MOTOROLA MC68HC908AP8CFA Microcontroller Datasheet

Freescale Semiconductor, Inc...
Freescale Semiconductor, Inc.
MC68HC908AP64
MC68HC908AP32
MC68HC908AP16
MC68HC908AP8
Data Sheet
M68HC08
Microcontrollers
MC68HC908AP64/D
Rev. 2.5
10/2003
MOTOROLA.COM/SEMICONDUCTORS
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Freescale Semiconductor, Inc...
Freescale Semiconductor, Inc.
For More Information On This Product,
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Freescale Semiconductor, Inc.
Freescale Semiconductor, Inc...
MC68HC908AP64
MC68HC908AP32
MC68HC908AP16
MC68HC908AP8
Data Sheet
To provide the most up-to-date information, the revision of our
documents on the World Wide Web will be the most current. Your printed
copy may be an earlier revision. To verify you have the latest information
available, refer to:
http://motorola.com/semiconductors/
The following revision history table summarizes changes contained in
this document. For your convenience, the page number designators
have been linked to the appropriate location.
Motorola and the Stylized M Logo are registered trademarks of Motorola, Inc.
DigitalDNA is a trademark of Motorola, Inc.
This product incorporates SuperFlash® technology licensed from SST.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
© Motorola, Inc., 2003
Data Sheet
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Revision History
Revision History
Date
Revision
Level
Page
Number(s)
Description
Added MC68HC908AP16/AP8 information throughout.
Freescale Semiconductor, Inc...
October 2003
August 2003
July 2003
May 2003
Data Sheet
2.5
2.4
2.3
2.2
—
Section 10. Monitor ROM (MON) — Corrected RAM address to
$60.
167
Section 24. Electrical Specifications — Added run and wait
IDD data for 8MHz at 3V.
421
Section 24. Electrical Specifications — Updated stop IDD data.
417, 421
Removed MC68HC908AP16 references throughout.
—
Table 1-2 . Pin Functions — Added footnote for VREG.
30
5.3 Configuration Register 1 (CONFIG1) — Clarified LVIPWRD
and LVIREGD bits.
67
Section 8. Clock Generator Module (CGM), 8.7.2 Stop Mode
— Updated BSC bit behavior.
125
10.5 ROM-Resident Routines — Corrected data size limits and
control byte size for EE_READ and EE_WRITE.
168–193
Figure 12-2 . Timebase Control Register (TBCR) — Corrected
register address.
207
Section 24. Electrical Specifications — Updated.
415
Updated for fNOM = 125kHz and filter components
in CGM section.
101
Updated electricals.
415
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
List of Sections
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Section 1. General Description. . . . . . . . . . . . . . . . . . . . . . . . . . 23
Section 2. Memory Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
Section 3. Random-Access Memory (RAM) . . . . . . . . . . . . . . . 53
Section 4. FLASH Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Section 5. Configuration & Mask Option Registers
(CONFIG & MOR) . . . . . . . . . . . . . . . . . . . . . . . . . . 65
Section 6. Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . 73
Section 7. Oscillator (OSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Section 8. Clock Generator Module (CGM) . . . . . . . . . . . . . . . 101
Section 9. System Integration Module (SIM) . . . . . . . . . . . . . . 129
Section 10. Monitor ROM (MON) . . . . . . . . . . . . . . . . . . . . . . . 153
Section 11. Timer Interface Module (TIM) . . . . . . . . . . . . . . . . 181
Section 12. Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . 205
Section 13. Serial Communications Interface Module
(SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
Section 14. Infrared Serial Communications Interface
Module (IRSCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
Section 15. Serial Peripheral Interface Module (SPI) . . . . . . . 289
Section 16. Multi-Master IIC Interface (MMIIC) . . . . . . . . . . . . 319
Section 17. Analog-to-Digital Converter (ADC). . . . . . . . . . . . 345
Section 18. Input/Output (I/O) Ports. . . . . . . . . . . . . . . . . . . . . 363
Section 19. External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . 379
Section 20. Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . 387
Section 21. Computer Operating Properly (COP) . . . . . . . . . . 395
Section 22. Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . 401
Section 23. Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . 407
Section 24. Electrical Specifications . . . . . . . . . . . . . . . . . . . . 415
Section 25. Mechanical Specifications . . . . . . . . . . . . . . . . . . 433
Section 26. Ordering Information. . . . . . . . . . . . . . . . . . . . . . . 437
MC68HC908AP Family — Rev. 2.5
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List of Sections
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Table of Contents
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Section 1. General Description
1.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
1.3
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
1.4
Pin Assignment. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
1.5
Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.6
Power Supply Bypassing (VDD, VDDA, VSS, VSSA) . . . . . . . 32
1.7
Regulator Power Supply Configuration (VREG) . . . . . . . . . . . . 33
Section 2. Memory Map
2.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.2
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . 35
2.3
Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . 35
2.4
Input/Output (I/O) Section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Section 3. Random-Access Memory (RAM)
3.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
3.2
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .53
Section 4. FLASH Memory
4.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4.2
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
4.3
FLASH Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
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4.4
FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . 58
4.5
FLASH Mass Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.6
FLASH Program Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . .60
4.7
FLASH Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .62
4.7.1
FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . 62
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Section 5. Configuration & Mask Option Registers (CONFIG & MOR)
5.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
5.2
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .66
5.3
Configuration Register 1 (CONFIG1) . . . . . . . . . . . . . . . . . . . . 67
5.4
Configuration Register 2 (CONFIG2) . . . . . . . . . . . . . . . . . . . . 69
5.5
Mask Option Register (MOR) . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Section 6. Central Processor Unit (CPU)
6.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
6.3
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
6.3.1
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
6.3.2
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
6.3.3
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
6.3.4
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
6.3.5
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
6.4
Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.5
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
6.5.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .79
6.5.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
Data Sheet
6.6
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 80
6.7
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
6.8
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
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Table of Contents
Section 7. Oscillator (OSC)
7.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
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7.2
Clock Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
7.2.1
CGM Reference Clock Selection . . . . . . . . . . . . . . . . . . . . . 93
7.2.2
TBM Reference Clock Selection . . . . . . . . . . . . . . . . . . . . . 94
7.3
Internal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 94
7.4
RC Oscillator. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
7.5
X-tal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.6
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.6.1
Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . . 97
7.6.2
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . . 98
7.6.3
Oscillator Enable Signal (SIMOSCEN). . . . . . . . . . . . . . . . . 98
7.6.4
CGM Oscillator Clock (CGMXCLK) . . . . . . . . . . . . . . . . . . . 98
7.6.5
CGM Reference Clock (CGMRCLK) . . . . . . . . . . . . . . . . . . 98
7.6.6
Oscillator Clock to Time Base Module (OSCCLK) . . . . . . . . 98
7.7
Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
7.7.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
7.7.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .99
7.8
Oscillator During Break Mode. . . . . . . . . . . . . . . . . . . . . . . . . . 99
Section 8. Clock Generator Module (CGM)
8.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
8.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
8.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .102
8.3.1
Oscillator Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
8.3.2
Phase-Locked Loop Circuit (PLL) . . . . . . . . . . . . . . . . . . . 105
8.3.3
PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
8.3.4
Acquisition and Tracking Modes . . . . . . . . . . . . . . . . . . . . 107
8.3.5
Manual and Automatic PLL Bandwidth Modes. . . . . . . . . . 107
8.3.6
Programming the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
8.3.7
Special Programming Exceptions . . . . . . . . . . . . . . . . . . . 113
8.3.8
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . 113
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8.3.9
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . 114
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8.4
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
8.4.1
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . 115
8.4.2
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . 115
8.4.3
PLL Analog Ground Pin (VSSA) . . . . . . . . . . . . . . . . . . . . . 115
8.4.4
Oscillator Output Frequency Signal (CGMXCLK) . . . . . . . 115
8.4.5
CGM Reference Clock (CGMRCLK) . . . . . . . . . . . . . . . . . 115
8.4.6
CGM VCO Clock Output (CGMVCLK) . . . . . . . . . . . . . . . . 116
8.4.7
CGM Base Clock Output (CGMOUT). . . . . . . . . . . . . . . . . 116
8.4.8
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . 116
8.5
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
8.5.1
PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
8.5.2
PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . .119
8.5.3
PLL Multiplier Select Registers . . . . . . . . . . . . . . . . . . . . . 121
8.5.4
PLL VCO Range Select Register . . . . . . . . . . . . . . . . . . . .122
8.5.5
PLL Reference Divider Select Register . . . . . . . . . . . . . . . 123
8.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
8.7
Special Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
8.7.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
8.7.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
8.7.3
CGM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . 125
8.8
Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . . . . . 126
8.8.1
Acquisition/Lock Time Definitions. . . . . . . . . . . . . . . . . . . .126
8.8.2
Parametric Influences on Reaction Time . . . . . . . . . . . . . . 126
8.8.3
Choosing a Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
Section 9. System Integration Module (SIM)
9.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
9.2
SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . 131
9.2.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
9.2.2
Clock Start-up from POR or LVI Reset. . . . . . . . . . . . . . . . 132
9.2.3
Clocks in Stop Mode and Wait Mode . . . . . . . . . . . . . . . . . 133
9.3
Reset and System Initialization. . . . . . . . . . . . . . . . . . . . . . . . 133
9.3.1
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 134
Data Sheet
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9.3.2
9.3.2.1
9.3.2.2
9.3.2.3
9.3.2.4
9.3.2.5
9.3.2.6
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . 134
Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .135
Computer Operating Properly (COP) Reset. . . . . . . . . . 136
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . .137
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . 137
Monitor Mode Entry Module Reset. . . . . . . . . . . . . . . . . 137
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9.4
SIM Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
9.4.1
SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . 138
9.4.2
SIM Counter During Stop Mode Recovery . . . . . . . . . . . . . 138
9.4.3
SIM Counter and Reset States. . . . . . . . . . . . . . . . . . . . . . 138
9.5
Exception Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139
9.5.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
9.5.1.1
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
9.5.1.2
SWI Instruction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
9.5.1.3
Interrupt Status Registers . . . . . . . . . . . . . . . . . . . . . . .142
9.5.1.4
Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . 142
9.5.1.5
Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . 144
9.5.1.6
Interrupt Status Register 3 . . . . . . . . . . . . . . . . . . . . . . . 144
9.5.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
9.5.3
Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
9.5.4
Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . 145
9.6
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
9.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .146
9.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .147
9.7
SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148
9.7.1
SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 149
9.7.2
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . 150
9.7.3
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . .151
Section 10. Monitor ROM (MON)
10.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
10.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
10.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .154
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10.3.1
10.3.2
10.3.3
10.3.4
10.3.5
10.4
Entering Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .160
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
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10.5 ROM-Resident Routines. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
10.5.1 PRGRNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
10.5.2 ERARNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .172
10.5.3 LDRNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
10.5.4 MON_PRGRNGE. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
10.5.5 MON_ERARNGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
10.5.6 EE_WRITE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
10.5.7 EE_READ. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Section 11. Timer Interface Module (TIM)
11.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
11.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
11.3
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
11.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
11.4.1 TIM Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
11.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
11.4.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
11.4.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . 187
11.4.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . .188
11.4.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . 188
11.4.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . 189
11.4.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . 190
11.4.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
11.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
11.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 192
11.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
11.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .193
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11.7
TIM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 193
11.8
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
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11.9 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194
11.9.1 TIM Status and Control Register . . . . . . . . . . . . . . . . . . . . 195
11.9.2 TIM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
11.9.3 TIM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . 198
11.9.4 TIM Channel Status and Control Registers . . . . . . . . . . . . 199
11.9.5 TIM Channel Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
Section 12. Timebase Module (TBM)
12.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
12.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
12.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .206
12.4
Timebase Register Description. . . . . . . . . . . . . . . . . . . . . . . . 207
12.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
12.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
12.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
12.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
Section 13. Serial Communications Interface Module
(SCI)
13.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
13.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
13.3
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
13.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .213
13.4.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
13.4.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 216
13.4.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 218
13.4.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . 218
13.4.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
13.4.2.4
Idle Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219
13.4.2.5
Inversion of Transmitted Output. . . . . . . . . . . . . . . . . . . 220
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13.4.2.6
Transmitter Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . .220
13.4.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
13.4.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
13.4.3.2
Character Reception . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
13.4.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
13.4.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
13.4.3.5
Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . .225
13.4.3.6
Receiver Wakeup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228
13.4.3.7
Receiver Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
13.4.3.8
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
13.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
13.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .230
13.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .230
13.6
SCI During Break Module Interrupts. . . . . . . . . . . . . . . . . . . .230
13.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
13.7.1 TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
13.7.2 RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
13.8 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
13.8.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
13.8.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
13.8.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
13.8.4 SCI Status Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
13.8.5 SCI Status Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 244
13.8.6 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
13.8.7 SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . .246
Section 14. Infrared Serial Communications
Interface Module (IRSCI)
Data Sheet
14.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
14.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
14.3
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
14.4
IRSCI Module Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
14.5
Infrared Functional Description. . . . . . . . . . . . . . . . . . . . . . . . 253
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14.5.1
14.5.2
Infrared Transmit Encoder . . . . . . . . . . . . . . . . . . . . . . . . . 254
Infrared Receive Decoder . . . . . . . . . . . . . . . . . . . . . . . . . 254
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14.6 SCI Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . .255
14.6.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
14.6.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
14.6.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
14.6.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . 258
14.6.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
14.6.2.4
Idle Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
14.6.2.5
Transmitter Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . .260
14.6.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
14.6.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
14.6.3.2
Character Reception . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
14.6.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
14.6.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
14.6.3.5
Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . .264
14.6.3.6
Receiver Wakeup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
14.6.3.7
Receiver Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
14.6.3.8
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
14.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
14.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269
14.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .269
14.8
SCI During Break Module Interrupts. . . . . . . . . . . . . . . . . . . .269
14.9 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 270
14.9.1 PTC6/SCTxD (Transmit Data) . . . . . . . . . . . . . . . . . . . . . . 270
14.9.2 PTC7/SCRxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . 270
14.10 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271
14.10.1 IRSCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . 272
14.10.2 IRSCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . 274
14.10.3 IRSCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . 277
14.10.4 IRSCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . .279
14.10.5 IRSCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . .283
14.10.6 IRSCI Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
14.10.7 IRSCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . 285
14.10.8 IRSCI Infrared Control Register . . . . . . . . . . . . . . . . . . . . . 288
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Section 15. Serial Peripheral Interface Module (SPI)
15.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
15.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
15.3
Pin Name Conventions and I/O Register Addresses . . . . . . . 290
15.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .291
15.4.1 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
15.4.2 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
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15.5 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .294
15.5.1 Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . 294
15.5.2 Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . 295
15.5.3 Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . 297
15.5.4 Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . 298
15.6
Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . 300
15.7 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
15.7.1 Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
15.7.2 Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
15.8
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .305
15.9
Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 307
15.10 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
15.10.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308
15.10.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .308
15.11 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 309
15.12 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
15.12.1 MISO (Master In/Slave Out) . . . . . . . . . . . . . . . . . . . . . . . . 310
15.12.2 MOSI (Master Out/Slave In) . . . . . . . . . . . . . . . . . . . . . . . . 310
15.12.3 SPSCK (Serial Clock). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
15.12.4 SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 311
15.12.5 CGND (Clock Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
15.13 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
15.13.1 SPI Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 313
15.13.2 SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . 315
15.13.3 SPI Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
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Section 16. Multi-Master IIC Interface (MMIIC)
16.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
16.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
16.3
I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
16.4
Multi-Master IIC System Configuration . . . . . . . . . . . . . . . . . . 322
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16.5 Multi-Master IIC Bus Protocol . . . . . . . . . . . . . . . . . . . . . . . . . 322
16.5.1 START Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
16.5.2 Slave Address Transmission . . . . . . . . . . . . . . . . . . . . . . .323
16.5.3 Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
16.5.4 Repeated START Signal . . . . . . . . . . . . . . . . . . . . . . . . . . 324
16.5.5 STOP Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
16.5.6 Arbitration Procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
16.5.7 Clock Synchronization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
16.5.8 Handshaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
16.5.9 Packet Error Code . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
16.6 MMIIC I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
16.6.1 MMIIC Address Register (MMADR) . . . . . . . . . . . . . . . . . . 326
16.6.2 MMIIC Control Register 1 (MMCR1) . . . . . . . . . . . . . . . . . 328
16.6.3 MMIIC Control Register 2 (MMCR2) . . . . . . . . . . . . . . . . . 330
16.6.4 MMIIC Status Register (MMSR). . . . . . . . . . . . . . . . . . . . . 332
16.6.5 MMIIC Data Transmit Register (MMDTR) . . . . . . . . . . . . . 334
16.6.6 MMIIC Data Receive Register (MMDRR). . . . . . . . . . . . . . 335
16.6.7 MMIIC CRC Data Register (MMCRCDR). . . . . . . . . . . . . . 336
16.6.8 MMIIC Frequency Divider Register (MMFDR) . . . . . . . . . . 337
16.7 Program Algorithm. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 338
16.7.1 Data Sequence. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .339
16.8 SMBus Protocols with PEC and without PEC. . . . . . . . . . . . . 340
16.8.1 Quick Command. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
16.8.2 Send Byte. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
16.8.3 Receive Byte . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
16.8.4 Write Byte/Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
16.8.5 Read Byte/Word . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
16.8.6 Process Call . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
16.8.7 Block Read/Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
16.9
SMBus Protocol Implementation . . . . . . . . . . . . . . . . . . . . . . 343
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Section 17. Analog-to-Digital Converter (ADC)
17.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
17.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
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17.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347
17.3.1 ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
17.3.2 Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347
17.3.3 Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
17.3.4 Continuous Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
17.3.5 Auto-Scan Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
17.3.6 Result Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
17.3.7 Data Register Interlocking . . . . . . . . . . . . . . . . . . . . . . . . . 351
17.3.8 Monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
17.4
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352
17.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
17.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352
17.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .352
17.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 352
17.6.1 ADC Voltage In (VADIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
17.6.2 ADC Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . 353
17.6.3 ADC Analog Ground Pin (VSSA). . . . . . . . . . . . . . . . . . . . . 353
17.6.4 ADC Voltage Reference High Pin (VREFH). . . . . . . . . . . . . 353
17.6.5 ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . . . 353
17.7 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
17.7.1 ADC Status and Control Register. . . . . . . . . . . . . . . . . . . .354
17.7.2 ADC Clock Control Register. . . . . . . . . . . . . . . . . . . . . . . . 356
17.7.3 ADC Data Register 0 (ADRH0 and ADRL0). . . . . . . . . . . . 358
17.7.4 ADC Auto-Scan Mode Data Registers (ADRL1–ADRL3). . 360
17.7.5 ADC Auto-Scan Control Register (ADASCR). . . . . . . . . . . 360
Section 18. Input/Output (I/O) Ports
18.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
18.2 Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
18.2.1 Port A Data Register (PTA) . . . . . . . . . . . . . . . . . . . . . . . . 366
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18.2.2
18.2.3
Data Direction Register (DDRA). . . . . . . . . . . . . . . . . . . . . 367
Port-A LED Control Register (LEDA) . . . . . . . . . . . . . . . . . 369
18.3 Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
18.3.1 Port B Data Register (PTB) . . . . . . . . . . . . . . . . . . . . . . . . 370
18.3.2 Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . . 371
18.4 Port C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
18.4.1 Port C Data Register (PTC) . . . . . . . . . . . . . . . . . . . . . . . . 373
18.4.2 Data Direction Register C (DDRC). . . . . . . . . . . . . . . . . . . 374
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18.5 Port D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 376
18.5.1 Port D Data Register (PTD) . . . . . . . . . . . . . . . . . . . . . . . . 376
18.5.2 Data Direction Register D (DDRD). . . . . . . . . . . . . . . . . . . 377
Section 19. External Interrupt (IRQ)
19.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
19.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
19.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .380
19.4
IRQ1 and IRQ2 Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
19.5
IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . 383
19.6 IRQ Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 383
19.6.1 IRQ1 Status and Control Register . . . . . . . . . . . . . . . . . . . 384
19.6.2 IRQ2 Status and Control Register . . . . . . . . . . . . . . . . . . . 385
Section 20. Keyboard Interrupt Module (KBI)
20.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387
20.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387
20.3
I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 388
20.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .388
20.4.1 Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 390
20.5 Keyboard Interrupt Registers . . . . . . . . . . . . . . . . . . . . . . . . . 391
20.5.1 Keyboard Status and Control Register. . . . . . . . . . . . . . . . 391
20.5.2 Keyboard Interrupt Enable Register . . . . . . . . . . . . . . . . . . 392
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20.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393
20.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .393
20.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .393
20.7
Keyboard Module During Break Interrupts . . . . . . . . . . . . . . . 393
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Section 21. Computer Operating Properly (COP)
21.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395
21.2
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .395
21.3 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
21.3.1 ICLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
21.3.2 STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396
21.3.3 COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .397
21.3.4 Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
21.3.5 Internal Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
21.3.6 Reset Vector Fetch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
21.3.7 COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397
21.3.8 COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . 398
21.4
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398
21.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399
21.6
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399
21.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399
21.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399
21.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .399
21.8
COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . 400
Section 22. Low-Voltage Inhibit (LVI)
22.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
22.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 401
22.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .402
22.3.1 Low VDD Detector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
22.3.2 Low VREG Detector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 403
22.3.3 Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
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22.3.4
22.3.5
Forced Reset Operation . . . . . . . . . . . . . . . . . . . . . . . . . . .404
Voltage Hysteresis Protection . . . . . . . . . . . . . . . . . . . . . . 404
22.4
LVI Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 404
22.5
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405
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22.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405
22.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405
22.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .405
Section 23. Break Module (BRK)
23.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
23.2
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 407
23.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .408
23.3.1 Flag Protection During Break Interrupts . . . . . . . . . . . . . . . 409
23.3.2 CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . .409
23.3.3 TIMI and TIM2 During Break Interrupts . . . . . . . . . . . . . . . 410
23.3.4 COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . 410
23.4 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410
23.4.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .410
23.4.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .410
23.5 Break Module Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 410
23.5.1 Break Status and Control Register. . . . . . . . . . . . . . . . . . . 411
23.5.2 Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 412
23.5.3 SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 412
23.5.4 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . 414
Section 24. Electrical Specifications
24.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 415
24.2
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . 415
24.3
Functional Operating Range. . . . . . . . . . . . . . . . . . . . . . . . . . 416
24.4
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 416
24.5
5V DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . 417
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24.6
5V Control Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .419
24.7
5V Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 419
24.8
5V ADC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . 420
24.9
3V DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . 421
24.10 3V Control Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .422
24.11 3V Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . 423
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24.12 3V ADC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . 424
24.13 MMIIC Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . . . 425
24.14 CGM Electrical Specification . . . . . . . . . . . . . . . . . . . . . . . . . 427
24.15 5V SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 428
24.16 3V SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 429
24.17 FLASH Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . 432
Section 25. Mechanical Specifications
25.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 433
25.2
48-Pin Low-Profile Quad Flat Pack (LQFP) . . . . . . . . . . . . . . 434
25.3
44-Pin Quad Flat Pack (QFP). . . . . . . . . . . . . . . . . . . . . . . . . 435
25.4
42-Pin Shrink Dual In-Line Package (SDIP) . . . . . . . . . . . . . . 436
Section 26. Ordering Information
Data Sheet
26.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437
26.2
MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 437
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Data Sheet – MC68HC908AP Family
Section 1. General Description
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1.1 Introduction
The MC68HC908AP64 is a member of the low-cost, high-performance
M68HC08 Family of 8-bit microcontroller units (MCUs). 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.
Table 1-1. Summary of Device Variations
Device
RAM Size
(bytes)
FLASH Memory Size
(bytes)
MC68HC908AP64
2,048
62,368
MC68HC908AP32
2,048
32,768
MC68HC908AP16
1,024
16,384
MC68HC908AP8
1,024
8,192
1.2 Features
Features of the MC68HC908AP64 include the following:
•
High-performance M68HC08 architecture
•
Fully upward-compatible object code with M6805, M146805, and
M68HC05 Families
•
Maximum internal bus frequency:
– 8-MHz at 5V or 3V operating voltage
•
Clock input options:
– RC-oscillator
– 32-kHz crystal-oscillator with 32MHz internal phase-lock-loop
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General Description
•
User program FLASH memory with security1 feature
– 62,368 bytes for MC68HC908AP64
– 32,768 bytes for MC68HC908AP32
– 16,384 bytes for MC68HC908AP16
– 8,192 bytes for MC68HC908AP8
•
On-chip RAM
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– 2,048 bytes for MC68HC908AP64 and MC68HC908AP32
– 1,024 bytes for MC68HC908AP16 and MC68HC908AP8
•
Two 16-bit, 2-channel timer interface modules (TIM1 and TIM2)
with selectable input capture, output compare, and PWM
capability on each channel
•
Timebase module
•
Serial communications interface module 1 (SCI)
•
Serial communications interface module 2 (SCI) with
infrared (IR) encoder/decoder
•
Serial peripheral interface module (SPI)
•
System management bus (SMBus), version 1.0/1.1
(multi-master IIC bus)
•
8-channel, 10-bit analog-to-digital converter (ADC)
•
IRQ1 external interrupt pin with integrated pullup
•
IRQ2 external interrupt pin with programmable pullup
•
8-bit keyboard wakeup port with integrated pullup
•
32 general-purpose input/output (I/O) pins:
– 31 shared-function I/O pins
– 8 LED drivers (sink)
– 6 × 25mA open-drain I/O with pullup
•
Low-power design (fully static with stop and wait modes)
1. No security feature is absolutely secure. However, Motorola’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
Data Sheet
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General Description
MCU Block Diagram
•
Master reset pin (with integrated pullup) and power-on reset
•
System protection features
– Optional computer operating properly (COP) reset, driven by
internal RC oscillator
– Low-voltage detection with optional reset or interrupt
– Illegal opcode detection with reset
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– Illegal address detection with reset
•
48-pin low quad flat pack (LQFP), 44-pin quad flat pack (QFP),
and 42-pin shrink dual-in-line package (SDIP)
•
Specific features of the MC68HC908AP64 in 42-pin SDIP are:
– 30 general-purpose l/Os only
– External interrupt on IRQ1 only
Features of the CPU08 include the following:
•
Enhanced HC05 programming model
•
Extensive loop control functions
•
16 addressing modes (eight more than the HC05)
•
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
•
Efficient C language support
1.3 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908AP64.
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General Description
PORTA
PTA7/ADC7 ‡
PTA6/ADC6 ‡
PTA5/ADC5 ‡
PTA4/ADC4 ‡
PTA3/ADC3 ‡
PTA2/ADC2 ‡
PTA1/ADC1 ‡
PTA0/ADC0 ‡
PORTB
PTB7/T2CH1
PTB6/T2CH0
PTB5/T1CH1
PTB4/T1CH0
PTB3/RxD †
PTB2/TxD †
PTB1/SCL †
PTB0/SDA †
PORTC
PTC7/SCRxD †
PTC6/SCTxD †
PTC5/SPSCK
PTC4/SS
PTC3/MOSI
PTC2/MISO
PTC1 #
PTC0/IRQ2 **#
PORTD
INTERNAL BUS
PTD7/KBI7 ***
PTD6/KBI6 ***
PTD5/KBI5 ***
PTD4/KBI4 ***
PTD3/KBI3 ***
PTD2/KBI2 ***
PTD1/KBI1 ***
PTD0/KBI0 ***
M68HC08 CPU
ARITHMETIC/LOGIC
UNIT (ALU)
CONTROL AND STATUS REGISTERS — 96 BYTES
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
DDRA
CPU
REGISTERS
TIMEBASE
MODULE
USER FLASH — (SEE TABLE)
2-CHANNEL TIMER INTERFACE
MODULE 1
USER RAM — (SEE TABLE)
USER FLASH VECTOR SPACE — 48 BYTES
OSCILLATORS AND
CLOCK GENERATOR MODULE
DDRB
Freescale Semiconductor, Inc...
MONITOR ROM — 959 BYTES
2-CHANNEL TIMER INTERFACE
MODULE 2
SERIAL COMMUNICATIONS
INTERFACE MODULE 1
INTERNAL OSCILLATOR
X-TAL OSCILLATOR
CGMXFC
PHASE-LOCKED LOOP
* RST
SYSTEM INTEGRATION
MODULE
* IRQ1
** IRQ2
VDD
VDDA
VSS
VSSA
SERIAL PERIPHERAL
INTERFACE MODULE
COMPUTER OPERATING
PROPERLY MODULE
KEYBOARD INTERRUPT
MODULE
POWER-ON RESET
MODULE
LOW-VOLTAGE INHIBIT
MODULE
VREG
VREFH
VREFL
SERIAL COMMUNICATIONS
INTERFACE MODULE 2
(WITH INFRARED
MODULATOR/DEMODULATOR)
EXTERNAL INTERRUPT
MODULE
POWER
ADC REFERENCE
DDRC
OSC2
MULTI-MASTER IIC (SMBUS)
INTERFACE MODULE
DDRD
OSC1
RC OSCILLATOR
* Pin contains integrated pullup device.
** Pin contains configurable pullup device.
*** Pin contains integrated pullup device when configured as KBI.
†
Pin is open-drain when configured as output.
‡
LED direct sink pin.
#
Pin not bonded on 42-pin SDIP.
.
DEVICE
USER RAM
(bytes)
USER FLASH
(bytes)
MC68HC908AP64
2,048
62,368
MC68HC908AP32
2,048
32,768
MC68HC908AP16
1,024
16,384
MC68HC908AP8
1,024
8,192
Figure 1-1. MC68HC908AP64 Block Diagram
Data Sheet
MC68HC908AP Family — Rev. 2.5
26
MOTOROLA
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Freescale Semiconductor, Inc.
General Description
Pin Assignment
PTD0/KBI0
PTD1/KBI1
PTD2/KBI2
VDDA
VSSA
PTD3/KBI3
PTD4/KBI4
PTD5/KBI5
PTD6/KBI6
46
45
44
43
42
41
40
39
38
37 PTD7/KBI7
PTB7/T2CH1
36 VREFH
NC
VSS
7
30
PTA1/ADC1
PTB4/T1CH0
8
29
PTA2/ADC2
IRQ1
9
28
PTA3/ADC3
PTB3/RxD
10
27
PTA4/ADC4
RST
11
26
PTA5/ADC5
25 PTA6/ADC6
NC 24
PTB1/SCL 13
PTB2/TxD 12
23
31
PTA7/ADC7
6
22
OSC2
PTC0/IRQ2
PTA0/ADC0
21
32
PTC1
5
20
OSC1
PTC2/MISO
NC
19
33
PTC3/MOSI
4
18
VDD
PTC4/SS
NC
17
34
PTC5/SPSCK
3
16
PTB5/T1CH1
PTC6/SCTxD
VREFL
15
35
PTC7/SCRxD
2
14
VREG
PTB0/SDA
Freescale Semiconductor, Inc...
PTB6/T2CH0 1
47
48 CGMXFC
1.4 Pin Assignment
NC: No connection
Figure 1-2. 48-Pin LQFP Pin Assignments
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
27
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Freescale Semiconductor, Inc.
PTD0/KBI0
PTD1/KBI1
PTD2/KBI2
VDDA
VSSA
PTD3/KBI3
PTD4/KBI4
PTD5/KBI5
42
41
40
39
38
37
36
35
34 PTD6/KBI6
PTB7/T2CH1
33 PTD7/KBI7
6
28
PTA2/ADC2
VSS
7
27
PTA3/ADC3
PTB4/T1CH0
8
26
PTA4/ADC4
IRQ1
9
25
PTA5/ADC5
10
24
PTA6/ADC6
PTB2/TxD 12
RST 11
23 PTA7/ADC7
PTC0/IRQ2 22
PTB3/RxD
21
OSC2
PTC1
PTA1/ADC1
20
29
PTC2/MISO
5
19
OSC1
PTC3/MOSI
PTA0/ADC0
18
30
PTC4/SS
4
17
VDD
PTC5/SPSCK
VREFL
16
31
PTC6/SCTxD
3
15
PTB5/T1CH1
PTC7/SCRxD
VREFH
14
32
PTB0/SDA
2
13
VREG
PTB1/SCL
Freescale Semiconductor, Inc...
PTB6/T2CH0 1
43
44 CGMXFC
General Description
Figure 1-3. 44-Pin QFP Pin Assignments
Data Sheet
MC68HC908AP Family — Rev. 2.5
28
MOTOROLA
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Freescale Semiconductor, Inc.
Freescale Semiconductor, Inc...
General Description
Pin Assignment
PTD2/KBI2
1
42
VDDA
PTD1/KBI1
2
41
VSSA
PTD0/KBI0
3
40
PTD3/KBI3
PTB7/T2CH1
4
39
PTD4/KBI4
CGMXFC
5
38
PTD5/KBI5
PTB6/T2CH0
6
37
PTD6/KBI6
VREG
7
36
PTD7/KBI7
PTB5/T1CH1
8
35
VREFH
VDD
9
34
VREFL
OSC1
10
33
PTA0/ADC0
OSC2
11
32
PTA1/ADC1
VSS
12
31
PTA2/ADC2
PTB4/T1CH0
13
30
PTA3/ADC3
IRQ1
14
29
PTA4/ADC4
PTB3/RxD
15
28
PTA5/ADC5
RST
16
27
PTA6/ADC6
PTB2/TxD
17
26
PTA7/ADC7
PTB1/SCL
18
25
PTC2/MISO
PTB0/SDA
19
24
PTC3/MOSI
PTC7/SCRxD
20
23
PTC4/SS
PTC6/SCTxD
21
22
PTC5/SPSCK
Pins not available on 42-pin package
Internal connection
PTC0/IRQ2
Unconnected
PTC1
Unconnected
Figure 1-4. 42-Pin SDIP Pin Assignment
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
29
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Freescale Semiconductor, Inc.
General Description
1.5 Pin Functions
Description of the pin functions are provided in Table 1-2.
Table 1-2. Pin Functions
Freescale Semiconductor, Inc...
PIN NAME
PIN DESCRIPTION
IN/OUT
VOLTAGE
LEVEL
In
4.5 to 5.5
or
2.7 to 3.3
Out
0V
In
VDD
Out
VSS
VDD
Power supply.
VSS
Power supply ground.
VDDA
Power supply for analog circuits.
VSSA
Power supply ground for analog circuits.
VREFH
ADC input reference high.
In
VDDA
VREFL
ADC input reference low.
Out
VSSA
VREG
Internal (2.5V) regulator output.
Require external capacitors for decoupling.
Out
2.5V(1)
RST
Reset input, active low; with internal pullup and schmitt
trigger input.
In
VDD
External IRQ1 pin; with internal pullup and schmitt trigger
input.
In
VDD
Used for mode entry selection.
In
VDD to VTST
Crystal or RC oscillator input.
In
VREG
Crystal OSC option: crystal oscillator output; inverted
OSC1.
Out
VREG
RC OSC option: bus clock output.
Out
VREG
Internal OSC option: bus clock output.
Out
VREG
CGM external filter capacitor connection.
In/Out
Analog
8-bit general purpose I/O port.
In/Out
VDD
In
VREFH
Out
VDD
IRQ1
OSC1
OSC2
CGMXFC
PTA0/ADC0
:
PTA7/ADC7
Pins as ADC inputs, ADC0–ADC7.
Each pin has high current sink for LED.
Data Sheet
MC68HC908AP Family — Rev. 2.5
30
MOTOROLA
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Freescale Semiconductor, Inc.
General Description
Pin Functions
Table 1-2. Pin Functions
PIN DESCRIPTION
IN/OUT
VOLTAGE
LEVEL
8-bit general purpose I/O port; PTB0–PTB3 are open drain
when configured as output. PTB4–PTB7 have schmitt
trigger inputs.
In/Out
VDD
PTB0 as SDA of MMIIC.
In/Out
VDD
PTB1 as SCL of MMIIC.
In/Out
VDD
Out
VDD
In
VDD
PTB4 as T1CH0 of TIM1.
In/Out
VDD
PTB5 as T1CH1 of TIM1.
In/Out
VDD
PTB6 as T2CH0 of TIM2.
In/Out
VDD
PTB7 as T2CH1 of TIM2.
In/Out
VDD
8-bit general purpose I/O port; PTC6 and PTC7 are open
drain when configured as output.
In/Out
VDD
PTC0 is shared with IRQ2 and has schmitt trigger input.
In
VDD
PTC2/MISO
PTC2 as MISO of SPI.
In
VDD
PTC3/MOSI
PTC3 as MOSI of SPI.
Out
VDD
In
VDD
In/Out
VDD
Out
VDD
In
VDD
In/Out
VDD
In
VDD
PIN NAME
PTB0/SDA
PTB1/SCL
Freescale Semiconductor, Inc...
PTB2/TxD
PTB3/RxD
PTB4/T1CH0
PTB5/T1CH1
PTB2 as TxD of SCI; open drain output.
PTB3 as RxD of SCI.
PTB6/T2CH0
PTB7/T2CH1
PTC0/IRQ2
PTC1
PTC4/SS
PTC4 as SS of SPI.
PTC5/SPSCK
PTC6/SCTxD
PTC7/SCRxD
PTC5 as SPSCK of SPI.
PTC6 as SCTxD of IRSCI; open drain output.
PTC7 as SCRxD of IRSCI.
PTD0/KBI0
:
PTD7/KBI7
8-bit general purpose I/O port with schmitt trigger inputs.
Pins as keyboard interrupts (with pullup), KBI0–KBI7.
Notes:
1. See Section 24. Electrical Specifications for VREG tolerance.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
31
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Freescale Semiconductor, Inc.
General Description
1.6 Power Supply Bypassing (VDD, VDDA, VSS, VSSA)
VDD and VSS are the power supply and ground pins, the MCU operates
from a single power supply together with an on chip voltage regulator.
Freescale Semiconductor, Inc...
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 1-5
shows. Place the bypass capacitors as close to the MCU power pins as
possible. Use high-frequency-response ceramic capacitor for CBYPASS,
CBULK are optional bulk current bypass capacitors for use in applications
that require the port pins to source high current level.
VDDA and VSSA are the power supply and ground pins for the analog
circuits of the MCU. These pins should be decoupled as per the digital
power supply pins.
MCU
VSS
VDD
C1(a)
0.1 µF
VDD
VSSA
VDDA
C1(b)
0.1 µF
+
+
C2(a)
C2(b)
VDD
NOTE: Component values shown represent typical applications.
Figure 1-5. Power Supply Bypassing
Data Sheet
MC68HC908AP Family — Rev. 2.5
32
MOTOROLA
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General Description
Regulator Power Supply Configuration (VREG)
1.7 Regulator Power Supply Configuration (VREG)
VREG is the output from the on-chip regulator. All internal logics, except
for the I/O pads, are powered by VREG output. VREG requires an external
ceramic bypass capacitor of 100 nF as Figure 1-6 shows. Place the
bypass capacitor as close to the VREG pin as possible.
Freescale Semiconductor, Inc...
MCU
VREG
VSS
CVREGBYPASS
100 nF
Figure 1-6. Regulator Power Supply Bypassing
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
33
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Freescale Semiconductor, Inc.
Freescale Semiconductor, Inc...
General Description
Data Sheet
MC68HC908AP Family — Rev. 2.5
34
MOTOROLA
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Freescale Semiconductor, Inc.
Data Sheet – MC68HC908AP Family
Section 2. Memory Map
Freescale Semiconductor, Inc...
2.1 Introduction
The CPU08 can address 64k-bytes of memory space. The memory map,
shown in Figure 2-1, includes:
•
62,368 bytes of user FLASH — MC68HC908AP64
32,768 bytes of user FLASH — MC68HC908AP32
16,384 bytes of user FLASH — MC68HC908AP16
8,192 bytes of user FLASH — MC68HC908AP8
•
2,048 bytes of RAM — MC68HC908AP64 and MC68HC908AP32
1,024 bytes of RAM — MC68HC908AP16 and MC68HC908AP8
•
48 bytes of user-defined vectors
•
959 bytes of monitor ROM
2.2 Unimplemented Memory Locations
Accessing an unimplemented location can cause an illegal address
reset if illegal address resets are enabled. In the memory map
(Figure 2-1) and in register figures in this document, unimplemented
locations are shaded.
2.3 Reserved Memory Locations
Accessing a reserved location can have unpredictable effects on MCU
operation. In the Figure 2-1 and in register figures in this document,
reserved locations are marked with the word Reserved or with the
letter R.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
35
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Freescale Semiconductor, Inc.
Memory Map
2.4 Input/Output (I/O) Section
Freescale Semiconductor, Inc...
Most of the control, status, and data registers are in the zero page area
of $0000–$005F. Additional I/O registers have these addresses:
•
$FE00; SIM break status register, SBSR
•
$FE01; SIM reset status register, SRSR
•
$FE02; Reserved
•
$FE03; SIM break flag control register, SBFCR
•
$FE04; interrupt status register 1, INT1
•
$FE05; interrupt status register 2, INT2
•
$FE06; interrupt status register 3, INT3
•
$FE07; Reserved
•
$FE08; FLASH control register, FLCR
•
$FE09; FLASH block protect register, FLBPR
•
$FE0A; Reserved
•
$FE0B; Reserved
•
$FE0C; Break address register high, BRKH
•
$FE0D; Break address register low, BRKL
•
$FE0E; Break status and control register, BRKSCR
•
$FE0F; LVI Status register, LVISR
•
$FFCF; Mask option register, MOR (FLASH register)
•
$FFFF; COP control register, COPCTL
Data registers are shown in Figure 2-2. Table 2-1 is a list of vector
locations.
Data Sheet
MC68HC908AP Family — Rev. 2.5
36
MOTOROLA
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Freescale Semiconductor, Inc.
Memory Map
Input/Output (I/O) Section
$0000
↓
$005F
$0060
↓
$085F
$0860
I/O Registers
96 Bytes
MC68HC908AP32
RAM
2,048 Bytes
(MC68HC908AP64)
RAM
2,048 Bytes
MC68HC908AP16
$0060
↓
$085F
$0860
RAM
1,024 Bytes
Unimplemented
1,024 Bytes
Freescale Semiconductor, Inc...
↓
FLASH Memory
62,368 Bytes
(MC68HC908AP64)
↓
$885F
$8860
Unimplemented
29,600 Bytes
RAM
1,024 Bytes
Unimplemented
1,024 Bytes
FLASH Memory
8,192 Bytes
$0060
$045F
$0860
$285F
$2860
$485F
$4860
↓
Unimplemented
45,984 Bytes
$FBFF
$FC00
↓
$FDFF
$FE00
$FE01
$FE02
$FE03
$FE04
$FE05
$FE06
$FE07
$FE08
$FE09
$FE0A
$FE0B
$FE0C
$FE0D
$FE0E
$FE0F
$FE10
↓
$FFCE
$FFCF
$FFD0
↓
$FFFF
$0060
$045F
$0860
FLASH Memory
16,384 Bytes
FLASH Memory
32,768 Bytes
MC68HC908AP8
↓
Unimplemented
54,176 Bytes
↓
↓
$FBFF
$FBFF
$FBFF
Monitor ROM 2
512 Bytes
SIM Break Status Register
SIM Reset Status Register
Reserved
SIM Break Flag Control Register
Interrupt Status Register 1
Interrupt Status Register 2
Interrupt Status Register 3
Reserved
FLASH Control Register
FLASH Block Protect Register
Reserved
Reserved
Break Address Register High
Break Address Register Low
Break Status and Control Register
LVI Status Register
Monitor ROM 1
447 Bytes
Mask Option Register
FLASH Vectors
48 Bytes
Figure 2-1. Memory Map
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
37
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Freescale Semiconductor, Inc.
Memory Map
Addr.
Register Name
$0000
Read:
Port A Data Register
Write:
(PTA)
Reset:
Read:
Port B Data Register
Write:
(PTB)
Reset:
Freescale Semiconductor, Inc...
$0001
Read:
Port C Data Register
Write:
(PTC)
Reset:
$0002
Read:
Port D Data Register
Write:
(PTD)
Reset:
$0003
$0004
$0005
$0006
$0007
Bit 7
6
5
4
3
2
1
Bit 0
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
PTC2
PTC1
PTC0
PTD2
PTD1
PTD0
Unaffected by reset
PTB7
PTB6
PTB5
PTB4
PTB3
Unaffected by reset
PTC7
PTC6
PTC5
PTC4
PTC3
Unaffected by reset
PTD7
PTD6
PTD5
PTD4
PTD3
Unaffected by reset
Read:
DDRA7
Data Direction Register A
Write:
(DDRA)
Reset:
0
Read:
DDRB7
Data Direction Register B
Write:
(DDRB)
Reset:
0
Read:
DDRC7
Data Direction Register C
Write:
(DDRC)
Reset:
0
Read:
DDRD7
Data Direction Register D
Write:
(DDRD)
Reset:
0
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
0
DDRD6
DDRD5
DDRD4
DDRD3
DDRD2
DDRD1
DDRD0
0
0
0
0
0
0
0
= Unimplemented
R
Read:
$0008
Unimplemented
Write:
Reset:
Read:
$0009
Unimplemented Write:
Reset:
U = Unaffected
X = Indeterminate
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 12)
Data Sheet
MC68HC908AP Family — Rev. 2.5
38
MOTOROLA
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Memory Map
Input/Output (I/O) Section
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
LEDA7
LEDA6
LEDA5
LEDA4
LEDA3
LEDA2
LEDA1
LEDA0
0
0
0
0
0
0
0
0
SPRIE
R
SPMSTR
CPOL
CPHA
SPWOM
SPE
SPTIE
0
0
1
0
1
0
0
0
OVRF
MODF
SPTE
MODFEN
SPR1
SPR0
Read:
$000A
Unimplemented Write:
Reset:
Read:
Unimplemented Write:
$000B
Freescale Semiconductor, Inc...
Reset:
Read:
Port-A LED Control
Register Write:
(LEDA)
Reset:
$000C
Read:
$000D
Unimplemented Write:
Reset:
Read:
$000E
Unimplemented Write:
Reset:
Read:
$000F
Unimplemented Write:
Reset:
$0010
$0011
Read:
SPI Control Register
Write:
(SPCR)
Reset:
Read:
SPI Status and Control
Register Write:
(SPSCR)
Reset:
Read:
SPI Data Register
Write:
(SPDR)
Reset:
$0012
$0013
SPRF
0
0
0
0
1
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
Unaffected by reset
Read:
LOOPS
SCI Control Register 1
Write:
(SCC1)
Reset:
0
U = Unaffected
ERRIE
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
= Unimplemented
R
X = Indeterminate
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 12)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
39
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Freescale Semiconductor, Inc.
Memory Map
Addr.
$0014
Freescale Semiconductor, Inc...
$0015
$0016
$0017
Register Name
Read:
SCI Control Register 2
Write:
(SCC2)
Reset:
4
3
2
1
Bit 0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
T8
DMARE
DMATE
ORIE
NEIE
FEIE
PEIE
U
U
0
0
0
0
0
0
Read:
SCI Status Register 1
Write:
(SCS1)
Reset:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
Read:
SCI Status Register 2
Write:
(SCS2)
Reset:
0
0
0
0
0
0
BKF
RPF
0
0
0
0
0
0
0
0
Read:
SCI Data Register
Write:
(SCDR)
Reset:
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
Read:
SCI Baud Rate Register
Write:
(SCBR)
Reset:
0
0
0
0
Unaffected by reset
Read:
Keyboard Status and
Control Register Write:
(KBSCR)
Reset:
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
0
0
KEYF
0
IMASK
MODE
ACK
Read:
Keyboard Interrupt
Enable Register Write:
(KBIER)
Reset:
$001B
$001D
5
R8
$001A
$001C
6
Read:
SCI Control Register 3
Write:
(SCC3)
Reset:
$0018
$0019
Bit 7
Read:
IRQ2 Status and Control
Register Write:
(INTSCR2)
Reset:
0
0
0
0
0
0
0
0
KBIE7
KBIE6
KBIE5
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
0
0
0
0
0
IRQ2F
0
IMASK2
MODE2
0
0
0
0
0
SCIBDSRC
0
0
0
0
= Unimplemented
R
0
0
Read: STOP_
Configuration Register 2
Write: ICLKDIS
(CONFIG2)†
Reset:
0
PUC0ENB
0
STOP_
RCLKEN
0
ACK2
0
0
0
STOP_
OSCCLK1 OSCCLK0
XCLKEN
0
0
† One-time writable register after each reset.
U = Unaffected
X = Indeterminate
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 12)
Data Sheet
MC68HC908AP Family — Rev. 2.5
40
MOTOROLA
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Memory Map
Input/Output (I/O) Section
Addr.
$001E
$001F
Register Name
Read:
IRQ1 Status and Control
Register Write:
(INTSCR1)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
IRQ1F
0
IMASK1
MODE1
0
0
0
SSREC
STOP
COPD
0
0
0
PS2
PS1
PS0
ACK1
0
Read:
COPRS
Configuration Register 1
Write:
(CONFIG1)†
Reset:
0
0
0
0
0
LVISTOP LVIRSTD LVIPWRD LVIREGD
0
0
TOIE
TSTOP
0
0
0
0
Freescale Semiconductor, Inc...
† One-time writable register after each reset.
$0020
$0021
$0022
$0023
$0024
$0025
Read:
Timer 1 Status and
Control Register Write:
(T1SC)
Reset:
TOF
0
0
1
0
0
0
0
0
Read:
Timer 1 Counter
Register High Write:
(T1CNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
Timer 1 Counter
Register Low Write:
(T1CNTL)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
1
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
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Read:
Timer 1 Counter Modulo
Register High Write:
(T1MODH)
Reset:
Read:
Timer 1 Counter Modulo
Register Low Write:
(T1MODL)
Reset:
Read:
Timer 1 Channel 0 Status
and Control Register Write:
(T1SC0)
Reset:
$0026
$0027
Read:
Timer 1 Channel 0
Register High Write:
(T1CH0H)
Reset:
Read:
Timer 1 Channel 0
Register Low Write:
(T1CH0L)
Reset:
U = Unaffected
0
CH0F
0
TRST
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
X = Indeterminate
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 12)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
41
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Memory Map
Addr.
$0028
Register Name
Read:
Timer 1 Channel 1 Status
and Control Register Write:
(T1SC1)
Reset:
Read:
Timer 1 Channel 1
Register High Write:
(T1CH1H)
Reset:
Freescale Semiconductor, Inc...
$0029
Read:
Timer 1 Channel 1
Register Low Write:
(T1CH1L)
Reset:
$002A
$002B
$002C
$002D
$002E
$002F
$0030
Bit 7
0
CH1IE
5
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
PS2
PS1
PS0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
Read:
Timer 2 Status and
Control Register Write:
(T2SC)
Reset:
TOF
0
0
TOIE
TSTOP
0
0
1
0
0
0
0
0
Read:
Timer 2 Counter
Register High Write:
(T2CNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
Timer 2 Counter
Register Low Write:
(T2CNTL)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
1
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
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
Read:
Timer 2 Counter Modulo
Register High Write:
(T2MODH)
Reset:
Read:
Timer 2 Counter Modulo
Register Low Write:
(T2MODL)
Reset:
Read:
Timer 2 Channel 0 Status
and Control Register Write:
(T2SC0)
Reset:
$0031
CH1F
6
Read:
Timer 2 Channel 0
Register High Write:
(T2CH0H)
Reset:
U = Unaffected
0
CH0F
0
TRST
Indeterminate after reset
X = Indeterminate
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 12)
Data Sheet
MC68HC908AP Family — Rev. 2.5
42
MOTOROLA
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Memory Map
Input/Output (I/O) Section
Addr.
Register Name
Read:
Timer 2 Channel 0
Register Low Write:
(T2CH0L)
Reset:
$0032
Freescale Semiconductor, Inc...
$0033
Read:
Timer 2 Channel 1 Status
and Control Register Write:
(T2SC1)
Reset:
Read:
Timer 2 Channel 1
Register High Write:
(T2CH1H)
Reset:
$0034
Read:
Timer 2 Channel 1
Register Low Write:
(T2CH1L)
Reset:
$0035
$0036
$0037
$0038
$0039
$003A
$003B
Read:
PLL Control Register
Write:
(PCTL)
Reset:
Read:
PLL Bandwidth Control
Register Write:
(PBWC)
Reset:
Read:
PLL Multiplier Select
Register High Write:
(PMSH)
Reset:
Read:
PLL Multiplier Select
Register Low Write:
(PMSL)
Reset:
Read:
PLL VCO Range Select
Register Write:
(PMRS)
Reset:
Read:
PLL Reference Divider
Select Register Write:
(PMDS)
Reset:
U = Unaffected
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
CH1F
0
CH1IE
0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
PLLIE
0
AUTO
PLLF
0
LOCK
PLLON
BCS
PRE1
PRE0
VPR1
VPR0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
MUL11
MUL10
MUL9
MUL8
ACQ
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
MUL3
MUL2
MUL1
MUL0
0
1
0
0
0
0
0
0
VRS7
VRS6
VRS5
VRS4
VRS3
VRS2
VRS1
VRS0
0
1
0
0
0
0
0
0
0
0
0
0
RDS3
RDS2
RDS1
RDS0
0
0
0
0
0
0
0
1
= Unimplemented
R
X = Indeterminate
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 6 of 12)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
43
For More Information On This Product,
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Freescale Semiconductor, Inc.
Memory Map
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
M
WAKE
ILTY
PEN
PTY
Read:
$003C
Unimplemented Write:
Reset:
Read:
Unimplemented Write:
$003D
Reset:
Freescale Semiconductor, Inc...
Read:
Unimplemented Write:
$003E
Reset:
Read:
$003F
Unimplemented Write:
Reset:
$0040
$0041
$0042
$0043
$0044
Read:
LOOPS
IRSCI Control Register 1
Write:
(IRSCC1)
Reset:
0
Read:
IRSCI Control Register 2
Write:
(IRSCC2)
Reset:
ENSCI
0
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
T8
DMARE
DMATE
ORIE
NEIE
FEIE
PEIE
Read:
IRSCI Control Register 3
Write:
(IRSCC3)
Reset:
R8
U
U
0
0
0
0
0
0
Read:
IRSCI Status Register 1
Write:
(IRSCS1)
Reset:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
BKF
RPF
Read:
IRSCI Status Register 2
Write:
(IRSCS2)
Reset:
$0045
Read:
IRSCI Data Register
Write:
(IRSCDR)
Reset:
U = Unaffected
0
0
0
0
0
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
Unaffected by reset
X = Indeterminate
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 7 of 12)
Data Sheet
MC68HC908AP Family — Rev. 2.5
44
MOTOROLA
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Memory Map
Input/Output (I/O) Section
Addr.
Register Name
Bit 7
Read:
IRSCI Baud Rate Register
$0046
Write:
(IRSCBR)
Reset:
Freescale Semiconductor, Inc...
$0047
$0048
Read:
IRSCI Infrared Control
Register Write:
(IRSCIRCR)
Reset:
$004A
Read:
MMIIC Control Register 1
Write:
(MMCR1)
Reset:
$004D
2
1
Bit 0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
0
0
R
TNP1
TNP0
IREN
0
0
0
0
0
0
0
MMAD6
MMAD5
MMAD4
MMAD3
MMAD2
1
0
1
0
0
0
0
MMEN
MMIEN
0
0
MMTXAK
REPSEN
MMCRCBYTE
0
0
0
0
MMAST
MMRW
0
0
0
0
0
R
0
0
MMAD1 MMEXTAD
0
0
MMCLRBB
0
0
MMIIC Status Register Read: MMRXIF
(MMSR) Write:
0
Reset:
$004C
3
0
MMIIC Control Register 2 Read: MMALIF MMNAKIF
(MMCR2) Write:
0
0
Reset:
$004B
4
MMIIC Address Register Read:
MMAD7
(MMADR) Write:
Reset:
$0049
5
CKS
6
0
Read:
MMIIC Data Transmit
MMTD7
Register Write:
(MMDTR)
Reset:
0
Read: MMRD7
MMIIC Data Receive
Register Write:
(MMDRR)
Reset:
0
0
0
MMBB
0
MMTXIF MMATCH
0
MMCRCEF
0
0
Unaffected
MMSRW MMRXAK MMCRCBF MMTXBE MMRXBF
0
0
0
0
1
0
1
0
MMTD6
MMTD5
MMTD4
MMTD3
MMTD2
MMTD1
MMTD0
0
0
0
0
0
0
0
MMRD6
MMRD5
MMRD4
MMRD3
MMRD2
MMRD1
MMRD0
0
0
0
0
0
0
0
MMIIC CRC Data Register Read: MMCRCD7 MMCRCD6 MMCRCD5 MMCRCD4 MMCRCD3 MMCRCD2 MMCRCD1 MMCRCD0
(MMCRDR) Write:
$004E
$004F
Reset:
0
0
0
0
0
Read:
MMIIC Frequency Divider
Register Write:
(MMFDR)
Reset:
0
0
0
0
0
0
0
0
0
U = Unaffected
X = Indeterminate
0
0
0
MMBR2
MMBR1
MMBR0
0
1
0
0
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 8 of 12)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
45
For More Information On This Product,
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Freescale Semiconductor, Inc.
Memory Map
Addr.
Register Name
Read:
Reserved Write:
$0050
Bit 7
6
5
4
3
2
1
Bit 0
R
R
R
R
R
R
R
R
TBR2
TBR1
TBR0
TBIE
TBON
R
0
0
0
0
0
0
0
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
0
0
1
1
1
1
1
ADIV2
ADIV1
ADIV0
ADICLK
MODE1
MODE0
0
0
0
0
0
0
0
0
0
0
ADx
ADx
ADx
ADx
ADx
ADx
ADx
ADx
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
= Unimplemented
R
Reset:
Timebase Control Read:
Register
Write:
(TBCR)
Reset:
$0051
TBIF
0
0
TACK
Freescale Semiconductor, Inc...
Read:
Unimplemented Write:
$0052
Reset:
Read:
Unimplemented Write:
$0053
Reset:
Read:
Unimplemented Write:
$0054
Reset:
Read:
Unimplemented Write:
$0055
Reset:
Read:
$0056
Unimplemented Write:
Reset:
$0057
Read:
ADC Status and Control
Register Write:
(ADSCR)
Reset:
$0058
Read:
ADC Clock Control
Register Write:
(ADICLK)
Reset:
Read:
ADC Data Register High 0
$0059
Write:
(ADRH0)
Reset:
U = Unaffected
COCO
X = Indeterminate
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 9 of 12)
Data Sheet
MC68HC908AP Family — Rev. 2.5
46
MOTOROLA
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Memory Map
Input/Output (I/O) Section
Addr.
$005A
Register Name
ADC Data Register Low 0 Read:
(ADRL0) Write:
Reset:
$005B
ADC Data Register Low 1 Read:
(ADRL1) Write:
Freescale Semiconductor, Inc...
Reset:
$005C ADC Data Register Low 2 Read:
(ADRL2) Write:
Reset:
$005D
ADC Data Register Low 3 Read:
(ADRL3) Write:
Reset:
$005E
Read:
ADC Auto-scan Control
Register Write:
(ADASCR)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
ADx
ADx
ADx
ADx
ADx
ADx
ADx
ADx
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
AUTO1
AUTO0
ASCAN
0
0
0
0
0
0
0
0
R
R
R
R
R
R
Read:
$005F
Unimplemented Write:
Reset:
Read:
SIM Break Status Register
$FE00
Write:
(SBSR)
Reset:
SBSW
R
Note
0
Note: Writing a logic 0 clears SBSW.
Read:
SIM Reset Status Register
$FE01
Write:
(SRSR)
Reset:
Read:
$FE02
Reserved Write:
POR
PIN
COP
ILOP
ILAD
MODRST
LVI
0
1
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
= Unimplemented
R
Reset:
U = Unaffected
X = Indeterminate
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 10 of 12)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
47
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Memory Map
Addr.
Freescale Semiconductor, Inc...
$FE03
Register Name
Read:
SIM Break Flag Control
Register Write:
(SBFCR)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
0
Read:
Interrupt Status Register 1
$FE04
Write:
(INT1)
Reset:
IF6
IF5
IF4
IF3
IF2
IF1
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
Interrupt Status Register 2
$FE05
Write:
(INT2)
Reset:
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
Interrupt Status Register 3
$FE06
Write:
(INT3)
Reset:
0
IF21
IF20
IF19
IF18
IF17
IF16
IF15
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
HVEN
MASS
ERASE
PGM
0
0
0
0
0
0
0
0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
R
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
= Unimplemented
R
Read:
Reserved Write:
$FE07
Reset:
$FE08
Read:
FLASH Control Register
Write:
(FLCR)
Reset:
$FE09
Read:
FLASH Block Protect
Register Write:
(FLBPR)
Reset:
Read:
$FE0A
Reserved Write:
Reset:
Read:
$FE0B
Reserved Write:
Reset:
$FE0C
Read:
Break Address
Register High Write:
(BRKH)
Reset:
U = Unaffected
X = Indeterminate
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 11 of 12)
Data Sheet
MC68HC908AP Family — Rev. 2.5
48
MOTOROLA
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Memory Map
Input/Output (I/O) Section
Addr.
Register Name
Read:
Break Address
Register Low Write:
(BRKL)
Reset:
$FE0D
Freescale Semiconductor, Inc...
$FE0E
Reset:
Break Status and Control
Register Read:
(BRKSCR)
Write:
#
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
BRKE
BRKA
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
R
R
R
R
R
R
1
1
1
1
1
1
U
U
U
U
U
U
Read:
OSCSEL1 OSCSEL0
Mask Option Register
# Write:
(MOR)
Erased:
1
1
Reset:
$FFFF
6
Reset: LVIOUT
LVI Status Register
Read:
(LVISR)
Write:
0
$FE0F
$FFCF
Bit 7
U
U
Read:
COP Control Register
Write:
(COPCTL)
Reset:
Low byte of reset vector
Writing clears COP counter (any value)
Unaffected by reset
MOR is a non-volatile FLASH register; write by programming.
U = Unaffected
X = Indeterminate
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 12 of 12)
MC68HC908AP Family — Rev. 2.5
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Memory Map
Table 2-1. Vector Addresses
Priority
INT Flag
Lowest
Address
Vector
$FFD0
Reserved
$FFD1
Reserved
$FFD2
TBM Vector (High)
$FFD3
TBM Vector (Low)
$FFD4
SCI2 (IRSCI) Transmit Vector (High)
$FFD5
SCI2 (IRSCI) Transmit Vector (Low)
$FFD6
SCI2 (IRSCI) Receive Vector (High)
$FFD7
SCI2 (IRSCI) Receive Vector (Low)
$FFD8
SCI2 (IRSCI) Error Vector (High)
$FFD9
SCI2 (IRSCI) Error Vector (Low)
$FFDA
SPI Transmit Vector (High)
$FFDB
SPI Transmit Vector (Low)
$FFDC
SPI Receive Vector (High)
$FFDD
SPI Receive Vector (Low)
$FFDE
ADC Conversion Complete Vector (High)
$FFDF
ADC Conversion Complete Vector (Low)
$FFE0
Keyboard Vector (High)
$FFE1
Keyboard Vector (Low)
$FFE2
SCI Transmit Vector (High)
$FFE3
SCI Transmit Vector (Low)
$FFE4
SCI Receive Vector (High)
$FFE5
SCI Receive Vector (Low)
$FFE6
SCI Error Vector (High)
$FFE7
SCI Error Vector (Low)
$FFE8
MMIIC Interrupt Vector (High)
$FFE9
MMIIC Interrupt Vector (Low)
$FFEA
TIM2 Overflow Vector (High)
$FFEB
TIM2 Overflow Vector (Low)
—
IF21
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IF20
IF19
IF18
IF17
IF16
IF15
IF14
IF13
IF12
IF11
IF10
IF9
Data Sheet
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Memory Map
Input/Output (I/O) Section
Table 2-1. Vector Addresses (Continued)
Priority
INT Flag
Address
Vector
$FFEC
TIM2 Channel 1 Vector (High)
$FFED
TIM2 Channel 1 Vector (Low)
$FFEE
TIM2 Channel 0 Vector (High)
$FFEF
TIM2 Channel 0 Vector (Low)
$FFF0
TIM1 Overflow Vector (High)
$FFF1
TIM1 Overflow Vector (Low)
$FFF2
TIM1 Channel 1 Vector (High)
$FFF3
TIM1 Channel 1 Vector (Low)
$FFF4
TIM1 Channel 0 Vector (High)
$FFF5
TIM1 Channel 0 Vector (Low)
$FFF6
PLL Vector (High)
$FFF7
PLL Vector (Low)
$FFF8
IRQ2 Vector (High)
$FFF9
IRQ2 Vector (Low)
$FFFA
IRQ1 Vector (High)
$FFFB
IRQ1 Vector (Low)
$FFFC
SWI Vector (High)
$FFFD
SWI Vector (Low)
$FFFE
Reset Vector (High)
$FFFF
Reset Vector (Low)
IF8
IF7
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IF6
IF5
IF4
IF3
IF2
IF1
—
—
Highest
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Memory Map
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 3. Random-Access Memory (RAM)
3.1 Introduction
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This section describes the 2,048 (or 1,024) bytes of RAM.
3.2 Functional Description
Addresses $0060 through $085F (or $045F) are RAM locations. The
location of the stack RAM is programmable. The 16-bit stack pointer
allows the stack to be anywhere in the 64k-byte 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 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 CPU registers.
NOTE:
For M6805 compatibility, the H register is not stacked.
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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Random-Access Memory (RAM)
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 4. FLASH Memory
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4.1 Introduction
This section describes the operation of the 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.
Addr.
$FE08
$FE09
Device
FLASH Memory Size
(Bytes)
Memory Address Range
MC68HC908AP64
62,368
$0860—$FBFF
MC68HC908AP32
32,768
$0860—$885F
MC68HC908AP16
16,384
$0860—$485F
MC68HC908AP8
8,192
$0860—$285F
Register Name
Read:
FLASH Control Register
Write:
(FLCR)
Reset:
Read:
FLASH Block Protect
Register Write:
(FLBPR)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
HVEN
MASS
ERASE
PGM
0
0
0
0
0
0
0
0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 4-1. FLASH I/O Register Summary
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FLASH Memory
4.2 Functional Description
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The FLASH memory consists of an array of 62,368 bytes for user
memory plus a block of 48 bytes for user interrupt vectors and one byte
for the mask option register. An erased bit reads as logic 1 and a
programmed bit reads as a logic 0. The FLASH memory page size is
defined as 512 bytes, and is the minimum size that can be erased in a
page erase operation. Program and erase operations are facilitated
through control bits in FLASH control register (FLCR). The address
ranges for the FLASH memory are:
•
$0860–$FBFF; user memory, 62,368 bytes
•
$FFD0–$FFFF; user interrupt vectors, 48 bytes
•
$FFCF; mask option register
Programming tools are available from Motorola. Contact your local
Motorola representative for more information.
NOTE:
A security feature prevents viewing of the FLASH contents.1
1. No security feature is absolutely secure. However, Motorola’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
Data Sheet
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FLASH Memory
FLASH Control Register
4.3 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase
operation.
Address:
Read:
$FE08
Bit 7
6
5
4
0
0
0
0
3
2
1
Bit 0
HVEN
MASS
ERASE
PGM
0
0
0
0
Write:
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Reset:
0
0
0
0
Figure 4-2. 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 only be set if
either PGM = 1 or ERASE = 1 and the proper sequence for program
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 or
page erase operation when the ERASE bit is set.
1 = Mass erase operation selected
0 = Page erase operation selected
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
equal to 1 or set to 1 at the same time.
1 = Erase operation selected
0 = Erase operation not selected
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
equal to 1 or set to 1 at the same time.
1 = Program operation selected
0 = Program operation not selected
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FLASH Memory
4.4 FLASH Page Erase Operation
Use the following procedure to erase a page of FLASH memory. A page
consists of 512 consecutive bytes starting from addresses $X000,
$X200, $X400, $X600, $X800, $XA00, $XC00, or $XE00. The 48-byte
user interrupt vectors cannot be erased by the page erase operation
because of security reasons. Mass erase is required to erase this page.
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1. Set the ERASE bit and clear the MASS bit in the FLASH control
register.
2. Write any data to any FLASH location within the page address
range desired.
3. Wait for a time, tnvs (5 µs).
4. Set the HVEN bit.
5. Wait for a time terase (20 ms).
6. Clear the ERASE bit.
7. Wait for a time, tnvh (5 µs).
8. Clear the HVEN bit.
9. After time, trcv (1 µs), the memory can be accessed in read mode
again.
NOTE:
Data Sheet
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 as shown, but other unrelated operations
may occur between the steps.
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FLASH Memory
FLASH Mass Erase Operation
4.5 FLASH Mass Erase Operation
Use the following procedure to erase the entire FLASH memory:
1. Set both the ERASE bit and the MASS bit in the FLASH control
register.
2. Write any data to any FLASH location within the FLASH memory
address range.
3. Wait for a time, tnvs (5 µs).
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4. Set the HVEN bit.
5. Wait for a time tme (200 ms).
6. Clear the ERASE bit.
7. Wait for a time, tnvh1 (100 µs).
8. Clear the HVEN bit.
9. After time, trcv (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 as shown, but other unrelated operations
may occur between the steps.
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FLASH Memory
4.6 FLASH Program Operation
Programming of the FLASH memory is done on a row basis. A row
consists of 64 consecutive bytes starting from addresses $XX00,
$XX40, $XX80 or $XXC0. Use the following procedure to program a row
of FLASH memory. (Figure 4-3 shows a flowchart of the programming
algorithm.)
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1. Set the PGM bit. This configures the memory for program
operation and enables the latching of address and data for
programming.
2. Write any data to any FLASH location within the address range of
the row to be programmed.
3. Wait for a time, tnvs (5 µs).
4. Set the HVEN bit.
5. Wait for a time, tpgs (10 µs).
6. Write data to the FLASH location to be programmed.
7. Wait for time, tprog (20 µs to 40 µs).
8. Repeat steps 6 and 7 until all bytes within the row are
programmed.
9. Clear the PGM bit.
10. Wait for time, tnvh (5 µs).
11. Clear the HVEN bit.
12. After time, trcv (1 µs), the memory can be accessed in read mode
again.
This program sequence is repeated throughout the memory until all data
is programmed.
Data Sheet
NOTE:
The time between each FLASH address change (step 6 to step 6), or the
time between the last FLASH addressed programmed to clearing the
PGM bit (step 6 to step 9), must not exceed the maximum programming
time, tprog max.
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.
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FLASH Memory
FLASH Program Operation
1
Set PGM bit
Algorithm for programming
a row (64 bytes) of FLASH memory
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2
Write any data to any FLASH address
within the row address range desired
3
Wait for a time, tnvs
4
Set HVEN bit
5
Wait for a time, tpgs
6
7
Write data to the FLASH address
to be programmed
Wait for a time, tprog
Completed
programming
this row?
Y
N
NOTE:
The time between each FLASH address change (step 6 to step 6), or
the time between the last FLASH address programmed
to clearing PGM bit (step 6 to step 9)
must not exceed the maximum programming
time, tPROG max.
9
Clear PGM bit
10
Wait for a time, tnvh
11
Clear HVEN bit
12
Wait for a time, trcv
This row program algorithm assumes the row/s
to be programmed are initially erased.
End of Programming
Figure 4-3. FLASH Programming Flowchart
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FLASH Memory
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4.7 FLASH 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 to protect
pages of memory from unintentional erase or program operations due to
system malfunction. This protection is done by use of a FLASH block
protect 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 to 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:
The mask option register ($FFCF) and the 48 bytes of user interrupt
vectors ($FFD0–$FFFF) are always protected, regardless of the value in
the FLASH block protect register. A mass erase is required to erase
these locations.
4.7.1 FLASH Block Protect Register
The FLASH block protect register is implemented as an 8-bit I/O register.
The value in this register determines the starting address of the
protected range within the FLASH memory.
Address:
$FE09
Bit 7
6
5
4
3
2
1
Bit 0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
0
0
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 4-4. FLASH Block Protect Register (FLBPR)
BPR[7:0] — FLASH Block Protect Bits
BPR[7:1] represent bits [15:9] of a 16-bit memory address. Bits [8:0]
are logic 0’s.
16-bit memory address
Start address of FLASH block protect
0 0 0 0 0 0 0 0 0
BPR[7:1]
Data Sheet
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FLASH Memory
FLASH Protection
BPR0 is used only for BPR[7:0] = $FF, for no block protection.
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 X000, X200, X400,
X0600, X800, XA00, XC00, or XE00 (at page boundaries — 512
bytes) within the FLASH memory.
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Examples of protect start address:
Table 4-1 FLASH Block Protect Range
BPR[7:0]
Protected Range
$00 to $09
The entire FLASH memory is protected.
$0A or $0B
(0000 101x)
$0A00 to $FFFF
$0C or $0D
(0000 110x)
$0C00 to $FFFF
and so on...
$FA or $FB
(1111 1101x)
$FA00 to $FFFF
$FC or $FD or $FE
$FFCF to $FFFF
$FF
The entire FLASH memory is NOT protected.(1)
Notes:
1. Except for the mask option register ($FFCF) and
the 48-byte user vectors ($FFD0–$FFFF). These FLASH locations are always protected.
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FLASH Memory
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 5. Configuration & Mask Option Registers
(CONFIG & MOR)
5.1 Introduction
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This section describes the configuration registers, CONFIG1 and
CONFIG2; and the mask option register, MOR.
The configuration registers enable or disable these options:
•
Computer operating properly module (COP)
•
COP timeout period (218 – 24 or 213 – 24 ICLK cycles)
•
Low-voltage inhibit (LVI) on VDD
•
LVI on VREG
•
LVI module reset
•
LVI module in stop mode
•
STOP instruction
•
Stop mode recovery time (32 ICLK or 4096 ICLK cycles)
•
Oscillator (internal, RC, and crystal) during stop mode
•
Serial communications interface clock source (CGMXCLK or fBUS)
The mask option register selects one of the following oscillator options:
•
Internal oscillator
•
RC oscillator
•
Crystal oscillator
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Configuration & Mask Option Registers
Addr.
$001D
Register Name
Bit 7
Read: STOP_
Configuration Register 2
ICLKDIS
(CONFIG2)† Write:
Reset:
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$001F
$FFCF
0
Read:
COPRS
Configuration Register 1
† Write:
(CONFIG1)
Reset:
0
6
STOP_
RCLKEN
0
1
4
3
0
1
2
1
Bit 0
0
0
SCIBDSRC
0
0
0
SSREC
STOP
COPD
STOP_
OSCCLK1 OSCCLK0
XCLKEN
0
0
0
LVISTOP LVIRSTD LVIPWRD LVIREGD
Read:
Mask-Option-Register
OSCSEL1 OSCSEL0
(MOR)# Write:
Erased:
5
0
0
0
0
0
0
R
R
R
R
R
R
1
1
1
1
1
1
† One-time writable register after each reset.
# MOR is a non-volatile FLASH register; write by programming.
= Unimplemented
R
= Reserved
Figure 5-1. CONFIG and MOR Registers Summary
5.2 Functional Description
The configuration registers and the mask option register are used in the
initialization of various options. These two types of registers are
configured differently:
•
Configuration registers — Write-once registers after reset
•
Mask option register — FLASH register (write by programming)
The configuration registers can be written once after each reset. All of
the configuration register bits are cleared during reset. Since the various
options affect the operation of the MCU, it is recommended that these
registers be written immediately after reset. The configuration registers
are located at $001D and $001F. The configuration registers may be
read at anytime.
NOTE:
Data Sheet
The CONFIG registers are not in the FLASH memory but are special
registers containing one-time writable latches after each reset. Upon a
reset, the CONFIG registers default to predetermined settings as shown
in Figure 5-2 and Figure 5-3.
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Configuration & Mask Option Registers (CONFIG & MOR)
Configuration Register 1 (CONFIG1)
The mask option register (MOR) is used for selecting one of the three
clock options for the MCU. The MOR is a byte located in FLASH
memory, and is written to by a FLASH programming routine.
5.3 Configuration Register 1 (CONFIG1)
Address:
$001F
Bit 7
6
5
4
3
2
1
Bit 0
SSREC
STOP
COPD
0
0
0
Read:
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COPRS
LVISTOP LVIRSTD LVIPWRD LVIREGD
Write:
Reset:
0
0
0
0
0
Figure 5-2. Configuration Register 1 (CONFIG1)
COPRS — COP Rate Select Bit
COPRS selects the COP time out period. Reset clears COPRS. (See
Section 21. Computer Operating Properly (COP).)
1 = COP time out period = 213 – 24 ICLK cycles
0 = COP time out period = 218 – 24 ICLK cycles
LVISTOP — LVI Enable in Stop Mode Bit
When the LVIPWRD or LVIREGD bit is clear, setting the LVISTOP bit
enables the LVI to operate during stop mode. Reset clears LVISTOP.
(See Section 22. Low-Voltage Inhibit (LVI).)
1 = LVI enabled during stop mode
0 = LVI disabled during stop mode
NOTE:
If LVISTOP=0, set LVIRSTD=1 before entering stop mode.
LVIRSTD — LVI Reset Disable Bit
LVIRSTD disables the reset signal from the LVI module. (See
Section 22. Low-Voltage Inhibit (LVI).)
1 = LVI module resets disabled
0 = LVI module resets enabled
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Configuration & Mask Option Registers
LVIPWRD — VDD LVI Circuit Disable Bit
LVIPWRD disables the VDD LVI circuit. (See Section 22. LowVoltage Inhibit (LVI).)
1 = VDD LVI circuit disabled
0 = VDD LVI circuit enabled
LVIREGD — VREG LVI Circuit Disable Bit
LVIREGD disables the VREG LVI circuit. (See Section 22. Low-
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Voltage Inhibit (LVI).)
1 = VREG LVI circuit disabled
0 = VREG LVI circuit enabled
NOTE:
If LVIPWRD=1 and LVIREGD=1, set LVIRSTD=1 before entering stop
mode.
SSREC — Short Stop Recovery Bit
SSREC enables the CPU to exit stop mode with a delay of 32 ICLK
cycles instead of a 4096 ICLK cycle delay.
1 = Stop mode recovery after 32 ICLK cycles
0 = Stop mode recovery after 4096 ICLK cycles
NOTE:
Exiting stop mode by pulling reset will result in the long stop recovery.
If using an external crystal oscillator, do not set the SSREC bit.
When the LVI is disabled in stop mode (LVISTOP=0), the system
stabilization time for long stop recovery (4096 ICLK cycles) gives a delay
longer than the LVI’s turn-on time. There is no period where the MCU is
not protected from a low power condition. However, when using the
short stop recovery configuration option, the 32 ICLK delay is less than
the LVI’s turn-on time and there exists a period in start-up where the LVI
is not protecting the MCU.
STOP — STOP Instruction Enable Bit
STOP enables the STOP instruction.
1 = STOP instruction enabled
0 = STOP instruction treated as illegal opcode
Data Sheet
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Configuration & Mask Option Registers (CONFIG & MOR)
Configuration Register 2 (CONFIG2)
COPD — COP Disable Bit
COPD disables the COP module. (See Section 21. Computer
Operating Properly (COP).)
1 = COP module disabled
0 = COP module enabled
5.4 Configuration Register 2 (CONFIG2)
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Address:
$001D
Bit 7
Read:
STOP_
ICLKDIS
Write:
Reset:
0
6
STOP_
RCLKEN
0
5
4
3
STOP_
OSCCLK1 OSCCLK0
XCLKEN
0
0
0
2
1
0
0
Bit 0
SCIBDSRC
0
0
0
Figure 5-3. Configuration Register 2 (CONFIG2)
STOP_ICLKDIS — Internal Oscillator Stop Mode Disable
STOP_ICLKDIS disables the internal oscillator during stop mode.
Setting the STOP_ICLKDIS bit disables the oscillator during stop
mode. (See Section 7. Oscillator (OSC).)
Reset clears this bit.
1 = Internal oscillator disabled during stop mode
0 = Internal oscillator enabled to operate during stop mode
STOP_RCLKEN — RC Oscillator Stop Mode Enable Bit
STOP_RCLKEN enables the RC oscillator to continue operating
during stop mode. Setting the STOP_RCLKEN bit allows the
oscillator to operate continuously even during stop mode. This is
useful for driving the timebase module to allow it to generate periodic
wake up while in stop mode. (See Section 7. Oscillator (OSC).)
Reset clears this bit.
1 = RC oscillator enabled to operate during stop mode
0 = RC oscillator disabled during stop mode
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Configuration & Mask Option Registers
STOP_XCLKEN — X-tal Oscillator Stop Mode Enable Bit
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STOP_XCLKEN enables the crystal (x-tal) oscillator to continue
operating during stop mode. Setting the STOP_XCLKEN bit allows
the x-tal oscillator to operate continuously even during stop mode.
This is useful for driving the timebase module to allow it to generate
periodic wake up while in stop mode. (See Section 7. Oscillator
(OSC).) Reset clears this bit.
1 = X-tal oscillator enabled to operate during stop mode
0 = X-tal oscillator disabled during stop mode
OSCCLK1, OSCCLK0 — Oscillator Output Control Bits
OSCCLK1 and OSCCLK0 select which oscillator output to be driven
out as OSCCLK to the timebase module (TBM). Reset clears these
two bits.
OSCCLK1
OSCCLK0
Timebase Clock Source
0
0
Internal oscillator (ICLK)
0
1
RC oscillator (RCCLK)
1
0
X-tal oscillator (XTAL)
1
1
Not used
SCIBDSRC — SCI Baud Rate Clock Source
SCIBDSRC selects the clock source used for the standard SCI
module (non-infrared SCI). The setting of this bit affects the frequency
at which the SCI operates.
1 = Internal data bus clock, fBUS, is used as clock source for SCI
0 = Oscillator clock, CGMXCLK, is used as clock source for SCI
Data Sheet
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Configuration & Mask Option Registers (CONFIG & MOR)
Mask Option Register (MOR)
5.5 Mask Option Register (MOR)
The mask option register (MOR) is used for selecting one of the three
clock options for the MCU. The MOR is a byte located in FLASH
memory, and is written to by a FLASH programming routine.
Address:
$FFCF
Bit 7
6
5
4
3
2
1
Bit 0
R
R
R
R
R
R
1
1
1
Read:
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OSCSEL1 OSCSEL0
Write:
Reset:
Erased:
Unaffected by reset
1
1
R
1
1
1
= Reserved
Figure 5-4. Mask Option Register (MOR)
OSCSEL1, OSCSEL0 — Oscillator Selection Bits
OSCSEL1 and OSCSEL0 select which oscillator is used for the MCU
CGMXCLK clock. The erase state of these two bits is logic 1. These
bits are unaffected by reset. (See Table 5-1).
Bits 5–0 — Should be left as 1’s.
Table 5-1. CGMXCLK Clock Selection
OSCSEL1
OSCSEL0
CGMXCLK
OSC2 pin
0
0
—
—
0
1
ICLK
fBUS
Internal oscillator generates the CGMXCLK.
1
0
RCCLK
fBUS
RC oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.
1
1
X-TAL
Inverting
output of
XTAL
X-tal oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.
NOTE:
Comments
Not used
The internal oscillator is a free running oscillator and is available after
each POR or reset. It is turned-off in stop mode by setting the
STOP_ICLKDIS bit in CONFIG2.
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Configuration & Mask Option Registers
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 6. Central Processor Unit (CPU)
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6.1 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully
object-code-compatible version of the M68HC05 CPU. The CPU08
Reference Manual (Motorola document order number CPU08RM/AD)
contains a description of the CPU instruction set, addressing modes,
and architecture.
6.2 Features
Feature of the CPU include:
•
Object code fully upward-compatible 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
•
16 addressing modes
•
Memory-to-memory data moves without using 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
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Central Processor Unit (CPU)
6.3 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
INDEX REGISTER (H:X)
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15
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
6.3.1 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)
Data Sheet
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Central Processor Unit (CPU)
CPU Registers
6.3.2 Index Register
The 16-bit index register allows indexed addressing of a 64K-byte
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.
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The index register can serve also as a temporary data storage location.
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)
6.3.3 Stack Pointer
The stack pointer 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)
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Central Processor Unit (CPU)
NOTE:
The location of the stack is arbitrary and may be relocated anywhere in
RAM. Moving the SP out of page 0 ($0000 to $00FF) frees direct
address (page 0) space. For correct operation, the stack pointer must
point only to RAM locations.
6.3.4 Program Counter
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The program counter 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)
Data Sheet
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Central Processor Unit (CPU)
CPU Registers
6.3.5 Condition Code Register
The 8-bit condition code register contains the interrupt mask and five
flags that indicate the results of the instruction just executed. Bits 6 and
5 are set permanently to logic 1. The following paragraphs describe the
functions of the condition code register.
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
Read:
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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 addwith-carry (ADC) operation. The half-carry flag is required for binarycoded 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
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Central Processor Unit (CPU)
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.
1 = Interrupts disabled
0 = Interrupts enabled
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NOTE:
To maintain M6805 Family 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
Data Sheet
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Central Processor Unit (CPU)
Arithmetic/Logic Unit (ALU)
C — Carry/Borrow Flag
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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
6.4 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the
instruction set.
Refer to the CPU08 Reference Manual (Motorola document order
number CPU08RM/AD) for a description of the instructions and
addressing modes and more detail about the architecture of the CPU.
6.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption
standby modes.
6.5.1 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.
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Central Processor Unit (CPU)
6.5.2 Stop Mode
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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.
6.6 CPU During Break Interrupts
If the break module is enabled, a break interrupt causes the CPU to
execute the software interrupt instruction (SWI) at the completion of the
current CPU instruction. (See Section 23. Break Module (BRK).) The
program counter vectors to $FFFC–$FFFD ($FEFC–$FEFD in monitor
mode).
A return-from-interrupt instruction (RTI) in the break routine ends the
break interrupt and returns the MCU to normal operation if the break
interrupt has been deasserted.
6.7 Instruction Set Summary
Table 6-1 provides a summary of the M68HC08 instruction set.
6.8 Opcode Map
The opcode map is provided in Table 6-2.
Data Sheet
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Central Processor Unit (CPU)
Opcode Map
V H I N Z C
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ADC #opr
ADC opr
ADC opr
ADC opr,X
ADC opr,X
ADC ,X
ADC opr,SP
ADC opr,SP
A ← (A) + (M) + (C)
Add with Carry
IMM
DIR
EXT
IX2
R R – R R R
IX1
IX
SP1
SP2
A9
B9
C9
D9
E9
F9
9EE9
9ED9
ii
dd
hh ll
ee ff
ff
IMM
DIR
EXT
IX2
R R – R R R
IX1
IX
SP1
SP2
AB
BB
CB
DB
EB
FB
9EEB
9EDB
ii
dd
hh ll
ee ff
ff
ff
ee ff
A7
ii
2
– – – – – – IMM
AF
ii
2
IMM
DIR
EXT
IX2
0 – – R R –
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
DIR
INH
INH
R – – R R R
IX1
IX
SP1
38
48
58
68
78
9E68
dd
DIR
INH
INH
R – – R R R
IX1
IX
SP1
37
47
57
67
77
9E67
dd
ff
4
1
1
4
3
5
– – – – – – REL
24
rr
3
DIR (b0)
DIR (b1)
DIR (b2)
DIR (b3)
– – – – – –
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
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
Logical AND
Arithmetic Shift Left
(Same as LSL)
C
ASR opr
ASRA
ASRX
ASR opr,X
ASR opr,X
ASR opr,SP
Arithmetic Shift Right
BCC rel
Branch if Carry Bit Clear
BCLR n, opr
0
b7
b0
C
b7
b0
PC ← (PC) + 2 + rel ? (C) = 0
Mn ← 0
Clear Bit n in M
2
3
4
4
3
2
4
5
2
3
4
4
3
2
4
5
ADD #opr
ADD opr
ADD opr
ADD opr,X
ADD opr,X
ADD ,X
ADD opr,SP
ADD opr,SP
A ← (A) + (M)
ff
ee ff
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 1 of 8)
MC68HC908AP Family — Rev. 2.5
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ff
ee ff
ff
ff
ff
4
1
1
4
3
5
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Central Processor Unit (CPU)
Effect on
CCR
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V H I N Z C
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 2 of 8)
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 ⊕ V) = 0
– – – – – – REL
90
rr
3
BGT opr
Branch if Greater Than (Signed
Operands)
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ 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
3
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
IX2
0 – – R R –
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
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 ⊕ 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 ⊕ 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
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
Data Sheet
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Central Processor Unit (CPU)
Opcode Map
Table 6-1. Instruction Set Summary (Sheet 3 of 8)
Operand
Cycles
Effect on
CCR
Opcode
Operation
DIR (b0)
DIR (b1)
DIR (b2)
DIR (b3)
– – – – – R
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)
DIR (b3)
– – – – – R
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)
DIR (b3)
– – – – – –
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
– – – – – – REL
AD
rr
4
dd rr
ii rr
ii rr
ff rr
rr
ff rr
5
4
4
5
4
6
Description
V H I N Z C
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BRCLR n,opr,rel Branch if Bit n in M Clear
BRN rel
PC ← (PC) + 2
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; push (PCL)
SP ← (SP) – 1; push (PCH)
SP ← (SP) – 1
PC ← (PC) + rel
CBEQ opr,rel
CBEQA #opr,rel
CBEQX #opr,rel
Compare and Branch if Equal
CBEQ opr,X+,rel
CBEQ X+,rel
CBEQ opr,SP,rel
Address
Mode
Source
Form
DIR
PC ← (PC) + 3 + rel ? (A) – (M) = $00
IMM
PC ← (PC) + 3 + rel ? (A) – (M) = $00
IMM
PC ← (PC) + 3 + rel ? (X) – (M) = $00
– – – – – –
IX1+
PC ← (PC) + 3 + rel ? (A) – (M) = $00
IX+
PC ← (PC) + 2 + rel ? (A) – (M) = $00
SP1
PC ← (PC) + 4 + rel ? (A) – (M) = $00
31
41
51
61
71
9E61
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
3F
4F
5F
8C
6F
7F
9E6F
CLR opr
CLRA
CLRX
CLRH
CLR opr,X
CLR ,X
CLR opr,SP
Clear
MC68HC908AP Family — Rev. 2.5
MOTOROLA
dd
ff
ff
3
1
1
1
3
2
4
Data Sheet
83
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Freescale Semiconductor, Inc.
Central Processor Unit (CPU)
Effect on
CCR
V H I N Z C
Freescale Semiconductor, Inc...
CMP #opr
CMP opr
CMP opr
CMP opr,X
CMP opr,X
CMP ,X
CMP opr,SP
CMP opr,SP
Compare A with M
(A) – (M)
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
M ← (M) = $FF – (M)
A ← (A) = $FF – (M)
X ← (X) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
IMM
DIR
EXT
IX2
R – – R R R
IX1
IX
SP1
SP2
A1
B1
C1
D1
E1
F1
9EE1
9ED1
ii
dd
hh ll
ee ff
ff
DIR
INH
INH
0 – – R R 1
IX1
IX
SP1
33
43
53
63
73
9E63
dd
ff
ee ff
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 4 of 8)
2
3
4
4
3
2
4
5
ff
4
1
1
4
3
5
65
75
ii ii+1
dd
3
4
IMM
DIR
EXT
IX2
R – – R R R
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
U – – R R R INH
72
PC ← (PC) + 3 + rel ? (result) ≠ 0
PC ← (PC) + 2 + rel ? (result) ≠ 0
PC ← (PC) + 2 + rel ? (result) ≠ 0
PC ← (PC) + 3 + rel ? (result) ≠ 0
PC ← (PC) + 2 + rel ? (result) ≠ 0
PC ← (PC) + 4 + rel ? (result) ≠ 0
DIR
INH
– – – – – – INH
IX1
IX
SP1
3B
4B
5B
6B
7B
9E6B
dd rr
rr
rr
ff rr
rr
ff rr
5
3
3
5
4
6
M ← (M) – 1
A ← (A) – 1
X ← (X) – 1
M ← (M) – 1
M ← (M) – 1
M ← (M) – 1
DIR
INH
INH
R – – R R –
IX1
IX
SP1
3A
4A
5A
6A
7A
9E6A
dd
4
1
1
4
3
5
A ← (H:A)/(X)
H ← Remainder
– – – – R R INH
52
A ← (A ⊕ M)
IMM
DIR
EXT
IX2
0 – – R R –
IX1
IX
SP1
SP2
A8
B8
C8
D8
E8
F8
9EE8
9ED8
(H:X) – (M:M + 1)
(X) – (M)
(A)10
R – – R R R
IMM
DIR
ff
ff
ee ff
2
A ← (A) – 1 or M ← (M) – 1 or X ← (X) – 1
DBNZ opr,rel
DBNZA rel
Decrement and Branch if Not Zero
DBNZX rel
DBNZ opr,X,rel
DBNZ X,rel
DBNZ opr,SP,rel
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
Data Sheet
Exclusive OR M with A
ff
ff
7
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
MC68HC908AP Family — Rev. 2.5
84
MOTOROLA
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Central Processor Unit (CPU)
Opcode Map
V H I N Z C
Freescale Semiconductor, Inc...
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
LSL opr
LSLA
LSLX
LSL opr,X
LSL ,X
LSL opr,SP
LSR opr
LSRA
LSRX
LSR opr,X
LSR ,X
LSR opr,SP
DIR
INH
INH
R – – R R –
IX1
IX
SP1
3C
4C
5C
6C
7C
9E6C
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
IX2
0 – – R R –
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
ii jj
dd
3
4
2
3
4
4
3
2
4
5
Jump
LDA #opr
LDA opr
LDA opr
LDA opr,X
LDA opr,X
LDA ,X
LDA opr,SP
LDA opr,SP
LDX #opr
LDX opr
LDX opr
LDX opr,X
LDX opr,X
LDX ,X
LDX opr,SP
LDX opr,SP
M ← (M) + 1
A ← (A) + 1
X ← (X) + 1
M ← (M) + 1
M ← (M) + 1
M ← (M) + 1
Increment
Jump to Subroutine
H:X ← (M:M + 1)
0 – – R R –
X ← (M)
Load X from M
Logical Shift Left
(Same as ASL)
C
0
b7
b0
0
Logical Shift Right
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 5 of 8)
C
b7
b0
IMM
DIR
45
55
dd
ff
ff
IMM
DIR
EXT
IX2
0 – – R R –
IX1
IX
SP1
SP2
AE
BE
CE
DE
EE
FE
9EEE
9EDE
ii
dd
hh ll
ee ff
ff
DIR
INH
INH
R – – R R R
IX1
IX
SP1
38
48
58
68
78
9E68
dd
DIR
INH
INH
R – – 0 R R
IX1
IX
SP1
34
44
54
64
74
9E64
dd
MC68HC908AP Family — Rev. 2.5
MOTOROLA
ff
ee ff
ff
ff
ff
ff
4
1
1
4
3
5
4
1
1
4
3
5
4
1
1
4
3
5
Data Sheet
85
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Freescale Semiconductor, Inc.
Central Processor Unit (CPU)
Table 6-1. Instruction Set Summary (Sheet 6 of 8)
Opcode
Operand
Cycles
Effect on
CCR
DD
DIX+
0 – – R R –
IMD
IX+D
4E
5E
6E
7E
dd dd
dd
ii dd
dd
5
4
4
4
X:A ← (X) × (A)
– 0 – – – 0 INH
42
M ← –(M) = $00 – (M)
A ← –(A) = $00 – (A)
X ← –(X) = $00 – (X)
M ← –(M) = $00 – (M)
M ← –(M) = $00 – (M)
DIR
INH
INH
R – – R R R
IX1
IX
SP1
30
40
50
60
70
9E60
Operation
Description
Freescale Semiconductor, Inc...
V H I N Z C
MOV opr,opr
MOV opr,X+
MOV #opr,opr
MOV X+,opr
Move
MUL
Unsigned multiply
(M)Destination ← (M)Source
H:X ← (H:X) + 1 (IX+D, DIX+)
Address
Mode
Source
Form
5
dd
4
1
1
4
3
5
NEG opr
NEGA
NEGX
NEG opr,X
NEG ,X
NEG opr,SP
Negate (Two’s Complement)
NOP
No Operation
None
– – – – – – INH
9D
1
NSA
Nibble Swap A
A ← (A[3:0]:A[7:4])
– – – – – – INH
62
3
A ← (A) | (M)
IMM
DIR
EXT
IX2
0 – – R R –
IX1
IX
SP1
SP2
AA
BA
CA
DA
EA
FA
9EEA
9EDA
ff
ff
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
39
49
59
69
79
9E69
dd
C
DIR
INH
INH
R – – R R R
IX1
IX
SP1
DIR
INH
INH
R – – R R R
IX1
IX
SP1
36
46
56
66
76
9E66
dd
– – – – – – INH
9C
ROL opr
ROLA
ROLX
ROL opr,X
ROL ,X
ROL opr,SP
Rotate Left through Carry
b7
ROR opr
RORA
RORX
ROR opr,X
ROR ,X
ROR opr,SP
Rotate Right through Carry
RSP
Reset Stack Pointer
Data Sheet
b0
C
b7
b0
SP ← $FF
ii
dd
hh ll
ee ff
ff
ff
ee ff
ff
ff
ff
ff
2
3
4
4
3
2
4
5
4
1
1
4
3
5
4
1
1
4
3
5
1
MC68HC908AP Family — Rev. 2.5
86
MOTOROLA
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Freescale Semiconductor, Inc.
Central Processor Unit (CPU)
Opcode Map
Effect on
CCR
Freescale Semiconductor, Inc...
V H I N Z C
RTI
Return from Interrupt
RTS
Return from Subroutine
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 7 of 8)
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)
R R R R R R INH
80
7
SP ← SP + 1; Pull (PCH)
SP ← SP + 1; Pull (PCL)
– – – – – – INH
81
4
A ← (A) – (M) – (C)
IMM
DIR
EXT
IX2
R – – R R R
IX1
IX
SP1
SP2
A2
B2
C2
D2
E2
F2
9EE2
9ED2
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
SBC #opr
SBC opr
SBC opr
SBC opr,X
SBC opr,X
SBC ,X
SBC opr,SP
SBC opr,SP
Subtract with Carry
SEC
Set Carry Bit
C←1
– – – – – 1 INH
99
1
SEI
Set Interrupt Mask
I←1
– – 1 – – – INH
9B
2
M ← (A)
DIR
EXT
IX2
0 – – R R – IX1
IX
SP1
SP2
B7
C7
D7
E7
F7
9EE7
9ED7
(M:M + 1) ← (H:X)
0 – – R R – DIR
35
I ← 0; Stop Oscillator
– – 0 – – – INH
8E
M ← (X)
DIR
EXT
IX2
0 – – R R – IX1
IX
SP1
SP2
BF
CF
DF
EF
FF
9EEF
9EDF
dd
hh ll
ee ff
ff
IMM
DIR
EXT
IX2
R – – R R R
IX1
IX
SP1
SP2
A0
B0
C0
D0
E0
F0
9EE0
9ED0
ii
dd
hh ll
ee ff
ff
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
A ← (A) – (M)
Subtract
MC68HC908AP Family — Rev. 2.5
MOTOROLA
ff
ee ff
ff
ee ff
3
4
4
3
2
4
5
dd
4
dd
hh ll
ee ff
ff
1
ff
ee ff
ff
ee ff
3
4
4
3
2
4
5
2
3
4
4
3
2
4
5
Data Sheet
87
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Freescale Semiconductor, Inc.
Central Processor Unit (CPU)
Freescale Semiconductor, Inc...
V H I N Z C
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 6-1. Instruction Set Summary (Sheet 8 of 8)
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)
R R R R R R INH
84
2
TAX
Transfer A to X
X ← (A)
– – – – – – INH
97
1
TPA
Transfer CCR to A
A ← (CCR)
– – – – – – INH
85
1
(A) – $00 or (X) – $00 or (M) – $00
DIR
INH
INH
0 – – R R –
IX1
IX
SP1
3D
4D
5D
6D
7D
9E6D
H:X ← (SP) + 1
– – – – – – INH
95
2
A ← (X)
– – – – – – INH
9F
1
(SP) ← (H:X) – 1
– – – – – – INH
94
2
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
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
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
Data Sheet
n
opr
PC
PCH
PCL
REL
rel
rr
SP1
SP2
SP
U
V
X
Z
&
|
⊕
()
–( )
#
«
←
?
:
R
—
– – 1 – – – INH
83
9
dd
ff
ff
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
MC68HC908AP Family — Rev. 2.5
88
MOTOROLA
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MOTOROLA
MC68HC908AP Family — Rev. 2.5
Central Processor Unit (CPU)
For More Information On This Product,
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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
0
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
1
3
BRA
2 REL
3
BRN
2 REL
3
BHI
2 REL
3
BLS
2 REL
3
BCC
2 REL
3
BCS
2 REL
3
BNE
2 REL
3
BEQ
2 REL
3
BHCC
2 REL
3
BHCS
2 REL
3
BPL
2 REL
3
BMI
2 REL
3
BMC
2 REL
3
BMS
2 REL
3
BIL
2 REL
3
BIH
2 REL
2
Branch
REL
4
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
5
4
NEG
2
IX1
5
CBEQ
3 IX1+
3
NSA
1 INH
4
COM
2 IX1
4
LSR
2 IX1
3
CPHX
3 IMM
4
ROR
2 IX1
4
ASR
2 IX1
4
LSL
2 IX1
4
ROL
2 IX1
4
DEC
2 IX1
5
DBNZ
3 IX1
4
INC
2 IX1
3
TST
2 IX1
4
MOV
3 IMD
3
CLR
2 IX1
6
7
IX
9
7
3
RTI
BGE
1 INH 2 REL
4
3
RTS
BLT
1 INH 2 REL
3
BGT
2 REL
9
3
SWI
BLE
1 INH 2 REL
2
2
TAP
TXS
1 INH 1 INH
1
2
TPA
TSX
1 INH 1 INH
2
PULA
1 INH
2
1
PSHA
TAX
1 INH 1 INH
2
1
PULX
CLC
1 INH 1 INH
2
1
PSHX
SEC
1 INH 1 INH
2
2
PULH
CLI
1 INH 1 INH
2
2
PSHH
SEI
1 INH 1 INH
1
1
CLRH
RSP
1 INH 1 INH
1
NOP
1 INH
1
STOP
*
1 INH
1
1
WAIT
TXA
1 INH 1 INH
8
Control
INH
INH
B
DIR
MSB
0
LSB
3
SUB
2 DIR
3
CMP
2 DIR
3
SBC
2 DIR
3
CPX
2 DIR
3
AND
2 DIR
3
BIT
2 DIR
3
LDA
2 DIR
3
STA
2 DIR
3
EOR
2 DIR
3
ADC
2 DIR
3
ORA
2 DIR
3
ADD
2 DIR
2
JMP
2 DIR
4
4
BSR
JSR
2 REL 2 DIR
2
3
LDX
LDX
2 IMM 2 DIR
2
3
AIX
STX
2 IMM 2 DIR
2
SUB
2 IMM
2
CMP
2 IMM
2
SBC
2 IMM
2
CPX
2 IMM
2
AND
2 IMM
2
BIT
2 IMM
2
LDA
2 IMM
2
AIS
2 IMM
2
EOR
2 IMM
2
ADC
2 IMM
2
ORA
2 IMM
2
ADD
2 IMM
A
IMM
Low Byte of Opcode in Hexadecimal
5
3
NEG
NEG
3 SP1 1 IX
6
4
CBEQ
CBEQ
4 SP1 2 IX+
2
DAA
1 INH
5
3
COM
COM
3 SP1 1 IX
5
3
LSR
LSR
3 SP1 1 IX
4
CPHX
2 DIR
5
3
ROR
ROR
3 SP1 1 IX
5
3
ASR
ASR
3 SP1 1 IX
5
3
LSL
LSL
3 SP1 1 IX
5
3
ROL
ROL
3 SP1 1 IX
5
3
DEC
DEC
3 SP1 1 IX
6
4
DBNZ
DBNZ
4 SP1 2 IX
5
3
INC
INC
3 SP1 1 IX
4
2
TST
TST
3 SP1 1 IX
4
MOV
2 IX+D
4
2
CLR
CLR
3 SP1 1 IX
9E6
SP1
Table 6-2. Opcode Map
Read-Modify-Write
INH
IX1
SP1 Stack Pointer, 8-Bit Offset
SP2 Stack Pointer, 16-Bit Offset
IX+ Indexed, No Offset with
Post Increment
IX1+ Indexed, 1-Byte Offset with
Post Increment
4
1
NEG
NEGA
2 DIR 1 INH
5
4
CBEQ CBEQA
3 DIR 3 IMM
5
MUL
1 INH
4
1
COM
COMA
2 DIR 1 INH
4
1
LSR
LSRA
2 DIR 1 INH
4
3
STHX
LDHX
2 DIR 3 IMM
4
1
ROR
RORA
2 DIR 1 INH
4
1
ASR
ASRA
2 DIR 1 INH
4
1
LSL
LSLA
2 DIR 1 INH
4
1
ROL
ROLA
2 DIR 1 INH
4
1
DEC
DECA
2 DIR 1 INH
5
3
DBNZ DBNZA
3 DIR 2 INH
4
1
INC
INCA
2 DIR 1 INH
3
1
TST
TSTA
2 DIR 1 INH
5
MOV
3 DD
3
1
CLR
CLRA
2 DIR 1 INH
3
DIR
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
F
E
D
C
B
A
9
8
7
6
5
4
3
2
1
0
LSB
MSB
Bit Manipulation
DIR
DIR
E
3
SUB
2 IX1
3
CMP
2 IX1
3
SBC
2 IX1
3
CPX
2 IX1
3
AND
2 IX1
3
BIT
2 IX1
3
LDA
2 IX1
3
STA
2 IX1
3
EOR
2 IX1
3
ADC
2 IX1
3
ORA
2 IX1
3
ADD
2 IX1
3
JMP
2 IX1
5
JSR
2 IX1
5
3
LDX
LDX
4 SP2 2 IX1
5
3
STX
STX
4 SP2 2 IX1
5
SUB
4 SP2
5
CMP
4 SP2
5
SBC
4 SP2
5
CPX
4 SP2
5
AND
4 SP2
5
BIT
4 SP2
5
LDA
4 SP2
5
STA
4 SP2
5
EOR
4 SP2
5
ADC
4 SP2
5
ORA
4 SP2
5
ADD
4 SP2
9ED
IX1
F
IX
2
SUB
1 IX
2
CMP
1 IX
2
SBC
1 IX
2
CPX
1 IX
2
AND
1 IX
2
BIT
1 IX
2
LDA
1 IX
2
STA
1 IX
2
EOR
1 IX
2
ADC
1 IX
2
ORA
1 IX
2
ADD
1 IX
2
JMP
1 IX
4
JSR
1 IX
4
2
LDX
LDX
3 SP1 1 IX
4
2
STX
STX
3 SP1 1 IX
4
SUB
3 SP1
4
CMP
3 SP1
4
SBC
3 SP1
4
CPX
3 SP1
4
AND
3 SP1
4
BIT
3 SP1
4
LDA
3 SP1
4
STA
3 SP1
4
EOR
3 SP1
4
ADC
3 SP1
4
ORA
3 SP1
4
ADD
3 SP1
9EE
SP1
High Byte of Opcode in Hexadecimal
4
SUB
3 IX2
4
CMP
3 IX2
4
SBC
3 IX2
4
CPX
3 IX2
4
AND
3 IX2
4
BIT
3 IX2
4
LDA
3 IX2
4
STA
3 IX2
4
EOR
3 IX2
4
ADC
3 IX2
4
ORA
3 IX2
4
ADD
3 IX2
4
JMP
3 IX2
6
JSR
3 IX2
4
LDX
3 IX2
4
STX
3 IX2
D
Register/Memory
IX2
SP2
5
Cycles
BRSET0 Opcode Mnemonic
3 DIR Number of Bytes / Addressing Mode
0
4
SUB
3 EXT
4
CMP
3 EXT
4
SBC
3 EXT
4
CPX
3 EXT
4
AND
3 EXT
4
BIT
3 EXT
4
LDA
3 EXT
4
STA
3 EXT
4
EOR
3 EXT
4
ADC
3 EXT
4
ORA
3 EXT
4
ADD
3 EXT
3
JMP
3 EXT
5
JSR
3 EXT
4
LDX
3 EXT
4
STX
3 EXT
C
EXT
Freescale Semiconductor, Inc...
Freescale Semiconductor, Inc.
Central Processor Unit (CPU)
Opcode Map
Data Sheet
89
Freescale Semiconductor, Inc.
Freescale Semiconductor, Inc...
Central Processor Unit (CPU)
Data Sheet
MC68HC908AP Family — Rev. 2.5
90
MOTOROLA
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Freescale Semiconductor, Inc.
Data Sheet – MC68HC908AP Family
Section 7. Oscillator (OSC)
7.1 Introduction
Freescale Semiconductor, Inc...
The oscillator module consist of three types of oscillator circuits:
•
Internal oscillator
•
RC oscillator
•
32.768kHz crystal (x-tal) oscillator
The reference clock for the CGM and other MCU sub-systems is
selected by programming the mask option register located at $FFCF.
The reference clock for the timebase module (TBM) is selected by the
two bits, OSCCLK1 and OSCCLK0, in the CONFIG2 register.
The internal oscillator runs continuously after a POR or reset, and is
always available. The RC and crystal oscillator cannot run concurrently;
one is disabled while the other is selected; because the RC and x-tal
circuits share the same OSC1 pin.
NOTE:
The oscillator circuits are powered by the on-chip VREG regulator,
therefore, the output swing on OSC1 and OSC2 is from VSS to VREG.
Figure 7-1. shows the block diagram of the oscillator module.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
91
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Freescale Semiconductor, Inc.
Oscillator (OSC)
To CGM and others To CGM PLL
CGMXCLK
To TBM
CGMRCLK
OSCCLK
MOR
CONFIG2
OSCSEL1
OSCCLK1
MUX
MUX
Freescale Semiconductor, Inc...
OSCSEL0
OSCCLK0
X
RC
I
X
RC
I
To SIM
(and COP)
XCLK
ICLK
RCCLK
X-TAL OSCILLATOR
RC OSCILLATOR
INTERNAL OSCILLATOR
BUS CLOCK
OSC1
From SIM
OSC2
Figure 7-1. Oscillator Module Block Diagram
7.2 Clock Selection
Reference clocks are selectable for the following sub-systems:
Data Sheet
•
CGMXCLK and CGMRCLK — Reference clock for clock
generator module (CGM) and other MCU sub-systems other than
TBM and COP. This is the main reference clock for the MCU.
•
OSCCLK — Reference clock for timebase module (TBM).
MC68HC908AP Family — Rev. 2.5
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MOTOROLA
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Freescale Semiconductor, Inc.
Oscillator (OSC)
Clock Selection
7.2.1 CGM Reference Clock Selection
The clock generator module (CGM) reference clock (CGMXCLK) is the
reference clock input to the MCU. It is selected by programming two bits
in a FLASH memory location; the mask option register (MOR), at
$FFCF. See 5.5 Mask Option Register (MOR).
Address:
$FFCF
Bit 7
6
5
4
3
2
1
Bit 0
R
R
R
R
R
R
1
1
1
Freescale Semiconductor, Inc...
Read:
OSCSEL1 OSCSEL0
Write:
Reset:
Erased:
Unaffected by reset
1
1
R
1
1
1
= Reserved
Figure 7-2. Mask Option Register (MOR)
Table 7-1. CGMXCLK Clock Selection
OSCSEL1
OSCSEL0
CGMXCLK
OSC2 Pin
Comments
0
0
—
—
0
1
ICLK
fBUS
Internal oscillator generates the CGMXCLK.
1
0
RCCLK
fBUS
RC oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.
1
1
XCLK
Inverting
output of
X-TAL
X-tal oscillator generates the CGMXCLK.
Internal oscillator is available after each POR
or reset.
Not used
The internal oscillator is a free running oscillator and is available after
each POR or reset. It is turned-off in stop mode by setting the
STOP_ICLKDIS bit in CONFIG2.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
93
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Freescale Semiconductor, Inc.
Oscillator (OSC)
7.2.2 TBM Reference Clock Selection
The timebase module reference clock (OSCCLK) is selected by
configuring two bits in the CONFIG2 register, at $001D. See 5.4
Configuration Register 2 (CONFIG2).
Address:
$001D
Bit 7
Read:
Freescale Semiconductor, Inc...
STOP_
ICLKDIS
Write:
Reset:
0
6
STOP_
RCLKEN
0
5
4
3
STOP_
OSCCLK1 OSCCLK0
XCLKEN
0
0
0
2
1
0
0
Bit 0
SCIBDSRC
0
0
0
Figure 7-3. Configuration Register 2 (CONFIG2)
Table 7-2. Timebase Module Reference Clock Selection
NOTE:
OSCCLK1
OSCCLK0
Timebase Clock Source
0
0
Internal oscillator (ICLK)
0
1
RC oscillator (RCCLK)
1
0
X-tal oscillator (XCLK)
1
1
Not used
The RCCLK or XCLK is only available if that clock is selected as the
CGM reference clock, whereas the ICLK is always available.
7.3 Internal Oscillator
The internal oscillator clock (ICLK), with a frequency of fICLK, is a free
running clock that requires no external components. It can be selected
as the CGMXCLK for the CGM and MCU sub-systems; and the
OSCCLK clock for the TBM. The ICLK is also the reference clock input
to the computer operating properly (COP) module.
Due to the simplicity of the internal oscillator, it does not have the
accuracy and stability of the RC oscillator or the x-tal oscillator.
Therefore, the ICLK is not suitable where an accurate bus clock is
required and it should not be used as the CGMRCLK to the CGM PLL.
Data Sheet
MC68HC908AP Family — Rev. 2.5
94
MOTOROLA
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Oscillator (OSC)
RC Oscillator
The internal oscillator by default is always available and is free running
after POR or reset. It can be turned-off in stop mode by setting the
STOP_ICLKDIS bit before executing the STOP instruction.
Figure 7-4 shows the logical representation of components of the
internal oscillator circuitry.
From SIM
To Clock Selection MUX
and COP
Freescale Semiconductor, Inc...
SIMOSCEN
ICLK
From SIM
BUS CLOCK
CONFIG2
STOP_ICLKDIS
EN
INTERNAL OSCILLATOR
MCU
OSC2
Figure 7-4. Internal Oscillator
7.4 RC Oscillator
The RC oscillator circuit is designed for use with an external resistor and
a capacitor.
In its typical configuration, the RC oscillator requires two external
components, one R and one C. Component values should have a
tolerance of 1% or less, to obtain a clock source with less than 10%
tolerance. The oscillator configuration uses two components:
•
CEXT
•
REXT
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
95
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Freescale Semiconductor, Inc.
Oscillator (OSC)
To Clock Selection MUX
From SIM
SIMOSCEN
RCCLK
From SIM
BUS CLOCK
CONFIG2
EN
Freescale Semiconductor, Inc...
STOP_RCLKEN
RC OSCILLATOR
MCU
OSC1
OSC2
See Section 24. for component value requirements.
VREG
REXT
CEXT
Figure 7-5. RC Oscillator
7.5 X-tal Oscillator
The crystal (x-tal) oscillator circuit is designed for use with an external
32.768kHz crystal to provide an accurate clock source.
In its typical configuration, the x-tal oscillator is connected in a Pierce
oscillator configuration, as shown in Figure 7-6. This figure shows only
the logical representation of the internal components and may not
represent actual circuitry. The oscillator configuration uses five
components:
Data Sheet
•
Crystal, X1 (32.768kHz)
•
Fixed capacitor, C1
•
Tuning capacitor, C2 (can also be a fixed capacitor)
•
Feedback resistor, RB
•
Series resistor, RS (optional)
MC68HC908AP Family — Rev. 2.5
96
MOTOROLA
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Freescale Semiconductor, Inc.
Oscillator (OSC)
I/O Signals
From SIM
To Clock Selection MUX
SIMOSCEN
XCLK
CONFIG2
STOP_XCLKEN
Freescale Semiconductor, Inc...
MCU
OSC1
OSC2
RB
RS
X1
See Section 24. for component value requirements.
C1
32.768kHz
C2
Figure 7-6. Crystal Oscillator
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.
7.6 I/O Signals
The following paragraphs describe the oscillator I/O signals.
7.6.1 Crystal Amplifier Input Pin (OSC1)
OSC1 pin is an input to the crystal oscillator amplifier or the input to the
RC oscillator circuit.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
97
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Freescale Semiconductor, Inc.
Oscillator (OSC)
7.6.2 Crystal Amplifier Output Pin (OSC2)
When the x-tal oscillator is selected, OSC2 pin is the output of the crystal
oscillator inverting amplifier.
When the RC oscillator or internal oscillator is selected, OSC2 pin is the
output of the internal bus clock.
Freescale Semiconductor, Inc...
7.6.3 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal from the system integration module (SIM)
enables/disables the x-tal oscillator, the RC-oscillator, or the internal
oscillator circuit.
7.6.4 CGM Oscillator Clock (CGMXCLK)
The CGMXCLK clock is output from the x-tal oscillator, RC oscillator or
the internal oscillator. This clock drives to CGM and other MCU subsystems.
7.6.5 CGM Reference Clock (CGMRCLK)
This is buffered signal of CGMXCLK, it is used by the CGM as the
phase-locked-loop (PLL) reference clock.
7.6.6 Oscillator Clock to Time Base Module (OSCCLK)
The OSCCLK is the reference clock that drives the timebase module.
See Section 12. Timebase Module (TBM).
7.7 Low Power Modes
The WAIT and STOP instructions put the MCU in low-power
consumption standby modes.
Data Sheet
MC68HC908AP Family — Rev. 2.5
98
MOTOROLA
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Freescale Semiconductor, Inc.
Oscillator (OSC)
Oscillator During Break Mode
7.7.1 Wait Mode
The WAIT instruction has no effect on the oscillator module. CGMXCLK
continues to drive to the clock generator module, and OSCCLK
continues to drive the timebase module.
Freescale Semiconductor, Inc...
7.7.2 Stop Mode
The STOP instruction disables the x-tal or the RC oscillator circuit, and
hence the CGMXCLK clock stops running. For continuous x-tal or RC
oscillator operation in stop mode, set the STOP_XCLKEN (for x-tal) or
STOP_RCLKEN (for RC) bit to logic 1 before entering stop mode.
The internal oscillator clock continues operation in stop mode. It can be
disabled by setting the STOP_ICLKDIS bit to logic 1 before entering stop
mode.
7.8 Oscillator During Break Mode
The oscillator continues to drive CGMXCLK when the device enters the
break state.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
99
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Freescale Semiconductor, Inc.
Freescale Semiconductor, Inc...
Oscillator (OSC)
Data Sheet
MC68HC908AP Family — Rev. 2.5
100
MOTOROLA
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Freescale Semiconductor, Inc.
Data Sheet – MC68HC908AP Family
Section 8. Clock Generator Module (CGM)
Freescale Semiconductor, Inc...
8.1 Introduction
This section describes the clock generator module (CGM). The CGM
generates the base clock signal, CGMOUT, which is based on either the
oscillator clock divided by two or the divided phase-locked loop (PLL)
clock, CGMPCLK, divided by two. CGMOUT is the clock from which the
SIM derives the system clocks, including the bus clock, which is at a
frequency of CGMOUT÷2.
The PLL is a frequency generator designed for use with a low frequency
crystal (typically 32.768kHz) to generate a base frequency and dividing
to a maximum bus frequency of 8MHz.
8.2 Features
Features of the CGM include:
•
Phase-locked loop with output frequency in integer multiples of an
integer dividend of the crystal reference
•
Low-frequency crystal operation with low-power operation and
high-output frequency resolution
•
Programmable prescaler for power-of-two increases in frequency
•
Programmable hardware voltage-controlled oscillator (VCO) for
low-jitter operation
•
Automatic bandwidth control mode for low-jitter operation
•
Automatic frequency lock detector
•
CPU interrupt on entry or exit from locked condition
•
Configuration register bit to allow oscillator operation during stop
mode
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
101
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Freescale Semiconductor, Inc.
Clock Generator Module (CGM)
8.3 Functional Description
Freescale Semiconductor, Inc...
The CGM consists of three major sub-modules:
•
Oscillator module — The oscillator module generates the constant
reference frequency clock, CGMRCLK (buffered CGMXCLK).
•
Phase-locked loop (PLL) — The PLL generates the
programmable VCO frequency clock, CGMVCLK, and the divided
VCO clock, CGMPCLK.
•
Base clock selector circuit — This software-controlled circuit
selects either CGMXCLK divided by two or the divided VCO clock,
CGMPCLK, divided by two as the base clock, CGMOUT. The SIM
derives the system clocks from either CGMOUT or CGMXCLK.
Figure 8-1 shows the structure of the CGM.
Figure 8-2 is a summary of the CGM registers.
Data Sheet
MC68HC908AP Family — Rev. 2.5
102
MOTOROLA
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Clock Generator Module (CGM)
Functional Description
OSC2
OSC1
OSCILLATOR (OSC) MODULE
See Section 7. Oscillator (OSC).
ICLK
INTERNAL OSCILLATOR
OSCCLK
RC OSCILLATOR
OSCSEL[1:0]
To Timebase Module (TBM)
CGMXCLK
MUX
To ADC
CGMRCLK
CRYSTAL OSCILLATOR
OSCCLK[1:0]
To SIM (and COP)
Freescale Semiconductor, Inc...
SIMOSCEN
From SIM
PHASE-LOCKED LOOP (PLL)
CGMRDV
CGMRCLK
REFERENCE
DIVIDER
R
RDS[3:0]
VDDA
CGMXFC
CGMOUT
A
CLOCK
SELECT
CIRCUIT
BCS
÷2
1
B S*
*WHEN S = 1,
CGMOUT = B
VSSA
To SIM
SIMDIV2
From SIM
VPR[1:0]
VRS[7:0]
L
PHASE
DETECTOR
2E
CGMPCLK
VOLTAGE
CONTROLLED
OSCILLATOR
LOOP
FILTER
PLL ANALOG
AUTOMATIC
MODE
CONTROL
LOCK
DETECTOR
LOCK
AUTO
MUL[11:0]
PLLIE
CGMINT
To SIM
PLLF
PRE[1:0]
N
CGMVDV
ACQ
INTERRUPT
CONTROL
2P
FREQUENCY
DIVIDER
FREQUENCY
DIVIDER
CGMVCLK
Figure 8-1. CGM Block Diagram
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
103
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Freescale Semiconductor, Inc.
Clock Generator Module (CGM)
Addr.
Register Name
Bit 7
Read:
PLL Control Register
Write:
(PTCL)
Reset:
$0036
Freescale Semiconductor, Inc...
$0037
Read:
PLL Bandwidth Control
Register Write:
(PBWC)
Reset:
Read:
PLL Multiplier Select
Register High Write:
(PMSH)
Reset:
$0038
Read:
PLL Multiplier Select
Register Low Write:
(PMSL)
Reset:
$0039
$003A
$003B
Read:
PLL VCO Range Select
Register Write:
(PMRS)
Reset:
Read:
PLL Reference Divider
Select Register Write:
(PMDS)
Reset:
6
5
4
3
2
1
Bit 0
PLLON
BCS
PRE1
PRE0
VPR1
VPR0
1
0
0
0
0
0
0
0
0
0
PLLF
PLLIE
0
0
LOCK
AUTO
ACQ
R
0
0
0
0
0
0
0
0
0
0
0
MUL11
MUL10
MUL9
MUL8
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
MUL3
MUL2
MUL1
MUL0
0
1
0
0
0
0
0
0
VRS7
VRS6
VRS5
VRS4
VRS3
VRS2
VRS1
VRS0
0
1
0
0
0
0
0
0
0
0
0
0
RDS3
RDS2
RDS1
RDS0
0
0
0
1
0
0
0
0
= Unimplemented
R
= Reserved
NOTES:
1. When AUTO = 0, PLLIE is forced clear and is read-only.
2. When AUTO = 0, PLLF and LOCK read as clear.
3. When AUTO = 1, ACQ is read-only.
4. When PLLON = 0 or VRS7:VRS0 = $0, BCS is forced clear 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 8-2. CGM I/O Register Summary
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Clock Generator Module (CGM)
Functional Description
8.3.1 Oscillator Module
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The oscillator module provides two clock outputs CGMXCLK and
CGMRCLK to the CGM module. CGMXCLK when selected, is driven to
SIM module to generate the system bus clock. CGMRCLK is used by the
phase-lock-loop to provide a higher frequency system bus clock. The
oscillator module also provides the reference clock for the timebase
module (TBM). See Section 7. Oscillator (OSC) for detailed oscillator
circuit description. See Section 12. Timebase Module (TBM) for
detailed description on TBM.
8.3.2 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.
8.3.3 PLL Circuits
The PLL consists of these circuits:
•
Voltage-controlled oscillator (VCO)
•
Reference divider
•
Frequency pre-scaler
•
Modulo VCO frequency divider
•
Phase detector
•
Loop filter
•
Lock detector
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Clock Generator Module (CGM)
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, (125 kHz) times a linear factor, L, and a power-of-two
factor, E, or (L × 2E)fNOM.
Freescale Semiconductor, Inc...
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
programmable modulo reference divider, which divides fRCLK by a
factor, R. The divider’s output is the final reference clock, CGMRDV,
running at a frequency, fRDV = fRCLK/R. With an external crystal
(30kHz–100kHz), always set R = 1 for specified performance. With an
external high-frequency clock source, use R to divide the external
frequency to between 30kHz and 100kHz.
The VCO’s output clock, CGMVCLK, running at a frequency, fVCLK, is
fed back through a programmable pre-scaler divider and a
programmable modulo divider. The pre-scaler divides the VCO clock by
a power-of-two factor P (the CGMPCLK) and the modulo divider reduces
the VCO clock by a factor, N. The dividers’ output is the VCO feedback
clock, CGMVDV, running at a frequency, fVDV = fVCLK/(N × 2P). (See
8.3.6 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 8.3.4 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.
Data Sheet
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Clock Generator Module (CGM)
Functional Description
8.3.4 Acquisition and Tracking Modes
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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 start
up 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 8.5.2 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. (See 8.3.8 Base Clock Selector Circuit.) The PLL is
automatically in tracking mode when not in acquisition mode or
when the ACQ bit is set.
8.3.5 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter
manually or automatically. Automatic mode is recommended for most
users.
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. (See 8.5.2 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 start-up, 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 8.3.8 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 8.6 Interrupts for information and precautions on using interrupts.)
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Clock Generator Module (CGM)
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The following conditions apply when the PLL is in automatic bandwidth
control mode:
•
The ACQ bit (See 8.5.2 PLL Bandwidth Control Register.) is a
read-only indicator of the mode of the filter. (See 8.3.4
Acquisition and Tracking Modes.)
•
The ACQ bit is set when the VCO frequency is within a certain
tolerance and is cleared when the VCO frequency is out of a
certain tolerance. (See 8.8 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 and is cleared when the VCO frequency is out of a
certain tolerance. (See 8.8 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 8.5.1 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.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Clock Generator Module (CGM)
Functional Description
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The following conditions apply when in manual mode:
•
ACQ is a writable control bit that controls the mode of the filter.
Before turning on the PLL in manual mode, the ACQ bit must be
clear.
•
Before entering tracking mode (ACQ = 1), software must wait a
given time, tACQ (See 8.8 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.
8.3.6 Programming the PLL
The following 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, or the desired VCO
frequency, fVCLKDES; and then solve for the other.
The relationship between fBUS and fVCLK is governed by the
equation:
P
P
f VCLK = 2 × f CGMPCLK = 2 × 4
× fBUS
where P is the power of two multiplier, and can be 0, 1, 2, or 3
2. Choose a practical PLL reference frequency, fRCLK, and the
reference clock divider, R. Typically, the reference is 32.768kHz
and R = 1.
Frequency errors to the PLL are corrected at a rate of fRCLK/R. For
stability and lock time reduction, this rate must be as fast as
possible. The VCO frequency must be an integer multiple of this
rate.
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Clock Generator Module (CGM)
The relationship between the VCO frequency, fVCLK, and the
reference frequency, fRCLK, is
P
2 N
f VCLK = ----------- ( f RCLK )
R
where N is the integer range multiplier, between 1 and 4095.
In cases where desired bus frequency has some tolerance,
choose fRCLK to a value determined either by other module
Freescale Semiconductor, Inc...
requirements (such as modules which are clocked by CGMXCLK),
cost requirements, or ideally, as high as the specified range
allows. See Section 24. Electrical Specifications.
Choose the reference divider, R = 1.
When the tolerance on the bus frequency is tight, choose fRCLK to
an integer divisor of fBUSDES, and R = 1. If fRCLK cannot meet this
requirement, use the following equation to solve for R with
practical choices of fRCLK, and choose the fRCLK that gives the
lowest R.
⎛ f VCLKDES⎞ ⎫
⎧ ⎛ f VCLKDES⎞
R = round R MAX × ⎨ ⎜ --------------------------⎟ – integer ⎜ --------------------------⎟ ⎬
⎝ f RCLK ⎠ ⎭
⎩ ⎝ f RCLK ⎠
3. Calculate N:
⎛ R × f VCLKDES⎞
N = round ⎜ -------------------------------------⎟
P
⎝ f
⎠
RCLK × 2
4. Calculate and verify the adequacy of the VCO and bus
frequencies fVCLK and fBUS.
P
2 N
f VCLK = ----------- ( f RCLK )
R
f BUS =
Data Sheet
f
VCLK
---------P
2 ×4
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Clock Generator Module (CGM)
Functional Description
5. Select the VCO’s power-of-two range multiplier E, according to
this table:
Frequency Range
E
0 < fVCLK < 9,830,400
0
9,830,400 ≤ fVCLK < 19,660,800
1
19,660,800 ≤ fVCLK < 39,321,600
2
Freescale Semiconductor, Inc...
NOTE: Do not program E to a value of 3.
6. Select a VCO linear range multiplier, L, where fNOM = 125kHz
⎛ f VCLK ⎞
L = round ⎜ --------------------------⎟
⎝ 2E × f
⎠
NOM
7. Calculate and verify the adequacy of the VCO programmed
center-of-range frequency, fVRS. The center-of-range frequency is
the midpoint between the minimum and maximum frequencies
attainable by the PLL.
E
f VRS = ( L × 2 )f NOM
For proper operation,
E
f NOM × 2
f VRS – f VCLK ≤ -------------------------2
8. Verify the choice of P, R, N, E, 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.
NOTE:
Exceeding the recommended maximum bus frequency or VCO
frequency can crash the MCU.
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Clock Generator Module (CGM)
9. Program the PLL registers accordingly:
a. In the PRE bits of the PLL control register (PCTL), program
the binary equivalent of P.
b. In the VPR bits of the PLL control register (PCTL), program
the binary equivalent of E.
c. In the PLL multiplier select register low (PMSL) and the PLL
multiplier select register high (PMSH), program the binary
equivalent of N.
Freescale Semiconductor, Inc...
d. In the PLL VCO range select register (PMRS), program the
binary coded equivalent of L.
e. In the PLL reference divider select register (PMDS), program
the binary coded equivalent of R.
NOTE:
The values for P, E, N, L, and R can only be programmed when the PLL
is off (PLLON = 0).
Table 8-1 provides numeric examples (numbers are in hexadecimal
notation):
Table 8-1. Numeric Examples
Data Sheet
CGMVCLK
CGMPCLK
fBUS
fRCLK
R
N
P
E
L
8.0 MHz
8.0 MHz
2.0 MHz
32.768 kHz
1
F5
0
0
40
9.8304 MHz
9.8304 MHz
2.4576 MHz
32.768 kHz
1
12C
0
1
27
10.0 MHz
10.0 MHz
2.5 MHz
32.768 kHz
1
132
0
1
28
16 MHz
16 MHz
4.0 MHz
32.768 kHz
1
1E9
0
1
40
19.6608 MHz
19.6608 MHz
4.9152 MHz
32.768 kHz
1
258
0
2
27
20 MHz
20 MHz
5.0 MHz
32.768 kHz
1
263
0
2
28
29.4912 MHz
29.4912 MHz
7.3728 MHz
32.768 kHz
1
384
0
2
3B
32 MHz
32 MHz
8.0 MHz
32.768 kHz
1
3D1
0
2
40
32 MHz
16 MHz
4.0 MHz
32.768 kHz
1
1E9
1
2
40
32 MHz
8 MHz
2.0 MHz
32.768 kHz
1
F5
2
2
40
32 MHz
4 MHz
1.0 MHz
32.768 kHz
1
7B
3
2
40
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Functional Description
8.3.7 Special Programming Exceptions
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The programming method described in 8.3.6 Programming the PLL
does not account for three possible exceptions. A value of 0 for R, N, or
L is meaningless when used in the equations given. To account for these
exceptions:
•
A 0 value for R or 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 8.3.8 Base Clock Selector Circuit.)
8.3.8 Base Clock Selector Circuit
This circuit is used to select either the oscillator clock, CGMXCLK, or the
divided VCO clock, CGMPCLK, 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 CGMPCLK cycles to
change from one clock source to the other. During this time, CGMOUT
is held in stasis. 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 CGMPCLK).
The BCS bit in the PLL control register (PCTL) selects which clock drives
CGMOUT. The divided 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
divided VCO clock is selected. The PLL cannot be turned on or off
simultaneously with the selection or deselection of the divided VCO
clock. The divided 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 oscillator clock would be forced as the source
of the base clock.
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Clock Generator Module (CGM)
8.3.9 CGM External Connections
In its typical configuration, the CGM requires up to four external
components.
Figure 8-3 shows the external components for the PLL:
•
Bypass capacitor, CBYP
•
Filter network
Freescale Semiconductor, Inc...
Care should be taken with PCB routing in order to minimize signal cross
talk and noise. (See 8.8 Acquisition/Lock Time Specifications for
routing information, filter network and its effects on PLL performance.)
MCU
VSSA
CGMXFC
VDDA
VDD
1 kΩ
CBYP
0.1 µF
10 nF
0.22 µF
Note: Filter network in box can be replaced with a 0.47µF capacitor, but will degrade stability.
Figure 8-3. CGM External Connections
8.4 I/O Signals
The following paragraphs describe the CGM I/O signals.
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Clock Generator Module (CGM)
I/O Signals
8.4.1 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase
corrections. An external filter network is connected to this pin. (See
Figure 8-3.)
Freescale Semiconductor, Inc...
NOTE:
To prevent noise problems, the filter network should be placed as close
to the CGMXFC pin as possible, with minimum routing distances and no
routing of other signals across the network.
8.4.2 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.
8.4.3 PLL Analog Ground Pin (VSSA)
VSSA is a ground pin used by the analog portions of the PLL. Connect
the VSSA pin to the same voltage potential as the VSS pin.
NOTE:
Route VSSA carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
8.4.4 Oscillator Output Frequency Signal (CGMXCLK)
CGMXCLK is the oscillator output signal. It runs at the full speed of the
oscillator, and is generated directly from the crystal oscillator circuit, the
RC oscillator circuit, or the internal oscillator circuit.
8.4.5 CGM Reference Clock (CGMRCLK)
CGMRCLK is a buffered version of CGMXCLK, this clock is the
reference clock for the phase-locked-loop circuit.
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Clock Generator Module (CGM)
8.4.6 CGM VCO Clock Output (CGMVCLK)
CGMVCLK is the clock output from the VCO.
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8.4.7 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 divided VCO clock, CGMPCLK, divided by two.
8.4.8 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
8.5 CGM Registers
The following registers control and monitor operation of the CGM:
Data Sheet
•
PLL control register (PCTL)
(See 8.5.1 PLL Control Register.)
•
PLL bandwidth control register (PBWC)
(See 8.5.2 PLL Bandwidth Control Register.)
•
PLL multiplier select registers (PMSH and PMSL)
(See 8.5.3 PLL Multiplier Select Registers.)
•
PLL VCO range select register (PMRS)
(See 8.5.4 PLL VCO Range Select Register.)
•
PLL reference divider select register (PMDS)
(See 8.5.5 PLL Reference Divider Select Register.)
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Clock Generator Module (CGM)
CGM Registers
8.5.1 PLL Control Register
The PLL control register (PCTL) contains the interrupt enable and flag
bits, the on/off switch, the base clock selector bit, the prescaler bits, and
the VCO power-of-two range selector bits.
Address:
$0036
Bit 7
Read:
6
5
4
3
2
1
Bit 0
PLLON
BCS
PRE1
PRE0
VPR1
VPR0
1
0
0
0
0
0
PLLF
PLLIE
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Write:
Reset:
0
0
= Unimplemented
Figure 8-4. PLL Control Register (PCTL)
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.
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Clock Generator Module (CGM)
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). (See 8.3.8 Base Clock Selector
Circuit.) Reset sets this bit so that the loop can stabilize as the MCU
is powering up.
1 = PLL on
0 = PLL off
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BCS — Base Clock Select Bit
This read/write bit selects either the oscillator output, CGMXCLK, or
the divided VCO clock, CGMPCLK, 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
CGMPCLK cycles to complete the transition from one source clock to
the other. During the transition, CGMOUT is held in stasis. (See 8.3.8
Base Clock Selector Circuit.) Reset clears the BCS bit.
1 = CGMPCLK divided by two drives CGMOUT
0 = CGMXCLK divided by two drives CGMOUT
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 CGMPCLK requires two writes to the PLL control
register. (See 8.3.8 Base Clock Selector Circuit.)
PRE1 and PRE0 — Prescaler Program Bits
These read/write bits control a prescaler that selects the prescaler
power-of-two multiplier, P. (See 8.3.3 PLL Circuits and 8.3.6
Programming the PLL.) PRE1 and PRE0 cannot be written when
the PLLON bit is set. Reset clears these bits.
These prescaler bits affects the relationship between the VCO clock
and the final system bus clock.
Data Sheet
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Clock Generator Module (CGM)
CGM Registers
Table 8-2. PRE1 and PRE0 Programming
PRE1 and PRE0
P
Prescaler Multiplier
00
0
1
01
1
2
10
2
4
11
3
8
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VPR1 and VPR0 — VCO Power-of-Two Range Select Bits
These read/write bits control the VCO’s hardware power-of-two range
multiplier E that, in conjunction with L (See 8.3.3 PLL Circuits, 8.3.6
Programming the PLL, and 8.5.4 PLL VCO Range Select
Register.) controls the hardware center-of-range frequency, fVRS.
VPR1:VPR0 cannot be written when the PLLON bit is set. Reset
clears these bits.
Table 8-3. VPR1 and VPR0 Programming
VPR1 and VPR0
E
VCO Power-of-Two
Range Multiplier
00
0
1
01
1
2
10
2
4
NOTE: Do not program E to a value of 3.
8.5.2 PLL Bandwidth Control Register
The PLL bandwidth control register (PBWC):
•
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
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Clock Generator Module (CGM)
Address:
$0037
Bit 7
Read:
6
5
LOCK
AUTO
4
3
2
1
0
0
0
0
Bit 0
ACQ
R
Write:
Reset:
0
0
0
= Unimplemented
0
0
R
0
0
= Reserved
Figure 8-5. PLL Bandwidth Control Register (PBWCR)
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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. The write one function of this bit is
reserved for test, so this bit must always be written a 0. Reset clears
the LOCK bit.
1 = VCO frequency correct or locked
0 = VCO frequency incorrect or unlocked
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
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Clock Generator Module (CGM)
CGM Registers
8.5.3 PLL Multiplier Select Registers
The PLL multiplier select registers (PMSH and PMSL) contain the
programming information for the modulo feedback divider.
Address:
Read:
$0038
Bit 7
6
5
4
0
0
0
0
3
2
1
Bit 0
MUL11
MUL10
MUL9
MUL8
0
0
0
0
Write:
Freescale Semiconductor, Inc...
Reset:
0
0
0
0
= Unimplemented
Figure 8-6. PLL Multiplier Select Register High (PMSH)
Address:
$0039
Bit 7
6
5
4
3
2
1
Bit 0
MUL7
MUL6
MUL5
MUL4
MUL3
MUL2
MUL1
MUL0
0
1
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 8-7. PLL Multiplier Select Register Low (PMSL)
MUL[11:0] — Multiplier Select Bits
These read/write bits control the modulo feedback divider that selects
the VCO frequency multiplier N. (See 8.3.3 PLL Circuits and 8.3.6
Programming the PLL.) A value of $0000 in the multiplier select
registers configure the modulo feedback divider the same as a value
of $0001. Reset initializes the registers to $0040 for a default multiply
value of 64.
NOTE:
The multiplier select bits have built-in protection such that they cannot
be written when the PLL is on (PLLON = 1).
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Clock Generator Module (CGM)
8.5.4 PLL VCO Range Select Register
The PLL VCO range select register (PMRS) contains the programming
information required for the hardware configuration of the VCO.
Address:
$003A
Bit 7
6
5
4
3
2
1
Bit 0
VRS7
VRS6
VRS5
VRS4
VRS3
VRS2
VRS1
VRS0
0
1
0
0
0
0
0
0
Read:
Write:
Freescale Semiconductor, Inc...
Reset:
Figure 8-8. PLL VCO Range Select Register (PMRS)
VRS[7:0] — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear
multiplier L which, in conjunction with E (See 8.3.3 PLL Circuits,
8.3.6 Programming the PLL, and 8.5.1 PLL Control Register.),
controls the hardware center-of-range frequency, fVRS. VRS[7:0]
cannot be written when the PLLON bit in the PCTL is set. (See 8.3.7
Special Programming Exceptions.) A value of $00 in the VCO
range select register disables the PLL and clears the BCS bit in the
PLL control register (PCTL). (See 8.3.8 Base Clock Selector Circuit
and 8.3.7 Special Programming Exceptions.). Reset initializes the
register to $40 for a default range multiply value of 64.
NOTE:
The VCO range select bits have built-in protection such that they cannot
be written when the PLL is on (PLLON = 1) and such that the VCO clock
cannot be selected as the source of the base clock (BCS = 1) if the VCO
range select bits are all clear.
The PLL VCO range select register must be programmed correctly.
Incorrect programming can result in failure of the PLL to achieve lock.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Clock Generator Module (CGM)
CGM Registers
8.5.5 PLL Reference Divider Select Register
The PLL reference divider select register (PMDS) contains the
programming information for the modulo reference divider.
Address:
Read:
$003B
Bit 7
6
5
4
0
0
0
0
3
2
1
Bit 0
RDS3
RDS2
RDS1
RDS0
0
0
0
1
Write:
Freescale Semiconductor, Inc...
Reset:
0
0
0
0
= Unimplemented
Figure 8-9. PLL Reference Divider Select Register (PMDS)
RDS[3:0] — Reference Divider Select Bits
These read/write bits control the modulo reference divider that selects
the reference division factor, R. (See 8.3.3 PLL Circuits and 8.3.6
Programming the PLL.) RDS[3:0] cannot be written when the
PLLON bit in the PCTL is set. A value of $00 in the reference divider
select register configures the reference divider the same as a value of
$01. (See 8.3.7 Special Programming Exceptions.) Reset
initializes the register to $01 for a default divide value of 1.
NOTE:
The reference divider select bits have built-in protection such that they
cannot be written when the PLL is on (PLLON = 1).
NOTE:
The default divide value of 1 is recommended for all applications.
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Clock Generator Module (CGM)
8.6 Interrupts
Freescale Semiconductor, Inc...
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 divided VCO clock, CGMPCLK, 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 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 CGMPCLK 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.
8.7 Special Modes
The WAIT instruction puts the MCU in low power-consumption standby
modes.
8.7.1 Wait 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) to save power. Less
power-sensitive applications can disengage the PLL without turning it
off, so that the PLL clock is immediately available at WAIT exit. This
would be the case also when the PLL is to wake the MCU from wait
mode, such as when the PLL is first enabled and waiting for LOCK or
LOCK is lost.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Clock Generator Module (CGM)
Special Modes
8.7.2 Stop Mode
The STOP instruction disables the PLL analog circuits and no clock will
be driven out of the VCO.
When entering stop mode with the VCO clock (CGMPCLK) selected,
before executing the STOP instruction:
Freescale Semiconductor, Inc...
1. Set the oscillator stop mode enable bit (STOP_XCLKEN in
CONFIG2) if continuos clock is required in stop mode.
2. Clear the BCS bit to select CGMXCLK as CGMOUT.
On exit from stop mode:
1. Set the PLLON bit if cleared before entering stop mode.
2. Wait for PLL to lock by checking the LOCK bit.
3. Set BCS bit to select CGMPCLK as CGMOUT.
8.7.3 CGM During Break Interrupts
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 9.7.3 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 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.
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Clock Generator Module (CGM)
8.8 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.
8.8.1 Acquisition/Lock Time Definitions
Freescale Semiconductor, Inc...
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 0Hz to 1MHz, the
acquisition time is the time taken for the frequency to reach
1MHz ±50kHz. 50kHz = 5% of the 1MHz step input. If the system is
operating at 1MHz and suffers a –100kHz noise hit, the acquisition time
is the time taken to return from 900kHz to 1MHz ±5kHz. 5kHz = 5% of
the 100kHz 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.
8.8.2 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.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Clock Generator Module (CGM)
Acquisition/Lock Time Specifications
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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 under user control via the choice of crystal
frequency fXCLK and the R value programmed in the reference divider.
(See 8.3.3 PLL Circuits, 8.3.6 Programming the PLL, and 8.5.5 PLL
Reference Divider Select Register.)
Another critical parameter is the external filter network. The PLL
modifies the voltage on the VCO by adding or subtracting charge from
capacitors in this network. Therefore, the rate at which the voltage
changes for a given frequency error (thus change in charge) is
proportional to the capacitance. 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 8.8.3 Choosing a Filter.)
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.
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Clock Generator Module (CGM)
8.8.3 Choosing a Filter
As described in 8.8.2 Parametric Influences on Reaction Time, the
external filter network is critical to the stability and reaction time of the
PLL. The PLL is also dependent on reference frequency and supply
voltage.
Freescale Semiconductor, Inc...
Either of the filter networks in Figure 8-10 is recommended when using
a 32.768kHz reference clock (CGMRCLK). Figure 8-10 (a) is used for
applications requiring better stability. Figure 8-10 (b) is used in low-cost
applications where stability is not critical.
CGMXFC
CGMXFC
1 kΩ
10 nF
0.22 µF
0.22 µF
VSSA
VSSA
(a)
(b)
Figure 8-10. PLL Filter
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Section 9. System Integration Module (SIM)
9.1 Introduction
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This section describes the system integration module (SIM). Together
with the CPU, the SIM controls all MCU activities. A block diagram of the
SIM is shown in Figure 9-1. Table 9-1 is a summary of the SIM
input/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 COP
timeout
•
Interrupt control:
– Acknowledge timing
– Arbitration control timing
– Vector address generation
•
CPU enable/disable timing
•
Modular architecture expandable to 128 interrupt sources
Table 9-1 shows the internal signal names used in this section.
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System Integration Module (SIM)
MODULE STOP
MODULE WAIT
CPU STOP (FROM CPU)
CPU WAIT (FROM CPU)
STOP/WAIT
CONTROL
SIMOSCEN (TO CGM, OSC)
SIM
COUNTER
COP CLOCK
ICLK (FROM OSC)
Freescale Semiconductor, Inc...
CGMOUT (FROM CGM)
÷2
CLOCK
CONTROL
VDD
CLOCK GENERATORS
INTERNAL CLOCKS
INTERNAL
PULLUP
DEVICE
RESET
PIN LOGIC
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 SOURCES
INTERRUPT CONTROL
AND PRIORITY DECODE
CPU INTERFACE
Figure 9-1. SIM Block Diagram
Table 9-1. Signal Name Conventions
Signal Name
ICLK
CGMXCLK
CGMVCLK, CGMPCLK
CGMOUT
IAB
IDB
PORRST
Data Sheet
Description
Internal oscillator clock
Selected oscillator clock from oscillator module
PLL output and the divided PLL output
CGMPCLK-based or oscillator-based clock output from CGM module
(Bus clock = CGMOUT ÷ 2)
Internal address bus
Internal data bus
Signal from the power-on reset module to the SIM
IRST
Internal reset signal
R/W
Read/write signal
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System Integration Module (SIM)
SIM Bus Clock Control and Generation
Addr.
Register Name
Read:
SIM Break Status Register
$FE00
Write:
(SBSR)
Reset:
Bit 7
6
5
4
3
2
1
R
R
R
R
R
R
0
0
0
0
0
0
0
0
POR
PIN
COP
ILOP
ILAD
MODRST
LVI
0
1
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
SBSW
NOTE
Bit 0
R
Note: Writing a logic 0 clears SBSW.
Freescale Semiconductor, Inc...
Read:
SIM Reset Status Register
$FE01
Write:
(SRSR)
POR:
$FE03
Read:
SIM Break Flag Control
Write:
Register (SBFCR)
Reset:
0
Read:
Interrupt Status Register 1
$FE04
Write:
(INT1)
Reset:
IF6
IF5
IF4
IF3
IF2
IF1
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
Interrupt Status Register 2
$FE05
Write:
(INT2)
Reset:
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
Interrupt Status Register 3
$FE06
Write:
(INT3)
Reset:
0
IF21
IF20
IF19
IF18
IF17
IF16
IF15
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
= Unimplemented
Figure 9-2. SIM I/O Register Summary
9.2 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 9-3. This clock can come
from either an external oscillator or from the on-chip PLL. (See Section
8. Clock Generator Module (CGM).)
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System Integration Module (SIM)
OSC2
OSCCLK
TO TBM
OSCILLATOR (OSC) MODULE
CGMXCLK
OSC1
ICLK
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STOP MODE CLOCK
ENABLE SIGNALS
FROM CONFIG2
TO TIM, ADC
SIM COUNTER
SIMOSCEN
SYSTEM INTEGRATION MODULE
CGMRCLK
CGMOUT
BUS CLOCK
GENERATORS
÷2
PHASE-LOCKED LOOP (PLL)
IT12
TO REST
OF MCU
IT23
TO REST
OF MCU
PTB0
SIMDIV2
MONITOR MODE
USER MODE
CGMVCLK
TO PWM
Figure 9-3. CGM Clock Signals
9.2.1 Bus Timing
In user mode, the internal bus frequency is either the oscillator output
(CGMXCLK) divided by four or the divided PLL output (CGMPCLK)
divided by four.
9.2.2 Clock Start-up from POR or LVI Reset
When the power-on reset module or the low-voltage inhibit module
generates a reset, the clocks to the CPU and peripherals are inactive
and held in an inactive phase until after the 4096 ICLK 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.
Data Sheet
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System Integration Module (SIM)
Reset and System Initialization
9.2.3 Clocks in Stop Mode and Wait Mode
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Upon exit from stop mode by an interrupt, break, or reset, the SIM allows
ICLK to clock the SIM counter. The CPU and peripheral clocks do not
become active until after the stop delay timeout. This timeout is
selectable as 4096 or 32 ICLK cycles. (See 9.6.2 Stop 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.
9.3 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 9.4 SIM Counter), but an
external reset does not. Each of the resets sets a corresponding bit in
the SIM reset status register (SRSR). (See 9.7 SIM Registers.)
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System Integration Module (SIM)
9.3.1 External Pin Reset
The RST pin circuit includes an internal pull-up device. 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 ICLK cycles, assuming that neither the POR nor the LVI
was the source of the reset. See Table 9-2 for details.
Figure 9-4 shows the relative timing.
Freescale Semiconductor, Inc...
Table 9-2. PIN Bit Set Timing
Reset Type
Number of Cycles Required to Set PIN
POR/LVI
4163 (4096 + 64 + 3)
All others
67 (64 + 3)
ICLK
RST
IAB
VECT H VECT L
PC
Figure 9-4. External Reset Timing
9.3.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 ICLK cycles
to allow resetting of external peripherals. The internal reset signal IRST
continues to be asserted for an additional 32 cycles (see Figure 9-5). An
internal reset can be caused by an illegal address, illegal opcode, COP
timeout, LVI, or POR (see Figure 9-6).
NOTE:
Data Sheet
For LVI or POR resets, the SIM cycles through 4096 + 32 ICLK cycles
during which the SIM forces the RST pin low. The internal reset signal
then follows the sequence from the falling edge of RST shown in
Figure 9-5.
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System Integration Module (SIM)
Reset and System Initialization
IRST
RST
RST PULLED LOW BY MCU
32 CYCLES
32 CYCLES
ICLK
IAB
VECTOR HIGH
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Figure 9-5. Internal Reset Timing
The COP reset is asynchronous to the bus clock.
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
POR
INTERNAL RESET
Figure 9-6. 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.
9.3.2.1 Power-On Reset
When power is first applied to the MCU, the power-on reset module
(POR) 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 + 32 ICLK cycles. Thirty-two ICLK 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
ICLK cycles to allow stabilization of the oscillator.
•
The 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.
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System Integration Module (SIM)
OSC1
PORRST
4096
CYCLES
32
CYCLES
32
CYCLES
ICLK
Freescale Semiconductor, Inc...
CGMOUT
RST
IRST
$FFFE
IAB
$FFFF
Figure 9-7. POR Recovery
9.3.2.2 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 through 5
of the SIM counter. The SIM counter output, which occurs at least every
213 – 24 ICLK 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 IRQ1 pin is held at
VTST 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 IRQ1 pin. This prevents the COP from
becoming disabled as a result of external noise. During a break state,
VTST on the RST pin disables the COP module.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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System Integration Module (SIM)
Reset and System Initialization
9.3.2.3 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.
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If the stop enable bit, STOP, in the mask option register is logic 0, the
SIM treats the STOP instruction as an illegal opcode and causes an
illegal opcode reset. The SIM actively pulls down the RST pin for all
internal reset sources.
9.3.2.4 Illegal Address Reset
An opcode fetch from an unmapped address generates an illegal
address reset. 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. The SIM actively pulls down the RST pin for all internal
reset sources.
9.3.2.5 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when
the VDD voltage falls to the LVITRIPF voltage. 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 + 32 ICLK cycles. Thirty-two ICLK
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.
9.3.2.6 Monitor Mode Entry Module Reset
The monitor mode entry module reset asserts its output to the SIM when
monitor mode is entered in the condition where the reset vectors are
blank ($FF). (See Section 10. Monitor ROM (MON).) When MODRST
gets asserted, an internal reset occurs. The SIM actively pulls down the
RST pin for all internal reset sources.
MC68HC908AP Family — Rev. 2.5
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System Integration Module (SIM)
9.4 SIM Counter
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The SIM counter is used by the power-on reset module (POR) and in
stop mode recovery to allow the oscillator time to stabilize before
enabling the internal bus (IBUS) clocks. The SIM counter also serves as
a prescaler for the computer operating properly module (COP). 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.
9.4.1 SIM Counter During Power-On Reset
The power-on reset module (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.
9.4.2 SIM Counter During Stop Mode Recovery
The SIM counter also is used for stop mode recovery. The STOP
instruction clears the SIM counter. After an interrupt, break, or reset, the
SIM senses the state of the short stop recovery bit, SSREC, in the mask
option register. If the SSREC bit is a logic 1, then the stop recovery is
reduced from the normal delay of 4096 CGMXCLK cycles down to 32
CGMXCLK cycles. This is ideal for applications using canned oscillators
that do not require long start-up times from stop mode. External crystal
applications should use the full stop recovery time, that is, with SSREC
cleared.
9.4.3 SIM Counter and Reset States
External reset has no effect on the SIM counter. (See 9.6.2 Stop Mode
for details.) The SIM counter is free-running after all reset states. (See
9.3.2 Active Resets from Internal Sources for counter control and
internal reset recovery sequences.)
Data Sheet
MC68HC908AP Family — Rev. 2.5
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System Integration Module (SIM)
Exception Control
9.5 Exception Control
Normal, sequential program execution can be changed in three different
ways:
•
Interrupts:
– Maskable hardware CPU interrupts
Freescale Semiconductor, Inc...
– Non-maskable software interrupt instruction (SWI)
•
Reset
•
Break interrupts
9.5.1 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 RTI instruction
recovers the CPU register contents from the stack so that normal
processing can resume. Figure 9-8 shows interrupt entry timing, and
Figure 9-9 shows interrupt recovery timing.
MODULE
INTERRUPT
I-BIT
IAB
IDB
SP
DUMMY
DUMMY
SP – 1
SP – 2
PC – 1[7:0] PC – 1[15:8]
SP – 3
X
SP – 4
A
VECT H
CCR
VECT L
V DATA H
START ADDR
V DATA L
OPCODE
R/W
Figure 9-8. Interrupt Entry Timing
MODULE
INTERRUPT
I-BIT
IAB
SP – 4
IDB
SP – 3
CCR
SP – 2
A
SP – 1
X
SP
PC
PC – 1[15:8] PC – 1[7:0]
PC + 1
OPCODE
OPERAND
R/W
Figure 9-9. Interrupt Recovery Timing
MC68HC908AP Family — Rev. 2.5
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System Integration Module (SIM)
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 9-10.)
Freescale Semiconductor, Inc...
FROM RESET
BREAK
I BIT
SET?
INTERRUPT?
YES
NO
YES
I-BIT SET?
NO
IRQ1
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 9-10. Interrupt Processing
Data Sheet
MC68HC908AP Family — Rev. 2.5
140
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System Integration Module (SIM)
Exception Control
9.5.1.1 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.
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If more than one interrupt is pending at the end of an instruction
execution, the highest priority interrupt is serviced first. Figure 9-11
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.
CLI
BACKGROUND
ROUTINE
LDA #$FF
INT1
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 9-11. Interrupt Recognition Example
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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System Integration Module (SIM)
9.5.1.2 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.
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9.5.1.3 Interrupt Status Registers
The flags in the interrupt status registers identify maskable interrupt
sources. Table 9-3 summarizes the interrupt sources and the interrupt
status register flags that they set. The interrupt status registers can be
useful for debugging.
9.5.1.4 Interrupt Status Register 1
Address:
$FE04
Bit 7
6
5
4
3
2
1
Bit 0
Read:
IF6
IF5
IF4
IF3
IF2
IF1
0
0
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 9-12. Interrupt Status Register 1 (INT1)
IF6–IF1 — Interrupt Flags 6–1
These flags indicate the presence of interrupt requests from the
sources shown in Table 9-3.
1 = Interrupt request present
0 = No interrupt request present
Bit 0 and Bit 1 — Always read 0
Data Sheet
MC68HC908AP Family — Rev. 2.5
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System Integration Module (SIM)
Exception Control
Table 9-3. Interrupt Sources
Priority
Lowest
INT
Flag
—
IF21
IF20
IF19
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IF18
IF17
IF16
IF15
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
IF6
IF5
IF4
IF3
IF2
IF1
—
Highest
—
Vector
Address
$FFD0
$FFD1
$FFD2
$FFD3
$FFD4
$FFD5
$FFD6
$FFD7
$FFD8
$FFD9
$FFDA
$FFDB
$FFDC
$FFDD
$FFDE
$FFDF
$FFE0
$FFE1
$FFE2
$FFE3
$FFE4
$FFE5
$FFE6
$FFE7
$FFE8
$FFE9
$FFEA
$FFEB
$FFEC
$FFED
$FFEE
$FFEF
$FFF0
$FFF1
$FFF2
$FFF3
$FFF4
$FFF5
$FFF6
$FFF7
$FFF8
$FFF9
$FFFA
$FFFB
$FFFC
$FFFD
$FFFE
$FFFF
Interrupt Source
Reserved
Timebase
Infrared SCI Transmit
Infrared SCI Receive
Infrared SCI Error
SPI Transmit
SPI Receive
ADC Conversion Complete
Keyboard
SCI Transmit
SCI Receive
SCI Error
MMIIC
TIM2 Overflow
TIM2 Channel 1
TIM2 Channel 0
TIM1 Overflow
TIM1 Channel 1
TIM1 Channel 0
PLL
IRQ2
IRQ1
SWI
Reset
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System Integration Module (SIM)
9.5.1.5 Interrupt Status Register 2
Address:
$FE05
Bit 7
6
5
4
3
2
1
Bit 0
Read:
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
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R
= Reserved
Figure 9-13. Interrupt Status Register 2 (INT2)
IF14–IF7 — Interrupt Flags 14–7
These flags indicate the presence of interrupt requests from the
sources shown in Table 9-3.
1 = Interrupt request present
0 = No interrupt request present
9.5.1.6 Interrupt Status Register 3
Address:
$FE06
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
IF21
IF20
IF19
IF18
IF17
IF16
IF15
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 9-14. Interrupt Status Register 3 (INT3)
IF21–IF15 — Interrupt Flags 21–15
These flags indicate the presence of an interrupt request from the
source shown in Table 9-3.
1 = Interrupt request present
0 = No interrupt request present
Data Sheet
MC68HC908AP Family — Rev. 2.5
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System Integration Module (SIM)
Exception Control
9.5.2 Reset
All reset sources always have equal and highest priority and cannot be
arbitrated.
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9.5.3 Break Interrupts
The break module can stop normal program flow at a softwareprogrammable break point by asserting its break interrupt output. (See
Section 23. Break Module (BRK).) The SIM puts the CPU into the
break state by forcing it to the SWI vector location. Refer to the break
interrupt subsection of each module to see how each module is affected
by the break state.
9.5.4 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).
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.
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System Integration Module (SIM)
9.6 Low-Power Modes
Executing the WAIT or STOP instruction puts the MCU in a low powerconsumption mode for standby situations. The SIM holds the CPU in a
non-clocked state. The operation of each of these modes is described in
the following subsections. Both STOP and WAIT clear the interrupt mask
(I) in the condition code register, allowing interrupts to occur.
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9.6.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks
continue to run. Figure 9-15 shows the timing for wait mode entry.
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. In
wait mode, the CPU clocks are inactive. 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.
Wait mode also can 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 mask
option register is logic 0, then the computer operating properly module
(COP) is enabled and remains active in wait mode.
IAB
IDB
WAIT ADDR
WAIT ADDR + 1
PREVIOUS DATA
SAME
NEXT OPCODE
SAME
SAME
SAME
R/W
NOTE: Previous data can be operand data or the WAIT opcode, depending on the
last instruction.
Figure 9-15. Wait Mode Entry Timing
Figure 9-16 and Figure 9-17 show the timing for WAIT recovery.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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System Integration Module (SIM)
Low-Power Modes
IAB
$6E0B
IDB
$A6
$6E0C
$A6
$A6
$01
$00FF
$0B
$00FE
$00FD
$00FC
$6E
EXITSTOPWAIT
NOTE: EXITSTOPWAIT = RST pin OR CPU interrupt OR break interrupt
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Figure 9-16. Wait Recovery from Interrupt or Break
32
CYCLES
IAB
IDB
32
CYCLES
$6E0B
$A6
$A6
RST VCT H RST VCT L
$A6
RST
ICLK
Figure 9-17. Wait Recovery from Internal Reset
9.6.2 Stop Mode
In stop mode, the SIM counter is reset and the system clocks are
disabled. An interrupt request from a module can cause an exit from stop
mode. Stacking for interrupts begins after the selected stop recovery
time has elapsed. Reset or break also causes an exit from stop mode.
The SIM disables the clock generator module output (CGMOUT) in stop
mode, stopping the CPU and peripherals. Stop recovery time is
selectable using the SSREC bit in the configuration register 1
(CONFIG1). If SSREC is set, stop recovery is reduced from the normal
delay of 4096 ICLK cycles down to 32. This is ideal for applications using
canned oscillators that do not require long start-up times from stop
mode.
NOTE:
External crystal applications should use the full stop recovery time by
clearing the SSREC bit.
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System Integration Module (SIM)
A break interrupt during stop mode sets the SIM break stop/wait bit
(SBSW) in the SIM break status register (SBSR).
The SIM counter is held in reset from the execution of the STOP
instruction until the beginning of stop recovery. It is then used to time the
recovery period. Figure 9-18 shows stop mode entry timing.
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NOTE:
To minimize stop current, all pins configured as inputs should be driven
to a logic 1 or logic 0.
CPUSTOP
IAB
IDB
STOP ADDR
STOP ADDR + 1
PREVIOUS DATA
SAME
NEXT OPCODE
SAME
SAME
SAME
R/W
NOTE: Previous data can be operand data or the STOP opcode, depending on the last
instruction.
Figure 9-18. Stop Mode Entry Timing
STOP RECOVERY PERIOD
ICLK
INT/BREAK
IAB
STOP +1
STOP + 2
STOP + 2
SP
SP – 1
SP – 2
SP – 3
Figure 9-19. Stop Mode Recovery from Interrupt or Break
9.7 SIM Registers
The SIM has three memory-mapped registers:
Data Sheet
•
SIM Break Status Register (SBSR) — $FE00
•
SIM Reset Status Register (SRSR) — $FE01
•
SIM Break Flag Control Register (SBFCR) — $FE03
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System Integration Module (SIM)
SIM Registers
9.7.1 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a
break caused an exit from stop mode or wait mode.
Address:
$FE00
Bit 7
6
5
4
3
2
R
R
R
R
R
R
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Read:
1
Bit 0
SBSW
R
Write:
Note
Reset:
0
Note: Writing a logic 0 clears SBSW.
R
= Reserved
Figure 9-20. SIM Break Status Register (SBSR)
SBSW — Break Wait Bit
This status bit is set when a break interrupt causes an exit from wait
mode or stop mode. Clear SBSW by writing a logic 0 to it. Reset clears
SBSW.
1 = Stop mode or wait mode was exited by break interrupt
0 = Stop mode or wait mode was not exited by break interrupt
SBSW can be read within the break interrupt routine. The user can
modify the return address on the stack by subtracting 1 from it. The
following code is an example.
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 or stop 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/STOP opcode.
RETURN
PULH
RTI
;Restore H register.
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System Integration Module (SIM)
9.7.2 SIM Reset Status Register
This register contains six flags that show the source of the last reset
provided all previous reset status bits have been cleared. Clear the SIM
reset status register by reading it. A power-on reset sets the POR bit and
clears all other bits in the register.
Address:
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Read:
$FE01
Bit 7
6
5
4
3
2
1
Bit 0
POR
PIN
COP
ILOP
ILAD
MODRST
LVI
0
1
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 9-21. 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
MODRST — Monitor Mode Entry Module Reset Bit
1 = Last reset caused by monitor mode entry when vector locations
$FFFE and $FFFF are $FF after POR while IRQ1 = VDD
0 = POR or read of SRSR
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System Integration Module (SIM)
SIM Registers
LVI — Low-Voltage Inhibit Reset Bit
1 = Last reset caused by the LVI circuit
0 = POR or read of SRSR
9.7.3 SIM Break Flag Control Register
The SIM break control register contains a bit that enables software to
clear status bits while the MCU is in a break state.
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Address:
$FE03
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
Read:
Write:
Reset:
0
R
= Reserved
Figure 9-22. 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
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System Integration Module (SIM)
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 10. Monitor ROM (MON)
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10.1 Introduction
This section describes the monitor ROM (MON) and the monitor mode
entry methods. The monitor ROM allows complete testing of the MCU
through a single-wire interface with a host computer. Monitor mode entry
can be achieved without use of the higher test voltage, VTST, as long as
vector addresses $FFFE and $FFFF are blank, thus reducing the
hardware requirements for in-circuit programming.
In addition, to simplify user coding, routines are also stored in the
monitor ROM area for FLASH memory program /erase and EEPROM
emulation.
10.2 Features
Features of the monitor ROM include:
•
Normal user-mode pin functionality
•
One pin dedicated to serial communication between monitor ROM
and host computer
•
Standard mark/space non-return-to-zero (NRZ) communication
with host computer
•
Execution of code in RAM or FLASH
•
FLASH memory security feature1
•
FLASH memory programming interface
•
Enhanced PLL (phase-locked loop) option to allow use of external
32.768-kHz crystal to generate internal frequency of 2.4576 MHz
1. No security feature is absolutely secure. However, Motorola’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
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Monitor ROM (MON)
•
959 bytes monitor ROM code size
($FC00–$FDFF and $FE10–$FFCE)
•
Monitor mode entry without high voltage, VTST, if reset vector is
blank ($FFFE and $FFFF contain $FF)
•
Standard monitor mode entry if high voltage, VTST, is applied to
IRQ1
•
Resident routines for in-circuit programming and EEPROM
emulation
10.3 Functional Description
The monitor ROM receives and executes commands from a host
computer. Figure 10-1 shows an example 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 code downloaded into RAM by a host
computer while most MCU pins retain normal operating mode functions.
All communication between the host computer and the MCU is through
the PTA0 pin. A level-shifting and multiplexing interface is required
between PTA0 and the host computer. PTA0 is used in a wired-OR
configuration and requires a pullup resistor.
The monitor code allows enabling the PLL to generate the internal clock,
provided the reset vector is blank, when the device is being clocked by
a low-frequency crystal. This entry method, which is enabled when IRQ1
is held low out of reset, is intended to support serial communication/
programming at 9600 baud in monitor mode by stepping up the external
frequency (assumed to be 32.768 kHz) by a fixed amount to generate
the desired internal frequency (2.4576 MHz). Since this feature is
enabled only when IRQ1 is held low out of reset, it cannot be used when
the reset vector is non-zero because entry into monitor mode in this case
requires VTST on IRQ1.
Data Sheet
MC68HC908AP Family — Rev. 2.5
154
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Monitor ROM (MON)
Functional Description
RST
0.1 µF
HC908AP
VDD
VDD
VDDA
0.1 µF
VREFH
VREG
VREFL
VSS
VSSA
4.9152MHz/9.8304MHz
(50% DUTY)
OSC1
CGMXFC
0.01 µF
10k
MUST BE USED IF SW2 IS AT POSITION C.
CONNECT TO OSC1, WITH OSC2 UNCONNECTED.
EXT OSC
32.768kHz
OSC1
6–30 pF
MAX232
1
1 µF
+
3
4
1 µF
C1+
C1–
C2+
GND
V+
OSC2
16
+
6–30 pF
1 µF
15
1 µF
+
XTAL CIRCUIT
C
VTST
2
VDD
+
5 C2–
330k
VDD
VCC
V–
6
1 µF
10
3
8
9
(SEE NOTE 1)
IRQ1
D
10 k
74HC125
5
6
DB9
7
SW2
1k
8.5 V
+
2
0.033 µF
10M
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VREG
2
74HC125
3
PTA0
4
VDD
VDD
1
5
10 k
10 k
A
PTA1
SW1
PTB0
(SEE NOTE 2)
NOTES:
1. Monitor mode entry method:
SW2: Position C — High voltage entry (VTST); must use external OSC
Bus clock depends on SW1 (note 2).
SW2: Position D — Reset vector must be blank ($FFFE:$FFFF = $FF)
Bus clock = 2.4576MHz.
2. Affects high voltage entry to monitor mode only (SW2 at position C):
SW1: Position A — Bus clock = OSC1 ÷ 4
SW1: Position B — Bus clock = OSC1 ÷ 2
5. See Table 24-4 for VTST voltage level requirements.
B
10 k
PTA2
10 k
Figure 10-1. Monitor Mode Circuit
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Monitor ROM (MON)
10.3.1 Entering Monitor Mode
Table 10-1 shows the pin conditions for entering monitor mode. As
specified in the table, monitor mode may be entered after a POR and will
allow communication at 9600 baud provided one of the following sets of
conditions is met:
1. If $FFFE and $FFFF do not contain $FF (programmed state):
Freescale Semiconductor, Inc...
– The external clock is 4.9152 MHz with PTB0 low or
9.8304 MHz with PTB0 high
– IRQ1 = VTST (PLL off)
2. If $FFFE and $FFFF both contain $FF (erased state):
– The external clock is 9.8304 MHz
– IRQ1 = VDD (this can be implemented through the internal
IRQ1 pullup; PLL off)
3. If $FFFE and $FFFF both contain $FF (erased state):
– The external clock is 32.768 kHz (crystal)
– IRQ1 = VSS (this setting initiates the PLL to boost the external
32.768 kHz to an internal bus frequency of 2.4576 MHz
If VTST is applied to IRQ1 and PTB0 is low upon monitor mode entry
(above condition set 1), the bus frequency is a divide-by-two of the input
clock. If PTB0 is high with VTST applied to IRQ1 upon monitor mode
entry, the bus frequency will be a divide-by-four of the input clock.
Holding the PTB0 pin low when entering monitor mode causes a bypass
of a divide-by-two stage at the oscillator only if VTST is applied to IRQ1.
In this event, the CGMOUT frequency is equal to the CGMXCLK
frequency, and the OSC1 input directly generates internal bus clocks. In
this case, the OSC1 signal must have a 50% duty cycle at maximum bus
frequency.
If entering monitor mode without high voltage on IRQ1 (above condition
set 2 or 3, where applied voltage is either VDD or VSS), then all port A pin
requirements and conditions, including the PTB0 frequency divisor
selection, are not in effect. This is to reduce circuit requirements when
performing in-circuit programming.
Data Sheet
MC68HC908AP Family — Rev. 2.5
156
MOTOROLA
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MOTOROLA
X
X
VDD
or
VTST
VDD
or
VTST
VDD
VDD
VTST
VDD
or
VTST
VTST(3)
VTST(3)
VDD
GND
VDD
or
GND
VDD
or
GND
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X
X
X
X
0
0
X
PTA2
X
X
X
X
1
1
X
PTA1
X
X
1
1
1
1
X
PTA0(1)
X
X
X
X
1
0
X
PTB0
X
X
32.768
kHz
9.8304
MHz
9.8304
MHz
4.9152
MHz
X
External
Clock(2)
—
—
2.4576
MHz
2.4576
MHz
2.4576
MHz
2.4576
MHz
0
Bus
Frequency
OFF
OFF
ON
OFF
OFF
OFF
X
PLL
Enabled
Enabled
Disabled
Disabled
Disabled
Disabled
Disabled
COP
—
—
9600
9600
9600
9600
0
Baud
Rate
Enters user mode
Enters user
mode — will
encounter an illegal
address reset
PLL enabled
(BCS set)
in monitor code
External frequency
always divided by 4
PTA1 and PTA2
voltages only
required if
IRQ1 = VTST;
PTB0 determines
frequency divider
PTA1 and PTA2
voltages only
required if
IRQ1 = VTST;
PTB0 determines
frequency divider
No operation until
reset goes high
Comment
Notes:
1. PTA0 = 1 if serial communication; PTA0 = 0 if parallel communication
2. External clock is derived by a 32.768 kHz crystal or a 4.9152/9.8304 MHz off-chip oscillator
3. Monitor mode entry by IRQ1= VTST, a 4.9152/9.8304 MHz off-chip oscillator must be used. The MCU internal crystal oscillator circuit is bypassed.
Not Blank
Blank
"$FFFF"
Blank
"$FFFF"
Blank
"$FFFF"
X
GND
X
Address
$FFFE/
$FFFF
RST
IRQ1
Table 10-1. Monitor Mode Signal Requirements and Options
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Monitor ROM (MON)
Functional Description
Data Sheet
157
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Monitor ROM (MON)
NOTE:
If the reset vector is blank and monitor mode is entered, the chip will see
an additional reset cycle after the initial POR reset. Once the part has
been programmed, the traditional method of applying a voltage, VTST, to
IRQ1 must be used to enter monitor mode.
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The COP module is disabled in monitor mode based on these
conditions:
•
If monitor mode was entered as a result of the reset vector being
blank (above condition set 2 or 3), the COP is always disabled
regardless of the state of IRQ1 or RST.
•
If monitor mode was entered with VTST on IRQ1 (condition set 1),
then the COP is disabled as long as VTST is applied to either IRQ1
or RST.
The second condition states that as long as VTST is maintained on the
IRQ1 pin after entering monitor mode, or if VTST is applied to RST after
the initial reset to get into monitor mode (when VTST was applied to
IRQ1), then the COP will be disabled. In the latter situation, after VTST is
applied to the RST pin, VTST can be removed from the IRQ1 pin in the
interest of freeing the IRQ1 for normal functionality in monitor mode.
Figure 10-2 shows a simplified diagram of the monitor mode entry when
the reset vector is blank and just VDD voltage is applied to the IRQ1 pin.
An external oscillator of 9.8304 MHz is required for a baud rate of 9600,
as the internal bus frequency is automatically set to the external
frequency divided by four.
Enter monitor mode with pin configuration shown in Figure 10-1 by
pulling RST low and then high. The rising edge of RST latches monitor
mode. Once monitor mode is latched, the values on the specified pins
can change.
Once out of reset, the MCU waits for the host to send eight security
bytes. (See 10.4 Security.) After the security bytes, the MCU sends a
break signal (10 consecutive logic 0’s) to the host, indicating that it is
ready to receive a command.
Data Sheet
MC68HC908AP Family — Rev. 2.5
158
MOTOROLA
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Monitor ROM (MON)
Functional Description
POR RESET
IS VECTOR
BLANK?
NO
NORMAL USER
MODE
YES
MONITOR MODE
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EXECUTE
MONITOR
CODE
POR
TRIGGERED?
NO
YES
Figure 10-2. Low-Voltage Monitor Mode Entry Flowchart
In monitor mode, the MCU uses different vectors for reset, SWI
(software interrupt), and break interrupt than those for user mode. 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.
NOTE:
Exiting monitor mode after it has been initiated by having a blank reset
vector requires a power-on reset (POR). Pulling RST low will not exit
monitor mode in this situation.
Table 10-2 summarizes the differences between user mode and monitor
mode vectors.
Table 10-2. Mode Differences (Vectors)
Functions
Modes
Reset
Vector
High
Reset
Vector
Low
Break
Vector
High
Break
Vector
Low
SWI
Vector
High
SWI
Vector
Low
User
$FFFE
$FFFF
$FFFC
$FFFD
$FFFC
$FFFD
Monitor
$FEFE
$FEFF
$FEFC
$FEFD
$FEFC
$FEFD
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Monitor ROM (MON)
10.3.2 Data Format
Communication with the monitor ROM is in standard non-return-to-zero
(NRZ) mark/space data format. Transmit and receive baud rates must
be identical.
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START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
NEXT
START
STOP
BIT
BIT
BIT 7
Figure 10-3. Monitor Data Format
10.3.3 Break Signal
A start bit (logic 0) followed by nine logic 0 bits is a break signal. When
the monitor receives a break signal, it drives the PTA0 pin high for the
duration of two bits and then echoes back the break signal.
MISSING STOP BIT
2-STOP BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 10-4. Break Transaction
10.3.4 Baud Rate
The communication baud rate is controlled by the crystal frequency and
the state of the PTB0 pin (when IRQ1 is set to VTST) upon entry into
monitor mode. When PTB0 is high, the divide by ratio is 1024. If the
PTB0 pin is at logic 0 upon entry into monitor mode, the divide by ratio
is 512.
If monitor mode was entered with VDD on IRQ1, then the divide by ratio
is set at 1024, regardless of PTB0. If monitor mode was entered with VSS
on IRQ1, then the internal PLL steps up the external frequency,
presumed to be 32.768 kHz, to 2.4576 MHz. These latter two conditions
for monitor mode entry require that the reset vector is blank.
Data Sheet
MC68HC908AP Family — Rev. 2.5
160
MOTOROLA
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Monitor ROM (MON)
Functional Description
Table 10-3 lists external frequencies required to achieve a standard
baud rate of 9600 BPS. Other standard baud rates can be accomplished
using proportionally higher or lower frequency generators. If using a
crystal as the clock source, be aware of the upper frequency limit that the
internal clock module can handle.
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Table 10-3. Monitor Baud Rate Selection
External
Frequency
IRQ1
PTB0
Internal
Frequency
Baud Rate
(BPS)
4.9152 MHz
VTST
0
2.4576 MHz
9600
9.8304 MHz
VTST
1
2.4576 MHz
9600
9.8304 MHz
VDD
X
2.4576 MHz
9600
32.768 kHz
VSS
X
2.4576 MHz
9600
10.3.5 Commands
The monitor ROM firmware uses these commands:
•
READ (read memory)
•
WRITE (write memory)
•
IREAD (indexed read)
•
IWRITE (indexed write)
•
READSP (read stack pointer)
•
RUN (run user program)
The monitor ROM firmware echoes each received byte back to the PTA0
pin for error checking. An 11-bit delay at the end of each command
allows the host to send a break character to cancel the command. A
delay of two bit times occurs before each echo and before READ,
IREAD, or READSP data is returned. The data returned by a read
command appears after the echo of the last byte of the command.
NOTE:
Wait one bit time after each echo before sending the next byte.
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Monitor ROM (MON)
FROM HOST
4
ADDRESS
HIGH
READ
READ
4
1
ADDRESS
HIGH
ADDRESS
LOW
1
ADDRESS
LOW
DATA
1
4
3, 2
4
ECHO
RETURN
Notes:
1 = Echo delay, 2 bit times
2 = Data return delay, 2 bit times
3 = Cancel command delay, 11 bit times
4 = Wait 1 bit time before sending next byte.
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Figure 10-5. Read Transaction
FROM HOST
3
ADDRESS
HIGH
WRITE
WRITE
1
3
ADDRESS
HIGH
1
ADDRESS
LOW
3
ADDRESS
LOW
1
DATA
DATA
3
1
2, 3
ECHO
Notes:
1 = Echo delay, 2 bit times
2 = Cancel command delay, 11 bit times
3 = Wait 1 bit time before sending next byte.
Figure 10-6. Write Transaction
A brief description of each monitor mode command is given in
Table 10-4 through Table 10-9.
Table 10-4. READ (Read Memory) Command
Description
Read byte from memory
Operand
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
ADDRESS
HIGH
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
ECHO
Data Sheet
DATA
RETURN
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Monitor ROM (MON)
Functional Description
Table 10-5. WRITE (Write Memory) Command
Description
Operand
2-byte address in high-byte:low-byte order;
low byte followed by data byte
Data
Returned
None
Opcode
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Write byte to memory
$49
Command Sequence
FROM
HOST
WRITE
ADDRESS
HIGH
WRITE
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
DATA
ECHO
Table 10-6. IREAD (Indexed Read) Command
Description
Read next 2 bytes in memory from last address accessed
Operand
2-byte address in high byte:low byte order
Data
Returned
Returns contents of next two addresses
Opcode
$1A
Command Sequence
FROM
HOST
IREAD
IREAD
DATA
ECHO
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DATA
RETURN
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Monitor ROM (MON)
Table 10-7. IWRITE (Indexed Write) Command
Description
Write to last address accessed + 1
Operand
Single data byte
Data
Returned
None
Opcode
$19
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Command Sequence
FROM
HOST
IWRITE
IWRITE
DATA
DATA
ECHO
A sequence of IREAD or IWRITE commands can access a block of
memory sequentially over the full 64-Kbyte memory map.
Table 10-8. READSP (Read Stack Pointer) Command
Description
Reads stack pointer
Operand
None
Data
Returned
Returns incremented stack pointer value (SP + 1) in
high-byte:low-byte order
Opcode
$0C
Command Sequence
FROM
HOST
READSP
READSP
SP
HIGH
ECHO
Data Sheet
SP
LOW
RETURN
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Monitor ROM (MON)
Functional Description
Table 10-9. RUN (Run User Program) Command
Description
Executes PULH and RTI instructions
Operand
None
Data
Returned
None
Opcode
$28
Command Sequence
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FROM
HOST
RUN
RUN
ECHO
The MCU executes the SWI and PSHH instructions when it enters
monitor mode. The RUN command tells the MCU to execute the PULH
and RTI instructions. Before sending the RUN command, the host can
modify the stacked CPU registers to prepare to run the host program.
The READSP command returns the incremented stack pointer value,
SP + 1. The high and low bytes of the program counter are at addresses
SP + 5 and SP + 6.
SP
HIGH BYTE OF INDEX REGISTER
SP + 1
CONDITION CODE REGISTER
SP + 2
ACCUMULATOR
SP + 3
LOW BYTE OF INDEX REGISTER
SP + 4
HIGH BYTE OF PROGRAM COUNTER SP + 5
LOW BYTE OF PROGRAM COUNTER SP + 6
SP + 7
Figure 10-7. Stack Pointer at Monitor Mode Entry
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Monitor ROM (MON)
10.4 Security
A security feature discourages unauthorized reading of FLASH locations
while in monitor mode. The host can bypass the security feature at
monitor mode entry by sending eight security bytes that match the bytes
at locations $FFF6–$FFFD. Locations $FFF6–$FFFD contain userdefined data.
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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 PTA0. If the received
bytes match those at locations $FFF6–$FFFD, the host bypasses the
security feature and can read all FLASH locations and execute code
from FLASH. Security remains bypassed until a power-on reset occurs.
If the reset was not a power-on reset, security remains bypassed and
security code entry is not required. (See Figure 10-8.)
VDD
4096 + 32 ICLK CYCLES
RST
COMMAND
BYTE 8
BYTE 2
BYTE 1
256 BUS CYCLES (MINIMUM)
FROM HOST
PTA0
4
BREAK
2
1
COMMAND ECHO
NOTES:
1 = Echo delay, 2 bit times.
2 = Data return delay, 2 bit times.
4 = Wait 1 bit time before sending next byte.
1
BYTE 8 ECHO
BYTE 1 ECHO
FROM MCU
1
BYTE 2 ECHO
4
1
Figure 10-8. Monitor Mode Entry Timing
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Monitor ROM (MON)
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 bypass the
security feature. The MCU remains in monitor mode, but reading a
FLASH location returns an invalid value and trying to execute code from
FLASH 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.
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NOTE:
The MCU does not transmit a break character until after the host sends
the eight security bits.
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 FLASH can be accessed.
If the security sequence fails, the device should be reset by a power-on
reset and brought up in monitor mode to attempt another entry. After
failing the security sequence, the FLASH module can also be mass
erased by executing an erase routine that was downloaded into internal
RAM. The mass erase operation clears the security code locations so
that all eight security bytes become $FF (blank).
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Monitor ROM (MON)
10.5 ROM-Resident Routines
Seven routines stored in the monitor ROM area (thus ROM-resident) are
provided for FLASH memory manipulation. Five of the seven routines
are intended to simplify FLASH program, erase, and load operations.
The other two routines are intended to simplify the use of the FLASH
memory as EEPROM. Table 10-10 shows a summary of the ROMresident routines.
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Table 10-10. Summary of ROM-Resident Routines
Routine Name
Routine Description
Call
Address
Stack Used
(bytes)
PRGRNGE
Program a range of locations
$FC34
15
ERARNGE
Erase a page or the entire array
$FCE4
9
Loads data from a range of locations
$FC00
7
MON_PRGRNGE
Program a range of locations in
monitor mode
$FF24
17
MON_ERARNGE
Erase a page or the entire array in
monitor mode
$FF28
11
EE_WRITE
Emulated EEPROM write. Data size
ranges from 7 to 15 bytes at a time.
$FF36
30
EE_READ
Emulated EEPROM read. Data size
ranges from 7 to 15 bytes at a time.
$FD5B
18
LDRNGE
The routines are designed to be called as stand-alone subroutines in the
user program or monitor mode. The parameters that are passed to a
routine are in the form of a contiguous data block, stored in RAM. The
index register (H:X) is loaded with the address of the first byte of the data
block (acting as a pointer), and the subroutine is called (JSR). Using the
start address as a pointer, multiple data blocks can be used, any area of
RAM be used. A data block has the control and data bytes in a defined
order, as shown in Figure 10-9.
During the software execution, it does not consume any dedicated RAM
location, the run-time heap will extend the system stack, all other RAM
location will not be affected.
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Monitor ROM (MON)
ROM-Resident Routines
R
FILE_PTR
$XXXX
ADDRESS AS POINTER
A
M
BUS SPEED (BUS_SPD)
DATA SIZE (DATASIZE)
START ADDRESS HIGH (ADDRH)
START ADDRESS LOW (ADDRL)
DATA 0
DATA 1
DATA
BLOCK
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DATA
ARRAY
DATA N
Figure 10-9. Data Block Format for ROM-Resident Routines
The control and data bytes are described below.
•
Bus speed — This one byte indicates the operating bus speed of
the MCU. The value of this byte should be equal to 4 times the bus
speed. E.g., for a 4MHz bus, the value is 16 ($10). This control
byte is useful where the MCU clock source is switched between
the PLL clock and the crystal clock.
•
Data size — This one byte indicates the number of bytes in the
data array that are to be manipulated. The maximum data array
size is 255. Routines EE_WRITE and EE_READ are restricted to
manipulate a data array between 7 to 15 bytes. Whereas routines
ERARNGE and MON_ERARNGE do not manipulate a data array,
thus, this data size byte has no meaning.
•
Start address — These two bytes, high byte followed by low byte,
indicate the start address of the FLASH memory to be
manipulated.
•
Data array — This data array contains data that are to be
manipulated. Data in this array are programmed to FLASH
memory by the programming routines: PRGRNGE,
MON_PRGRNGE, EE_WRITE. For the read routines: LDRNGE
and EE_READ, data is read from FLASH and stored in this array.
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Monitor ROM (MON)
10.5.1 PRGRNGE
PRGRNGE is used to program a range of FLASH locations with data
loaded into the data array.
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Table 10-11. PRGRNGE Routine
Routine Name
PRGRNGE
Routine Description
Program a range of locations
Calling Address
$FC34
Stack Used
15 bytes
Data Block Format
Bus speed (BUS_SPD)
Data size (DATASIZE)
Start address high (ADDRH)
Start address (ADDRL)
Data 1 (DATA1)
:
Data N (DATAN)
The start location of the FLASH to be programmed is specified by the
address ADDRH:ADDRL and the number of bytes from this location is
specified by DATASIZE. The maximum number of bytes that can be
programmed in one routine call is 255 bytes (max. DATASIZE is 255).
ADDRH:ADDRL do not need to be at a page boundary, the routine
handles any boundary misalignment during programming. A check to
see that all bytes in the specified range are erased is not performed by
this routine prior programming. Nor does this routine do a verification
after programming, so there is no return confirmation that programming
was successful. User must assure that the range specified is first
erased.
The coding example below is to program 64 bytes of data starting at
FLASH location $EE00, with a bus speed of 4.9152 MHz. The coding
assumes the data block is already loaded in RAM, with the address
pointer, FILE_PTR, pointing to the first byte of the data block.
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Monitor ROM (MON)
ROM-Resident Routines
ORG
RAM
:
FILE_PTR:
BUS_SPD
DATASIZE
START_ADDR
DATAARRAY
DS.B
DS.B
DS.W
DS.B
1
1
1
64
PRGRNGE
FLASH_START
EQU
EQU
$FC34
$EE00
;
;
;
;
Indicates 4x bus frequency
Data size to be programmed
FLASH start address
Reserved data array
Freescale Semiconductor, Inc...
ORG
FLASH
INITIALISATION:
MOV
#20,
BUS_SPD
MOV
#64,
DATASIZE
LDHX
#FLASH_START
STHX
START_ADDR
RTS
MAIN:
BSR
INITIALISATION
:
:
LDHX
#FILE_PTR
JSR
PRGRNGE
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Monitor ROM (MON)
10.5.2 ERARNGE
ERARNGE is used to erase a range of locations in FLASH.
Freescale Semiconductor, Inc...
Table 10-12. ERARNGE Routine
Routine Name
ERARNGE
Routine Description
Erase a page or the entire array
Calling Address
$FCE4
Stack Used
9 bytes
Data Block Format
Bus speed (BUS_SPD)
Data size (DATASIZE)
Starting address (ADDRH)
Starting address (ADDRL)
There are two sizes of erase ranges: a page or the entire array. The
ERARNGE will erase the page (512 consecutive bytes) in FLASH
specified by the address ADDRH:ADDRL. This address can be any
address within the page. Calling ERARNGE with ADDRH:ADDRL equal
to $FFFF will erase the entire FLASH array (mass erase). Therefore,
care must be taken when calling this routine to prevent an accidental
mass erase.
The ERARNGE routine do not use a data array. The DATASIZE byte is
a dummy byte that is also not used.
The coding example below is to perform a page erase, from
$EE00–$EFFF. The Initialization subroutine is the same as the coding
example for PRGRNGE (see 10.5.1 PRGRNGE).
ERARNGE
MAIN:
EQU
BSR
:
:
LDHX
JSR
:
Data Sheet
$FCE4
INITIALISATION
#FILE_PTR
ERARNGE
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Monitor ROM (MON)
ROM-Resident Routines
10.5.3 LDRNGE
LDRNGE is used to load the data array in RAM with data from a range
of FLASH locations.
Freescale Semiconductor, Inc...
Table 10-13. LDRNGE Routine
Routine Name
LDRNGE
Routine Description
Loads data from a range of locations
Calling Address
$FC00
Stack Used
7 bytes
Data Block Format
Bus speed (BUS_SPD)
Data size (DATASIZE)
Starting address (ADDRH)
Starting address (ADDRL)
Data 1
:
Data N
The start location of FLASH from where data is retrieved is specified by
the address ADDRH:ADDRL and the number of bytes from this location
is specified by DATASIZE. The maximum number of bytes that can be
retrieved in one routine call is 255 bytes. The data retrieved from FLASH
is loaded into the data array in RAM. Previous data in the data array will
be overwritten. User can use this routine to retrieve data from FLASH
that was previously programmed.
The coding example below is to retrieve 64 bytes of data starting from
$EE00 in FLASH. The Initialization subroutine is the same as the coding
example for PRGRNGE (see 10.5.1 PRGRNGE).
LDRNGE
MAIN:
EQU
BSR
:
:
LDHX
JSR
:
$FC00
INITIALIZATION
#FILE_PTR
LDRNGE
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Monitor ROM (MON)
10.5.4 MON_PRGRNGE
In monitor mode, MON_PRGRNGE is used to program a range of
FLASH locations with data loaded into the data array.
Freescale Semiconductor, Inc...
Table 10-14. MON_PRGRNGE Routine
Routine Name
MON_PRGRNGE
Routine Description
Program a range of locations, in monitor mode
Calling Address
$FF24
Stack Used
17 bytes
Data Block Format
Bus speed
Data size
Starting address (high byte)
Starting address (low byte)
Data 1
:
Data N
The MON_PRGRNGE routine is designed to be used in monitor mode.
It performs the same function as the PRGRNGE routine (see 10.5.1
PRGRNGE), except that MON_PRGRNGE returns to the main program
via an SWI instruction. After a MON_PRGRNGE call, the SWI instruction
will return the control back to the monitor code.
Data Sheet
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Monitor ROM (MON)
ROM-Resident Routines
10.5.5 MON_ERARNGE
In monitor mode, ERARNGE is used to erase a range of locations in
FLASH.
Freescale Semiconductor, Inc...
Table 10-15. MON_ERARNGE Routine
Routine Name
MON_ERARNGE
Routine Description
Erase a page or the entire array, in monitor mode
Calling Address
$FF28
Stack Used
11 bytes
Data Block Format
Bus speed
Data size
Starting address (high byte)
Starting address (low byte)
The MON_ERARNGE routine is designed to be used in monitor mode.
It performs the same function as the ERARNGE routine (see 10.5.2
ERARNGE), except that MON_ERARNGE returns to the main program
via an SWI instruction. After a MON_ERARNGE call, the SWI instruction
will return the control back to the monitor code.
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Monitor ROM (MON)
10.5.6 EE_WRITE
EE_WRITE is used to write a set of data from the data array to FLASH.
Freescale Semiconductor, Inc...
Table 10-16. EE_WRITE Routine
Routine Name
EE_WRITE
Routine Description
Emulated EEPROM write. Data size ranges from 7 to 15
bytes at a time.
Calling Address
$FF36
Stack Used
30 bytes
Data Block Format
Bus speed (BUS_SPD)
Data size (DATASIZE)(1)
Starting address (ADDRH)(2)
Starting address (ADDRL)(1)
Data 1
:
Data N
Notes:
1. The minimum data size is 7 bytes. The maximum data size is 15 bytes.
2. The start address must be a page boundary start address.
The start location of the FLASH to be programmed is specified by the
address ADDRH:ADDRL and the number of bytes in the data array is
specified by DATASIZE. The minimum number of bytes that can be
programmed in one routine call is 7 bytes, the maximum is 15 bytes.
ADDRH:ADDRL must always be the start of boundary address (the page
start address: $X000, $X200, $X400, $X600, $X800, $XA00, $XC00, or
$XE00) and DATASIZE must be the same size when accessing the
same page.
In some applications, the user may want to repeatedly store and read a
set of data from an area of non-volatile memory. This is easily possible
when using an EEPROM array. As the write and erase operations can
be executed on a byte basis. For FLASH memory, the minimum erase
size is the page — 512 bytes per page for MC68HC908AP64. If the data
array size is less than the page size, writing and erasing to the same
page cannot fully utilize the page. Unused locations in the page will be
wasted. The EE_WRITE routine is designed to emulate the properties
similar to the EEPROM. Allowing a more efficient use of the FLASH page
for data storage.
Data Sheet
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Monitor ROM (MON)
ROM-Resident Routines
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When the user dedicates a page of FLASH for data storage, and the size
of the data array defined, each call of the EE_WRTIE routine will
automatically transfer the data in the data array (in RAM) to the next
blank block of locations in the FLASH page. Once a page is filled up, the
EE_WRITE routine automatically erases the page, and starts reuse the
page again. In the 512-byte page, an 9-byte control block is used by the
routine to monitor the utilization of the page. In effect, only 503 bytes are
used for data storage. (see Figure 10-10). The page control operations
are transparent to the user.
F L A S H
PAGE BOUNDARY
CONTROL: 9 BYTES
DATA ARRAY
DATA ARRAY
DATA ARRAY
ONE PAGE = 512 BYTES
PAGE BOUNDARY
Figure 10-10. EE_WRITE FLASH Memory Usage
When using this routine to store a 8-byte data array, the FLASH page
can be programmed 62 times before the an erase is required. In effect,
the write/erase endurance is increased by 62 times. When a 15-byte
data array is used, the write/erase endurance is increased by 33 times.
Due to the FLASH page size limitation, the data array is limited from 7
bytes to 15 bytes.
The coding example below uses the $EE00–$EFFF page for data
storage. The data array size is 15 bytes, and the bus speed is
4.9152 MHz. The coding assumes the data block is already loaded in
RAM, with the address pointer, FILE_PTR, pointing to the first byte of the
data block.
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Monitor ROM (MON)
ORG
RAM
:
FILE_PTR:
BUS_SPD
DATASIZE
START_ADDR
DATAARRAY
DS.B
DS.B
DS.W
DS.B
1
1
1
15
EE_WRITE
FLASH_START
EQU
EQU
$FF36
$EE00
;
;
;
;
Indicates 4x bus frequency
Data size to be programmed
FLASH starting address
Reserved data array
Freescale Semiconductor, Inc...
ORG
FLASH
INITIALISATION:
MOV
#20,
BUS_SPD
MOV
#15,
DATASIZE
LDHX
#FLASH_START
STHX
START_ADDR
RTS
MAIN:
BSR
INITIALISATION
:
:
LHDX
#FILE_PTR
JSR
EE_WRITE
NOTE:
Data Sheet
The EE_WRITE routine is unable to check for incorrect data blocks,
such as the FLASH page boundary address and data size. It is the
responsibility of the user to ensure the starting address indicated in the
data block is at the FLASH page boundary and the data size is 7 to 15.
If the FLASH page is already programmed with a data array with a
different size, the EE_WRITE call will be ignored.
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Monitor ROM (MON)
ROM-Resident Routines
10.5.7 EE_READ
EE_READ is used to load the data array in RAM with a set of data from
FLASH.
Freescale Semiconductor, Inc...
Table 10-17. EE_READ Routine
Routine Name
EE_READ
Routine Description
Emulated EEPROM read. Data size ranges from 7 to 15
bytes at a time.
Calling Address
$FD5B
Stack Used
18 bytes
Data Block Format
Bus speed (BUS_SPD)
Data size (DATASIZE)
Starting address (ADDRH)(1)
Starting address (ADDRL)(1)
Data 1
:
Data N
Notes:
1. The start address must be a page boundary start address.
The EE_READ routine reads data stored by the EE_WRITE routine. An
EE_READ call will retrieve the last data written to a FLASH page and
loaded into the data array in RAM. Same as EE_WRITE, the data size
indicated by DATASIZE is 7 to 15, and the start address
ADDRH:ADDRL must the FLASH page boundary address.
The coding example below uses the data stored by the EE_WRITE
coding example (see 10.5.6 EE_WRITE). It loads the 15-byte data set
stored in the $EE00–$EFFF page to the data array in RAM. The
initialization subroutine is the same as the coding example for
EE_WRITE (see 10.5.6 EE_WRITE).
EE_READ
EQU
$FD5B
MAIN:
BSR
:
:
LDHX
JSR
:
INITIALIZATION
#FILE_PTR
EE_READ
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Monitor ROM (MON)
The EE_READ routine is unable to check for incorrect data blocks, such
as the FLASH page boundary address and data size. It is the
responsibility of the user to ensure the starting address indicated in the
data block is at the FLASH page boundary and the data size is 7 to 15.
If the FLASH page is programmed with a data array with a different size,
the EE_READ call will be ignored.
Freescale Semiconductor, Inc...
NOTE:
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 11. Timer Interface Module (TIM)
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11.1 Introduction
This section describes the timer interface (TIM) module. The TIM is a
two-channel timer that provides a timing reference with input capture,
output compare, and pulse-width-modulation functions. Figure 11-1 is a
block diagram of the TIM.
This particular MCU has two timer interface modules which are denoted
as TIM1 and TIM2.
11.2 Features
Features of the TIM 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 TIM clock input with 7-frequency internal bus clock
prescaler selection
•
Free-running or modulo up-count operation
•
Toggle any channel pin on overflow
•
TIM counter stop and reset bits
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Timer Interface Module (TIM)
11.3 Pin Name Conventions
The text that follows describes both timers, TIM1 and TIM2. The TIM
input/output (I/O) pin names are T[1,2]CH0 (timer channel 0) and
T[1,2]CH1 (timer channel 1), where “1” is used to indicate TIM1 and “2”
is used to indicate TIM2. The two TIMs share four I/O pins with four I/O
port pins. The full names of the TIM I/O pins are listed in
Table 11-1. The generic pin names appear in the text that follows.
Freescale Semiconductor, Inc...
Table 11-1. Pin Name Conventions
TIM Generic Pin Names:
Full TIM
Pin Names:
NOTE:
T[1,2]CH0
T[1,2]CH1
TIM1
PTB4/T1CH0
PTB5/T1CH1
TIM2
PTB6/T2CH0
PTB7/T2CH1
References to either timer 1 or timer 2 may be made in the following text
by omitting the timer number. For example, TCH0 may refer generically
to T1CH0 and T2CH0, and TCH1 may refer to T1CH1 and T2CH1.
11.4 Functional Description
Figure 11-1 shows the structure of the TIM. The central component of
the TIM is the 16-bit TIM counter that can operate as a free-running
counter or a modulo up-counter. The TIM counter provides the timing
reference for the input capture and output compare functions. The TIM
counter modulo registers, TMODH:TMODL, control the modulo value of
the TIM counter. Software can read the TIM counter value at any time
without affecting the counting sequence.
The two TIM channels (per timer) are programmable independently as
input capture or output compare channels.
Data Sheet
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Timer Interface Module (TIM)
Functional Description
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
INTERRUPT
LOGIC
TMODH:TMODL
TOV0
ELS0B
CHANNEL 0
ELS0A
CH0MAX
16-BIT COMPARATOR
TCH0H:TCH0L
PORT
LOGIC
T[1,2]CH0
CH0F
INTERRUPT
LOGIC
16-BIT LATCH
MS0A
CH0IE
MS0B
TOV1
INTERNAL BUS
Freescale Semiconductor, Inc...
16-BIT COMPARATOR
ELS1B
CHANNEL 1
ELS1A
CH1MAX
PORT
LOGIC
T[1,2]CH1
16-BIT COMPARATOR
TCH1H:TCH1L
CH1F
INTERRUPT
LOGIC
16-BIT LATCH
MS1A
CH1IE
Figure 11-1. TIM Block Diagram
Figure 11-2 summarizes the timer registers.
NOTE:
References to either timer 1 or timer 2 may be made in the following text
by omitting the timer number. For example, TSC may generically refer to
both T1SC and T2SC.
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Timer Interface Module (TIM)
Addr.
Register Name
Bit 7
Read:
Timer 1 Status and Control
$0020
Register Write:
(T1SC)
Reset:
TOF
0
0
1
0
Read:
Timer 1 Counter
Register High Write:
(T1CNTH)
Reset:
Bit 15
14
13
0
0
Read:
Timer 1 Counter
Register Low Write:
(T1CNTL)
Reset:
Bit 7
Freescale Semiconductor, Inc...
$0021
$0022
$0023
$0024
Read:
Timer 1 Counter Modulo
Register High Write:
(T1MODH)
Reset:
Read:
Timer 1 Counter Modulo
Register Low Write:
(T1MODL)
Reset:
Read:
Timer 1 Channel 0 Status
$0025
and Control Register Write:
(T1SC0)
Reset:
$0026
$0027
Read:
Timer 1 Channel 0
Register High Write:
(T1CH0H)
Reset:
Read:
Timer 1 Channel 0
Register Low Write:
(T1CH0L)
Reset:
Read:
Timer 1 Channel 1 Status
$0028
and Control Register Write:
(T1SC1)
Reset:
6
5
TOIE
TSTOP
2
1
Bit 0
PS2
PS1
PS0
0
0
0
0
12
11
10
9
Bit 8
0
0
0
0
0
0
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
1
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
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
0
4
3
0
0
TRST
CH0F
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH1F
0
CH1IE
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 11-2. TIM I/O Register Summary (Sheet 1 of 3)
Data Sheet
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Timer Interface Module (TIM)
Functional Description
Addr.
Register Name
Read:
Timer 1 Channel 1
Register High Write:
(T1CH1H)
Reset:
$0029
Read:
Timer 1 Channel 1
Register Low Write:
(T1CH1L)
Reset:
Freescale Semiconductor, Inc...
$002A
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
PS2
PS1
PS0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
Read:
Timer 2 Status and Control
$002B
Register Write:
(T2SC)
Reset:
TOF
0
0
1
0
0
0
0
0
Read:
Timer 2 Counter
Register High Write:
(T2CNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
Timer 2 Counter
Register Low Write:
(T2CNTL)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
1
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
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
$002C
$002D
$002E
$002F
Read:
Timer 2 Counter Modulo
Register High Write:
(T2MODH)
Reset:
Read:
Timer 2 Counter Modulo
Register Low Write:
(T2MODL)
Reset:
Read:
Timer 2 Channel 0 Status
$0030
and Control Register Write:
(T2SC0)
Reset:
$0031
Read:
Timer 2 Channel 0
Register High Write:
(T2CH0H)
Reset:
0
TOIE
0
TSTOP
0
TRST
CH0F
0
Indeterminate after reset
= Unimplemented
Figure 11-2. TIM I/O Register Summary (Sheet 2 of 3)
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Timer Interface Module (TIM)
Addr.
Register Name
$0032
Read:
Timer 2 Channel 0
Register Low Write:
(T2CH0L)
Reset:
Freescale Semiconductor, Inc...
Read:
Timer 2 Channel 1 Status
$0033
and Control Register Write:
(T2SC1)
Reset:
$0034
$0035
Read:
Timer 2 Channel 1
Register High Write:
(T2CH1H)
Reset:
Read:
Timer 2 Channel 1
Register Low Write:
(T2CH1L)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
CH1F
0
CH1IE
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
= Unimplemented
Figure 11-2. TIM I/O Register Summary (Sheet 3 of 3)
11.4.1 TIM Counter Prescaler
The TIM 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 TIM status and control register
select the TIM clock source.
11.4.2 Input Capture
With the input capture function, the TIM can capture the time at which an
external event occurs. When an active edge occurs on the pin of an input
capture channel, the TIM latches the contents of the TIM counter into the
TIM channel registers, TCHxH:TCHxL. The polarity of the active edge is
programmable. Input captures can generate TIM CPU interrupt
requests.
Data Sheet
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Timer Interface Module (TIM)
Functional Description
11.4.3 Output Compare
With the output compare function, the TIM 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 TIM can set, clear, or toggle the channel pin. Output compares can
generate TIM CPU interrupt requests.
Freescale Semiconductor, Inc...
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 TIM channel registers.
An unsynchronized write to the TIM 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 TIM overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIM may pass
the new value before it is written.
Use the following 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 TIM
overflow interrupts and write the new value in the TIM overflow
interrupt routine. The TIM 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 Module (TIM)
11.4.3.2 Buffered Output Compare
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Channels 0 and 1 can be linked to form a buffered output compare
channel whose output appears on the TCH0 pin. The TIM channel
registers of the linked pair alternately control the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0)
links channel 0 and channel 1. The output compare value in the TIM
channel 0 registers initially controls the output on the TCH0 pin. Writing
to the TIM channel 1 registers enables the TIM channel 1 registers to
synchronously control the output after the TIM overflows. At each
subsequent overflow, the TIM 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 TIM channel 1 status and control
register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin,
TCH1, is available as a general-purpose 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 TIM can generate a PWM signal. The value in the TIM counter
modulo registers determines the period of the PWM signal. The channel
pin toggles when the counter reaches the value in the TIM 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 TIM channel
registers determines the pulse width of the PWM signal. The time
between overflow and output compare is the pulse width. Program the
TIM to clear the channel pin on output compare if the state of the PWM
pulse is logic 1. Program the TIM to set the pin if the state of the PWM
pulse is logic 0.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Timer Interface Module (TIM)
Functional Description
The value in the TIM 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 TIM counter modulo registers produces a PWM
period of 256 times the internal bus clock period if the prescaler select
value is $000. See 11.9.1 TIM Status and Control Register.
OVERFLOW
OVERFLOW
OVERFLOW
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PERIOD
PULSE
WIDTH
TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 11-3. PWM Period and Pulse Width
The value in the TIM 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 TIM channel registers produces
a duty cycle of 128/256 or 50%.
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 old value currently in the TIM channel
registers.
An unsynchronized write to the TIM 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 TIM overflow interrupt routine to
write a new, smaller pulse width value may cause the compare to be
missed. The TIM may pass the new value before it is written.
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Timer Interface Module (TIM)
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Use the following 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 TIM overflow
interrupts and write the new value in the TIM overflow interrupt
routine. The TIM 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%
duty cycle generation and removes the ability of the channel to selfcorrect 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 TCH0 pin. The TIM channel registers of the linked
pair alternately control the pulse width of the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0)
links channel 0 and channel 1. The TIM channel 0 registers initially
control the pulse width on the TCH0 pin. Writing to the TIM channel 1
registers enables the TIM channel 1 registers to synchronously control
the pulse width at the beginning of the next PWM period. At each
subsequent overflow, the TIM channel registers (0 or 1) that control the
pulse width are the ones written to last. TSC0 controls and monitors the
buffered PWM function, and TIM channel 1 status and control register
(TSC1) is unused. While the MS0B bit is set, the channel 1 pin, TCH1,
is available as a general-purpose I/O pin.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Timer Interface Module (TIM)
Functional Description
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
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To ensure correct operation when generating unbuffered or buffered
PWM signals, use the following initialization procedure:
1. In the TIM status and control register (TSC):
a. Stop the TIM counter by setting the TIM stop bit, TSTOP.
b. Reset the TIM counter and prescaler by setting the TIM reset
bit, TRST.
2. In the TIM counter modulo registers (TMODH:TMODL), write the
value for the required PWM period.
3. In the TIM channel x registers (TCHxH:TCHxL), write the value for
the required pulse width.
4. In TIM channel x status and control register (TSCx):
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 11-3.)
b. Write 1 to the toggle-on-overflow bit, TOVx.
c. 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 11-3.)
NOTE:
In PWM signal generation, do not program the PWM channel to toggle
on output compare. Toggling on output compare prevents reliable 0%
duty cycle generation and removes the ability of the channel to selfcorrect 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 TIM status control register (TSC), clear the TIM stop bit,
TSTOP.
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Timer Interface Module (TIM)
Setting MS0B links channels 0 and 1 and configures them for buffered
PWM operation. The TIM channel 0 registers (TCH0H:TCH0L) initially
control the buffered PWM output. TIM channel 0 status and control
register (TSC0) controls and monitors the PWM signal from the linked
channels.
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Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIM
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% duty cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the
TOVx bit generates a 100% duty cycle output. (See 11.9.4 TIM Channel
Status and Control Registers.)
11.5 Interrupts
The following TIM sources can generate interrupt requests:
•
TIM overflow flag (TOF) — The TOF bit is set when the TIM
counter reaches the modulo value programmed in the TIM counter
modulo registers. The TIM overflow interrupt enable bit, TOIE,
enables TIM overflow CPU interrupt requests. TOF and TOIE are
in the TIM status and control register.
•
TIM channel flags (CH1F:CH0F) — The CHxF bit is set when an
input capture or output compare occurs on channel x. Channel x
TIM CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE. Channel x TIM CPU interrupt requests
are enabled when CHxIE = 1. CHxF and CHxIE are in the TIM
channel x status and control register.
11.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Timer Interface Module (TIM)
TIM During Break Interrupts
11.6.1 Wait Mode
The TIM remains active after the execution of a WAIT instruction. In wait
mode, the TIM registers are not accessible by the CPU. Any enabled
CPU interrupt request from the TIM can bring the MCU out of wait mode.
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If TIM functions are not required during wait mode, reduce power
consumption by stopping the TIM before executing the WAIT instruction.
11.6.2 Stop Mode
The TIM is inactive after the execution of a STOP instruction. The STOP
instruction does not affect register conditions or the state of the TIM
counter. TIM operation resumes when the MCU exits stop mode after an
external interrupt.
11.7 TIM During Break Interrupts
A break interrupt stops the TIM counter.
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 9.7.3 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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Data Sheet
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Timer Interface Module (TIM)
11.8 I/O Signals
Port B shares four of its pins with the TIM. The four TIM channel I/O pins
are T1CH0, T1CH1, T2CH0, and T2CH1 as described in 11.3 Pin Name
Conventions.
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Each channel I/O pin is programmable independently as an input
capture pin or an output compare pin. T1CH0 and T2CH0 can be
configured as buffered output compare or buffered PWM pins.
11.9 I/O Registers
NOTE:
References to either timer 1 or timer 2 may be made in the following text
by omitting the timer number. For example, TSC may generically refer to
both T1SC AND T2SC.
These I/O registers control and monitor operation of the TIM:
Data Sheet
•
TIM status and control register (TSC)
•
TIM counter registers (TCNTH:TCNTL)
•
TIM counter modulo registers (TMODH:TMODL)
•
TIM channel status and control registers (TSC0, TSC1)
•
TIM channel registers (TCH0H:TCH0L, TCH1H:TCH1L)
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Timer Interface Module (TIM)
I/O Registers
11.9.1 TIM Status and Control Register
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The TIM status and control register (TSC):
•
Enables TIM overflow interrupts
•
Flags TIM overflows
•
Stops the TIM counter
•
Resets the TIM counter
•
Prescales the TIM counter clock
Address: T1SC, $0020 and T2SC, $002B
Bit 7
Read:
6
5
TOIE
TSTOP
TOF
Write:
0
Reset:
0
4
3
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
TRST
0
1
0
0
= Unimplemented
Figure 11-4. TIM Status and Control Register (TSC)
TOF — TIM Overflow Flag Bit
This read/write flag is set when the TIM counter reaches the modulo
value programmed in the TIM counter modulo registers. Clear TOF by
reading the TIM status and control register when TOF is set and then
writing a logic 0 to TOF. If another TIM 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 = TIM counter has reached modulo value
0 = TIM counter has not reached modulo value
TOIE — TIM Overflow Interrupt Enable Bit
This read/write bit enables TIM overflow interrupts when the TOF bit
becomes set. Reset clears the TOIE bit.
1 = TIM overflow interrupts enabled
0 = TIM overflow interrupts disabled
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Timer Interface Module (TIM)
TSTOP — TIM Stop Bit
This read/write bit stops the TIM counter. Counting resumes when
TSTOP is cleared. Reset sets the TSTOP bit, stopping the TIM
counter until software clears the TSTOP bit.
1 = TIM counter stopped
0 = TIM counter active
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NOTE:
Do not set the TSTOP bit before entering wait mode if the TIM is required
to exit wait mode.
TRST — TIM Reset Bit
Setting this write-only bit resets the TIM counter and the TIM
prescaler. Setting TRST has no effect on any other registers.
Counting resumes from $0000. TRST is cleared automatically after
the TIM counter is reset and always reads as logic 0. Reset clears the
TRST bit.
1 = Prescaler and TIM counter cleared
0 = No effect
NOTE:
Setting the TSTOP and TRST bits simultaneously stops the TIM 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 TIM counter as Table 11-2 shows. Reset clears the
PS[2:0] bits.
Table 11-2. Prescaler Selection
Data Sheet
PS2
PS1
PS0
TIM Clock Source
0
0
0
Internal bus clock ÷ 1
0
0
1
Internal bus clock ÷ 2
0
1
0
Internal bus clock ÷ 4
0
1
1
Internal bus clock ÷ 8
1
0
0
Internal bus clock ÷ 16
1
0
1
Internal bus clock ÷ 32
1
1
0
Internal bus clock ÷ 64
1
1
1
Not available
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Timer Interface Module (TIM)
I/O Registers
11.9.2 TIM Counter Registers
The two read-only TIM counter registers contain the high and low bytes
of the value in the TIM counter. Reading the high byte (TCNTH) latches
the contents of the low byte (TCNTL) into a buffer. Subsequent reads of
TCNTH do not affect the latched TCNTL value until TCNTL is read.
Reset clears the TIM counter registers. Setting the TIM reset bit (TRST)
also clears the TIM counter registers.
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NOTE:
If you read TCNTH during a break interrupt, be sure to unlatch TCNTL
by reading TCNTL before exiting the break interrupt. Otherwise, TCNTL
retains the value latched during the break.
Address: T1CNTH, $0021 and T2CNTH, $002C
Read:
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
Write:
Reset:
= Unimplemented
Figure 11-5. TIM Counter Registers High (TCNTH)
Address: T1CNTL, $0022 and T2CNTL, $002D
Read:
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
Write:
Reset:
= Unimplemented
Figure 11-6. TIM Counter Registers Low (TCNTL)
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Timer Interface Module (TIM)
11.9.3 TIM Counter Modulo Registers
The read/write TIM modulo registers contain the modulo value for the
TIM counter. When the TIM counter reaches the modulo value, the
overflow flag (TOF) becomes set, and the TIM 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 TIM counter modulo registers.
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Address: T1MODH, $0023 and T2MODH, $002E
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
1
1
1
1
1
1
1
1
Read:
Write:
Reset:
Figure 11-7. TIM Counter Modulo Register High (TMODH)
Address: T1MODL, $0024 and T2MODL, $002F
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
1
1
1
1
1
1
1
1
Read:
Write:
Reset:
Figure 11-8. TIM Counter Modulo Register Low (TMODL)
NOTE:
Data Sheet
Reset the TIM counter before writing to the TIM counter modulo registers.
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Timer Interface Module (TIM)
I/O Registers
11.9.4 TIM Channel Status and Control Registers
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Each of the TIM 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 TIM overflow
•
Selects 0% and 100% PWM duty cycle
•
Selects buffered or unbuffered output compare/PWM operation
Address: T1SC0, $0025 and T2SC0, $0030
Bit 7
Read:
CH0F
Write:
0
Reset:
0
6
5
4
3
2
1
Bit 0
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
Figure 11-9. TIM Channel 0 Status and Control Register (TSC0)
Address: T1SC1, $0028 and T2SC1, $0033
Bit 7
Read:
6
CH1F
5
0
Reset:
0
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
CH1IE
Write:
4
0
0
Figure 11-10. TIM Channel 1 Status and Control Register (TSC1)
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Timer Interface Module (TIM)
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 TIM
counter registers matches the value in the TIM channel x registers.
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When TIM CPU interrupt requests are enabled (CHxIE = 1), clear
CHxF by reading TIM 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 TIM CPU interrupt service requests 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 TIM1 channel 0 and TIM2 channel 0 status
and control registers.
Setting MS0B disables the channel 1 status and control register and
reverts TCH1 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:ELSxA ≠ 0:0, this read/write bit selects either input
capture operation or unbuffered output compare/PWM operation.
See Table 11-3.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
Data Sheet
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Timer Interface Module (TIM)
I/O Registers
When ELSxB:ELSxA = 0:0, this read/write bit selects the initial output
level of the TCHx pin. See Table 11-3. Reset clears the MSxA bit.
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 TIM status and control register
(TSC).
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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 an I/O port, and pin TCHx is available as a general-purpose I/O pin.
Table 11-3 shows how ELSxB and ELSxA work. Reset clears the
ELSxB and ELSxA bits.
Table 11-3. Mode, Edge, and Level Selection
MSxB:MSxA
ELSxB:ELSxA
X0
00
Mode
Configuration
Pin under port control;
initial output level high
Output preset
X1
00
Pin under port control;
initial output level low
00
01
Capture on rising edge only
00
10
00
11
01
01
01
10
01
11
1X
01
1X
10
1X
11
Input capture
Capture on falling edge only
Capture on rising or
falling edge
Output
compare or
PWM
Buffered
output
compare or
buffered PWM
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Toggle output on compare
Clear output on compare
Set output on compare
Toggle output on compare
Clear output on compare
Set output on compare
Data Sheet
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Timer Interface Module (TIM)
NOTE:
Before enabling a TIM channel register for input capture operation, make
sure that the TCHx pin is stable for at least two bus clocks.
TOVx — Toggle On Overflow Bit
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When channel x is an output compare channel, this read/write bit
controls the behavior of the channel x output when the TIM 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 TIM counter overflow
0 = Channel x pin does not toggle on TIM counter overflow
NOTE:
When TOVx is set, a TIM 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%. As
Figure 11-11 shows, the CHxMAX bit takes effect in the cycle after it
is set or cleared. The output stays at the 100% duty cycle level until
the cycle after CHxMAX is cleared.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
Figure 11-11. CHxMAX Latency
11.9.5 TIM Channel Registers
These read/write registers contain the captured TIM counter value of the
input capture function or the output compare value of the output
compare function. The state of the TIM channel registers after reset is
unknown.
Data Sheet
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Timer Interface Module (TIM)
I/O Registers
In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the
TIM channel x registers (TCHxH) inhibits input captures until the low
byte (TCHxL) is read.
In output compare mode (MSxB:MSxA ≠ 0:0), writing to the high byte of
the TIM channel x registers (TCHxH) inhibits output compares until the
low byte (TCHxL) is written.
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Address: T1CH0H, $0026 and T2CH0H, $0031
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Read:
Write:
Reset:
Indeterminate after reset
Figure 11-12. TIM Channel 0 Register High (TCH0H)
Address: T1CH0L, $0027 and T2CH0L $0032
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Indeterminate after reset
Figure 11-13. TIM Channel 0 Register Low (TCH0L)
Address: T1CH1H, $0029 and T2CH1H, $0034
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Read:
Write:
Reset:
Indeterminate after reset
Figure 11-14. TIM Channel 1 Register High (TCH1H)
Address: T1CH1L, $002A and T2CH1L, $0035
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Indeterminate after reset
Figure 11-15. TIM Channel 1 Register Low (TCH1L)
MC68HC908AP Family — Rev. 2.5
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Freescale Semiconductor, Inc...
Timer Interface Module (TIM)
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Section 12. Timebase Module (TBM)
Freescale Semiconductor, Inc...
12.1 Introduction
This section describes the timebase module (TBM). The TBM will
generate periodic interrupts at user selectable rates using a counter
clocked by the selected OSCCLK clock from the oscillator module. This
TBM version uses 18 divider stages, eight of which are user selectable.
12.2 Features
Features of the TBM module include:
•
Software programmable 8s, 4s, 2s, 1s, 2ms, 1ms, 0.5ms, and
0.25ms periodic interrupt using 32.768-kHz OSCCLK clock
•
User selectable oscillator clock source enable during stop mode to
allow periodic wake-up from stop
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Timebase Module (TBM)
This module can generate a periodic interrupt by dividing the oscillator
clock frequency, OSCCLK. The counter is initialized to all 0s when
TBON bit is cleared. The counter, shown in Figure 12-1, starts counting
when the TBON bit is set. When the counter overflows at the tap
selected by TBR[2:0], the TBIF bit gets set. If the TBIE bit is set, an
interrupt request is sent to the CPU. The TBIF flag is cleared by writing
a 1 to the TACK bit. The first time the TBIF flag is set after enabling the
timebase module, the interrupt is generated at approximately half of the
overflow period. Subsequent events occur at the exact period.
The reference clock OSCCLK is derived from the oscillator module, see
7.2.2 TBM Reference Clock Selection.
TBON
÷2
OSCCLK
÷2
÷2
From OSC module
(See Section 7. Oscillator (OSC).)
÷2
÷8
÷2
÷ 16
÷2
÷ 32
÷2
÷2
÷2
÷2
÷2
÷ 64
÷ 2048
÷2
÷2
÷2
÷ 32768
÷2
÷ 65536
÷2
÷ 131072
TACK
÷2
TBR1
÷2
TBR0
TBMINT
TBR2
Freescale Semiconductor, Inc...
12.3 Functional Description
÷ 262144
TBIF
000
TBIE
R
001
010
011
100
SEL
101
110
111
Figure 12-1. Timebase Block Diagram
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Timebase Module (TBM)
Timebase Register Description
12.4 Timebase Register Description
The timebase has one register, the TBCR, which is used to enable the
timebase interrupts and set the rate.
Address:
$0051
Bit 7
Read:
6
5
4
TBR2
TBR1
TBR0
TBIF
Freescale Semiconductor, Inc...
2
1
Bit 0
TBIE
TBON
R
0
0
0
0
Write:
Reset:
3
TACK
0
0
0
0
= Unimplemented
0
R
= Reserved
Figure 12-2. Timebase Control Register (TBCR)
TBIF — Timebase Interrupt Flag
This read-only flag bit is set when the timebase counter has rolled
over.
1 = Timebase interrupt pending
0 = Timebase interrupt not pending
TBR[2:0] — Timebase Rate Selection
These read/write bits are used to select the rate of timebase interrupts
as shown in Table 12-1.
Table 12-1. Timebase Rate Selection for OSCCLK = 32.768 kHz
Timebase Interrupt Rate
TBR2
TBR1
TBR0
Divider
Hz
ms
0
0
0
262144
0.125
8000
0
0
1
131072
0.25
4000
0
1
0
65536
0.5
2000
0
1
1
32768
1
1000
1
0
0
64
512
~2
1
0
1
32
1024
~1
1
1
0
16
2048
~0.5
1
1
1
8
4096
~0.24
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Timebase Module (TBM)
NOTE:
Do not change TBR[2:0] bits while the timebase is enabled
(TBON = 1).
TACK — Timebase ACKnowledge
Freescale Semiconductor, Inc...
The TACK bit is a write-only bit and always reads as 0. Writing a logic
1 to this bit clears TBIF, the timebase interrupt flag bit. Writing a logic
0 to this bit has no effect.
1 = Clear timebase interrupt flag
0 = No effect
TBIE — Timebase Interrupt Enabled
This read/write bit enables the timebase interrupt when the TBIF bit
becomes set. Reset clears the TBIE bit.
1 = Timebase interrupt enabled
0 = Timebase interrupt disabled
TBON — Timebase Enabled
This read/write bit enables the timebase. Timebase may be turned off
to reduce power consumption when its function is not necessary. The
counter can be initialized by clearing and then setting this bit. Reset
clears the TBON bit.
1 = Timebase enabled
0 = Timebase disabled and the counter initialized to 0’s
12.5 Interrupts
The timebase module can interrupt the CPU on a regular basis with a
rate defined by TBR[2:0]. When the timebase counter chain rolls over,
the TBIF flag is set. If the TBIE bit is set, enabling the timebase interrupt,
the counter chain overflow will generate a CPU interrupt request. The
interrupt vector is defined in Table 2-1 . Vector Addresses.
Interrupts must be acknowledged by writing a logic 1 to the TACK bit.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Timebase Module (TBM)
Low-Power Modes
12.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
Freescale Semiconductor, Inc...
12.6.1 Wait Mode
The timebase module remains active after execution of the WAIT
instruction. In wait mode, the timebase register is not accessible by the
CPU.
If the timebase functions are not required during wait mode, reduce the
power consumption by stopping the timebase before enabling the WAIT
instruction.
12.6.2 Stop Mode
The timebase module may remain active after execution of the STOP
instruction if the oscillator has been enabled to operate during stop mode
through the stop mode oscillator enable bit (STOP_ICLKDIS,
STOP_RCLKEN, or STOP_XCLKEN) for the selected oscillator in the
CONFIG2 register. The timebase module can be used in this mode to
generate a periodic walk-up from stop mode.
If the oscillator has not been enabled to operate in stop mode, the
timebase module will not be active during stop mode. In stop mode the
timebase register is not accessible by the CPU.
If the timebase functions are not required during stop mode, reduce the
power consumption by stopping the timebase before enabling the STOP
instruction.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Freescale Semiconductor, Inc...
Timebase Module (TBM)
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Section 13. Serial Communications Interface Module
(SCI)
13.1 Introduction
Freescale Semiconductor, Inc...
The MC68HC908AP64 has two SCI modules:
•
SCI1 is a standard SCI module, and
•
SCI2 is an infrared SCI module.
This section describes SCI1, the serial communications interface (SCI)
module, which allows high-speed asynchronous communications with
peripheral devices and other MCUs.
NOTE:
When the SCI is enabled, the TxD pin is an open-drain output and
requires a pullup resistor to be connected for proper SCI operation.
NOTE:
References to DMA (direct-memory access) and associated functions
are only valid if the MCU has a DMA module. This MCU does not have
the DMA function. Any DMA-related register bits should be left in their
reset state for normal MCU operation.
MC68HC908AP Family — Rev. 2.5
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Serial Communications Interface
13.2 Features
Freescale Semiconductor, Inc...
Features of the SCI module include the following:
•
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
•
Programmable transmitter output polarity
•
Two receiver wakeup methods:
– Idle line wakeup
– Address mark wakeup
•
Interrupt-driven operation with eight interrupt flags:
– Transmitter empty
– Transmission complete
– Receiver full
– Idle receiver input
– Receiver overrun
– Noise error
– Framing error
– Parity error
Data Sheet
•
Receiver framing error detection
•
Hardware parity checking
•
1/16 bit-time noise detection
•
Configuration register bit, SCIBDSRC, to allow selection of baud
rate clock source
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Serial Communications Interface Module (SCI)
Pin Name Conventions
13.3 Pin Name Conventions
Freescale Semiconductor, Inc...
The generic names of the SCI I/O pins are:
•
RxD (receive data)
•
TxD (transmit data)
SCI I/O (input/output) lines are implemented by sharing parallel I/O port
pins. The full name of an SCI input or output reflects the name of the
shared port pin. Table 13-1 shows the full names and the generic names
of the SCI I/O pins. The generic pin names appear in the text of this
section.
Table 13-1. Pin Name Conventions
NOTE:
Generic Pin Names:
RxD
TxD
Full Pin Names:
PTB3/RxD
PTB2/TxD
When the SCI is enabled, the TxD pin is an open-drain output and
requires a pullup resistor to be connected for proper SCI operation.
13.4 Functional Description
Figure 13-1 shows the structure of the SCI module. The SCI allows fullduplex, 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.
The baud rate clock source for the SCI can be selected via the
configuration bit, SCIBDSRC, of the CONFIG2 register ($001D). Source
selection values are shown in Figure 13-1.
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Serial Communications Interface
INTERNAL BUS
SCI DATA
REGISTER
ERROR
INTERRUPT
CONTROL
RECEIVER
INTERRUPT
CONTROL
DMA
INTERRUPT
CONTROL
RECEIVE
SHIFT REGISTER
RxD
TRANSMITTER
INTERRUPT
CONTROL
SCI DATA
REGISTER
TRANSMIT
SHIFT REGISTER
TxD
TXINV
SCTIE
R8
Freescale Semiconductor, Inc...
TCIE
T8
SCRIE
ILIE
DMARE
TE
SCTE
RE
DMATE
TC
RWU
SBK
SCRF
OR
ORIE
IDLE
NF
NEIE
FE
FEIE
PE
PEIE
LOOPS
LOOPS
WAKEUP
CONTROL
SCIBDSRC
FROM
CONFIG
FLAG
CONTROL
RECEIVE
CONTROL
ENSCI
ENSCI
TRANSMIT
CONTROL
BKF
M
RPF
WAKE
ILTY
SL
A
CGMXCLK
X
B
IT12
SL = 0 => X = A
SL = 1 => X = B
÷4
CGMXCLK is from CGM module
IT12 = fBUS
PRESCALER
BAUD
DIVIDER
÷ 16
PEN
PTY
DATA SELECTION
CONTROL
Figure 13-1. SCI Module Block Diagram
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Serial Communications Interface Module (SCI)
Functional Description
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
T8
DMARE
DMATE
ORIE
NEIE
FEIE
PEIE
U
U
0
0
0
0
0
0
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
BKF
RPF
Read:
$0013
LOOPS
SCI Control Register 1
Write:
(SCC1)
Reset:
0
Read:
Freescale Semiconductor, Inc...
$0014
SCI Control Register 2
Write:
(SCC2)
Reset:
Read:
$0015
SCI Control Register 3
Write:
(SCC3)
Reset:
Read:
$0016
SCI Status Register 1
Write:
(SCS1)
Reset:
R8
Read:
$0017
SCI Status Register 2
Write:
(SCS2)
Reset:
0
0
0
0
0
0
0
0
Read:
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
SCI Data Register
Write:
(SCDR)
Reset:
$0018
Read:
$0019
SCI Baud Rate Register
Write:
(SCBR)
Reset:
Unaffected by reset
0
0
0
0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
= Unimplemented
R = Reserved
U = Unaffected
Figure 13-2. SCI I/O Register Summary
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Serial Communications Interface
13.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format
illustrated in Figure 13-3.
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
Freescale Semiconductor, Inc...
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
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
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.
The baud rate clock source for the SCI can be selected via the
configuration bit, SCIBDSRC. Source selection values are shown in
Figure 13-4.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Serial Communications Interface Module (SCI)
Functional Description
SCIBDSRC
FROM
CONFIG2
SL
CGMXCLK
A
X
B
IT12
SL = 0 => X = A
SL = 1 => X = B
INTERNAL BUS
Freescale Semiconductor, Inc...
BAUD
DIVIDER
÷ 16
SCI DATA REGISTER
SCP1
11-BIT
TRANSMIT
SHIFT REGISTER
STOP
SCP0
SCR1
H
SCR2
8
7
6
5
4
3
2
START
PRESCALER
÷4
1
0
L
TxD
MSB
TRANSMITTER DMA SERVICE REQUEST
TXINV
PARITY
GENERATION
T8
DMATE
DMATE
SCTIE
SCTE
DMATE
SCTE
SCTIE
TC
TCIE
BREAK
ALL 0s
PTY
PREAMBLE
ALL 1s
PEN
SHIFT ENABLE
M
LOAD FROM SCDR
TRANSMITTER CPU INTERRUPT REQUEST
SCR0
TRANSMITTER
CONTROL LOGIC
SCTE
SBK
LOOPS
SCTIE
ENSCI
TC
TE
TCIE
Figure 13-4. SCI Transmitter
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Serial Communications Interface
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
Freescale Semiconductor, Inc...
During an SCI transmission, the transmit shift register shifts a character
out to the 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.
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 position of the transmit shift register. A logic 1 stop bit goes
into the most significant bit 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 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 pin.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Serial Communications Interface Module (SCI)
Functional Description
Freescale Semiconductor, Inc...
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.
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
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 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.
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Serial Communications Interface
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 TxD pin. Setting TE after
the stop bit appears on TxD causes data previously written to the SCDR
to be lost.
Toggle the TE bit for a queued idle character when the SCTE bit
becomes set and just before writing the next byte to the SCDR.
Freescale Semiconductor, Inc...
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 13.8.1 SCI Control Register 1.)
13.4.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the SCI
transmitter:
Data Sheet
•
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.
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Serial Communications Interface Module (SCI)
Functional Description
13.4.3 Receiver
Figure 13-5 shows the structure of the SCI receiver.
Freescale Semiconductor, Inc...
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 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.
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Serial Communications Interface
INTERNAL BUS
SCIBDSRC
FROM
CONFIG2
SCR1
SCP0
SCR0
PRESCALER
BAUD
DIVIDER
÷ 16
DATA
RECOVERY
RxD
Freescale Semiconductor, Inc...
ALL 1s
RPF
CPU INTERRUPT REQUEST
H
11-BIT
RECEIVE SHIFT REGISTER
8
7
6
5
M
WAKE
ILTY
PEN
PTY
4
3
2
1
0
L
ALL 0s
BKF
ERROR CPU INTERRUPT REQUEST
DMA SERVICE REQUEST
STOP
÷4
SCI DATA REGISTER
START
SCR2
MSB
SL
CGMXCLK
A
X
B
IT12
SL = 0 => X = A
SL = 1 => X = B
SCP1
SCRF
WAKEUP
LOGIC
RWU
IDLE
R8
PARITY
CHECKING
IDLE
ILIE
DMARE
ILIE
SCRF
SCRIE
DMARE
SCRIE
SCRF
SCRIE
DMARE
DMARE
OR
OR
ORIE
ORIE
NF
NF
NEIE
NEIE
FE
FE
FEIE
FEIE
PE
PE
PEIE
PEIE
Figure 13-5. SCI Receiver Block Diagram
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Serial Communications Interface Module (SCI)
Functional Description
13.4.3.3 Data Sampling
•
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
returns a valid logic 1 and the majority of the next RT8, RT9, and
RT10 samples returns 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.
START BIT
LSB
RxD
START BIT
QUALIFICATION
SAMPLES
START BIT
VERIFICATION
DATA
SAMPLING
RT4
RT3
RT2
RT1
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT CLOCK
STATE
RT1
RT
CLOCK
RT1
Freescale Semiconductor, Inc...
The receiver samples the 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 the following
times (see Figure 13-6):
RT CLOCK
RESET
Figure 13-6. Receiver Data Sampling
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Serial Communications Interface
To verify the start bit and to detect noise, data recovery logic takes
samples at RT3, RT5, and RT7. Table 13-2 summarizes the results of
the start bit verification samples.
Freescale Semiconductor, Inc...
Table 13-2. 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
Start bit verification is not successful if any two of the three verification
samples are logic 1s. If start bit verification is not successful, the RT
clock is reset and a new search for a start bit begins.
To determine the value of a data bit and to detect noise, recovery logic
takes samples at RT8, RT9, and RT10. Table 13-3 summarizes the
results of the data bit samples.
Table 13-3. Data Bit Recovery
Data Sheet
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
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Serial Communications Interface Module (SCI)
Functional Description
NOTE:
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 13-4 summarizes the results of the stop bit
samples.
Freescale Semiconductor, Inc...
Table 13-4. 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
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. A break character also sets the FE bit because a break character
has no stop bit. The FE bit is set at the same time that the SCRF bit is
set.
13.4.3.5 Baud Rate Tolerance
A transmitting device may be operating at a baud rate below or above
the receiver baud rate. Accumulated bit time misalignment can cause
one of the three stop bit data samples to fall outside the actual stop bit.
Then a noise error occurs. If more than one of the samples is outside the
stop bit, a framing error occurs. In most applications, the baud rate
tolerance is much more than the degree of misalignment that is likely to
occur.
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Serial Communications Interface
As the receiver samples an incoming character, it resynchronizes the RT
clock on any valid falling edge within the character. Resynchronization
within characters corrects misalignments between transmitter bit times
and receiver bit times.
Slow Data Tolerance
RT16
RT15
RT14
RT13
RT11
RT10
RT9
RT8
RT7
RT6
STOP
RT5
RT4
RT3
RT2
RECEIVER
RT CLOCK
RT1
MSB
RT12
Freescale Semiconductor, Inc...
Figure 13-7 shows how much a slow received character can be
misaligned without causing a noise error or a framing error. The slow
stop bit begins at RT8 instead of RT1 but arrives in time for the stop bit
data samples at RT8, RT9, and RT10.
DATA
SAMPLES
Figure 13-7. Slow Data
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 13-7, the receiver counts
154 RT cycles at the point when the count of the transmitting device is
9 bit times × 16 RT cycles + 3 RT cycles = 147 RT cycles.
The maximum percent difference between the receiver count and the
transmitter count of a slow 8-bit character with no errors is
154 – 147
-------------------------- × 100 = 4.54%
154
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 13-7, the receiver counts
170 RT cycles at the point when the count of the transmitting device is
10 bit times × 16 RT cycles + 3 RT cycles = 163 RT cycles.
Data Sheet
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Serial Communications Interface Module (SCI)
Functional Description
The maximum percent difference between the receiver count and the
transmitter count of a slow 9-bit character with no errors is
170 – 163
-------------------------- × 100 = 4.12%
170
Fast Data Tolerance
RT16
RT15
RT14
RT13
RT12
RT10
RT9
RT8
RT7
IDLE OR NEXT CHARACTER
RT6
RT5
RT4
RT3
RT2
RECEIVER
RT CLOCK
RT1
STOP
RT11
Freescale Semiconductor, Inc...
Figure 13-8 shows how much a fast received character can be
misaligned without causing a noise error or a framing error. The fast stop
bit ends at RT10 instead of RT16 but is still there for the stop bit data
samples at RT8, RT9, and RT10.
DATA
SAMPLES
Figure 13-8. Fast Data
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 13-8, the receiver counts
154 RT cycles at the point when the count of the transmitting device is
10 bit times × 16 RT cycles = 160 RT cycles.
The maximum percent difference between the receiver count and the
transmitter count of a fast 8-bit character with no errors is
·
154 – 160
-------------------------- × 100 = 3.90%
154
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 13-8, the receiver counts
170 RT cycles at the point when the count of the transmitting device is
11 bit times × 16 RT cycles = 176 RT cycles.
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Serial Communications Interface
The maximum percent difference between the receiver count and the
transmitter count of a fast 9-bit character with no errors is
170 – 176
-------------------------- × 100 = 3.53%
170
13.4.3.6 Receiver Wakeup
Freescale Semiconductor, Inc...
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 RxD pin can bring the receiver out of the standby state:
NOTE:
Data Sheet
•
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 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.
With the WAKE bit clear, setting the RWU bit after the RxD pin has been
idle may cause the receiver to wake up immediately.
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Serial Communications Interface Module (SCI)
Functional Description
13.4.3.7 Receiver Interrupts
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The following 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 RxD pin. The idle line
interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate
CPU interrupt requests.
13.4.3.8 Error Interrupts
The following 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
13.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
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13.5.1 Wait Mode
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.
Refer to 9.6 Low-Power Modes for information on exiting wait mode.
13.5.2 Stop Mode
The SCI module is inactive after the execution of a STOP instruction.
The STOP instruction does not affect SCI register states. SCI module
operation resumes after an external interrupt.
Because the internal clock is inactive during stop mode, entering stop
mode during an SCI transmission or reception results in invalid data.
Refer to 9.6 Low-Power Modes for information on exiting stop mode.
13.6 SCI During Break Module Interrupts
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.
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.
Data Sheet
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Serial Communications Interface Module (SCI)
I/O Signals
Freescale Semiconductor, Inc...
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.
13.7 I/O Signals
Port B shares two of its pins with the SCI module.
The two SCI I/O pins are:
•
PTB2/TxD — Transmit data
•
PTB3/RxD — Receive data
13.7.1 TxD (Transmit Data)
When the SCI is enabled (ENSCI=1), the PTB2/TxD pin becomes the
serial data output, TxD, from the SCI transmitter regardless of the state
of the DDRB2 bit in data direction register B (DDRB). The TxD pin is an
open-drain output and requires a pullup resistor to be connected for
proper SCI operation.
NOTE:
The PTB2/TxD pin is an open-drain pin when configured as an output.
Therefore, when configured as a general purpose output pin (PTB2), a
pullup resistor must be connected to this pin.
13.7.2 RxD (Receive Data)
When the SCI is enabled (ENSCI=1), the PTB3/RxD pin becomes the
serial data input, RxD, to the SCI receiver regardless of the state of the
DDRB3 bit in data direction register B (DDRB).
NOTE:
The PTB3/RxD pin is an open-drain pin when configured as an output.
Therefore, when configured as a general purpose output pin (PTB3), a
pullup resistor must be connected to this pin.
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Serial Communications Interface
13.8 I/O Registers
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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)
13.8.1 SCI Control Register 1
SCI control register 1:
Data Sheet
•
Enables loop mode operation
•
Enables the SCI
•
Controls output polarity
•
Controls character length
•
Controls SCI wakeup method
•
Controls idle character detection
•
Enables parity function
•
Controls parity type
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Serial Communications Interface Module (SCI)
I/O Registers
Address:
$0013
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
Read:
Write:
Reset:
Figure 13-9. SCI Control Register 1 (SCC1)
LOOPS — Loop Mode Select Bit
Freescale Semiconductor, Inc...
This read/write bit enables loop mode operation. In loop mode the
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
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.
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Serial Communications Interface
M — Mode (Character Length) Bit
This read/write bit determines whether SCI characters are eight or
nine bits long. (See Table 13-5.) 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
Freescale Semiconductor, Inc...
This read/write bit determines which condition wakes up the SCI: a
logic 1 (address mark) in the most significant bit position of a received
character or an idle condition on the 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
PEN — Parity Enable Bit
This read/write bit enables the SCI parity function. (See Table 13-5.)
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
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Serial Communications Interface Module (SCI)
I/O Registers
PTY — Parity Bit
This read/write bit determines whether the SCI generates and checks
for odd parity or even parity. (See Table 13-5.) Reset clears the PTY
bit.
1 = Odd parity
0 = Even parity
Freescale Semiconductor, Inc...
NOTE:
Changing the PTY bit in the middle of a transmission or reception can
generate a parity error.
Table 13-5. Character Format Selection
Control Bits
Character Format
M
PEN:PTY
Start
Bits
Data
Bits
Parity
Stop
Bits
Character
Length
0
0X
1
8
None
1
10 bits
1
0X
1
9
None
1
11 bits
0
10
1
7
Even
1
10 bits
0
11
1
7
Odd
1
10 bits
1
10
1
8
Even
1
11 bits
1
11
1
8
Odd
1
11 bits
13.8.2 SCI Control Register 2
SCI control register 2:
•
Enables the following 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 wakeup
•
Transmits SCI break characters
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Serial Communications Interface
Address:
$0014
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
Read:
Write:
Reset:
Figure 13-10. SCI Control Register 2 (SCC2)
Freescale Semiconductor, Inc...
SCTIE — SCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate SCI transmitter
CPU interrupt requests. Reset clears the SCTIE bit.
1 = SCTE enabled to generate CPU interrupt
0 = SCTE not enabled to generate CPU interrupt
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. 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
TxD pin. If software clears the TE bit, the transmitter completes any
transmission in progress before the TxD returns to the idle condition
Data Sheet
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Serial Communications Interface Module (SCI)
I/O Registers
(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.
Freescale Semiconductor, Inc...
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
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 before the preamble begins causes the SCI to send a
break character instead of a preamble.
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Serial Communications Interface
13.8.3 SCI Control Register 3
SCI control register 3:
•
Stores the ninth SCI data bit received and the ninth SCI data bit to
be transmitted
•
Enables these interrupts:
– Receiver overrun interrupts
Freescale Semiconductor, Inc...
– Noise error interrupts
– Framing error interrupts
•
Parity error interrupts
Address:
$0015
Bit 7
Read:
6
5
4
3
2
1
Bit 0
T8
DMARE
DMATE
ORIE
NEIE
FEIE
PEIE
U
0
0
0
0
0
0
R8
Write:
Reset:
U
= Unimplemented
U = Unaffected
Figure 13-11. 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.
Data Sheet
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Serial Communications Interface Module (SCI)
I/O Registers
DMARE — DMA Receive Enable Bit
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CAUTION:
The DMA module is not included on this MCU. Writing a logic 1 to
DMARE or DMATE may adversely affect MCU performance.
1 = DMA not enabled to service SCI receiver DMA service requests
generated by the SCRF bit (SCI receiver CPU interrupt
requests enabled)
0 = DMA not enabled to service SCI receiver DMA service requests
generated by the SCRF bit (SCI receiver CPU interrupt
requests enabled)
DMATE — DMA Transfer Enable Bit
CAUTION:
The DMA module is not included on this MCU. Writing a logic 1 to
DMARE or DMATE may adversely affect MCU performance.
1 = SCTE DMA service requests enabled; SCTE CPU interrupt
requests disabled
0 = SCTE DMA service requests disabled; SCTE CPU interrupt
requests enabled
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
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
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Serial Communications Interface
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt
requests generated by the parity error bit, PE. (See 13.8.4 SCI Status
Register 1.) Reset clears PEIE.
1 = SCI error CPU interrupt requests from PE bit enabled
0 = SCI error CPU interrupt requests from PE bit disabled
Freescale Semiconductor, Inc...
13.8.4 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
Address:
Read:
$0016
Bit 7
6
5
4
3
2
1
Bit 0
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 13-12. SCI Status Register 1 (SCS1)
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
Data Sheet
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Serial Communications Interface Module (SCI)
I/O Registers
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
Freescale Semiconductor, Inc...
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 automatically cleared 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 receiver 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
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)
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Serial Communications Interface
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
Freescale Semiconductor, Inc...
Software latency may allow an overrun to occur between reads of
SCS1 and SCDR in the flag-clearing sequence. Figure 13-13 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 flagclearing 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 flagclearing 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
RxD pin. NF generates an SCI error 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
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
Data Sheet
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Serial Communications Interface Module (SCI)
I/O Registers
Freescale Semiconductor, Inc...
BYTE 1
BYTE 2
BYTE 3
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
NORMAL FLAG CLEARING SEQUENCE
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
BYTE 3
SCRF = 0
OR = 0
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 1
SCRF = 1
OR = 1
DELAYED FLAG CLEARING SEQUENCE
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 1
READ SCDR
BYTE 3
Figure 13-13. Flag Clearing Sequence
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the SCI detects a parity error
in incoming data. PE generates an SCI error 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
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Serial Communications Interface
13.8.5 SCI Status Register 2
SCI status register 2 contains flags to signal the following conditions:
•
Break character detected
•
Incoming data
Address:
$0017
Freescale Semiconductor, Inc...
Bit 7
6
5
4
3
2
Read:
1
Bit 0
BKF
RPF
0
0
Write:
Reset:
0
0
0
0
0
0
= Unimplemented
Figure 13-14. 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 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 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
Data Sheet
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Serial Communications Interface Module (SCI)
I/O Registers
13.8.6 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.
Freescale Semiconductor, Inc...
Address:
$0018
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 13-15. SCI Data Register (SCDR)
R7/T7–R0/T0 — Receive/Transmit Data Bits
Reading the SCDR accesses the read-only received data bits,
R7–R0. Writing to the SCDR writes the data to be transmitted, T7–T0.
Reset has no effect on the SCDR.
NOTE:
Do not use read/modify/write instructions on the SCI data register.
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Serial Communications Interface
13.8.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver
and the transmitter.
Address:
Read:
$0019
Bit 7
6
0
0
5
4
3
2
1
Bit 0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
R
= Reserved
Freescale Semiconductor, Inc...
Write:
Reset:
0
0
= Unimplemented
Figure 13-16. SCI Baud Rate Register (SCBR)
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown
in Table 13-6. Reset clears SCP1 and SCP0.
Table 13-6. SCI Baud Rate Prescaling
SCP1 and 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 13-7. Reset clears SCR2–SCR0.
Data Sheet
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Serial Communications Interface Module (SCI)
I/O Registers
Freescale Semiconductor, Inc...
Table 13-7. SCI Baud Rate Selection
SCR2, SCR1, and 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:
SCI clock source
baud rate = --------------------------------------------64 × PD × BD
where:
SCI clock source = fBUS or CGMXCLK
(selected by SCIBDSRC bit in CONFIG2 register)
PD = prescaler divisor
BD = baud rate divisor
Table 13-8 shows the SCI baud rates that can be generated with a
4.9152-MHz bus clock when fBUS is selected as SCI clock source.
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Serial Communications Interface
Freescale Semiconductor, Inc...
Table 13-8. SCI Baud Rate Selection Examples
SCP1 and
SCP0
Prescaler
Divisor (PD)
SCR2, SCR1,
and SCR0
Baud Rate
Divisor (BD)
Baud Rate
(fBUS = 4.9152 MHz)
00
1
000
1
76,800
00
1
001
2
38,400
00
1
010
4
19,200
00
1
011
8
9600
00
1
100
16
4800
00
1
101
32
2400
00
1
110
64
1200
00
1
111
128
600
01
3
000
1
25,600
01
3
001
2
12,800
01
3
010
4
6400
01
3
011
8
3200
01
3
100
16
1600
01
3
101
32
800
01
3
110
64
400
01
3
111
128
200
10
4
000
1
19,200
10
4
001
2
9600
10
4
010
4
4800
10
4
011
8
2400
10
4
100
16
1200
10
4
101
32
600
10
4
110
64
300
10
4
111
128
150
11
13
000
1
5908
11
13
001
2
2954
11
13
010
4
1477
11
13
011
8
739
11
13
100
16
369
11
13
101
32
185
11
13
110
64
92
11
13
111
128
46
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 14. Infrared Serial Communications
Interface Module (IRSCI)
14.1 Introduction
Freescale Semiconductor, Inc...
The MC68HC908AP64 has two SCI modules:
•
SCI1 is a standard SCI module, and
•
SCI2 is an infrared SCI module.
This section describes SCI2, the infrared serial communications
interface (IRSCI) module which allows high-speed asynchronous
communications with peripheral devices and other MCUs. This IRSCI
consists of an SCI module for conventional SCI functions and a software
programmable infrared encoder/decoder sub-module for
encoding/decoding the serial data for connection to infrared LEDs in
remote control applications.
NOTE:
When the IRSCI is enabled, the SCTxD pin is an open-drain output and
requires a pullup resistor to be connected for proper SCI operation.
NOTE:
References to DMA (direct-memory access) and associated functions
are only valid if the MCU has a DMA module. This MCU does not have
the DMA function. Any DMA-related register bits should be left in their
reset state for normal MCU operation.
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Infrared Serial Communications
14.2 Features
Freescale Semiconductor, Inc...
Features of the SCI module include the following:
•
Full duplex operation
•
Standard mark/space non-return-to-zero (NRZ) format
•
Programmable 8-bit or 9-bit character length
•
Separately enabled transmitter and receiver
•
Separate receiver and transmitter CPU interrupt requests
•
Two receiver wakeup methods:
– Idle line wakeup
– Address mark wakeup
•
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
Features of the infrared (IR) sub-module include the following:
Data Sheet
•
IR sub-module enable/disable for infrared SCI or conventional SCI
on SCTxD and SCRxD pins
•
Software selectable infrared modulation/demodulation
(3/16, 1/16 or 1/32 width pulses)
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Infrared Serial Communications Interface Module (IRSCI)
Features
Addr.
Register Name
Bit 7
Freescale Semiconductor, Inc...
Read:
LOOPS
IRSCI Control Register 1
$0040
Write:
(IRSCC1)
Reset:
0
Read:
IRSCI Control Register 2
$0041
Write:
(IRSCC2)
Reset:
Read:
IRSCI Control Register 3
$0042
Write:
(IRSCC3)
Reset:
$0043
$0044
$0045
Read:
IRSCI Status Register 1
Write:
(IRSCS1)
Reset:
Read:
IRSCI Status Register 2
Write:
(IRSCS2)
Reset:
Read:
IRSCI Data Register
Write:
(IRSCDR)
Reset:
Read:
IRSCI Baud Rate Register
$0046
Write:
(IRSCBR)
Reset:
$0047
Read:
IRSCI Infrared Control
Register Write:
(IRSCIRCR)
Reset:
6
5
4
3
2
1
Bit 0
M
WAKE
ILTY
PEN
PTY
0
ENSCI
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
T8
DMARE
DMATE
ORIE
NEIE
FEIE
PEIE
U
U
0
0
0
0
0
0
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
BKF
RPF
R8
0
0
0
0
0
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
Unaffected by reset
0
CKS
0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
0
0
R
TNP1
TNP0
IREN
0
0
0
0
R
0
0
0
= Unimplemented
0
R = Reserved
U = Unaffected
Figure 14-1. IRSCI I/O Registers Summary
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Infrared Serial Communications
14.3 Pin Name Conventions
Freescale Semiconductor, Inc...
The generic names of the IRSCI I/O pins are:
•
RxD (receive data)
•
TxD (transmit data)
IRSCI I/O (input/output) lines are implemented by sharing parallel I/O
port pins. The full name of an IRSCI input or output reflects the name of
the shared port pin. Table 14-1 shows the full names and the generic
names of the IRSCI I/O pins. The generic pin names appear in the text
of this section.
Table 14-1. Pin Name Conventions
NOTE:
Generic Pin Names:
RxD
TxD
Full Pin Names:
PTC7/SCRxD
PTC6/SCTxD
When the IRSCI is enabled, the SCTxD pin is an open-drain output and
requires a pullup resistor to be connected for proper SCI operation.\
14.4 IRSCI Module Overview
The IRSCI consists of a serial communications interface (SCI) and a
infrared interface sub-module as shown in Figure 14-2.
INTERNAL BUS
SCI_TxD
CGMXCLK
BUS CLOCK
SERIAL
COMMUNICATIONS
INTERFACE MODULE
(SCI)
SCTxD
SCI_R32XCLK
SCI_R16XCLK
INFRARED
SUB-MODULE
SCI_RxD
SCRxD
Figure 14-2. IRSCI Block Diagram
The SCI module provides serial data transmission and reception, with a
programmable baud rate clock based on the bus clock or the CGMXCLK.
Data Sheet
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Infrared Serial Communications Interface Module (IRSCI)
Infrared Functional Description
The infrared sub-module receives two clock sources from the SCI
module: SCI_R16XCLK and SCI_R32XCLK. Both reference clocks are
used to generate the narrow pulses during data transmission.
The SCI_R16XCLK and SCI_R32XCLK are internal clocks with
frequencies that are 16 and 32 times the baud rate respectively. Both
SCI_R16XCLK and SCI_R32XCLK clocks are used for transmitting
data. The SCI_R16XCLK clock is used only for receiving data.
Freescale Semiconductor, Inc...
NOTE:
For proper SCI function (transmit or receive), the bus clock MUST be
programmed to at least 32 times that of the selected baud rate.
When the infrared sub-module is disabled, signals on the TxD and RxD
pins pass through unchanged to the SCI module.
14.5 Infrared Functional Description
Figure 14-3 shows the structure of the infrared sub-module.
TNP[1:0]
TRANSMIT
ENCODER
SCI_TxD
IREN
IR_TxD
MUX
SCTxD
SCI_R32XCLK
SCI_R16XCLK
IR_RxD
SCI_RxD
RECEIVE
DECODER
SCRxD
MUX
Figure 14-3. Infrared Sub-Module Diagram
The infrared sub-module provides the capability of transmitting narrow
pulses to an infrared LED and receiving narrow pulses and transforming
them to serial bits, which are sent to the SCI module. The infrared submodule receives two clocks from the SCI. One of these two clocks is
selected as the base clock to generate the 3/16, 1/16, or 1/32 bit width
narrow pulses during transmission.
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Infrared Serial Communications
Freescale Semiconductor, Inc...
The sub-module consists of two main blocks: the transmit encoder and
the receive decoder. When transmitting data, the SCI data stream is
encoded by the infrared sub-module. For every "0" bit, a narrow "low"
pulse is transmitted; no pulse is transmitted for "1" bits. When receiving
data, the infrared pulses should be detected using an infrared photo
diode for conversion to CMOS voltage levels before connecting to the
RxD pin for the infrared decoder. The SCI data stream is reconstructed
by stretching the "0" pulses.
14.5.1 Infrared Transmit Encoder
The infrared transmit encoder converts the "0" bits in the serial data
stream from the SCI module to narrow "low" pulses, to the TxD pin. The
narrow pulse is sent with a duration of 1/32, 1/16, or 3/16 of a data bit
width. When two consecutive zeros are sent, the two consecutive narrow
pulses will be separated by a time equal to a data bit width.
DATA BIT WIDTH DETERMINED BY BAUD RATE
SCI DATA
INFRARED
SCI DATA
PULSE WIDTH = 1/32, 1/16, OR 3/16 DATA BIT WIDTH
Figure 14-4. Infrared SCI Data Example
14.5.2 Infrared Receive Decoder
The infrared receive decoder converts low narrow pulses from the RxD
pin to standard SCI data bits. The reference clock, SCI_R16XCLK,
clocks a four bit internal counter which counts from 0 to 15. An incoming
pulse starts the internal counter and a "0" is sent out to the IR_RxD
output. Subsequent incoming pulses are ignored when the counter count
is between 0 and 7; IR_RxD remains "0". Once the counter passes 7, an
incoming pulse will reset the counter; IR_RxD remains "0". When the
counter reaches 15, the IR_RxD output returns to "1", the counter stops
and waits for further pulses. A pulse is interpreted as jitter if it arrives
shortly after the counter reaches 15; IR_RxD remains "1".
Data Sheet
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Infrared Serial Communications Interface Module (IRSCI)
SCI Functional Description
14.6 SCI Functional Description
Figure 14-5 shows the structure of the SCI.
INTERNAL BUS
SCI DATA
REGISTER
ERROR
INTERRUPT
CONTROL
RECEIVER
INTERRUPT
CONTROL
Freescale Semiconductor, Inc...
DMA
INTERRUPT
CONTROL
RECEIVE
SHIFT REGISTER
SCI_RxD
TRANSMITTER
INTERRUPT
CONTROL
SCI DATA
REGISTER
SCTIE
TRANSMIT
SHIFT REGISTER
SCI_TxD
R8
TCIE
T8
SCRIE
ILIE
DMARE
TE
SCTE
RE
DMATE
TC
RWU
SBK
SCRF
OR
ORIE
IDLE
NF
NEIE
FE
FEIE
PE
PEIE
LOOPS
LOOPS
FLAG
CONTROL
RECEIVE
CONTROL
WAKEUP
CONTROL
CKS
ENSCI
ENSCI
TRANSMIT
CONTROL
BKF
M
RPF
WAKE
ILTY
A SL
X
B
CGMXCLK
BUS CLOCK
BAUD RATE
GENERATOR
PEN
PTY
SL = 0 => X = A
SL = 1 => X = B
÷16
SCI_R32XCLK
DATA SELECTION
CONTROL
SCI_R16XCLK
Figure 14-5. SCI Module Block Diagram
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications
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The SCI allows full-duplex, asynchronous, NRZ serial communication
between 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.
NOTE:
For SCI operations, the IR sub-module is transparent to the SCI module.
Data at going out of the SCI transmitter and data going into the SCI
receiver is always in SCI format. It makes no difference to the SCI
module whether the IR sub-module is enabled or disabled.
NOTE:
This SCI module is a standard HC08 SCI module with the following
modifications:
•
A control bit, CKS, is added to the SCI baud rate control register
to select between two input clocks for baud rate clock generation
•
The TXINV bit is removed from the SCI control register 1
14.6.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format
illustrated in Figure 14-6.
8-BIT DATA FORMAT
BIT M IN IRSCC1 CLEAR
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
PARITY
BIT
BIT 6
BIT 7
9-BIT DATA FORMAT
BIT M IN IRSCC1 SET
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
STOP
BIT
NEXT
START
BIT
PARITY
BIT
BIT 6
BIT 7
BIT 8
STOP
BIT
NEXT
START
BIT
Figure 14-6. SCI Data Formats
Data Sheet
MC68HC908AP Family — Rev. 2.5
256
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Infrared Serial Communications Interface Module (IRSCI)
SCI Functional Description
14.6.2 Transmitter
Figure 14-7 shows the structure of the SCI transmitter.
The baud rate clock source for the SCI can be selected by the CKS bit,
in the SCI baud rate register (see 14.10.7 IRSCI Baud Rate Register).
SL = 0 => X = A
SL = 1 => X = B
PRESCALER
BAUD
DIVIDER
÷ 16
SCI DATA REGISTER
SCP1
SCP0
11-BIT
TRANSMIT
SHIFT REGISTER
SCR1
H
SCR2
8
7
6
5
4
3
2
START
A SL
X
B
STOP
CGMXCLK
BUS CLOCK
INTERNAL BUS
1
0
L
SCI_TxD
PARITY
GENERATION
T8
DMATE
DMATE
SCTIE
SCTE
DMATE
SCTE
SCTIE
TC
TCIE
BREAK
ALL 0s
PTY
PREAMBLE
ALL 1s
PEN
LOAD FROM IRSCDR
M
SHIFT ENABLE
MSB
TRANSMITTER DMA SERVICE REQUEST
SCR0
TRANSMITTER CPU INTERRUPT REQUEST
Freescale Semiconductor, Inc...
CKS
TRANSMITTER
CONTROL LOGIC
SCTE
SBK
LOOPS
SCTIE
ENSCI
TC
TE
TCIE
Figure 14-7. SCI Transmitter
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications
14.6.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of
the M bit in IRSCI control register 1 (IRSCC1) determines character
length. When transmitting 9-bit data, bit T8 in IRSCI control register 3
(IRSCC3) is the ninth bit (bit 8).
14.6.2.2 Character Transmission
Freescale Semiconductor, Inc...
During an SCI transmission, the transmit shift register shifts a character
out to the TxD pin. The IRSCI data register (IRSCDR) 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 IRSCI control register 1 (IRSCC1).
2. Enable the transmitter by writing a logic 1 to the transmitter enable
bit (TE) in IRSCI control register 2 (IRSCC2).
3. Clear the SCI transmitter empty bit by first reading IRSCI status
register 1 (IRSCS1) and then writing to the IRSCDR.
4. Repeat step 3 for each subsequent transmission.
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 IRSCDR data into the
transmit shift register. A logic 0 start bit automatically goes into the least
significant bit position of the transmit shift register. A logic 1 stop bit goes
into the most significant bit position.
The SCI transmitter empty bit, SCTE, in IRSCS1 becomes set when the
IRSCDR transfers a byte to the transmit shift register. The SCTE bit
indicates that the IRSCDR can accept new data from the internal data
bus. If the SCI transmit interrupt enable bit, SCTIE, in IRSCC2 is also
set, the SCTE bit generates a transmitter interrupt request.
When the transmit shift register is not transmitting a character, the TxD
pin goes to the idle condition, logic 1. If at any time software clears the
ENSCI bit in IRSCI control register 1 (IRSCC1), the transmitter and
receiver relinquish control of the port pins.
Data Sheet
MC68HC908AP Family — Rev. 2.5
258
MOTOROLA
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Infrared Serial Communications Interface Module (IRSCI)
SCI Functional Description
Freescale Semiconductor, Inc...
14.6.2.3 Break Characters
Writing a logic 1 to the send break bit, SBK, in IRSCC2 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 IRSCC1. 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.
Receiving a break character has the following effects on SCI registers:
•
Sets the framing error bit (FE) in IRSCS1
•
Sets the SCI receiver full bit (SCRF) in IRSCS1
•
Clears the SCI data register (IRSCDR)
•
Clears the R8 bit in IRSCC3
•
Sets the break flag bit (BKF) in IRSCS2
•
May set the overrun (OR), noise flag (NF), parity error (PE), or
reception in progress flag (RPF) bits
14.6.2.4 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 IRSCC1. The preamble is
a synchronizing idle character that begins every transmission.
If the TE bit is cleared during a transmission, the 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.
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications
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 TxD pin. Setting TE after
the stop bit appears on TxD causes data previously written to the
IRSCDR to be lost.
Toggle the TE bit for a queued idle character when the SCTE bit
becomes set and just before writing the next byte to the IRSCDR.
Freescale Semiconductor, Inc...
14.6.2.5 Transmitter Interrupts
The following conditions can generate CPU interrupt requests from the
SCI transmitter:
•
SCI transmitter empty (SCTE) — The SCTE bit in IRSCS1
indicates that the IRSCDR 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 IRSCC2 enables the SCTE bit to generate transmitter
CPU interrupt requests.
•
Transmission complete (TC) — The TC bit in IRSCS1 indicates
that the transmit shift register and the IRSCDR are empty and that
no break or idle character has been generated. The transmission
complete interrupt enable bit, TCIE, in IRSCC2 enables the TC bit
to generate transmitter CPU interrupt requests.
14.6.3 Receiver
Figure 14-8 shows the structure of the SCI receiver.
14.6.3.1 Character Length
The receiver can accommodate either 8-bit or 9-bit data. The state of the
M bit in IRSCI control register 1 (IRSCC1) determines character length.
When receiving 9-bit data, bit R8 in IRSCI control register 2 (IRSCC2) is
the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the
eighth bit (bit 7).
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications Interface Module (IRSCI)
SCI Functional Description
INTERNAL BUS
SCR1
SCR0
PRESCALER
SL = 0 => X = A
SL = 1 => X = B
÷ 16
DATA
RECOVERY
SCI_RxD
BKF
Freescale Semiconductor, Inc...
BAUD
DIVIDER
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
RPF
ERROR CPU INTERRUPT REQUEST
DMA SERVICE REQUEST
SCI DATA REGISTER
START
SCP0
STOP
A SL
X
B
SCR2
ALL 1s
CGMXCLK
BUS CLOCK
SCP1
MSB
CKS
SCRF
WAKEUP
LOGIC
PARITY
CHECKING
IDLE
ILIE
DMARE
SCRF
SCRIE
DMARE
SCRF
SCRIE
DMARE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
RWU
IDLE
R8
ILIE
SCRIE
DMARE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
Figure 14-8. SCI Receiver Block Diagram
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications
14.6.3.2 Character Reception
After a complete character shifts into the receive shift register, the data
portion of the character transfers to the IRSCDR. The SCI receiver full
bit, SCRF, in IRSCI status register 1 (IRSCS1) becomes set, indicating
that the received byte can be read. If the SCI receive interrupt enable bit,
SCRIE, in IRSCC2 is also set, the SCRF bit generates a receiver CPU
interrupt request.
14.6.3.3 Data Sampling
The receiver samples the 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 the following
times (see Figure 14-9):
•
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
returns a valid logic 1 and the majority of the next RT8, RT9, and
RT10 samples returns a valid logic 0)
START BIT
LSB
SCI_RxD
START BIT
QUALIFICATION
SAMPLES
START BIT
VERIFICATION
DATA
SAMPLING
RT4
RT3
RT2
RT1
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT CLOCK
STATE
RT1
RT
CLOCK
RT1
Freescale Semiconductor, Inc...
During an SCI reception, the receive shift register shifts characters in
from the RxD pin. The SCI data register (IRSCDR) is the read-only buffer
between the internal data bus and the receive shift register.
RT CLOCK
RESET
Figure 14-9. Receiver Data Sampling
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications Interface Module (IRSCI)
SCI Functional Description
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.
To verify the start bit and to detect noise, data recovery logic takes
samples at RT3, RT5, and RT7. Table 14-2 summarizes the results of
the start bit verification samples.
Freescale Semiconductor, Inc...
Table 14-2. 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.
To determine the value of a data bit and to detect noise, recovery logic
takes samples at RT8, RT9, and RT10. Table 14-3 summarizes the
results of the data bit samples.
Table 14-3. Data Bit Recovery
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
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications
NOTE:
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 14-4 summarizes the results of the stop bit
samples.
Freescale Semiconductor, Inc...
Table 14-4. 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
14.6.3.4 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
IRSCS1. 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.
14.6.3.5 Baud Rate Tolerance
A transmitting device may be operating at a baud rate below or above
the receiver baud rate. Accumulated bit time misalignment can cause
one of the three stop bit data samples to fall outside the actual stop bit.
Then a noise error occurs. If more than one of the samples is outside the
stop bit, a framing error occurs. In most applications, the baud rate
tolerance is much more than the degree of misalignment that is likely to
occur.
Data Sheet
MC68HC908AP Family — Rev. 2.5
264
MOTOROLA
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Infrared Serial Communications Interface Module (IRSCI)
SCI Functional Description
As the receiver samples an incoming character, it resynchronizes the RT
clock on any valid falling edge within the character. Resynchronization
within characters corrects misalignments between transmitter bit times
and receiver bit times.
Slow Data Tolerance
RT16
RT15
RT14
RT13
RT11
RT10
RT9
RT8
RT7
RT6
STOP
RT5
RT4
RT3
RT2
RECEIVER
RT CLOCK
RT1
MSB
RT12
Freescale Semiconductor, Inc...
Figure 14-10 shows how much a slow received character can be
misaligned without causing a noise error or a framing error. The slow
stop bit begins at RT8 instead of RT1 but arrives in time for the stop bit
data samples at RT8, RT9, and RT10.
DATA
SAMPLES
Figure 14-10. Slow Data
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 14-10, the receiver
counts 154 RT cycles at the point when the count of the transmitting
device is 9 bit times × 16 RT cycles + 3 RT cycles = 147 RT cycles.
The maximum percent difference between the receiver count and the
transmitter count of a slow 8-bit character with no errors is
154 – 147
-------------------------- × 100 = 4.54%
154
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 14-10, the receiver
counts 170 RT cycles at the point when the count of the transmitting
device is 10 bit times × 16 RT cycles + 3 RT cycles = 163 RT cycles.
MC68HC908AP Family — Rev. 2.5
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Infrared Serial Communications
The maximum percent difference between the receiver count and the
transmitter count of a slow 9-bit character with no errors is
170 – 163
-------------------------- × 100 = 4.12%
170
Fast Data Tolerance
RT16
RT15
RT14
RT13
RT12
RT10
RT9
RT8
RT7
IDLE OR NEXT CHARACTER
RT6
RT5
RT4
RT3
RT2
RECEIVER
RT CLOCK
RT1
STOP
RT11
Freescale Semiconductor, Inc...
Figure 14-11 shows how much a fast received character can be
misaligned without causing a noise error or a framing error. The fast stop
bit ends at RT10 instead of RT16 but is still there for the stop bit data
samples at RT8, RT9, and RT10.
DATA
SAMPLES
Figure 14-11. Fast Data
For an 8-bit character, data sampling of the stop bit takes the receiver
9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 14-11, the receiver
counts 154 RT cycles at the point when the count of the transmitting
device is 10 bit times × 16 RT cycles = 160 RT cycles.
The maximum percent difference between the receiver count and the
transmitter count of a fast 8-bit character with no errors is
·
154 – 160
-------------------------- × 100 = 3.90%
154
For a 9-bit character, data sampling of the stop bit takes the receiver
10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 14-11, the receiver
counts 170 RT cycles at the point when the count of the transmitting
device is 11 bit times × 16 RT cycles = 176 RT cycles.
Data Sheet
MC68HC908AP Family — Rev. 2.5
266
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Infrared Serial Communications Interface Module (IRSCI)
SCI Functional Description
The maximum percent difference between the receiver count and the
transmitter count of a fast 9-bit character with no errors is
170 – 176
-------------------------- × 100 = 3.53%
170
14.6.3.6 Receiver Wakeup
Freescale Semiconductor, Inc...
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 IRSCC2 puts the
receiver into a standby state during which receiver interrupts are
disabled.
Depending on the state of the WAKE bit in IRSCC1, either of two
conditions on the 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 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 RxD pin has been idle may cause the
receiver to wake up immediately.
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Infrared Serial Communications
14.6.3.7 Receiver Interrupts
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The following sources can generate CPU interrupt requests from the SCI
receiver:
•
SCI receiver full (SCRF) — The SCRF bit in IRSCS1 indicates that
the receive shift register has transferred a character to the
IRSCDR. SCRF can generate a receiver interrupt request. Setting
the SCI receive interrupt enable bit, SCRIE, in IRSCC2 enables
the SCRF bit to generate receiver CPU interrupts.
•
Idle input (IDLE) — The IDLE bit in IRSCS1 indicates that 10 or 11
consecutive logic 1s shifted in from the RxD pin. The idle line
interrupt enable bit, ILIE, in IRSCC2 enables the IDLE bit to
generate CPU interrupt requests.
14.6.3.8 Error Interrupts
The following receiver error flags in IRSCS1 can generate CPU interrupt
requests:
Data Sheet
•
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 IRSCDR. The previous character
remains in the IRSCDR, and the new character is lost. The
overrun interrupt enable bit, ORIE, in IRSCC3 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 IRSCC3 enables
NF to generate SCI error CPU interrupt requests.
•
Framing error (FE) — The FE bit in IRSCS1 is set when a logic 0
occurs where the receiver expects a stop bit. The framing error
interrupt enable bit, FEIE, in IRSCC3 enables FE to generate SCI
error CPU interrupt requests.
•
Parity error (PE) — The PE bit in IRSCS1 is set when the SCI
detects a parity error in incoming data. The parity error interrupt
enable bit, PEIE, in IRSCC3 enables PE to generate SCI error
CPU interrupt requests.
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Infrared Serial Communications Interface Module (IRSCI)
Low-Power Modes
14.7 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
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14.7.1 Wait Mode
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.
Refer to 9.6 Low-Power Modes for information on exiting wait mode.
14.7.2 Stop Mode
The SCI module is inactive after the execution of a STOP instruction.
The STOP instruction does not affect SCI register states. SCI module
operation resumes after an external interrupt.
Because the internal clock is inactive during stop mode, entering stop
mode during an SCI transmission or reception results in invalid data.
Refer to 9.6 Low-Power Modes for information on exiting stop mode.
14.8 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.
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Infrared Serial Communications
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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 two-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.
14.9 I/O Signals
The two IRSCI I/O pins are:
•
PTC6/SCTxD — Transmit data
•
PTC7/SCRxD — Receive data
14.9.1 PTC6/SCTxD (Transmit Data)
The PTC6/SCTxD pin is the serial data (standard or infrared) output from
the SCI transmitter. The IRSCI shares the PTC6/SCTxD pin with port C.
When the IRSCI is enabled, the PTC6/SCTxD pin is an output
regardless of the state of the DDRC6 bit in data direction register C
(DDRC).
NOTE:
The PTC6/SCTxD pin is an open-drain pin when configured as an
output. Therefore, when configured as SCTxD or a general purpose
output pin (PTC6), a pullup resistor must be connected to this pin.
14.9.2 PTC7/SCRxD (Receive Data)
The PTC7/SCRxD pin is the serial data input to the IRSCI receiver. The
IRSCI shares the PTC7/SCRxD pin with port C. When the IRSCI is
enabled, the PTC7/SCRxD pin is an input regardless of the state of the
DDRC7 bit in data direction register C (DDRC).
NOTE:
Data Sheet
The PTC7/SCRxD pin is an open-drain pin when configured as an
output. Therefore, when configured as a general purpose output pin
(PTC7), a pullup resistor must be connected to this pin.
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
Table 14-5 shows a summary of I/O pin functions when the SCI is
enabled.
Freescale Semiconductor, Inc...
Table 14-5. SCI Pin Functions (Standard and Infrared)
IRSCC1
[ENSCI]
IRSCIRCR
[IREN]
IRSCC2
[TE]
IRSCC2
[RE]
1
0
0
0
Hi-Z(1)
Input ignored (terminate externally)
1
0
0
1
Hi-Z(1)
Input sampled, pin should idle high
1
0
1
0
Output SCI (idle high)
Input ignored (terminate externally)
1
0
1
1
Output SCI (idle high)
Input sampled, pin should idle high
1
1
0
0
Hi-Z(1)
Input ignored (terminate externally)
1
1
0
1
Hi-Z(1)
Input sampled, pin should idle high
1
1
1
0
Output IR SCI (idle high)
Input ignored (terminate externally)
1
1
1
1
Output IR SCI (idle high)
Input sampled, pin should idle high
0
X
X
X
Pins under port control (standard I/O port)
TxD Pin
RxD Pin
Notes:
1. After completion of transmission in progress.
14.10 I/O Registers
The following I/O registers control and monitor SCI operation:
•
IRSCI control register 1 (IRSCC1)
•
IRSCI control register 2 (IRSCC2)
•
IRSCI control register 3 (IRSCC3)
•
IRSCI status register 1 (IRSCS1)
•
IRSCI status register 2 (IRSCS2)
•
IRSCI data register (IRSCDR)
•
IRSCI baud rate register (IRSCBR)
•
IRSCI infrared control register (IRSCIRCR)
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Infrared Serial Communications
14.10.1 IRSCI Control Register 1
Freescale Semiconductor, Inc...
SCI control register 1:
•
Enables loop mode operation
•
Enables the SCI
•
Controls output polarity
•
Controls character length
•
Controls SCI wakeup method
•
Controls idle character detection
•
Enables parity function
•
Controls parity type
Address:
$0040
Bit 7
6
LOOPS
ENSCI
0
0
Read:
5
4
3
2
1
Bit 0
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
Write:
Reset:
0
Figure 14-12. IRSCI Control Register 1 (IRSCC1)
LOOPS — Loop Mode Select Bit
This read/write bit enables loop mode operation for the SCI only. In
loop mode the 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. The infrared
encoder/decoder is not in the loop. 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
Data Sheet
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
M — Mode (Character Length) Bit
This read/write bit determines whether SCI characters are eight or
nine bits long. (See Table 14-6.) 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
Freescale Semiconductor, Inc...
This read/write bit determines which condition wakes up the SCI: a
logic 1 (address mark) in the most significant bit position of a received
character or an idle condition on the 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
PEN — Parity Enable Bit
This read/write bit enables the SCI parity function. (See Table 14-6.)
When enabled, the parity function inserts a parity bit in the most
significant bit position. (See Figure 14-6.) Reset clears the PEN bit.
1 = Parity function enabled
0 = Parity function disabled
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Infrared Serial Communications
PTY — Parity Bit
This read/write bit determines whether the SCI generates and checks
for odd parity or even parity. (See Table 14-6.) Reset clears the PTY
bit.
1 = Odd parity
0 = Even parity
Freescale Semiconductor, Inc...
NOTE:
Changing the PTY bit in the middle of a transmission or reception can
generate a parity error.
Table 14-6. Character Format Selection
Control Bits
Character Format
M
PEN:PTY
Start
Bits
Data
Bits
Parity
Stop
Bits
Character
Length
0
0X
1
8
None
1
10 bits
1
0X
1
9
None
1
11 bits
0
10
1
7
Even
1
10 bits
0
11
1
7
Odd
1
10 bits
1
10
1
8
Even
1
11 bits
1
11
1
8
Odd
1
11 bits
14.10.2 IRSCI Control Register 2
IRSCI control register 2:
•
Enables the following 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
Data Sheet
•
Enables the transmitter
•
Enables the receiver
•
Enables SCI wakeup
•
Transmits SCI break characters
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
Address:
$0041
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
Read:
Write:
Reset:
Figure 14-13. IRSCI Control Register 2 (IRSCC2)
Freescale Semiconductor, Inc...
SCTIE — SCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate SCI transmitter
CPU interrupt requests. Reset clears the SCTIE bit.
1 = SCTE enabled to generate CPU interrupt
0 = SCTE not enabled to generate CPU interrupt
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. 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
TxD pin. If software clears the TE bit, the transmitter completes any
transmission in progress before the TxD returns to the idle condition
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Infrared Serial Communications
(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.
Freescale Semiconductor, Inc...
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
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 IRSCC1 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:
Data Sheet
Do not toggle the SBK bit immediately after setting the SCTE bit.
Toggling SBK before the preamble begins causes the SCI to send a
break character instead of a preamble.
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
14.10.3 IRSCI Control Register 3
IRSCI control register 3:
•
Stores the ninth SCI data bit received and the ninth SCI data bit to
be transmitted
•
Enables the following interrupts:
– Receiver overrun interrupts
Freescale Semiconductor, Inc...
– Noise error interrupts
– Framing error interrupts
– Parity error interrupts
Address:
$0042
Bit 7
Read:
6
5
4
3
2
1
Bit 0
T8
DMARE
DMATE
ORIE
NEIE
FEIE
PEIE
U
0
0
0
0
0
0
R8
Write:
Reset:
U
= Unimplemented
U = Unaffected
Figure 14-14. IRSCI Control Register 3 (IRSCC3)
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 IRSCDR 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 IRSCDR is loaded into
the transmit shift register. Reset has no effect on the T8 bit.
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DMARE — DMA Receive Enable Bit
CAUTION:
The DMA module is not included on this MCU. Writing a logic 1 to
DMARE or DMATE may adversely affect MCU performance.
Freescale Semiconductor, Inc...
1 = DMA not enabled to service SCI receiver DMA service requests
generated by the SCRF bit (SCI receiver CPU interrupt
requests enabled)
0 = DMA not enabled to service SCI receiver DMA service requests
generated by the SCRF bit (SCI receiver CPU interrupt
requests enabled)
DMATE — DMA Transfer Enable Bit
CAUTION:
The DMA module is not included on this MCU. Writing a logic 1 to
DMARE or DMATE may adversely affect MCU performance.
1 = SCTE DMA service requests enabled; SCTE CPU interrupt
requests disabled
0 = SCTE DMA service requests disabled; SCTE CPU interrupt
requests enabled
ORIE — Receiver Overrun Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests
generated by the receiver overrun bit, OR. Reset clears ORIE.
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
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
Data Sheet
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt
requests generated by the parity error bit, PE. (See 14.10.4 IRSCI
Status Register 1.) Reset clears PEIE.
1 = SCI error CPU interrupt requests from PE bit enabled
0 = SCI error CPU interrupt requests from PE bit disabled
Freescale Semiconductor, Inc...
14.10.4 IRSCI Status Register 1
SCI status register 1 contains flags to signal these conditions:
•
Transfer of IRSCDR data to transmit shift register complete
•
Transmission complete
•
Transfer of receive shift register data to IRSCDR complete
•
Receiver input idle
•
Receiver overrun
•
Noisy data
•
Framing error
•
Parity error
Address:
Read:
$0043
Bit 7
6
5
4
3
2
1
Bit 0
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 14-15. IRSCI Status Register 1 (IRSCS1)
SCTE — SCI Transmitter Empty Bit
This clearable, read-only bit is set when the IRSCDR transfers a
character to the transmit shift register. SCTE can generate an SCI
transmitter CPU interrupt request. When the SCTIE bit in IRSCC2 is
set, SCTE generates an SCI transmitter CPU interrupt request. In
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normal operation, clear the SCTE bit by reading IRSCS1 with SCTE
set and then writing to IRSCDR. Reset sets the SCTE bit.
1 = IRSCDR data transferred to transmit shift register
0 = IRSCDR data not transferred to transmit shift register
TC — Transmission Complete Bit
Freescale Semiconductor, Inc...
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 IRSCC2 is also
set. TC is automatically cleared 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 IRSCC2 is set,
SCRF generates a CPU interrupt request. In normal operation, clear
the SCRF bit by reading IRSCS1 with SCRF set and then reading the
IRSCDR. Reset clears SCRF.
1 = Received data available in IRSCDR
0 = Data not available in IRSCDR
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 receiver CPU
interrupt request if the ILIE bit in IRSCC2 is also set. Clear the IDLE
bit by reading IRSCS1 with IDLE set and then reading the IRSCDR.
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 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)
Data Sheet
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
OR — Receiver Overrun Bit
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This clearable, read-only bit is set when software fails to read the
IRSCDR before the receive shift register receives the next character.
The OR bit generates an SCI error CPU interrupt request if the ORIE
bit in IRSCC3 is also set. The data in the shift register is lost, but the
data already in the IRSCDR is not affected. Clear the OR bit by
reading IRSCS1 with OR set and then reading the IRSCDR. 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
IRSCS1 and IRSCDR in the flag-clearing sequence. Figure 14-16
shows the normal flag-clearing sequence and an example of an
overrun caused by a delayed flag-clearing sequence. The delayed
read of IRSCDR does not clear the OR bit because OR was not set
when IRSCS1 was read. Byte 2 caused the overrun and is lost. The
next flag-clearing sequence reads byte 3 in the IRSCDR 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 flagclearing routine can check the OR bit in a second read of IRSCS1
after reading the data register.
NF — Receiver Noise Flag Bit
This clearable, read-only bit is set when the SCI detects noise on the
RxD pin. NF generates an SCI error CPU interrupt request if the NEIE
bit in IRSCC3 is also set. Clear the NF bit by reading IRSCS1 and
then reading the IRSCDR. Reset clears the NF bit.
1 = Noise detected
0 = No noise detected
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 IRSCC3 also is set. Clear the FE bit by reading IRSCS1 with FE
set and then reading the IRSCDR. Reset clears the FE bit.
1 = Framing error detected
0 = No framing error detected
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Infrared Serial Communications
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BYTE 1
BYTE 2
BYTE 3
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
NORMAL FLAG CLEARING SEQUENCE
BYTE 4
READ IRSCS1
SCRF = 1
OR = 0
READ IRSCS1
SCRF = 1
OR = 0
READ IRSCS1
SCRF = 1
OR = 0
READ IRSCDR
BYTE 1
READ IRSCDR
BYTE 2
READ IRSCDR
BYTE 3
BYTE 1
BYTE 2
BYTE 3
SCRF = 0
OR = 0
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 1
SCRF = 1
OR = 1
DELAYED FLAG CLEARING SEQUENCE
BYTE 4
READ IRSCS1
SCRF = 1
OR = 0
READ IRSCS1
SCRF = 1
OR = 1
READ IRSCDR
BYTE 1
READ IRSCDR
BYTE 3
Figure 14-16. Flag Clearing Sequence
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the SCI detects a parity error
in incoming data. PE generates an SCI error CPU interrupt request if
the PEIE bit in IRSCC3 is also set. Clear the PE bit by reading
IRSCS1 with PE set and then reading the IRSCDR. Reset clears the
PE bit.
1 = Parity error detected
0 = No parity error detected
Data Sheet
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
14.10.5 IRSCI Status Register 2
IRSCI status register 2 contains flags to signal the following conditions:
•
Break character detected
•
Incoming data
Address:
$0044
Bit 7
6
5
4
3
2
Freescale Semiconductor, Inc...
Read:
1
Bit 0
BKF
RPF
0
0
Write:
Reset:
0
0
0
0
0
0
= Unimplemented
Figure 14-17. IRSCI Status Register 2 (IRSCS2)
BKF — Break Flag Bit
This clearable, read-only bit is set when the SCI detects a break
character on the RxD pin. In IRSCS1, the FE and SCRF bits are also
set. In 9-bit character transmissions, the R8 bit in IRSCC3 is cleared.
BKF does not generate a CPU interrupt request. Clear BKF by
reading IRSCS2 with BKF set and then reading the IRSCDR. Once
cleared, BKF can become set again only after logic 1s again appear
on the 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
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Infrared Serial Communications
14.10.6 IRSCI Data Register
The IRSCI data register is the buffer between the internal data bus and
the receive and transmit shift registers. Reset has no effect on data in
the IRSCI data register.
Freescale Semiconductor, Inc...
Address:
$0045
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 14-18. IRSCI Data Register (IRSCDR)
R7/T7–R0/T0 — Receive/Transmit Data Bits
Reading the IRSCDR accesses the read-only received data bits,
R7–R0. Writing to the IRSCDR writes the data to be transmitted,
T7–T0. Reset has no effect on the IRSCDR.
NOTE:
Data Sheet
Do not use read/modify/write instructions on the IRSCI data register.
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Infrared Serial Communications Interface Module (IRSCI)
I/O Registers
14.10.7 IRSCI Baud Rate Register
The baud rate register selects the baud rate for both the receiver and the
transmitter.
Address:
$0046
Bit 7
Read:
6
5
4
3
2
1
Bit 0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
R
= Reserved
0
CKS
Write:
Freescale Semiconductor, Inc...
Reset:
0
0
= Unimplemented
Figure 14-19. IRSCI Baud Rate Register (IRSCBR)
CKS — Baud Clock Input Select
This read/write bit selects the source clock for the baud rate
generator. Reset clears the CKS bit, selecting CGMXCLK.
1 = Bus clock drives the baud rate generator
0 = CGMXCLK drives the baud rate generator
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown
in Table 14-7. Reset clears SCP1 and SCP0.
Table 14-7. SCI Baud Rate Prescaling
SCP1 and 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 14-8. Reset clears SCR2–SCR0.
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Infrared Serial Communications
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Table 14-8. IRSCI Baud Rate Selection
SCR2, SCR1, and 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:
SCI clock source
baud rate = --------------------------------------------16 × PD × BD
where:
SCI clock source = fBUS or CGMXCLK
(selected by CKS bit)
PD = prescaler divisor
BD = baud rate divisor
Table 14-9 shows the SCI baud rates that can be generated with a
4.9152-MHz bus clock when fBUS is selected as SCI clock source.
Data Sheet
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I/O Registers
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Table 14-9. IRSCI Baud Rate Selection Examples
SCP1 and
SCP0
Prescaler
Divisor (PD)
SCR2, SCR1,
and SCR0
Baud Rate
Divisor (BD)
Baud Rate
(fBUS = 4.9152 MHz)
00
1
000
1
—
00
1
001
2
—
00
1
010
4
76800
00
1
011
8
38400
00
1
100
16
19200
00
1
101
32
9600
00
1
110
64
4800
00
1
111
128
2400
01
3
000
1
—
01
3
001
2
51200
01
3
010
4
25600
01
3
011
8
12800
01
3
100
16
6400
01
3
101
32
3200
01
3
110
64
1600
01
3
111
128
800
10
4
000
1
76800
10
4
001
2
38400
10
4
010
4
19200
10
4
011
8
9600
10
4
100
16
4800
10
4
101
32
2400
10
4
110
64
1200
10
4
111
128
600
11
13
000
1
23632
11
13
001
2
11816
11
13
010
4
5908
11
13
011
8
2954
11
13
100
16
1477
11
13
101
32
739
11
13
110
64
369
11
13
111
128
185
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Infrared Serial Communications
14.10.8 IRSCI Infrared Control Register
The infrared control register contains the control bits for the infrared submodule.
•
Enables the infrared sub-module
•
Selects the infrared transmitter narrow pulse width
Address:
$0047
Freescale Semiconductor, Inc...
Bit 7
Read:
6
5
4
0
0
0
R
3
2
1
Bit 0
R
TNP1
TNP0
IREN
0
0
0
0
R
= Reserved
Write:
Reset:
0
0
0
= Unimplemented
0
Figure 14-20. IRSCI Infrared Control Register (IRSCIRCR)
TNP1 and TNP0 — Transmitter Narrow Pulse Bits
These read/write bits select the infrared transmitter narrow pulse
width as shown in Table 14-10. Reset clears TNP1 and TNP0.
Table 14-10. Infrared Narrow Pulse Selection
TNP1 and TNP0
Prescaler Divisor (PD)
00
SCI transmits a 3/16 narrow pulse
01
SCI transmits a 1/16 narrow pulse
10
SCI transmits a 1/32 narrow pulse
11
IREN — Infrared Enable Bit
This read/write bit enables the infrared sub-module for encoding and
decoding the SCI data stream. When this bit is clear, the infrared submodule is disabled. Reset clears the IREN bit.
1 = infrared sub-module enabled
0 = infrared sub-module disabled
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 15. Serial Peripheral Interface Module (SPI)
Freescale Semiconductor, Inc...
15.1 Introduction
This section describes the serial peripheral interface (SPI) module,
which allows full-duplex, synchronous, serial communications with
peripheral devices.
15.2 Features
Features of the SPI module include the following:
•
Full-duplex operation
•
Master and slave modes
•
Double-buffered operation with separate transmit and receive
registers
•
Four master mode frequencies (maximum = bus frequency ÷ 2)
•
Maximum slave mode frequency = bus frequency
•
Serial clock with programmable polarity and phase
•
Two separately enabled interrupts:
– SPRF (SPI receiver full)
– SPTE (SPI transmitter empty)
•
Mode fault error flag with CPU interrupt capability
•
Overflow error flag with CPU interrupt capability
•
Programmable wired-OR mode
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Serial Peripheral Interface Module (SPI)
15.3 Pin Name Conventions and I/O Register Addresses
The text that follows describes the SPI. The SPI I/O pin names are SS
(slave select), SPSCK (SPI serial clock), CGND (clock ground), MOSI
(master out slave in), and MISO (master in/slave out). The SPI shares
four I/O pins with four parallel I/O ports.
Freescale Semiconductor, Inc...
The full names of the SPI I/O pins are shown in Table 15-1. The generic
pin names appear in the text that follows.
Table 15-1. Pin Name Conventions
SPI Generic
Pin Names:
MISO
MOSI
SS
Full SPI
SPI PTC2/MISO PTC3/MOSI PTC4/SS
Pin Names:
SPSCK
CGND
PTC5/SPSCK
VSS
Figure 15-1 summarizes the SPI I/O registers.
=
Addr.
Register Name
$0010
Read:
SPI Control Register
Write:
(SPCR)
Reset:
$0011
Read:
SPI Status and Control
Register Write:
(SPSCR)
Reset:
$0012
Read:
SPI Data Register
Write:
(SPDR)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
SPRIE
R
SPMSTR
CPOL
CPHA
SPWOM
SPE
SPTIE
0
0
1
0
1
0
0
0
OVRF
MODF
SPTE
MODFEN
SPR1
SPR0
SPRF
ERRIE
0
0
0
0
1
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
Unaffected by reset
= Unimplemented
R
= Reserved
Figure 15-1. SPI I/O Register Summary
Data Sheet
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Serial Peripheral Interface Module (SPI)
Functional Description
15.4 Functional Description
Figure 15-2 shows the structure of the SPI module.
INTERNAL BUS
TRANSMIT DATA REGISTER
CGMOUT ÷ 2
FROM SIM
SHIFT REGISTER
Freescale Semiconductor, Inc...
7
6
5
4
3
2
1
MISO
0
÷2
MOSI
÷8
CLOCK
DIVIDER ÷ 32
RECEIVE DATA REGISTER
PIN
CONTROL
LOGIC
÷ 128
SPMSTR
SPE
CLOCK
SELECT
SPR1
SPSCK
M
CLOCK
LOGIC
S
SS
SPR0
SPMSTR
RESERVED
MODFEN
TRANSMITTER CPU INTERRUPT REQUEST
RESERVED
CPHA
CPOL
SPWOM
ERRIE
SPI
CONTROL
SPTIE
SPRIE
RECEIVER/ERROR CPU INTERRUPT REQUEST
R
SPE
SPRF
SPTE
OVRF
MODF
Figure 15-2. SPI Module Block Diagram
The SPI module allows full-duplex, synchronous, serial communication
between the MCU and peripheral devices, including other MCUs.
Software can poll the SPI status flags or SPI operation can be interruptdriven.
The following paragraphs describe the operation of the SPI module.
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Serial Peripheral Interface Module (SPI)
15.4.1 Master Mode
The SPI operates in master mode when the SPI master bit, SPMSTR, is
set.
NOTE:
Configure the SPI modules as master or slave before enabling them.
Enable the master SPI before enabling the slave SPI. Disable the slave
SPI before disabling the master SPI. (See 15.13.1 SPI Control
Register.)
Freescale Semiconductor, Inc...
Only a master SPI module can initiate transmissions. Software begins
the transmission from a master SPI module by writing to the transmit
data register. If the shift register is empty, the byte immediately transfers
to the shift register, setting the SPI transmitter empty bit, SPTE. The byte
begins shifting out on the MOSI pin under the control of the serial clock.
(See Figure 15-3.)
MASTER MCU
SHIFT REGISTER
SLAVE MCU
MISO
MISO
MOSI
MOSI
SPSCK
BAUD RATE
GENERATOR
SS
SHIFT REGISTER
SPSCK
SS
VDD
Figure 15-3. Full-Duplex Master-Slave Connections
Data Sheet
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Serial Peripheral Interface Module (SPI)
Functional Description
Freescale Semiconductor, Inc...
The SPR1 and SPR0 bits control the baud rate generator and determine
the speed of the shift register. (See 15.13.2 SPI Status and Control
Register.) Through the SPSCK pin, the baud rate generator of the
master also controls the shift register of the slave peripheral.
As the byte shifts out on the MOSI pin of the master, another byte shifts
in from the slave on the master’s MISO pin. The transmission ends when
the receiver full bit, SPRF, becomes set. At the same time that SPRF
becomes set, the byte from the slave transfers to the receive data
register. In normal operation, SPRF signals the end of a transmission.
Software clears SPRF by reading the SPI status and control register with
SPRF set and then reading the SPI data register. Writing to the SPI data
register clears the SPTE bit.
15.4.2 Slave Mode
The SPI operates in slave mode when the SPMSTR bit is clear. In slave
mode, the SPSCK pin is the input for the serial clock from the master
MCU. Before a data transmission occurs, the SS pin of the slave SPI
must be at logic 0. SS must remain low until the transmission is
complete. (See 15.7.2 Mode Fault Error.)
In a slave SPI module, data enters the shift register under the control of
the serial clock from the master SPI module. After a byte enters the shift
register of a slave SPI, it transfers to the receive data register, and the
SPRF bit is set. To prevent an overflow condition, slave software then
must read the receive data register before another full byte enters the
shift register.
The maximum frequency of the SPSCK for an SPI configured as a slave
is the bus clock speed (which is twice as fast as the fastest master
SPSCK clock that can be generated). The frequency of the SPSCK for
an SPI configured as a slave does not have to correspond to any SPI
baud rate. The baud rate only controls the speed of the SPSCK
generated by an SPI configured as a master. Therefore, the frequency
of the SPSCK for an SPI configured as a slave can be any frequency
less than or equal to the bus speed.
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Serial Peripheral Interface Module (SPI)
Freescale Semiconductor, Inc...
When the master SPI starts a transmission, the data in the slave shift
register begins shifting out on the MISO pin. The slave can load its shift
register with a new byte for the next transmission by writing to its transmit
data register. The slave must write to its transmit data register at least
one bus cycle before the master starts the next transmission. Otherwise,
the byte already in the slave shift register shifts out on the MISO pin.
Data written to the slave shift register during a transmission remains in
a buffer until the end of the transmission.
When the clock phase bit (CPHA) is set, the first edge of SPSCK starts
a transmission. When CPHA is clear, the falling edge of SS starts a
transmission. (See 15.5 Transmission Formats.)
NOTE:
SPSCK must be in the proper idle state before the slave is enabled to
prevent SPSCK from appearing as a clock edge.
15.5 Transmission Formats
During an SPI transmission, data is simultaneously transmitted (shifted
out serially) and received (shifted in serially). A serial clock synchronizes
shifting and sampling on the two serial data lines. A slave select line
allows selection of an individual slave SPI device; slave devices that are
not selected do not interfere with SPI bus activities. On a master SPI
device, the slave select line can optionally be used to indicate multiplemaster bus contention.
15.5.1 Clock Phase and Polarity Controls
Software can select any of four combinations of serial clock (SPSCK)
phase and polarity using two bits in the SPI control register (SPCR). The
clock polarity is specified by the CPOL control bit, which selects an
active high or low clock and has no significant effect on the transmission
format.
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Serial Peripheral Interface Module (SPI)
Transmission Formats
The clock phase (CPHA) control bit selects one of two fundamentally
different transmission formats. The clock phase and polarity should be
identical for the master SPI device and the communicating slave device.
In some cases, the phase and polarity are changed between
transmissions to allow a master device to communicate with peripheral
slaves having different requirements.
Freescale Semiconductor, Inc...
NOTE:
Before writing to the CPOL bit or the CPHA bit, disable the SPI by
clearing the SPI enable bit (SPE).
15.5.2 Transmission Format When CPHA = 0
Figure 15-4 shows an SPI transmission in which CPHA is logic 0. The
figure should not be used as a replacement for data sheet parametric
information.
Two waveforms are shown for SPSCK: one for CPOL = 0 and another
for CPOL = 1. The diagram may be interpreted as a master or slave
timing diagram since the serial clock (SPSCK), master in/slave out
(MISO), and master out/slave in (MOSI) pins are directly connected
between the master and the slave. The MISO signal is the output from
the slave, and the MOSI signal is the output from the master. The SS line
is the slave select input to the slave. The slave SPI drives its MISO
output only when its slave select input (SS) is at logic 0, so that only the
selected slave drives to the master. The SS pin of the master is not
shown but is assumed to be inactive. The SS pin of the master must be
high or must be reconfigured as general-purpose I/O not affecting the
SPI. (See 15.7.2 Mode Fault Error.) When CPHA = 0, the first SPSCK
edge is the MSB capture strobe. Therefore, the slave must begin driving
its data before the first SPSCK edge, and a falling edge on the SS pin is
used to start the slave data transmission. The slave’s SS pin must be
toggled back to high and then low again between each byte transmitted
as shown in Figure 15-5.
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Serial Peripheral Interface Module (SPI)
SPSCK CYCLE #
FOR REFERENCE
1
2
3
4
5
6
7
8
MSB
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
SPSCK; CPOL = 0
SPSCK; CPOL =1
MOSI
FROM MASTER
MISO
FROM SLAVE
MSB
SS; TO SLAVE
Freescale Semiconductor, Inc...
CAPTURE STROBE
Figure 15-4. Transmission Format (CPHA = 0)
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 15-5. CPHA/SS Timing
When CPHA = 0 for a slave, the falling edge of SS indicates the
beginning of the transmission. This causes the SPI to leave its idle state
and begin driving the MISO pin with the MSB of its data. Once the
transmission begins, no new data is allowed into the shift register from
the transmit data register. Therefore, the SPI data register of the slave
must be loaded with transmit data before the falling edge of SS. Any data
written after the falling edge is stored in the transmit data register and
transferred to the shift register after the current transmission.
Data Sheet
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Serial Peripheral Interface Module (SPI)
Transmission Formats
15.5.3 Transmission Format When CPHA = 1
Freescale Semiconductor, Inc...
Figure 15-6 shows an SPI transmission in which CPHA is logic 1. The
figure should not be used as a replacement for data sheet parametric
information. Two waveforms are shown for SPSCK: one for CPOL = 0
and another for CPOL = 1. The diagram may be interpreted as a master
or slave timing diagram since the serial clock (SPSCK), master in/slave
out (MISO), and master out/slave in (MOSI) pins are directly connected
between the master and the slave. The MISO signal is the output from
the slave, and the MOSI signal is the output from the master. The SS line
is the slave select input to the slave. The slave SPI drives its MISO
output only when its slave select input (SS) is at logic 0, so that only the
selected slave drives to the master. The SS pin of the master is not
shown but is assumed to be inactive. The SS pin of the master must be
high or must be reconfigured as general-purpose I/O not affecting the
SPI. (See 15.7.2 Mode Fault Error.) When CPHA = 1, the master
begins driving its MOSI pin on the first SPSCK edge. Therefore, the
slave uses the first SPSCK edge as a start transmission signal. The SS
pin can remain low between transmissions. This format may be
preferable in systems having only one master and only one slave driving
the MISO data line.
SPSCK CYCLE #
FOR REFERENCE
1
2
3
4
5
6
7
8
MOSI
FROM MASTER
MSB
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
LSB
MISO
FROM SLAVE
MSB
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
SPSCK; CPOL = 0
SPSCK; CPOL =1
LSB
SS; TO SLAVE
CAPTURE STROBE
Figure 15-6. Transmission Format (CPHA = 1)
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Serial Peripheral Interface Module (SPI)
Freescale Semiconductor, Inc...
When CPHA = 1 for a slave, the first edge of the SPSCK indicates the
beginning of the transmission. This causes the SPI to leave its idle state
and begin driving the MISO pin with the MSB of its data. Once the
transmission begins, no new data is allowed into the shift register from
the transmit data register. Therefore, the SPI data register of the slave
must be loaded with transmit data before the first edge of SPSCK. Any
data written after the first edge is stored in the transmit data register and
transferred to the shift register after the current transmission.
15.5.4 Transmission Initiation Latency
When the SPI is configured as a master (SPMSTR = 1), writing to the
SPDR starts a transmission. CPHA has no effect on the delay to the start
of the transmission, but it does affect the initial state of the SPSCK
signal. When CPHA = 0, the SPSCK signal remains inactive for the first
half of the first SPSCK cycle. When CPHA = 1, the first SPSCK cycle
begins with an edge on the SPSCK line from its inactive to its active
level. The SPI clock rate (selected by SPR1:SPR0) affects the delay
from the write to SPDR and the start of the SPI transmission. (See
Figure 15-7.) The internal SPI clock in the master is a free-running
derivative of the internal MCU clock. To conserve power, it is enabled
only when both the SPE and SPMSTR bits are set. SPSCK edges occur
halfway through the low time of the internal MCU clock. Since the SPI
clock is free-running, it is uncertain where the write to the SPDR occurs
relative to the slower SPSCK. This uncertainty causes the variation in
the initiation delay shown in Figure 15-7. This delay is no longer than a
single SPI bit time. That is, the maximum delay is two MCU bus cycles
for DIV2, eight MCU bus cycles for DIV8, 32 MCU bus cycles for DIV32,
and 128 MCU bus cycles for DIV128.
Data Sheet
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Serial Peripheral Interface Module (SPI)
Transmission Formats
WRITE
TO SPDR
INITIATION DELAY
BUS
CLOCK
MOSI
MSB
BIT 6
1
2
BIT 5
SPSCK
CPHA = 1
SPSCK
CPHA = 0
Freescale Semiconductor, Inc...
SPSCK CYCLE
NUMBER
3
INITIATION DELAY FROM WRITE SPDR TO TRANSFER BEGIN
WRITE
TO SPDR
BUS
CLOCK
EARLIEST
LATEST
WRITE
TO SPDR
SPSCK = INTERNAL CLOCK ÷ 2;
2 POSSIBLE START POINTS
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
SPSCK = INTERNAL CLOCK ÷ 8;
8 POSSIBLE START POINTS
LATEST
SPSCK = INTERNAL CLOCK ÷ 32;
32 POSSIBLE START POINTS
LATEST
SPSCK = INTERNAL CLOCK ÷ 128;
128 POSSIBLE START POINTS
LATEST
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
BUS
CLOCK
EARLIEST
Figure 15-7. Transmission Start Delay (Master)
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Serial Peripheral Interface Module (SPI)
15.6 Queuing Transmission Data
Freescale Semiconductor, Inc...
The double-buffered transmit data register allows a data byte to be
queued and transmitted. For an SPI configured as a master, a queued
data byte is transmitted immediately after the previous transmission has
completed. The SPI transmitter empty flag (SPTE) indicates when the
transmit data buffer is ready to accept new data. Write to the transmit
data register only when the SPTE bit is high. Figure 15-8 shows the
timing associated with doing back-to-back transmissions with the SPI
(SPSCK has CPHA: CPOL = 1:0).
WRITE TO SPDR
SPTE
1
3
2
8
5
10
SPSCK
CPHA:CPOL = 1:0
MOSI
MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT
6 5 4
6 5 4 3 2 1
6 5 4 3 2 1
BYTE 1
BYTE 2
BYTE 3
4
SPRF
9
6
READ SPSCR
11
7
READ SPDR
12
1 CPU WRITES BYTE 1 TO SPDR, CLEARING SPTE BIT.
7 CPU READS SPDR, CLEARING SPRF BIT.
2 BYTE 1 TRANSFERS FROM TRANSMIT DATA
REGISTER TO SHIFT REGISTER, SETTING SPTE BIT.
8 CPU WRITES BYTE 3 TO SPDR, QUEUEING BYTE
3 AND CLEARING SPTE BIT.
9 SECOND INCOMING BYTE TRANSFERS FROM SHIFT
REGISTER TO RECEIVE DATA REGISTER, SETTING
SPRF BIT.
10 BYTE 3 TRANSFERS FROM TRANSMIT DATA
REGISTER TO SHIFT REGISTER, SETTING SPTE BIT.
11 CPU READS SPSCR WITH SPRF BIT SET.
3 CPU WRITES BYTE 2 TO SPDR, QUEUEING BYTE 2
AND CLEARING SPTE BIT.
FIRST INCOMING BYTE TRANSFERS FROM SHIFT
REGISTER TO RECEIVE DATA REGISTER, SETTING
SPRF BIT.
5 BYTE 2 TRANSFERS FROM TRANSMIT DATA
REGISTER TO SHIFT REGISTER, SETTING SPTE BIT.
6 CPU READS SPSCR WITH SPRF BIT SET.
4
12 CPU READS SPDR, CLEARING SPRF BIT.
Figure 15-8. SPRF/SPTE CPU Interrupt Timing
The transmit data buffer allows back-to-back transmissions without the
slave precisely timing its writes between transmissions as in a system
with a single data buffer. Also, if no new data is written to the data buffer,
the last value contained in the shift register is the next data word to be
transmitted.
Data Sheet
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Serial Peripheral Interface Module (SPI)
Error Conditions
Freescale Semiconductor, Inc...
For an idle master or idle slave that has no data loaded into its transmit
buffer, the SPTE is set again no more than two bus cycles after the
transmit buffer empties into the shift register. This allows the user to
queue up a 16-bit value to send. For an already active slave, the load of
the shift register cannot occur until the transmission is completed. This
implies that a back-to-back write to the transmit data register is not
possible. The SPTE indicates when the next write can occur.
15.7 Error Conditions
The following flags signal SPI error conditions:
•
Overflow (OVRF) — Failing to read the SPI data register before
the next full byte enters the shift register sets the OVRF bit. The
new byte does not transfer to the receive data register, and the
unread byte still can be read. OVRF is in the SPI status and control
register.
•
Mode fault error (MODF) — The MODF bit indicates that the
voltage on the slave select pin (SS) is inconsistent with the mode
of the SPI. MODF is in the SPI status and control register.
15.7.1 Overflow Error
The overflow flag (OVRF) becomes set if the receive data register still
has unread data from a previous transmission when the capture strobe
of bit 1 of the next transmission occurs. The bit 1 capture strobe occurs
in the middle of SPSCK cycle 7. (See Figure 15-4 and Figure 15-6.) If
an overflow occurs, all data received after the overflow and before the
OVRF bit is cleared does not transfer to the receive data register and
does not set the SPI receiver full bit (SPRF). The unread data that
transferred to the receive data register before the overflow occurred can
still be read. Therefore, an overflow error always indicates the loss of
data. Clear the overflow flag by reading the SPI status and control
register and then reading the SPI data register.
OVRF generates a receiver/error CPU interrupt request if the error
interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF
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Serial Peripheral Interface Module (SPI)
interrupts share the same CPU interrupt vector. (See Figure 15-11.) It is
not possible to enable MODF or OVRF individually to generate a
receiver/error CPU interrupt request. However, leaving MODFEN low
prevents MODF from being set.
Freescale Semiconductor, Inc...
If the CPU SPRF interrupt is enabled and the OVRF interrupt is not,
watch for an overflow condition. Figure 15-9 shows how it is possible to
miss an overflow. The first part of Figure 15-9 shows how it is possible
to read the SPSCR and SPDR to clear the SPRF without problems.
However, as illustrated by the second transmission example, the OVRF
bit can be set in between the time that SPSCR and SPDR are read.
BYTE 1
BYTE 2
BYTE 3
BYTE 4
1
4
6
8
SPRF
OVRF
READ
SPSCR
2
READ
SPDR
5
3
1
BYTE 1 SETS SPRF BIT.
2
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
BYTE 2 SETS SPRF BIT.
3
4
7
5
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
6
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
7
CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT,
BUT NOT OVRF BIT.
8
BYTE 4 FAILS TO SET SPRF BIT BECAUSE
OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST.
Figure 15-9. Missed Read of Overflow Condition
In this case, an overflow can be missed easily. Since no more SPRF
interrupts can be generated until this OVRF is serviced, it is not obvious
that bytes are being lost as more transmissions are completed. To
prevent this, either enable the OVRF interrupt or do another read of the
SPSCR following the read of the SPDR. This ensures that the OVRF
was not set before the SPRF was cleared and that future transmissions
can set the SPRF bit. Figure 15-10 illustrates this process. Generally, to
avoid this second SPSCR read, enable the OVRF to the CPU by setting
the ERRIE bit.
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Serial Peripheral Interface Module (SPI)
Error Conditions
BYTE 1
SPI RECEIVE
COMPLETE
BYTE 2
5
1
BYTE 3
7
BYTE 4
11
SPRF
OVRF
READ
SPSCR
2
Freescale Semiconductor, Inc...
READ
SPDR
4
3
1
BYTE 1 SETS SPRF BIT.
2
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
3
6
9
8
12
10
14
13
8
CPU READS BYTE 2 IN SPDR,
CLEARING SPRF BIT.
9
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
10 CPU READS BYTE 2 SPDR,
CLEARING OVRF BIT.
4
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
5
BYTE 2 SETS SPRF BIT.
12 CPU READS SPSCR.
6
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
13 CPU READS BYTE 4 IN SPDR,
CLEARING SPRF BIT.
7
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
14 CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
11 BYTE 4 SETS SPRF BIT.
Figure 15-10. Clearing SPRF When OVRF Interrupt Is Not Enabled
15.7.2 Mode Fault Error
Setting the SPMSTR bit selects master mode and configures the
SPSCK and MOSI pins as outputs and the MISO pin as an input.
Clearing SPMSTR selects slave mode and configures the SPSCK and
MOSI pins as inputs and the MISO pin as an output. The mode fault bit,
MODF, becomes set any time the state of the slave select pin, SS, is
inconsistent with the mode selected by SPMSTR.
To prevent SPI pin contention and damage to the MCU, a mode fault
error occurs if:
•
The SS pin of a slave SPI goes high during a transmission
•
The SS pin of a master SPI goes low at any time
For the MODF flag to be set, the mode fault error enable bit (MODFEN)
must be set. Clearing the MODFEN bit does not clear the MODF flag but
does prevent MODF from being set again after MODF is cleared.
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Serial Peripheral Interface Module (SPI)
MODF generates a receiver/error CPU interrupt request if the error
interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF
interrupts share the same CPU interrupt vector. (See Figure 15-11.) It is
not possible to enable MODF or OVRF individually to generate a
receiver/error CPU interrupt request. However, leaving MODFEN low
prevents MODF from being set.
Freescale Semiconductor, Inc...
In a master SPI with the mode fault enable bit (MODFEN) set, the mode
fault flag (MODF) is set if SS goes to logic 0. A mode fault in a master
SPI causes the following events to occur:
NOTE:
•
If ERRIE = 1, the SPI generates an SPI receiver/error CPU
interrupt request.
•
The SPE bit is cleared.
•
The SPTE bit is set.
•
The SPI state counter is cleared.
•
The data direction register of the shared I/O port regains control of
port drivers.
To prevent bus contention with another master SPI after a mode fault
error, clear all SPI bits of the data direction register of the shared I/O port
before enabling the SPI.
When configured as a slave (SPMSTR = 0), the MODF flag is set if SS
goes high during a transmission. When CPHA = 0, a transmission begins
when SS goes low and ends once the incoming SPSCK goes back to its
idle level following the shift of the eighth data bit. When CPHA = 1, the
transmission begins when the SPSCK leaves its idle level and SS is
already low. The transmission continues until the SPSCK returns to its
idle level following the shift of the last data bit. (See 15.5 Transmission
Formats.)
NOTE:
Setting the MODF flag does not clear the SPMSTR bit. The SPMSTR bit
has no function when SPE = 0. Reading SPMSTR when MODF = 1
shows the difference between a MODF occurring when the SPI is a
master and when it is a slave.
When CPHA = 0, a MODF occurs if a slave is selected (SS is at logic 0)
and later unselected (SS is at logic 1) even if no SPSCK is sent to that
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Serial Peripheral Interface Module (SPI)
Interrupts
slave. This happens because SS at logic 0 indicates the start of the
transmission (MISO driven out with the value of MSB) for CPHA = 0.
When CPHA = 1, a slave can be selected and then later unselected with
no transmission occurring. Therefore, MODF does not occur since a
transmission was never begun.
Freescale Semiconductor, Inc...
In a slave SPI (MSTR = 0), the MODF bit generates an SPI
receiver/error CPU interrupt request if the ERRIE bit is set. The MODF
bit does not clear the SPE bit or reset the SPI in any way. Software can
abort the SPI transmission by clearing the SPE bit of the slave.
NOTE:
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a high
impedance state. Also, the slave SPI ignores all incoming SPSCK
clocks, even if it was already in the middle of a transmission.
To clear the MODF flag, read the SPSCR with the MODF bit set and then
write to the SPCR register. This entire clearing mechanism must occur
with no MODF condition existing or else the flag is not cleared.
15.8 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt
requests.
Table 15-2. SPI Interrupts
Flag
Request
SPTE
Transmitter empty
SPI transmitter CPU interrupt request
(SPTIE = 1, SPE = 1)
SPRF
Receiver full
SPI receiver CPU interrupt request
(SPRIE = 1)
OVRF
Overflow
SPI receiver/error interrupt request (ERRIE = 1)
MODF
Mode fault
SPI receiver/error interrupt request (ERRIE = 1)
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Serial Peripheral Interface Module (SPI)
Reading the SPI status and control register with SPRF set and then
reading the receive data register clears SPRF. The clearing mechanism
for the SPTE flag is always just a write to the transmit data register.
The SPI transmitter interrupt enable bit (SPTIE) enables the SPTE flag
to generate transmitter CPU interrupt requests, provided that the SPI is
enabled (SPE = 1).
Freescale Semiconductor, Inc...
The SPI receiver interrupt enable bit (SPRIE) enables the SPRF bit to
generate receiver CPU interrupt requests, regardless of the state of the
SPE bit. (See Figure 15-11.)
The error interrupt enable bit (ERRIE) enables both the MODF and
OVRF bits to generate a receiver/error CPU interrupt request.
The mode fault enable bit (MODFEN) can prevent the MODF flag from
being set so that only the OVRF bit is enabled by the ERRIE bit to
generate receiver/error CPU interrupt requests.
NOT AVAILABLE
SPTE
SPTIE
SPE
SPI TRANSMITTER
CPU INTERRUPT REQUEST
R
NOT AVAILABLE
SPRIE
SPRF
SPI RECEIVER/ERROR
CPU INTERRUPT REQUEST
ERRIE
MODF
OVRF
Figure 15-11. SPI Interrupt Request Generation
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Serial Peripheral Interface Module (SPI)
Resetting the SPI
Freescale Semiconductor, Inc...
The following sources in the SPI status and control register can generate
CPU interrupt requests:
•
SPI receiver full bit (SPRF) — The SPRF bit becomes set every
time a byte transfers from the shift register to the receive data
register. If the SPI receiver interrupt enable bit, SPRIE, is also set,
SPRF generates an SPI receiver/error CPU interrupt request.
•
SPI transmitter empty (SPTE) — The SPTE bit becomes set every
time a byte transfers from the transmit data register to the shift
register. If the SPI transmit interrupt enable bit, SPTIE, is also set,
SPTE generates an SPTE CPU interrupt request.
15.9 Resetting the SPI
Any system reset completely resets the SPI. Partial resets occur
whenever the SPI enable bit (SPE) is low. Whenever SPE is low, the
following occurs:
•
The SPTE flag is set.
•
Any transmission currently in progress is aborted.
•
The shift register is cleared.
•
The SPI state counter is cleared, making it ready for a new
complete transmission.
•
All the SPI port logic is defaulted back to being general-purpose
I/O.
These items are reset only by a system reset:
•
All control bits in the SPCR register
•
All control bits in the SPSCR register (MODFEN, ERRIE, SPR1,
and SPR0)
•
The status flags SPRF, OVRF, and MODF
By not resetting the control bits when SPE is low, the user can clear SPE
between transmissions without having to set all control bits again when
SPE is set back high for the next transmission.
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Serial Peripheral Interface Module (SPI)
By not resetting the SPRF, OVRF, and MODF flags, the user can still
service these interrupts after the SPI has been disabled. The user can
disable the SPI by writing 0 to the SPE bit. The SPI can also be disabled
by a mode fault occurring in an SPI that was configured as a master with
the MODFEN bit set.
Freescale Semiconductor, Inc...
15.10 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
15.10.1 Wait Mode
The SPI module remains active after the execution of a WAIT instruction.
In wait mode the SPI module registers are not accessible by the CPU.
Any enabled CPU interrupt request from the SPI module can bring the
MCU out of wait mode.
If SPI module functions are not required during wait mode, reduce power
consumption by disabling the SPI module before executing the WAIT
instruction.
To exit wait mode when an overflow condition occurs, enable the OVRF
bit to generate CPU interrupt requests by setting the error interrupt
enable bit (ERRIE). (See 15.8 Interrupts.)
15.10.2 Stop Mode
The SPI module is inactive after the execution of a STOP instruction.
The STOP instruction does not affect register conditions. SPI operation
resumes after an external interrupt. If stop mode is exited by reset, any
transfer in progress is aborted, and the SPI is reset.
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Serial Peripheral Interface Module (SPI)
SPI During Break Interrupts
15.11 SPI During Break Interrupts
Freescale Semiconductor, Inc...
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 Section 9. System Integration
Module (SIM).)
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.
Since the SPTE bit cannot be cleared during a break with the BCFE bit
cleared, a write to the transmit data register in break mode does not
initiate a transmission nor is this data transferred into the shift register.
Therefore, a write to the SPDR in break mode with the BCFE bit cleared
has no effect.
15.12 I/O Signals
The SPI module has five I/O pins and shares four of them with a parallel
I/O port. They are:
•
MISO — Data received
•
MOSI — Data transmitted
•
SPSCK — Serial clock
•
SS — Slave select
•
CGND — Clock ground (internally connected to VSS)
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Serial Peripheral Interface Module (SPI)
The SPI has limited inter-integrated circuit (I2C) capability (requiring
software support) as a master in a single-master environment. To
communicate with I2C peripherals, MOSI becomes an open-drain output
when the SPWOM bit in the SPI control register is set. In I2C
communication, the MOSI and MISO pins are connected to a
bidirectional pin from the I2C peripheral and through a pullup resistor to
VDD.
Freescale Semiconductor, Inc...
15.12.1 MISO (Master In/Slave Out)
MISO is one of the two SPI module pins that transmits serial data. In full
duplex operation, the MISO pin of the master SPI module is connected
to the MISO pin of the slave SPI module. The master SPI simultaneously
receives data on its MISO pin and transmits data from its MOSI pin.
Slave output data on the MISO pin is enabled only when the SPI is
configured as a slave. The SPI is configured as a slave when its
SPMSTR bit is logic 0 and its SS pin is at logic 0. To support a multipleslave system, a logic 1 on the SS pin puts the MISO pin in a highimpedance state.
When enabled, the SPI controls data direction of the MISO pin
regardless of the state of the data direction register of the shared I/O
port.
15.12.2 MOSI (Master Out/Slave In)
MOSI is one of the two SPI module pins that transmits serial data. In fullduplex operation, the MOSI pin of the master SPI module is connected
to the MOSI pin of the slave SPI module. The master SPI simultaneously
transmits data from its MOSI pin and receives data on its MISO pin.
When enabled, the SPI controls data direction of the MOSI pin
regardless of the state of the data direction register of the shared I/O
port.
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Serial Peripheral Interface Module (SPI)
I/O Signals
15.12.3 SPSCK (Serial Clock)
Freescale Semiconductor, Inc...
The serial clock synchronizes data transmission between master and
slave devices. In a master MCU, the SPSCK pin is the clock output. In a
slave MCU, the SPSCK pin is the clock input. In full-duplex operation,
the master and slave MCUs exchange a byte of data in eight serial clock
cycles.
When enabled, the SPI controls data direction of the SPSCK pin
regardless of the state of the data direction register of the shared I/O
port.
15.12.4 SS (Slave Select)
The SS pin has various functions depending on the current state of the
SPI. For an SPI configured as a slave, the SS is used to select a slave.
For CPHA = 0, the SS is used to define the start of a transmission. (See
15.5 Transmission Formats.) Since it is used to indicate the start of a
transmission, the SS must be toggled high and low between each byte
transmitted for the CPHA = 0 format. However, it can remain low
between transmissions for the CPHA = 1 format. See Figure 15-12.
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 15-12. CPHA/SS Timing
When an SPI is configured as a slave, the SS pin is always configured
as an input. It cannot be used as a general-purpose I/O regardless of the
state of the MODFEN control bit. However, the MODFEN bit can still
prevent the state of the SS from creating a MODF error. (See 15.13.2
SPI Status and Control Register.)
NOTE:
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a highimpedance state. The slave SPI ignores all incoming SPSCK clocks,
even if it was already in the middle of a transmission.
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Serial Peripheral Interface Module (SPI)
Freescale Semiconductor, Inc...
When an SPI is configured as a master, the SS input can be used in
conjunction with the MODF flag to prevent multiple masters from driving
MOSI and SPSCK. (See 15.7.2 Mode Fault Error.) For the state of the
SS pin to set the MODF flag, the MODFEN bit in the SPSCK register
must be set. If the MODFEN bit is low for an SPI master, the SS pin can
be used as a general-purpose I/O under the control of the data direction
register of the shared I/O port. With MODFEN high, it is an input-only pin
to the SPI regardless of the state of the data direction register of the
shared I/O port.
The CPU can always read the state of the SS pin by configuring the
appropriate pin as an input and reading the port data register. (See
Table 15-3.)
Table 15-3. SPI Configuration
SPE
SPMSTR
MODFEN
SPI Configuration
State of SS Logic
0
X(1)
X
Not enabled
General-purpose I/O;
SS ignored by SPI
1
0
X
Slave
Input-only to SPI
1
1
0
Master without MODF
General-purpose I/O;
SS ignored by SPI
1
1
1
Master with MODF
Input-only to SPI
Note 1. X = Don’t care
15.12.5 CGND (Clock Ground)
CGND is the ground return for the serial clock pin, SPSCK, and the
ground for the port output buffers. It is internally connected to VSS as
shown in Table 15-1.
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Serial Peripheral Interface Module (SPI)
I/O Registers
15.13 I/O Registers
Freescale Semiconductor, Inc...
Three registers control and monitor SPI operation:
•
SPI control register (SPCR)
•
SPI status and control register (SPSCR)
•
SPI data register (SPDR)
15.13.1 SPI Control Register
The SPI control register:
•
Enables SPI module interrupt requests
•
Configures the SPI module as master or slave
•
Selects serial clock polarity and phase
•
Configures the SPSCK, MOSI, and MISO pins as open-drain
outputs
•
Enables the SPI module
Address: $0010
Bit 7
6
5
4
3
2
1
Bit 0
SPRIE
R
SPMSTR
CPOL
CPHA
SPWOM
SPE
SPTIE
0
0
1
0
1
0
0
0
Read:
Write:
Reset:
= Unimplemented
R
= Reserved
Figure 15-13. SPI Control Register (SPCR)
SPRIE — SPI Receiver Interrupt Enable Bit
This read/write bit enables CPU interrupt requests generated by the
SPRF bit. The SPRF bit is set when a byte transfers from the shift
register to the receive data register. Reset clears the SPRIE bit.
1 = SPRF CPU interrupt requests enabled
0 = SPRF CPU interrupt requests disabled
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Serial Peripheral Interface Module (SPI)
SPMSTR — SPI Master Bit
This read/write bit selects master mode operation or slave mode
operation. Reset sets the SPMSTR bit.
1 = Master mode
0 = Slave mode
CPOL — Clock Polarity Bit
Freescale Semiconductor, Inc...
This read/write bit determines the logic state of the SPSCK pin
between transmissions. (See Figure 15-4 and Figure 15-6.) To
transmit data between SPI modules, the SPI modules must have
identical CPOL values. Reset clears the CPOL bit.
CPHA — Clock Phase Bit
This read/write bit controls the timing relationship between the serial
clock and SPI data. (See Figure 15-4 and Figure 15-6.) To transmit
data between SPI modules, the SPI modules must have identical
CPHA values. When CPHA = 0, the SS pin of the slave SPI module
must be set to logic 1 between bytes. (See Figure 15-12.) Reset sets
the CPHA bit.
SPWOM — SPI Wired-OR Mode Bit
This read/write bit disables the pullup devices on pins SPSCK, MOSI,
and MISO so that those pins become open-drain outputs.
1 = Wired-OR SPSCK, MOSI, and MISO pins
0 = Normal push-pull SPSCK, MOSI, and MISO pins
SPE — SPI Enable
This read/write bit enables the SPI module. Clearing SPE causes a
partial reset of the SPI. (See 15.9 Resetting the SPI.) Reset clears
the SPE bit.
1 = SPI module enabled
0 = SPI module disabled
SPTIE— SPI Transmit Interrupt Enable
This read/write bit enables CPU interrupt requests generated by the
SPTE bit. SPTE is set when a byte transfers from the transmit data
register to the shift register. Reset clears the SPTIE bit.
1 = SPTE CPU interrupt requests enabled
0 = SPTE CPU interrupt requests disabled
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Serial Peripheral Interface Module (SPI)
I/O Registers
15.13.2 SPI Status and Control Register
Freescale Semiconductor, Inc...
The SPI status and control register contains flags to signal these
conditions:
•
Receive data register full
•
Failure to clear SPRF bit before next byte is received (overflow
error)
•
Inconsistent logic level on SS pin (mode fault error)
•
Transmit data register empty
The SPI status and control register also contains bits that perform these
functions:
•
Enable error interrupts
•
Enable mode fault error detection
•
Select master SPI baud rate
Address: $0011
Bit 7
Read:
6
SPRF
5
4
3
OVRF
MODF
SPTE
ERRIE
2
1
Bit 0
MODFEN
SPR1
SPR0
0
0
0
Write:
Reset:
0
0
0
0
1
= Unimplemented
Figure 15-14. SPI Status and Control Register (SPSCR)
SPRF — SPI Receiver Full Bit
This clearable, read-only flag is set each time a byte transfers from
the shift register to the receive data register. SPRF generates a CPU
interrupt request if the SPRIE bit in the SPI control register is set also.
During an SPRF CPU interrupt, the CPU clears SPRF by reading the
SPI status and control register with SPRF set and then reading the
SPI data register. Reset clears the SPRF bit.
1 = Receive data register full
0 = Receive data register not full
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Serial Peripheral Interface Module (SPI)
ERRIE — Error Interrupt Enable Bit
This read/write bit enables the MODF and OVRF bits to generate
CPU interrupt requests. Reset clears the ERRIE bit.
1 = MODF and OVRF can generate CPU interrupt requests
0 = MODF and OVRF cannot generate CPU interrupt requests
OVRF — Overflow Bit
Freescale Semiconductor, Inc...
This clearable, read-only flag is set if software does not read the byte
in the receive data register before the next full byte enters the shift
register. In an overflow condition, the byte already in the receive data
register is unaffected, and the byte that shifted in last is lost. Clear the
OVRF bit by reading the SPI status and control register with OVRF set
and then reading the receive data register. Reset clears the OVRF bit.
1 = Overflow
0 = No overflow
MODF — Mode Fault Bit
This clearable, read-only flag is set in a slave SPI if the SS pin goes
high during a transmission with the MODFEN bit set. In a master SPI,
the MODF flag is set if the SS pin goes low at any time with the
MODFEN bit set. Clear the MODF bit by reading the SPI status and
control register (SPSCR) with MODF set and then writing to the SPI
control register (SPCR). Reset clears the MODF bit.
1 = SS pin at inappropriate logic level
0 = SS pin at appropriate logic level
SPTE — SPI Transmitter Empty Bit
This clearable, read-only flag is set each time the transmit data
register transfers a byte into the shift register. SPTE generates an
SPTE CPU interrupt request if the SPTIE bit in the SPI control register
is set also.
NOTE:
Do not write to the SPI data register unless the SPTE bit is high.
During an SPTE CPU interrupt, the CPU clears the SPTE bit by
writing to the transmit data register.
Reset sets the SPTE bit.
1 = Transmit data register empty
0 = Transmit data register not empty
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Serial Peripheral Interface Module (SPI)
I/O Registers
MODFEN — Mode Fault Enable Bit
This read/write bit, when set to 1, allows the MODF flag to be set. If
the MODF flag is set, clearing the MODFEN does not clear the MODF
flag. If the SPI is enabled as a master and the MODFEN bit is low,
then the SS pin is available as a general-purpose I/O.
Freescale Semiconductor, Inc...
If the MODFEN bit is set, then this pin is not available as a generalpurpose I/O. When the SPI is enabled as a slave, the SS pin is not
available as a general-purpose I/O regardless of the value of
MODFEN. (See 15.12.4 SS (Slave Select).)
If the MODFEN bit is low, the level of the SS pin does not affect the
operation of an enabled SPI configured as a master. For an enabled
SPI configured as a slave, having MODFEN low only prevents the
MODF flag from being set. It does not affect any other part of SPI
operation. (See 15.7.2 Mode Fault Error.)
SPR1 and SPR0 — SPI Baud Rate Select Bits
In master mode, these read/write bits select one of four baud rates as
shown in Table 15-4. SPR1 and SPR0 have no effect in slave mode.
Reset clears SPR1 and SPR0.
Table 15-4. SPI Master Baud Rate Selection
SPR1 and SPR0
Baud Rate Divisor (BD)
00
2
01
8
10
32
11
128
Use this formula to calculate the SPI baud rate:
CGMOUT
Baud rate = -------------------------2 × BD
where:
CGMOUT = base clock output of the clock generator module (CGM)
BD = baud rate divisor
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Serial Peripheral Interface Module (SPI)
15.13.3 SPI Data Register
The SPI data register consists of the read-only receive data register and
the write-only transmit data register. Writing to the SPI data register
writes data into the transmit data register. Reading the SPI data register
reads data from the receive data register. The transmit data and receive
data registers are separate registers that can contain different values.
(See Figure 15-2.)
Freescale Semiconductor, Inc...
Address: $0012
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 15-15. SPI Data Register (SPDR)
R7–R0/T7–T0 — Receive/Transmit Data Bits
NOTE:
Data Sheet
Do not use read-modify-write instructions on the SPI data register since
the register read is not the same as the register written.
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Data Sheet – MC68HC908AP Family
Section 16. Multi-Master IIC Interface (MMIIC)
16.1 Introduction
Freescale Semiconductor, Inc...
The multi-master IIC (MMIIC) interface is a two wire, bidirectional serial
bus which provides a simple, efficient way for data exchange between
devices. The interface is designed for internal serial communication
between the MCU and other IIC devices. It has hardware generated
START and STOP signals; and byte by byte interrupt driven software
algorithm.
This bus is suitable for applications which need frequent
communications over a short distance between a number of devices. It
also provides a flexibility that allows additional devices to be connected
to the bus. The maximum data rate is 100k-bps, and the maximum
communication distance and number of devices that can be connected
is limited by a maximum bus capacitance of 400pF.
This MMIIC interface is also SMBus (System Management Bus) version
1.0 and 1.1 compatible, with hardware cyclic redundancy code (CRC)
generation, making it suitable for smart battery applications.
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Multi-Master IIC Interface (MMIIC)
16.2 Features
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Features of the MMIC module include:
•
Full SMBus version 1.0/1.1 compliance
•
Multi-master IIC bus standard
•
Software programmable for one of eight different serial clock
frequencies
•
Software controllable acknowledge bit generation
•
Interrupt driven byte by byte data transfer
•
Calling address identification interrupt
•
Arbitration loss detection and no-ACK awareness in master mode
and automatic mode switching from master to slave
•
Auto detection of R/W bit and switching of transmit or receive
mode accordingly
•
Detection of START, repeated START, and STOP signals
•
Auto generation of START and STOP condition in master mode
•
Repeated start generation
•
Master clock generator with eight selectable baud rates
•
Automatic recognition of the received acknowledge bit
•
Busy detection
•
Software enabled 8-bit CRC generation/decoding
16.3 I/O Pins
The MMIIC module uses two I/O pins, shared with standard port I/O pins.
The full name of the MMIIC I/O pins are listed in Table 16-1. The generic
pin name appear in the text that follows.
The SDA and SDL pins are open-drain. When configured as general
purpose output pins (PTB0 and PTB1), pullup resistors must be
connected to these pins.
Data Sheet
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Multi-Master IIC Interface (MMIIC)
Table 16-1. Pin Name Conventions
MMIIC Generic Pin Names:
Full MCU Pin Names:
SDA
PTB0/SDA
SCL
PTB1/SCL
Addr.
Freescale Semiconductor, Inc...
$0048
Register Name
Bit 7
Read:
MMAD7
MMIIC Address Register
Write:
(MMADR)
Reset:
1
Read:
MMIIC Control Register 1
$0049
Write:
(MMCR1)
Reset:
MMEN
5
4
3
2
MMAD6
MMAD5
MMAD4
MMAD3
MMAD2
0
1
0
0
0
0
0
MMIEN
$004D
MMTXAK REPSEN
1
Bit 0
MMAD1 MMEXTAD
0
0
0
MMCRCBYTE
MMCLRBB
0
Read: MMRXIF
MMIIC Status Register
Write:
0
(MMSR)
Reset:
0
$004C
MMEN bit in MMCR1 ($0049)
6
0
Read: MMALIF MMNAKIF
MMIIC Control Register 2
$004A
Write:
0
0
(MMCR2)
Reset:
0
0
$004B
Pin Selected for MMIIC Function By:
Read:
MMIIC Data Transmit
MMTD7
Register Write:
(MMDTR)
Reset:
0
Read: MMRD7
MMIIC Data Receive
Register Write:
(MDDRR)
Reset:
0
MMTXIF
0
MMBB
0
0
0
MMAST
MMRW
0
0
0
0
0
0
0
MMCRCEF
0
0
Unaffected
MMATCH MMSRW MMRXAK MMCRCBF MMTXBE MMRXBF
0
0
0
0
1
0
1
0
MMTD6
MMTD5
MMTD4
MMTD3
MMTD2
MMTD1
MMTD0
0
0
0
0
0
0
0
MMRD6
MMRD5
MMRD4
MMRD3
MMRD2
MMRD1
MMRD0
0
0
0
0
0
0
0
Read: MMCRCD7 MMCRCD6 MMCRCD5 MMCRCD4 MMCRCD3 MMCRCD2 MMCRCD1 MMCRCD0
MMIIC CRC Data Register
Write:
$004E
(MMCRDR)
Reset:
0
0
0
0
0
0
0
0
Read:
MMIIC Frequency Divider
$004F
Register Write:
(MMFDR)
Reset:
0
0
0
0
0
0
0
0
0
0
MMBR2
MMBR1
MMBR0
1
0
0
= Unimplemented
Figure 16-1. MMIIC I/O Register Summary
Data Sheet
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Multi-Master IIC Interface (MMIIC)
16.4 Multi-Master IIC System Configuration
The multi-master IIC system uses a serial data line SDA and a serial
clock line SCL for data transfer. All devices connected to it must have
open collector (drain) outputs and the logical-AND function is performed
on both lines by two pull-up resistors.
Freescale Semiconductor, Inc...
16.5 Multi-Master IIC Bus Protocol
Normally a standard communication is composed of four parts:
1. START signal,
2. slave address transmission,
3. data transfer, and
4. STOP signal.
These are described briefly in the following sections and illustrated in
Figure 16-2.
9th clock pulse
MSB
SCL
1
1
0
0
0
0
1
9th clock pulse
LSB
MSB
1
1
LSB
1
0
1
0
0
1
1
SDA
Data must be stable
when SCL is HIGH
ACK
START
signal
MSB
SCL
1
LSB
1
0
0
0
0
1
No ACK
STOP
signal
MSB
1
1
LSB
1
0
1
0
0
1
1
SDA
ACK
START
signal
No ACK
Repeated
START
signal
STOP
signal
Figure 16-2. Multi-Master IIC Bus Transmission Signal Diagram
Data Sheet
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Multi-Master IIC Interface (MMIIC)
Multi-Master IIC Bus Protocol
16.5.1 START Signal
Freescale Semiconductor, Inc...
When the bus is free, (i.e. no master device is engaging the bus — both
SCL and SDA lines are at logic high) a master may initiate
communication by sending a START signal. As shown in Figure 16-2, a
START signal is defined as a high to low transition of SDA while SCL is
high. This signal denotes the beginning of a new data transfer (each data
transfer may contain several bytes of data) and wakes up all slaves.
16.5.2 Slave Address Transmission
The first byte transferred immediately after the START signal is the slave
address transmitted by the master. This is a 7-bit calling address
followed by a R/W-bit. The R/W-bit dictates to the slave the desired
direction of the data transfer. A logic 0 indicates that the master wishes
to transmit data to the slave; a logic 1 indicates that the master wishes
to receive data from the slave.
Only the slave with a matched address will respond by sending back an
acknowledge bit by pulling SDA low on the 9th clock cycle.
(See Figure 16-2.)
16.5.3 Data Transfer
Once a successful slave addressing is achieved, the data transfer can
proceed byte by byte in the direction specified by the R/W-bit sent by the
calling master.
Each data byte is 8 bits. Data can be changed only when SCL is low and
must be held stable when SCL is high as shown in Figure 16-2. The
MSB is transmitted first and each byte has to be followed by an
acknowledge bit. This is signalled by the receiving device by pulling the
SDA low on the 9th clock cycle. Therefore, one complete data byte
transfer requires 9 clock cycles.
If the slave receiver does not acknowledge the master, the SDA line
should be left high by the slave. The master can then generate a STOP
signal to abort the data transfer or a START signal (repeated START) to
commence a new transfer.
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Multi-Master IIC Interface (MMIIC)
If the master receiver does not acknowledge the slave transmitter after
a byte has been transmitted, it means an “end of data” to the slave. The
slave should release the SDA line for the master to generate a STOP or
START signal.
Freescale Semiconductor, Inc...
16.5.4 Repeated START Signal
As shown in Figure 16-2, a repeated START signal is used to generate
START signal without first generating a STOP to terminate the
communication. This is used by the master to communicate with another
slave or with the same slave in a different mode (transmit/receive mode)
without releasing the bus.
16.5.5 STOP Signal
The master can terminate the communication by generating a STOP
signal to free the bus. However, the master may generate a START
signal followed by a calling command without first generating a STOP
signal. This is called repeat START. A STOP signal is defined as a low
to high transition of SDA while SCL is at logic high (see Figure 16-2).
16.5.6 Arbitration Procedure
The interface circuit is a multi-master system which allows more than
one master to be connected. If two or more masters try to control the bus
at the same time, a clock synchronization procedure determines the bus
clock. The clock low period is equal to the longest clock low period and
the clock high period is equal to the shortest one among the masters. A
data arbitration procedure determines the priority. A master will lose
arbitration if it transmits a logic 1 while another transmits a logic 0. The
losing master will immediately switch over to slave receive mode and
stops its data and clock outputs. The transition from master to slave will
not generate a STOP condition. Meanwhile a software bit will be set by
hardware to indicates loss of arbitration.
Data Sheet
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Multi-Master IIC Interface (MMIIC)
Multi-Master IIC Bus Protocol
16.5.7 Clock Synchronization
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Since wired-AND logic is performed on SCL line, a high to low transition
on the SCL line will affect the devices connected to the bus. The devices
start counting their low period once a device’s clock has gone low, it will
hold the SCL line low until the clock high state is reached. However, the
change of low to high in this device clock may not change the state of the
SCL line if another device clock is still in its low period. Therefore the
synchronized clock SCL will be held low by the device which last
releases SCL to logic high. Devices with shorter low periods enter a high
wait state during this time. When all devices concerned have counted off
their low period, the synchronized SCL line will be released and go high,
and all devices will start counting their high periods. The first device to
complete its high period will again pull the SCL line low. Figure 16-3
illustrates the clock synchronization waveforms.
WAIT
Start counting high period
SCL1
SCL2
SCL
Internal counter reset
Figure 16-3. Clock Synchronization
16.5.8 Handshaking
The clock synchronization mechanism can be used as a handshake in
data transfer. A slave device may hold the SCL low after completion of
one byte data transfer and will halt the bus clock, forcing the master
clock into a wait state until the slave releases the SCL line.
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Multi-Master IIC Interface (MMIIC)
16.5.9 Packet Error Code
The packet error code (PEC) for the MMIIC interface is in the form a
cyclic redundancy code (CRC). The PEC is generated by hardware for
every transmitted and received byte of data. The transmission of the
generated PEC is controlled by user software.
Freescale Semiconductor, Inc...
The CRC data register, MMCRCDR, contains the generated PEC byte,
with three other bits in the MMIIC control registers and status register
monitoring and controlling the PEC byte.
16.6 MMIIC I/O Registers
These I/O registers control and monitor MMIIC operation:
•
MMIIC address register (MMADR) — $0048
•
MMIIC control register 1 (MMCR1) — $0049
•
MMIIC control register 2 (MMCR2) — $004A
•
MMIIC status register (MMSR) — $004B
•
MMIIC data transmit register (MMDTR) — $004C
•
MMIIC data receive register (MMDRR) — $004D
•
MMIIC CRC data register (MMCRCDR) — $004E
•
MMIIC frequency divide register (MMFDR) — $004F
16.6.1 MMIIC Address Register (MMADR)
Address:
$0048
Bit 7
6
5
4
3
2
1
Bit 0
MMAD7
MMAD6
MMAD5
MMAD4
MMAD3
MMAD2
MMAD1
MMEXTAD
1
0
1
0
0
0
0
0
Read:
Write:
Reset:
Figure 16-4. MMIIC Address Register (MMADR)
Data Sheet
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Multi-Master IIC Interface (MMIIC)
MMIIC I/O Registers
MMAD[7:1] — Multi-Master Address
These seven bits represent the MMIIC interface’s own specific slave
address when in slave mode, and the calling address when in master
mode. Software must update MMAD[7:1] as the calling address while
entering master mode and restore its own slave address after master
mode is relinquished. This register is cleared as $A0 upon reset.
MMEXTAD — Multi-Master Expanded Address
Freescale Semiconductor, Inc...
This bit is set to expand the address of the MMIIC in slave mode.
When set, the MMIIC will acknowledge the following addresses from
a calling master: $MMAD[7:1], 0000000, and 0001100.
Reset clears this bit.
1 = MMIIC responds to the following calling addresses:
$MMAD[7:1], 0000000, and 0001100.
0 = MMIIC responds to address $MMAD[7:1]
For example, when MMADR is configured as:
MMAD7 MMAD6 MMAD5 MMAD4 MMAD3 MMAD2 MMAD1 MMEXTAD
1
1
0
1
0
1
0
1
The MMIIC module will respond to the calling address:
Bit 7
6
5
4
3
2
Bit 1
1
1
0
1
0
1
0
0
0
0
0
0
or the general calling address:
0
0
or the calling address:
Bit 7
6
5
4
3
2
Bit 1
0
0
0
1
1
0
0
Note that bit-0 of the 8-bit calling address is the MMRW bit from the
calling master.
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16.6.2 MMIIC Control Register 1 (MMCR1)
Address:
$0049
Bit 7
6
MMEN
MMIEN
Read:
Write:
Reset:
5
4
0
0
3
2
1
Bit 0
0
MMTXAK REPSEN
MMCRCBYTE
MMCLRBB
0
0
0
0
0
0
0
0
= Unimplemented
Freescale Semiconductor, Inc...
Figure 16-5. MMIIC Control Register 1 (MMCR1)
MMEN — MMIIC Enable
This bit is set to enable the Multi-master IIC module. When
MMEN = 0, module is disabled and all flags will restore to its poweron default states. Reset clears this bit.
1 = MMIIC module enabled
0 = MMIIC module disabled
MMIEN — MMIIC Interrupt Enable
When this bit is set, the MMTXIF, MMRXIF, MMALIF, and MMNAKIF
flags are enabled to generate an interrupt request to the CPU. When
MMIEN is cleared, the these flags are prevented from generating an
interrupt request. Reset clears this bit.
1 = MMTXIF, MMRXIF, MMALIF, and/or MMNAKIF bit set will
generate interrupt request to CPU
0 = MMTXIF, MMRXIF, MMALIF, and/or MMNAKIF bit set will not
generate interrupt request to CPU
MMCLRBB — MMIIC Clear Busy Flag
Writing a logic 1 to this write-only bit clears the MMBB flag.
MMCLRBB always reads as a logic 0. Reset clears this bit.
1 = Clear MMBB flag
0 = No affect on MMBB flag
Data Sheet
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Multi-Master IIC Interface (MMIIC)
MMIIC I/O Registers
MMTXAK — MMIIC Transmit Acknowledge Enable
This bit is set to disable the MMIIC from sending out an acknowledge
signal to the bus at the 9th clock bit after receiving 8 data bits. When
MMTXAK is cleared, an acknowledge signal will be sent at the 9th
clock bit. Reset clears this bit.
1 = MMIIC does not send acknowledge signals at 9th clock bit
0 = MMIIC sends acknowledge signal at 9th clock bit
REPSEN — Repeated Start Enable
Freescale Semiconductor, Inc...
This bit is set to enable repeated START signal to be generated when
in master mode transfer (MMAST = 1). The REPSEN bit is cleared by
hardware after the completion of repeated START signal or when the
MMAST bit is cleared. Reset clears this bit.
1 = Repeated START signal will be generated if MMAST bit is set
0 = No repeated START signal will be generated
MMCRCBYTE — MMIIC CRC Byte
In receive mode, this bit is set by software to indicate that the next
receiving byte will be the packet error checking (PEC) data.
In master receive mode, after completion of CRC generation on the
received PEC data, an acknowledge signal is sent if MMTXAK = 0; no
acknowledge is sent If MMTXAK = 1.
In slave receive mode, no acknowledge signal is sent if a CRC error
is detected on the received PEC data. If no CRC error is detected, an
acknowledge signal is sent if MMTXAK = 0; no acknowledge is sent If
MMTXAK = 1.
Under normal operation, the user software should clear MMTXAK bit
before setting MMCRCBYTE bit to ensure that an acknowledge signal
is sent when no CRC error is detected.
The MMCRCBYTE bit should not be set in transmit mode. This bit is
cleared by the next START signal. Reset also clears this bit.
1 = Next receiving byte is the packet error checking (PEC) data
0 = Next receiving byte is not PEC data
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16.6.3 MMIIC Control Register 2 (MMCR2)
Address:
$004A
Bit 7
6
Read: MMALIF MMNAKIF
Write:
0
0
Reset:
0
0
5
4
3
MMAST
MMRW
0
0
MMBB
0
2
1
0
0
Bit 0
MMCRCEF
0
0
Unaffected
= Unimplemented
Freescale Semiconductor, Inc...
Figure 16-6. MMIIC Control Register 2 (MMCR2)
MMALIF — Arbitration Loss Interrupt Flag
This flag is set when software attempt to set MMAST but the MMBB
has been set by detecting the start condition on the lines or when the
MMIIC is transmitting a "1" to SDA line but detected a "0" from SDA
line in master mode — an arbitration loss. This bit generates an
interrupt request to the CPU if the MMIEN bit in MMCR1 is set. This
bit is cleared by writing "0" to it or by reset.
1 = Lost arbitration in master mode
0 = No arbitration lost
MMNAKIF — No AcKnowledge Interrupt Flag (Master Mode)
This flag is only set in master mode (MMAST = 1) when there is no
acknowledge bit detected after one data byte or calling address is
transferred. This flag also clears MMAST. MMNAKIF generates an
interrupt request to CPU if the MMIEN bit in MMCR1 is set. This bit is
cleared by writing "0" to it or by reset.
1 = No acknowledge bit detected
0 = Acknowledge bit detected
MMBB — MMIIC Bus Busy Flag
This flag is set after a start condition is detected (bus busy), and is
cleared when a stop condition (bus idle) is detected or the MMIIC is
disabled. Reset clears this bit.
1 = Start condition detected
0 = Stop condition detected or MMIIC is disabled
Data Sheet
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Multi-Master IIC Interface (MMIIC)
MMIIC I/O Registers
MMAST — MMIIC Master Control
Freescale Semiconductor, Inc...
This bit is set to initiate a master mode transfer. In master mode, the
module generates a start condition to the SDA and SCL lines,
followed by sending the calling address stored in MMADR.
When the MMAST bit is cleared by MMNAKIF set (no acknowledge)
or by software, the module generates the stop condition to the lines
after the current byte is transmitted.
If an arbitration loss occurs (MMALIF = 1), the module reverts to slave
mode by clearing MMAST, and releasing SDA and SCL lines
immediately.
This bit is cleared by writing "0" to it or by reset.
1 = Master mode operation
0 = Slave mode operation
MMRW — MMIIC Master Read/Write
This bit is transmitted out as bit 0 of the calling address when the
module sets the MMAST bit to enter master mode. The MMRW bit
determines the transfer direction of the data bytes that follows. When
it is "1", the module is in master receive mode. When it is "0", the
module is in master transmit mode. Reset clears this bit.
1 = Master mode receive
0 = Master mode transmit
MMCRCEF — MMIIC CRC Error Flag
This flag is set when a CRC error is detected, and cleared when no
CRC error is detected. The MMCRCEF is only meaningful after
receiving a PEC data. This flag is unaffected by reset.
1 = CRC error detected on PEC byte
0 = No CRC error detected on PEC byte
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16.6.4 MMIIC Status Register (MMSR)
Address:
$004B
Bit 7
Read: MMRXIF
6
MMTXIF
Write:
0
0
Reset:
0
0
5
4
3
2
1
Bit 0
MMATCH MMSRW MMRXAK MMCRCBF MMTXBE MMRXBF
0
0
1
0
1
0
= Unimplemented
Freescale Semiconductor, Inc...
Figure 16-7. MMIIC Status Register (MMSR)
MMRXIF — MMIIC Receive Interrupt Flag
This flag is set after the data receive register (MMDRR) is loaded with
a new received data. Once the MMDRR is loaded with received data,
no more received data can be loaded to the MMDRR register until the
CPU reads the data from the MMDRR to clear MMRXBF flag.
MMRXIF generates an interrupt request to CPU if the MMIEN bit in
MMCR is also set. This bit is cleared by writing "0" to it or by reset; or
when the MMEN = 0.
1 = New data in data receive register (MMDRR)
0 = No data received
MMTXIF — MMIIC Transmit Interrupt Flag
This flag is set when data in the data transmit register (MMDTR) is
downloaded to the output circuit, and that new data can be written to
the MMDTR. MMTXIF generates an interrupt request to CPU if the
MMIEN bit in MMCR is also set. This bit is cleared by writing "0" to it
or when the MMEN = 0.
1 = Data transfer completed
0 = Data transfer in progress
MMATCH — MMIIC Address Match Flag
This flag is set when the received data in the data receive register
(MMDRR) is a calling address which matches with the address or its
extended addresses (MMEXTAD = 1) specified in the address
register (MMADR). The MMATCH flag is set at the 9th clock of the
calling address and will be cleared on the 9th clock of the next
receiving data. Note: slave transmits do not clear MMATCH.
Data Sheet
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Multi-Master IIC Interface (MMIIC)
MMIIC I/O Registers
1 = Received address matches MMADR
0 = Received address does not match
MMSRW — MMIIC Slave Read/Write Select
Freescale Semiconductor, Inc...
This bit indicates the data direction when the module is in slave mode.
It is updated after the calling address is received from a master
device. MMSRW = 1 when the calling master is reading data from the
module (slave transmit mode). MMSRW = 0 when the master is
writing data to the module (receive mode).
1 = Slave mode transmit
0 = Slave mode receive
MMRXAK — MMIIC Receive Acknowledge
When this bit is cleared, it indicates an acknowledge signal has been
received after the completion of eight data bits transmission on the
bus. When MMRXAK is set, it indicates no acknowledge signal has
been detected at the 9th clock; the module will release the SDA line
for the master to generate STOP or repeated START condition. Reset
sets this bit.
1 = No acknowledge signal received at 9th clock
0 = Acknowledge signal received at 9th clock
MMCRCBF — CRC Data Buffer Full Flag
This flag is set when the CRC data register (MMCRCDR) is loaded
with a CRC byte for the current received or transmitted data.
In transmit mode, after a byte of data has been sent (MMTXIF = 1),
the MMCRCBF will be set when the CRC byte has been generated
and ready in the MMCRCDR. The content of the MMCRCDR should
be copied to the MMDTR for transmission.
In receive mode, the MMCRCBF is set when the CRC byte has been
generated and ready in MMCRCDR, for the current byte of received
data.
The MMCRCBF bit is cleared when the CRC data register is read.
Reset also clears this bit.
1 = Data ready in CRC data register (MMCRCDR)
0 = Data not ready in CRC data register (MMCRCDR)
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Multi-Master IIC Interface (MMIIC)
MMTXBE — MMIIC Transmit Buffer Empty
This flag indicates the status of the data transmit register (MMDTR).
When the CPU writes the data to the MMDTR, the MMTXBE flag will
be cleared. MMTXBE is set when MMDTR is emptied by a transfer of
its data to the output circuit. Reset sets this bit.
1 = Data transmit register empty
0 = Data transmit register full
Freescale Semiconductor, Inc...
MMRXBF — MMIIC Receive Buffer Full
This flag indicates the status of the data receive register (MMDRR).
When the CPU reads the data from the MMDRR, the MMRXBF flag
will be cleared. MMRXBF is set when MMDRR is full by a transfer of
data from the input circuit to the MMDRR. Reset clears this bit.
1 = Data receive register full
0 = Data receive register empty
16.6.5 MMIIC Data Transmit Register (MMDTR)
Address:
$004C
Bit 7
6
5
4
3
2
1
Bit 0
MMTD7
MMTD6
MMTD5
MMTD4
MMTD3
MMTD2
MMTD1
MMTD0
0
0
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 16-8. MMIIC Data Transmit Register (MMDTR)
When the MMIIC module is enabled, MMEN = 1, data written into this
register depends on whether module is in master or slave mode.
In slave mode, the data in MMDTR will be transferred to the output circuit
when:
Data Sheet
•
the module detects a matched calling address (MMATCH = 1),
with the calling master requesting data (MMSRW = 1); or
•
the previous data in the output circuit has be transmitted and the
receiving master returns an acknowledge bit, indicated by a
received acknowledge bit (MMRXAK = 0).
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Multi-Master IIC Interface (MMIIC)
MMIIC I/O Registers
If the calling master does not return an acknowledge bit (MMRXAK = 1),
the module will release the SDA line for master to generate a STOP or
repeated START condition. The data in the MMDTR will not be
transferred to the output circuit until the next calling from a master. The
transmit buffer empty flag remains cleared (MMTXBE = 0).
Freescale Semiconductor, Inc...
In master mode, the data in MMDTR will be transferred to the output
circuit when:
•
the module receives an acknowledge bit (MMRXAK = 0), after
setting master transmit mode (MMRW = 0), and the calling
address has been transmitted; or
•
the previous data in the output circuit has be transmitted and the
receiving slave returns an acknowledge bit, indicated by a
received acknowledge bit (MMRXAK = 0).
If the slave does not return an acknowledge bit (MMRXAK = 1), the
master will generate a STOP or repeated START condition. The data in
the MMDTR will not be transferred to the output circuit. The transmit
buffer empty flag remains cleared (MMTXBE = 0).
The sequence of events for slave transmit and master transmit are
illustrated in Figure 16-12.
16.6.6 MMIIC Data Receive Register (MMDRR)
Address:
$004D
Bit 7
Read: MMRD7
6
5
4
3
2
1
Bit 0
MMRD6
MMRD5
MMRD4
MMRD3
MMRD2
MMRD1
MMRD0
0
0
0
0
0
0
0
Write:
Reset:
0
= Unimplemented
Figure 16-9. MMIIC Data Receive Register (MMDRR)
When the MMIIC module is enabled, MMEN = 1, data in this read-only
register depends on whether module is in master or slave mode.
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Multi-Master IIC Interface (MMIIC)
In slave mode, the data in MMDRR is:
•
the calling address from the master when the address match flag
is set (MMATCH = 1); or
•
the last data received when MMATCH = 0.
In master mode, the data in the MMDRR is:
Freescale Semiconductor, Inc...
•
the last data received.
When the MMDRR is read by the CPU, the receive buffer full flag is
cleared (MMRXBF = 0), and the next received data is loaded to the
MMDRR. Each time when new data is loaded to the MMDRR, the
MMRXIF interrupt flag is set, indicating that new data is available in
MMDRR.
The sequence of events for slave receive and master receive are
illustrated in Figure 16-12.
16.6.7 MMIIC CRC Data Register (MMCRCDR)
Address:
$004E
Bit 7
6
5
4
3
2
1
Bit 0
Read: MMCRCD7 MMCRCD6 MMCRCD5 MMCRCD4 MMCRCD3 MMCRCD2 MMCRCD1 MMCRCD0
Write:
Reset:
0
0
0
0
0
0
0
0
= Unimplemented
Figure 16-10. MMIIC CRC Data Register (MMCRCDR)
When the MMIIC module is enabled, MMEN = 1, and the CRC buffer full
flag is set (MMCRCBF = 1), data in this read-only register contains the
generated CRC byte for the last byte of received or transmitted data.
A CRC byte is generated for each received and transmitted data byte
and loaded to the CRC data register. The MMCRCBF bit will be set to
indicate the CRC byte is ready in the CRC data register.
Reading the CRC data register clears the MMCRCBF bit. If the CRC
data register is not read, the MMCRCBF bit will be cleared by hardware
before the next CRC byte is loaded.
Data Sheet
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Multi-Master IIC Interface (MMIIC)
MMIIC I/O Registers
16.6.8 MMIIC Frequency Divider Register (MMFDR)
Address:
Read:
$004F
Bit 7
6
5
4
3
0
0
0
0
0
2
1
Bit 0
MMBR2
MMBR1
MMBR0
1
0
0
Write:
Reset:
0
0
0
0
0
Freescale Semiconductor, Inc...
= Unimplemented
Figure 16-11. MMIIC Frequency Divider Register (MMFDR)
The three bits in the frequency divider register (MMFDR) selects the
divider to divide the bus clock to the desired baud rate for the MMIIC data
transfer.
Table 16-2 shows the divider values for MMBR[2:0].
Table 16-2. MMIIC Baud Rate Selection
MMIIC Baud Rates for Bus Clocks:
MMBR2
MMBR1
MMBR0
Divider
8MHz
4MHz
2MHz
1MHz
0
0
0
20
400kHz
200kHz
100kHz
50kHz
0
0
1
40
200kHz
100kHz
50kHz
25kHz
0
1
0
80
100kHz
50kHz
25kHz
12.5kHz
0
1
1
160
50kHz
25kHz
12.5kHz
6.25kHz
1
0
0
320
25kHz
12.5kHz
6.25kHz
3.125kHz
1
0
1
640
12.5kHz
6.25kHz
3.125kHz
1.5625kHz
1
1
0
1280
6.25kHz
3.125kHz
1.5625kHz
0.78125kHz
1
1
1
2560
3.125kHz
1.5625kHz
0.78125kHz
0.3906kHz
NOTE:
The frequency of the MMIIC baud rate is only guaranteed for 100kHz to
10kHz. The divider is available for the flexibility on bus frequency
selection.
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Multi-Master IIC Interface (MMIIC)
16.7 Program Algorithm
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When the MMIIC module detects an arbitration loss in master mode, it
releases both SDA and SCL lines immediately. But if there are no further
STOP conditions detected, the module will hang up. Therefore, it is
recommended to have time-out software to recover from this condition.
The software can start the time-out counter by looking at the MMBB (bus
busy) flag and reset the counter on the completion of one byte
transmission. If a time-out has occurred, software can clear the MMEN
bit (disable MMIIC module) to release the bus, and hence clear the
MMBB flag. This is the only way to clear the MMBB flag by software if
the module hangs up due to a no STOP condition received. The MMIIC
can resume operation again by setting the MMEN bit.
Data Sheet
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Multi-Master IIC Interface (MMIIC)
Program Algorithm
16.7.1 Data Sequence
(a) Master Transmit Mode
START
Address
0
TX Data1
MMTXBE=1
MMTXIF=1
Data2 → MMDTR
MMTXBE=0
MMRW=0
MMAST=1
Data1 → MMDTR
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ACK
ACK
MMTXBE=1
MMTXIF=1
Data3 → MMDTR
TX DataN
ACK
STOP
MMTXBE=1 MMNAKIF=1
MMTXIF=1 MMAST=0
DataN+2 → MMDTR MMTXBE=0
(b) Master Receive Mode
START
Address
1
ACK
RX Data1
ACK
Data1 → MMDRR
MMRXIF=1
MMRXBF=1
MMRXBF=0
MMRW=1
MMAST=1
MMTXBE=0
(dummy data → MMDTR)
RX DataN
NAK
STOP
DataN → MMDRR MMNAKIF=1
MMRXIF=1 MMAST=0
MMRXBF=1
(c) Slave Transmit Mode
START
Address
1
MMTXBE=1
MMRXBF=0
ACK
TX Data1
MMRXIF=1
MMRXBF=1
MMATCH=1
MMSRW=1
Data1 → MMDTR
ACK
MMTXBE=1
MMTXIF=1
Data2 → MMDTR
TX DataN
NAK
STOP
MMTXBE=1 MMNAKIF=1
MMTXIF=1 MMTXBE=0
DataN+2 → MMDTR
(d) Slave Receive Mode
START
Address
0
MMTXBE=0
MMRXBF=0
ACK
RX Data1
MMRXIF=1
MMRXBF=1
MMATCH=1
MMSRW=0
ACK
Data1 → MMDRR
MMRXIF=1
MMRXBF=1
RX DataN
ACK
STOP
DataN → MMDRR
MMRXIF=1
MMRXBF=1
Shaded data packets indicate transmissions by the MCU
Figure 16-12. Data Transfer Sequences for Master/Slave Transmit/Receive Modes
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Multi-Master IIC Interface (MMIIC)
16.8 SMBus Protocols with PEC and without PEC
Following is a description of the various MMIIC bus protocols with and
without a packet error code (PEC).
16.8.1 Quick Command
1
7
1
1
Slave Address RW ACK
START
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1
Master to Slave
STOP
Start Condition
Slave to Master
Stop Condition
Command Bit
Acknowledge
Figure 16-13. Quick Command
16.8.2 Send Byte
START
Slave Address
W
ACK
Command Code
ACK
W
ACK
Command Code
ACK
STOP
(a) Send Byte Protocol
START
Slave Address
PEC
ACK
STOP
NAK
STOP
(b) Send Byte Protocol with PEC
Figure 16-14. Send Byte
16.8.3 Receive Byte
START
Slave Address
R
ACK
Data Byte
NAK
R
ACK
Data Byte
ACK
STOP
(a) Receive Byte Protocol
START
Slave Address
PEC
(b) Receive Byte Protocol with PEC
Figure 16-15. Receive Byte
Data Sheet
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Multi-Master IIC Interface (MMIIC)
SMBus Protocols with PEC and without PEC
16.8.4 Write Byte/Word
START
Slave Address
W ACK
Command Code
ACK
Data Byte
ACK
W ACK
Command Code
ACK
Data Byte
ACK
PEC
ACK
STOP
W ACK
Command Code
ACK
Data Byte Low
ACK
Data Byte High
ACK
STOP
W ACK
Command Code
ACK
Data Byte Low
ACK
Data Byte High
ACK
STOP
(a) Write Byte Protocol
START
Slave Address
(b) Write Byte Protocol with PEC
START
Slave Address
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(c) Write Word Protocol
START
Slave Address
PEC
ACK
STOP
(d) Write Word Protocol with PEC
Figure 16-16. Write Byte/Word
16.8.5 Read Byte/Word
START
Slave Address
W ACK
Command Code
ACK
START
Slave Address
R
ACK
Data Byte
NAK
W ACK
Command Code
ACK
START
Slave Address
R
ACK
Data Byte
ACK
Command Code
ACK
START
Slave Address
R
ACK
Data Byte Low
ACK
Command Code
ACK
START
Slave Address
R
ACK
Data Byte Low
ACK
STOP
(a) Read Byte Protocol
START
Slave Address
PEC
NAK
STOP
(b) Read Byte Protocol with PEC
START
Slave Address
Data Byte High
NAK
W ACK
STOP
(c) Read Word Protocol
START
Slave Address
Data Byte High
ACK
W ACK
PEC
NAK
STOP
(d) Read Word Protocol with PEC
Figure 16-17. Read Byte/Word
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Multi-Master IIC Interface (MMIIC)
16.8.6 Process Call
START
Slave Address
W ACK
START
Slave Address
R
START
Slave Address
W ACK
START
Slave Address
R
ACK
Command Code
ACK
Data Byte Low
ACK
Data Byte Low
ACK
Data Byte High
NAK
Command Code
ACK
Data Byte Low
ACK
Data Byte Low
ACK
Data Byte High
ACK
Data Byte High
ACK
STOP
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(a) Process Call
ACK
Data Byte High
ACK
PEC
STOP
NAK
STOP
(b) Process Call with PEC
Figure 16-18. Process Call
16.8.7 Block Read/Write
START
Slave Address
Data Byte 2
ACK
W ACK
Command Code
Data Byte N
ACK
ACK
Byte Count = N
ACK
Data Byte 1
ACK
ACK
Data Byte 1
ACK
R
ACK
Byte Count = N
ACK
R
ACK
Byte Count = N
ACK
STOP
(a) Block Read
START
Slave Address
Data Byte 2
ACK
W ACK
Command Code
Data Byte N
ACK
Byte Count = N
PEC
ACK
ACK
STOP
(b) Block Read with PEC
START
Slave Address
Data Byte 1
ACK
W ACK
Command Code
Data Byte 2
ACK
ACK
START
Data Byte N
Slave Address
NAK
STOP
(c) Block Write
START
Slave Address
Data Byte 1
ACK
W ACK
Command Code
Data Byte 2
ACK
ACK
START
Data Byte N
Slave Address
ACK
PEC
NAK
STOP
(d) Block Write with PEC
Figure 16-19. Block Read/Write
Data Sheet
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Multi-Master IIC Interface (MMIIC)
SMBus Protocol Implementation
16.9 SMBus Protocol Implementation
Shaded data packets indicate transmissions by the MCU
MASTER MODE
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START
Address
0 ACK
Command
ACK START
Address
1 ACK
RX Data1
ACK
ACK
RX DataN
NAK STOP
OPERATION:
Prepare for repeated START
OPERATION:
Get ready to receive data
OPERATION:
Read received data
OPERATION:
Generate STOP
FLAGS:
MMTXIF set
MMRXAK clear
FLAGS:
MMTXIF set
MMRXAK clear
FLAGS:
MMRXIF set
FLAGS:
MMRXIF set
ACTION:
1. Set MMRW
2. Set REPSEN
3. Clear MMTXAK
4. Load dummy ($FF) to MMDTR
ACTION:
Load dummy ($FF) to MMDTR
ACTION:
Read Data1 from MMDRR
ACTION:
Read DataN from MMDRR
OPERATION:
Read received data and prepare for STOP
OPERATION:
Prepare for Master mode
FLAGS:
MMRXIF set
ACTION:
1. Load slave address to MMADR
2. Clear MMRW
3. Load command to MMDTR
4. Set MMAST
ACTION:
1. Set MMTXAK
2. Read Data(N-1) from MMDRR
3. Clear MMAST
SLAVE MODE
START
Address
0 ACK
Command
ACK START
Address
1 ACK
OPERATION:
Slave address match and
check for data direction
OPERATION:
Slave address match and
get ready to transmit data
FLAGS:
MMRXIF set
MMATCH set
MMSRW depends on 8th
bit of calling address byte
ACTION:
1. Check MMSRW
2. Read Slave address
FLAGS:
MMRXIF set
MMATCH set
MMSRW depends on 8th
bit of calling address byte
OPERATION:
Prepare for Slave mode
ACTION:
1. Load slave address to MMADR
2. Clear MMTXAK
3. Clear MMAST
TX Data1
ACK
ACK
TX DataN
NAK STOP
OPERATION:
Transmit data
OPERATION:
Last data sent
FLAGS:
MMTXIF set
MMRXAK clear
FLAGS:
MMTXIF set
MMRXAK set
ACTION:
Load Data3 to MMDTR
ACTION:
Load dummy ($FF) to MMDTR
ACTION:
Check MMSRW
OPERATION:
Read and decode received command
FLAGS:
MMRXIF set
MMATCH clear
ACTION:
Load Data1 to MMDTR
OPERATION:
Transmit data
OPERATION:
Last data is going to be sent
FLAGS:
MMTXIF set
FLAGS:
MMTXIF set
MMRXAK clear
ACTION:
Load Data2 to MMDTR
ACTION:
Load dummy ($FF) to MMDTR
Figure 16-20. SMBus Protocol Implementation
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Multi-Master IIC Interface (MMIIC)
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Section 17. Analog-to-Digital Converter (ADC)
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17.1 Introduction
This section describes the analog-to-digital converter (ADC). The ADC
is a 8-channel 10-bit linear successive approximation ADC.
17.2 Features
Features of the ADC module include:
•
Fourteen channels with multiplexed input
•
High impedance buffered input
•
Linear successive approximation with monotonicity
•
10-bit resolution
•
Single or continuous conversion
•
Auto-scan conversion on four channels
•
Conversion complete flag or conversion complete interrupt
•
Selectable ADC clock
•
Conversion result justification
– 8-bit truncated mode
– Right justified mode
– Left justified mode
– Left justified sign mode
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Analog-to-Digital Converter (ADC)
Addr.
6
5
4
3
2
1
Bit 0
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
0
0
1
1
1
1
1
ADIV2
ADIV1
ADIV0
ADICLK
MODE1
MODE0
0
0
0
0
0
0
0
1
0
0
Read:
ADC Data Register High 0
$0059
Write:
(ADRH0)
Reset:
ADx
ADx
ADx
ADx
ADx
ADx
ADx
ADx
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 0
$005A
Write:
(ADRL0)
Reset:
ADx
ADx
ADx
ADx
ADx
ADx
ADx
ADx
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 1
$005B
Write:
(ADRL1)
Reset:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 2
$005C
Write:
(ADRL3)
Reset:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 3
$005D
Write:
(ADRL3)
Reset:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
0
0
0
0
0
AUTO1
AUTO0
ASCAN
0
0
0
0
0
0
0
0
$0057
Register Name
Read:
ADC Status and Control
Register Write:
(ADSCR)
Reset:
Read:
ADC Clock Control
Register Write:
(ADICLK)
Reset:
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$0058
$005E
Bit 7
Read:
ADC Auto-scan Control
Register Write:
(ADASCR)
Reset:
COCO
= Unimplemented
R
R
= Reserved
Figure 17-1. ADC I/O Register Summary
Data Sheet
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Analog-to-Digital Converter (ADC)
Functional Description
17.3 Functional Description
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The ADC provides eight pins for sampling external sources at pins
PTA0/ADC0–PTA7/ADC7. An analog multiplexer allows the single ADC
converter to select one of eight ADC channels as ADC voltage in
(VADIN). VADIN is converted by the successive approximation registerbased analog-to-digital converter. When the conversion is completed,
ADC places the result in the ADC data register, high and low byte
(ADRH0 and ADRL0), and sets a flag or generates an interrupt.
An additional three ADC data registers (ADRL1–ADRL3) are available to
store the individual converted data for ADC channels ADC1–ADC3
when the auto-scan mode is enabled. Data from channel ADC0 is stored
in ADRL0 in the auto-scan mode.
Figure 17-2 shows the structure of the ADC module.
17.3.1 ADC Port I/O Pins
PTA0–PTA7 are general-purpose I/O pins that are shared with the ADC
channels. The channel select bits, ADCH[4:0], define which ADC
channel/port pin will be used as the input signal. The ADC overrides the
port I/O logic by forcing that pin as input to the ADC. The remaining ADC
channels/port pins are controlled by the port I/O logic and can be used
as general-purpose I/O. Writes to the port data register or data direction
register will not have any affect on the port pin that is selected by the
ADC. Read of a port pin which is in use by the ADC will return the pin
condition if the corresponding DDR bit is at logic 0. If the DDR bit is at
logic 1, the value in the port data latch is read.
17.3.2 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 VREFL, the ADC
converts it to $000. Input voltages between VREFH and VREFL are a
straight-line linear conversion. All other input voltages will result in $3FF
if greater than VREFH and $000 if less than VREFL.
NOTE:
Input voltage should not exceed the analog supply voltages.
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Analog-to-Digital Converter (ADC)
INTERNAL
DATA BUS
READ DDRAx
DISABLE
WRITE DDRAx
DDRAx
RESET
WRITE PTAx
PTAx
PTAx/ADCx
Freescale Semiconductor, Inc...
READ PTAx
ADC0–ADC7
(8 CHANNELS)
ADC DATA REGISTERS
DISABLE
ADRH0 ADRL0
ADRL1
ADRL2
VREFH
ADRL3
INTERRUPT
LOGIC
AIEN
VREFL
ADC
VOLTAGE IN
(VADIN)
CONVERSION
COMPLETE
10-BIT ADC
CHANNEL
SELECT
ADCICLK
COCO
MUX
CGMXCLK
BUS CLOCK
ASCAN
CLOCK
GENERATOR
ADCH[4:0]
ADIV[2:0]
ADICLK
2-BIT UP-COUNTER
AUTO[1:0]
Figure 17-2. ADC Block Diagram
Data Sheet
MC68HC908AP Family — Rev. 2.5
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MOTOROLA
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Analog-to-Digital Converter (ADC)
Functional Description
17.3.3 Conversion Time
Conversion starts after a write to the ADSCR. One conversion will take
between 16 and 17 ADC clock cycles, therefore:
Conversion time =
16 to17 ADC cycles
ADC frequency
Number of bus cycles = conversion time × bus frequency
Freescale Semiconductor, Inc...
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 the ADICLK bit located in the ADC clock
register. The divide ratio is selected by the ADIV[2:0] bits.
For example, if a 4MHz CGMXCLK is selected as the ADC input clock
source, with a divide-by-four prescale, and the bus speed is set at 2MHz:
Conversion time =
16 to17 ADC cycles
= 16 to 17 µs
4MHz ÷ 4
Number of bus cycles = 16 µs × 2MHz = 32 to 34 cycles
NOTE:
The ADC frequency must be between fADIC minimum and fADIC
maximum to meet A/D specifications. (See 24.5 5V DC Electrical
Characteristics.).
Since an ADC cycle may be comprised of several bus cycles (four in the
previous 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.
17.3.4 Continuous Conversion
In the continuous conversion mode, the ADC continuously converts the
selected channel, filling the ADC data register 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 each conversion and
can be cleared by writing to the ADC status and control register or
reading of the ADRL0 data register.
MC68HC908AP Family — Rev. 2.5
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Analog-to-Digital Converter (ADC)
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17.3.5 Auto-Scan Mode
In auto-scan mode, the ADC input channel is selected by the value of the
2-bit up-counter, instead of the channel select bits, ADCH[4:0]. The
value of the counter also defines the data register ADRLx to be used to
store the conversion result. When ASCAN bit is set, a write to ADC
status and control register (ADSCR) will reset the auto-scan up-counter
and ADC conversion will start on the channel 0 up to the channel number
defined by the integer value of AUTO[1:0]. After a channel conversion is
completed, data is stored in ADRLx and the COCO-bit will be set. The
counter value will be incremented by 1 and a new conversion will start.
This process will continue until the counter value reaches the value of
AUTO[1:0]. When this happens, it indicates that the current channel is
the last channel to be converted. Upon the completion on the last
channel, the counter value will not be incremented and no further
conversion will be performed. To start another auto-scan cycle, a write
to ADSCR must be performed.
NOTE:
The system only provides 8-bit data storage in auto-scan code, user
must clear MODE[1:0] bits to select 8-bit truncation mode before
entering auto-scan mode.
It is recommended that user should disable the auto-scan function
before switching channel and also before entering STOP mode.
17.3.6 Result Justification
The conversion result may be formatted in four different ways.
•
Left justified
•
Right justified
•
Left justified sign data mode
•
8-bit truncation
All four of these modes are controlled using MODE0 and MODE1 bits
located in the ADC clock control register (ADICLK).
Data Sheet
MC68HC908AP Family — Rev. 2.5
350
MOTOROLA
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Analog-to-Digital Converter (ADC)
Functional Description
Freescale Semiconductor, Inc...
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 least significant two
bits, located in the ADC data register low (ADRL) can be ignored.
However, you must read ADRL 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 LSB bits in ADC data register
low (ADRL). This mode of operation typically is 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
is used when compatibility with 8-bit ADC designs are required. No
interlocking between ADRH and ADRL is present.
17.3.7 Data Register Interlocking
Reading ADRH in any 10-bit mode latches the contents of ADRL until
ADRL is read. Until ADRL is read all subsequent ADC results will be lost.
This register interlocking can also be reset by a write to the ADC status
and control register, or ADC clock control register. A power-on reset or
reset will also clear the interlocking. Note that an external conversion
request will not reset the lock.
17.3.8 Monotonicity
The conversion process is monotonic and has no missing codes.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Analog-to-Digital Converter (ADC)
17.4 Interrupts
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When the AIEN bit is set, the ADC module is capable of generating a
CPU interrupt after each ADC conversion or after an auto-scan
conversion cycle. 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. The interrupt vector is defined in Table 2-1 .
Vector Addresses.
17.5 Low-Power Modes
The STOP and WAIT instructions put the MCU in low powerconsumption standby modes.
17.5.1 Wait Mode
The ADC continues normal operation in 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 the ADCH[4:0] bits to logic 1’s before executing the
WAIT instruction.
17.5.2 Stop Mode
The ADC module is inactive after the execution of a STOP instruction.
Any pending conversion is aborted. ADC conversions resume when the
MCU exits stop mode. Allow one conversion cycle to stabilize the analog
circuitry before attempting a new ADC conversion after exiting stop
mode.
17.6 I/O Signals
The ADC module has eight channels shared with port A I/O pins.
Data Sheet
MC68HC908AP Family — Rev. 2.5
352
MOTOROLA
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Analog-to-Digital Converter (ADC)
I/O Signals
17.6.1 ADC Voltage In (VADIN)
VADIN is the input voltage signal from one of the eight ADC channels to
the ADC module.
Freescale Semiconductor, Inc...
17.6.2 ADC Analog Power Pin (VDDA)
The ADC analog portion uses VDDA as its power pin. Connect the VDDA
pin to the same voltage potential as VDD. External filtering may be
necessary to ensure clean VDDA for good results.
NOTE:
Route VDDA carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
17.6.3 ADC Analog Ground Pin (VSSA)
The ADC analog portion uses VSSA as its ground pin. Connect the VSSA
pin to the same voltage potential as VSS.
17.6.4 ADC Voltage Reference High Pin (VREFH)
VREFH is the power supply for setting the reference voltage VREFH.
Connect the VREFH pin to the same voltage potential as VDDA. There will
be a finite current associated with VREFH (see Section 24. Electrical
Specifications).
NOTE:
Route VREFH carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
17.6.5 ADC Voltage Reference Low Pin (VREFL)
VREFL is the lower reference supply for the ADC. Connect the VREFL pin
to the same voltage potential as VSSA. There will be a finite current
associated with VREFL (see Section 24. Electrical Specifications).
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Analog-to-Digital Converter (ADC)
17.7 I/O Registers
Freescale Semiconductor, Inc...
These I/O registers control and monitor ADC operation:
•
ADC status and control register (ADSCR) — $0057
•
ADC clock control register (ADICLK) — $0058
•
ADC data register high:low 0 (ADRH0:ADRL0) — $0059:$005A
•
ADC data register low 1–3 (ADRL1–ADRL3) — $005B–$005D
•
ADC auto-scan control register (ADASCR) — $005E
17.7.1 ADC Status and Control Register
Function of the ADC status and control register is described here.
Address:
$0057
Read:
COCO
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
0
1
1
1
1
1
Write:
Reset:
0
Figure 17-3. ADC Status and Control Register (ADSCR)
COCO — Conversions Complete Bit
When the AIEN bit is a logic 0, the COCO is a read-only bit which is
set each time a conversion is completed. This bit is cleared whenever
the ADSCR is written, or whenever the ADC clock control register is
written, or whenever the ADC data register low, ADRLx, is read.
If the AIEN bit is logic 1, the COCO bit always read as logic 0. ADC
interrupt will be generated at the end if an ADC conversion. Reset
clears the COCO bit.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0)/CPU interrupt (AIEN=1)
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,
ADR0, is read or the ADSCR is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
Data Sheet
MC68HC908AP Family — Rev. 2.5
354
MOTOROLA
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Analog-to-Digital Converter (ADC)
I/O Registers
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the
ADC data 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
Freescale Semiconductor, Inc...
This bit should not be set when auto-scan mode is enabled; i.e. when
ASCAN=1.
ADCH[4:0] — ADC Channel Select Bits
ADCH[4:0] form a 5-bit field which is used to select one of the ADC
channels when not in auto-scan mode. The five channel select bits
are detailed in Table 17-1.
NOTE:
Care should be taken when using a port pin as both an analog and a
digital input simultaneously to prevent switching noise from corrupting
the analog signal. Recovery from the disabled state requires one
conversion cycle to stabilize.
Table 17-1. MUX Channel Select
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
ADC Channel
Input Select
0
0
0
0
0
ADC0
PTA0
0
0
0
0
1
ADC1
PTA1
0
0
0
1
0
ADC2
PTA2
0
0
0
1
1
ADC3
PTA3
0
0
1
0
0
ADC4
PTA4
0
0
1
0
1
ADC5
PTA5
0
0
1
1
0
ADC6
PTA6
0
0
1
1
1
ADC7
PTA7
0
↓
1
1
↓
1
0
↓
1
0
↓
0
0
↓
0
ADC8
↓
ADC28
Reserved
1
1
1
0
1
ADC29
VREFH (see Note 2)
1
1
1
1
0
ADC30
VREFL (see Note 2)
1
1
1
1
1
ADC powered-off
—
NOTES:
1. If any unused channels are selected, the resulting ADC conversion will be unknown.
2. The voltage levels supplied from internal reference nodes as specified in the table are used to verify the operation of
the ADC converter both in production test and for user applications.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Analog-to-Digital Converter (ADC)
17.7.2 ADC Clock Control Register
The ADC clock control register (ADICLK) selects the clock frequency for
the ADC.
Address:
$0058
Read:
0
ADIV2
ADIV1
ADIV0
ADICLK
MODE1
0
MODE0
Write:
Reset:
R
0
0
0
0
Freescale Semiconductor, Inc...
= Unimplemented
0
1
R
0
0
= Reserved
Figure 17-4. ADC Clock Control Register (ADICLK)
ADIV[2:0] — 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 17-2 shows the available clock configurations. The ADC clock
should be set to between 500kHz and 2MHz.
Table 17-2. 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.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Analog-to-Digital Converter (ADC)
I/O Registers
If the external clock (CGMXCLK) is equal to or greater than 1MHz,
CGMXCLK can be used as the clock source for the ADC. If
CGMXCLK is less than 1MHz, 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
CGMXCLK or bus frequency
ADIV[2:0]
Freescale Semiconductor, Inc...
fADIC =
MODE1 and MODE0 — Modes of Result Justification
MODE1 and MODE0 selects between 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.
Table 17-3. ADC Mode Select
MODE1
MODE0
Justification Mode
0
0
8-bit truncated mode
0
1
Right justified mode
1
0
Left justified mode
1
1
Left justified sign data mode
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Analog-to-Digital Converter (ADC)
17.7.3 ADC Data Register 0 (ADRH0 and ADRL0)
Freescale Semiconductor, Inc...
The ADC data register 0 consist of a pair of 8-bit registers: high byte
(ADRH0), and low byte (ADRL0). This pair form a 16-bit register to store
the 10-bit ADC result for the selected ADC result justification mode.
In 8-bit truncated mode, the ADRL0 holds the eight most significant bits
(MSBs) of the 10-bit result. The ADRL0 is updated each time an ADC
conversion completes. In 8-bit truncated mode, ADRL0 contains no
interlocking with ADRH0.
(See Figure 17-5 . ADRH0 and ADRL0 in 8-Bit Truncated Mode.)
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
ADC Data Register High 0
$0059
Write:
(ADRH0)
Reset:
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 0
$005A
Write:
(ADRL0)
Reset:
Figure 17-5. ADRH0 and ADRL0 in 8-Bit Truncated Mode
In right justified mode the ADRH0 holds the two MSBs, and the ADRL0
holds the eight least significant bits (LSBs), of the 10-bit result. ADRH0
and ADRL0 are updated each time a single channel ADC conversion
completes. Reading ADRH0 latches the contents of ADRL0. Until
ADRL0 is read all subsequent ADC results will be lost.
(See Figure 17-6 . ADRH0 and ADRL0 in Right Justified Mode.)
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
ADC Data Register High 0
$0059
Write:
(ADRH0)
Reset:
0
0
0
0
0
0
AD9
AD8
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 0
$005A
Write:
(ADRL0)
Reset:
Figure 17-6. ADRH0 and ADRL0 in Right Justified Mode
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Analog-to-Digital Converter (ADC)
I/O Registers
In left justified mode the ADRH0 holds the eight most significant bits
(MSBs), and the ADRL0 holds the two least significant bits (LSBs), of the
10-bit result. The ADRH0 and ADRL0 are updated each time a single
channel ADC conversion completes. Reading ADRH0 latches the
contents of ADRL0. Until ADRL0 is read all subsequent ADC results will
be lost. (See Figure 17-7 . ADRH0 and ADRL0 in Left Justified Mode.)
Freescale Semiconductor, Inc...
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
ADC Data Register High 0
$0059
Write:
(ADRH0)
Reset:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 0
Write:
$005A
(ADRL0)
Reset:
AD1
AD0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Figure 17-7. ADRH0 and ADRL0 in Left Justified Mode
In left justified sign mode the ADRH0 holds the eight MSBs with the MSB
complemented, and the ADRL0 holds the two least significant bits
(LSBs), of the 10-bit result. The ADRH0 and ADRL0 are updated each
time a single channel ADC conversion completes. Reading ADRH0
latches the contents of ADRL0. Until ADRL0 is read all subsequent ADC
results will be lost. (See Figure 17-8 ADRH0 and ADRL0 in Left
Justified Sign Data Mode.)
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Read:
ADC Data Register High 0
$0059
Write:
(ADRH0)
Reset:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
ADC Data Register Low 0
$005A
Write:
(ADRL0)
Reset:
AD1
AD0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Figure 17-8 ADRH0 and ADRL0 in Left Justified Sign Data Mode
MC68HC908AP Family — Rev. 2.5
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Analog-to-Digital Converter (ADC)
17.7.4 ADC Auto-Scan Mode Data Registers (ADRL1—ADRL3)
The ADC data registers 1 to 3 (ADRL1–ADRL3), are 8-bit registers for
conversion results in 8-bit truncated mode, for channels ADC1 to ADC3,
when the ADC is operating in auto-scan mode (MODE[1:0] = 00).
Freescale Semiconductor, Inc...
Address: ADRL1, $005B; ADRL2, $005C; and ADRL3, $005D
Read:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 17-9. ADC Data Register Low 1 to 3 (ADRL1–ADRL3)
17.7.5 ADC Auto-Scan Control Register (ADASCR)
The ADC auto-scan control register (ADASCR) enables and controls the
ADC auto-scan function.
Address:
Read:
$005E
0
0
0
0
0
AUTO1
AUTO0
ASCAN
0
0
0
Write:
Reset:
0
0
0
= Unimplemented
0
0
R
= Reserved
Figure 17-10. ADC Scan Control Register (ADASCR)
AUTO[1:0] — Auto-Scan Mode Channel Select Bits
AUTO1 and AUTO0 form a 2-bit field which is used to define the
number of auto-scan channels used when in auto-scan mode.
Reset clears these bits.
Table 17-4. Auto-scan Mode Channel Select
Data Sheet
AUTO1
AUTO0
Auto-Scan Channels
0
0
ADC0 only
0
1
ADC0 to ADC1
1
0
ADC0 to ADC2
1
1
ADC0 to ADC3
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Analog-to-Digital Converter (ADC)
I/O Registers
ASCAN — Auto-scan Mode Enable Bit
This bit enable/disable the auto-scan mode. Reset clears this bit.
1 = Auto-scan mode is enabled
0 = Auto-scan mode is disabled
Freescale Semiconductor, Inc...
Auto-scan mode should not be enabled when ADC continuous
conversion is enabled; i.e. when ADCO=1.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Analog-to-Digital Converter (ADC)
Data Sheet
MC68HC908AP Family — Rev. 2.5
362
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Data Sheet – MC68HC908AP Family
Section 18. Input/Output (I/O) Ports
18.1 Introduction
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Thirty-two (32) bidirectional input-output (I/O) pins form four parallel
ports. All I/O pins are programmable as inputs or outputs.
NOTE:
Connect any unused I/O pins to an appropriate logic level, either VDD or
VSS. Although the I/O ports do not require termination for proper
operation, termination reduces excess current consumption and the
possibility of electrostatic damage.
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Input/Output (I/O) Ports
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
PTC2
PTC1
PTC0
PTD2
PTD1
PTD0
Read:
Port A Data Register
Write:
(PTA)
Reset:
$0000
Unaffected by reset
Read:
Port B Data Register
Write:
(PTB)
Reset:
Freescale Semiconductor, Inc...
$0001
PTB7
PTB6
PTB5
PTB4
PTB3
Unaffected by reset
Read:
Port C Data Register
Write:
(PTC)
Reset:
$0002
PTC7
PTC6
PTC5
PTC4
PTC3
Unaffected by reset
Read:
Port D Data Register
Write:
(PTD)
Reset:
$0003
PTD7
PTD6
PTD5
PTD4
PTD3
Unaffected by reset
Read:
$0004
DDRA7
Data Direction Register A
Write:
(DDRA)
Reset:
0
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
0
DDRD6
DDRD5
DDRD4
DDRD3
DDRD2
DDRD1
DDRD0
0
0
0
0
0
0
0
LEDA7
LEDA6
LEDA5
LEDA4
LEDA3
LEDA2
LEDA1
LEDA0
0
0
0
0
0
0
0
0
Read:
$0005
DDRB7
Data Direction Register B
Write:
(DDRB)
Reset:
0
Read:
$0006
DDRC7
Data Direction Register C
Write:
(DDRC)
Reset:
0
Read:
$0007
DDRD7
Data Direction Register D
Write:
(DDRD)
Reset:
0
$000C
Read:
Port-A LED Control
Register Write:
(LEDA)
Reset:
Figure 18-1. I/O Port Register Summary
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Input/Output (I/O) Ports
Introduction
Table 18-1. Port Control Register Bits Summary
Port
Freescale Semiconductor, Inc...
A
B
C
D
Module Control
Bit
DDR
0
DDRA0
PTA0/ADC0
1
DDRA1
PTA1/ADC1
2
DDRA2
PTA2/ADC2
3
DDRA3
4
DDRA4
5
DDRA5
PTA5/ADC5
6
DDRA6
PTA6/ADC6
7
DDRA7
PTA7/ADC7
0
DDRB0
1
DDRB1
2
DDRB2
3
DDRB3
4
DDRB4
5
DDRB5
6
DDRB6
7
DDRB7
0
DDRC0
1
DDRC1
2
DDRC2
3
DDRC3
4
DDRC4
5
DDRC5
6
DDRC6
7
DDRC7
0
DDRD0
KBIE0
PTD0/KBI0(2)
1
DDRD1
KBIE1
PTD1/KBI1(2)
2
DDRD2
KBIE2
PTD2/KBI2(2)
3
DDRD3
KBIE3
PTD3/KBI3(2)
4
DDRD4
KBIE4
PTD4/KBI4(2)
5
DDRD5
KBIE5
PTD5/KBI5(2)
6
DDRD6
KBIE6
PTD6/KBI6(2)
7
DDRD7
KBIE7
PTD7/KBI7(2)
Module
ADC
Register
ADSCR ($0057)
Control Bit
ADCH[4:0]
Pin
PTA3/ADC3
PTA4/ADC4
PTB0/SDA(1)
MBUS
MMCR1 ($0049)
MMEN
SCI
SCC1 ($0013)
ENSCI
T1SC0 ($0025)
ELS0B:ELS0A
PTB4/T1CH0(2)
T1SC1 ($0028)
ELS1B:ELS1A
PTB5/T1CH1(2)
T2SC0 ($0030)
ELS0B:ELS0A
PTB6/T2CH0(2)
T2SC1 ($0033)
ELS1B:ELS1A
PTB7/T2CH1(2)
IRQ2
INTSCR2 ($001C)
IMASK2
—
—
—
TIM1
TIM2
PTB1/SCL(1)
PTB2/TxD(1)
PTB3/RxD(1)
PTC0/IRQ2(2)
PTC1
PTC2/MISO
SPI
SPCR ($0010)
SPE
PTC3/MOSI
PTC4/SS
PTC5/SPSCK
IRSCI
KBI
IRSCC1 ($0040)
KBIER ($001B)
ENSCI
PTC6/SCTxD(1)
PTC7/SCRxD(1)
Notes:
1. Pin is open-drain when configured as output. Pullup resistor must be connected when configured as output.
2. Pin has schmitt trigger when configured as input.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
365
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Input/Output (I/O) Ports
18.2 Port A
Port A is an 8-bit special-function port that shares all of its pins with the
analog-to-digital converter (ADC) module. Port A pins also have LED
direct drive capability.
18.2.1 Port A Data Register (PTA)
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The port A data register contains a data latch for each of the eight port A
pins.
Address:
$0000
Bit 7
6
5
4
3
2
1
Bit 0
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
ADC2
ADC1
ADC0
Read:
Write:
Reset:
Alternative Function:
Unaffected by reset
ADC7
ADC6
ADC5
ADC4
ADC3
Additional Function: LED drive LED drive LED drive LED drive LED drive LED drive LED drive LED drive
Figure 18-2. Port A Data Register (PTA)
PTA[7:0] — 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.
ADC7–ADC0 — ADC Channels 7 to 0
ADC7–ADC0 are pins used for the input channels to the analog-todigital converter module. The channel select bits, ADCH[4:0], in the
ADC status and control register define which port pin will be used as
an ADC input and overrides any control from the port I/O logic.
NOTE:
Data Sheet
Care must be taken when reading port A while applying analog voltages
to ADC7–ADC0 pins. If the appropriate ADC channel is not enabled,
excessive current drain may occur if analog voltages are applied to the
PTAx/ADCx pin, while PTA is read as a digital input. Those ports not
selected as analog input channels are considered digital I/O ports.
MC68HC908AP Family — Rev. 2.5
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Input/Output (I/O) Ports
Port A
LED drive — Direct LED drive pins
PTA7–PTA0 pins can be configured for direct LED drive. See 18.2.3
Port-A LED Control Register (LEDA).
18.2.2 Data Direction Register (DDRA)
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Data direction register A 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
6
5
4
3
2
1
Bit 0
DDRA7
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 18-3. Data Direction Register A (DDRA)
DDRA[7:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears
DDRA[7:0], 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.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Input/Output (I/O) Ports
Figure 18-4 shows the port A I/O logic.
READ DDRA ($0004)
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INTERNAL DATA BUS
WRITE DDRA ($0004)
RESET
DDRAx
WRITE PTA ($0000)
PTAx
PTAx
READ PTA ($0000)
Figure 18-4. Port A I/O Circuit
When DDRAx is a logic 1, reading address $0000 reads the PTAx data
latch. When 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 18-2 summarizes the operation of the port A pins.
Table 18-2. Port A Pin Functions
Accesses to DDRA
DDRA
Bit
PTA
Bit
I/O Pin Mode
0
X(1)
1
X
Accesses to PTA
Read/Write
Read
Write
Input, Hi-Z(2)
DDRA[7:0]
Pin
PTA[7:0](3)
Output
DDRA[7:0]
PTA[7:0]
PTA[7:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
Data Sheet
MC68HC908AP Family — Rev. 2.5
368
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Input/Output (I/O) Ports
Port A
18.2.3 Port-A LED Control Register (LEDA)
The port-A LED control register (LEDA) controls the direct LED drive
capability on PTA7–PTA0 pins. Each bit is individually configurable and
requires that the data direction register, DDRA, bit be configured as an
output.
Address:
$000C
Bit 7
6
5
4
3
2
1
Bit 0
LEDA7
LEDA6
LEDA5
LEDA4
LEDA3
LEDA2
LEDA1
LEDA0
0
0
0
0
0
0
0
0
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Read:
Write:
Reset:
Figure 18-5. Port A LED Control Register (LEDA)
LEDA[7:0] — Port A LED Drive Enable Bits
These read/write bits are software programmable to enable the direct
LED drive on an output port pin.
1 = Corresponding port A pin is configured for direct LED drive,
with 15mA current sinking capability
0 = Corresponding port A pin is configured for standard drive
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Input/Output (I/O) Ports
18.3 Port B
Port B is an 8-bit special-function port that shares two of its pins with the
multi-master IIC (MMIIC) module, two of its pins with SCI module, and
four of its pins with two timer interface (TIM1 and TIM2) modules.
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NOTE:
PTB3–PTB0 are open-drain pins when configured as outputs regardless
whether the pins are used as general purpose I/O pins, MMIIC pins, or
SCI pins. Therefore, when configured as general purpose output pins,
MMIIC pins, or SCI pins (the TxD pin), pullup resistors must be
connected to these pins.
18.3.1 Port B Data Register (PTB)
The port B data register contains a data latch for each of the eight port B
pins.
Address:
$0001
Bit 7
6
5
4
3
2
1
Bit 0
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
TxD
SCL
SDA
Read:
Write:
Reset:
Alternative Function:
Unaffected by reset
T2CH1
T2CH0
T1CH1
T1CH0
RxD
Figure 18-6. Port B Data Register (PTB)
PTB[7:0] — 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.
SDA and SCL — Multi-Master IIC Data and Clock
The SDA and SCL pins are multi-master IIC data and clock pins.
Setting the MMEN bit in the MMIIC control register 1 (MMCR1)
configures the PTB0/SDA and PTB1/SCL pins for MMIIC function and
overrides any control from the port I/O logic.
Data Sheet
MC68HC908AP Family — Rev. 2.5
370
MOTOROLA
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Input/Output (I/O) Ports
Port B
TxD and RxD — SCI Transmit and Receive Data
The TxD and RxD pins are SCI transmit and receive data pins. Setting
the ENSCI bit in the SCI control register 1 (SCC1) configures the
PTB2/TxD and PTB3/RxD pins for SCI function and overrides any
control from the port I/O logic.
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T1CH0 and T1CH1 — Timer 1 Channel I/O
The T1CH0 and T1CH1 pins are the TIM1 input capture/output
compare pins. The edge/level select bits, ELSxB:ELSxA, determine
whether the PTB4/T1CH0–PTB5/T1CH1 pins are timer channel I/O
pins or general-purpose I/O pins.
T2CH0 and T2CH1 — Timer 2 Channel I/O
The T2CH0 and T2CH1 pins are the TIM2 input capture/output
compare pins. The edge/level select bits, ELSxB:ELSxA, determine
whether the PTB6/T2CH0–PTB7/T2CH1 pins are timer channel I/O
pins or general-purpose I/O pins.
18.3.2 Data Direction Register B (DDRB)
Data direction register B 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
6
5
4
3
2
1
Bit 0
DDRB7
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 18-7. Data Direction Register B (DDRB)
DDRB[7:0] — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears
DDRB[7:0], configuring all port B pins as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Input/Output (I/O) Ports
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 18-8 shows the port B I/O logic.
READ DDRB ($0005)
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INTERNAL DATA BUS
WRITE DDRB ($0005)
RESET
DDRBx
WRITE PTB ($0001)
PTBx #
PTBx
READ PTB ($0001)
# PTB3–PTB0 are open-drain pins when configured as outputs.
PTB7–PTB4 have schmitt trigger inputs.
Figure 18-8. Port B I/O Circuit
When DDRBx is a logic 1, reading address $0001 reads the PTBx data
latch. When 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 18-3 summarizes the operation of the port B pins.
Table 18-3. Port B Pin Functions
Accesses to DDRB
DDRB
Bit
PTB
Bit
I/O Pin Mode
0
X(1)
1
X
Accesses to PTB
Read/Write
Read
Write
Input, Hi-Z(2)
DDRB[7:0]
Pin
PTB[7:0](3)
Output
DDRB[7:0]
PTB[7:0]
PTB[7:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Input/Output (I/O) Ports
Port C
18.4 Port C
Port C is an 8-bit special-function port that shares one of its pins with the
IRQ2, four of its pins with the SPI module, and two of its pins with the
IRSCI module.
18.4.1 Port C Data Register (PTC)
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The port C data register contains a data latch for each of the eight port C
pins.
Address:
$0002
Bit 7
6
5
4
3
2
1
Bit 0
PTC7
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1
PTC0
Read:
Write:
Reset:
Alternative Function:
Unaffected by reset
SCRxD
SCTxD
SPSCK
SS
MOSI
MISO
IRQ2
Figure 18-9. Port C Data Register (PTC)
PTC[7:0] — 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.
IRQ2 — IRQ2 input pin
The PTC0/IRQ2 pin is always available as input pin to the IRQ2
module. Care must be taken to available unwanted interrupts when
this pin is used as general purpose I/O. PTC0/IRQ2 pin has an
internal pullup, and can be disabled by setting the PUC0ENB bit in the
IRQ2 status and control register (INTSCR2).
MISO, MOSI, SS, and SPSCK — SPI Data I/O, Select, and Clock Pins
These pins are the SPI data in/out, select, and clock pins. Setting the
SPE bit in the SPI control register (SPCR) configures PTC2/MISO,
PTC3/MOSI, PTC4/SS, and PTC5/SPSCK pins for SPI function and
overrides any control from the port I/O logic.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Input/Output (I/O) Ports
SCTxD and SCRxD — IrSCI Transmit and Receive Data
The SCTxD and SCRxD pins are IRSCI transmit and receive data
pins. Setting the ENSCI bit in the IRSCI control register 1 (IRSCC1)
configures the PTC6/SCTxD and PTC7/SCRxD pins for IRSCI
function and overrides any control from the port I/O logic.
18.4.2 Data Direction Register C (DDRC)
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Data direction register C 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
1
Bit 0
DDRC7
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 18-10. Data Direction Register C (DDRC)
DDRC[7:0] — Data Direction Register C Bits
These read/write bits control port C data direction. Reset clears
DDRC[7:0], 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 18-11 shows the port C I/O logic.
NOTE:
Data Sheet
For those devices packaged in a 42-pin shrink dual in-line package,
PTC0 and PTC1 are not connected. DDRC0 and DDRC1 should be set
to a 1 to configure PTC0 and PTC1 as outputs.
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Input/Output (I/O) Ports
Port C
READ DDRC ($0006)
INTERNAL DATA BUS
WRITE DDRC ($0006)
RESET
DDRCx
WRITE PTC ($0002)
PTCx #
PTCx
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READ PTC ($0002)
# PTC0 has schmitt trigger input.
Figure 18-11. Port C I/O Circuit
When DDRCx is a logic 1, reading address $0002 reads the PTCx data
latch. When 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 18-4 summarizes the operation of the port C pins.
Table 18-4. Port C Pin Functions
Accesses to DDRC
DDRC
Bit
PTC
Bit
I/O Pin Mode
0
X(1)
1
X
Accesses to PTC
Read/Write
Read
Input, Hi-Z(2)
DDRC[7:0]
Pin
Output
DDRC[7:0]
PTC[7:0]
Write
PTC[7:0]
(3)
PTC[7:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Input/Output (I/O) Ports
18.5 Port D
Port D is an 8-bit special function port that shares all of its pins with the
keyboard interrupt module.
18.5.1 Port D Data Register (PTD)
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The port D data register contains a data latch for each of the eight port D
pins.
Address:
$0003
Bit 7
6
5
4
3
2
1
Bit 0
PTD7
PTD6
PTD5
PTD4
PTD3
PTD2
PTD1
PTD0
KBI2
KBI1
KBI0
Read:
Write:
Reset:
Alternative Function:
Unaffected by reset
KBI7
KBI6
KBI5
KBI4
KBI3
Figure 18-12. Port D Data Register (PTD)
PTD[7:0] — Port D Data Bits
These read/write bits are software programmable. Data direction of
each port D pin is under the control of the corresponding bit in data
direction register D. Reset has no effect on port D data.
KBI7–KBI0 — Keyboard Interrupt Inputs
The keyboard interrupt enable bits, KBIE[7:0], in the keyboard
interrupt enable register (KBIER), enable the port D pins as external
interrupt pins. See Section 20. Keyboard Interrupt Module (KBI).
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Input/Output (I/O) Ports
Port D
18.5.2 Data Direction Register D (DDRD)
Data direction register D determines whether each port D pin is an input
or an output. Writing a logic 1 to a DDRD bit enables the output buffer for
the corresponding port D pin; a logic 0 disables the output buffer.
Address:
$0007
Bit 7
6
5
4
3
2
1
Bit 0
DDRD7
DDRD6
DDRD5
DDRD4
DDRD3
DDRD2
DDRD1
DDRD0
0
0
0
0
0
0
0
0
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Read:
Write:
Reset:
Figure 18-13. Data Direction Register D (DDRD)
DDRD[7:0] — Data Direction Register D Bits
These read/write bits control port D data direction. Reset clears
DDRD[7:0], configuring all port D pins as inputs.
1 = Corresponding port D pin configured as output
0 = Corresponding port D pin configured as input
NOTE:
Avoid glitches on port D pins by writing to the port D data register before
changing data direction register D bits from 0 to 1.
Figure 18-14 shows the port D I/O logic.
READ DDRD ($0007)
KBIEx
INTERNAL DATA BUS
WRITE DDRD ($0007)
RESET
DDRDx
WRITE PTD ($0003)
PTDx #
PTDx
READ PTD ($0003)
# PTD7–PTD0 have schmitt trigger inputs.
Figure 18-14. Port D I/O Circuit
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Input/Output (I/O) Ports
When bit DDRDx is a logic 1, reading address $0003 reads the PTDx
data latch. When bit DDRDx is a logic 0, reading address $0003 reads
the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit.
Table 18-5 summarizes the operation of the port D pins.
Freescale Semiconductor, Inc...
Table 18-5. Port D Pin Functions
Accesses to DDRD
DDRD
Bit
PTD
Bit
I/O Pin Mode
0
X(1)
1
X
Accesses to PTD
Read/Write
Read
Input, Hi-Z(2)
DDRD[7:0]
Pin
Output
DDRD[7:0]
PTD[7:0]
Write
PTD[7:0]
(3)
PTD[7:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 19. External Interrupt (IRQ)
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19.1 Introduction
The external interrupt (IRQ) module provides two maskable interrupt
inputs: IRQ1 and IRQ2.
19.2 Features
Features of the IRQ module include:
NOTE:
Addr.
$001C
$001E
•
A dedicated external interrupt pin, IRQ1
•
An external interrupt pin shared with a port pin, PTC0/IRQ2
•
Separate IRQ interrupt control bits for IRQ1 and IRQ2
•
Hysteresis buffers
•
Programmable edge-only or edge and level interrupt sensitivity
•
Automatic interrupt acknowledge
•
Internal pullup resistor, with disable option on IRQ2
References to either IRQ1 or IRQ2 may be made in the following text by
omitting the IRQ number. For example, IRQF may refer generically to
IRQ1F and IRQ2F, and IMASK may refer to IMASK1 and IMASK2.
Register Name
Bit 7
Read:
IRQ2 Status and Control
Register Write:
(INTSCR2)
Reset:
Read:
IRQ1 Status and Control
Register Write:
(INTSCR1)
Reset:
0
6
PUC0ENB
5
4
3
2
0
0
IRQ2F
0
ACK2
0
0
0
0
0
0
0
0
0
0
IRQ1F
0
ACK1
0
0
0
0
0
0
1
Bit 0
IMASK2
MODE2
0
0
IMASK1
MODE1
0
0
= Unimplemented
Figure 19-1. External Interrupt I/O Register Summary
MC68HC908AP Family — Rev. 2.5
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External Interrupt (IRQ)
19.3 Functional Description
A logic 0 applied to the external interrupt pin can latch a CPU interrupt
request. Figure 19-2 and Figure 19-3 shows the structure of the IRQ
module.
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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 (INTSCR). Writing a logic 1 to the ACK bit clears
the IRQ latch.
•
Reset — A reset automatically clears the interrupt latch.
The external interrupt pin is falling-edge-triggered and is softwareconfigurable to be either falling-edge or falling-edge and low-leveltriggered. The MODE bit in the INTSCR controls the triggering sensitivity
of the IRQ pin.
When an interrupt pin is edge-triggered only, the interrupt remains set
until a vector fetch, software clear, or reset occurs.
When an interrupt pin is both falling-edge and low-level-triggered, the
interrupt remains set until both of the following occur:
•
Vector fetch or software clear
•
Return of the interrupt pin to logic 1
The vector fetch or software clear may occur before or after the interrupt
pin returns to logic 1. As long as the pin is low, the interrupt request
remains pending. A reset will clear the latch and the MODE1 control bit,
thereby clearing the interrupt even if the pin stays low.
When set, the IMASK bit in the INTSCR mask all external interrupt
requests. A latched interrupt request is not presented to the interrupt
priority logic unless the IMASK bit is clear.
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MC68HC908AP Family — Rev. 2.5
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External Interrupt (IRQ)
Functional Description
The interrupt mask (I) in the condition code register (CCR) masks all
interrupt requests, including external interrupt requests.
INTERNAL ADDRESS BUS
ACK1
RESET
TO CPU FOR
BIL/BIH
INSTRUCTIONS
VECTOR
FETCH
DECODER
VDD
INTERNAL
PULLUP
DEVICE
VDD
IRQ1F
D
CLR
Q
SYNCHRONIZER
CK
IRQ1
IRQ1
INTERRUPT
REQUEST
IRQ1
FF
IMASK1
MODE1
TO MODE
SELECT
LOGIC
HIGH
VOLTAGE
DETECT
Figure 19-2. IRQ1 Block Diagram
ACK2
RESET
INTERNAL ADDRESS BUS
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NOTE:
VECTOR
FETCH
DECODER
VDD
INTERNAL
PULLUP
DEVICE
VDD
IRQ2F
PUC0ENB
D
CLR
CK
IRQ2
Q
SYNCHRONIZER
IRQ2
INTERRUPT
REQUEST
IRQ2
FF
IMASK2
MODE2
Figure 19-3. IRQ2 Block Diagram
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External Interrupt (IRQ)
19.4 IRQ1 and IRQ2 Pins
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.
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If the MODE bit is set, the IRQ pin is both falling-edge-sensitive and lowlevel-sensitive. With MODE set, both of the following actions must occur
to clear IRQ:
•
Vector fetch or software clear — A vector fetch generates an
interrupt acknowledge signal to clear the latch. Software may
generate the interrupt acknowledge signal by writing a logic 1 to
the ACK bit in the interrupt status and control register (INTSCR).
The ACK bit is useful in applications that poll the IRQ pin and
require software to clear the IRQ latch. Writing to the ACK bit prior
to leaving an interrupt service routine can also prevent spurious
interrupts due to noise. Setting ACK does not affect subsequent
transitions on the IRQ pin. A falling edge that occurs after writing
to the ACK bit another interrupt request. If the IRQ mask bit,
IMASK, is clear, the CPU loads the program counter with the
vector address at location defined in Table 2-1 . Vector
Addresses.
•
Return of the IRQ pin to logic 1 — As long as the IRQ pin is at
logic 0, IRQ remains active.
The vector fetch or software clear and the return of the IRQ pin to logic 1
may occur in any order. The interrupt request remains pending as long
as the IRQ pin is at logic 0. A reset will clear the latch and the MODE
control bit, thereby clearing the interrupt even if the pin stays low.
If the MODE bit is clear, the IRQ pin is falling-edge-sensitive only. With
MODE clear, a vector fetch or software clear immediately clears the IRQ
latch.
The IRQF bit in the INTSCR register can be used to check for pending
interrupts. The IRQF bit is not affected by the IMASK bit, which makes it
useful in applications where polling is preferred.
Use the BIH or BIL instruction to read the logic level on the IRQ1 pin.
NOTE:
Data Sheet
The BIH and BIL instructions do not read the logic level on the IRQ2 pin.
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External Interrupt (IRQ)
IRQ Module During Break Interrupts
NOTE:
When using the level-sensitive interrupt trigger, avoid false interrupts by
masking interrupt requests in the interrupt routine.
The IRQ1 pin has a permanent internal pullup device connected, while
the IRQ2 pin has an optional pullup device that can be enabled or
disabled by the PUC0ENB bit in the INTSCR2 register.
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19.5 IRQ Module During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables
software to clear the latch during the break state. (See Section 23.
Break Module (BRK).)
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 CPU interrupt flags during the break state, write a logic 0 to
the BCFE bit. With BCFE at logic 0 (its default state), writing to the ACK
bit in the IRQ status and control register during the break state has no
effect on the IRQ interrupt flags.
19.6 IRQ Registers
Each IRQ is controlled and monitored by an status and control register.
•
IRQ1 Status and Control Register — $001E
•
IRQ2 Status and Control Register — $001C
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External Interrupt (IRQ)
19.6.1 IRQ1 Status and Control Register
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The IRQ1 status and control register (INTSCR1) controls and monitors
operation of IRQ1. The INTSCR1 has the following functions:
•
Shows the state of the IRQ1 flag
•
Clears the IRQ1 latch
•
Masks IRQ1 interrupt request
•
Controls triggering sensitivity of the IRQ1 interrupt pin
Address:
Read:
$001E
Bit 7
6
5
4
3
2
0
0
0
0
IRQ1F
0
Write:
Reset:
1
Bit 0
IMASK1
MODE1
0
0
ACK1
0
0
0
0
0
0
= Unimplemented
Figure 19-4. IRQ1 Status and Control Register (INTSCR1)
IRQ1F — IRQ1 Flag Bit
This read-only status bit is high when the IRQ1 interrupt is pending.
1 = IRQ1 interrupt pending
0 = IRQ1 interrupt not pending
ACK1 — IRQ1 Interrupt Request Acknowledge Bit
Writing a logic 1 to this write-only bit clears the IRQ1 latch. ACK1
always reads as logic 0. Reset clears ACK1.
IMASK1 — IRQ1 Interrupt Mask Bit
Writing a logic 1 to this read/write bit disables IRQ1 interrupt requests.
Reset clears IMASK1.
1 = IRQ1 interrupt requests disabled
0 = IRQ1 interrupt requests enabled
MODE1 — IRQ1 Edge/Level Select Bit
This read/write bit controls the triggering sensitivity of the IRQ1 pin.
Reset clears MODE1.
1 = IRQ1 interrupt requests on falling edges and low levels
0 = IRQ1 interrupt requests on falling edges only
Data Sheet
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External Interrupt (IRQ)
IRQ Registers
19.6.2 IRQ2 Status and Control Register
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The IRQ2 status and control register (INTSCR2) controls and monitors
operation of IRQ2. The INTSCR2 has the following functions:
•
Enables/disables the internal pullup device on IRQ2 pin
•
Shows the state of the IRQ2 flag
•
Clears the IRQ2 latch
•
Masks IRQ2 interrupt request
•
Controls triggering sensitivity of the IRQ2 interrupt pin
Address:
$001C
Bit 7
Read:
6
0
5
4
3
2
0
0
IRQ2F
0
PUC0ENB
Write:
Reset:
1
Bit 0
IMASK2
MODE2
0
0
ACK2
0
0
0
0
0
0
= Unimplemented
Figure 19-5. IRQ2 Status and Control Register (INTSCR2)
PUC0ENB — IRQ2 Pin Pullup Enable Bit.
Setting this bit to logic 1 disables the pullup on PTC0/IRQ2 pin.
Reset clears this bit.
1 = IRQ2 pin internal pullup is disabled
0 = IRQ2 pin internal pullup is enabled
IRQ2F — IRQ2 Flag Bit
This read-only status bit is high when the IRQ2 interrupt is pending.
1 = IRQ2 interrupt pending
0 = IRQ2 interrupt not pending
ACK2 — IRQ2 Interrupt Request Acknowledge Bit
Writing a logic 1 to this write-only bit clears the IRQ2 latch. ACK2
always reads as logic 0. Reset clears ACK2.
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External Interrupt (IRQ)
IMASK2 — IRQ2 Interrupt Mask Bit
Writing a logic 1 to this read/write bit disables IRQ2 interrupt requests.
Reset clears IMASK2.
1 = IRQ2 interrupt requests disabled
0 = IRQ2 interrupt requests enabled
MODE2 — IRQ2 Edge/Level Select Bit
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This read/write bit controls the triggering sensitivity of the IRQ2 pin.
Reset clears MODE2.
1 = IRQ2 interrupt requests on falling edges and low levels
0 = IRQ2 interrupt requests on falling edges only
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 20. Keyboard Interrupt Module (KBI)
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20.1 Introduction
The keyboard interrupt module (KBI) provides eight independently
maskable external interrupts which are accessible via PTD0–PTD7.
When a port pin is enabled for keyboard interrupt function, an internal
30kΩ pullup device is also enabled on the pin.
20.2 Features
Features of the keyboard interrupt module include the following:
•
Eight keyboard interrupt pins with pullup devices
•
Separate keyboard interrupt enable bits and one keyboard
interrupt mask
•
Programmable edge-only or edge- and level- interrupt sensitivity
•
Exit from low-lower modes
Addr.
Register Name
$001A
Read:
Keyboard Status
and Control Register Write:
(KBSCR)
Reset:
Read:
Keyboard Interrupt Enable
$001B
Write:
Register (KBIER)
Reset:
Bit 7
6
5
4
3
2
0
0
0
0
KEYF
0
1
Bit 0
IMASKK
MODEK
ACKK
0
0
0
0
0
0
0
0
KBIE7
KBIE6
KBIE5
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 20-1. KBI I/O Register Summary
MC68HC908AP Family — Rev. 2.5
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Keyboard Interrupt Module (KBI)
20.3 I/O Pins
The eight keyboard interrupt pins are shared with standard port I/O pins.
The full name of the KBI pins are listed in Table 20-1. The generic pin
name appear in the text that follows.
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Table 20-1. Pin Name Conventions
KBI
Generic Pin Name
Full MCU Pin Name
Pin Selected for KBI Function by
KBIEx Bit in KBIER
KBI0–KBI7
PTD0/KBI0–PTD7/KBI7
KBIE0–KBIE7
20.4 Functional Description
INTERNAL BUS
KBI0
ACKK
VDD
VECTOR FETCH
DECODER
KEYF
RESET
.
KBIE0
D
CLR
Q
SYNCHRONIZER
.
CK
TO PULLUP ENABLE
.
KEYBOARD
INTERRUPT FF
KBI7
Keyboard
Interrupt
Request
IMASKK
MODEK
KBIE7
TO PULLUP ENABLE
Figure 20-2. Keyboard Interrupt Block Diagram
Writing to the KBIE7–KBIE0 bits in the keyboard interrupt enable register
independently enables or disables each port D pin as a keyboard
interrupt pin. Enabling a keyboard interrupt pin in port D also enables its
internal pull-up device. A logic 0 applied to an enabled keyboard
interrupt pin latches a keyboard interrupt request.
A keyboard interrupt is latched when one or more keyboard pins goes
low after all were high. The MODEK bit in the keyboard status and
control register controls the triggering mode of the keyboard interrupt.
Data Sheet
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Keyboard Interrupt Module (KBI)
Functional Description
•
If the keyboard interrupt is edge-sensitive only, a falling edge on a
keyboard pin does not latch an interrupt request if another
keyboard pin is already low. To prevent losing an interrupt request
on one pin because another pin is still low, software can disable
the latter pin while it is low.
•
If the keyboard interrupt is falling edge- and low level-sensitive, an
interrupt request is present as long as any keyboard pin is low.
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If the MODEK bit is set, the keyboard interrupt pins are both falling edgeand low level-sensitive, and both of the following actions must occur to
clear a keyboard interrupt request:
•
Vector fetch or software clear — A vector fetch generates an
interrupt acknowledge signal to clear the interrupt request.
Software may generate the interrupt acknowledge signal by
writing a logic 1 to the ACKK bit in the keyboard status and control
register KBSCR. The ACKK bit is useful in applications that poll
the keyboard interrupt pins and require software to clear the
keyboard interrupt request. Writing to the ACKK bit prior to leaving
an interrupt service routine can also prevent spurious interrupts
due to noise. Setting ACKK does not affect subsequent transitions
on the keyboard interrupt pins. A falling edge that occurs after
writing to the ACKK bit latches another interrupt request. If the
keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the
program counter with the vector address at locations $FFE0 and
$FFE1.
•
Return of all enabled keyboard interrupt pins to logic 1 — As long
as any enabled keyboard interrupt pin is at logic 0, the keyboard
interrupt remains set.
The vector fetch or software clear and the return of all enabled keyboard
interrupt pins to logic 1 may occur in any order.
If the MODEK bit is clear, the keyboard interrupt pin is falling-edgesensitive only. With MODEK clear, a vector fetch or software clear
immediately clears the keyboard interrupt request.
Reset clears the keyboard interrupt request and the MODEK bit, clearing
the interrupt request even if a keyboard interrupt pin stays at logic 0.
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Keyboard Interrupt Module (KBI)
The keyboard flag bit (KEYF) in the keyboard status and control register
can be used to see if a pending interrupt exists. The KEYF bit is not
affected by the keyboard interrupt mask bit (IMASKK) which makes it
useful in applications where polling is preferred.
To determine the logic level on a keyboard interrupt pin, use the data
direction register to configure the pin as an input and read the data
register.
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NOTE:
Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding
keyboard interrupt pin to be an input, overriding the data direction
register. However, the data direction register bit must be a logic 0 for
software to read the pin.
20.4.1 Keyboard Initialization
When a keyboard interrupt pin is enabled, it takes time for the internal
pull-up to reach a logic 1. Therefore a false interrupt can occur as soon
as the pin is enabled.
To prevent a false interrupt on keyboard initialization:
1. Mask keyboard interrupts by setting the IMASKK bit in the
keyboard status and control register.
2. Enable the KBI pins by setting the appropriate KBIEx bits in the
keyboard interrupt enable register.
3. Write to the ACKK bit in the keyboard status and control register
to clear any false interrupts.
4. Clear the IMASKK bit.
An interrupt signal on an edge-triggered pin can be acknowledged
immediately after enabling the pin. An interrupt signal on an edge- and
level-triggered interrupt pin must be acknowledged after a delay that
depends on the external load.
Another way to avoid a false interrupt:
1. Configure the keyboard pins as outputs by setting the appropriate
DDR bits in data direction register.
Data Sheet
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Keyboard Interrupt Module (KBI)
Keyboard Interrupt Registers
2. Write logic 1s to the appropriate data register bits.
3. Enable the KBI pins by setting the appropriate KBIEx bits in the
keyboard interrupt enable register.
20.5 Keyboard Interrupt Registers
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Two registers control the operation of the keyboard interrupt module:
•
Keyboard Status and Control Register — $001A
•
Keyboard Interrupt Enable Register — $001B
20.5.1 Keyboard Status and Control Register
•
Flags keyboard interrupt requests
•
Acknowledges keyboard interrupt requests
•
Masks keyboard interrupt requests
•
Controls keyboard interrupt triggering sensitivity
Address:
Read:
$001A
Bit 7
6
5
4
3
2
0
0
0
0
KEYF
0
Write:
Reset:
1
Bit 0
IMASKK
MODEK
0
0
ACKK
0
0
0
0
0
0
= Unimplemented
Figure 20-3. Keyboard Status and Control Register (KBSCR)
KEYF — Keyboard Flag Bit
This read-only bit is set when a keyboard interrupt is pending.
Reset clears the KEYF bit.
1 = Keyboard interrupt pending
0 = No keyboard interrupt pending
ACKK — Keyboard Acknowledge Bit
Writing a logic 1 to this write-only bit clears the keyboard interrupt
request. ACKK always reads as logic 0. Reset clears ACKK.
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Keyboard Interrupt Module (KBI)
IMASKK — Keyboard Interrupt Mask Bit
Writing a logic 1 to this read/write bit prevents the output of the
keyboard interrupt mask from generating interrupt requests. Reset
clears the IMASKK bit.
1 = Keyboard interrupt requests masked
0 = Keyboard interrupt requests not masked
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MODEK — Keyboard Triggering Sensitivity Bit
This read/write bit controls the triggering sensitivity of the keyboard
interrupt pins. Reset clears MODEK.
1 = Keyboard interrupt requests on falling edges and low levels
0 = Keyboard interrupt requests on falling edges only
20.5.2 Keyboard Interrupt Enable Register
The port-D keyboard interrupt enable register enables or disables each
port-D pin to operate as a keyboard interrupt pin.
Address:
$001B
Bit 7
6
5
4
3
2
1
Bit 0
KBIE7
KBIE6
KBIE5
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 20-4. Keyboard Interrupt Enable Register (KBIER)
KBIE7–KBIE0 — Keyboard Interrupt Enable Bits
Each of these read/write bits enables the corresponding keyboard
interrupt pin to latch interrupt requests. Reset clears the keyboard
interrupt enable register.
1 = KBIx pin enabled as keyboard interrupt pin
0 = KBIx pin not enabled as keyboard interrupt pin
Data Sheet
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Keyboard Interrupt Module (KBI)
Low-Power Modes
20.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
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20.6.1 Wait Mode
The keyboard interrupt module remains active in wait mode. Clearing the
IMASKK bit in the keyboard status and control register enables keyboard
interrupt requests to bring the MCU out of wait mode.
20.6.2 Stop Mode
The keyboard interrupt module remains active in stop mode. Clearing
the IMASKK bit in the keyboard status and control register enables
keyboard interrupt requests to bring the MCU out of stop mode.
20.7 Keyboard Module During Break Interrupts
The system integration module (SIM) controls whether the keyboard
interrupt latch can be cleared during the break state. The BCFE bit in the
SIM break flag control register (BFCR) enables software to clear status
bits during the break state.
To allow software to clear the keyboard interrupt 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 latch during the break state, write a logic 0 to the BCFE
bit. With BCFE at logic 0 (its default state), writing to the keyboard
acknowledge bit (ACKK) in the keyboard status and control register
during the break state has no effect.
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Keyboard Interrupt Module (KBI)
Data Sheet
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Data Sheet – MC68HC908AP Family
Section 21. Computer Operating Properly (COP)
The computer operating properly (COP) module contains 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
clearing the COP counter periodically. The COP module can be disabled
through the COPD bit in the configuration register 1 (CONFIG1).
21.2 Functional Description
Figure 21-1 shows the structure of the COP module.
RESET CIRCUIT
RESET STATUS REGISTER
COP TIMEOUT
STOP INSTRUCTION
INTERNAL RESET SOURCES
RESET VECTOR FETCH
CLEAR STAGES 5–12
12-BIT COP PRESCALER
ICLK
CLEAR ALL STAGES
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21.1 Introduction
COPCTL WRITE
COP CLOCK
6-BIT COP COUNTER
COPEN (FROM SIM)
COP DISABLE
(COPD FROM CONFIG1)
RESET
CLEAR
COP COUNTER
COPCTL WRITE
COP RATE SEL
(COPRS FROM CONFIG1)
Figure 21-1. COP Block Diagram
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Computer Operating Properly (COP)
The COP counter is a free-running 6-bit counter preceded by a 12-bit
prescaler counter. If not cleared by software, the COP counter overflows
and generates an asynchronous reset after 218 – 24 or 213 – 24 ICLK
cycles, depending on the state of the COP rate select bit, COPRS, in the
CONFIG1 register. With a 213 – 24 ICLK cycle overflow option, a 24-kHz
ICLK gives a COP timeout period of 341ms. Writing any value to location
$FFFF before an overflow occurs prevents a COP reset by clearing the
COP counter and stages 12 through 5 of the prescaler.
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NOTE:
Service the COP immediately after reset and before entering or after
exiting STOP Mode to guarantee the maximum time before the first COP
counter overflow.
A COP reset pulls the RST pin low for 32 ICLK cycles and sets the COP
bit in the SIM reset status register (SRSR).
In monitor mode, the COP is disabled if the RST pin or the IRQ1 is held
at VTST. During the break state, VTST on the RST pin disables the COP.
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.
21.3 I/O Signals
The following paragraphs describe the signals shown in Figure 21-1.
21.3.1 ICLK
ICLK is the internal oscillator output signal. See Section 24. Electrical
Specifications for ICLK frequency specification.
21.3.2 STOP Instruction
The STOP instruction clears the COP prescaler.
Data Sheet
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Computer Operating Properly (COP)
I/O Signals
21.3.3 COPCTL Write
Writing any value to the COP control register (COPCTL) (see 21.4 COP
Control Register) clears the COP counter and clears bits 12 through 5
of the prescaler. Reading the COP control register returns the low byte
of the reset vector.
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21.3.4 Power-On Reset
The power-on reset (POR) circuit clears the COP prescaler 4096 ICLK
cycles after power-up.
21.3.5 Internal Reset
An internal reset clears the COP prescaler and the COP counter.
21.3.6 Reset Vector Fetch
A reset vector fetch occurs when the vector address appears on the data
bus. A reset vector fetch clears the COP prescaler.
21.3.7 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the
CONFIG1 register. (See Figure 21-2 . Configuration Register 1
(CONFIG1).)
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Computer Operating Properly (COP)
21.3.8 COPRS (COP Rate Select)
The COPRS signal reflects the state of the COP rate select bit (COPRS)
in the CONFIG1 register.
Address:
$001F
Bit 7
6
5
4
3
2
1
Bit 0
SSREC
STOP
COPD
0
0
0
Read:
COPRS
LVISTOP LVIRSTD LVIPWRD LVIREGD
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Write:
Reset:
0
0
0
0
0
Figure 21-2. Configuration Register 1 (CONFIG1)
COPRS — COP Rate Select Bit
COPRS selects the COP time out period. Reset clears COPRS.
1 = COP time out period = 213 – 24 ICLK cycles
0 = COP time out period = 218 – 24 ICLK cycles
COPD — COP Disable Bit
COPD disables the COP module.
1 = COP module disabled
0 = COP module enabled
21.4 COP Control Register
The COP control register 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.
Address:
$FFFF
Bit 7
6
5
4
3
Read:
Low byte of reset vector
Write:
Clear COP counter
Reset:
Unaffected by reset
2
1
Bit 0
Figure 21-3. COP Control Register (COPCTL)
Data Sheet
MC68HC908AP Family — Rev. 2.5
398
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Computer Operating Properly (COP)
Interrupts
21.5 Interrupts
The COP does not generate CPU interrupt requests.
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21.6 Monitor Mode
When monitor mode is entered with VTST on the IRQ1 pin, the COP is
disabled as long as VTST remains on the IRQ1 pin or the RST pin. When
monitor mode is entered by having blank reset vectors and not having
VTST on the IRQ1 pin, the COP is automatically disabled until a POR
occurs.
21.7 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
21.7.1 Wait Mode
The COP remains active during wait mode. To prevent a COP reset
during wait mode, periodically clear the COP counter in a CPU interrupt
routine.
21.7.2 Stop Mode
Stop mode turns off the ICLK input to the COP and clears the COP
prescaler. Service the COP immediately before entering or after exiting
stop mode to ensure a full COP timeout period after entering or exiting
stop mode.
To prevent inadvertently turning off the COP with a STOP instruction, a
configuration option is available that disables the STOP instruction.
When the STOP bit in the configuration register has the STOP
instruction is disabled, execution of a STOP instruction results in an
illegal opcode reset.
MC68HC908AP Family — Rev. 2.5
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Computer Operating Properly (COP)
21.8 COP Module During Break Mode
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The COP is disabled during a break interrupt when VTST is present on
the RST pin.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Section 22. Low-Voltage Inhibit (LVI)
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22.1 Introduction
This section describes the low-voltage inhibit (LVI) module. The LVI
module monitors the voltage on the VDD pin and VREG pin, and can force
a reset when VDD voltage falls below VTRIPF1, or VREG voltage falls
below VTRIPF2.
NOTE:
The VREG pin is the output of the internal voltage regulator and is
guaranteed to meet operating specification as long as VDD is within the
MCU operating voltage.
The LVI feature is intended to provide the safe shutdown of the
microcontroller and thus protection of related circuitry prior to any
application VDD voltage collapsing completely to an unsafe level. It is not
intended that users operate the microcontroller at lower than the
specified operating voltage, VDD.
22.2 Features
Features of the LVI module include:
•
Independent voltage monitoring circuits for VDD and VREG
•
Independent disable for VDD and VREG LVI circuits
•
Programmable LVI reset
•
Programmable stop mode operation
MC68HC908AP Family — Rev. 2.5
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Low-Voltage Inhibit (LVI)
Addr.
$FE0F
Register Name
Bit 7
Read: LVIOUT
LVI Status Register
Write:
(LVISR)
Reset:
0
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
= Unimplemented
Freescale Semiconductor, Inc...
Figure 22-1. LVI I/O Register Summary
22.3 Functional Description
Figure 22-2 shows the structure of the LVI module. The LVI is enabled
out of reset. The LVI module contains independent bandgap reference
circuit and comparator for monitoring the VDD voltage and the VREG
voltage. An LVI reset performs a MCU internal reset and drives the RST
pin low to provide low-voltage protection to external peripheral devices.
LVISTOP, LVIPWRD, LVIRSTD, and LVIREGD are in the CONFIG1
register. See Section 5. Configuration & Mask Option Registers
(CONFIG & MOR) for details of the LVI configuration bits. Once an LVI
reset occurs, the MCU remains in reset until VDD rises above VTRIPR1
and VREG rises above VTRIPR2, which causes the MCU to exit reset. The
output of the comparator controls the state of the LVIOUT flag in the LVI
status register (LVISR).
An LVI reset also drives the RST pin low to provide low-voltage
protection to external peripheral devices.
Data Sheet
MC68HC908AP Family — Rev. 2.5
402
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Low-Voltage Inhibit (LVI)
Functional Description
VDD
STOP INSTRUCTION
LVISTOP
FROM CONFIG1
LVIPWRD
FROM CONFIG1
FROM CONFIG1
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LOW VDD
DETECTOR
LOW VREG
DETECTOR
LVIRSTD
VDD > VTRIPR1 = 0
VDD ≤ VTRIPF1 = 1
LVI RESET
VREG > VTRIPR2 = 0
VREG ≤ VTRIPF2 = 1
LVIOUT
FROM CONFIG1
TO LVISR
LVIREGD
FROM CONFIG1
LVISTOP
STOP INSTRUCTION
VREG
Figure 22-2. LVI Module Block Diagram
22.3.1 Low VDD Detector
The low VDD detector circuit monitors the VDD voltage and forces a LVI
reset when the VDD voltage falls below the trip voltage, VTRIPF1. The VDD
LVI circuit can be disabled by the setting the LVIPWRD bit in CONFIG1
register.
22.3.2 Low VREG Detector
The low VREG detector circuit monitors the VREG voltage and forces a
LVI reset when the VREG voltage falls below the trip voltage, VTRIPF2.
The VREG LVI circuit can be disabled by the setting the LVIREGD bit in
CONFIG1 register.
MC68HC908AP Family — Rev. 2.5
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Low-Voltage Inhibit (LVI)
22.3.3 Polled LVI Operation
In applications that can operate at VDD levels below the VTRIPF1 level,
software can monitor VDD by polling the LVIOUT bit. In the CONFIG1
register, the LVIPWRD bit must be at logic 0 to enable the LVI module,
and the LVIRSTD bit must be at logic 1 to disable LVI resets.
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22.3.4 Forced Reset Operation
In applications that require VDD to remain above the VTRIPF1 level,
enabling LVI resets allows the LVI module to reset the MCU when VDD
falls below the VTRIPF1 level. In the CONFIG1 register, the LVIPWRD
and LVIRSTD bits must be at logic 0 to enable the LVI module and to
enable LVI resets.
22.3.5 Voltage Hysteresis Protection
Once the LVI has triggered (by having VDD fall below VTRIPF1), the LVI
will maintain a reset condition until VDD rises above the rising trip point
voltage, VTRIPR1. This prevents a condition in which the MCU is
continually entering and exiting reset if VDD is approximately equal to
VTRIPF1. VTRIPR1 is greater than VTRIPF1 by the hysteresis voltage,
VHYS.
22.4 LVI Status Register
The LVI status register (LVISR) indicates if the VDD voltage was
detected below VTRIPF1 or VREG voltage was detected below VTRIPF2.
Address:
Read:
$FE0F
Bit 7
6
5
4
3
2
1
Bit 0
LVIOUT
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 22-3. LVI Status Register
Data Sheet
MC68HC908AP Family — Rev. 2.5
404
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Low-Voltage Inhibit (LVI)
LVI Interrupts
LVIOUT — LVI Output Bit
This read-only flag becomes set when the VDD or VREG falls below
their respective trip voltages. Reset clears the LVIOUT bit.
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Table 22-1. LVIOUT Bit Indication
VDD, VREG
LVIOUT
VDD > VTRIPR1
and
VREG > VTRIPR2
0
VDD < VTRIPF1
or
VDD < VTRIPF2
1
VTRIPF1 < VDD < VTRIPR1
or
VTRIPF2 < VREG< VTRIPR2
Previous value
22.5 LVI Interrupts
The LVI module does not generate interrupt requests.
22.6 Low-Power Modes
The STOP and WAIT instructions put the MCU in low powerconsumption standby modes.
22.6.1 Wait Mode
If enabled, the LVI module remains active in wait mode. If enabled to
generate resets, the LVI module can generate a reset and bring the MCU
out of wait mode.
22.6.2 Stop Mode
If enabled in stop mode (LVISTOP = 1), the LVI module remains active
in stop mode. If enabled to generate resets (LVIRSTD = 0), the LVI
module can generate a reset and bring the MCU out of stop mode.
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Low-Voltage Inhibit (LVI)
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Section 23. Break Module (BRK)
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23.1 Introduction
This section describes the break module. The break module can
generate a break interrupt that stops normal program flow at a defined
address to enter a background program.
23.2 Features
Features of the break module include:
•
Accessible input/output (I/O) registers during the break interrupt
•
CPU-generated break interrupts
•
Software-generated break interrupts
•
COP disabling during break interrupts
MC68HC908AP Family — Rev. 2.5
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Data Sheet
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Break Module (BRK)
23.3 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).
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The following 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 MCU to normal
operation. Figure 23-1 shows the structure of the break module.
IAB15–IAB8
BREAK ADDRESS REGISTER HIGH
8-BIT COMPARATOR
IAB15–IAB0
CONTROL
BREAK
8-BIT COMPARATOR
BREAK ADDRESS REGISTER LOW
IAB7–IAB0
Figure 23-1. Break Module Block Diagram
Data Sheet
MC68HC908AP Family — Rev. 2.5
408
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Break Module (BRK)
Functional Description
Addr.
Register Name
Read:
SIM Break Status Register
$FE00
Write:
(SBSR)
Reset:
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$FE03
Read:
SIM Break Flag Control
Register Write:
(SBFCR)
Reset:
$FE0C
$FE0D
Read:
Break Address
Register High Write:
(BRKH)
Reset:
Read:
Break Address
Register Low Write:
(BRKL)
Reset:
Read:
Break Status and Control
$FE0E
Register Write:
(BRKSCR)
Reset:
Bit 7
6
5
4
3
2
R
R
R
R
R
R
1
SBSW
Note
Bit 0
R
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
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
BRKE
BRKA
0
0
0
0
0
0
0
0
0
0
0
0
0
0
= Unimplemented
R
= Reserved
0
Note: Writing a logic 0 clears BW.
Figure 23-2. Break Module I/O Register Summary
23.3.1 Flag Protection During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables
software to clear status bits during the break state.
23.3.2 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.
MC68HC908AP Family — Rev. 2.5
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Break Module (BRK)
23.3.3 TIMI and TIM2 During Break Interrupts
A break interrupt stops the timer counters.
23.3.4 COP During Break Interrupts
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The COP is disabled during a break interrupt when VTST is present on
the RST pin.
23.4 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
23.4.1 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. (see Section 9. System Integration Module (SIM)) Clear the BW
bit by writing logic 0 to it.
23.4.2 Stop Mode
A break interrupt causes exit from stop mode and sets the SBSW bit in
the break status register.
23.5 Break Module Registers
These registers control and monitor operation of the break module:
Data Sheet
•
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)
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Break Module (BRK)
Break Module Registers
23.5.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module
enable and status bits.
Address:
$FE0E
Bit 7
6
BRKE
BRKA
0
0
Read:
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
Write:
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Reset:
= Unimplemented
Figure 23-3. 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
MC68HC908AP Family — Rev. 2.5
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Break Module (BRK)
23.5.2 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.
Address:
$FE0C
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
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Read:
Write:
Reset:
Figure 23-4. Break Address Register High (BRKH)
Address:
$FE0D
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Read:
Write:
Reset:
Figure 23-5. Break Address Register Low (BRKL)
23.5.3 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.
Address:
$FE00
Bit 7
6
5
4
3
2
R
R
R
R
R
R
Read:
1
Bit 0
SBSW
R
Write:
Note
Reset:
0
Note: Writing a logic 0 clears SBSW.
R
= Reserved
Figure 23-6. SIM Break Status Register (SBSR)
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Break Module (BRK)
Break Module Registers
SBSW — Break Wait Bit
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This status bit is set when a break interrupt causes an exit from wait
mode or stop mode. Clear SBSW by writing a logic 0 to it. Reset clears
SBSW.
1 = Stop mode or wait mode was exited by break interrupt
0 = Stop mode or wait mode was not exited by break interrupt
SBSW can be read within the break interrupt routine. The user can
modify the return address on the stack by subtracting 1 from it. The
following code is an example.
; 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 or stop 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/STOP opcode.
RETURN
PULH
RTI
;Restore H register.
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Break Module (BRK)
23.5.4 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.
Address:
$FE03
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
Read:
Write:
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Reset:
0
R
= Reserved
Figure 23-7. 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
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Data Sheet – MC68HC908AP Family
Section 24. Electrical Specifications
24.1 Introduction
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This section contains electrical and timing specifications.
24.2 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 DC Electrical Characteristics for guaranteed
operating conditions.
Table 24-1. Absolute Maximum Ratings
Characteristic(1)
Symbol
Value
Unit
Supply voltage
VDD
–0.3 to +6.0
V
Input voltage
All pins (except IRQ1)
IRQ1 pin
VIN
VSS –0.3 to VDD +0.3
VSS –0.3 to 8.5
V
V
I
±25
mA
Maximum current out of VSS
IMVSS
100
mA
Maximum current into VDD
IMVDD
100
mA
Storage temperature
TSTG
–55 to +150
°C
Maximum current per pin
excluding VDD and VSS
Notes:
1. Voltages 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
MC68HC908AP Family — Rev. 2.5
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Electrical Specifications
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.)
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24.3 Functional Operating Range
Table 24-2. Operating Range
Characteristic
Operating temperature range
Operating voltage range
Symbol
Value
Unit
TA
– 40 to +85
°C
VDD
2.7 to 5.5
V
24.4 Thermal Characteristics
Table 24-3. Thermal Characteristics
Characteristic
Symbol
Value
Unit
Thermal resistance
42-Pin SDIP
44-Pin QFP
48-Pin LQFP
θJA
60
95
80
°C/W
°C/W
°C/W
I/O pin power dissipation
PI/O
User determined
W
Power dissipation(1)
PD
PD = (IDD × VDD) + PI/O =
K/(TJ + 273 °C)
W
Constant(2)
K
Average junction temperature
Maximum junction temperature
PD x (TA + 273 °C)
+ PD2 × θJA
W/°C
TJ
TA + (PD × θJA)
°C
TJM
100
°C
Notes:
1. Power dissipation is a function of temperature.
2. K 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.
Data Sheet
MC68HC908AP Family — Rev. 2.5
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Electrical Specifications
5V DC Electrical Characteristics
24.5 5V DC Electrical Characteristics
Table 24-4. DC Electrical Characteristics (5V)
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
VOH
VDD –0.8
—
—
V
VOL
VOL
VOLSCI
VOLIIC
—
—
—
—
—
—
—
—
0.4
0.4
0.4
0.4
V
V
V
V
LED sink current (VOL = 3V)
PTA[0:7]
IOL
9
15
25
mA
Input high voltage
PTA[0:7], PTB[0:7], PTC[0:7], PTD[0:7], RST, IRQ1
OSC1
VIH
0.7 × VDD
0.7 × VREG
—
—
VDD
VREG
V
V
Input low voltage
PTA[0:7], PTB[0:7], PTC[0:7], PTD[0:7], RST, IRQ1
OSC1
VIL
VSS
VSS
—
—
0.3 × VDD
0.3 × VREG
V
V
—
10
20
—
2.5
10
mA
mA
—
—
—
0.8
22
20
1.8
150
125
mA
µA
µA
—
—
—
1
45
42
2.5
300
250
mA
µA
µA
Freescale Semiconductor, Inc...
Output high voltage (ILOAD = –12mA)
PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7]
Output low voltage
(ILOAD = 8mA) PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7]
(ILOAD = 15mA) PTB[0:3], PTC[6:7]
(ILOAD = 15mA) as TxD, RxD, SCTxD, SCRxD
(ILOAD = see Table 24-12) as SDA, SCL
VDD supply current, fOP = 8 MHz
Run(3)
Wait(4)
Stop (25°C)
with OSC, TBM, and LVI modules on(5)
with OSC and TBM modules on(5)
all modules off(6)
IDD
Stop (0 to 85°C)
with OSC, TBM, and LVI modules on(5)
with OSC and TBM modules on(5)
all modules off(6)
Digital I/O ports Hi-Z leakage current
IIL
—
—
± 10
µA
Input current
IIN
—
—
±1
µA
COUT
CIN
—
—
—
—
12
8
pF
pF
Capacitance
Ports (as input or output)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
417
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Electrical Specifications
Table 24-4. DC Electrical Characteristics (5V)
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
POR rearm voltage(7)
VPOR
0
—
100
mV
POR rise time ramp rate(8)
RPOR
0.035
—
—
V/ms
Monitor mode entry voltage
VHI
1.4 × VDD
8.5
V
RPU1
RPU2
21
21
27
27
39
39
kΩ
kΩ
Low-voltage inhibit, trip falling voltage1(10)
VTRIPF1
2.25
2.45
2.65
V
Low-voltage inhibit, trip rising voltage1(10)
VTRIPR1
2.35
2.55
2.75
V
Low-voltage inhibit, trip voltage2(10)
VTRIPF2
2.25
2.45
2.65
V
VREG
2.25
2.50
2.75
V
Freescale Semiconductor, Inc...
Pullup resistors(9)
PTD[0:7]
RST, IRQ1, IRQ2
VREG(10), (11)
Notes:
1. VDD = 4.5 to 5.5 Vdc, 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 32MHz clock to OSC1; all inputs 0.2 V from rail; no dc loads; less than 100pF
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 32MHz to OSC1; 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.
5. STOP IDD measured using external 32.768kHz clock to OSC1; no port pins sourcing current.
6. STOP IDD measured with OSC1 grounded; no port pins sourcing current.
7. Maximum is highest voltage that POR is guaranteed. The rearm voltage is triggered by VREG.
8. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum
VDD is reached.
9. RPU1 and RPU2 are measured at VDD = 5.0V
10. Values are not affected by operating VDD; they are the same for 3V and 5V.
11. Measured from VDD = VTRIPF1 (Min) to 5.5 V.
Data Sheet
MC68HC908AP Family — Rev. 2.5
418
MOTOROLA
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Freescale Semiconductor, Inc.
Electrical Specifications
5V Control Timing
24.6 5V Control Timing
Table 24-5. Control Timing (5V)
Freescale Semiconductor, Inc...
Characteristic(1)
Symbol
Min
Max
Unit
Internal operating frequency(2)
fOP
—
8
MHz
RST input pulse width low(3)
tIRL
750
—
ns
Notes:
1. VDD = 4.5 to 5.5 Vdc, VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD, unless otherwise noted.
2. Some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this
information.
3. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause a reset.
24.7 5V Oscillator Characteristics
Table 24-6. Oscillator Specifications (5V)
Characteristic(1)
Symbol
Min
Typ
Max
Unit
Internal oscillator clock frequency
fICLK
16k
22k(2)
26k
Hz
External reference clock to OSC1(3)
fOSC
dc
16M
Hz
Crystal reference frequency(4)
fXTALCLK
32k
Hz
Crystal load capacitance(5)
CL
—
—
—
Crystal fixed capacitance(5)
C1
—
2 × CL
—
Crystal tuning capacitance(5)
C2
—
2 × CL
—
Feedback bias resistor
RB
—
10MΩ
—
Series resistor(5)
RS
—
100kΩ
—
fRCCLK
External RC clock frequency
RC oscillator external R
REXT
RC oscillator external C
CEXT
7.6M
Ω
See Figure 24-1
—
10
Hz
—
pF
Notes:
1. The oscillator circuit operates at VREG.
2. Typical value reflect average measurements at midpoint of voltage range, 25 °C only.
3. No more than 10% duty cycle deviation from 50%. The max. frequency is limited by an EMC filter.
4. Fundamental mode crystals only.
5. Consult crystal vendor data sheet.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
419
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Freescale Semiconductor, Inc.
Electrical Specifications
24.8 5V ADC Electrical Characteristics
Table 24-7. ADC Electrical Characteristics (5V)
Freescale Semiconductor, Inc...
Characteristic(1)
Symbol
Min
Max
Unit
Notes
Supply voltage
VDDA
4.5
5.5
V
VDDA is an dedicated pin and
should be tied to VDD on the
PCB with proper decoupling.
Input range
VADIN
0
VDDA
V
VADIN ≤ VDDA
Resolution
BAD
10
10
bits
Absolute accuracy
AAD
—
± 1.5
LSB
ADC internal clock
fADIC
500k
1.048M
Hz
Conversion range
RAD
VREFL
VREFH
V
ADC voltage
reference high
VREFH
—
VDDA + 0.1
V
ADC voltage
reference low
VREFL
VSSA – 0.1
—
V
Conversion time
tADC
16
17
tADIC
cycles
Sample time
tADS
5
—
tADIC
cycles
Monotonicity
MAD
Zero input reading
ZADI
000
001
HEX
VADIN = VREFL
Full-scale reading
FADI
3FD
3FF
HEX
VADIN = VREFH
Input capacitance
CADI
—
20
pF
Input impedance
RADI
20M
—
Ω
VREFH/VREFL
IVREF
—
1.6
mA
Includes quantization.
±0.5 LSB = ±1 ADC step.
tADIC = 1/fADIC
Guaranteed
Not tested.
Not tested.
Notes:
1. VDD = 4.5 to 5.5 Vdc, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted.
Data Sheet
MC68HC908AP Family — Rev. 2.5
420
MOTOROLA
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Freescale Semiconductor, Inc.
Electrical Specifications
3V DC Electrical Characteristics
24.9 3V DC Electrical Characteristics
Table 24-8. DC Electrical Characteristics (3V)
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
VOH
VDD –0.4
—
—
V
VOL
VOL
VOLSCI
VOLIIC
—
—
—
—
—
—
—
—
0.4
0.4
0.4
0.4
V
V
V
V
LED sink current (VOL = 2V)
PTA[0:7]
IOL
3
7
15
mA
Input high voltage
PTA[0:7], PTB[0:7], PTC[0:7], PTD[0:7], RST, IRQ1
OSC1
VIH
0.7 × VDD
0.7 × VREG
—
—
VDD
VREG
V
V
Input low voltage
PTA[0:7], PTB[0:7], PTC[0:7], PTD[0:7], RST, IRQ1
OSC1
VIL
VSS
VSS
—
—
0.3 × VDD
0.3 × VREG
V
V
Run(4)
with fOP = 4 MHz
with fOP = 8 MHz
—
6
10
mA
—
7.5
10
mA
Wait(5)
with fOP = 4 MHz
with fOP = 8 MHz
—
2
5
mA
—
2.9
5
mA
—
—
—
1.2
7
5
1.6
60
50
mA
µA
µA
—
—
—
1.3
35
30
2.2
220
200
mA
µA
µA
Freescale Semiconductor, Inc...
Output high voltage (ILOAD = –4mA)
PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7]
Output low voltage
(ILOAD = 4mA) PTA[0:7], PTB[4:7], PTC[0:5], PTD[0:7]
(ILOAD = 10mA) PTB[0:3], PTC[6:7]
(ILOAD = 10mA) as TxD, RxD, SCTxD, SCRxD
(ILOAD = see Table 24-12) as SDA, SCL
VDD supply current(3)
Stop (25°C)
with OSC, TBM, and LVI modules on(6)
with OSC and TBM modules on(6)
all modules off(7)
IDD
Stop (0 to 85°C)
with OSC, TBM, and LVI modules on(6)
with OSC and TBM modules on(6)
all modules off(7)
Digital I/O ports Hi-Z leakage current
IIL
—
—
± 10
µA
Input current
IIN
—
—
±1
µA
COUT
CIN
—
—
—
—
12
8
pF
pF
Capacitance
Ports (as input or output)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
421
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Electrical Specifications
Table 24-8. DC Electrical Characteristics (3V)
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
POR rearm voltage(8)
VPOR
0
—
100
mV
POR rise time ramp rate(9)
RPOR
0.02
—
—
V/ms
Monitor mode entry voltage
VHI
1.4 × VDD
8.5
V
RPU1
RPU2
21
21
27
27
39
39
kΩ
kΩ
Low-voltage inhibit, trip falling voltage1(11)
VTRIPF1
2.25
2.45
2.65
V
Low-voltage inhibit, trip rising voltage1(11)
VTRIPR1
2.35
2.55
2.75
V
Low-voltage inhibit, trip voltage2(11)
VTRIPF2
2.25
2.45
2.65
V
VREG
2.25
2.50
2.75
V
Freescale Semiconductor, Inc...
Pullup resistors(10)
PTD[0:7]
RST, IRQ1, IRQ2
VREG(11), (12)
Notes:
1. VDD = 2.7 to 3.3 Vdc, 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. At VDD = 3V, an on-chip charge pump is activated for the VREG regulator, therefore some IDD values will appear higher
than the IDD values at VDD = 5V.
4. Run (operating) IDD measured using external 16MHz/32MHz clock to OSC1; 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.
5. Wait IDD measured using external 16MHz/32MHz clock to OSC1; 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.
6. STOP IDD measured with external 32.768kHz clock to OSC1; no port pins sourcing current.
7. STOP IDD measured with OSC1 grounded; no port pins sourcing current.
8. Maximum is highest voltage that POR is guaranteed. The rearm voltage is triggered by VREG.
9. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum
VDD is reached.
10. RPU1 and RPU2 are measured at VDD = 5.0V
11. Values are not affected by operating VDD; they are the same for 3V and 5V.
12. Measured from VDD = VTRIPF1 (Min) to 5.5 V.
24.10 3V Control Timing
Table 24-9. Control Timing (3V)
Characteristic(1)
Symbol
Min
Max
Unit
Internal operating frequency(2)
fOP
—
8
MHz
RST input pulse width low(3)
tIRL
1.5
—
µs
Notes:
1. VDD = 2.7 to 3.3 Vdc, VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD, unless otherwise noted.
2. Some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this
information.
3. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause a reset.
Data Sheet
MC68HC908AP Family — Rev. 2.5
422
MOTOROLA
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Electrical Specifications
3V Oscillator Characteristics
24.11 3V Oscillator Characteristics
Table 24-10. Oscillator Specifications (3V)
Characteristic(1)
Symbol
Min
Typ
Max
Unit
Internal oscillator clock frequency
fICLK
16k
22k(2)
26k
Hz
External reference clock to OSC1(3)
fOSC
dc
16M
Hz
fXTALCLK
32k
Hz
Crystal load capacitance(5)
CL
—
—
—
Crystal fixed capacitance(5)
C1
—
2 × CL
—
Crystal tuning capacitance(5)
C2
—
2 × CL
—
Feedback bias resistor
RB
—
10MΩ
—
Series resistor(5)
RS
—
100kΩ
—
fRCCLK
External RC clock frequency
RC oscillator external R
REXT
RC oscillator external C
CEXT
7.6M
Hz
Ω
See Figure 24-1
—
10
—
pF
Notes:
1. The oscillator circuit operates at VREG.
2. Typical value reflect average measurements at midpoint of voltage range, 25 °C only.
3. No more than 10% duty cycle deviation from 50%. The max. frequency is limited by an EMC filter.
4. Fundamental mode crystals only.
5. Consult crystal vendor data sheet.
RC frequency, fRCCLK (MHz)
Freescale Semiconductor, Inc...
Crystal reference frequency(4)
MCU
CEXT = 10 pF
8
VDD = 3V, 5V, @ 25°C
OSC1
6
4
VREG
REXT
2
CEXT
0
0
10
20
30
Resistor, REXT (kΩ)
40
50
Figure 24-1. RC vs. Frequency
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
423
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Freescale Semiconductor, Inc.
Electrical Specifications
24.12 3V ADC Electrical Characteristics
Table 24-11. ADC Electrical Characteristics (3V)
Freescale Semiconductor, Inc...
Characteristic(1)
Symbol
Min
Max
Unit
Notes
Supply voltage
VDDA
2.7
3.3
V
VDDA is an dedicated pin and
should be tied to VDD on the
PCB with proper decoupling.
Input range
VADIN
0
VDDA
V
VADIN ≤ VDDA
Resolution
BAD
10
10
bits
Absolute accuracy
AAD
—
± 1.5
LSB
ADC internal clock
fADIC
500k
2M
Hz
Conversion range
RAD
VREFL
VREFH
V
ADC voltage
reference high
VREFH
—
VDDA + 0.1
V
ADC voltage
reference low
VREFL
VSSA – 0.1
—
V
Conversion time
tADC
16
17
tADIC
cycles
Sample time
tADS
5
—
tADIC
cycles
Monotonicity
MAD
Zero input reading
ZADI
000
001
HEX
VADIN = VREFL
Full-scale reading
FADI
3FD
3FF
HEX
VADIN = VREFH
Input capacitance
CADI
—
20
pF
Input impedance
RADI
20M
—
Ω
VREFH/VREFL
IVREF
—
1.6
mA
Includes quantization.
±0.5 LSB = ±1 ADC step.
tADIC = 1/fADIC
Guaranteed
Not tested.
Not tested.
Notes:
1. VDD = 4.5 to 5.5 Vdc, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted.
Data Sheet
MC68HC908AP Family — Rev. 2.5
424
MOTOROLA
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Freescale Semiconductor, Inc.
Electrical Specifications
MMIIC Electrical Characteristics
24.13 MMIIC Electrical Characteristics
Table 24-12. MMIIC DC Electrical Characteristics
Freescale Semiconductor, Inc...
Characteristic(1)
Symbol
Min
Typ
Max
Unit
Input low
VIL
–0.5
—
0.8
V
Data, clock input low.
Input high
VIH
2.1
—
5.5
V
Data, clock input high.
Output low
VOL
—
—
0.4
V
Data, clock output low;
@IPULLUP,MAX
ILEAK
—
—
±5
µA
Input leakage current
µA
Current through pull-up
resistor or current source.
See note.(2)
Input leakage
IPULLUP
Pullup current
100
—
350
Comments
Notes:
1. VDD = 2.7 to 5.5Vdc, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted.
2. The IPULLUP (max) specification is determined primarily by the need to accommodate a maximum of 1.1kΩ equivalent series resistor of removable SMBus devices, such as the smart battery, while maintaining the VOL (max) of the bus.
SDA
SCL
tHD.STA
tLOW
tHIGH
tSU.DAT
tHD.DAT
tSU.STA
tSU.STO
Figure 24-2. MMIIC Signal Timings
See Table 24-13 for MMIIC timing parameters.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
425
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Electrical Specifications
Table 24-13. MMIIC Interface Input/Output Signal Timing
Freescale Semiconductor, Inc...
Characteristic
Symbol
Min
Typ
Max
Unit
Comments
Operating frequency
fSMB
10
—
100
kHz
Bus free time
tBUF
4.7
—
—
µs
Bus free time between STOP and
START condition
Repeated start hold time.
tHD.STA
4.0
—
—
µs
Hold time after (repeated) START
condition. After this period, the
first clock is generated.
Repeated start setup time.
tSU.STA
4.7
—
—
µs
Repeated START condition setup
time.
Stop setup time
tSU.STO
4.0
—
—
µs
Stop condition setup time.
Hold time
tHD.DAT
300
—
—
ns
Data hold time.
Setup time
tSU.DAT
250
—
—
ns
Data setup time.
Clock low time-out
tTIMEOUT
25
—
35
ms
Clock low time-out.(1)
Clock low
tLOW
4.7
—
—
µs
Clock low period
Clock high
tHIGH
4.0
—
—
µs
Clock high period.(2)
Slave clock low extend time
tLOW.SEXT
—
—
25
ms
Cumulative clock low extend time
(slave device)(3)
Master clock low extend time
tLOW.MEXT
—
—
10
ms
Cumulative clock low extend time
(master device) (4)
Fall time
tF
—
—
300
ns
Clock/Data Fall Time(5)
Rise time
tR
—
—
1000
ns
Clock/Data Rise Time(5)
MMIIC operating frequency
Notes:
1. Devices participating in a transfer will timeout when any clock low exceeds the value of TTIMEOUT min. of 25ms. Devices
that have detected a timeout condition must reset the communication no later than TTIMEOUT max of 35ms. The maximum
value specified must be adhered to by both a master and a slave as it incorporates the cumulative limit for both a master
(10 ms) and a slave (25 ms).
Software should turn-off the MMIIC module to release the SDA and SCL lines.
2. THIGH MAX provides a simple guaranteed method for devices to detect the idle conditions.
3. TLOW.SEXT is the cumulative time a slave device is allowed to extend the clock cycles in one message from the initial start
to the stop. If a slave device exceeds this time, it is expected to release both its clock and data lines and reset itself.
4. TLOW.MEXT is the cumulative time a master device is allowed to extend its clock cycles within each byte of a message as
defined from start-to-ack, ack-to-ack, or ack-to-stop.
5. Rise and fall time is defined as follows: TR = (VILMAX – 0.15) to (VIHMIN + 0.15), TF = 0.9×VDD to (VILMAX – 0.15).
Data Sheet
MC68HC908AP Family — Rev. 2.5
426
MOTOROLA
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Electrical Specifications
CGM Electrical Specification
24.14 CGM Electrical Specification
Table 24-14. CGM Electrical Specifications
Freescale Semiconductor, Inc...
Characteristic
Symbol
Min
Typ
Max
Unit
Reference frequency
fRDV
30
32.768
100
kHz
Range nominal multiplies
fNOM
—
125
—
kHz
VCO center-of-range frequency
fVRS
125k
—
40M
Hz
VCO range linear range multiplier
L
1
—
255
VCO power-of-two-range multiplier
2E
1
—
4
VCO multiply factor
N
1
—
4095
VCO prescale multiplier
2P
1
—
8
Reference divider factor
R
1
1
15
VCO operating frequency
fVCLK
125k
—
40M
Hz
Manual acquisition time
tLOCK
—
—
50
ms
Automatic lock time
tLOCK
—
—
50
ms
(1)
fJ
—
fRCLK ×
0.025% ×
2P N/4
Hz
PLL jitter
0
Notes:
1. Deviation of average bus frequency over 2ms. N = VCO multiplier.
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
427
For More Information On This Product,
Go to: www.freescale.com
Freescale Semiconductor, Inc.
Electrical Specifications
24.15 5V SPI Characteristics
Freescale Semiconductor, Inc...
Diagram
Number(1)
Characteristic(2)
Symbol
Min
Max
Unit
Operating frequency
Master
Slave
fOP(M)
fOP(S)
fOP/128
dc
fOP/2
fOP
MHz
MHz
1
Cycle time
Master
Slave
tCYC(M)
tCYC(S)
2
1
128
—
tCYC
tCYC
2
Enable lead time
tLead(S)
1
—
tCYC
3
Enable lag time
tLag(S)
1
—
tCYC
4
Clock (SPSCK) high time
Master
Slave
tSCKH(M)
tSCKH(S)
tCYC –25
1/2 tCYC –25
64 tCYC
—
ns
ns
5
Clock (SPSCK) low time
Master
Slave
tSCKL(M)
tSCKL(S)
tCYC –25
1/2 tCYC –25
64 tCYC
—
ns
ns
6
Data setup time (inputs)
Master
Slave
tSU(M)
tSU(S)
30
30
—
—
ns
ns
7
Data hold time (inputs)
Master
Slave
tH(M)
tH(S)
30
30
—
—
ns
ns
8
Access time, slave(3)
CPHA = 0
CPHA = 1
tA(CP0)
tA(CP1)
0
0
40
40
ns
ns
9
Disable time, slave(4)
tDIS(S)
—
40
ns
10
Data valid time, after enable edge
Master
Slave(5)
tV(M)
tV(S)
—
—
50
50
ns
ns
11
Data hold time, outputs, after enable edge
Master
Slave
tHO(M)
tHO(S)
0
0
—
—
ns
ns
Notes:
1. Numbers refer to dimensions in Figure 24-3 and Figure 24-4.
2. All timing is shown with respect to 20% VDD and 70% VDD, unless noted; 100 pF load on all SPI pins.
3. Time to data active from high-impedance state
4. Hold time to high-impedance state
5. With 100 pF on all SPI pins
Data Sheet
MC68HC908AP Family — Rev. 2.5
428
MOTOROLA
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Electrical Specifications
3V SPI Characteristics
24.16 3V SPI Characteristics
Freescale Semiconductor, Inc...
Diagram
Number(1)
Characteristic(2)
Symbol
Min
Max
Unit
Operating frequency
Master
Slave
fOP(M)
fOP(S)
fOP/128
dc
fOP/2
fOP
MHz
MHz
1
Cycle time
Master
Slave
tCYC(M)
tCYC(S)
2
1
128
—
tCYC
tCYC
2
Enable lead time
tLead(s)
1
—
tCYC
3
Enable lag time
tLag(s)
1
—
tCYC
4
Clock (SPSCK) high time
Master
Slave
tSCKH(M)
tSCKH(S)
tCYC –35
1/2 tCYC –35
64 tCYC
—
ns
ns
5
Clock (SPSCK) low time
Master
Slave
tSCKL(M)
tSCKL(S)
tCYC –35
1/2 tCYC –35
64 tCYC
—
ns
ns
6
Data setup time (inputs)
Master
Slave
tSU(M)
tSU(S)
40
40
—
—
ns
ns
7
Data hold time (inputs)
Master
Slave
tH(M)
tH(S)
40
40
—
—
ns
ns
8
Access time, slave(3)
CPHA = 0
CPHA = 1
tA(CP0)
tA(CP1)
0
0
50
50
ns
ns
9
Disable time, slave(4)
tDIS(S)
—
50
ns
10
Data valid time, after enable edge
Master
Slave(5)
tV(M)
tV(S)
—
—
60
60
ns
ns
11
Data hold time, outputs, after enable edge
Master
Slave
tHO(M)
tHO(S)
0
0
—
—
ns
ns
Notes:
1. Numbers refer to dimensions in Figure 24-3 and Figure 24-4.
2. All timing is shown with respect to 20% VDD and 70% VDD, unless noted; 100 pF load on all SPI pins.
3. Time to data active from high-impedance state
4. Hold time to high-impedance state
5. With 100 pF on all SPI pins
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
429
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Electrical Specifications
SS
INPUT
SS PIN OF MASTER HELD HIGH
1
SPSCK OUTPUT
CPOL = 0
NOTE
SPSCK OUTPUT
CPOL = 1
NOTE
5
4
5
4
6
MISO
INPUT
BITS 6–1
MSB IN
Freescale Semiconductor, Inc...
11
MOSI
OUTPUT
MASTER MSB OUT
7
LSB IN
10
11
BITS 6–1
MASTER LSB OUT
Note: This first clock edge is generated internally, but is not seen at the SPSCK pin.
a) SPI Master Timing (CPHA = 0)
SS
INPUT
SS PIN OF MASTER HELD HIGH
1
SPSCK OUTPUT
CPOL = 0
5
NOTE
4
SPSCK OUTPUT
CPOL = 1
5
NOTE
4
6
MISO
INPUT
MSB IN
10
MOSI
OUTPUT
BITS 6–1
11
MASTER MSB OUT
7
LSB IN
10
BITS 6–1
MASTER LSB OUT
Note: This last clock edge is generated internally, but is not seen at the SPSCK pin.
b) SPI Master Timing (CPHA = 1)
Figure 24-3. SPI Master Timing
Data Sheet
MC68HC908AP Family — Rev. 2.5
430
MOTOROLA
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Electrical Specifications
3V SPI Characteristics
SS
INPUT
3
1
SPSCK INPUT
CPOL = 0
5
4
2
SPSCK INPUT
CPOL = 1
5
4
9
8
Freescale Semiconductor, Inc...
MISO
INPUT
SLAVE
MSB OUT
6
MOSI
OUTPUT
BITS 6–1
7
NOTE
11
11
10
MSB IN
SLAVE LSB OUT
BITS 6–1
LSB IN
Note: Not defined but normally MSB of character just received
a) SPI Slave Timing (CPHA = 0)
SS
INPUT
1
SPSCK INPUT
CPOL = 0
5
4
2
3
SPSCK INPUT
CPOL = 1
8
MISO
OUTPUT
5
4
10
NOTE
MOSI
INPUT
9
SLAVE
MSB OUT
6
7
BITS 6–1
11
10
MSB IN
SLAVE LSB OUT
BITS 6–1
LSB IN
Note: Not defined but normally LSB of character previously transmitted
b) SPI Slave Timing (CPHA = 1)
Figure 24-4. SPI Slave Timing
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
431
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Electrical Specifications
24.17 FLASH Memory Characteristics
Table 24-15. FLASH Memory Electrical Characteristics
Characteristic
Freescale Semiconductor, Inc...
Data retention voltage
Symbol
Min.
Max.
Unit
VRDR
1.3
—
V
Number of rows per page
8
Rows
Number of bytes per page
512
Bytes
Read bus clock frequency
fread(1)
32k
8M
Hz
Page erase time
terase(2)
20
—
ms
Mass erase time
tme(3)
200
—
ms
PGM/ERASE to HVEN setup time
tnvs
5
—
µs
High-voltage hold time
tnvh
5
—
µs
High-voltage hold time (mass erase)
tnvh1
100
—
µs
Program hold time
tpgs
10
—
µs
Program time
tprog
20
40
µs
Address/data setup time
tads
20
—
ns
Address/data hold time
tadh
—
30
ns
Recovery time
trcv(4)
1
—
µs
Cumulative HV period
thv(5)
—
8
ms
Row erase endurance(6)
—
10k
—
Cycles
Row program endurance(7)
—
10k
—
Cycles
Data retention time(8)
—
10
—
Years
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 tme (Min.), there is no erase-disturb, but is reduces the endurance of the FLASH
memory.
4. It 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 the cumulative high voltage programming time to the same row before next erase, and the same address can not be
programmed twice before next erase.
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. The minimum row endurance value specifies each row of the FLASH memory is guaranteed to work for at least this many
erase/program cycle.
8. The FLASH is guaranteed to retain data over the entire operating temperature range for at least the minimum time
specified.
Data Sheet
MC68HC908AP Family — Rev. 2.5
432
MOTOROLA
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Data Sheet – MC68HC908AP Family
Section 25. Mechanical Specifications
25.1 Introduction
Freescale Semiconductor, Inc...
This section gives the dimensions for:
•
48-pin plastic low-profile quad flat pack (case #932)
•
44-pin plastic quad flat pack (case #824A)
•
42-pin shrink dual in-line package (case #858)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
433
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Mechanical Specifications
25.2 48-Pin Low-Profile Quad Flat Pack (LQFP)
4X
NOTES:
1. DIMENSIONING AND TOLERANCING PER ASME
Y14.5M, 1994.
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 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
0.350.
8. MINIMUM SOLDER PLATE THICKNESS SHALL BE
0.0076.
9. EXACT SHAPE OF EACH CORNER IS OPTIONAL.
0.200 AB T–U Z
DETAIL Y
A
P
A1
48
37
1
36
Freescale Semiconductor, Inc...
T
U
B
V
AE
B1
12
25
13
AE
V1
24
DIM
A
A1
B
B1
C
D
E
F
G
H
J
K
L
M
N
P
R
S
S1
V
V1
W
AA
Z
S1
T, U, Z
S
DETAIL Y
4X
0.200 AC T–U Z
0.080 AC
G
AB
AD
AC
MILLIMETERS
MAX
MIN
7.000 BSC
3.500 BSC
7.000 BSC
3.500 BSC
1.400
1.600
0.170
0.270
1.350
1.450
0.170
0.230
0.500 BSC
0.050
0.150
0.090
0.200
0.500
0.700
1°
5°
12° REF
0.090
0.160
0.250 BSC
0.150
0.250
9.000 BSC
4.500 BSC
9.000 BSC
4.500 BSC
0.200 REF
1.000 REF
M°
BASE METAL
TOP & BOTTOM
J
0.250
N
R
C
E
GAUGE PLANE
9
F
D
0.080
M
AC T–U Z
SECTION AE–AE
W
H
L°
K
DETAIL AD
AA
Figure 25-1. 48-Pin LQFP (Case #932)
Data Sheet
MC68HC908AP Family — Rev. 2.5
434
MOTOROLA
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Mechanical Specifications
44-Pin Quad Flat Pack (QFP)
25.3 44-Pin Quad Flat Pack (QFP)
B
L
B
33
23
22
DETAIL A
S
D
S
V
F
BASE METAL
M
C A–B
S
S
H A–B
DETAIL A
0.20 (0.008)
B
0.20 (0.008)
M
–B–
0.05 (0.002) A–B
–A–
D
–A–, –B–, –D–
L
Freescale Semiconductor, Inc...
34
J
N
D
44
0.20 (0.008)
12
1
11
M
C A–B
S
D
S
SECTION B–B
VIEW ROTATED 90°
–D–
A
0.20 (0.008)
M
H A–B
S
D
S
S
D
S
0.05 (0.002) A–B
S
0.20 (0.008)
M
C A–B
M
DETAIL C
C E
–H–
–C–
DATUM
PLANE
0.10 (0.004)
H
SEATING
PLANE
G
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: MILLIMETER.
3. DATUM PLANE –H– 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 –A–, –B– AND –D– TO BE DETERMINED AT
DATUM PLANE –H–.
5. DIMENSIONS S AND V TO BE DETERMINED AT
SEATING PLANE –C–.
6. DIMENSIONS A AND B DO NOT INCLUDE MOLD
PROTRUSION. ALLOWABLE PROTRUSION IS 0.25
(0.010) PER SIDE. DIMENSIONS A AND B DO
INCLUDE MOLD MISMATCH AND ARE DETERMINED
AT DATUM PLANE –H–.
7. DIMENSION D DOES NOT INCLUDE DAMBAR
PROTRUSION. ALLOWABLE DAMBAR PROTRUSION
SHALL BE 0.08 (0.003) TOTAL IN EXCESS OF THE D
DIMENSION AT MAXIMUM MATERIAL CONDITION.
DAMBAR CANNOT BE LOCATED ON THE LOWER
RADIUS OR THE FOOT.
M
M
T
DATUM
PLANE
–H–
R
K
W
Q
X
DETAIL C
DIM
A
B
C
D
E
F
G
H
J
K
L
M
N
Q
R
S
T
U
V
W
X
MILLIMETERS
MIN
MAX
9.90
10.10
9.90
10.10
2.10
2.45
0.30
0.45
2.00
2.10
0.30
0.40
0.80 BSC
—
0.25
0.13
0.23
0.65
0.95
8.00 REF
5°
10°
0.13
0.17
0°
7°
0.13
0.30
12.95
13.45
0.13
—
0°
—
12.95
13.45
0.40
—
1.6 REF
INCHES
MIN
MAX
0.390
0.398
0.390
0.398
0.083
0.096
0.012
0.018
0.079
0.083
0.012
0.016
0.031 BSC
—
0.010
0.005
0.009
0.026
0.037
0.315 REF
5°
10°
0.005
0.007
0°
7°
0.005
0.012
0.510
0.530
0.005
—
0°
—
0.510
0.530
0.016
—
0.063 REF
Figure 25-2. 44-Pin QFP (Case #824A)
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
435
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Mechanical Specifications
25.4 42-Pin Shrink Dual In-Line Package (SDIP)
NOTES:
1. DIMENSIONING AND TOLERANCING PER ANSI
Y14.5M, 1982.
2. CONTROLLING DIMENSION: INCH.
3. DIMENSION L TO CENTER OF LEAD WHEN
FORMED PARALLEL.
4. DIMENSIONS A AND B DO NOT INCLUDE MOLD
FLASH. MAXIMUM MOLD FLASH 0.25 (0.010).
–A–
42
22
–B–
1
21
L
H
C
Freescale Semiconductor, Inc...
DIM
A
B
C
D
F
G
H
J
K
L
M
N
–T–
SEATING
PLANE
0.25 (0.010)
N
G
F
D 42 PL
K
M
T A
S
M
J 42 PL
0.25 (0.010)
M
T B
INCHES
MIN
MAX
1.435
1.465
0.540
0.560
0.155
0.200
0.014
0.022
0.032
0.046
0.070 BSC
0.300 BSC
0.008
0.015
0.115
0.135
0.600 BSC
0°
15°
0.020
0.040
MILLIMETERS
MIN
MAX
36.45
37.21
13.72
14.22
3.94
5.08
0.36
0.56
0.81
1.17
1.778 BSC
7.62 BSC
0.20
0.38
2.92
3.43
15.24 BSC
0°
15°
0.51
1.02
S
Figure 25-3. 42-Pin SDIP (Case #858)
Data Sheet
MC68HC908AP Family — Rev. 2.5
436
MOTOROLA
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Data Sheet – MC68HC908AP Family
Section 26. Ordering Information
26.1 Introduction
Freescale Semiconductor, Inc...
This section contains device ordering numbers.
26.2 MC Order Numbers
Table 26-1. MC Order Numbers
RAM Size
(bytes)
FLASH Size
(bytes)
Package
Operating
Temperature Range
MC68HC908AP64CB
2,048
62,368
42-pin SDIP
– 40 to +85 °C
MC68HC908AP64CFB
2,048
62,368
44-pin QFP
– 40 to +85 °C
MC68HC908AP64CFA
2,048
62,368
48-pin LQFP
– 40 to +85 °C
MC68HC908AP32CB
2,048
32,768
42-pin SDIP
– 40 to +85 °C
MC68HC908AP32CFB
2,048
32,768
44-pin QFP
– 40 to +85 °C
MC68HC908AP32CFA
2,048
32,768
48-pin LQFP
– 40 to +85 °C
MC68HC908AP16CB
1,024
16,384
42-pin SDIP
– 40 to +85 °C
MC68HC908AP16CFB
1,024
16,384
44-pin QFP
– 40 to +85 °C
MC68HC908AP16CFA
1,024
16,384
48-pin LQFP
– 40 to +85 °C
MC68HC908AP8CB
1,024
8,192
42-pin SDIP
– 40 to +85 °C
MC68HC908AP8CFB
1,024
8,192
44-pin QFP
– 40 to +85 °C
MC68HC908AP8CFA
1,024
8,192
48-pin LQFP
– 40 to +85 °C
MC Order Number
MC68HC908AP Family — Rev. 2.5
MOTOROLA
Data Sheet
437
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Freescale Semiconductor, Inc.
Freescale Semiconductor, Inc...
Ordering Information
Data Sheet
MC68HC908AP Family — Rev. 2.5
438
MOTOROLA
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Freescale Semiconductor, Inc...
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Freescale Semiconductor, Inc.
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Freescale Semiconductor, Inc...
JAPAN:
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© Motorola Inc. 2003
MC68HC908AP64/D
Rev. 2.5
10/2003
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