual output frequency and the desired output
frequency to less than the lock mode entry tolerance, ∆Lock. Lock
time is based on an initial frequency error, (fDES–fORIG)/fDES, of
not more than ± 100 percent. In automatic bandwidth control
mode, lock time expires when the LOCK bit becomes set in the
PLL bandwidth control register (PBWC). See 8.4.2.3 Manual and
Automatic PLL Bandwidth Modes.
Obviously, the acquisition and lock times can vary according to how
large the frequency error is and may be shorter or longer in many cases.
8.11.2 Parametric Influences on Reaction Time
Acquisition and lock times are designed to be as short as possible while
still providing the highest possible stability. These reaction times are not
constant, however. Many factors directly and indirectly affect the
acquisition time.
The most critical parameter which affects the reaction times of the PLL
is the reference frequency, fRDV. This frequency is the input to the phase
detector and controls how often the PLL makes corrections. For stability,
the corrections must be small compared to the desired frequency, so
several corrections are required to reduce the frequency error.
Therefore, the slower the reference the longer it takes to make these
corrections. This parameter is also under user control via the choice of
crystal frequency, fXCLK.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
135
Clock Generator Module (CGM)
Another critical parameter is the external filter capacitor. The PLL
modifies the voltage on the VCO by adding or subtracting charge from
this capacitor. Therefore, the rate at which the voltage changes for a
given frequency error (thus change in charge) is proportional to the
capacitor size. The size of the capacitor also is related to the stability of
the PLL. If the capacitor is too small, the PLL cannot make small enough
adjustments to the voltage and the system cannot lock. If the capacitor
is too large, the PLL may not be able to adjust the voltage in a
reasonable time. See 8.11.3 Choosing a Filter Capacitor.
Also important is the operating voltage potential applied to VDDA. The
power supply potential alters the characteristics of the PLL. A fixed value
is best. Variable supplies, such as batteries, are acceptable if they vary
within a known range at very slow speeds. Noise on the power supply is
not acceptable, because it causes small frequency errors which
continually change the acquisition time of the PLL.
Temperature and processing also can affect acquisition time because
the electrical characteristics of the PLL change. The part operates as
specified as long as these influences stay within the specified limits.
External factors, however, can cause drastic changes in the operation of
the PLL. These factors include noise injected into the PLL through the
filter capacitor, filter capacitor leakage, stray impedances on the circuit
board, and even humidity or circuit board contamination.
8.11.3 Choosing a Filter Capacitor
As described in 8.11.2 Parametric Influences on Reaction Time, the
external filter capacitor, CF, is critical to the stability and reaction time of
the PLL. The PLL is also dependent on reference frequency and supply
voltage. The value of the capacitor must, therefore, be chosen with
supply potential and reference frequency in mind. For proper operation,
the external filter capacitor must be chosen according to this equation:
C
F
= C
 V DDA
-----------------
FACT  f
RDV 
For acceptable values of CFACT, see 8.11 Acquisition/Lock Time
Specifications. For the value of VDDA, choose the voltage potential at
which the MCU is operating. If the power supply is variable, choose a
value near the middle of the range of possible supply values.
Technical Data
136
MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
Acquisition/Lock Time Specifications
This equation does not always yield a commonly available capacitor
size, so round to the nearest available size. If the value is between two
different sizes, choose the higher value for better stability. Choosing the
lower size may seem attractive for acquisition time improvement, but the
PLL can become unstable. Also, always choose a capacitor with a tight
tolerance (±20 percent or better) and low dissipation.
8.11.4 Reaction Time Calculation
The actual acquisition and lock times can be calculated using the
equations here. These equations yield nominal values under these
conditions:
•
Correct selection of filter capacitor, CF; see 8.11.3 Choosing a
Filter Capacitor
•
Room temperature operation
•
Negligible external leakage on CGMXFC
•
Negligible noise
The K factor in the equations is derived from internal PLL parameters.
KACQ is the K factor when the PLL is configured in acquisition mode, and
KTRK is the K factor when the PLL is configured in tracking mode. See
8.4.2.2 Acquisition and Tracking Modes.
t
 V DDA
8
=  -----------------  -----------------

ACQ
K
f
 RDV  ACQ
t
 V DDA
4
=  -----------------  ----------------

AL
f
K
 RDV  TRK
t
NOTE:
Lock
= t
ACQ
+t
AL
Inverse proportionality between the lock time and the reference
frequency
In automatic bandwidth control mode, the acquisition and lock times are
quantized into units based on the reference frequency, see 8.4.2.3
Manual and Automatic PLL Bandwidth Modes. A certain number of
clock cycles, nACQ, is required to ascertain that the PLL is within the
tracking mode entry tolerance, ∆TRK, before exiting acquisition mode. A
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Clock Generator Module (CGM)
137
Clock Generator Module (CGM)
certain number of clock cycles, nTRK, is required to ascertain that the
PLL is within the lock mode entry tolerance, ∆Lock. Therefore, the
acquisition time, tACQ, is an integer multiple of nACQ/fRDV, and the
acquisition to lock time, tAL, is an integer multiple of nTRK/fRDV. Also,
since the average frequency over the entire measurement period must
be within the specified tolerance, the total time usually is longer than
tLock as calculated above.
In manual mode, it is usually necessary to wait considerably longer than
tLock before selecting the PLL clock (see 8.4.3 Base Clock Selector
Circuit) because the factors described in 8.11.2 Parametric Influences
on Reaction Time may slow the lock time considerably.
Technical Data
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MC68HC908MR8 — Rev 4.1
Clock Generator Module (CGM)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 9. Pulse-Width Modulator for Motor Control
(PWMMC)
9.1 Contents
9.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .140
9.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .141
9.4
Timebase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .146
9.4.1
Resolution. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .146
9.4.2
Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
9.5
PWM Generators. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
9.5.1
Load Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .148
9.5.2
PWM Data Overflow and Underflow Conditions . . . . . .152
9.6
Output Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .152
9.6.1
Selecting Six Independent PWMs or Three
Complementary PWM Pairs. . . . . . . . . . . . . . . . . . . . . . .152
9.6.2
Dead-Time Insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . .154
9.6.3
Output Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
9.6.4
Output Port Control Register . . . . . . . . . . . . . . . . . . . . .159
9.7
Fault Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .161
9.7.1
Fault Condition Input Pins. . . . . . . . . . . . . . . . . . . . . . . .164
9.7.2
Software Output Disable . . . . . . . . . . . . . . . . . . . . . . . . .168
9.7.3
Output Port Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
9.8
Initialization and the PWMEN Bit. . . . . . . . . . . . . . . . . . . . .169
9.9
PWM Operation in Wait Mode . . . . . . . . . . . . . . . . . . . . . . .170
9.10
PWM Operation in Stop Mode . . . . . . . . . . . . . . . . . . . . . . .170
9.11
PWM Operation in Break Mode . . . . . . . . . . . . . . . . . . . . . .171
9.12 Control Logic Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172
9.12.1 PWM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . .172
9.12.2 PWM Counter Modulo Registers. . . . . . . . . . . . . . . . . . .173
9.12.3 PWMx Value Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .174
9.12.4 PWM Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . .175
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
139
Pulse-Width Modulator for Motor Control
9.12.5
9.12.6
9.12.7
9.12.8
9.12.9
9.12.10
9.12.11
9.13
PWM Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . .177
Dead-Time Write-Once Register . . . . . . . . . . . . . . . . . . .179
PWM Disable Mapping Write-Once Register . . . . . . . . .179
Fault Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . .180
Fault Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . .181
Fault Acknowledge Register . . . . . . . . . . . . . . . . . . . . . .182
PWM Output Control Register. . . . . . . . . . . . . . . . . . . . .184
PWM Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .185
9.2 Introduction
This section describes the pulse-width modulator for motor control
(PWMMC, version A). The MC68HC908MR8 PWM module can
generate three complementary PWM pairs or six independent PWM
signals. These PWM signals can be center-aligned or edge-aligned. A
block diagram of the PWM module is shown in Figure 9-1.
A 12-bit timer PWM counter is common to all six channels. PWM
resolution is one clock period for edge-aligned operation and two clock
periods for center-aligned operation. The clock period is dependent on
the internal operating frequency (fOP) and a programmable prescaler.
The highest resolution for edge-aligned operation is 125 ns
(fOP = 8 MHz). The highest resolution for center-aligned operation is
250 ns (fOP = 8 MHz).
When generating complementary PWM signals, the module features
automatic dead-time insertion to the PWM output pairs.
A summary of the PWM registers is shown in Figure 9-2.
Technical Data
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MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Features
9.3 Features
Features of the PWMMC include:
•
Three complimentary PWM pairs or six independent PWM signals
•
Edge-aligned PWM signals or center-aligned PWM signals
•
PWM signal polarity control
•
Manual PWM output control through software
•
Programmable fault protection
•
Complimentary mode also features:
– Dead-time insertion
– Separate top/bottom pulse width correction via current sensing
or programmable software bits
8
CPU BUS
PWM1 PIN
FAULT PROTECTION
PWM CHANNELS 3 & 4
PWM2 PIN
OUTPUT CONTROL
CONTROL LOGIC BLOCK
PWM CHANNELS 1 & 2
PWM3 PIN
PWM4 PIN
PWM5 PIN
PWM CHANNELS 5 & 6
12
PWM6 PIN
2
FAULT
INTERRUPT
PINS
TIMEBASE
Figure 9-1. PWM Module Block Diagram
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
141
Pulse-Width Modulator for Motor Control
Addr.
Register Name
Bit 7
Read:
DISX
PWM Control Register 1
Write:
$0020
(PCTL1)
See page 175. Reset
0
:
6
5
4
DISY
PWMIN
T
PWMF
0
0
0
0
SEL12
SEL34
0
0
Read:
LDFQ1 LDFQ0
PWM Control Register 2
Write:
$0021
(PCTL2)
See page 177. Reset
0
0
:
Read:
$0022
FINT4
Fault Control Register
Write:
(FCR)
See page 180. Reset
0
:
Fault Status Register
(FSR) Write:
See page 181.
Reset
:
Read:
$0024
Fault Acknowledge
Write:
Register (FTACK)
See page 182.
Reset
:
Read:
$0025
PWM Output Control
Write:
(PWMOUT)
See page 159. Reset
:
Read:
$0026
PWM Counter Register
Write:
High (PCNTH)
See page 172. Reset
:
U = Unaffected
minate
X = Indeter-
0
2
0
1
Bit 0
LDOK
PWME
N
0
0
SEL56 PRSC1 PRSC0
0
FMODE
4
0
0
FINT1
FMODE
1
0
0
0
0
0
0
0
FFLAG
4
0
0
0
0
FPIN1
FFLAG
1
U
0
U
0
U
0
U
0
0
0
0
0
0
0
0
0
Read: FPIN4
$0023
0
3
FTACK
4
FTACK
1
0
0
0
0
0
0
0
0
0
OUTCT
L
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
0
0
0
0
0
0
0
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
R
= Reserved
Bold
= Buffered
Figure 9-2. Register Summary (Sheet 1 of 4)
Technical Data
142
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Features
Addr.
Register Name
Read:
$0027
PWM Counter Register
Write:
Low (PCNTL)
See page 172. Reset
:
Read:
PWM Counter Modulo
Write:
$0028 Register High (PMODH)
See page 173. Reset
:
Read:
$0029
$002A
PWM Counter Modulo
Write:
Register Low (PMODL)
See page 173. Reset
:
$002C
PWM 1 Value Register
Write:
Low (PVAL1L)
See page 174. Reset
:
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
X
X
X
X
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Read:
Bit 15
PWM 2 Value Register
Write:
High (PVAL2H)
See page 174. Reset
0
:
Read:
$002D
6
Read:
Bit 15
PWM 1 Value Register
Write:
High (PVAL1H)
See page 174. Reset
0
:
Read:
$002B
Bit 7
PWM 2 Value Register
Write:
Low (PVAL2L)
See page 174. Reset
:
U = Unaffected
minate
X = Indeter-
R
= Reserved
Bold
= Buffered
Figure 9-2. Register Summary (Sheet 2 of 4)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
143
Pulse-Width Modulator for Motor Control
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
Read:
$002E
$002F
Bit 15
PWM 3 Value Register
Write:
High (PVAL3H)
See page 174. Reset
0
:
Read:
PWM 3 Value Register
Write:
Low (PVAL3L)
See page 174. Reset
:
Read:
$0030
$0031
Bit 15
PWM 4 Value Register
Write:
High (PVAL4H)
See page 174. Reset
0
:
Read:
PWM 4 Value Register
Write:
Low (PVAL4L)
See page 174. Reset
:
Read:
$0032
$0033
Bit 15
PWM 5 Value Register
Write:
High (PMVAL5H)
See page 174. Reset
0
:
Read:
PWM 5 Value Register
Write:
Low (PVAL5L)
See page 174. Reset
:
Read:
$0034
Bit 15
PWM 6 Value Register
Write:
High (PVAL6H)
See page 174. Reset
0
:
U = Unaffected
minate
X = Indeter-
R
= Reserved
Bold
= Buffered
Figure 9-2. Register Summary (Sheet 3 of 4)
Technical Data
144
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Features
Addr.
Register Name
Read:
$0035
$0036
$0037
PWM 6 Value Register
Write:
Low (PMVAL6L)
See page 174. Reset
:
Read:
Dead-Time Write-Once
Write:
Register (DEADTM)
See page 179. Reset
:
Read:
PWM Disable Mapping
Write-Once Register Write:
(DISMAP)
See page 179. Reset
:
U = Unaffected
minate
X = Indeter-
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
R
= Reserved
Bold
= Buffered
Figure 9-2. Register Summary (Sheet 4 of 4)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
145
Pulse-Width Modulator for Motor Control
9.4 Timebase
This subsection provides for a discussion of the timebase.
9.4.1 Resolution
In center-aligned mode, a 12-bit up/down counter is used to create the
PWM period. Therefore, the PWM resolution in center-aligned mode is
two clocks (highest resolution is 250 ns @ fOP = 8 MHz) as shown in
Figure 9-3. The up/down counter uses the value in the timer modulus
register to determine its maximum count. The PWM period will equal:
(timer modulus) x (PWM clock period) x 2
For edge-aligned mode, a 12-bit up-only counter is used to create the
PWM period. Therefore, the PWM resolution in edge-aligned mode is
one clock (highest resolution is 125 ns @ fOP = 8 MHz) as shown in
Figure 9-4. Again, the timer modulus register is used to determine the
maximum count. The PWM period will equal:
(timer modulus) x (PWM clock period)
Center-aligned operation versus edge-aligned operation is determined
by the option EDGE. See 5.4 CONFIG Bits.
Technical Data
146
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Timebase
UP/DOWN COUNTER
MODULUS = 4
PERIOD = 8 x (PWM CLOCK PERIOD)
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
Figure 9-3. Center-Aligned PWM (Positive Polarity)
UP-ONLY COUNTER
MODULUS = 4
PERIOD = 4 x (PWM
CLOCK PERIOD)
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
Figure 9-4. Edge-Aligned PWM (Positive Polarity)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
147
Pulse-Width Modulator for Motor Control
9.4.2 Prescaler
To permit lower PWM frequencies, a prescaler is provided which will
divide the PWM clock frequency by 1, 2, 4, or 8. Table 9-1 shows how
setting the prescaler bits in PWM control register 2 affects the PWM
clock frequency. This prescaler is buffered and will not be used by the
PWM generator until the LDOK bit is set and a new PWM reload-cycle
begins.
Table 9-1. PWM Prescaler
Prescaler Bits
PRSC1:PRSC0
PWM Clock Frequency
00
fOP
01
fOP/2
10
fOP/4
11
fOP/8
9.5 PWM Generators
This subsection describes the pulse-width modulator (PWM) generators.
9.5.1 Load Operation
To help avoid erroneous pulse widths and PWM periods, the modulus,
prescaler, and PWM value registers are buffered. New PWM values,
counter modulus values, and prescalers can be loaded from their buffers
into the PWM module every one, two, four, or eight PWM cycles.
LDFQ1:LDFQ0 in PWM control register 2 are used to control this reload
frequency, as shown in Table 9-2. When a reload cycle arrives,
regardless of whether an actual reload occurs (as determined by the
LDOK bit), the PWM reload flag bit in PWM control register 1 will be set.
If the PWMINT bit in PWM control register 1 is set, a CPU interrupt
request will be generated when PWMF is set. Software can use this
interrupt to calculate new PWM parameters in real time for the PWM
module.
Technical Data
148
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
PWM Generators
Table 9-2. PWM Reload Frequency
Reload Frequency Bits
LDFQ1:LDFQ0
PWM Reload Frequency
00
Every PWM cycle
01
Every 2 PWM cycles
10
Every 4 PWM cycles
11
Every 8 PWM cycles
For ease of software, the LDFQx bits are buffered. When the LDFQx bits
are changed, the reload frequency will not change until the previous
reload cycle is completed. See Figure 9-5.
NOTE:
When reading the LDFQx bits, the value is the buffered value (for
example, not necessarily the value being acted upon).
RELOAD
RELOAD
CHANGE RELOAD
FREQUENCY TO
EVERY 4 CYCLES
RELOAD
RELOAD
RELOAD RELOAD RELOAD
CHANGE RELOAD
FREQUENCY TO
EVERY CYCLE
Figure 9-5. Reload Frequency Change
PWMINT enables CPU interrupt requests as shown in Figure 9-6. When
this bit is set, CPU interrupt requests are generated when the PWMF bit
is set. When the PWMINT bit is clear, PWM interrupt requests are
inhibited. PWM reloads will still occur at the reload rate, but no interrupt
requests will be generated.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
149
Pulse-Width Modulator for Motor Control
READ PWMF AS 1,
WRITE PWMF AS 0
OR RESET
VDD
RESET
PWMF
D
CPU INTERRUPT
REQUEST
LATCH
PWMINT
PWM RELOAD
CK
Figure 9-6. PWM Interrupt Requests
To prevent a partial reload of PWM parameters from occurring while the
software is still calculating them, an interlock bit controlled from software
is provided. This bit informs the PWM module that all the PWM
parameters have been calculated, and it is okay to use them. A new
modulus, prescaler, and/or PWM value cannot be loaded into the PWM
module until the LDOK bit in PWM control register 1 is set. When the
LDOK bit is set, these new values are loaded into a second set of
registers and used by the PWM generator at the beginning of the next
PWM reload cycle as shown in Figure 9-7, Figure 9-8, Figure 9-9, and
Figure 9-10. After these values are loaded, the LDOK bit is cleared.
NOTE:
When the PWM module is enabled (via the PWMEN bit), a load will occur
if the LDOK bit is set. Even if it is not set, an interrupt will occur if the
PWMINT bit is set. To prevent this, the software should clear the
PWMINT bit before enabling the PWM module.
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP/DOWN
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE= 1
PWMF SET
LDOK = 0
MODULUS = 3
PWM VALUE= 2
PWMF SET
LDOK = 1
MODULUS = 3
PWM VALUE= 2
PWMF SET
LDOK = 0
MODULUS = 3
PWM VALUE= 1
PWMF SET
PWM
Figure 9-7. Center-Aligned PWM Value Loading
Technical Data
150
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
PWM Generators
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP/DOWN
COUNTER
LDOK = 1
MODULUS = 2
PWM VALUE = 1
PWMF SET
LDOK = 1
MODULUS = 3
PWM VALUE= 1
PWMF SET
LDOK = 1
MODULUS = 2
PWMVALUE= 1
PWMF SET
LDOK = 1
LDOK = 0
MODULUS = 1 MODULUS = 2
PWM VALUE= 1 PWM VALUE= 1
PWMF SET
PWMF SET
PWM
Figure 9-8. Center-Aligned Loading of Modulus
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
LDOK = 1
LDOK = 0
LDOK = 0
LDOK = 0
MODULUS = 3 MODULUS = 3 MODULUS = 3 MODULUS = 3 MODULUS = 3
PWM VALUE= 1. PWM VALUE= 2. PWM VALUE = 2 PWM VALUE = 1 PWM VALUE = 1
PWMF SET
PWMF SET
PWMF SET
PWMF SET
PWMF SET
PWM
Figure 9-9. Edge-Aligned PWM Value Loading
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE= 2
PWMF SET
LDOK = 1
MODULUS = 4
PWM VALUE = 2
PWMF SET
LDOK = 1
LDOK = 0
MODULUS = 2 MODULUS = 1
PWM VALUE = 2 PWM VALUE= 2
PWMF SET
PWMF SET
PWM
Figure 9-10. Edge-Aligned Modulus Loading
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
151
Pulse-Width Modulator for Motor Control
9.5.2 PWM Data Overflow and Underflow Conditions
The PWM value registers are 16-bit registers. Although the counter is
only 12 bits, the user may write a 16-bit signed value to a PWM value
register. As shown in Figure 9-3 and Figure 9-4, if the PWM value is
less than or equal to 0, the PWM will be inactive for the entire period.
Conversely, if the PWM value is greater than or equal to the timer
modulus, the PWM will be active for the entire period. Refer to Table 9-3.
NOTE:
The terms active and inactive refer to the asserted and negated states
of the PWM signals and should not be confused with the highimpedance state of the PWM pins.
Table 9-3. PWM Data Overflow and Underflow Conditions
PWMVALxH:PWMVALxL
Condition
PWM Value Used
$0000–$0FFF
Normal
Per registers contents
$1000–$7FFF
Overflow
$FFF
$8000–$FFFF
Underflow
$000
9.6 Output Control
This subsection discusses output control.
9.6.1 Selecting Six Independent PWMs or Three Complementary PWM Pairs
The PWM outputs can be configured as six independent PWM channels
or three complementary channel pairs. The option INDEP determines
which mode is used (see 5.4 CONFIG Bits). If complementary operation
is chosen, the PWM pins are paired as shown in Figure 9-11. Operation
of one pair is then determined by one PWM value register. This type of
operation is meant for use in motor drive circuits such as the one in
Figure 9-12.
Technical Data
152
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Output Control
PWM1
OUTPUT CONTROL
(POLARITY & DEAD-TIME INSERTION)
PWMS 1 & 2
PWM VALUE REGISTER
PWMS 3 & 4
PWM VALUE REGISTER
PWM2
PWM3
PWM4
PWM5
PWMS 5 & 6
PWM VALUE REGISTER
PWM6
Figure 9-11. Complementary Pairing
PWM
1
PWM
3
PWM
5
TO
AC
MOTOR
INPUTS
PWM
2
PWM
4
PWM
6
Figure 9-12. Typical AC Motor Drive
When complementary operation is used, two additional features are
provided:
•
Dead-time insertion
•
Separate top/bottom pulse width correction to correct for
distortions caused by the motor drive characteristics.
If independent operation is chosen, each PWM has its own PWM value
register.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
153
Pulse-Width Modulator for Motor Control
9.6.2 Dead-Time Insertion
As shown in Figure 9-12, in complementary mode, each PWM pair can
be used to drive top-side/bottom-side transistors.
NOTE:
When controlling DC-to-AC inverters such as this, the top and bottom
PWMs in one pair should never be active at the same time.
In Figure 9-12, if PWM1 and PWM2 were on at the same time, large
currents would flow through the two transistors as they discharge the
bus capacitor. The IGBTs could be weakened or destroyed.
Simply forcing the two PWMs to be inversions of each other is not always
sufficient. Since a time delay is associated with turning off the transistors
in the motor drive, there must be a “dead-time” between the deactivation
of one PWM and the activation of the other.
A dead-time can be specified in the dead-time write-once register. This
8-bit value specifies the number of CPU clock cycles to use for the
dead-time. The dead-time is not affected by changes in the PWM period
caused by the prescaler.
Dead-time insertion is achieved by feeding the top PWM outputs of the
PWM generator into dead-time generators, as shown in Figure 9-13.
When output control is enabled, the odd OUT bits, rather than the
PWM generator outputs, are fed into the dead-time generators. See
9.6.4 Output Port Control Register.
Technical Data
154
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Output Control
OUT2
OUT4
OUT6
DEAD-TIME
POSTDT (TOP)
DEAD-TIME
POSTDT (TOP)
TOP
(PWM1)
PWM1
BOTTOM
(PWM2)
PWM2
PWM (TOP)
PREDT (TOP)
OUTX
SELECT
TOP
(PWM3)
BOTTOM
(PWM4)
FAULT
PWMPAIR34
(TOP)
TOP/BOTTOM
GENERATION
MUX
POLARITY/OUTPUT DRIVE
DEAD TIMER
DEAD-TIME
POSTDT (TOP)
DEAD TIMER
PREDT(TOP)
PREDT
(TOP)
OUTX
SELECT
SEL1–SEL6 MUX
PWM GEN[1:6]
PWM GENERATOR
6
PWM
(TOP)
PWM(TOP)
DEAD TIMER
MUX
MUX
PWMPAIR12
(TOP)
TOP/BOTTOM
GENERATION
OUTCTL
OUT5
OUT3
OUT1
OUTPUT CONTROL
(OUTCTL)
PWM3
PWM4
PWM (TOP)
PREDT (TOP)
OUTX
SELECT
TOP/BOTTOM
GENERATION
MUX
PWMPAIR56
(TOP)
TOP
(PWM5)
PWM5
BOTTOM
(PWM6)
PWM6
Figure 9-13. Dead-Time Generators
Whenever an input to a dead-time generator transitions, a dead-time is
inserted (for example, both PWMs in the pair are forced to their inactive
state). The BOTTOM PWM signal is generated from the TOP PWM and
the dead-time. In the case of output control enabled, the odd OUTx bits
control the top PWMs, the even OUTx bits control the bottom PWMs with
respect to the odd OUTx bits (see Table 9-4). Figure 9-14 shows the
effects of the dead-time insertion.
Examples of dead-time insertion are shown in Figure 9-14 through
Figure 9-16. Figure 9-15 shows the effects of dead-time insertion at the
duty cycle boundaries (near 0% and 100% duty cycles). Figure 9-16
shows the effects of dead-time insertion on pulse widths smaller than the
dead-time.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
155
Pulse-Width Modulator for Motor Control
UP/DOWN COUNTER
MODULUS = 4
PWM VALUE = 2
PWM VALUE = 2
PWM VALUE = 3
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 2
2
PWM2 W/
DEAD-TIME = 2
2
2
2
2
2
Figure 9-14. Effects of Dead-Time Insertion
UP/DOWN COUNTER
MODULUS = 3
PWM VALUE = 1
PWM VALUE = 1
PWM VALUE = 3
PWM VALUE = 3
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 2
PWM2 W/
DEAD-TIME = 2
2
2
2
2
Figure 9-15. Dead-Time at Duty Cycle Boundaries
Technical Data
156
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Output Control
UP/DOWN COUNTER
MODULUS = 3
PWM VALUE = 2
PWM VALUE = 3
PWM VALUE = 2
PWM VALUE= 1
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 3
3
3
PWM2 W/
DEAD-TIME = 3
3
3
3
3
Figure 9-16. Dead-Time and Small Pulse Widths
9.6.3 Output Polarity
The output polarity of the PWMs is determined by two options: TOPNEG
and BOTNEG. The top polarity option, TOPNEG, controls the polarity of
PWMs 1, 3, and 5. The bottom polarity option, BOTNEG, controls the
polarity of PWMs 2, 4, and 6. Positive polarity means that when the PWM
is active, the PWM output is high. Conversely, negative polarity means
that when the PWM is active, PWM output is low. See Figure 9-17.
NOTE:
Both bits are found in the CONFIG register, which is a write-once
register. This reduces the chances of the software inadvertently
changing the polarity of the PWM signals and possibly damaging the
motor drive hardware.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
157
Pulse-Width Modulator for Motor Control
CENTER-ALIGNED POSITIVE POLARITY
EDGE-ALIGNED POSITIVE POLARITY
UP-ONLY COUNTER
UP/DOWN COUNTER
MODULUS = 4
MODULUS = 4
PWM = 0
PWM = 0
PWM = 1
PWM = 1
PWM = 2
PWM = 2
PWM = 3
PWM = 3
PWM = 4
PWM = 4
CENTER-ALIGNED NEGATIVE POLARITY
EDGE-ALIGNED NEGATIVE POLARITY
UP-ONLY COUNTER
MODULUS = 4
UP/DOWN COUNTER
MODULUS = 4
PWM = 0
PWM = 1
PWM = 0
PWM = 2
PWM = 1
PWM = 3
PWM = 2
PWM = 4
PWM = 3
PWM = 4
Figure 9-17. PWM Polarity
Technical Data
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MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Output Control
9.6.4 Output Port Control Register
Conditions may arise in which the PWM pins need to be individually
controlled. This is made possible by the PWM output control register
(PWMOUT) shown in Figure 9-18.
Address:
$0025
Read:
BIt 7
6
5
4
3
2
1
Bit 0
0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 9-18. PWM Output Control Register (PWMOUT)
If the OUTCTL bit is set, the PWM pins can be controlled by the OUTx
bits. These bits behave according to Table 9-4.
Table 9-4. OUTx Bits
OUTx Bit
Complementary Mode
Independent Mode
OUT1
1 — PWM1 is active.
0 — PWM1 is inactive.
1 — PWM1 is active
0 — PWM1 is inactive
OUT2
1 — PWM2 is complement of PWM1.
0 — PWM2 is inactive.
1 — PWM2 is active
0 — PWM2 is inactive
OUT3
1 — PWM3 is active.
0 — PWM3 is inactive.
1 — PWM3 is active
0 — PWM3 is inactive
OUT4
1 — PWM4 is complement of PWM3.
0 — PWM4 is inactive.
1 — PWM4 is active
0 — PWM4 is inactive
OUT5
1 — PWM5 is active.
0 — PWM5 is inactive.
1 — PWM5 is active
0 — PWM5 is inactive
OUT6
1 — PWM6 is complement of PWM5.
0 — PWM6 is inactive.
1 — PWM6 is active
0 — PWM6 is inactive
When OUTCTL is set, the polarity options TOPPOL and BOTPOL will
still affect the outputs. In addition, if complementary operation is in use,
the PWM pairs will not be allowed to be active simultaneously, and
dead-time will still not be violated. When OUTCTL is set and
MC68HC908MR8 — Rev 4.1
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Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
159
Pulse-Width Modulator for Motor Control
complimentary operation is in use, the odd OUTx bits are inputs to the
dead-time generators as shown in Figure 9-14. Dead-time is inserted
whenever the odd OUTx bit toggles as shown in Figure 9-19. Although
dead-time is not inserted when the even OUTx bits change, there will be
no dead-time violation as shown in Figure 9-20.
Setting the OUTCTL bit does not disable the PWM generator and current
sensing circuitry. They continue to run, but are no longer controlling the
output pins. In addition, OUTCTL will control the PWM pins even when
PWMEN = 0. When OUTCTL is cleared, the outputs of the PWM
generator become the inputs to the dead-time and output circuitry at the
beginning of the next PWM cycle.
NOTE:
To avoid an unexpected dead-time occurrence, it is recommended that
the OUTx bits be cleared prior to entering and prior to exiting individual
PWM output control mode.
UP/DOWN COUNTER
MODULUS=4
DEAD-TIME = 2
PWM VALUE = 3
OUTCTL
OUT1
OUT2
PWM1
PWM2
PWM1/PWM2
DEAD-TIME
2
2
DEAD-TIME INSERTED AS PART OF DEAD-TIME INSERTED DUE
NORMAL PWM OPERATION AS
TO SETTING OF OUT1 BIT
CONTROLLED BY CURRENT
SENSING AND PWM GENERATOR
2
DEAD-TIME INSERTED
DUE TO CLEARING OF
OUT1 BIT
Figure 9-19. Dead-Time Insertion During OUTCTL = 1
Technical Data
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MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Fault Protection
UP/DOWN COUNTER
MODULUS = 4
DEAD-TIME = 2
PWM VALUE = 3
OUTCTL
OUT1
OUT2
PWM1
PWM2
2
PWM1/PWM2
DEAD-TIME
2
DEAD-TIME INSERTED BECAUSE
WHEN OUTCTL WAS SET, THE
STATE OF OUT1 WAS SUCH THAT
PWM1 WAS DIRECTED TO TOGGLE
2
2
DEAD-TIMES INSERTED
BECAUSE OUT1 TOGGLES,
DIRECTING PWM1 TO
TOGGLE.
NO DEAD-TIME INSERTED
BECAUSE OUT1 IS NOT
TOGGLING.
Figure 9-20. Dead-Time Insertion During OUTCTL = 1
9.7 Fault Protection
Conditions may arise in the external drive circuitry which require that the
PWM signals become inactive immediately, such as an overcurrent fault
condition. Furthermore, it may be desirable to selectively disable
PWM(s) solely with software.
One or more PWM pins can be disabled (forced to their inactive state)
by applying a logic high to either of the two external fault pins or by
writing a logic high to either of the disable bits (DISX and DISY in PWM
control register 1). Figure 9-21 shows the structure of the PWM
disabling scheme. While the PWM pins are disabled, they are forced to
their inactive state. The PWM generator continues to run — only the
output pins are disabled
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Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
161
Pulse-Width Modulator for Motor Control
DISY
CYCLE START
SOFTWARE X DISABLE
S
Q
R
FMODE4
TWO
SAMPLE
FILTER
FAULT
PIN4
AUTO
MODE
FPIN4
LOGIC HIGH FOR FAULT
ONE
SHOT
S
Q FFLAG4
R
BANK Y
DISABLE
FAULT PIN 4 DISABLE
S
Q
R
MANUAL
MODE
CLEAR BY WRITING 1 TO FTACK4
INTERRUPT REQUEST
FINT4
The example is of fault pin 4 with DISY.
Note: In manual mode (FMODE = 0), fault 4 may be cleared only if a logic level low
at the input of the fault pin is present.
CYCLE START
FMODE1
LOGIC HIGH FOR FAULT
FAULT
PIN1
TWO
SAMPLE
FILTER
AUTO
MODE
FPIN1
ONE
SHOT
S
R
Q FFLAG1
FAULT PIN 1 DISABLE
S
Q
BANK X DISABLE
R
MANUAL
MODE
CLEAR BY WRITING 1 TO FTACK1
FINT1
INTERRUPT REQUEST
The example is of fault pin 1.
Note: In manual mode (FMODE = 0), fault 1 may be cleared regardless of the logic level
at the input of the fault pin.
Figure 9-21. PWM Disabling Scheme
To allow for different motor configurations and the controlling of more
than one motor, the PWM disabling function is organized as two banks,
bank X and bank Y. Bank information combines with information from
the disable mapping register to allow selective PWM disabling. Fault
Technical Data
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Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Fault Protection
pin 1 and PWM disable bit X constitute the disabling function of bank X.
Fault pin 4 and PWM disable bit Y constitute the disabling function of
bank Y. Figure 9-22 and Figure 9-23 show the disable mapping
write-once register and the decoding scheme of the bank which
selectively disables PWM(s). When all bits of the disable mapping
register are set, any disable condition will disable all PWMs.
A fault can also generate a CPU interrupt. Each fault pin has its own
interrupt vector.
Address:
Read:
Write:
Reset:
$0037
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 9-22. PWM Disable Mapping Write-Once Register (DISMAP)
MC68HC908MR8 — Rev 4.1
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Technical Data
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163
Pulse-Width Modulator for Motor Control
BIT 7
DISABLE
PWM PIN 1
BIT 6
BANK X
DISABLE
BANK Y
DISABLE
BIT 5
DISABLE
PWM PIN 2
BIT 4
DISABLE
PWM PIN 3
BIT 3
DISABLE
PWM PIN 4
BIT 2
DISABLE
PWM PIN 5
BIT 1
BIT 0
DISABLE
PWM PIN 6
Figure 9-23. PWM Disabling Decode Scheme
9.7.1 Fault Condition Input Pins
A logic high level on a fault pin disables the respective PWM(s)
determined by the bank and the disable mapping register. Each fault pin
incorporates a filter to assist in rejecting spurious faults. All of the
external fault pins are software-configurable to re-enable the PWMs
either with the fault pin (automatic mode) or with software (manual
mode). Each fault pin has an associated FMODE bit to control the PWM
re-enabling method. Automatic mode is selected by setting the FMODEx
bit in the fault control register. Manual mode is selected when FMODEx
is clear.
NOTE:
PORTC, when used as an input port, mirrors the state of the fault input
pins, as PORTC has the capability of being used as an output port.
When either pin of PORTC is set as an output, by setting its respective
PORTC data direction register bit, the respective fault pin logic is
disconnected from that pin and the fault input will be defaulted to normal
Technical Data
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Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Fault Protection
non-fault condition to facilitate the use of PORTC as an output pin and
not interfere with the PWM generator. To regain the fault capability for
the respective fault input pin, clear the PORTC data direction register bit
for that pin.
Additionally, when the device is reset, by default, PORTC is configured
as an input. If either bit(s) of PORTC is intended to be used as an output,
the logic state of the driven device’s input is indeterminate. The state of
the driven device, if at a logic one will drive the respective bit of PORTC
input high, thus causing a fault to be input to the respective PORTC input
and to the PWM module.
After setting the PORTC data direction register, clear the respective fault
bits by writing a 1 to bit(s) 0 and or bit 6 in the FTACK Fault Acknowledge
Register (FTACK) and Fault Status Registers (FSR), based on which
PORTC bits that are used as output(s).
9.7.1.1 Fault Pin Filter
The two fault pins incorporate a filter to assist in determining a genuine
fault condition. After a fault pin has been logic low for one CPU cycle, a
rising edge (logic high) will be synchronously sampled once per CPU
cycle for two cycles. If both samples are detected logic high, the
corresponding FPIN bit and FFLAG bit will be set. The FPIN bit will
remain set until the corresponding fault pin is logic low and
synchronously sampled once in the following CPU cycle.
9.7.1.2 Automatic Mode
In automatic mode, the PWM(s) are disabled immediately once a filtered
fault condition is detected (logic high). The PWM(s) remain disabled until
the filtered fault condition is cleared (logic low) and a new PWM cycle
begins as shown in Figure 9-24. Clearing the corresponding FFLAGx
event bit will not enable the PWMs in automatic mode.
MC68HC908MR8 — Rev 4.1
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Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
165
Pulse-Width Modulator for Motor Control
FILTERED FAULT PIN
PWM(s) ENABLED
PWM(S) DISABLED (INACTIVE)
PWM(S) ENABLED
Figure 9-24. PWM Disabling in Automatic Mode
The filtered fault pin’s logic state is reflected in the respective FPINx bit.
Any write to this bit is overwritten by the pin state. The FFLAGx event bit
is set with each rising edge of the respective fault pin after filtering has
been applied. To clear the FFLAGx bit, the user must write a 1 to the
corresponding FTACKx bit.
If the FINTx bit is set, a fault condition resulting in setting the
corresponding FFLAG bit will also latch a CPU interrupt request. The
interrupt request latch is not cleared until one of these actions occurs:
•
The FFLAGx bit is cleared by writing a 1 to the corresponding
FTACKx bit.
•
The FINTx bit is cleared. (This will not clear the FFLAGx bit.)
•
Reset — A reset automatically clears all four interrupt latches.
If prior to a vector fetch the interrupt request latch is cleared by one of
the above actions, a CPU interrupt will no longer be requested. A vector
fetch does not alter the state of the PWMs, the FFLAGx event flag, or
FINTx.
NOTE:
If the FFLAGx or FINTx bits are not cleared during the interrupt service
routine, the interrupt request latch will not be cleared.
Technical Data
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Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Fault Protection
9.7.1.3 Manual Mode
In manual mode, the PWM(s) are disabled immediately once a filtered
fault condition is detected (logic high). The PWM(s) remain disabled until
software clears the corresponding FFLAGx event bit and a new PWM
cycle begins. In manual mode, the fault pins are grouped in pairs, each
pair sharing common functionality. A fault condition on fault 1 may be
cleared, allowing the PWM(s) to enable at the start of a PWM cycle
regardless of the logic level at the fault pin. See Figure 9-25. A fault
condition on fault 4 can be cleared, allowing the PWM(s) to enable, only
if a logic low level at the fault pin is present at the start of a PWM cycle.
See Figure 9-26.
FILTERED FAULT PIN 1
PWM(S) ENABLED
PWM(S) DISABLED
PWM(S) ENABLED
FFLAGx CLEARED
Figure 9-25. PWM Disabling in Manual Mode (Example 1)
FILTERED FAULT PIN 4
PWM(S) ENABLED
PWM(S) DISABLED
PWM(S) ENABLED
FFLAGx CLEARED
Figure 9-26. PWM Disabling in Manual Mode (Example 2)
MC68HC908MR8 — Rev 4.1
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Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
167
Pulse-Width Modulator for Motor Control
The function of the fault control and event bits is the same as in
automatic mode except that the PWMs are not re-enabled until the
FFLAGx event bit is cleared by writing to the FTACKx bit and the filtered
fault condition is cleared (logic low).
9.7.2 Software Output Disable
Setting PWM disable bit DISX or DISY in PWM control register 1
immediately disables the corresponding PWM pins as determined by the
bank and disable mapping register. The PWM pin(s) remain disabled
until the PWM disable bit is cleared and a new PWM cycle begins as
shown in Figure 9-27. Setting a PWM disable bit does not latch a CPU
interrupt request, and there are no event flags associated with the PWM
disable bits.
9.7.3 Output Port Control
When operating the PWMs using the OUTx bits (OUTCTL = 1), fault
protection applies as described in this section. Due to the absence of
periodic PWM cycles, fault conditions are cleared upon each CPU cycle
and the PWM outputs are re-enabled, provided all fault clearing
conditions are satisfied.
DISABLE BIT
PWM(S) ENABLED
PWM(S) DISABLED
PWM(S) ENABLED
Figure 9-27. PWM Software Disable
Technical Data
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MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Initialization and the PWMEN Bit
9.8 Initialization and the PWMEN Bit
For proper operation, all registers should be initialized and the LDOK bit
should be set before enabling the PWM via the PWMEN bit. When the
PWMEN bit is first set, a reload will occur immediately, setting the PWMF
flag and generating an interrupt if PWMINT is set. In addition, in
complementary mode, PWM value registers 1, 3, and 5 will be used for
the first PWM cycle if current sensing is selected.
NOTE:
If the LDOK bit is not set when PWMEN is set after a RESET, the
prescaler and PWM values will be 0, but the modulus will be unknown.
If the LDOK bit is not set after the PWMEN bit has been cleared then set
(without a RESET), the modulus value that was last loaded will be used.
If the dead-time register (DEADTM) is changed after PWMEN or
OUTCTL is set, an improper dead-time insertion could occur. However,
the dead-time can never be shorter than the specified value.
Because of the equals-comparator architecture of this PWM, the
modulus = 0 case is considered illegal. Therefore, the modulus register
is not reset, and a modulus value of 0 will result in waveforms
inconsistent with the other modulus waveforms. See 9.12.2 PWM
Counter Modulo Registers.
When PWMEN is set, the PWM pins change from high impedance to
outputs. At this time, assuming no fault condition is present, the PWM
pins will drive according to the PWM values, polarity, and dead-time.
See the timing diagram in Figure 9-28.
CPU CLOCK
PWMEN
DRIVE ACCORDING TO PWM
VALUE, POLARITY, AND DEAD-TIME
PWM PINS
HI-Z IF OUTCTL = 0
HI-Z IF OUTCTL = 0
Figure 9-28. PWMEN and PWM Pins
MC68HC908MR8 — Rev 4.1
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Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
169
Pulse-Width Modulator for Motor Control
When the PWMEN bit is cleared, the following will occur:
•
PWM pins will be three-stated unless OUTCTL = 1.
•
PWM counter is cleared and will not be clocked.
•
Internally, the PWM generator will force its outputs to 0 to avoid
glitches when the PWMEN is set again.
When PWMEN is cleared, these features remain active:
NOTE:
•
All fault circuitry
•
Manual PWM pin control via the PWMOUT register
•
Dead-time insertion when PWM pins change via the PWMOUT
register
The PWMF flag and pending CPU interrupts are NOT cleared when
PWMEN = 0.
9.9 PWM Operation in Wait Mode
When the microcontroller is put in low-power wait mode via the WAIT
instruction, all clocks to the PWM module will continue to run. If an
interrupt is issued from the PWM module (via a reload or a fault), the
microcontroller will exit wait mode.
Clearing the PWMEN bit before entering wait mode will reduce power
consumption in wait mode because the counter, prescaler divider, and
LDFQ divider will no longer be clocked. In addition, power will be
reduced because the PWMs will no longer toggle.
9.10 PWM Operation in Stop Mode
When the microcontroller is put in low-power wait mode via the STOP
instruction, all clocks to the PWM module will stop.
NOTE:
It is imperative that the program to clear the PWMEN bit before entering
stop mode. Leaving the PWM module enabled during stop mode can
destroy power stages connected to the PWM outputs. The PWM
generator will no longer be clocked during stop mode and the PWM
outputs will no longer toggle.
Technical Data
170
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
PWM Operation in Break Mode
9.11 PWM Operation in Break Mode
If the microcontroller goes into break mode (or background mode), the
clocks to the PWM generator and output control blocks will freeze. This
allows the user to set a breakpoint on a development system and
examine the register contents and PWM outputs at that point. It also
allows the user to single-step through the code.
The clocks to the fault block will continue to run. Therefore, if a fault
occurs while the microcontroller is in break mode, the PWM outputs will
immediately be driven to their inactive state(s).
During break mode, the system integration module (SIM) controls
whether status bits in other modules can be cleared during the break
state. The BCFE bit in the SIM break flag control register (SBFCR)
enables software to clear status bits during the break state. Refer to
7.7.5 SIM Break Flag Control Register.
To allow software to clear status bits during a break interrupt, write a
logic 1 to the BCFE bit. If a status bit is cleared during the break state, it
remains cleared when the MCU exits the break state.
To protect the PWMF and FFLAGx bits during the break state, make
sure BCFE is a logic 0. With BCFE at logic 0 (its default state), software
can read and write the status and control registers during the break state
without affecting the PWMF and FFLAGx bits.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
171
Pulse-Width Modulator for Motor Control
9.12 Control Logic Block
This subsection provides a description of the control logic block.
9.12.1 PWM Counter Registers
The PWM counter registers (PCNTH and PCNTL) display the12-bit
up/down or up-only counter. When the high byte of the counter is read,
the lower byte is latched. PCNTL will hold this latched value until it is
read.
Address:
Read:
$0026
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
Bit11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 9-29. PWM Counter Register High (PCNTH)
Address:
Read:
$0027
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 9-30. PWM Counter Register Low (PCNTH)
Technical Data
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MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Control Logic Block
9.12.2 PWM Counter Modulo Registers
The PWM counter modulus registers (PDMODH and PDMODL) hold a
12-bit unsigned number that determines the maximum count for the
up/down or up-only counter. In center-aligned mode, the PWM period
will be twice the modulus (assuming no prescaler). In edge-aligned
mode, the PWM period will equal the modulus.
Address:
Read:
$0028
Bit 7
6
5
4
0
0
0
0
0
0
0
0
Write:
Reset:
3
2
1
Bit 0
Bit 11
Bit 10
Bit 9
Bit 8
X
X
X
X
= Unimplemented X = Indeterminate
Figure 9-31. PWM Counter Modulo Register High (PDMODH)
Address:
Read:
Write:
Reset:
$0029
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
= Unimplemented X = Indeterminate
Figure 9-32. PWM Counter Modulo Register Low (PDMODL)
To avoid erroneous PWM periods, this value is buffered and will not be
used by the PWM generator until the LDOK bit has been set and the next
PWM load cycle begins.
NOTE:
When reading this register, the value read is the buffer (not necessarily
the value the PWM generator is currently using).
Because of the equals-comparator architecture of this PWM, the
modulus = 0 case is considered illegal. Therefore, the modulus register
is not reset, and a modulus value of 0 will result in waveforms
inconsistent with the other modulus waveforms. If a modulus of 0 is
loaded, the counter will continually count down from $FFF. This
operation will not be tested or guaranteed. (The user should consider it
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Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
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Pulse-Width Modulator for Motor Control
illegal.) However, the dead-time constraints and fault conditions will still
be guaranteed.
9.12.3 PWMx Value Registers
Each of the six PWMs has a 16-bit PWM value register.
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
Figure 9-33. PWMx Value Registers High (PVALxH)
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Figure 9-34. PWMx Value Registers Low (PVALxL)
The 16-bit signed value stored in this register determines the duty cycle
of the PWM. The duty cycle is defined as: (PWM value/modulus) x 100.
Writing a number less than or equal to 0 causes the PWM to be off for
the entire PWM period. Writing a number greater than or equal to the
12-bit modulus causes the PWM to be on for the entire PWM period.
If the complementary mode is selected, the PWM pairs share PWM
value registers.
To avoid erroneous PWM pulses, this value is buffered and will not be
used by the PWM generator until the LDOK bit has been set and the next
PWM load cycle begins.
NOTE:
When reading these registers, the value read is the buffer (not
necessarily the value the PWM generator is currently using).
Technical Data
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Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Control Logic Block
9.12.4 PWM Control Register 1
PWM control register 1 controls PWM enabling/disabling, the loading of
new modulus, prescaler, and PWM values, and the PWM correction
method. In addition, this register contains the software disable bits to
force the PWM outputs to their inactive states (according to the disable
mapping register).
Address:
Read:
Write:
Reset:
$0020
Bit 7
6
5
4
DISX
DISY
PWMINT
PWMF
0
0
0
0
3
0
2
1
Bit 0
LDOK
PWMEN
0
0
0
= Unimplemented
Figure 9-35. PWM Control Register 1 (PCTL1)
DISX — Software Disable for Bank X Bit
This read/write bit allows the user to disable one or more PWM pins
in bank X. The pins that are disabled are determined by the disable
mapping write-once register.
1 = Disable PWM pins in bank X
0 = Re-enable PWM pins at beginning of next PWM cycle
DISY — Software Disable for Bank Y Bit
This read/write bit allows the user to disable one or more PWM pins
in bank Y. The pins that are disabled are determined by the disable
mapping write-once register.
1 = Disable PWM pins in Bank Y Bit
0 = Re-enable PWM pins at beginning of next PWM cycle
PWMINT — PWM Interrupt Enable Bit
This read/write bit allows the user to enable and disable PWM CPU
interrupts. If set, a CPU interrupt will be pending when the PWMF flag
is set.
1 = Enable PWM CPU interrupts
0 = Disable PWM CPU interrupts
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
175
Pulse-Width Modulator for Motor Control
NOTE:
When PWMINT is cleared, pending CPU interrupts are inhibited.
PWMF— PWM Reload Flag
This read/write bit is set at the beginning of every reload cycle
regardless of the state of the LDOK bit. This bit is cleared by reading
PWM control register 1 with the PWMF flag set, then writing a logic 0
to PWMF. If another reload occurs before the clearing sequence is
complete, then writing logic 0 to PWMF has no effect.
1 = New reload cycle began.
0 = New reload cycle has not begun.
NOTE:
CAUTION:
When PWMF is cleared, pending PWM CPU interrupts are cleared
(excluding fault interrupts).
Bits 2 and/or 3 of PCTL1 are reserved and must never be set to a 1.
Setting these bits to a 1 will affect the active PWM value registers.
Undesirable results will occur.
LDOK— Load OK Bit
This read/write bit allows the counter modulus, counter prescaler, and
PWM values in the buffered registers to be used by the PWM
generator. These values will not be used until the LDOK bit is set and
a new PWM load cycle begins. LDOK may be cleared, if it is set, by
writing a logic 0 to it prior to the beginning of a new PWM load cycle.
Internally this bit is automatically cleared after the new values are
loaded.
1 = Okay to load new modulus, prescaler, and PWM values at
beginning of next PWM load cycle
0 = Not okay to load new modulus, prescaler, and PWM values
NOTE:
The user should initialize the PWM registers and set the LDOK bit before
enabling the PWM.
PWMEN — PWM Module Enable Bit
This read/write bit enables and disables the PWM generator and the
PWM pins. When PWMEN is clear, the PWM generator is disabled
and the PWM pins are in the high-impedance state (unless
OUTCTL = 1). When the PWMEN bit is set, the PWM generator and
PWM pins are activated. For more information, see 9.8 Initialization
and the PWMEN Bit.
1 = PWM generator and PWM pins enabled
0 = PWM generator and PWM pins disabled
Technical Data
176
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Control Logic Block
NOTE:
A PWM CPU interrupt request can still be generated when LDOK is 0.
9.12.5 PWM Control Register 2
PWM control register 2 controls the PWM load frequency, the PWM
correction method, and the PWM counter prescaler. For ease of
software and to avoid erroneous PWM periods, some of these register
bits are buffered. The PWM generator will not use the prescaler value
until the LDOK bit has been set, and a new PWM cycle is starting. The
correction bits are used at the beginning of each PWM cycle (if the
ISENSx bits are configured for software correction). The load frequency
bits are not used until the current load cycle is complete.
NOTE:
The user should initialize this register before enabling the PWM.
Address:
Read:
Write:
Reset:
$0021
Bit 7
6
5
LDFQ1
LDFQ0
0
0
0
0
= Unimplemented
4
3
2
SEL12
SEL34
SEL56
0
0
0
Bold
1
Bit 0
PRSC1 PRSC0
0
0
= Buffered
Figure 9-36. PWM Control Register 2 (PCTL2)
LDFQ1 and LDFQ0 — PWM Load Frequency Bits
These buffered read/write bits select the PWM CPU load frequency
according to Table 9-5.
NOTE:
When reading these bits, the value read is the buffer value (not
necessarily the value the PWM generator is currently using).
Table 9-5. PWM Reload Frequency
Reload Frequency Bits
LDFQ1:LDFQ0
PWM Reload Frequency
00
Every PWM cycle
01
Every 2 PWM cycles
10
Every 4 PWM cycles
11
Every 8 PWM cycles
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
177
Pulse-Width Modulator for Motor Control
SEL12 — Top/Bottom Correction Bit for PWM Pair 1 (PWMs 1 and 2)
This buffered read/write bit selects which PWM value register is used
for PWM pins 1 and 2 in complementary mode.
1 = Use PWM value register 2.
0 = Use PWM value register 1.
NOTE:
When reading this bit, the value read is the buffer value (not necessarily
the value the output control block is currently using).
SEL34 — Top/Bottom Correction Bit for PWM Pair 2 (PWMs 3 and 4)
This buffered read/write bit selects which PWM value register is used
for PWM pins 3 and 4 in complementary mode.
1 = Use PWM value register 4.
0 = Use PWM value register 3.
NOTE:
When reading this bit, the value read is the buffer value (not necessarily
the value the output control block is currently using).
SEL56 — Top/Bottom Correction Bit for PWM Pair 3 (PWMs 5 and 6)
This buffered read/write bit selects which PWM value register is used
for PWM pins 5 and 6 in complementary mode.
1 = Use PWM value register 6.
0 = Use PWM value register 5.
NOTE:
When reading this bit, the value read is the buffer value (not necessarily
the value the output control block is currently using).
PRSC1:PRSC0 — PWM Prescaler Bits
These buffered read/write bits allow the PWM clock frequency to be
modified as shown in Table 9-6.
NOTE:
When reading these bits, the value read is the buffer value (not
necessarily the value the PWM generator is currently using).
Table 9-6. PWM Prescaler
Prescaler Bits
PRSC1:PRSC0
PWM Clock Frequency
00
fOP
01
fOP/2
10
fOP/4
11
fOP/8
Technical Data
178
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Control Logic Block
NOTE:
If PRSC1 and PRSC2 are set to any value other than 0, there is a one
PWM cycle latency time before the PWM pins are driven after the
PWMEN bit is set.
9.12.6 Dead-Time Write-Once Register
The dead-time write-once register (DEADTM) holds an 8-bit value which
specifies the number of CPU clock cycles to use for the dead-time when
complementary PWM mode is selected. After this register is written for
the first time, it cannot be rewritten unless a RESET occurs. The
dead-time is not affected by changes to the prescaler value.
Address:
Read:
Write:
Reset:
$0036
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 9-37. Dead-Time Write-Once Register (DEADTM)
9.12.7 PWM Disable Mapping Write-Once Register
The PWM disable mapping write-once register (DISMAP) holds an 8-bit
value which determines which PWM pins will be disabled if an external
fault or software disable occur. For a further description of the disable
mapping, see 9.7 Fault Protection. After this register is written for the
first time, it cannot be rewritten unless a reset occurs.
Address:
Read:
Write:
Reset:
$0037
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 9-38. PWM Disable Mapping Write-Once Register (DISMAP)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
179
Pulse-Width Modulator for Motor Control
9.12.8 Fault Control Register
This register controls the fault protection circuitry.
Address:
Read:
Write:
Reset:
$0022
Bit 7
6
FINT4
FMODE
4
0
0
5
0
4
0
3
0
2
1
Bit 0
FINT1
FMODE
1
0
0
0
= Unimplemented
Figure 9-39. Fault Control Register (FCR)
FMODE1 — Fault Mode Selection for Fault Pin 1 Bit (Automatic versus
Manual Mode)
This read/write bit allows the user to select between automatic and
manual mode faults. For further description of each mode, see
9.7 Fault Protection.
1 = Automatic mode
0 = Manual mode
FINT1 — Fault 1 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault
pin 1 to be enabled. The fault protection circuitry is independent of this
bit and will always be active. If a fault is detected, the PWM pins will
still be disabled according to the disable mapping register.
1 = Fault pin 1 will cause CPU interrupts.
0 = Fault pin 1 will not cause CPU interrupts.
FMODE4 — Fault Mode Selection for Fault Pin 4 Bit (Automatic versus
Manual Mode)
This read/write bit allows the user to select between automatic and
manual mode faults. For further description of each mode, see
9.7 Fault Protection.
1 = Automatic mode
0 = Manual mode
Technical Data
180
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Control Logic Block
FINT4 — Fault 4 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault
pin 4 to be enabled. The fault protection circuitry is independent of this
bit and will always be active. If a fault is detected, the PWM pins will
still be disabled according to the disable mapping register.
1 = Fault pin 4 will cause CPU interrupts.
0 = Fault pin 4 will not cause CPU interrupts.
9.12.9 Fault Status Register
This read-only register indicates the current fault status.
Address:
Read:
$0023
Bit 7
6
5
4
3
2
1
Bit 0
FPIN4
FFLAG
4
0
0
0
0
FPIN1
FFLAG
1
U
0
U
0
U
0
U
0
Write:
Reset:
= Unimplemented
U = Unaffected
Figure 9-40. Fault Status Register (FSR)
FFLAG1 — Fault Event Flag 1
The FFLAG1 event bit is set within two CPU cycles after a rising edge
on fault pin 1. To clear the FFLAG1 bit, the user must write a 1 to the
FTACK1 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 1
0 = No new fault on fault pin 1
FPIN1 — State of Fault Pin 1
This read-only bit allows the user to read the current state of fault
pin 1.
1 = Fault pin 1 is at logic 1
0 = Fault pin 1 is at logic 0
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
181
Pulse-Width Modulator for Motor Control
FFLAG4 — Fault Event Flag 4
The FFLAG4 event bit is set within two CPU cycles after a rising edge
on fault pin 4. To clear the FFLAG4 bit, the user must write a 1 to the
FTACK4 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 4
0 = No new fault on fault pin 4
FPIN4 — State of Fault Pin 4 Bit
This read-only bit allows the user to read the current state of fault
pin 4.
1 = Fault pin 4 is at logic 1.
0 = Fault pin 4 is at logic 0.
9.12.10 Fault Acknowledge Register
The fault acknowledge register (FTACK) is used to acknowledge and
clear the FFLAGs. In addition, it is used to monitor the current sensing
bits to test proper operation.
Address:
Read:
$0024
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
FTACK
4
Write:
Reset:
0
0
FTACK
1
0
0
0
0
0
0
= Unimplemented
Figure 9-41. Fault Acknowledge Register (FTACK)
Technical Data
182
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
Control Logic Block
FTACK1 — Fault Acknowledge 1 Bit
The FTACK1 bit is used to acknowledge and clear FFLAG1. This bit
will always read 0. Writing a 1 to this bit will clear FFLAG1. Writing a 0
will have no effect.
FTACK4 — Fault Acknowledge 4 Bit
The FTACK4 bit is used to acknowledge and clear FFLAG4. This bit
will always read 0. Writing a 1 to this bit will clear FFLAG4. Writing a 0
will have no effect.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
183
Pulse-Width Modulator for Motor Control
9.12.11 PWM Output Control Register
This register is used to manually control the PWM pins.
Address:
Read:
$0025
Bit 7
6
5
4
3
2
1
Bit 0
0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
U = Unaffected
Figure 9-42. PWM Output Control Register (PWMOUT)
OUTCTL— Output control enable
This read/write bit allows the user to manually control the PWM pins.
When set, the PWM generator is no longer the input to the dead-time
and output circuitry. The OUTx bits determine the state of the PWM
pins. Setting the OUTCTL bit does not disable the PWM generator.
The generator continues to run, but is no longer the input to the PWM
dead-time and output circuitry. When OUTCTL is cleared, the outputs
of the PWM generator immediately become the inputs to the
dead-time and output circuitry.
1 = PWM outputs controlled manually
0 = PWM outputs determined by PWM generator
Technical Data
184
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Pulse-Width Modulator for Motor Control (PWMMC)
PWM Glossary
OUT6:OUT1— PWM Pin Output Control Bits
These read/write bits control the PWM pins according to Table 9-7.
Table 9-7. OUTx Bits
OUTx Bit
Complementary Mode
Independent Mode
OUT1
1 — PWM1 is active
0 — PWM1 is inactive
1 — PWM1 is active
0 — PWM1 is inactive
OUT2
1 — PWM2 is complement of PWM 1 1 — PWM2 is active
0 — PWM2 is inactive
0 — PWM2 is inactive
OUT3
1 — PWM3 is active
0 — PWM3 is inactive
OUT4
1 — PWM4 is complement of PWM 3 1 — PWM4 is active
0 — PWM4 is inactive
0 — PWM4 is inactive
OUT5
1 — PWM5 is active
0 — PWM5 is inactive
OUT6
1 — PWM 6 is complement of PWM 5 1 — PWM6 is active
0 — PWM6 is inactive
0 — PWM6 is inactive
1 — PWM3 is active
0 — PWM3 is inactive
1 — PWM5 is active
0 — PWM5 is inactive
9.13 PWM Glossary
CPU Cycle — One internal bus cycle (1/fOP)
PWM Clock Cycle (or Period) — One tick of the PWM counter (1/fOP
with no prescaler). See Figure 9-43.
PWM Cycle (or Period)
•
Center-aligned mode: The time it takes the PWM counter to count
up and count down (modulus * 2/fOP assuming no prescaler). See
Figure 9-43.
•
Edge-aligned mode: The time it takes the PWM counter to count
up (modulus/fOP). See Figure 9-43.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Pulse-Width Modulator for Motor Control (PWMMC)
185
Pulse-Width Modulator for Motor Control
CENTER-ALIGNED MODE
PWM CLOCK CYCLE
PWM CYCLE (OR PERIOD)
EDGE-ALIGNED MODE
PWM
CLOCK
CYCLE
PWM CYCLE (OR PERIOD)
Figure 9-43. PWM Clock Cycle and PWM Cycle Definitions
PWM Load Frequency — The frequency at which new PWM
parameters get loaded into the PWM. See Figure 9-44.
LDFQ1:LDFQ0 = 01 — RELOAD EVERY TWO CYCLES
PWM LOAD CYCLE
(1/PWM LOAD FREQUENCY)
RELOAD NEW
MODULUS,
PRESCALER,
AND PWM VALUES
IF LDOK = 1
RELOAD NEW
MODULUS,
PRESCALER,
AND PWM VALUES
IF LDOK = 1
Figure 9-44. PWM Load Cycle/Frequency Definition
Technical Data
186
MC68HC908MR8 — Rev 4.1
Pulse-Width Modulator for Motor Control (PWMMC)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 10. Monitor ROM (MON)
10.1 Contents
10.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
10.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .187
10.4 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .188
10.4.1 Entering Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . .188
10.4.2 Forced Monitor Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . .190
10.4.3 Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
10.4.4 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191
10.4.5 Echoing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
10.4.6 Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
10.4.7 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
10.5
Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .196
10.2 Introduction
This section describes the monitor read-only memory (ROM). The
monitor ROM (MON) allows complete testing of the microcontroller unit
(MCU) through a 2-wire interface with a host computer.
10.3 Features
Features of the monitor ROM include:
•
Normal user-mode pin functionality
•
Standard mark/space non-return-to-zero (NRZ) communication
with host computer
•
9600 baud communication with host computer
•
Execution of code in random-access memory (RAM) or ROM
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Monitor ROM (MON)
187
Monitor ROM (MON)
10.4 Functional Description
The monitor ROM receives and executes commands from a host
computer. Figure 10-1 shows a sample circuit used to enter monitor
mode and communicate with a host computer via a standard RS-232
interface.
Simple monitor commands can access any memory address. In monitor
mode, the MCU can execute host-computer code in RAM while all MCU
pins retain normal operating mode functions. All communication
between the host computer and the MCU is through the serial
communications interface (SCI). A level-shifting RS-232 interface is
required between the SCI and the host computer. PTB1 requires a
pulldown resistor to ensure proper entry into monitor mode.
10.4.1 Entering Monitor Mode
Table 10-1 shows the pin conditions for entering monitor mode.
Table 10-1. Mode Selection
$FFFE/
$FFFF
IRQ
RESET
Pin
PLL PTB0 PTB1
External
CGMOUT
Clock
fop
COP
Baud
Rate
0
Disabled
0
Comment
No operation
until reset = VDD
X
VSS
X
X
X
X
VHI
VDD
or
VHI
X
ON
VDD
VSS
PLL configured with
4.0 MHz 16.0 MHz 8.0 MHz Disabled 9600 BCS set by monitor
code
VDD
VDD
Blank
(FF)
ON
X
X
PLL configured with
4.0 MHz 16.0 MHz 8.0 MHz Disabled 9600 BCS set by monitor
code
X
0
VSS
VDD
Blank
(FF)
OFF
X
X
fOSC
fOSC/2
fOSC/4
VDD
VDD
Non-blank
X
X
X
X
X
X
Enters monitor
mode with any
f
Disabled OSC external clock rate
/1024
within operating
spec
Enabled
X
Enters user mode
X = Don’t care
PTB0 = VDD and PTB1 = VSS to enter monitor mode
PTB0 (RXD) and PTB1 (TXD) used for serial communications (all monitor mode)
Technical Data
188
MC68HC908MR8 — Rev 4.1
Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
Functional Description
VDD
10 kΩ
MC68HC908MR8
RST
0.1 µF
VHI
10 kΩ
IRQ
VDDA
VDDA
0.1 µF
VSSA
VREFH
VREFH
1
10 µF
10 µF
+
+
MC145407
+
3
18
4
17
2
0.1 µF
20
19
CGMXFC
0.02 µF
10 µF
OSC1
+
10 µF
VDD
X1
4.00 MHz
20 pF
10 MΩ
OSC2
20 pF
DB-25
2
5
16
3
6
15
VSS
VDD
7
VDD
0.1 µF
PTB0/RXD
PTB1/TXD
10 kΩ
Figure 10-1. Monitor Mode Circuit
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Monitor ROM (MON)
189
Monitor ROM (MON)
Enter monitor mode by applying a logic 0 and then a logic 1 to the RST
pin (see Table 10-1)
Once out of reset, the MCU waits for the host to send eight security
bytes. After receiving the security bytes, the MCU sends a break signal
(10 consecutive logic 0s) to the host computer, indicating that it is ready
to receive a command.
Monitor mode uses alternate vectors for reset and SWI. The alternate
vectors are in the $FE page instead of the $FF page and allow code
execution from the internal monitor firmware instead of user code. The
computer operating properly (COP) module is disabled in monitor mode
as long as VHI is applied to either the IRQ pin or the RST pin. Refer to
Section 7. System Integration Module (SIM) for more information on
modes of operation.
10.4.2 Forced Monitor Mode
On FLASH parts, if the voltage applied to the IRQ1 is less than VHI, the
MCU will come out of reset in user mode. The memory reset module
monitors the reset vector fetches and will assert an internal reset if it
detects that the reset vectors are erased. When the MCU comes out of
reset with its reset vector erased, it is forced into monitor mode without
requiring high voltage on the IRQ1 pin.
The computer operating properly (COP) module is disabled in forced
monitor mode. Any reset other than a power-on reset (POR) will
automatically force the MCU to come back to the forced monitor mode.
Table 10-2 is a summary of the differences between user mode and
monitor mode.
Table 10-2. Mode Differences
Functions
Modes
COP
Reset
Vector High
Reset
Vector Low
SWI
Vector High
SWI
Vector Low
User
Enabled
$FFFE
$FFFF
$FFFC
$FFFD
Monitor
Disabled(1)
$FEFE
$FEFF
$FEFC
$FEFD
1. If the high voltage (VHI) is removed from the IRQ pin or the RST pin, the SIM
asserts its COP enable output.
Technical Data
190
MC68HC908MR8 — Rev 4.1
Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
Functional Description
10.4.3 Baud Rate
With a 4.0-MHz reference clock source, data is transferred between the
monitor and host at 9600 baud. The communication baud rate is
achieved by stepping up the internal CPU frequency to 8 MHz, using the
phase-locked loop (PLL). A 4.0-MHz reference frequency is necessary
in this mode as the PLL will not lock with any other reference clock.
As described in Table 10-1, on FLASH parts when VSS is applied to IRQ
with $FFFE and $FFFF = 0, the PLL setup is bypassed and the baud rate
is equal to the reference frequency divided by 1024. This facilitates a
faster communication rate in the interest of a first time programmed
device. This allows selection of other reference frequencies and thus,
facilities a faster communication rate. The reference frequency, in this
case while not utilizing the PLL, is limited to the range of fOP. Refer to
21.8 Control Timing.
10.4.4 Data Format
Communication with the monitor ROM is in standard non-return-to-zero
(NRZ) mark/space data format. See Figure 10-2 and Figure 10-3.
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
NEXT
START
BIT
STOP
BIT
Figure 10-2. Monitor Data Format
$A5
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BREAK
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
STOP
BIT
NEXT
START
BIT
NEXT
START
BIT
Figure 10-3. Sample Monitor Waveforms
The data transmit and receive rate is 9600 baud. Transmit and receive
baud rates will be identical.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Monitor ROM (MON)
191
Monitor ROM (MON)
10.4.5 Echoing
As shown in Figure 10-4, the monitor ROM immediately echoes each
received byte back to the PTB1/TXD pin for error checking.
SENT TO
MONITOR
READ
READ
ADDR. HIGH ADDR. HIGH
ADDR. LOW
ADDR. LOW
ECHO
DATA
RESULT
Figure 10-4. Read Transaction
Any result of a command appears after the echo of the last byte of the
command.
10.4.6 Break Signal
A start bit, followed by nine low bits, is a break signal. See Figure 10-5.
When the monitor receives a break signal, it delays two bit times before
echoing the break signal.
MISSING STOP BIT
TWO-STOP-BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 10-5. Break Transaction
Technical Data
192
MC68HC908MR8 — Rev 4.1
Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
Functional Description
10.4.7 Commands
The monitor ROM uses these commands:
•
READ, read memory
•
WRITE, write memory
•
IREAD, indexed read
•
IWRITE, indexed write
•
READSP, read stack pointer
•
RUN, run user program
Refer to Table 10-3 through Table 10-8.
Table 10-3. READ (Read Memory) Command
Description
Read byte from memory
Operand
Specifies 2-byte address in high byte:low byte order
Data returned
Returns contents of specified address
Opcode
$4A
Command sequence
SENT TO
MONITOR
READ
READ
ADDR. HIGH
ADDR. HIGH
ADDR. LOW
ADDR. LOW
ECHO
DATA
RESULT
Table 10-4. WRITE (Write Memory) Command
Description
Write byte to memory
Operand
Specifies 2-byte address in high byte:low byte order; low byte followed by data byte
Data returned
None
Opcode
$49
Command sequence
SENT TO
MONITOR
WRITE
WRITE
ADDR. HIGH
ADDR. HIGH
ADDR. LOW
ADDR. LOW
DATA
DATA
ECHO
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Monitor ROM (MON)
Table 10-5. IREAD (Indexed Read) Command
Description
Read next 2 bytes in memory from last address accessed
Operand
Specifies 2-byte address in high byte:low byte order
Data returned
Returns contents of next two addresses
Opcode
$1A
Command sequence
SENT TO
MONITOR
IREAD
IREAD
DATA
DATA
RESULT
ECHO
Table 10-6. IWRITE (Indexed Write) Command
Description
Write to last address accessed + 1
Operand
Specifies single data byte
Data returned
None
Opcode
$19
Command sequence
SENT TO
MONITOR
IWRITE
IWRITE
DATA
DATA
ECHO
NOTE:
A sequence of IREAD or IWRITE commands can sequentially access a
block of memory over the full 64-Kbyte memory map.
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Functional Description
Table 10-7. READSP (Read Stack Pointer) Command
Description
Reads stack pointer
Operand
None
Data returned
Returns stack pointer in high byte:low byte order
Opcode
$0C
Command sequence
SENT TO
MONITOR
READSP
READSP
SP HIGH
SP LOW
RESULT
ECHO
Table 10-8. RUN (Run User Program) Command
Description
Executes RTI instruction
Operand
None
Data returned
None
Opcode
$28
Command sequence
SENT TO
MONITOR
RUN
RUN
ECHO
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195
Monitor ROM (MON)
10.5 Security
A security feature discourages unauthorized reading of ROM locations
while in monitor mode. The host can satisfy the security feature at
monitor mode entry by sending eight security bytes that match the bytes
at locations $FFF6–$FFFD. Locations $FFF6–$FFFD contain
user-defined data.
NOTE:
Do not leave locations $FFF6–$FFFD blank. For security reasons,
program locations $FFF6–$FFFD even if they are not used for vectors.
During monitor mode entry, the MCU waits after the power-on reset for
the host to send the eight security bytes on pin PTB0 (RXD). If the
received bytes match those at locations $FFF6–$FFFD, the host
satisfies the security feature and can read all ROM locations and
execute code from ROM. Security remains satisfied until a power-on
reset occurs. If the reset was not a power-on reset, security remains
satisfied and security code entry is not required. See Figure 10-6.
VDD
4096 + 32 CGMXCLK CYCLES
RST
24 BUS CYCLES
PA7
COMMAND
BYTE 8
BYTE 2
FROM HOST
BYTE 1
256 BUS CYCLES (MINIMUM)
PA0
4
1
1
1
4
2
1
COMMAND ECHO
BREAK
BYTE 8 ECHO
Notes:
1 = Echo delay, 2 bit times
2 = Data return delay, 2 bit times
4 = Wait 1 bit time before sending next byte.
BYTE 2 ECHO
BYTE 1 ECHO
FROM MCU
Figure 10-6. Monitor Mode Entry Timing
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Security
Upon power-on reset, if the received bytes of the security code do not
match the data at locations $FFF6–$FFFD, the host fails to satisfy the
security feature. The MCU remains in monitor mode, but reading a ROM
location returns an invalid value and trying to execute code from ROM
causes an illegal address reset. After receiving the eight security bytes
from the host, the MCU transmits a break character, signifying that it is
ready to receive a command.
NOTE:
The MCU does not transmit a break character until after the host sends
the eight security bytes.
To determine whether the security code entered is correct, check to see
if bit 6 of RAM address $60 is set. If it is, then the correct security code
has been entered and ROM can be accessed.
If the security sequence fails, the device can be reset (via power-pin
reset only) and brought up in monitor mode to attempt another entry.
After failing the security sequence, the FLASH memory can also be bulk
erased by executing an erase routine that was downloaded into internal
RAM. The bulk erase operation clears the security code locations so that
all eight security bytes become $FF.
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Monitor ROM (MON)
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Technical Data — MC68HC908MR8
Section 11. Timer Interface A (TIMA)
11.1 Contents
11.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
11.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .200
11.4 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
11.4.1 TIMA Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . .204
11.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .204
11.4.3 Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .205
11.4.4 Pulse-Width Modulation (PWM) . . . . . . . . . . . . . . . . . . .207
11.5
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211
11.6
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .211
11.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212
11.8
TIMA During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . .212
11.9 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .212
11.9.1 TIMA Clock Pin (PTB2/TCLKA) . . . . . . . . . . . . . . . . . . . .213
11.9.2 TIMA Channel I/O Pins (PTB3/TCH0A–PTB4/TCH1A) . . 213
11.10 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213
11.10.1 TIMA Status and Control Register . . . . . . . . . . . . . . . . .214
11.10.2 TIMA Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . .216
11.10.3 TIMA Counter Modulo Registers. . . . . . . . . . . . . . . . . . .217
11.10.4 TIMA Channel Status and Control Registers. . . . . . . . .218
11.10.5 TIMA Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . .222
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Timer Interface A (TIMA)
11.2 Introduction
This section describes the timer interface module (TIMA). The TIMA is a
2-channel timer that provides:
•
Timing reference with input capture
•
Output compare
•
Pulse-width modulation (PWM) functions
Refer to Figure 11-1 for a block diagram of the TIMA and to Figure 11-2
for a summary of the registers.
For further information regarding timers on M68HC08 family devices,
please consult the HC08 Timer Reference Manual, TIM08RM/AD.
11.3 Features
Features of the TIMA include:
•
Two input capture/output compare channels:
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
•
Buffered and unbuffered pulse-width modulation (PWM) signal
generation
•
Programmable TIMA clock input:
– 7-frequency internal bus clock prescaler selection
– External TIMA clock input (4-MHz maximum frequency)
•
Free-running or modulo up-count operation
•
Toggle any channel pin on overflow
•
TIMA counter stop and reset bits
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Timer Interface A (TIMA)
Features
TCLK
PTB2/TCLKA
INTERNAL BUS CLOCK
PRESCALER SELECT
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
INTERRUPT
LOGIC
TOV0
CH0MAX
PTB3
LOGIC
CH0IE
INTERRUPT
LOGIC
16-BIT COMPARATOR
TMODH:TMODL
CHANNEL 0
ELS0B
ELS0A
16-BIT COMPARATOR
TCH0H:TCH0L
CH0F
16-BIT LATCH
MS0A
CHANNEL 1
PTB3/TCH0A
ELS1B
MS0B
ELS1A
TOV1
CH1MAX
16-BIT COMPARATOR
TCH1H:TCH1L
PTB4
LOGIC
PTB4/TCH1A
CH1F
16-BIT LATCH
INTERRUPT
LOGIC
CH1IE
MS1A
Figure 11-1. TIMA Block Diagram
Addr.
Register Name
Bit 7
Read
:
$000
E
TIMA Status/Control RegisWrite
ter (TASC)
:
See page 214.
Reset:
TIMA Counter Register High
Write
(TACNTH)
:
See page 216.
Reset:
5
TOF
TOIE
0
4
3
0
0
TRST
R
TSTOP
0
2
1
Bit 0
PS2
PS1
PS0
0
1
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read
Bit 15
:
$000
F
6
R
= Reserved
Figure 11-2. TIMA I/O Register Summary
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Timer Interface A (TIMA)
Addr.
Register Name
Read
:
$0010
TIMA Counter Register Low
Write
(TACNTL)
:
See page 216.
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
CH0IE
MS0B
MS0A
TOV0
CH0MA
X
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 1
Bit 0
Read
:
Bit 15
TIMA Counter Modulo RegWrite
$0011
ister High (TAMODH)
:
See page 217.
Re1
set:
Read
:
$0012
TIMA Counter Modulo RegWrite
ister Low (TAMODL)
:
See page 217.
Reset:
Read
CH0F
:
$0013
TIMA Channel 0 Status/Control Register Write
:
(TASC0)
See page 218.
Reset:
0
0
Read
:
$0014
Bit 15
TIMA Channel 0 Register
Write
High (TACH0H)
:
See page 222.
Reset:
Read
:
$0015
TIMA Channel 0 Register
Write
Low (TACH0L)
:
See page 218.
Reset:
ELS0B ELS0A
Bit 7
Indeterminate after reset
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Indeterminate after reset
R
= Reserved
Figure 11-2. TIMA I/O Register Summary (Continued)
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Features
Addr.
Register Name
Bit 7
Read
CH1F
:
$0016
TIMA Channel 1 Status/Control Write
:
Register (TASC1)
See page 218.
Reset:
0
Bit 15
TIMA Channel 1 Register
Write
High (TACH1H)
:
See page 222.
Reset:
Read
:
$0018
TIMA Channel 1 Register
Write
Low (TACH1L)
:
See page 222.
Reset:
5
Bit 7
4
3
2
1
Bit 0
TOV1
CH1MA
X
0
CH1IE
MS1A
0
Read
:
$0017
6
ELS1B ELS1A
R
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 1
Bit 0
Indeterminate after reset
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Indeterminate after reset
R
= Reserved
Figure 11-2. TIMA I/O Register Summary (Continued)
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11.4 Functional Description
Figure 11-1 shows the TIMA structure. The central component of the
TIMA is the 16-bit TIMA counter that can operate as a free-running
counter or a modulo up-counter. The TIMA counter provides the timing
reference for the input capture and output compare functions. The TIMA
counter modulo registers, TAMODH–TAMODL, control the modulo
value of the TIMA counter. Software can read the TIMA counter value at
any time without affecting the counting sequence.
The two TIMA channels are programmable independently as input
capture or output compare channels.
11.4.1 TIMA Counter Prescaler
The TIMA clock source can be one of the seven prescaler outputs or the
TIMA clock pin, PTB2/TCLKA. The prescaler generates seven clock
rates from the internal bus clock. The prescaler select bits, PS[2:0], in
the TIMA status and control register select the TIMA clock source.
11.4.2 Input Capture
An input capture function has three basic parts:
1. Edge select logic
2. Input capture latch
3. 16-bit counter
Two 8-bit registers, which make up the 16-bit input capture register, are
used to latch the value of the free-running counter after the
corresponding input capture edge detector senses a defined transition.
The polarity of the active edge is programmable. The level transition
which triggers the counter transfer is defined by the corresponding input
edge bits (ELSxB and ELSxA in the TASC0 and TASC1 control registers
with x referring to the active channel number).
When an active edge occurs on the pin of an input capture channel, the
TIMA latches the contents of the TIMA counter into the TIMA channel
registers, TCHxH–TCHxL. Input captures can generate TIMA CPU
interrupt requests. Software can determine that an input capture event
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Timer Interface A (TIMA)
Functional Description
has occurred by enabling input capture interrupts or by polling the status
flag bit.
The free-running counter contents are transferred to the TIMA channel
status and control registers TACHxH and TACHxL (see 11.10.5 TIMA
Channel Registers) on each proper signal transition regardless of
whether the TIMA channel flag (CH0F–CH1F in the TASC0–TASC1
registers) is set or clear. When the status flag is set, a CPU interrupt is
generated if enabled. The value of the count latched or captured is the
time of the event. Because this value is stored in the input capture
register two bus cycles after the actual event occurs, user software can
respond to this event at a later time and determine the actual time of the
event. However, this must be done prior to another input capture on the
same pin; otherwise, the previous time value will be lost.
By recording the times for successive edges on an incoming signal,
software can determine the period and/or pulse width of the signal. To
measure a period, two successive edges of the same polarity are
captured. To measure a pulse width, two alternate polarity edges are
captured. Software should track the overflows at the 16-bit module
counter to extend its range.
Another use for the input capture function is to establish a time
reference. In this case, an input capture function is used in conjunction
with an output compare function. For example, to activate an output
signal a specified number of clock cycles after detecting an input event
(edge), use the input capture function to record the time at which the
edge occurred. A number corresponding to the desired delay is added to
this captured value and stored to an output compare register (see
11.10.5 TIMA Channel Registers). Because both input captures and
output compares are referenced to the same 16-bit modulo counter, the
delay can be controlled to the resolution of the counter independent of
software latencies.
NOTE:
Reset does not affect the contents of the input capture channel register
(TACHxH–TACHxL).
11.4.3 Output Compare
With the output compare function, the TIMA can generate a periodic
pulse with a programmable polarity, duration, and frequency. When the
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Timer Interface A (TIMA)
counter reaches the value in the registers of an output compare channel,
the TIMA can set, clear, or toggle the channel pin. Output compares can
generate TIMA CPU interrupt requests.
11.4.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare
pulses as described in 11.4.3 Output Compare. The pulses are
unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change an
output compare value could cause incorrect operation for up to two
counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new
value prevents any compare during that counter overflow period. Also,
using a TIMA overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMA may
pass the new value before it is written.
Use these methods to synchronize unbuffered changes in the output
compare value on channel x:
•
When changing to a smaller value, enable channel x output
compare interrupts and write the new value in the output compare
interrupt routine. The output compare interrupt occurs at the end
of the current output compare pulse. The interrupt routine has until
the end of the counter overflow period to write the new value.
•
When changing to a larger output compare value, enable TIMA
overflow interrupts and write the new value in the TIMA overflow
interrupt routine. The TIMA overflow interrupt occurs at the end of
the current counter overflow period. Writing a larger value in an
output compare interrupt routine (at the end of the current pulse)
could cause two output compares to occur in the same counter
overflow period.
11.4.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare
channel whose output appears on the PTB3/TCH0A pin. The TIMA
channel registers of the linked pair alternately control the output.
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Functional Description
Setting the MS0B bit in TIMA channel 0 status and control register
(TASC0) links channel 0 and channel 1. The output compare value in the
TIMA channel 0 registers initially controls the output on the
PTB3/TCH0A pin. Writing to the TIMA channel 1 registers enables the
TIMA channel 1 registers to synchronously control the output after the
TIMA overflows. At each subsequent overflow, the TIMA channel
registers (0 or 1) that control the output are the ones written to last. TSC0
controls and monitors the buffered output compare function, and TIMA
channel 1 status and control register (TASC1) is unused. While the
MS0B bit is set, the channel 1 pin, PTB4/TCH1A, is available as a
general-purpose input/output (I/O) pin.
NOTE:
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. User software should
track the currently active channel to prevent writing a new value to the
active channel. Writing to the active channel registers is the same as
generating unbuffered output compares.
11.4.4 Pulse-Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel,
the TIMA can generate a PWM signal. The value in the TIMA counter
modulo registers determines the period of the PWM signal. The channel
pin toggles when the counter reaches the value in the TIMA counter
modulo registers. The time between overflows is the period of the PWM
signal.
As Figure 11-3 shows, the output compare value in the TIMA channel
registers determines the pulse width of the PWM signal. The time
between overflow and output compare is the pulse width. Program the
TIMA to clear the channel pin on output compare if the state of the PWM
pulse is logic 1. Program the TIMA to set the pin if the state of the PWM
pulse is logic 0.
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Timer Interface A (TIMA)
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PULSE
WIDTH
PTBx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 11-3. PWM Period and Pulse Width
The value in the TIMA counter modulo registers and the selected
prescaler output determines the frequency of the PWM output. The
frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMA counter modulo registers produces a PWM
period of 256 times the internal bus clock period if the prescaler select
value is $000. See 11.10.1 TIMA Status and Control Register.
The value in the TIMA channel registers determines the pulse width of
the PWM output. The pulse width of an 8-bit PWM signal is variable in
256 increments. Writing $0080 (128) to the TIMA channel registers
produces a duty cycle of 128/256 or 50 percent.
11.4.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as
described in 11.4.4 Pulse-Width Modulation (PWM). The pulses are
unbuffered because changing the pulse width requires writing the new
pulse width value over the value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change a
pulse width value could cause incorrect operation for up to two PWM
periods. For example, writing a new value before the counter reaches
the old value but after the counter reaches the new value prevents any
compare during that PWM period. Also, using a TIMA overflow interrupt
routine to write a new, smaller pulse width value may cause the compare
to be missed. The TIMA may pass the new value before it is written to
the TIMA channel registers.
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Functional Description
Use these methods to synchronize unbuffered changes in the PWM
pulse width on channel x:
NOTE:
•
When changing to a shorter pulse width, enable channel x output
compare interrupts and write the new value in the output compare
interrupt routine. The output compare interrupt occurs at the end
of the current pulse. The interrupt routine has until the end of the
PWM period to write the new value.
•
When changing to a longer pulse width, enable TIMA overflow
interrupts and write the new value in the TIMA overflow interrupt
routine. The TIMA overflow interrupt occurs at the end of the
current PWM period. Writing a larger value in an output compare
interrupt routine (at the end of the current pulse) could cause two
output compares to occur in the same PWM period.
In PWM signal generation, do not program the PWM channel to toggle
on output compare. Toggling on output compare prevents reliable
0 percent duty cycle generation and removes the ability of the channel
to self-correct in the event of software error or noise. Toggling on output
compare also can cause incorrect PWM signal generation when
changing the PWM pulse width to a new, much larger value.
11.4.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose
output appears on the PTB3/TCH0A pin. The TIMA channel registers of
the linked pair alternately control the pulse width of the output.
Setting the MS0B bit in TIMA channel 0 status and control register
(TASC0) links channel 0 and channel 1. The TIMA channel 0 registers
initially control the pulse width on the PTB3/TCH0A pin. Writing to the
TIMA channel 1 registers enables the TIMA channel 1 registers to
synchronously control the pulse width at the beginning of the next PWM
period. At each subsequent overflow, the TIMA channel registers (0 or
1) that control the pulse width are the ones written to last. TASC0
controls and monitors the buffered PWM function, and TIMA channel 1
status and control register (TASC1) is unused. While the MS0B bit is set,
the channel 1 pin, PTB4/TCH1A, is available as a general-purpose I/O
pin.
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Timer Interface A (TIMA)
NOTE:
In buffered PWM signal generation, do not write new pulse width values
to the currently active channel registers. User software should track the
currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as
generating unbuffered PWM signals.
11.4.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered
PWM signals, use this initialization procedure:
1. In the TIMA status and control register (TASC):
a. Stop the TIMA counter by setting the TIMA stop bit, TSTOP.
b. Reset the TIMA counter and prescaler by setting the TIMA
reset bit, TRST.
2. In the TIMA counter modulo registers (TAMODH–TAMODL), write
the value for the required PWM period.
3. In the TIMA channel x registers (TACHxH–TACHxL), write the
value for the required pulse width.
4. In TIMA channel x status and control register (TASCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or
1:0 (for buffered output compare or PWM signals) to the mode
select bits, MSxB–MSxA. See Table 11-2.
b. Write 1 to the toggle-on-overflow bit, TOVx.
c.
NOTE:
Write 1:0 (to clear output on compare) or 1:1 (to set output on
compare) to the edge/level select bits, ELSxB–ELSxA. The
output action on compare must force the output to the
complement of the pulse width level. See Table 11-2.
In PWM signal generation, do not program the PWM channel to toggle
on output compare. Toggling on output compare prevents reliable
0 percent duty cycle generation and removes the ability of the channel
to self-correct in the event of software error or noise. Toggling on output
compare can also cause incorrect PWM signal generation when
changing the PWM pulse width to a new, much larger value.
5. In the TIMA status control register (TASC), clear the TIMA stop bit,
TSTOP.
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Freescale Semiconductor
Timer Interface A (TIMA)
Interrupts
Setting MS0B links channels 0 and 1 and configures them for buffered
PWM operation. The TIMA channel 0 registers (TACH0H–TACH0L)
initially control the buffered PWM output. TIMA status control register 0
(TASC0) controls and monitors the PWM signal from the linked
channels. MS0B takes priority over MS0A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on
TIMA overflows. Subsequent output compares try to force the output to
a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the
TOVx bit generates a 100 percent duty cycle output. See 11.10.4 TIMA
Channel Status and Control Registers.
11.5 Interrupts
These TIMA sources can generate interrupt requests:
•
TIMA overflow flag (TOF) — The TOF bit is set when the TIMA
counter reaches the modulo value programmed in the TIMA
counter modulo registers. The TIMA overflow interrupt enable bit,
TOIE, enables TIMA overflow CPU interrupt requests. TOF and
TOIE are in the TIMA status and control register.
•
TIMA channel flags (CH1F–CH0F) — The CHxF bit is set when an
input capture or output compare occurs on channel x. Channel x
TIMA CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE.
11.6 Wait Mode
The WAIT instruction puts the MCU in low-power standby mode.
The TIMA remains active after the execution of a WAIT instruction. In
wait mode, the TIMA registers are not accessible by the CPU. Any
enabled CPU interrupt request from the TIMA can bring the MCU out of
wait mode.
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Technical Data
Timer Interface A (TIMA)
211
Timer Interface A (TIMA)
If TIMA functions are not required during wait mode, reduce power
consumption by stopping the TIMA before executing the WAIT
instruction.
11.7 Stop Mode
TIMA is inactive after execution of a STOP instruction. The STOP
instruction does not affect register conditions or the state of the TIMA
counter. TIMA operation resumes when the MCU exits stop mode after
an external interrupt.
11.8 TIMA During Break Interrupts
A break interrupt stops the TIMA counter and inhibits input captures.
The system integration module (SIM) controls whether status bits in
other modules can be cleared during the break state. The BCFE bit in
the SIM break flag control register (SBFCR) enables software to clear
status bits during the break state. See 7.7.5 SIM Break Flag Control
Register.
To allow software to clear status bits during a break interrupt, write a
logic 1 to the BCFE bit. If a status bit is cleared during the break state, it
remains cleared when the MCU exits the break state.
To protect status bits during the break state, write a logic 0 to the BCFE
bit. With BCFE at logic 0 (its default state), software can read and write
I/O registers during the break state without affecting status bits. Some
status bits have a 2-step read/write clearing procedure. If software does
the first step on such a bit before the break, the bit cannot change during
the break state as long as BCFE is at logic 0. After the break, doing the
second step clears the status bit.
11.9 I/O Signals
Port B shares three of its pins with the TIMA. PTB2/TCLKA is an external
clock input to the TIMA prescaler. The two TIMA channel I/O pins are
PTB3/TCH0A and PTB4/TCH1A.
Technical Data
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Timer Interface A (TIMA)
Freescale Semiconductor
Timer Interface A (TIMA)
I/O Registers
11.9.1 TIMA Clock Pin (PTB2/TCLKA)
PTB2/TCLKA is an external clock input that can be the clock source for
the TIMA counter instead of the prescaled internal bus clock. Select the
PTB2/TCLKA input by writing logic 1s to the three prescaler select bits,
PS[2:0] (see 11.10.1 TIMA Status and Control Register). The
minimum TCLK pulse width, TCLKLMIN or TCLKHMIN, is:
1
------------------------------------- + t su
bus frequency
The maximum TCLK frequency is the least: 4 MHz or bus frequency ÷ 2.
PTB2/TCLKA is available as a general-purpose I/O pin or ADC channel
when not used as the TIMA clock input. When the PTB2/TCLKA pin is
the TIMA clock input, it is an input regardless of the state of the DDRB2
bit in data direction register B.
11.9.2 TIMA Channel I/O Pins (PTB3/TCH0A–PTB4/TCH1A)
Each channel I/O pin is programmable independently as an input
capture pin or an output compare pin. PTB3/TCH0A and PTB3/TCH1A
can be configured as buffered output compare or buffered PWM pins.
11.10 I/O Registers
These I/O registers control and monitor TIMA operation:
•
TIMA status and control register (TASC)
•
TIMA control registers (TACNTH–TACNTL)
•
TIMA counter modulo registers (TAMODH–TAMODL)
•
TIMA channel status and control registers (TASC0 and TASC1)
•
TIMA channel registers (TACH0H–TACH0L and
TACH1H–TACH1L)
MC68HC908MR8 — Rev 4.1
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Technical Data
Timer Interface A (TIMA)
213
Timer Interface A (TIMA)
11.10.1 TIMA Status and Control Register
The TIMA status and control register:
•
Enables TIMA overflow interrupts
•
Flags TIMA overflows
•
Stops the TIMA counter
•
Resets the TIMA counter
•
Prescales the TIMA counter clock
Address $000E
:
Bit 7
Read:
TOF
Write:
0
Reset:
0
R
6
5
TOIE
TSTOP
0
1
4
3
0
0
TRST
R
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
= Reserved
Figure 11-4. TIMA Status and Control Register (TASC)
TOF — TIMA Overflow Flag Bit
This read/write flag is set when the TIMA counter reaches the modulo
value programmed in the TIMA counter modulo registers. Clear TOF
by reading the TIMA status and control register when TOF is set and
then writing a logic 0 to TOF. If another TIMA overflow occurs before
the clearing sequence is complete, then writing logic 0 to TOF has no
effect. Therefore, a TOF interrupt request cannot be lost due to
inadvertent clearing of TOF. Reset clears the TOF bit. Writing a logic
1 to TOF has no effect.
1 = TIMA counter has reached modulo value.
0 = TIMA counter has not reached modulo value.
TOIE — TIMA Overflow Interrupt Enable Bit
This read/write bit enables TIMA overflow interrupts when the TOF bit
becomes set. Reset clears the TOIE bit.
1 = TIMA overflow interrupts enabled
0 = TIMA overflow interrupts disabled
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Timer Interface A (TIMA)
Freescale Semiconductor
Timer Interface A (TIMA)
I/O Registers
TSTOP — TIMA Stop Bit
This read/write bit stops the TIMA counter. Counting resumes when
TSTOP is cleared. Reset sets the TSTOP bit, stopping the TIMA
counter until software clears the TSTOP bit.
1 = TIMA counter stopped
0 = TIMA counter active
NOTE:
Do not set the TSTOP bit before entering wait mode if the TIMA is
required to exit wait mode. Also, when the TSTOP bit is set and the timer
is configured for input capture operation, input captures are inhibited
until TSTOP is cleared.
TRST — TIMA Reset Bit
Setting this write-only bit resets the TIMA counter and the TIMA
prescaler. Setting TRST has no effect on any other registers.
Counting resumes from $0000. TRST is cleared automatically after
the TIMA counter is reset and always reads as logic 0. Reset clears
the TRST bit.
1 = Prescaler and TIMA counter cleared
0 = No effect
NOTE:
Setting the TSTOP and TRST bits simultaneously stops the TIMA
counter at a value of $0000.
PS[2:0] — Prescaler Select Bits
These read/write bits select either the PTB2/TCLKA pin or one of the
seven prescaler outputs as the input to the TIMA counter as
Table 11-1 shows. Reset clears the PS[2:0] bits.
Table 11-1. Prescaler Selection
PS[2:0]
TIMA Clock Source
000
Internal bus clock ÷ 1
001
Internal bus clock ÷ 2
010
Internal bus clock ÷ 4
011
Internal bus clock ÷ 8
100
Internal bus clock ÷ 16
101
Internal bus clock ÷ 32
110
Internal bus clock ÷ 64
111
PTB2/TCLKA
MC68HC908MR8 — Rev 4.1
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Technical Data
Timer Interface A (TIMA)
215
Timer Interface A (TIMA)
11.10.2 TIMA Counter Registers
The two read-only TIMA counter registers contain the high and low bytes
of the value in the TIMA counter. Reading the high byte (TACNTH)
latches the contents of the low byte (TACNTL) into a buffer. Subsequent
reads of TACNTH do not affect the latched TACNTL value until TACNTL
is read. Reset clears the TIMA counter registers. Setting the TIMA reset
bit (TRST) also clears the TIMA counter registers.
NOTE:
If TACNTH is read during a break interrupt, be sure to unlatch TACNTL
by reading TACNTL before exiting the break interrupt. Otherwise,
TACNTL retains the value latched during the break.
Register Name and Address:
TACNTH — $000F
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
Register Name and Address:
TACNTL — $0010
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 11-5. TIMA Counter Registers (TACNTH and TACNTL)
Technical Data
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Timer Interface A (TIMA)
Freescale Semiconductor
Timer Interface A (TIMA)
I/O Registers
11.10.3 TIMA Counter Modulo Registers
The read/write TIMA modulo registers contain the modulo value for the
TIMA counter. When the TIMA counter reaches the modulo value, the
overflow flag (TOF) becomes set, and the TIMA counter resumes
counting from $0000 at the next timer clock. Writing to the high byte
(TMODH) inhibits the TOF bit and overflow interrupts until the low byte
(TMODL) is written. Reset sets the TIMA counter modulo registers.
Register Name and Address:
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
1
Register Name and Address:
Read:
Write:
Reset:
TAMODH — $0011
TAMODL — $0012
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 11-6. TIMA Counter Modulo Registers (TMODH and TMODL)
NOTE:
Reset the TIMA counter before writing to the TIMA counter modulo
registers.
MC68HC908MR8 — Rev 4.1
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Technical Data
Timer Interface A (TIMA)
217
Timer Interface A (TIMA)
11.10.4 TIMA Channel Status and Control Registers
Each of the TIMA channel status and control registers:
•
Flags input captures and output compares
•
Enables input capture and output compare interrupts
•
Selects input capture, output compare, or PWM operation
•
Selects high, low, or toggling output on output compare
•
Selects rising edge, falling edge, or any edge as the active input
capture trigger
•
Selects output toggling on TIMA overflow
•
Selects 0% and 100% PWM duty cycle
•
Selects buffered or unbuffered output compare/PWM operation
Register Name and Address:
Bit 7
Read:
CH0F
Write:
0
Reset:
0
6
5
4
3
2
1
Bit 0
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MA
X
0
0
0
0
0
0
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MA
X
0
0
0
0
0
Register Name and Address:
Bit 7
Read:
CH1F
Write:
0
Reset:
0
R
TASC0 — $0013
TASC1 — $0016
6
CH1IE
0
5
0
R
0
= Reserved
Figure 11-7. TIMA Channel Status and Control Registers
(TASC0–TASC1)
Technical Data
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Timer Interface A (TIMA)
Freescale Semiconductor
Timer Interface A (TIMA)
I/O Registers
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set
when an active edge occurs on the channel x pin. When channel x is
an output compare channel, CHxF is set when the value in the TIMA
counter registers matches the value in the TIMA channel x registers.
When CHxIE = 1, clear CHxF by reading TIMA channel x status and
control register with CHxF set, and then writing a logic 0 to CHxF. If
another interrupt request occurs before the clearing sequence is
complete, then writing logic 0 to CHxF has no effect. Therefore, an
interrupt request cannot be lost due to inadvertent clearing of CHxF.
Reset clears the CHxF bit. Writing a logic 1 to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIMA CPU interrupts on channel x. Reset
clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation.
MSxB exists only in the TIMA channel 0. Setting MS0B disables the
channel 1 status and control register and reverts TCH1A to
general-purpose I/O. Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture
operation or unbuffered output compare/PWM operation. See
Table 11-2.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level
of the TCHx pin once PWM, input capture, or output compare
operation is enabled. Reset clears the MSxA bit. See Table 11-2.
1 = Initial output level low
0 = Initial output level high
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface A (TIMA)
219
Timer Interface A (TIMA)
NOTE:
Before changing a channel function by writing to the MSxB or MSxA bit,
set the TSTOP and TRST bits in the TIMA status and control register
(TASC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits
control the active edge-sensing logic on channel x.
When channel x is an output compare channel, ELSxB and ELSxA
control the channel x output behavior when an output compare
occurs.
When ELSxB and ELSxA are both clear, channel x is not connected
to port B, and pin PTBx/TCHxA is available as a general-purpose I/O
pin. However, channel x is at a state determined by these bits and
becomes transparent to the respective pin when PWM, input capture,
or output compare mode is enabled. Table 11-2 shows how ELSxA
and ELSxA work. Reset clears the ELSxB and ELSxA bits.
Table 11-2. Mode, Edge, and Level Selection
MSxB:MSxA
ELSxB:ELSxA
X0
00
X1
00
00
01
00
10
00
11
01
01
01
10
01
11
1X
01
1X
10
1X
11
Mode
Output
preset
Pin under port control:
Initialize timer
Output level high
Pin under port control:
Initialize timer
Output level low
Capture on rising edge only
Input
capture
Capture on falling edge only
Capture on rising or falling edge
Output
compare
or PWM
Buffered
output
compare
or
buffered
PWM
Technical Data
220
Configuration
Toggle output on compare
Clear output on compare
Set output on compare
Toggle output on compare
Clear output on compare
Set output on compare
MC68HC908MR8 — Rev 4.1
Timer Interface A (TIMA)
Freescale Semiconductor
Timer Interface A (TIMA)
I/O Registers
NOTE:
Before enabling a TIMA channel register for input capture operation,
make sure that the PTBx/TACHx pin is stable for at least two bus clocks.
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit
controls the behavior of the channel x output when the TIMA counter
overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMA counter overflow.
0 = Channel x pin does not toggle on TIMA counter overflow.
NOTE:
When TOVx is set, a TIMA counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx bit is at logic 1, setting the CHxMAX bit forces the
duty cycle of buffered and unbuffered PWM signals to 100 percent. As
Figure 11-8 shows, the CHxMAX bit takes effect in the cycle after it
is set or cleared. The output stays at the 100 percent duty cycle level
until the cycle after CHxMAX is cleared.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTBx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
TOVx
Figure 11-8. CHxMAX Latency
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface A (TIMA)
221
Timer Interface A (TIMA)
11.10.5 TIMA Channel Registers
These read/write registers contain the captured TIMA counter value of
the input capture function or the output compare value of the output
compare function. The state of the TIMA channel registers after reset is
unknown.
In input capture mode (MSxB–MSxA = 0:0), reading the high byte of the
TIMA channel x registers (TACHxH) inhibits input captures until the low
byte (TACHxL) is read.
In output compare mode (MSxB–MSxA ≠ 0:0), writing to the high byte of
the TIMA channel x registers (TACHxH) inhibits output compares until
the low byte (TACHxL) is written.
Register Name and Address:
Read:
Write:
TACH0H — $0014
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
TACH0L — $0015
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
TACH1H — $0017
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
Reset:
TACH1L — $0018
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Figure 11-9. TIMA Channel Registers (TACH0H/L–TACH1H/L)
Technical Data
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Timer Interface A (TIMA)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 12. Timer Interface B (TIMB)
12.1 Contents
12.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
12.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
12.4 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .227
12.4.1 TIMB Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . .228
12.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .228
12.4.3 Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .230
12.4.4 Pulse-Width Modulation (PWM) . . . . . . . . . . . . . . . . . . .231
12.5
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .235
12.6
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .235
12.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .236
12.8
TIMB During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . .236
12.9
TIMB Channel I/O Pins (PTB5/TCH0B–PTB6/TCH1B) . . . .237
12.10 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .237
12.10.1 TIMB Status and Control Register . . . . . . . . . . . . . . . . .237
12.10.2 TIMB Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . .240
12.10.3 TIMB Counter Modulo Registers. . . . . . . . . . . . . . . . . . .241
12.10.4 TIMB Channel Status and Control Registers. . . . . . . . .242
12.10.5 TIMB Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . .245
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface B (TIMB)
223
Timer Interface B (TIMB)
12.2 Introduction
This section describes the timer interface module (TIMB). The TIMB is a
2-channel timer that provides:
•
A timing reference with input capture
•
Output compare
•
Pulse width modulation (PWM) functions
Refer to Figure 12-1 for a block diagram of the TIMB and to Figure 12-2
for a summary of the registers.
For further information regarding timers on M68HC08 family devices,
please consult the HC08 Timer Reference Manual, TIM08RM/AD.
12.3 Features
Features of the TIMB include:
•
Two input capture/output compare channels
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
•
Buffered and unbuffered PWM signal generation
•
Programmable TIMB clock with 7-frequency internal bus clock
prescaler selection
•
Free-running or modulo up-count operation
•
Toggle any channel pin on overflow
•
TIMB counter stop and reset bits
Technical Data
224
MC68HC908MR8 — Rev 4.1
Timer Interface B (TIMB)
Freescale Semiconductor
Timer Interface B (TIMB)
Features
INTERNAL
BUS CLOCK
PRESCALER SELECT
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
INTERRUPT
LOGIC
TOIE
16-BIT COMPARATOR
TMODH:TMODL
CHANNEL 0
ELS0B
ELS0A
TOV0
CH0MAX
16-BIT COMPARATOR
TCH0H:TCH0L
CH0F
16-BIT LATCH
MS0A
CHANNEL 1
PTB5
LOGIC
ELS1B
ELS1A
TOV1
CH1MAX
16-BIT COMPARATOR
TCH1H:TCH1L
INTERRUPT
LOGIC
CH0IE
MS0B
PTB6
LOGIC
CH1F
16-BIT LATCH
PTB6/TCH1B
INTERRUPT
LOGIC
CH1IE
MS1A
PTB5/TCH0B
Figure 12-1. TIMB Block Diagram
Addr.
Register Name
Bit 7
Read
:
TIMB Status/Control Register Write
$0051
:
(TBSC)
See page 238.
Reset:
TIMB Counter Register High
Write
(TBCNTH)
:
See page 240.
Reset:
5
TOF
TOIE
0
4
3
0
0
TSTOP
0
TRST
R
2
1
Bit 0
PS2
PS1
PS0
0
1
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read
Bit 15
:
$0052
6
R
= Reserved
Figure 12-2. TIMB I/O Register Summary
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface B (TIMB)
225
Timer Interface B (TIMB)
Addr.
Register Name
Read
:
$0053
TIMB Counter Register Low
Write
(TBCNTL)
:
See page 240.
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
CH0IE
MS0B
MS0A
TOV0
CH0MA
X
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Read
:
TIMB Counter Modulo RegBit 15
ister High Write
$0054
:
(TBMODH)
See page 241.
Re1
set:
Read
:
TIMB Counter Modulo Register Low Write
$0055
:
(TBMODL)
See page 241.
Reset:
Read
CH0F
:
$0056
TIMB Channel 0 Status/Control Register Write
:
(TBSC0)
See page 242.
Reset:
0
0
Read
:
$0057
ELS0B ELS0A
TIMB Channel 0 Register
Bit 15
High Write
:
(TBCH0H)
See page 246.
Reset:
R
Indeterminate after reset
= Reserved
Figure 12-2. TIMB I/O Register Summary (Continued)
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Freescale Semiconductor
Timer Interface B (TIMB)
Functional Description
Addr.
Register Name
Read
:
$0058
TIMB Channel 0 Register
Low Write
:
(TBCH0L)
See page 246.
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
TOV1
CH1MA
X
Indeterminate after reset
Read
CH1F
:
$0059
TIMB Channel 1 Status/Control Register Write
:
(TBSC1)
See page 246.
Reset:
0
TIMB Channel 1 Register
Bit 15
High Write
:
(TBCH1H)
See page 246.
Reset:
Read
:
$005
B
TIMB Channel 1 Register
Low Write
:
(TBCH1L)
See page 246.
Reset:
CH1IE
0
Read
:
$005
A
0
Bit 7
MS1A
ELS1B ELS1A
R
0
0
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 1
Bit 0
Indeterminate after reset
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Indeterminate after reset
R
= Reserved
Figure 12-2. TIMB I/O Register Summary (Continued)
12.4 Functional Description
Figure 12-1 shows the TIMB structure. The central component of the
TIMB is the 16-bit TIMB counter that can operate as a free-running
counter or a modulo up-counter. The TIMB counter provides the timing
reference for the input capture and output compare functions. The TIMB
counter modulo registers, TBMODH–TBMODL, control the modulo
value of the TIMB counter. Software can read the TIMB counter value at
any time without affecting the counting sequence.
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Timer Interface B (TIMB)
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Timer Interface B (TIMB)
The two TIMB channels are programmable independently as input
capture or output compare channels.
12.4.1 TIMB Counter Prescaler
The TIMB clock source can be one of the seven prescaler outputs. The
prescaler generates seven clock rates from the internal bus clock. The
prescaler select bits, PS[2:0], in the TIMB status and control register
select the TIMB clock source.
12.4.2 Input Capture
An input capture function has three basic parts:
•
Edge select logic
•
Input capture latch
•
16-bit counter
Two 8-bit registers, which make up the 16-bit input capture register, are
used to latch the value of the free-running counter after the
corresponding input capture edge detector senses a defined transition.
The polarity of the active edge is programmable. The level transition
which triggers the counter transfer is defined by the corresponding input
edge bits (ELSxB and ELSxA in TBSC0 through TBSC1 control registers
with x referring to the active channel number). When an active edge
occurs on the pin of an input capture channel, the TIMB latches the
contents of the TIMB counter into the TIMB channel registers,
TCHxH–TCHxL. Input captures can generate TIMB CPU interrupt
requests. Software can determine that an input capture event has
occurred by enabling input capture interrupts or by polling the status flag
bit.
The free-running counter contents are transferred to the TIMB channel
status and control register, TBCHxH–TBCHxL, (see 12.10.5 TIMB
Channel Registers) on each proper signal transition regardless of
whether the TIMB channel flag (CH0F–CH1F in TBSC0–TBSC1
registers) is set or clear. When the status flag is set, a CPU interrupt is
generated if enabled. The value of the count latched or “captured” is the
time of the event. Because this value is stored in the input capture
register two bus cycles after the actual event occurs, user software can
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Freescale Semiconductor
Timer Interface B (TIMB)
Functional Description
respond to this event at a later time and determine the actual time of the
event. However, this must be done prior to another input capture on the
same pin; otherwise, the previous time value will be lost.
By recording the times for successive edges on an incoming signal,
software can determine the period and/or pulse width of the signal. To
measure a period, two successive edges of the same polarity are
captured. To measure a pulse width, two alternate polarity edges are
captured. Software should track the overflows at the 16-bit module
counter to extend its range.
Another use for the input capture function is to establish a time
reference. In this case, an input capture function is used in conjunction
with an output compare function. For example, to activate an output
signal a specified number of clock cycles after detecting an input event
(edge), use the input capture function to record the time at which the
edge occurred. A number corresponding to the desired delay is added to
this captured value and stored to an output compare register (see
12.10.5 TIMB Channel Registers). Because both input captures and
output compares are referenced to the same 16-bit modulo counter, the
delay can be controlled to the resolution of the counter independent of
software latencies.
NOTE:
Reset does not affect the contents of the input capture channel register
(TBCHxH–TBCHxL).
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Timer Interface B (TIMB)
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Timer Interface B (TIMB)
12.4.3 Output Compare
With the output compare function, the TIMB can generate a periodic
pulse with a programmable polarity, duration, and frequency. When the
counter reaches the value in the registers of an output compare channel,
the TIMB can set, clear, or toggle the channel pin. Output compares can
generate TIMB CPU interrupt requests.
12.4.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare
pulses as described in 12.4.3 Output Compare. The pulses are
unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMB channel registers.
An unsynchronized write to the TIMB channel registers to change an
output compare value could cause incorrect operation for up to two
counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new
value prevents any compare during that counter overflow period. Also,
using a TIMB overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMB may
pass the new value before it is written.
Use these methods to synchronize unbuffered changes in the output
compare value on channel x:
•
When changing to a smaller value, enable channel x output
compare interrupts and write the new value in the output compare
interrupt routine. The output compare interrupt occurs at the end
of the current output compare pulse. The interrupt routine has until
the end of the counter overflow period to write the new value.
•
When changing to a larger output compare value, enable TIMB
overflow interrupts and write the new value in the TIMB overflow
interrupt routine. The TIMB overflow interrupt occurs at the end of
the current counter overflow period. Writing a larger value in an
output compare interrupt routine (at the end of the current pulse)
could cause two output compares to occur in the same counter
overflow period.
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Timer Interface B (TIMB)
Functional Description
12.4.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare
channel whose output appears on the PTB5/TCH0B pin. The TIMB
channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIMB channel 0 status and control register
(TBSC0) links channel 0 and channel 1. The output compare value in the
TIMB channel 0 registers initially controls the output on the
PTB5/TCH0B pin. Writing to the TIMB channel 1 registers enables the
TIMB channel 1 registers to synchronously control the output after the
TIMB overflows. At each subsequent overflow, the TIMB channel
registers (0 or 1) that control the output are the ones written to last. TSC0
controls and monitors the buffered output compare function, and TIMB
channel 1 status and control register (TBSC1) is unused. While the
MS0B bit is set, the channel 1 pin, PTB6/TCH1B, is available as a
general-purpose input/output (I/O) pin.
NOTE:
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. User software should
track the currently active channel to prevent writing a new value to the
active channel. Writing to the active channel registers is the same as
generating unbuffered output compares.
12.4.4 Pulse-Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel,
the TIMB can generate a PWM signal. The value in the TIMB counter
modulo registers determines the period of the PWM signal. The channel
pin toggles when the counter reaches the value in the TIMB counter
modulo registers. The time between overflows is the period of the PWM
signal.
As Figure 12-3 shows, the output compare value in the TIMB channel
registers determines the pulse width of the PWM signal. The time
between overflow and output compare is the pulse width. Program the
TIMB to clear the channel pin on output compare if the state of the PWM
pulse is logic 1. Program the TIMB to set the pin if the state of the PWM
pulse is logic 0.
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Technical Data
Timer Interface B (TIMB)
231
Timer Interface B (TIMB)
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PULSE
WIDTH
PTBx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 12-3. PWM Period and Pulse Width
The value in the TIMB counter modulo registers and the selected
prescaler output determines the frequency of the PWM output. The
frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMB counter modulo registers produces a PWM
period of 256 times the internal bus clock period if the prescaler select
value is $000 (see 12.10.1 TIMB Status and Control Register).
The value in the TIMB channel registers determines the pulse width of
the PWM output. The pulse width of an 8-bit PWM signal is variable in
256 increments. Writing $0080 (128) to the TIMB channel registers
produces a duty cycle of 128/256 or 50 percent.
12.4.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as
described in 12.4.4 Pulse-Width Modulation (PWM). The pulses are
unbuffered because changing the pulse width requires writing the new
pulse width value over the value currently in the TIMB channel registers.
An unsynchronized write to the TIMB channel registers to change a
pulse width value could cause incorrect operation for up to two PWM
periods. For example, writing a new value before the counter reaches
the old value but after the counter reaches the new value prevents any
compare during that PWM period. Also, using a TIMB overflow interrupt
routine to write a new, smaller pulse width value may cause the compare
to be missed. The TIMB may pass the new value before it is written to
the TIMB channel registers.
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Freescale Semiconductor
Timer Interface B (TIMB)
Functional Description
Use these methods to synchronize unbuffered changes in the PWM
pulse width on channel x:
NOTE:
•
When changing to a shorter pulse width, enable channel x output
compare interrupts and write the new value in the output compare
interrupt routine. The output compare interrupt occurs at the end
of the current pulse. The interrupt routine has until the end of the
PWM period to write the new value.
•
When changing to a longer pulse width, enable TIMB overflow
interrupts and write the new value in the TIMB overflow interrupt
routine. The TIMB overflow interrupt occurs at the end of the
current PWM period. Writing a larger value in an output compare
interrupt routine (at the end of the current pulse) could cause two
output compares to occur in the same PWM period.
In PWM signal generation, do not program the PWM channel to toggle
on output compare. Toggling on output compare prevents reliable
0 percent duty cycle generation and removes the ability of the channel
to self-correct in the event of software error or noise. Toggling on output
compare also can cause incorrect PWM signal generation when
changing the PWM pulse width to a new, much larger value.
12.4.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose
output appears on the PTB5/TCH0B pin. The TIMB channel registers of
the linked pair alternately control the pulse width of the output.
Setting the MS0B bit in TIMB channel 0 status and control register
(TBSC0) links channel 0 and channel 1. The TIMB channel 0 registers
initially control the pulse width on the PTB5/TCH0B pin. Writing to the
TIMB channel 1 registers enables the TIMB channel 1 registers to
synchronously control the pulse width at the beginning of the next PWM
period. At each subsequent overflow, the TIMB channel registers (0 or
1) that control the pulse width are the ones written to last. TBSC0
controls and monitors the buffered PWM function, and TIMB channel 1
status and control register (TBSC1) is unused. While the MS0B bit is set,
the channel 1 pin, PTB6/TCH1B, is available as a general-purpose I/O
pin.
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Technical Data
Timer Interface B (TIMB)
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Timer Interface B (TIMB)
NOTE:
In buffered PWM signal generation, do not write new pulse width values
to the currently active channel registers. User software should track the
currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as
generating unbuffered PWM signals.
12.4.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered
PWM signals, use this initialization procedure:
1. In the TIMB status and control register (TBSC):
a. Stop the TIMB counter by setting the TIMB stop bit, TSTOP.
b. Reset the TIMB counter and prescaler by setting the TIMB
reset bit, TRST.
2. In the TIMB counter modulo registers (TBMODH–TBMODL), write
the value for the required PWM period.
3. In the TIMB channel x registers (TBCHxH–TBCHxL), write the
value for the required pulse width.
4. In TIMB channel x status and control register (TBSCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or
1:0 (for buffered output compare or PWM signals) to the mode
select bits, MSxB–MSxA. See Table 12-2.
b. Write 1 to the toggle-on-overflow bit, TOVx.
c.
NOTE:
Write 1:0 (to clear output on compare) or 1:1 (to set output on
compare) to the edge/level select bits, ELSxB–ELSxA. The
output action on compare must force the output to the
complement of the pulse width level. See Table 12-2.
In PWM signal generation, do not program the PWM channel to toggle
on output compare. Toggling on output compare prevents reliable
0 percent duty cycle generation and removes the ability of the channel
to self-correct in the event of software error or noise. Toggling on output
compare can also cause incorrect PWM signal generation when
changing the PWM pulse width to a new, much larger value.
5. In the TIMB status control register (TBSC), clear the TIMB stop bit,
TSTOP.
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Timer Interface B (TIMB)
Interrupts
Setting MS0B links channels 0 and 1 and configures them for buffered
PWM operation. The TIMB channel 0 registers (TBCH0H–TBCH0L)
initially control the buffered PWM output. TIMB status control register 0
(TBSC0) controls and monitors the PWM signal from the linked
channels. MS0B takes priority over MS0A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on
TIMB overflows. Subsequent output compares try to force the output to
a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the
TOVx bit generates a 100 percent duty cycle output. See 12.10.4 TIMB
Channel Status and Control Registers.
12.5 Interrupts
These TIMB sources can generate interrupt requests:
•
TIMB overflow flag (TOF) — The TOF bit is set when the TIMB
counter reaches the modulo value programmed in the TIMB
counter modulo registers. The TIMB overflow interrupt enable bit,
TOIE, enables TIMB overflow CPU interrupt requests. TOF and
TOIE are in the TIMB status and control register.
•
TIMB channel flags (CH1F–CH0F) — The CHxF bit is set when an
input capture or output compare occurs on channel x. Channel x
TIMB CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE.
12.6 Wait Mode
The WAIT instruction puts the MCU in low-power standby mode.
The TIMB remains active after the execution of a WAIT instruction. In
wait mode, the TIMB registers are not accessible by the CPU. Any
enabled CPU interrupt request from the TIMB can bring the MCU out of
wait mode.
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Technical Data
Timer Interface B (TIMB)
235
Timer Interface B (TIMB)
If TIMB functions are not required during wait mode, reduce power
consumption by stopping the TIMB before executing the WAIT
instruction.
12.7 Stop Mode
TIMB is inactive after execution of a STOP instruction. The STOP
instruction does not affect register conditions or the state of the TIMB
counter.
TIMB operation resumes when the MCU exits stop mode after an
external interrupt.
12.8 TIMB During Break Interrupts
A break interrupt stops the TIMB counter and inhibits input captures.
The system integration module (SIM) controls whether status bits in
other modules can be cleared during the break state. The BCFE bit in
the SIM break flag control register (SBFCR) enables software to clear
status bits during the break state. See 7.7.5 SIM Break Flag Control
Register.
To allow software to clear status bits during a break interrupt, write a
logic 1 to the BCFE bit. If a status bit is cleared during the break state, it
remains cleared when the MCU exits the break state.
To protect status bits during the break state, write a logic 0 to the BCFE
bit. With BCFE at logic 0 (its default state), software can read and write
I/O registers during the break state without affecting status bits. Some
status bits have a 2-step read/write clearing procedure. If software does
the first step on such a bit before the break, the bit cannot change during
the break state as long as BCFE is at logic 0. After the break, doing the
second step clears the status bit.
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Freescale Semiconductor
Timer Interface B (TIMB)
TIMB Channel I/O Pins (PTB5/TCH0B–PTB6/TCH1B)
12.9 TIMB Channel I/O Pins (PTB5/TCH0B–PTB6/TCH1B)
Port B shares two of its pins with the TIMB. The two TIMB channel I/O
pins are PTB5/TCH0B and PTB6/TCH1B.
Each channel I/O pin is programmable independently as an input
capture pin or an output compare pin. PTB5/TCH0B and PTB6/TCH1B
can be configured as buffered output compare or buffered PWM pins.
12.10 I/O Registers
These I/O registers control and monitor TIMB operation:
•
TIMB status and control register (TBSC)
•
TIMB control registers (TBCNTH–TBCNTL)
•
TIMB counter modulo registers (TBMODH–TBMODL)
•
TIMB channel status and control registers (TBSC0 and TBSC1)
•
TIMB channel registers (TBCH0H–TBCH0L and
TBCH1H–TBCH1L)
12.10.1 TIMB Status and Control Register
The TIMB status and control register:
•
Enables TIMB overflow interrupts
•
Flags TIMB overflows
•
Stops the TIMB counter
•
Resets the TIMB counter
•
Prescales the TIMB counter clock
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface B (TIMB)
237
Timer Interface B (TIMB)
Address $0051
:
Bit 7
Read:
TOF
Write:
0
Reset:
0
R
6
5
TOIE
TSTOP
0
1
4
3
0
0
TRST
R
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
= Reserved
Figure 12-4. TIMB Status and Control Register (TBSC)
TOF — TIMB Overflow Flag Bit
This read/write flag is set when the TIMB counter reaches the modulo
value programmed in the TIMB counter modulo registers. Clear TOF
by reading the TIMB status and control register when TOF is set and
then writing a logic 0 to TOF. If another TIMB overflow occurs before
the clearing sequence is complete, then writing logic 0 to TOF has no
effect. Therefore, a TOF interrupt request cannot be lost due to
inadvertent clearing of TOF. Reset clears the TOF bit. Writing a logic
1 to TOF has no effect.
1 = TIMB counter has reached modulo value.
0 = TIMB counter has not reached modulo value.
TOIE — TIMB Overflow Interrupt Enable Bit
This read/write bit enables TIMB overflow interrupts when the TOF bit
becomes set. Reset clears the TOIE bit.
1 = TIMB overflow interrupts enabled
0 = TIMB overflow interrupts disabled
TSTOP — TIMB Stop Bit
This read/write bit stops the TIMB counter. Counting resumes when
TSTOP is cleared. Reset sets the TSTOP bit, stopping the TIMB
counter until software clears the TSTOP bit.
1 = TIMB counter stopped
0 = TIMB counter active
NOTE:
Do not set the TSTOP bit before entering wait mode if the TIMB is
required to exit wait mode. Also, when the TSTOP bit is set and the timer
is configured for input capture operation, input captures are inhibited
until TSTOP is cleared.
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Timer Interface B (TIMB)
Freescale Semiconductor
Timer Interface B (TIMB)
I/O Registers
TRST — TIMB Reset Bit
Setting this write-only bit resets the TIMB counter and the TIMB
prescaler. Setting TRST has no effect on any other registers.
Counting resumes from $0000. TRST is cleared automatically after
the TIMB counter is reset and always reads as logic 0. Reset clears
the TRST bit.
1 = Prescaler and TIMB counter cleared
0 = No effect
NOTE:
Setting the TSTOP and TRST bits simultaneously stops the TIMB
counter at a value of $0000.
PS[2:0] — Prescaler Select Bits
These read/write bits select one of the seven prescaler outputs as the
input to the TIMB counter as Table 12-1 shows. Reset clears the
PS[2:0] bits.
Table 12-1. Prescaler Selection
PS[2:0]
TIMB Clock Source
000
Internal Bus Clock ÷ 1
001
Internal Bus Clock ÷ 2
010
Internal Bus Clock ÷ 4
011
Internal Bus Clock ÷ 8
100
Internal Bus Clock ÷ 16
101
Internal Bus Clock ÷ 32
110
Internal Bus Clock ÷ 64
111
Invalid: do not use this value
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface B (TIMB)
239
Timer Interface B (TIMB)
12.10.2 TIMB Counter Registers
The two read-only TIMB counter registers contain the high and low bytes
of the value in the TIMB counter. Reading the high byte (TBCNTH)
latches the contents of the low byte (TBCNTL) into a buffer. Subsequent
reads of TBCNTH do not affect the latched TBCNTL value until TBCNTL
is read. Reset clears the TIMB counter registers. Setting the TIMB reset
bit (TRST) also clears the TIMB counter registers.
NOTE:
If TBCNTH is read during a break interrupt, be sure to unlatch TBCNTL
by reading TBCNTL before exiting the break interrupt. Otherwise,
TBCNTL retains the value latched during the break.
Register Name and Address:
TBCNTH — $0052
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
Register Name and Address:
TBCNTL — $0053
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 12-5. TIMB Counter Registers (TBCNTH and TBCNTL)
Technical Data
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Timer Interface B (TIMB)
Freescale Semiconductor
Timer Interface B (TIMB)
I/O Registers
12.10.3 TIMB Counter Modulo Registers
The read/write TIMB modulo registers contain the modulo value for the
TIMB counter. When the TIMB counter reaches the modulo value, the
overflow flag (TOF) becomes set, and the TIMB counter resumes
counting from $0000 at the next timer clock. Writing to the high byte
(TMODH) inhibits the TOF bit and overflow interrupts until the low byte
(TMODL) is written. Reset sets the TIMB counter modulo registers.
Register Name and Address:
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
1
Register Name and Address:
Read:
Write:
Reset:
TBMODH — $0054
TBMODL — $0055
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 12-6. TIMB Counter Modulo Registers (TMODH and TMODL)
NOTE:
Reset the TIMB counter before writing to the TIMB counter modulo
registers.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface B (TIMB)
241
Timer Interface B (TIMB)
12.10.4 TIMB Channel Status and Control Registers
Each of the TIMB channel status and control registers:
•
Flags input captures and output compares
•
Enables input capture and output compare interrupts
•
Selects input capture, output compare, or PWM operation
•
Selects high, low, or toggling output on output compare
•
Selects rising edge, falling edge, or any edge as the active input
capture trigger
•
Selects output toggling on TIMB overflow
•
Selects 0% and 100% PWM duty cycle
•
Selects buffered or unbuffered output compare/PWM operation
Register Name and Address:
Bit 7
Read:
CH0F
Write:
0
Reset:
0
6
5
4
3
2
1
Bit 0
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MA
X
0
0
0
0
0
0
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MA
X
0
0
0
0
0
Register Name and Address:
Bit 7
Read:
CH1F
Write:
0
Reset:
0
R
TBSC0 — $0056
TBSC1 — $0059
6
CH1IE
0
5
0
R
0
= Reserved
Figure 12-7. TIMB Channel Status and Control Registers
(TBSC0–TBSC1)
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set
when an active edge occurs on the channel x pin. When channel x is
an output compare channel, CHxF is set when the value in the TIMB
counter registers matches the value in the TIMB channel x registers.
Technical Data
242
MC68HC908MR8 — Rev 4.1
Timer Interface B (TIMB)
Freescale Semiconductor
Timer Interface B (TIMB)
I/O Registers
When CHxIE = 1, clear CHxF by reading TIMB channel x status and
control register with CHxF set, and then writing a logic 0 to CHxF. If
another interrupt request occurs before the clearing sequence is
complete, then writing logic 0 to CHxF has no effect. Therefore, an
interrupt request cannot be lost due to inadvertent clearing of CHxF.
Reset clears the CHxF bit. Writing a logic 1 to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIMB CPU interrupts on channel x. Reset
clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation.
MSxB exists only in the TIMB channel 0. Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture
operation or unbuffered output compare/PWM operation. See
Table 12-2.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level
of the TCHx pin once PWM, input capture, or output compare
operation is enabled. Reset clears the MSxA bit. See Table 12-2.
1 = Initial output level low
0 = Initial output level high
NOTE:
Before changing a channel function by writing to the MSxB or MSxA bit,
set the TSTOP and TRST bits in the TIMB status and control register
(TBSC).
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface B (TIMB)
243
Timer Interface B (TIMB)
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits
control the active edge-sensing logic on channel x.
When channel x is an output compare channel, ELSxB and ELSxA
control the channel x output behavior when an output compare
occurs.
When ELSxB and ELSxA are both clear, channel x is not connected
to port B, and pin PTBx/TCHxB is available as a general-purpose I/O
pin. However, channel x is at a state determined by these bits and
becomes transparent to the respective pin when PWM, input capture,
or output compare mode is enabled. Table 12-2 shows how ELSxA
and ELSxA work. Reset clears the ELSxB and ELSxA bits.
Table 12-2. Mode, Edge, and Level Selection
NOTE:
MSxB:MSxA
ELSxB:ELSxA
X0
00
X1
00
00
01
00
10
00
11
01
01
01
10
01
11
1X
01
1X
10
1X
11
Mode
Output
preset
Pin under port control;
Initialize timer
Output level high
Pin under port control;
Initialize timer
Output level low
Capture on rising edge only
Input
capture
Capture on falling edge only
Capture on rising or falling edge
Output
compare
or PWM
Buffered
output
compare
or
buffered
PWM
Toggle output on compare
Clear output on compare
Set output on compare
Toggle output on compare
Clear output on compare
Set output on compare
Before enabling a TIMB channel register for input capture operation,
make sure that the PTBx/TBCHx pin is stable for at least two bus clocks.
Technical Data
244
Configuration
MC68HC908MR8 — Rev 4.1
Timer Interface B (TIMB)
Freescale Semiconductor
Timer Interface B (TIMB)
I/O Registers
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit
controls the behavior of the channel x output when the TIMB counter
overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMB counter overflow.
0 = Channel x pin does not toggle on TIMB counter overflow.
NOTE:
When TOVx is set, a TIMB counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx bit is at logic 1, setting the CHxMAX bit forces the
duty cycle of buffered and unbuffered PWM signals to 100 percent. As
Figure 12-8 shows, the CHxMAX bit takes effect in the cycle after it
is set or cleared. The output stays at the 100 percent duty cycle level
until the cycle after CHxMAX is cleared.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTBx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
TOVx
Figure 12-8. CHxMAX Latency
12.10.5 TIMB Channel Registers
These read/write registers contain the captured TIMB counter value of
the input capture function or the output compare value of the output
compare function. The state of the TIMB channel registers after reset is
unknown.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Timer Interface B (TIMB)
245
Timer Interface B (TIMB)
In input capture mode (MSxB–MSxA = 0:0), reading the high byte of the
TIMB channel x registers (TBCHxH) inhibits input captures until the low
byte (TBCHxL) is read.
In output compare mode (MSxB–MSxA ≠ 0:0), writing to the high byte of
the TIMB channel x registers (TBCHxH) inhibits output compares until
the low byte (TBCHxL) is written.
Register Name and Address:
Read:
Write:
TBCH0H — $0057
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Bit 7
Read:
Write:
Bit 7
6
TBCH0L — $0058
5
Bit 6
4
Bit 5
Reset:
3
Bit 4
Write:
Reset:
Bit 2
Bit 1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Indeterminate after reset
Register Name and Address:
Write:
Bit 3
Bit 0
TBCH1H — $005A
Reset:
Read:
1
Indeterminate after reset
Register Name and Address:
Read:
2
TBCH1L — $005B
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Figure 12-9. TIMB Channel Registers (TBCH0H/L–TBCH1H/L)
Technical Data
246
MC68HC908MR8 — Rev 4.1
Timer Interface B (TIMB)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 13. Serial Communications Interface (SCI)
13.1 Contents
13.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .248
13.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .248
13.4 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .249
13.4.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .251
13.4.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .252
13.4.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .256
13.5
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .262
13.6
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .262
13.7
SCI During Break Module Interrupts. . . . . . . . . . . . . . . . . .262
13.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263
13.8.1 PTE2/TxD (Transmit Data) . . . . . . . . . . . . . . . . . . . . . . . .263
13.8.2 PTB0/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . .263
13.9 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .263
13.9.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . .264
13.9.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . .267
13.9.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . .269
13.9.4 SCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . .271
13.9.5 SCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . .275
13.9.6 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .276
13.9.7 SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . .276
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
247
Serial Communications Interface (SCI)
13.2 Introduction
This section describes the serial communications interface (SCI) module
which allows high-speed asynchronous communications with peripheral
devices and other microcontroller units (MCUs).
13.3 Features
Features of the SCI module include:
•
Full duplex operation
•
Standard mark/space non-return-to-zero (NRZ) format
•
32 programmable baud rates
•
Programmable 8-bit or 9-bit character length
•
Separately enabled transmitter and receiver
•
Separate receiver and transmitter cpu interrupt requests
•
Separate receiver and transmitter
•
Programmable transmitter output polarity
•
Two receiver wakeup methods:
– Idle line wakeup
– Address mark wakeup
Technical Data
248
MC68HC908MR8 — Rev 4.1
Serial Communications Interface (SCI)
Freescale Semiconductor
Serial Communications Interface (SCI)
Functional Description
•
Interrupt-driven operation with eight interrupt flags:
– Transmitter empty
– Transmission complete
– Receiver full
– Idle receiver input
– Receiver overrun
– Noise error
– Framing error
– Parity error
•
Receiver framing error detection
•
Hardware parity checking
•
1/16 bit-time noise detection
13.4 Functional Description
The SCI allows full-duplex, asynchronous, NRZ serial communication
among the MCU and remote devices, including other MCUs. The
transmitter and receiver of the SCI operate independently, although they
use the same baud rate generator. During normal operation, the CPU
monitors the status of the SCI, writes the data to be transmitted, and
processes received data.
Figure 13-1 shows the structure of the SCI module. Figure 13-2
provides a summary of the input/output (I/O) registers.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
249
Serial Communications Interface (SCI)
INTERNAL BUS
ERROR
INTERRUPT
CONTROL
RECEIVE
SHIFT REGISTER
PTB0/RxD
SCI DATA
REGISTER
RECEIVER
INTERRUPT
CONTROL
TRANSMITTER
INTERRUPT
CONTROL
SCI DATA
REGISTER
TRANSMIT
SHIFT REGISTER
PTB1/TxD
TXINV
SCTIE
R8
TCIE
T8
SCRIE
ILIE
TE
SCTE
RE
TC
RWU
SBK
SCRF
OR
ORIE
IDLE
NF
NEIE
FE
FEIE
PE
PEIE
LOOPS
LOOPS
FLAG
CONTROL
RECEIVE
CONTROL
WAKEUP
CONTROL
ENSCI
ENSCI
TRANSMIT
CONTROL
BKF
M
RPF
WAKE
ILTY
fOP
÷4
PRESCALER
BAUD RATE
GENERATOR
PEN
PTY
fOP = F bus frequency
÷ 16
DATA SELECTION
CONTROL
Figure 13-1. SCI Module Block Diagram
Technical Data
250
MC68HC908MR8 — Rev 4.1
Serial Communications Interface (SCI)
Freescale Semiconductor
Serial Communications Interface (SCI)
Functional Description
Addr.
$0038
$0039
$003A
$003B
$003C
$003D
$003E
Register Name
Bit 7
SCI Control Register 1
(SCC1)
See page 264.
SCI Control Register 2
(SCC2)
See page 267.
SCI Control Register 3
(SCC3)
See page 270.
SCI Status Register 1
(SCS1)
See page 271.
SCI Status Register 2
(SCS2)
See page 275.
SCI Data Register
(SCDR)
See page 276.
SCI Baud Rate Register
(SCBR)
See page 276.
6
5
4
3
2
1
Bit 0
Read: LOOP
ENSCI TXINV
S
Write:
M
WAKE
ILTY
PEN
PTY
Reset:
0
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
Reset:
0
0
0
0
0
0
0
0
Read:
R8
0
0
Write:
R
R
R
ORIE
NEIE
FEIE
PEIE
Reset:
U
U
0
0
0
0
0
0
TC
SCRF
IDLE
OR
NF
FE
PE
Read:
Write:
Read: SCTE
T8
Write:
R
R
R
R
R
R
R
R
Reset:
1
1
0
0
0
0
0
0
Read:
0
0
0
0
0
0
BKF
RPF
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
Read:
R7
R6
R5
R4
R3
R2
R1
R0
Write:
T7
T6
T5
T4
T3
T2
T1
T0
SCR2
SCR1
SCR0
0
0
0
Reset:
Unaffected by reset
Read:
0
0
Write:
R
R
Reset:
0
0
R
SCP1
SCP0
0
0
= Reserved
0
R
0
U = Unaffected
Figure 13-2. SCI I/O Register Summary
13.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format
illustrated in Figure 13-3.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
251
Serial Communications Interface (SCI)
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
POSSIBLE
PARITY
BIT
BIT 6
BIT 7
9-BIT DATA FORMAT
BIT M IN SCC1 SET
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
STOP
BIT
NEXT
START
BIT
POSSIBLE
PARITY
BIT
BIT 6
BIT 7
BIT 8
STOP
BIT
NEXT
START
BIT
Figure 13-3. SCI Data Formats
13.4.2 Transmitter
Figure 13-4 shows the structure of the SCI transmitter.
13.4.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of
the M bit in SCI control register 1 (SCC1) determines character length.
When transmitting 9-bit data, bit T8 in SCI control register 3 (SCC3) is
the ninth bit (bit 8).
13.4.2.2 Character Transmission
During an SCI transmission, the transmit shift register shifts a character
out to the PTB1/TxD pin. The SCI data register (SCDR) is the write-only
buffer between the internal data bus and the transmit shift register.
To initiate an SCI transmission:
1. Enable the SCI by writing a logic 1 to the enable SCI bit (ENSCI)
in SCI control register 1 (SCC1).
2. Enable the transmitter by writing a logic 1 to the transmitter enable
bit (TE) in SCI control register 2 (SCC2).
3. Clear the SCI transmitter empty bit by first reading SCI status
register 1 (SCS1) and then writing to the SCDR.
4. Repeat step 3 for each subsequent transmission.
Technical Data
252
MC68HC908MR8 — Rev 4.1
Serial Communications Interface (SCI)
Freescale Semiconductor
Serial Communications Interface (SCI)
Functional Description
At the start of a transmission, transmitter control logic automatically
loads the transmit shift register with a preamble of logic 1s. After the
preamble shifts out, control logic transfers the SCDR data into the
transmit shift register. A logic 0 start bit automatically goes into the least
significant bit (LSB) position of the transmit shift register. A logic 1 stop
bit goes into the most significant bit (MSB) position.
The SCI transmitter empty bit, SCTE, in SCS1 becomes set when the
SCDR transfers a byte to the transmit shift register. The SCTE bit
indicates that the SCDR can accept new data from the internal data bus.
If the SCI transmit interrupt enable bit, SCTIE, in SCC2 is also set, the
SCTE bit generates a transmitter CPU interrupt request.
When the transmit shift register is not transmitting a character, the
PTB1/TxD pin goes to the idle condition, logic 1. If at any time software
clears the ENSCI bit in SCI control register 1 (SCC1), the transmitter and
receiver relinquish control of the port B pins.
13.4.2.3 Break Characters
Writing a logic 1 to the send break bit, SBK, in SCC2 loads the transmit
shift register with a break character. A break character contains all logic
0s and has no start, stop, or parity bit. Break character length depends
on the M bit in SCC1. As long as SBK is at logic 1, transmitter logic
continuously loads break characters into the transmit shift register. After
software clears the SBK bit, the shift register finishes transmitting the
last break character and then transmits at least one logic 1. The
automatic logic 1 at the end of a break character guarantees the
recognition of the start bit of the next character.
The SCI recognizes a break character when a start bit is followed by
eight or nine logic 0 data bits and a logic 0 where the stop bit should be.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
253
Serial Communications Interface (SCI)
INTERNAL BUS
BAUD
DIVIDER
÷ 16
SCI DATA REGISTER
SCP1
SCP0
11-BIT
TRANSMIT
SHIFT REGISTER
SCR1
H
SCR2
8
7
6
5
4
3
2
START
PRESCALER
STOP
fOP
÷4
1
0
L
PTB1/TxD
MSB
SCR0
TXINV
T8
BREAK
ALL 0s
PARITY
GENERATION
PREAMBLE
ALL 1s
PTY
SHIFT ENABLE
PEN
LOAD FROM SCDR
M
TRANSMITTER
CONTROL LOGIC
TRANSMITTER CPU
INTERRUPT REQUEST
SCTE
SCTE
SCTIE
TC
TCIE
SBK
LOOPS
SCTIE
ENSCI
TC
TE
TCIE
Figure 13-4. SCI Transmitter
Receiving a break character has these effects on SCI registers:
•
Sets the framing error bit (FE) in SCS1
•
Sets the SCI receiver full bit (SCRF) in SCS1
•
Clears the SCI data register (SCDR)
•
Clears the R8 bit in SCC3
•
Sets the break flag bit (BKF) in SCS2
•
May set the overrun (OR), noise flag (NF), parity error (PE), or
reception-in-progress flag (RPF) bits
Technical Data
254
MC68HC908MR8 — Rev 4.1
Serial Communications Interface (SCI)
Freescale Semiconductor
Serial Communications Interface (SCI)
Functional Description
13.4.2.4 Idle Characters
An idle character contains all logic 1s and has no start, stop, or parity bit.
Idle character length depends on the M bit in SCC1. The preamble is a
synchronizing idle character that begins every transmission.
If the TE bit is cleared during a transmission, the PTB1/TxD pin becomes
idle after completion of the transmission in progress. Clearing and then
setting the TE bit during a transmission queues an idle character to be
sent after the character currently being transmitted.
NOTE:
When queueing an idle character, return the TE bit to logic 1 before the
stop bit of the current character shifts out to the PTB1/TxD pin. Setting
TE after the stop bit appears on PTB1/TxD causes data previously
written to the SCDR to be lost.
A good time to toggle the TE bit is when the SCTE bit becomes set and
just before writing the next byte to the SCDR.
13.4.2.5 Inversion of Transmitted Output
The transmit inversion bit (TXINV) in SCI control register 1 (SCC1)
reverses the polarity of transmitted data. All transmitted values, including
idle, break, start, and stop bits, are inverted when TXINV is at logic 1.
See 13.9.1 SCI Control Register 1.
13.4.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the SCI
transmitter:
•
SCI transmitter empty (SCTE) — The SCTE bit in SCS1 indicates
that the SCDR has transferred a character to the transmit shift
register. SCTE can generate a transmitter CPU interrupt request.
Setting the SCI transmit interrupt enable bit, SCTIE, in SCC2
enables the SCTE bit to generate transmitter CPU interrupt
requests.
•
Transmission complete (TC) — The TC bit in SCS1 indicates that
the transmit shift register and the SCDR are empty and that no
break or idle character has been generated. The transmission
complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to
generate transmitter CPU interrupt requests.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
255
Serial Communications Interface (SCI)
13.4.3 Receiver
Figure 13-5 shows the structure of the SCI receiver.
INTERNAL BUS
SCR1
SCR2
SCP0
SCR0
BAUD
PRESCALER DIVIDER
fOP
DATA
RECOVERY
PTB0/Rx
ALL 1s
RPF
CPU INTERRUPT REQUEST
H
11-BIT
RECEIVE SHIFT REGISTER
8
7
6
M
WAKE
ILTY
PEN
PTY
5
4
3
2
1
0
L
ALL 0s
BKF
ERROR CPU INTERRUPT REQUEST
STOP
÷ 16
MSB
÷4
SCI DATA REGISTER
START
SCP1
SCRF
WAKEUP
LOGIC
PARITY
CHECKING
IDLE
ILIE
RWU
IDLE
R8
ILIE
SCRF
SCRIE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
SCRIE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
Figure 13-5. SCI Receiver Block Diagram
Technical Data
256
MC68HC908MR8 — Rev 4.1
Serial Communications Interface (SCI)
Freescale Semiconductor
Serial Communications Interface (SCI)
Functional Description
13.4.3.1 Character Length
The receiver can accommodate either 8-bit or 9-bit data. The state of the
M bit in SCI control register 1 (SCC1) determines character length.
When receiving 9-bit data, bit R8 in SCI control register 2 (SCC2) is the
ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth
bit (bit 7).
13.4.3.2 Character Reception
During an SCI reception, the receive shift register shifts characters in
from the PTB0/RxD pin. The SCI data register (SCDR) is the read-only
buffer between the internal data bus and the receive shift register.
After a complete character shifts into the receive shift register, the data
portion of the character transfers to the SCDR. The SCI receiver full bit,
SCRF, in SCI status register 1 (SCS1) becomes set, indicating that the
received byte can be read. If the SCI receive interrupt enable bit, SCRIE,
in SCC2 is also set, the SCRF bit generates a receiver CPU interrupt
request.
13.4.3.3 Data Sampling
The receiver samples the PTB0/RxD pin at the RT clock rate. The RT
clock is an internal signal with a frequency 16 times the baud rate. To
adjust for baud rate mismatch, the RT clock is resynchronized at these
times (see Figure 13-6):
•
After every start bit
•
After the receiver detects a data bit change from logic 1 to logic 0
(after the majority of data bit samples at RT8, RT9, and RT10
return a valid logic 1 and the majority of the next RT8, RT9, and
RT10 samples return a valid logic 0)
To locate the start bit, data recovery logic does an asynchronous search
for a logic 0 preceded by three logic 1s. When the falling edge of a
possible start bit occurs, the RT clock begins to count to 16.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
257
Serial Communications Interface (SCI)
START BIT
LSB
PTB0/RxD
START BIT
QUALIFICATION
SAMPLES
START BIT
VERIFICATION
DATA
SAMPLING
RT4
RT3
RT2
RT16
RT1
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT CLOCK
STATE
RT1
RT
CLOCK
RT CLOCK
RESET
Figure 13-6. Receiver Data Sampling
To verify the start bit and to detect noise, data recovery logic takes
samples at RT3, RT5, and RT7. Table 13-1 summarizes the results of
the start bit verification samples.
Table 13-1. Start Bit Verification
RT3, RT5, and RT7
Samples
Start Bit
Verification
Noise Flag
000
Yes
0
001
Yes
1
010
Yes
1
011
No
0
100
Yes
1
101
No
0
110
No
0
111
No
0
If start bit verification is not successful, the RT clock is reset and a new
search for a start bit begins.
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Serial Communications Interface (SCI)
Functional Description
To determine the value of a data bit and to detect noise, recovery logic
takes samples at RT8, RT9, and RT10. Table 13-2 summarizes the
results of the data bit samples.
Table 13-2. Data Bit Recovery
NOTE:
RT8, RT9, and RT10
Samples
Data Bit
Determination
Noise Flag
000
0
0
001
0
1
010
0
1
011
1
1
100
0
1
101
1
1
110
1
1
111
1
0
The RT8, RT9, and RT10 samples do not affect start bit verification. If
any or all of the RT8, RT9, and RT10 start bit samples are logic 1s
following a successful start bit verification, the noise flag (NF) is set and
the receiver assumes that the bit is a start bit.
To verify a stop bit and to detect noise, recovery logic takes samples at
RT8, RT9, and RT10. Table 13-3 summarizes the results of the stop bit
samples.
Table 13-3. Stop Bit Recovery
RT8, RT9, and RT10
Samples
Framing
Error Flag
Noise Flag
000
1
0
001
1
1
010
1
1
011
0
1
100
1
1
101
0
1
110
0
1
111
0
0
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Serial Communications Interface (SCI)
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Serial Communications Interface (SCI)
13.4.3.4 Framing Errors
If the data recovery logic does not detect a logic 1 where the stop bit
should be in an incoming character, it sets the framing error bit, FE, in
SCS1. The FE flag is set at the same time that the SCRF bit is set. A
break character that has no stop bit also sets the FE bit.
13.4.3.5 Receiver Wakeup
So that the MCU can ignore transmissions intended only for other
receivers in multiple-receiver systems, the receiver can be put into a
standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the
receiver into a standby state during which receiver interrupts are
disabled.
Depending on the state of the WAKE bit in SCC1, either of two
conditions on the PTB0/RxD pin can bring the receiver out of the standby
state:
NOTE:
•
Address mark — An address mark is a logic 1 in the most
significant bit position of a received character. When the WAKE bit
is set, an address mark wakes the receiver from the standby state
by clearing the RWU bit. The address mark also sets the SCI
receiver full bit, SCRF. Software can then compare the character
containing the address mark to the user-defined address of the
receiver. If they are the same, the receiver remains awake and
processes the characters that follow. If they are not the same,
software can set the RWU bit and put the receiver back into the
standby state.
•
Idle input line condition — When the WAKE bit is clear, an idle
character on the PTB0/RxD pin wakes the receiver from the
standby state by clearing the RWU bit. The idle character that
wakes the receiver does not set the receiver idle bit, IDLE, or the
SCI receiver full bit, SCRF. The idle line type bit, ILTY, determines
whether the receiver begins counting logic 1s as idle character bits
after the start bit or after the stop bit.
Clearing the WAKE bit after the PTB0/RxD pin has been idle can cause
the receiver to wake up immediately.
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Serial Communications Interface (SCI)
Functional Description
13.4.3.6 Receiver Interrupts
These sources can generate CPU interrupt requests from the SCI
receiver:
•
SCI receiver full (SCRF) — The SCRF bit in SCS1 indicates that
the receive shift register has transferred a character to the SCDR.
SCRF can generate a receiver CPU interrupt request. Setting the
SCI receive interrupt enable bit, SCRIE, in SCC2 enables the
SCRF bit to generate receiver CPU interrupts.
•
Idle input (IDLE) — The IDLE bit in SCS1 indicates that 10 or 11
consecutive logic 1s shifted in from the PTB0/RxD pin. The idle
line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to
generate CPU interrupt requests.
13.4.3.7 Error Interrupts
These receiver error flags in SCS1 can generate CPU interrupt requests:
•
Receiver overrun (OR) — The OR bit indicates that the receive
shift register shifted in a new character before the previous
character was read from the SCDR. The previous character
remains in the SCDR, and the new character is lost. The overrun
interrupt enable bit, ORIE, in SCC3 enables OR to generate SCI
error CPU interrupt requests.
•
Noise flag (NF) — The NF bit is set when the SCI detects noise on
incoming data or break characters, including start, data, and stop
bits. The noise error interrupt enable bit, NEIE, in SCC3 enables
NF to generate SCI error CPU interrupt requests.
•
Framing error (FE) — The FE bit in SCS1 is set when a logic 0
occurs where the receiver expects a stop bit. The framing error
interrupt enable bit, FEIE, in SCC3 enables FE to generate SCI
error CPU interrupt requests.
•
Parity error (PE) — The PE bit in SCS1 is set when the SCI
detects a parity error in incoming data. The parity error interrupt
enable bit, PEIE, in SCC3 enables PE to generate SCI error CPU
interrupt requests.
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Serial Communications Interface (SCI)
13.5 Wait Mode
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
The SCI module remains active after the execution of a WAIT
instruction. In wait mode the SCI module registers are not accessible by
the CPU. Any enabled CPU interrupt request from the SCI module can
bring the MCU out of wait mode.
If SCI module functions are not required during wait mode, reduce power
consumption by disabling the module before executing the WAIT
instruction.
13.6 Stop Mode
The SCI module is inactive after execution of a STOP instruction. The
STOP instruction does not affect register conditions of the SCI. SCI
operation resumes when the MCU exits stop mode after an external
interrupt.
13.7 SCI During Break Module Interrupts
The system integration module (SIM) controls whether status bits in
other modules can be cleared during interrupts generated by the break
module. The BCFE bit in the SIM break flag control register (SBFCR)
enables software to clear status bits during the break state.
To allow software to clear status bits during a break interrupt, write a
logic 1 to the BCFE bit. If a status bit is cleared during the break state, it
remains cleared when the MCU exits the break state.
To protect status bits during the break state, write a logic 0 to the BCFE
bit. With BCFE at logic 0 (its default state), software can read and write
I/O registers during the break state without affecting status bits. Some
status bits have a 2-step read/write clearing procedure. If software does
the first step on such a bit before the break, the bit cannot change during
the break state as long as BCFE is at logic 0. After the break, doing the
second step clears the status bit.
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Serial Communications Interface (SCI)
I/O Signals
13.8 I/O Signals
Port B shares two of its pins with the SCI module. The two SCI I/O pins
are:
•
PTB1/TxD — Transmit data
•
PTB0/RxD — Receive data
13.8.1 PTE2/TxD (Transmit Data)
The PTB1/TxD pin is the serial data output from the SCI transmitter. The
SCI shares the PTB1/TxD pin with port B. When the SCI is enabled, the
PTB1/TxD pin is an output regardless of the state of the DDRF1 bit in
data direction register B (DDRB).
13.8.2 PTB0/RxD (Receive Data)
The PTB0/RxD pin is the serial data input to the SCI receiver. The SCI
shares the PTB0/RxD pin with port B. When the SCI is enabled, the
PTB0/RxD pin is an input regardless of the state of the DDRB0 bit in data
direction register B (DDRB).
13.9 I/O Registers
These I/O registers control and monitor SCI operation:
•
SCI control register 1 (SCC1)
•
SCI control register 2 (SCC2)
•
SCI control register 3 (SCC3)
•
SCI status register 1 (SCS1)
•
SCI status register 2 (SCS2)
•
SCI data register (SCDR)
•
SCI baud rate register (SCBR)
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Serial Communications Interface (SCI)
13.9.1 SCI Control Register 1
SCI control register 1 (SCC1):
•
Enables loop mode operation
•
Enables the SCI
•
Controls output polarity
•
Controls character length
•
Controls SCI wake-up method
•
Controls idle character detection
•
Enables parity function
•
Controls parity type
Address:
Read:
Write:
Reset:
$0038
Bit 7
6
5
4
3
2
1
Bit 0
LOOPS
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
0
Figure 13-7. SCI Control Register 1 (SCC1)
LOOPS — Loop Mode Select Bit
This read/write bit enables loop mode operation. In loop mode the
PTB0/RxD pin is disconnected from the SCI, and the transmitter
output goes into the receiver input. Both the transmitter and the
receiver must be enabled to use loop mode. Reset clears the LOOPS
bit.
1 = Loop mode enabled
0 = Normal operation enabled
ENSCI — Enable SCI Bit
This read/write bit enables the SCI and the SCI baud rate generator.
Clearing ENSCI sets the SCTE and TC bits in SCI status register 1
and disables transmitter interrupts. Reset clears the ENSCI bit.
1 = SCI enabled
0 = SCI disabled
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I/O Registers
TXINV — Transmit Inversion Bit
This read/write bit reverses the polarity of transmitted data. Reset
clears the TXINV bit.
1 = Transmitter output inverted
0 = Transmitter output not inverted
NOTE:
Setting the TXINV bit inverts all transmitted values, including idle, break,
start, and stop bits.
M — Mode (Character Length) Bit
This read/write bit determines whether SCI characters are eight or
nine bits long. (See Table 13-4.) The ninth bit can serve as an extra
stop bit, as a receiver wakeup signal, or as a parity bit. Reset clears
the M bit.
1 = 9-bit SCI characters
0 = 8-bit SCI characters
WAKE — Wakeup Condition Bit
This read/write bit determines which condition wakes up the SCI: a
logic 1 (address mark) in the most significant bit (MSB) position of a
received character or an idle condition on the PTB0/RxD pin. Reset
clears the WAKE bit.
1 = Address mark wakeup
0 = Idle line wakeup
ILTY — Idle Line Type Bit
This read/write bit determines when the SCI starts counting logic 1s
as idle character bits. The counting begins either after the start bit or
after the stop bit. If the count begins after the start bit, then a string of
logic 1s preceding the stop bit may cause false recognition of an idle
character. Beginning the count after the stop bit avoids false idle
character recognition, but requires properly synchronized
transmissions. Reset clears the ILTY bit.
1 = Idle character bit count begins after stop bit.
0 = Idle character bit count begins after start bit.
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Serial Communications Interface (SCI)
PEN — Parity Enable Bit
This read/write bit enables the SCI parity function (see Table 13-4).
When enabled, the parity function inserts a parity bit in the most
significant bit position (see Figure 13-3). Reset clears the PEN bit.
1 = Parity function enabled
0 = Parity function disabled
PTY — Parity Bit
This read/write bit determines whether the SCI generates and checks
for odd parity or even parity (see Table 13-4). Reset clears the PTY
bit.
1 = Odd parity
0 = Even parity
NOTE:
Changing the PTY bit in the middle of a transmission or reception can
generate a parity error.
Table 13-4. Character Format Selection
Control Bits
Character Format
M
PEN:PTY
Start
Bits
Data
Bits
Parity
Stop
Bits
Character
Length
(Bits)
0
0X
1
8
None
1
10
1
0X
1
9
None
1
11
0
10
1
7
Even
1
10
0
11
1
7
Odd
1
10
1
10
1
8
Even
1
11
1
11
1
8
Odd
1
11
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I/O Registers
13.9.2 SCI Control Register 2
SCI control register 2 (SCC2):
•
Enables these CPU interrupt requests:
– Enables the SCTE bit to generate transmitter CPU interrupt
requests
– Enables the TC bit to generate transmitter CPU interrupt
requests
– Enables the SCRF bit to generate receiver CPU interrupt
requests
– Enables the IDLE bit to generate receiver CPU interrupt
requests
•
Enables the transmitter
•
Enables the receiver
•
Enables SCI wake up
•
Transmits SCI break characters
Address:
Read:
Write:
Reset:
$0039
Bit 7
6
5
4
3
2
1
Bit 0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
Figure 13-8. SCI Control Register 2 (SCC2)
SCTIE — SCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate SCI transmitter
CPU interrupt requests. Setting the SCTIE bit in SCC3 enables SCTE
CPU interrupt requests. Reset clears the SCTIE bit.
1 = SCTE enabled to generate CPU interrupt
0 = SCTE not enabled to generate CPU interrupt
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Serial Communications Interface (SCI)
TCIE — Transmission Complete Interrupt Enable Bit
This read/write bit enables the TC bit to generate SCI transmitter CPU
interrupt requests. Reset clears the TCIE bit.
1 = TC enabled to generate CPU interrupt requests
0 = TC not enabled to generate CPU interrupt requests
SCRIE — SCI Receive Interrupt Enable Bit
This read/write bit enables the SCRF bit to generate SCI receiver
CPU interrupt requests. Setting the SCRIE bit in SCC3 enables the
SCRF bit to generate CPU interrupt requests. Reset clears the SCRIE
bit.
1 = SCRF enabled to generate CPU interrupt
0 = SCRF not enabled to generate CPU interrupt
ILIE — Idle Line Interrupt Enable Bit
This read/write bit enables the IDLE bit to generate SCI receiver CPU
interrupt requests. Reset clears the ILIE bit.
1 = IDLE enabled to generate CPU interrupt requests
0 = IDLE not enabled to generate CPU interrupt requests
TE — Transmitter Enable Bit
Setting this read/write bit begins the transmission by sending a
preamble of 10 or 11 logic 1s from the transmit shift register to the
PTB1/TxD pin. If software clears the TE bit, the transmitter completes
any transmission in progress before the PTB1/TxD returns to the idle
condition (logic 1). Clearing and then setting TE during a transmission
queues an idle character to be sent after the character currently being
transmitted. Reset clears the TE bit.
1 = Transmitter enabled
0 = Transmitter disabled
NOTE:
Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is
clear. ENSCI is in SCI control register 1.
RE — Receiver Enable Bit
Setting this read/write bit enables the receiver. Clearing the RE bit
disables the receiver but does not affect receiver interrupt flag bits.
Reset clears the RE bit.
1 = Receiver enabled
0 = Receiver disabled
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I/O Registers
NOTE:
Writing to the RE bit is not allowed when the enable SCI bit (ENSCI) is
clear. ENSCI is in SCI control register 1.
RWU — Receiver Wakeup Bit
This read/write bit puts the receiver in a standby state during which
receiver interrupts are disabled. The WAKE bit in SCC1 determines
whether an idle input or an address mark brings the receiver out of the
standby state and clears the RWU bit. Reset clears the RWU bit.
1 = Standby state
0 = Normal operation
SBK — Send Break Bit
Setting and then clearing this read/write bit transmits a break
character followed by a logic 1. The logic 1 after the break character
guarantees recognition of a valid start bit. If SBK remains set, the
transmitter continuously transmits break characters with no logic 1s
between them. Reset clears the SBK bit.
1 = Transmit break characters
0 = No break characters being transmitted
NOTE:
Do not toggle the SBK bit immediately after setting the SCTE bit.
Toggling SBK too early causes the SCI to send a break character
instead of a preamble.
13.9.3 SCI Control Register 3
SCI control register 3 (SCC3):
•
Stores the ninth SCI data bit received and the ninth SCI data bit to
be transmitted
•
Enables SCI receiver full (SCRF)
•
Enables SCI transmitter empty (SCTE)
•
Enables the following interrupts:
– Receiver overrun interrupts
– Noise error interrupts
– Framing error interrupts
– Parity error interrupts
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Serial Communications Interface (SCI)
Address:
$003A
Bit 7
Read:
R8
Write:
R
Reset:
U
R
6
T8
U
= Reserved
5
4
0
0
R
R
0
0
3
2
1
Bit 0
ORIE
NEIE
FEIE
PEIE
0
0
0
0
U = Unaffected
Figure 13-9. SCI Control Register 3 (SCC3)
R8 — Received Bit 8
When the SCI is receiving 9-bit characters, R8 is the read-only ninth
bit (bit 8) of the received character. R8 is received at the same time
that the SCDR receives the other 8 bits.
When the SCI is receiving 8-bit characters, R8 is a copy of the eighth
bit (bit 7). Reset has no effect on the R8 bit.
T8 — Transmitted Bit 8
When the SCI is transmitting 9-bit characters, T8 is the read/write
ninth bit (bit 8) of the transmitted character. T8 is loaded into the
transmit shift register at the same time that the SCDR is loaded into
the transmit shift register. Reset has no effect on the T8 bit.
ORIE — Receiver Overrun Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests
generated by the receiver overrun bit, OR.
1 = SCI error CPU interrupt requests from OR bit enabled
0 = SCI error CPU interrupt requests from OR bit disabled
NEIE — Receiver Noise Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests
generated by the noise error bit, NE. Reset clears NEIE.
1 = SCI error CPU interrupt requests from NE bit enabled
0 = SCI error CPU interrupt requests from NE bit disabled
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I/O Registers
FEIE — Receiver Framing Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests
generated by the framing error bit, FE. Reset clears FEIE.
1 = SCI error CPU interrupt requests from FE bit enabled
0 = SCI error CPU interrupt requests from FE bit disabled
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables SCI receiver CPU interrupt requests
generated by the parity error bit, PE. Reset clears PEIE. See 13.9.4
SCI Status Register 1
1 = SCI error CPU interrupt requests from PE bit enabled
0 = SCI error CPU interrupt requests from PE bit disabled
13.9.4 SCI Status Register 1
SCI status register 1 (SCS1) contains flags to signal these conditions:
•
Transfer of SCDR data to transmit shift register complete
•
Transmission complete
•
Transfer of receive shift register data to SCDR complete
•
Receiver input idle
•
Receiver overrun
•
Noisy data
•
Framing error
•
Parity error
Ad- $003B
dress:
Bit 7
6
5
4
3
2
1
Bit 0
Read:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
Write:
R
R
R
R
R
R
R
R
Reset:
1
1
0
0
0
0
0
0
R
= Reserved
Figure 13-10. SCI Status Register 1 (SCS1)
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Serial Communications Interface (SCI)
SCTE — SCI Transmitter Empty Bit
This clearable, read-only bit is set when the SCDR transfers a
character to the transmit shift register. SCTE can generate an SCI
transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set,
SCTE generates an SCI transmitter CPU interrupt request. In normal
operation, clear the SCTE bit by reading SCS1 with SCTE set and
then writing to SCDR. Reset sets the SCTE bit.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
TC — Transmission Complete Bit
This read-only bit is set when the SCTE bit is set, and no data,
preamble, or break character is being transmitted. TC generates an
SCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also
set. TC is cleared automatically when data, preamble, or break is
queued and ready to be sent. There may be up to 1.5 transmitter
clocks of latency between queueing data, preamble, and break and
the transmission actually starting. Reset sets the TC bit.
1 = No transmission in progress
0 = Transmission in progress
SCRF — SCI Receiver Full Bit
This clearable, read-only bit is set when the data in the receive shift
register transfers to the SCI data register. SCRF can generate an SCI
receiver CPU interrupt request. When the SCRIE bit in SCC2 is set,
SCRF generates a CPU interrupt request. In normal operation, clear
the SCRF bit by reading SCS1 with SCRF set and then reading the
SCDR. Reset clears SCRF.
1 = Received data available in SCDR
0 = Data not available in SCDR
IDLE — Receiver Idle Bit
This clearable, read-only bit is set when 10 or 11 consecutive logic 1s
appear on the receiver input. IDLE generates an SCI error CPU
interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE bit
by reading SCS1 with IDLE set and then reading the SCDR. After the
receiver is enabled, it must receive a valid character that sets the
SCRF bit before an idle condition can set the IDLE bit. Also, after the
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I/O Registers
IDLE bit has been cleared, a valid character must again set the SCRF
bit before an idle condition can set the IDLE bit. Reset clears the IDLE
bit.
1 = Receiver input idle
0 = Receiver input active or idle since the IDLE bit was cleared
OR — Receiver Overrun Bit
This clearable, read-only bit is set when software fails to read the
SCDR before the receive shift register receives the next character.
The OR bit generates an SCI error CPU interrupt request if the ORIE
bit in SCC3 is also set. The data in the shift register is lost, but the data
already in the SCDR is not affected. Clear the OR bit by reading SCS1
with OR set and then reading the SCDR. Reset clears the OR bit.
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
Software latency may allow an overrun to occur between reads of
SCS1 and SCDR in the flag-clearing sequence. Figure 13-11 shows
the normal flag-clearing sequence and an example of an overrun
caused by a delayed flag-clearing sequence. The delayed read of
SCDR does not clear the OR bit because OR was not set when SCS1
was read. Byte 2 caused the overrun and is lost. The next
flag-clearing sequence reads byte 3 in the SCDR instead of byte 2.
In applications that are subject to software latency or in which it is
important to know which byte is lost due to an overrun, the
flag-clearing routine can check the OR bit in a second read of SCS1
after reading the data register.
NF — Receiver Noise Flag Bit
This clearable, read-only bit is set when the SCI detects noise on the
PTB0/RxD pin. NF generates an NF CPU interrupt request if the NEIE
bit in SCC3 is also set. Clear the NF bit by reading SCS1 and then
reading the SCDR. Reset clears the NF bit.
1 = Noise detected
0 = No noise detected
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Serial Communications Interface (SCI)
FE — Receiver Framing Error Bit
This clearable, read-only bit is set when a logic 0 is accepted as the
stop bit. FE generates an SCI error CPU interrupt request if the FEIE
bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set
and then reading the SCDR. Reset clears the FE bit.
1 = Framing error detected
0 = No framing error detected
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the SCI detects a parity error
in incoming data. PE generates a PE CPU interrupt request if the
PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with
PE set and then reading the SCDR. Reset clears the PE bit.
1 = Parity error detected
0 = No parity error detected
BYTE 1
BYTE 2
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
NORMAL FLAG CLEARING SEQUENCE
BYTE 3
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCDR
BYTE 1
READ SCDR
BYTE 2
READ SCDR
BYTE 3
BYTE 1
BYTE 2
SCRF = 0
OR = 0
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 1
OR = 1
SCRF = 1
DELAYED FLAG CLEARING SEQUENCE
BYTE 3
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 1
READ SCDR
BYTE 3
Figure 13-11. Flag Clearing Sequence
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I/O Registers
13.9.5 SCI Status Register 2
SCI status register 2 (SCS2) contains flags to signal these conditions:
•
Break character detected
•
Incoming data
Ad$003C
dress:
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
0
0
BKF
RPF
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 13-12. SCI Status Register 2 (SCS2)
BKF — Break Flag Bit
This clearable, read-only bit is set when the SCI detects a break
character on the PTB0/RxD pin. In SCS1, the FE and SCRF bits are
also set. In 9-bit character transmissions, the R8 bit in SCC3 is
cleared. BKF does not generate a CPU interrupt request. Clear BKF
by reading SCS2 with BKF set and then reading the SCDR. Once
cleared, BKF can become set again only after logic 1s again appear
on the PTB0/RxD pin followed by another break character. Reset
clears the BKF bit.
1 = Break character detected
0 = No break character detected
RPF —Reception-in-Progress Flag Bit
This read-only bit is set when the receiver detects a logic 0 during the
RT1 time period of the start bit search. RPF does not generate an
interrupt request. RPF is reset after the receiver detects false start bits
(usually from noise or a baud rate mismatch, or when the receiver
detects an idle character. Polling RPF before disabling the SCI
module or entering stop mode can show whether a reception is in
progress.
1 = Reception in progress
0 = No reception in progress
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
275
Serial Communications Interface (SCI)
13.9.6 SCI Data Register
The SCI data register (SCDR) is the buffer between the internal data bus
and the receive and transmit shift registers. Reset has no effect on data
in the SCI data register.
Ad$003D
dress:
Bit 7
6
5
4
3
2
1
Bit 0
Read:
R7
R6
R5
R4
R3
R2
R1
R0
Write:
T7
T6
T5
T4
T3
T2
T1
T0
Reset:
Unaffected by reset
Figure 13-13. SCI Data Register (SCDR)
R7/T7:R0/T0 — Receive/Transmit Data Bits
Reading address $003D accesses the read-only received data bits,
R7:R0. Writing to address $003D writes the data to be transmitted,
T7:T0. Reset has no effect on the SCI data register.
13.9.7 SCI Baud Rate Register
The SCI baud rate register (SCBR) selects the baud rate for both the
receiver and the transmitter.
Address:
$003E
Bit 7
6
Read:
0
0
Write:
R
R
Reset:
0
0
R
5
4
SCP1
SCP0
0
0
3
0
R
0
2
1
Bit 0
SCR2
SCR1
SCR0
0
0
0
= Reserved
Figure 13-14. SCI Baud Rate Register (SCBR)
Technical Data
276
MC68HC908MR8 — Rev 4.1
Serial Communications Interface (SCI)
Freescale Semiconductor
Serial Communications Interface (SCI)
I/O Registers
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown
in Table 13-5. Reset clears SCP1 and SCP0.
Table 13-5. SCI Baud Rate Prescaling
SCP1:SCP0
Prescaler Divisor (PD)
00
1
01
3
10
4
11
13
SCR2–SCR0 — SCI Baud Rate Select Bits
These read/write bits select the SCI baud rate divisor as shown in
Table 13-6. Reset clears SCR2–SCR0.
Table 13-6. SCI Baud Rate Selection
SCR2:SCR1:SCR0
Baud Rate Divisor (BD)
000
1
001
2
010
4
011
8
100
16
101
32
110
64
111
128
Use this formula to calculate the SCI baud rate:
Baud rate = fOP / 64 x PD x BD
where:
fOP = clock source (fBus)
PD = prescaler divisor
BD = baud rate divisor
Table 13-7 shows the SCI baud rates that can be generated with a
4.00-MHz crystal and the CGM set for an fOP of 8.00 MHz and with a
4.9152-MHz crystal with the CGM set for an an fOP of 7.3728 MHz.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Serial Communications Interface (SCI)
277
Serial Communications Interface (SCI)
Table 13-7. SCI Baud Rate Selection Examples
SCP1:SCP0
Prescaler
Divisor
(PD)
SCR2:SCR1:
SCR0
Baud Rate
Divisor (BD)
Baud Rate
(fOP = 7.3728 MHz)
Baud Rate
(fOP = 8.00 MHz)
00
1
000
1
115,200.00
125,000.00
00
1
001
2
57,600.00
62,500.00
00
1
010
4
28,800.00
31,250.00
00
1
011
8
14,400.00
15,625.00
00
1
100
16
7200.00
7812.50
00
1
101
32
3600.00
3906.25
00
1
110
64
1800.00
1953.13
00
1
111
128
900.00
976.56
01
3
000
1
38,400.00
41,666.67
01
3
001
2
19,200.00
20,833.33
01
3
010
4
9600.00
10,416.67
01
3
011
8
4800.00
5208.33
01
3
100
16
2400.00
2604.17
01
3
101
32
1200.00
1302.08
01
3
110
64
600.00
651.04
01
3
111
128
300.00
325.52
10
4
000
1
28,800.00
31,250.00
10
4
001
2
14,400.00
15,625.50
10
4
010
4
7200.00
7812.50
10
4
011
8
3600.00
3906.25
10
4
100
16
1800.00
1953.13
10
4
101
32
900.00
976.56
10
4
110
64
450.00
488.28
10
4
111
128
225.00
244.14
11
13
000
1
8861.54
9615.38
11
13
001
2
4430.77
4807.69
11
13
010
4
2215.38
2403.85
11
13
011
8
1107.69
1201.92
11
13
100
16
553.85
600.96
11
13
101
32
276.92
300.48
11
13
110
64
138.46
150.24
11
13
111
128
69.23
75.12
Technical Data
278
MC68HC908MR8 — Rev 4.1
Serial Communications Interface (SCI)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 14. Input/Output (I/O) Ports
14.1 Contents
14.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
14.3 Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281
14.3.1 Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . .281
14.3.2 Data Direction Register A . . . . . . . . . . . . . . . . . . . . . . . .282
14.4 Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .284
14.4.1 Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . .284
14.4.2 Data Direction Register B . . . . . . . . . . . . . . . . . . . . . . . .285
14.5 Port C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .286
14.5.1 Port C Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . .287
14.5.2 Data Direction Register C . . . . . . . . . . . . . . . . . . . . . . . .288
14.2 Introduction
Fourteen bidirectional input-output (I/O) pins, two input pins, and six
output pins form three parallel ports.
When using the 28-pin package versions of the MC68HC908MR8, set
the data direction register bits in DDRA such that bits 6, 5, and 4 are
written to a logic 1 (along with any other output bits on PORTA). Setting
PORTA’s data direction register bits 6, 5, and 4 will terminate the input
buffers on that port.
NOTE:
Connect any unused I/O pins to an appropriate logic level, either VDD or
VSS. (PWM6–PWM1 pins require no termination). Although the I/O ports
do not require termination for proper operation, termination reduces
excess current consumption and the possibility of electrostatic damage.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
279
Input/Output (I/O) Ports
Addr.
Register Name
Bit 7
Port A Data Register
(PTA)
See page 281.
$0000
Port B Data Register
(PTB)
See page 284.
$0001
Port C Data Register
(PTC)
See page 287.
$0002
$0003
Unimplemented
$0004
Data Direction Register A
(DDRA)
See page 282.
$0005
$0006
Data Direction Register B
(DDRB)
See page 284.
Data Direction Register C
(DDRC)
See page 287.
Read:
Write:
6
5
4
3
2
1
Bit 0
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
PTC1
PTC0
Reset:
Unaffected by reset
Read:
PTB6
Write:
PTB5
Reset:
PTB4
PTB3
Unaffected by reset
Read:
Write:
Reset:
Unaffected by reset
Read:
DDRA DDRA DDRA DDRA DDRA DDRA DDRA
6
5
4
3
2
1
0
Write:
Reset:
0
Read:
0
0
0
0
0
0
0
0
0
0
Read:
0
0
0
DDRC DDRC
1
0
Write:
Reset:
0
DDRB DDRB DDRB DDRB DDRB DDRB DDRB
6
5
4
3
2
1
0
Write:
Reset:
0
U
U
= Unimplemented
U
R
U
U
= Reserved
U
U
0
0
= Unaffected
Figure 14-1. I/O Port Register Summary
Technical Data
280
MC68HC908MR8 — Rev 4.1
Input/Output (I/O) Ports
Freescale Semiconductor
Input/Output (I/O) Ports
Port A
14.3 Port A
Port A is a 7-bit, general-purpose, bidirectional I/O port.
14.3.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the eight
port A pins.
Address:
$0000
Bit 7
Read:
Write:
6
5
4
3
2
1
Bit 0
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
Reset:
Unaffected by reset
= Unimplemented
Figure 14-2. Port A Data Register (PTA)
PTA[6:0] — Port A Data Bits
These read/write bits are software programmable. Data direction of
each port A pin is under the control of the corresponding bit in data
direction register A. Reset has no effect on port A data.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
281
Input/Output (I/O) Ports
14.3.2 Data Direction Register A
Data direction register A (DDRA) determines whether each port A pin is
an input or an output. Writing a logic 1 to a DDRA bit enables the output
buffer for the corresponding port A pin; a logic 0 disables the output
buffer.
Address:
$0004
Bit 7
Read:
5
4
3
2
1
Bit 0
DDRA6 DDRA5 DDRA4 DDRA3 DDRA2 DDRA1 DDRA0
Write:
Reset:
6
0
0
0
0
0
0
0
0
= Unimplemented
Figure 14-3. Data Direction Register A (DDRA)
DDRA[6:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears
DDRA[6:0], configuring all port A pins as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
NOTE:
Avoid glitches on port A pins by writing to the port A data register before
changing data direction register A bits from 0 to 1.
Figure 14-4 shows the port A I/O logic.
Technical Data
282
MC68HC908MR8 — Rev 4.1
Input/Output (I/O) Ports
Freescale Semiconductor
Input/Output (I/O) Ports
Port A
READ DDRA ($0004)
INTERNAL DATA BUS
WRITE DDRA ($0004)
DDRAx
RESET
WRITE PTA ($0000)
PTAx
PTAx
READ PTA ($0000)
Figure 14-4. Port A I/O Circuit
When bit DDRAx is a logic 1, reading address $0000 reads the PTAx
data latch. When bit DDRAx is a logic 0, reading address $0000 reads
the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 14-1 summarizes
the operation of the port A pins.
Table 14-1. Port A Pin Functions
DDRA
Bit
PTA
Bit
I/O Pin
Mode
0
X(1)
1
X
Accesses
to DDRA
Accesses to PTA
Read/Write
Read
Write
Input, Hi-Z(2)
DDRA[6:0]
Pin
PTA[6:0](3)
Output
DDRA[6:0]
PTA[6:0]
PTA[6:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
283
Input/Output (I/O) Ports
14.4 Port B
Port B is a 7-bit general-purpose bidirectional I/O port that shares its pins
with the serial communications interface (SCI) module.
14.4.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the eight
port B pins.
Address:
$0001
Bit 7
Read:
Write:
6
5
4
3
2
1
Bit 0
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
Reset:
Unaffected by reset
= Unimplemented
Figure 14-5. Port B Data Register (PTB)
PTB[6:0] — Port B Data Bits
These read/write bits are software-programmable. Data direction of
each port B pin is under the control of the corresponding bit in data
direction register B. Reset has no effect on port B data.
Technical Data
284
MC68HC908MR8 — Rev 4.1
Input/Output (I/O) Ports
Freescale Semiconductor
Input/Output (I/O) Ports
Port B
14.4.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is
an input or an output. Writing a logic 1 to a DDRB bit enables the output
buffer for the corresponding port B pin; a logic 0 disables the output
buffer.
Address:
$0005
Bit 7
Read:
5
4
3
2
1
Bit 0
DDRB6 DDRB5 DDRB4 DDRB3 DDRB2 DDRB1 DDRB0
Write:
Reset:
6
0
0
0
0
0
0
0
0
= Unimplemented
Figure 14-6. Data Direction Register B (DDRB)
DDRB[6:0] — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears
DDRB[6:0], configuring all port B pins as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE:
Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1.
Figure 14-7 shows the port B I/O logic.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
285
Input/Output (I/O) Ports
READ DDRB ($0005)
INTERNAL DATA BUS
WRITE DDRB ($0005)
DDRBx
RESET
WRITE PTB ($0001)
PTBx
PTBx
READ PTB ($0001)
Figure 14-7. Port B I/O Circuit
When bit DDRBx is a logic 1, reading address $0001 reads the PTBx
data latch. When bit DDRBx is a logic 0, reading address $0001 reads
the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 14-2 summarizes
the operation of the port B pins.
Table 14-2. Port B Pin Functions
DDRB
Bit
PTB
Bit
I/O Pin Mode
0
X(1)
1
X
Accesses
to DDRB
Accesses to PTB
Read/Write
Read
Write
Input, Hi-Z(2)
DDRB[6:0]
Pin
PTB[6:0](3)
Output
DDRB[6:0]
PTB[6:0]
PTB[6:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
14.5 Port C
Port C is a 2-bit special-purpose I/O port sharing its pins with the pulse
width modulator for motor control module (PMC) FAULT input pins.
These two pins mirror the state of FAULT1 and FAULT4 pins. Level
changes on these input pins will be interpreted as fault conditions.
The port C data register contains a data latch for each of the two port
pins.
Technical Data
286
MC68HC908MR8 — Rev 4.1
Input/Output (I/O) Ports
Freescale Semiconductor
Input/Output (I/O) Ports
Port C
Port C bit 1 is not used on the 28-pin packages. For that reason, a
pull-down resistor is connected to VSS to prevent a false fault input on
FAULT4.
NOTE:
PORTC has the capability of being used as an output port. When either
pin of PORTC is set as an output, by setting its respective PORTC data
direction register bit, the respective fault pin logic is disconnected from
that pin and the fault input will be defaulted to normal non-fault condition
to facilitate the use of PORTC as an output pin and not interfere with the
PWM generator. To regain the fault capability for the respective fault
input pin, clear the PORTC data direction register bit for that pin.
14.5.1 Port C Data Register
The port C data register (PTC) contains a data latch for each of the two
port C pins.
Address:
$0002
Bit 7
6
5
4
3
2
Read:
Write:
Reset:
1
Bit 0
PTC1
PTC0
Unaffected by reset
= Unimplemented
Figure 14-8. Port C Data Register (PTC)
PTC[1:0] — Port C Data Bits
These read/write bits are software programmable. Data direction of
each port C pin is under the control of the corresponding bit in data
direction register C. Reset has no effect on port C data.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
287
Input/Output (I/O) Ports
14.5.2 Data Direction Register C
Data direction register C (DDRC) determines whether each port C pin is
an input or an output. Writing a logic 1 to a DDRC bit enables the output
buffer for the corresponding port C pin; a logic 0 disables the output
buffer.
Address:
$0006
Bit 7
6
5
4
3
2
Read:
Bit 0
DDRC1 DDRC0
Write:
Reset:
1
U
U
U
U
U
U
0
0
= Unimplemented U = Unaffected
Figure 14-9. Data Direction Register C (DDRC)
DDRC[1:0] — Data Direction Register C Bits
These read/write bits control port C data direction. Reset clears
DDRC[1:0], configuring all port C pins as inputs.
1 = Corresponding port C pin configured as output
0 = Corresponding port C pin configured as input
NOTE:
Avoid glitches on port C pins by writing to the port C data register before
changing data direction register C bits from 0 to 1.
Figure 14-10 shows the port C I/O logic.
Technical Data
288
MC68HC908MR8 — Rev 4.1
Input/Output (I/O) Ports
Freescale Semiconductor
Input/Output (I/O) Ports
Port C
READ DDRC ($0006)
INTERNAL DATA BUS
WRITE DDRC ($0006)
RESET
DDRCx
WRITE PTC ($0002)
PTCx
PTCx
READ PTC ($0002)
Figure 14-10. Port C I/O Circuit
When bit DDRCx is a logic 1, reading address $0002 reads the PTCx
data latch. When bit DDRCx is a logic 0, reading address $0002 reads
the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 14-3 summarizes
the operation of the port C pins.
Table 14-3. Port C Pin Functions
DDRC
Bit
PTC
Bit
I/O Pin Mode
0
X(1)
1
X
Accesses to DDRC
Accesses to PTC
Read/Write
Read
Write
Input, Hi-Z(2)
DDRC[1:0]
Pin
PTC[1:0](3)
Output
DDRC[1:0]
PTC[1:0]
PTC[1:0]
1. X = don’t care
2. Hi-Z = high impedance on PTC0 and a pull-down RPD on PTC1
3. Writing affects data register, but does not affect input.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
289
Input/Output (I/O) Ports
Technical Data
290
MC68HC908MR8 — Rev 4.1
Input/Output (I/O) Ports
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 15. Computer Operating Properly (COP)
15.1 Contents
15.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
15.3
Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .292
15.4 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
15.4.1 CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
15.4.2 COPCTL Write. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
15.4.3 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .293
15.4.4 Internal Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
15.4.5 Reset Vector Fetch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
15.4.6 COP Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
15.5
COP Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
15.6
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
15.7
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
15.8
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
15.9
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .295
15.10 COP Module During Break Mode . . . . . . . . . . . . . . . . . . . .295
15.2 Introduction
This section describes the computer operating properly module (COP,
version B), a free-running counter that generates a reset if allowed to
overflow. The COP module helps software recover from runaway code.
Prevent a COP reset by periodically clearing the COP counter.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Computer Operating Properly (COP)
291
Computer Operating Properly (COP)
15.3 Functional Description
Figure 15-1 shows the structure of the COP module.
SIM
CGMXCLK
SIM RESET CIRCUIT
SIM RESET STATUS REGISTER
CLEAR BITS 12–4
CLEAR ALL BITS
13-BIT SIM COUNTER
INTERNAL RESET SOURCES(1)
RESET VECTOR FETCH
COPCTL WRITE
COP MODULE
6-BIT COP COUNTER
COPD (FROM CONFIG)
RESET
COPCTL WRITE
CLEAR
COP COUNTER
Note: See 7.4.2 Active Resets from Internal Sources.
Figure 15-1. COP Block Diagram
Addr.
Register Name
Bit 7
Read
:
$FFFF
COP Control Register
Write:
(COPCTL)
See page 294.
Reset
:
6
5
4
3
2
1
Bit 0
Low byte of reset vector
Clear COP counter
Unaffected by reset
Figure 15-2. COP I/O Register Summary
Technical Data
292
MC68HC908MR8 — Rev 4.1
Computer Operating Properly (COP)
Freescale Semiconductor
Computer Operating Properly (COP)
I/O Signals
The COP counter is a free-running, 6-bit counter preceded by the 13-bit
system integration module (SIM) counter. If not cleared by software, the
COP counter overflows and generates an asynchronous reset after
218–24 CGMXCLK cycles. With a 4.9152-MHz crystal, the COP timeout
period is 53.3 ms. Writing any value to location $FFFF before overflow
occurs clears the COP counter and prevents reset.
A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the
COP bit in the SIM reset status register (SRSR) (see 7.7.4 SIM Reset
Status Register).
NOTE:
Place COP clearing instructions in the main program and not in an
interrupt subroutine. Such an interrupt subroutine could keep the COP
from generating a reset even while the main program is not working
properly.
15.4 I/O Signals
This subsection describes the signals shown in Figure 15-1.
15.4.1 CGMXCLK
CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency
is equal to the crystal frequency.
15.4.2 COPCTL Write
Writing any value to the COP control register (COPCTL) (see 15.5 COP
Control Register) clears the COP counter and clears bits 12–4 of the
SIM counter. Reading the COP control register returns the reset vector.
15.4.3 Power-On Reset
The power-on reset (POR) circuit in the SIM clears the SIM counter 4096
CGMXCLK cycles after power-up.
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Technical Data
Computer Operating Properly (COP)
293
Computer Operating Properly (COP)
15.4.4 Internal Reset
An internal reset clears the SIM counter and the COP counter.
15.4.5 Reset Vector Fetch
A reset vector fetch occurs when the vector address appears on the data
bus. A reset vector fetch clears the SIM counter.
15.4.6 COP Disable
The COP disable (COPD) signal reflects the state of the COP disable bit
(COPD) in the configuration register (CONFIG). See 5.4 CONFIG Bits.
15.5 COP Control Register
The COP control register (COPCTL) is located at address $FFFF and
overlaps the reset vector. Writing any value to $FFFF clears the COP
counter and starts a new timeout period. Reading location $FFFF
returns the low byte of the reset vector.
Ad$FFFF
dress:
Bit 7
6
5
4
3
2
Read:
Low byte of reset vector
Write:
Clear COP counter
Reset:
Unaffected by reset
1
Bit 0
Figure 15-3. COP Control Register (COPCTL)
15.6 Interrupts
The COP does not generate CPU interrupt requests.
Technical Data
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Freescale Semiconductor
Computer Operating Properly (COP)
Monitor Mode
15.7 Monitor Mode
The COP is disabled in monitor mode when VDD + VHI is present on the
IRQ pin or on the RST pin.
15.8 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby
mode.
The COP continues to operate during wait mode.
15.9 Stop Mode
Stop mode turns off the COP prescaler clock. Service the COP
immediately before entering or after exiting stop mode to ensure a full
COP timeout period after entering or exiting stop mode.
15.10 COP Module During Break Mode
The COP is disabled during a break interrupt when VDD + VHI is present
on the RST pin.
MC68HC908MR8 — Rev 4.1
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Technical Data
Computer Operating Properly (COP)
295
Computer Operating Properly (COP)
Technical Data
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MC68HC908MR8 — Rev 4.1
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Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 16. External Interrupt (IRQ)
16.1 Contents
16.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297
16.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .297
16.4
Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .298
16.5
IRQ Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .301
16.6
IRQ Module During Wait Mode . . . . . . . . . . . . . . . . . . . . . .302
16.7
IRQ Module During Stop Mode . . . . . . . . . . . . . . . . . . . . . .302
16.8
IRQ Module During Break Mode . . . . . . . . . . . . . . . . . . . . .302
16.9
IRQ Status and Control Register. . . . . . . . . . . . . . . . . . . . .303
16.2 Introduction
This section describes the external interrupt module, which supports
external interrupt functions.
16.3 Features
Features of the IRQ module include:
•
A dedicated external interrupt pin, IRQ
•
Hysteresis buffers
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Technical Data
External Interrupt (IRQ)
297
External Interrupt (IRQ)
16.4 Functional Description
A logic 0 applied to any of the external interrupt pins can latch a CPU
interrupt request. Figure 16-1 shows the structure of the IRQ module.
Interrupt signals on the IRQ pin are latched into the IRQ latch. An
interrupt latch remains set until one of the following actions occurs:
•
Vector fetch — A vector fetch automatically generates an interrupt
acknowledge signal that clears the latch that caused the vector
fetch.
•
Software clear — Software can clear an interrupt latch by writing
to the appropriate acknowledge bit in the interrupt status and
control register (ISCR). Writing a logic 1 to the ACK1 bit clears the
IRQ latch.
•
Reset — A reset automatically clears both interrupt latches.
ACK1
VDD
D
CLR
Q
CK
IRQ
SYNCHRONIZER
IRQ
INTERRUPT
REQUEST
HIGHVOLTAGE
DETECT
TO MODE
SELECT
LOGIC
IRQ
LATCH
IMASK1
MODE1
Figure 16-1. IRQ Module Block Diagram
Addr.
Register Name
$003F
IRQ Status/Control Register
(ISCR)
See page 303.
Bit 7
6
5
4
Read:
0
0
0
0
Write:
R
R
R
R
Reset:
0
0
0
0
R
3
2
IRQF
0
1
Bit 0
0
IMASK MODE
1
1
ACK1
0
0
0
= Reserved
Figure 16-2. IRQ I/O Register Summary
Technical Data
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Freescale Semiconductor
External Interrupt (IRQ)
Functional Description
The external interrupt pins are falling-edge-triggered and are
software-configurable to be both falling-edge and low-level-triggered.
The MODE1 bit in the ISCR controls the triggering sensitivity of the IRQ
pin.
When the interrupt pin is edge-triggered only, the interrupt latch remains
set until a vector fetch, software clear, or reset occurs.
When the interrupt pin is both falling-edge and low-level-triggered, the
interrupt latch remains set until both of these occur:
•
Vector fetch, software clear, or reset
•
Return of the interrupt pin to logic 1
The vector fetch or software clear can occur before or after the interrupt
pin returns to logic 1. As long as the pin is low, the interrupt request
remains pending.
When set, the IMASK1 bit in the ISCR mask all external interrupt
requests. A latched interrupt request is not presented to the interrupt
priority logic unless the IMASK bit is clear.
NOTE:
The interrupt mask (I) in the condition code register (CCR) masks all
interrupt requests, including external interrupt requests.
See Figure 16-3.
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Technical Data
External Interrupt (IRQ)
299
External Interrupt (IRQ)
FROM RESET
YES
I BIT SET?
NO
INTERRUPT?
YES
NO
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION?
YES
NO
RTI
INSTRUCTION?
YES
UNSTACK CPU REGISTERS
NO
EXECUTE INSTRUCTION
Figure 16-3. IRQ Interrupt Flowchart
Technical Data
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Freescale Semiconductor
External Interrupt (IRQ)
IRQ Pin
16.5 IRQ Pin
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch.
A vector fetch, software clear, or reset clears the IRQ latch.
If the MODE1 bit is set, the IRQ pin is both falling-edge-sensitive and
low-level-sensitive. With MODE1 set, both of these actions must occur
to clear the IRQ latch:
•
Vector fetch, software clear, or reset — A vector fetch generates
an interrupt acknowledge signal to clear the latch. Software can
generate the interrupt acknowledge signal by writing a logic 1 to
the ACK1 bit in the interrupt status and control register (ISCR).
The ACK1 bit is useful in applications that poll the IRQ pin and
require software to clear the IRQ latch. Writing to the ACK1 bit can
also prevent spurious interrupts due to noise. Setting ACK1 does
not affect subsequent transitions on the IRQ pin. A falling edge
that occurs after writing to the ACK1 bit latches another interrupt
request. If the IRQ mask bit, IMASK1, is clear, the CPU loads the
program counter with the vector address at locations $FFFA and
$FFFB.
•
Return of the IRQ pin to logic 1 — As long as the IRQ pin is at logic
0, the IRQ latch remains set.
The vector fetch or software clear and the return of the IRQ pin to logic
1 can occur in any order. The interrupt request remains pending as long
as the IRQ pin is at logic 0.
If the MODE1 bit is clear, the IRQ pin is falling-edge-sensitive only. With
MODE1 clear, a vector fetch or software clear immediately clears the
IRQ latch.
Use the branch if IRQ pin high (BIH) or branch if IRQ pin low (BIL)
instruction to read the logic level on the IRQ pin.
NOTE:
When using the level-sensitive interrupt trigger, avoid false interrupts by
masking interrupt requests in the interrupt routine.
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External Interrupt (IRQ)
301
External Interrupt (IRQ)
16.6 IRQ Module During Wait Mode
The IRQ module remains active in wait mode. Clearing the IMASK1 bit
in the IRQ status and control register (ISCR) enables IRQ central
processor unit (CPU) interrupt requests to bring the microcontroller unit
(MCU) out of wait mode.
16.7 IRQ Module During Stop Mode
The IRQ module remains active in stop mode. Clearing the IMASK1 bit
in the IRQ status and control register (ISCR) enables IRQ CPU interrupt
requests to bring the MCU out of stop mode.
16.8 IRQ Module During Break Mode
The system integration (SIM) module controls whether the IRQ interrupt
latch can be cleared during the break state. The BCFE bit in the SIM
break flag control register (SBFCR) enables software to clear the latches
during the break state. See 7.7.5 SIM Break Flag Control Register.
To allow software to clear the IRQ latch during a break interrupt, write a
logic 1 to the BCFE bit. If a latch is cleared during the break state, it
remains cleared when the MCU exits the break state.
To protect the latches during the break state, write a logic 0 to the BCFE
bit. With BCFE at logic 0 (its default state), writing to the ACK1 bit in the
IRQ status and control register during the break state has no effect on
the IRQ latches. See 16.9 IRQ Status and Control Register.
Technical Data
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External Interrupt (IRQ)
Freescale Semiconductor
External Interrupt (IRQ)
IRQ Status and Control Register
16.9 IRQ Status and Control Register
The IRQ status and control register (ISCR) has these functions:
•
Clears the IRQ interrupt latch
•
Masks IRQ interrupt requests
•
Controls triggering sensitivity of the IRQ interrupt pin
Address:
$003F
Bit 7
6
5
4
Read:
0
0
0
0
Write:
R
R
R
R
Reset:
0
0
0
0
R
3
IRQF
2
0
ACK1
0
0
1
Bit 0
IMASK1 MODE1
0
0
= Reserved
Figure 16-4. IRQ Status and Control Register (ISCR)
ACK1 — IRQ Interrupt Request Acknowledge Bit
Writing a logic 1 to this write-only bit clears the IRQ latch. ACK1
always reads as logic 0. Reset clears ACK1.
IMASK1 — IRQ Interrupt Mask Bit
Writing a logic 1 to this read/write bit disables IRQ interrupt requests.
Reset clears IMASK1.
1 = IRQ interrupt requests disabled
0 = IRQ interrupt requests enabled
MODE1 — IRQ Edge/Level Select Bit
This read/write bit controls the triggering sensitivity of the IRQ pin.
Reset clears MODE1.
1 = IRQ interrupt requests on falling edges and low levels
0 = IRQ interrupt requests on falling edges only
IRQF — IRQ Flag
This read-only bit acts as a status flag, indicating an IRQ event
occurred.
1 = External IRQ event occurred.
0 = External IRQ event did not occur.
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Technical Data
External Interrupt (IRQ)
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External Interrupt (IRQ)
Technical Data
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MC68HC908MR8 — Rev 4.1
External Interrupt (IRQ)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 17. Low-Voltage Inhibit (LVI)
17.1 Contents
17.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
17.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
17.4 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .306
17.4.1 Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . .307
17.4.2 Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . .307
17.4.3 False Reset Protection. . . . . . . . . . . . . . . . . . . . . . . . . . .307
17.4.4 LVI Trip Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308
17.5
LVI Status and Control Register . . . . . . . . . . . . . . . . . . . . .308
17.6
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309
17.7
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309
17.8
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .309
17.2 Introduction
This section describes the low-voltage inhibit (LVI) module, which
monitors the voltage on the VDD pin and can force a reset when the VDD
voltage falls to the LVI trip voltage.
17.3 Features
Features of the LVI module include:
•
Programmable LVI reset
•
Programmable power consumption
•
Digital filtering of VDD pin level
•
Selectable LVI trip voltage
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Technical Data
Low-Voltage Inhibit (LVI)
305
Low-Voltage Inhibit (LVI)
17.4 Functional Description
Figure 17-1 shows the structure of the LVI module. The LVI is enabled
out of reset. The LVI module contains a bandgap reference circuit and
comparator.
The LVI power bit, LVIPWR, enables the LVI to monitor VDD voltage. The
LVI reset bit, LVIRST, enables the LVI module to generate a reset when
VDD falls below a voltage, VLVRX, and remains at or below that level for
nine or more consecutive CGMXCLK.
•
VLVRX and VLVHX are determined by the TRPSEL bit in the LVI
status and control register (LVISCR). See Figure 17-2.
•
LVIPWR and LVIRST are in the configuration (CONFIG) register.
See 5.4 CONFIG Bits.
Once an LVI reset occurs, the MCU remains in reset until VDD rises
above a voltage, VLVRX + VLVHX. VDD must be above VLVRX + VLVHX for
only one central processor unit (CPU) cycle to bring the microcontroller
unit (MCU) out of reset. See 7.4.2.5 Low-Voltage Inhibit (LVI) Reset.
The output of the comparator controls the state of the LVIOUT flag in the
LVISCR.
NOTE:
An LVI reset also drives the RST pin low to provide low-voltage
protection to external peripheral devices.
VDD
LVIPWR
FROM CONFIG
FROM CONFIG
CPU CLOCK
LOW VDD
DETECTOR
VDD > LVITRIP = 0
VDD < LVITRIP = 1
LVIRST
VDD
DIGITAL FILTER
LVI RESET
TRPSEL
FROM LVISCR
ANLGTRIP
LVIOUT
Figure 17-1. LVI Module Block Diagram
Technical Data
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Freescale Semiconductor
Low-Voltage Inhibit (LVI)
Functional Description
Addr.
Register Name
Read
:
LVI Status and Control Register Write
$FE0F
:
(LVISCR)
See page 308.
Reset:
Bit 7
6
LVIOUT
0
R
R
0
0
R
5
TRPSEL
0
4
3
2
1
Bit 0
0
0
0
0
0
R
R
R
R
R
0
0
0
0
0
= Reserved
Figure 17-2. LVI I/O Register Summary
17.4.1 Polled LVI Operation
In applications that can operate at VDD levels below VLVRX, software can
monitor VDD by polling the LVIOUT bit. In the configuration register, the
LVIPWR bit must be at logic 1 to enable the LVI module, and the LVIRST
bit must be at logic 0 to disable LVI resets. TRPSEL in the LVISCR
selects VLVRX. See 5.4 CONFIG Bits.
17.4.2 Forced Reset Operation
In applications that require VDD to remain above VLVRX, enabling LVI
resets allows the LVI module to reset the MCU when VDD falls to the
VLVRX level and remains at or below that level for nine or more
consecutive CPU cycles. In the CONFIG register, the LVIPWR and
LVIRST bits must be at logic 1 to enable the LVI module and to enable
LVI resets. TRPSEL in the LVISCR selects VLVRX.
17.4.3 False Reset Protection
The VDD pin level is digitally filtered to reduce false resets due to power
supply noise. In order for the LVI module to reset the MCU, VDD must
remain at or below VLVRX for nine or more consecutive CPU cycles. VDD
must be above VLVRX + VLVHX for only one CPU cycle to bring the MCU
out of reset. TRPSEL in the LVISCR selects VLVRX + VLVHX.
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Technical Data
Low-Voltage Inhibit (LVI)
307
Low-Voltage Inhibit (LVI)
17.4.4 LVI Trip Selection
The TRPSEL bit allows the user to choose between 5 percent and
10 percent tolerance when monitoring the supply voltage. The
10 percent option is enabled out of reset. Writing a logic 1 to TRPSEL
will enable the 5 percent option.
NOTE:
The MCU is guaranteed to operate at a minimum supply voltage. The trip
point (VLVR1 or VLVR2) may be lower than this.
17.5 LVI Status and Control Register
The LVI status register flags VDD voltages below the VLVRX level.
Ad$FE0F
dress:
Bit 7
6
5
4
3
2
1
Bit 0
Read: LVIOUT
0
0
0
0
0
0
Write:
R
R
TRPSEL
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 17-3. LVI Status and Control Register (LVISCR)
LVIOUT — LVI Output Bit
This read-only flag becomes set when the VDD voltage falls below the
VLVRX voltage for 32 to 40 CGMXCLK cycles. See Table 17-1. Reset
clears the LVIOUT bit.
Table 17-1. LVIOUT Bit Indication
VDD
For number of CGMXCLK cycles:
VDD > VLVRX + VLVHX
Any
0
VDD < VLVRX
< 32 CGMXCLK CYCLES
0
VDD < VLVRX
Between 32 and 40 CGMXCLK cycles
0 or 1
VDD < VLVRX
> 40 CGMXCLK cycles
1
Technical Data
308
LVIOUT
At level:
MC68HC908MR8 — Rev 4.1
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Freescale Semiconductor
Low-Voltage Inhibit (LVI)
LVI Interrupts
Table 17-1. LVIOUT Bit Indication
VDD
At level:
For number of CGMXCLK cycles:
VLVRX < VDD < VLVRX + VLVHX
Any
LVIOUT
Previous value
TRPSEL — LVI Trip Select Bit
This bit selects the LVI trip point. Reset clears this bit.
1 = 5 percent tolerance. The trip point and recovery point are
determined by VLVR1 and VLVH1 respectively.
0 = 10 percent tolerance. The trip point and recovery point are
determined by VLVR2 and VLVH2 respectively.
NOTE:
If LVIPWR and LVIRST are at logic 1, note that when changing the
tolerance, LVI reset will be generated if the supply voltage is below the
trip point.
17.6 LVI Interrupts
The LVI module does not generate interrupt requests.
17.7 Wait Mode
The WAIT instruction puts the microcontroller unit (MCU) in low
power-consumption standby mode.
With the LVIPWR bit in the configuration register programmed to logic 1,
the LVI module is active after a WAIT instruction.
With the LVIRST bit in the configuration register programmed to logic 1,
the LVI module can generate a reset and bring the MCU out of wait
mode.
17.8 Stop Mode
The STOP instruction puts the MCU in low power-consumption standby
mode.
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Technical Data
Low-Voltage Inhibit (LVI)
309
Low-Voltage Inhibit (LVI)
With the LVIPWR bit in the configuration register programmed to logic 1,
the LVI module is active after a STOP instruction.
With the LVIRST bit in the configuration register programmed to logic 1,
the LVI module can generate a reset and bring the MCU out of stop
mode.
Technical Data
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Technical Data — MC68HC908MR8
Section 18.
Analog-to-Digital Converter (ADC)
18.1 Contents
18.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .312
18.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .312
18.4 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .312
18.4.1 ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .313
18.4.2 Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314
18.4.3 Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .314
18.4.4 Continuous Conversion. . . . . . . . . . . . . . . . . . . . . . . . . .315
18.4.5 Result Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . .315
18.4.6 Monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .316
18.5
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .316
18.6
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317
18.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317
18.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .317
18.8.1 ADC Voltage Reference Pin (VREFH) . . . . . . . . . . . . . . . .317
18.8.2 ADC Voltage In (ADVIN). . . . . . . . . . . . . . . . . . . . . . . . . .318
18.8.3 ADC External Connection . . . . . . . . . . . . . . . . . . . . . . . .318
18.9 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .319
18.9.1 ADC Status and Control Register . . . . . . . . . . . . . . . . . .319
18.9.2 ADC Data Register High . . . . . . . . . . . . . . . . . . . . . . . . .322
18.9.3 ADC Data Register Low . . . . . . . . . . . . . . . . . . . . . . . . . .323
18.9.4 ADC Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . .324
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Technical Data
Analog-to-Digital Converter (ADC)
311
Analog-to-Digital Converter (ADC)
18.2 Introduction
This section describes the 10-bit analog-to-digital converter (ADC).
For further information regarding analog-to-digital converters on
Freescale microcontrollers, please consult the HC08 ADC Reference
Manual, ADCRM/AD.
18.3 Features
Features of the ADC module include:
•
Four to seven channels with multiplexed input
•
Linear successive approximation
•
10-bit resolution, 8-bit accuracy
•
Single or continuous conversion
•
Conversion complete flag or conversion complete interrupt
•
Selectable ADC clock
•
Left or right justified result.
•
Left justified sign data mode
•
High impedance buffered ADC input
18.4 Functional Description
Depending on the package option, up to seven ADC channels are
available for sampling external sources at pins PTA6/ATD6:PT00/ATD0.
To achieve the best possible accuracy, these pins are implemented as
input-only pins when the analog-to-digital (A/D) feature is enabled. An
analog multiplexer allows the single ADC to select one of the seven ADC
channels as ADC voltage IN (ADCVIN). ADCVIN is converted by the
successive approximation algorithm. When the conversion is completed,
the ADC places the result in the ADC data register (ADRH and ADRL)
and sets a flag or generates an interrupt. See Figure 18-1.
Technical Data
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Freescale Semiconductor
Analog-to-Digital Converter (ADC)
Functional Description
INTERNAL
DATA BUS
PTAx
ADC CHANNEL X
READ PTA
DISABLE
ADC DATA REGISTERS
ADC
INTERRUPT
CONVERSION
COMPLETE
INTERRUPT
LOGIC
ADC VOLTAGE IN
ADVIN
ADC
CHANNEL
SELECT
ADCH6:ADCH0
AIEN
ADC CLOCK
CGMXCLK
fOP
CLOCK
GENERATOR
ADIV[2:0]
ADICLK
Figure 18-1. ADC Block Diagram
18.4.1 ADC Port I/O Pins
PTA6/ATD6:PTA0/ATD6 are general-purpose input/output (I/O) pins
that are shared with the ADC channels.
The channel select bits define which ADC channel/port pin will be used
as the input signal. The ADC overrides the port logic when that port is
selected by the ADC multiplexer. The remaining ADC channels/port pins
are controlled by the port logic and can be used as general-purpose
input/output (I/O) pins. Writes to the port register or data direction
register (DDR) will not have any effect on the port pin that is selected by
the ADC. Read of a port pin which is in use by the ADC will return a
logic 0.
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Analog-to-Digital Converter (ADC)
18.4.2 Voltage Conversion
When the input voltage to the ADC equals VREFH, the ADC converts the
signal to $3FF (full scale). If the input voltage equals VSS, the ADC
converts it to $000. Input voltages between VREFH and VREFL are
straight-line linear conversions. All other input voltages will result in
$3FF if greater than VREFH and $000 if less than VSS.
NOTE:
Input voltage should not exceed the analog supply voltages.
18.4.3 Conversion Time
Conversion starts after a write to the ADC status and control register
(ADSCR). A conversion is between 16 and 17 ADC clock cycles,
therefore:
Conversion time =
16 to 17 ADC cycles
ADC frequency
Number of bus cycles = conversion time x bus frequency
The ADC conversion time is determined by the clock source chosen and
the divide ratio selected. The clock source is either the bus clock or
CGMXCLK and is selectable by ADICLK located in the ADC clock
register. For example, if CGMXCLK is 4 MHz and is selected as the ADC
input clock source, the ADC input clock /4 prescale is selected:
Conversion time =
NOTE:
16 to 17 ADC cycles
= 16 to 17 µs
4 MHz/4
The ADC frequency must be between fADIC minimum and fADIC
maximum to meet A/D specifications.
Since an ADC cycle may be comprised of several bus cycles (four in the
prior example) and the start of a conversion is initiated by a bus cycle
write to the ADSCR, from zero to four additional bus cycles may occur
before the start of the initial ADC cycle. This results in a fractional ADC
cycle and is represented as the 17th cycle.
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Freescale Semiconductor
Analog-to-Digital Converter (ADC)
Functional Description
18.4.4 Continuous Conversion
In the continuous conversion mode, the ADC data registers (ADRH and
ADRL) will be filled with new data after each conversion. Data from the
previous conversion will be overwritten whether that data has been read
or not. Conversions will continue until the ADCO bit is cleared. The
COCO bit is set after the first conversion and will stay set for the next
several conversions until the next write of the ADC status and control
register or the next read of the ADC data register.
18.4.5 Result Justification
The conversion result may be formatted in four different ways:
1. Left justified
2. Right justified
3. Left justified sign data mode
4. 8-bit truncation mode
All four of these modes are controlled using MODE0 and MODE1 bits
located in the ADC clock register (ADCLK).
Left justification will place the eight most significant bits (MSB) in the
corresponding ADC data register high, ADRH. This may be useful if the
result is to be treated as an 8-bit result where the two least significant
bits (LSB), located in the ADC data register low, ADRL, can be ignored.
However, ADRL must be read after ADRH or else the interlocking will
prevent all new conversions from being stored.
Right justification will place only the two MSBs in the corresponding ADC
data register high, ADRH, and the eight LSBs in ADC data register low,
ADRL. This mode of operation is typically used when a 10-bit unsigned
result is desired.
Left justified sign data mode is similar to left justified mode with one
exception. The MSB of the 10-bit result, AD9 located in ADRH, is
complemented. This mode of operation is useful when a result,
represented as a signed magnitude from mid-scale, is needed.
Finally, 8-bit truncation mode will place the eight MSBs in ADC data
register low, ADRL. The two LSBs are dropped. This mode of operation
MC68HC908MR8 — Rev 4.1
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Technical Data
Analog-to-Digital Converter (ADC)
315
Analog-to-Digital Converter (ADC)
is used when compatibility with 8-bit ADC designs are required. No
interlocking between ADRH and ADRL is present.
NOTE:
Quantization error is affected when only the most significant eight bits
are used as a result. See Figure 18-2.
8-BIT 10-BIT
RESULT RESULT
IDEAL8-BIT CHARACTERISTIC
WITH QUANTIZATION = ±1/2
10-BIT TRUNCATED
TO 8-BIT RESULT
003
00B
00A
009
002
IDEAL 10-BIT CHARACTERISTIC
WITH QUANTIZATION = ±1/2
008
007
006
005
001
004
WHEN TRUNCATION IS USED,
ERROR FROM IDEAL 8 BIT = 3/8 LSB
DUE TO NON-IDEAL QUANTIZATION.
003
002
001
000
000
1/2
2 1/2
1 1/2
1/2
4 1/2
3 1/2
6 1/2
5 1/2
INPUT VOLTAGE
REPRESENTED AS 10-BIT
8 1/2
7 1/2
1 1/2
9 1/2
2 1/2
INPUT VOLTAGE
REPRESENTED AS 8-BIT
Figure 18-2. 8-Bit Truncation Mode Error
18.4.6 Monotonicity
The conversion process is monotonic and has no missing codes.
18.5 Interrupts
When the AIEN bit is set, the ADC module is capable of generating a
CPU interrupt after each ADC conversion. A CPU interrupt is generated
if the COCO bit is at logic 0. The COCO bit is not used as a conversion
complete flag when interrupts are enabled.
Technical Data
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Freescale Semiconductor
Analog-to-Digital Converter (ADC)
Wait Mode
18.6 Wait Mode
The WAIT instruction can put the MCU in low power-consumption
standby mode.
The ADC continues normal operation during wait mode. Any enabled
CPU interrupt request from the ADC can bring the MCU out of wait
mode. If the ADC is not required to bring the MCU out of wait mode,
power down the ADC by setting ADCH[4:0] in the ADC status and control
register before executing the WAIT instruction.
18.7 Stop Mode
The STOP instruction can put the MCU in low power-consumption
standby mode.
The ADC module becomes inactive after the execution of a STOP
instruction. Any pending conversion is aborted. ADC conversions
resume when the MCU exits stop mode after an external interrupt. Allow
one conversion cycle to stabilize the analog circuitry after exiting stop
mode.
18.8 I/O Signals
The ADC module has seven input signals that are shared with port A.
18.8.1 ADC Voltage Reference Pin (VREFH)
VREFH is the power supply for setting the reference voltage. Connect the
VREFH pin to the same voltage potential as VDDA. There will be a finite
current associated with VREFH.
NOTE:
Route VREFH carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
MC68HC908MR8 — Rev 4.1
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Technical Data
Analog-to-Digital Converter (ADC)
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Analog-to-Digital Converter (ADC)
18.8.2 ADC Voltage In (ADVIN)
ADVIN is the input voltage signal from one of the seven ADC channels
to the ADC module.
18.8.3 ADC External Connection
18.8.3.1 VREFH
Both ac and dc current are drawn through VREFH. The ac current is in the
form of current spikes required to supply charge to the capacitor array at
each successive approximation step. The dc current flows through the
internal resistor string. The best external component to meet both these
current demands is a capacitor in the 0.01 µF to 1 µF range with good
high-frequency characteristics. This capacitor is connected between
VREFH and VSS and must be placed as close as possible to the package
pins. Resistance in the path is not recommended because the dc current
will cause a voltage drop which could result in conversion errors.
18.8.3.2 ANx
Empirical data shows that capacitors from the analog inputs to VRL
improve ADC performance. 0.01 µF and 0.1 µF capacitors with good
high-frequency characteristics are sufficient. These capacitors must be
placed as close as possible to the package pins.
18.8.3.3 Grounding
In cases where separate power supplies are used for analog and digital
power, the ground connection between these supplies should be at the
VSS pin. This should be the only ground connection between these
supplies if possible. The VSS pin makes a good single-point ground
location.
Technical Data
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Freescale Semiconductor
Analog-to-Digital Converter (ADC)
I/O Registers
18.9 I/O Registers
These I/O registers control and monitor operation of the ADC:
•
ADC status and control register (ADSCR)
•
ADC data registers (ADRH and ARDL)
•
ADC control register (ADCR)
•
ADC clock register (ADCLK)
18.9.1 ADC Status and Control Register
These paragraphs describe the function of the ADC status and control
register (ADSCR). Writing ADSCR aborts the current conversion and
initiates a new conversion.
Address:
Read:
Write:
Reset:
$0040
Bit 7
6
5
COCO
AIEN
ADCO
0
0
0
4
3
2
1
Bit 0
ADCH4 ADCH3 ADCH2 ADCH1 ADCH0
1
1
1
1
1
Figure 18-3. ADC Status and Control Register (ADSCR)
COCO — Conversions Complete Bit
When AIEN bit is a logic 0, the COCO is a read-only bit which is set
each time a conversion is completed except in the continuous
conversion mode where it is set after the first conversion. This bit is
cleared whenever the ADC status and control register is written or
whenever the ADC data register is read.
If AIEN bit is a logic 1, the COCO is a read/write bit which selects the
CPU to service the ADC interrupt request. Reset clears this bit.
1 = Conversion completed (AIEN = 0) interrupt (AIEN = 1)
0 = Conversion not completed (AIEN = 0)/CPU interrupt (AIEN = 1)
MC68HC908MR8 — Rev 4.1
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Technical Data
Analog-to-Digital Converter (ADC)
319
Analog-to-Digital Converter (ADC)
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC
conversion. The interrupt signal is cleared when the data register is
read or the status/control register is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the
ADR register at the end of each conversion. Only one conversion is
allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH[4:0] — ADC Channel Select Bits
ADCH4, ADCH3, ADCH2, ADCH1, and ADCH0 form a 5-bit field
which is used to select one of the ADC channels detailed in Table
18-1. Take care to prevent switching noise from corrupting the analog
signal when simultaneously using a port pin as both an analog and
digital input.
The ADC subsystem is turned off when the channel select bits are all
set to 1. This feature allows for reduced power consumption for the
MCU when the ADC is not used.
NOTE:
Recovery from the disabled state requires one conversion cycle to
stabilize.
The voltage levels supplied from internal reference nodes as specified in
Table 18-1 are used to verify the operation of the ADC converter both in
production test and for user applications.
Technical Data
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MC68HC908MR8 — Rev 4.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
I/O Registers
Table 18-1. Mux Channel Select
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
Input select
0
0
0
0
0
PTA0
0
0
0
0
1
PTA1
0
0
0
1
0
PTA2
0
0
0
1
1
PTA3
0
0
1
0
0
PTA4
0
0
1
0
1
PTA5
0
0
1
1
0
PTA6
0
0
1
1
1
Unused*
0
1
0
0
0
Unused*
0
1
0
0
1
Unused*
0
1
0
1
0
Unused*
0
1
0
1
1
Ø
0
1
1
0
0
Ø
0
1
1
0
1
Ø
0
1
1
1
0
Ø
0
1
1
1
1
Ø
1
0
0
0
0
Ø
1
1
0
1
0
Unused*
1
1
0
1
1
Reserved**
1
1
1
0
0
Unused*
1
1
1
0
1
VREFH
1
1
1
1
0
VSS
1
1
1
1
1
ADC power off
* If any unused channels are selected, the resulting ADC conversion will be unknown.
** Used for factory testing.
MC68HC908MR8 — Rev 4.1
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Technical Data
Analog-to-Digital Converter (ADC)
321
Analog-to-Digital Converter (ADC)
18.9.2 ADC Data Register High
In left justified mode, this 8-bit result register holds the eight MSBs of the
10-bit result. This register is updated each time an ADC single channel
conversion completes. Reading ADRH latches the contents of ADRL
until ADRL is read. Until ADRL is read, all subsequent ADC results will
be lost.
Address:
$0041
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by Reset
R
= Reserved
Figure 18-4. ADC Data Register High (ADRH)
Left Justified Mode
In right justified mode, this 8-bit result register holds the two MSBs of the
10-bit result. All other bits read as 0. This register is updated each time
a single channel ADC conversion completes. Reading ADRH latches the
contents of ADRL until ADRL is read. Until ADRL is read, all subsequent
ADC results will be lost.
Address:
$0041
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
0
0
AD9
AD8
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by Reset
R
= Reserved
Figure 18-5. ADC Data Register High (ADRH)
Right Justified Mode
Technical Data
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Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
I/O Registers
18.9.3 ADC Data Register Low
In left justified mode, this 8-bit result register holds the two LSBs of the
10-bit result. All other bits read as 0. This register is updated each time
a single channel ADC conversion completes. Reading ADRH latches the
contents of ADRL until ADRL is read. Until ADRL is read all subsequent
ADC results will be lost.
Address:
$0042
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD1
AD0
0
0
0
0
0
0
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by Reset
R
= Reserved
Figure 18-6. ADC Data Register Low (ADRL)
Left Justified Mode
In right justified mode, this 8-bit result register holds the eight LSBs of
the 10-bit result. This register is updated each time an ADC conversion
completes. Reading ADRH latches the contents of ADRL until ADRL is
read. Until ADRL is read all subsequent ADC results will be lost.
Address:
$0042
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by Reset
R
= Reserved
Figure 18-7. ADC Data Register Low (ADRL)
Right Justified Mode
MC68HC908MR8 — Rev 4.1
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Technical Data
Analog-to-Digital Converter (ADC)
323
Analog-to-Digital Converter (ADC)
In 8-bit mode, this 8-bit result register holds the eight MSBs of the 10-bit
result. This register is updated each time an ADC conversion completes.
In 8-bit mode, this register contains no interlocking with ADRH.
Address:
$0042
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by Reset
R
= Reserved
Figure 18-8. ADC Data Register Low (ADRL)
8-Bit Mode
18.9.4 ADC Clock Register
This register selects the clock frequency for the ADC, selecting between
modes of operation.
Address:
Read:
Write:
Reset:
$0043
Bit 7
6
5
ADIV2
ADIV1
ADIV0
0
0
0
R
4
3
2
ADICLK MODE1 MODE0
0
0
1
1
0
0
Bit 0
0
R
0
= Reserved
Figure 18-9. ADC Clock Register (ADCLK)
ADIV2:ADIV0 — ADC Clock Prescaler Bits
ADIV2, ADIV1, and ADIV0 form a 3-bit field which selects the divide
ratio used by the ADC to generate the internal ADC clock. Table 18-2
shows the available clock configurations. The ADC clock should be
set to between 500 kHz and 1 MHz.
Technical Data
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MC68HC908MR8 — Rev 4.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
I/O Registers
Table 18-2. ADC Clock Divide Ratio
ADIV2
ADIV1
ADIV0
ADC Clock Rate
0
0
0
ADC input clock /1
0
0
1
ADC input clock /2
0
1
0
ADC input clock /4
0
1
1
ADC input clock /8
1
X
X
ADC input clock /16
X = don’t care
ADICLK — ADC Input Clock Select Bit
ADICLK selects either bus clock or CGMXCLK as the input clock
source to generate the internal ADC clock. Reset selects CGMXCLK
as the ADC clock source.
If the external clock (CGMXCLK) is equal or greater than 1 MHz,
CGMXCLK can be used as the clock source for the ADC. If
CGMXCLK is less than 1 MHz, use the PLL-generated bus clock as
the clock source. As long as the internal ADC clock is at fADIC, correct
operation can be guaranteed.
1 = Internal bus clock
0 = External clock, CGMXCLK
fADIC =
CGMXCLK or bus frequency
ADIV[2:0]
MODE1:MODE0 — Modes of Result Justification Bits
MODE1:MODE0 selects among four modes of operation. The
manner in which the ADC conversion results will be placed in the ADC
data registers is controlled by these modes of operation. Reset
returns right-justified mode.
00 = 8-bit truncation mode
01 = Right justified mode
10 = Left justified mode
11 = Left justified sign data mode
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Analog-to-Digital Converter (ADC)
325
Analog-to-Digital Converter (ADC)
Technical Data
326
MC68HC908MR8 — Rev 4.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 19.
Power-On Reset (POR)
19.1 Contents
19.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .327
19.3
Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .327
19.2 Introduction
This section describes the power-on reset (POR) module.
19.3 Functional Description
The POR module provides a known, stable signal to the MCU at
power-on. This signal tracks VDD until the MCU generates a feedback
signal to indicate that it is properly initialized. At this time, the POR drives
its output low. The POR is not a brown-out detector, low-voltage
detector, or glitch detector. VDD at the POR must go completely to 0 to
reset the MCU. To detect power-loss conditions, use a low-voltage
inhibit module (LVI) or other suitable circuit.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Power-On Reset (POR)
327
Power-On Reset (POR)
Technical Data
328
MC68HC908MR8 — Rev 4.1
Power-On Reset (POR)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 20. Break (BRK)
20.1 Contents
20.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .329
20.3
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .330
20.4 Functional Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . .330
20.4.1 Flag Protection During Break Interrupts . . . . . . . . . . . .330
20.4.2 CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . .332
20.4.3 TIM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . .332
20.4.4 COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . .332
20.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333
20.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333
20.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .333
20.6 Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . .333
20.6.1 Break Status and Control Register. . . . . . . . . . . . . . . . .333
20.6.2 Break Address Registers. . . . . . . . . . . . . . . . . . . . . . . . .334
20.6.3 SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . .336
20.6.4 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . .337
20.2 Introduction
This section describes the break (BRK) module. The break module can
generate a break interrupt that stops normal program flow at a defined
address to enter a background program.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Break (BRK)
329
Break (BRK)
20.3 Features
Features of the break module include:
•
Accessible input/output (I/O) registers during the break interrupt
•
Central processor unit (CPU) generated break interrupts
•
Software-generated break interrupts
•
Computer operating properly (COP) disabling during break
interrupts
20.4 Functional Description
When the internal address bus matches the value written in the break
address registers, the break module issues a breakpoint signal to the
CPU. The CPU then loads the instruction register with a software
interrupt instruction (SWI) after completion of the current CPU
instruction. The program counter vectors to $FFFC and $FFFD ($FEFC
and $FEFD in monitor mode).
These events can cause a break interrupt to occur:
•
A CPU-generated address (the address in the program counter)
matches the contents of the break address registers.
•
Software writes a logic 1 to the BRKA bit in the break status and
control register.
When a CPU-generated address matches the contents of the break
address registers, the break interrupt begins after the CPU completes its
current instruction. A return-from-interrupt instruction (RTI) in the break
routine ends the break interrupt and returns the microcontroller unit
(MCU) to normal operation. Figure 20-1 shows the structure of the break
module.
20.4.1 Flag Protection During Break Interrupts
The BCFE bit in the system integration module (SIM) break flag control
register (SBFCR) enables software to clear status bits during the break
state.
Technical Data
330
MC68HC908MR8 — Rev 4.1
Break (BRK)
Freescale Semiconductor
Break (BRK)
Functional Description
IAB15–IAB8
BREAK ADDRESS REGISTER HIGH
8-BIT COMPARATOR
IAB15–IAB0
CONTROL
BREAK
8-BIT COMPARATOR
BREAK ADDRESS REGISTER LOW
IAB7–IAB0
Figure 20-1. Break Module Block Diagram
Addr.
Register Name
Read
:
$FE0
0
SIM Break Status
Write
Register (SBSR)
:
See page 336.
Reset:
Read
:
SIM Break Flag ConWrite
$FE0
trol Register (SBFCR)
:
3
See page 337.
Reset:
Read
:
$FE0
C
Break Address RegisWrite
ter High (BRKH)
:
See page 334.
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
1
0
0
BW
0
R
R
R
R
R
R
NOTE
R
0
0
0
1
0
0
0
0
BCFE
R
R
R
R
R
R
R
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
0
Figure 20-2. I/O Register Summary
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Break (BRK)
331
Break (BRK)
Read
:
$FE0
D
Break Address RegisWrite
ter Low (BRKL)
:
See page 334.
Reset:
Read
:
$FE0
E
Break Status and
Control Register Write
:
(BRKSCR)
See page 333.
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
BRKE
BRKA
0
0
Note: Writing a logic 0 clears
BW.
= Unimplemented
R
= Reserved
Figure 20-2. I/O Register Summary
20.4.2 CPU During Break Interrupts
The CPU starts a break interrupt by:
•
Loading the instruction register with the SWI instruction
•
Loading the program counter with $FFFC and $FFFD ($FEFC and
$FEFD in monitor mode)
The break interrupt begins after completion of the CPU instruction in
progress. If the break address register match occurs on the last cycle of
a CPU instruction, the break interrupt begins immediately.
20.4.3 TIM During Break Interrupts
A break interrupt stops the timer counters.
20.4.4 COP During Break Interrupts
The COP is disabled during a break interrupt when VTST is present on
the RST pin.
Technical Data
332
MC68HC908MR8 — Rev 4.1
Break (BRK)
Freescale Semiconductor
Break (BRK)
Low-Power Modes
20.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
20.5.1 Wait Mode
If enabled, the break module is active in wait mode. In the break routine,
the user can subtract one from the return address on the stack if SBSW
is set. Clear the BW bit by writing logic 0 to it.
20.5.2 Stop Mode
A break interrupt causes exit from stop mode and sets the SBSW bit in
the break status register.
20.6 Break Module Registers
These registers control and monitor operation of the break module:
•
Break status and control register (BRKSCR)
•
Break address register high (BRKH)
•
Break address register low (BRKL)
•
SIM break status register (SBSR)
•
SIM break flag control register (SBFCR)
20.6.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module
enable and status bits.
Ad$FE0E
dress:
Bit 7
6
5
4
3
2
1
Bit 0
Figure 20-3. Break Status and Control Register (BRKSCR)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Break (BRK)
333
Break (BRK)
Read:
Write:
Reset:
BRKE
BRKA
0
0
0
0
0
0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 20-3. Break Status and Control Register (BRKSCR)
BRKE — Break Enable Bit
This read/write bit enables breaks on break address register matches.
Clear BRKE by writing a logic 0 to bit 7. Reset clears the BRKE bit.
1 = Breaks enabled on 16-bit address match
0 = Breaks disabled on 16-bit address match
BRKA — Break Active Bit
This read/write status and control bit is set when a break address
match occurs. Writing a logic 1 to BRKA generates a break interrupt.
Clear BRKA by writing a logic 0 to it before exiting the break routine.
Reset clears the BRKA bit.
1 = When read, break address match
0 = When read, no break address match
20.6.2 Break Address Registers
The break address registers (BRKH and BRKL) contain the high and low
bytes of the desired breakpoint address. Reset clears the break address
registers.
Ad$FE0C
dress:
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Figure 20-4. Break Address Register High (BRKH)
Technical Data
334
MC68HC908MR8 — Rev 4.1
Break (BRK)
Freescale Semiconductor
Break (BRK)
Break Module Registers
Ad$FE0D
dress:
Read:
Write:
Reset:
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
Figure 20-5. Break Address Register Low (BRKL)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Break (BRK)
335
Break (BRK)
20.6.3 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a
break caused an exit from wait mode. The flag is useful in applications
requiring a return to wait mode after exiting from a break interrupt.
Ad$FE00
dress:
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
1
0
0
BW
0
Write:
R
R
R
R
R
R
Note
R
Reset:
0
0
0
1
0
0
0
0
Note: Writing a logic 0
clears BW.
R
= Reserved
Figure 20-6. SIM Break Status Register (SBSR)
BW — Break Wait Bit
This read/write bit is set when a break interrupt causes an exit from
wait mode. Clear BW by writing a logic 0 to it. Reset clears BW.
1 = Break interrupt during wait mode
0 = No break interrupt during wait mode
BW can be read within the break interrupt routine. The user can modify
the return address on the stack by subtracting 1 from it. The example
code shown in Figure 20-7 works if the H register was stacked in the
break interrupt routine. Execute this code at the end of the break
interrupt routine.
Technical Data
336
MC68HC908MR8 — Rev 4.1
Break (BRK)
Freescale Semiconductor
Break (BRK)
Break Module Registers
HIBYTE EQU
LOBYTE EQU
5
6
;
BRCLR BW,BSR, RETURN ;
;
TST
LOBYTE,SP
;
BNE
DOLO
;
DEC
HIBYTE,SP
;
DOLO
DEC
LOBYTE,SP
;
RETURN PULH
;
RTI
If not BW, do RTI
See if wait mode or stop
mode was exited by break.
If RETURNLO is not 0,
then just decrement low byte.
Else deal with high byte also.
Point to WAIT/STOP opcode.
Restore H register.
Figure 20-7. Example Code
20.6.4 SIM Break Flag Control Register
The SIM break flag control register (SBFCR) contains a bit that enables
software to clear status bits while the MCU is in a break state.
Ad$FE03
dress:
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
0
R
= Reserved
Figure 20-8. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing
status registers while the MCU is in a break state. To clear status bits
during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Break (BRK)
337
Break (BRK)
Technical Data
338
MC68HC908MR8 — Rev 4.1
Break (BRK)
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 21. Electrical Specifications
21.1 Contents
21.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .339
21.3
Absolute Maximum Ratings. . . . . . . . . . . . . . . . . . . . . . . . .340
21.4
Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . .341
21.5
Thermal Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . .342
21.6
DC Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . . . .343
21.7
Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . .345
21.8
Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .346
21.9
TImer Interface Module Characteristics . . . . . . . . . . . . . . .346
21.10 Clock Generation Module Component Specifications . . . 347
21.11 CGM Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . .347
21.12 CGM Acquisition/Lock Time Specifications. . . . . . . . . . . .348
21.13 Analog-to-Digital Converter (ADC) Characteristics. . . . . . 349
21.2 Introduction
This section contains electrical and timing specifications. These values
are design targets and have not yet been fully characterized.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Electrical Specifications
339
Electrical Specifications
21.3 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the MCU can be
exposed without permanently damaging it.
NOTE:
This device is not guaranteed to operate properly at the maximum
ratings. Refer to 21.6 DC Electrical Characteristics for guaranteed
operating conditions.
Characteristic(1)
Symbol
Value
Unit
Supply voltage
VDD
–0.3 to +6.0
V
Input voltage
VIn
VSS – 0.3
to VDD + 0.3
V
Input high voltage
VHI
VDD + 4
V
I
± 25
mA
tSTG
–55 to +150
°C
Maximum current out of VSS
IMVSS
100
mA
Maximum current Into VDD
IMVDD
100
mA
Maximum current per pin
excluding VDD and VSS
Storage temperature
1. Voltages are referenced to VSS.
NOTE:
This device contains circuitry to protect the inputs against damage due
to high static voltages or electric fields; however, it is advised that normal
precautions be taken to avoid application of any voltage higher than
maximum-rated voltages to this high-impedance circuit. For proper
operation, it is recommended that VIn and VOut be constrained to the
range VSS ≤ (VIn or VOut) ≤ VDD. Reliability of operation is enhanced if
unused inputs are connected to an appropriate logic voltage level (for
example, either VSS or VDD).
Technical Data
340
MC68HC908MR8 — Rev 4.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
Functional Operating Range
21.4 Functional Operating Range
Characteristic
Operating temperature range(1)
MC68HC908MR8CP
MC68HC908MR8CFA
MC68HC908MR8CDW
MC68HC908MR8VFA
MC68HC908MR8VP
MC68HC908MR8VDW
MC68HC908MR8MFA
MC68HC908MR8MP
MC68HC908MR8MDW
Operating voltage range
Symbol
TA
VDD
Value
Unit
–40 to +85
–40 to +85
–40 to +85
–40 to +105
–40 to +105
–40 to +105
–40 to +125
–40 to +125
–40 to +125
5.0 ± 10%
°C
V
1. Contact a Freescale representative for temperature availability.
C = Extended temperature range (–40 to +85°C)
V = Industrial temperature range (–40 to +105°C)
M = Automotive temperature range (–40 to +125°C)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Electrical Specifications
341
Electrical Specifications
21.5 Thermal Characteristics
Characteristic
Symbol
Value
Unit
Thermal resistance
32-pin LQFP
28-pin PDIP
28-pin SOIC
θJA
I/O pin power dissipation
PI/O
User determined
W
Power dissipation(2)
PD
PD = (IDD x VDD)
+ PI/O = K/(TJ + 273°C)
W
Constant(3)
K
Average junction temperature
TJ
TA + (PD x θJA)
°C
TJM
125
°C
Maximum junction temperature
68.9(1)
—
—
PD x (TA + 273°C)
+ PD2 x θJA
°C/W
W/°C
1. 32-pin LQFP resistance measured at 200 ft/min.
2. Power dissipation is a function of temperature.
3. K is a constant unique to the device. K can be determined for a known TA and measured
PD. With this value of K, PD and TJ can be determined for any value of TA.
Technical Data
342
MC68HC908MR8 — Rev 4.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
DC Electrical Characteristics
21.6 DC Electrical Characteristics
Characteristic(1)
Symbol
Output high voltage
ILoad = –2.0 mA for all I/O pins except:
Port A bits 0 and 1
Port B bits 5 and 6
ILoad = –7.0 mA for:
Port A bits 0 and 1 and port B bits 5–6,
a maximum of four 15-mA outputs may be active
at any time
Typ(2)
Max
Unit
—
—
V
—
—
0.4
Min
VDD –0.8
VOH
VDD –1.0
Output low voltage
ILoad = 1.6 mA for all I/O pins except:
Port A bits 0 and 1
Port B bits 5 and 6
ILoad = 15 mA for:
Port A bits 0 and 1 and Port B bits 5–6,
a maximum of four 15-mA outputs may be active
at any time
VOL
—
—
1.5
Input high voltage
All ports, IRQs, RESET, OSC1
VIH
0.7 x VDD
—
VDD
V
Input low voltage
All ports, IRQs, RESET, OSC1
VIL
VSS
—
0.3 x VDD
V
—
—
—
—
40
12
mA
mA
—
—
—
—
—
—
—
—
5
15
350
100
µA
µA
µA
µA
V
VDD supply current
Run(3)
Wait(4)
Stop(5)
Up to 85°C
Above 85°C
25°C with LVI enabled
Quiescent(5)
IDD
I/O ports high-impedance leakage current
IIL
—
—
±10
µA
Input current except PTC1/FAULT4
IIn
—
—
±1
µA
Input current PTC1/FAULT4
IIn
80
208
µA
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
Low-voltage inhibit falling
VLVRF1
4.0
4.4
—
V
Low-voltage reset/recover hysteresis
VLVH1
20
50
—
mV
Low-voltage recover rising
VLVRR1
—
4.5
4.75
V
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Electrical Specifications
343
Electrical Specifications
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
— Continued
Low-voltage inhibit falling
VLVRF2
3.8
4.1
—
V
Low-voltage reset/recover hysteresis
VLVH2
50
100
—
mV
Low-voltage recover rising
VLVRR2
—
4.2
4.6
V
POR re-arm voltage(6)
VPOR
0
—
100
mV
POR rise time ramp rate(7)
RPOR
0.035
—
—
V/ms
1. VDD = 5.0 Vdc ±10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using external square wave clock source (fOSC = 8.2 MHz); all inputs 0.2 V from rail; no dc
loads; less than 100 pF on all outputs; CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly
affects run IDD; measured with all modules enabled
4. Wait IDD measured using external square wave clock source (fOSC = 8.2 MHz); all inputs 0.2 V from rail; no dc loads; less
than 100 pF on all outputs; CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly affects wait IDD;
measured with PLL and LVI enabled
5. Quiescent IDD measured with PLL and LVI disengaged; OCS1 grounded; no port pins sourcing current. It is measured
through combination of VDD and VDDA.
6. Maximum is highest guaranteed voltage for POR.
7. Maximum is the highest possible voltage for POR. If minimum VDD is not reached before the internal POR reset is released,
RST must be driven low externally until minimum VDD is reached.
Technical Data
344
MC68HC908MR8 — Rev 4.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
Memory Characteristics
21.7 Memory Characteristics
Characteristic
Symbol
Min
Typ
Max
Unit
VRDR
1.3
—
—
V
—
1
—
—
MHz
FLASH read bus clock frequency
fRead(1)
32k
—
8.4M
Hz
FLASH page erase time
tErase(2)
1
—
—
ms
FLASH mass erase time
tMErase(3)
4
—
—
ms
FLASH PGM/ERASE to HVEN set up time
tnvs
10
—
—
µs
FLASH high-voltage hold time
tnvh
5
—
—
µs
FLASH high-voltage hold time (mass erase)
tnvhl
100
—
—
µs
FLASH program hold time
tpgs
5
—
—
µs
FLASH program time
tPROG
30
—
40
µs
FLASH return to read time
trcv(4)
1
—
—
µs
FLASH cumulative program HV period
tHV(5)
—
—
4
ms
FLASH row erase endurance(6)
—
10k
100k(7)
—
Cycles
FLASH row program endurance(8)
—
10k
100k(7)
—
Cycles
FLASH data retention time(9)
—
10
100(10)
—
Years
RAM data retention voltage
FLASH program bus clock frequency
Notes:
1. fRead is defined as the frequency range for which the FLASH memory can be read.
2. If the page erase time is longer than tErase (Min), there is no erase-disturb, but it reduces the endurance of the FLASH
memory.
3. If the mass erase time is longer than tMErase (Min), there is no erase-disturb, but it reduces the endurance of the FLASH
memory.
4. trcv is defined as the time it needs before the FLASH can be read after turning off the high voltage charge pump, by clearing
HVEN to logic 0.
5. tHV is defined as the cumulative high voltage programming time to the same row before next erase.
tHV must satisfy this condition: tnvs + tnvh + tpgs + (tPROG × 64) ≤ tHV max.
6. The minimum row endurance value specifies each row of the FLASH memory is guaranteed to work for at
least this many erase / program cycles.
7. FLASH endurance is a function of the temperature at which erasure occurs. Typical endurance degrades when the temperature while erasing is less than 25°C.
8. The minimum row endurance value specifies each row of the FLASH memory is guaranteed to work for at
least this many erase / program cycles.
9. The FLASH is guaranteed to retain data over the entire operating temperature range for at least the minimum
time specified.
10. Freescale performs reliability testing for data retention. These tests are based on samples tested at elevated temperatures. Due to the higher activation energy of the elevated test temperature, calculated life tests correspond to more than
100 years of operation/storage at 55°C
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Electrical Specifications
345
Electrical Specifications
21.8 Control Timing
Characteristic(1)
Symbol
Min
Max
Unit
Frequency of operation(2)
Crystal option
External clock option(3)
fOSC
1
dc(4)
8
32.8
MHz
Internal operating frequency
fOP
—
8.2
MHz
RESET input pulse width low(5)
tIRL
50
—
ns
1. VDD = 5.0 Vdc ± 10%; VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD, unless otherwise noted
2. See 21.8 Control Timing for more information.
3. No more than 10 percent duty cycle deviation from 50 percent.
4. Some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this information.
5. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause reset.
21.9 TImer Interface Module Characteristics
Characteristic
Symbol
Min
Max
Unit
Input capture pulse width
tTIH
tTIL
125
—
ns
Input clock pulse width
tTCH
tTCL
(1/fOP) + 5
—
ns
Technical Data
346
MC68HC908MR8 — Rev 4.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
Clock Generation Module Component Specifications
21.10 Clock Generation Module Component Specifications
Characteristic
Symbol
Min
Typ
Max
Crystal load capacitance
CL
—
—
—
Consult crystal
manufacturing data
Crystal fixed capacitance
C1
—
2 * CL
—
Consult crystal
manufacturing data
Crystal tuning capacitance
C2
—
2 * CL
—
Consult crystal
manufacturing data
Feedback bias resistor
RB
—
22 MΩ
—
Series resistor
RS
0
330 kΩ
1 MΩ
Filter capacitor
CF
—
CFACT*
(VDDA/fXCLK)
—
—
—
CBYP must provide low ac
impedance from
f = fXCLK/100 to
100 * fVCLK, so series
resistance must be
considered.
CBYP
Bypass capacitor
—
0.1 µF
Notes
Not required
21.11 CGM Operating Conditions
Characteristic
Symbol
Min
Typ
Max
Crystal reference frequency
fXCLK
1 MHz
—
8 MHz
Range nominal multiplier
fNOM
—
4.9152 MHz
—
VCO center-of-range frequency
fVRS
4.9152 MHz
—
32.8 MHz
VCO frequency multiplier
N
1
—
15
VCO center of range multiplier
L
1
—
15
fVCLK
fVRSMIN
—
fVRSMAX
VCO operating frequency
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Electrical Specifications
347
Electrical Specifications
21.12 CGM Acquisition/Lock Time Specifications
Description
Symbol
Min
Typ
Max
Notes
Filter capacitor multiply factor
CFACT
—
0.0154
—
F/sV
Acquisition mode time factor
KACQ
—
0.1135
—
V
Tracking mode time factor
KTRK
—
0.0174
—
V
Manual mode time to stable
tACQ
—
(8 * VDDA)/
(fXCLK * KACQ)
—
If CF chosen
correctly
tAL
—
(4 * VDDA)/
(fXCLK * KTRK)
—
If CF chosen
correctly
Manual acquisition time
tLock
—
tACQ + tAL
—
—
Tracking mode entry frequency
tolerance
∆TRK
0
—
±3.6%
—
Acquisition mode entry frequency
tolerance
∆ACQ
±6.3%
—
±7.2%
—
Lock entry frequency tolerance
∆Lock
0
—
±0.9%
—
Lock exit frequency tolerance
∆UNL
±0.9%
—
±1.8%
—
Reference cycles per acquisition
mode measurement
nACQ
—
32
—
—
Reference cycles per tracking mode
measurement
nTRK
—
128
—
—
Automatic mode time to stable
tACQ
nACQ/fXCLK
(8 * VDDA)/
(fXCLK * KACQ)
—
If CF chosen
correctly
tAL
nTRK/fXCLK
(4 * VDDA)/
(fXCLK * KTRK)
—
If CF chosen
correctly
tLock
—
tACQ + tAL
—
—
fJ
0
—
± (fCRYS)
* (0.025 %)
* (N/4)
N = VCO
freq. mult.
(GBNT)
Manual stable to lock time
Automatic stable to lock time
Automatic lock time
PLL jitter (deviation of average bus
frequency over 2 ms)
Technical Data
348
MC68HC908MR8 — Rev 4.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
Analog-to-Digital Converter (ADC) Characteristics
21.13 Analog-to-Digital Converter (ADC) Characteristics
Characteristic
Symbol
Min
Typ
Max
Unit
Notes
A/D reference voltage
VREFH
4.5
—
5.5
V
—
Input voltages
VADIN
0
—
VREFH
V
VADIN <= VREFH
Resolution
BAD
10
—
10
Bits
—
Absolute accuracy
AAD
—
—
4
Counts
Includes
quantization
ADC internal clock
fADIC
500 k
—
1M
Hz
tAIC = 1/fADIC
Conversion range
RAD
VSSA
—
VREFH
V
—
Power-up time
tADPU
16
—
tAIC cycles
—
Conversion time
tADC
16
—
17
tAIC cycles
—
Sample time
tADS
5
—
—
tAIC cycles
—
Monotonicity
MAD
Zero input reading
ZADI
000
—
003
Hex
VADIN = VSSA
Full-scale reading
FADI
3FD
—
3FF
Hex
VADIN = VREFH
Input capacitance
CADI
—
—
30
pF
Not
characterized
Absolute accuracy
(8-bit truncation mode)
AAD
—
—
±1
Counts
Includes
quantization
Quantization error
(8-bit truncation mode)
—
—
—
+7/8
–1/8
LSB
—
Guaranteed
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Electrical Specifications
349
Electrical Specifications
Technical Data
350
MC68HC908MR8 — Rev 4.1
Electrical Specifications
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 22. Mechanical Specifications
22.1 Contents
22.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .351
22.3
32-Pin LQFP (Case #873A). . . . . . . . . . . . . . . . . . . . . . . . . .352
22.4
28-Pin PDIP (Case #710). . . . . . . . . . . . . . . . . . . . . . . . . . . .353
22.5
28-Pin SOIC (Case #751F) . . . . . . . . . . . . . . . . . . . . . . . . . .353
22.2 Introduction
The MC68HC908MR8 is available in these packages:
•
32-pin low-profile quad flat pack (LQFP)
•
28-pin dual in-line package (PDIP)
•
28-pin small outline package (SOIC)
The package information contained in this section is the latest available
at the time of this publication. To make sure that you have the latest
package specifications, please visit the Freescale website at
http://freescale.com. Follow World Wide Web on-line instructions to
retrieve the current mechanical specifications.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Mechanical Specifications
351
Mechanical Specifications
A
32
–T–, –U–, –Z–
22.3 32-Pin LQFP (Case #873A)
4X
A1
0.20 (0.008) AB T–U Z
25
1
–U–
–T–
B
V
AE
P
B1
DETAIL Y
17
8
V1
AE
DETAIL Y
9
4X
–Z–
9
0.20 (0.008) AC T–U Z
S1
S
DETAIL AD
G
–AB–
0.10 (0.004) AC
AC T–U Z
–AC–
BASE
METAL
ÉÉ
ÉÉ
ÉÉ
ÉÉ
F
8X
M_
R
J
M
N
D
0.20 (0.008)
SEATING
PLANE
SECTION AE–AE
W
K
X
DETAIL AD
Q_
GAUGE PLANE
H
0.250 (0.010)
C E
Technical Data
352
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DATUM PLANE –AB– IS LOCATED AT BOTTOM
OF LEAD AND IS COINCIDENT WITH THE LEAD
WHERE THE LEAD EXITS THE PLASTIC BODY AT
THE BOTTOM OF THE PARTING LINE.
4. DATUMS –T–, –U–, AND –Z– TO BE DETERMINED
AT DATUM PLANE –AB–.
5. DIMENSIONS S AND V TO BE DETERMINED AT
SEATING PLANE –AC–.
6. DIMENSIONS A AND B DO NOT INCLUDE MOLD
PROTRUSION. ALLOWABLE PROTRUSION IS
0.250 (0.010) PER SIDE. DIMENSIONS A AND B
DO INCLUDE MOLD MISMATCH AND ARE
DETERMINED AT DATUM PLANE –AB–.
7. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. DAMBAR PROTRUSION SHALL
NOT CAUSE THE D DIMENSION TO EXCEED
0.520 (0.020).
8. MINIMUM SOLDER PLATE THICKNESS SHALL BE
0.0076 (0.0003).
9. EXACT SHAPE OF EACH CORNER MAY VARY
FROM DEPICTION.
DIM
A
A1
B
B1
C
D
E
F
G
H
J
K
M
N
P
Q
R
S
S1
V
V1
W
X
MILLIMETERS
MIN
MAX
7.000 BSC
3.500 BSC
7.000 BSC
3.500 BSC
1.400
1.600
0.300
0.450
1.350
1.450
0.300
0.400
0.800 BSC
0.050
0.150
0.090
0.200
0.500
0.700
12_ REF
0.090
0.160
0.400 BSC
1_
5_
0.150
0.250
9.000 BSC
4.500 BSC
9.000 BSC
4.500 BSC
0.200 REF
1.000 REF
INCHES
MIN
MAX
0.276 BSC
0.138 BSC
0.276 BSC
0.138 BSC
0.055
0.063
0.012
0.018
0.053
0.057
0.012
0.016
0.031 BSC
0.002
0.006
0.004
0.008
0.020
0.028
12_ REF
0.004
0.006
0.016 BSC
1_
5_
0.006
0.010
0.354 BSC
0.177 BSC
0.354 BSC
0.177 BSC
0.008 REF
0.039 REF
MC68HC908MR8 — Rev 4.1
Mechanical Specifications
Freescale Semiconductor
Mechanical Specifications
28-Pin PDIP (Case #710)
22.4 28-Pin PDIP (Case #710)
28
NOTES:
1. POSITIONAL TOLERANCE OF LEADS (D),
SHALL BE WITHIN 0.25mm (0.010) AT
MAXIMUM MATERIAL CONDITION, IN
RELATION TO SEATING PLANE AND
EACH OTHER.
2. DIMENSION L TO CENTER OF LEADS
WHEN FORMED PARALLEL.
3. DIMENSION B DOES NOT INCLUDE
MOLD FLASH.
15
B
1
14
A
DIM
A
B
C
D
F
G
H
J
K
L
M
N
L
C
N
H
G
F
M
K
D
J
SEATING
PLANE
MILLIMETERS
MIN
MAX
36.45 37.21
13.72 14.22
3.94
5.08
0.36
0.56
1.02
1.52
2.54 BSC
1.65
2.16
0.20
0.38
2.92
3.43
15.24 BSC
0°
15°
0.51
1.02
INCHES
MIN
MAX
1.435 1.465
0.540 0.560
0.155 0.200
0.014 0.022
0.040 0.060
0.100 BSC
0.065 0.085
0.008 0.015
0.115 0.135
0.600 BSC
0°
15°
0.020 0.040
22.5 28-Pin SOIC (Case #751F)
-A28
NOTES:
1. DIMENSIONING AND TOLERANCING PER
ANSI Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DIMENSION A AND B DO NOT INCLUDE MOLD
PROTRUSION.
4. MAXIMUM MOLD PROTRUSION 0.15
(0.006) PER SIDE.
5. DIMENSION D DOES NOT INCLUDE
DAMBAR PROTRUSION. ALLOWABLE
DAMBAR PROTRUSION SHALL BE 0.13
(0.005) TOTAL IN EXCESS OF D
DIMENSION AT MAXIMUM MATERIAL
CONDITION.
15
14X
-B1
P
0.010 (0.25)
M
B
M
14
28X D
0.010 (0.25)
M
T
A
S
B
M
S
R X 45°
C
-T26X
-T-
G
K
SEATING
PLANE
F
J
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
DIM
A
B
C
D
F
G
J
K
M
P
R
MILLIMETERS
MIN
MAX
17.80 18.05
7.60
7.40
2.65
2.35
0.49
0.35
0.90
0.41
1.27 BSC
0.32
0.23
0.29
0.13
8°
0°
10.05 10.55
0.75
0.25
INCHES
MIN
MAX
0.701 0.711
0.292 0.299
0.093 0.104
0.014 0.019
0.016 0.035
0.050 BSC
0.009 0.013
0.005 0.011
8°
0°
0.395 0.415
0.010 0.029
Technical Data
Mechanical Specifications
353
Mechanical Specifications
Technical Data
354
MC68HC908MR8 — Rev 4.1
Mechanical Specifications
Freescale Semiconductor
Technical Data — MC68HC908MR8
Section 23. Ordering Information
23.1 Contents
23.2
Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
23.3
MC Order Numbers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
23.2 Introduction
This section contains instructions for ordering the MC68HC908MR8.
23.3 MC Order Numbers
Table 23-1. MC Order Numbers
MC Order Number
(1)
MC68HC908MR8CFA
MC68HC908MR8CP
MC68HC908MR8CDW
MC68HC908MR8VFA
MC68HC908MR8VP
MC68HC908MR8VDW
MC68HC908MR8MFA
MC68HC908MR8MP
MC68HC908MR8MDW
Operating
Temperature Range
(°C)
– 40 to + 85
– 40 to + 85
– 40 to + 85
– 40 to + 105
– 40 to + 105
– 40 to + 105
– 40 to + 125
– 40 to + 125
– 40 to + 125
1. FA = quad flat pack
P = plastic dual in line package
DW = Small outline integrated circuit (SOIC) package
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
Ordering Information
355
Ordering Information
Technical Data
356
MC68HC908MR8 — Rev 4.1
Ordering Information
Freescale Semiconductor
Technical Data — MC68HC908MR8
Revision History
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357
Changes from Rev 3.0 published in April 2002 to Rev 4.0 published in
July 2002 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
Introduction
This section contains the revision history for the MC68HC908MR8
advance information data book.
Changes from Rev 3.0 published in April 2002 to Rev 4.0 published in July
2002
Section
Page (in Rev 0.4)
Electrical
Specifications
343
Description of change
VOL max updated for ILoad = 15 mA
Stop IDD limits updated for different temperature specs
MC68HC908MR8 — Rev 4.0
Freescale Semiconductor
Technical Data
Revision History
357
Revision History
Technical Data
358
MC68HC908MR8 — Rev 4.0
Revision History
Freescale Semiconductor
Technical Data — MC68HC908MR8
Glossary
A — See accumulator (A).
accumulator (A) — An 8-bit general-purpose register in the CPU08. The CPU08 uses the
accumulator to hold operands and results of arithmetic and logic operations.
acquisition mode — A mode of PLL operation during startup before the PLL locks on a
frequency. 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 M68HC08 CPU has 16 addressing modes.
ALU — See arithmetic logic unit (ALU).
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
baud rate — The total number of bits transmitted per unit of time.
BCD — See binary-coded decimal (BCD)
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)
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
359
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 — A module in the M68HC08 Family. The break module allows software to halt
program execution at a programmable point 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 clocks — There are two bus clocks, IT12 and IT23. These clocks are generated by the CGM
and distributed throughout the MCU by the SIM. The frequency of the bus clocks, or operating
frequency, is fOP. While the frequency of these two clocks is the same, the phase is different.
byte — A set of eight bits.
C — The carry/borrow bit in the condition code register. The CPU08 sets the carry/borrow bit
when an addition operation produces a carry out of bit 7 of the accumulator or when a
subtraction operation requires a borrow. Some logical operations and data manipulation
instructions also clear or set the carry/borrow bit (as in bit test and branch instructions and
shifts and rotates).
CCR — See condition code register.
central processor unit (CPU) — The primary functioning unit of any computer system. The
CPU controls the execution of instructions.
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) — A module in the M68HC08 Family. The CGM 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.
Technical Data
360
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
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 in the M68HC08 Family that
resets the MCU if allowed to overflow.
condition code register (CCR) — An 8-bit register in the CPU08 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).
counter clock — The input clock to the TIM counter. This clock is an output of the prescaler
sub-module. The frequency of the counter clock is fTCNT, and the period is tTCNT.
CPU — See central processor unit (CPU).
CPU08 — The central processor unit of the M68HC08 Family.
CPU cycles — A CPU clock cycle is one period of the internal bus-rate clock, fOP, 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 M68HC08 are:
•
A, 8-bit accumulator
•
H:X, 16-bit index register
•
SP, 16-bit stack pointer
•
PC, 16-bit program counter
•
CCR, condition code register containing the V, H, I, N, Z, and C bits
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
361
CSIC — customer-specified integrated circuit
cycle time — The period of the operating frequency: tCYC = 1/fOP.
decimal number system — Base 10 numbering system that uses the digits zero through nine.
direct memory access module (DMA) — A M68HC08 Family module that can perform data
transfers between any two CPU-addressable locations without CPU intervention. For
transmitting or receiving blocks of data to or from peripherals, DMA transfers are faster and
more code-efficient than CPU interrupts.
DMA — See direct memory access module (DMA).
DMA service request — A signal from a peripheral to the DMA module that enables the DMA
module to transfer data.
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.
EEPROM — Electrically erasable, programmable, read-only memory. A non-volatile type of
memory that can be electrically reprogrammed.
EPROM — Erasable, programmable, read-only memory. A non-volatile type of memory that can
be erased by exposure to an ultraviolet light source and then reprogrammed.
exception — An event such as an interrupt or a reset that stops the sequential execution of the
instructions in the main program.
external interrupt module (IRQ) — A module in the M68HC08 Family with both dedicated
external interrupt pins and port pins that can be enabled as interrupt pins.
fetch — To copy data from a memory location into the accumulator.
firmware — Instructions and data programmed into non-volatile 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.
H — The upper byte of the 16-bit index register (H:X) in the CPU08.
Technical Data
362
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
H — The half-carry bit in the condition code register of the CPU08. This bit indicates a carry from
the low-order four bits of the accumulator value to the high-order four bits. The half-carry bit
is required for binary-coded decimal arithmetic operations. The decimal adjust accumulator
(DAA) instruction uses the state of the H and C bits to determine the appropriate correction
factor.
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 non-existent opcode.
I — The interrupt mask bit in the condition code register of the CPU08. When I is set, all interrupts
are disabled.
index register (H:X) — A 16-bit register in the CPU08. The upper byte of H:X is called H. The
lower byte is called X. In the indexed addressing modes, the CPU uses the contents of H:X
to determine the effective address of the operand. H:X can also serve as a temporary data
storage location.
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.
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).
IRQ — See external interrupt module (IRQ).
jitter — Short-term signal instability.
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.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
363
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.
low voltage inhibit module (LVI) — A module in the M68HC08 Family that monitors power
supply voltage.
LVI — See low-voltage inhibit module (LVI).
M68HC08 — A Freescale family of 8-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.
mask option — An optional microcontroller feature that the customer chooses to enable or
disable.
MCU — Microcontroller unit. See microcontroller.
memory location — Each M68HC08 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.
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.
monitor ROM — A section of ROM that can execute commands from a host computer for testing
purposes.
most significant bit (MSB) — The leftmost digit of a binary number.
Technical Data
364
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
multiplexer — A device that can select one of a number of inputs and pass the logic level of that
input on to the output.
N — The negative bit in the condition code register of the CPU08. The CPU sets the negative bit
when an arithmetic operation, logical operation, or data manipulation produces a negative
result.
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.
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).
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) — An oscillator circuit in which the frequency of the oscillator is
synchronized to a reference signal.
PLL — See phase-locked loop (PLL).
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
365
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 causes a computer to perform a desired
operation or operations.
program counter (PC) — A 16-bit register in the CPU08. 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.
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.
PMC — Pulse width modulated motor control module
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.
Technical Data
366
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
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.
ROM — Read-only memory. A type of memory that can be read but cannot be changed (written).
The contents of ROM must be specified before manufacturing the MCU.
SCI — See serial communication interface module (SCI).
serial — Pertaining to sequential transmission over a single line.
serial communication interface module (SCI) — A module in the M68HC08 Family that
supports asynchronous communication.
serial peripheral interface module (SPI) — A module in the M68HC08 Family 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.
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.
SIM — See system integration module (SIM).
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 CPU08 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.
MC68HC908MR8 — Rev 4.1
Freescale Semiconductor
Technical Data
367
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.
system integration module (SIM) — One of a number of modules that handle a variety of
control functions in the modular M68HC08 Family. The SIM controls mode of operation,
resets and interrupts, and system clock distribution.
TIM — See timer interface module (TIM).
timer interface module (TIM) — A module used to relate events in a system to a point in time.
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 — Mode of low-jitter PLL operation during which the PLL is locked on a
frequency. 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.
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. Executing an opcode at an unimplemented location causes an illegal
address reset.
V — The overflow bit in the condition code register of the CPU08. The CPU08 sets the V bit when
a two's complement overflow occurs. The signed branch instructions BGT, BGE, BLE, and
BLT use the overflow bit.
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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.
X — The lower byte of the index register (H:X) in the CPU08.
Z — The zero bit in the condition code register of the CPU08. The CPU08 sets the zero bit when
an arithmetic operation, logical operation, or data manipulation produces a result of $00.
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