MC68HC908AB32
Technical Data
M68HC08
Microcontrollers
Rev. 1.1
MC68HC908AB32/D
August 2, 2005
freescale.com
Technical Data — MC68HC908AB32
List of Sections
Section 1. General Description . . . . . . . . . . . . . . . . . . . . 29
Section 2. Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Section 3. Random-Access Memory (RAM) . . . . . . . . . . 57
Section 4. FLASH Memory . . . . . . . . . . . . . . . . . . . . . . . . 59
Section 5. EEPROM. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
Section 6. Configuration Register (CONFIG) . . . . . . . . . 85
Section 7. Central Processor Unit (CPU) . . . . . . . . . . . . 89
Section 8. System Integration Module (SIM) . . . . . . . . 109
Section 9. Clock Generator Module (CGM) . . . . . . . . . . 131
Section 10. Monitor ROM (MON) . . . . . . . . . . . . . . . . . . 157
Section 11. Timer Interface Module A (TIMA) . . . . . . . . 169
Section 12. Timer Interface Module B (TIMB) . . . . . . . . 195
Section 13. Programmable Interrupt Timer (PIT) . . . . . 221
Section 14. Analog-to-Digital Converter (ADC) . . . . . . 229
Section 15. Serial Communications Interface
Module (SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
Section 16. Serial Peripheral Interface Module (SPI) . . 279
Section 17. Input/Output (I/O) Ports . . . . . . . . . . . . . . . 311
Section 18. External Interrupt (IRQ) . . . . . . . . . . . . . . . 339
Section 19. Keyboard Interrupt Module (KBI). . . . . . . . 345
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Section 20. Computer Operating Properly (COP) . . . . 353
Section 21. Low-Voltage Inhibit (LVI) . . . . . . . . . . . . . . 359
Section 22. Break Module (BRK) . . . . . . . . . . . . . . . . . . 365
Section 23. Electrical Specifications. . . . . . . . . . . . . . . 373
Section 24. Mechanical Specifications . . . . . . . . . . . . . 387
Section 25. Ordering Information . . . . . . . . . . . . . . . . . 389
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MC68HC908AB32 — Rev. 1.1
List of Sections
Freescale Semiconductor
Technical Data — MC68HC908AB32
Table of Contents
Section 1. General Description
1.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
1.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.4
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
1.5
Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1.6
Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
1.6.1
Power Supply Pins (VDD and VSS) . . . . . . . . . . . . . . . . . . . . 34
1.6.2
Oscillator Pins (OSC1 and OSC2) . . . . . . . . . . . . . . . . . . . . 35
1.6.3
External Reset Pin (RST) . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.6.4
External Interrupt Pin (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.6.5
Analog Power Supply Pin (VDDA) . . . . . . . . . . . . . . . . . . . . .35
1.6.6
Analog Ground Pin (VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.6.7
Analog Ground Pin (AVSS/VREFL). . . . . . . . . . . . . . . . . . . . .35
1.6.8
ADC Voltage Reference Pin (VREFH) . . . . . . . . . . . . . . . . . . 36
1.6.9
Analog Supply Pin (VDDAREF) . . . . . . . . . . . . . . . . . . . . . . . 36
1.6.10 External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . 36
1.6.11 Port A Input/Output (I/O) Pins (PTA7–PTA0) . . . . . . . . . . . . 36
1.6.12 Port B I/O Pins (PTB7/ATD7–PTB0/ATD0) . . . . . . . . . . . . . 36
1.6.13 Port C I/O Pins (PTC5–PTC0) . . . . . . . . . . . . . . . . . . . . . . . 36
1.6.14 Port D I/O Pins (PTD7–PTD0) . . . . . . . . . . . . . . . . . . . . . . . 37
1.6.15 Port E I/O Pins (PTE7/SPSCK–PTE0/TxD) . . . . . . . . . . . . . 37
1.6.16 Port F I/O Pins (PTF7–PTF0/TACH2) . . . . . . . . . . . . . . . . . 37
1.6.17 Port G I/O Pins (PTG2/KBD2–PTG0/KBD0) . . . . . . . . . . . . 37
1.6.18 Port H I/O Pins (PTH1/KBD4–PTH0/KBD3). . . . . . . . . . . . . 37
1.7
I/O Pin Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1.8
Signal Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
1.9
Clock Source Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
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Section 2. Memory Map
2.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41
2.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.3
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . 41
2.4
Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.5
Input/Output (I/O) Section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
Section 3. Random-Access Memory (RAM)
3.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
3.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
Section 4. FLASH Memory
4.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
4.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
4.4
FLASH Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.5
FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.6
FLASH Mass Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.7
FLASH Program/Read Operation . . . . . . . . . . . . . . . . . . . . . . . 63
4.8
FLASH Block Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.8.1
FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . 66
4.9
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.10
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Section 5. EEPROM
5.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .69
5.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
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5.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
5.5
EEPROM Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.6
EEPROM Timebase Requirements . . . . . . . . . . . . . . . . . . . . . 72
5.7
EEPROM Security Options. . . . . . . . . . . . . . . . . . . . . . . . . . . .72
5.8
EEPROM Block Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
5.9
EEPROM Programming and Erasing . . . . . . . . . . . . . . . . . . . . 73
5.9.1
EEPROM Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
5.9.2
EEPROM Erasing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.10 Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.10.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
5.10.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
5.11 EEPROM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.11.1 EEPROM Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.11.2 EEPROM Array Configuration Register . . . . . . . . . . . . . . . . 79
5.11.2.1
EEPROM Non-Volatile Register. . . . . . . . . . . . . . . . . . . . 80
5.11.3 EEPROM Timebase Divider Register . . . . . . . . . . . . . . . . . 80
5.11.3.1
EEPROM Timebase Divider Non-Volatile Register . . . . . 82
Section 6. Configuration Register (CONFIG)
6.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .85
6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.3
Functional description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.4
Configuration Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.5
Configuration Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
Section 7. Central Processor Unit (CPU)
7.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .89
7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
7.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
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7.4
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
7.4.1
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.4.2
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
7.4.3
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
7.4.4
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.4.5
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.5
Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.6
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
7.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
7.7
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.8
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.9
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Section 8. System Integration Module (SIM)
8.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .109
8.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
8.3
SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . 112
8.3.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
8.3.2
Clock Start-Up from POR or LVI Reset . . . . . . . . . . . . . . . 113
8.3.3
Clocks in Stop and Wait Modes . . . . . . . . . . . . . . . . . . . . . 113
8.4
Reset and System Initialization. . . . . . . . . . . . . . . . . . . . . . . . 113
8.4.1
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
8.4.2
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . 114
8.4.2.1
Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
8.4.2.2
Computer Operating Properly (COP) Reset. . . . . . . . . . 116
8.4.2.3
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
8.4.2.4
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . .117
8.4.2.5
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . 117
8.5
SIM Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
8.5.1
SIM Counter during Power-On Reset. . . . . . . . . . . . . . . . . 118
8.5.2
SIM Counter during Stop Mode Recovery . . . . . . . . . . . . . 118
8.5.3
SIM Counter and Reset States. . . . . . . . . . . . . . . . . . . . . . 118
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8.6
Exception Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
8.6.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
8.6.1.1
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
8.6.1.2
SWI Instruction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
8.6.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
8.6.3
Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
8.6.4
Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . 123
8.7
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
8.7.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
8.7.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
8.8
SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
8.8.1
SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 127
8.8.2
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 128
8.8.3
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . 129
Section 9. Clock Generator Module (CGM)
9.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131
9.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
9.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
9.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
9.4.1
Crystal Oscillator Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . .134
9.4.2
Phase-Locked Loop (PLL) Circuit . . . . . . . . . . . . . . . . . . . 135
9.4.2.1
PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
9.4.2.2
Acquisition and Tracking Modes . . . . . . . . . . . . . . . . . . 136
9.4.2.3
Manual and Automatic PLL Bandwidth Modes . . . . . . . 136
9.4.2.4
Programming the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . 138
9.4.2.5
Special Programming Exceptions . . . . . . . . . . . . . . . . . 139
9.4.3
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . 140
9.4.4
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . 140
9.5
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
9.5.1
Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . 142
9.5.2
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . 142
9.5.3
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . 142
9.5.4
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . 142
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9.5.5
9.5.6
9.5.7
9.5.8
Oscillator Enable Signal (SIMOSCEN). . . . . . . . . . . . . . . . 142
Crystal Output Frequency Signal (CGMXCLK) . . . . . . . . . 143
CGM Base Clock Output (CGMOUT). . . . . . . . . . . . . . . . . 143
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . 143
9.6
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
9.6.1
PLL Control Register (PCTL) . . . . . . . . . . . . . . . . . . . . . . . 144
9.6.2
PLL Bandwidth Control Register (PBWC) . . . . . . . . . . . . . 146
9.6.3
PLL Programming Register (PPG) . . . . . . . . . . . . . . . . . . . 148
9.7
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
9.8
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
9.8.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
9.8.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151
9.9
CGM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 151
9.10 Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . . . . . 151
9.10.1 Acquisition/Lock Time Definitions. . . . . . . . . . . . . . . . . . . .152
9.10.2 Parametric Influences On Reaction Time. . . . . . . . . . . . . . 153
9.10.3 Choosing a Filter Capacitor . . . . . . . . . . . . . . . . . . . . . . . . 154
9.10.4 Reaction Time Calculation . . . . . . . . . . . . . . . . . . . . . . . . . 155
Section 10. Monitor ROM (MON)
10.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .157
10.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
10.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
10.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
10.4.1 Entering Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
10.4.2 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
10.4.3 Echoing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
10.4.4 Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
10.4.5 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
10.4.6 Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
10.5
Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
10.6
Extended Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
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Section 11. Timer Interface Module A (TIMA)
11.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .169
11.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
11.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
11.4
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
11.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171
11.5.1 TIMA Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . .171
11.5.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
11.5.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
11.5.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . 175
11.5.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . .176
11.5.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . 177
11.5.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . 178
11.5.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . 179
11.5.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
11.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181
11.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
11.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
11.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
11.8
TIMA During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 182
11.9 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
11.9.1 TIMA Clock Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
11.9.2 TIMA Channel I/O Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
11.10 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
11.10.1 TIMA Status and Control Register . . . . . . . . . . . . . . . . . . . 184
11.10.2 TIMA Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .186
11.10.3 TIMA Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . 187
11.10.4 TIMA Channel Status and Control Registers . . . . . . . . . . . 188
11.10.5 TIMA Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 192
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Section 12. Timer Interface Module B (TIMB)
12.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .195
12.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
12.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
12.4
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
12.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
12.5.1 TIMB Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . .197
12.5.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
12.5.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
12.5.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . 201
12.5.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . .202
12.5.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . 203
12.5.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . 204
12.5.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . 205
12.5.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
12.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
12.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
12.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
12.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
12.8
TIMB During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 208
12.9 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
12.9.1 TIMB Clock Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
12.9.2 TIMB Channel I/O Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
12.10 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
12.10.1 TIMB Status and Control Register . . . . . . . . . . . . . . . . . . . 210
12.10.2 TIMB Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .212
12.10.3 TIMB Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . 213
12.10.4 TIMB Channel Status and Control Registers . . . . . . . . . . . 214
12.10.5 TIMB Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 218
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Section 13. Programmable Interrupt Timer (PIT)
13.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .221
13.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
13.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
13.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222
13.4.1 PIT Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
13.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
13.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
13.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
13.6
PIT During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 224
13.7 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
13.7.1 PIT Status and Control Register. . . . . . . . . . . . . . . . . . . . . 225
13.7.2 PIT Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
13.7.3 PIT Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . 228
Section 14. Analog-to-Digital Converter (ADC)
14.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .229
14.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
14.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
14.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .231
14.4.1 ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
14.4.2 Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232
14.4.3 Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
14.4.4 Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
14.4.5 Accuracy and Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
14.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233
14.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
14.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233
14.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233
14.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
14.7.1 ADC Analog Power Pin (VDDAREF). . . . . . . . . . . . . . . . . . . 234
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14.7.2
14.7.3
14.7.4
ADC Analog Ground Pin (AVSS/VREFL) . . . . . . . . . . . . . . . 234
ADC Voltage Reference High Pin (VREFH). . . . . . . . . . . . . 234
ADC Voltage In (VADIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
14.8 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
14.8.1 ADC Status and Control Register (ADSCR). . . . . . . . . . . . 235
14.8.2 ADC Data Register (ADR) . . . . . . . . . . . . . . . . . . . . . . . . . 237
14.8.3 ADC Clock Register (ADCLK) . . . . . . . . . . . . . . . . . . . . . . 237
Section 15. Serial Communications Interface
Module (SCI)
15.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .239
15.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
15.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
15.4
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
15.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242
15.5.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
15.5.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
15.5.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
15.5.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . 247
15.5.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
15.5.2.4
Idle Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
15.5.2.5
Inversion of Transmitted Output. . . . . . . . . . . . . . . . . . . 249
15.5.2.6
Transmitter Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . .249
15.5.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
15.5.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
15.5.3.2
Character Reception . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
15.5.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
15.5.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
15.5.3.5
Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . .254
15.5.3.6
Receiver Wakeup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
15.5.3.7
Receiver Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
15.5.3.8
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
15.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
15.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
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15.6.2
15.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
SCI During Break Module Interrupts. . . . . . . . . . . . . . . . . . . .260
15.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
15.8.1 PTE0/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . 260
15.8.2 PTE1/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . 260
15.9 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
15.9.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
15.9.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
15.9.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
15.9.4 SCI Status Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
15.9.5 SCI Status Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
15.9.6 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
15.9.7 SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . .275
Section 16. Serial Peripheral Interface Module (SPI)
16.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .279
16.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
16.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
16.4
Pin Name Conventions and I/O Register Addresses . . . . . . . 281
16.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281
16.5.1 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
16.5.2 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
16.6 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .285
16.6.1 Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . 285
16.6.2 Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . 286
16.6.3 Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . 288
16.6.4 Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . 289
16.7
Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . 291
16.8 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
16.8.1 Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
16.8.2 Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
16.9
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296
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16.10 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
16.11 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
16.11.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
16.11.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
16.12 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 300
16.13 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
16.13.1 MISO (Master In/Slave Out) . . . . . . . . . . . . . . . . . . . . . . . . 301
16.13.2 MOSI (Master Out/Slave In) . . . . . . . . . . . . . . . . . . . . . . . . 301
16.13.3 SPSCK (Serial Clock). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
16.13.4 SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
16.13.5 CGND (Clock Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
16.14 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
16.14.1 SPI Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
16.14.2 SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . 306
16.14.3 SPI Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
Section 17. Input/Output (I/O) Ports
17.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .311
17.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
17.3 Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
17.3.1 Port A Data Register (PTA) . . . . . . . . . . . . . . . . . . . . . . . . 316
17.3.2 Data Direction Register A (DDRA) . . . . . . . . . . . . . . . . . . . 316
17.4 Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
17.4.1 Port B Data Register (PTB) . . . . . . . . . . . . . . . . . . . . . . . . 318
17.4.2 Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . . 319
17.5 Port C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
17.5.1 Port C Data Register (PTC) . . . . . . . . . . . . . . . . . . . . . . . . 320
17.5.2 Data Direction Register C (DDRC). . . . . . . . . . . . . . . . . . . 321
17.6 Port D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
17.6.1 Port D Data Register (PTD) . . . . . . . . . . . . . . . . . . . . . . . . 323
17.6.2 Data Direction Register D (DDRD). . . . . . . . . . . . . . . . . . . 324
17.6.3 Port D Input Pullup Enable Register (PTDPUE). . . . . . . . . 325
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17.7 Port E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
17.7.1 Port E Data Register (PTE) . . . . . . . . . . . . . . . . . . . . . . . . 326
17.7.2 Data Direction Register E (DDRE) . . . . . . . . . . . . . . . . . . . 328
17.8 Port F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
17.8.1 Port F Data Register (PTF) . . . . . . . . . . . . . . . . . . . . . . . . 329
17.8.2 Data Direction Register F (DDRF) . . . . . . . . . . . . . . . . . . . 330
17.8.3 Port F Input Pullup Enable Register (PTFPUE) . . . . . . . . . 332
17.9 Port G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
17.9.1 Port G Data Register (PTG) . . . . . . . . . . . . . . . . . . . . . . . . 332
17.9.2 Data Direction Register G (DDRG) . . . . . . . . . . . . . . . . . . 333
17.10 Port H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
17.10.1 Port H Data Register (PTH) . . . . . . . . . . . . . . . . . . . . . . . . 335
17.10.2 Data Direction Register H (DDRH). . . . . . . . . . . . . . . . . . . 335
Section 18. External Interrupt (IRQ)
18.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .339
18.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
18.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
18.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .340
18.4.1 IRQ Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
18.5
IRQ Status and Control Register (ISCR) . . . . . . . . . . . . . . . . 343
18.6
IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . 344
Section 19. Keyboard Interrupt Module (KBI)
19.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .345
19.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
19.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
19.4
I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
19.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347
19.5.1 Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
19.5.2 Keyboard Status and Control Register. . . . . . . . . . . . . . . . 349
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19.5.3
Keyboard Interrupt Enable Register . . . . . . . . . . . . . . . . . . 351
19.6
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
19.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
19.8
Keyboard Module During Break Interrupts . . . . . . . . . . . . . . . 352
Section 20. Computer Operating Properly (COP)
20.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .353
20.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
20.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .354
20.4 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
20.4.1 CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
20.4.2 STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
20.4.3 COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
20.4.4 Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
20.4.5 Internal Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
20.4.6 Reset Vector Fetch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
20.4.7 COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
20.4.8 COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . 356
20.5
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
20.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357
20.7
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357
20.8 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
20.8.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358
20.8.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358
20.9
COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . 358
Section 21. Low-Voltage Inhibit (LVI)
21.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .359
21.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
21.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
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21.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .360
21.4.1 Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
21.4.2 Forced Reset Operation . . . . . . . . . . . . . . . . . . . . . . . . . . .361
21.4.3 False Reset Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
21.5
LVI Status Register (LVISR) . . . . . . . . . . . . . . . . . . . . . . . . . . 362
21.6
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .362
21.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
21.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363
21.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363
Section 22. Break Module (BRK)
22.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .365
22.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
22.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
22.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366
22.4.1 Flag Protection During Break Interrupts . . . . . . . . . . . . . . . 368
22.4.2 CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . .368
22.4.3 PIT, TIMA, and TIMB During Break Interrupts . . . . . . . . . . 368
22.4.4 COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . 368
22.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
22.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368
22.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369
22.6 Break Module Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
22.6.1 Break Status and Control Register. . . . . . . . . . . . . . . . . . . 369
22.6.2 Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 370
22.6.3 SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 370
22.6.4 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . 372
Section 23. Electrical Specifications
23.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .373
23.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
23.3
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . 374
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23.4
Functional Operating Range. . . . . . . . . . . . . . . . . . . . . . . . . . 375
23.5
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
23.6
5.0-V DC Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . 376
23.7
EEPROM and Memory Characteristics . . . . . . . . . . . . . . . . . 377
23.8
5.0-V Control Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
23.9
Timer Interface Module Characteristics . . . . . . . . . . . . . . . . . 378
23.10 ADC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
23.11 SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
23.12 Clock Generation Module Characteristics . . . . . . . . . . . . . . . 383
23.12.1 CGM Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . 383
23.12.2 CGM Component Information . . . . . . . . . . . . . . . . . . . . . . 383
23.12.3 CGM Acquisition/Lock Time Information . . . . . . . . . . . . . . 384
23.13 FLASH Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . 385
Section 24. Mechanical Specifications
24.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .387
24.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387
24.3
64-Pin Plastic Quad Flat Pack (QFP) . . . . . . . . . . . . . . . . . . . 388
Section 25. Ordering Information
25.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .389
25.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
25.3
MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
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Figure
Title
1-1
1-2
1-3
MC68HC908AB32 Block Diagram . . . . . . . . . . . . . . . . . . . . . . 32
64-Pin QFP Pin Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
Power Supply Bypassing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34
2-1
2-2
Memory Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
Control, Status, and Data Registers . . . . . . . . . . . . . . . . . . . . .45
4-1
4-2
4-4
4-3
FLASH Control Register (FLCR) . . . . . . . . . . . . . . . . . . . . . . . 60
FLASH Programming Flowchart . . . . . . . . . . . . . . . . . . . . . . . . 65
FLASH Block Protect Start Address . . . . . . . . . . . . . . . . . . . . .66
FLASH Block Protect Register (FLBPR). . . . . . . . . . . . . . . . . . 66
5-1
5-2
5-3
5-4
5-5
5-6
5-7
5-8
EEPROM I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . 70
EEPROM Control Register (EECR) . . . . . . . . . . . . . . . . . . . . . 77
EEPROM Array Configuration Register (EEACR) . . . . . . . . . . 79
EEPROM Non-Volatile Register (EENVR) . . . . . . . . . . . . . . . . 80
EEPROM Divider Register High (EEDIVH) . . . . . . . . . . . . . . . 81
EEPROM Divider Register Low (EEDIVL) . . . . . . . . . . . . . . . . 81
EEPROM Divider Non-volatile Register High(EEDIVHNVR) . . 82
EEPROM Divider Non-volatile Register Low (EEDIVLNVR) . . 82
6-1
6-2
Configuration Register 1 (CONFIG1) . . . . . . . . . . . . . . . . . . . . 86
Configuration Register 2 (CONFIG2) . . . . . . . . . . . . . . . . . . . . 88
7-1
7-2
7-3
7-4
7-5
7-6
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Accumulator (A) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Index Register (H:X) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Stack Pointer (SP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
Program Counter (PC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93
Condition Code Register (CCR) . . . . . . . . . . . . . . . . . . . . . . . . 94
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Title
Page
8-1
8-2
8-3
8-4
8-5
8-6
8-7
8-8
8-9
8-10
8-11
8-12
8-13
8-14
8-15
8-16
8-17
8-18
8-19
SIM Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
SIM I/O Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . . .112
CGM Clock Signals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
External Reset Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .114
Internal reset timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Sources of Internal Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
POR Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
Interrupt Entry Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Interrupt Recovery Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
Interrupt Processing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
Interrupt Recognition Example . . . . . . . . . . . . . . . . . . . . . . . . 121
Wait Mode Entry Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Wait Recovery from Interrupt or Break . . . . . . . . . . . . . . . . . . 125
Wait Recovery from Internal Reset. . . . . . . . . . . . . . . . . . . . . 125
Stop Mode Entry Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
Stop Mode Recovery from Interrupt or Break . . . . . . . . . . . . . 126
SIM Break Status Register (SBSR) . . . . . . . . . . . . . . . . . . . . 127
SIM Reset Status Register (SRSR) . . . . . . . . . . . . . . . . . . . . 128
SIM Break Flag Control Register (SBFCR) . . . . . . . . . . . . . . 129
9-1
9-2
9-3
9-4
9-5
9-7
9-8
CGM Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133
CGM I/O Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . . 134
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . 141
CGM I/O Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . . 144
PLL Control Register (PCTL) . . . . . . . . . . . . . . . . . . . . . . . . . 144
PLL Bandwidth Control Register (PBWC) . . . . . . . . . . . . . . . 146
PLL Programming Register (PPG) . . . . . . . . . . . . . . . . . . . . . 148
10-1
10-2
10-3
10-4
10-5
10-6
Monitor Mode Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
Monitor Data Format. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Sample Monitor Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . 161
Read Transaction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162
Break Transaction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .162
Monitor Mode Entry Timing. . . . . . . . . . . . . . . . . . . . . . . . . . .167
11-1 TIMA Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
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11-2 TIMA I/O Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . . 173
11-3 PWM Period and Pulse Width . . . . . . . . . . . . . . . . . . . . . . . . 177
11-4 TIMA Status and Control Register (TASC) . . . . . . . . . . . . . . . 184
11-5 TIMA Counter Register High (TACNTH). . . . . . . . . . . . . . . . . 186
11-6 TIMA Counter Register Low (TACNTL) . . . . . . . . . . . . . . . . . 187
11-7 TIMA Counter Modulo Register High (TAMODH). . . . . . . . . . 187
11-8 TIMA Counter Modulo Register Low (TAMODL) . . . . . . . . . . 187
11-9 TIMA Channel 0 Status and Control Register (TASC0) . . . . . 188
11-10 TIMA Channel 1 Status and Control Register (TASC1) . . . . . 188
11-11 TIMA Channel 2 Status and Control Register (TASC2) . . . . . 189
11-12 TIMA Channel 3 Status and Control Register (TASC3) . . . . . 189
11-13. CHxMAX Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .192
11-14 TIMA Channel 0 Register High (TACH0H) . . . . . . . . . . . . . . . 192
11-15 TIMA Channel 0 Register Low (TACH0L). . . . . . . . . . . . . . . . 192
11-16 TIMA Channel 1 Register High (TACH1H) . . . . . . . . . . . . . . . 193
11-17 TIMA Channel 1 Register Low (TACH1L). . . . . . . . . . . . . . . . 193
11-18 TIMA Channel 2 Register High (TACH2H) . . . . . . . . . . . . . . . 193
11-19 TIMA Channel 2 Register Low (TACH2L). . . . . . . . . . . . . . . . 193
11-20 TIMA Channel 3 Register High (TACH3H) . . . . . . . . . . . . . . . 194
11-21 TIMA Channel 3 Register Low (TACH3L). . . . . . . . . . . . . . . . 194
12-1 TIMB Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 198
12-2 TIMB I/O Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . . 199
12-3 PWM Period and Pulse Width . . . . . . . . . . . . . . . . . . . . . . . . 203
12-4 TIMB Status and Control Register (TBSC) . . . . . . . . . . . . . . . 210
12-5 TIMB Counter Register High (TBCNTH). . . . . . . . . . . . . . . . . 212
12-6 TIMB Counter Register Low (TBCNTL) . . . . . . . . . . . . . . . . . 213
12-7 TIMB Counter Modulo Register High (TBMODH). . . . . . . . . . 213
12-8 TIMB Counter Modulo Register Low (TBMODL) . . . . . . . . . . 213
12-9 TIMB Channel 0 Status and Control Register (TBSC0) . . . . . 214
12-10 TIMB Channel 1 Status and Control Register (TBSC1) . . . . . 214
12-11 TIMB Channel 2 Status and Control Register (TBSC2) . . . . . 215
12-12 TIMB Channel 3 Status and Control Register (TBSC3) . . . . . 215
12-13. CHxMAX Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .218
12-14 TIMB Channel 0 Register High (TBCH0H) . . . . . . . . . . . . . . . 218
12-15 TIMB Channel 0 Register Low (TBCH0L). . . . . . . . . . . . . . . . 218
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Title
12-16
12-17
12-18
12-19
12-20
12-21
TIMB Channel 1 Register High (TBCH1H) . . . . . . . . . . . . . . . 219
TIMB Channel 1 Register Low (TBCH1L). . . . . . . . . . . . . . . . 219
TIMB Channel 2 Register High (TBCH2H) . . . . . . . . . . . . . . . 219
TIMB Channel 2 Register Low (TBCH2L). . . . . . . . . . . . . . . . 219
TIMB Channel 3 Register High (TBCH3H) . . . . . . . . . . . . . . . 220
TIMB Channel 3 Register Low (TBCH3L). . . . . . . . . . . . . . . . 220
13-1
13-2
13-3
13-4
13-5
13-6
13-7
PIT Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
PIT I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
PIT Status and Control Register (PSC) . . . . . . . . . . . . . . . . . 225
PIT Counter Register High (PCNTH) . . . . . . . . . . . . . . . . . . . 227
PIT Counter Register Low (PCNTL) . . . . . . . . . . . . . . . . . . . .228
PIT Counter Modulo Register High (PMODH) . . . . . . . . . . . . 228
PIT Counter Modulo Register Low (PMODL) . . . . . . . . . . . . . 228
14-1
14-2
14-3
14-4
14-5
ADC Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
ADC Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
ADC Status and Control Register (ADSCR) . . . . . . . . . . . . . . 235
ADC Data Register (ADR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
ADC Clock Register (ADCLK) . . . . . . . . . . . . . . . . . . . . . . . . 237
15-1
15-2
15-3
15-4
15-5
15-6
15-7
15-8
15-9
15-10
15-11
15-12
15-13
15-14
15-15
15-16
SCI Module Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . .243
SCI I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .244
SCI Data Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .245
SCI Transmitter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
SCI Receiver Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . 251
Receiver Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
Slow Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
Fast Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
SCI Control Register 1 (SCC1). . . . . . . . . . . . . . . . . . . . . . . . 262
SCI Control Register 2 (SCC2). . . . . . . . . . . . . . . . . . . . . . . . 265
SCI Control Register 3 (SCC3). . . . . . . . . . . . . . . . . . . . . . . . 267
SCI Status Register 1 (SCS1) . . . . . . . . . . . . . . . . . . . . . . . . 269
Flag Clearing Sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
SCI Status Register 2 (SCS2) . . . . . . . . . . . . . . . . . . . . . . . . 273
SCI Data Register (SCDR) . . . . . . . . . . . . . . . . . . . . . . . . . . .274
SCI Baud Rate Register (SCBR) . . . . . . . . . . . . . . . . . . . . . . 275
Technical Data
24
Page
MC68HC908AB32 — Rev. 1.1
List of Figures
Freescale Semiconductor
List of Figures
Figure
Title
16-1
16-2
16-3
16-4
16-5
16-6
16-7
16-8
16-9
16-10
16-11
16-12
16-13
16-14
16-15
SPI I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .281
SPI Module Block Diagram. . . . . . . . . . . . . . . . . . . . . . . . . . .282
Full-Duplex Master-Slave Connections . . . . . . . . . . . . . . . . . 283
Transmission Format (CPHA = 0) . . . . . . . . . . . . . . . . . . . . . 287
CPHA/SS Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 287
Transmission Format (CPHA = 1) . . . . . . . . . . . . . . . . . . . . . 288
Transmission Start Delay (Master) . . . . . . . . . . . . . . . . . . . . . 290
SPRF/SPTE CPU Interrupt Timing . . . . . . . . . . . . . . . . . . . . . 291
Missed Read of Overflow Condition . . . . . . . . . . . . . . . . . . . .293
Clearing SPRF When OVRF Interrupt Is Not Enabled . . . . . . 294
SPI Interrupt Request Generation . . . . . . . . . . . . . . . . . . . . . 297
CPHA/SS Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
SPI Control Register (SPCR) . . . . . . . . . . . . . . . . . . . . . . . . . 304
SPI Status and Control Register (SPSCR) . . . . . . . . . . . . . . . 306
SPI Data Register (SPDR) . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
17-1
17-2
17-3
17-4
17-5
17-6
17-7
17-8
17-9
17-10
17-11
17-12
17-13
17-14
17-15
17-16
17-17
17-18
17-19
17-20
I/O Port Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . . .312
Port A Data Register (PTA) . . . . . . . . . . . . . . . . . . . . . . . . . . 316
Data Direction Register A (DDRA) . . . . . . . . . . . . . . . . . . . . . 316
Port A I/O Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Port B Data Register (PTB) . . . . . . . . . . . . . . . . . . . . . . . . . . 318
Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . . . . 319
Port B I/O Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
Port C Data Register (PTC) . . . . . . . . . . . . . . . . . . . . . . . . . . 320
Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . . . . 321
Port C I/O Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
Port D Data Register (PTD) . . . . . . . . . . . . . . . . . . . . . . . . . . 323
Data Direction Register D (DDRD) . . . . . . . . . . . . . . . . . . . . . 324
Port D I/O Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
Port D Input Pullup Enable Register (PTDPUE) . . . . . . . . . . . 325
Port E Data Register (PTE) . . . . . . . . . . . . . . . . . . . . . . . . . . 326
Data Direction Register E (DDRE) . . . . . . . . . . . . . . . . . . . . . 328
Port E I/O Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
Port F Data Register (PTF). . . . . . . . . . . . . . . . . . . . . . . . . . .329
Data Direction Register F (DDRF) . . . . . . . . . . . . . . . . . . . . . 330
Port F I/O Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Page
Technical Data
List of Figures
25
List of Figures
Figure
17-21
17-22
17-23
17-24
17-25
17-26
17-27
Title
Page
Port F Input Pullup Enable Register (PTFPUE) . . . . . . . . . . . 332
Port G Data Register (PTG) . . . . . . . . . . . . . . . . . . . . . . . . . . 333
Data Direction Register G (DDRG). . . . . . . . . . . . . . . . . . . . . 333
Port G I/O Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
Port H Data Register (PTH) . . . . . . . . . . . . . . . . . . . . . . . . . . 335
Data Direction Register H (DDRH) . . . . . . . . . . . . . . . . . . . . . 336
Port H I/O Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
18-1 IRQ Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . 341
18-2 IRQ I/O Register Summary. . . . . . . . . . . . . . . . . . . . . . . . . . .341
18-3 IRQ Status and Control Register (ISCR) . . . . . . . . . . . . . . . . 343
19-1
19-2
19-3
19-4
KBI I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .346
Keyboard Interrupt Block Diagram . . . . . . . . . . . . . . . . . . . . . 347
Keyboard Status and Control Register (KBSCR) . . . . . . . . . . 350
Keyboard Interrupt Enable Register (KBIER) . . . . . . . . . . . . . 351
20-1 COP Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
20-2 Configuration Register 1 (CONFIG1) . . . . . . . . . . . . . . . . . . . 356
20-3 COP Control Register (COPCTL) . . . . . . . . . . . . . . . . . . . . . . 357
21-1 LVI Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . .360
21-2 LVI I/O Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
21-3 LVI Status Register (LVISR) . . . . . . . . . . . . . . . . . . . . . . . . . . 362
22-1
22-2
22-3
22-4
22-5
22-6
22-7
Break Module Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . 367
Break Module I/O Register Summary . . . . . . . . . . . . . . . . . . . 367
Break Status and Control Register (BRKSCR). . . . . . . . . . . . 369
Break Address Register High (BRKH) . . . . . . . . . . . . . . . . . . 370
Break Address Register Low (BRKL) . . . . . . . . . . . . . . . . . . . 370
SIM Break Status Register (SBSR) . . . . . . . . . . . . . . . . . . . . 371
SIM Break Flag Control Register (SBFCR) . . . . . . . . . . . . . . 372
23-1 SPI Master Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 381
23-2 SPI Slave Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 382
24-1 64-Pin Plastic Quad Flat Pack (QFP) . . . . . . . . . . . . . . . . . . . 388
Technical Data
26
MC68HC908AB32 — Rev. 1.1
List of Figures
Freescale Semiconductor
Technical Data — MC68HC908AB32
List of Tables
Table
Title
Page
1-1
1-2
1-3
I/O Pins Summary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38
Signal Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Clock Source Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
2-1
Vector Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .56
5-1
5-2
EEPROM Array Address Blocks. . . . . . . . . . . . . . . . . . . . . . . . 73
EEPROM Program/Erase Mode Select . . . . . . . . . . . . . . . . . . 78
7-1
7-2
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
8-1
8-2
8-3
8-4
Signal naming conventions. . . . . . . . . . . . . . . . . . . . . . . . . . .111
PIN Bit Set Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
Vector Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .122
SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
9-1
VCO Frequency Multiplier (N) Selection. . . . . . . . . . . . . . . . . 149
10-1
10-2
10-3
10-4
10-5
10-6
10-7
10-8
10-9
Monitor Mode Entry Conditions . . . . . . . . . . . . . . . . . . . . . . .160
Mode Differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
READ (Read Memory) Command . . . . . . . . . . . . . . . . . . . . . 163
WRITE (Write Memory) Command. . . . . . . . . . . . . . . . . . . . . 164
IREAD (Indexed Read) Command . . . . . . . . . . . . . . . . . . . . . 164
IWRITE (Indexed Write) Command . . . . . . . . . . . . . . . . . . . . 165
READSP (Read Stack Pointer) Command . . . . . . . . . . . . . . . 165
RUN (Run User Program) Command . . . . . . . . . . . . . . . . . . . 166
Monitor Baud Rate Selection . . . . . . . . . . . . . . . . . . . . . . . . . 166
11-1 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
11-2 Prescaler Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186
11-3 Mode, Edge, and Level Selection . . . . . . . . . . . . . . . . . . . . . . 191
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
List of Tables
27
List of Tables
Table
Title
Page
12-1 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
12-2 Prescaler Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
12-3 Mode, Edge, and Level Selection . . . . . . . . . . . . . . . . . . . . . . 217
13-1 PIT Prescaler Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
14-1 Mux Channel Select . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
14-2 ADC Clock Divide Ratio . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 238
15-1
15-2
15-3
15-4
15-5
15-6
15-7
15-8
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
Start Bit Verification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
Data Bit Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .253
Stop Bit Recovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .254
Character Format Selection . . . . . . . . . . . . . . . . . . . . . . . . . . 264
SCI Baud Rate Prescaling . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
SCI Baud Rate Selection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
SCI Baud Rate Selection Examples . . . . . . . . . . . . . . . . . . . .277
16-1
16-2
16-3
16-4
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
SPI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296
SPI Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
SPI Master Baud Rate Selection . . . . . . . . . . . . . . . . . . . . . . 308
17-1
17-2
17-3
17-4
17-5
17-6
17-7
17-8
17-9
Port Control Register Bits Summary. . . . . . . . . . . . . . . . . . . .314
Port A Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317
Port B Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
Port C Pin Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 322
Port D Pin Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 325
Port E Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
Port F Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
Port G Pin Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
Port H Pin Functions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 337
19-1 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
21-1 LVIOUT Bit Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 362
25-1 MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
Technical Data
28
MC68HC908AB32 — Rev. 1.1
List of Tables
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 1. General Description
1.1 Contents
1.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
1.4
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
1.5
Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33
1.6
Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
1.6.1
Power Supply Pins (VDD and VSS) . . . . . . . . . . . . . . . . . . . . 34
1.6.2
Oscillator Pins (OSC1 and OSC2) . . . . . . . . . . . . . . . . . . . . 35
1.6.3
External Reset Pin (RST) . . . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.6.4
External Interrupt Pin (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.6.5
Analog Power Supply Pin (VDDA) . . . . . . . . . . . . . . . . . . . . .35
1.6.6
Analog Ground Pin (VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . 35
1.6.7
Analog Ground Pin (AVSS/VREFL). . . . . . . . . . . . . . . . . . . . .35
1.6.8
ADC Voltage Reference Pin (VREFH) . . . . . . . . . . . . . . . . . . 36
1.6.9
Analog Supply Pin (VDDAREF) . . . . . . . . . . . . . . . . . . . . . . . 36
1.6.10 External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . 36
1.6.11 Port A Input/Output (I/O) Pins (PTA7–PTA0) . . . . . . . . . . . . 36
1.6.12 Port B I/O Pins (PTB7/ATD7–PTB0/ATD0) . . . . . . . . . . . . . 36
1.6.13 Port C I/O Pins (PTC5–PTC0) . . . . . . . . . . . . . . . . . . . . . . . 36
1.6.14 Port D I/O Pins (PTD7–PTD0) . . . . . . . . . . . . . . . . . . . . . . . 37
1.6.15 Port E I/O Pins (PTE7/SPSCK–PTE0/TxD) . . . . . . . . . . . . . 37
1.6.16 Port F I/O Pins (PTF7–PTF0/TACH2) . . . . . . . . . . . . . . . . . 37
1.6.17 Port G I/O Pins (PTG2/KBD2–PTG0/KBD0) . . . . . . . . . . . . 37
1.6.18 Port H I/O Pins (PTH1/KBD4–PTH0/KBD3). . . . . . . . . . . . . 37
1.7
I/O Pin Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
1.8
Signal Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
1.9
Clock Source Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
General Description
29
General Description
1.2 Introduction
The MC68HC908AB32 is a member of the low-cost, high-performance
M68HC08 Family of 8-bit microcontroller units (MCUs) with embedded
EEPROM for user data storage. 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.
1.3 Features
Features of the MC68HC908AB32 include the following:
•
High-performance M68HC08 architecture
•
Fully upward-compatible object code with M6805, M146805, and
M68HC05 Families
•
Memory map and pin functions compatible with MC68HC08AB32
and MC68HC08AB16
•
8-MHz internal bus frequency
•
32K-bytes user program FLASH memory with security1 feature
•
512 bytes of on-chip EEPROM with security feature
•
1K-byte of on-chip RAM
•
Clock generator module (CGM)
•
Two 16-bit, 4-channel timer interface modules (TIMA and TIMB)
with selectable input capture, output compare, and PWM
capability on each channel
•
Programmable interrupt timer (PIT)
•
Serial peripheral interface module (SPI)
•
Serial communications interface module (SCI)
•
8-channel. 8-bit analog-to-digital converter (ADC)
•
Low-power design (fully static with STOP and WAIT modes)
•
Master reset pin and power-on reset
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
Technical Data
30
MC68HC908AB32 — Rev. 1.1
General Description
Freescale Semiconductor
General Description
•
51 general-purpose input/output (I/O) pins:
– 30 shared-function I/O pins
– 5-bit keyboard wakeup port
– Selectable pullups on inputs on port D and port F
•
System protection features
– Optional computer operating properly (COP) reset
– Low-voltage detection with optional reset
– Illegal opcode detection with optional reset
– Illegal address detection with optional reset
•
64-pin quad flat pack (QFP)
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
1.4 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908AB32.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
General Description
31
DDRA
PORTA
PORTB
PTB7/ATD7 – PTB0/ATD0
PORTC
PORTD
PROGRAMMABLE INTERRUPT
TIMER MODULE
DDRB
4-CHANNEL TIMER INTERFACE
MODULE B
DDRC
CONTROL AND STATUS REGISTERS — 80 BYTES
PTA7 – PTA0
DDRD
4-CHANNEL TIMER INTERFACE
MODULE A
DDRE
ARITHMETIC/LOGIC
UNIT (ALU)
PORTE
CPU
REGISTERS
USER FLASH — 32,256 BYTES
SERIAL COMMUNICATIONS
INTERFACE MODULE
MONITOR ROM — 307 BYTES
SERIAL PERIPHERAL
INTERFACE MODULE
* RST
* IRQ
Freescale Semiconductor
MC68HC908AB32 — Rev. 1.1
VREFH
AVSS/VREFL
VDDAREF
VDD
VSS
VDDA
VSSA
PHASE-LOCKED LOOP
SYSTEM INTEGRATION
MODULE
SINGLE EXTERNAL IRQ
MODULE
8-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
KEYBOARD
INTERRUPT MODULE
COMPUTER OPERATING
PROPERLY MODULE
LOW-VOLTAGE
INHIBIT MODULE
PTF7 †
PTF6 †
PTF5/TBCH1 †
PTF4/TBCH0 †
PTF3/TBCH3 †
PTF2/TBCH2 †
PTF1/TACH3 †
PTF0/TACH2 †
PORTG
CGMXFC
4.9125-MHz OSCILLATOR
PTG2/KBD2 – PTG0/KBD0 **
PORTH
OSC1
OSC2
DDRF
General Description
CLOCK GENERATOR MODULE
PORTF
USER FLASH VECTORS — 48 BYTES
PTD7 – PTD0 †‡
(PTD6/TACLK)
(PTD4/TBCLK)
PTE7/SPSCK
PTE6/MOSI
PTE5/MISO
PTE4/SS
PTE3/TACH1
PTE2/TACH0
PTE1/RxD
PTE0/TxD
DDRG
USER EEPROM — 512 BYTES
PTC5 – PTC0
(PTC2/MCLK)
DDRH
USER RAM — 1024 BYTES
PTH1/KBD4 – PTH0/KBD3 **
POWER-ON RESET
MODULE
POWER
† Ports are software configurable with pullup device if input port.
‡ Higher current drive port pins
* Pin contains integrated pullup device
** Pullup enabled when configured as keyboard interrupt pin
Figure 1-1. MC68HC908AB32 Block Diagram
General Description
Technical Data
32
INTERNAL BUS
M68HC08 CPU
General Description
1.5 Pin Assignments
PTC1
PTC0
OSC1
OSC2
CGMXFC
VSSA
VDDA
VREFH
PTD7
PTD6/TACLK
PTD5
PTD4/TBCLK
61
60
59
58
57
56
55
54
53
52
51
50
PTH1/KBD4
PTC2/MCLK
62
PTC4
49
PTC3
63
64
PTC5
Figure 1-2 shows the pin assignment for the MC68HC908AB32.
1
48
PTH0/KBD3
41
PTB7/ATD7
NC
9
40
PTB6/ATD6
PTF7
10
39
PTB5/ATD5
PTF5/TBCH1
11
38
PTB4/ATD4
PTF6
12
37
PTB3/ATD3
PTE0/TxD
13
36
PTB2/ATD2
PTE1/RxD
14
35
PTB1/ATD1
PTE2/TACH0
15
34
PTB0/ATD0
33
PTA7
PTA6 32
PTE5/MISO
PTE4/SS 17
18
PTE3/TACH1 16
31
8
PTA5
PTF4/TBCH0
30
PTD0
PTA4
42
29
7
PTA3
PTF3/TBCH3
28
PTD1
PTA2
43
27
6
PTA1
PTF2/TBCH2
26
VDDAREF
PTA0
44
25
5
PTG2/KBD2
PTF1/TACH3
24
AVSS/VREFL
PTG1/KBD1
45
23
4
PTG0/KBD0
PTF0/TACH2
22
PTD2
VDD
46
21
3
VSS
RST
20
PTD3
PTE7/SPSCK
47
19
2
PTE6/MOSI
IRQ
Figure 1-2. 64-Pin QFP Pin Assignment
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
General Description
33
General Description
1.6 Pin Functions
Description of pin functions are provided here.
1.6.1 Power Supply Pins (VDD and VSS)
VDD and VSS are the power supply and ground pins. The MCU operates
from a single power supply.
Fast signal transitions on MCU pins place high, short-duration current
demands on the power supply. To prevent noise problems, take special
care to provide power supply bypassing at the MCU as Figure 1-3
shows. Place the C1 bypass capacitor as close to the MCU as possible.
Use a high-frequency-response ceramic capacitor for C1. C2 is an
optional bulk current bypass capacitor for use in applications that require
the port pins to source high current levels.
MCU
VSS
VDD
C1
0.1 µF
+
C2
VDD
NOTE: Component values shown
represent typical applications.
Figure 1-3. Power Supply Bypassing
VSS is also the ground for the port output buffers and the ground return
for the serial clock in the serial peripheral interface module (SPI). See
Section 16. Serial Peripheral Interface Module (SPI).
VSS must be grounded for proper MCU operation.
Technical Data
34
MC68HC908AB32 — Rev. 1.1
General Description
Freescale Semiconductor
General Description
1.6.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscillator
circuit. See Section 9. Clock Generator Module (CGM).
1.6.3 External Reset Pin (RST)
A logic 0 on the RST pin forces the MCU to a known start-up state. RST
is bidirectional, allowing a reset of the entire system. It is driven low when
any internal reset source is asserted. This pin contains an internal pullup
resistor. See Section 8. System Integration Module (SIM).
1.6.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. This pin contains an
internal pullup resistor. See Section 18. External Interrupt (IRQ).
1.6.5 Analog Power Supply Pin (VDDA)
VDDA is the power supply pin for the clock generator module (CGM).
1.6.6 Analog Ground Pin (VSSA)
The VSSA analog ground pin is used only for the ground connections for
the clock generator module (CGM) section of the circuit and should be
decoupled as per the VSS digital ground pin. See Section 9. Clock
Generator Module (CGM).
1.6.7 Analog Ground Pin (AVSS/VREFL)
The AVSS analog ground pin is used only for the ground connections for
the analog to digital convertor (ADC) and should be decoupled as per the
VSS digital ground pin.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
General Description
35
General Description
1.6.8 ADC Voltage Reference Pin (VREFH)
VREFH is the power supply for setting the reference voltage VREFH.
Connect this pin to a voltage such that 1.5V < VREFH ≤ VDDAREF.
1.6.9 Analog Supply Pin (VDDAREF)
The VDDAREF analog supply pin is used only for the supply connections
for the analog-to-digital convertor (ADC).
1.6.10 External Filter Capacitor Pin (CGMXFC)
CGMXFC is an external filter capacitor connection for the CGM. See
Section 9. Clock Generator Module (CGM).
1.6.11 Port A Input/Output (I/O) Pins (PTA7–PTA0)
PTA7–PTA0 are general-purpose bidirectional I/O port pins. See
Section 17. Input/Output (I/O) Ports.
1.6.12 Port B I/O Pins (PTB7/ATD7–PTB0/ATD0)
PTB7–PTB0 are special function, bidirectional port pins. PTB7–PTB0
are shared with the analog to digital convertor (ADC) input pins
ATD7–ATD0. See Section 14. Analog-to-Digital Converter (ADC) and
Section 17. Input/Output (I/O) Ports.
1.6.13 Port C I/O Pins (PTC5–PTC0)
PTC5–PTC0 are general-purpose bidirectional I/O port pins. PTC2 is a
special function port pin that is shared with the system clock output pin,
MCLK. See Section 17. Input/Output (I/O) Ports.
Technical Data
36
MC68HC908AB32 — Rev. 1.1
General Description
Freescale Semiconductor
General Description
1.6.14 Port D I/O Pins (PTD7–PTD0)
PTD7–PTD0 are general-purpose bidirectional I/O port pins. PTD6 and
PTD4 are special function port pins that are shared with the timer
interface modules (TIMA and TIMB). See Section 11. Timer Interface
Module A (TIMA) and Section 12. Timer Interface Module B (TIMB).
1.6.15 Port E I/O Pins (PTE7/SPSCK–PTE0/TxD)
PTE7–PTE0 are special function, bidirectional port pins. PTE7–PTE4
are shared with the serial peripheral interface mode (SPI), PTE3–PTE2
are shared with timer A (TIMA), and PTE1–PTE0 are shared with the
serial communications interface (SCI). See Section 15. Serial
Communications Interface Module (SCI), Section 16. Serial
Peripheral Interface Module (SPI), Section 11. Timer Interface
Module A (TIMA), and Section 17. Input/Output (I/O) Ports.
1.6.16 Port F I/O Pins (PTF7–PTF0/TACH2)
PTF7–PTF6 are general-purpose bidirectional I/O port pins.
PTF5–PTF0 are special function, bidirectional port pins. PTF5–PTF2 are
shared with timer B (TIMB), and PTF1–PTF0 are shared with timer A
(TIMA). See Section 11. Timer Interface Module A (TIMA), Section
12. Timer Interface Module B (TIMB), and Section 17. Input/Output
(I/O) Ports.
1.6.17 Port G I/O Pins (PTG2/KBD2–PTG0/KBD0)
PTG2–PTG0 are general-purpose bidirectional I/O pins with keyboard
wakeup function. See Section 19. Keyboard Interrupt Module (KBI)
and Section 17. Input/Output (I/O) Ports.
1.6.18 Port H I/O Pins (PTH1/KBD4–PTH0/KBD3)
PTH1–PTH0 are general-purpose bidirectional I/O pins with Keyboard
wakeup function. See Section 19. Keyboard Interrupt Module (KBI)
and Section 17. Input/Output (I/O) Ports.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
General Description
37
General Description
1.7 I/O Pin Summary
Table 1-1. I/O Pins Summary
Pin Name
Function
Driver Type
Hysteresis
Reset State
PTA7–PTA0
General purpose I/O
Dual State
No
Input (Hi-Z)
PTB7/ATD7–PTB0/ATD0
General purpose I/O
/ ADC channel
Dual State
No
Input (Hi-Z)
PTC5–PTC3
General purpose I/O
Dual State
No
Input (Hi-Z)
PTC2/MCLK
General purpose I/O
/ System clock
Dual State
No
Input (Hi-Z)
PTC1–PTC0
General purpose I/O
Dual State
No
Input (Hi-Z)
PTD7
General purpose I/O
Dual State
No
Input (Hi-Z)
PTD6/TACLK
General purpose I/O
/ Timer external input clock
Dual State
No
Input (Hi-Z)
PTD5
General purpose I/O
Dual State
No
Input (Hi-Z)
PTD4/TBCLK
General purpose I/O
/ Timer external input clock
Dual State
No
Input (Hi-Z)
PTD3–PTD0
General purpose I/O
Dual State
No
Input (Hi-Z)
PTE7/SPSCK
General purpose I/O
/ SPI clock
Dual State
(open drain)
Yes
Input (Hi-Z)
PTE6/MOSI
General purpose I/O
/ SPI data path
Dual State
(open drain)
Yes
Input (Hi-Z)
PTE5/MISO
General purpose I/O
/ SPI data path
Dual State
(open drain)
Yes
Input (Hi-Z)
PTE4/SS
General purpose I/O
/ SPI slave select
Dual State
Yes
Input (Hi-Z)
PTE3/TACH1
General purpose I/O
/ Timer A channel 1
Dual State
Yes
Input (Hi-Z)
PTE2/TACH0
General purpose I/O
/ Timer A channel 0
Dual State
Yes
Input (Hi-Z)
PTE1/RxD
General purpose I/O
/ SCI receive data
Dual State
Yes
Input (Hi-Z)
PTE0/TxD
General purpose I/O
/ SCI transmit data
Dual State
Yes
Input (Hi-Z)
PTF7–PTF6
General purpose I/O
Dual State
Yes
Input (Hi-Z)
PTF5/TBCH1
General purpose I/O
/ Timer B channel 1
Dual State
Yes
Input (Hi-Z)
Technical Data
38
MC68HC908AB32 — Rev. 1.1
General Description
Freescale Semiconductor
General Description
Table 1-1. I/O Pins Summary
Pin Name
Function
Driver Type
Hysteresis
Reset State
PTF4/TBCH0
General purpose I/O
/ Timer B channel 0
Dual State
Yes
Input (Hi-Z)
PTF3/TBCH3
General purpose I/O
/ Timer B channel 3
Dual State
Yes
Input (Hi-Z)
PTF2/TBCH2
General purpose I/O
/ Timer B channel 2
Dual State
Yes
Input (Hi-Z)
PTF1/TACH3
General purpose I/O
/ Timer A channel 3
Dual State
Yes
Input (Hi-Z)
PTF0/TACH2
General purpose I/O
/ Timer A channel 2
Dual State
Yes
Input (Hi-Z)
PTG2/KBD2–PTG0/KBD0
General purpose I/O with
key wakeup feature
Dual State
Yes
Input (Hi-Z)
PTH1/KBD4–PTH0/KBD3
General purpose I/O with
key wakeup feature
Dual State
Yes
Input (Hi-Z)
VDD
Logical chip power supply
NA
NA
NA
VSS
Logical chip ground
NA
NA
NA
VDDA
Analog power supply (CGM)
NA
NA
NA
VSSA
Analog ground (CGM)
NA
NA
NA
VREFH
ADC reference voltage
NA
NA
NA
AVSS/VREFL
ADC ground and reference
voltage
NA
NA
NA
VDDAREF
ADC power supply
NA
NA
NA
OSC1
External clock in
NA
NA
Input (Hi-Z)
OSC2
External clock out
NA
NA
Output
CGMXFC
PLL loop filter cap
NA
NA
NA
IRQ
External interrupt request
NA
NA
Input (pullup)
RST
Reset
NA
NA
Input (pullup)
Details of the clock connections to each of the modules on the
MC68HC908AB32 are shown in Table 1-2. A short description of each
clock source is also given in Table 1-3.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
General Description
39
General Description
1.8 Signal Name Conventions
Table 1-2. Signal Name Conventions
Signal name
Description
CGMXCLK
Buffered version of OSC1 from clock generator module (CGM)
CGMOUT
PLL-based or OSC1-based clock output from CGM module)
Bus clock
CGMOUT divided by two
SPSCK
SPI serial clock
(see 16.13.3 SPSCK (Serial Clock))
TACLK
External clock input for TIMA
(see 11.9.1 TIMA Clock Pin)
TBCLK
External clock input for TIMB
(see 12.9.1 TIMB Clock Pin)
1.9 Clock Source Summary
Table 1-3. Clock Source Summary
Module
Clock Source
ADC
CGMXCLK or bus clock
COP
CGMXCLK
CPU
Bus clock
EEPROM
CGMXCLK or bus clock
ROM
Bus clock
RAM
Bus clock
SPI
SPSCK
SCI
CGMXCLK
TIMA
Bus clock or PTD6/TACLK
TIMB
Bus clock or PTD4/TBCLK
PIT
Bus clock
KBI
Bus clock
Technical Data
40
MC68HC908AB32 — Rev. 1.1
General Description
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 2. Memory Map
2.1 Contents
2.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
2.3
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . 41
2.4
Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.5
Input/Output (I/O) Section. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
2.2 Introduction
The CPU08 can address 64K-bytes of memory space. The memory
map, shown in Figure 2-1, includes:
•
32, 256 bytes of user FLASH memory
•
512 bytes of EEPROM
•
1024 bytes of random-access memory (RAM)
•
48 bytes of user-defined vectors
•
307 bytes of monitor ROM
2.3 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.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Memory Map
41
Memory Map
2.4 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.
2.5 Input/Output (I/O) Section
Most of the control, status, and data registers are in the zero page
$0000–$004F. Additional I/O registers have the following addresses:
•
$FE00; SIM break status register, SBSR
•
$FE01; SIM reset status register, SRSR
•
$FE03; SIM break flag control register, SBFCR
•
$FE08; FLASH control register, FLCR
•
$FE0C; break address register high, BRKH
•
$FE0D; break address register low, BRKL
•
$FE0E; break status and control register, BRKSCR
•
$FE0F; LVI status register, LVISR
•
$FE10; EEPROM divider non-volatile register high, EEDIVHNVR
•
$FE11; EEPROM divider non-volatile register low, EEDIVLNVR
•
$FE1A; EEPROM timebase divider register high, EEDIVH
•
$FE1B; EEPROM timebase divider register low, EEDIVL
•
$FE1C; EEPROM non-volatile register, EENVR
•
$FE1D; EEPROM control register, EECR
•
$FE1F; EEPROM array configuration register, EEACR
•
$FF7E; FLASH block protect register, FLBPR
•
$FFFF; COP control register, COPCTL
Data registers are shown in Figure 2-2, Table 2-1 is a list of vector
locations.
Technical Data
42
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Memory Map
$0000
I/O Registers
80 Bytes
↓
$004F
$0050
RAM
1,024 Bytes
↓
$044F
$0450
Unimplemented
176 Bytes
↓
$04FF
$0500
Reserved
128 Bytes
↓
$057F
$0580
Unimplemented
640 Bytes
↓
$07FF
$0800
EEPROM
512 Bytes
↓
$09FF
$0A00
Unimplemented
30,208 Bytes
↓
$7FFF
$8000
FLASH Memory
32,256 Bytes
↓
$FDFF
$FE00
SIM Break Status Register (SBSR)
$FE01
SIM Reset Status Register (SRSR)
$FE02
Reserved
$FE03
SIM Break Flag Control Register (SBFCR)
$FE04
↓
$FE07
Reserved
4 Bytes
$FE08
FLASH Control Register (FLCR)
Figure 2-1. Memory Map
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Memory Map
43
Memory Map
$FE09
↓
$FE0B
Reserved
3 Bytes
$FE0C
Break Address Register High (BRKH)
$FE0D
Break Address Register Low (BRKL)
$FE0E
Break Status and Control Register (BRKSCR)
$FE0F
LVI Status Register (LVISR)
$FE10
EEPROM Divider Non-volatile Register High (EEDIVHNVR)
$FE11
EEPROM Divider Non-volatile Register Low (EEDIVLNVR)
$FE12
↓
$FE19
Reserved
8 Bytes
$FE1A
EEPROM Timebase Divider Register High (EEDIVH)
$FE1B
EEPROM Timebase Divider Register Low (EEDIVL)
$FE1C
EEPROM Non-volatile Register (EENVR)
$FE1D
EEPROM Control Register (EECR)
$FE1E
Reserved
$FE1F
EEPROM Array Configuration Register (EEACR)
$FE20
↓
Monitor ROM
307 Bytes
$FF52
$FF53
↓
Unimplemented
43 Bytes
$FF7D
$FF7E
FLASH Block Protect Register (FLBPR)
$FF7F
↓
Unimplemented
65 Bytes
$FFBF
$FFC0
↓
$FFCF
Reserved FLASH Memory
16 Bytes
Reserved for Compatibility with HC08AB16/24/32
$FFD0
↓
FLASH Vectors
48 Bytes
$FFFF
Figure 2-1. Memory Map (Continued)
Technical Data
44
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Memory Map
Addr.
Register Name
$0000
Read:
Port A Data Register
Write:
(PTA)
Reset:
$0001
$0002
$0003
Read:
Port B Data Register
Write:
(PTB)
Reset:
Read:
Port C Data Register
Write:
(PTC)
Reset:
Read:
Port D Data Register
Write:
(PTD)
Reset:
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
0
PTD7
Read:
DDRD7
Data Direction Register D
$0007
Write:
(DDRD)
Reset:
0
$0009
PTB3
0
PTC5
PTC4
PTC3
PTD6
PTD5
PTD4
PTD3
Unaffected by reset
Read:
MCLKEN
Data Direction Register C
$0006
Write:
(DDRC)
Reset:
0
Read:
Port F Data Register
Write:
(PTF)
Reset:
PTB4
Unaffected by reset
Read:
DDRB7
Data Direction Register B
$0005
Write:
(DDRB)
Reset:
0
$0008
PTB5
Unaffected by reset
Read:
DDRA7
Data Direction Register A
Write:
$0004
(DDRA)
Reset:
0
Read:
Port E Data Register
Write:
(PTE)
Reset:
PTB6
PTE7
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
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
PTE6
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
PTF2
PTF1
PTF0
0
Unaffected by reset
PTF7
PTF6
PTF5
PTF4
PTF3
Unaffected by reset
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 11)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Memory Map
45
Memory Map
Addr.
Register Name
$000A
$000B
Bit 7
6
5
4
3
Read:
Port G Data Register
Write:
(PTG)
Reset:
0
0
0
0
0
Read:
Port H Data Register
Write:
(PTH)
Reset:
0
$0010
$0011
$0012
$0013
Read:
SPI Control Register
Write:
(SPCR)
Reset:
Read:
SPI Status and Control
Register Write:
(SPSCR)
Reset:
Read:
SPI Data Register
Write:
(SPDR)
Reset:
Bit 0
PTG2
PTG1
PTG0
0
0
0
0
PTH1
PTH0
0
Unaffected by reset
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
DDRF6
DDRF5
DDRF4
DDRF3
DDRF2
DDRF1
DDRF0
0
0
0
0
0
0
0
0
0
0
0
0
DDRG2
DDRG1
DDRG0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
DDRH1
DDRH0
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:
DDRF7
Data Direction Register F
$000D
Write:
(DDRF)
Reset:
0
Read:
Data Direction Register H
$000F
Write:
(DDRH)
Reset:
1
Unaffected by reset
Read:
DDRE7
Data Direction Register E
$000C
Write:
(DDRE)
Reset:
0
Read:
Data Direction Register G
$000E
Write:
(DDRG)
Reset:
2
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
Read:
LOOPS
SCI Control Register 1
Write:
(SCC1)
Reset:
0
Unaffected by reset
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 11)
Technical Data
46
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Memory Map
Addr.
$0014
$0015
$0016
$0017
$0018
$0019
$001A
$001B
$001C
$001D
Register Name
Read:
SCI Control Register 2
Write:
(SCC2)
Reset:
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
R
R
ORIE
NEIE
FEIE
PEIE
0
0
0
0
0
0
Read:
R8
T8
SCI Control Register 3
Write:
(SCC3)
Reset: Unaffected Unaffected
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
Read:
IRQ Status and Control
Register Write:
(ISCR)
Reset:
0
Keyboard Status and Read:
Control Register
Write:
(KBSCR)
Reset:
Read:
PLL Control Register
Write:
(PCTL)
Reset:
Read:
PLL Bandwidth Control
Register Write:
(PBWC)
Reset:
Unaffected by reset
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
0
0
IRQF
0
IMASK
MODE
0
0
IMASKK
MODEK
ACK
0
0
0
0
0
0
0
0
0
0
KEYF
0
ACKK
0
PLLIE
0
AUTO
0
0
PLLF
0
LOCK
0
0
0
PLLON
BCS
1
0
ACQ
XLD
0
0
= Unimplemented
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 11)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Memory Map
47
Memory Map
Addr.
$001E
$001F
Register Name
Read:
PLL Programming
Register Write:
(PPG)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
SSREC
COPRS
STOP
COPD
0
0
0
0
0
0
0
PS2
PS1
PS0
Read:
LVISTOP
Configuration Register 1
Write:
†
(CONFIG1)
Reset:
0
R
LVIRSTD LVIPWRD
0
0
TOIE
TSTOP
0
0
1
0
0
0
0
0
Read:
Timer A Counter
Register High Write:
(TACNTH)
Reset:
Bit 15
Read:
Timer A Counter
Register Low Write:
(TACNTL)
Reset:
† One-time writable register after each reset.
$0020
Read:
Timer A Status and
Control Register Write:
(TASC)
Reset:
Read:
Keyboard Interrupt Enable
Register Write:
$0021
(KBIER)
Reset:
$0022
$0023
$0024
$0025
Read:
Timer A Counter Modulo
Register High Write:
(TAMODH)
Reset:
Read:
Timer A Counter Modulo
Register Low Write:
(TAMODL)
Reset:
Read:
Timer A Channel 0 Status
$0026
and Control Register Write:
(TASC0)
Reset:
$0027
Read:
Timer A Channel 0
Register High Write:
(TACH0H)
Reset:
TOF
0
TRST
0
0
0
0
0
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
0
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
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
CH0F
0
Indeterminate after reset
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 11)
Technical Data
48
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Memory Map
Addr.
$0028
Register Name
Read:
Timer A Channel 0
Register Low Write:
(TACH0L)
Reset:
Read:
Timer A Channel 1 Status
$0029
and Control Register Write:
(TASC1)
Reset:
$002A
$002B
Read:
Timer A Channel 1
Register High Write:
(TACH1H)
Reset:
Read:
Timer A Channel 1
Register Low Write:
(TACH1L)
Reset:
Read:
Timer A Channel 2 Status
$002C
and Control Register Write:
(TASC2)
Reset:
$002D
$002E
Read:
Timer A Channel 2
Register High Write:
(TACH2H)
Reset:
Read:
Timer A Channel 2
Register Low Write:
(TACH2L)
Reset:
Read:
Timer A Channel 3 Status
$002F
and Control Register Write:
(TASC3)
Reset:
$0030
$0031
Read:
Timer A Channel 3
Register High Write:
(TACH3H)
Reset:
Read:
Timer A Channel 3
Register Low Write:
(TACH3L)
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
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
CH2F
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH3F
0
CH3IE
0
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
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
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 11)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Memory Map
49
Memory Map
Addr.
Register Name
Bit 7
Read:
Timer B Channel 2 Status
$0032
and Control Register Write:
(TBSC2)
Reset:
CH2F
$0033
$0034
Read:
Timer B Channel 2
Register High Write:
(TBCH2H)
Reset:
Read:
Timer B Channel 2
Register Low Write:
(TBCH2L)
Reset:
Read:
Timer B Channel 3 Status
$0035
and Control Register Write:
(TBSC3)
Reset:
$0036
$0037
$0038
$0039
$003A
Read:
Timer B Channel 3
Register High Write:
(TACH3H)
Reset:
Read:
Timer B Channel 3
Register Low Write:
(TBCH3L)
Reset:
Read:
Analog-to-Digital Status
and Control Register Write:
(ADSCR)
Reset:
Read:
Analog-to-Digital Data
Register Write:
(ADR)
Reset:
Read:
Analog-to-Digital Clock
Register Write:
(ADCLK)
Reset:
Read:
$003B
Reserved Write:
6
5
4
3
2
1
Bit 0
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH3F
0
CH3IE
0
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
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
COCO
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
0
0
1
1
1
1
1
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
0
0
0
0
0
0
0
0
ADIV2
ADIV1
ADIV0
ADICLK
0
0
0
0
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
Reset:
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 6 of 11)
Technical Data
50
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Memory Map
Addr.
Register Name
Read:
$003C
Reserved Write:
Bit 7
6
5
4
3
2
1
Bit 0
R
R
R
R
R
R
R
R
Reset:
Read:
Port D Input Pullup Enable
PTDPUE7 PTDPUE6 PTDPUE5 PTDPUE4 PTDPUE3 PTDPUE2 PTDPUE1 PTDPUE0
$003D
Register Write:
(PTDPUE)
Reset:
0
0
0
0
0
0
0
0
Read:
Port F Input Pullup Enable
PTFPUE7 PTFPUE6 PTFPUE5 PTFPUE4 PTFPUE3 PTFPUE2 PTFPUE1 PTFPUE0
$003E
Register Write:
(PTFPUE)
Reset:
0
0
0
0
0
0
0
0
$003F
Read:
Configuration Register 2
Write:
(CONFIG2)†
Reset:
R
EEDIVCLK
R
R
R
0
0
R
R
R
PS2
PS1
PS0
0
† One-time writable register after each reset.
$0040
$0041
$0042
$0043
$0044
Read:
Timer B Status and
Control Register Write:
(TBSC)
Reset:
TOF
TOIE
TSTOP
0
0
1
0
0
0
0
0
Read:
Timer B Counter
Register High Write:
(TBCNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
Timer B Counter
Register Low Write:
(TBCNTL)
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
Read:
Timer B Counter Modulo
Register High Write:
(TBMODH)
Reset:
Read:
Timer B Counter Modulo
Register Low Write:
(TBMODL)
Reset:
Read:
Timer B Channel 0 Status
$0045
and Control Register Write:
(TBSC0)
Reset:
0
CH0F
0
0
= Unimplemented
TRST
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 7 of 11)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Memory Map
51
Memory Map
Addr.
$0046
$0047
Register Name
Read:
Timer B Channel 0
Register High Write:
(TBCH0H)
Reset:
Read:
Timer B Channel 0
Register Low Write:
(TBCH0L)
Reset:
Read:
Timer B Channel 1 Status
$0048
and Control Register Write:
(TBSC1)
Reset:
$0049
$004A
Read:
Timer B Channel 1
Register High Write:
(TBCH1H)
Reset:
Read:
Timer B Channel 1
Register Low Write:
(TBCH1L)
Reset:
Bit 7
6
5
4
3
2
1
Bit 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
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
PPS2
PPS1
PPS0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
Read:
PIT Status and Control
Register Write:
(PSC)
Reset:
POF
0
0
POIE
PSTOP
0
0
1
0
0
0
0
0
Read:
PIT Counter Register High
$004C
Write:
(PCNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
PIT Counter Register Low
$004D
Write:
(PCNTL)
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
$004B
$004E
$004F
Read:
PIT Counter Modulo
Register High Write:
(PMODH)
Reset:
Read:
PIT Counter Modulo
Register Low Write:
(PMODL)
Reset:
0
= Unimplemented
PRST
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 8 of 11)
Technical Data
52
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Memory Map
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
0
LVI
0
1
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
R
0
0
0
0
HVEN
MASS
ERASE
PGM
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
SBSW
Note
Bit 0
R
Note: Writing a logic 0 clears SBSW.
Read:
SIM Reset Status Register
$FE01
Write:
(SRSR)
POR:
Read:
$FE02
Reserved Write:
Reset:
$FE03
Read:
SIM Break Flag Control
Register Write:
(SBFCR)
Reset:
Read:
$FE04
Reserved Write:
0
Reset:
Read:
$FE05
Reserved Write:
Reset:
Read:
$FE06
Reserved Write:
Reset:
Read:
$FE07
Reserved Write:
Reset:
$FE08
Read:
FLASH Control Register
Write:
(FLCR)
Reset:
Read:
$FE09
Reserved Write:
Reset:
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 9 of 11)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Memory Map
53
Memory Map
Addr.
Register Name
Read:
$FE0A
Reserved Write:
Bit 7
6
5
4
3
2
1
Bit 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
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
EEDIV10
EEDIV9
EEDIV8
EEDIV1
EEDIV0
EEDIV9
EEDIV8
EEDIV1
EEDIV0
Reset:
Read:
$FE0B
Reserved Write:
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:
Read: LVIOUT
Low-Voltage Inhibit Status
Register Write:
$FE0F
(LVISR)
Reset:
0
$FE10
$FE11
Read:
EEDIV Non-volatile
EEDIVSECD
Register High Write:
(EEDIVHNVR)*
Reset:
Read:
EEDIV Non-volatile
EEDIV7
Register Low Write:
(EEDIVLNVR)*
Reset:
Unaffected by reset; $FF when blank
EEDIV6
EEDIV5
EEDIV4
EEDIV3
EEDIV2
Unaffected by reset; $FF when blank
* Non-volatile FLASH register; write by programming.
Read:
EEDIVSECD
EE Divider Register High
$FE1A
Write:
(EEDIVH)
Reset:
$FE1B
Read:
EEDIV7
EE Divider Register Low
Write:
(EEDIVL)
Reset:
R
R
R
R
EEDIV10
Contents of EEDIVHNVR ($FE10)
EEDIV6
EEDIV5
EEDIV4
EEDIV3
EEDIV2
Contents of EEDIVLNVR ($FE11)
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 10 of 11)
Technical Data
54
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Memory Map
Addr.
$FE1C
Register Name
Read:
EEPROM Non-volatile
Register Write:
(EENVR)*
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
CON3
CON2
CON1
EEPRTCT
EEBP3
EEBP2
EEBP1
EEBP0
Unaffected by reset; $FF when blank
Read:
EEDUM
EEPROM Control Register
$FE1D
Write:
(EECR)
Reset:
0
Read:
$FE1E
Reserved Write:
0
EEOFF
EERAS1
EERAS0
EELAT
AUTO
EEPGM
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
CON3
CON2
CON1
EEPRTCT
EEBP3
EEBP2
EEBP1
EEBP0
BPR1
BPR0
Reset:
$FE1F
$FF7E
Read:
EEPROM Array
Configuration Register Write:
(EEACR)
Reset:
Read:
FLASH Block Protect
Write:
Register (FLBPR)*
Reset:
Contents of EENVR ($FE1C)
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
Unaffected by reset
* Non-volatile FLASH register; write by programming.
$FFFF
Read:
COP Control Register
Write:
(COPCTL)
Reset:
Low byte of reset vector
Writing clears COP counter (any value)
Unaffected by reset
= Unimplemented
R
= Reserved
Figure 2-2. Control, Status, and Data Registers (Sheet 11 of 11)
MC68HC908AB32 — Rev. 1.1
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Technical Data
Memory Map
55
Memory Map
Table 2-1. Vector Addresses
Vector Priority
Lowest
Highest
Address
$FFD0
$FFD1
ADC Conversion Complete Vector (Low)
$FFD2
Keyboard Vector (High)
$FFD3
Keyboard Vector (Low)
$FFD4
SCI Transmit Vector (High)
$FFD5
SCI Transmit Vector (Low)
$FFD6
SCI Receive Vector (High)
$FFD7
SCI Receive Vector (Low)
$FFD8
SCI Error Vector (High)
$FFD9
SCI Error Vector (Low)
$FFDA
Reserved
$FFDB
Reserved
$FFDC
Reserved
$FFDD
Reserved
$FFDE
Timer B Channel 3 Vector (High)
$FFDF
Timer B Channel 3 Vector (Low)
$FFE0
Timer B Channel 2 Vector (High)
$FFE1
Timer B Channel 2 Vector (Low)
$FFE2
SPI Transmit Vector (High)
$FFE3
SPI Transmit Vector (Low)
$FFE4
SPI Receive Vector (High)
$FFE5
SPI Receive Vector (Low)
$FFE6
Timer B Overflow Vector (High)
$FFE7
Timer B Overflow Vector (Low)
$FFE8
Timer B Channel 1 Vector (High)
$FFE9
Timer B Channel 1 Vector (Low)
$FFEA
Timer B Channel 0 Vector (High)
$FFEB
Timer B Channel 0 Vector (Low)
$FFEC
Timer A Overflow Vector (High)
$FFED
Timer A Overflow Vector (Low)
$FFEE
Timer A Channel 3 Vector (High)
$FFEF
Timer A Channel 3 Vector (Low)
$FFF0
Timer A Channel 2 Vector (High)
$FFF1
Timer A Channel 2 Vector (Low)
$FFF2
Timer A Channel 1 Vector (High)
$FFF3
Timer A Channel 1 Vector (Low)
$FFF4
Timer A Channel 0 Vector (High)
$FFF5
Timer A Channel 0 Vector (Low)
$FFF6
Programmable Interrupt Timer (High)
$FFF7
Programmable Interrupt Timer (Low)
$FFF8
PLL Vector (High)
$FFF9
PLL Vector (Low)
$FFFA
IRQ Vector (High)
$FFFB
IRQ Vector (Low)
$FFFC
SWI Vector (High)
$FFFD
SWI Vector (Low)
$FFFE
Reset Vector (High)
$FFFF
Reset Vector (Low)
Technical Data
56
Vector
ADC Conversion Complete Vector (High)
MC68HC908AB32 — Rev. 1.1
Memory Map
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 3. Random-Access Memory (RAM)
3.1 Contents
3.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
3.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57
3.2 Introduction
This section describes the 1024 bytes of RAM (random-access
memory).
3.3 Functional Description
Addresses $0050 through $044F 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 176 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 out of page zero, direct addressing mode
instructions can efficiently access 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.
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Random-Access Memory (RAM)
57
Random-Access Memory (RAM)
During a subroutine call, the CPU uses two bytes of the stack to store
the return address. The stack pointer decrements during pushes and
increments during pulls.
NOTE:
Be careful when using nested subroutines. The CPU may overwrite data
in the RAM during a subroutine or during the interrupt stacking
operation.
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58
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Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 4. FLASH Memory
4.1 Contents
4.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
4.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
4.4
FLASH Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
4.5
FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . 61
4.6
FLASH Mass Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . 62
4.7
FLASH Program/Read Operation . . . . . . . . . . . . . . . . . . . . . . . 63
4.8
FLASH Block Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
4.8.1
FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . 66
4.9
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.10
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.2 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.
4.3 Functional Description
The FLASH memory is an array of 32,256 bytes with an additional 48
bytes of user vectors and one byte of block protection. An erased bit
reads as logic 1 and a programmed bit reads as a logic 0. Memory in the
FLASH array is organized into two rows per page basis. For the 32K
word by 8-Bit Embedded FLASH Memory, the page size is 128 bytes per
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Technical Data
FLASH Memory
59
FLASH Memory
page. Hence the minimum erase page size is 128 bytes. Program and
erase operations are facilitated through control bits in the FLASH Control
Register (FLCR). Details for these operations appear later in this
section. The address ranges for the user memory and vectors are:
•
$8000–$FDFF; user memory.
•
$FF7E; FLASH block protect register.
•
$FE08; FLASH control register.
•
$FFDC–$FFFF; these locations are reserved for user-defined
interrupt and reset vectors.
Programming tools are available from Freescale. Contact your local
Freescale representative for more information.
NOTE:
A security feature prevents viewing of the FLASH contents.1
4.4 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase
operations.
Address:
Read:
$FE08
Bit 7
6
5
4
0
0
0
0
0
0
0
0
Write:
Reset:
3
2
1
Bit 0
HVEN
MASS
ERASE
PGM
0
0
0
0
Figure 4-1. FLASH Control Register (FLCR)
HVEN — High-Voltage Enable Bit
This read/write bit enables the charge pump to drive high voltages for
program and erase operations in the array. HVEN can 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
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
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FLASH Memory
Freescale Semiconductor
FLASH Memory
MASS — Mass Erase Control Bit
Setting this read/write bit configures the 32K-byte FLASH array for
mass erase operation.
1 = MASS erase operation selected
0 = MASS erase operation unselected
ERASE — Erase Control Bit
This read/write bit configures the memory for erase operation.
ERASE is interlocked with the PGM bit such that both bits cannot be
equal to 1 or set to 1 at the same time.
1 = Erase operation selected
0 = Erase operation unselected
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 unselected
4.5 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (128 bytes) of FLASH
memory to read as logic 1:
1. Set the ERASE bit, and clear the MASS bit in the FLASH control
register.
2. Read the FLASH block protect register.
3. Write any data to any FLASH address within the page address
range desired.
4. Wait for a time, tnvs (min. 10µs)
5. Set the HVEN bit.
6. Wait for a time, tErase (min. 1ms)
7. Clear the ERASE bit.
8. Wait for a time, tnvh (min. 5µs)
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61
FLASH Memory
9. Clear the HVEN bit.
10. After a time, trcv (typ. 1µs), the memory can be accessed again in
read mode.
NOTE:
While these operations must be performed in the order shown, other
unrelated operations may occur between the steps.
4.6 FLASH Mass Erase Operation
Use this step-by-step procedure to erase entire FLASH memory to read
as logic 1:
1. Set both the ERASE bit, and the MASS bit in the FLASH control
register.
2. Read from the FLASH block protect register.
3. Write any data to any FLASH address* within the FLASH memory
address range.
4. Wait for a time, tnvs (min. 10µs)
5. Set the HVEN bit.
6. Wait for a time, tMErase (min. 4ms)
7. Clear the ERASE bit.
8. Wait for a time, tnvhl (min. 100µs)
9. Clear the HVEN bit.
10. After a time, trcv (min. 1µs), the memory can be accessed again in
read mode.
* When in Monitor mode, with security sequence failed (see 10.5 Security), write to the FLASH
block protect register instead of any FLASH address.
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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Freescale Semiconductor
FLASH Memory
4.7 FLASH Program/Read Operation
Programming of the FLASH memory is done on a row basis. A row
consists of 64 consecutive bytes starting from addresses $XX00,
$XX40, $0080 and $XXC0. Use this step-by-step procedure to program
a row of FLASH memory (Figure 4-2 is a flowchart representation):
NOTE:
In order to avoid program disturbs, the row must be erased before any
byte on that row is programmed.
1. Set the PGM bit. This configures the memory for program
operation and enables the latching of address and data for
programming.
2. Read from the FLASH block protect register.
3. Write any data to any FLASH address within the row address
range desired.
4. Wait for a time, tnvs (min. 10µs).
5. Set the HVEN bit.
6. Wait for a time, tpgs (min. 5µs).
7. Write data to the FLASH address to be programmed.*
8. Wait for a time, tPROG (min. 30µs).
9. Repeat step 7 and 8 until all the bytes within the row are
programmed.
10. Clear the PGM bit.*
11. Wait for a time, tnvh (min. 5µs).
12. Clear the HVEN bit.
13. After time, trcv (min. 1µs), the memory can be accessed in read
mode again.
* The time between each FLASH address change, or the time between the last FLASH address
programmed to clearing PGM bit, must not exceed the maximum programming time, tPROG max.
This program sequence is repeated throughout the memory until all data
is programmed.
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Technical Data
FLASH Memory
63
FLASH Memory
NOTE:
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps. Do not exceed tPROG maximum. See 23.13
FLASH Memory Characteristics.
4.8 FLASH Block Protection
Due to the ability of the on-board charge pump to erase and program the
FLASH memory in the target application, provision is made for protecting
a block of memory from unintentional erase or program operations due
to system malfunction. This protection is done by using 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 at the bottom of
the FLASH memory ($FFFF). When the memory is protected, the HVEN
bit cannot be set in either ERASE or PROGRAM operations.
NOTE:
In performing a program or erase operation, the FLASH block protect
register must be read after setting the PGM or ERASE bit and before
asserting the HVEN bit
When the FLBPR is program with all 0’s, the entire memory is protected
from being programmed and erased. When all the bits are erased (all
1’s), the entire memory is accessible for program and erase.
When bits within the FLBPR are programmed, they lock a block of
memory, address ranges as shown in 4.8.1 FLASH Block Protect
Register. Once the FLBPR is programmed with a value other than $FF,
any erase or program of the FLBPR or the protected block of FLASH
memory is prohibited. The FLBPR itself can be erased or programmed
only with an external voltage, VTST, present on the IRQ pin. This voltage
also allows entry from reset into the monitor mode.
Technical Data
64
MC68HC908AB32 — Rev. 1.1
FLASH Memory
Freescale Semiconductor
FLASH Memory
Algorithm for programming
a row (64 bytes) of FLASH memory
1
Set PGM bit
2
Read the FLASH block protect register
3
Write any data to any FLASH address
within the row address range desired
4
Wait for a time, tnvs
5
Set HVEN bit
6
Wait for a time, tpgs
7
Write data to the FLASH address
to be programmed
8
Wait for a time, tPROG
Completed
programming
this row?
Y
N
NOTE:
The time between each FLASH address change (step 7 to step 7), or
the time between the last FLASH address programmed
to clearing PGM bit (step 7 to step 10)
must not exceed the maximum programming
time, tPROG max.
10
Clear PGM bit
11
Wait for a time, tnvh
12
Clear HVEN bit
13
Wait for a time, trcv
This row program algorithm assumes the row/s
to be programmed are initially erased.
End of programming
Figure 4-2. FLASH Programming Flowchart
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Technical Data
FLASH Memory
65
FLASH Memory
4.8.1 FLASH Block Protect Register
The FLASH block protect register (FLBPR) is implemented as a byte
within the FLASH memory, and therefore can only be written during a
programming sequence of the FLASH memory. The value in this register
determines the starting location of the protected range within the FLASH
memory.
Address:
Read:
Write:
Reset:
$FF7E
Bit 7
6
5
4
3
2
1
Bit 0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
U
U
U
U
U
U
U
U
U = Unaffected by reset. Initial value from factory is 1.
Write to this register is by a programming sequence to the FLASH memory.
Figure 4-3. FLASH Block Protect Register (FLBPR)
BPR[7:0] — FLASH Block Protect Bits
These eight bits represent bits [14:7] of a 16-bit memory address.
Bit-15 is logic 1 and bits [6:0] are logic 0s.
The resultant 16-bit address is used for specifying the start address
of the FLASH memory for block protection. The FLASH is protected
from this start address to the end of FLASH memory, at $FFFF. With
this mechanism, the protect start address can be XX00 and XX80
(128 bytes page boundaries) within the FLASH memory.
16-bit memory address
Start address of FLASH block protect
1
FLBPR value
0
0
0
0
0
0
0
Figure 4-4. FLASH Block Protect Start Address
Technical Data
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FLASH Memory
Freescale Semiconductor
FLASH Memory
Examples of protect start address:
BPR[7:0]
Start of Address of Protect Range
$00
The entire FLASH memory is protected.
$01 (0000 0001)
$8080 (1000 0000 1000 0000)
$02 (0000 0010)
$8100 (1000 0001 0000 0000)
and so on...
$FE (1111 1110)
$FF00 (1111 1111 0000 0000)
$FF
The entire FLASH memory is not protected.
Note:
The end address of the protected range is always $FFFF.
4.9 Wait Mode
Putting the MCU into wait mode while the FLASH is in read mode does
not affect the operation of the FLASH memory directly, but there will not
be any memory activity since the CPU is inactive.
The WAIT instruction should not be executed while performing a
program or erase operation on the FLASH, otherwise the operation will
discontinue, and the FLASH will be on Standby Mode.
4.10 Stop Mode
Putting the MCU into stop mode while the FLASH is in read mode does
not affect the operation of the FLASH memory directly, but there will not
be any memory activity since the CPU is inactive.
The STOP instruction should not be executed while performing a
program or erase operation on the FLASH, otherwise the operation will
discontinue, and the FLASH will be on Standby Mode
NOTE:
Standby Mode is the power saving mode of the FLASH module in which
all internal control signals to the FLASH are inactive and the current
consumption of the FLASH is at a minimum.
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Freescale Semiconductor
Technical Data
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FLASH Memory
Technical Data
68
MC68HC908AB32 — Rev. 1.1
FLASH Memory
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 5. EEPROM
5.1 Contents
5.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
5.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
5.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .71
5.5
EEPROM Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
5.6
EEPROM Timebase Requirements . . . . . . . . . . . . . . . . . . . . . 72
5.7
EEPROM Security Options. . . . . . . . . . . . . . . . . . . . . . . . . . . .72
5.8
EEPROM Block Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . .72
5.9
EEPROM Programming and Erasing . . . . . . . . . . . . . . . . . . . . 73
5.9.1
EEPROM Programming . . . . . . . . . . . . . . . . . . . . . . . . . . . .74
5.9.2
EEPROM Erasing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5.10 Low Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76
5.10.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .76
5.10.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77
5.11 EEPROM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.11.1 EEPROM Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . 77
5.11.2 EEPROM Array Configuration Register . . . . . . . . . . . . . . . . 79
5.11.2.1
EEPROM Non-Volatile Register. . . . . . . . . . . . . . . . . . . . 80
5.11.3 EEPROM Timebase Divider Register . . . . . . . . . . . . . . . . . 80
5.11.3.1
EEPROM Timebase Divider Non-Volatile Register . . . . . 82
5.2 Introduction
This section describes the 512 bytes electrically erasable programmable
read-only-memory (EEPROM).
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Technical Data
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69
EEPROM
5.3 Features
Features of the EEPROM include the following:
Addr.
$FE10
$FE11
•
512 bytes non-volatile memory
•
Byte, block or bulk erasable operations
•
Non-volatile EEPROM configuration and block protection options
•
On-chip charge pump for programming/erasing
•
Security option
Register Name
Bit 7
Read:
EEDIV Non-volatile
EEDIVSECD
Register High Write:
(EEDIVHNVR)*
Reset:
Read:
EEDIV Non-volatile
EEDIV7
Register Low Write:
(EEDIVLNVR)*
Reset:
Read:
EEDIVSECD
EE Divider Register High
Write:
$FE1A
(EEDIVH)
Reset:
$FE1B
$FE1C
Read:
EEDIV7
EE Divider Register Low
Write:
(EEDIVL)
Reset:
Read:
EEPROM Non-volatile
Register Write:
(EENVR)*
Reset:
CON3
Read:
EEDUM
EEPROM Control Register
$FE1D
Write:
(EECR)
Reset:
0
6
5
4
3
2
1
Bit 0
R
R
R
R
EEDIV10
EEDIV9
EEDIV8
EEDIV1
EEDIV0
EEDIV9
EEDIV8
EEDIV1
EEDIV0
EEBP1
EEBP0
Unaffected by reset; $FF when blank
EEDIV6
EEDIV5
EEDIV4
EEDIV3
EEDIV2
Unaffected by reset; $FF when blank
R
R
R
R
EEDIV10
Contents of EEDIVHNVR ($FE10)
EEDIV6
EEDIV5
EEDIV4
EEDIV3
EEDIV2
Contents of EEDIVLNVR ($FE11)
CON2
CON1
EEPRTCT
EEBP3
EEBP2
Unaffected by reset; $FF when blank; factory programmed $10
0
0
EEOFF
EERAS1
EERAS0
EELAT
AUTO
EEPGM
0
0
0
0
0
0
Figure 5-1. EEPROM I/O Register Summary
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Freescale Semiconductor
EEPROM
$FE1F
Read:
EEPROM Array
Configuration Register Write:
(EEACR)
Reset:
CON3
CON2
CON1
EEPRTCT
EEBP3
EEBP2
EEBP1
EEBP0
Contents of EENVR ($FE1C)
* Non-volatile EEPROM register; write by programming.
= Unimplemented
R
= Reserved
Figure 5-1. EEPROM I/O Register Summary
5.4 Functional Description
The 512 bytes of EEPROM is located at $0800–$09FF, and can be
programmed or erased without an additional external high voltage
supply. The program and erase operations are enabled through the use
of an internal charge pump. For each byte of EEPROM, the write/erase
endurance is 10,000 cycles.
5.5 EEPROM Configuration
The 8-bit EEPROM non-volatile register (EENVR) and the 16-bit
EEPROM timebase divider non-volatile register (EEDIVNVR) contain
the default settings for the following EEPROM configurations:
•
Security option
•
Block protection
•
EEPROM timebase reference
EENVR and EEDIVNVR are non-volatile, EEPROM registers. They are
programmed and erased in the same way as EEPROM bytes. The
contents of these registers are loaded into their respective volatile
registers during a MCU reset. The values in these read/write, volatile
registers define the EEPROM configurations.
For EENVR, the corresponding volatile register is the EEPROM array
configuration register (EEACR).
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EEPROM
For the EEDIVNVR (two 8-bit registers: EEDIVHNVR and EEDIVLNVR),
the corresponding volatile register is the EEPROM timebase divider
register (EEDIV: EEDIVH and EEDIVL)
Technical Data
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EEPROM
5.6 EEPROM Timebase Requirements
A 35µs timebase is required by the EEPROM control circuit for program
and erase of EEPROM content. This timebase is derived from dividing
the CGMXCLK or bus clock (selected by EEDIVCLK bit in CONFIG2
register) using a timebase divider circuit, controlled by the 16-bit
EEPROM timebase divider register (EEDIVH and EEDIVL).
As the CGMXCLK or bus clock is user selected, the EEPROM timebase
divider register must be configured with the appropriate value to obtain
the 35µs. The timebase divider is calculated using the following formula:
EEDIV = INT [ Reference frequency (Hz) × 35 × 10 –6 + 0.5 ]
This value is written to the EEPROM timebase divider register (EEDIVH
and EEDIVL) or programmed into the EEPROM timebase divider nonvolatile register prior to any EEPROM program or erase operations (see
5.5 EEPROM Configuration and 5.11.3.1 EEPROM Timebase Divider
Non-Volatile Register).
5.7 EEPROM Security Options
The EEPROM has a special security option, enabled by programming
the EEPRTCT bit to 0 in the EEPROM non-volatile register (EENVR).
Once security is enabled, the following limitations apply to the EEPROM:
•
The 16-byte EEPROM locations from $08F0 to $08FF are
protected from erase and program operations.
•
The block erase and bulk erase modes are disabled. Byte erase
can be used for all EEPROM locations except $08F0 to $08FF.
•
The EENVR is protected from further erase or program
operations.
5.8 EEPROM Block Protection
The 512 bytes of EEPROM is divided into four 128-byte blocks. Each of
these blocks can be protected from erase/program operations by setting
the EEBPx bit in the EENVR. Table 5-1 shows the address ranges for
the blocks.
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EEPROM
Table 5-1. EEPROM Array Address Blocks
Block Number (EEBPx)
Address Range
EEBP0
$0800–$087F
EEBP1
$0880–$08FF
EEBP2
$0900–$097F
EEBP3
$0980–$09FF
These bits are effective after a reset or a read to EENVR register. The
block protect configuration can be modified by erasing/programming the
corresponding bits in the EENVR register and then reading the EENVR
register.
5.9 EEPROM Programming and Erasing
The unprogrammed or erased state of an EEPROM bit is a logic 1. The
factory default for the EEPROM array is $FF for all bytes.
The programming operation changes an EEPROM bit from logic 1 to
logic 0 (programming cannot change a bit from logic 0 to a logic 1). In a
single programming operation, the minimum EEPROM programming
size is zero bits; the maximum is eight bits (one byte).
The erase operation changes an EEPROM bit from logic 0 to logic 1. In
a single erase operation, the minimum EEPROM erase size is one byte;
the maximum is the entire EEPROM array.
For each EEPROM byte, the write/erase endurance is 10,000 cycles.
One write/erase cycle is defined as: a maximum of eight programming
operations on the same byte followed by an erase operation of the that
byte. Therefore, it is possible to program a byte, bit by bit to logic 0
before requiring an erase on that byte.
NOTE:
Although programming a bit (from 0 or 1) with a logic 1 does not change
the state of that bit, it is still regarded as a programming operation. That
is, if the same byte is programmed eight times (with any value), that byte
must be erased before it can be successfully programmed again.
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5.9.1 EEPROM Programming
The unprogrammed or erased state of an EEPROM bit is a logic 1.
Programming changes the state to a logic 0. Only EEPROM bytes in the
non-protected blocks and the EENVR register can be programmed.
Use the following procedure to program a byte of EEPROM:
1. Clear EERAS1 and EERAS0, and set EELAT in the EECR.(A)
2. Write the desired data to the desired EEPROM address.(B)
3. Set the EEPGM bit.(C)
Go to step 7 if AUTO is set.
4. Wait for a time, tEEPGM, to program the byte.
5. Clear EEPGM bit.
6. Wait for a time, tEEFPV, for the programming voltage to fall.
Go to step 8.
7. Poll the EEPGM bit until it is cleared by the internal timer.(D)
8. Clear EELAT bit.(E)
NOTE:
A. EERAS1 and EERAS0 must be cleared for programming. Setting the
EELAT bit configures the address and data buses to latch data for
programming the array. Only data with a valid EEPROM address will be
latched. If EELAT is set, other writes to the EECR will be allowed after a
valid EEPROM write.
B. If more than one valid EEPROM writes occur, the last address and
data will be latched, overriding the previous address and data. Once
written data to the desired address, do not read EEPROM locations
other than the written location. (Reading an EEPROM location returns
the latched data, and causes the read address to be latched.)
C. The EEPGM bit cannot be set if the EELAT bit is cleared or a nonvalid EEPROM address is latched. This is to ensure proper
programming sequence. Once EEPGM is set, do not read any EEPROM
locations, otherwise the current program cycle will be unsuccessful.
When EEPGM is set, the on-board programming sequence will be
activated.
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EEPROM
D. The delay time for the EEPGM bit to be cleared in AUTO mode is less
than tEEPGM. However, on other MCUs, this delay time may be different.
For forward compatibility, software should not make any dependency on
this delay time.
E. Any attempt to clear both EEPGM and EELAT bits with a single
instruction will only clear EEPGM. This is to allow time for removal of
high voltage from the EEPROM array.
5.9.2 EEPROM Erasing
The programmed state of an EEPROM bit is logic 0. Erasing changes
the state to a logic 1. Only EEPROM bytes in the non-protected blocks
and EENVR register can be erased.
Use the following procedure to erase a byte, block, or the entire
EEPROM:
1. Configure EERAS1 and EERAS0 for byte, block, or bulk erase; set
EELAT in EECR.(A)
2. Byte erase: write any data to the desired address.(B)
Block erase: write any data to an address within the desired
block.(B)
Bulk erase: write any data to an address within the array.(B)
3. Set the EEPGM bit.(C)
Go to step 7 if AUTO is set.
4. Wait for a time: tEBYTE for byte erase; tEBLOCK for block erase;
tEBULK for bulk erase.
5. Clear EEPGM bit.
6. Wait for a time, tEEFPV, for the erasing voltage to fall.
Go to step 8.
7. Poll the EEPGM bit until it is cleared by the internal timer.(D)
8. Clear EELAT bits.(E)
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NOTE:
A. Setting the EELAT bit configures the address and data buses to latch
data for erasing the array. Only valid EEPROM addresses will be
latched. If EELAT is set, other writes to the EECR will be allowed after a
valid EEPROM write.
B. If more than one valid EEPROM writes occur, the last address and
data will be latched, overriding the previous address and data. Once
written data to the desired address, do not read EEPROM locations
other than the written location. (Reading an EEPROM location returns
the latched data, and causes the read address to be latched.)
EENVR is not affected by block or bulk erase.
C. The EEPGM bit cannot be set if the EELAT bit is cleared or a nonvalid EEPROM address is latched. This is to ensure proper
programming sequence. Once EEPGM is set, do not read any EEPROM
locations, otherwise the current erase cycle will be unsuccessful. When
EEPGM is set, the erase mode cannot be changed, and the on-board
erasing sequence will be activated.
D. The delay time for the EEPGM bit to be cleared in AUTO mode is less
than tEBYTE / tEBLOCK / tEBULK. However, on other MCUs, this delay time
may be different. For forward compatibility, software should not make
any dependency on this delay time.
E. Any attempt to clear both EEPGM and EELAT bits with a single
instruction will only clear EEPGM. This is to allow time for removal of
high voltage from the EEPROM array.
5.10 Low Power Modes
The WAIT and STOP instructions can put the MCU in low power
consumption standby modes.
5.10.1 Wait Mode
The WAIT instruction does not affect the EEPROM. It is possible to start
the program or erase sequence on the EEPROM and put the MCU in
wait mode.
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5.10.2 Stop Mode
The STOP instruction reduces the EEPROM power consumption to a
minimum. The STOP instruction should not be executed while the
programming and erasing sequence is in progress.
If stop mode is entered while EELAT and EEPGM is set, the
programming sequence will be stopped and the programming voltage to
the EEPROM array removed. The programming sequence will be
restarted after leaving stop mode; access to the EEPROM is only
possible after the programming sequence has completed.
If stop mode is entered while EELAT and EEPGM is cleared, the
programming sequence will be terminated abruptly.
In either case, the data integrity of the EEPROM is not guaranteed.
5.11 EEPROM Registers
Four I/O registers and three non-volatile registers control program,
erase, and options of the EEPROM array.
5.11.1 EEPROM Control Register
This read/write register controls programming/erasing of the EEPROM
array.
Address:
$FE1D
Bit 7
Read:
Write:
Reset:
EEDUM
0
6
0
0
5
4
3
2
1
Bit 0
EEOFF
EERAS1
EERAS0
EELAT
AUTO
EEPGM
0
0
0
0
0
0
Figure 5-2. EEPROM Control Register (EECR)
EEDUM — Dummy Bit
This read/write bit has no function.
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EEOFF — EEPROM Power-Off
This read/write bit disables the EEPROM module for lower power
consumption. Any attempts to access the array will give unpredictable
results. Reset clears this bit.
1 = Disable EEPROM array
0 = Enable EEPROM array
EERAS[1:0] — Erase/Program Mode Select Bits
These read/write bits set the erase modes. Reset clears these bits.
Table 5-2. EEPROM Program/Erase Mode Select
EEBPx
EERAS1
EERAS0
Mode
0
0
0
Byte Program
0
0
1
Byte Erase
0
1
0
Block Erase
0
1
1
Bulk Erase
1
X
X
No Erase/Program
X = don’t care
EELAT — EEPROM Latch Control
This read/write bit latches the address and data buses for
programming the EEPROM array. EELAT can not be cleared if
EEPGM is still set. Reset clears this bit.
1 = Buses configured for EEPROM program or erase operation
0 = Buses configured for normal operation
AUTO — Automatic termination of program/erase cycle
When AUTO is set, EEPGM is cleared automatically after the
program/erase cycle is terminated by the internal timer.
(See note D for 5.9.1 EEPROM Programming and 5.9.2 EEPROM
Erasing.)
0 = Automatic clear of EEPGM is disabled
1 = Automatic clear of EEPGM is enabled
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EEPROM
EEPGM — EEPROM Program/Erase Enable
This read/write bit enables the internal charge pump and applies the
programming/erasing voltage to the EEPROM array if the EELAT bit
is set and a write to a valid EEPROM location has occurred. Reset
clears the EEPGM bit.
1 = EEPROM programming/erasing power switched on
0 = EEPROM programming/erasing power switched off
NOTE:
Writing 0s to both the EELAT and EEPGM bits with a single instruction
will only clear EEPGM. This is to allow time for the removal of high
voltage.
5.11.2 EEPROM Array Configuration Register
The EEPROM array configuration register configures EEPROM security
and EEPROM block protection.
This read-only register is loaded with the contents of the EEPROM nonvolatile register (EENVR) after a reset.
Address:
Read:
$FE1F
Bit 7
6
5
4
3
2
1
Bit 0
CON3
CON2
CON1
EEPRTCT
EEBP3
EEBP2
EEBP1
EEBP0
Write:
Reset:
Contents of EENVR ($FE1C)
Figure 5-3. EEPROM Array Configuration Register (EEACR)
CON[3:1] — Unused
EEPRTCT — EEPROM Protection Bit
The EEPRTCT bit is used to enable the security feature in the
EEPROM (see 5.7 EEPROM Security Options).
1 = EEPROM security disabled
0 = EEPROM security enabled
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EEBP[3:0] — EEPROM Block Protection Bits
These bits prevent blocks of EEPROM array from being programmed
or erased.
1 = EEPROM array block is protected
0 = EEPROM array block is unprotected
Block Number (EEBPx)
Address Range
EEBP0
$0800–$087F
EEBP1
$0880–$08FF
EEBP2
$0900–$097F
EEBP3
$0980–$09FF
5.11.2.1 EEPROM Non-Volatile Register
The contents of this register is loaded into the EEPROM array
configuration register (EEACR) after a reset.
This register is erased and programmed in the same way as an
EEPROM byte.
Address:
Read:
Write:
Reset:
$FE1C
Bit 7
6
5
4
3
2
1
Bit 0
CON3
CON2
CON1
EEPRTCT
EEBP3
EEBP2
EEBP1
EEBP0
Unaffected by reset; $FF when blank; factory programmed $10
Note: Non-volatile EEPROM register; write by programming.
Figure 5-4. EEPROM Non-Volatile Register (EENVR)
NOTE:
The EENVR is factory programmed with $10.
5.11.3 EEPROM Timebase Divider Register
The 16-bit EEPROM timebase divider register consists of two 8-bit
registers: EEDIVH and EEDIVL. The 11-bit value in this register is used
to configure the timebase divider circuit to obtain the 35µs timebase for
EEPROM control.
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EEPROM
These two read/write registers are respectively loaded with the contents
of the EEPROM timebase divider non-volatile registers (EEDIVHNVR
and EEDIVLNVR) after a reset.
Address:
$FE1A
Bit 7
6
5
4
3
2
1
Bit 0
EEDIVSECD
R
R
R
R
EEDIV10
EEDIV9
EEDIV8
Read:
Write:
Reset:
Contents of EEDIVHNVR ($FE10)
Figure 5-5. EEPROM Divider Register High (EEDIVH)
Address:
Read:
Write:
Reset:
$FE1B
Bit 7
6
5
4
3
2
1
Bit 0
EEDIV7
EEDIV6
EEDIV5
EEDIV4
EEDIV3
EEDIV2
EEDIV1
EEDIV0
Contents of EEDIVLNVR ($FE11)
Figure 5-6. EEPROM Divider Register Low (EEDIVL)
EEDIVSECD — EEPROM Divider Security Disable
This bit enables/disables the security feature of the EEDIV registers.
When EEDIV security feature is enabled, the state of the registers
EEDIVH and EEDIVL are locked (including this EEDIVSECD bit). The
EEDIVHNVR and EEDIVLNVR non-volatile memory registers are
also protected from being erased/programmed.
1 = EEDIV security feature disabled
0 = EEDIV security feature enabled
EEDIV[10:0] — EEPROM Timebase Prescaler
These prescaler bits store the value of EEDIV which is used as the
divisor to derive a timebase of 35µs from the selected reference clock
source (CGMXCLK or bus clock, see 6.5 Configuration Register 2)
for the EEPROM related internal timer and circuits. EEDIV[10:0] bits
are readable at any time. They are writable when EELAT=0 and
EEDIVSECD=1.
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The EEDIV value is calculated by the following formula:
EEDIV = INT [ Reference frequency (Hz) × 35 × 10 –6 + 0.5 ]
Where the result inside the bracket is rounded down to the nearest
integer value.
For example, if the reference frequency is 4.9152MHz, the EEDIV
value is 172.
NOTE:
Programming/erasing the EEPROM with an improper EEDIV value may
result in data lost and reduce endurance of the EEPROM device.
5.11.3.1 EEPROM Timebase Divider Non-Volatile Register
The 16-bit EEPROM timebase divider non-volatile register consists of
two 8-bit registers: EEDIVHNVR and EEDIVLNVR. The contents of
these two registers are respectively loaded into the EEPROM timebase
divider registers, EEDIVH and EEDIVL, after a reset.
These two registers are erased and programmed in the same way as an
EEPROM byte.
Address:
$FE10
Bit 7
6
5
4
3
2
1
Bit 0
EEDIVSECD
R
R
R
R
EEDIV10
EEDIV9
EEDIV8
Read:
Write:
Reset:
Unaffected by reset; $FF when blank
Figure 5-7. EEPROM Divider Non-volatile Register High(EEDIVHNVR)
Address:
Read:
Write:
Reset:
$FE11
Bit 7
6
5
4
3
2
1
Bit 0
EEDIV7
EEDIV6
EEDIV5
EEDIV4
EEDIV3
EEDIV2
EEDIV1
EEDIV0
Unaffected by reset; $FF when blank
Figure 5-8. EEPROM Divider Non-volatile Register Low (EEDIVLNVR)
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EEPROM
These two registers are protected from erase and program operations if
the EEDIVSECD is set to logic 1 in the EEDIVH (see 5.11.3 EEPROM
Timebase Divider Register), or programmed to a logic 1 in the
EEDIVHNVR.
NOTE:
Once EEDIVSECD in the EEDIVHNVR is programmed to 0 and after a
system reset, the EEDIV security feature is permanently enabled
because the EEDIVSECD bit in the EEDIVH is always loaded with a 0
thereafter. Once this security feature is armed, erase and program
operations are disabled for EEDIVHNVR and EEDIVLNVR.
Modifications to the EEDIVH and EEDIVL registers are also disabled.
Therefore, care should be taken before programming a value into the
EEDIVHNVR.
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Technical Data — MC68HC908AB32
Section 6. Configuration Register (CONFIG)
6.1 Contents
6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85
6.3
Functional description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.4
Configuration Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
6.5
Configuration Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
6.2 Introduction
This section describes the configuration registers, CONFIG1 and
CONFIG2. The configuration registers enable or disable these options:
•
Low-voltage inhibit (LVI) in stop mode
•
LVI reset
•
LVI module power
•
Stop mode recovery time (32 CGMXCLK cycles or 4096
CGMXCLK cycles)
•
COP timeout period (218 – 24 or 213 – 24 CGMXCLK cycles)
•
STOP instruction
•
Computer operating properly module (COP)
•
EEPROM reference clock source (CPU bus clock or CGMXCLK)
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Configuration Register (CONFIG)
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Configuration Register (CONFIG)
6.3 Functional description
The configuration registers are used in the initialization of various
options. 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 $001F and $003F. The configuration register
may be read at anytime.
6.4 Configuration Register 1
Address:
Read:
Write:
Reset:
$001F
Bit 7
6
LVISTOP
R
0
0
R
5
4
LVIRSTD LVIPWRD
0
3
2
1
Bit 0
SSREC
COPRS
STOP
COPD
0
0
0
0
0
= Reserved
Figure 6-1. Configuration Register 1 (CONFIG1)
LVISTOP — LVI Enable in Stop Mode Bit
When the LVIPWRD bit is clear, setting the LVISTOP bit enables the
LVI to operate in stop mode. Reset clears LVISTOP. (See Section
21. Low-Voltage Inhibit (LVI).)
1 = LVI enabled during stop mode
0 = LVI disabled during stop mode
LVIRSTD — LVI Reset Disable Bit
LVIRSTD disables the reset signal from the LVI module. (See
Section 21. Low-Voltage Inhibit (LVI).)
1 = LVI module resets disabled
0 = LVI module resets enabled
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Configuration Register (CONFIG)
LVIPWRD — LVI Power Disable Bit
LVIPWRD disables the LVI module. (See Section 21. Low-Voltage
Inhibit (LVI).)
1 = LVI module power disabled
0 = LVI module power enabled
SSREC — Short Stop Recovery Bit
SSREC enables the CPU to exit stop mode with a delay of 32
CGMXCLK cycles instead of a 4096 CGMXCLK cycle delay.
1 = STOP mode recovery after 32 CGMXCLK cycles
0 = STOP mode recovery after 4096 CGMXCLK cycles
NOTE:
If using an external crystal oscillator, do not set the SSREC bit.
COPRS — COP Rate Select Bit
COPRS selects the COP timeout period. Reset clears COPRS. (See
Section 20. Computer Operating Properly (COP).)
1 = COP timeout period is 218 – 24 CGMXCLK cycles
0 = COP timeout period is 213 – 24 CGMXCLK cycles
STOP — STOP Instruction Enable Bit
STOP enables the STOP instruction.
1 = STOP instruction enabled
0 = STOP instruction treated as illegal opcode
COPD — COP Disable Bit
COPD disables the COP module. (See Section 20. Computer
Operating Properly (COP).)
1 = COP module disabled
0 = COP module enabled
Extra care should be exercised when using this emulation part for
development of code to be run in ROM AB, AS or AZ parts that the
options selected by setting the CONFIG1 register match exactly the
options selected on any ROM code request submitted. The
enable/disable logic is not necessarily identical in all parts of the
AB, AS, and AZ families. If in doubt, check with your local field
applications representative.
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Configuration Register (CONFIG)
6.5 Configuration Register 2
Address:
Read:
Write:
$003F
Bit 7
6
5
4
3
2
1
Bit 0
R
EEDIVCLK
R
R
R
R
R
R
Reset:
0
R
= Reserved
Figure 6-2. Configuration Register 2 (CONFIG2)
EEDIVCLK — EEPROM Timebase Divider Clock Select Bit
EEDIVCLK selects the reference clock source for the EEPROM
timebase divider. (See Section 5. EEPROM.)
1 = CPU bus clock drives the EEPROM timebase divider
0 = CGMXCLK drives the EEPROM timebase divider
Extra care should be exercised when using this emulation part for
development of code to be run in ROM AB, AS or AZ parts that the
options selected by setting the CONFIG2 register match exactly the
options selected on any ROM code request submitted. The
enable/disable logic is not necessarily identical in all parts of the
AB, AS, and AZ families. If in doubt, check with your local field
applications representative.
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Technical Data — MC68HC908AB32
Section 7. Central Processor Unit (CPU)
7.1 Contents
7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
7.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
7.4
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90
7.4.1
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
7.4.2
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
7.4.3
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
7.4.4
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.4.5
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
7.5
Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.6
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
7.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .96
7.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .97
7.7
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.8
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.9
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
7.2 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully
object-code-compatible version of the M68HC05 CPU. The CPU08
Reference Manual (Freescale document order number CPU08RM/AD)
contains a description of the CPU instruction set, addressing modes,
and architecture.
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Central Processor Unit (CPU)
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Central Processor Unit (CPU)
7.3 Features
•
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
•
64K-byte 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 64K-bytes
•
Low-power stop and wait modes
7.4 CPU Registers
Figure 7-1 shows the five CPU registers. CPU registers are not part of
the memory map.
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Central Processor Unit (CPU)
7
0
ACCUMULATOR (A)
15
0
H
X
INDEX REGISTER (H:X)
0
15
STACK POINTER (SP)
0
15
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 7-1. CPU Registers
7.4.1 Accumulator
The accumulator is a general-purpose 8-bit register. The CPU uses the
accumulator to hold operands and the results of arithmetic/logic
operations.
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Unaffected by reset
Figure 7-2. Accumulator (A)
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Central Processor Unit (CPU)
7.4.2 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.
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 7-3. Index Register (H:X)
7.4.3 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.
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Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
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 7-4. Stack Pointer (SP)
NOTE:
The location of the stack is arbitrary and may be relocated anywhere in
RAM. Moving the SP out of page 0 ($0000 to $00FF) frees direct
address (page 0) space. For correct operation, the stack pointer must
point only to RAM locations.
7.4.4 Program Counter
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 7-5. Program Counter (PC)
7.4.5 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
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Central Processor Unit (CPU)
93
Central Processor Unit (CPU)
5 are set permanently to logic 1. The following paragraphs describe the
functions of the condition code register.
Read:
Write:
Reset:
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
X = Indeterminate
Figure 7-6. 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
Technical Data
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Central Processor Unit (CPU)
Freescale Semiconductor
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
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
MC68HC908AB32 — Rev. 1.1
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Technical Data
Central Processor Unit (CPU)
95
Central Processor Unit (CPU)
C — Carry/Borrow Flag
The CPU sets the carry/borrow flag when an addition operation
produces a carry out of bit 7 of the accumulator or when a subtraction
operation requires a borrow. Some instructions — such as bit test and
branch, shift, and rotate — also clear or set the carry/borrow flag.
1 = Carry out of bit 7
0 = No carry out of bit 7
7.5 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the
instruction set.
Refer to the CPU08 Reference Manual (Freescale document order
number CPU08RM/AD) for a description of the instructions and
addressing modes and more detail about the architecture of the CPU.
7.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption
standby modes.
7.6.1 Wait Mode
The WAIT instruction:
•
Clears the interrupt mask (I bit) in the condition code register,
enabling interrupts. After exit from wait mode by interrupt, the I bit
remains clear. After exit by reset, the I bit is set.
•
Disables the CPU clock
Technical Data
96
MC68HC908AB32 — Rev. 1.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
7.6.2 Stop Mode
The STOP instruction:
•
Clears the interrupt mask (I bit) in the condition code register,
enabling external interrupts. After exit from stop mode by external
interrupt, the I bit remains clear. After exit by reset, the I bit is set.
•
Disables the CPU clock
After exiting stop mode, the CPU clock begins running after the oscillator
stabilization delay.
7.7 CPU During Break Interrupts
If a break module is present on the MCU, the CPU starts a break
interrupt by:
•
Loading the instruction register with the SWI instruction
•
Loading the program counter with $FFFC:$FFFD or with
$FEFC:$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.
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.
7.8 Instruction Set Summary
7.9 Opcode Map
See Table 7-2.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Central Processor Unit (CPU)
97
Central Processor Unit (CPU)
V H I N Z C
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
– ↕ ↕ ↕
IX1
IX
SP1
SP2
A9
B9
C9
D9
E9
F9
9EE9
9ED9
ii
dd
hh ll
ee ff
ff
IMM
DIR
EXT
IX2
– ↕ ↕ ↕
IX1
IX
SP1
SP2
AB
BB
CB
DB
EB
FB
9EEB
9EDB
ii
dd
hh ll
ee ff
ff
ADD #opr
ADD opr
ADD opr
ADD opr,X
ADD opr,X
ADD ,X
ADD opr,SP
ADD opr,SP
Add without Carry
AIS #opr
Add Immediate Value (Signed) to SP
SP ← (SP) + (16 « M)
– – – – – – IMM
AIX #opr
Add Immediate Value (Signed) to H:X
H:X ← (H:X) + (16 « M)
– – – – – – IMM
AND #opr
AND opr
AND opr
AND opr,X
AND opr,X
AND ,X
AND opr,SP
AND opr,SP
ASL opr
ASLA
ASLX
ASL opr,X
ASL ,X
ASL opr,SP
Arithmetic Shift Left
(Same as LSL)
Arithmetic Shift Right
BCC rel
Branch if Carry Bit Clear
C
C
PC ← (PC) + 2 + rel ? (C) = 0
Mn ← 0
Technical Data
98
ff
ee ff
2
3
4
4
3
2
4
5
A7
ii
2
AF
ii
2
2
3
4
4
3
2
4
5
A4
B4
C4
D4
E4
F4
9EE4
9ED4
ii
dd
hh ll
ee ff
ff
DIR
INH
INH
– – ↕ ↕ ↕
IX1
IX
SP1
38
48
58
68
78
9E68
dd
DIR
INH
INH
– – ↕ ↕ ↕
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
↕
b0
b0
2
3
4
4
3
2
4
5
IMM
DIR
EXT
IX2
–
IX1
IX
SP1
SP2
0 – – ↕ ↕
0
b7
b7
Clear Bit n in M
↕ ↕
A ← (A) & (M)
Logical AND
ASR opr
ASRA
ASRX
ASR opr,X
ASR opr,X
ASR opr,SP
BCLR n, opr
A ← (A) + (M)
ff
ee ff
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary
↕
ff
ee ff
ff
ff
ff
4
1
1
4
3
5
MC68HC908AB32 — Rev. 1.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
Effect on
CCR
V H I N Z C
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Continued)
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) =
– – – – – – REL
0
92
rr
3
BHCC rel
Branch if Half Carry Bit Clear
PC ← (PC) + 2 + rel ? (H) = 0
– – – – – – REL
28
rr
3
BHCS rel
Branch if Half Carry Bit Set
PC ← (PC) + 2 + rel ? (H) = 1
– – – – – – REL
29
rr
BHI rel
Branch if Higher
PC ← (PC) + 2 + rel ? (C) | (Z) = 0
– – – – – – REL
22
rr
3
BHS rel
Branch if Higher or Same
(Same as BCC)
PC ← (PC) + 2 + rel ? (C) = 0
– – – – – – REL
24
rr
3
BIH rel
Branch if IRQ Pin High
PC ← (PC) + 2 + rel ? IRQ = 1
– – – – – – REL
2F
rr
3
BIL rel
Branch if IRQ Pin Low
PC ← (PC) + 2 + rel ? IRQ = 0
– – – – – – REL
2E
rr
3
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
93
rr
3
BIT #opr
BIT opr
BIT opr
BIT opr,X
BIT opr,X
BIT ,X
BIT opr,SP
BIT opr,SP
Bit Test
BLE opr
Branch if Less Than or Equal To
(Signed Operands)
BLO rel
Branch if Lower (Same as BCS)
BLS rel
(A) & (M)
0 – – ↕ ↕
IMM
DIR
EXT
IX2
–
IX1
IX
SP1
SP2
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) =
– – – – – – REL
1
A5
B5
C5
D5
E5
F5
9EE5
9ED5
3
PC ← (PC) + 2 + rel ? (C) = 1
– – – – – – REL
25
rr
3
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
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Central Processor Unit (CPU)
99
Central Processor Unit (CPU)
Table 7-1. Instruction Set Summary (Continued)
DIR (b0)
DIR (b1)
DIR (b2)
DIR (b3)
– – – – – ↕
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)
– – – – – ↕
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
BRCLR n,opr,rel Branch if Bit n in M Clear
BRN rel
Branch Never
BRSET n,opr,rel Branch if Bit n in M Set
BSET n,opr
BSR rel
Set Bit n in M
Branch to Subroutine
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
PC ← (PC) + 3 + rel ? (Mn) = 0
PC ← (PC) + 2
PC ← (PC) + 2; push (PCL)
SP ← (SP) – 1; push (PCH)
SP ← (SP) – 1
PC ← (PC) + rel
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
Cycles
Operand
Effect on
CCR
Opcode
Operation
Address
Mode
Source
Form
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
Technical Data
100
dd
ff
ff
3
1
1
1
3
2
4
MC68HC908AB32 — Rev. 1.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
V H I N Z C
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
(H:X) – (M:M + 1)
(X) – (M)
(A)10
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
M ← (M) = $FF – (M)
A ← (A) = $FF – (M)
X ← (X) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
A1
B1
C1
D1
E1
F1
9EE1
9ED1
ii
dd
hh ll
ee ff
ff
DIR
INH
INH
1
IX1
IX
SP1
33
43
53
63
73
9E63
dd
0 – – ↕ ↕
IMM
DIR
↕
– – ↕ ↕ ↕
↕
IMM
DIR
EXT
IX2
– – ↕ ↕ ↕
IX1
IX
SP1
SP2
U – – ↕ ↕ ↕ INH
A ← (A) – 1 or M ← (M) – 1 or X ← (X) –
1
DIR
PC ← (PC) + 3 + rel ? (result) ≠ 0
INH
PC ← (PC) + 2 + rel ? (result) ≠ 0
– – – – – – INH
PC ← (PC) + 2 + rel ? (result) ≠ 0
IX1
PC ← (PC) + 3 + rel ? (result) ≠ 0
IX
PC ← (PC) + 2 + rel ? (result) ≠ 0
SP1
PC ← (PC) + 4 + rel ? (result) ≠ 0
M ← (M) – 1
A ← (A) – 1
X ← (X) – 1
M ← (M) – 1
M ← (M) – 1
M ← (M) – 1
A ← (H:A)/(X)
H ← Remainder
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
↕
IMM
DIR
EXT
IX2
– – ↕ ↕ ↕
IX1
IX
SP1
SP2
↕
– – ↕ ↕
DIR
INH
INH
–
IX1
IX
SP1
– – – – ↕ ↕ INH
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Continued)
2
3
4
4
3
2
4
5
ff
ee ff
ff
4
1
1
4
3
5
65
75
ii ii+1
dd
3
4
A3
B3
C3
D3
E3
F3
9EE3
9ED3
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
ff
ff
ee ff
72
2
3B
4B
5B
6B
7B
9E6B
dd rr
rr
rr
ff rr
rr
ff rr
3A
4A
5A
6A
7A
9E6A
dd
52
ff
ff
5
3
3
5
4
6
4
1
1
4
3
5
7
Technical Data
Central Processor Unit (CPU)
101
Central Processor Unit (CPU)
V H I N Z C
EOR #opr
EOR opr
EOR opr
EOR opr,X
EOR opr,X
EOR ,X
EOR opr,SP
EOR opr,SP
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
DIR
INH
INH
–
IX1
IX
SP1
3C
4C
5C
6C
7C
9E6C
dd
ff
ee ff
ff
ff
2
3
4
4
3
2
4
5
4
1
1
4
3
5
PC ← Jump Address
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
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
A ← (M)
0 – – ↕ ↕
H:X ← (M:M + 1)
X ← (M)
C
0
b7
b0
Technical Data
102
– – ↕ ↕
ii
dd
hh ll
ee ff
ff
BC
CC
DC
EC
FC
Load X from M
Logical Shift Left
(Same as ASL)
↕
A8
B8
C8
D8
E8
F8
9EE8
9ED8
DIR
EXT
– – – – – – IX2
IX1
IX
Jump
Jump to Subroutine
0 – – ↕ ↕
M ← (M) + 1
A ← (A) + 1
X ← (X) + 1
M ← (M) + 1
M ← (M) + 1
M ← (M) + 1
Increment
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
A ← (A ⊕ M)
Exclusive OR M with A
IMM
DIR
EXT
IX2
–
IX1
IX
SP1
SP2
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Continued)
IMM
DIR
EXT
IX2
–
IX1
IX
SP1
SP2
IMM
DIR
45
55
0 – – ↕ ↕
–
0 – – ↕ ↕
IMM
DIR
EXT
IX2
–
IX1
IX
SP1
SP2
AE
BE
CE
DE
EE
FE
9EEE
9EDE
ii
dd
hh ll
ee ff
ff
DIR
INH
INH
– – ↕ ↕ ↕
IX1
IX
SP1
38
48
58
68
78
9E68
dd
↕
ff
ee ff
ff
ff
4
1
1
4
3
5
MC68HC908AB32 — Rev. 1.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
V H I N Z C
LSR opr
LSRA
LSRX
LSR opr,X
LSR ,X
LSR opr,SP
Logical Shift Right
0
C
b7
MOV opr,opr
MOV opr,X+
MOV #opr,opr
MOV X+,opr
Move
MUL
Unsigned multiply
↕
b0
DIR
INH
INH
– – 0 ↕ ↕
IX1
IX
SP1
(M)Destination ← (M)Source
0 – – ↕ ↕
H:X ← (H:X) + 1 (IX+D, DIX+)
X:A ← (X) × (A)
DD
DIX+
–
IMD
IX+D
– 0 – – – 0 INH
DIR
INH
INH
– – ↕ ↕ ↕
IX1
IX
SP1
34
44
54
64
74
9E64
4E
5E
6E
7E
dd
ff
4
1
1
4
3
5
dd dd
dd
ii dd
dd
5
4
4
4
ff
42
30
40
50
60
70
9E60
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Continued)
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
M ← –(M) = $00 – (M)
A ← –(A) = $00 – (A)
X ← –(X) = $00 – (X)
M ← –(M) = $00 – (M)
M ← –(M) = $00 – (M)
↕
IMM
DIR
EXT
IX2
–
IX1
IX
SP1
SP2
AA
BA
CA
DA
EA
FA
9EEA
9EDA
ff
ff
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
ORA #opr
ORA opr
ORA opr
ORA opr,X
ORA opr,X
ORA ,X
ORA opr,SP
ORA opr,SP
Inclusive OR A and M
PSHA
Push A onto Stack
Push (A); SP ← (SP) – 1
– – – – – – INH
87
2
PSHH
Push H onto Stack
Push (H); SP ← (SP) – 1
– – – – – – INH
8B
2
PSHX
Push X onto Stack
Push (X); SP ← (SP) – 1
– – – – – – INH
89
2
PULA
Pull A from Stack
SP ← (SP + 1); Pull (A)
– – – – – – INH
86
2
PULH
Pull H from Stack
SP ← (SP + 1); Pull (H)
– – – – – – INH
8A
2
PULX
Pull X from Stack
SP ← (SP + 1); Pull (X)
– – – – – – INH
88
2
ROL opr
ROLA
ROLX
ROL opr,X
ROL ,X
ROL opr,SP
Rotate Left through Carry
A ← (A) | (M)
0 – – ↕ ↕
C
↕
b7
b0
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
DIR
INH
INH
– – ↕ ↕ ↕
IX1
IX
SP1
39
49
59
69
79
9E69
ff
ee ff
dd
ff
ff
4
1
1
4
3
5
Technical Data
Central Processor Unit (CPU)
103
Central Processor Unit (CPU)
V H I N Z C
DIR
INH
INH
– – ↕ ↕ ↕
IX1
IX
SP1
36
46
56
66
76
9E66
dd
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Continued)
4
1
1
4
3
5
ROR opr
RORA
RORX
ROR opr,X
ROR ,X
ROR opr,SP
Rotate Right through Carry
RSP
Reset Stack Pointer
SP ← $FF
– – – – – – INH
9C
1
RTI
Return from Interrupt
SP ← (SP) + 1; Pull (CCR)
SP ← (SP) + 1; Pull (A)
SP ← (SP) + 1; Pull (X)
SP ← (SP) + 1; Pull (PCH)
SP ← (SP) + 1; Pull (PCL)
↕ ↕ ↕ ↕ ↕ ↕ INH
80
7
RTS
Return from Subroutine
SP ← SP + 1; Pull (PCH)
SP ← SP + 1; Pull (PCL)
– – – – – – INH
81
4
C
b7
↕
b0
IMM
DIR
EXT
IX2
– – ↕ ↕ ↕
IX1
IX
SP1
SP2
A2
B2
C2
D2
E2
F2
9EE2
9ED2
ff
ff
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
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
Store X in M
A ← (A) – (M) – (C)
M ← (A)
(M:M + 1) ← (H:X)
I ← 0; Stop Oscillator
M ← (X)
Technical Data
104
↕
DIR
EXT
IX2
– IX1
IX
SP1
SP2
B7
C7
D7
E7
F7
9EE7
9ED7
– DIR
35
– – 0 – – – INH
8E
0 – – ↕ ↕
0 – – ↕ ↕
0 – – ↕ ↕
DIR
EXT
IX2
– IX1
IX
SP1
SP2
BF
CF
DF
EF
FF
9EEF
9EDF
ff
ee ff
ff
ee ff
3
4
4
3
2
4
5
dd
4
dd
hh ll
ee ff
ff
1
dd
hh ll
ee ff
ff
ff
ee ff
3
4
4
3
2
4
5
MC68HC908AB32 — Rev. 1.1
Central Processor Unit (CPU)
Freescale Semiconductor
Central Processor Unit (CPU)
V H I N Z C
SUB #opr
SUB opr
SUB opr
SUB opr,X
SUB opr,X
SUB ,X
SUB opr,SP
SUB opr,SP
Subtract
A ← (A) – (M)
↕
IMM
DIR
EXT
IX2
– – ↕ ↕ ↕
IX1
IX
SP1
SP2
A0
B0
C0
D0
E0
F0
9EE0
9ED0
ii
dd
hh ll
ee ff
ff
ff
ee ff
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Continued)
2
3
4
4
3
2
4
5
SWI
Software Interrupt
PC ← (PC) + 1; Push (PCL)
SP ← (SP) – 1; Push (PCH)
SP ← (SP) – 1; Push (X)
SP ← (SP) – 1; Push (A)
SP ← (SP) – 1; Push (CCR)
SP ← (SP) – 1; I ← 1
PCH ← Interrupt Vector High Byte
PCL ← Interrupt Vector Low Byte
TAP
Transfer A to CCR
CCR ← (A)
↕ ↕ ↕ ↕ ↕ ↕ INH
84
2
TAX
Transfer A to X
X ← (A)
– – – – – – INH
97
1
TPA
Transfer CCR to A
A ← (CCR)
– – – – – – INH
85
1
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) – $00 or (X) – $00 or (M) – $00
83
9
0 – – ↕ ↕
DIR
INH
INH
–
IX1
IX
SP1
3D
4D
5D
6D
7D
9E6D
dd
ff
ff
3
1
1
3
2
4
H:X ← (SP) + 1
– – – – – – INH
95
2
A ← (X)
– – – – – – INH
9F
1
(SP) ← (H:X) – 1
– – – – – – INH
94
2
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
– – 1 – – – INH
Technical Data
Central Processor Unit (CPU)
105
Central Processor Unit (CPU)
V H I N Z C
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
n
opr
PC
PCH
PCL
REL
rel
rr
SP1
SP2
SP
U
V
X
Z
&
|
⊕
()
–( )
#
«
←
?
:
↕
—
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
Technical Data
106
Cycles
Effect on
CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Continued)
MC68HC908AB32 — Rev. 1.1
Central Processor Unit (CPU)
Freescale Semiconductor
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Table 7-2. Opcode Map
Bit Manipulation
DIR
DIR
MSB
Branch
REL
DIR
INH
3
4
1
2
5
BRSET0
3 DIR
5
BRCLR0
3 DIR
5
BRSET1
3 DIR
5
BRCLR1
3 DIR
5
BRSET2
3 DIR
5
BRCLR2
3 DIR
5
BRSET3
3 DIR
5
BRCLR3
3 DIR
5
BRSET4
3 DIR
5
BRCLR4
3 DIR
5
BRSET5
3 DIR
5
BRCLR5
3 DIR
5
BRSET6
3 DIR
5
BRCLR6
3 DIR
5
BRSET7
3 DIR
5
BRCLR7
3 DIR
4
BSET0
2 DIR
4
BCLR0
2 DIR
4
BSET1
2 DIR
4
BCLR1
2 DIR
4
BSET2
2 DIR
4
BCLR2
2 DIR
4
BSET3
2 DIR
4
BCLR3
2 DIR
4
BSET4
2 DIR
4
BCLR4
2 DIR
4
BSET5
2 DIR
4
BCLR5
2 DIR
4
BSET6
2 DIR
4
BCLR6
2 DIR
4
BSET7
2 DIR
4
BCLR7
2 DIR
3
BRA
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
5
6
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
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
SP1
IX
9E6
7
Control
INH
INH
8
9
Register/Memory
IX2
SP2
IMM
DIR
EXT
A
B
C
D
9ED
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
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
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
IX1
SP1
IX
E
9EE
F
LSB
0
1
2
3
4
Central Processor Unit (CPU)
0
Read-Modify-Write
INH
IX1
5
6
7
8
9
A
B
C
E
F
Technical Data
107
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
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
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
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
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
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
MSB
0
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
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
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
High Byte of Opcode in Hexadecimal
LSB
Low Byte of Opcode in Hexadecimal
0
5
Cycles
BRSET0 Opcode Mnemonic
3 DIR Number of Bytes / Addressing Mode
Central Processor Unit (CPU)
D
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
Central Processor Unit (CPU)
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Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 8. System Integration Module (SIM)
8.1 Contents
8.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110
8.3
SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . 112
8.3.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
8.3.2
Clock Start-Up from POR or LVI Reset . . . . . . . . . . . . . . . 113
8.3.3
Clocks in Stop and Wait Modes . . . . . . . . . . . . . . . . . . . . . 113
8.4
Reset and System Initialization. . . . . . . . . . . . . . . . . . . . . . . . 113
8.4.1
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114
8.4.2
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . 114
8.4.2.1
Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .115
8.4.2.2
Computer Operating Properly (COP) Reset. . . . . . . . . . 116
8.4.2.3
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
8.4.2.4
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . .117
8.4.2.5
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . 117
8.5
SIM Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117
8.5.1
SIM Counter during Power-On Reset. . . . . . . . . . . . . . . . . 118
8.5.2
SIM Counter during Stop Mode Recovery . . . . . . . . . . . . . 118
8.5.3
SIM Counter and Reset States. . . . . . . . . . . . . . . . . . . . . . 118
8.6
Exception Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .118
8.6.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
8.6.1.1
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120
8.6.1.2
SWI Instruction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
8.6.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
8.6.3
Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
8.6.4
Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . 123
8.7
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
8.7.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .124
8.7.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .125
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System Integration Module (SIM)
8.8
SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
8.8.1
SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 127
8.8.2
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 128
8.8.3
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . 129
8.2 Introduction
This section describes the system integration module (SIM), which
supports up to 24 external and/or internal interrupts. Together with the
CPU, the SIM controls all MCU activities. A block diagram of the SIM is
shown in Figure 8-1. Figure 8-2 is a summary of the SIM 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 8-1 shows the internal signal names used in this section.
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Freescale Semiconductor
System Integration Module (SIM)
MODULE STOP
MODULE WAIT
CPU STOP (FROM CPU)
CPU WAIT (FROM CPU)
STOP/WAIT
CONTROL
SIMOSCEN (TO CGM)
SIM
COUNTER
COP CLOCK
CGMXCLK (FROM CGM)
CGMOUT (FROM CGM)
÷2
CLOCK
CONTROL
RESET
PIN LOGIC
CLOCK GENERATORS
INTERNAL CLOCKS
LVI (FROM LVI MODULE)
POR CONTROL
MASTER
RESET
CONTROL
RESET PIN CONTROL
SIM RESET STATUS REGISTER
ILLEGAL OPCODE (FROM CPU)
ILLEGAL ADDRESS (FROM ADDRESS
MAP DECODERS)
COP (FROM COP MODULE)
RESET
INTERRUPT SOURCES
INTERRUPT CONTROL
AND PRIORITY DECODE
CPU INTERFACE
Figure 8-1. SIM Block Diagram
Table 8-1. Signal naming conventions
Signal Name
Description
CGMXCLK
Buffered version of OSC1 from clock generator module (CGM)
CGMVCLK
PLL output
CGMOUT
PLL-based or OSC1-based clock output from CGM module
(Bus clock = CGMOUT divided by two)
IAB
Internal address bus
IDB
Internal data bus
PORRST
Signal from the power-on reset module to the SIM
IRST
Internal reset signal
R/W
Read/write signal
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Freescale Semiconductor
Technical Data
System Integration Module (SIM)
111
System Integration Module (SIM)
Addr.
Register Name
Bit 7
6
5
4
3
2
R
R
R
R
R
R
0
0
0
0
0
0
0
0
POR
PIN
COP
ILOP
ILAD
0
LVI
0
1
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
Read:
SIM Break Status Register
$FE00
Write:
(SBSR)
Reset:
1
SBSW
Note
Bit 0
R
Note: Writing a logic 0 clears SBSW.
Read:
SIM Reset Status Register
$FE01
Write:
(SRSR)
POR:
$FE03
Read:
SIM Break Flag Control
Register Write:
(SBFCR)
Reset:
0
= Unimplemented
R
= Reserved
Figure 8-2. SIM I/O Register Summary
8.3 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and
peripherals on the MCU. The system clocks are generated from an
incoming clock, CGMOUT, as shown in Figure 8-3. This clock can come
from either an external oscillator or from the on-chip PLL.
See Section 9. Clock Generator Module (CGM).
CGMXCLK
OSC1
CGMVCLK
CLOCK
SELECT
CIRCUIT
÷2
A
CGMOUT
B S*
SIM COUNTER
÷2
BUS CLOCK
GENERATORS
*When S = 1,
CGMOUT = B
PLL
SIM
BCS
PTC3
MONITOR MODE
USER MODE
CGM
Figure 8-3. CGM Clock Signals
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Freescale Semiconductor
System Integration Module (SIM)
8.3.1 Bus Timing
In user mode, the internal bus frequency is either the crystal oscillator
output (CGMXCLK) divided by four or the PLL output (CGMVCLK)
divided by four. See Section 9. Clock Generator Module (CGM).
8.3.2 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 CGMXCLK cycle POR
timeout has been completed. The RST pin is driven low by the SIM
during this entire period. The IBUS clocks start upon completion of the
timeout.
8.3.3 Clocks in Stop and Wait Modes
Upon exit from stop mode (by an interrupt, break, or reset), the SIM
allows CGMXCLK 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 CGMXCLK cycles. (See 8.7.2 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.
8.4 Reset and System Initialization
The MCU has the following 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
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System Integration Module (SIM)
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 8.5 SIM Counter), but an
external reset does not. Each of the resets sets a corresponding bit in
the SIM reset status register (SRSR). (See 8.8 SIM Registers.)
8.4.1 External Pin Reset
Pulling the asynchronous RST pin low halts all processing. The PIN bit
of the SIM reset status register (SRSR) is set as long as RST is held low
for a minimum of 67 CGMXCLK cycles, assuming that neither the POR
nor the LVI was the source of the reset. See Table 8-2 for details.
Figure 8-4 shows the relative timing.
Table 8-2. PIN Bit Set Timing
Reset Type
Number of Cycles Required to Set PIN
POR/LVI
4163 (4096 + 64 + 3)
All others
67 (64 + 3)
CGMOUT
RST
IAB
VECT H VECT L
PC
Figure 8-4. External Reset Timing
8.4.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 CGMXCLK
cycles to allow for resetting of external peripherals. The internal reset
signal IRST continues to be asserted for an additional 32 cycles. See
Figure 8-5. An internal reset can be caused by an illegal address, illegal
opcode, COP timeout, LVI, or POR. See Figure 8-6. Note that for LVI or
POR resets, the SIM cycles through 4096 CGMXCLK cycles, during
which the SIM forces the RST pin low. The internal reset signal then
follows the sequence from the falling edge of RST as shown in
Figure 8-5.
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Freescale Semiconductor
System Integration Module (SIM)
IRST
RST
RST PULLED LOW BY MCU
32 CYCLES
32 CYCLES
CGMXCLK
IAB
VECTOR HIGH
Figure 8-5. Internal reset timing
The COP reset is asynchronous to the bus clock.
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
POR
INTERNAL RESET
Figure 8-6. 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.
8.4.2.1 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 CGMXCLK cycles. 64 CGMXCLK cycles later, the CPU and
memories are released from reset to allow the reset vector sequence to
occur.
At power-on, the following events occur:
•
A POR pulse is generated
•
The internal reset signal is asserted
•
The SIM enables CGMOUT
•
Internal clocks to the CPU and modules are held inactive for 4096
CGMXCLK cycles to allow the oscillator to stabilize
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Freescale Semiconductor
Technical Data
System Integration Module (SIM)
115
System Integration Module (SIM)
•
The RST pin is driven low during the oscillator stabilization time
•
The POR bit of the SIM reset status register (SRSR) is set and all
other bits in the register are cleared
OSC1
PORRST
4096
CYCLES
32
CYCLES
32
CYCLES
CGMXCLK
CGMOUT
RST
$FFFE
IAB
$FFFF
Figure 8-7. POR Recovery
8.4.2.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of
the COP counter causes an internal reset and sets the COP bit in the
SIM reset status register (SRSR). The SIM actively pulls down the RST
pin for all internal reset sources.
To prevent a COP module timeout, a value (any value) should be written
to location $FFFF. Writing to location $FFFF clears the COP counter and
bits 12 through 4 of the SIM counter. The SIM counter output, which
occurs at least every 213 – 24 CGMXCLK cycles, drives the COP
counter. The COP should be serviced as soon as possible out of reset
to guarantee the maximum amount of time before the first timeout.
The COP module is disabled if the RST pin or the IRQ pin is held at 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 IRQ 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.
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Freescale Semiconductor
System Integration Module (SIM)
8.4.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An
illegal instruction sets the ILOP bit in the SIM reset status register
(SRSR) and causes a reset.
If the STOP enable bit, STOP, in the configuration register 1 (CONFIG1)
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.
8.4.2.4 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.
8.4.2.5 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when
the VDD voltage falls to the trip voltage, VLVII. The LVI bit in the SIM reset
status register (SRSR) is set, and the external reset pin (RST) is held low
while the SIM counter counts out 4096 CGMXCLK cycles. 64 CGMXCLK
cycles later, the CPU is released from reset to allow the reset vector
sequence to occur. The SIM actively pulls down the RST pin for all
internal reset sources.
8.5 SIM Counter
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 (COP) module. The SIM
counter overflow supplies the clock for the COP module. The SIM
counter is 13 bits long and is clocked by the falling edge of CGMXCLK.
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Freescale Semiconductor
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System Integration Module (SIM)
8.5.1 SIM Counter during Power-On Reset
The power-on reset (POR) module 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.
8.5.2 SIM Counter during Stop Mode Recovery
The SIM counter is also 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
configuration register 1 (CONFIG1). 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.
8.5.3 SIM Counter and Reset States
External reset has no effect on the SIM counter. (See 8.7.2 Stop Mode
for details.) The SIM counter is free-running after all reset states. (See
8.4.2 Active Resets from Internal Sources for counter control and
internal reset recovery sequences.)
8.6 Exception Control
Normal, sequential program execution can be changed in three different
ways:
•
Interrupts
– Maskable hardware CPU interrupts
– Non-maskable software interrupt instruction (SWI)
•
Reset
•
Break interrupts
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Freescale Semiconductor
System Integration Module (SIM)
8.6.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register
contents onto 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 8-8 shows interrupt entry timing, and
Figure 8-9 shows interrupt recovery timing.
MODULE
INTERRUPT
I-BIT
IAB
SP
DUMMY
IDB
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 8-8. Interrupt Entry Timing
MODULE
INTERRUPT
I-BIT
IAB
SP – 4
IDB
SP – 3
CCR
SP – 2
A
SP – 1
X
SP
PC
PC + 1
PC – 1[7:0] PC – 1[15:8] OPCODE
OPERAND
R/W
Figure 8-9. Interrupt Recovery Timing
Interrupts are latched, and arbitration is performed in the SIM at the start
of interrupt processing. The arbitration result is a constant that the CPU
uses to determine which vector to fetch. Once an interrupt is latched by
the SIM, no other interrupt may take precedence, regardless of priority,
until the latched interrupt is serviced (or the I-bit is cleared).
(See Figure 8-10.)
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Technical Data
System Integration Module (SIM)
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System Integration Module (SIM)
FROM RESET
BREAK
I BIT
SET?
INTERRUPT?
YES
NO
YES
I-BIT SET?
NO
IRQ
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 8-10. Interrupt Processing
8.6.1.1 Hardware Interrupts
Processing of a hardware interrupt begins after completion of the current
instruction. When the 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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System Integration Module (SIM)
If more than one interrupt is pending at the end of an instruction
execution, the highest priority interrupt is serviced first. Figure 8-11
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
LDA #$FF
INT1
BACKGROUND
ROUTINE
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 8-11. 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.
8.6.1.2 SWI Instruction
The SWI instruction is a non-maskable instruction that causes an
interrupt regardless of the state of the interrupt mask (I-bit) in the
condition code register.
NOTE:
A software interrupt pushes PC onto the stack. A software interrupt does
not push PC – 1, as a hardware interrupt does.
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System Integration Module (SIM)
Table 8-3. Vector Addresses
Vector Priority
Lowest
Highest
Address
$FFD0
Vector
ADC Conversion Complete Vector (High)
$FFD1
ADC Conversion Complete Vector (Low)
$FFD2
Keyboard Vector (High)
$FFD3
Keyboard Vector (Low)
$FFD4
SCI Transmit Vector (High)
$FFD5
SCI Transmit Vector (Low)
$FFD6
SCI Receive Vector (High)
$FFD7
SCI Receive Vector (Low)
$FFD8
SCI Error Vector (High)
$FFD9
SCI Error Vector (Low)
$FFDA
Reserved
$FFDB
Reserved
$FFDC
Reserved
$FFDD
Reserved
$FFDE
Timer B Channel 3 Vector (High)
$FFDF
Timer B Channel 3 Vector (Low)
$FFE0
Timer B Channel 2 Vector (High)
$FFE1
Timer B Channel 2 Vector (Low)
$FFE2
SPI Transmit Vector (High)
$FFE3
SPI Transmit Vector (Low)
$FFE4
SPI Receive Vector (High)
$FFE5
SPI Receive Vector (Low)
$FFE6
Timer B Overflow Vector (High)
$FFE7
Timer B Overflow Vector (Low)
$FFE8
Timer B Channel 1 Vector (High)
$FFE9
Timer B Channel 1 Vector (Low)
$FFEA
Timer B Channel 0 Vector (High)
$FFEB
Timer B Channel 0 Vector (Low)
$FFEC
Timer A Overflow Vector (High)
$FFED
Timer A Overflow Vector (Low)
$FFEE
Timer A Channel 3 Vector (High)
$FFEF
Timer A Channel 3 Vector (Low)
$FFF0
Timer A Channel 2 Vector (High)
$FFF1
Timer A Channel 2 Vector (Low)
$FFF2
Timer A Channel 1 Vector (High)
$FFF3
Timer A Channel 1 Vector (Low)
$FFF4
Timer A Channel 0 Vector (High)
$FFF5
Timer A Channel 0 Vector (Low)
$FFF6
Programmable Interrupt Timer (High)
$FFF7
Programmable Interrupt Timer (Low)
$FFF8
PLL Vector (High)
$FFF9
PLL Vector (Low)
$FFFA
IRQ Vector (High)
$FFFB
IRQ Vector (Low)
$FFFC
SWI Vector (High)
$FFFD
SWI Vector (Low)
$FFFE
Reset Vector (High)
$FFFF
Reset Vector (Low)
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System Integration Module (SIM)
8.6.2 Reset
All reset sources always have equal and highest priority and cannot be
arbitrated.
8.6.3 Break Interrupts
The break module can stop normal program flow at a softwareprogrammable break point by asserting its break interrupt output. See
Section 22. 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.
8.6.4 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 two-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.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
System Integration Module (SIM)
123
System Integration Module (SIM)
8.7 Low-Power Modes
Executing the STOP or WAIT 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
below. Both STOP and WAIT clear the interrupt mask (I) in the condition
code register, allowing interrupts to occur.
8.7.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks
continue to run. Figure 8-12 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 can also be exited by a reset or break. A break interrupt
during wait mode sets the SIM break STOP/WAIT bit, SBSW, in the SIM
break status register (SBSR). If the COP disable bit, COPD, in the
configuration register 1 (CONFIG1) is 0, then the computer operating
properly (COP) module 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 8-12. Wait Mode Entry Timing
Figure 8-13 and Figure 8-14 show the timing for wait recovery.
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System Integration Module (SIM)
Freescale Semiconductor
System Integration Module (SIM)
IAB
$6E0B
IDB
$A6
$A6
$6E0C
$A6
$00FF
$01
$0B
$00FE
$00FD
$00FC
$6E
EXITSTOPWAIT
NOTE: EXITSTOPWAIT = RST pin OR CPU interrupt OR break interrupt
Figure 8-13. Wait Recovery from Interrupt or Break
32
Cycles
IAB
IDB
$6E0B
$A6
$A6
32
Cycles
RST VCT H RST VCT L
$A6
RST
CGMXCLK
Figure 8-14. Wait Recovery from Internal Reset
8.7.2 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 outputs (CGMOUT and
CGMXCLK) 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 CGMXCLK 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.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
System Integration Module (SIM)
125
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 8-15 shows stop mode entry timing.
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 8-15. Stop Mode Entry Timing
STOP RECOVERY PERIOD
CGMXCLK
INT/BREAK
IAB
STOP +1
STOP + 2
STOP + 2
SP
SP – 1
SP – 2
SP – 3
Figure 8-16. Stop Mode Recovery from Interrupt or Break
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System Integration Module (SIM)
Freescale Semiconductor
System Integration Module (SIM)
8.8 SIM Registers
The SIM has three memory mapped registers. Table 8-4 shows the
mapping of these registers.
Table 8-4. SIM Registers
Address
Register
Access Mode
$FE00
SBSR
User
$FE01
SRSR
User
$FE03
SBFCR
User
8.8.1 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a
break caused an exit from stop or wait mode.
Address:
Read:
Write:
Reset:
$FE00
Bit 7
6
5
4
3
2
R
R
R
R
R
R
0
0
0
0
0
0
R
1
SBSW
Note(1)
0
Bit 0
R
0
= Reserved
Note: 1. Writing a logic 0 clears SBSW.
Figure 8-17. SIM Break Status Register (SBSR)
SBSW — SIM Break STOP/WAIT
This status bit is useful in applications requiring a return to stop or wait
mode after exiting from a break interrupt. SBSW can be cleared by
writing a logic 0 to it. Reset clears SBSW.
1 = Stop or wait mode was exited by break interrupt
0 = Stop or wait mode was not exited by break interrupt
SBSW can be read within the break state SWI routine. The user can
modify the return address on the stack by subtracting one from it. The
following code is an example of this.
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Freescale Semiconductor
Technical Data
System Integration Module (SIM)
127
System Integration Module (SIM)
; 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 STOP or WAIT mode was exited by
; break.
TST
LOBYTE,SP
; If RETURNLO is not 0,
BNE
DOLO
; then just decrement low byte.
DEC
HIBYTE,SP
; Else deal with high byte, too.
DOLO
DEC
LOBYTE,SP
; Point to STOP/WAIT opcode.
RETURN
PULH
RTI
; Restore H register.
8.8.2 SIM Reset Status Register
This register contains six flags that show the source of the last reset. The
SIM reset status register can be cleared by reading it. A power-on reset
sets the POR bit and clears all other bits in the register.
Address:
Read:
$FE01
Bit 7
6
5
4
3
2
1
Bit 0
POR
PIN
COP
ILOP
ILAD
0
LVI
0
1
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 8-18. SIM Reset Status Register (SRSR)
POR — Power-On Reset Bit
1 = Last reset caused by POR circuit
0 = Read of SRSR
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System Integration Module (SIM)
Freescale Semiconductor
System Integration Module (SIM)
PIN — External Reset Bit
1 = Last reset caused by external reset pin (RST)
0 = POR or read of SRSR
COP — Computer Operating Properly Reset Bit
1 = Last reset caused by COP counter
0 = POR or read of SRSR
ILOP — Illegal Opcode Reset Bit
1 = Last reset caused by an illegal opcode
0 = POR or read of SRSR
ILAD — Illegal Address Reset Bit (opcode fetches only)
1 = Last reset caused by an opcode fetch from an illegal address
0 = POR or read of SRSR
LVI — Low-Voltage Inhibit Reset Bit
1 = Last reset was caused by the LVI circuit
0 = POR or read of SRSR
8.8.3 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.
Address:
Read:
Write:
Reset:
$FE03
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
0
R
= Reserved
Figure 8-19. 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
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
System Integration Module (SIM)
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System Integration Module (SIM)
Technical Data
130
MC68HC908AB32 — Rev. 1.1
System Integration Module (SIM)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 9. Clock Generator Module (CGM)
9.1 Contents
9.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
9.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132
9.4
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .133
9.4.1
Crystal Oscillator Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . .134
9.4.2
Phase-Locked Loop (PLL) Circuit . . . . . . . . . . . . . . . . . . . 135
9.4.2.1
PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135
9.4.2.2
Acquisition and Tracking Modes . . . . . . . . . . . . . . . . . . 136
9.4.2.3
Manual and Automatic PLL Bandwidth Modes . . . . . . . 136
9.4.2.4
Programming the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . 138
9.4.2.5
Special Programming Exceptions . . . . . . . . . . . . . . . . . 139
9.4.3
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . 140
9.4.4
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . 140
9.5
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
9.5.1
Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . 142
9.5.2
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . 142
9.5.3
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . 142
9.5.4
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . 142
9.5.5
Oscillator Enable Signal (SIMOSCEN). . . . . . . . . . . . . . . . 142
9.5.6
Crystal Output Frequency Signal (CGMXCLK) . . . . . . . . . 143
9.5.7
CGM Base Clock Output (CGMOUT). . . . . . . . . . . . . . . . . 143
9.5.8
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . 143
9.6
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143
9.6.1
PLL Control Register (PCTL) . . . . . . . . . . . . . . . . . . . . . . . 144
9.6.2
PLL Bandwidth Control Register (PBWC) . . . . . . . . . . . . . 146
9.6.3
PLL Programming Register (PPG) . . . . . . . . . . . . . . . . . . . 148
9.7
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
9.8
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
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Technical Data
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131
Clock Generator Module (CGM)
9.8.1
9.8.2
9.9
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .150
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .151
CGM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 151
9.10 Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . . . . . 151
9.10.1 Acquisition/Lock Time Definitions. . . . . . . . . . . . . . . . . . . .152
9.10.2 Parametric Influences On Reaction Time. . . . . . . . . . . . . . 153
9.10.3 Choosing a Filter Capacitor . . . . . . . . . . . . . . . . . . . . . . . . 154
9.10.4 Reaction Time Calculation . . . . . . . . . . . . . . . . . . . . . . . . . 155
9.2 Introduction
This section describes the clock generator module (CGM). The CGM
generates the crystal clock signal, CGMXCLK, which operates at the
frequency of the crystal. The CGM also generates the base clock signal,
CGMOUT, from which the system integration module (SIM) derives the
system clocks. CGMOUT is based on either the crystal clock divided by
two or the phase-locked loop (PLL) clock, CGMVCLK, divided by two.
The PLL is a frequency generator designed for use with 1MHz to 8MHz
crystals or ceramic resonators. The PLL can generate an 8MHz bus
frequency without using a higher frequency crystal.
9.3 Features
Features of the CGM include the following:
•
Phase-locked loop with output frequency in integer multiples of the
crystal reference
•
Programmable hardware voltage-controlled oscillator (VCO) for
low-jitter operation
•
Automatic bandwidth control mode for low-jitter operation
•
Automatic frequency lock detector
•
CPU interrupt on entry or exit from locked condition
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Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
9.4 Functional Description
The CGM consists of three major sub-modules:
•
Crystal oscillator circuit which generates the constant crystal
frequency clock, CGMXCLK.
•
Phase-locked loop (PLL) which generates the programmable
VCO frequency clock CGMVCLK.
•
Base clock selector circuit; this software-controlled circuit selects
either CGMXCLK divided by two or the VCO clock CGMVCLK
divided by two, as the base clock CGMOUT. The SIM derives the
system clocks from CGMOUT.
Figure 9-1 shows the structure of the CGM.
CRYSTAL OSCILLATOR
OSC2
CGMXCLK
CLOCK
SELECT
CIRCUIT
OSC1
÷2
A
TO SIM, SCI
CGMOUT
B S*
TO SIM
*When S = 1, CGMOUT = B
SIMOSCEN
CGMRDV
CGMRCLK
VDDA
BCS
CGMXFC
USER MODE
VSS
VRS[7:4]
PTC3
MONITOR MODE
PHASE
DETECTOR
VOLTAGE
CONTROLLED
OSCILLATOR
LOOP
FILTER
PLL ANALOG
LOCK
DETECTOR
LOCK
BANDWIDTH
CONTROL
AUTO
ACQ
INTERRUPT
CONTROL
PLLIE
CGMINT
PLLF
MUL[7:4]
CGMVDV
FREQUENCY
DIVIDER
CGMVCLK
Figure 9-1. CGM Block Diagram
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Freescale Semiconductor
Technical Data
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Clock Generator Module (CGM)
Addr.
$001C
$001D
$001E
Register Name
Bit 7
Read:
PLL Control Register
Write:
(PCTL)
Reset:
Read:
PLL Bandwidth Control
Register Write:
(PBWC)
Reset:
Read:
PLL Programming
Register Write:
(PPG)
Reset:
PLLIE
0
AUTO
6
PLLF
0
LOCK
5
4
PLLON
BCS
1
0
ACQ
XLD
3
2
1
Bit 0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
= Unimplemented
Figure 9-2. CGM I/O Register Summary
9.4.1 Crystal Oscillator Circuit
The crystal oscillator circuit consists of an inverting amplifier and an
external crystal. The OSC1 pin is the input to the amplifier and the OSC2
pin is the output. The SIMOSCEN signal from the system integration
module (SIM) enables the crystal oscillator circuit.
The CGMXCLK signal is the output of the crystal oscillator circuit and
runs at a rate equal to the crystal frequency. CGMXCLK is then buffered
to produce CGMRCLK, the PLL reference clock.
CGMXCLK can be used by other modules which require precise timing
for operation. The duty cycle of CGMXCLK is not guaranteed to be 50%
and depends on external factors, including the crystal and related
external components.
An externally generated clock can also feed the OSC1 pin of the crystal
oscillator circuit. For this configuration, the external clock should be
connected to the OSC1 pin and the OSC2 pin allowed to float.
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Clock Generator Module (CGM)
Freescale Semiconductor
Clock Generator Module (CGM)
9.4.2 Phase-Locked Loop (PLL) Circuit
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.
9.4.2.1 PLL Circuits
The PLL consists of the following circuits:
•
Voltage-controlled oscillator (VCO)
•
Modulo VCO frequency divider
•
Phase detector
•
Loop filter
•
Lock detector
The operating range of the VCO is programmable for a wide range of
frequencies and for maximum immunity to external noise, including
supply and CGMXFC noise. The VCO frequency is bound to a range
from roughly one-half to twice the center-of-range frequency, fVRS.
Modulating the voltage on the CGMXFC pin changes the frequency
within this range. By design, fVRS is equal to the nominal center-of-range
frequency, fNOM, (4.9152MHz) times a linear factor L, or (L)fNOM.
CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK.
CGMRCLK runs at a frequency fRCLK, and is fed to the PLL through a
buffer. The buffer output is the final reference clock, CGMRDV, running
at a frequency fRDV = fRCLK.
The VCO’s output clock, CGMVCLK, running at a frequency fVCLK, is fed
back through a programmable modulo divider. The modulo divider
reduces the VCO clock by a factor N. The divider’s output is the VCO
feedback clock, CGMVDV, running at a frequency fVDV = fVCLK/N. (See
9.4.2.4 Programming the PLL for more information).
The phase detector then compares the VCO feedback clock, CGMVDV,
with the final reference clock, CGMRDV. A correction pulse is generated
based on the phase difference between the two signals. The loop filter
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Clock Generator Module (CGM)
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 9.4.2.2 Acquisition and Tracking Modes. The value of the
external capacitor and the reference frequency determines the speed of
the corrections and the stability of the PLL.
The lock detector compares the frequencies of the VCO feedback clock,
CGMVDV, and the final reference clock, CGMRDV. Therefore, the
speed of the lock detector is directly proportional to the final reference
frequency fRDV. The circuit determines the mode of the PLL and the lock
condition based on this comparison.
9.4.2.2 Acquisition and Tracking Modes
The PLL filter is manually or automatically configurable into one of two
operating modes:
•
Acquisition mode — in acquisition mode, the filter can make large
frequency corrections to the VCO. This mode is used at PLL startup or when the PLL has suffered a severe noise hit and the
resulting VCO frequency is much different from the desired
frequency. When in acquisition mode, the ACQ bit is clear in the
PLL bandwidth control register. See 9.6.2 PLL Bandwidth
Control Register (PBWC).
•
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 9.4.3 Base Clock Selector Circuit. The PLL is
automatically in tracking mode when not in acquisition mode or
when the ACQ bit is set.
9.4.2.3 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter
manually or automatically.
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Freescale Semiconductor
Clock Generator Module (CGM)
In automatic bandwidth control mode (AUTO = 1), the lock detector
automatically switches between acquisition and tracking modes.
Automatic bandwidth control mode is used also to determine when the
VCO clock, CGMVCLK, is safe to use as the source for the base clock,
CGMOUT. See 9.6.2 PLL Bandwidth Control Register (PBWC). 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 9.4.3 Base Clock Selector
Circuit. If the VCO is selected as the source for the base clock and the
LOCK bit is clear, the PLL has suffered a severe noise hit and the
software must take appropriate action, depending on the application.
(See 9.7 Interrupts for information and precautions on using interrupts).
The following conditions apply when the PLL is in automatic bandwidth
control mode:
•
The ACQ bit (see 9.6.2 PLL Bandwidth Control Register
(PBWC)) is a read-only indicator of the mode of the filter. (See
9.4.2.2 Acquisition and Tracking Modes)
•
The ACQ bit is set when the VCO frequency is within a certain
tolerance ∆TRK and is cleared when the VCO frequency is out of a
certain tolerance ∆UNT. (See 9.10 Acquisition/Lock Time
Specifications)
•
The LOCK bit is a read-only indicator of the locked state of the
PLL.
•
The LOCK bit is set when the VCO frequency is within a certain
tolerance ∆LOCK and is cleared when the VCO frequency is out of
a certain tolerance ∆UNL. (See 9.10 Acquisition/Lock Time
Specifications)
•
CPU interrupts can occur if enabled (PLLIE = 1) when the PLL’s
lock condition changes, toggling the LOCK bit. (See 9.6.1 PLL
Control Register (PCTL))
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
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Clock Generator Module (CGM)
and require fast start-up. 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 9.10 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.
9.4.2.4 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.
2. Calculate the desired VCO frequency (four times the desired bus
frequency).
f VCLKDES = 4 × f BUSDES
3. Choose a practical PLL reference frequency, fRCLK.
4. Select a VCO frequency multiplier, N.
f VCLKDES
N = round --------------------f RCLK
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Freescale Semiconductor
Clock Generator Module (CGM)
5. Calculate and verify the adequacy of the VCO and bus
frequencies fVCLK and fBUS.
f VCLK = N × f RCLK
f BUS = ( f VCLK ) ⁄ 4
6. Select a VCO linear range multiplier, L.
f VCLK
L = round ----------- f NOM
where fNOM = 4.9152MHz
7. Calculate and verify the adequacy of the VCO programmed
center-of-range frequency fVRS.
fVRS = (L)fNOM
8. Verify the choice of N and L by comparing fVCLK to fVRS and
fVCLKDES. For proper operation, fVCLK must be within the
application’s tolerance of fVCLKDES, and fVRS must be as close as
possible to fVCLK.
NOTE:
Exceeding the recommended maximum bus frequency or VCO
frequency can cause the MCU to “crash”.
9. Program the PLL registers accordingly:
a. In the upper 4 bits of the PLL programming register (PPG),
program the binary equivalent of N.
b. In the lower 4 bits of the PLL programming register (PPG),
program the binary equivalent of L.
9.4.2.5 Special Programming Exceptions
The programming method described in 9.4.2.4 Programming the PLL
does not account for two possible exceptions — a value of zero for N or
L is meaningless when used in the equations given. To account for these
exceptions:
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Clock Generator Module (CGM)
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Clock Generator Module (CGM)
•
A zero value for N is interpreted exactly the same as a value of
one.
•
A zero value for L disables the PLL and prevents its selection as
the source for the base clock. (See 9.4.3 Base Clock Selector
Circuit)
9.4.3 Base Clock Selector Circuit
This circuit is used to select either the crystal clock, CGMXCLK, or the
VCO clock, CGMVCLK, as the source of the base clock, CGMOUT. The
two input clocks go through a transition control circuit that waits up to
three CGMXCLK cycles and three CGMVCLK cycles to change from
one clock source to the other. During this time, CGMOUT is held in
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 CGMVCLK).
The BCS bit in the PLL control register (PCTL) selects which clock drives
CGMOUT. The VCO clock cannot be selected as the base clock source
if the PLL is not turned on. The PLL cannot be turned off if the VCO clock
is selected. The PLL cannot be turned on or off simultaneously with the
selection or deselection of the VCO clock. The VCO clock also cannot
be selected as the base clock source if the factor L is programmed to a
zero. This value would set up a condition inconsistent with the operation
of the PLL, so that the PLL would be disabled and the crystal clock would
be forced as the source of the base clock.
9.4.4 CGM External Connections
In its typical configuration, the CGM requires seven external
components. Five of these are for the crystal oscillator and two are for
the PLL.
The crystal oscillator is normally connected in a Pierce oscillator
configuration, as shown in Figure 9-3. This figure shows only the logical
representation of the internal components and may not represent actual
circuitry. The oscillator configuration uses five components:
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•
Crystal, X1
•
Fixed capacitor, C1
•
Tuning capacitor, C2 (can also be a fixed capacitor)
•
Feedback resistor, RB
•
Series resistor, RS (optional)
The series resistor (RS) is included in the diagram to follow strict Pierce
oscillator guidelines and may not be required for all ranges of operation,
especially with high frequency crystals. Refer to the crystal
manufacturer’s data for more information.
Figure 9-3 also shows the external components for the PLL:
•
Bypass capacitor, CBYP
•
Filter capacitor, CF
Care should be taken with routing in order to minimize signal cross talk
and noise. (See 9.10 Acquisition/Lock Time Specifications for routing
information and more information on the filter capacitor’s value and its
effects on PLL performance).
SIMOSCEN
CGMXCLK
OSC1
OSC2
VSSA
CGMXFC
VDDA
RB
VDD
CF
CBYP
R S*
X1
C1
C2
*RS can be zero (shorted) when used with higher-frequency crystals. Refer to manufacturer’s data.
Figure 9-3. CGM External Connections
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9.5 I/O Signals
The following paragraphs describe the CGM I/O signals.
9.5.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
9.5.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
9.5.3 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase
corrections. A small external capacitor is connected to this pin.
NOTE:
To prevent noise problems, CF should be placed as close to the
CGMXFC pin as possible, with minimum routing distances and no
routing of other signals across the CF connection.
9.5.4 PLL Analog Power Pin (VDDA)
VDDA is a power pin used by the analog portions of the PLL. The pin
should be connected 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.
9.5.5 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM)
and enables the oscillator and PLL.
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9.5.6 Crystal Output Frequency Signal (CGMXCLK)
CGMXCLK is the crystal oscillator output signal. It runs at the full speed
of the crystal (fXCLK) and is generated directly from the crystal oscillator
circuit. Figure 9-3 shows only the logical relation of CGMXCLK to OSC1
and OSC2 and may not represent the actual circuitry. The duty cycle of
CGMXCLK is unknown and may depend on the crystal and other
external factors. Also, the frequency and amplitude of CGMXCLK can be
unstable at start-up.
9.5.7 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM,
which generates the MCU clocks. CGMOUT is a 50% duty cycle clock
running at twice the bus frequency. CGMOUT is software programmable
to be either the oscillator output (CGMXCLK) divided by two or the VCO
clock (CGMVCLK) divided by two.
9.5.8 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
9.6 CGM Registers
The following registers control and monitor operation of the CGM:
•
PLL control register (PCTL). (See 9.6.1 PLL Control Register
(PCTL))
•
PLL bandwidth control register (PBWC). (See 9.6.2 PLL
Bandwidth Control Register (PBWC))
•
PLL programming register (PPG). (See 9.6.3 PLL Programming
Register (PPG))
Figure 9-4 is a summary of the CGM registers.
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Addr.
Register Name
Bit 7
Read:
$001C
$001D
$001E
PLL Control Register
Write:
(PCTL)
Reset:
Read:
PLL Bandwidth Control
Register Write:
(PBWC)
Reset:
Read:
PLL Programming
Register Write:
(PPG)
Reset:
PLLIE
0
AUTO
6
PLLF
0
LOCK
5
4
PLLON
BCS
1
0
ACQ
XLD
3
2
1
Bit 0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
= Unimplemented
NOTES:
1. When AUTO = 0, PLLIE is forced to logic zero and is read-only.
2. When AUTO = 0, PLLF and LOCK read as logic zero.
3. When AUTO = 1, ACQ is read-only.
4. When PLLON = 0 or VRS[7:4] = $0, BCS is forced to logic zero 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 9-4. CGM I/O Register Summary
9.6.1 PLL Control Register (PCTL)
The PLL control register contains the interrupt enable and flag bits, the
on/off switch, and the base clock selector bit.
Address:
$001C
Bit 7
Read:
Write:
Reset:
PLLIE
0
6
PLLF
0
5
4
PLLON
BCS
1
0
3
2
1
Bit 0
1
1
1
1
1
1
1
1
= Unimplemented
Figure 9-5. PLL Control Register (PCTL)
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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 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 is set also. PLLF
always reads as 0 when the AUTO bit in the PLL bandwidth control
register (PBWC) is clear. The PLLF bit should be cleared by reading
the PLL control register. Reset clears the PLLF bit.
1 = Change in lock condition
0 = No change in lock condition
NOTE:
The PLLF bit should not be inadvertently cleared. Any read or readmodify-write operation on the PLL control register clears the PLLF bit.
PLLON — PLL On Bit
This read/write bit activates the PLL and enables the VCO clock,
CGMVCLK. PLLON cannot be cleared if the VCO clock is driving the
base clock, CGMOUT (BCS = 1). See 9.4.3 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
BCS — Base Clock Select Bit
This read/write bit selects either the crystal oscillator output,
CGMXCLK, or the VCO clock, CGMVCLK, as the source of the CGM
output, CGMOUT. CGMOUT frequency is one-half the frequency of
the selected clock. BCS cannot be set while the PLLON bit is clear.
After toggling BCS, it may take up to three CGMXCLK and three
CGMVCLK cycles to complete the transition from one source clock to
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the other. During the transition, CGMOUT is held in stasis. See 9.4.3
Base Clock Selector Circuit. Reset and the STOP instruction clear
the BCS bit.
1 = CGMOUT driven by CGMVCLK/2
0 = CGMOUT driven by CGMXCLK/2
NOTE:
PLLON and BCS have built-in protection that prevents the base clock
selector circuit from selecting the VCO clock as the source of the base
clock if the PLL is off. Therefore, PLLON cannot be cleared when BCS
is set, and BCS cannot be set when PLLON is clear. If the PLL is off
(PLLON = 0), selecting CGMVCLK requires two writes to the PLL control
register. See 9.4.3 Base Clock Selector Circuit.
Bits [3:0] — Unimplemented bits
These bits provide no function and always read as 1.
9.6.2 PLL Bandwidth Control Register (PBWC)
The PLL bandwidth control register does the following:
•
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.
Address:
$001D
Bit 7
Read:
Write:
Reset:
AUTO
0
6
LOCK
0
5
4
ACQ
XLD
0
0
3
2
1
Bit 0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 9-7. PLL Bandwidth Control Register (PBWC)
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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), the ACQ
bit should be cleared before turning the PLL on. 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
0 and has no meaning. 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
XLD — Crystal Loss Detect Bit
When the VCO output, CGMVCLK, is driving CGMOUT, this
read/write bit indicates whether the crystal reference frequency is
active or not. To check the status of the crystal reference, the
following procedure should be followed:
1. Write a 1 to XLD.
2. Wait 4 × N cycles. (N is the VCO frequency multiplier.)
3. Read XLD.
1 = Crystal reference is not active
0 = Crystal reference is active
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The crystal loss detect function works only when the BCS bit is set,
selecting CGMVCLK to drive CGMOUT. When BCS is clear, XLD
always reads as 0.
Bits [3:0] — Reserved for test
These bits enable test functions not available in user mode. To ensure
software portability from development systems to user applications,
software should write zeros to Bits [3:0] whenever writing to PBWC.
9.6.3 PLL Programming Register (PPG)
The PLL programming register contains the programming information for
the modulo feedback divider and the programming information for the
hardware configuration of the VCO.
Address:
Read:
Write:
Reset:
$001E
Bit 7
6
5
4
3
2
1
Bit 0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
Figure 9-8. PLL Programming Register (PPG)
MUL[7:4] — Multiplier Select Bits
These read/write bits control the modulo feedback divider that selects
the VCO frequency multiplier, N. (See 9.4.2.1 PLL Circuits and
9.4.2.4 Programming the PLL). A value of $0 in the multiplier select
bits configures the modulo feedback divider the same as a value of
$1. Reset initializes these bits to $6 to give a default multiply value
of 6.
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Table 9-1. VCO Frequency Multiplier (N) Selection
NOTE:
MUL7:MUL6:MUL5:MUL4
VCO Frequency Multiplier (N)
0000
1
0001
1
0010
2
0011
3
1101
13
1110
14
1111
15
The multiplier select bits have built-in protection that prevents them from
being written when the PLL is on (PLLON = 1).
VRS[7:4] — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear
multiplier L, which controls the hardware center-of-range frequency
fVRS. (See 9.4.2.1 PLL Circuits, 9.4.2.4 Programming the PLL, and
9.6.1 PLL Control Register (PCTL)). VRS[7:4] cannot be written
when the PLLON bit in the PLL control register (PCTL) is set. (See
9.4.2.5 Special Programming Exceptions). A value of $0 in the
VCO range select bits disables the PLL and clears the BCS bit in the
PCTL. (See 9.4.3 Base Clock Selector Circuit and 9.4.2.5 Special
Programming Exceptions for more information). Reset initializes
the bits to $6 to give a default range multiply value of 6.
NOTE:
The VCO range select bits have built-in protection that prevents them
from being written when the PLL is on (PLLON = 1) and prevents
selection of the VCO clock as the source of the base clock (BCS = 1) if
the VCO range select bits are all clear.
The VCO range select bits must be programmed correctly. Incorrect
programming may result in failure of the PLL to achieve lock.
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9.7 Interrupts
When the AUTO bit is set in the PLL bandwidth control register (PBWC),
the PLL can generate a CPU interrupt request every time the LOCK bit
changes state. The PLLIE bit in the PLL control register (PCTL) enables
CPU interrupts from the PLL. PLLF, the interrupt flag in the PCTL,
becomes set whether interrupts are enabled or not. When the AUTO bit
is clear, CPU interrupts from the PLL are disabled and PLLF reads as 0.
Software should read the LOCK bit after a PLL interrupt request to see
if the request was due to an entry into lock or an exit from lock. When the
PLL enters lock, the VCO clock CGMVCLK, divided by two can be
selected as the CGMOUT source by setting BCS in the PCTL. When the
PLL exits lock, the VCO clock frequency is corrupt, and appropriate
precautions should be taken. If the application is not frequencysensitive, interrupts should be disabled to prevent PLL interrupt service
routines from impeding software performance or from exceeding stack
limitations.
NOTE:
Software can select CGMVCLK/2 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.
9.8 Low-Power Modes
The WAIT and STOP instructions put the MCU in low-powerconsumption standby modes.
9.8.1 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). Less power-sensitive
applications can disengage the PLL without turning it off. Applications
that require the PLL to wake the MCU from WAIT mode also can
deselect the PLL output without turning off the PLL.
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9.8.2 Stop Mode
When the STOP instruction executes, the SIM drives the SIMOSCEN
signal low, disabling the CGM and holding low all CGM outputs
(CGMXCLK, CGMOUT, and CGMINT).
If the STOP instruction is executed with the VCO clock, CGMVCLK,
divided by two driving CGMOUT, the PLL automatically clears the BCS
bit in the PLL control register (PCTL), thereby selecting the crystal clock,
CGMXCLK, divided by two as the source of CGMOUT. When the MCU
recovers from STOP, the crystal clock divided by two drives CGMOUT
and BCS remains clear.
9.9 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 Section 8. System Integration
Module (SIM).
To allow software to clear status bits during a break interrupt, a 1 should
be written 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 0 to the BCFE bit.
With BCFE at 0 (its default state), software can read and write the PLL
control register during the break state without affecting the PLLF bit.
9.10 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.
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9.10.1 Acquisition/Lock Time Definitions
Typical control systems refer to the acquisition time or lock time as the
reaction time of the system, within specified tolerances, 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 percentage of
the step input or when the output settles to the desired value plus or
minus a percentage 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% 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.
The discrepancy in these definitions makes it difficult to specify an
acquisition or lock time for a typical PLL. Therefore, the definitions for
acquisition and lock times for this module are as follows:
•
Acquisition time, tACQ, is the time the PLL takes to reduce the error
between the actual output frequency and the desired output
frequency to less than the tracking mode entry tolerance ∆TRK.
Acquisition time is based on an initial frequency error,
(fDES – fORIG)/fDES, of not more than ±100%. In automatic
bandwidth control mode (see 9.4.2.3 Manual and Automatic PLL
Bandwidth Modes), acquisition time expires when the ACQ bit
becomes set in the PLL bandwidth control register (PBWC).
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•
Lock time, tLOCK, is the time the PLL takes to reduce the error
between the actual output frequency and the desired output
frequency to less than the lock mode entry tolerance ∆LOCK. Lock
time is based on an initial frequency error, (fDES – fORIG)/fDES, of
not more than ±100%. In automatic bandwidth control mode, lock
time expires when the LOCK bit becomes set in the PLL
bandwidth control register (PBWC). See 9.4.2.3 Manual and
Automatic PLL Bandwidth Modes.
Obviously, the acquisition and lock times can vary according to how
large the frequency error is and may be shorter or longer in many cases.
9.10.2 Parametric Influences On Reaction Time
Acquisition and lock times are designed to be as short as possible while
still providing the highest possible stability. These reaction times are not
constant, however. Many factors directly and indirectly affect the
acquisition time.
The most critical parameter which affects the reaction times of the PLL
is the reference frequency, fRDV. This frequency is the input to the phase
detector and controls how often the PLL makes corrections. For stability,
the corrections must be small compared to the desired frequency, so
several corrections are required to reduce the frequency error.
Therefore, the slower the reference the longer it takes to make these
corrections. This parameter is also under user control via the choice of
crystal frequency fXCLK.
Another critical parameter is the external filter capacitor. The PLL
modifies the voltage on the VCO by adding or subtracting charge from
this capacitor. Therefore, the rate at which the voltage changes for a
given frequency error (thus change in charge) is proportional to the
capacitor size. The size of the capacitor also is related to the stability of
the PLL. If the capacitor is too small, the PLL cannot make small enough
adjustments to the voltage and the system cannot lock. If the capacitor
is too large, the PLL may not be able to adjust the voltage in a
reasonable time. See 9.10.3 Choosing a Filter Capacitor.
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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.
9.10.3 Choosing a Filter Capacitor
As described in 9.10.2 Parametric Influences On Reaction Time, the
external filter capacitor CF is critical to the stability and reaction time of
the PLL. The PLL is also dependent on reference frequency and supply
voltage. The value of the capacitor must, therefore, be chosen with
supply potential and reference frequency in mind. For proper operation,
the external filter capacitor must be chosen according to the following
equation:
V DDA
C F = C FACT ----------- f RDV
For the value of VDDA, the voltage potential at which the MCU is
operating should be used. If the power supply is variable, choose a value
near the middle of the range of possible supply values.
This equation does not always yield a commonly available capacitor
size, so round to the nearest available size. If the value is between two
different sizes, choose the higher value for better stability. Choosing the
lower size may seem attractive for acquisition time improvement, but the
PLL may become unstable. Also, always choose a capacitor with a tight
tolerance (±20% or better) and low dissipation.
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9.10.4 Reaction Time Calculation
The actual acquisition and lock times can be calculated using the
equations below. These equations yield nominal values under the
following conditions:
•
Correct selection of filter capacitor, CF,
(see 9.10.3 Choosing a Filter Capacitor)
•
Room temperature operation
•
Negligible external leakage on CGMXFC
•
Negligible noise
The K factor in the equations is derived from internal PLL parameters.
KACQ is the K factor when the PLL is configured in acquisition mode, and
KTRK is the K factor when the PLL is configured in tracking mode. See
9.4.2.2 Acquisition and Tracking Modes.
V DDA 8
- ------------t ACQ = ----------- f RDV K ACQ
V DDA 4
- -----------t AL = -----------f RDV K TRK
t LOCK = t ACQ + t AL
Note the inverse proportionality between the lock time and the reference
frequency.
In automatic bandwidth control mode the acquisition and lock times are
quantized into units based on the reference frequency. See 9.4.2.3
Manual and Automatic PLL Bandwidth Modes. A certain number of
clock cycles, nACQ, is required to ascertain whether the PLL is within the
tracking mode entry tolerance ∆TRK, before exiting acquisition mode.
Also, a certain number of clock cycles, nTRK, is required to ascertain
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whether the PLL is within the lock mode entry tolerance ∆LOCK.
Therefore, the acquisition time tACQ, is an integer multiple of nACQ/fRDV,
and the acquisition to lock time tAL, is an integer multiple of nTRK/fRDV.
Also, since the average frequency over the entire measurement period
must be within the specified tolerance, the total time usually is longer
than tLOCK as calculated above.
In manual mode, it is usually necessary to wait considerably longer than
tLOCK before selecting the PLL clock (see 9.4.3 Base Clock Selector
Circuit), because the factors described in 9.10.2 Parametric
Influences On Reaction Time may slow the lock time considerably.
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Technical Data — MC68HC908AB32
Section 10. Monitor ROM (MON)
10.1 Contents
10.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
10.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
10.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .158
10.4.1 Entering Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
10.4.2 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
10.4.3 Echoing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
10.4.4 Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
10.4.5 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
10.4.6 Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .166
10.5
Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
10.6
Extended Security. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .168
10.2 Introduction
This section describes the monitor ROM (MON). The monitor ROM
allows complete testing of the MCU through a single-wire interface with
a host computer.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Monitor ROM (MON)
157
Monitor ROM (MON)
10.3 Features
Features of the monitor ROM include the following:
•
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
•
4800 baud to 28.8 k-baud communication with host computer
•
FLASH memory security feature1
•
Execution of code in RAM or FLASH
10.4 Functional Description
The monitor ROM receives and executes commands from a host
computer. Figure 10-1 shows a example circuit used to enter monitor
mode and communicate with a host computer via a standard RS-232
interface.
While simple monitor commands can access any memory address, the
MCU has a FLASH security feature to prevent external viewing of the
contents of FLASH. Proper procedures must be followed to verify
FLASH content. Access to the FLASH is denied to unauthorized users
of customer specified software.
In monitor mode, the MCU can execute host-computer code in RAM
while all MCU pins except PTA0 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.
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or
copying the FLASH difficult for unauthorized users.
Technical Data
158
MC68HC908AB32 — Rev. 1.1
Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
VDD
10 kΩ
MC68HC908AB32
RST
0.1 µF
VTST
10 Ω
IRQ
VDDA
VDDA
VCGMXFC
1
10 µF
10 µF
+
+
MC145407
+
3
18
4
17
2
0.1 µF
20
19
10 µF
OSC1
+
10 µF
VDD
X1
4.9152 MHz
20 pF
10 MΩ
OSC2
20 pF
DB-25
2
5
16
3
6
15
VSS
VDD
VDD
7
0.1 µF
VDD
1
MC74HC125
14
2
3
6
5
4
7
VDD
10 kΩ
VDD
VDD
10 kΩ
10 kΩ
PTC0
PTC1
A
NOTES:
Position A — Bus clock = CGMXCLK ÷ 4 or CGMVCLK ÷ 4
Position B — Bus clock = CGMXCLK ÷ 2
(See
NOTES)
PTA0
PTC3
B
Figure 10-1. Monitor Mode Circuit
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Monitor ROM (MON)
159
Monitor ROM (MON)
10.4.1 Entering Monitor Mode
Table 10-1 shows the pin conditions for entering monitor mode.
1
0
1
0
1
VTST
PTC3 Pin
PTC1 Pin
(1)
VTST
PTA0 Pin
IRQ Pin
PTC0 Pin
Table 10-1. Monitor Mode Entry Conditions
CGMOUT
Bus Frequency
(CGMOUT ÷ 2)
1
1
CGMXCLK ÷ 2
or
CGMVCLK ÷ 2
CGMXCLK ÷ 4
or
CGMVCLK ÷ 4
0
CGMXCLK
CGMXCLK ÷ 2
Notes:
1. For VTST, see Section 23. Electrical Specifications.
Enter monitor mode by either
•
Executing a software interrupt instruction (SWI) or
•
Applying a logic 0 and then a logic 1 to the RST pin.
The MCU sends a break signal (10 consecutive logic 0s) to the host
computer, indicating that it is ready to receive a command. The break
signal also provides a timing reference to allow the host to determine the
necessary baud rate.
Monitor mode uses alternate vectors for reset, SWI, and break interrupt.
The alternate vectors are in the $FE page instead of the $FF page and
allow code execution from the internal monitor firmware instead of user
code. The COP module is disabled in monitor mode as long as VTST (see
Section 23. Electrical Specifications) is applied to either the IRQ pin
or the RST pin. (See Section 8. System Integration Module (SIM) for
more information on modes of operation.)
NOTE:
Holding the PTC3 pin low when entering monitor mode causes a bypass
of a divide-by-two stage at the oscillator. 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.
Technical Data
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MC68HC908AB32 — Rev. 1.1
Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
Table 10-2 is a summary of the differences between user mode and
monitor mode.
Table 10-2. Mode Differences
Functions
Modes
COP
Reset
Vector
High
Reset
Vector
Low
Break
Vector
High
Break
Vector
Low
SWI
Vector
High
SWI
Vector
Low
User
Enabled
$FFFE
$FFFF
$FFFC
$FFFD
$FFFC
$FFFD
Monitor
Disabled(1)
$FEFE
$FEFF
$FEFC
$FEFD
$FEFC
$FEFD
Notes:
1. If the high voltage (VTST) is removed from the IRQ pin while in monitor mode, the SIM
asserts its COP enable output. The COP can be enabled or disabled by the COPD bit in
the configuration register 1 (CONFIG1). (See 23.6 5.0-V DC Electrical Characteristics.)
10.4.2 Data Format
Communication with the monitor ROM is in standard non-return-to-zero
(NRZ) mark/space data format. (See Figure 10-2 and Figure 10-3.)
The data transmit and receive rate can be anywhere from 4800 baud to
28.8 k-baud. Transmit and receive baud rates must be identical.
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
NEXT
START
BIT
Figure 10-2. Monitor Data Format
$A5
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BREAK
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
NEXT
START
BIT
STOP
BIT
Figure 10-3. Sample Monitor Waveforms
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Monitor ROM (MON)
161
Monitor ROM (MON)
10.4.3 Echoing
As shown in Figure 10-4, the monitor ROM immediately echoes each
received byte back to the PTA0 pin for error checking.
Any result of a command appears after the echo of the last byte of the
command.
SENT TO
MONITOR
READ
READ
ADDR. HIGH ADDR. HIGH ADDR. LOW
ADDR. LOW
ECHO
DATA
RESULT
Figure 10-4. Read Transaction
10.4.4 Break Signal
A start bit followed by nine low bits is a break signal. (See Figure 10-5.)
When the monitor receives a break signal, it drives the PTA0 pin high for
the duration of two bits before echoing the break signal.
MISSING STOP BIT
TWO-STOP-BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 10-5. Break Transaction
Technical Data
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MC68HC908AB32 — Rev. 1.1
Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
10.4.5 Commands
The monitor ROM uses these commands:
•
READ, read memory
•
WRITE, write memory
•
IREAD, indexed read
•
IWRITE, indexed write
•
READSP, read stack pointer
•
RUN, run user program
A sequence of IREAD or IWRITE commands can access a block of
memory sequentially over the full 64k-byte memory map.
Table 10-3. READ (Read Memory) Command
Description
Read byte from memory
Operand
Specifies 2-byte address in high byte:low byte order
Data
Returned
Returns contents of specified address
Opcode
$4A
Command Sequence
SENT TO
MONITOR
READ
READ
ADDRESS
HIGH
ADDRESS
HIGH
ECHO
ADDRESS
LOW
DATA
RETURN
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
ADDRESS
LOW
Technical Data
Monitor ROM (MON)
163
Monitor ROM (MON)
Table 10-4. WRITE (Write Memory) Command
Description
Write byte to memory
Operand
Specifics 2-byte address in high byte:low byte order; low byte
followed by data byte
Data
Returned
None
Opcode
$49
Command Sequence
SENT TO
MONITOR
WRITE
WRITE
ADDRESS
HIGH
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
DATA
ECHO
Table 10-5. IREAD (Indexed Read) Command
Description
Read next 2 bytes in memory from last address accessed
Operand
Specifies 2-byte address in high byte:low byte order
Data
Returned
Returns contents of next two addresses
Opcode
$1A
Command Sequence
SENT TO
MONITOR
IREAD
IREAD
ECHO
Technical Data
164
DATA
DATA
RETURN
MC68HC908AB32 — Rev. 1.1
Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
Table 10-6. IWRITE (Indexed Write) Command
Description
Write to last address accessed + 1
Operand
Specifies single data byte
Data
Returned
None
Opcode
$19
Command Sequence
SENT TO
MONITOR
IWRITE
IWRITE
DATA
DATA
ECHO
Table 10-7. READSP (Read Stack Pointer) Command
Description
Reads stack pointer
Operand
None
Data
Returned
Returns stack pointer in high byte:low byte order
Opcode
$0C
Command Sequence
SENT TO
MONITOR
READSP
READSP
ECHO
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
SP
HIGH
SP
LOW
RETURN
Technical Data
Monitor ROM (MON)
165
Monitor ROM (MON)
Table 10-8. RUN (Run User Program) Command
Description
Executes RTI instruction
Operand
None
Data
Returned
None
Opcode
$28
Command Sequence
SENT TO
MONITOR
RUN
RUN
ECHO
10.4.6 Baud Rate
With a 4.9152-MHz crystal and the PTC3 pin at logic 1 during reset, data
is transferred between the monitor and host at 4800 baud. If the PTC3
pin is at logic 0 during reset, the monitor baud rate is 9600. When the
CGM output, CGMOUT, is driven by the PLL, the baud rate is
determined by the MUL[7:4] bits in the PLL programming register (PPG).
(See Section 9. Clock Generator Module (CGM).)
Table 10-9. Monitor Baud Rate Selection
Monitor
Baud Rate
VCO Frequency Multiplier (N)
1
2
3
4
5
6
4.9152 MHz
4800
9600
14,400
19,200
24,000
28,800
4.194 MHz
4096
8192
12,288
16,384
20,480
24,576
Technical Data
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Monitor ROM (MON)
Freescale Semiconductor
Monitor ROM (MON)
10.5 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.
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 10-6.)
VDD
4096 + 32 CGMXCLK 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 10-6. Monitor Mode Entry Timing
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Monitor ROM (MON)
167
Monitor ROM (MON)
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.
To determine whether the security code entered is correct, check to see
if bit 6 of RAM address $50 is set. If it is, then the correct security code
has been entered and FLASH can be accessed.
NOTE:
The MCU does not transmit a break character until after the host sends
the eight security bits.
If the host fails the security bypass as described in 10.5 Security, 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. The MCU monitor commands are still valid and user
software can execute from RAM. A bulk-erase operation is possible,
erasing the entire FLASH memory, including the security bytes at
$FFF6–$FFFD.
10.6 Extended Security
To further disable monitor mode functions, an extended security
command keyword can be programmed at FLASH locations
$FFC0–$FFC7. The keyword is eight bytes long with a 7-byte ASCII
string and 1-byte $00 delimiter. The keyword for the MC68HC908AB32
MCU is "PSWDOPT" + $00.
Entry to monitor mode with extended security command keyword
programmed, the MCU stops communicating with the host after
transmitting a break character if the host fails the security bypass as
described in 10.5 Security.
NOTE:
Once the extended security command keyword is programmed, the
FLASH memory cannot be erased without a valid security code
(matching $FFF6–$FFFD). Therefore, the extended security command
keyword should not be programmed during software development.
Technical Data
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MC68HC908AB32 — Rev. 1.1
Monitor ROM (MON)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 11. Timer Interface Module A (TIMA)
11.1 Contents
11.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
11.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
11.4
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
11.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .171
11.5.1 TIMA Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . .171
11.5.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
11.5.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
11.5.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . 175
11.5.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . .176
11.5.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . 177
11.5.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . 178
11.5.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . 179
11.5.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180
11.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .181
11.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
11.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
11.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .182
11.8
TIMA During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 182
11.9 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
11.9.1 TIMA Clock Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .183
11.9.2 TIMA Channel I/O Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
11.10 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
11.10.1 TIMA Status and Control Register . . . . . . . . . . . . . . . . . . . 184
11.10.2 TIMA Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .186
11.10.3 TIMA Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . 187
11.10.4 TIMA Channel Status and Control Registers . . . . . . . . . . . 188
11.10.5 TIMA Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 192
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module A (TIMA)
169
Timer Interface Module A (TIMA)
11.2 Introduction
This section describes the timer interface module A (TIMA). The TIMA is
a four-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 TIMA.
11.3 Features
Features of the TIMA include the following:
•
Four input capture/output compare channels:
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
•
Buffered and unbuffered pulse-width-modulation (PWM) signal
generation
•
Programmable TIMA clock input:
– Seven-frequency internal bus clock prescaler selection
– External TIMA clock input (4MHz maximum frequency)
•
Free-running or modulo up-count operation
•
Toggle any channel pin on overflow
•
TIMA counter stop and reset bits
•
Modular architecture expandable to eight channels
Technical Data
170
MC68HC908AB32 — Rev. 1.1
Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
11.4 Pin Name Conventions
The TIMA share five I/O pins with port D, E, and F I/O pins. The full name
of the TIMA I/O pin is listed in Table 11-1. The generic pin name appear
in the text that follows.
Table 11-1. Pin Name Conventions
TIMA Generic Pin Names:
Full TIMA Pin Names:
TACLK
PTD6/TACLK
TACH0
PTE2/TACH0
TACH1
PTE3/TACH1
TACH2
PTF0/TACH2
TACH3
PTF1/TACH3
11.5 Functional Description
Figure 11-1 shows the structure of the TIMA. The central component of
the TIMA is the 16-bit TIMA counter that can operate as a free-running
counter or a modulo up-counter. The TIMA counter provides the timing
reference for the input capture and output compare functions. The TIMA
counter modulo registers, TAMODH:TAMODL, control the modulo value
of the TIMA counter. Software can read the TIMA counter value at any
time without affecting the counting sequence.
The four TIMA channels are programmable independently as input
capture or output compare channels.
11.5.1 TIMA Counter Prescaler
The TIMA clock source can be one of the seven prescaler outputs or the
TIMA clock pin, PTD6/TACLK. The prescaler generates seven clock
rates from the internal bus clock. The prescaler select bits, PS[2:0], in
the TIMA status and control register select the TIMA clock source.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module A (TIMA)
171
Timer Interface Module A (TIMA)
PTD6/TACLK
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
16-BIT COMPARATOR
INTERRUPT
LOGIC
TAMODH:TAMODL
TOV0
CHANNEL 0
ELS0B
ELS0A
CH0MAX
16-BIT COMPARATOR
TACH0H:TACH0L
PTE2
LOGIC
PTE2/TACH0
CH0F
16-BIT LATCH
MS0A
CH0IE
INTERRUPT
LOGIC
MS0B
INTERNAL BUS
TOV1
CHANNEL 1
ELS1B
ELS1A
CH1MAX
16-BIT COMPARATOR
TACH1H:TACH1L
PTE3
LOGIC
PTE3/TACH1
CH1F
16-BIT LATCH
MS1A
CH1IE
INTERRUPT
LOGIC
TOV2
CHANNEL 2
ELS2B
ELS2A
CH2MAX
16-BIT COMPARATOR
TACH2H:TACH2L
PTF0
LOGIC
PTF0/TACH2
CH2F
16-BIT LATCH
MS2A
CH2IE
INTERRUPT
LOGIC
MS2B
TOV3
CHANNEL 3
ELS3B
ELS3A
CH3MAX
16-BIT COMPARATOR
TACH3H:TACH3L
PTF1
LOGIC
PTF1/TACH3
CH3F
16-BIT LATCH
MS3A
CH3IE
INTERRUPT
LOGIC
Figure 11-1. TIMA Block Diagram
Technical Data
172
MC68HC908AB32 — Rev. 1.1
Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
Addr.
$0020
$0022
$0023
$0024
$0025
Register Name
$0028
5
TOIE
TSTOP
4
3
0
0
2
1
Bit 0
PS2
PS1
PS0
TOF
0
0
1
0
0
0
0
0
Read:
Timer A Counter
Register High Write:
(TACNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
Timer A Counter
Register Low Write:
(TACNTL)
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 A Counter Modulo
Register High Write:
(TAMODH)
Reset:
Read:
Timer A Counter Modulo
Register Low Write:
(TAMODL)
Reset:
Read:
Timer A Channel 0
Register High Write:
(TACH0H)
Reset:
Read:
Timer A Channel 0
Register Low Write:
(TACH0L)
Reset:
Read:
Timer A Channel 1 Status
$0029
and Control Register Write:
(TASC1)
Reset:
$002A
6
Read:
Timer A Status and
Control Register Write:
(TASC)
Reset:
Read:
Timer A Channel 0 Status
$0026
and Control Register Write:
(TASC0)
Reset:
$0027
Bit 7
Read:
Timer A Channel 1
Register High Write:
(TACH1H)
Reset:
0
CH0F
0
TRST
Indeterminate after reset
Bit 7
6
5
4
3
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
Indeterminate after reset
= Unimplemented
Figure 11-2. TIMA I/O Register Summary (Sheet 1 of 2)
MC68HC908AB32 — Rev. 1.1
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Technical Data
Timer Interface Module A (TIMA)
173
Timer Interface Module A (TIMA)
Addr.
$002B
Register Name
Read:
Timer A Channel 1
Register Low Write:
(TACH1L)
Reset:
Read:
Timer A Channel 2 Status
$002C
and Control Register Write:
(TASC2)
Reset:
$002D
$002E
Read:
Timer A Channel 2
Register High Write:
(TACH2H)
Reset:
Read:
Timer A Channel 2
Register Low Write:
(TACH2L)
Reset:
Read:
Timer A Channel 3 Status
$002F
and Control Register Write:
(TASC3)
Reset:
$0030
$0031
Read:
Timer A Channel 3
Register High Write:
(TACH3H)
Reset:
Read:
Timer A Channel 3
Register Low Write:
(TACH3L)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
CH2F
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH3F
0
CH3IE
0
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
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. TIMA I/O Register Summary (Sheet 2 of 2)
11.5.2 Input Capture
With the input capture function, the TIMA can capture the time at which
an external event occurs. When an active edge occurs on the pin of an
input capture channel, the TIMA latches the contents of the TIMA
counter into the TIMA channel registers, TACHxH:TACHxL. The polarity
of the active edge is programmable. Input captures can generate
TIMA CPU interrupt requests.
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
11.5.3 Output Compare
With the output compare function, the TIMA 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 TIMA can set, clear, or toggle the channel pin. Output compares can
generate TIMA CPU interrupt requests.
11.5.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare
pulses as described in 11.5.3 Output Compare. The pulses are
unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change an
output compare value could cause incorrect operation for up to two
counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new
value prevents any compare during that counter overflow period. Also,
using a TIMA overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMA may
pass the new value before it is written.
Use 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
channel x TIMA overflow interrupts and write the new value in the
TIMA overflow interrupt routine. The TIMA overflow interrupt
occurs at the end of the current counter overflow period. Writing a
larger value in an output compare interrupt routine (at the end of
the current pulse) could cause two output compares to occur in the
same counter overflow period.
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Technical Data
Timer Interface Module A (TIMA)
175
Timer Interface Module A (TIMA)
11.5.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare
channel whose output appears on the PTE2/TACH0 pin. The TIMA
channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIMA channel 0 status and control register
(TASC0) links channel 0 and channel 1. The output compare value in the
TIMA channel 0 registers initially controls the output on the
PTE2/TACH0 pin. Writing to the TIMA channel 1 registers enables the
TIMA channel 1 registers to synchronously control the output after the
TIMA overflows. At each subsequent overflow, the TIMA channel
registers (0 or 1) that control the output are the ones written to last.
TASC0 controls and monitors the buffered output compare function, and
TIMA channel 1 status and control register (TASC1) is unused. While the
MS0B bit is set, the channel 1 pin, PTE3/TACH1, is available as a
general-purpose I/O pin.
Channels 2 and 3 can be linked to form a buffered output compare
channel whose output appears on the PTF0/TACH2 pin. The TIMA
channel registers of the linked pair alternately control the output.
Setting the MS2B bit in TIMA channel 2 status and control register
(TASC2) links channel 2 and channel 3. The output compare value in the
TIMA channel 2 registers initially controls the output on the
PTF0/TACH2 pin. Writing to the TIMA channel 3 registers enables the
TIMA channel 3 registers to synchronously control the output after the
TIMA overflows. At each subsequent overflow, the TIMA channel
registers (2 or 3) that control the output are the ones written to last.
TASC2 controls and monitors the buffered output compare function, and
TIMA channel 3 status and control register (TASC3) is unused. While the
MS2B bit is set, the channel 3 pin, PTF1/TACH3, 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. Writing to the active
channel registers is the same as generating unbuffered output
compares.
Technical Data
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
11.5.4 Pulse Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel,
the TIMA can generate a PWM signal. The value in the TIMA counter
modulo registers determines the period of the PWM signal. The channel
pin toggles when the counter reaches the value in the TIMA counter
modulo registers. The time between overflows is the period of the PWM
signal.
As Figure 11-3 shows, the output compare value in the TIMA channel
registers determines the pulse width of the PWM signal. The time
between overflow and output compare is the pulse width. Program the
TIMA to clear the channel pin on output compare if the state of the PWM
pulse is logic one. Program the TIMA to set the pin if the state of the
PWM pulse is logic zero.
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PULSE
WIDTH
TACHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 11-3PWM Period and Pulse Width
The value in the TIMA counter modulo registers and the selected
prescaler output determines the frequency of the PWM output. The
frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMA counter modulo registers produces a PWM
period of 256 times the internal bus clock period if the prescaler select
value is $000. See 11.10.1 TIMA Status and Control Register.
The value in the TIMA channel registers determines the pulse width of
the PWM output. The pulse width of an 8-bit PWM signal is variable in
256 increments. Writing $0080 (128) to the TIMA channel registers
produces a duty cycle of 128/256 or 50%.
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Technical Data
Timer Interface Module A (TIMA)
177
Timer Interface Module A (TIMA)
11.5.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as
described in 11.5.4 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 TIMA channel
registers.
An unsynchronized write to the TIMA channel registers to change a
pulse width value could cause incorrect operation for up to two PWM
periods. For example, writing a new value before the counter reaches
the old value but after the counter reaches the new value prevents any
compare during that PWM period. Also, using a TIMA overflow interrupt
routine to write a new, smaller pulse width value may cause the compare
to be missed. The TIMA may pass the new value before it is written.
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 channel x TIMA
overflow interrupts and write the new value in the TIMA overflow
interrupt routine. The TIMA overflow interrupt occurs at the end of
the current PWM period. Writing a larger value in an output
compare interrupt routine (at the end of the current pulse) could
cause two output compares to occur in the same PWM period.
In PWM signal generation, do not program the PWM channel to toggle
on output compare. Toggling on output compare prevents reliable 0%
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.
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
11.5.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose
output appears on the PTE2/TACH0 pin. The TIMA channel registers of
the linked pair alternately control the pulse width of the output.
Setting the MS0B bit in TIMA channel 0 status and control register
(TASC0) links channel 0 and channel 1. The TIMA channel 0 registers
initially control the pulse width on the PTE2/TACH0 pin. Writing to the
TIMA channel 1 registers enables the TIMA channel 1 registers to
synchronously control the pulse width at the beginning of the next PWM
period. At each subsequent overflow, the TIMA channel registers (0 or
1) that control the pulse width are the ones written to last. TASC0
controls and monitors the buffered PWM function, and TIMA channel 1
status and control register (TASC1) is unused. While the MS0B bit is set,
the channel 1 pin, PTE3/TACH1, is available as a general-purpose I/O
pin.
Channels 2 and 3 can be linked to form a buffered PWM channel whose
output appears on the PTF0/TACH2 pin. The TIMA channel registers of
the linked pair alternately control the pulse width of the output.
Setting the MS2B bit in TIMA channel 2 status and control register
(TASC2) links channel 2 and channel 3. The TIMA channel 2 registers
initially control the pulse width on the PTF0/TACH2 pin. Writing to the
TIMA channel 3 registers enables the TIMA channel 3 registers to
synchronously control the pulse width at the beginning of the next PWM
period. At each subsequent overflow, the TIMA channel registers (2 or
3) that control the pulse width are the ones written to last. TASC2
controls and monitors the buffered PWM function, and TIMA channel 3
status and control register (TASC3) is unused. While the MS2B bit is set,
the channel 3 pin, PTF1/TACH3, is available as a general-purpose I/O
pin.
NOTE:
In buffered PWM signal generation, do not write new pulse width values
to the currently active channel registers. Writing to the active channel
registers is the same as generating unbuffered PWM signals.
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Technical Data
Timer Interface Module A (TIMA)
179
Timer Interface Module A (TIMA)
11.5.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered
PWM signals, use the following initialization procedure:
1. In the TIMA status and control register (TASC):
a. Stop the TIMA counter by setting the TIMA stop bit, TSTOP.
b. Reset the TIMA counter by setting the TIMA reset bit, TRST.
2. In the TIMA counter modulo registers (TAMODH:TAMODL), write
the value for the required PWM period.
3. In the TIMA channel x registers (TACHxH:TACHxL), write the
value for the required pulse width.
4. In TIMA channel x status and control register (TASCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or
1:0 (for buffered output compare or PWM signals) to the
mode select bits, MSxB:MSxA. See Table 11-3.
a. Write 1 to the toggle-on-overflow bit, TOVx.
b. 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 TIMA status control register (TASC), clear the TIMA stop bit,
TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered
PWM operation. The TIMA channel 0 registers (TACH0H:TACH0L)
initially control the buffered PWM output. TIMA channel 0 status and
control register 0 (TASC0) controls and monitors the PWM signal from
the linked channels. MS0B takes priority over MS0A.
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
Setting MS2B links channels 2 and 3 and configures them for buffered
PWM operation. The TIMA channel 2 registers (TACH2H:TACH2L)
initially control the PWM output. TIMA channel 2 status and control
register (TASC2) controls and monitors the PWM signal from the linked
channels. MS2B takes priority over MS2A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on
TIMA overflows. Subsequent output compares try to force the output to
a state it is already in and have no effect. The result is a 0% duty cycle
output.
Setting the channel x maximum duty cycle bit (CHxMAX) and clearing
the TOVx bit generates a 100% duty cycle output. See 11.10.4 TIMA
Channel Status and Control Registers.
11.6 Interrupts
The following TIMA sources can generate interrupt requests:
•
TIMA overflow flag (TOF) — The TOF bit is set when the TIMA
counter value rolls over to $0000 after matching the value in the
TIMA counter modulo registers. The TIMA overflow interrupt
enable bit, TOIE, enables TIMA overflow CPU interrupt requests.
TOF and TOIE are in the TIMA status and control register.
•
TIMA channel flags (CH3F–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 TIMA
channel x status and control register.
11.7 Low-Power Modes
The WAIT and STOP instructions puts the MCU in low-powerconsumption standby modes.
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Technical Data
Timer Interface Module A (TIMA)
181
Timer Interface Module A (TIMA)
11.7.1 Wait Mode
The TIMA remains active after the execution of a WAIT instruction. In
wait mode the TIMA registers are not accessible by the CPU. Any
enabled CPU interrupt request from the TIMA can bring the MCU out of
wait mode.
If TIMA functions are not required during wait mode, reduce power
consumption by stopping the TIMA before executing the WAIT
instruction.
11.7.2 Stop Mode
The TIMA is inactive after the execution of a STOP instruction. The
STOP instruction does not affect register conditions or the state of the
TIMA counter. TIMA operation resumes when the MCU exit stop mode
after an external interrupt.
11.8 TIMA During Break Interrupts
A break interrupt stops the TIMA 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 8.8.3 SIM Break Flag Control
Register.
To allow software to clear status bits during a break interrupt, write a
logic one 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 zero to the
BCFE bit. With BCFE at logic zero (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 zero. After the
break, doing the second step clears the status bit.
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
11.9 I/O Signals
Ports E and F each share two pins with the TIMA and port D shares one.
PTD6/TACLK is an external clock input to the TIMA prescaler. The four
TIMA channel I/O pins are PTE2/TACH0, PTE3/TACH1, PTF0/TACH2,
and PTF1/TACH3.
11.9.1 TIMA Clock Pin
PTD6/TACLK is an external clock input that can be the clock source for
the TIMA counter instead of the prescaled internal bus clock. Select the
PTD6/TACLK input by writing logic 1s to the three prescaler select bits,
PS[2:0]. See 11.10.1 TIMA Status and Control Register. The minimum
TACLK pulse width, TACLKLMIN or TACLKHMIN, is:
1
------------------------------------- + t SU
bus frequency
The maximum TACLK frequency is:
bus frequency ÷ 2
PTD6/TACLK is available as a general-purpose I/O pin when not used
as the TIMA clock input. When the PTD6/TACLK pin is the TIMA clock
input, it is an input regardless of the state of the DDRD6 bit in data
direction register D.
11.9.2 TIMA Channel I/O Pins
Each channel I/O pin is programmable independently as an input
capture pin or an output compare pin. PTF0/TACH2 and PTE3/TACH1
can be configured as buffered output compare or buffered PWM pins.
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Freescale Semiconductor
Technical Data
Timer Interface Module A (TIMA)
183
Timer Interface Module A (TIMA)
11.10 I/O Registers
The following I/O registers control and monitor operation of the TIMA:
•
TIMA status and control register (TASC)
•
TIMA counter registers (TACNTH:TACNTL)
•
TIMA counter modulo registers (TAMODH:TAMODL)
•
TIMA channel status and control registers (TASC0, TASC1,
TASC2, and TASC3)
•
TIMA channel registers (TACH0H:TACH0L, TACH1H:TACH1L,
TACH2H:TACH2L, and TACH3H:TACH3L)
11.10.1 TIMA Status and Control Register
The TIMA status and control register does the following:
•
Enables TIMA overflow interrupts
•
Flags TIMA overflows
•
Stops the TIMA counter
•
Resets the TIMA counter
•
Prescales the TIMA counter clock
Address:
$0020
Bit 7
Read:
TOF
Write:
0
Reset:
0
6
5
TOIE
TSTOP
0
1
4
3
0
0
TRST
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
= Unimplemented
Figure 11-4. TIMA Status and Control Register (TASC)
Technical Data
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
TOF — TIMA Overflow Flag Bit
This read/write flag is set when the TIMA counter resets to $0000 after
reaching the modulo value programmed in the TIMA counter modulo
registers. Clear TOF by reading the TIMA status and control register
when TOF is set and then writing a logic zero to TOF. If another TIMA
overflow occurs before the clearing sequence is complete, then
writing logic zero 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 one to TOF has no effect.
1 = TIMA counter has reached modulo value
0 = TIMA counter has not reached modulo value
TOIE — TIMA Overflow Interrupt Enable Bit
This read/write bit enables TIMA overflow interrupts when the TOF bit
becomes set. Reset clears the TOIE bit.
1 = TIMA overflow interrupts enabled
0 = TIMA overflow interrupts disabled
TSTOP — TIMA Stop Bit
This read/write bit stops the TIMA counter. Counting resumes when
TSTOP is cleared. Reset sets the TSTOP bit, stopping the TIMA
counter until software clears the TSTOP bit.
1 = TIMA counter stopped
0 = TIMA counter active
NOTE:
Do not set the TSTOP bit before entering wait mode if the TIMA is
required to exit wait mode.
TRST — TIMA Reset Bit
Setting this write-only bit resets the TIMA counter and the TIMA
prescaler. Setting TRST has no effect on any other registers.
Counting resumes from $0000. TRST is cleared automatically after
the TIMA counter is reset and always reads as logic zero. Reset
clears the TRST bit.
1 = Prescaler and TIMA counter cleared
0 = No effect
NOTE:
Setting the TSTOP and TRST bits simultaneously stops the TIMA
counter at a value of $0000.
MC68HC908AB32 — Rev. 1.1
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Technical Data
Timer Interface Module A (TIMA)
185
Timer Interface Module A (TIMA)
PS[2:0] — Prescaler Select Bits
These read/write bits select either the PTD6/TACLK pin or one of the
seven prescaler outputs as the input to the TIMA counter as
Table 11-2 shows. Reset clears the PS[2:0] bits.
Table 11-2. Prescaler Selection
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
PTD6/TACLK
11.10.2 TIMA Counter Registers
The two read-only TIMA counter registers contain the high and low bytes
of the value in the TIMA counter. Reading the high byte (TACNTH)
latches the contents of the low byte (TACNTL) into a buffer. Subsequent
reads of TACNTH do not affect the latched TACNTL value until TACNTL
is read. Reset clears the TIMA counter registers. Setting the TIMA reset
bit (TRST) also clears the TIMA counter registers.
NOTE:
If you read TACNTH during a break interrupt, be sure to unlatch TACNTL
by reading TACNTL before exiting the break interrupt. Otherwise,
TACNTL retains the value latched during the break.
Address:
Read:
$0022
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 11-5. TIMA Counter Register High (TACNTH)
Technical Data
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
Address:
Read:
$0023
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 11-6. TIMA Counter Register Low (TACNTL)
11.10.3 TIMA Counter Modulo Registers
The read/write TIMA modulo registers contain the modulo value for the
TIMA counter. When the TIMA counter reaches the modulo value, the
overflow flag (TOF) becomes set, and the TIMA counter resumes
counting from $0000 at the next clock. Writing to the high byte
(TAMODH) inhibits the TOF bit and overflow interrupts until the low byte
(TAMODL) is written. Reset sets the TIMA counter modulo registers.
Address:
Read:
Write:
Reset:
$0024
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
Figure 11-7. TIMA Counter Modulo Register High (TAMODH)
Address:
Read:
Write:
Reset:
$0025
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
Figure 11-8. TIMA Counter Modulo Register Low (TAMODL)
NOTE:
Reset the TIMA counter before writing to the TIMA counter modulo
registers.
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Technical Data
Timer Interface Module A (TIMA)
187
Timer Interface Module A (TIMA)
11.10.4 TIMA Channel Status and Control Registers
Each of the TIMA channel status and control registers does the
following:
•
Flags input captures and output compares
•
Enables input capture and output compare interrupts
•
Selects input capture, output compare, or PWM operation
•
Selects high, low, or toggling output on output compare
•
Selects rising edge, falling edge, or any edge as the active input
capture trigger
•
Selects output toggling on TIMA overflow
•
Selects 100% PWM duty cycle
•
Selects buffered or unbuffered output compare/PWM operation
Address:
$0026
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. TIMA Channel 0 Status and Control Register (TASC0)
Address:
$0029
Bit 7
Read:
CH1F
Write:
0
Reset:
0
6
CH1IE
0
5
0
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
Figure 11-10. TIMA Channel 1 Status and Control Register (TASC1)
Technical Data
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Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
Address:
$002C
Bit 7
Read:
CH2F
Write:
0
Reset:
0
6
5
4
3
2
1
Bit 0
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
Figure 11-11. TIMA Channel 2 Status and Control Register (TASC2)
Address:
$002F
Bit 7
Read:
CH3F
Write:
0
Reset:
0
6
CH3IE
0
5
0
0
4
3
2
1
Bit 0
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
0
0
0
0
0
Figure 11-12. TIMA Channel 3 Status and Control Register (TASC3)
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set
when an active edge occurs on the channel x pin. When channel x is
an output compare channel, CHxF is set when the value in the TIMA
counter registers matches the value in the TIMA channel x registers.
When TIM CPU interrupt requests are enabled (CHxIE = 1), clear
CHxF by reading TIMA channel x status and control register with
CHxF set and then writing a logic zero to CHxF. If another interrupt
request occurs before the clearing sequence is complete, then writing
logic zero 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 one to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIMA CPU interrupts on channel x.
Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module A (TIMA)
189
Timer Interface Module A (TIMA)
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation.
MSxB exists only in the TIMA channel 0 and TIMA channel 2 status
and control registers.
Setting MS0B disables the channel 1 status and control register and
reverts TCH1B to general-purpose I/O.
Setting MS2B disables the channel 3 status and control register and
reverts TCH3B to general-purpose I/O.
Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture
operation or unbuffered output compare/PWM operation.
See Table 11-3.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level
of the TBCHx 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 TIMA status and control register
(TASC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits
control the active edge-sensing logic on channel x.
When channel x is an output compare channel, ELSxB and ELSxA
control the channel x output behavior when an output compare
occurs.
When ELSxB and ELSxA are both clear, channel x is not connected
to the port I/O, and pin TACHx 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.
Technical Data
190
MC68HC908AB32 — Rev. 1.1
Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
Table 11-3. Mode, Edge, and Level Selection
MSxB
MSxA
ELSxB
ELSxA
X
0
0
0
Mode
Output
Preset
NOTE:
X
1
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
1
0
1
1
0
0
1
1
1
1
X
0
1
1
X
1
0
1
X
1
1
Configuration
Pin under Port Control;
Initial Output Level High
Pin under Port Control;
Initial Output Level Low
Capture on Rising Edge Only
Input
Capture
Capture on Falling Edge Only
Capture on Rising or Falling Edge
Output
Compare
or PWM
Toggle Output on Compare
Clear Output on Compare
Set Output on Compare
Toggle Output on Compare
Buffered
Output
Clear Output on Compare
Compare or
Buffered
Set Output on Compare
PWM
Before enabling a TIMA channel register for input capture operation,
make sure that the TACHx pin is stable for at least two bus clocks.
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit
controls the behavior of the channel x output when the TIMA counter
overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMA counter overflow.
0 = Channel x pin does not toggle on TIMA counter overflow.
NOTE:
When TOVx is set, a TIMA counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx bit is at logic zero, setting the CHxMAX bit forces the
duty cycle of buffered and unbuffered PWM signals to 100%. As
Figure 11-13 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.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module A (TIMA)
191
Timer Interface Module A (TIMA)
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
TACHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
Figure 11-13. CHxMAX Latency
11.10.5 TIMA Channel Registers
These read/write registers contain the captured TIMA counter value of
the input capture function or the output compare value of the output
compare function. The state of the TIMA channel registers after reset is
unknown.
In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the
TIMA channel x registers (TACHxH) inhibits input captures until the low
byte (TACHxL) is read.
In output compare mode (MSxB:MSxA ≠ 0:0), writing to the high byte of
the TIMA channel x registers (TACHxH) inhibits output compares until
the low byte (TACHxL) is written.
Address:
Read:
Write:
$0027
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 11-14. TIMA Channel 0 Register High (TACH0H)
Address:
Read:
Write:
Reset:
$0028
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 11-15. TIMA Channel 0 Register Low (TACH0L)
Technical Data
192
MC68HC908AB32 — Rev. 1.1
Timer Interface Module A (TIMA)
Freescale Semiconductor
Timer Interface Module A (TIMA)
Address:
Read:
Write:
$002A
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 11-16. TIMA Channel 1 Register High (TACH1H)
Address:
Read:
Write:
$002B
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Reset:
Indeterminate after reset
Figure 11-17. TIMA Channel 1 Register Low (TACH1L)
Address:
Read:
Write:
$002D
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 11-18. TIMA Channel 2 Register High (TACH2H)
Address:
Read:
Write:
Reset:
$002E
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 11-19. TIMA Channel 2 Register Low (TACH2L)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module A (TIMA)
193
Timer Interface Module A (TIMA)
Address:
Read:
Write:
$0030
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 11-20. TIMA Channel 3 Register High (TACH3H)
Address:
Read:
Write:
Reset:
$0031
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 11-21. TIMA Channel 3 Register Low (TACH3L)
Technical Data
194
MC68HC908AB32 — Rev. 1.1
Timer Interface Module A (TIMA)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 12. Timer Interface Module B (TIMB)
12.1 Contents
12.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
12.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196
12.4
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 197
12.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .197
12.5.1 TIMB Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . .197
12.5.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200
12.5.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
12.5.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . 201
12.5.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . .202
12.5.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . 203
12.5.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . 204
12.5.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . 205
12.5.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
12.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207
12.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
12.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
12.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .208
12.8
TIMB During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . 208
12.9 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
12.9.1 TIMB Clock Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .209
12.9.2 TIMB Channel I/O Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
12.10 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
12.10.1 TIMB Status and Control Register . . . . . . . . . . . . . . . . . . . 210
12.10.2 TIMB Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . .212
12.10.3 TIMB Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . 213
12.10.4 TIMB Channel Status and Control Registers . . . . . . . . . . . 214
12.10.5 TIMB Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 218
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module B (TIMB)
195
Timer Interface Module B (TIMB)
12.2 Introduction
This section describes the timer interface module A (TIMB). The TIMB is
a four-channel timer that provides a timing reference with input capture,
output compare, and pulse-width-modulation functions. Figure 12-1 is a
block diagram of the TIMB.
12.3 Features
Features of the TIMB include the following:
•
Four 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 TIMB clock input:
– Seven-frequency internal bus clock prescaler selection
– External TIMB clock input (4MHz maximum frequency)
•
Free-running or modulo up-count operation
•
Toggle any channel pin on overflow
•
TIMB counter stop and reset bits
•
Modular architecture expandable to eight channels
Technical Data
196
MC68HC908AB32 — Rev. 1.1
Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
12.4 Pin Name Conventions
The TIMB share five I/O pins with port D and F I/O pins. The full name of
the TIMB I/O pin is listed in Table 12-1. The generic pin name appear in
the text that follows.
Table 12-1. Pin Name Conventions
TIMB Generic Pin Names:
Full TIMB Pin Names:
TBCLK
PTD4/TBCLK
TBCH0
PTF4/TBCH0
TBCH1
PTF5/TBCH1
TBCH2
PTF2/TBCH2
TBCH3
PTF3/TBCH3
12.5 Functional Description
Figure 12-1 shows the structure of the TIMB. The central component of
the TIMB is the 16-bit TIMB counter that can operate as a free-running
counter or a modulo up-counter. The TIMB counter provides the timing
reference for the input capture and output compare functions. The TIMB
counter modulo registers, TBMODH:TBMODL, control the modulo value
of the TIMB counter. Software can read the TIMB counter value at any
time without affecting the counting sequence.
The four TIMB channels are programmable independently as input
capture or output compare channels.
12.5.1 TIMB Counter Prescaler
The TIMB clock source can be one of the seven prescaler outputs or the
TIMB clock pin, PTD4/TBCLK. The prescaler generates seven clock
rates from the internal bus clock. The prescaler select bits, PS[2:0], in
the TIMB status and control register select the TIMB clock source.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module B (TIMB)
197
Timer Interface Module B (TIMB)
PTD4/TBCLK
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
16-BIT COMPARATOR
INTERRUPT
LOGIC
TBMODH:TBMODL
TOV0
CHANNEL 0
ELS0B
ELS0A
CH0MAX
16-BIT COMPARATOR
TBCH0H:TBCH0L
PTF4
LOGIC
PTF4/TBCH0
CH0F
16-BIT LATCH
MS0A
CH0IE
INTERRUPT
LOGIC
MS0B
INTERNAL BUS
TOV1
CHANNEL 1
ELS1B
ELS1A
CH1MAX
16-BIT COMPARATOR
TBCH1H:TBCH1L
PTF5
LOGIC
PTF5/TBCH1
CH1F
16-BIT LATCH
MS1A
CH1IE
INTERRUPT
LOGIC
TOV2
CHANNEL 2
ELS2B
ELS2A
CH2MAX
16-BIT COMPARATOR
TBCH2H:TBCH2L
PTF2
LOGIC
PTF2/TBCH2T
CH2F
16-BIT LATCH
MS2A
CH2IE
INTERRUPT
LOGIC
MS2B
TOV3
CHANNEL 3
ELS3B
ELS3A
CH3MAX
16-BIT COMPARATOR
TBCH3H:TBCH3L
PTF3
LOGIC
PTF3/TBCH3
CH3F
16-BIT LATCH
MS3A
CH3IE
INTERRUPT
LOGIC
Figure 12-1. TIMB Block Diagram
Technical Data
198
MC68HC908AB32 — Rev. 1.1
Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
Addr.
$0040
$0041
$0042
$0043
$0044
Register Name
$0047
5
TOIE
TSTOP
4
3
0
0
2
1
Bit 0
PS2
PS1
PS0
TOF
0
0
1
0
0
0
0
0
Read:
Timer B Counter
Register High Write:
(TBCNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
Timer B Counter
Register Low Write:
(TBCNTL)
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 B Counter Modulo
Register High Write:
(TBMODH)
Reset:
Read:
Timer B Counter Modulo
Register Low Write:
(TBMODL)
Reset:
Read:
Timer B Channel 0
Register High Write:
(TBCH0H)
Reset:
Read:
Timer B Channel 0
Register Low Write:
(TBCH0L)
Reset:
Read:
Timer B Channel 1 Status
$0048
and Control Register Write:
(TBSC1)
Reset:
$0049
6
Read:
Timer B Status and
Control Register Write:
(TBSC)
Reset:
Read:
Timer B Channel 0 Status
$0045
and Control Register Write:
(TBSC0)
Reset:
$0046
Bit 7
Read:
Timer B Channel 1
Register High Write:
(TBCH1H)
Reset:
0
CH0F
0
TRST
Indeterminate after reset
Bit 7
6
5
4
3
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
Indeterminate after reset
= Unimplemented
Figure 12-2. TIMB I/O Register Summary (Sheet 1 of 2)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module B (TIMB)
199
Timer Interface Module B (TIMB)
Addr.
$004A
Register Name
Read:
Timer B Channel 1
Register Low Write:
(TBCH1L)
Reset:
Read:
Timer B Channel 2 Status
$0032
and Control Register Write:
(TBSC2)
Reset:
$0033
$0034
Read:
Timer B Channel 2
Register High Write:
(TBCH2H)
Reset:
Read:
Timer B Channel 2
Register Low Write:
(TBCH2L)
Reset:
Read:
Timer B Channel 3 Status
$0035
and Control Register Write:
(TBSC3)
Reset:
$0036
$0037
Read:
Timer B Channel 3
Register High Write:
(TBCH3H)
Reset:
Read:
Timer B Channel 3
Register Low Write:
(TBCH3L)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
CH2F
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH3F
0
CH3IE
0
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
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 12-2. TIMB I/O Register Summary (Sheet 2 of 2)
12.5.2 Input Capture
With the input capture function, the TIMB can capture the time at which
an external event occurs. When an active edge occurs on the pin of an
input capture channel, the TIMB latches the contents of the TIMB
counter into the TIMB channel registers, TBCHxH:TBCHxL. The polarity
of the active edge is programmable. Input captures can generate
TIMB CPU interrupt requests.
Technical Data
200
MC68HC908AB32 — Rev. 1.1
Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
12.5.3 Output Compare
With the output compare function, the TIMB can generate a periodic
pulse with a programmable polarity, duration, and frequency. When the
counter reaches the value in the registers of an output compare channel,
the TIMB can set, clear, or toggle the channel pin. Output compares can
generate TIMB CPU interrupt requests.
12.5.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare
pulses as described in 12.5.3 Output Compare. The pulses are
unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMB channel registers.
An unsynchronized write to the TIMB channel registers to change an
output compare value could cause incorrect operation for up to two
counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new
value prevents any compare during that counter overflow period. Also,
using a TIMB overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMB may
pass the new value before it is written.
Use 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
channel x TIMB overflow interrupts and write the new value in the
TIMB overflow interrupt routine. The TIMB overflow interrupt
occurs at the end of the current counter overflow period. Writing a
larger value in an output compare interrupt routine (at the end of
the current pulse) could cause two output compares to occur in the
same counter overflow period.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module B (TIMB)
201
Timer Interface Module B (TIMB)
12.5.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare
channel whose output appears on the PTF4/TBCH0 pin. The TIMB
channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIMB channel 0 status and control register
(TBSC0) links channel 0 and channel 1. The output compare value in the
TIMB channel 0 registers initially controls the output on the
PTF4/TBCH0 pin. Writing to the TIMB channel 1 registers enables the
TIMB channel 1 registers to synchronously control the output after the
TIMB overflows. At each subsequent overflow, the TIMB channel
registers (0 or 1) that control the output are the ones written to last.
TBSC0 controls and monitors the buffered output compare function, and
TIMB channel 1 status and control register (TBSC1) is unused. While the
MS0B bit is set, the channel 1 pin, PTF5/TBCH1, is available as a
general-purpose I/O pin.
Channels 2 and 3 can be linked to form a buffered output compare
channel whose output appears on the PTF2/TBCH2 pin. The TIMB
channel registers of the linked pair alternately control the output.
Setting the MS2B bit in TIMB channel 2 status and control register
(TBSC2) links channel 2 and channel 3. The output compare value in the
TIMB channel 2 registers initially controls the output on the
PTF2/TBCH2 pin. Writing to the TIMB channel 3 registers enables the
TIMB channel 3 registers to synchronously control the output after the
TIMB overflows. At each subsequent overflow, the TIMB channel
registers (2 or 3) that control the output are the ones written to last.
TBSC2 controls and monitors the buffered output compare function, and
TIMB channel 3 status and control register (TBSC3) is unused. While the
MS2B bit is set, the channel 3 pin, PTF3/TBCH3, 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. Writing to the active
channel registers is the same as generating unbuffered output
compares.
Technical Data
202
MC68HC908AB32 — Rev. 1.1
Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
12.5.4 Pulse Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel,
the TIMB can generate a PWM signal. The value in the TIMB counter
modulo registers determines the period of the PWM signal. The channel
pin toggles when the counter reaches the value in the TIMB counter
modulo registers. The time between overflows is the period of the PWM
signal.
As Figure 12-3 shows, the output compare value in the TIMB channel
registers determines the pulse width of the PWM signal. The time
between overflow and output compare is the pulse width. Program the
TIMB to clear the channel pin on output compare if the state of the PWM
pulse is logic one. Program the TIMB to set the pin if the state of the
PWM pulse is logic zero.
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PULSE
WIDTH
TBCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 12-3PWM Period and Pulse Width
The value in the TIMB counter modulo registers and the selected
prescaler output determines the frequency of the PWM output. The
frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMB counter modulo registers produces a PWM
period of 256 times the internal bus clock period if the prescaler select
value is $000. See 12.10.1 TIMB Status and Control Register.
The value in the TIMB channel registers determines the pulse width of
the PWM output. The pulse width of an 8-bit PWM signal is variable in
256 increments. Writing $0080 (128) to the TIMB channel registers
produces a duty cycle of 128/256 or 50%.
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Technical Data
Timer Interface Module B (TIMB)
203
Timer Interface Module B (TIMB)
12.5.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as
described in 12.5.4 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 TIMB channel
registers.
An unsynchronized write to the TIMB channel registers to change a
pulse width value could cause incorrect operation for up to two PWM
periods. For example, writing a new value before the counter reaches
the old value but after the counter reaches the new value prevents any
compare during that PWM period. Also, using a TIMB overflow interrupt
routine to write a new, smaller pulse width value may cause the compare
to be missed. The TIMB may pass the new value before it is written.
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 channel x TIMB
overflow interrupts and write the new value in the TIMB overflow
interrupt routine. The TIMB overflow interrupt occurs at the end of
the current PWM period. Writing a larger value in an output
compare interrupt routine (at the end of the current pulse) could
cause two output compares to occur in the same PWM period.
In PWM signal generation, do not program the PWM channel to toggle
on output compare. Toggling on output compare prevents reliable 0%
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.
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Freescale Semiconductor
Timer Interface Module B (TIMB)
12.5.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose
output appears on the PTF4/TBCH0 pin. The TIMB channel registers of
the linked pair alternately control the pulse width of the output.
Setting the MS0B bit in TIMB channel 0 status and control register
(TBSC0) links channel 0 and channel 1. The TIMB channel 0 registers
initially control the pulse width on the PTF4/TBCH0 pin. Writing to the
TIMB channel 1 registers enables the TIMB channel 1 registers to
synchronously control the pulse width at the beginning of the next PWM
period. At each subsequent overflow, the TIMB channel registers (0 or
1) that control the pulse width are the ones written to last. TBSC0
controls and monitors the buffered PWM function, and TIMB channel 1
status and control register (TBSC1) is unused. While the MS0B bit is set,
the channel 1 pin, PTF5/TBCH1, is available as a general-purpose I/O
pin.
Channels 2 and 3 can be linked to form a buffered PWM channel whose
output appears on the PTF2/TBCH2 pin. The TIMB channel registers of
the linked pair alternately control the pulse width of the output.
Setting the MS2B bit in TIMB channel 2 status and control register
(TBSC2) links channel 2 and channel 3. The TIMB channel 2 registers
initially control the pulse width on the PTF2/TBCH2 pin. Writing to the
TIMB channel 3 registers enables the TIMB channel 3 registers to
synchronously control the pulse width at the beginning of the next PWM
period. At each subsequent overflow, the TIMB channel registers (2 or
3) that control the pulse width are the ones written to last. TBSC2
controls and monitors the buffered PWM function, and TIMB channel 3
status and control register (TBSC3) is unused. While the MS2B bit is set,
the channel 3 pin, PTF3/TBCH3, is available as a general-purpose I/O
pin.
NOTE:
In buffered PWM signal generation, do not write new pulse width values
to the currently active channel registers. Writing to the active channel
registers is the same as generating unbuffered PWM signals.
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Technical Data
Timer Interface Module B (TIMB)
205
Timer Interface Module B (TIMB)
12.5.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered
PWM signals, use the following initialization procedure:
1. In the TIMB status and control register (TBSC):
a. Stop the TIMB counter by setting the TIMB stop bit, TSTOP.
b. Reset the TIMB counter by setting the TIMB reset bit, TRST.
2. In the TIMB counter modulo registers (TBMODH:TBMODL), write
the value for the required PWM period.
3. In the TIMB channel x registers (TBCHxH:TBCHxL), write the
value for the required pulse width.
4. In TIMB channel x status and control register (TBSCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or
1:0 (for buffered output compare or PWM signals) to the
mode select bits, MSxB:MSxA. See Table 12-3.
a. Write 1 to the toggle-on-overflow bit, TOVx.
b. Write 1:0 (to clear output on compare) or 1:1 (to set output on
compare) to the edge/level select bits, ELSxB:ELSxA. The
output action on compare must force the output to the
complement of the pulse width level. See Table 12-3.
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 TIMB status control register (TBSC), clear the TIMB stop bit,
TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered
PWM operation. The TIMB channel 0 registers (TBCH0H:TBCH0L)
initially control the buffered PWM output. TIMB channel 0 status and
control register (TBSC0) controls and monitors the PWM signal from the
linked channels. MS0B takes priority over MS0A.
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Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
Setting MS2B links channels 2 and 3 and configures them for buffered
PWM operation. The TIMB channel 2 registers (TBCH2H:TBCH2L)
initially control the PWM output. TIMB channel 2 status and control
register (TBSC2) controls and monitors the PWM signal from the linked
channels. MS2B takes priority over MS2A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on
TIMB overflows. Subsequent output compares try to force the output to
a state it is already in and have no effect. The result is a 0% duty cycle
output.
Setting the channel x maximum duty cycle bit (CHxMAX) and clearing
the TOVx bit generates a 100% duty cycle output. See 12.10.4 TIMB
Channel Status and Control Registers.
12.6 Interrupts
The following TIMB sources can generate interrupt requests:
•
TIMB overflow flag (TOF) — The TOF bit is set when the TIMB
counter value rolls over to $0000 after matching the value in the
TIMB counter modulo registers. The TIMB overflow interrupt
enable bit, TOIE, enables TIMB overflow CPU interrupt requests.
TOF and TOIE are in the TIMB status and control register.
•
TIMB channel flags (CH3F–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 TIMB
channel x status and control register.
12.7 Low-Power Modes
The WAIT and STOP instructions puts the MCU in low-powerconsumption standby modes.
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Technical Data
Timer Interface Module B (TIMB)
207
Timer Interface Module B (TIMB)
12.7.1 Wait Mode
The TIMB remains active after the execution of a WAIT instruction. In
wait mode the TIMB registers are not accessible by the CPU. Any
enabled CPU interrupt request from the TIMB can bring the MCU out of
wait mode.
If TIMB functions are not required during wait mode, reduce power
consumption by stopping the TIMB before executing the WAIT
instruction.
12.7.2 Stop Mode
The TIMB is inactive after the execution of a STOP instruction. The
STOP instruction does not affect register conditions or the state of the
TIMB counter. TIMB operation resumes when the MCU exit stop mode
after an external interrupt.
12.8 TIMB During Break Interrupts
A break interrupt stops the TIMB 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 8.8.3 SIM Break Flag Control
Register.
To allow software to clear status bits during a break interrupt, write a
logic one 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 zero to the
BCFE bit. With BCFE at logic zero (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 zero. After the
break, doing the second step clears the status bit.
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Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
12.9 I/O Signals
Port F shares four pins with the TIMB and port D shares one.
PTD4/TBCLK is an external clock input to the TIMB prescaler. The four
TIMB channel I/O pins are PTF4/TBCH0, PTF5/TBCH1, PTF2/TBCH2,
and PTF3/TBCH3.
12.9.1 TIMB Clock Pin
PTD4/TBCLK is an external clock input that can be the clock source for
the TIMB counter instead of the prescaled internal bus clock. Select the
PTD4/TBCLK input by writing logic 1s to the three prescaler select bits,
PS[2:0]. See 12.10.1 TIMB Status and Control Register. The minimum
TBCLK pulse width, TBCLKLMIN or TBCLKHMIN, is:
1
------------------------------------- + t SU
bus frequency
The maximum TBCLK frequency is:
bus frequency ÷ 2
PTD4/TBCLK is available as a general-purpose I/O pin when not used
as the TIMB clock input. When the PTD4/TBCLK pin is the TIMB clock
input, it is an input regardless of the state of the DDRD6 bit in data
direction register D.
12.9.2 TIMB Channel I/O Pins
Each channel I/O pin is programmable independently as an input
capture pin or an output compare pin. PTF2/TBCH2 and PTF5/TBCH1
can be configured as buffered output compare or buffered PWM pins.
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Technical Data
Timer Interface Module B (TIMB)
209
Timer Interface Module B (TIMB)
12.10 I/O Registers
The following I/O registers control and monitor operation of the TIMB:
•
TIMB status and control register (TBSC)
•
TIMB counter registers (TBCNTH:TBCNTL)
•
TIMB counter modulo registers (TBMODH:TBMODL)
•
TIMB channel status and control registers (TBSC0, TBSC1,
TBSC2, and TBSC3)
•
TIMB channel registers (TBCH0H:TBCH0L, TBCH1H:TBCH1L,
TBCH2H:TBCH2L, and TBCH3H:TBCH3L)
12.10.1 TIMB Status and Control Register
The TIMB status and control register does the following:
•
Enables TIMB overflow interrupts
•
Flags TIMB overflows
•
Stops the TIMB counter
•
Resets the TIMB counter
•
Prescales the TIMB counter clock
Address:
$0040
Bit 7
Read:
TOF
Write:
0
Reset:
0
6
5
TOIE
TSTOP
0
1
4
3
0
0
TRST
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
= Unimplemented
Figure 12-4. TIMB Status and Control Register (TBSC)
Technical Data
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Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
TOF — TIMB Overflow Flag Bit
This read/write flag is set when the TIMB counter resets to $0000 after
reaching the modulo value programmed in the TIMB counter modulo
registers. Clear TOF by reading the TIMB status and control register
when TOF is set and then writing a logic zero to TOF. If another TIMB
overflow occurs before the clearing sequence is complete, then
writing logic zero 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 one to TOF has no effect.
1 = TIMB counter has reached modulo value
0 = TIMB counter has not reached modulo value
TOIE — TIMB Overflow Interrupt Enable Bit
This read/write bit enables TIMB overflow interrupts when the TOF bit
becomes set. Reset clears the TOIE bit.
1 = TIMB overflow interrupts enabled
0 = TIMB overflow interrupts disabled
TSTOP — TIMB Stop Bit
This read/write bit stops the TIMB counter. Counting resumes when
TSTOP is cleared. Reset sets the TSTOP bit, stopping the TIMB
counter until software clears the TSTOP bit.
1 = TIMB counter stopped
0 = TIMB counter active
NOTE:
Do not set the TSTOP bit before entering wait mode if the TIMB is
required to exit wait mode.
TRST — TIMB Reset Bit
Setting this write-only bit resets the TIMB counter and the TIMB
prescaler. Setting TRST has no effect on any other registers.
Counting resumes from $0000. TRST is cleared automatically after
the TIMB counter is reset and always reads as logic zero. Reset
clears the TRST bit.
1 = Prescaler and TIMB counter cleared
0 = No effect
NOTE:
Setting the TSTOP and TRST bits simultaneously stops the TIMB
counter at a value of $0000.
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Technical Data
Timer Interface Module B (TIMB)
211
Timer Interface Module B (TIMB)
PS[2:0] — Prescaler Select Bits
These read/write bits select either the PTD4/TBCLK pin or one of the
seven prescaler outputs as the input to the TIMB counter as
Table 12-2 shows. Reset clears the PS[2:0] bits.
Table 12-2. Prescaler Selection
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
PTD4/TBCLK
12.10.2 TIMB Counter Registers
The two read-only TIMB counter registers contain the high and low bytes
of the value in the TIMB counter. Reading the high byte (TBCNTH)
latches the contents of the low byte (TBCNTL) into a buffer. Subsequent
reads of TBCNTH do not affect the latched TBCNTL value until TBCNTL
is read. Reset clears the TIMB counter registers. Setting the TIMB reset
bit (TRST) also clears the TIMB counter registers.
NOTE:
If you read TBCNTH during a break interrupt, be sure to unlatch TBCNTL
by reading TBCNTL before exiting the break interrupt. Otherwise,
TBCNTL retains the value latched during the break.
Address:
Read:
$0041
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 12-5. TIMB Counter Register High (TBCNTH)
Technical Data
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Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
Address:
Read:
$0042
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 12-6. TIMB Counter Register Low (TBCNTL)
12.10.3 TIMB Counter Modulo Registers
The read/write TIMB modulo registers contain the modulo value for the
TIMB counter. When the TIMB counter reaches the modulo value, the
overflow flag (TOF) becomes set, and the TIMB counter resumes
counting from $0000 at the next clock. Writing to the high byte
(TBMODH) inhibits the TOF bit and overflow interrupts until the low byte
(TBMODL) is written. Reset sets the TIMB counter modulo registers.
Address:
Read:
Write:
Reset:
$0043
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
Figure 12-7. TIMB Counter Modulo Register High (TBMODH)
Address:
Read:
Write:
Reset:
$0044
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
Figure 12-8. TIMB Counter Modulo Register Low (TBMODL)
NOTE:
Reset the TIMB counter before writing to the TIMB counter modulo
registers.
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Technical Data
Timer Interface Module B (TIMB)
213
Timer Interface Module B (TIMB)
12.10.4 TIMB Channel Status and Control Registers
Each of the TIMB channel status and control registers does the
following:
•
Flags input captures and output compares
•
Enables input capture and output compare interrupts
•
Selects input capture, output compare, or PWM operation
•
Selects high, low, or toggling output on output compare
•
Selects rising edge, falling edge, or any edge as the active input
capture trigger
•
Selects output toggling on TIMB overflow
•
Selects 100% PWM duty cycle
•
Selects buffered or unbuffered output compare/PWM operation
Address:
$0045
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 12-9. TIMB Channel 0 Status and Control Register (TBSC0)
Address:
$0048
Bit 7
Read:
CH1F
Write:
0
Reset:
0
6
CH1IE
0
5
0
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
Figure 12-10. TIMB Channel 1 Status and Control Register (TBSC1)
Technical Data
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Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
Address:
$0032
Bit 7
Read:
CH2F
Write:
0
Reset:
0
6
5
4
3
2
1
Bit 0
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
Figure 12-11. TIMB Channel 2 Status and Control Register (TBSC2)
Address:
$0035
Bit 7
Read:
CH3F
Write:
0
Reset:
0
6
CH3IE
0
5
0
0
4
3
2
1
Bit 0
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
0
0
0
0
0
Figure 12-12. TIMB Channel 3 Status and Control Register (TBSC3)
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set
when an active edge occurs on the channel x pin. When channel x is
an output compare channel, CHxF is set when the value in the TIMB
counter registers matches the value in the TIMB channel x registers.
When TIM CPU interrupt requests are enabled (CHxIE = 1), clear
CHxF by reading TIMB channel x status and control register with
CHxF set and then writing a logic zero to CHxF. If another interrupt
request occurs before the clearing sequence is complete, then writing
logic zero 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 one to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIMB CPU interrupts on channel x.
Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
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Technical Data
Timer Interface Module B (TIMB)
215
Timer Interface Module B (TIMB)
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation.
MSxB exists only in the TIMB channel 0 and TIMB channel 2 status
and control registers.
Setting MS0B disables the channel 1 status and control register and
reverts TCH1B to general-purpose I/O.
Setting MS2B disables the channel 3 status and control register and
reverts TCH3B to general-purpose I/O.
Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture
operation or unbuffered output compare/PWM operation. See Table
12-3.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level
of the TBCHx pin. See Table 12-3. 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 TIMB status and control register
(TBSC).
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 the port I/O, and pin TBCHx is available as a general-purpose I/O
pin. Table 12-3 shows how ELSxB and ELSxA work. Reset clears the
ELSxB and ELSxA bits.
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Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
Table 12-3. Mode, Edge, and Level Selection
MSxB
MSxA
ELSxB
ELSxA
X
0
0
0
Mode
Output
Preset
NOTE:
X
1
0
0
0
0
0
1
0
0
1
0
0
0
1
1
0
1
0
1
0
1
1
0
0
1
1
1
1
X
0
1
1
X
1
0
1
X
1
1
Configuration
Pin under Port Control;
Initial Output Level High
Pin under Port Control;
Initial Output Level Low
Capture on Rising Edge Only
Input
Capture
Capture on Falling Edge Only
Capture on Rising or Falling Edge
Output
Compare
or PWM
Toggle Output on Compare
Clear Output on Compare
Set Output on Compare
Toggle Output on Compare
Buffered
Output
Clear Output on Compare
Compare or
Buffered
Set Output on Compare
PWM
Before enabling a TIMB channel register for input capture operation,
make sure that the TBCHx pin is stable for at least two bus clocks.
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit
controls the behavior of the channel x output when the TIMB counter
overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMB counter overflow.
0 = Channel x pin does not toggle on TIMB counter overflow.
NOTE:
When TOVx is set, a TIMB counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx bit is at logic zero, setting the CHxMAX bit forces the
duty cycle of buffered and unbuffered PWM signals to 100%. As
Figure 12-13 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.
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Technical Data
Timer Interface Module B (TIMB)
217
Timer Interface Module B (TIMB)
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
TBCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
Figure 12-13. CHxMAX Latency
12.10.5 TIMB Channel Registers
These read/write registers contain the captured TIMB counter value of
the input capture function or the output compare value of the output
compare function. The state of the TIMB channel registers after reset is
unknown.
In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the
TIMB channel x registers (TBCHxH) inhibits input captures until the low
byte (TBCHxL) is read.
In output compare mode (MSxB:MSxA ≠ 0:0), writing to the high byte of
the TIMB channel x registers (TBCHxH) inhibits output compares until
the low byte (TBCHxL) is written.
Address:
Read:
Write:
$0046
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 12-14. TIMB Channel 0 Register High (TBCH0H)
Address:
Read:
Write:
Reset:
$0047
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 12-15. TIMB Channel 0 Register Low (TBCH0L)
Technical Data
218
MC68HC908AB32 — Rev. 1.1
Timer Interface Module B (TIMB)
Freescale Semiconductor
Timer Interface Module B (TIMB)
Address:
Read:
Write:
$0049
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 12-16. TIMB Channel 1 Register High (TBCH1H)
Address:
Read:
Write:
$004A
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Reset:
Indeterminate after reset
Figure 12-17. TIMB Channel 1 Register Low (TBCH1L)
Address:
Read:
Write:
$0033
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 12-18. TIMB Channel 2 Register High (TBCH2H)
Address:
Read:
Write:
Reset:
$0034
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 12-19. TIMB Channel 2 Register Low (TBCH2L)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Timer Interface Module B (TIMB)
219
Timer Interface Module B (TIMB)
Address:
Read:
Write:
$0036
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
Reset:
Indeterminate after reset
Figure 12-20. TIMB Channel 3 Register High (TBCH3H)
Address:
Read:
Write:
Reset:
$0037
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 12-21. TIMB Channel 3 Register Low (TBCH3L)
Technical Data
220
MC68HC908AB32 — Rev. 1.1
Timer Interface Module B (TIMB)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 13. Programmable Interrupt Timer (PIT)
13.1 Contents
13.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
13.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
13.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .222
13.4.1 PIT Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . 223
13.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224
13.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
13.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .224
13.6
PIT During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 224
13.7 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
13.7.1 PIT Status and Control Register. . . . . . . . . . . . . . . . . . . . . 225
13.7.2 PIT Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227
13.7.3 PIT Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . 228
13.2 Introduction
This section describes the programmable interrupt timer (PIT), which is
a timer whose counter is clocked internally via software programmable
options. Figure 13-1 is a block diagram of the PIT.
MC68HC908AB32 — Rev. 1.1
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Technical Data
Programmable Interrupt Timer (PIT)
221
Programmable Interrupt Timer (PIT)
13.3 Features
Features of the PIT include the following:
•
Programmable PIT clock input
•
Free-running or modulo up-count operation
•
PIT counter stop and reset bits
13.4 Functional Description
Figure 13-1 shows the structure of the PIT. The central component of
the PIT is the 16-bit PIT counter that can operate as a free-running
counter or a modulo up-counter. The counter provides the timing
reference for the interrupt. The PIT counter modulo registers,
PMODH:PMODL, control the modulo value of the counter. Software can
read the counter value at any time without affecting the counting
sequence.
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
PSTOP
PPS2
PRST
PPS1
PPS0
16-BIT COUNTER
POF
POIE
16-BIT COMPARATOR
INTERRUPT
LOGIC
PMODH:PMODL
Figure 13-1. PIT Block Diagram
Technical Data
222
MC68HC908AB32 — Rev. 1.1
Programmable Interrupt Timer (PIT)
Freescale Semiconductor
Programmable Interrupt Timer (PIT)
Addr.
Register Name
Bit 7
6
5
POIE
PSTOP
4
3
0
0
2
1
Bit 0
PPS2
PPS1
PPS0
Read:
PIT Status and Control
Register Write:
(PSC)
Reset:
POF
0
0
1
0
0
0
0
0
Read:
PIT Counter Register High
$004C
Write:
(PCNTH)
Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Read:
PIT Counter Register Low
$004D
Write:
(PCNTL)
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
$004B
$004E
$004F
Read:
PIT Counter Modulo
Register High Write:
(PMODH)
Reset:
Read:
PIT Counter Modulo
Register Low Write:
(PMODL)
Reset:
0
PRST
= Unimplemented
Figure 13-2. PIT I/O Register Summary
13.4.1 PIT Counter Prescaler
The 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, PPS[2:0] in the status and control register select
the PIT clock source.
The value in the PIT counter modulo registers and the selected prescaler
output determines the frequency of the Periodic Interrupt. The PIT
overflow flag (POF) is set when the PIT counter value rolls over to $0000
after matching the value in the PIT counter modulo registers. The PIT
interrupt enable bit, POIE, enables PIT overflow CPU interrupt requests.
POF and POIE are in the PIT status and control register.
MC68HC908AB32 — Rev. 1.1
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Technical Data
Programmable Interrupt Timer (PIT)
223
Programmable Interrupt Timer (PIT)
13.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low-powerconsumption standby modes.
13.5.1 Wait Mode
The PIT remains active after the execution of a WAIT instruction. In wait
mode the PIT registers are not accessible by the CPU. Any enabled CPU
interrupt request from the PIT can bring the MCU out of wait mode.
If PIT functions are not required during wait mode, reduce power
consumption by stopping the PIT before executing the WAIT instruction.
13.5.2 Stop Mode
The PIT is inactive after the execution of a STOP instruction. The STOP
instruction does not affect register conditions or the state of the PIT
counter. PIT operation resumes when the MCU exits stop mode after an
external interrupt.
13.6 PIT During Break Interrupts
A break interrupt stops the PIT 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 8.8.3 SIM Break Flag Control
Register.
To allow software to clear status bits during a break interrupt, write a
logic one 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 zero to the
BCFE bit. With BCFE at logic zero (its default state), software can read
and write I/O registers during the break state without affecting status
Technical Data
224
MC68HC908AB32 — Rev. 1.1
Programmable Interrupt Timer (PIT)
Freescale Semiconductor
Programmable Interrupt Timer (PIT)
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 zero. After the
break, doing the second step clears the status bit.
13.7 I/O Registers
The following I/O registers control and monitor operation of the PIT:
•
PIT status and control register (PSC)
•
PIT counter registers (PCNTH:PCNTL)
•
PIT counter modulo registers (PMODH:PMODL)
13.7.1 PIT Status and Control Register
The PIT status and control register does the following:
•
Enables PIT interrupt
•
Flags PIT overflows
•
Stops the PIT counter
•
Resets the PIT counter
•
Prescales the PIT counter clock
Address:
$004B
Bit 7
Read:
POF
Write:
0
Reset:
0
6
5
POIE
PSTOP
0
1
4
3
0
0
PRST
0
0
2
1
Bit 0
PPS2
PPS1
PPS0
0
0
0
= Unimplemented
Figure 13-3. PIT Status and Control Register (PSC)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Programmable Interrupt Timer (PIT)
225
Programmable Interrupt Timer (PIT)
POF — PIT Overflow Flag Bit
This read/write flag is set when the PIT counter resets to $0000 after
reaching the modulo value programmed in the PIT counter modulo
registers. Clear POF by reading the PIT status and control register
when POF is set and then writing a logic zero to POF. If another PIT
overflow occurs before the clearing sequence is complete, then
writing logic zero to POF has no effect. Therefore, a POF interrupt
request cannot be lost due to inadvertent clearing of POF. Reset
clears the POF bit. Writing a logic one to POF has no effect.
1 = PIT counter has reached modulo value
0 = PIT counter has not reached modulo value
POIE — PIT Overflow Interrupt Enable Bit
This read/write bit enables PIT overflow interrupts when the POF bit
becomes set. Reset clears the POIE bit.
1 = PIT overflow interrupts enabled
0 = PIT overflow interrupts disabled
PSTOP — PIT Stop Bit
This read/write bit stops the PIT counter. Counting resumes when
PSTOP is cleared. Reset sets the PSTOP bit, stopping the PIT
counter until software clears the PSTOP bit.
1 = PIT counter stopped
0 = PIT counter active
NOTE:
Do not set the PSTOP bit before entering wait mode if the PIT is required
to exit wait mode.
PRST — PIT Reset Bit
Setting this write-only bit resets the PIT counter and the PIT prescaler.
Setting PRST has no effect on any other registers. Counting resumes
from $0000. PRST is cleared automatically after the PIT counter is
reset and always reads as logic zero. Reset clears the PRST bit.
1 = Prescaler and PIT counter cleared
0 = No effect
NOTE:
Setting the PSTOP and PRST bits simultaneously stops the PIT counter
at a value of $0000.
Technical Data
226
MC68HC908AB32 — Rev. 1.1
Programmable Interrupt Timer (PIT)
Freescale Semiconductor
Programmable Interrupt Timer (PIT)
PPS[2:0] — PIT Prescaler Select Bits
These read/write bits select one of the seven prescaler outputs as the
input to the PIT counter as Table 13-1 shows. Reset clears the
PPS[2:0] bits.
Table 13-1. PIT Prescaler Selection
PPS2
PPS1
PPS0
PIT 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
Internal Bus Clock ÷ 64
13.7.2 PIT Counter Registers
The two read-only PIT counter registers contain the high and low bytes
of the value in the PIT counter. Reading the high byte (PCNTH) latches
the contents of the low byte (PCNTL) into a buffer. Subsequent reads of
PCNTH do not affect the latched PCNTL value until PCNTL is read.
Reset clears the PIT counter registers. Setting the PIT reset bit (PRST)
also clears the PIT counter registers.
NOTE:
If you read PCNTH during a break interrupt, be sure to unlatch PCNTL
by reading PCNTL before exiting the break interrupt. Otherwise, PCNTL
retains the value latched during the break.
Address:
Read:
$004C
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 13-4. PIT Counter Register High (PCNTH)
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Programmable Interrupt Timer (PIT)
227
Programmable Interrupt Timer (PIT)
Address:
Read:
$004D
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 13-5. PIT Counter Register Low (PCNTL)
13.7.3 PIT Counter Modulo Registers
The read/write PIT modulo registers contain the modulo value for the PIT
counter. When the PIT counter reaches the modulo value, the overflow
flag (POF) becomes set, and the PIT counter resumes counting from
$0000 at the next clock. Writing to the high byte (PMODH) inhibits the
POF bit and overflow interrupts until the low byte (PMODL) is written.
Reset sets the PIT counter modulo registers.
Address:
Read:
Write:
Reset:
$004E
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
Figure 13-6. PIT Counter Modulo Register High (PMODH)
Address:
Read:
Write:
Reset:
$004F
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
Figure 13-7. PIT Counter Modulo Register Low (PMODL)
NOTE:
Reset the PIT counter before writing to the PIT counter modulo registers.
Technical Data
228
MC68HC908AB32 — Rev. 1.1
Programmable Interrupt Timer (PIT)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 14. Analog-to-Digital Converter (ADC)
14.1 Contents
14.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
14.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230
14.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .231
14.4.1 ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
14.4.2 Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .232
14.4.3 Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
14.4.4 Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
14.4.5 Accuracy and Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
14.5
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233
14.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
14.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233
14.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .233
14.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 233
14.7.1 ADC Analog Power Pin (VDDAREF). . . . . . . . . . . . . . . . . . . 234
14.7.2 ADC Analog Ground Pin (AVSS/VREFL) . . . . . . . . . . . . . . . 234
14.7.3 ADC Voltage Reference High Pin (VREFH). . . . . . . . . . . . . 234
14.7.4 ADC Voltage In (VADIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
14.8 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
14.8.1 ADC Status and Control Register (ADSCR). . . . . . . . . . . . 235
14.8.2 ADC Data Register (ADR) . . . . . . . . . . . . . . . . . . . . . . . . . 237
14.8.3 ADC Clock Register (ADCLK) . . . . . . . . . . . . . . . . . . . . . . 237
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Analog-to-Digital Converter (ADC)
229
Analog-to-Digital Converter (ADC)
14.2 Introduction
This section describes the 8-bit analog-to-digital converter (ADC).
14.3 Features
Features of the ADC module include:
Addr.
Eight channels with multiplexed input
•
Linear successive approximation with monotonicity
•
8-bit resolution
•
Single or continuous conversion
•
Conversion complete flag or conversion complete interrupt
•
Selectable ADC clock
Register Name
$0038 ADC Status and Control
Register
(ADSCR)
$0039
•
ADC Data Register
(ADR)
Bit 7
6
5
4
3
2
1
Bit 0
COCO
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
Reset:
0
0
0
1
1
1
1
1
Read:
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
0
0
0
0
0
0
0
0
ADIV2
ADIV1
ADIV0
ADICLK
0
0
0
0
0
0
0
0
0
0
0
0
Read:
Write:
Write:
Reset:
$003A
Read:
ADC Clock Register
(ADCLK)
Write:
Reset:
= Unimplemented
Figure 14-1. ADC Register Summary
Technical Data
230
MC68HC908AB32 — Rev. 1.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
14.4 Functional Description
The ADC provides eight pins for sampling external sources at pins
PTB7/ATD7–PTB0/ATD0. 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
register-based analog-to-digital converter. When the conversion is
completed, ADC places the result in the ADC data register and sets a
flag or generates an interrupt. (See Figure 14-2.)
INTERNAL
DATA BUS
READ DDRBx
WRITE DDRBx
DISABLE
DDRBx
RESET
WRITE PTBx
PTBx
PTBx
ADC CHANNEL x
READ PTBx
DISABLE
ADC DATA REGISTER
CONVERSION
INTERRUPT COMPLETE
LOGIC
AIEN
ADC I/P CHANNELS
ADC
VOLTAGE IN
(VADIN)
ADC
CHANNEL
SELECT
ADCH[4:0]
ADC CLOCK
COCO
CGMXCLK
BUS CLOCK
CLOCK
GENERATOR
ADIV[2:0]
ADICLK
Figure 14-2. ADC Block Diagram
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Analog-to-Digital Converter (ADC)
231
Analog-to-Digital Converter (ADC)
14.4.1 ADC Port I/O Pins
PTB7/ATD7–PTB0/ATD0 are general-purpose I/O (input/output) pins
that share with the ADC channels. The channel select bits define which
ADC channel/port pin will be used as the input signal. The ADC
overrides the port 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 register or
DDR will not have any affect on the port pin that is selected by the ADC.
Read of a port pin in use by the ADC will return a logic 0.
14.4.2 Voltage Conversion
When the input voltage to the ADC equals VREFH, the ADC converts the
signal to $FF (full scale). If the input voltage equals VREFL, the ADC
converts it to $00. Input voltages between VREFH and VREFL are a
straight-line linear conversion.
14.4.3 Conversion Time
Conversion starts after a write to the ADSCR. One conversion will take
between 16 and 17 ADC clock cycles. The ADIVx and ADICLK bits
should be set to provide a 1-MHz ADC clock frequency.
Conversion time = 16 to 17 ADC cycles
ADC frequency
Number of bus cycles = conversion time × bus frequency
14.4.4 Conversion
In continuous conversion mode, the ADC data register will be filled with
new data after each conversion. Data from the previous conversion will
be overwritten whether that data has been read or not. Conversions will
continue until the ADCO bit is cleared. The COCO bit is set after the first
conversion and will stay set until the next write of the ADC status and
control register or the next read of the ADC data register.
In single conversion mode, conversion begins with a write to the
ADSCR. Only one conversion occurs between writes to the ADSCR.
Technical Data
232
MC68HC908AB32 — Rev. 1.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
14.4.5 Accuracy and Precision
The conversion process is monotonic and has no missing codes.
14.5 Interrupts
When the AIEN bit is set, the ADC module is capable of generating CPU
interrupts after each ADC conversion. A CPU interrupt is generated if the
COCO bit is at logic 0. The COCO bit is not used as a conversion
complete flag when interrupts are enabled.
14.6 Low-Power Modes
The WAIT and STOP instruction can put the MCU in low powerconsumption standby modes.
14.6.1 Wait Mode
The ADC continues normal operation during wait mode. Any enabled
CPU interrupt request from the ADC can bring the MCU out of wait
mode. If the ADC is not required to bring the MCU out of wait mode,
power down the ADC by setting ADCH[4:0] bits in the ADC status and
control register before executing the WAIT instruction.
14.6.2 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 after an external interrupt. Allow one conversion
cycle to stabilize the analog circuitry.
14.7 I/O Signals
The ADC module has eight pins shared with port B,
PTB7/ATD7–PTB0/ATD0.
MC68HC908AB32 — Rev. 1.1
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Technical Data
Analog-to-Digital Converter (ADC)
233
Analog-to-Digital Converter (ADC)
14.7.1 ADC Analog Power Pin (VDDAREF)
The ADC analog portion uses VDDAREF as its power pin. Connect the
VDDAREF pin to the same voltage potential as VDD. External filtering may
be necessary to ensure clean VDDAREF for good results.
NOTE:
For maximum noise immunity, route VDDAREF carefully and place
bypass capacitors as close as possible to the package.
14.7.2 ADC Analog Ground Pin (AVSS/VREFL)
The ADC analog portion uses AVSS/VREFL as its ground pin. Connect the
AVSS/VREFL pin to the same voltage potential as VSS.
NOTE:
Route AVSS/VREFL cleanly to avoid any offset errors.
14.7.3 ADC Voltage Reference High Pin (VREFH)
VREFH is the reference voltage for the ADC.
14.7.4 ADC Voltage In (VADIN)
VADIN is the input voltage signal from one of the eight ADC channels to
the ADC module.
14.8 I/O Registers
These I/O registers control and monitor ADC operation:
•
ADC status and control register (ADSCR)
•
ADC data register (ADR)
•
ADC clock register (ADCLK)
Technical Data
234
MC68HC908AB32 — Rev. 1.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
14.8.1 ADC Status and Control Register (ADSCR)
Function of the ADC status and control register is described here.
Address:
Read:
Write:
Reset:
$0038
Bit 7
6
5
4
3
2
1
Bit 0
COCO
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
0
0
1
1
1
1
1
Figure 14-3. ADC Status and Control Register (ADSCR)
COCO — Conversions Complete
When the AIEN bit is a logic 0, the COCO is a read-only bit which is
set each time a conversion is completed except in the continuous
conversion mode where it is set after the first conversion. This bit is
cleared whenever the ADSCR is written or whenever the ADR is read.
If the AIEN bit is a logic 1, the COCO becomes a read/write bit, which
should be cleared to logic 0 for CPU to service the ADC interrupt
request. 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 is
read or the status/control register is written.Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the
ADR register at the end of each conversion. Only one conversion is
completed between writes to the ADSCR when this bit is cleared.
Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Analog-to-Digital Converter (ADC)
235
Analog-to-Digital Converter (ADC)
ADCH[4:0] — ADC Channel Select Bits
ADCH[4:0] form a 5-bit field which is used to select one of the eight
ADC channels, ATD7–ATD0. The channels are detailed in
Table 14-1. Care should be taken when using a port pin as both an
analog and digital input simultaneously to prevent switching noise
from corrupting the analog signal.
The ADC subsystem is turned off when the channel select bits are all
set to 1. This feature allows for reduced power consumption for the
MCU when the ADC is not being used.
NOTE:
Recovery from the disabled state requires one conversion cycle to
stabilize.
The voltage levels supplied from internal reference nodes, as specified
in Table 14-1, are used to verify the operation of the ADC converter both
in production test and for user applications.
Table 14-1. Mux Channel Select
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
Input Select
0
0
0
0
0
PTB0/ATD0
0
0
0
0
1
PTB1/ATD1
0
0
0
1
0
PTB2/ATD2
0
0
0
1
1
PTB3/ATD3
0
0
1
0
0
PTB4/ATD4
0
0
1
0
1
PTB5/ATD5
0
0
1
1
0
PTB6/ATD6
0
0
1
1
1
PTB7/ATD7
0
1
0
0
0
↓
↓
↓
↓
↓
1
1
1
0
0
1
1
1
0
1
VREFH
1
1
1
1
0
VREFL
1
1
1
1
1
ADC power off
Reserved
NOTE: If any unused channels are selected, the resulting ADC conversion will be unknown
or reserved.
Technical Data
236
MC68HC908AB32 — Rev. 1.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Analog-to-Digital Converter (ADC)
14.8.2 ADC Data Register (ADR)
One 8-bit result register, ADC data register (ADR), is provided. This
register is updated each time an ADC conversion completes.
Address:
Read:
$0039
Bit 7
6
5
4
3
2
1
Bit 0
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 14-4. ADC Data Register (ADR)
14.8.3 ADC Clock Register (ADCLK)
The ADC clock register (ADCLK) selects the clock frequency for the
ADC.
Address:
Read:
Write:
Reset:
$003A
Bit 7
6
5
4
ADIV2
ADIV1
ADIV0
ADICLK
0
0
0
0
3
2
1
Bit 0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 14-5. ADC Clock Register (ADCLK)
ADIV[2:0] — ADC Clock Prescaler Bits
ADIV[2:0] form a 3-bit field which selects the divide ratio used by the
ADC to generate the internal ADC clock. Table 14-2 shows the
available clock configurations. The ADC clock should be set to
approximately 1 MHz.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Analog-to-Digital Converter (ADC)
237
Analog-to-Digital Converter (ADC)
Table 14-2. 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 the bus clock or CGMXCLK as the input clock
source to generate the internal ADC clock. Reset selects CGMXCLK
as the ADC clock source.
If the external clock (CGMXCLK) is equal to or greater than 1 MHz,
CGMXCLK can be used as the clock source for the ADC. If
CGMXCLK is less than 1 MHz, use the PLL-generated bus clock as
the clock source. As long as the internal ADC clock is at
approximately 1 MHz, correct operation can be guaranteed.
1 = Internal bus clock
0 = External clock (CGMXCLK)
ADC input clock frequency
----------------------------------------------------------------------- = 1MHz
ADIV[2:0]
Technical Data
238
MC68HC908AB32 — Rev. 1.1
Analog-to-Digital Converter (ADC)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 15. Serial Communications Interface Module
(SCI)
15.1 Contents
15.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
15.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
15.4
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 242
15.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .242
15.5.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
15.5.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245
15.5.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
15.5.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . 247
15.5.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
15.5.2.4
Idle Characters. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
15.5.2.5
Inversion of Transmitted Output. . . . . . . . . . . . . . . . . . . 249
15.5.2.6
Transmitter Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . .249
15.5.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
15.5.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
15.5.3.2
Character Reception . . . . . . . . . . . . . . . . . . . . . . . . . . . 250
15.5.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 252
15.5.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 254
15.5.3.5
Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . .254
15.5.3.6
Receiver Wakeup. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
15.5.3.7
Receiver Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
15.5.3.8
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 258
15.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
15.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
15.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .259
15.7
SCI During Break Module Interrupts. . . . . . . . . . . . . . . . . . . .260
15.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 260
15.8.1 PTE0/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . 260
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Serial Communications Interface Module (SCI)
239
Serial Communications Interface
15.8.2
PTE1/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . 260
15.9 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
15.9.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
15.9.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
15.9.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
15.9.4 SCI Status Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269
15.9.5 SCI Status Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 273
15.9.6 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
15.9.7 SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . .275
15.2 Introduction
This section describes the serial communications interface (SCI)
module, which allows high-speed asynchronous communications with
peripheral devices and other MCUs.
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.
15.3 Features
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
Technical Data
240
MC68HC908AB32 — Rev. 1.1
Serial Communications Interface Module (SCI)
Freescale Semiconductor
Serial Communications Interface Module (SCI)
•
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
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Serial Communications Interface Module (SCI)
241
Serial Communications Interface
15.4 Pin Name Conventions
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 15-1 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 15-1. Pin Name Conventions
Generic Pin Names:
RxD
TxD
Full Pin Names:
PTE1/RxD
PTE0/TxD
15.5 Functional Description
Figure 15-1 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.
Technical Data
242
MC68HC908AB32 — Rev. 1.1
Serial Communications Interface Module (SCI)
Freescale Semiconductor
Serial Communications Interface Module (SCI)
INTERNAL BUS
SCI DATA
REGISTER
ERROR
INTERRUPT
CONTROL
RECEIVER
INTERRUPT
CONTROL
DMA
INTERRUPT
CONTROL
RECEIVE
SHIFT REGISTER
PTE1/RxD
TRANSMITTER
INTERRUPT
CONTROL
SCI DATA
REGISTER
TRANSMIT
SHIFT REGISTER
PTE0/TxD
TXINV
SCTIE
R8
TCIE
T8
SCRIE
ILIE
R
TE
SCTE
RE
R
TC
RWU
SBK
SCRF
OR
ORIE
IDLE
NF
NEIE
FE
FEIE
PE
PEIE
LOOPS
LOOPS
FLAG
CONTROL
RECEIVE
CONTROL
WAKEUP
CONTROL
ENSCI
ENSCI
TRANSMIT
CONTROL
BKF
M
RPF
WAKE
ILTY
CGMXCLK
÷4
PRESCALER
BAUD
DIVIDER
÷ 16
PEN
PTY
DATA SELECTION
CONTROL
Figure 15-1. SCI Module Block Diagram
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Serial Communications Interface Module (SCI)
243
Serial Communications Interface
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
R
R
ORIE
NEIE
FEIE
PEIE
Read:
$0013
LOOPS
SCI Control Register 1
Write:
(SCC1)
Reset:
0
Read:
$0014
$0015
SCI Control Register 2
Write:
(SCC2)
Reset:
Read:
R8
SCI Control Register 3
Write:
(SCC3)
Reset:
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:
$0016
SCI Status Register 1
Write:
(SCS1)
Reset:
Read:
$0017
$0018
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:
Unaffected by reset
Read:
$0019
SCI Baud Rate Register
Write:
(SCBR)
Reset:
0
0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
= Unimplemented
R = Reserved
U = Unaffected
Figure 15-2. SCI I/O Register Summary
Technical Data
244
MC68HC908AB32 — Rev. 1.1
Serial Communications Interface Module (SCI)
Freescale Semiconductor
Serial Communications Interface Module (SCI)
15.5.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format
illustrated in Figure 15-3.
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
START
BIT
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
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 15-3. SCI Data Formats
15.5.2 Transmitter
Figure 15-4 shows the structure of the SCI transmitter.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Serial Communications Interface Module (SCI)
245
Serial Communications Interface
INTERNAL BUS
÷ 16
SCI DATA REGISTER
SCP1
11-BIT
TRANSMIT
SHIFT REGISTER
STOP
SCP0
SCR1
H
SCR2
7
6
5
4
3
2
1
0
L
PTE0/TxD
MSB
TXINV
PEN
PTY
PARITY
GENERATION
T8
R
R
SCTIE
SCTE
R
SCTE
SCTIE
TC
TCIE
BREAK
ALL 0s
M
LOAD FROM SCDR
TRANSMITTER DMA SERVICE REQUEST
TRANSMITTER CPU INTERRUPT REQUEST
SCR0
8
START
BAUD
DIVIDER
PREAMBLE
ALL 1s
PRESCALER
÷4
SHIFT ENABLE
CGMXCLK
TRANSMITTER
CONTROL LOGIC
SCTE
SBK
LOOPS
SCTIE
ENSCI
TC
TE
TCIE
Figure 15-4. SCI Transmitter
Technical Data
246
MC68HC908AB32 — Rev. 1.1
Serial Communications Interface Module (SCI)
Freescale Semiconductor
Serial Communications Interface Module (SCI)
15.5.2.1 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).
15.5.2.2 Character Transmission
During an SCI transmission, the transmit shift register shifts a character
out to the PTE0/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
PTE0/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 E pins.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Serial Communications Interface Module (SCI)
247
Serial Communications Interface
15.5.2.3 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
15.5.2.4 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 PTE0/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.
Technical Data
248
MC68HC908AB32 — Rev. 1.1
Serial Communications Interface Module (SCI)
Freescale Semiconductor
Serial Communications Interface Module (SCI)
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.
15.5.2.5 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 15.9.1 SCI Control Register 1.)
15.5.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the SCI
transmitter:
•
SCI transmitter empty (SCTE) — The SCTE bit in SCS1 indicates
that the SCDR has transferred a character to the transmit shift
register. SCTE can generate a transmitter CPU interrupt request.
Setting the SCI transmit interrupt enable bit, SCTIE, in SCC2
enables the SCTE bit to generate transmitter CPU interrupt
requests.
•
Transmission complete (TC) — The TC bit in SCS1 indicates that
the transmit shift register and the SCDR are empty and that no
break or idle character has been generated. The transmission
complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to
generate transmitter CPU interrupt requests.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Serial Communications Interface Module (SCI)
249
Serial Communications Interface
15.5.3 Receiver
Figure 15-5 shows the structure of the SCI receiver.
15.5.3.1 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).
15.5.3.2 Character Reception
During an SCI reception, the receive shift register shifts characters in
from the PTE1/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.
Technical Data
250
MC68HC908AB32 — Rev. 1.1
Serial Communications Interface Module (SCI)
Freescale Semiconductor
Serial Communications Interface Module (SCI)
INTERNAL BUS
SCR1
SCR2
SCP0
SCR0
BAUD
DIVIDER
÷ 16
DATA
RECOVERY
PTE1/RxD
CPU INTERRUPT REQUEST
8
7
6
5
M
WAKE
ILTY
PEN
PTY
4
3
2
1
0
L
ALL 0s
RPF
ERROR CPU INTERRUPT REQUEST
DMA SERVICE REQUEST
H
ALL 1s
BKF
11-BIT
RECEIVE SHIFT REGISTER
STOP
PRESCALER
MSB
÷4
CGMXCLK
SCI DATA REGISTER
START
SCP1
SCRF
WAKEUP
LOGIC
PARITY
CHECKING
IDLE
ILIE
R
SCRF
SCRIE
R
SCRF
SCRIE
R
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
RWU
IDLE
R8
ILIE
SCRIE
R
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
Figure 15-5. SCI Receiver Block Diagram
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Serial Communications Interface
15.5.3.3 Data Sampling
The receiver samples the PTE1/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 15-6):
•
After every start bit
•
After the receiver detects a data bit change from logic 1 to logic 0
(after the majority of data bit samples at RT8, RT9, and RT10
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
START BIT
VERIFICATION
DATA
SAMPLING
RT8
START BIT
QUALIFICATION
SAMPLES
RT3
PTE1/RxD
RT4
RT3
RT2
RT1
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT7
RT6
RT5
RT4
RT2
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT CLOCK
STATE
RT1
RT
CLOCK
RT CLOCK
RESET
Figure 15-6. Receiver Data Sampling
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Serial Communications Interface Module (SCI)
To verify the start bit and to detect noise, data recovery logic takes
samples at RT3, RT5, and RT7. Table 15-2 summarizes the results of
the start bit verification samples.
Table 15-2. 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 15-3 summarizes the
results of the data bit samples.
Table 15-3. 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
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Serial Communications Interface
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 15-4 summarizes the results of the stop bit
samples.
Table 15-4. 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
15.5.3.4 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.
15.5.3.5 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
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Serial Communications Interface Module (SCI)
tolerance is much more than the degree of misalignment that is likely to
occur.
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
Figure 15-7 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.
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
STOP
RT5
RT4
RT3
RT2
RECEIVER
RT CLOCK
RT1
MSB
DATA
SAMPLES
Figure 15-7. 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 15-7, 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.
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Serial Communications Interface
With the misaligned character shown in Figure 15-7, 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.
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
Figure 15-8 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.
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
IDLE OR NEXT CHARACTER
RT6
RT5
RT4
RT3
RT2
RECEIVER
RT CLOCK
RT1
STOP
DATA
SAMPLES
Figure 15-8. 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 15-8, 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
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Serial Communications Interface Module (SCI)
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 15-8, 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.
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
15.5.3.6 Receiver Wakeup
So that the MCU can ignore transmissions intended only for other
receivers in multiple-receiver systems, the receiver can be put into a
standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the
receiver into a standby state during which receiver interrupts are
disabled.
Depending on the state of the WAKE bit in SCC1, either of two
conditions on the PTE1/RxD pin can bring the receiver out of the standby
state:
•
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 PTE1/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
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Serial Communications Interface
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.
NOTE:
With the WAKE bit clear, setting the RWU bit after the RxD pin has been
idle may cause the receiver to wake up immediately.
15.5.3.7 Receiver Interrupts
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 PTE1/RxD pin. The idle
line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to
generate CPU interrupt requests.
15.5.3.8 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.
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Serial Communications Interface Module (SCI)
•
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.
15.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
15.6.1 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 8.7 Low-Power Modes for information on exiting wait mode.
15.6.2 Stop Mode
The SCI module is inactive after the execution of a STOP instruction,
and thus the SCI cannot cause an interrupt to exit stop mode. 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 8.7 Low-Power Modes for information on exiting stop mode.
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Serial Communications Interface
15.7 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.
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.
15.8 I/O Signals
Port E shares two of its pins with the SCI module. The two SCI I/O pins
are:
•
PTE0/TxD — Transmit data
•
PTE1/RxD — Receive data
15.8.1 PTE0/TxD (Transmit Data)
The PTE0/TxD pin is the serial data output from the SCI transmitter. The
SCI shares the PTE0/TxD pin with port E. When the SCI is enabled, the
PTE0/TxD pin is an output regardless of the state of the DDRE2 bit in
data direction register E (DDRE).
15.8.2 PTE1/RxD (Receive Data)
The PTE1/RxD pin is the serial data input to the SCI receiver. The SCI
shares the PTE1/RxD pin with port E. When the SCI is enabled, the
PTE1/RxD pin is an input regardless of the state of the DDRE1 bit in data
direction register E (DDRE).
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Serial Communications Interface Module (SCI)
15.9 I/O Registers
These I/O registers control and monitor SCI operation:
•
SCI control register 1 (SCC1)
•
SCI control register 2 (SCC2)
•
SCI control register 3 (SCC3)
•
SCI status register 1 (SCS1)
•
SCI status register 2 (SCS2)
•
SCI data register (SCDR)
•
SCI baud rate register (SCBR)
15.9.1 SCI Control Register 1
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
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Address:
Read:
Write:
Reset:
$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
Figure 15-9. SCI Control Register 1 (SCC1)
LOOPS — Loop Mode Select Bit
This read/write bit enables loop mode operation. In loop mode the
PTE1/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 Module (SCI)
M — Mode (Character Length) Bit
This read/write bit determines whether SCI characters are eight or
nine bits long. (See Table 15-5.) 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
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 PTE1/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 15-5.)
When enabled, the parity function inserts a parity bit in the most
significant bit position. (See Figure 15-3.) Reset clears the PEN bit.
1 = Parity function enabled
0 = Parity function disabled
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Serial Communications Interface
PTY — Parity Bit
This read/write bit determines whether the SCI generates and checks
for odd parity or even parity. (See Table 15-5.) Reset clears the PTY
bit.
1 = Odd parity
0 = Even parity
NOTE:
Changing the PTY bit in the middle of a transmission or reception can
generate a parity error.
Table 15-5. Character Format Selection
Control Bits
Character Format
M
PEN and
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
15.9.2 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
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Serial Communications Interface Module (SCI)
•
Enables the transmitter
•
Enables the receiver
•
Enables SCI wakeup
•
Transmits SCI break characters
Address:
Read:
Write:
Reset:
$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
Figure 15-10. SCI Control Register 2 (SCC2)
SCTIE — SCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate SCI transmitter
CPU interrupt requests. 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
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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
PTE0/TxD pin. If software clears the TE bit, the transmitter completes
any transmission in progress before the PTE0/TxD returns to the idle
condition (logic 1). Clearing and then setting TE during a transmission
queues an idle character to be sent after the character currently being
transmitted. Reset clears the TE bit.
1 = Transmitter enabled
0 = Transmitter disabled
NOTE:
Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is
clear. ENSCI is in SCI control register 1.
RE — Receiver Enable Bit
Setting this read/write bit enables the receiver. Clearing the RE bit
disables the receiver but does not affect receiver interrupt flag bits.
Reset clears the RE bit.
1 = Receiver enabled
0 = Receiver disabled
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
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Serial Communications Interface Module (SCI)
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.
15.9.3 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
– Noise error interrupts
– Framing error interrupts
•
Parity error interrupts
Address:
$0015
Bit 7
Read:
R8
Write:
Reset:
U
6
5
4
3
2
1
Bit 0
T8
R
R
ORIE
NEIE
FEIE
PEIE
U
0
0
0
0
0
0
= Unimplemented
R = Reserved
U = Unaffected
Figure 15-11. SCI Control Register 3 (SCC3)
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Serial Communications Interface
R8 — Received Bit 8
When the SCI is receiving 9-bit characters, R8 is the read-only ninth
bit (bit 8) of the received character. R8 is received at the same time
that the SCDR receives the other 8 bits.
When the SCI is receiving 8-bit characters, R8 is a copy of the eighth
bit (bit 7). Reset has no effect on the R8 bit.
T8 — Transmitted Bit 8
When the SCI is transmitting 9-bit characters, T8 is the read/write
ninth bit (bit 8) of the transmitted character. T8 is loaded into the
transmit shift register at the same time that the SCDR is loaded into
the transmit shift register. Reset has no effect on the T8 bit.
ORIE — Receiver Overrun Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests
generated by the receiver overrun bit, OR.
1 = SCI error CPU interrupt requests from OR bit enabled
0 = SCI error CPU interrupt requests from OR bit disabled
NEIE — Receiver Noise Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests
generated by the noise error bit, NE. Reset clears NEIE.
1 = SCI error CPU interrupt requests from NE bit enabled
0 = SCI error CPU interrupt requests from NE bit disabled
FEIE — Receiver Framing Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests
generated by the framing error bit, FE. Reset clears FEIE.
1 = SCI error CPU interrupt requests from FE bit enabled
0 = SCI error CPU interrupt requests from FE bit disabled
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables SCI receiver CPU interrupt
requests generated by the parity error bit, PE. (See 15.9.4 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
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Serial Communications Interface Module (SCI)
15.9.4 SCI Status Register 1
SCI status register 1 (SCS1) contains flags to signal these conditions:
•
Transfer of SCDR data to transmit shift register complete
•
Transmission complete
•
Transfer of receive shift register data to SCDR complete
•
Receiver input idle
•
Receiver overrun
•
Noisy data
•
Framing error
•
Parity error
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 15-12. 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
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
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Serial Communications Interface
TC — Transmission Complete Bit
This read-only bit is set when the SCTE bit is set, and no data,
preamble, or break character is being transmitted. TC generates an
SCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also
set. TC is 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 error CPU
interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE bit
by reading SCS1 with IDLE set and then reading the SCDR. After the
receiver is enabled, it must receive a valid character that sets the
SCRF bit before an idle condition can set the IDLE bit. Also, after the
IDLE bit has been cleared, a valid character must again set the SCRF
bit before an idle condition can set the IDLE bit. Reset clears the IDLE
bit.
1 = Receiver input idle
0 = Receiver input active (or idle since the IDLE bit was cleared)
OR — Receiver Overrun Bit
This clearable, read-only bit is set when software fails to read the
SCDR before the receive shift register receives the next character.
The OR bit generates an SCI error CPU interrupt request if the ORIE
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Serial Communications Interface Module (SCI)
bit in SCC3 is also set. The data in the shift register is lost, but the data
already in the SCDR is not affected. Clear the OR bit by reading SCS1
with OR set and then reading the SCDR. Reset clears the OR bit.
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
Software latency may allow an overrun to occur between reads of
SCS1 and SCDR in the flag-clearing sequence. Figure 15-13 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
PTE1/RxD pin. NF generates an NF CPU interrupt request if the NEIE
bit in SCC3 is also set. Clear the NF bit by reading SCS1 and then
reading the SCDR. Reset clears the NF bit.
1 = Noise detected
0 = No noise detected
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
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BYTE 1
BYTE 2
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
NORMAL FLAG CLEARING SEQUENCE
BYTE 3
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCDR
BYTE 1
READ SCDR
BYTE 2
READ SCDR
BYTE 3
BYTE 1
BYTE 2
SCRF = 0
OR = 0
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 1
SCRF = 1
OR = 1
DELAYED FLAG CLEARING SEQUENCE
BYTE 3
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 1
READ SCDR
BYTE 3
Figure 15-13. 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 a PE CPU interrupt request if the
PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with
PE set and then reading the SCDR. Reset clears the PE bit.
1 = Parity error detected
0 = No parity error detected
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Serial Communications Interface Module (SCI)
15.9.5 SCI Status Register 2
SCI status register 2 contains flags to signal the following conditions:
•
Break character detected
•
Incoming data
Address:
$0017
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 15-14. 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 PTE1/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 PTE1/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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15.9.6 SCI Data Register
The SCI data register (SCDR) is the buffer between the internal data bus
and the receive and transmit shift registers. Reset has no effect on data
in the SCI data register.
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 15-15. SCI Data Register (SCDR)
R7/T7–R0/T0 — Receive/Transmit Data Bits
Reading address $0018 accesses the read-only received data bits,
R7:R0. Writing to address $0018 writes the data to be transmitted,
T7:T0. Reset has no effect on the SCI data register.
NOTE:
Do not use read/modify/write instructions on the SCI data register.
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Serial Communications Interface Module (SCI)
15.9.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver
and the transmitter.
Address:
$0019
Bit 7
6
Read:
Write:
Reset:
0
5
4
3
2
1
Bit 0
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
R
= Reserved
0
= Unimplemented
Figure 15-16. 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 15-6. Reset clears SCP1 and SCP0.
Table 15-6. 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 15-7. Reset clears SCR2–SCR0.
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Serial Communications Interface
Table 15-7. 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 = CGMXCLK
(See 9.5.6 Crystal Output Frequency Signal (CGMXCLK).)
PD = prescaler divisor
BD = baud rate divisor
This makes the formula:
CGMXCLK
baud rate = -----------------------------------64 × PD × BD
Table 15-8 shows the SCI baud rates that can be generated with a
4.9152MHz CGMXCLK.
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Serial Communications Interface Module (SCI)
Table 15-8. SCI Baud Rate Selection Examples
SCP1 and SCP0
Prescaler
Divisor (PD)
SCR2, SCR1,
and SCR0
Baud Rate
Divisor (BD)
Baud Rate
(CGMXCLK=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
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Technical Data
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Technical Data — MC68HC908AB32
Section 16. Serial Peripheral Interface Module (SPI)
16.1 Contents
16.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
16.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
16.4
Pin Name Conventions and I/O Register Addresses . . . . . . . 281
16.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .281
16.5.1 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283
16.5.2 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284
16.6 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .285
16.6.1 Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . 285
16.6.2 Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . 286
16.6.3 Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . 288
16.6.4 Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . 289
16.7
Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . 291
16.8 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
16.8.1 Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
16.8.2 Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 294
16.9
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .296
16.10 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 298
16.11 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
16.11.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
16.11.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .299
16.12 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . 300
16.13 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
16.13.1 MISO (Master In/Slave Out) . . . . . . . . . . . . . . . . . . . . . . . . 301
16.13.2 MOSI (Master Out/Slave In) . . . . . . . . . . . . . . . . . . . . . . . . 301
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16.13.3 SPSCK (Serial Clock). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
16.13.4 SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
16.13.5 CGND (Clock Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 303
16.14 I/O Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
16.14.1 SPI Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 304
16.14.2 SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . 306
16.14.3 SPI Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 309
16.2 Introduction
This section describes the serial peripheral interface (SPI) module,
which allows full-duplex, synchronous, serial communications with
peripheral devices.
16.3 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
•
I2C (inter-integrated circuit) compatibility
•
I/O (input/output) port bit(s) software configurable with pullup
device(s) if configured as input port bit(s)
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Serial Peripheral Interface Module (SPI)
16.4 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.
The full names of the SPI I/O pins are shown in Table 16-1. The generic
pin names appear in the text that follows.
Table 16-1. Pin Name Conventions
SPI Generic
Pin Names:
MISO
MOSI
Full SPI
Pin Names: SPI PTE5/MISO
SS
PTE6/MOSI PTE4/SS
SPSCK
CGND
PTE7/SPSCK
VSS
16.5 Functional Description
Figure 16-1 summarizes the SPI I/O registers and Figure 16-2 shows
the structure of the SPI module.
Addr.
$0010
$0011
$0012
Register Name
Read:
SPI Control Register
Write:
(SPCR)
Reset:
Read:
SPI Status and Control
Write:
Register (SPSCR)
Reset:
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 16-1. SPI I/O Register Summary
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Serial Peripheral Interface Module (SPI)
INTERNAL BUS
TRANSMIT DATA REGISTER
CGMOUT ÷ 2
FROM SIM
SHIFT REGISTER
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 16-2. 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)
16.5.1 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 16.14.1 SPI Control
Register.)
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 16-3.)
MASTER MCU
SHIFT REGISTER
SLAVE MCU
MISO
MISO
MOSI
MOSI
SPSCK
BAUD RATE
GENERATOR
SS
SHIFT REGISTER
SPSCK
VDD
SS
Figure 16-3. Full-Duplex Master-Slave Connections
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Serial Peripheral Interface Module (SPI)
The SPR1 and SPR0 bits control the baud rate generator and determine
the speed of the shift register. (See 16.14.2 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.
16.5.2 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 16.8.2 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)
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 16.6 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.
16.6 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.
16.6.1 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)
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.
NOTE:
Before writing to the CPOL bit or the CPHA bit, disable the SPI by
clearing the SPI enable bit (SPE).
16.6.2 Transmission Format When CPHA = 0
Figure 16-4 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 16.8.2 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 16-5.
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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
CAPTURE STROBE
Figure 16-4. Transmission Format (CPHA = 0)
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 16-5. 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.
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Serial Peripheral Interface Module (SPI)
16.6.3 Transmission Format When CPHA = 1
Figure 16-6 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 16.8.2 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 16-6. Transmission Format (CPHA = 1)
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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.
16.6.4 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 16-7.) 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 16-7. 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.
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Serial Peripheral Interface Module (SPI)
WRITE
TO SPDR
INITIATION DELAY
BUS
CLOCK
MOSI
MSB
BIT 6
1
2
BIT 5
SPSCK
CPHA = 1
SPSCK
CPHA = 0
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 16-7. Transmission Start Delay (Master)
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Serial Peripheral Interface Module (SPI)
16.7 Queuing Transmission Data
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 16-8 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
8
5
2
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
9
4
SPRF
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 16-8. 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.
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Serial Peripheral Interface Module (SPI)
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.
16.8 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.
16.8.1 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 16-4 and Figure 16-6.) 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 16-11.) 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.
If the CPU SPRF interrupt is enabled and the OVRF interrupt is not,
watch for an overflow condition. Figure 16-9 shows how it is possible to
miss an overflow. The first part of Figure 16-9 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 16-9. 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 16-10 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)
BYTE 1
SPI RECEIVE
COMPLETE
BYTE 2
5
1
BYTE 3
7
BYTE 4
11
SPRF
OVRF
READ
SPSCR
2
READ
SPDR
4
6
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
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.
11 BYTE 4 SETS SPRF 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.
Figure 16-10. Clearing SPRF When OVRF Interrupt Is Not Enabled
16.8.2 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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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 16-11.) 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.
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 16.6 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)
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.
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.
16.9 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt
requests.
Table 16-2. 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).
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 16-11.)
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 16-11. SPI Interrupt Request Generation
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Serial Peripheral Interface Module (SPI)
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.
16.10 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.
16.11 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
16.11.1 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 16.9 Interrupts.)
16.11.2 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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16.12 SPI 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 Section 8. 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.
16.13 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.
16.13.1 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.
16.13.2 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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16.13.3 SPSCK (Serial Clock)
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.
16.13.4 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
16.6 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 16-12.
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 16-12. 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 16.14.2
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.
Technical Data
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Freescale Semiconductor
Serial Peripheral Interface Module (SPI)
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 16.8.2 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 16-3.)
Table 16-3. 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
16.13.5 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 16-1.
MC68HC908AB32 — Rev. 1.1
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Serial Peripheral Interface Module (SPI)
16.14 I/O Registers
Three registers control and monitor SPI operation:
•
SPI control register (SPCR)
•
SPI status and control register (SPSCR)
•
SPI data register (SPDR)
16.14.1 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
Read:
Write:
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
= Unimplemented
R
= Reserved
Figure 16-13. 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)
Freescale Semiconductor
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
This read/write bit determines the logic state of the SPSCK pin
between transmissions. (See Figure 16-4 and Figure 16-6.) 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 16-4 and Figure 16-6.) 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 16-12.) 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 16.10 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
MC68HC908AB32 — Rev. 1.1
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Technical Data
Serial Peripheral Interface Module (SPI)
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Serial Peripheral Interface Module (SPI)
16.14.2 SPI Status and Control Register
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:
SPRF
Write:
Reset:
0
6
ERRIE
0
5
4
3
OVRF
MODF
SPTE
0
0
1
2
1
Bit 0
MODFEN
SPR1
SPR0
0
0
0
= Unimplemented
Figure 16-14. 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
Technical Data
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Freescale Semiconductor
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
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
MC68HC908AB32 — Rev. 1.1
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Technical Data
Serial Peripheral Interface Module (SPI)
307
Serial Peripheral Interface Module (SPI)
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.
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 16.13.4 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 16.8.2 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 16-4. SPR1 and SPR0 have no effect in slave mode.
Reset clears SPR1 and SPR0.
Table 16-4. 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
Technical Data
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MC68HC908AB32 — Rev. 1.1
Serial Peripheral Interface Module (SPI)
Freescale Semiconductor
Serial Peripheral Interface Module (SPI)
16.14.3 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 16-2.)
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 16-15. SPI Data Register (SPDR)
R7–R0/T7–T0 — Receive/Transmit Data Bits
NOTE:
Do not use read-modify-write instructions on the SPI data register since
the register read is not the same as the register written.
MC68HC908AB32 — Rev. 1.1
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Technical Data
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Serial Peripheral Interface Module (SPI)
Technical Data
310
MC68HC908AB32 — Rev. 1.1
Serial Peripheral Interface Module (SPI)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 17. Input/Output (I/O) Ports
17.1 Contents
17.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 312
17.3 Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 316
17.3.1 Port A Data Register (PTA) . . . . . . . . . . . . . . . . . . . . . . . . 316
17.3.2 Data Direction Register A (DDRA) . . . . . . . . . . . . . . . . . . . 316
17.4 Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
17.4.1 Port B Data Register (PTB) . . . . . . . . . . . . . . . . . . . . . . . . 318
17.4.2 Data Direction Register B (DDRB) . . . . . . . . . . . . . . . . . . . 319
17.5 Port C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
17.5.1 Port C Data Register (PTC) . . . . . . . . . . . . . . . . . . . . . . . . 320
17.5.2 Data Direction Register C (DDRC). . . . . . . . . . . . . . . . . . . 321
17.6 Port D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
17.6.1 Port D Data Register (PTD) . . . . . . . . . . . . . . . . . . . . . . . . 323
17.6.2 Data Direction Register D (DDRD). . . . . . . . . . . . . . . . . . . 324
17.6.3 Port D Input Pullup Enable Register (PTDPUE). . . . . . . . . 325
17.7 Port E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 326
17.7.1 Port E Data Register (PTE) . . . . . . . . . . . . . . . . . . . . . . . . 326
17.7.2 Data Direction Register E (DDRE) . . . . . . . . . . . . . . . . . . . 328
17.8 Port F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 329
17.8.1 Port F Data Register (PTF) . . . . . . . . . . . . . . . . . . . . . . . . 329
17.8.2 Data Direction Register F (DDRF) . . . . . . . . . . . . . . . . . . . 330
17.8.3 Port F Input Pullup Enable Register (PTFPUE) . . . . . . . . . 332
17.9 Port G . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 332
17.9.1 Port G Data Register (PTG) . . . . . . . . . . . . . . . . . . . . . . . . 332
17.9.2 Data Direction Register G (DDRG) . . . . . . . . . . . . . . . . . . 333
17.10 Port H . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
17.10.1 Port H Data Register (PTH) . . . . . . . . . . . . . . . . . . . . . . . . 335
17.10.2 Data Direction Register H (DDRH). . . . . . . . . . . . . . . . . . . 335
MC68HC908AB32 — Rev. 1.1
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Technical Data
Input/Output (I/O) Ports
311
Input/Output (I/O) Ports
17.2 Introduction
Fifty-one bidirectional input-output (I/O) pins form eight 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.
Addr.
Register Name
$0000
Read:
Port A Data Register
Write:
(PTA)
Reset:
$0001
$0002
$0003
Read:
Port B Data Register
Write:
(PTB)
Reset:
Read:
Port C Data Register
Write:
(PTC)
Reset:
Read:
Port D Data Register
Write:
(PTD)
Reset:
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
0
0
PTC5
PTC4
PTC3
Unaffected by reset
PTD7
Read:
DDRA7
Data Direction Register A
$0004
Write:
(DDRA)
Reset:
0
Read:
DDRB7
Data Direction Register B
$0005
Write:
(DDRB)
Reset:
0
Read:
MCLKEN
Data Direction Register C
$0006
Write:
(DDRC)
Reset:
0
Read:
DDRD7
Data Direction Register D
$0007
Write:
(DDRD)
Reset:
0
PTD6
PTD5
PTD4
PTD3
Unaffected by reset
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
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
0
Figure 17-1. I/O Port Register Summary
Technical Data
312
MC68HC908AB32 — Rev. 1.1
Input/Output (I/O) Ports
Freescale Semiconductor
Input/Output (I/O) Ports
Addr.
Register Name
$0008
Read:
Port E Data Register
Write:
(PTE)
Reset:
$0009
$000A
$000B
Read:
Port F Data Register
Write:
(PTF)
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
PTE7
PTE6
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
PTF2
PTF1
PTF0
PTG2
PTG1
PTG0
PTH1
PTH0
Unaffected by reset
PTF7
0
Read:
Port H Data Register
Write:
(PTH)
Reset:
0
PTF4
PTF3
0
0
0
0
Unaffected by reset
0
0
0
0
0
Unaffected by reset
Read:
DDRE7
Data Direction Register E
$000C
Write:
(DDRE)
Reset:
0
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
DDRF6
DDRF5
DDRF4
DDRF3
DDRF2
DDRF1
DDRF0
0
0
0
0
0
0
0
0
0
0
0
0
DDRG2
DDRG1
DDRG0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
DDRH1
DDRH0
0
0
0
0
0
0
0
0
Read:
DDRF7
Data Direction Register F
$000D
Write:
(DDRF)
Reset:
0
Read:
Data Direction Register H
$000F
Write:
(DDRH)
Reset:
PTF5
Unaffected by reset
Read:
Port G Data Register
Write:
(PTG)
Reset:
Read:
Data Direction Register G
$000E
Write:
(DDRG)
Reset:
PTF6
Read:
Port D Input Pullup Enable
PTDPUE7 PTDPUE6 PTDPUE5 PTDPUE4 PTDPUE3 PTDPUE2 PTDPUE1 PTDPUE0
$003D
Register Write:
(PTDPUE)
Reset:
0
0
0
0
0
0
0
0
Read:
Port F Input Pullup Enable
PTFPUE7 PTFPUE6 PTFPUE5 PTFPUE4 PTFPUE3 PTFPUE2 PTFPUE1 PTFPUE0
$003E
Register Write:
(PTFPUE)
Reset:
0
0
0
0
0
0
0
0
Figure 17-1. I/O Port Register Summary
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
313
Input/Output (I/O) Ports
Table 17-1. Port Control Register Bits Summary (Sheet 1 of 2)
Port
A
B
C
D
Module Control
Bit
DDR
0
DDRA0
PTA0
1
DDRA1
PTA1
2
DDRA2
PTA2
3
DDRA3
4
DDRA4
5
DDRA5
PTA5
6
DDRA6
PTA6
7
DDRA7
PTA7
0
DDRB0
PTB0/ATD0
1
DDRB1
PTB1/ATD1
2
DDRB2
PTB2/ATD2
3
DDRB3
4
DDRB4
5
DDRB5
PTB5/ATD5
6
DDRB6
PTB6/ATD6
7
DDRB7
PTB7/ATD7
0
DDRC0
1
DDRC1
2
DDRC2
3
DDRC3
4
DDRC4
5
DDRC5
PTC5
0
DDRD0
PTD0
1
DDRD1
2
DDRD2
3
DDRD3
4
DDRD4
TIMB
TBSC
$0040
PS[2:0]
PTD4/TBCLK
5
DDRD5
—
—
—
PTD5
6
DDRD6
TIMA
TASC
$0020
PS[2:0]
PTD6/TACLK
7
DDRD7
—
—
—
PTD7
Module
—
ADC
Register
—
ADSCR
$0038
Pin
PTA3
—
PTA4
ADCH[4:0]
PTB3/ATD3
PTB4/ATD4
PTC0
—
—
—
—
DDRC
$0006
MCLKEN
PTC1
PTC2/MCLK
PTC3
—
—
—
—
—
PTC4
PTD1
—
PTD2
PTD3
Technical Data
314
Control Bit
MC68HC908AB32 — Rev. 1.1
Input/Output (I/O) Ports
Freescale Semiconductor
Input/Output (I/O) Ports
Table 17-1. Port Control Register Bits Summary (Sheet 2 of 2)
Port
Bit
DDR
0
DDRE0
1
DDRE1
2
DDRE2
Module Control
Register
Control Bit
SCI
SCC1
$0013
ENSCI
TASC0
$0026
ELS0B:ELS0A
PTE2/TACH0
TASC1
$0029
ELS1B:ELS1A
PTE3/TACH1
SPE, SPMSTR
PTE4/SS
TIMA
E
3
DDRE3
4
DDRE4
5
DDRE5
6
DDRE6
7
DDRE7
0
DDRF0
SPI
H
PTE1/RxD
PTE5/MISO
SPE
PTE6/MOSI
TASC2
$002C
ELS2B:ELS2A
PTF0/TACH2
1
DDRF1
TASC3
$002F
ELS3B:ELS3A
PTF1/TACH3
2
DDRF2
TBSC2
$0032
ELS2B:ELS2A
PTF2/TBCH2
3
DDRF3
TBSC3
$0035
ELS3B:ELS3A
PTF3/TBCH3
TIMB
G
SPCR
$0010
PTE0/TxD
PTE7SPSCK
TIMA
F
Pin
Module
4
DDRF4
TBSC0
$0045
ELS0B:ELS0A
PTF4/TBCH0
5
DDRF5
TBSC1
$0048
ELS1B:ELS1A
PTF5/TBCH1
6
DDRF6
7
DDRF7
—
—
0
DDRG0
1
DDRG1
—
KBIER
$0021
PTF6
PTF7
KBIE0
PTG0/KBD0
KBIE1
PTG1/KBD1
KBIE2
PTG2/KBD2
2
DDRG2
0
DDRH0
KBIE3
PTH0/KBD3
1
DDRH1
KBIE4
PTH1/KBD4
KBI
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
315
Input/Output (I/O) Ports
17.3 Port A
Port A is an 8-bit general-purpose bidirectional I/O port.
17.3.1 Port A Data Register (PTA)
The port A data register contains a data latch for each of the eight port
A pins.
Address:
Read:
Write:
$0000
Bit 7
6
5
4
3
2
1
Bit 0
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
Reset:
Unaffected by Reset
Figure 17-2. 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.
17.3.2 Data Direction Register A (DDRA)
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:
Read:
Write:
Reset:
$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
Figure 17-3. Data Direction Register A (DDRA)
Technical Data
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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. Figure 17-4 shows
the port A I/O logic.
READ DDRA ($0004)
INTERNAL DATA BUS
WRITE DDRA ($0004)
RESET
DDRAx
WRITE PTA ($0000)
PTAx
PTAx
READ PTA ($0000)
Figure 17-4. 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 17-2 summarizes the operation of the port A pins.
Table 17-2. Port A Pin Functions
Accesses to DDRA
DDRA
Bit
PTA Bit
0
X(1)
1
X
Accesses to PTA
I/O Pin Mode
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.
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17.4 Port B
Port B is an 8-bit special function port that shares all eight of its port pins
with the analog-to-digital converter (ADC) module (see Section 14.
Analog-to-Digital Converter (ADC)).
17.4.1 Port B Data Register (PTB)
The port B data register contains a data latch for each of the eight port B
pins.
Address:
Read:
Write:
$0001
Bit 7
6
5
4
3
2
1
Bit 0
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
ATD2
ATD2
ATD0
Reset:
Alternative Function:
Unaffected by reset
ATD7
ATD6
ATD5
ATD4
ATD3
Figure 17-5. 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.
ATD[7:0] — ADC channels
ATD[7:0] are pins used for the input channels to the analog-to-digital
converter module. The channel select bits in the ADC status and
control register define which port B pin will be used as an ADC input
and overrides any control from the port I/O logic by forcing that pin as
the input to the analog circuitry.
NOTE:
Care must be taken when reading port B while applying analog voltages
to ATD[7:0] pins. If the appropriate ADC channel is not enabled,
excessive current drain may occur if analog voltages are applied to the
PTBx/ATDx pin, while PTB is read as a digital input. Those ports not
selected as analog input channels are considered digital I/O ports.
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17.4.2 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:
Read:
Write:
Reset:
$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
Figure 17-6. 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
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 17-7 shows
the port B I/O logic.
READ DDRB ($0005)
INTERNAL DATA BUS
WRITE DDRB ($0005)
RESET
DDRBx
WRITE PTB ($0001)
PTBx
PTBx
READ PTB ($0001)
To Analog-To-Digital Converter
Figure 17-7. Port B I/O Circuit
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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 17-3 summarizes the operation of the port B pins.
Table 17-3. Port B Pin Functions
Accesses to DDRB
DDRB
Bit
PTB Bit
0
X(1)
1
X
Accesses to PTB
I/O Pin Mode
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.
17.5 Port C
Port C is a 6-bit general-purpose bidirectional I/O port. PTC2 pin can be
configured as an output pin for the system MCLK clock.
17.5.1 Port C Data Register (PTC)
The port C data register contains a data latch for each of the six port C
pins.
Address:
Read:
Write:
Reset:
$0002
Bit 7
6
0
0
5
4
3
2
1
Bit 0
PTC5
PTC4
PTC3
PTC2
PTC1
PTC0
Unaffected by reset
Alternative Function:
MCLK
Figure 17-8. Port C Data Register (PTC)
Technical Data
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Input/Output (I/O) Ports
PTC[5:0] — 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.
MCLK — T12 System Clock
The system clock is driven out of the PTC2 pin when MCLKEN is set.
17.5.2 Data Direction Register C (DDRC)
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
Read:
Write:
Reset:
MCLKEN
0
6
0
0
5
4
3
2
1
Bit 0
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
Figure 17-9. Data Direction Register B (DDRB)
MCLKEN — T12 System Clock Enable Bit
This read/write bit enables MCLK to be an output signal on PTC2 pin.
Reset clears MCLKEN.
1 = PTC2 pin configured as MCLK output
0 = PTC2 pin configured as standard I/O pin
DDRC[5:0] — Data Direction Register C Bits
These read/write bits control port C data direction. Reset clears
DDRC[5:0], 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 17-10 shows
the port C I/O logic.
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READ DDRC ($0006)
INTERNAL DATA BUS
WRITE DDRC ($0006)
RESET
DDRCx
WRITE PTC ($0002)
PTCx
PTCx
READ PTC ($0002)
PTC2 ONLY
MCLK
MCLKEN
Figure 17-10. 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 17-4 summarizes the operation of the port C pins.
Table 17-4. Port C Pin Functions
Accesses to DDRC
DDRC
Bit
PTC Bit
0
2
1
Accesses to PTC
I/O Pin Mode
Read/Write
Read
Write
Input, Hi-Z
DDRC7
Pin
PTC2
2
Output
DDRC7
0
—
0
X(1)
Input, Hi-Z(2)
DDRC[5:0]
Pin
PTC[5:0](3)
1
X
Output
DDRC[5:0]
PTC[5:0]
PTC[5:0]
Notes:
1. X = don’t care; except PTC2.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect input.
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17.6 Port D
Port D is an 8-bit special function port that shares two of its pins with the
timer interface module (see Section 11. Timer Interface Module A
(TIMA) and Section 12. Timer Interface Module B (TIMB)). Each
port D pin has 15mA current drive (sink) and programmable pullup.
17.6.1 Port D Data Register (PTD)
The port D data register contains a data latch for each of the eight port D
pins.
Address:
Read:
Write:
$0003
Bit 7
6
5
4
3
2
1
Bit 0
PTD7
PTD6
PTD5
PTD4
PTD3
PTD2
PTD1
PTD0
Reset:
Alternative Function:
Unaffected by reset
TACLK
TBCLK
Additional Functions: 15mA sink 15mA sink 15mA sink 15mA sink 15mA sink 15mA sink 15mA sink 15mA sink
Input pullup Input pullup Input pullup Input pullup Input pullup Input pullup Input pullup Input pullup
Figure 17-11. 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.
TACLK — Timer A Clock Input
The PTD6 pin becomes TACLK, the timer A (TIMA) external clock
input when the TIMA prescaler select bits, PS[2:0] = 111. See
Section 11. Timer Interface Module A (TIMA).
TBCLK — Timer B Clock Input
The PTD4 pin becomes TBCLK, the timer B (TIMB) external clock
input when the TIMB prescaler select bits, PS[2:0] = 111. See
Section 12. Timer Interface Module B (TIMB).
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17.6.2 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:
Read:
Write:
Reset:
$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
Figure 17-12. 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 17-13 shows
the port D I/O logic.
VDD
READ DDRD ($0007)
PTDPUEx
INTERNAL DATA BUS
WRITE DDRD ($0007)
RESET
DDRDx
WRITE PTD ($0003)
PTDx
PTDx
READ PTD ($0003)
PTD6 to TACLK of TIMA
PTD4 to TBCLK of TIMB
Figure 17-13. Port D I/O Circuit
Technical Data
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When DDRDx is a logic 1, reading address $0003 reads the PTDx data
latch. When 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 17-5 summarizes the operation of the port D pins.
Table 17-5. Port D Pin Functions
DDRD
Bit
PTD Bit
Accesses
to DDRD
I/O Pin
Mode
Accesses to PTD
Read/Write
Read
Write
0
X(1)
Input, Hi-Z(2)
DDRD[7:0]
Pin
PTD[7:0](3)
1
X
Output
DDRD[7:0]
PTD[7:0]
PTD[7:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect the input.
17.6.3 Port D Input Pullup Enable Register (PTDPUE)
The port D input pullup enable register (PTDPUE) controls the input
pullup device for each of the eight port D pins. Each bit is individually
configurable and requires that the data direction register, DDRD, bit be
configured as an input. Each pullup is automatically and dynamically
disabled when a port bit’s DDRD is configured for output mode.
Address:
$003D
Bit 7
Read:
Write:
Reset:
6
5
4
3
2
1
Bit 0
PTDPUE7 PTDPUE6 PTDPUE5 PTDPUE4 PTDPUE3 PTDPUE2 PTDPUE1 PTDPUE0
0
0
0
0
0
0
0
0
Figure 17-14. Port D Input Pullup Enable Register (PTDPUE)
PTDPUE[7:0] — Port D Input Pullup Enable Bits
These writable bits are software programmable to enable pullup
devices on an input port pin.
1 = Corresponding port D pin configured to have internal pullup
0 = Corresponding port D pin internal pullup disconnected
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17.7 Port E
Port E is an 8-bit special function port that shares two of its pins with the
timer interface module (TIMA), two of its pins with the serial
communications interface module (SCI) and four of its pins with the
serial peripheral interface module (SPI).
17.7.1 Port E Data Register (PTE)
The port E data register contains a data latch for each of the eight port E
pins.
Address:
Read:
Write:
$0008
Bit 7
6
5
4
3
2
1
Bit 0
PTE7
PTE6
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
TACH0
RxD
TxD
Reset:
Alternative Function:
Unaffected by reset
SPSCK
MOSI
MISO
SS
TACH1
Figure 17-15. Port E Data Register (PTE)
PTE[7:0] — Port E Data Bits
These read/write bits are software programmable. Data direction of
each port E pin is under the control of the corresponding bit in data
direction register E. Reset has no effect on port E data.
SPSCK — SPI Serial Clock
The PTE7/SPSCK pin is the serial clock input of a SPI slave module
and serial clock output of a SPI master modules. When the SPE bit is
clear, the PTE7/SPSCK pin is available for general-purpose I/O. See
16.14.1 SPI Control Register.
MOSI — Master Out/Slave In
The PTE6/MOSI pin is the master out/slave in terminal of the SPI
module. When the SPE bit is clear, the PTE6/MOSI pin is available for
general-purpose I /O. See 16.14.1 SPI Control Register.
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MISO — Master In/Slave Out
The PTE5/MISO pin is the master in/slave out terminal of the SPI
module. When the SPI enable bit, SPE, is clear, the SPI module is
disabled, and the PTE5/MISO pin is available for general-purpose
I/O. See 16.14.1 SPI Control Register.
SS — Slave Select
The PTE4/SS pin is the slave select input of the SPI module. When
the SPE bit is clear, or when the SPI master bit, SPMSTR, is set, the
PTE4/SS pin is available for general-purpose I/O. See 16.14.1 SPI
Control Register. When the SPI is enabled as a slave, the DDRE4
bit in data direction register E (DDRE) has no effect on the PTE4/SS
pin.
TACH[1:0] — Timer A Channel I/O Bits
The PTE3/TACH1–PTE2/TACH0 pins are the TIMA input
capture/output compare pins. The edge/level select bits,
ELSxB:ELSxA, determine whether the PTE3/TACH1–PTE2/TACH0
pins are timer channel I/O pins or general-purpose I/O pins. See
11.10.4 TIMA Channel Status and Control Registers.
RxD — SCI Receive Data Input
The PTE1/RxD pin is the receive data input for the SCI module. When
the enable SCI bit, ENSCI, is clear, the SCI module is disabled, and
the PTE1/RxD pin is available for general-purpose I/O. See 15.9.1
SCI Control Register 1.
TxD — SCI Transmit Data Output
The PTE0/TxD pin is the transmit data output for the SCI module.
When the enable SCI bit, ENSCI, is clear, the SCI module is disabled,
and the PTE0/TxD pin is available for general-purpose I/O. See
15.9.1 SCI Control Register 1.
NOTE:
Data direction register E (DDRE) does not affect the data direction of
port E pins that are being used by the SPI module, TIMA, and SCI
module. However, the DDRE bits always determine whether reading
port E returns the states of the latches or the states of the pins. See
Table 17-6.
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17.7.2 Data Direction Register E (DDRE)
Data direction register E determines whether each port E pin is an input
or an output. Writing a logic 1 to a DDRE bit enables the output buffer for
the corresponding port E pin; a logic 0 disables the output buffer.
Address:
Read:
Write:
Reset:
$000C
Bit 7
6
5
4
3
2
1
Bit 0
DDRE7
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
0
Figure 17-16. Data Direction Register E (DDRE)
DDRE[7:0] — Data Direction Register E Bits
These read/write bits control port E data direction. Reset clears
DDRE[7:0], configuring all port E pins as inputs.
1 = Corresponding port E pin configured as output
0 = Corresponding port E pin configured as input
NOTE:
Avoid glitches on port E pins by writing to the port E data register before
changing data direction register E bits from 0 to 1. Figure 17-17 shows
the port E I/O logic.
READ DDRE ($000C)
INTERNAL DATA BUS
WRITE DDRE ($000C)
RESET
DDREx
WRITE PTE ($0008)
PTEx
PTEx
READ PTE ($0008)
Figure 17-17. Port E I/O Circuit
Technical Data
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When DDREx is a logic 1, reading address $0008 reads the PTEx data
latch. When DDREx is a logic 0, reading address $0008 reads the
voltage level on the pin. The data latch can always be written, regardless
of the state of its data direction bit.
Table 17-6 summarizes the operation of the port E pins.
Table 17-6. Port E Pin Functions
DDRE
Bit
PTE Bit
Accesses
to DDRE
I/O Pin
Mode
Accesses to PTE
Read/Write
Read
Write
0
X(1)
Input, Hi-Z(2)
DDRE[7:0]
Pin
PTE[7:0](3)
1
X
Output
DDRE[7:0]
PTE[7:0]
PTE[7:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect the input.
17.8 Port F
Port F is an 8-bit special function port that shares six of its pins with the
timer interface modules (TIMA and TIMB).
17.8.1 Port F Data Register (PTF)
The port F data register contains a data latch for each of the eight port F
pins.
Address:
Read:
Write:
$0009
Bit 7
6
5
4
3
2
1
Bit 0
PTF7
PTF6
PTF5
PTF4
PTF3
PTF2
PTF1
PTF0
TBCH2
TACH3
TACH2
Reset:
Alternative Function:
Unaffected by reset
TBCH1
TBCH0
TBCH3
Additional Function: Input pullup Input pullup Input pullup Input pullup Input pullup Input pullup Input pullup Input pullup
Figure 17-18. Port F Data Register (PTF)
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PTF[7:0] — Port F Data Bits
These read/write bits are software programmable. Data direction of
each port F pin is under the control of the corresponding bit in data
direction register F. Reset has no effect on port F data.
TACH[3:2] and TBCH[3:0] — Timer channel I/O bits
The PTF5/TBCH1–PTF0/TACH2 pins are the TIMA and TIMB input
capture/output compare pins. The edge/level select bits,
ELSxB:ELSxA, determine whether the PTF5/TBCH1–PTF0/TACH2
pins are timer channel I/O pins or general-purpose I/O pins. See
11.10.4 TIMA Channel Status and Control Registers and 12.10.4
TIMB Channel Status and Control Registers.
NOTE:
Data direction register F (DDRF) does not affect the data direction of
port F pins that are being used by TIMA and TIMB. However, the DDRF
bits always determine whether reading port F returns the states of the
latches or the states of the pins. See Table 17-7.
17.8.2 Data Direction Register F (DDRF)
Data direction register F determines whether each port F pin is an input
or an output. Writing a logic 1 to a DDRF bit enables the output buffer for
the corresponding port F pin; a logic 0 disables the output buffer.
Address:
Read:
Write:
Reset:
$000D
Bit 7
6
5
4
3
2
1
Bit 0
DDRF7
DDRF6
DDRF5
DDRF4
DDRF3
DDRF2
DDRF1
DDRF0
0
0
0
0
0
0
0
0
Figure 17-19. Data Direction Register F (DDRF)
DDRF[7:0] — Data Direction Register F Bits
These read/write bits control port F data direction. Reset clears
DDRF[7:0], configuring all port F pins as inputs.
1 = Corresponding port F pin configured as output
0 = Corresponding port F pin configured as input
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NOTE:
Avoid glitches on port F pins by writing to the port F data register before
changing data direction register F bits from 0 to 1. Figure 17-20 shows
the port F I/O logic.
VDD
READ DDRF ($000D)
PTFPUEx
INTERNAL DATA BUS
WRITE DDRF ($000D)
DDRFx
RESET
WRITE PTF ($0009)
PTFx
PTFx
READ PTF ($0009)
PTF5 to TBCH1, PTF4 to TBCH0, PTF3 to TBCH3, PTF2 to TBCH2 of TIMB
PTF1 to TACH3, PTF0 to TACH2 of TIMA
Figure 17-20. Port F I/O Circuit
When DDRFx is a logic 1, reading address $0009 reads the PTFx data
latch. When DDRFx is a logic 0, reading address $0009 reads the
voltage level on the pin. The data latch can always be written, regardless
of the state of its data direction bit.
Table 17-7 summarizes the operation of the port F pins.
Table 17-7. Port F Pin Functions
DDRF
Bit
PTF Bit
I/O Pin
Mode
Accesses
to DDRF
Accesses to PTF
Read/Write
Read
Write
0
X(1)
Input, Hi-Z(2)
DDRF[7:0]
Pin
PTF[7:0](3)
1
X
Output
DDRF[7:0]
PTF[7:0]
PTF[7:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect the input.
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Input/Output (I/O) Ports
17.8.3 Port F Input Pullup Enable Register (PTFPUE)
The port F input pullup enable register (PTFPUE) controls the input
pullup device for each of the eight port F pins. Each bit is individually
configurable and requires that the data direction register, DDRF, bit be
configured as an input. Each pullup is automatically and dynamically
disabled when a port bit’s DDRF is configured for output mode.
Address:
$003E
Bit 7
Read:
Write:
Reset:
6
5
4
3
2
1
Bit 0
PTFPUE7 PTFPUE6 PTFPUE5 PTFPUE4 PTFPUE3 PTFPUE2 PTFPUE1 PTFPUE0
0
0
0
0
0
0
0
0
Figure 17-21. Port F Input Pullup Enable Register (PTFPUE)
PTFPUE[7:0] — Port F Input Pullup Enable Bits
These writable bits are software programmable to enable pullup
devices on an input port pin.
1 = Corresponding port F pin configured to have internal pullup
0 = Corresponding port F pin internal pullup disconnected
17.9 Port G
Port G is a 3-bit special-function port that shares all three of its pins with
the keyboard interrupt (KBI) module.
17.9.1 Port G Data Register (PTG)
The port G data register (PTG) contains a data latch for each of the three
port G pins.
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Input/Output (I/O) Ports
Address:
Read:
$000A
Bit 7
6
5
4
3
0
0
0
0
0
Write:
Reset:
2
1
Bit 0
PTG2
PTG1
PTG0
KBD2
KBD1
KBD0
Unaffected by reset
Alternative Function:
Figure 17-22. Port G Data Register (PTG)
PTG[2:0] — Port G Data Bits
These read/write bits are software programmable. Data direction of
each port G pin is under the control of the corresponding bit in data
direction register G. Reset has no effect on port G data.
KBD[2:0] — The keyboard interrupt enable bits, KBIE[2:0], in the
keyboard interrupt enable register (KBIER), enable the port G pins as
external interrupt pins. See Section 19. Keyboard Interrupt Module
(KBI).
17.9.2 Data Direction Register G (DDRG)
Data direction register G determines whether each port G pin is an input
or an output. Writing logic 1 to a DDRG bit enables the output buffer for
the corresponding port G pin; a logic 0 disables the output buffer.
Address:
Read:
$000E
Bit 7
6
5
4
3
0
0
0
0
0
0
0
0
0
0
Write:
Reset:
2
1
Bit 0
DDRG2
DDRG1
DDRG0
0
0
0
Figure 17-23. Data Direction Register G (DDRG)
MC68HC908AB32 — Rev. 1.1
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Input/Output (I/O) Ports
DDRG[2:0] — Data Direction Register G Bits
These read/write bits control port G data direction. Reset clears
DDRG[2:0], configuring all port G pins as inputs.
1 = Corresponding port G pin configured as output
0 = Corresponding port G pin configured as input
NOTE:
Avoid glitches on port G pins by writing to the port G data register before
changing data direction register G bits from 0 to 1. Figure 17-24 shows
the port G I/O logic.
READ DDRG ($000E)
INTERNAL DATA BUS
WRITE DDRG ($000E)
DDRGx
RESET
WRITE PTG ($000A)
PTGx
PTGx
READ PTG ($000A)
KBI
Figure 17-24. Port G I/O Circuit
When DDRGx is a logic 1, reading address $000A reads the PTGx data
latch. When DDRGx is a logic 0, reading address $000A reads the
voltage level on the pin. The data latch can always be written, regardless
of the state of its data direction bit.
Table 17-6 summarizes the operation of the port G pins.
Table 17-8. Port G Pin Functions
DDRG
Bit
PTG Bit
I/O Pin
Mode
Accesses
to DDRG
Accesses to PTG
Read/Write
Read
Write
0
X(1)
Input, Hi-Z(2)
DDRG[2:0]
Pin
PTG[2:0](3)
1
X
Output
DDRG[2:0]
PTG[2:0]
PTG[2:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect the input.
Technical Data
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Freescale Semiconductor
Input/Output (I/O) Ports
17.10 Port H
Port H is a 2-bit special-function port that shares all two of its pins with
the keyboard interrupt (KBI) module.
17.10.1 Port H Data Register (PTH)
The port H data register (PTH) contains a data latch for each of the two
port H pins.
Address:
Read:
$000B
Bit 7
6
5
4
3
2
0
0
0
0
0
0
Write:
Reset:
1
Bit 0
PTH1
PTH0
KBD4
KBD3
Unaffected by reset
Alternative Function:
Figure 17-25. Port H Data Register (PTH)
PTH[1:0] — Port H Data Bits
These read/write bits are software programmable. Data direction of
each port H pin is under the control of the corresponding bit in data
direction register H. Reset has no effect on port H data.
KBD[4:3] — The keyboard interrupt enable bits, KBIE[4:3], in the
keyboard interrupt enable register (KBIER), enable the port H pins as
external interrupt pins. See Section 19. Keyboard Interrupt Module
(KBI).
17.10.2 Data Direction Register H (DDRH)
Data direction register H determines whether each port H pin is an input
or an output. Writing logic 1 to a DDRH bit enables the output buffer for
the corresponding port H pin; a logic 0 disables the output buffer.
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Input/Output (I/O) Ports
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Input/Output (I/O) Ports
Address:
Read:
$000F
Bit 7
6
5
4
3
2
0
0
0
0
0
0
0
0
0
0
0
0
Write:
Reset:
1
Bit 0
DDRH1
DDRH0
0
0
Figure 17-26. Data Direction Register H (DDRH)
DDRH[1:0] — Data Direction Register H Bits
These read/write bits control port H data direction. Reset clears
DDRH[1:0], configuring all port H pins as inputs.
1 = Corresponding port H pin configured as output
0 = Corresponding port H pin configured as input
NOTE:
Avoid glitches on port H pins by writing to the port H data register before
changing data direction register H bits from 0 to 1. Figure 17-27 shows
the port H I/O logic.
READ DDRH ($000F)
INTERNAL DATA BUS
WRITE DDRH ($000F)
RESET
DDRHx
WRITE PTH ($000B)
PTHx
PTHx
READ PTH ($000B)
KBI
Figure 17-27. Port H I/O Circuit
When DDRHx is a logic 1, reading address $000B reads the PTHx data
latch. When DDRHx is a logic 0, reading address $000B reads the
voltage level on the pin. The data latch can always be written, regardless
of the state of its data direction bit.
Table 17-6 summarizes the operation of the port H pins.
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Input/Output (I/O) Ports
Table 17-9. Port H Pin Functions
DDRH
Bit
PTH Bit
I/O Pin
Mode
Accesses
to DDRH
Accesses to PTH
Read/Write
Read
Write
0
X(1)
Input, Hi-Z(2)
DDRH[1:0]
Pin
PTH[1:0](3)
1
X
Output
DDRH[1:0]
PTH[1:0]
PTH[1:0]
Notes:
1. X = don’t care.
2. Hi-Z = high impedance.
3. Writing affects data register, but does not affect the input.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Input/Output (I/O) Ports
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Input/Output (I/O) Ports
Technical Data
338
MC68HC908AB32 — Rev. 1.1
Input/Output (I/O) Ports
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 18. External Interrupt (IRQ)
18.1 Contents
18.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
18.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
18.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .340
18.4.1 IRQ Pin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
18.5
IRQ Status and Control Register (ISCR) . . . . . . . . . . . . . . . . 343
18.6
IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . 344
18.2 Introduction
The IRQ (external interrupt) module provides a maskable interrupt input.
18.3 Features
Features of the IRQ module include the following:
•
A dedicated external interrupt pin, IRQ
•
IRQ interrupt control bits
•
Hysteresis buffer
•
Programmable edge-only or edge and level interrupt sensitivity
•
Automatic interrupt acknowledge
•
Internal pullup resistor
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Technical Data
External Interrupt (IRQ)
339
External Interrupt (IRQ)
18.4 Functional Description
A logic 0 applied to the external interrupt pin can latch a CPU interrupt
request. Figure 18-1 shows the structure of the IRQ module.
Interrupt signals on the IRQ pin are latched into the IRQ latch. An
interrupt latch remains set until one of the following actions occurs:
•
Vector fetch — A vector fetch automatically generates an interrupt
acknowledge signal that clears the IRQ latch.
•
Software clear — Software can clear the interrupt latch by writing
to the acknowledge bit in the interrupt status and control register
(ISCR). 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 ISCR controls the triggering sensitivity of
the IRQ pin.
When the interrupt pin is edge-triggered only, the CPU interrupt request
remains set until a vector fetch, software clear, or reset occurs.
When the interrupt pin is both falling-edge and low-level-triggered, the
CPU interrupt request 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 MODE control bit,
thereby clearing the interrupt even if the pin stays low.
When set, the IMASK bit in the ISCR mask all external interrupt
requests. A latched interrupt request is not presented to the interrupt
priority logic unless the IMASK bit is clear.
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Freescale Semiconductor
External Interrupt (IRQ)
NOTE:
The interrupt mask (I) in the condition code register (CCR) masks all
interrupt requests, including external interrupt requests. (See 8.6
Exception Control.)
INTERNAL ADDRESS BUS
ACK
RESET
TO CPU FOR
BIL/BIH
INSTRUCTIONS
VECTOR
FETCH
DECODER
VDD
INTERNAL
PULLUP
VDD
IRQF
DEVICE
D
CLR
Q
CK
IRQ
SYNCHRONIZER
IRQ
INTERRUPT
REQUEST
HIGH
VOLTAGE
DETECT
TO MODE
SELECT
LOGIC
IRQ
FF
IMASK
MODE
Figure 18-1. IRQ Module Block Diagram
Addr.
$001A
Register Name
Read:
IRQ Status and Control
Register Write:
(ISCR)
Reset:
Bit 7
6
5
4
3
2
0
0
0
0
IRQF
0
ACK
0
0
0
0
0
0
1
Bit 0
IMASK
MODE
0
0
= Unimplemented
Figure 18-2. IRQ I/O Register Summary
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External Interrupt (IRQ)
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External Interrupt (IRQ)
18.4.1 IRQ Pin
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch.
A vector fetch, software clear, or reset clears the IRQ latch.
If the 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 (ISCR). 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 latches another interrupt request. If the IRQ mask
bit, IMASK, is clear, the CPU loads the program counter with the
vector address at locations $FFFA and $FFFB.
•
Return of the IRQ pin to logic 1 — As long as the IRQ pin is at logic
0, 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 ISCR 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 IRQ pin.
NOTE:
When using the level-sensitive interrupt trigger, avoid false interrupts by
masking interrupt requests in the interrupt routine.
Technical Data
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Freescale Semiconductor
External Interrupt (IRQ)
18.5 IRQ Status and Control Register (ISCR)
The IRQ Status and Control Register (ISCR) controls and monitors
operation of the IRQ module. The ISCR has the following functions:
•
Shows the state of the IRQ flag
•
Clears the IRQ latch
•
Masks IRQ interrupt request
•
Controls triggering sensitivity of the IRQ interrupt pin
Address:
Read:
$001A
Bit 7
6
5
4
3
2
0
0
0
0
IRQF
0
ACK
Write:
Reset:
0
0
0
0
0
0
1
Bit 0
IMASK
MODE
0
0
= Unimplemented
Figure 18-3. IRQ Status and Control Register (ISCR)
IRQF — IRQ Flag
This read-only status bit is high when the IRQ interrupt is pending.
1 = IRQ interrupt pending
0 = IRQ interrupt not pending
ACK — IRQ Interrupt Request Acknowledge Bit
Writing a logic 1 to this write-only bit clears the IRQ latch. ACK always
reads as logic 0. Reset clears ACK.
IMASK — IRQ Interrupt Mask Bit
Writing a logic 1 to this read/write bit disables IRQ interrupt requests.
Reset clears IMASK.
1 = IRQ interrupt requests disabled
0 = IRQ interrupt requests enabled
MODE — IRQ Edge/Level Select Bit
This read/write bit controls the triggering sensitivity of the IRQ pin.
Reset clears MODE.
1 = IRQ interrupt requests on falling edges and low levels
0 = IRQ interrupt requests on falling edges only
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Technical Data
External Interrupt (IRQ)
343
External Interrupt (IRQ)
18.6 IRQ Module During Break Interrupts
The system integration module (SIM) controls whether the IRQ latch can
be cleared during the break state. The BCFE bit in the break flag control
register (BFCR) enables software to clear the latches during the break
state. (See Section 8. System Integration Module (SIM).)
To allow software to clear the IRQ latch during a break interrupt, write a
logic 1 to the BCFE bit. If a latch is cleared during the break state, it
remains cleared when the MCU exits the break state.
To protect the latches during the break state, write a logic 0 to the BCFE
bit. With BCFE at logic 0 (its default state), writing to the ACK bit in the
IRQ status and control register during the break state has no effect on
the IRQ latch.
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Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 19. Keyboard Interrupt Module (KBI)
19.1 Contents
19.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
19.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
19.4
I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 346
19.5 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .347
19.5.1 Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
19.5.2 Keyboard Status and Control Register. . . . . . . . . . . . . . . . 349
19.5.3 Keyboard Interrupt Enable Register . . . . . . . . . . . . . . . . . . 351
19.6
Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
19.7
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 351
19.8
Keyboard Module During Break Interrupts . . . . . . . . . . . . . . . 352
19.2 Introduction
The keyboard interrupt module (KBI) provides five independently
maskable external interrupts which are accessible via PTG0–PTG2 and
PTH0–PTH1 pins.
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Technical Data
Keyboard Interrupt Module (KBI)
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Keyboard Interrupt Module (KBI)
19.3 Features
Features of the keyboard interrupt module include the following:
Addr.
$001B
•
Five keyboard interrupt pins with pullup devices
•
Separate keyboard interrupt enable bits and one keyboard
interrupt mask
•
Built-in pull-up device if input pin is configured as input port bit
•
Programmable edge-only or edge- and level- interrupt sensitivity
•
Exit from low-power modes
Register Name
Read:
Keyboard Status
and Control Register Write:
(KBSCR)
Reset:
Read:
Keyboard Interrupt Enable
Write:
$0021
Register (KBIER)
Reset:
Bit 7
6
5
4
3
2
0
0
0
0
KEYF
0
ACKK
0
0
0
0
0
0
0
0
0
1
Bit 0
IMASKK
MODEK
0
0
0
0
0
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
= Unimplemented
Figure 19-1. KBI I/O Register Summary
19.4 I/O Pins
The five keyboard interrupt pins are shared with standard port I/O pins.
The full name of the KBI pins are listed in Table 19-1. The generic pin
name appear in the text that follows.
Table 19-1. Pin Name Conventions
KBI
Generic Pin Name
Full MCU Pin Name
Pin Selected for KBI Function by
KBIEx Bit in KBIER
KBD0
PTG0/KBD0
KBIE0
KBD1
PTG1/KBD1
KBIE1
KBD2
PTG2/KBD2
KBIE2
KBD3
PTH0/KBD3
KBIE3
KBD4
PTH1/KBD4
KBIE4
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Freescale Semiconductor
Keyboard Interrupt Module (KBI)
19.5 Functional Description
INTERNAL BUS
KBD0
ACKK
VDD
.
KBIE0
TO PULLUP ENABLE
D
.
CLR
VECTOR FETCH
DECODER
KEYF
RESET
Q
SYNCHRONIZER
CK
.
KEYBOARD
INTERRUPT FF
KBD4
Keyboard
Interrupt
Request
IMASKK
MODEK
KBIE4
TO PULLUP ENABLE
Figure 19-2. Keyboard Interrupt Block Diagram
Writing to the KBIE4–KBIE0 bits in the keyboard interrupt enable register
independently enables or disables the corresponding port pin as a
keyboard interrupt pin. Enabling a keyboard interrupt pin 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.
•
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.
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:
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Keyboard Interrupt Module (KBI)
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Keyboard Interrupt Module (KBI)
•
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 $FFD2 and
$FFD3.
•
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.
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, disable the pullup device, use the data direction register to configure the pin as an input
and then read the data register.
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.
Technical Data
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Freescale Semiconductor
Keyboard Interrupt Module (KBI)
19.5.1 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 the data direction register.
2. Write logic 1s to the appropriate port data register bits.
3. Enable the KBI pins by setting the appropriate KBIEx bits in the
keyboard interrupt enable register.
19.5.2 Keyboard Status and Control Register
•
Flags keyboard interrupt requests.
•
Acknowledges keyboard interrupt requests.
•
Masks keyboard interrupt requests.
•
Controls keyboard interrupt triggering sensitivity.
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Technical Data
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Keyboard Interrupt Module (KBI)
Address:
Read:
$001B
Bit 7
6
5
4
3
2
0
0
0
0
KEYF
0
Write:
Reset:
ACKK
0
0
0
0
0
0
1
Bit 0
IMASKK
MODEK
0
0
= Unimplemented
Figure 19-3. Keyboard Status and Control Register (KBSCR)
Bits 7–4 — Not used
These read-only bits always read as logic 0s.
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.
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
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
Technical Data
350
MC68HC908AB32 — Rev. 1.1
Keyboard Interrupt Module (KBI)
Freescale Semiconductor
Keyboard Interrupt Module (KBI)
19.5.3 Keyboard Interrupt Enable Register
The keyboard interrupt enable register enables or disables the
corresponding port pin to operate as a keyboard interrupt pin.
Address:
Read:
$0021
Bit 7
6
5
0
0
0
Write:
Port Pin:
Reset:
0
0
0
4
3
2
1
Bit 0
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
PTH1/
KBD4
PTH0/
KBD3
PTG2/
KBD2
PTG1/
KBD1
PTG0
/KBD0
0
0
0
0
0
Figure 19-4. Keyboard Interrupt Enable Register (KBIER)
KBIE4–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 = KBDx pin enabled as keyboard interrupt pin
0 = KBDx pin not enabled as keyboard interrupt pin
19.6 Wait Mode
The keyboard modules remain 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.
19.7 Stop Mode
The keyboard 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.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Keyboard Interrupt Module (KBI)
351
Keyboard Interrupt Module (KBI)
19.8 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
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.
Technical Data
352
MC68HC908AB32 — Rev. 1.1
Keyboard Interrupt Module (KBI)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 20. Computer Operating Properly (COP)
20.1 Contents
20.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353
20.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .354
20.4 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
20.4.1 CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
20.4.2 STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
20.4.3 COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .355
20.4.4 Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
20.4.5 Internal Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
20.4.6 Reset Vector Fetch. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
20.4.7 COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . 356
20.4.8 COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . 356
20.5
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
20.6
Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357
20.7
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .357
20.8 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 357
20.8.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358
20.8.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .358
20.9
COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . 358
20.2 Introduction
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 configuration register 1 (CONFIG1).
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Computer Operating Properly (COP)
353
Computer Operating Properly (COP)
20.3 Functional Description
Figure 20-1 shows the structure of the COP module.
RESET CIRCUIT
RESET STATUS REGISTER
COP TIMEOUT
CLEAR STAGES 5–12
STOP INSTRUCTION
INTERNAL RESET SOURCES
RESET VECTOR FETCH
CLEAR ALL STAGES
12-BIT COP PRESCALER
CGMXCLK
COPCTL WRITE
COP CLOCK
COP MODULE
6-BIT COP COUNTER
COPEN (FROM SIM)
COP DISABLE
(COPD FROM CONFIG1)
RESET
COPCTL WRITE
CLEAR
COP COUNTER
COP RATE SEL
(COPRS FROM CONFIG1)
Figure 20-1. COP Block Diagram
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
CGMXCLK cycles, depending on the state of the COP rate select bit,
COPRS, in configuration register 1. With a 218 – 24 CGMXCLK cycle
overflow option, a 4.9152MHz crystal gives a COP timeout period of
53.3ms. 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.
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.
Technical Data
354
MC68HC908AB32 — Rev. 1.1
Computer Operating Properly (COP)
Freescale Semiconductor
Computer Operating Properly (COP)
A COP reset pulls the RST pin low for 32 CGMXCLK 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 IRQ 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.
20.4 I/O Signals
The following paragraphs describe the signals shown in Figure 20-1.
20.4.1 CGMXCLK
CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency
is equal to the crystal frequency.
20.4.2 STOP Instruction
The STOP instruction clears the COP prescaler.
20.4.3 COPCTL Write
Writing any value to the COP control register (COPCTL) (see 20.5 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.
20.4.4 Power-On Reset
The power-on reset (POR) circuit clears the COP prescaler 4096
CGMXCLK cycles after power-up.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Computer Operating Properly (COP)
355
Computer Operating Properly (COP)
20.4.5 Internal Reset
An internal reset clears the COP prescaler and the COP counter.
20.4.6 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.
20.4.7 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the
configuration register 1. (See Figure 20-2.)
20.4.8 COPRS (COP Rate Select)
The COPRS signal reflects the state of the COP rate select bit (COPRS)
in the configuration register 1. (See Figure 20-2.)
Address:
Read:
Write:
Reset:
$001F
Bit 7
6
LVISTOP
R
0
0
R
5
4
LVIRSTD LVIPWRD
0
0
3
2
1
Bit 0
SSREC
COPRS
STOP
COPD
0
0
0
0
= Reserved
Figure 20-2. Configuration Register 1 (CONFIG1)
COPRS — COP Rate Select Bit
COPRS selects the COP timeout period. Reset clears COPRS.
1 = COP timeout period is 218 – 24 CGMXCLK cycles
0 = COP timeout period is 213 – 24 CGMXCLK cycles
COPD — COP Disable Bit
COPD disables the COP module.
1 = COP module disabled
0 = COP module enabled
Technical Data
356
MC68HC908AB32 — Rev. 1.1
Computer Operating Properly (COP)
Freescale Semiconductor
Computer Operating Properly (COP)
20.5 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 20-3. COP Control Register (COPCTL)
20.6 Interrupts
The COP does not generate CPU interrupt requests.
20.7 Monitor Mode
When monitor mode is entered with VTST on the IRQ pin, the COP is
disabled as long as VTST remains on the IRQ pin or the RST pin. When
monitor mode is entered by having blank reset vectors and not having
VTST on the IRQ pin, the COP is automatically disabled until a POR
occurs.
20.8 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Computer Operating Properly (COP)
357
Computer Operating Properly (COP)
20.8.1 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.
20.8.2 Stop Mode
Stop mode turns off the CGMXCLK 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.
20.9 COP Module During Break Mode
The COP is disabled during a break interrupt when VTST is present on
the RST pin.
Technical Data
358
MC68HC908AB32 — Rev. 1.1
Computer Operating Properly (COP)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 21. Low-Voltage Inhibit (LVI)
21.1 Contents
21.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
21.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 359
21.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .360
21.4.1 Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
21.4.2 Forced Reset Operation . . . . . . . . . . . . . . . . . . . . . . . . . . .361
21.4.3 False Reset Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
21.5
LVI Status Register (LVISR) . . . . . . . . . . . . . . . . . . . . . . . . . . 362
21.6
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .362
21.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 363
21.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363
21.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .363
21.2 Introduction
This section describes the low-voltage inhibit module, which monitors
the voltage on the VDD pin and can force a reset when the VDD voltage
falls to the LVI trip voltage.
21.3 Features
Features of the LVI module include the following:
•
Programmable LVI reset
•
Programmable LVI module power
•
Programmable stop mode operation
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Low-Voltage Inhibit (LVI)
359
Low-Voltage Inhibit (LVI)
21.4 Functional Description
Figure 21-1 shows the structure of the LVI module. The LVI is enabled
out of reset. The LVI module contains a bandgap reference circuit and
comparator. The LVI power bit, LVIPWRD, enables the LVI to monitor
VDD voltage. The LVI reset bit, LVIRSTD, enables the LVI module to
generate a reset when VDD falls below a voltage, LVITRIPF, and remains
at or below that level for 9 or more consecutive CPU cycles. Setting the
LVI enable in stop mode bit, LVISTOP, enables the LVI to operate in stop
mode.
LVISTOP, LVIPWRD, and LVIRSTD are in the configuration register 1
(CONFIG1). See Section 6. Configuration Register (CONFIG) for
details of the LVI’s configuration bits. Once an LVI reset occurs, the MCU
remains in reset until VDD rises above a voltage, LVITRIPR, which causes
the MCU to exit reset. See 8.4.2.5 Low-Voltage Inhibit (LVI) Reset for
details of the interaction between the SIM and the LVI. 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.
NOTE:
Where LVI trip falling voltage LVITRIPF = VLVII
and LVI trip rising voltage LVITRIPR = VLVII + HLVI
(See Section 23. Electrical Specifications.)
VDD
STOP INSTRUCTION
LVISTOP
FROM CONFIG1
FROM CONFIG1
LVIRSTD
LVIPWRD
FROM CONFIG1
LOW VDD
DETECTOR
VDD > LVITrip = 0
LVI RESET
VDD ≤ LVITrip = 1
LVIOUT
TO LVISR
Figure 21-1. LVI Module Block Diagram
Technical Data
360
MC68HC908AB32 — Rev. 1.1
Low-Voltage Inhibit (LVI)
Freescale Semiconductor
Low-Voltage Inhibit (LVI)
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 21-2. LVI I/O Register Summary
21.4.1 Polled LVI Operation
In applications that can operate at VDD levels below the LVITRIPF level,
software can monitor VDD by polling the LVIOUT bit. In configuration
register 1, 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.
21.4.2 Forced Reset Operation
In applications that require VDD to remain above the LVITRIPF level,
enabling LVI resets allows the LVI module to reset the MCU when VDD
falls below the LVITRIPF level and remains at or below that level for 9 or
more consecutive CPU cycles. In configuration register 1, the LVIPWRD
and LVIRSTD bits must be at logic 0 to enable the LVI module and to
enable LVI resets.
21.4.3 False Reset Protection
The VDD pin level is digitally filtered to reduce false resets due to power
supply noise. In order for the LVI module to reset the MCU, VDD must
remain at or below the LVITRIPF level for 9 or more consecutive CPU
cycles. VDD must be above LVITRIPR for only one CPU cycle to bring the
MCU out of reset.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Low-Voltage Inhibit (LVI)
361
Low-Voltage Inhibit (LVI)
21.5 LVI Status Register (LVISR)
The LVI status register flags VDD voltages below the LVITRIPF level.
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 21-3. LVI Status Register (LVISR)
LVIOUT — LVI Output Bit
This read-only flag becomes set when VDD falls below the LVITRIPF
voltage for 32 to 40 CGMXCLK cycles. (See Table 21-1.) Reset
clears the LVIOUT bit.
Table 21-1. LVIOUT Bit Indication
VDD
At level:
For number of CGMXCLK
cycles:
LVIOUT
VDD > LVITRIPR
Any
0
VDD < LVITRIPF
< 32 CGMXCLK cycles
0
VDD < LVITRIPF
32 to 40 CGMXCLK cycles
0 or 1
VDD < LVITRIPF
> 40 CGMXCLK cycles
1
LVITRIPF < VDD < LVITRIPR
Any
Previous value
21.6 LVI Interrupts
The LVI module does not generate interrupt requests.
Technical Data
362
MC68HC908AB32 — Rev. 1.1
Low-Voltage Inhibit (LVI)
Freescale Semiconductor
Low-Voltage Inhibit (LVI)
21.7 Low-Power Modes
The STOP and WAIT instructions put the MCU in low powerconsumption standby modes.
21.7.1 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.
21.7.2 Stop Mode
If enabled in stop mode (LVISTOP set), the LVI module remains active
in stop mode. If enabled to generate resets, the LVI module can
generate a reset and bring the MCU out of stop mode.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Low-Voltage Inhibit (LVI)
363
Low-Voltage Inhibit (LVI)
Technical Data
364
MC68HC908AB32 — Rev. 1.1
Low-Voltage Inhibit (LVI)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 22. Break Module (BRK)
22.1 Contents
22.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 365
22.3
Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
22.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .366
22.4.1 Flag Protection During Break Interrupts . . . . . . . . . . . . . . . 368
22.4.2 CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . .368
22.4.3 PIT, TIMA, and TIMB During Break Interrupts . . . . . . . . . . 368
22.4.4 COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . 368
22.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
22.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .368
22.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .369
22.6 Break Module Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
22.6.1 Break Status and Control Register. . . . . . . . . . . . . . . . . . . 369
22.6.2 Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . 370
22.6.3 SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . 370
22.6.4 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . 372
22.2 Introduction
This section describes the break module (BRK). The break module can
generate a break interrupt that stops normal program flow at a defined
address to enter a background program.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Break Module (BRK)
365
Break Module (BRK)
22.3 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
22.4 Functional Description
When the internal address bus matches the value written in the break
address registers, the break module issues a breakpoint signal to the
CPU. The CPU then loads the instruction register with a software
interrupt instruction (SWI) after completion of the current CPU
instruction. The program counter vectors to $FFFC and $FFFD ($FEFC
and $FEFD in monitor mode).
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 22-1 shows the structure of the break module.
Technical Data
366
MC68HC908AB32 — Rev. 1.1
Break Module (BRK)
Freescale Semiconductor
Break Module (BRK)
IAB15–IAB8
BREAK ADDRESS REGISTER HIGH
8-BIT COMPARATOR
IAB15–IAB0
BREAK
CONTROL
8-BIT COMPARATOR
BREAK ADDRESS REGISTER LOW
IAB7–IAB0
Figure 22-1. Break Module Block Diagram
Addr.
Register Name
Read:
SIM Break Status Register
$FE00
Write:
(SBSR)
Reset:
$FE03
$FE0C
$FE0D
Read:
SIM Break Flag Control
Write:
Register (SBFCR)
Reset:
Read:
Break Address Register
Write:
High (BRKH)
Reset:
Read:
Break Address Register
Write:
Low (BRKL)
Reset:
Read:
Break Status and Control
$FE0E
Write:
Register (BRKSCR)
Reset:
Note: Writing a logic 0 clears SBSW.
Bit 7
6
5
4
3
2
1
R
R
R
R
R
R
0
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
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
SBSW
Note
Bit 0
R
0
= Unimplemented
R
= Reserved
Figure 22-2. Break Module I/O Register Summary
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Break Module (BRK)
367
Break Module (BRK)
22.4.1 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.
22.4.2 CPU During Break Interrupts
The CPU starts a break interrupt by:
•
Loading the instruction register with the SWI instruction
•
Loading the program counter with $FFFC and $FFFD ($FEFC and
$FEFD in monitor mode)
The break interrupt begins after completion of the CPU instruction in
progress. If the break address register match occurs on the last cycle of
a CPU instruction, the break interrupt begins immediately.
22.4.3 PIT, TIMA, and TIMB During Break Interrupts
A break interrupt stops all timer counters.
22.4.4 COP During Break Interrupts
The COP is disabled during a break interrupt when VTST is present on
the RST pin.
22.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low powerconsumption standby modes.
22.5.1 Wait Mode
If enabled, the break module is active in wait mode. In the break routine,
the user can subtract one from the return address on the stack if SBSW
is set (see Section 8. System Integration Module (SIM)). Clear the
SBSW bit by writing logic 0 to it.
Technical Data
368
MC68HC908AB32 — Rev. 1.1
Break Module (BRK)
Freescale Semiconductor
Break Module (BRK)
22.5.2 Stop Mode
A break interrupt causes exit from stop mode and sets the SBSW bit in
the break status register.
22.6 Break Module Registers
These registers control and monitor operation of the break module:
•
Break status and control register (BRKSCR)
•
Break address register high (BRKH)
•
Break address register low (BRKL)
•
SIM Break status register (SBSR)
•
SIM Break flag control register (SBFCR)
22.6.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module
enable and status bits.
Address:
Read:
Write:
Reset:
$FE0E
Bit 7
6
BRKE
BRKA
0
0
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 22-3. 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
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Break Module (BRK)
369
Break Module (BRK)
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
22.6.2 Break Address Registers
The break address registers (BRKH and BRKL) contain the high and low
bytes of the desired breakpoint address. Reset clears the break address
registers.
Address:
Read:
Write:
Reset:
$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
Figure 22-4. Break Address Register High (BRKH)
Address:
Read:
Write:
Reset:
$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
Figure 22-5. Break Address Register Low (BRKL)
22.6.3 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a
break caused an exit from wait mode. The flag is useful in applications
requiring a return to wait mode after exiting from a break interrupt.
Technical Data
370
MC68HC908AB32 — Rev. 1.1
Break Module (BRK)
Freescale Semiconductor
Break Module (BRK)
Address:
Read:
Write:
Reset:
$FE00
Bit 7
6
5
4
3
2
R
R
R
R
R
R
0
0
0
0
0
0
R
= Reserved
Note: Writing a logic 0 clears SBSW.
1
SBSW
Note
0
Bit 0
R
0
Figure 22-6. SIM Break Status Register (SBSR)
SBSW — SIM Break Stop/Wait Bit
This status bit is useful in applications requiring a return to wait or stop
mode after exiting from a break interrupt. 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 one 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.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Break Module (BRK)
371
Break Module (BRK)
22.6.4 SIM Break Flag Control Register
The SIM break flag control register (SBFCR) contains a bit that enables
software to clear status bits while the MCU is in a break state.
Address:
Read:
Write:
Reset:
$FE03
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
0
R
= Reserved
Figure 22-7. 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
Technical Data
372
MC68HC908AB32 — Rev. 1.1
Break Module (BRK)
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 23. Electrical Specifications
23.1 Contents
23.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
23.3
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . 374
23.4
Functional Operating Range. . . . . . . . . . . . . . . . . . . . . . . . . . 375
23.5
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375
23.6
5.0-V DC Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . 376
23.7
EEPROM and Memory Characteristics . . . . . . . . . . . . . . . . . 377
23.8
5.0-V Control Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 378
23.9
Timer Interface Module Characteristics . . . . . . . . . . . . . . . . . 378
23.10 ADC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 379
23.11 SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 380
23.12 Clock Generation Module Characteristics . . . . . . . . . . . . . . . 383
23.12.1 CGM Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . 383
23.12.2 CGM Component Information . . . . . . . . . . . . . . . . . . . . . . 383
23.12.3 CGM Acquisition/Lock Time Information . . . . . . . . . . . . . . 384
23.13 FLASH Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . 385
23.2 Introduction
This section contains electrical and timing specifications.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Electrical Specifications
373
Electrical Specifications
23.3 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the MCU can be
exposed without permanently damaging it.
NOTE:
This device is not guaranteed to operate properly at the maximum
ratings. Refer to 23.6 5.0-V DC Electrical Characteristics for
guaranteed operating conditions.
Characteristic(1)
Symbol
Value
Unit
Supply voltage
VDD
–0.3 to + 6.0
V
Input voltage
VIn
VSS – 0.3 to VDD + 0.3
V
Maximum current per pin
excluding VDD, VSS ,
and PTD0–PTD7
I
± 15
mA
Maximum current for pins
PTD0–PTD7
IPTD0–PTD7
± 25
mA
Maximum current into VDD
Imvdd
100
mA
Maximum current out of VSS
Imvss
100
mA
Tstg
–55 to +150
°C
Storage temperature
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
maximum-rated voltages to this high-impedance circuit. For proper
operation, it is recommended that VIn and VOut be constrained to the
range VSS ≤ (VIn or VOut) ≤ VDD. Reliability of operation is enhanced if
unused inputs are connected to an appropriate logic voltage level (for
example, either VSS or VDD).
Technical Data
374
MC68HC908AB32 — Rev. 1.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
23.4 Functional Operating Range
Characteristic
Symbol
Operating temperature range
TA
–40 to +85
–40 to +125
°C
VDD
5.0 ±10%
5.0 ±10%
V
Operating voltage range
Value
Unit
23.5 Thermal Characteristics
Characteristic
Symbol
Value
Unit
Thermal resistance
QFP (64-pin)
θJA
70
°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
TJ
PD × (TA + 273 °C)
+ PD2 × θJA
W/°C
TA + (PD × θJA)
°C
Notes:
1. Power dissipation is a function of temperature.
2. K is a constant unique to the device. K can be determined for a known TA and measured
PD. With this value of K, PD and TJ can be determined for any value of TA.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Electrical Specifications
375
Electrical Specifications
23.6 5.0-V DC Electrical Characteristics
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
VOH
VOH
VOH
IOH1
VDD – 0.8
VDD – 1.5
VDD – 0.8
—
—
—
—
—
—
—
—
50
V
V
V
mA
IOH2
—
—
50
mA
IOHT
—
—
100
mA
VOL
VOL
VOL
IOL1
—
—
—
—
—
—
—
—
0.4
1.5
1.0
50
V
V
V
mA
IOL2
—
—
50
mA
IOLT
—
—
100
mA
Input high voltage
All ports, IRQ, RST, OSC1
VIH
0.7 × VDD
—
VDD
V
Input low voltage
All ports, IRQ, RST, OSC1
VIL
VSS
—
0.3 × VDD
V
—
—
—
—
30
12
mA
mA
—
—
—
—
300
20
400
50
400
50
500
100
µA
µA
µA
µA
Output high voltage
(ILoad = –2.0 mA) all I/O pins
(ILoad = –10.0 mA) all I/O pins
(ILoad = –10.0 mA) pins PTD0–PTD7 only
Maximum combined IOH for port C, port E,
port F, port G, port H
Maximum combined IOH for port D,
port A, port B
Maximum total IOH for all port pins
Output low voltage
(ILoad = 1.6 mA) all I/O pins
(ILoad = 10 mA) all I/O pins
(ILoad = 15 mA) pins PTD0–PTD7 only
Maximum combined IOL for port C, port E,
port F, port G, port H
Maximum combined IOL for port D,
port A, port B
Maximum total IOL for all port pins
VDD supply current
Run(3)
Wait(4)
Stop(5)
LVI enabled, TA = 25 °C
LVI disabled, TA = 25 °C
LVI enabled, TA = –40 °C to 125 °C
LVI disabled, TA = –40 °C to 125 °C
IDD
I/O ports Hi-Z leakage current(6)
IIL
—
1
±10
µA
Input current
IIn
—
—
±1
µA
Pullup resistors (as input only)
RPU
20
33
50
kΩ
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
Monitor mode entry voltage
VTST
VDD + 2.5
—
8
V
Low-voltage inhibit, trip falling voltage – target
VLVII
—
4.11
—
V
Technical Data
376
MC68HC908AB32 — Rev. 1.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
Low-voltage inhibit reset/recover hysteresis – target
HLVI
100
150
—
mV
POR rearm voltage(7)
VPOR
0
—
200
mV
POR reset voltage(8)
VPORRST
0
—
800
mV
RPOR
0.02
—
—
V/ms
POR rise time ramp rate(9)
Notes:
1. VDD = 5.0 Vdc ± 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25 °C only.
3. Run (operating) IDD measured using external square wave clock source (fBUS = 8.4 MHz). All inputs 0.2 V from rail. No dc
loads. Less than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly
affects run IDD. Measured with all modules enabled.
4. Wait IDD measured using external square wave clock source (fBUS = 8.4 MHz). All inputs 0.2 V from rail. No dc loads. Less
than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly affects wait
IDD. Measured with PLL and LVI enabled.
5. Stop IDD is measured with OSC1 = VSS.
6. Pullups are disabled. Port B leakage is specified in 23.10 ADC Characteristics.
7. Maximum is highest voltage that POR is guaranteed.
8. Maximum is highest voltage that POR is possible.
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.
23.7 EEPROM and Memory Characteristics
Characteristic
Symbol
Min
Max
Unit
VRDR
0.7
—
V
EEPROM programming time per byte
tEEPGM
10
—
ms
EEPROM erasing time per byte
tEBYTE
10
—
ms
EEPROM erasing time per block
tEBLOCK
10
—
ms
EEPROM erasing time per bulk
tEBULK
10
—
ms
EEPROM programming voltage discharge period
tEEFPV
100
—
µs
Number of programming operations to the same EEPROM
byte before erase(1)
—
—
8
—
EEPROM write/erase cycles at 10ms write time (85°C)
—
10,000
—
Cycles
EEPROM data retention after 10,000 write/erase cycles
—
10
—
Years
RAM data retention voltage
Notes:
1. Programming a byte more times than the specified maximum may affect the data integrity of that byte. The byte must
be erased before it can be programmed again.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Electrical Specifications
377
Electrical Specifications
23.8 5.0-V Control Timing
Characteristic(1)
Symbol
Min
Max
Unit
Frequency of operation
Crystal option(2)
External clock option(3)
fosc
1
dc(4)
8.4
33.6
MHz
MHz
Internal operating frequency
fBUS
Note(5)
8.4
MHz
RESET input pulse width low(6)
tIRL
1.5
—
tcyc
IRQ interrupt pulse width low(7)
(Edge-triggered)
tILIH
1.5
—
tcyc
IRQ interrupt pulse period
tILIL
Note(8)
—
tcyc
16-bit timer
Input capture pulse width
Input capture period
tTH,tTL
tTLTL
2
Note(9)
—
—
tcyc
tcyc
Notes:
1. VDD = 5.0 Vdc ± 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted
2. See 23.12 Clock Generation Module Characteristics for more information.
3. No more than 10% duty cycle deviation from 50%
4. Some modules may require a minimum frequency greater than dc for proper operation.
See appropriate table for this information.
5. Some modules may require a minimum frequency greater than dc for proper operation.
See appropriate table for this information.
6. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse
width to cause a reset.
7. Minimum pulse width is for guaranteed interrupt. It is possible for a smaller pulse width to
be recognized.
8. Minimum pulse width is for guaranteed interrupt. It is possible for a smaller pulse width to
be recognized. The minimum period, tILIL or tTLTL, should not be less than the number of
cycles it takes to execute the interrupt service routine plus TBD tcyc.
9. The minimum period, tILIL or tTLTL, should not be less than the number of cycles it takes to
execute the interrupt service routine plus TBD tcyc.
23.9 Timer Interface Module Characteristics
Characteristic
Input capture pulse width
Input clock pulse width
Symbol
Min
Max
Unit
tTIH, tTIL
125
—
ns
tTCH, tTCL
(1/fBUS)+5
—
ns
Technical Data
378
MC68HC908AB32 — Rev. 1.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
23.10 ADC Characteristics
Characteristic(1)
Symbol
Min
Max
Unit
Comments
Supply voltage
VDDAD
4.5
(VDD min)
5.5
(VDD max)
V
VDDAREF should be tied
to the same potential as
VDD via separate
traces.
Input voltages
VADIN
VREFH
0
1.5
VDDAREF
VDDAREF
V
VADIN ≤ VREFH
Resolution
BAD
8
8
Bits
Absolute accuracy
(VREFL = 0 V,
VREFH = VDDAD = 5 V ± 10%)
AAD
± 1/2
±1
LSB
ADC internal clock
fADIC
0.5
1.048
MHz
Conversion range
RAD
VREFL
VREFH
V
Power-up time
tADPU
16
Conversion time
tADC
16
17
tAIC cycles
Sample time(2)
tADS
5
—
tAIC cycles
Zero input reading(3)
ZADI
00
01
Hex
VIN = VREFL
Full-scale reading(3)
FADI
FE
FF
Hex
VIN = VREFH
Input capacitance
CADI
—
(20) 8
pF
Not tested
—
—
±1
µA
Input leakage(4)
Port B
Includes quantization
tAIC = 1/fADIC, tested
only at 1 MHz
VREFL = VSSA
tAIC cycles
Notes:
1. VDD = 5.0 Vdc ± 10%, VDDA = VDDAREF = 5.0 Vdc ± 10%, VREFH = 5.0 Vdc ± 10%, VSS = 0 Vdc, VREFL = VSSA = 0 Vdc
2. Source impedances greater than 10 kΩ adversely affect internal RC charging time during input sampling.
3. Zero-input/full-scale reading requires sufficient decoupling measures for accurate conversions.
4. The external system error caused by input leakage current is approximately equal to the product of R source and input
current.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Electrical Specifications
379
Electrical Specifications
23.11 SPI Characteristics
Diagram
Number(1)
Characteristic(2)
Symbol
Min
Max
Unit
Operating frequency
Master
Slave
fBUS(M)
fBUS(S)
fBUS/128
DC
fBUS/2
fBUS
MHz
MHz
1
Cycle time
Master
Slave
tcyc(M)
tcyc(S)
2
1
128
—
tcyc
tcyc
2
Enable lead time
tLead(S)
15
—
ns
3
Enable lag time
tLag(S)
15
—
ns
4
Clock (SPSCK) high time
Master
Slave
tSCKH(M)
tSCKH(S)
100
50
—
—
ns
ns
5
Clock (SPSCK) low time
Master
Slave
tSCKL(M)
tSCKL(S)
100
50
—
—
ns
ns
6
Data setup time (inputs)
Master
Slave
tSU(M)
tSU(S)
45
5
—
—
ns
ns
7
Data hold time (inputs)
Master
Slave
tH(M)
tH(S)
0
15
—
—
ns
ns
8
Access time, slave(3)
CPHA = 0
CPHA = 1
tA(CP0)
tA(CP1)
0
0
40
20
ns
ns
9
Disable time, slave(4)
tDIS(S)
—
25
ns
10
Data valid time, after enable edge
Master
Slave(5)
tV(M)
tV(S)
—
—
10
40
ns
ns
11
Data hold time, outputs, after enable edge
Master
Slave
tHO(M)
tHO(S)
0
5
—
—
ns
ns
Notes:
1. Numbers refer to dimensions in Figure 23-1 and Figure 23-2.
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
Technical Data
380
MC68HC908AB32 — Rev. 1.1
Electrical Specifications
Freescale Semiconductor
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
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 23-1. SPI Master Timing
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Electrical Specifications
381
Electrical Specifications
SS
INPUT
3
1
SPSCK INPUT
CPOL = 0
5
4
2
SPSCK INPUT
CPOL = 1
5
4
9
8
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
MOSI
INPUT
5
4
10
NOTE
9
SLAVE
MSB OUT
6
7
BITS 6–1
SLAVE LSB OUT
11
10
BITS 6–1
MSB IN
LSB IN
Note: Not defined but normally LSB of character previously transmitted
b) SPI Slave Timing (CPHA = 1)
Figure 23-2. SPI Slave Timing
Technical Data
382
MC68HC908AB32 — Rev. 1.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
23.12 Clock Generation Module Characteristics
23.12.1 CGM Operating Conditions
Characteristic
Symbol
Min
Typ
Max
Comments
Operating Voltage
VDD
4.5 V
—
5.5 V
Crystal Reference Frequency
fRCLK
1
—
8.4
Module Crystal Reference
Frequency
fXCLK
—
4.9152 MHz
—
Same Frequency as
fRCLK
Range Nominal Multiplier
fNOM
—
4.9152 MHz
—
4.5 to 5.5 V, VDD only
VCO Center-of-Range Frequency
(MHz)
fVRS
4.9152
—
32.0
4.5 to 5.5 V, VDD only
VCO Operating Frequency (MHz)
fVCLK
4.9152
—
32.0
23.12.2 CGM Component Information
Characteristic
Symbol
Min
Typ
Max
Crystal load capacitance
CL
—
—
—
Consult crystal
manufacturer’s data
Crystal fixed capacitance
C1
—
2 × CL
—
Consult crystal
manufacturer’s data
Crystal tuning capacitance
C2
—
2 × CL
—
Consult crystal
manufacturer’s data
Feedback bias resistor
RB
—
22MΩ
—
Series resistor
RS
—
330kΩ
1MΩ
CFact
—
0.0154
—
F/s V
CF
—
CFact × (VDDA/fXCLK)
—
See 9.5.3 External Filter
Capacitor Pin
(CGMXFC).
—
CBYP must provide low
AC impedance from f =
fXCLK/100 to 100 ×
fVCLK, so series
resistance must be
considered.
Filter capacitor multiply factor
Filter capacitor
Bypass capacitor
CBYP
—
0.1 µF
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Unit
Not required
Technical Data
Electrical Specifications
383
Electrical Specifications
23.12.3 CGM Acquisition/Lock Time Information
Description(1)
Symbol
Min
Typ
Max
Notes
Manual mode time to stable
tACQ
—
(8 × VDDA)/(fXCLK × KACQ)
—
If CF chosen
correctly
tAL
—
(4 × VDDA)/(fXCLK × KTRK)
—
If CF chosen
correctly
Manual acquisition time
tLock
—
tACQ+tAL
—
Tracking mode entry
frequency tolerance
DTRK
0
—
± 3.6%
Acquisition mode entry
frequency tolerance
DUNT
± 6.3%
—
± 7.2%
LOCK entry freq. tolerance
DLOCK
0
—
± 0.9%
LOCK exit freq. tolerance
DUNL
± 0.9%
—
± 1.8%
Reference cycles per
Acquisition mode
measurement
nACQ
—
32
—
Reference cycles per
Tracking mode
measurement
nTRK
—
128
—
Automatic mode time
to stable
tACQ
nACQ/fXCLK
(8 × VDDA)/(fXCLK ×
KACQ)
tAL
nTRK/fXCLK
(4 × VDDA)/(fXCLK × KTRK)
—
tLock
—
tACQ + tAL
—
0
—
± (fCRYS)
× (.025%)
× (N/4)
Manual stable to lock time
Automatic stable to lock time
Automatic lock time
PLL jitter, deviation of
average bus frequency
over 2 ms
If CF Chosen
Correctly
If CF Chosen
Correctly
N = VCO
Freq. Mult.
(GBNT)(2)
Notes:
1. VDD = 5.0 Vdc ± 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted.
2. GBNT guaranteed but not tested.
Technical Data
384
MC68HC908AB32 — Rev. 1.1
Electrical Specifications
Freescale Semiconductor
Electrical Specifications
23.13 FLASH Memory Characteristics
Characteristic
Symbol
Min
Max
Unit
—
1
—
MHz
FLASH read bus clock frequency
fRead(1)
32k
8.4M
Hz
FLASH page erase time
tErase(2)
1
—
ms
FLASH mass erase time
tMErase(3)
4
—
ms
FLASH PGM/ERASE to HVEN set up time
tnvs
10
—
µs
FLASH high-voltage hold time
tnvh
5
—
µs
FLASH high-voltage hold time (mass erase)
tnvhl
100
—
µs
FLASH program hold time
tpgs
5
—
µs
FLASH program time
tPROG
30
40
µs
FLASH return to read time
trcv(4)
1
—
µs
FLASH cumulative program hv period
tHV(5)
—
4
ms
FLASH row erase endurance(6)
—
10,000
—
Cycles
FLASH row program endurance(7)
—
10,000
—
Cycles
—
10
—
Years
FLASH program bus clock frequency
FLASH data retention time
(8)
Notes:
1. fRead is defined as the frequency range for which the FLASH memory can be read.
2. If the page erase time is longer than tErase (Min), there is no erase-disturb, but it reduces the endurance of the
FLASH memory.
3. If the mass erase time is longer than tMErase (Min), there is no erase-disturb, but it reduces the endurance of
the FLASH memory.
4. trcv is defined as the time it needs before the FLASH can be read after turning off the high voltage charge pump,
by clearing HVEN to logic 0.
5. tHV is defined as the cumulative high voltage programming time to the same row before next erase.
tHV must satisfy this condition: tnvs + tnvh + tpgs + (tPROG × 64) ≤ tHV max.
6. The minimum row endurance value specifies each row of the FLASH memory is guaranteed to work for at least
this many erase / program cycles.
7. The minimum row endurance value specifies each row of the FLASH memory is guaranteed to work for at least
this many erase / program cycles.
8. The FLASH is guaranteed to retain data over the entire operating temperature range for at least the minimum
time specified.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Electrical Specifications
385
Electrical Specifications
Technical Data
386
MC68HC908AB32 — Rev. 1.1
Electrical Specifications
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 24. Mechanical Specifications
24.1 Contents
24.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 387
24.3
64-Pin Plastic Quad Flat Pack (QFP) . . . . . . . . . . . . . . . . . . . 388
24.2 Introduction
This section gives the dimensions for:
•
64-pin plastic quad flat pack (case 840B-01)
Figure 24-1 shows the latest package drawing at the time of this
publication. To make sure that you have the latest package
specifications, please visit the Freescale website at http://freescale.com.
Follow the World Wide Web on-line instructions to retrieve the current
mechanical specifications.
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Mechanical Specifications
387
Mechanical Specifications
24.3 64-Pin Plastic Quad Flat Pack (QFP)
L
48
33
DETAIL A
S
D
S
H A–B
V
0.20 (0.008)
M
B
P
B
M
L
B
0.20 (0.008)
–B–
C A–B
–A–
0.05 (0.002) A–B
S
D
32
S
49
–A–, –B–, –D–
DETAIL A
64
17
F
1
16
–D–
A
0.20 (0.008)
C A–B
S
D
S
0.05 (0.002) A–B
S
0.20 (0.008) M H A–B
S
D
S
M
J
N
E
M
C
M
H
0.02 (0.008)
DATUM
PLANE
M
C A–B
S
D
S
SECTION B–B
0.01 (0.004)
G
U
T
R
–H–
DETAILC
–H–
–C–
SEATING
PLANE
BASE
METAL
D
DATUM
PLANE
Q
K
W
X
DETAIL C
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) PER SIDE.
TOTAL IN EXCESS OF THE D DIMENSION AT
MAXIMUM MATERIAL CONDITION. DAMBAR
CANNOT BE LOCATED ON THE LOWER RADIUS
OR THE FOOT.
DIM
A
B
C
D
E
F
G
H
J
K
L
M
N
P
Q
R
S
T
U
V
W
X
MILLIMETERS
MIN
MAX
13.90
14.10
13.90
14.10
2.15
2.45
0.30
0.45
2.00
2.40
0.30
0.40
0.80 BSC
—
0.25
0.13
0.23
0.65
0.95
12.00 REF
5°
10°
0.13
0.17
0.40 BSC
0°
7°
0.13
0.30
16.95
17.45
0.13
—
0°
—
16.95
17.45
0.35
0.45
1.6 REF
INCHES
MIN
MAX
0.547
0.555
0.547
0.555
0.085
0.096
0.012
0.018
0.079
0.094
0.012
0.016
0.031 BSC
—
0.010
0.005
0.009
0.026
0.037
0.472 REF
5°
10°
0.005
0.007
0.016 BSC
0°
7°
0.005
0.012
0.667
0.687
0.005
—
0°
—
0.667
0.687
0.014
0.018
0.063 REF
Figure 24-1. 64-Pin Plastic Quad Flat Pack (QFP)
Technical Data
388
MC68HC908AB32 — Rev. 1.1
Mechanical Specifications
Freescale Semiconductor
Technical Data — MC68HC908AB32
Section 25. Ordering Information
25.1 Contents
25.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
25.3
MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 389
25.2 Introduction
This section contains ordering numbers for the MC68HC908AB32.
25.3 MC Order Numbers
Table 25-1. MC Order Numbers
MC order number(1)
Operating
temperature range
MC68HC908AB32CFU
–40 °C to +85 °C
MC68HC908AB32MFU
–40 °C to +125 °C
Notes:
1. FU = Quad Flat Pack
C = Operating temperature range: –40 °C to +85 °C
M = Operating temperature range: –40 °C to +125 °C
MC68HC908AB32 — Rev. 1.1
Freescale Semiconductor
Technical Data
Ordering Information
389
Ordering Information
Technical Data
390
MC68HC908AB32 — Rev. 1.1
Ordering Information
Freescale Semiconductor
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Rev. 1.1
MC68HC908AB32/D
August 2, 2005
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