MC68HC908GR16A
Data Sheet
M68HC08
Microcontrollers
MC68HC908GR16A
Rev. 1.0
03/2006
freescale.com
MC68HC908GR16A
Data Sheet
To provide the most up-to-date information, the revision of our documents on the World Wide Web will be
the most current. Your printed copy may be an earlier revision. To verify you have the latest information
available, refer to:
http://freescale.com/
The following revision history table summarizes changes contained in this document. For your
convenience, the page number designators have been linked to the appropriate location.
Revision History
Date
Revision
Level
October,
2004
N/A
Initial release
N/A
March,
2006
1.0
10.5 Clock Generator Module (CGM) — Updated description to remove
erroneous information.
106
Description
Page
Number(s)
Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc.
This product incorporates SuperFlash® technology licensed from SST.
© Freescale Semiconductor, Inc., 2004, 2006. All rights reserved.
MC68HC908GR16A Data Sheet, Rev. 1.0
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Revision History
MC68HC908GR16A Data Sheet, Rev. 1.0
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Freescale Semiconductor
List of Chapters
Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Chapter 2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Chapter 3 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Chapter 4 Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Chapter 5 Configuration Register (CONFIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 6 Computer Operating Properly (COP) Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Chapter 7 Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
Chapter 8 External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95
Chapter 9 Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Chapter 10 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
Chapter 11 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
Chapter 12 Input/Output (I/O) Ports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
Chapter 13 Resets and Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .131
Chapter 14 Enhanced Serial Communications Interface (ESCI) Module . . . . . . . . . . . . . 143
Chapter 15 System Integration Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
Chapter 16 Serial Peripheral Interface (SPI) Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
Chapter 17 Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
Chapter 18 Timer Interface Module (TIM1 and TIM2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Chapter 19 Development Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
Chapter 20 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
Chapter 21 Ordering Information and Mechanical Specifications . . . . . . . . . . . . . . . . . . 263
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List of Chapters
MC68HC908GR16A Data Sheet, Rev. 1.0
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Freescale Semiconductor
Table of Contents
Chapter 1
General Description
1.1
1.2
1.2.1
1.2.2
1.3
1.4
1.5
1.5.1
1.5.2
1.5.3
1.5.4
1.5.5
1.5.6
1.5.7
1.5.8
1.5.9
1.5.10
1.5.11
1.5.12
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Standard Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features of the CPU08 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power Supply Pins (VDD and VSS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oscillator Pins (OSC1 and OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Reset Pin (RST). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Interrupt Pin (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Power Supply Pins (VDDA and VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Filter Capacitor Pin (VCGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Power Supply/Reference Pins (VDDAD/VREFH and VSSAD/VREFL). . . . . . . . . . . . . .
Port A Input/Output (I/O) Pins (PTA7/KBD7–PTA0/KBD0) . . . . . . . . . . . . . . . . . . . . . . . . .
Port B I/O Pins (PTB7/AD7–PTB0/AD0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port C I/O Pins (PTC6–PTC0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port D I/O Pins (PTD7/T2CH1–PTD0/SS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port E I/O Pins (PTE5–PTE2 and PTE0/TxD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19
19
19
21
21
21
24
24
24
24
24
25
25
25
25
25
25
25
26
Chapter 2
Memory
2.1
2.2
2.3
2.4
2.5
2.6
2.6.1
2.6.2
2.6.3
2.6.4
2.6.5
2.6.6
2.6.7
2.6.8
2.6.9
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Input/Output (I/O) Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Program/Read Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Block Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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27
27
27
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37
37
38
39
39
40
41
43
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Chapter 3
Analog-to-Digital Converter (ADC)
3.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.2
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.1
ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.2
Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.3
Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.4
Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.5
Accuracy and Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.6
Result Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4
Monotonicity. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.1
ADC Analog Power Pin (VDDAD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.2
ADC Analog Ground Pin (VSSAD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.3
ADC Voltage Reference High Pin (VREFH). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.4
ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.5
ADC Voltage In (VADIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.1
ADC Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.2
ADC Data Register High and Data Register Low. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.2.1
Left Justified Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.2.2
Right Justified Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.2.3
Left Justified Signed Data Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.2.4
Eight Bit Truncation Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.8.3
ADC Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
45
45
45
47
48
48
48
48
49
49
49
50
50
50
50
50
50
51
51
51
51
53
53
53
54
54
55
Chapter 4
Clock Generator Module (CGM)
4.1
4.2
4.3
4.3.1
4.3.2
4.3.3
4.3.4
4.3.5
4.3.6
4.3.7
4.3.8
4.3.9
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crystal Oscillator Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Phase-Locked Loop Circuit (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acquisition and Tracking Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Manual and Automatic PLL Bandwidth Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Programming the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Special Programming Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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57
57
59
59
59
60
60
61
63
63
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4.4
4.4.1
4.4.2
4.4.3
4.4.4
4.4.5
4.4.6
4.4.7
4.4.8
4.4.9
4.4.10
4.5
4.5.1
4.5.2
4.5.3
4.5.4
4.5.5
4.6
4.7
4.7.1
4.7.2
4.7.3
4.8
4.8.1
4.8.2
4.8.3
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Analog Ground Pin (VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oscillator Enable Signal (SIMOSCEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oscillator Enable in Stop Mode Bit (OSCENINSTOP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crystal Output Frequency Signal (CGMXCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Base Clock Output (CGMOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Multiplier Select Register High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Multiplier Select Register Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL VCO Range Select Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Special Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acquisition/Lock Time Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acquisition/Lock Time Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parametric Influences on Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Choosing a Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
65
65
65
65
65
65
65
65
65
66
66
66
67
68
69
70
70
71
71
71
72
72
72
72
72
73
Chapter 5
Configuration Register (CONFIG)
5.1
5.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 6
Computer Operating Properly (COP) Module
6.1
6.2
6.3
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.3.7
6.3.8
6.4
6.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reset Vector Fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
79
79
80
80
80
80
80
80
81
81
81
81
81
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9
Table of Contents
6.6
6.7
6.7.1
6.7.2
6.8
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
81
81
81
82
82
Chapter 7
Central Processor Unit (CPU)
7.1
7.2
7.3
7.3.1
7.3.2
7.3.3
7.3.4
7.3.5
7.4
7.5
7.5.1
7.5.2
7.6
7.7
7.8
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
83
83
83
84
84
85
85
86
87
87
87
87
87
88
93
Chapter 8
External Interrupt (IRQ)
8.1
8.2
8.3
8.4
8.5
8.6
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IRQ Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
95
95
95
97
97
98
Chapter 9
Keyboard Interrupt Module (KBI)
9.1
9.2
9.3
9.4
9.5
9.5.1
9.5.2
9.6
9.7
9.7.1
9.7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Keyboard Module During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Keyboard Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
Keyboard Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
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Freescale Semiconductor
Chapter 10
Low-Power Modes
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.1.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.1.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.2.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.3 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.3.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.3.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.4 Central Processor Unit (CPU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.4.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.4.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.5 Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.5.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.5.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.6 Computer Operating Properly Module (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.7 External Interrupt Module (IRQ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.7.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.7.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8 Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.8.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.9 Low-Voltage Inhibit Module (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.9.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.9.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.10 Enhanced Serial Communications Interface Module (ESCI) . . . . . . . . . . . . . . . . . . . . . . . . . .
10.10.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.10.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.11 Serial Peripheral Interface Module (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.11.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.11.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.12 Timer Interface Module (TIM1 and TIM2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.12.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.12.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.13 Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.13.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.13.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
10.14 Exiting Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
105
105
105
105
105
105
106
106
106
106
106
106
106
106
106
107
107
107
107
107
107
107
107
107
108
108
108
108
108
108
108
108
108
109
109
109
109
109
109
109
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Table of Contents
Chapter 11
Low-Voltage Inhibit (LVI)
11.1
11.2
11.3
11.3.1
11.3.2
11.3.3
11.3.4
11.4
11.5
11.6
11.6.1
11.6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Voltage Hysteresis Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LVI Trip Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LVI Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
111
111
111
112
112
113
113
113
113
113
114
114
Chapter 12
Input/Output (I/O) Ports
12.1
12.2
12.2.1
12.2.2
12.2.3
12.3
12.3.1
12.3.2
12.4
12.4.1
12.4.2
12.4.3
12.5
12.5.1
12.5.2
12.5.3
12.6
12.6.1
12.6.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port A Input Pullup Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port C Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port C Input Pullup Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port D Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port D Input Pullup Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port E Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
115
118
118
118
120
120
120
121
122
122
122
124
124
124
125
127
127
127
128
Chapter 13
Resets and Interrupts
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2 Resets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.1
Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.2
External Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3
Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3.1
Power-On Reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3.2
Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
131
131
131
131
131
131
132
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13.2.3.3
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3.4
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.3.5
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2.4
System Integration Module (SIM) Reset Status Register. . . . . . . . . . . . . . . . . . . . . . . . . .
13.3 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1
Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2
Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.1
Software Interrupt (SWI) Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.2
Break Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.3
IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.4
Clock Generator (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.5
Timer Interface Module 1 (TIM1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.6
Timer Interface Module 2 (TIM2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.7
Serial Peripheral Interface (SPI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.8
Serial Communications Interface (SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.9
KBD0–KBD7 Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.10
Analog-to-Digital Converter (ADC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.11
Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3
Interrupt Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.1
Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.2
Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.3
Interrupt Status Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
132
132
133
133
134
134
135
135
135
138
138
138
138
138
139
139
139
139
140
140
141
141
Chapter 14
Enhanced Serial Communications Interface (ESCI) Module
14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.1
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2.4
Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2.5
Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2.6
Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.2
Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.5
Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.6
Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.7
Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.3.8
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
143
143
143
145
147
147
148
148
148
149
149
149
149
150
151
151
152
152
154
155
155
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Table of Contents
14.5
14.5.1
14.5.2
14.6
14.7
14.7.1
14.7.2
14.8
14.8.1
14.8.2
14.8.3
14.8.4
14.8.5
14.8.6
14.8.7
14.8.8
14.9
14.9.1
14.9.2
14.9.3
14.9.4
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
ESCI During Break Module Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
PTE0/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
PTE1/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
ESCI Control Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
ESCI Control Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158
ESCI Control Register 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
ESCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161
ESCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
ESCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164
ESCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 165
ESCI Prescaler Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
ESCI Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
ESCI Arbiter Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
ESCI Arbiter Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Bit Time Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Arbitration Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
Chapter 15
System Integration Module (SIM)
15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.2 SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.2.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.2.2
Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.2.3
Clocks in Stop Mode and Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.1
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.2
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.2.1
Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.2.2
Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.2.3
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.2.4
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.2.5
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.3.2.6
Monitor Mode Entry Module Reset (MODRST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.4 SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.4.1
SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.4.2
SIM Counter During Stop Mode Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.4.3
SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5 Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.1.1
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.1.2
SWI Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.1.3
Interrupt Status Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
173
175
175
175
175
176
176
176
177
178
178
178
178
179
179
179
179
179
179
180
182
182
183
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15.5.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.3
Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.4
Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.7 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.7.1
SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.7.2
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.7.3
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
184
184
184
185
185
186
187
187
188
189
Chapter 16
Serial Peripheral Interface (SPI) Module
16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1
Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.2
Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.4 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.4.1
Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.4.2
Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.4.3
Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.4.4
Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.5 Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.6 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.6.1
Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.6.2
Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.8 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.9 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.9.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.9.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.10 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.11 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.11.1
MISO (Master In/Slave Out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.11.2
MOSI (Master Out/Slave In). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.11.3
SPSCK (Serial Clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.11.4
SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.12 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.12.1
SPI Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.12.2
SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.12.3
SPI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
191
191
191
194
194
195
195
195
196
197
199
200
200
201
202
204
204
204
204
204
205
205
205
205
206
207
207
208
210
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Freescale Semiconductor
15
Table of Contents
Chapter 17
Timebase Module (TBM)
17.1
17.2
17.3
17.4
17.5
17.6
17.6.1
17.6.2
17.7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TBM Interrupt Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Timebase Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
211
211
211
211
212
213
213
213
214
Chapter 18
Timer Interface Module (TIM1 and TIM2)
18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.1
TIM Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.2
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.3
Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.4
Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.4.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.5 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.7 TIM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.9 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.9.1
TIM Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.9.2
TIM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.9.3
TIM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.9.4
TIM Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.9.5
TIM Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
215
217
217
217
219
219
220
220
220
221
221
222
222
223
223
223
224
224
224
224
224
226
226
227
230
MC68HC908GR16A Data Sheet, Rev. 1.0
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Freescale Semiconductor
Chapter 19
Development Support
19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.1.1
Flag Protection During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.1.2
TIM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.1.3
COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.2
Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.2.1
Break Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.2.2
Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.2.3
SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.2.4
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.2.3
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3 Monitor Module (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1.1
Normal Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1.2
Forced Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1.3
Monitor Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1.4
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1.5
Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1.6
Baud Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.1.7
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
19.3.2
Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
231
231
231
234
234
234
234
235
235
236
236
236
237
237
241
241
241
242
242
242
242
246
Chapter 20
Electrical Specifications
20.1
20.2
20.3
20.4
20.5
20.6
20.7
20.8
20.9
20.9.1
20.9.2
20.10
20.11
20.12
20.13
20.14
20.15
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5-Vdc Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3-Vdc Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.0-Volt Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3-Volt Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Clock Generation Module (CGM) Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Component Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.0-Volt ADC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3-Volt ADC Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
5.0-Volt SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3-Volt SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Timer Interface Module Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
247
247
248
248
249
251
253
253
254
254
254
255
256
257
258
261
262
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
17
Table of Contents
Chapter 21
Ordering Information and Mechanical Specifications
21.1
21.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
MC68HC908GR16A Data Sheet, Rev. 1.0
18
Freescale Semiconductor
Chapter 1
General Description
1.1 Introduction
The MC68HC908GR16A is a member of the low-cost, high-performance M68HC08 Family of 8-bit
microcontroller units (MCUs). 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.
1.2 Features
For convenience, features have been organized to reflect:
• Standard features
• Features of the CPU08
1.2.1 Standard Features
Features include:
• High-performance M68HC08 architecture optimized for C-compilers
• Fully upward-compatible object code with M6805, M146805, and M68HC05 Families
• 8-MHz internal bus frequency
• Clock generation module supporting 1-MHz to 8-MHz crystals
• FLASH program memory security(1)
• On-chip programming firmware for use with host personal computer which does not require high
voltage for entry
• In-system programming (ISP)
• System protection features:
– Optional computer operating properly (COP) reset
– Low-voltage detection with optional reset and selectable trip points for 3.3-V and 5.0-V
operation
– Illegal opcode detection with reset
– Illegal address detection with reset
• Low-power design; fully static with stop and wait modes
• Standard low-power modes of operation:
– Wait mode
– Stop mode
• Master reset pin and power-on reset (POR)
• 16 Kbytes of on-chip FLASH memory
• 1 Kbyte of on-chip random-access memory (RAM)
• 406 bytes of FLASH programming routines read-only memory (ROM)
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
19
General Description
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Serial peripheral interface (SPI) module
Enhanced serial communications interface (ESCI) module
Fine adjust baud rate prescalers for precise control of baud rate
Arbiter module:
– Measurement of received bit timings for baud rate recovery without use of external timer
– Bitwise arbitration for arbitrated UART communications
LIN specific enhanced features:
– Generation of LIN 1.2 break symbols without extra software steps on each message
– Break detection filtering to prevent false interrupts
Two 16-bit, 2-channel timer interface modules (TIM1 and TIM2) with selectable input capture,
output compare, and pulse-width modulation (PWM) capability on each channel
Up to 8-channel, 10-bit successive approximation analog-to-digital converter (ADC) depending on
package choice
BREAK (BRK) module to allow single breakpoint setting during in-circuit debugging
Internal pullups on IRQ and RST to reduce customer system cost
Up to 37 general-purpose input/output (I/O) pins, including:
– 28 shared-function I/O pins
– Up to nine dedicated I/O pins, depending on package choice
Selectable pullups on inputs only on ports A, C, and D. Selection is on an individual port bit basis.
During output mode, pullups are disengaged.
High current 10-mA sink/source capability on all port pins
Higher current 20-mA sink/source capability on PTC0–PTC4
Timebase module (TBM) with clock prescaler circuitry for eight user selectable periodic real-time
interrupts with optional active clock source during stop mode for periodic wakeup from stop using
an external crystal
User selection of having the oscillator enabled or disabled during stop mode
Up to 8-bit keyboard wakeup port depending on package choice
2 mA maximum current injection on all port pins to maintain input protection
Available packages:
– 32-pin quad flat pack (LQFP)
– 48-pin quad flat pack (LQFP)
Specific features of the MC68HC908GR16A in 32-pin LQFP are:
– Port A is only 4 bits: PTA0–PTA3; 4-pin keyboard interrupt (KBI) module
– Port B is only 6 bits: PTB0–PTB5; 6-channel ADC module
– Port C is only 2 bits: PTC0–PTC1
– Port D is only 7 bits: PTD0–PTD6; shared with SPI, TIM1, and TIM2 modules
– Port E is only 2 bits: PTE0–PTE1; shared with ESCI module
Specific features of the MC68HC908GR16A in 48-pin LQFP are:
– Port A is 8 bits: PTA0–PTA7; 8-pin KBI module
– Port B is 8 bits: PTB0–PTB7; 8-channel ADC module
– Port C is only 7 bits: PTC0–PTC6
– Port D is 8 bits: PTD0–PTD7; shared with SPI, TIM1, and TIM2 modules
– Port E is only 6 bits: PTE0–PTE5; shared with ESCI module
MC68HC908GR16A Data Sheet, Rev. 1.0
20
Freescale Semiconductor
MCU Block Diagram
1.2.2 Features of the CPU08
Features of the CPU08 include:
• Enhanced HC05 programming model
• Extensive loop control functions
• 16 addressing modes (eight more than the HC05)
• 16-bit index register and stack pointer
• Memory-to-memory data transfers
• Fast 8 × 8 multiply instruction
• Fast 16/8 divide instruction
• Binary-coded decimal (BCD) instructions
• Optimization for controller applications
• Efficient C language support
1.3 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908GR16A.
1.4 Pin Assignments
Figure 1-2 and Figure 1-3 illustrate the pin assignments for the 32-pin LQFP and 48-pin LQFP
respectively.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
21
General Description
INTERNAL BUS
DDRA
PORTA
PTB7/AD7
PTB6/AD6
PTB5/AD5
PTB4/AD4
PTB3/AD3
PTB2/AD2
PTB1/AD1
PTB0/AD0
PTC6(1)
PTC5(1)
PTC4(1), (2)
PTC3(1), (2)
PTC2(1), (2)
PTC1(1), (2)
PTC0(1), (2)
PTD7/T2CH1(1)
PTD6/T2CH0(1)
PTD5/T1CH1(1)
PTD4/T1CH0(1)
PTD3/SPSCK(1)
PTD2/MOSI(1)
PTD1/MISO(1)
PTD0/SS(1)
PTE5–PTE2
PTE1/RxD
PTE0/TxD
DDRB
SINGLE BREAKPOINT
BREAK MODULE
DUAL VOLTAGE
LOW-VOLTAGE INHIBIT
MODULE
USER FLASH — 15,872 BYTES
PTA7/KBD7–
PTA0/KBD0(1)
PORTB
CONTROL AND STATUS REGISTERS — 64 BYTES
PROGRAMMABLE TIMEBASE
MODULE
PORTC
ARITHMETIC/LOGIC
UNIT (ALU)
PORTD
CPU
REGISTERS
PORTE
M68HC08 CPU
USER RAM — 1024 BYTES
FLASH PROGRAMMING ROUTINES ROM — 406 BYTES
USER FLASH VECTOR SPACE — 36 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 1
DDRC
8-BIT KEYBOARD
INTERRUPT MODULE
MONITOR ROM — 350 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 2
CLOCK GENERATOR MODULE
PHASE LOCKED LOOP
COMPUTER OPERATING
PROPERLY MODULE
RST(3)
SYSTEM INTEGRATION
MODULE
IRQ(3)
SINGLE EXTERNAL
INTERRUPT MODULE
SERIAL PERIPHERAL
INTERFACE MODULE
MONITOR MODULE
VDDAD/VREFH
VSSAD/VREFL
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
POWER-ON RESET
MODULE
VDD
VSS
VDDA
VSSA
DDRD
CGMXFC
ENHANCED SERIAL
COMUNICATIONS
INTERFACE MODULE
1–8 MHz OSCILLATOR
DDRE
OSC1
OSC2
MEMORY MAP
MODULE
CONFIGURATION
REGISTER 1–2
MODULE
SECURITY
MODULE
POWER
MONITOR MODE ENTRY
MODULE
1. Ports are software configurable with pullup device if input port.
2. Higher current drive port pins
3. Pin contains integrated pullup device
Figure 1-1. MCU Block Diagram
MC68HC908GR16A Data Sheet, Rev. 1.0
22
Freescale Semiconductor
CGMXFC
VSSA
VDDA
PTC1
PTC0
PTA3/KBD3
30
29
28
27
26
25
1
OSC2
RST
31
32 OSC1
Pin Assignments
24
PTA2/KBD2
PTD1/MISO
6
19
PTB5/AD5
PTD2/MOSI
7
18
PTB4/AD4
PTD3/SPSCK
8
17
PTB3/AD3
16
VDDAD/VREFH
PTB2/AD2
20
15
5
PTB1/AD1
PTD0/SS
14
VSSAD/VREFL
PTB0/AD0
21
13
4
PTD6/T2CH0
IRQ
12
PTA0/KBD0
PTD5/T1CH1
22
11
3
PTD4/T1CH0
PTE1/RxD
10
PTA1/KBD1
VDD
23
9
2
VSS
PTE0/TxD
CGMXFC
VSSA
VDDA
PTC1
PTC0
PTA7/KBD7
PTA6/KBD6
PTA5/KBD5
PTA4/KBD4
46
45
44
43
42
41
40
39
38
37 PTA3/KBD3
OSC2
RST 1
47
48 OSC1
Figure 1-2. 32-Pin LQFP Pin Assignments
36 PTA2/KBD2
PTE5
7
30
VDDAD/VREFH
IRQ
8
29
PTB7/AD7
PTD0/SS
9
28
PTB6/AD6
PTD1/MISO
10
27
PTB5/AD5
PTD2/MOSI
11
26
PTB4/AD4
25 PTB3/AD3
PTB2/AD2 24
VSS 13
PTD3/SPSCK 12
23
VSSAD/VREFL
PTB1/AD1
31
22
6
21
PTE4
PTB0/AD0
PTC5
PTC4
32
20
5
PTC3
PTE3
19
PTC6
PTC2
33
18
4
PTD7/T2CH1
PTE2
17
PTA0/KBD0
PTD6/T2CH0
34
16
3
PTD5/T1CH1
PTE1/RxD
15
PTA1/KBD1
14
35
PTD4/T1CH0
2
VDD
PTE0/TxD
Figure 1-3. 48-Pin LQFP Pin Assignments
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
23
General Description
1.5 Pin Functions
Descriptions of the pin functions are provided here.
1.5.1 Power Supply Pins (VDD and VSS)
VDD and VSS are the power supply and ground pins. The MCU operates from a single power supply.
Fast signal transitions on MCU pins place high, short-duration current demands on the power supply. To
prevent noise problems, take special care to provide power supply bypassing at the MCU as Figure 1-4
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 1-4. Power Supply Bypassing
1.5.2 Oscillator Pins (OSC1 and OSC2)
OSC1 and OSC2 are the connections for an external crystal, resonator, or clock circuit. See Chapter 4
Clock Generator Module (CGM).
1.5.3 External Reset Pin (RST)
A 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset of the
entire system. It is driven low when any internal reset source is asserted. This pin contains an internal
pullup resistor. See Chapter 15 System Integration Module (SIM).
1.5.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. This pin contains an internal pullup resistor. See
Chapter 8 External Interrupt (IRQ).
MC68HC908GR16A Data Sheet, Rev. 1.0
24
Freescale Semiconductor
Pin Functions
1.5.5 CGM Power Supply Pins (VDDA and VSSA)
VDDA and VSSA are the power supply pins for the analog portion of the clock generator module (CGM).
Decoupling of these pins should be as per the digital supply. See Chapter 4 Clock Generator Module
(CGM).
1.5.6 External Filter Capacitor Pin (VCGMXFC)
CGMXFC is an external filter capacitor connection for the CGM. See Chapter 4 Clock Generator Module
(CGM).
1.5.7 ADC Power Supply/Reference Pins (VDDAD/VREFH and VSSAD/VREFL)
VDDAD and VSSAD are the power supply pins to the analog-to-digital converter (ADC). VREFH and VREFL
are the reference voltage pins for the ADC. VREFH is the high reference supply for the ADC, and by default
the VDDAD/VREFH pin should be externally filtered and connected to the same voltage potential as VDD.
VREFL is the low reference supply for the ADC, and by default the VSSAD/VREFL pin should be connected
to the same voltage potential as VSS. See Chapter 3 Analog-to-Digital Converter (ADC).
1.5.8 Port A Input/Output (I/O) Pins (PTA7/KBD7–PTA0/KBD0)
PTA7–PTA0 are general-purpose, bidirectional I/O port pins. Any or all of the port A pins can be
programmed to serve as keyboard interrupt pins. PTA7–PTA4 are only available on the 48-pin LQFP
package. See Chapter 12 Input/Output (I/O) Ports and Chapter 9 Keyboard Interrupt Module (KBI).
These port pins also have selectable pullups when configured for input mode. The pullups are disengaged
when configured for output mode. The pullups are selectable on an individual port bit basis.
1.5.9 Port B I/O Pins (PTB7/AD7–PTB0/AD0)
PTB7–PTB0 are general-purpose, bidirectional I/O port pins that can also be used for analog-to-digital
converter (ADC) inputs. PTB7–PTB4 are only available on the 48-pin LQFP package. See Chapter 12
Input/Output (I/O) Ports and Chapter 3 Analog-to-Digital Converter (ADC).
1.5.10 Port C I/O Pins (PTC6–PTC0)
PTC6 and PTC5 are general-purpose, bidirectional I/O port pins. PTC4–PTC0 are general-purpose,
bidirectional I/O port pins that contain higher current sink/source capability. PTC6–PTC2 are only
available on the 48-pin LQFP package. See Chapter 12 Input/Output (I/O) Ports.
These port pins also have selectable pullups when configured for input mode. The pullups are disengaged
when configured for output mode. The pullups are selectable on an individual port bit basis.
1.5.11 Port D I/O Pins (PTD7/T2CH1–PTD0/SS)
PTD7–PTD0 are special-function, bidirectional I/O port pins. PTD3–PTD0 can be programmed to be
serial peripheral interface (SPI) pins, while PTD7–PTD4 can be individually programmed to be timer
interface module (TIM1 and TIM2) pins. PTD7 is only available on the 48-pin LQFP package. See
Chapter 18 Timer Interface Module (TIM1 and TIM2), Chapter 16 Serial Peripheral Interface (SPI)
Module, and Chapter 12 Input/Output (I/O) Ports.
These port pins also have selectable pullups when configured for input mode. The pullups are disengaged
when configured for output mode. The pullups are selectable on an individual port bit basis.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
25
General Description
1.5.12 Port E I/O Pins (PTE5–PTE2 and PTE0/TxD)
PTE5–PTE0 are general-purpose, bidirectional I/O port pins. PTE1 and PTE0 can also be programmed
to be enhanced serial communications interface (ESCI) pins. PTE5–PTE2 are only available on the
48-pin LQFP package. See Chapter 14 Enhanced Serial Communications Interface (ESCI) Module and
Chapter 12 Input/Output (I/O) Ports.
NOTE
Any unused inputs and I/O ports should be tied to an appropriate logic level
(either VDD or VSS). Although the I/O ports of the MC68HC908GR16A do
not require termination, termination is recommended to reduce the
possibility of static damage.
MC68HC908GR16A Data Sheet, Rev. 1.0
26
Freescale Semiconductor
Chapter 2
Memory
2.1 Introduction
The CPU08 can address 64 Kbytes of memory space. The memory map, shown in Figure 2-1, includes:
• 15,872 bytes of user FLASH memory
• 1024 bytes of random-access memory (RAM)
• 406 bytes of FLASH programming routines read-only memory (ROM)
• 36 bytes of user-defined vectors
• 350 bytes of monitor ROM
2.2 Unimplemented Memory Locations
Accessing an unimplemented location can cause an illegal address reset. In the memory map
(Figure 2-1) and in register figures in this document, unimplemented locations are shaded.
2.3 Reserved Memory Locations
Accessing a reserved location can have unpredictable effects on microcontroller (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.
2.4 Input/Output (I/O) Section
Most of the control, status, and data registers are in the zero page area of $0000–$003F. Additional I/O
registers have these addresses:
• $FE00; break status register, SBSR
• $FE01; SIM reset status register, SRSR
• $FE02; reserved
• $FE03; break flag control register, SBFCR
• $FE04; interrupt status register 1, INT1
• $FE05; interrupt status register 2, INT2
• $FE06; interrupt status register 3, INT3
• $FE07; reserved
• $FE08; FLASH control register, FLCR
• $FE09; break address register high, BRKH
• $FE0A; break address register low, BRKL
• $FE0B; break status and control register, BRKSCR
• $FE0C; LVI status register, LVISR
• $FF7E; FLASH block protect register, FLBPR
Data registers are shown in Figure 2-2. Table 2-1 is a list of vector locations.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
27
Memory
$0000
↓
I/O REGISTERS
64 BYTES
$003F
$0040
↓
RAM
1024 BYTES
$043F
$0440
↓
UNIMPLEMENTED
192 BYTES
$04FF
$0500
↓
RESERVED
128 BYTES
INTERRUPT STATUS REGISTER 1 (INT1)
$FE05
INTERRUPT STATUS REGISTER 2 (INT2)
$FE06
INTERRUPT STATUS REGISTER 3 (INT3)
$FE07
RESERVED
$FE08
FLASH CONTROL REGISTER (FLCR)
$FE09
BREAK ADDRESS REGISTER HIGH (BRKH)
$FE0A
BREAK ADDRESS REGISTER LOW (BRKL)
$FE0B
BREAK STATUS AND CONTROL REGISTER (BRKSCR)
$FE0C
LVI STATUS REGISTER (LVISR)
$FE10
↓
$1C00
$FE1F
FLASH PROGRAMMING ROUTINES ROM
406 BYTES
UNIMPLEMENTED
16 BYTES
RESERVED FOR COMPATIBILITY WITH MONITOR CODE
FOR A-FAMILY PART
$FE20
MONITOR ROM
350 BYTES
↓
$1D95
$FF7D
$1D96
UNIMPLEMENTED
41,578 BYTES
$FF7E
$BFFF
$FF7F
$C000
↓
↓
UNIMPLEMENTED
3 BYTES
$FE0F
UNIMPLEMENTED
5760 BYTES
$1BFF
↓
$FE04
↓
$0580
↓
BREAK FLAG CONTROL REGISTER (SBFCR)
$FE0D
$057F
↓
$FE03
FLASH MEMORY
15,872 BYTES
FLASH BLOCK PROTECT REGISTER (FLBPR)
UNIMPLEMENTED
93 BYTES
$FFDB
$FDFF
$FFDC
$FE00
BREAK STATUS REGISTER (SBSR)
↓
$FE01
SIM RESET STATUS REGISTER (SRSR)
$FFFF(1)
$FE02
RESERVED
FLASH VECTORS
36 BYTES
1. $FFF6–$FFFD used for eight security bytes
Figure 2-1. Memory Map
MC68HC908GR16A Data Sheet, Rev. 1.0
28
Freescale Semiconductor
Input/Output (I/O) Section
Addr.
$0000
Register Name
Port A Data Register Read:
(PTA) Write:
See page 118. Reset:
$0001
Port B Data Register Read:
(PTB) Write:
See page 120. Reset:
$0002
Port C Data Register Read:
(PTC) Write:
See page 122. Reset:
$0003
$0004
Port D Data Register Read:
(PTD) Write:
See page 124. Reset:
Data Direction Register A Read:
(DDRA) Write:
See page 118. Reset:
$0005
Data Direction Register B Read:
(DDRB) Write:
See page 121. Reset:
$0006
Data Direction Register C Read:
(DDRC) Write:
See page 122. Reset:
$0007
$0008
Data Direction Register D Read:
(DDRD) Write:
See page 125. Reset:
Port E Data Register Read:
(PTE) Write:
See page 127. Reset:
$0009
ESCI Prescaler Register Read:
(SCPSC) Write:
See page 166. Reset:
$000A
ESCI Arbiter Control Read:
Register (SCIACTL) Write:
See page 170. Reset:
$000B
ESCI Arbiter Data Read:
Register (SCIADAT) Write:
See page 171. 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
1
PTC6
PTC5
PTC4
PTC3
Unaffected by reset
PTD7
PTD6
PTD5
PTD4
PTD3
Unaffected by reset
DDRA7
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
0
DDRB7
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
0
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
0
0
DDRD7
DDRD6
DDRD5
DDRD4
DDRD3
DDRD2
DDRD1
DDRD0
0
0
0
0
0
0
0
0
0
0
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
PSSB2
PSSB1
PSSB0
0
Unaffected by reset
PDS2
0
AM1
PDS1
PDS0
PSSB4
0
0
0
ALOST
AM0
ACLK
PSSB3
0
0
0
0
AFIN
ARUN
AROVFL
ARD8
0
0
0
0
0
0
0
0
ARD7
ARD6
ARD5
ARD4
ARD3
ARD2
ARD1
ARD0
0
0
0
0
0
0
0
0
= Unimplemented
R = Reserved
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 7)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
29
Memory
Addr.
$000C
$000D
$000E
$000F
$0010
$0011
$0012
Register Name
Data Direction Register E Read:
(DDRE) Write:
See page 128. Reset:
Port C Input Pullup Enable Read:
Register (PTCPUE) Write:
See page 124. Reset:
SPI Control Register Read:
(SPCR) Write:
See page 207. Reset:
SPI Status and Control Read:
Register (SPSCR) Write:
See page 208. Reset:
SPI Data Register Read:
(SPDR) Write:
See page 210. Reset:
$0014
ESCI Control Register 2 Read:
(SCC2) Write:
See page 159. Reset:
$0017
0
5
4
3
2
1
Bit 0
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
0
PTAPUE6
PTAPUE5
PTAPUE4
PTAPUE3
PTAPUE2
PTAPUE1
PTAPUE0
0
0
0
0
0
0
0
PTCPUE6
PTCPUE5
PTCPUE4
PTCPUE3
PTCPUE2
PTCPUE1
PTCPUE0
0
0
0
0
0
0
0
PTDPUE6
PTDPUE5
PTDPUE4
PTDPUE3
PTDPUE2
PTDPUE1
PTDPUE0
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
0
0
Port D Input Pullup Enable Read: PTDPUE7
Register (PTDPUE) Write:
See page 127. Reset:
0
$0013
$0016
6
0
Port A Input Pullup Enable Read: PTAPUE7
Register (PTAPUE) Write:
See page 120. Reset:
0
ESCI Control Register 1 Read:
(SCC1) Write:
See page 157. Reset:
$0015
Bit 7
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
LOOPS
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
T8
R
R
ORIE
NEIE
FEIE
PEIE
ESCI Control Register 3 Read:
(SCC3) Write:
See page 160. Reset:
R8
U
0
0
0
0
0
0
0
ESCI Status Register 1 Read:
(SCS1) Write:
See page 161. Reset:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
ESCI Status Register 2 Read:
(SCS2) Write:
See page 164. Reset:
0
0
0
0
0
0
BKF
RPF
0
0
0
0
0
0
0
1
0
= Unimplemented
R = Reserved
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 7)
MC68HC908GR16A Data Sheet, Rev. 1.0
30
Freescale Semiconductor
Input/Output (I/O) Section
Addr.
$0018
$0019
$001A
$001B
Register Name
ESCI Data Register Read:
(SCDR) Write:
See page 164. Reset:
ESCI Baud Rate Register Read:
(SCBR) Write:
See page 165. Reset:
Keyboard Status Read:
and Control Register Write:
(INTKBSCR)
See page 103. Reset:
Keyboard Interrupt Enable Read:
Register (INTKBIER) Write:
See page 104. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
Unaffected by reset
LINT
LINR
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
0
0
0
0
KEYF
0
IMASKK
MODEK
ACKK
0
0
0
0
0
0
0
0
KBIE7
KBIE6
KBIE5
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
0
0
0
TBR2
TBR1
TBR0
TBIE
TBON
R
0
0
IMASK
MODE
0
0
$001C
Timebase Module Control Read:
Register (TBCR) Write:
See page 214. Reset:
0
0
0
0
0
0
0
0
0
0
IRQF
0
$001D
IRQ Status and Control Read:
Register (INTSCR) Write:
See page 98. Reset:
0
0
0
0
Configuration Register 2 Read:
(CONFIG2)(1) Write:
See page 75.
Reset:
0
0
0
0
0
0
0
0
0
0
0
1
COPRS
LVISTOP
LVIRSTD
LVIPWRD
LVI5OR3
(Note 1)
SSREC
STOP
COPD
0
0
0
0
0
0
0
0
$001E
$001F
Configuration Register 1 Read:
(CONFIG1)(1) Write:
See page 76. Reset:
TBIF
0
TACK
ACK
0
R
0
TBMCLK- OSCENINSEL
STOP
ESCIBDSRC
1. One-time writable register after each reset, except LVI5OR3 bit. LVI5OR3 bit is only reset via POR (power-on reset).
TOF
$0020
Timer 1 Status and Control Read:
Register (T1SC) Write:
See page 225. Reset:
0
0
1
0
Bit 15
14
13
12
$0021
Timer 1 Counter Read:
Register High (T1CNTH) Write:
See page 226. Reset:
0
0
0
0
Timer 1 Counter Read:
Register Low (T1CNTL) Write:
See page 226. Reset:
Bit 7
6
5
0
0
Bit 15
1
$0022
$0023
Timer 1 Counter Modulo Read:
Register High (T1MODH) Write:
See page 227. Reset:
0
TOIE
TSTOP
0
0
PS2
PS1
0
0
0
0
11
10
9
Bit 8
0
0
0
0
4
3
2
1
Bit 0
0
0
0
0
0
0
14
13
12
11
10
9
Bit 8
1
1
1
1
1
1
1
= Unimplemented
TRST
R = Reserved
PS0
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 7)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
31
Memory
Addr.
$0024
$0025
$0026
$0027
Register Name
Timer 1 Counter Modulo Read:
Register Low (T1MODL) Write:
See page 227. Reset:
Timer 1 Channel 0 Status and Read:
Control Register (T1SC0) Write:
See page 230. Reset:
Timer 1 Channel 0 Read:
Register High (T1CH0H) Write:
See page 230. Reset:
Timer 1 Channel 0 Read:
Register Low (T1CH0L) Write:
See page 230. Reset:
Timer 1 Channel 1 Status and Read:
$0028
Control Register (T1SC1) Write:
See page 230. Reset:
$0029
$002A
Timer 1 Channel 1 Read:
Register High (T1CH1H) Write:
See page 230. Reset:
Timer 1 Channel 1 Read:
Register Low (T1CH1L) Write:
See page 230. Reset:
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
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
CH0F
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH1F
0
0
CH1IE
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
PS2
PS1
PS0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
TOF
$002B
Timer 2 Status and Control Read:
Register (T2SC) Write:
See page 227. Reset:
0
0
1
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
$002C
Timer 2 Counter Read:
Register High (T2CNTH) Write:
See page 226. Reset:
0
0
0
0
0
0
0
0
Timer 2 Counter Read:
Register Low (T2CNTL) Write:
See page 226. 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
$002D
$002E
$002F
Timer 2 Counter Modulo Read:
Register High (T2MODH) Write:
See page 227. Reset:
Timer 2 Counter Modulo Read:
Register Low (T2MODL) Write:
See page 227. Reset:
0
TOIE
TSTOP
= Unimplemented
0
0
TRST
R = Reserved
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 7)
MC68HC908GR16A Data Sheet, Rev. 1.0
32
Freescale Semiconductor
Input/Output (I/O) Section
Addr.
Register Name
Bit 7
Timer 2 Channel 0 Status and Read:
$0030
Control Register (T2SC0) Write:
See page 227. Reset:
CH0F
$0031
$0032
Timer 2 Channel 0 Read:
Register High (T2CH0H) Write:
See page 227. Reset:
Timer 2 Channel 0 Read:
Register Low (T2CH0L) Write:
See page 230. Reset:
Timer 2 Channel 1 Status and Read:
$0033
Control Register (T2SC1) Write:
See page 225. Reset:
$0034
$0035
$0036
Timer 2 Channel 1 Read:
Register High (T2CH1H) Write:
See page 230. Reset:
Timer 2 Channel 1 Read:
Register Low (T2CH1L) Write:
See page 230. Reset:
PLL Control Register Read:
(PCTL) Write:
See page 67. Reset:
$0037
PLL Bandwidth Control Read:
Register (PBWC) Write:
See page 68. Reset:
$0038
PLL Multiplier Select High Read:
Register (PMSH) Write:
See page 69. Reset:
$0039
$003A
PLL Multiplier Select Low Read:
Register (PMSL) Write:
See page 70. Reset:
PLL VCO Select Range Read:
Register (PMRS) Write:
See page 70. Reset:
Read:
$003B
6
5
4
3
2
1
Bit 0
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
0
Indeterminate after reset
Bit 7
6
5
4
Indeterminate after reset
CH1F
0
0
CH1IE
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
PLLIE
0
AUTO
PLLF
PLLON
BCS
R
R
VPR1
VPR0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
MUL11
MUL10
MUL9
MUL8
0
LOCK
ACQ
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
MUL3
MUL2
MUL1
MUL0
0
1
0
0
0
0
0
0
VRS7
VRS6
VRS5
VRS4
VRS3
VRS2
VRS1
VRS0
0
1
0
0
0
0
0
0
0
0
0
0
R
R
R
R
0
0
0
0
0
0
0
1
Reserved Write:
Reset:
3
= Unimplemented
R = Reserved
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 7)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
33
Memory
Addr.
$003C
$003D
$003E
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
0
0
1
1
1
1
1
ADC Data High Register Read:
(ADRH) Write:
See page 53. Reset:
0
0
0
0
0
0
AD9
AD8
ADC Data Low Register Read:
(ADRL) Write:
See page 53. Reset:
AD7
AD2
AD1
AD0
R
ADC Status and Control Read:
Register (ADSCR) Write:
See page 51. Reset:
COCO
$003F
ADC Clock Register Read:
(ADCLK) Write:
See page 55. Reset:
$FE00
SIM Break Status Register Read:
(SBSR) Write:
See page 236. Reset:
R
Unaffected by reset
AD6
AD5
AD4
A3
Unaffected by reset
ADIV2
ADIV1
ADIV0
ADICLK
MODE1
MODE0
0
0
0
0
0
1
0
SBSW
0
0
R
R
R
R
R
R
0
0
0
0
0
0
0
0
POR
PIN
COP
ILOP
ILAD
MODRST
LVI
0
1
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
IF6
IF5
IF4
IF3
IF2
IF1
0
0
$FE04
Interrupt Status Register 1 Read:
(INT1) Write:
See page 183. Reset:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
$FE05
Interrupt Status Register 2 Read:
(INT2) Write:
See page 184. Reset:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
(Note 1)
R
1. Writing a 0 clears SBSW.
$FE01
SIM Reset Status Register Read:
(SRSR) Write:
See page 188. POR:
Read:
$FE02
Reserved Write:
Reset:
$FE03
$FE06
SIM Break Flag Control Read:
Register (SBFCR) Write:
See page 236. Reset:
Interrupt Status Register 3 Read:
(INT3) Write:
See page 184. Reset:
Read:
$FE07
Reserved Write:
Reset:
0
0
IF20
IF19
IF18
IF17
IF16
IF15
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
= Unimplemented
R = Reserved
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 6 of 7)
MC68HC908GR16A Data Sheet, Rev. 1.0
34
Freescale Semiconductor
Input/Output (I/O) Section
Addr.
$FE08
$FE09
Register Name
FLASH Control Register Read:
(FLCR) Write:
See page 38. Reset:
Break Address Register High Read:
(BRKH) Write:
See page 235. Reset:
Break Address Register Low Read:
$FE0A
(BRKL) Write:
See page 235. Reset:
$FE0B
Break Status and Control Read:
Register (BRKSCR) Write:
See page 235. Reset:
Read:
$FE0C
$FF7E
LVI Status Register (LVISR)
Write:
See page 113.
Reset:
FLASH Block Protect Read:
Register (FLBPR)(1) Write:
See page 43. Reset:
Bit 7
6
5
4
0
0
0
0
3
2
1
Bit 0
HVEN
MASS
ERASE
PGM
0
0
0
0
0
0
0
0
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
LVIOUT
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
Unaffected by reset
1. Non-volatile FLASH register
$FFFF
COP Control Register Read:
(COPCTL) Write:
See page 81. Reset:
Low byte of reset vector
Writing clears COP counter (any value)
Unaffected by reset
= Unimplemented
R = Reserved
U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 7 of 7)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
35
Memory
.
Table 2-1. Vector Addresses
Vector Priority
Lowest
Vector
IF16
IF15
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
IF6
IF5
IF4
IF3
IF2
IF1
—
Highest
—
Address
Vector
$FFDC
Timebase Vector (High)
$FFDD
Timebase Vector (Low)
$FFDE
ADC Conversion Complete Vector (High)
$FFDF
ADC Conversion Complete Vector (Low)
$FFE0
Keyboard Vector (High)
$FFE1
Keyboard Vector (Low)
$FFE2
ESCI Transmit Vector (High)
$FFE3
ESCI Transmit Vector (Low)
$FFE4
ESCI Receive Vector (High)
$FFE5
ESCI Receive Vector (Low)
$FFE6
ESCI Error Vector (High)
$FFE7
ESCI Error Vector (Low)
$FFE8
SPI Transmit Vector (High)
$FFE9
SPI Transmit Vector (Low)
$FFEA
SPI Receive Vector (High)
$FFEB
SPI Receive Vector (Low)
$FFEC
TIM2 Overflow Vector (High)
$FFED
TIM2 Overflow Vector (Low)
$FFEE
TIM2 Channel 1 Vector (High)
$FFEF
TIM2 Channel 1 Vector (Low)
$FFF0
TIM2 Channel 0 Vector (High)
$FFF1
TIM2 Channel 0 Vector (Low)
$FFF2
TIM1 Overflow Vector (High)
$FFF3
TIM1 Overflow Vector (Low)
$FFF4
TIM1 Channel 1 Vector (High)
$FFF5
TIM1 Channel 1 Vector (Low)
$FFF6
TIM1 Channel 0 Vector (High)
$FFF7
TIM1 Channel 0 Vector (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)
MC68HC908GR16A Data Sheet, Rev. 1.0
36
Freescale Semiconductor
Random-Access Memory (RAM)
2.5 Random-Access Memory (RAM)
Addresses $0040 through $043F are RAM locations. The location of the stack RAM is programmable.
The 16-bit stack pointer allows the stack to be anywhere in the 64-Kbyte memory space.
NOTE
For correct operation, the stack pointer must point only to RAM locations.
Within page zero are 192 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.
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.
2.6 FLASH Memory (FLASH)
This subsection describes the operation of the embedded FLASH memory. This memory can be read,
programmed, and erased from a single external supply. The program, erase, and read operations are
enabled through the use of an internal charge pump.
2.6.1 Functional Description
The FLASH memory is an array of 15,872 bytes with an additional 36 bytes of user vectors and one byte
of block protection. An erased bit reads as 1 and a programmed bit reads as a 0. Memory in the FLASH
array is organized into two rows per page basis. For the 16-K word by 8-bit embedded FLASH memory,
the page size is 64 bytes per page and the row size is 32 bytes per row. Hence the minimum erase page
size is 64 bytes and the minimum program row size is 32 bytes. Program and erase operation operations
are facilitated through control bits in FLASH control register (FLCR). Details for these operations appear
later in this section.
The address ranges for the user memory and vectors are:
• $C000–$FDFF; user memory
• $FE08; FLASH control register
• $FF7E; FLASH block protect register
• $FFDC–$FFFF; these locations are reserved for user-defined interrupt and reset vectors
NOTE
A security feature prevents viewing of the FLASH contents.(1)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
37
Memory
2.6.2 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
= Unimplemented
Figure 2-3. FLASH Control Register (FLCR)
HVEN — High-Voltage Enable Bit
This read/write bit enables the charge pump to drive high voltages for program and erase operations
in the array. HVEN can only be set if either PGM = 1 or ERASE = 1 and the proper sequence for
program or erase is followed.
1 = High voltage enabled to array and charge pump on
0 = High voltage disabled to array and charge pump off
MASS — Mass Erase Control Bit
Setting this read/write bit configures the 16-Kbyte FLASH array for mass erase operation.
1 = MASS erase operation selected
0 = PAGE erase operation selected
ERASE — Erase Control Bit
This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit
such that both bits cannot be equal to 1 or set to 1 at the same time.
1 = Erase operation selected
0 = Erase operation 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
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908GR16A Data Sheet, Rev. 1.0
38
Freescale Semiconductor
FLASH Memory (FLASH)
2.6.3 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (64 bytes) of FLASH memory. A page consists of 64
consecutive bytes starting from addresses $XX00, $XX40, $XX80, or $XXC0. The 36-byte user interrupt
vectors area also forms a page. Any FLASH memory page can be erased alone.
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 location within the page address range of the block to be erased.
4. Wait for a time, tNVS (minimum 10 µs)
5. Set the HVEN bit.
6. Wait for a time, tErase (minimum 1 ms or 4 ms)
7. Clear the ERASE bit.
8. Wait for a time, tNVH (minimum 5 µs)
9. Clear the HVEN bit.
10. After a time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from FLASH memory. While these operations must be
performed in the order shown, other unrelated operations may occur
between the steps.
In applications that need more than 1000 program/erase cycles, use the 4-ms page erase specification
to get improved long-term reliability. Any application can use this 4-ms page erase specification.
However, in applications where a FLASH location will be erased and reprogrammed less than 1000 times,
and speed is important, use the 1-ms page erase specification to get a shorter cycle time.
2.6.4 FLASH Mass Erase Operation
Use this step-by-step procedure to erase entire FLASH memory:
1. Set both the ERASE bit, and the MASS bit in the FLASH control register.
2. Read the FLASH block protect register.
3. Write any data to any FLASH address(1) within the FLASH memory address range.
4. Wait for a time, tNVS (minimum 10 µs)
5. Set the HVEN bit.
6. Wait for a time, tMErase (minimum 4 ms)
7. Clear the ERASE and MASS bits.
NOTE
Mass erase is disabled whenever any block is protected (FLBPR does not
equal $FF).
8. Wait for a time, tNVHL (minimum 100 µs)
9. Clear the HVEN bit.
10. After a time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
1. When in monitor mode, with security sequence failed (see 19.3.2 Security), write to the FLASH block protect register instead
of any FLASH address.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
39
Memory
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from FLASH memory. While these operations must be
performed in the order shown, other unrelated operations may occur
between the steps.
2.6.5 FLASH Program/Read Operation
Programming of the FLASH memory is done on a row basis. A row consists of 32 consecutive bytes
starting from addresses $XX00, $XX20, $XX40, $XX60, $XX80, $XXA0, $XXC0, and $XXE0.
During the programming cycle, make sure that all addresses being written to fit within one of the ranges
specified above. Attempts to program addresses in different row ranges in one programming cycle will
fail. Use this step-by-step procedure to program a row of FLASH memory (Figure 2-4 is a flowchart
representation).
NOTE
Only bytes which are currently $FF may be 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 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 (minimum 10 µs).
5. Set the HVEN bit.
6. Wait for a time, tPGS (minimum 5 µs).
7. Write data to the FLASH address to be programmed.
8. Wait for a time, tPROG (minimum 30 µs).
9. Repeat step 7 and 8 until all the bytes within the row are programmed.
10. Clear the PGM bit.(1)
11. Wait for a time, tNVH (minimum 5 µs).
12. Clear the HVEN bit.
13. After time, tRCV (typical 1 µs), the memory can be accessed in read mode again.
This program sequence is repeated throughout the memory until all data is programmed.
NOTE
Programming and erasing of FLASH locations can not be performed by
code being executed from the same FLASH array.
NOTE
While these operations must be performed in the order shown, other
unrelated operations may occur between the steps. Care must be taken
within the FLASH array memory space such as the COP control register
(COPCTL) at $FFFF.
NOTE
It is highly recommended that interrupts be disabled during program/ erase
operations.
MC68HC908GR16A Data Sheet, Rev. 1.0
40
Freescale Semiconductor
FLASH Memory (FLASH)
NOTE
Do not exceed tPROG maximum or tHV maximum. 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 x 32) ≤ tHV maximum
Refer to 20.15 Memory Characteristics.
NOTE
The time between programming the FLASH address change (step 7 to
step 7), or the time between the last FLASH programmed to clearing the
PGM bit (step 7 to step 10) must not exceed the maximum programming
time, tPROG maximum.
CAUTION
Be cautious when programming the FLASH array to ensure that
non-FLASH locations are not used as the address that is written to when
selecting either the desired row address range in step 3 of the algorithm or
the byte to be programmed in step 7 of the algorithm. This applies
particularly to $FFD4–$FFDF.
2.6.6 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
2.6.7 FLASH Block Protect Register. Once the FLBPR is programmed with a value other than $FF or $FE,
any erase or program of the FLBPR or the protected block of FLASH memory is prohibited. Mass erase
is disabled whenever any block is protected (FLBPR does not equal $FF). The presence of a VTST on the
IRQ pin will bypass the block protection so that all of the memory included in the block protect register is
open for program and erase operations.
NOTE
The FLASH block protect register is not protected with special hardware or
software. Therefore, if this page is not protected by FLBPR the register is
erased by either a page or mass erase operation.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
41
Memory
Algorithm for programming
a row (32 bytes) of FLASH memory
1
2
3
SET PGM BIT
READ THE FLASH BLOCK PROTECT REGISTER
WRITE ANY DATA TO ANY FLASH ADDRESS
WITHIN THE ROW ADDRESS RANGE DESIRED
4
5
6
7
8
WAIT FOR A TIME, tNVS
SET HVEN BIT
WAIT FOR A TIME, tPGS
WRITE DATA TO THE FLASH ADDRESS
TO BE PROGRAMMED
WAIT FOR A TIME, tPROG
COMPLETED
PROGRAMMING
THIS ROW?
Y
N
10
11
CLEAR PGM BIT
WAIT FOR A TIME, tNVH
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.
12
13
This row program algorithm assumes the row/s
to be programmed are initially erased.
CLEAR HVEN BIT
WAIT FOR A TIME, tRCV
END OF PROGRAMMING
Figure 2-4. FLASH Programming Flowchart
MC68HC908GR16A Data Sheet, Rev. 1.0
42
Freescale Semiconductor
FLASH Memory (FLASH)
2.6.7 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:
$FF7E
Read:
Write:
Bit 7
6
5
4
3
2
1
Bit 0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
Reset:
Unaffected by reset. Initial value from factory is 1.
Write to this register is by a programming sequence to the FLASH memory.
Figure 2-5. FLASH Block Protect Register (FLBPR)
BPR[7:0] — FLASH Block Protect Bits
These eight bits represent bits [13:6] of a 16-bit memory address.
Bit 15 and Bit 14 are 1s and bits [5:0] are 0s.
The resultant 16-bit address is used for specifying the start address of the FLASH memory for block
protection. The FLASH is protected from this start address to the end of FLASH memory, at $FFFF.
With this mechanism, the protect start address can be $XX00, $XX40, $XX80, and $XXC0 (64 bytes
page boundaries) within the FLASH memory.
16-BIT MEMORY ADDRESS
START ADDRESS OF FLASH
1
BLOCK PROTECT
1
FLBPR VALUE
0
0
0
0
0
0
Figure 2-6. FLASH Block Protect Start Address
Table 2-2. Examples of Protect Address Ranges
BPR[7:0]
Addresses of Protect Range
$00
The entire FLASH memory is protected.
$01 (0000 0001)
$C040 (1100 0000 0100 0000) — $FFFF
$02 (0000 0010)
$C080 (1100 0000 1000 0000) — $FFFF
$03 (0000 0011)
$C0C0 (1100 0000 1100 0000) — $FFFF
$04 (0000 0100)
$C100 (1100 0001 0000 0000) — $FFFF
and so on...
$FC (1111 1100)
$FF00 (1111 1111 0000 0000) — FFFF
$FD (1111 1101)
$FF40 (1111 1111 0100 0000) — $FFFF
FLBPR and vectors are protected
$FE (1111 1110)
$FF80 (111 1111 1000 0000) — FFFF
Vectors are protected
$FF
The entire FLASH memory is not protected.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
43
Memory
2.6.8 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.
2.6.9 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
44
Freescale Semiconductor
Chapter 3
Analog-to-Digital Converter (ADC)
3.1 Introduction
This section describes the 10-bit analog-to-digital converter (ADC).
3.2 Features
Features of the ADC module include:
• Eight channels with multiplexed input
• Linear successive approximation with monotonicity
• 10-bit resolution
• Single or continuous conversion
• Conversion complete flag or conversion complete interrupt
• Selectable ADC clock
• Left or right justified result
• Left justified sign data mode
3.3 Functional Description
The ADC provides eight pins for sampling external sources at pins PTB7/KBD7–PTB0/KBD0. 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 3-2.
3.3.1 ADC Port I/O Pins
PTB7/AD7–PTB0/AD0 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 data
direction register (DDR) will not have any affect on the port pin that is selected by the ADC. A read of a
port pin in use by the ADC will return a 0.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
45
Analog-to-Digital Converter (ADC)
INTERNAL BUS
DDRA
PORTA
PTB7/AD7
PTB6/AD6
PTB5/AD5
PTB4/AD4
PTB3/AD3
PTB2/AD2
PTB1/AD1
PTB0/AD0
PTC6(1)
PTC5(1)
PTC4(1), (2)
PTC3(1), (2)
PTC2(1), (2)
PTC1(1), (2)
PTC0(1), (2)
PTD7/T2CH1(1)
PTD6/T2CH0(1)
PTD5/T1CH1(1)
PTD4/T1CH0(1)
PTD3/SPSCK(1)
PTD2/MOSI(1)
PTD1/MISO(1)
PTD0/SS(1)
PTE5–PTE2
PTE1/RxD
PTE0/TxD
DDRB
SINGLE BREAKPOINT
BREAK MODULE
DUAL VOLTAGE
LOW-VOLTAGE INHIBIT
MODULE
USER FLASH — 15,872 BYTES
PTA7/KBD7–
PTA0/KBD0(1)
PORTB
CONTROL AND STATUS REGISTERS — 64 BYTES
PROGRAMMABLE TIMEBASE
MODULE
PORTC
ARITHMETIC/LOGIC
UNIT (ALU)
PORTD
CPU
REGISTERS
PORTE
M68HC08 CPU
USER RAM — 1024 BYTES
FLASH PROGRAMMING ROUTINES ROM — 406 BYTES
USER FLASH VECTOR SPACE — 36 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 1
DDRC
8-BIT KEYBOARD
INTERRUPT MODULE
MONITOR ROM — 350 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 2
CLOCK GENERATOR MODULE
PHASE LOCKED LOOP
COMPUTER OPERATING
PROPERLY MODULE
RST(3)
SYSTEM INTEGRATION
MODULE
IRQ(3)
SINGLE EXTERNAL
INTERRUPT MODULE
SERIAL PERIPHERAL
INTERFACE MODULE
MONITOR MODULE
VDDAD/VREFH
VSSAD/VREFL
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
POWER-ON RESET
MODULE
VDD
VSS
VDDA
VSSA
DDRD
CGMXFC
ENHANCED SERIAL
COMUNICATIONS
INTERFACE MODULE
1–8 MHz OSCILLATOR
DDRE
OSC1
OSC2
MEMORY MAP
MODULE
SECURITY
MODULE
CONFIGURATION
REGISTER 1–2
MODULE
POWER
MONITOR MODE ENTRY
MODULE
1. Ports are software configurable with pullup device if input port.
2. Higher current drive port pins
3. Pin contains integrated pullup device
Figure 3-1. Block Diagram Highlighting ADC Block and Pins
MC68HC908GR16A Data Sheet, Rev. 1.0
46
Freescale Semiconductor
Functional Description
INTERNAL
DATA BUS
READ DDRBx
WRITE DDRBx
DISABLE
DDRBx
RESET
WRITE PTBx
PTBx
PTBx
ADC CHANNEL x
READ PTBx
DISABLE
ADC DATA REGISTER
INTERRUPT
LOGIC
AIEN
CONVERSION
COMPLETE
ADC
ADC
VOLTAGE IN
(VADIN)
CHANNEL
SELECT
ADCH4–ADCH0
ADC CLOCK
COCO
CGMXCLK
BUS CLOCK
CLOCK
GENERATOR
ADIV2–ADIV0
ADICLK
Figure 3-2. ADC Block Diagram
3.3.2 Voltage Conversion
When the input voltage to the ADC equals VREFH, the ADC converts the signal to $3FF (full scale). If the
input voltage equals VREFL, the ADC converts it to $000. Input voltages between VREFH and VREFL are a
straight-line linear conversion.
NOTE
The ADC input voltage must always be greater than VSSAD and less than
VDDAD. Connect the VDDAD pin to the same voltage potential as the VDD
pin, and connect the VSSAD pin to the same voltage potential as the VSS pin.
The VDDAD pin should be routed carefully for maximum noise immunity.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
47
Analog-to-Digital Converter (ADC)
3.3.3 Conversion Time
Conversion starts after a write to the ADC status and control register (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.
16 to 17 ADC cycles
Conversion time =
ADC frequency
Number of bus cycles = conversion time × bus frequency
3.3.4 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 each conversion and
will stay set until 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.
When a conversion is in process and the ADSCR is written, the current conversion data should be
discarded to prevent an incorrect reading.
3.3.5 Accuracy and Precision
The conversion process is monotonic and has no missing codes.
3.3.6 Result Justification
The conversion result may be formatted in four different ways:
1. Left justified
2. Right justified
3. Left Justified sign data mode
4. 8-bit truncation mode
All four of these modes are controlled using MODE0 and MODE1 bits located in the ADC clock register
(ADCLK).
Left justification will place the eight most significant bits (MSB) in the corresponding ADC data register
high, ADRH. This may be useful if the result is to be treated as an 8-bit result where the two least
significant bits (LSB), located in the ADC data register low, ADRL, can be ignored. However, ADRL must
be read after ADRH or else the interlocking will prevent all new conversions from being stored.
Right justification will place only the two MSBs in the corresponding ADC data register high, ADRH, and
the eight LSBs in ADC data register low, ADRL. This mode of operation typically is used when a 10-bit
unsigned result is desired.
Left justified sign data mode is similar to left justified mode with one exception. The MSB of the 10-bit
result, AD9 located in ADRH, is complemented. This mode of operation is useful when a result,
represented as a signed magnitude from mid-scale, is needed. Finally, 8-bit truncation mode will place
the eight MSBs in the ADC data register low, ADRL. The two LSBs are dropped. This mode of operation
MC68HC908GR16A Data Sheet, Rev. 1.0
48
Freescale Semiconductor
Monotonicity
is used when compatibility with 8-bit ADC designs are required. No interlocking between ADRH and ADRL
is present.
NOTE
Quantization error is affected when only the most significant eight bits are
used as a result. See Figure 3-3.
8-BIT 10-BIT
RESULT RESULT
IDEAL 8-BIT CHARACTERISTIC
WITH QUANTIZATION = ±1/2
10-BIT TRUNCATED
TO 8-BIT RESULT
003
00B
00A
009
002
IDEAL 10-BIT CHARACTERISTIC
WITH QUANTIZATION = ±1/2
008
007
006
005
001
004
WHEN TRUNCATION IS USED,
ERROR FROM IDEAL 8-BIT = 3/8 LSB
DUE TO NON-IDEAL QUANTIZATION.
003
002
001
000
000
1/2
2 1/2
1 1/2
1/2
4 1/2
3 1/2
6 1/2
5 1/2
1 1/2
8 1/2
7 1/2
9 1/2
2 1/2
INPUT VOLTAGE
REPRESENTED AS 10-BIT
INPUT VOLTAGE
REPRESENTED AS 8-BIT
Figure 3-3. Bit Truncation Mode Error
3.4 Monotonicity
The conversion process is monotonic and has no missing codes.
3.5 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 0. The COCO bit is not used as a
conversion complete flag when interrupts are enabled.
3.6 Low-Power Modes
The WAIT and STOP instruction can put the MCU in low power-consumption standby modes.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
49
Analog-to-Digital Converter (ADC)
3.6.1 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 ADCH4–ADCH0 bits in the ADC status and control register before executing the
WAIT instruction.
3.6.2 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.
3.7 I/O Signals
The ADC module has eight pins shared with port B, PTB7/AD7–PTB0/AD0.
3.7.1 ADC Analog Power Pin (VDDAD)
The ADC analog portion uses VDDAD as its power pin. Connect the VDDAD pin to the same voltage
potential as VDD. External filtering may be necessary to ensure clean VDDAD for good results.
NOTE
For maximum noise immunity, route VDDAD carefully and place bypass
capacitors as close as possible to the package.
VDDAD and VREFH are double-bonded on the MC68HC908GR16A.
3.7.2 ADC Analog Ground Pin (VSSAD)
The ADC analog portion uses VSSAD as its ground pin. Connect the VSSAD pin to the same voltage
potential as VSS.
NOTE
Route VSSAD cleanly to avoid any offset errors.
VSSAD and VREFL are double-bonded on the MC68HC908GR16A.
3.7.3 ADC Voltage Reference High Pin (VREFH)
The ADC analog portion uses VREFH as its upper voltage reference pin. By default, connect the VREFH
pin to the same voltage potential as VDD. External filtering is often necessary to ensure a clean VREFH for
good results. Any noise present on this pin will be reflected and possibly magnified in A/D conversion
values.
NOTE
For maximum noise immunity, route VREFH carefully and place bypass
capacitors as close as possible to the package. Routing VREFH close and
parallel to VREFL may improve common mode noise rejection.
VDDAD and VREFH are double-bonded on the MC68HC908GR16A.
MC68HC908GR16A Data Sheet, Rev. 1.0
50
Freescale Semiconductor
I/O Registers
3.7.4 ADC Voltage Reference Low Pin (VREFL)
The ADC analog portion uses VREFL as its lower voltage reference pin. By default, connect the VREFH pin
to the same voltage potential as VSS. External filtering is often necessary to ensure a clean VREFL for good
results. Any noise present on this pin will be reflected and possibly magnified in A/D conversion values.
NOTE
For maximum noise immunity, route VREFL carefully and, if not connected
to VSS, place bypass capacitors as close as possible to the package.
Routing VREFH close and parallel to VREFL may improve common mode
noise rejection.
VSSAD and VREFL are double-bonded on the MC68HC908GR16A.
3.7.5 ADC Voltage In (VADIN)
VADIN is the input voltage signal from one of the eight ADC channels to the ADC module.
3.8 I/O Registers
These I/O registers control and monitor ADC operation:
• ADC status and control register (ADSCR)
• ADC data register (ADRH and ADRL)
• ADC clock register (ADCLK)
3.8.1 ADC Status and Control Register
Function of the ADC status and control register (ADSCR) is described here.
Address:
$003C
Bit 7
6
5
4
3
2
1
Bit 0
AIEN
ADCO
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
0
1
1
1
1
1
Read:
COCO
Write:
R
Reset:
0
0
R
= Reserved
Figure 3-4. ADC Status and Control Register (ADSCR)
COCO — Conversions Complete Bit
In non-interrupt mode (AIEN = 0), COCO is a read-only bit that is set at the end of each conversion.
COCO will stay set until cleared by a read of the ADC data register. Reset clears this bit.
In interrupt mode (AIEN = 1), COCO is a read-only bit that is not set at the end of a conversion. It
always reads as a 0.
1 = Conversion completed (AIEN = 0)
0 = Conversion not completed (AIEN = 0) or CPU interrupt enabled (AIEN = 1)
NOTE
The write function of the COCO bit is reserved. When writing to the ADSCR
register, always have a 0 in the COCO bit position.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
51
Analog-to-Digital Converter (ADC)
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is
cleared when the data register is read or the status/control register is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the ADR register at the end of each
conversion. Only one conversion is completed between writes to the ADSCR when this bit is cleared.
Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH4–ADCH0 — ADC Channel Select Bits
ADCH4–ADCH0 form a 5-bit field which is used to select one of 32 ADC channels. Only eight
channels, AD7–AD0, are available on this MCU. The channels are detailed in Table 3-1. 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. See Table 3-1.
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 3-1, are used to verify the operation of the ADC converter both in production testing and for user
applications.
Table 3-1. Mux Channel Select(1)
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
Input Select
0
0
0
0
0
PTB0/AD0
0
0
0
0
1
PTB1/AD1
0
0
0
1
0
PTB2/AD2
0
0
0
1
1
PTB3/AD3
0
0
1
0
0
PTB4/AD4
0
0
1
0
1
PTB5/AD5
0
0
1
1
0
PTB6/AD6
0
0
1
1
1
PTB7/AD7
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
Unused
1. If any unused channels are selected, the resulting ADC conversion will be unknown or
reserved.
MC68HC908GR16A Data Sheet, Rev. 1.0
52
Freescale Semiconductor
I/O Registers
3.8.2 ADC Data Register High and Data Register Low
3.8.2.1 Left Justified Mode
In left justified mode, the ADRH register holds the eight MSBs of the 10-bit result. The only difference from
left justified mode is that the AD9 is complemented. The ADRL register holds the two LSBs of the 10-bit
result. All other bits read as 0. ADRH and ADRL are updated each time an ADC single channel conversion
completes. Reading ADRH latches the contents of ADRL until ADRL is read. All subsequent results will
be lost until the ADRH and ADRL reads are completed.
Address:
Read:
$003D
ADRH
Bit 7
6
5
4
3
2
1
Bit 0
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
Reset:
Address:
Read:
Unaffected by reset
$003E
AD1
ADRL
AD0
0
0
0
0
0
0
Write:
Reset:
Unaffected by reset
= Unimplemented
Figure 3-5. ADC Data Register High (ADRH) and Low (ADRL)
3.8.2.2 Right Justified Mode
In right justified mode, the ADRH register holds the two MSBs of the 10-bit result. All other bits read as 0.
The ADRL register holds the eight LSBs of the 10-bit result. ADRH and ADRL are updated each time an
ADC single channel conversion completes. Reading ADRH latches the contents of ADRL until ADRL is
read. All subsequent results will be lost until the ADRH and ADRL reads are completed.
Address:
Read:
$003D
ADRH
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
AD9
AD8
Write:
Reset:
Address:
Read:
Unaffected by reset
$003E
AD7
ADRL
AD6
AD5
AD4
AD3
AD2
AD1
AD0
Write:
Reset:
Unaffected by reset
= Unimplemented
Figure 3-6. ADC Data Register High (ADRH) and Low (ADRL)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
53
Analog-to-Digital Converter (ADC)
3.8.2.3 Left Justified Signed Data Mode
In left justified signed data mode, the ADRH register holds the eight MSBs of the 10-bit result. The only
difference from left justified mode is that the AD9 is complemented. The ADRL register holds the two
LSBs of the 10-bit result. All other bits read as 0. ADRH and ADRL are updated each time an ADC single
channel conversion completes. Reading ADRH latches the contents of ADRL until ADRL is read. All
subsequent results will be lost until the ADRH and ADRL reads are completed.
Address:
Read:
$003D
ADRH
Bit 7
6
5
4
3
2
1
Bit 0
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
Reset:
Address:
Read:
Unaffected by reset
$003E
AD1
ADRL
AD0
0
0
0
0
0
0
Write:
Reset:
Unaffected by reset
= Unimplemented
Figure 3-7. ADC Data Register High (ADRH) and Low (ADRL)
3.8.2.4 Eight Bit Truncation Mode
In 8-bit truncation mode, the ADRL register holds the eight MSBs of the 10-bit result. The ADRH register
is unused and reads as 0. The ADRL register is updated each time an ADC single channel conversion
completes. In 8-bit mode, the ADRL register contains no interlocking with ADRH.
Address:
Read:
$003D
ADRH
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Write:
Reset:
Address:
Read:
Unaffected by reset
$003E
AD9
ADRL
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
Reset:
Unaffected by reset
= Unimplemented
Figure 3-8. ADC Data Register High (ADRH) and Low (ADRL)
MC68HC908GR16A Data Sheet, Rev. 1.0
54
Freescale Semiconductor
I/O Registers
3.8.3 ADC Clock Register
The ADC clock register (ADCLK) selects the clock frequency for the ADC.
Address:
Read:
Write:
Reset:
$003F
Bit 7
6
5
4
3
2
1
ADIV2
ADIV1
ADIV0
ADICLK
MODE1
MODE0
R
0
0
0
0
0
1
0
R
= Reserved
Bit 0
0
0
= Unimplemented
Figure 3-9. ADC Clock Register (ADCLK)
ADIV2–ADIV0 — ADC Clock Prescaler Bits
ADIV2–ADIV0 form a 3-bit field which selects the divide ratio used by the ADC to generate the internal
ADC clock. Table 3-2 shows the available clock configurations. The ADC clock should be set to
approximately 1 MHz.
Table 3-2. 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
(1)
X(1)
ADC input clock ÷ 16
X
1. X = Don’t care
ADICLK — ADC Input Clock Select Bit
ADICLK selects either the bus clock or the oscillator output clock (CGMXCLK) as the input clock
source to generate the internal ADC clock. Reset selects CGMXCLK as the ADC clock source.
1 = Internal bus clock
0 = Oscillator output clock (CGMXCLK)
The ADC requires a clock rate of approximately 1 MHz for correct operation. If the selected clock
source is not fast enough, the ADC will generate incorrect conversions. See 20.10 5.0-Volt ADC
Characteristics.
f
or bus frequency
fADIC = CGMXCLK
≅ 1 MHz
ADIV[2:0]
MODE1 and MODE0 — Modes of Result Justification Bits
MODE1 and MODE0 select among four modes of operation. The manner in which the ADC conversion
results will be placed in the ADC data registers is controlled by these modes of operation. Reset returns
right-justified mode.
00 = 8-bit truncation mode
01 = Right justified mode
10 = Left justified mode
11 = Left justified signed data mode
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
55
Analog-to-Digital Converter (ADC)
MC68HC908GR16A Data Sheet, Rev. 1.0
56
Freescale Semiconductor
Chapter 4
Clock Generator Module (CGM)
4.1 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, which is based on either the crystal clock divided by two or the phase-locked loop (PLL)
clock, CGMVCLK, divided by two. In user mode, CGMOUT is the clock from which the SIM derives the
system clocks, including the bus clock, which is at a frequency of CGMOUT/2. The PLL is a fully functional
frequency generator designed for use with crystals or ceramic resonators. The PLL can generate a
maximum bus frequency of 8 MHz using a 1-8MHz crystal or external clock source.
4.2 Features
Features of the CGM include:
• Phase-locked loop with output frequency in integer multiples of an integer dividend of the crystal
reference
• High-frequency crystal operation with low-power operation and high-output frequency resolution
• Programmable hardware voltage-controlled oscillator (VCO) for low-jitter operation
• Automatic bandwidth control mode for low-jitter operation
• Automatic frequency lock detector
• CPU interrupt on entry or exit from locked condition
• Configuration register bit to allow oscillator operation during stop mode
4.3 Functional Description
The CGM consists of three major submodules:
• Crystal oscillator circuit — The crystal oscillator circuit generates the constant crystal frequency
clock, CGMXCLK.
• Phase-locked loop (PLL) — The PLL 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 either CGMOUT or CGMXCLK.
Figure 4-1 shows the structure of the CGM.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
57
Clock Generator Module (CGM)
OSCILLATOR (OSC)
OSC2
CGMXCLK
(TO: SIM, TIMEBASE, ADC)
OSC1
SIMOSCEN
(FROM SIM)
OSCENINSTOP
(FROM CONFIG)
PHASE-LOCKED LOOP (PLL)
CGMRCLK
CLOCK
SELECT
CIRCUIT
BCS
÷2
A
CGMOUT
B S*
(TO SIM)
*WHEN S = 1,
VDDA
CGMXFC
CGMOUT = B
VSSA
VPR1–VPR0
PTB4
VRS7–VRS0
PHASE
DETECTOR
MONITOR
MODE
VOLTAGE
CONTROLLED
OSCILLATOR
LOOP
FILTER
USER
MODE
CGMVCLK
PLL ANALOG
LOCK
DETECTOR
LOCK
AUTOMATIC
MODE
CONTROL
AUTO
ACQ
INTERRUPT
CONTROL
PLLIE
CGMINT
(TO SIM)
PLLF
MUL11–MUL0
CGMVDV
FREQUENCY
DIVIDER
Figure 4-1. CGM Block Diagram
MC68HC908GR16A Data Sheet, Rev. 1.0
58
Freescale Semiconductor
Functional Description
4.3.1 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) or the OSCENINSTOP bit in the CONFIG register enable 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 also can feed the OSC1 pin of the crystal oscillator
circuit. Connect the external clock to the OSC1 pin and let the OSC2 pin float.
4.3.2 Phase-Locked Loop Circuit (PLL)
The PLL is a frequency generator that can operate in either acquisition mode or tracking mode, depending
on the accuracy of the output frequency. The PLL can change between acquisition and tracking modes
either automatically or manually.
4.3.3 PLL Circuits
The PLL consists of these 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, (71.4 kHz) times a linear factor, L, and a power-of-two factor, E, or
(L × 2E)fNOM.
CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK. CGMRCLK runs at a frequency,
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 dividers
output is the VCO feedback clock, CGMVDV, running at a frequency, fVDV = fVCLK/(N). For more
information, see 4.3.6 Programming the PLL.
The phase detector then compares the VCO feedback clock, CGMVDV, with the final reference clock,
CGMRDV. A correction pulse is generated based on the phase difference between the two signals. The
loop filter then slightly alters the DC voltage on the external capacitor connected to CGMXFC based on
the width and direction of the correction pulse. The filter can make fast or slow corrections depending on
its mode, described in 4.3.4 Acquisition and Tracking Modes. The value of the external capacitor and the
reference frequency determines the speed of the corrections and the stability of the PLL.
The lock detector compares the frequencies of the VCO feedback clock, CGMVDV, and the reference
clock, CGMRCLK. Therefore, the speed of the lock detector is directly proportional to the reference
frequency, fRCLK. The circuit determines the mode of the PLL and the lock condition based on this
comparison.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
59
Clock Generator Module (CGM)
4.3.4 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 start up or when the PLL has suffered a severe noise hit and the
VCO frequency is far off the desired frequency. When in acquisition mode, the ACQ bit is clear in
the PLL bandwidth control register. (See 4.5.2 PLL Bandwidth Control Register.)
• Tracking mode — In tracking mode, the filter makes only small corrections to the frequency of the
VCO. PLL jitter is much lower in tracking mode, but the response to noise is also slower. The PLL
enters tracking mode when the VCO frequency is nearly correct, such as when the PLL is selected
as the base clock source. (See 4.3.8 Base Clock Selector Circuit.) The PLL is automatically in
tracking mode when not in acquisition mode or when the ACQ bit is set.
4.3.5 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter manually or automatically.
Automatic mode is recommended for most users.
In automatic bandwidth control mode (AUTO = 1), the lock detector automatically switches between
acquisition and tracking modes. Automatic bandwidth control mode also is used to determine when the
VCO clock, CGMVCLK, is safe to use as the source for the base clock, CGMOUT. (See 4.5.2 PLL
Bandwidth Control Register.) If PLL interrupts are enabled, the software can wait for a PLL interrupt
request and then check the LOCK bit. If interrupts are disabled, software can poll the LOCK bit
continuously (for example, during PLL start up) 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 4.3.8 Base Clock Selector
Circuit.) If the VCO is selected as the source for the base clock and the LOCK bit is clear, the PLL has
suffered a severe noise hit and the software must take appropriate action, depending on the application.
(See 4.6 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 4.5.2 PLL Bandwidth Control Register.) is a read-only indicator of the mode of
the filter. (See 4.3.4 Acquisition and Tracking Modes.)
• The ACQ bit is set when the VCO frequency is within a certain tolerance and is cleared when the
VCO frequency is out of a certain tolerance. (See 4.8 Acquisition/Lock Time Specifications for
more information.)
• The LOCK bit is a read-only indicator of the locked state of the PLL.
• The LOCK bit is set when the VCO frequency is within a certain tolerance and is cleared when the
VCO frequency is out of a certain tolerance. (See 4.8 Acquisition/Lock Time Specifications for
more information.)
• CPU interrupts can occur if enabled (PLLIE = 1) when the PLL’s lock condition changes, toggling
the LOCK bit. (See 4.5.1 PLL Control Register.)
The PLL also may operate in manual mode (AUTO = 0). Manual mode is used by systems that do not
require an indicator of the lock condition for proper operation. Such systems typically operate well below
fBUSMAX.
MC68HC908GR16A Data Sheet, Rev. 1.0
60
Freescale Semiconductor
Functional Description
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 4.8
Acquisition/Lock Time Specifications.), after turning on the PLL by setting PLLON in the PLL
control register (PCTL).
• Software must wait a given time, tAL, after entering tracking mode before selecting the PLL as the
clock source to CGMOUT (BCS = 1).
• The LOCK bit is disabled.
• CPU interrupts from the CGM are disabled.
4.3.6 Programming the PLL
Use the following procedure to program the PLL. For reference, the variables used and their meaning are
shown in Table 4-1.
Table 4-1. Variable Definitions
Variable
Definition
fBUSDES
Desired bus clock frequency
fVCLKDES
Desired VCO clock frequency
fRCLK
Chosen reference crystal frequency
fVCLK
Calculated VCO clock frequency
fBUS
Calculated bus clock frequency
fNOM
Nominal VCO center frequency
fVRS
Programmed VCO center frequency
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).
fVCLKDES = 4 x fBUSDES
3. Choose a practical PLL (crystal) reference frequency, fRCLK. Typically, the reference crystal is 1–8
MHz.
Frequency errors to the PLL are corrected at a rate of fRCLK. For stability and lock time reduction,
this rate must be as fast as possible. The VCO frequency must be an integer multiple of this rate.
The relationship between the VCO frequency, fVCLK, and the reference frequency, fRCLK, is:
fVCLK = (N) (fRCLK)
N, the range multiplier, must be an integer.
In cases where desired bus frequency has some tolerance, choose fRCLK to a value determined
either by other module requirements (such as modules which are clocked by CGMXCLK), cost
requirements, or ideally, as high as the specified range allows. See Chapter 20 Electrical
Specifications. After choosing N, the actual bus frequency can be determined using equation in 2
above.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
61
Clock Generator Module (CGM)
4. Select a VCO frequency multiplier, N.
⎛ f VCLKDES⎞
N = round ⎜ --------------------------⎟
⎝ f RCLK ⎠
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 the VCO’s power-of-two range multiplier E, according to Table 4-2.
Table 4-2. Power-of-Two Range Selectors
Frequency Range
E
0 < fVCLK ≤ 8 MHz
0
8 MHz< fVCLK ≤ 16 MHz
1
16 MHz< fVCLK ≤ 32 MHz
2(1)
1. Do not program E to a value of 3.
7. Select a VCO linear range multiplier, L, where fNOM = 71.4 kHz
fVCLK
L = Round
2E x fNOM
8. Calculate and verify the adequacy of the VCO programmed center-of-range frequency, fVRS. The
center-of-range frequency is the midpoint between the minimum and maximum frequencies
attainable by the PLL.
fVRS = (L x 2E) fNOM
9. For proper operation,
E
f NOM × 2
f VRS – f VCLK ≤ --------------------------2
10. Verify the choice of N, E, and L by comparing fVCLK to fVRS and fVCLKDES. For proper operation,
fVCLK must be within the application’s tolerance of fVCLKDES, and fVRS must be as close as possible
to fVCLK.
NOTE
Exceeding the recommended maximum bus frequency or VCO frequency
can crash the MCU.
11. Program the PLL registers accordingly:
a. In the VPR bits of the PLL control register (PCTL), program the binary equivalent of E.
b. In the PLL multiplier select register low (PMSL) and the PLL multiplier select register high
(PMSH), program the binary equivalent of N. If using a 1–8 MHz reference, the PMSL register
must be reprogrammed from the reset value before enabling the PLL.
c. In the PLL VCO range select register (PMRS), program the binary coded equivalent of L.
MC68HC908GR16A Data Sheet, Rev. 1.0
62
Freescale Semiconductor
Functional Description
Table 4-3 provides numeric examples (register values are in hexadecimal notation):
Table 4-3. Numeric Example
fBUS (MHz)
fRCLK (MHz)
PCTL
E
PMSH,L
N
PMRS
L
1.0
2.0
0
002
38
2.0
2.0
0
004
70
4.0
2.0
1
008
70
8.0
2.0
2
010
70
2.0
4.0
0
002
70
4.0
4.0
1
004
70
5.0
4.0
2
005
46
8.0
2.4576
4.0
4.9152
2
1
008
002
70
45
4.9152
4.9152
2
004
45
7.3728
4.9152
2
006
67
2.0
8.0
0
001
70
4.0
8.0
1
002
70
6.0
8.0
2
003
54
8.0
8.0
2
004
70
4.3.7 Special Programming Exceptions
The programming method described in 4.3.6 Programming the PLL does not account for two possible
exceptions. A value of 0 for N or L is meaningless when used in the equations given. To account for these
exceptions:
• A 0 value for N is interpreted exactly the same as a value of 1.
• A 0 value for L disables the PLL and prevents its selection as the source for the base clock.
See 4.3.8 Base Clock Selector Circuit.
4.3.8 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 0. This value would set up a condition inconsistent with the operation of the
PLL, so that the PLL would be disabled and the crystal clock would be forced as the source of the base
clock.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
63
Clock Generator Module (CGM)
4.3.9 CGM External Connections
In its typical configuration, the CGM requires external components. Five of these are for the crystal
oscillator and two or four are for the PLL.
The crystal oscillator is normally connected in a Pierce oscillator configuration, as shown in Figure 4-2.
Figure 4-2 shows only the logical representation of the internal components and may not represent actual
circuitry. The oscillator configuration uses five components:
• Crystal, X1
• Fixed capacitor, C1
• Tuning capacitor, C2 (can also be a fixed capacitor)
• Feedback resistor, RB
• Series resistor, RS
The series resistor (RS) is included in the diagram to follow strict Pierce oscillator guidelines. Refer to the
crystal manufacturer’s data for more information regarding values for C1 and C2.
Figure 4-2 also shows the external components for the PLL:
• Bypass capacitor, CBYP
• Filter network
Routing should be done with great care to minimize signal cross talk and noise.
SIMOSCEN
OSCENINSTOP
(FROM CONFIG)
CGMXCLK
OSC1
CGMXFC
OSC2
VSSA
VDDA
VDD
RB
RF1
RS
CF2
CBYP
0.1 µF
CF1
X1
C1
3 Component Filter
C2
Note: Filter network in box can be replaced with a single capacitor, but will degrade stability.
Figure 4-2. CGM External Connections
MC68HC908GR16A Data Sheet, Rev. 1.0
64
Freescale Semiconductor
I/O Signals
4.4 I/O Signals
The following paragraphs describe the CGM I/O signals.
4.4.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
4.4.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
4.4.3 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase corrections. An external filter network is
connected to this pin. (See Figure 4-2.)
NOTE
To prevent noise problems, the filter network should be placed as close to
the CGMXFC pin as possible, with minimum routing distances and no
routing of other signals across the network.
4.4.4 PLL Analog Power Pin (VDDA)
VDDA is a power pin used by the analog portions of the PLL. Connect the VDDA pin to the same voltage
potential as the VDD pin.
NOTE
Route VDDA carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
4.4.5 PLL Analog Ground Pin (VSSA)
VSSA is a ground pin used by the analog portions of the PLL. Connect the VSSA pin to the same voltage
potential as the VSS pin.
NOTE
Route VSSA carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
4.4.6 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM) and enables the oscillator and
PLL.
4.4.7 Oscillator Enable in Stop Mode Bit (OSCENINSTOP)
OSCENINSTOP is a bit in the CONFIG2 register that enables the oscillator to continue operating during
stop mode. If this bit is set, the oscillator continues running during stop mode. If this bit is not set (default),
the oscillator is controlled by the SIMOSCEN signal which will disable the oscillator during stop mode.
4.4.8 Crystal Output Frequency Signal (CGMXCLK)
CGMXCLK is the crystal oscillator output signal. It runs at the full speed of the crystal (fXCLK) and comes
directly from the crystal oscillator circuit. Figure 4-2 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
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
65
Clock Generator Module (CGM)
depend on the crystal and other external factors. Also, the frequency and amplitude of CGMXCLK can be
unstable at start up.
4.4.9 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM, which generates the MCU clocks.
CGMOUT is a 50 percent duty cycle clock running at twice the bus frequency. CGMOUT is software
programmable to be either the oscillator output, CGMXCLK, divided by two or the VCO clock, CGMVCLK,
divided by two.
4.4.10 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
4.5 CGM Registers
These registers control and monitor operation of the CGM:
• PLL control register (PCTL) — See 4.5.1 PLL Control Register
• PLL bandwidth control register (PBWC) — see 4.5.2 PLL Bandwidth Control Register
• PLL multiplier select register high (PMSH) — see 4.5.3 PLL Multiplier Select Register High
• PLL multiplier select register low (PMSL) — see 4.5.4 PLL Multiplier Select Register Low
• PLL VCO range select register (PMRS) — see 4.5.5 PLL VCO Range Select Register
Figure 4-3 is a summary of the CGM registers.
Addr.
$0036
$0037
$0038
$0039
$003A
$003B
Register Name
PLL Control Register
(PCTL)
See page 67.
PLL Bandwidth Control
Register (PBWC)
See page 68.
PLL Multiplier Select High
Register (PMSH)
See page 69.
PLL Multiplier Select Low
Register (PMSL)
See page 70.
PLL VCO Select Range
Register (PMRS)
See page 70.
Bit 7
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Reserved Register Write:
Reset:
PLLIE
0
AUTO
6
PLLF
0
LOCK
5
4
3
2
1
Bit 0
PLLON
BCS
R
R
VPR1
VPR0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
MUL11
MUL10
MUL9
MUL8
ACQ
R
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
MUL3
MUL2
MUL1
MUL0
0
1
0
0
0
0
0
0
VRS7
VRS6
VRS5
VRS4
VRS3
VRS2
VRS1
VRS0
0
0
1
0
0
0
0
0
0
0
0
0
R
R
R
R
0
0
= Unimplemented
0
R
0
= Reserved
0
0
1
0
NOTES:
1. When AUTO = 0, PLLIE is forced clear and is read-only.
2. When AUTO = 0, PLLF and LOCK read as clear.
3. When AUTO = 1, ACQ is read-only.
4. When PLLON = 0 or VRS7:VRS0 = $0, BCS is forced clear and is read-only.
5. When PLLON = 1, the PLL programming register is read-only.
6. When BCS = 1, PLLON is forced set and is read-only.
Figure 4-3. CGM I/O Register Summary
MC68HC908GR16A Data Sheet, Rev. 1.0
66
Freescale Semiconductor
CGM Registers
4.5.1 PLL Control Register
The PLL control register (PCTL) contains the interrupt enable and flag bits, the on/off switch, the base
clock selector bit, and the VCO power-of-two range selector bits.
Address:
$0036
Bit 7
Read:
Write:
Reset:
PLLIE
0
6
PLLF
5
4
3
2
1
Bit 0
PLLON
BCS
R
R
VPR1
VPR0
1
0
0
0
0
0
R
= Reserved
0
= Unimplemented
Figure 4-4. PLL Control Register (PCTL)
PLLIE — PLL Interrupt Enable Bit
This read/write bit enables the PLL to generate an interrupt request when the LOCK bit toggles, setting
the PLL flag, PLLF. When the AUTO bit in the PLL bandwidth control register (PBWC) is clear, PLLIE
cannot be written and reads as 0. Reset clears the PLLIE bit.
1 = PLL interrupts enabled
0 = PLL interrupts disabled
PLLF — PLL Interrupt Flag Bit
This read-only bit is set whenever the LOCK bit toggles. PLLF generates an interrupt request if the
PLLIE bit also is set. PLLF always reads as 0 when the AUTO bit in the PLL bandwidth control register
(PBWC) is clear. Clear the PLLF bit by reading the PLL control register. Reset clears the PLLF bit.
1 = Change in lock condition
0 = No change in lock condition
NOTE
Do not inadvertently clear the PLLF bit. Any read or read-modify-write
operation on the PLL control register clears the PLLF bit.
PLLON — PLL On Bit
This read/write bit activates the PLL and enables the VCO clock, CGMVCLK. PLLON cannot be
cleared if the VCO clock is driving the base clock, CGMOUT (BCS = 1). (See 4.3.8 Base Clock Selector
Circuit.) Reset sets this bit so that the loop can stabilize as the MCU is powering up.
1 = PLL on
0 = PLL off
BCS — Base Clock Select Bit
This read/write bit selects either the crystal oscillator output, CGMXCLK, or the VCO clock,
CGMVCLK, as the source of the CGM output, CGMOUT. CGMOUT frequency is one-half the
frequency of the selected clock. BCS cannot be set while the PLLON bit is clear. After toggling BCS,
it may take up to three CGMXCLK and three CGMVCLK cycles to complete the transition from one
source clock to the other. During the transition, CGMOUT is held in stasis. (See 4.3.8 Base Clock
Selector Circuit.) Reset clears the BCS bit.
1 = CGMVCLK divided by two drives CGMOUT
0 = CGMXCLK divided by two drives CGMOUT
NOTE
PLLON and BCS have built-in protection that prevents the base clock
selector circuit from selecting the VCO clock as the source of the base clock
if the PLL is off. Therefore, PLLON cannot be cleared when BCS is set, and
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
67
Clock Generator Module (CGM)
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
4.3.8 Base Clock Selector Circuit.).
VPR1 and VPR0 — VCO Power-of-Two Range Select Bits
These read/write bits control the VCO’s hardware power-of-two range multiplier E that, in conjunction
with L controls the hardware center-of-range frequency, fVRS. VPR1:VPR0 cannot be written when the
PLLON bit is set. Reset clears these bits. (See 4.3.3 PLL Circuits, 4.3.6 Programming the PLL, and
4.5.5 PLL VCO Range Select Register.)
Table 4-4. VPR1 and VPR0 Programming
VPR1 and VPR0
E
VCO Power-of-Two
Range Multiplier
00
0
1
01
1
2
10
(1)
4
2
1. Do not program E to a value of 3.
NOTE
Verify that the value of the VPR1 and VPR0 bits in the PCTL register are
appropriate for the given reference and VCO clock frequencies before
enabling the PLL. See 4.3.6 Programming the PLL for detailed instructions
on selecting the proper value for these control bits.
4.5.2 PLL Bandwidth Control Register
The PLL bandwidth control register (PBWC):
• Selects automatic or manual (software-controlled) bandwidth control mode
• Indicates when the PLL is locked
• In automatic bandwidth control mode, indicates when the PLL is in acquisition or tracking mode
• In manual operation, forces the PLL into acquisition or tracking mode
Address:
$0037
Bit 7
Read:
Write:
Reset:
AUTO
0
6
LOCK
5
ACQ
0
= Unimplemented
0
4
3
2
1
0
0
0
0
0
0
0
0
R
Bit 0
R
0
= Reserved
Figure 4-5. PLL Bandwidth Control Register (PBWC)
AUTO — Automatic Bandwidth Control Bit
This read/write bit selects automatic or manual bandwidth control. When initializing the PLL for manual
operation (AUTO = 0), clear the ACQ bit before turning on the PLL. Reset clears the AUTO bit.
1 = Automatic bandwidth control
0 = Manual bandwidth control
MC68HC908GR16A Data Sheet, Rev. 1.0
68
Freescale Semiconductor
CGM Registers
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. The write one function of this bit is reserved for test, so this bit must always be written
as a 0. Reset clears the LOCK bit.
1 = VCO frequency correct or locked
0 = VCO frequency incorrect or unlocked
ACQ — Acquisition Mode Bit
When the AUTO bit is set, ACQ is a read-only bit that indicates whether the PLL is in acquisition mode
or tracking mode. When the AUTO bit is clear, ACQ is a read/write bit that controls whether the PLL is
in acquisition or tracking mode.
In automatic bandwidth control mode (AUTO = 1), the last-written value from manual operation is
stored in a temporary location and is recovered when manual operation resumes. Reset clears this bit,
enabling acquisition mode.
1 = Tracking mode
0 = Acquisition mode
4.5.3 PLL Multiplier Select Register High
The PLL multiplier select register high (PMSH) contains the programming information for the high byte of
the modulo feedback divider.
Address:
Read:
$0038
Bit 7
6
5
4
0
0
0
0
0
0
0
0
Write:
Reset:
3
2
1
Bit 0
MUL11
MUL10
MUL9
MUL8
0
0
0
0
= Unimplemented
Figure 4-6. PLL Multiplier Select Register High (PMSH)
MUL11–MUL8 — Multiplier Select Bits
These read/write bits control the high byte of the modulo feedback divider that selects the VCO
frequency multiplier N. (See 4.3.3 PLL Circuits and 4.3.6 Programming the PLL.) A value of $0000 in
the multiplier select registers configures the modulo feedback divider the same as a value of $0001.
Reset initializes the registers to $0040 for a default multiply value of 64.
NOTE
The multiplier select bits have built-in protection such that they cannot be
written when the PLL is on (PLLON = 1).
PMSH[7:4] — Unimplemented Bits
These bits have no function and always read as 0s.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
69
Clock Generator Module (CGM)
4.5.4 PLL Multiplier Select Register Low
The PLL multiplier select register low (PMSL) contains the programming information for the low byte of
the modulo feedback divider.
Address:
Read:
Write:
Reset:
$0038
Bit 7
6
5
4
3
2
1
Bit 0
MUL7
MUL6
MUL5
MUL4
MUL3
MUL2
MUL1
MUL0
0
1
0
0
0
0
0
0
Figure 4-7. PLL Multiplier Select Register Low (PMSL)
NOTE
For applications using 1–8 MHz reference frequencies this register must be
reprogrammed before enabling the PLL. The reset value of this register will
cause applications using 1–8 MHz reference frequencies to become
unstable if the PLL is enabled without programming an appropriate value.
The programmed value must not allow the VCO clock to exceed 32 MHz.
See 4.3.6 Programming the PLL for detailed instructions on choosing the
proper value for PMSL.
MUL7–MUL0 — Multiplier Select Bits
These read/write bits control the low byte of the modulo feedback divider that selects the VCO
frequency multiplier, N. (See 4.3.3 PLL Circuits and 4.3.6 Programming the PLL.) MUL7–MUL0 cannot
be written when the PLLON bit in the PCTL is set. A value of $0000 in the multiplier select registers
configures the modulo feedback divider the same as a value of $0001. Reset initializes the register to
$40 for a default multiply value of 64.
NOTE
The multiplier select bits have built-in protection such that they cannot be
written when the PLL is on (PLLON = 1).
4.5.5 PLL VCO Range Select Register
The PLL VCO range select register (PMRS) contains the programming information required for the
hardware configuration of the VCO.
Address:
Read:
Write:
Reset:
$003A
Bit 7
6
5
4
3
2
1
Bit 0
VRS7
VRS6
VRS5
VRS4
VRS3
VRS2
VRS1
VRS0
0
1
0
0
0
0
0
0
Figure 4-8. PLL VCO Range Select Register (PMRS)
NOTE
Verify that the value of the PMRS register is appropriate for the given
reference and VCO clock frequencies before enabling the PLL. See 4.3.6
Programming the PLL for detailed instructions on selecting the proper value
for these control bits.
MC68HC908GR16A Data Sheet, Rev. 1.0
70
Freescale Semiconductor
Interrupts
VRS7–VRS0 — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear multiplier L which, in conjunction with
E (See 4.3.3 PLL Circuits, 4.3.6 Programming the PLL, and 4.5.1 PLL Control Register.), controls the
hardware center-of-range frequency, fVRS. VRS7–VRS0 cannot be written when the PLLON bit in the
PCTL is set. (See 4.3.7 Special Programming Exceptions.) A value of $00 in the VCO range select
register disables the PLL and clears the BCS bit in the PLL control register (PCTL). (See 4.3.8 Base
Clock Selector Circuit and 4.3.7 Special Programming Exceptions.). Reset initializes the register to $40
for a default range multiply value of 64.
NOTE
The VCO range select bits have built-in protection such that they cannot be
written when the PLL is on (PLLON = 1) and such that the VCO clock
cannot be selected as the source of the base clock (BCS = 1) if the VCO
range select bits are all clear.
The PLL VCO range select register must be programmed correctly.
Incorrect programming can result in failure of the PLL to achieve lock.
4.6 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 frequency
sensitive, interrupts should be disabled to prevent PLL interrupt service routines from impeding software
performance or from exceeding stack limitations.
NOTE
Software can select the CGMVCLK divided by two as the CGMOUT source
even if the PLL is not locked (LOCK = 0). Therefore, software should make
sure the PLL is locked before setting the BCS bit.
4.7 Special Modes
The WAIT instruction puts the MCU in low power-consumption standby modes.
4.7.1 Wait Mode
The WAIT instruction does not affect the CGM. Before entering wait mode, software can disengage and
turn off the PLL by clearing the BCS and PLLON bits in the PLL control register (PCTL) to save power.
Less power-sensitive applications can disengage the PLL without turning it off, so that the PLL clock is
immediately available at WAIT exit. This would be the case also when the PLL is to wake the MCU from
wait mode, such as when the PLL is first enabled and waiting for LOCK or LOCK is lost.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
71
Clock Generator Module (CGM)
4.7.2 Stop Mode
If the OSCENINSTOP bit in the CONFIG2 register is cleared (default), then the STOP instruction disables
the CGM (oscillator and phase locked loop) and holds low all CGM outputs (CGMXCLK, CGMOUT, and
CGMINT).
If the OSCENINSTOP bit in the CONFIG2 register is set, then the phase locked loop is shut off but the
oscillator will continue to operate in stop mode.
4.7.3 CGM During Break Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during
the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear
status bits during the break state. See 19.2.2.4 SIM Break Flag Control Register.
To allow software to clear status bits during a break interrupt, write a 1 to the BCFE bit. If a status bit is
cleared during the break state, it remains cleared when the MCU exits the break state.
To protect the PLLF bit during the break state, write a 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.
4.8 Acquisition/Lock Time Specifications
The acquisition and lock times of the PLL are, in many applications, the most critical PLL design
parameters. Proper design and use of the PLL ensures the highest stability and lowest acquisition/lock
times.
4.8.1 Acquisition/Lock Time Definitions
Typical control systems refer to the acquisition time or lock time as the reaction time, within specified
tolerances, of the system to a step input. In a PLL, the step input occurs when the PLL is turned on or
when it suffers a noise hit. The tolerance is usually specified as a percent of the step input or when the
output settles to the desired value plus or minus a percent of the frequency change. Therefore, the
reaction time is constant in this definition, regardless of the size of the step input. For example, consider
a system with a 5 percent acquisition time tolerance. If a command instructs the system to change from
0 Hz to 1 MHz, the acquisition time is the time taken for the frequency to reach 1 MHz ±50 kHz.
Fifty kHz = 5% of the 1-MHz step input. If the system is operating at 1 MHz and suffers a –100-kHz noise
hit, the acquisition time is the time taken to return from 900 kHz to 1 MHz ±5 kHz. Five kHz = 5% of the
100-kHz step input.
Other systems refer to acquisition and lock times as the time the system takes to reduce the error between
the actual output and the desired output to within specified tolerances. Therefore, the acquisition or lock
time varies according to the original error in the output. Minor errors may not even be registered. Typical
PLL applications prefer to use this definition because the system requires the output frequency to be
within a certain tolerance of the desired frequency regardless of the size of the initial error.
4.8.2 Parametric Influences on Reaction Time
Acquisition and lock times are designed to be as short as possible while still providing the highest possible
stability. These reaction times are not constant, however. Many factors directly and indirectly affect the
acquisition time.
MC68HC908GR16A Data Sheet, Rev. 1.0
72
Freescale Semiconductor
Acquisition/Lock Time Specifications
The most critical parameter which affects the reaction times of the PLL is the reference frequency, fRCLK.
This frequency is the input to the phase detector and controls how often the PLL makes corrections. For
stability, the corrections must be small compared to the desired frequency, so several corrections are
required to reduce the frequency error. Therefore, the slower the reference the longer it takes to make
these corrections. This parameter is under user control via the choice of crystal frequency fXCLK. (See
4.3.3 PLL Circuits and 4.3.6 Programming the PLL.)
Another critical parameter is the external filter network. The PLL modifies the voltage on the VCO by
adding or subtracting charge from capacitors in this network. Therefore, the rate at which the voltage
changes for a given frequency error (thus change in charge) is proportional to the capacitance. The size
of the capacitor also is related to the stability of the PLL. If the capacitor is too small, the PLL cannot make
small enough adjustments to the voltage and the system cannot lock. If the capacitor is too large, the PLL
may not be able to adjust the voltage in a reasonable time. (See 4.8.3 Choosing a Filter.)
Also important is the operating voltage potential applied to VDDA. The power supply potential alters the
characteristics of the PLL. A fixed value is best. Variable supplies, such as batteries, are acceptable if
they vary within a known range at very slow speeds. Noise on the power supply is not acceptable,
because it causes small frequency errors which continually change the acquisition time of the PLL.
Temperature and processing also can affect acquisition time because the electrical characteristics of the
PLL change. The part operates as specified as long as these influences stay within the specified limits.
External factors, however, can cause drastic changes in the operation of the PLL. These factors include
noise injected into the PLL through the filter capacitor, filter capacitor leakage, stray impedances on the
circuit board, and even humidity or circuit board contamination.
4.8.3 Choosing a Filter
As described in 4.8.2 Parametric Influences on Reaction Time, the external filter network is critical to the
stability and reaction time of the PLL. The PLL is also dependent on reference frequency and supply
voltage.
Figure 4-9 shows two types of filter circuits. In low-cost applications, where stability and reaction time of
the PLL are not critical, the three component filter network shown in Figure 4-9 (B) can be replaced by a
single capacitor, CF, as shown in shown in Figure 4-9 (A). Refer to Table 4-5 for recommended filter
components at various reference frequencies. For reference frequencies between the values listed in the
table, extrapolate to the nearest common capacitor value. In general, a slightly larger capacitor provides
more stability at the expense of increased lock time.
CGMXFC
CGMXFC
RF1
CF2
CF
CF1
VSSA
VSSA
(A)
(B)
Figure 4-9. PLL Filter
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
73
Clock Generator Module (CGM)
Table 4-5. Example Filter Component Values
fRCLK
CF1
CF2
RF1
CF
1 MHz
8.2 nF
820 pF
2k
18 nF
2 MHz
4.7 nF
470 pF
2k
6.8 nF
3 MHz
3.3 nF
330 pF
2k
5.6 nF
4 MHz
2.2 nF
220 pF
2k
4.7 nF
5 MHz
1.8 nF
180 pF
2k
3.9 nF
6 MHz
1.5 nF
150 pF
2k
3.3 nF
7 MHz
1.2 nF
120 pF
2k
2.7 nF
8 MHz
1 nF
100 pF
2k
2.2 nF
MC68HC908GR16A Data Sheet, Rev. 1.0
74
Freescale Semiconductor
Chapter 5
Configuration Register (CONFIG)
5.1 Introduction
This section describes the configuration registers, CONFIG1 and CONFIG2. The configuration registers
enable or disable these options:
• Stop mode recovery time (32 CGMXCLK cycles or 4096 CGMXCLK cycles)
• COP timeout period (262,128 or 8176 COPCLK cycles)
• STOP instruction
• Computer operating properly module (COP)
• Low-voltage inhibit (LVI) module control and voltage trip point selection
• Enable/disable the oscillator (OSC) during stop mode
• Enable/disable an extra divide by 128 prescaler in timebase module
5.2 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 microcontroller unit (MCU), it is recommended that these
registers be written immediately after reset. The configuration registers are located at $001E and $001F
and may be read at anytime.
NOTE
On a FLASH device, the options except LVI5OR3 are one-time writable by
the user after each reset. The LVI5OR3 bit is one-time writable by the user
only after each POR (power-on reset). The CONFIG registers are not in the
FLASH memory but are special registers containing one-time writable
latches after each reset. Upon a reset, the CONFIG registers default to
predetermined settings as shown in Figure 5-1 and Figure 5-2.
Address:
Read:
$001E
Bit 7
6
5
4
0
0
0
0
0
0
0
0
0
R
= Reserved
Write:
Reset:
= Unimplemented
3
R
2
1
Bit 0
TBMCLKSEL OSCENINSTOP ESCIBDSRC
0
0
1
Figure 5-1. Configuration Register 2 (CONFIG2)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
75
Configuration Register (CONFIG)
Address:
Read:
Write:
Reset:
$001F
Bit 7
6
5
4
3
2
1
Bit 0
COPRS
LVISTOP
LVIRSTD
LVIPWRD
LVI5OR3
SSREC
STOP
COPD
0
0
0
0
See note
0
0
0
Note: LVI5OR3 bit is only reset via POR (power-on reset).
Figure 5-2. Configuration Register 1 (CONFIG1)
TBMCLKSEL— Timebase Clock Select Bit
TBMCLKSEL enables an extra divide-by-128 prescaler in the timebase module. Setting this bit enables
the extra prescaler and clearing this bit disables it. See Chapter 4 Clock Generator Module (CGM) for
a more detailed description of the external clock operation.
1 = Enables extra divide-by-128 prescaler in timebase module
0 = Disables extra divide-by-128 prescaler in timebase module
OSCENINSTOP — Oscillator Enable In Stop Mode Bit
OSCENINSTOP, when set, will enable the oscillator to continue to generate clocks in stop mode. See
Chapter 4 Clock Generator Module (CGM). This function is used to keep the timebase running while
the reset of the MCU stops. See Chapter 17 Timebase Module (TBM). When clear, oscillator will cease
to generate clocks while in stop mode. The default state for this option is clear, disabling the oscillator
in stop mode.
1 = Oscillator enabled to operate during stop mode
0 = Oscillator disabled during stop mode (default)
ESCIBDSRC — SCI Baud Rate Clock Source Bit
ESCIBDSRC controls the clock source used for the serial communications interface (SCI). The setting
of this bit affects the frequency at which the SCI operates.See Chapter 14 Enhanced Serial
Communications Interface (ESCI) Module.
1 = Internal bus clock used as clock source for SCI (default)
0 = External oscillator used as clock source for SCI
COPRS — COP Rate Select Bit
COPRS selects the COP timeout period. Reset clears COPRS. See Chapter 6 Computer Operating
Properly (COP) Module
1 = COP timeout period = 8176 COPCLK cycles
0 = COP timeout period = 262,128 COPCLK cycles
LVISTOP — LVI Enable in Stop Mode Bit
When the LVIPWRD bit is clear, setting the LVISTOP bit enables the LVI to operate during stop mode.
Reset clears LVISTOP.
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 Chapter 11 Low-Voltage Inhibit (LVI).
1 = LVI module resets disabled
0 = LVI module resets enabled
MC68HC908GR16A Data Sheet, Rev. 1.0
76
Freescale Semiconductor
Functional Description
LVIPWRD — LVI Power Disable Bit
LVIPWRD disables the LVI module. See Chapter 11 Low-Voltage Inhibit (LVI).
1 = LVI module power disabled
0 = LVI module power enabled
LVI5OR3 — LVI 5-V or 3-V Operating Mode Bit
LVI5OR3 selects the voltage operating mode of the LVI module (see Chapter 11 Low-Voltage Inhibit
(LVI)). The voltage mode selected for the LVI should match the operating VDD (see Chapter 20
Electrical Specifications) for the LVI’s voltage trip points for each of the modes.
1 = LVI operates in 5-V mode
0 = LVI operates in 3-V mode
NOTE
The LVI5OR3 bit is cleared by a power-on reset (POR) only. Other resets
will leave this bit unaffected.
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 CGMXCLCK cycles
NOTE
Exiting stop mode by an LVI reset will result in the long stop recovery.
If the system clock source selected is the internal oscillator or the external crystal and the
OSCENINSTOP configuration bit is not set, the oscillator will be disabled during stop mode. The short
stop recovery does not provide enough time for oscillator stabilization and for this reason the SSREC
bit should not be set.
The system stabilization time for power-on reset and long stop recovery (both 4096 CGMXCLK cycles)
gives a delay longer than the LVI enable time for these startup scenarios. There is no period where the
MCU is not protected from a low-power condition. However, when using the short stop recovery
configuration option, the 32-CGMXCLK delay must be greater than the LVI’s turn on time to avoid a
period in startup where the LVI is not protecting the MCU.
STOP — STOP Instruction Enable Bit
STOP enables the STOP instruction.
1 = STOP instruction enabled
0 = STOP instruction treated as illegal opcode
COPD — COP Disable Bit
COPD disables the COP module. See Chapter 6 Computer Operating Properly (COP) Module.
1 = COP module disabled
0 = COP module enabled
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
77
Configuration Register (CONFIG)
MC68HC908GR16A Data Sheet, Rev. 1.0
78
Freescale Semiconductor
Chapter 6
Computer Operating Properly (COP) Module
6.1 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 the
CONFIG register.
6.2 Functional Description
Figure 6-1 shows the structure of the COP module.
SIM MODULE
RESET VECTOR FETCH
RESET STATUS REGISTER
COP TIMEOUT
CLEAR STAGES 5–12
CLEAR ALL STAGES
INTERNAL RESET SOURCES(1)
SIM RESET CIRCUIT
12-BIT SIM COUNTER
BUSCLKX4
COPCTL WRITE
COP CLOCK
COP MODULE
6-BIT COP COUNTER
COPEN (FROM SIM)
COPD (FROM CONFIG1)
RESET
CLEAR
COP COUNTER
COPCTL WRITE
COP RATE SELECT
(COPRS FROM CONFIG1)
1. See Chapter 15 System Integration Module (SIM) for more details.
Figure 6-1. COP Block Diagram
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
79
Computer Operating Properly (COP) Module
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 262,128 or 8176
CGMXCLK cycles, depending on the state of the COP rate select bit, COPRS, in the configuration
register. With a 262,128 CGMXCLK cycle overflow option, a 4.9152-MHz crystal gives a COP timeout
period of 53.3 ms. Writing any value to location $FFFF before an overflow occurs prevents a COP reset
by clearing the COP counter and stages 12–5 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.
A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the COP bit in the reset status
register (RSR).
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.
6.3 I/O Signals
The following paragraphs describe the signals shown in Figure 6-1.
6.3.1 CGMXCLK
CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency is equal to the crystal frequency.
6.3.2 STOP Instruction
The STOP instruction clears the COP prescaler.
6.3.3 COPCTL Write
Writing any value to the COP control register (COPCTL) clears the COP counter and clears bits 12–5 of
the prescaler. Reading the COP control register returns the low byte of the reset vector. See 6.4 COP
Control Register.
6.3.4 Power-On Reset
The power-on reset (POR) circuit clears the COP prescaler 4096 CGMXCLK cycles after power-up.
6.3.5 Internal Reset
An internal reset clears the COP prescaler and the COP counter.
MC68HC908GR16A Data Sheet, Rev. 1.0
80
Freescale Semiconductor
COP Control Register
6.3.6 Reset Vector Fetch
A reset vector fetch occurs when the vector address appears on the data bus. A reset vector fetch clears
the COP prescaler.
6.3.7 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the configuration register. See
Chapter 5 Configuration Register (CONFIG).
6.3.8 COPRS (COP Rate Select)
The COPRS signal reflects the state of the COP rate select bit (COPRS) in the configuration register. See
Chapter 5 Configuration Register (CONFIG).
6.4 COP Control Register
The COP control register (COPCTL) is located at address $FFFF and overlaps the reset vector. Writing
any value to $FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF
returns the low byte of the reset vector.
Address: $FFFF
Bit 7
6
Read:
5
4
3
2
1
Bit 0
Low byte of reset vector
Write:
Clear COP counter
Reset:
Unaffected by reset
Figure 6-2. COP Control Register (COPCTL)
6.5 Interrupts
The COP does not generate central processor unit (CPU) interrupt requests.
6.6 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.
6.7 Low-Power Modes
The WAIT and STOP instructions put the microcontroller unit (MCU) in low power-consumption standby
modes.
6.7.1 Wait Mode
The COP remains active during wait mode. If COP is enabled, a reset will occur at COP timeout.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
81
Computer Operating Properly (COP) Module
6.7.2 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 disabled, execution of a STOP instruction results in an illegal opcode reset.
6.8 COP Module During Break Mode
The COP is disabled during a break interrupt when VTST is present on the RST pin.
MC68HC908GR16A Data Sheet, Rev. 1.0
82
Freescale Semiconductor
Chapter 7
Central Processor Unit (CPU)
7.1 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully object-code-compatible version of
the M68HC05 CPU. The CPU08 Reference Manual (document order number CPU08RM/AD) contains a
description of the CPU instruction set, addressing modes, and architecture.
7.2 Features
Features of the CPU include:
• Object code fully upward-compatible with M68HC05 Family
• 16-bit stack pointer with stack manipulation instructions
• 16-bit index register with x-register manipulation instructions
• 8-MHz CPU internal bus frequency
• 64-Kbyte program/data memory space
• 16 addressing modes
• Memory-to-memory data moves without using accumulator
• Fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions
• Enhanced binary-coded decimal (BCD) data handling
• Modular architecture with expandable internal bus definition for extension of addressing range
beyond 64 Kbytes
• Low-power stop and wait modes
7.3 CPU Registers
Figure 7-1 shows the five CPU registers. CPU registers are not part of the memory map.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
83
Central Processor Unit (CPU)
0
7
ACCUMULATOR (A)
0
15
H
X
INDEX REGISTER (H:X)
15
0
STACK POINTER (SP)
15
0
PROGRAM COUNTER (PC)
7
0
V 1 1 H I N Z C
CONDITION CODE REGISTER (CCR)
CARRY/BORROW FLAG
ZERO FLAG
NEGATIVE FLAG
INTERRUPT MASK
HALF-CARRY FLAG
TWO’S COMPLEMENT OVERFLOW FLAG
Figure 7-1. CPU Registers
7.3.1 Accumulator
The accumulator is a general-purpose 8-bit register. The CPU uses the accumulator to hold operands and
the results of arithmetic/logic operations.
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Write:
Reset:
Unaffected by reset
Figure 7-2. Accumulator (A)
7.3.2 Index Register
The 16-bit index register allows indexed addressing of a 64-Kbyte memory space. H is the upper byte of
the index register, and X is the lower byte. H:X is the concatenated 16-bit index register.
In the indexed addressing modes, the CPU uses the contents of the index register to determine the
conditional address of the operand.
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)
MC68HC908GR16A Data Sheet, Rev. 1.0
84
Freescale Semiconductor
CPU Registers
7.3.3 Stack Pointer
The stack pointer is a 16-bit register that contains the address of the next location on the stack. During a
reset, the stack pointer is preset to $00FF. The reset stack pointer (RSP) instruction sets the least
significant byte to $FF and does not affect the most significant byte. The stack pointer decrements as data
is pushed onto the stack and increments as data is pulled from the stack.
In the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an
index register to access data on the stack. The CPU uses the contents of the stack pointer to determine
the conditional address of the operand.
Bit
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
Bit
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
Read:
Write:
Reset:
Figure 7-4. Stack Pointer (SP)
NOTE
The location of the stack is arbitrary and may be relocated anywhere in
random-access memory (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.
7.3.4 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)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
85
Central Processor Unit (CPU)
7.3.5 Condition Code Register
The 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the
instruction just executed. Bits 6 and 5 are set permanently to 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 add-with-carry (ADC) operation. The half-carry flag is required for
binary-coded decimal (BCD) arithmetic operations. The DAA instruction uses the states of the H and
C flags to determine the appropriate correction factor.
1 = Carry between bits 3 and 4
0 = No carry between bits 3 and 4
I — Interrupt Mask
When the interrupt mask is set, all maskable CPU interrupts are disabled. CPU interrupts are enabled
when the interrupt mask is cleared. When a CPU interrupt occurs, the interrupt mask is set
automatically after the CPU registers are saved on the stack, but before the interrupt vector is fetched.
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
MC68HC908GR16A Data Sheet, Rev. 1.0
86
Freescale Semiconductor
Arithmetic/Logic Unit (ALU)
Z — Zero Flag
The CPU sets the zero flag when an arithmetic operation, logic operation, or data manipulation
produces a result of $00.
1 = Zero result
0 = Non-zero result
C — Carry/Borrow Flag
The CPU sets the carry/borrow flag when an addition operation produces a carry out of bit 7 of the
accumulator or when a subtraction operation requires a borrow. Some instructions — such as bit test
and branch, shift, and rotate — also clear or set the carry/borrow flag.
1 = Carry out of bit 7
0 = No carry out of bit 7
7.4 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the instruction set.
Refer to the CPU08 Reference Manual (document order number CPU08RM/AD) for a description of the
instructions and addressing modes and more detail about the architecture of the CPU.
7.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
7.5.1 Wait Mode
The WAIT instruction:
• Clears the interrupt mask (I bit) in the condition code register, enabling interrupts. After exit from
wait mode by interrupt, the I bit remains clear. After exit by reset, the I bit is set.
• Disables the CPU clock
7.5.2 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.
7.6 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
87
Central Processor Unit (CPU)
7.7 Instruction Set Summary
Table 7-1 provides a summary of the M68HC08 instruction set.
ADC #opr
ADC opr
ADC opr
ADC opr,X
ADC opr,X
ADC ,X
ADC opr,SP
ADC opr,SP
ADD #opr
ADD opr
ADD opr
ADD opr,X
ADD opr,X
ADD ,X
ADD opr,SP
ADD opr,SP
V H I N Z C
A ← (A) + (M) + (C)
Add with Carry
A ← (A) + (M)
Add without 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
ff
ee ff
Cycles
Effect
on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Sheet 1 of 6)
2
3
4
4
3
2
4
5
ff
ee ff
2
3
4
4
3
2
4
5
AIS #opr
Add Immediate Value (Signed) to SP
SP ← (SP) + (16 « M)
– – – – – – IMM
A7
ii
2
AIX #opr
Add Immediate Value (Signed) to H:X
H:X ← (H:X) + (16 « M)
– – – – – – IMM
AF
ii
2
A ← (A) & (M)
IMM
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
A4
B4
C4
D4
E4
F4
9EE4
9ED4
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
0
DIR
INH
INH
– – IX1
IX
SP1
38 dd
48
58
68 ff
78
9E68 ff
4
1
1
4
3
5
C
DIR
INH
– – INH
IX1
IX
SP1
37 dd
47
57
67 ff
77
9E67 ff
4
1
1
4
3
5
AND #opr
AND opr
AND opr
AND opr,X
AND opr,X
AND ,X
AND opr,SP
AND opr,SP
ASL opr
ASLA
ASLX
ASL opr,X
ASL ,X
ASL opr,SP
Logical AND
Arithmetic Shift Left
(Same as LSL)
C
b7
ASR opr
ASRA
ASRX
ASR opr,X
ASR opr,X
ASR opr,SP
Arithmetic Shift Right
BCC rel
Branch if Carry Bit Clear
b0
b7
BCLR n, opr
Clear Bit n in M
b0
PC ← (PC) + 2 + rel ? (C) = 0
Mn ← 0
ff
ee ff
– – – – – – 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
BCS rel
Branch if Carry Bit Set (Same as BLO)
PC ← (PC) + 2 + rel ? (C) = 1
– – – – – – REL
25
rr
3
BEQ rel
Branch if Equal
PC ← (PC) + 2 + rel ? (Z) = 1
– – – – – – REL
27
rr
3
BGE opr
Branch if Greater Than or Equal To
(Signed Operands)
PC ← (PC) + 2 + rel ? (N ⊕ V) = 0
– – – – – – REL
90
rr
3
BGT opr
Branch if Greater Than (Signed
Operands)
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 0 – – – – – – REL
92
rr
3
BHCC rel
Branch if Half Carry Bit Clear
PC ← (PC) + 2 + rel ? (H) = 0
– – – – – – REL
28
rr
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
3
3
MC68HC908GR16A Data Sheet, Rev. 1.0
88
Freescale Semiconductor
Instruction Set Summary
Effect
on CCR
V H I N Z C
BHS rel
Branch if Higher or Same
(Same as BCC)
BIH rel
BIL rel
PC ← (PC) + 2 + rel ? (C) = 0
– – – – – – REL
Branch if IRQ Pin High
PC ← (PC) + 2 + rel ? IRQ = 1
Branch if IRQ Pin Low
PC ← (PC) + 2 + rel ? IRQ = 0
(A) & (M)
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)
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Sheet 2 of 6)
24
rr
3
– – – – – – REL
2F
rr
3
– – – – – – REL
2E
rr
3
IMM
DIR
EXT
0 – – – IX2
IX1
IX
SP1
SP2
A5
B5
C5
D5
E5
F5
9EE5
9ED5
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
rr
3
PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 1 – – – – – – REL
93
BLO rel
Branch if Lower (Same as BCS)
PC ← (PC) + 2 + rel ? (C) = 1
– – – – – – REL
25
rr
3
BLS rel
Branch if Lower or Same
PC ← (PC) + 2 + rel ? (C) | (Z) = 1
– – – – – – REL
23
rr
3
BLT opr
Branch if Less Than (Signed Operands)
PC ← (PC) + 2 + rel ? (N ⊕ V) =1
– – – – – – REL
91
rr
3
BMC rel
Branch if Interrupt Mask Clear
PC ← (PC) + 2 + rel ? (I) = 0
– – – – – – REL
2C
rr
3
BMI rel
Branch if Minus
PC ← (PC) + 2 + rel ? (N) = 1
– – – – – – REL
2B
rr
3
BMS rel
Branch if Interrupt Mask Set
PC ← (PC) + 2 + rel ? (I) = 1
– – – – – – REL
2D
rr
3
3
BNE rel
Branch if Not Equal
PC ← (PC) + 2 + rel ? (Z) = 0
– – – – – – REL
26
rr
BPL rel
Branch if Plus
PC ← (PC) + 2 + rel ? (N) = 0
– – – – – – REL
2A
rr
3
BRA rel
Branch Always
PC ← (PC) + 2 + rel
– – – – – – REL
20
rr
3
DIR (b0)
DIR (b1)
DIR (b2)
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
PC ← (PC) + 3 + rel ? (Mn) = 0
BRCLR n,opr,rel Branch if Bit n in M Clear
BRN rel
PC ← (PC) + 2
Branch Never
BRSET n,opr,rel Branch if Bit n in M Set
BSET n,opr
Set Bit n in M
BSR rel
Branch to Subroutine
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
– – – – – – 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
PC ← (PC) + 2; push (PCL)
SP ← (SP) – 1; push (PCH)
SP ← (SP) – 1
PC ← (PC) + rel
– – – – – – REL
AD
rr
4
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 3 + rel ? (X) – (M) = $00
PC ← (PC) + 3 + rel ? (A) – (M) = $00
PC ← (PC) + 2 + rel ? (A) – (M) = $00
PC ← (PC) + 4 + rel ? (A) – (M) = $00
DIR
IMM
– – – – – – IMM
IX1+
IX+
SP1
31
41
51
61
71
9E61
dd rr
ii rr
ii rr
ff rr
rr
ff rr
5
4
4
5
4
6
CLC
Clear Carry Bit
C←0
– – – – – 0 INH
98
1
CLI
Clear Interrupt Mask
I←0
– – 0 – – – INH
9A
2
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
89
Central Processor Unit (CPU)
CLR opr
CLRA
CLRX
CLRH
CLR opr,X
CLR ,X
CLR opr,SP
CMP #opr
CMP opr
CMP opr
CMP opr,X
CMP opr,X
CMP ,X
CMP opr,SP
CMP opr,SP
V H I N Z C
Clear
Compare A with 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
DEC opr
DECA
DECX
DEC opr,X
DEC ,X
DEC opr,SP
Decrement
DIV
Divide
INC opr
INCA
INCX
INC opr,X
INC ,X
INC opr,SP
Exclusive OR M with A
Increment
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 dd
4F
5F
8C
6F ff
7F
9E6F ff
(A) – (M)
IMM
DIR
EXT
IX2
– –
IX1
IX
SP1
SP2
A1
B1
C1
D1
E1
F1
9EE1
9ED1
DIR
INH
INH
0 – – 1
IX1
IX
SP1
33 dd
43
53
63 ff
73
9E63 ff
M ← (M) = $FF – (M)
A ← (A) = $FF – (M)
X ← (X) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
M ← (M) = $FF – (M)
(H:X) – (M:M + 1)
(X) – (M)
(A)10
DBNZ opr,rel
DBNZA rel
DBNZX rel
Decrement and Branch if Not Zero
DBNZ opr,X,rel
DBNZ X,rel
DBNZ opr,SP,rel
EOR #opr
EOR opr
EOR opr
EOR opr,X
EOR opr,X
EOR ,X
EOR opr,SP
EOR opr,SP
Effect
on CCR
ff
ee ff
2
3
4
4
3
2
4
5
4
1
1
4
3
5
ii ii+1
dd
3
4
IMM
DIR
EXT
IX2
– – IX1
IX
SP1
SP2
A3
B3
C3
D3
E3
F3
9EE3
9ED3
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
U – – INH
72
A ← (A) – 1 or M ← (M) – 1 or X ← (X) – 1
PC ← (PC) + 3 + rel ? (result) ≠ 0
DIR
PC ← (PC) + 2 + rel ? (result) ≠ 0
INH
PC ← (PC) + 2 + rel ? (result) ≠ 0
– – – – – – INH
PC ← (PC) + 3 + rel ? (result) ≠ 0
IX1
PC ← (PC) + 2 + rel ? (result) ≠ 0
IX
PC ← (PC) + 4 + rel ? (result) ≠ 0
SP1
3B
4B
5B
6B
7B
9E6B
ff
ee ff
2
dd rr
rr
rr
ff rr
rr
ff rr
M ← (M) – 1
A ← (A) – 1
X ← (X) – 1
M ← (M) – 1
M ← (M) – 1
M ← (M) – 1
DIR
INH
INH
– – –
IX1
IX
SP1
A ← (H:A)/(X)
H ← Remainder
– – – – INH
52
A ← (A ⊕ M)
IMM
DIR
EXT
0 – – – IX2
IX1
IX
SP1
SP2
A8
B8
C8
D8
E8
F8
9EE8
9ED8
DIR
INH
– – – INH
IX1
IX
SP1
3C dd
4C
5C
6C ff
7C
9E6C ff
M ← (M) + 1
A ← (A) + 1
X ← (X) + 1
M ← (M) + 1
M ← (M) + 1
M ← (M) + 1
3
1
1
1
3
2
4
65
75
– –
IMM
DIR
ii
dd
hh ll
ee ff
ff
Cycles
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Sheet 3 of 6)
3A dd
4A
5A
6A ff
7A
9E6A ff
5
3
3
5
4
6
4
1
1
4
3
5
7
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
4
1
1
4
3
5
MC68HC908GR16A Data Sheet, Rev. 1.0
90
Freescale Semiconductor
Instruction Set Summary
JSR opr
JSR opr
JSR opr,X
JSR opr,X
JSR ,X
Jump to Subroutine
LDHX #opr
LDHX opr
Load H:X from M
2
3
4
3
2
PC ← (PC) + n (n = 1, 2, or 3)
Push (PCL); SP ← (SP) – 1
Push (PCH); SP ← (SP) – 1
PC ← Unconditional Address
DIR
EXT
– – – – – – IX2
IX1
IX
BD
CD
DD
ED
FD
dd
hh ll
ee ff
ff
4
5
6
5
4
A ← (M)
IMM
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
A6
B6
C6
D6
E6
F6
9EE6
9ED6
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
ii jj
dd
3
4
ii
dd
hh ll
ee ff
ff
2
3
4
4
3
2
4
5
H:X ← (M:M + 1)
Logical Shift Left
(Same as ASL)
Logical Shift Right
MOV opr,opr
MOV opr,X+
MOV #opr,opr
MOV X+,opr
Move
MUL
Unsigned multiply
C
b7
45
55
AE
BE
CE
DE
EE
FE
9EEE
9EDE
0
DIR
INH
INH
– – IX1
IX
SP1
38 dd
48
58
68 ff
78
9E68 ff
4
1
1
4
3
5
C
DIR
INH
– – 0 INH
IX1
IX
SP1
34 dd
44
54
64 ff
74
9E64 ff
4
1
1
4
3
5
b0
0
IMM
DIR
IMM
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
X ← (M)
b7
Negate (Two’s Complement)
0 – – –
b0
H:X ← (H:X) + 1 (IX+D, DIX+)
DD
DIX+
0 – – – IMD
IX+D
X:A ← (X) × (A)
– 0 – – – 0 INH
M ← –(M) = $00 – (M)
A ← –(A) = $00 – (A)
X ← –(X) = $00 – (X)
M ← –(M) = $00 – (M)
M ← –(M) = $00 – (M)
DIR
INH
INH
– –
IX1
IX
SP1
(M)Destination ← (M)Source
4E
5E
6E
7E
dd dd
dd
ii dd
dd
42
No Operation
None
– – – – – – INH
9D
NSA
Nibble Swap A
A ← (A[3:0]:A[7:4])
– – – – – – INH
62
A ← (A) | (M)
IMM
DIR
EXT
IX2
0 – – –
IX1
IX
SP1
SP2
AA
BA
CA
DA
EA
FA
9EEA
9EDA
Inclusive OR A and M
ff
ee ff
5
4
4
4
5
30 dd
40
50
60 ff
70
9E60 ff
NOP
ORA #opr
ORA opr
ORA opr
ORA opr,X
ORA opr,X
ORA ,X
ORA opr,SP
ORA opr,SP
Cycles
dd
hh ll
ee ff
ff
Load X from M
LSR opr
LSRA
LSRX
LSR opr,X
LSR ,X
LSR opr,SP
NEG opr
NEGA
NEGX
NEG opr,X
NEG ,X
NEG opr,SP
BC
CC
DC
EC
FC
Jump
Load A from M
LSL opr
LSLA
LSLX
LSL opr,X
LSL ,X
LSL opr,SP
PC ← Jump Address
DIR
EXT
– – – – – – IX2
IX1
IX
Effect
on CCR
Description
V H I N Z C
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
Operand
JMP opr
JMP opr
JMP opr,X
JMP opr,X
JMP ,X
Operation
Address
Mode
Source
Form
Opcode
Table 7-1. Instruction Set Summary (Sheet 4 of 6)
4
1
1
4
3
5
1
3
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
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
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
91
Central Processor Unit (CPU)
V H I N Z C
Cycles
Effect
on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Sheet 5 of 6)
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
C
DIR
INH
INH
– – IX1
IX
SP1
39 dd
49
59
69 ff
79
9E69 ff
4
1
1
4
3
5
DIR
INH
– – INH
IX1
IX
SP1
36 dd
46
56
66 ff
76
9E66 ff
4
1
1
4
3
5
ROL opr
ROLA
ROLX
ROL opr,X
ROL ,X
ROL opr,SP
Rotate Left through Carry
b7
b0
88
2
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
A ← (A) – (M) – (C)
IMM
DIR
EXT
– – IX2
IX1
IX
SP1
SP2
A2
B2
C2
D2
E2
F2
9EE2
9ED2
SBC #opr
SBC opr
SBC opr
SBC opr,X
SBC opr,X
SBC ,X
SBC opr,SP
SBC opr,SP
C
b7
Subtract with Carry
b0
ii
dd
hh ll
ee ff
ff
ff
ee ff
2
3
4
4
3
2
4
5
SEC
Set Carry Bit
C←1
– – – – – 1 INH
99
1
SEI
Set Interrupt Mask
I←1
– – 1 – – – INH
9B
2
M ← (A)
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
B7
C7
D7
E7
F7
9EE7
9ED7
(M:M + 1) ← (H:X)
0 – – – DIR
35
I ← 0; Stop Processing
– – 0 – – – INH
8E
M ← (X)
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
BF
CF
DF
EF
FF
9EEF
9EDF
dd
hh ll
ee ff
ff
IMM
DIR
EXT
– – IX2
IX1
IX
SP1
SP2
A0
B0
C0
D0
E0
F0
9EE0
9ED0
ii
dd
hh ll
ee ff
ff
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 Interrupts, Stop Processing,
Refer to MCU Documentation
STX opr
STX opr
STX opr,X
STX opr,X
STX ,X
STX opr,SP
STX opr,SP
SUB #opr
SUB opr
SUB opr
SUB opr,X
SUB opr,X
SUB ,X
SUB opr,SP
SUB opr,SP
Store X in M
Subtract
A ← (A) – (M)
dd
hh ll
ee ff
ff
ff
ee ff
3
4
4
3
2
4
5
dd
4
1
ff
ee ff
ff
ee ff
3
4
4
3
2
4
5
2
3
4
4
3
2
4
5
MC68HC908GR16A Data Sheet, Rev. 1.0
92
Freescale Semiconductor
Opcode Map
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
– – 1 – – – INH
83
9
CCR ← (A)
INH
84
2
X ← (A)
– – – – – – INH
97
1
A ← (CCR)
– – – – – – INH
85
(A) – $00 or (X) – $00 or (M) – $00
DIR
INH
INH
0 – – –
IX1
IX
SP1
H:X ← (SP) + 1
– – – – – – INH
95
2
A ← (X)
– – – – – – INH
9F
1
(SP) ← (H:X) – 1
– – – – – – INH
94
2
I bit ← 0; Inhibit CPU clocking
until interrupted
– – 0 – – – INH
8F
1
TAP
Transfer A to CCR
Transfer A to X
TPA
Transfer CCR to A
Test for Negative or Zero
TSX
Transfer SP to H:X
TXA
Transfer X to A
TXS
Transfer H:X to SP
WAIT
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
Cycles
V H I N Z C
TAX
TST opr
TSTA
TSTX
TST opr,X
TST ,X
TST opr,SP
Effect
on CCR
Description
Operand
Operation
Opcode
Source
Form
Address
Mode
Table 7-1. Instruction Set Summary (Sheet 6 of 6)
Enable Interrupts; Wait for Interrupt
Accumulator
Carry/borrow bit
Condition code register
Direct address of operand
Direct address of operand and relative offset of branch instruction
Direct to direct addressing mode
Direct addressing mode
Direct to indexed with post increment addressing mode
High and low bytes of offset in indexed, 16-bit offset addressing
Extended addressing mode
Offset byte in indexed, 8-bit offset addressing
Half-carry bit
Index register high byte
High and low bytes of operand address in extended addressing
Interrupt mask
Immediate operand byte
Immediate source to direct destination addressing mode
Immediate addressing mode
Inherent addressing mode
Indexed, no offset addressing mode
Indexed, no offset, post increment addressing mode
Indexed with post increment to direct addressing mode
Indexed, 8-bit offset addressing mode
Indexed, 8-bit offset, post increment addressing mode
Indexed, 16-bit offset addressing mode
Memory location
Negative bit
n
opr
PC
PCH
PCL
REL
rel
rr
SP1
SP2
SP
U
V
X
Z
&
|
⊕
()
–( )
#
«
←
?
:
—
3D dd
4D
5D
6D ff
7D
9E6D ff
1
3
1
1
3
2
4
Any bit
Operand (one or two bytes)
Program counter
Program counter high byte
Program counter low byte
Relative addressing mode
Relative program counter offset byte
Relative program counter offset byte
Stack pointer, 8-bit offset addressing mode
Stack pointer 16-bit offset addressing mode
Stack pointer
Undefined
Overflow bit
Index register low byte
Zero bit
Logical AND
Logical OR
Logical EXCLUSIVE OR
Contents of
Negation (two’s complement)
Immediate value
Sign extend
Loaded with
If
Concatenated with
Set or cleared
Not affected
7.8 Opcode Map
See Table 7-2.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
93
MSB
Branch
REL
DIR
INH
3
4
0
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
Read-Modify-Write
INH
IX1
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
MC68HC908GR16A Data Sheet, Rev. 1.0
4
5
6
7
8
9
A
B
C
D
E
Freescale Semiconductor
F
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
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
Cycles
5
BRSET0 Opcode Mnemonic
3 DIR Number of Bytes / Addressing Mode
Central Processor Unit (CPU)
94
Table 7-2. Opcode Map
Bit Manipulation
DIR
DIR
Chapter 8
External Interrupt (IRQ)
8.1 Introduction
The IRQ (external interrupt) module provides a maskable interrupt input.
8.2 Features
Features of the IRQ module include:
• 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
8.3 Functional Description
A falling edge applied to the external interrupt pin can latch a central processor unit (CPU) interrupt
request. Figure 8-1 shows the structure of the IRQ module.
Interrupt signals on the IRQ pin are latched into the IRQ latch. An interrupt latch remains set until one of
the following actions occurs:
• Vector fetch — A vector fetch automatically generates an interrupt acknowledge signal that clears
the latch that caused the vector fetch.
• Software clear — Software can clear an interrupt latch by writing to the appropriate acknowledge
bit in the interrupt status and control register (INTSCR). Writing a 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 out of reset and is software-configurable to be either
falling-edge or falling-edge and low-level triggered. The MODE bit in the INTSCR controls the triggering
sensitivity of the IRQ pin.
When an interrupt pin is edge-triggered only (MODE = 0), the interrupt remains set until a vector fetch,
software clear, or reset occurs.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
95
External Interrupt (IRQ)
RESET
INTERNAL ADDRESS BUS
ACK
TO CPU FOR
BIL/BIH
INSTRUCTIONS
VECTOR
FETCH
DECODER
VDD
INTERNAL
PULLUP
DEVICE
VDD
IRQF
D
CLR
Q
IRQ
INTERRUPT
REQUEST
SYNCHRONIZER
CK
IRQ
IMASK
MODE
TO MODE
SELECT
LOGIC
HIGH
VOLTAGE
DETECT
Figure 8-1. IRQ Module Block Diagram
When an interrupt pin is both falling-edge and low-level triggered (MODE = 1), the interrupt remains set
until both of these events occur:
• Vector fetch or software clear
• Return of the interrupt pin to a high level
The vector fetch or software clear may occur before or after the interrupt pin returns to a high level. 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 INTSCR masks all external interrupt requests. A latched interrupt request
is not presented to the interrupt priority logic unless the IMASK bit is clear.
NOTE
The interrupt mask (I) in the condition code register (CCR) masks all
interrupt requests, including external interrupt requests.
Addr.
Register Name
$001D
Read:
IRQ Status and Control
Register (INTSCR) Write:
See page 98.
Reset:
Bit 7
6
5
4
3
2
0
0
0
0
IRQF
0
1
Bit 0
IMASK
MODE
0
0
ACK
0
0
0
0
0
0
= Unimplemented
Figure 8-2. IRQ I/O Register Summary
MC68HC908GR16A Data Sheet, Rev. 1.0
96
Freescale Semiconductor
IRQ Pin
8.4 IRQ Pin
A falling edge 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 low-level 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 1 to the ACK bit in
the interrupt status and control register (INTSCR). The ACK bit is useful in applications that poll the
IRQ pin and require software to clear the IRQ latch. Writing to the ACK bit prior to leaving an
interrupt service routine can also prevent spurious interrupts due to noise. Setting ACK does not
affect subsequent transitions on the IRQ pin. A falling edge that occurs after writing to the ACK bit
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 a high level — As long as the IRQ pin is low, IRQ remains active.
The vector fetch or software clear and the return of the IRQ pin to a high level may occur in any order.
The interrupt request remains pending as long as the IRQ pin is low. A reset will clear the latch and the
MODE control bit, thereby clearing the interrupt even if the pin stays low.
If the MODE bit is clear, the IRQ pin is falling-edge-sensitive only. With MODE clear, a vector fetch or
software clear immediately clears the IRQ latch.
The IRQF bit in the INTSCR register can be used to check for pending interrupts. The IRQF bit is not
affected by the IMASK bit, which makes it useful in applications where polling is preferred.
Use the BIH or BIL instruction to read the logic level on the IRQ pin.
NOTE
When using the level-sensitive interrupt trigger, avoid false interrupts by
masking interrupt requests in the interrupt routine.
8.5 IRQ Module During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear the latch during
the break state. See Chapter 19 Development Support.
To allow software to clear the IRQ latch during a break interrupt, write a 1 to the BCFE bit. If a latch is
cleared during the break state, it remains cleared when the MCU exits the break state.
To protect CPU interrupt flags during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default
state), writing to the ACK bit in the IRQ status and control register during the break state has no effect on
the IRQ interrupt flags.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
97
External Interrupt (IRQ)
8.6 IRQ Status and Control Register
The IRQ status and control register (INTSCR) controls and monitors operation of the IRQ module. The
INTSCR:
• 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:
$001D
Bit 7
6
5
4
3
2
0
0
0
0
IRQF
0
Write:
Reset:
ACK
0
0
0
0
0
0
1
Bit 0
IMASK
MODE
0
0
= Unimplemented
Figure 8-3. IRQ Status and Control Register (INTSCR)
IRQF — IRQ Flag Bit
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 1 to this write-only bit clears the IRQ latch. ACK always reads as 0. Reset clears ACK.
IMASK — IRQ Interrupt Mask Bit
Writing a 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
MC68HC908GR16A Data Sheet, Rev. 1.0
98
Freescale Semiconductor
Chapter 9
Keyboard Interrupt Module (KBI)
9.1 Introduction
The keyboard interrupt module (KBI) provides eight independently maskable external interrupts which are
accessible via PTA0–PTA7. When a port pin is enabled for keyboard interrupt function, an internal pullup
device is also enabled on the pin.
9.2 Features
Features include:
• Eight keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard
interrupt mask
• Hysteresis buffers
• Programmable edge-only or edge- and level- interrupt sensitivity
• Exit from low-power modes
• I/O (input/output) port bit(s) software configurable with pullup device(s) if configured as input port
bit(s)
9.3 Functional Description
Writing to the KBIE7–KBIE0 bits in the keyboard interrupt enable register independently enables or
disables each port A pin as a keyboard interrupt pin. Enabling a keyboard interrupt pin also enables its
internal pullup device. A low level 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 interrupt pin is low and the pin is keyboard interrupt enabled.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
99
Keyboard Interrupt Module (KBI)
INTERNAL BUS
DDRA
PORTA
PTB7/AD7
PTB6/AD6
PTB5/AD5
PTB4/AD4
PTB3/AD3
PTB2/AD2
PTB1/AD1
PTB0/AD0
PTC6(1)
PTC5(1)
PTC4(1), (2)
PTC3(1), (2)
PTC2(1), (2)
PTC1(1), (2)
PTC0(1), (2)
PTD7/T2CH1(1)
PTD6/T2CH0(1)
PTD5/T1CH1(1)
PTD4/T1CH0(1)
PTD3/SPSCK(1)
PTD2/MOSI(1)
PTD1/MISO(1)
PTD0/SS(1)
PTE5–PTE2
PTE1/RxD
PTE0/TxD
DDRB
SINGLE BREAKPOINT
BREAK MODULE
DUAL VOLTAGE
LOW-VOLTAGE INHIBIT
MODULE
USER FLASH — 15,872 BYTES
PTA7/KBD7–
PTA0/KBD0(1)
PORTB
CONTROL AND STATUS REGISTERS — 64 BYTES
PROGRAMMABLE TIMEBASE
MODULE
PORTC
ARITHMETIC/LOGIC
UNIT (ALU)
PORTD
CPU
REGISTERS
PORTE
M68HC08 CPU
USER RAM — 1024 BYTES
FLASH PROGRAMMING ROUTINES ROM — 406 BYTES
USER FLASH VECTOR SPACE — 36 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 1
DDRC
8-BIT KEYBOARD
INTERRUPT MODULE
MONITOR ROM — 350 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 2
CLOCK GENERATOR MODULE
PHASE LOCKED LOOP
COMPUTER OPERATING
PROPERLY MODULE
RST(3)
SYSTEM INTEGRATION
MODULE
IRQ(3)
SINGLE EXTERNAL
INTERRUPT MODULE
SERIAL PERIPHERAL
INTERFACE MODULE
MONITOR MODULE
VDDAD/VREFH
VSSAD/VREFL
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
POWER-ON RESET
MODULE
VDD
VSS
VDDA
VSSA
DDRD
CGMXFC
ENHANCED SERIAL
COMUNICATIONS
INTERFACE MODULE
1–8 MHz OSCILLATOR
DDRE
OSC1
OSC2
MEMORY MAP
MODULE
SECURITY
MODULE
CONFIGURATION
REGISTER 1–2
MODULE
POWER
MONITOR MODE ENTRY
MODULE
1. Ports are software configurable with pullup device if input port.
2. Higher current drive port pins
3. Pin contains integrated pullup device
Figure 9-1. Block Diagram Highlighting KBI Block and Pins
MC68HC908GR16A Data Sheet, Rev. 1.0
100
Freescale Semiconductor
Functional Description
INTERNAL BUS
VECTOR FETCH
DECODER
ACKK
RESET
KBD0
VDD
.
TO PULLUP ENABLE
KEYF
D
CLR
Q
SYNCHRONIZER
.
CK
KB0IE
.
KEYBOARD
INTERRUPT
REQUEST
IMASKK
KBD7
MODEK
TO PULLUP ENABLE
KB7IE
Figure 9-2. Keyboard Module Block Diagram
Addr.
$001A
$001B
Register Name
Keyboard Status Read:
and Control Register Write:
(INTKBSCR)
See page 103. Reset:
Keyboard Interrupt Enable Read:
Register Write:
(INTKBIER)
See page 104. Reset:
Bit 7
6
5
4
3
2
0
0
0
0
KEYF
0
ACKK
1
Bit 0
IMASKK
MODEK
0
0
0
0
0
0
0
0
KBIE7
KBIE6
KBIE5
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 9-3. I/O Register Summary
If the MODEK bit is set, the keyboard interrupt pins are both falling edge- and low-level sensitive, and both
of the following actions must occur to clear a keyboard interrupt request:
• Vector fetch or software clear — A vector fetch generates an interrupt acknowledge signal to clear
the interrupt request. Software may generate the interrupt acknowledge signal by writing a 1 to the
ACKK bit in the keyboard status and control register (INTKBSCR). The ACKK bit is useful in
applications that poll the keyboard interrupt pins and require software to clear the keyboard
interrupt request. Writing to the ACKK bit prior to leaving an interrupt service routine can also
prevent spurious interrupts due to noise. Setting ACKK does not affect subsequent transitions on
the keyboard interrupt pins. A falling edge that occurs after writing to the ACKK bit latches another
interrupt request. If the keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the program
counter with the vector address at locations $FFE0 and $FFE1.
• Return of all enabled keyboard interrupt pins to a high level — As long as any enabled keyboard
interrupt pin is low, the keyboard interrupt remains set.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
101
Keyboard Interrupt Module (KBI)
The vector fetch or software clear and the return of all enabled keyboard interrupt pins to a high level may
occur in any order.
If the MODEK bit is clear, the keyboard interrupt pin is falling-edge-sensitive 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 low.
The keyboard flag bit (KEYF) in the keyboard status and control register can be used to see if a pending
interrupt exists. The KEYF bit is not affected by the keyboard interrupt mask bit (IMASKK) which makes
it useful in applications where polling is preferred.
To determine the logic level on a keyboard interrupt pin, use the data direction register to configure the
pin as an input and read the data register.
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 0 for software to read the
pin.
9.4 Keyboard Initialization
When a keyboard interrupt pin is enabled, it takes time for the internal pullup to reach a 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 DDRA bits in data direction
register A.
2. Write 1s to the appropriate port A data register bits.
3. Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard interrupt enable register.
9.5 Low-Power Modes
The WAIT and STOP instructions put the microcontroller unit (MCU) in low power-consumption standby
modes.
9.5.1 Wait Mode
The keyboard module remains active in wait mode. Clearing the IMASKK bit in the keyboard status and
control register enables keyboard interrupt requests to bring the MCU out of wait mode.
MC68HC908GR16A Data Sheet, Rev. 1.0
102
Freescale Semiconductor
Keyboard Module During Break Interrupts
9.5.2 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.
9.6 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 (SBFCR) 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 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 0 to the BCFE bit. With BCFE at 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. See 9.7.1 Keyboard Status and Control Register.
9.7 I/O Registers
These registers control and monitor operation of the keyboard module:
• Keyboard status and control register (INTKBSCR)
• Keyboard interrupt enable register (INTKBIER)
9.7.1 Keyboard Status and Control Register
The keyboard status and control register:
• Flags keyboard interrupt requests
• Acknowledges keyboard interrupt requests
• Masks keyboard interrupt requests
• Controls keyboard interrupt triggering sensitivity
Address: $001A
Read:
Bit 7
6
5
4
3
0
0
0
0
KEYF
Write:
Reset:
2
0
ACKK
0
0
0
0
0
0
1
Bit 0
IMASKK
MODEK
0
0
= Unimplemented
Figure 9-4. Keyboard Status and Control Register (INTKBSCR)
Bits 7–4 — Not used
These read-only bits always read as 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 1 to this write-only bit clears the keyboard interrupt request. ACKK always reads as 0. Reset
clears ACKK.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
103
Keyboard Interrupt Module (KBI)
IMASKK — Keyboard Interrupt Mask Bit
Writing a 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
9.7.2 Keyboard Interrupt Enable Register
The keyboard interrupt enable register enables or disables each port A pin to operate as a keyboard
interrupt pin.
Address: $001B
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
KBIE7
KBIE6
KBIE5
KBIE4
KBIE3
KBIE2
KBIE1
KBIE0
0
0
0
0
0
0
0
0
Figure 9-5. Keyboard Interrupt Enable Register (INTKBIER)
KBIE7–KBIE0 — Keyboard Interrupt Enable Bits
Each of these read/write bits enables the corresponding keyboard interrupt pin to latch interrupt
requests. Reset clears the keyboard interrupt enable register.
1 = PTAx pin enabled as keyboard interrupt pin
0 = PTAx pin not enabled as keyboard interrupt pin
MC68HC908GR16A Data Sheet, Rev. 1.0
104
Freescale Semiconductor
Chapter 10
Low-Power Modes
10.1 Introduction
The microcontroller (MCU) may enter two low-power modes: wait mode and stop mode. They are
common to all HC08 MCUs and are entered through instruction execution. This section describes how
each module acts in the low-power modes.
10.1.1 Wait Mode
The WAIT instruction puts the MCU in a low-power standby mode in which the central processor unit
(CPU) clock is disabled but the bus clock continues to run. Power consumption can be further reduced by
disabling the low-voltage inhibit (LVI) module through bits in the CONFIG1 register. See Chapter 5
Configuration Register (CONFIG).
10.1.2 Stop Mode
Stop mode is entered when a STOP instruction is executed. The CPU clock is disabled and the bus clock
is disabled if the OSCENINSTOP bit in the CONFIG2 register is a 0. See Chapter 5 Configuration Register
(CONFIG).
10.2 Analog-to-Digital Converter (ADC)
10.2.1 Wait Mode
The analog-to-digital converter (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 ADCH4–ADCH0 bits in the ADC status and
control register before executing the WAIT instruction.
10.2.2 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
105
Low-Power Modes
10.3 Break Module (BRK)
10.3.1 Wait Mode
The break (BRK) module is active in wait mode. In the break routine, the user can subtract one from the
return address on the stack if the SBSW bit in the break status register is set.
10.3.2 Stop Mode
The break module is inactive in stop mode. The STOP instruction does not affect break module register
states.
10.4 Central Processor Unit (CPU)
10.4.1 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
10.4.2 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.
10.5 Clock Generator Module (CGM)
10.5.1 Wait Mode
The clock generator module (CGM) remains active in wait mode. 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.
10.5.2 Stop Mode
If the OSCENINSTOP bit in the CONFIG2 register is cleared (default), then the STOP instruction disables
the CGM (oscillator and phase-locked loop) and holds low all CGM outputs (CGMXCLK, CGMOUT, and
CGMINT).
If the OSCENINSTOP bit in the CONFIG2 register is set, then the phase locked loop is shut off, but the
oscillator will continue to operate in stop mode.
MC68HC908GR16A Data Sheet, Rev. 1.0
106
Freescale Semiconductor
Computer Operating Properly Module (COP)
10.6 Computer Operating Properly Module (COP)
10.6.1 Wait Mode
The COP remains active during wait mode. If COP is enabled, a reset will occur at COP timeout.
10.6.2 Stop Mode
Stop mode turns off the COPCLK input to the COP and clears the SIM counter. Service the COP
immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering
or exiting stop mode.
The STOP bit in the CONFIG1 register enables the STOP instruction. To prevent inadvertently turning off
the COP with a STOP instruction, disable the STOP instruction by clearing the STOP bit.
10.7 External Interrupt Module (IRQ)
10.7.1 Wait Mode
The external interrupt (IRQ) module remains active in wait mode. Clearing the IMASK bit in the IRQ status
and control register enables IRQ CPU interrupt requests to bring the MCU out of wait mode.
10.7.2 Stop Mode
The IRQ module remains active in stop mode. Clearing the IMASK bit in the IRQ status and control
register enables IRQ CPU interrupt requests to bring the MCU out of stop mode.
10.8 Keyboard Interrupt Module (KBI)
10.8.1 Wait Mode
The keyboard interrupt (KBI) module remains active in wait mode. Clearing the IMASKK bit in the
keyboard status and control register enables keyboard interrupt requests to bring the MCU out of wait
mode.
10.8.2 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
107
Low-Power Modes
10.9 Low-Voltage Inhibit Module (LVI)
10.9.1 Wait Mode
If enabled, the low-voltage inhibit (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.
10.9.2 Stop Mode
If enabled, 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.
10.10 Enhanced Serial Communications Interface Module (ESCI)
10.10.1 Wait Mode
The enhanced serial communications interface (ESCI), or SCI module for short, module remains active
in wait mode. 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.
10.10.2 Stop Mode
The SCI module is inactive in stop mode. The STOP instruction does not affect SCI register states. SCI
module operation resumes after the MCU exits stop mode.
Because the internal clock is inactive during stop mode, entering stop mode during an SCI transmission
or reception results in invalid data.
10.11 Serial Peripheral Interface Module (SPI)
10.11.1 Wait Mode
The serial peripheral interface (SPI) module remains active in wait mode. 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.
10.11.2 Stop Mode
The SPI module is inactive in stop mode. The STOP instruction does not affect SPI register states. 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
108
Freescale Semiconductor
Timer Interface Module (TIM1 and TIM2)
10.12 Timer Interface Module (TIM1 and TIM2)
10.12.1 Wait Mode
The timer interface modules (TIM) remain active in wait mode. Any enabled CPU interrupt request from
the TIM can bring the MCU out of wait mode.
If TIM functions are not required during wait mode, reduce power consumption by stopping the TIM before
executing the WAIT instruction.
10.12.2 Stop Mode
The TIM is inactive in stop mode. The STOP instruction does not affect register states or the state of the
TIM counter. TIM operation resumes when the MCU exits stop mode after an external interrupt.
10.13 Timebase Module (TBM)
10.13.1 Wait Mode
The timebase module (TBM) remains active after execution of the WAIT instruction. In wait mode, the
timebase register is not accessible by the CPU.
If the timebase functions are not required during wait mode, reduce the power consumption by stopping
the timebase before enabling the WAIT instruction.
10.13.2 Stop Mode
The timebase module may remain active after execution of the STOP instruction if the oscillator has been
enabled to operate during stop mode through the OSCENINSTOP bit in the CONFIG2 register. The
timebase module can be used in this mode to generate a periodic wakeup from stop mode.
If the oscillator has not been enabled to operate in stop mode, the timebase module will not be active
during stop mode. In stop mode, the timebase register is not accessible by the CPU.
If the timebase functions are not required during stop mode, reduce the power consumption by stopping
the timebase before enabling the STOP instruction.
10.14 Exiting Stop Mode
These events restart the system clocks and load the program counter with the reset vector or with an
interrupt vector:
• External reset — A 0 on the RST pin resets the MCU and loads the program counter with the
contents of locations $FFFE and $FFFF.
• External interrupt — A high-to-low transition on an external interrupt pin loads the program counter
with the contents of locations:
– $FFFA and $FFFB; IRQ pin
– $FFE0 and $FFE1; keyboard interrupt pins
• Low-voltage inhibit (LVI) reset — A power supply voltage below the VTRIPF voltage resets the MCU
and loads the program counter with the contents of locations $FFFE and $FFFF.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
109
Low-Power Modes
•
Timebase module (TBM) interrupt — A TBM interrupt loads the program counter with the contents
of locations $FFDC and $FFDD when the timebase counter has rolled over. This allows the TBM
to generate a periodic wakeup from stop mode.
Upon exit from stop mode, the system clocks begin running after an oscillator stabilization delay. A 12-bit
stop recovery counter inhibits the system clocks for 4096 CGMXCLK cycles after the reset or external
interrupt.
The short stop recovery bit, SSREC, in the CONFIG1 register controls the oscillator stabilization delay
during stop recovery. Setting SSREC reduces stop recovery time from 4096 CGMXCLK cycles to 32
CGMXCLK cycles.
NOTE
Use the full stop recovery time (SSREC = 0) in applications that use an
external crystal.
MC68HC908GR16A Data Sheet, Rev. 1.0
110
Freescale Semiconductor
Chapter 11
Low-Voltage Inhibit (LVI)
11.1 Introduction
This section describes the low-voltage inhibit (LVI) module, which monitors the voltage on the VDD pin
and can force a reset when the VDD voltage falls below the LVI trip falling voltage, VTRIPF.
11.2 Features
Features of the LVI module include:
• Programmable LVI reset
• Selectable LVI trip voltage
• Programmable stop mode operation
11.3 Functional Description
Figure 11-1 shows the structure of the LVI module. The LVI is enabled out of reset. The LVI module
contains a bandgap reference circuit and comparator. Clearing the LVI power disable bit, LVIPWRD,
enables the LVI to monitor VDD voltage. Clearing the LVI reset disable bit, LVIRSTD, enables the LVI
module to generate a reset when VDD falls below a voltage, VTRIPF. Setting the LVI enable in stop mode
bit, LVISTOP, enables the LVI to operate in stop mode. Setting the LVI 5-V or 3-V trip point bit, LVI5OR3,
enables the trip point voltage, VTRIPF, to be configured for 5-V operation. Clearing the LVI5OR3 bit
enables the trip point voltage, VTRIPF, to be configured for 3-V operation. The actual trip points are shown
in Chapter 20 Electrical Specifications.
NOTE
After a power-on reset (POR) the LVI’s default mode of operation is 3 V. If
a 5-V system is used, the user must set the LVI5OR3 bit to raise the trip
point to 5-V operation. Note that this must be done after every power-on
reset since the default will revert back to 3-V mode after each power-on
reset. If the VDD supply is below the 5-V mode trip voltage but above the
3-V mode trip voltage when POR is released, the part will operate because
VTRIPF defaults to 3-V mode after a POR. So, in a 5-V system care must be
taken to ensure that VDD is above the 5-V mode trip voltage after POR is
released.
If the user requires 5-V mode and sets the LVI5OR3 bit after a power-on
reset while the VDD supply is not above the VTRIPR for 5-V mode, the
microcontroller unit (MCU) will immediately go into reset. The LVI in this
case will hold the part in reset until either VDD goes above the rising 5-V trip
point, VTRIPR, which will release reset or VDD decreases to approximately 0
V which will re-trigger the power-on reset and reset the trip point to 3-V
operation.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
111
Low-Voltage Inhibit (LVI)
LVISTOP, LVIPWRD, LVI5OR3, and LVIRSTD are in the configuration register (CONFIG1). See
Figure 5-2. Configuration Register 1 (CONFIG1) for details of the LVI’s configuration bits. Once an LVI
reset occurs, the MCU remains in reset until VDD rises above a voltage, VTRIPR, which causes the MCU
to exit reset. See 15.3.2.5 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.
VDD
STOP INSTRUCTION
LVISTOP
FROM CONFIG1
FROM CONFIG1
LVIRSTD
LVIPWRD
FROM CONFIG
LOW VDD
DETECTOR
VDD > LVITrip = 0
LVI RESET
VDD ≤ LVITrip = 1
LVIOUT
LVI5OR3
FROM CONFIG1
Figure 11-1. LVI Module Block Diagram
Addr.
$FE0C
Register Name
Read:
LVI Status Register
(LVISR) Write:
See page 113.
Reset:
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
= Unimplemented
Figure 11-2. LVI I/O Register Summary
11.3.1 Polled LVI Operation
In applications that can operate at VDD levels below the VTRIPF level, software can monitor VDD by polling
the LVIOUT bit. In the configuration register, the LVIPWRD bit must be 0 to enable the LVI module, and
the LVIRSTD bit must be at 1 to disable LVI resets.
11.3.2 Forced Reset Operation
In applications that require VDD to remain above the VTRIPF level, enabling LVI resets allows the LVI
module to reset the MCU when VDD falls below the VTRIPF level. In the configuration register, the
LVIPWRD and LVIRSTD bits must be cleared to enable the LVI module and to enable LVI resets.
MC68HC908GR16A Data Sheet, Rev. 1.0
112
Freescale Semiconductor
LVI Status Register
11.3.3 Voltage Hysteresis Protection
Once the LVI has triggered (by having VDD fall below VTRIPF), the LVI will maintain a reset condition until
VDD rises above the rising trip point voltage, VTRIPR. This prevents a condition in which the MCU is
continually entering and exiting reset if VDD is approximately equal to VTRIPF. VTRIPR is greater than
VTRIPF by the hysteresis voltage, VHYS.
11.3.4 LVI Trip Selection
The LVI5OR3 bit in the configuration register selects whether the LVI is configured for 5-V or 3-V
protection.
NOTE
The microcontroller is guaranteed to operate at a minimum supply voltage.
The trip point (VTRIPF [5 V] or VTRIPF [3 V]) may be lower than this. See
Chapter 20 Electrical Specifications for the actual trip point voltages.
11.4 LVI Status Register
The LVI status register (LVISR) indicates if the VDD voltage was detected below the VTRIPF level.
Address:
Read:
$FE0C
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 11-3. LVI Status Register (LVISR)
LVIOUT — LVI Output Bit
This read-only flag becomes set when the VDD voltage falls below the VTRIPF trip voltage (see
Table 11-1). Reset clears the LVIOUT bit.
Table 11-1. LVIOUT Bit Indication
VDD
LVIOUT
VDD > VTRIPR
0
VDD < VTRIPF
1
VTRIPF < VDD < VTRIPR
Previous value
11.5 LVI Interrupts
The LVI module does not generate interrupt requests.
11.6 Low-Power Modes
The STOP and WAIT instructions put the MCU in low power-consumption standby modes.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
113
Low-Voltage Inhibit (LVI)
11.6.1 Wait Mode
If enabled, the LVI module remains active in wait mode. If enabled to generate resets, the LVI module can
generate a reset and bring the MCU out of wait mode.
11.6.2 Stop Mode
If enabled in stop mode (LVISTOP bit in the configuration register is 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
114
Freescale Semiconductor
Chapter 12
Input/Output (I/O) Ports
12.1 Introduction
Bidirectional input-output (I/O) pins form five parallel ports. All I/O pins are programmable as inputs or
outputs. All individual bits within port A, port C, and port D are software configurable with pullup devices
if configured as input port bits. The pullup devices are automatically and dynamically disabled when a port
bit is switched to output mode.
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.
Not all port pins are bonded out in all packages. Care sure be taken to make
any unbonded port pins an output to prevent them from being floating
inputs.
Addr.
$0000
$0001
$0002
$0003
$0004
Register Name
Read:
Port A Data Register
(PTA) Write:
See page 118.
Reset:
Read:
Port B Data Register
(PTB) Write:
See page 120.
Reset:
Read:
Port C Data Register
(PTC) Write:
See page 122.
Reset:
Read:
Port D Data Register
(PTD) Write:
See page 124.
Reset:
Read:
Data Direction Register A
(DDRA) Write:
See page 118.
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
1
PTC6
PTC5
PTC4
PTC3
Unaffected by reset
PTD7
PTD6
PTD5
PTD4
PTD3
Unaffected by reset
DDRA7
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 12-1. I/O Port Register Summary
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
115
Input/Output (I/O) Ports
Addr.
$0005
$0006
$0007
$0008
$000C
$000D
$000E
$000F
Register Name
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
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
0
0
DDRD7
DDRD6
DDRD5
DDRD4
DDRD3
DDRD2
DDRD1
DDRD0
0
0
0
0
0
0
0
0
Read:
Port E Data Register
(PTE) Write:
See page 127.
Reset:
0
0
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
Read:
Data Direction Register E
(DDRE) Write:
See page 128.
Reset:
0
Read:
Data Direction Register B
(DDRB) Write:
See page 121.
Reset:
Read:
Data Direction Register C
(DDRC) Write:
See page 122.
Reset:
Read:
Data Direction Register D
(DDRD) Write:
See page 125.
Reset:
0
Unaffected by reset
0
Read:
Port A Input Pullup Enable
PTAPUE7
Register (PTAPUE) Write:
See page 120.
Reset:
0
Read:
Port C Input Pullup Enable
Register (PTCPUE) Write:
See page 124.
Reset:
0
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
PTAPUE6
PTAPUE5
PTAPUE4
PTAPUE3
PTAPUE2
PTAPUE1
PTAPUE0
0
0
0
0
0
0
0
PTCPUE6
PTCPUE5
PTCPUE4
PTCPUE3
PTCPUE2
PTCPUE1
PTCPUE0
0
0
0
0
0
0
0
PTDPUE6
PTDPUE5
PTDPUE4
PTDPUE3
PTDPUE2
PTDPUE1
PTDPUE0
0
0
0
0
0
0
0
0
0
Read:
Port D Input Pullup Enable
PTDPUE7
Register (PTDPUE) Write:
See page 127.
Reset:
0
= Unimplemented
Figure 12-1. I/O Port Register Summary (Continued)
MC68HC908GR16A Data Sheet, Rev. 1.0
116
Freescale Semiconductor
Introduction
Table 12-1. Port Control Register Bits Summary
Port
A
B
C
D
E
Bit
DDR
Module Control
0
DDRA0
KBIE0
PTA0/KBD0
1
DDRA1
KBIE1
PTA1/KBD1
2
DDRA2
KBIE2
PTA2/KBD2
3
DDRA3
KBIE3
PTA3/KBD3
4
DDRA4
KBIE4
PTA4/KBD4
5
DDRA5
KBIE5
PTA5/KBD5
6
DDRA6
KBIE6
PTA6/KBD6
7
DDRA7
KBIE7
PTA7/KBD7
0
DDRB0
PTB0/AD0
1
DDRB1
PTB1/AD1
2
DDRB2
PTB2/AD2
3
DDRB3
4
DDRB4
5
DDRB5
PTB5/AD5
6
DDRB6
PTB6/AD6
7
DDRB7
PTB7/AD7
0
DDRC0
PTC0
1
DDRC1
PTC1
2
DDRC2
PTC2
3
DDRC3
PTC3
4
DDRC4
PTC4
5
DDRC5
PTC5
6
DDRC6
PTC6
0
DDRD0
PTD0/SS
1
DDRD1
2
DDRD2
3
DDRD3
4
DDRD4
5
DDRD5
6
DDRD6
7
DDRD7
0
DDRE0
1
DDRE1
2
DDRE2
PTE2
3
DDRE3
PTE3
4
DDRE4
PTE4
5
DDRE5
PTE5
KBD
ADC
SPI
ADCH4–ADCH0
SPE
Pin
PTB3/AD3
PTB4/AD4
PTD1/MISO
PTD2/MOSI
PTD3/SPSCK
TIM1
TIM2
SCI
ELS0B:ELS0A
PTD4/T1CH0
ELS1B:ELS1A
PTD5/T1CH1
ELS0B:ELS0A
PTD6/T2CH0
ELS1B:ELS1A
PTD7/T2CH1
ENSCI
PTE0/TxD
PTE1/RxD
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
117
Input/Output (I/O) Ports
12.2 Port A
Port A is an 8-bit special-function port that shares all eight of its pins with the keyboard interrupt (KBI)
module. Port A also has software configurable pullup devices if configured as an input port.
12.2.1 Port A Data Register
The port A data register (PTA) 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
KBD2
KBD1
KBD0
Reset:
Alternative
Function:
Unaffected by reset
KBD7
KBD6
KBD5
KBD4
KBD3
Figure 12-2. Port A Data Register (PTA)
PTA7–PTA0 — 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.
KBD7–KBD0 — Keyboard Inputs
The keyboard interrupt enable bits, KBIE7–KBIE0, in the keyboard interrupt control register (KBICR)
enable the port A pins as external interrupt pins. See Chapter 9 Keyboard Interrupt Module (KBI).
12.2.2 Data Direction Register A
Data direction register A (DDRA) determines whether each port A pin is an input or an output. Writing a 1
to a DDRA bit enables the output buffer for the corresponding port A pin; a 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 12-3. Data Direction Register A (DDRA)
DDRA7–DDRA0 — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears DDRA7–DDRA0, 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
118
Freescale Semiconductor
Port A
Figure 12-4 shows the port A I/O logic.
VDD
PTAPUEx
READ DDRA ($0004)
INTERNAL
PULLUP
DEVICE
WRITE DDRA ($0004)
DDRAx
INTERNAL DATA BUS
RESET
WRITE PTA ($0000)
PTAx
PTAx
READ PTA ($0000)
Figure 12-4. Port A I/O Circuit
When bit DDRAx is a 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a 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 12-2 summarizes the operation of the port A pins.
Table 12-2. Port A Pin Functions
PTAPUE
Bit
DDRA
Bit
PTA
Bit
1
0
X(1)
0
0
X
1
Accesses to DDRA
I/O Pin
Mode
Accesses to PTA
Read/Write
Read
Write
(2)
DDRA7–DDRA0
Pin
PTA7–PTA0(3)
X
Input, Hi-Z(4)
DDRA7–DDRA0
Pin
PTA7–PTA0(3)
X
Output
DDRA7–DDRA0
PTA7–PTA0
PTA7–PTA0
Input, VDD
1. X = Don’t care
2. I/O pin pulled up to VDD by internal pullup device
3. Writing affects data register, but does not affect input.
4. Hi-Z = High impedance
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
119
Input/Output (I/O) Ports
12.2.3 Port A Input Pullup Enable Register
The port A input pullup enable register (PTAPUE) contains a software configurable pullup device for each
of the eight port A pins. Each bit is individually configurable and requires that the data direction register,
DDRA, bit be configured as an input. Each pullup is automatically and dynamically disabled when a port
bit’s DDRA is configured for output mode.
Address:
$000D
Bit 7
Read:
PTAPUE7
Write:
Reset:
0
6
5
4
3
2
1
Bit 0
PTAPUE6
PTAPUE5
PTAPUE4
PTAPUE3
PTAPUE2
PTAPUE1
PTAPUE0
0
0
0
0
0
0
0
Figure 12-5. Port A Input Pullup Enable Register (PTAPUE)
PTAPUE7–PTAPUE0 — Port A Input Pullup Enable Bits
These writable bits are software programmable to enable pullup devices on an input port bit.
1 = Corresponding port A pin configured to have internal pullup
0 = Corresponding port A pin has internal pullup disconnected
12.3 Port B
Port B is an 8-bit special-function port that shares all eight of its pins with the analog-to-digital converter
(ADC) module.
12.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the eight port pins.
Address:
Read:
Write:
Reset:
Alternative
Function:
$0001
Bit 7
6
5
4
3
2
1
Bit 0
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
AD2
AD1
AD0
Unaffected by reset
AD7
AD6
AD5
AD4
AD3
Figure 12-6. Port B Data Register (PTB)
PTB7–PTB0 — 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.
AD7–AD0 — Analog-to-Digital Input Bits
AD7–AD0 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
AD7–AD0 pins. If the appropriate ADC channel is not enabled, excessive
current drain may occur if analog voltages are applied to the PTBx/ADx pin,
while PTB is read as a digital input. Those ports not selected as analog
input channels are considered digital I/O ports.
MC68HC908GR16A Data Sheet, Rev. 1.0
120
Freescale Semiconductor
Port B
12.3.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is an input or an output. Writing a 1
to a DDRB bit enables the output buffer for the corresponding port B pin; a 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 12-7. Data Direction Register B (DDRB)
DDRB7–DDRB0 — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears DDRB7–DDRB0, 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 12-8 shows the port B I/O logic.
READ DDRB ($0005)
INTERNAL DATA BUS
WRITE DDRB ($0005)
DDRBx
RESET
WRITE PTB ($0001)
PTBx
PTBx
READ PTB ($0001)
Figure 12-8. Port B I/O Circuit
When bit DDRBx is a 1, reading address $0001 reads the PTBx data latch. When bit DDRBx is a 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 12-3 summarizes the operation of the port B pins.
Table 12-3. Port B Pin Functions
DDRB
Bit
PTB
Bit
0
X(1)
1
X
Accesses to DDRB
I/O Pin
Mode
(2)
Input, Hi-Z
Output
Accesses to PTB
Read/Write
Read
Write
DDRB7–DDRB0
Pin
PTB7–PTB0(3)
DDRB7–DDRB0
PTB7–PTB0
PTB7–PTB0
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
121
Input/Output (I/O) Ports
12.4 Port C
Port C is a 7-bit, general-purpose bidirectional I/O port. Port C also has software configurable pullup
devices if configured as an input port.
12.4.1 Port C Data Register
The port C data register (PTC) contains a data latch for each of the seven port C pins.
Address:
$0002
Bit 7
Read:
1
Write:
6
5
4
3
2
1
Bit 0
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1
PTC0
Reset:
Unaffected by reset
= Unimplemented
Figure 12-9. Port C Data Register (PTC)
PTC6–PTC0 — 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.
12.4.2 Data Direction Register C
Data direction register C (DDRC) determines whether each port C pin is an input or an output. Writing a 1
to a DDRC bit enables the output buffer for the corresponding port C pin; a 0 disables the output buffer.
Address:
$0006
Bit 7
Read:
0
Write:
Reset:
0
6
5
4
3
2
1
Bit 0
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
0
= Unimplemented
Figure 12-10. Data Direction Register C (DDRC)
DDRC6–DDRC0 — Data Direction Register C Bits
These read/write bits control port C data direction. Reset clears DDRC6–DDRC0, 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
122
Freescale Semiconductor
Port C
Figure 12-11 shows the port C I/O logic.
VDD
PTCPUEx
READ DDRC ($0006)
INTERNAL
PULLUP
DEVICE
INTERNAL DATA BUS
WRITE DDRC ($0006)
DDRCx
RESET
WRITE PTC ($0002)
PTCx
PTCx
READ PTC ($0002)
Figure 12-11. Port C I/O Circuit
When bit DDRCx is a 1, reading address $0002 reads the PTCx data latch. When bit DDRCx is a 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 12-4 summarizes the operation of the port C pins.
Table 12-4. Port C Pin Functions
PTCPUE
Bit
DDRC
Bit
PTC
Bit
Accesses to DDRC
I/O Pin
Mode
Accesses to PTC
Read/Write
Read
Write
(2)
DDRC6–DDRC0
Pin
PTC6–PTC0(3)
1
0
X(1)
0
0
X
Input, Hi-Z(4)
DDRC6–DDRC0
Pin
PTC6–PTC0(3)
X
1
X
Output
DDRC6–DDRC0
PTC6–PTC0
PTC6–PTC0
Input, VDD
1. X = Don’t care
2. I/O pin pulled up to VDD by internal pullup device.
3. Writing affects data register, but does not affect input.
4. Hi-Z = High impedance
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
123
Input/Output (I/O) Ports
12.4.3 Port C Input Pullup Enable Register
The port C input pullup enable register (PTCPUE) contains a software configurable pullup device for each
of the seven port C pins. Each bit is individually configurable and requires that the data direction register,
DDRC, bit be configured as an input. Each pullup is automatically and dynamically disabled when a port
bit’s DDRC is configured for output mode.
Address:
$000E
Bit 7
0
Read:
Write:
Reset:
0
6
5
4
3
2
1
Bit 0
PTCPUE6
PTCPUE5
PTCPUE4
PTCPUE3
PTCPUE2
PTCPUE1
PTCPUE0
0
0
0
0
0
0
0
= Unimplemented
Figure 12-12. Port C Input Pullup Enable Register (PTCPUE)
PTCPUE6–PTCPUE0 — Port C Input Pullup Enable Bits
These writable bits are software programmable to enable pullup devices on an input port bit.
1 = Corresponding port C pin configured to have internal pullup
0 = Corresponding port C pin internal pullup disconnected
12.5 Port D
Port D is an 8-bit special-function port that shares four of its pins with the serial peripheral interface (SPI)
module and four of its pins with two timer interface (TIM1 and TIM2) modules. Port D also has software
configurable pullup devices if configured as an input port.
12.5.1 Port D Data Register
The port D data register (PTD) 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
MOSI
MISO
SS
Reset:
Alternative
Function:
Unaffected by reset
T2CH1
T2CH0
T1CH1
T1CH0
SPSCK
Figure 12-13. Port D Data Register (PTD)
PTD7–PTD0 — 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.
T2CH1 and T2CH0 — Timer 2 Channel I/O Bits
The PTD7/T2CH1–PTD6/T2CH0 pins are the TIM2 input capture/output compare pins. The edge/level
select bits, ELSxB:ELSxA, determine whether the PTD7/T2CH1–PTD6/T2CH0 pins are timer channel
I/O pins or general-purpose I/O pins. See Chapter 18 Timer Interface Module (TIM1 and TIM2).
MC68HC908GR16A Data Sheet, Rev. 1.0
124
Freescale Semiconductor
Port D
T1CH1 and T1CH0 — Timer 1 Channel I/O Bits
The PTD7/T1CH1–PTD6/T1CH0 pins are the TIM1 input capture/output compare pins. The edge/level
select bits, ELSxB and ELSxA, determine whether the PTD7/T1CH1–PTD6/T1CH0 pins are timer
channel I/O pins or general-purpose I/O pins. See Chapter 18 Timer Interface Module (TIM1 and
TIM2).
SPSCK — SPI Serial Clock
The PTD3/SPSCK pin is the serial clock input of the SPI module. When the SPE bit is clear, the
PTD3/SPSCK pin is available for general-purpose I/O.
MOSI — Master Out/Slave In
The PTD2/MOSI pin is the master out/slave in terminal of the SPI module. When the SPE bit is clear,
the PTD2/MOSI pin is available for general-purpose I/O.
MISO — Master In/Slave Out
The PTD1/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 PTD0/SS pin is available for general-purpose I/O.
Data direction register D (DDRD) does not affect the data direction of port D pins that are being used
by the SPI module. However, the DDRD bits always determine whether reading port D returns the
states of the latches or the states of the pins. See Table 12-5.
SS — Slave Select
The PTD0/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 PTD0/SS pin is available for general-purpose I/O. When the SPI
is enabled, the DDRB0 bit in data direction register B (DDRB) has no effect on the PTD0/SS pin.
12.5.2 Data Direction Register D
Data direction register D (DDRD) determines whether each port D pin is an input or an output. Writing a 1
to a DDRD bit enables the output buffer for the corresponding port D pin; a 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 12-14. Data Direction Register D (DDRD)
DDRD7–DDRD0 — Data Direction Register D Bits
These read/write bits control port D data direction. Reset clears DDRD7–DDRD0, 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
125
Input/Output (I/O) Ports
Figure 12-15 shows the port D I/O logic.
VDD
PTDPUEx
READ DDRD ($0007)
INTERNAL
PULLUP
DEVICE
WRITE DDRD ($0007)
INTERNAL DATA BUS
RESET
DDRDx
WRITE PTD ($0003)
PTDx
PTDx
READ PTD ($0003)
Figure 12-15. Port D I/O Circuit
When bit DDRDx is a 1, reading address $0003 reads the PTDx data latch. When bit DDRDx is a 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 12-5 summarizes the operation of the port D pins.
Table 12-5. Port D Pin Functions
PTDPUE
Bit
DDRD
Bit
PTD
Bit
I/O Pin
Mode
Accesses to DDRD
Read/Write
Read
Accesses to PTD
Write
1
0
X(1)
Input, VDD(2)
DDRD7–DDRD0
Pin
PTD7–PTD0(3)
0
0
X
Input, Hi-Z(4)
DDRD7–DDRD0
Pin
PTD7–PTD0(3)
X
1
X
Output
DDRD7–DDRD0
PTD7–PTD0
PTD7–PTD0
1. X = Don’t care
2. I/O pin pulled up to VDD by internal pullup device.
3. Writing affects data register, but does not affect input.
4. Hi-Z = High impedance
MC68HC908GR16A Data Sheet, Rev. 1.0
126
Freescale Semiconductor
Port E
12.5.3 Port D Input Pullup Enable Register
The port D input pullup enable register (PTDPUE) contains a software configurable 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:
$000F
Read:
Write:
Reset:
Bit 7
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 12-16. Port D Input Pullup Enable Register (PTDPUE)
PTDPUE7–PTDPUE0 — Port D Input Pullup Enable Bits
These writable bits are software programmable to enable pullup devices on an input port bit.
1 = Corresponding port D pin configured to have internal pullup
0 = Corresponding port D pin has internal pullup disconnected
12.6 Port E
Port E is a 6-bit special-function port that shares two of its pins with the enhanced serial communications
interface (ESCI) module.
12.6.1 Port E Data Register
The port E data register contains a data latch for each of the six port E pins.
Address:
Read:
Write:
$0008
Bit 7
6
0
0
5
4
3
2
1
Bit 0
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
RxD
TxD
Reset:
Unaffected by reset
Alternative
Function:
= Unimplemented
Figure 12-17. Port E Data Register (PTE)
PTE5-PTE0 — 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.
NOTE
Data direction register E (DDRE) does not affect the data direction of port
E pins that are being used by the ESCI 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 12-6.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
127
Input/Output (I/O) Ports
RxD — SCI Receive Data Input
The PTE1/RxD pin is the receive data input for the ESCI module. When the enable SCI bit, ENSCI, is
clear, the ESCI module is disabled, and the PTE1/RxD pin is available for general-purpose I/O. See
Chapter 14 Enhanced Serial Communications Interface (ESCI) Module.
TxD — SCI Transmit Data Output
The PTE0/TxD pin is the transmit data output for the ESCI module. When the enable SCI bit, ENSCI,
is clear, the ESCI module is disabled, and the PTE0/TxD pin is available for general-purpose I/O. See
Chapter 14 Enhanced Serial Communications Interface (ESCI) Module.
12.6.2 Data Direction Register E
Data direction register E (DDRE) determines whether each port E pin is an input or an output. Writing a 1
to a DDRE bit enables the output buffer for the corresponding port E pin; a 0 disables the output buffer.
Address:
Read:
$000C
Bit 7
6
0
0
0
0
Write:
Reset:
5
4
3
2
1
Bit 0
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
= Unimplemented
Figure 12-18. Data Direction Register E (DDRE)
DDRE5–DDRE0 — Data Direction Register E Bits
These read/write bits control port E data direction. Reset clears DDRE5–DDRE0, 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 12-19 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 12-19. Port E I/O Circuit
MC68HC908GR16A Data Sheet, Rev. 1.0
128
Freescale Semiconductor
Port E
When bit DDREx is a 1, reading address $0008 reads the PTEx data latch. When bit DDREx is a 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 12-6 summarizes the operation of the port E pins.
Table 12-6. Port E Pin Functions
DDRE
Bit
PTE
Bit
I/O Pin
Mode
Accesses to DDRE
Accesses to PTE
Read/Write
Read
Write
0
X(1)
Input, Hi-Z(2)
DDRE5–DDRE0
Pin
PTE5–PTE0(3)
1
X
Output
DDRE5–DDRE0
PTE5–PTE0
PTE5–PTE0
1. X = Don’t care
2. Hi-Z = High impedance
3. Writing affects data register, but does not affect input.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
129
Input/Output (I/O) Ports
MC68HC908GR16A Data Sheet, Rev. 1.0
130
Freescale Semiconductor
Chapter 13
Resets and Interrupts
13.1 Introduction
Resets and interrupts are responses to exceptional events during program execution. A reset re-initializes
the microcontroller (MCU) to its startup condition. An interrupt vectors the program counter to a service
routine.
13.2 Resets
A reset immediately returns the MCU to a known startup condition and begins program execution from a
user-defined memory location.
13.2.1 Effects
A reset:
• Immediately stops the operation of the instruction being executed
• Initializes certain control and status bits
• Loads the program counter with a user-defined reset vector address from locations $FFFE and
$FFFF, $FEFE and $FEFF in monitor mode
• Selects CGMXCLK divided by four as the bus clock
13.2.2 External Reset
A 0 applied to the RST pin for a time, tRL, generates an external reset. An external reset sets the PIN bit
in the system integration module (SIM) reset status register.
13.2.3 Internal Reset
Sources:
• Power-on reset (POR)
• Computer operating properly (COP)
• Low-power reset circuits
• Illegal opcode
• Illegal address
All internal reset sources pull the RST pin low for 32 CGMXCLK cycles to allow resetting of external
devices. The MCU is held in reset for an additional 32 CGMXCLK cycles after releasing the RST pin.
13.2.3.1 Power-On Reset (POR)
A power-on reset (POR) is an internal reset caused by a positive transition on the VDD pin. VDD at the
POR must go below VPOR to reset the MCU. This distinguishes between a reset and a POR. The POR is
not a brown-out detector, low-voltage detector, or glitch detector.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
131
Resets and Interrupts
A power-on reset:
• Holds the clocks to the central processor unit (CPU) and modules inactive for an oscillator
stabilization delay of 4096 CGMXCLK cycles
• Drives the RST pin low during the oscillator stabilization delay
• Releases the RST pin 32 CGMXCLK cycles after the oscillator stabilization delay
• Releases the CPU to begin the reset vector sequence 64 CGMXCLK cycles after the oscillator
stabilization delay
• Sets the POR and LVI bits in the SIM reset status register and clears all other bits in the register
OSC1
PORRST(1)
4096
CYCLES
32
CYCLES
CGMXCLK
CGMOUT
RST PIN
1. PORRST is an internally generated power-on reset pulse.
Figure 13-1. Power-On Reset Recovery
13.2.3.2 Computer Operating Properly (COP) Reset
A computer operating properly (COP) reset is an internal reset caused by an overflow of the COP counter.
A COP reset sets the COP bit in the SIM reset status register.
To clear the COP counter and prevent a COP reset, write any value to the COP control register at location
$FFFF.
13.2.3.3 Low-Voltage Inhibit (LVI) Reset
A low-voltage inhibit (LVI) reset is an internal reset caused by a drop in the power supply voltage to the
VTRIPF voltage.
An LVI reset:
• Holds the clocks to the CPU and modules inactive for an oscillator stabilization delay of 4096
CGMXCLK cycles after the power supply voltage rises to the LVITRIPR voltage
• Drives the RST pin low for as long as VDD is below the VTRIPR voltage and during the oscillator
stabilization delay
• Releases the RST pin 32 CGMXCLK cycles after the oscillator stabilization delay
• Releases the CPU to begin the reset vector sequence 64 CGMXCLK cycles after the oscillator
stabilization delay
• Sets the LVI bit in the SIM reset status register
13.2.3.4 Illegal Opcode Reset
An illegal opcode reset is an internal reset caused by an opcode that is not in the instruction set. An illegal
opcode reset sets the ILOP bit in the SIM reset status register.
MC68HC908GR16A Data Sheet, Rev. 1.0
132
Freescale Semiconductor
Resets
If the stop enable bit, STOP, in the CONFIG1 register is a 0, the STOP instruction causes an illegal
opcode reset.
13.2.3.5 Illegal Address Reset
An illegal address reset is an internal reset caused by opcode fetch from an unmapped address. An illegal
address reset sets the ILAD bit in the SIM reset status register.
A data fetch from an unmapped address does not generate a reset.
13.2.4 System Integration Module (SIM) Reset Status Register
This read-only register contains flags to show reset sources. All flag bits are automatically cleared
following a read of the register. Reset service can read the SIM reset status register to clear the register
after power-on reset and to determine the source of any subsequent reset.
The register is initialized on power-up as shown with the POR bit set and all other bits cleared. During a
POR or any other internal reset, the RST pin is pulled low. After the pin is released, it will be sampled 32
CGMXCLK cycles later. If the pin is not above a VIH at that time, then the PIN bit in the SRSR may be set
in addition to whatever other bits are set.
NOTE
Only a read of the SIM reset status register clears all reset flags. After
multiple resets from different sources without reading the register, multiple
flags remain set.
Address:
Read:
$FE01
Bit 7
6
5
4
3
2
1
Bit 0
POR
PIN
COP
ILOP
ILAD
MODRST
LVI
0
1
0
0
0
0
0
0
0
Write:
POR:
= Unimplemented
Figure 13-2. SIM Reset Status Register (SRSR)
POR — Power-On Reset Flag
1 = Power-on reset since last read of SRSR
0 = Read of SRSR since last power-on reset
PIN — External Reset Flag
1 = External reset via RST pin since last read of SRSR
0 = POR or read of SRSR since any reset
COP — Computer Operating Properly Reset Bit
1 = Last reset caused by timeout of COP counter
0 = POR or read of SRSR since any reset
ILOP — Illegal Opcode Reset Bit
1 = Last reset caused by an illegal opcode
0 = POR or read of SRSR since any reset
ILAD — Illegal Address Reset Bit
1 = Last reset caused by an opcode fetch from an illegal address
0 = POR or read of SRSR since any reset
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
133
Resets and Interrupts
MODRST — Monitor Mode Entry Module Reset Bit
1 = Last reset caused by forced monitor mode entry.
0 = POR or read of SRSR since any reset
LVI — Low-Voltage Inhibit Reset Bit
1 = Last reset caused by low-power supply voltage
0 = POR or read of SRSR since any reset
13.3 Interrupts
An interrupt temporarily changes the sequence of program execution to respond to a particular event. An
interrupt does not stop the operation of the instruction being executed, but begins when the current
instruction completes its operation.
13.3.1 Effects
An interrupt:
• Saves the CPU registers on the stack. At the end of the interrupt, the RTI instruction recovers the
CPU registers from the stack so that normal processing can resume.
• Sets the interrupt mask (I bit) to prevent additional interrupts. Once an interrupt is latched, no other
interrupt can take precedence, regardless of its priority.
• Loads the program counter with a user-defined vector address
•
•
•
STACKING
ORDER
5
CONDITION CODE REGISTER
1
4
ACCUMULATOR
2
3
INDEX REGISTER (LOW BYTE)(1)
3
2
PROGRAM COUNTER (HIGH BYTE)
4
1
PROGRAM COUNTER (LOW BYTE)
5
UNSTACKING
ORDER
•
•
•
$00FF DEFAULT ADDRESS ON RESET
1. High byte of index register is not stacked.
Figure 13-3. Interrupt Stacking Order
After every instruction, the CPU checks all pending interrupts if the I bit is not set. If more than one
interrupt is pending when an instruction is done, the highest priority interrupt is serviced first. In the
MC68HC908GR16A Data Sheet, Rev. 1.0
134
Freescale Semiconductor
Interrupts
example shown in Figure 13-4, if an interrupt is pending upon exit from the interrupt service routine, the
pending interrupt is serviced before the LDA instruction is executed.
CLI
BACKGROUND
ROUTINE
LDA #$FF
INT1
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 13-4. 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, save the H
register and then restore it prior to exiting the routine.
See Figure 13-5 for a flowchart depicting interrupt processing.
13.3.2 Sources
The sources in Table 13-1 can generate CPU interrupt requests.
13.3.2.1 Software Interrupt (SWI) Instruction
The software interrupt (SWI) instruction causes a non-maskable interrupt.
NOTE
A software interrupt pushes PC onto the stack. An SWI does not push PC
– 1, as a hardware interrupt does.
13.3.2.2 Break Interrupt
The break module causes the CPU to execute an SWI instruction at a software-programmable break
point.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
135
Resets and Interrupts
FROM RESET
BREAK
INTERRUPT
?
NO
YES
YES
BITSET?
SET?
IIBIT
NO
IRQ
INTERRUPT
?
NO
YES
CGM
INTERRUPT
?
NO
YES
OTHER
INTERRUPTS
?
YES
NO
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION
?
YES
NO
RTI
INSTRUCTION
?
YES
UNSTACK CPU REGISTERS
NO
EXECUTE INSTRUCTION
Figure 13-5. Interrupt Processing
MC68HC908GR16A Data Sheet, Rev. 1.0
136
Freescale Semiconductor
Interrupts
Table 13-1. Interrupt Sources
Flag
Mask(1)
INT Register
Flag
Priority(2)
Vector
Address
Reset
None
None
None
0
$FFFE–$FFFF
SWI instruction
None
None
None
0
$FFFC–$FFFD
IRQ pin
IRQF
IMASK1
IF1
1
$FFFA–$FFFB
CGM change in lock
PLLF
PLLIE
IF2
2
$FFF8–$FFF9
TIM1 channel 0
CH0F
CH0IE
IF3
3
$FFF6–$FFF7
TIM1 channel 1
CH1F
CH1IE
IF4
4
$FFF4–$FFF5
TOF
TOIE
IF5
5
$FFF2–$FFF3
TIM2 channel 0
CH0F
CH0IE
IF6
6
$FFF0–$FFF1
TIM2 channel 1
CH1F
CH1IE
IF7
7
$FFEE–$FFEF
TOF
TOIE
IF8
8
$FFEC–$FFED
SPI receiver full
SPRF
SPRIE
SPI overflow
OVRF
ERRIE
IF9
9
$FFEA–$FFEB
SPI mode fault
MODF
ERRIE
SPI transmitter empty
SPTE
SPTIE
IF10
10
$FFE8–$FFE9
SCI receiver overrun
OR
ORIE
SCI noise flag
NF
NEIE
IF11
11
$FFE6–$FFE7
SCI framing error
FE
FEIE
SCI parity error
PE
PEIE
SCI receiver full
SCRF
SCRIE
IF12
12
$FFE4–$FFE5
SCI input idle
IDLE
ILIE
SCI transmitter empty
SCTE
SCTIE
IF13
13
$FFE2–$FFE3
TC
TCIE
Keyboard pin
KEYF
IMASKK
IF14
14
$FFE0–$FFE1
ADC conversion complete
COCO
AIEN
IF15
15
$FFDE–$FFDF
TBIF
TBIE
IF16
16
$FFDC–$FFDD
Source
TIM1 overflow
TIM2 overflow
SCI transmission complete
Timebase
1. The I bit in the condition code register is a global mask for all interrupt sources except the SWI instruction.
2. 0 = highest priority
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
137
Resets and Interrupts
13.3.2.3 IRQ Pin
A 0 on the IRQ pin latches an external interrupt request.
13.3.2.4 Clock Generator (CGM)
The CGM can generate a CPU interrupt request every time the phase-locked loop circuit (PLL) enters or
leaves the locked state. When the LOCK bit changes state, the PLL flag (PLLF) is set. The PLL interrupt
enable bit (PLLIE) enables PLLF CPU interrupt requests. LOCK is in the PLL bandwidth control register.
PLLF is in the PLL control register.
13.3.2.5 Timer Interface Module 1 (TIM1)
TIM1 CPU interrupt sources:
• TIM1 overflow flag (TOF) — The TOF bit is set when the TIM1 counter value rolls over to $0000
after matching the value in the TIM1 counter modulo registers. The TIM1 overflow interrupt enable
bit, TOIE, enables TIM1 overflow CPU interrupt requests. TOF and TOIE are in the TIM1 status
and control register.
• TIM1 channel flags (CH1F–CH0F) — The CHxF bit is set when an input capture or output compare
occurs on channel x. The channel x interrupt enable bit, CHxIE, enables channel x TIM1 CPU
interrupt requests. CHxF and CHxIE are in the TIM1 channel x status and control register.
13.3.2.6 Timer Interface Module 2 (TIM2)
TIM2 CPU interrupt sources:
• TIM2 overflow flag (TOF) — The TOF bit is set when the TIM2 counter value rolls over to $0000
after matching the value in the TIM2 counter modulo registers. The TIM2 overflow interrupt enable
bit, TOIE, enables TIM2 overflow CPU interrupt requests. TOF and TOIE are in the TIM2 status
and control register.
• TIM2 channel flags (CH1F–CH0F) — The CHxF bit is set when an input capture or output compare
occurs on channel x. The channel x interrupt enable bit, CHxIE, enables channel x TIM2 CPU
interrupt requests. CHxF and CHxIE are in the TIM2 channel x status and control register.
13.3.2.7 Serial Peripheral Interface (SPI)
SPI CPU interrupt sources:
• SPI receiver full bit (SPRF) — The SPRF bit is set every time a byte transfers from the shift register
to the receive data register. The SPI receiver interrupt enable bit, SPRIE, enables SPRF CPU
interrupt requests. SPRF is in the SPI status and control register and SPRIE is in the SPI control
register.
• SPI transmitter empty (SPTE) — The SPTE bit is set every time a byte transfers from the transmit
data register to the shift register. The SPI transmit interrupt enable bit, SPTIE, enables SPTE CPU
interrupt requests. SPTE is in the SPI status and control register and SPTIE is in the SPI control
register.
• Mode fault bit (MODF) — The MODF bit is set in a slave SPI if the SS pin goes high during a
transmission with the mode fault enable bit (MODFEN) set. In a master SPI, the MODF bit is set if
the SS pin goes low at any time with the MODFEN bit set. The error interrupt enable bit, ERRIE,
enables MODF CPU interrupt requests. MODF, MODFEN, and ERRIE are in the SPI status and
control register.
MC68HC908GR16A Data Sheet, Rev. 1.0
138
Freescale Semiconductor
Interrupts
•
Overflow bit (OVRF) — The OVRF bit is set if software does not read the byte in the receive data
register before the next full byte enters the shift register. The error interrupt enable bit, ERRIE,
enables OVRF CPU interrupt requests. OVRF and ERRIE are in the SPI status and control
register.
13.3.2.8 Serial Communications Interface (SCI)
SCI CPU interrupt sources:
• SCI transmitter empty bit (SCTE) — SCTE is set when the SCI data register transfers a character
to the transmit shift register. The SCI transmit interrupt enable bit, SCTIE, enables transmitter CPU
interrupt requests. SCTE is in SCI status register 1. SCTIE is in SCI control register 2.
• Transmission complete bit (TC) — TC is set when the transmit shift register and the SCI data
register are empty and no break or idle character has been generated. The transmission complete
interrupt enable bit, TCIE, enables transmitter CPU interrupt requests. TC is in SCI status register
1. TCIE is in SCI control register 2.
• SCI receiver full bit (SCRF) — SCRF is set when the receive shift register transfers a character to
the SCI data register. The SCI receive interrupt enable bit, SCRIE, enables receiver CPU
interrupts. SCRF is in SCI status register 1. SCRIE is in SCI control register 2.
• Idle input bit (IDLE) — IDLE is set when 10 or 11 consecutive 1s shift in from the RxD pin. The idle
line interrupt enable bit, ILIE, enables IDLE CPU interrupt requests. IDLE is in SCI status register
1. ILIE is in SCI control register 2.
• Receiver overrun bit (OR) — OR is set when the receive shift register shifts in a new character
before the previous character was read from the SCI data register. The overrun interrupt enable
bit, ORIE, enables OR to generate SCI error CPU interrupt requests. OR is in SCI status register
1. ORIE is in SCI control register 3.
• Noise flag (NF) — NF 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, enables NF to
generate SCI error CPU interrupt requests. NF is in SCI status register 1. NEIE is in SCI control
register 3.
• Framing error bit (FE) — FE is set when a 0 occurs where the receiver expects a stop bit. The
framing error interrupt enable bit, FEIE, enables FE to generate SCI error CPU interrupt requests.
FE is in SCI status register 1. FEIE is in SCI control register 3.
• Parity error bit (PE) — PE is set when the SCI detects a parity error in incoming data. The parity
error interrupt enable bit, PEIE, enables PE to generate SCI error CPU interrupt requests. PE is in
SCI status register 1. PEIE is in SCI control register 3.
13.3.2.9 KBD0–KBD7 Pins
A 0 on a keyboard interrupt pin latches an external interrupt request.
13.3.2.10 Analog-to-Digital Converter (ADC)
When the AIEN bit is set, the ADC module is capable of generating a CPU interrupt after each ADC
conversion. The COCO bit is not used as a conversion complete flag when interrupts are enabled.
13.3.2.11 Timebase Module (TBM)
The timebase module can interrupt the CPU on a regular basis with a rate defined by TBR2–TBR0. When
the timebase counter chain rolls over, the TBIF flag is set. If the TBIE bit is set, enabling the timebase
interrupt, the counter chain overflow will generate a CPU interrupt request.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
139
Resets and Interrupts
Interrupts must be acknowledged by writing a 1 to the TACK bit.
13.3.3 Interrupt Status Registers
The flags in the interrupt status registers identify maskable interrupt sources.
Table 13-2 summarizes the interrupt sources and the interrupt status register flags that they set. The
interrupt status registers can be useful for debugging.
Table 13-2. Interrupt Source Flags
Interrupt Source
Interrupt Status Register Flag
Reset
—
SWI instruction
—
IRQ pin
IF1
CGM change of lock
IF2
TIM1 channel 0
IF3
TIM1 channel 1
IF4
TIM1 overflow
IF5
TIM2 channel 0
IF6
TIM2 channel 1
IF7
TIM2 overflow
IF8
SPI receive
IF9
SPI transmit
IF10
SCI error
IF11
SCI receive
IF12
SCI transmit
IF13
Keyboard
IF14
ADC conversion complete
IF15
Timebase
IF16
13.3.3.1 Interrupt Status Register 1
Address:
$FE04
Bit 7
6
5
4
3
2
1
Bit 0
Read:
IF6
IF5
IF4
IF3
IF2
IF1
0
0
Write:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
= Reserved
Reset:
Figure 13-6. Interrupt Status Register 1 (INT1)
IF6–IF1 — Interrupt Flags 6–1
These flags indicate the presence of interrupt requests from the sources shown in Table 13-2.
1 = Interrupt request present
0 = No interrupt request present
Bit 1 and Bit 0 — Always read 0
MC68HC908GR16A Data Sheet, Rev. 1.0
140
Freescale Semiconductor
Interrupts
13.3.3.2 Interrupt Status Register 2
Address:
$FE05
Bit 7
6
5
4
3
2
1
Bit 0
Read:
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 13-7. Interrupt Status Register 2 (INT2)
IF14–IF7 — Interrupt Flags 14–7
These flags indicate the presence of interrupt requests from the sources shown in Table 13-2.
1 = Interrupt request present
0 = No interrupt request present
13.3.3.3 Interrupt Status Register 3
Address:
$FE06
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
0
0
IF16
IF15
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 13-8. Interrupt Status Register 3 (INT3)
IF16 and IF15 — Interrupt Flags 16 and 15
This flag indicates the presence of an interrupt request from the source shown in Table 13-2.
1 = Interrupt request present
0 = No interrupt request present
Bits 7–2 — Always read 0
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
141
Resets and Interrupts
MC68HC908GR16A Data Sheet, Rev. 1.0
142
Freescale Semiconductor
Chapter 14
Enhanced Serial Communications Interface (ESCI) Module
14.1 Introduction
The enhanced serial communications interface (ESCI) module allows asynchronous communications
with peripheral devices and other microcontroller units (MCU).
14.2 Features
Features include:
• Full-duplex operation
• Standard mark/space non-return-to-zero (NRZ) format
• Programmable baud rates
• Programmable 8-bit or 9-bit character length
• Separately enabled transmitter and receiver
• Separate receiver and transmitter central processor unit (CPU) interrupt requests
• Programmable transmitter output polarity
• Two receiver wakeup methods:
– Idle line wakeup
– Address mark wakeup
• Interrupt-driven operation with eight interrupt flags:
– Transmitter empty
– Transmission complete
– Receiver full
– Idle receiver input
– Receiver overrun
– Noise error
– Framing error
– Parity error
• Receiver framing error detection
• Hardware parity checking
• 1/16 bit-time noise detection
14.3 Pin Name Conventions
The generic names of the ESCI input/output (I/O) pins are:
• RxD (receive data)
• TxD (transmit data)
ESCI I/O lines are implemented by sharing parallel I/O port pins. The full name of an ESCI input or output
reflects the name of the shared port pin. Table 14-1 shows the full names and the generic names of the
ESCI I/O pins. The generic pin names appear in the text of this section.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
143
Enhanced Serial Communications Interface (ESCI) Module
INTERNAL BUS
PORTB
PTB7/AD7
PTB6/AD6
PTB5/AD5
PTB4/AD4
PTB3/AD3
PTB2/AD2
PTB1/AD1
PTB0/AD0
PTC6(1)
PTC5(1)
PTC4(1), (2)
PTC3(1), (2)
PTC2(1), (2)
PTC1(1), (2)
PTC0(1), (2)
PTD7/T2CH1(1)
PTD6/T2CH0(1)
PTD5/T1CH1(1)
PTD4/T1CH0(1)
PTD3/SPSCK(1)
PTD2/MOSI(1)
PTD1/MISO(1)
PTD0/SS(1)
PTE5–PTE2
PTE1/RxD
PTE0/TxD
DDRA
PORTA
PTA7/KBD7–
PTA0/KBD0(1)
PORTC
PROGRAMMABLE TIMEBASE
MODULE
ARITHMETIC/LOGIC
UNIT (ALU)
PORTD
SINGLE BREAKPOINT
BREAK MODULE
CONTROL AND STATUS REGISTERS — 64 BYTES
DDRB
CPU
REGISTERS
PORTE
M68HC08 CPU
DUAL VOLTAGE
LOW-VOLTAGE INHIBIT
MODULE
USER FLASH — 15,872 BYTES
USER RAM — 1024 BYTES
8-BIT KEYBOARD
INTERRUPT MODULE
MONITOR ROM — 350 BYTES
USER FLASH VECTOR SPACE — 36 BYTES
DDRC
2-CHANNEL TIMER
INTERFACE MODULE 1
FLASH PROGRAMMING ROUTINES ROM — 406 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 2
CLOCK GENERATOR MODULE
OSC1
OSC2
CGMXFC
ENHANCED SERIAL
COMUNICATIONS
INTERFACE MODULE
1–8 MHz OSCILLATOR
PHASE LOCKED LOOP
RST(3)
SYSTEM INTEGRATION
MODULE
IRQ(3)
SINGLE EXTERNAL
INTERRUPT MODULE
DDRD
COMPUTER OPERATING
PROPERLY MODULE
SERIAL PERIPHERAL
INTERFACE MODULE
VSSAD/VREFL
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
MEMORY MAP
MODULE
POWER-ON RESET
MODULE
VDD
VSS
VDDA
VSSA
DDRE
MONITOR MODULE
VDDAD/VREFH
SECURITY
MODULE
CONFIGURATION
REGISTER 1–2
MODULE
POWER
MONITOR MODE ENTRY
MODULE
1. Ports are software configurable with pullup device if input port.
2. Higher current drive port pins
3. Pin contains integrated pullup device
Figure 14-1. Block Diagram Highlighting ESCI Block and Pins
Table 14-1. Pin Name Conventions
Generic Pin Names
Full Pin Names
RxD
TxD
PTE1/RxD
PTE0/TxD
MC68HC908GR16A Data Sheet, Rev. 1.0
144
Freescale Semiconductor
Functional Description
14.4 Functional Description
Figure 14-2 shows the structure of the ESCI module. The ESCI allows full-duplex, asynchronous, NRZ
serial communication between the MCU and remote devices, including other MCUs. The transmitter and
receiver of the ESCI operate independently, although they use the same baud rate generator. During
normal operation, the CPU monitors the status of the ESCI, writes the data to be transmitted, and
processes received data.
INTERNAL BUS
SCI_TxD
SCTIE
TxD
TRANSMIT
SHIFT REGISTER
TXINV
LINR
RxD
BUS_CLK
R8
TCIE
SL
T8
SCRIE
ILIE
TE
ACLK BIT
IN SCIACTL
SCTE
RE
ARBITER
RxD
ERROR
INTERRUPT
CONTROL
RECEIVE
SHIFT REGISTER
ESCI DATA
REGISTER
RECEIVER
INTERRUPT
CONTROL
TRANSMITTER
INTERRUPT
CONTROL
ESCI DATA
REGISTER
SBK
SCRF
OR
ORIE
IDLE
NF
NEIE
FE
FEIE
PE
PEIE
SCI_CLK
TC
RWU
LOOPS
LOOPS
WAKEUP
CONTROL
BUS
CLOCK
RECEIVE
CONTROL
ENSCI
ENHANCED
PRESCALER
CGMXCLK
TRANSMIT
CONTROL
FLAG
CONTROL
BKF
M
RPF
WAKE
LINT
ILTY
÷4
ESCIBDSRC
FROM
CONFIG2
SL
ENSCI
PRESCALER
PEN
BAUD RATE
GENERATOR
÷ 16
PTY
DATA SELECTION
CONTROL
SL = 1 -> SCI_CLK = BUSCLK
SL = 0 -> SCI_CLK = CGMSCLK (4x BUSCLK)
Figure 14-2. ESCI Module Block Diagram
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
145
Enhanced Serial Communications Interface (ESCI) Module
The baud rate clock source for the ESCI can be selected via the configuration bit, ESCIBDSRC, of the
CONFIG2 register ($001E).
For reference, a summary of the ESCI module input/output registers is provided in Figure 14-3.
Addr.
$0009
$000A
$000B
Register Name
ESCI Prescaler Register Read:
(SCPSC) Write:
See page 166. Reset:
ESCI Arbiter Control Read:
Register (SCIACTL) Write:
See page 170. Reset:
ESCI Arbiter Data Read:
Register (SCIADAT) Write:
See page 171. Reset:
$0013
ESCI Control Register 1 Read:
(SCC1) Write:
See page 157. Reset:
$0014
ESCI Control Register 2 Read:
(SCC2) Write:
See page 159. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
PDS2
PDS1
PDS0
PSSB4
PSSB3
PSSB2
PSSB1
PSSB0
0
0
0
0
0
0
0
0
AM0
ACLK
AFIN
ARUN
AROVFL
ARD8
AM1
ALOST
0
0
0
0
0
0
0
0
ARD7
ARD6
ARD5
ARD4
ARD3
ARD2
ARD1
ARD0
0
0
0
0
0
0
0
0
LOOPS
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
0
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
T8
R
R
ORIE
NEIE
FEIE
PEIE
ESCI Control Register 3 Read:
(SCC3) Write:
See page 160. Reset:
R8
U
0
0
0
0
0
0
0
ESCI Status Register 1 Read:
(SCS1) Write:
See page 161. Reset:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
0
0
0
0
0
0
BKF
RPF
$0017
ESCI Status Register 2 Read:
(SCS2) Write:
See page 164. Reset:
0
0
0
0
0
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
$0018
ESCI Data Register Read:
(SCDR) Write:
See page 164. Reset:
T7
T6
T5
T4
T3
T2
T1
T0
$0015
$0016
$0019
ESCI Baud Rate Register Read:
(SCBR) Write:
See page 165. Reset:
Unaffected by reset
LINT
LINR
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
R
= Reserved
= Unimplemented
U = Unaffected
Figure 14-3. ESCI I/O Register Summary
MC68HC908GR16A Data Sheet, Rev. 1.0
146
Freescale Semiconductor
Functional Description
14.4.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 14-4.
PARITY
OR DATA
BIT
8-BIT DATA FORMAT
(BIT M IN SCC1 CLEAR)
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
STOP
BIT
PARITY
OR DATA
BIT
9-BIT DATA FORMAT
(BIT M IN SCC1 SET)
START
BIT
NEXT
START
BIT
BIT 6
BIT 7
BIT 8
NEXT
START
BIT
STOP
BIT
Figure 14-4. SCI Data Formats
14.4.2 Transmitter
Figure 14-5 shows the structure of the SCI transmitter and the registers are summarized in Figure 14-3.
The baud rate clock source for the ESCI can be selected via the configuration bit, ESCIBDSRC.
INTERNAL BUS
BAUD
DIVIDER
÷ 16
ESCI DATA REGISTER
SCP1
11-BIT
TRANSMIT
SHIFT REGISTER
STOP
SCP0
SCR2
H
SCR1
8
7
6
5
4
3
2
START
PRESCALER
÷4
1
0
L
SCI_TxD
PSSB3
PTY
MSB
PARITY
GENERATION
T8
BREAK
(ALL ZEROS)
PEN
PREAMBLE
(ALL ONES)
PDS0
PSSB4
M
SHIFT ENABLE
PDS1
TXINV
LOAD FROM SCDR
PDS2
TRANSMITTER CPU INTERRUPT REQUEST
BUS CLOCK
PRESCALER
SCR0
TRANSMITTER
CONTROL LOGIC
PSSB2
PSSB1
PSSB0
SCTE
SCTE
SCTIE
TC
TCIE
SBK
LOOPS
SCTIE
ENSCI
TC
TE
TCIE
LINT
Figure 14-5. ESCI Transmitter
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
147
Enhanced Serial Communications Interface (ESCI) Module
14.4.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in ESCI control
register 1 (SCC1) determines character length. When transmitting 9-bit data, bit T8 in ESCI control
register 3 (SCC3) is the ninth bit (bit 8).
14.4.2.2 Character Transmission
During an ESCI transmission, the transmit shift register shifts a character out to the TxD pin. The ESCI
data register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register.
To initiate an ESCI transmission:
1. Enable the ESCI by writing a 1 to the enable ESCI bit (ENSCI) in ESCI control register 1 (SCC1).
2. Enable the transmitter by writing a 1 to the transmitter enable bit (TE) in ESCI control register 2
(SCC2).
3. Clear the ESCI transmitter empty bit (SCTE) by first reading ESCI status register 1 (SCS1) and
then writing to the SCDR. For 9-bit data, also write the T8 bit in SCC3.
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 1s. After the preamble shifts out, control logic transfers the SCDR data into the transmit
shift register. A 0 start bit automatically goes into the least significant bit (LSB) position of the transmit shift
register. A 1 stop bit goes into the most significant bit (MSB) position.
The ESCI 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 ESCI transmit interrupt enable bit, SCTIE, in SCC2 is also set, the SCTE bit generates a
transmitter CPU interrupt request.
When the transmit shift register is not transmitting a character, the TxD pin goes to the idle condition, high.
If at any time software clears the ENSCI bit in ESCI control register 1 (SCC1), the transmitter and receiver
relinquish control of the port E pins.
14.4.2.3 Break Characters
Writing a 1 to the send break bit, SBK, in SCC2 loads the transmit shift register with a break character.
For TXINV = 0 (output not inverted), a transmitted break character contains all 0s and has no start, stop,
or parity bit. Break character length depends on the M bit in SCC1 and the LINR bits in SCBR. As long as
SBK is at 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 1. The automatic 1 at the end of a break character guarantees the recognition of
the start bit of the next character.
When LINR is cleared in SCBR, the ESCI recognizes a break character when a start bit is followed by
eight or nine 0 data bits and a 0 where the stop bit should be, resulting in a total of 10 or 11 consecutive 0
data bits. When LINR is set in SCBR, the ESCI recognizes a break character when a start bit is followed
by 9 or 10 0 data bits and a 0 where the stop bit should be, resulting in a total of 11 or 12 consecutive 0
data bits.
Receiving a break character has these effects on ESCI registers:
• Sets the framing error bit (FE) in SCS1
• Sets the ESCI receiver full bit (SCRF) in SCS1
• Clears the ESCI data register (SCDR)
MC68HC908GR16A Data Sheet, Rev. 1.0
148
Freescale Semiconductor
Functional Description
•
•
•
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
14.4.2.4 Idle Characters
For TXINV = 0 (output not inverted), a transmitted idle character contains all 1s and has no start, stop, or
parity bit. Idle character length depends on the M bit in SCC1. The preamble is a synchronizing idle
character that begins every transmission.
If the TE bit is cleared during a transmission, the TxD pin becomes idle after completion of the
transmission in progress. Clearing and then setting the TE bit during a transmission queues an idle
character to be sent after the character currently being transmitted.
NOTE
When a break sequence is followed immediately by an idle character, this
SCI design exhibits a condition in which the break character length is
reduced by one half bit time. In this instance, the break sequence will
consist of a valid start bit, eight or nine data bits (as defined by the M bit in
SCC1) of 0 and one half data bit length of 0 in the stop bit position followed
immediately by the idle character. To ensure a break character of the
proper length is transmitted, always queue up a byte of data to be
transmitted while the final break sequence is in progress.
When queueing an idle character, return the TE bit to 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.
A good time to toggle the TE bit for a queued idle character is when the
SCTE bit becomes set and just before writing the next byte to the SCDR.
14.4.2.5 Inversion of Transmitted Output
The transmit inversion bit (TXINV) in ESCI 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 a 1. See
14.8.1 ESCI Control Register 1.
14.4.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the ESCI transmitter:
• ESCI 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 ESCI 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.
14.4.3 Receiver
Figure 14-6 shows the structure of the ESCI receiver. The receiver I/O registers are summarized in
Figure 14-3.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
149
Enhanced Serial Communications Interface (ESCI) Module
INTERNAL BUS
SCP1
SCR1
SCP0
SCR0
PDS2
STOP
÷ 16
DATA
RECOVERY
RxD
BKF
CGMXCLK
OR
BUS CLOCK
BAUD
DIVIDER
ALL ZEROS
RPF
H
ALL ONES
PRESCALER
PRESCALER
÷4
ESCI DATA REGISTER
START
SCR2
11-BIT
RECEIVE SHIFT REGISTER
8
7
6
5
4
3
2
1
0
L
MSB
LINR
PDS1
PDS0
PSSB4
PSSB3
PSSB2
M
WAKE
ILTY
PSSB1
PEN
PSSB0
PTY
SCRF
WAKEUP
LOGIC
PARITY
CHECKING
IDLE
ILIE
CPU INTERRUPT
REQUEST
SCRF
SCRIE
OR
ORIE
NF
NEIE
ERROR CPU
INTERRUPT REQUEST
FE
FEIE
PE
PEIE
RWU
IDLE
R8
ILIE
SCRIE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
Figure 14-6. ESCI Receiver Block Diagram
14.4.3.1 Character Length
The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in ESCI control register 1
(SCC1) determines character length. When receiving 9-bit data, bit R8 in ESCI control register 3 (SCC3)
is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7).
MC68HC908GR16A Data Sheet, Rev. 1.0
150
Freescale Semiconductor
Functional Description
14.4.3.2 Character Reception
During an ESCI reception, the receive shift register shifts characters in from the RxD pin. The ESCI 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 ESCI receiver full bit, SCRF, in ESCI status register 1 (SCS1) becomes set, indicating
that the received byte can be read. If the ESCI receive interrupt enable bit, SCRIE, in SCC2 is also set,
the SCRF bit generates a receiver CPU interrupt request.
14.4.3.3 Data Sampling
The receiver samples the RxD pin at the RT clock rate. The RT clock is an internal signal with a frequency
16 times the baud rate. To adjust for baud rate mismatch, the RT clock is resynchronized at these times
(see Figure 14-7):
• After every start bit
• After the receiver detects a data bit change from 1 to 0 (after the majority of data bit samples at
RT8, RT9, and RT10 returns a valid 1 and the majority of the next RT8, RT9, and RT10 samples
returns a valid 0)
To locate the start bit, data recovery logic does an asynchronous search for a 0 preceded by three 1s.
When the falling edge of a possible start bit occurs, the RT clock begins to count to 16.
START BIT
RxD
SAMPLES
START BIT
QUALIFICATION
LSB
START BIT
DATA
VERIFICATION SAMPLING
RT CLOCK
STATE
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT2
RT3
RT4
RT5
RT6
RT7
RT8
RT9
RT10
RT11
RT12
RT13
RT14
RT15
RT16
RT1
RT2
RT3
RT4
RT
CLOCK
RT CLOCK
RESET
Figure 14-7. Receiver Data Sampling
To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7.
Table 14-2 summarizes the results of the start bit verification samples.
Table 14-2. Start Bit Verification
RT3, RT5, and RT7 Samples
Start Bit Verification
Noise Flag
000
Yes
0
001
Yes
1
010
Yes
1
011
No
0
100
Yes
1
101
No
0
110
No
0
111
No
0
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
151
Enhanced Serial Communications Interface (ESCI) Module
If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins.
To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and
RT10. Table 14-3 summarizes the results of the data bit samples.
Table 14-3. Data Bit Recovery
RT8, RT9, and RT10 Samples
Data Bit Determination
Noise Flag
000
0
0
001
0
1
010
0
1
011
1
1
100
0
1
101
1
1
110
1
1
111
1
0
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 1s following a
successful start bit verification, the noise flag (NF) is set and the receiver
assumes that the bit is a start bit.
To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 14-4
summarizes the results of the stop bit samples.
Table 14-4. Stop Bit Recovery
RT8, RT9, and RT10 Samples
Framing Error Flag
Noise Flag
000
1
0
001
1
1
010
1
1
011
0
1
100
1
1
101
0
1
110
0
1
111
0
0
14.4.3.4 Framing Errors
If the data recovery logic does not detect a 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.
14.4.3.5 Baud Rate Tolerance
A transmitting device may be operating at a baud rate below or above the receiver baud rate.
Accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the
actual stop bit. Then a noise error occurs. If more than one of the samples is outside the stop bit, a framing
MC68HC908GR16A Data Sheet, Rev. 1.0
152
Freescale Semiconductor
Functional Description
error occurs. In most applications, the baud rate 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 14-8 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.
MSB
STOP
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RECEIVER
RT CLOCK
DATA
SAMPLES
•
•
•
Figure 14-8. Slow Data
For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times × 16 RT cycles
+ 10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 14-8, the receiver counts 154 RT cycles at the point
when the count of the transmitting device is 9 bit times × 16 RT cycles + 3 RT cycles
= 147 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a slow
8-bit character with no errors is:
154 – 147
-------------------------- × 100 = 4.54%
154
•
•
•
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times × 16 RT cycles
+ 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 14-8, 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 14-9 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
153
Enhanced Serial Communications Interface (ESCI) Module
STOP
IDLE OR NEXT CHARACTER
RT16
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RECEIVER
RT CLOCK
DATA
SAMPLES
Figure 14-9. Fast Data
For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times × 16 RT cycles
+ 10 RT cycles = 154 RT cycles.
With the misaligned character shown in Figure 14-9, the receiver counts 154 RT cycles at the point when
the count of the transmitting device is 10 bit times × 16 RT cycles = 160 RT cycles.
The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit
character with no errors is
154 – 160
-------------------------- × 100 = 3.90%
154
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times × 16 RT cycles
+ 10 RT cycles = 170 RT cycles.
With the misaligned character shown in Figure 14-9, 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
14.4.3.6 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 RxD pin can bring the
receiver out of the standby state:
1. Address mark — An address mark is a 1 in the MSB 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 ESCI 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.
2. Idle input line condition — When the WAKE bit is clear, an idle character on the RxD pin wakes the
receiver from the standby state by clearing the RWU bit. The idle character that wakes the receiver
does not set the receiver idle bit, IDLE, or the ESCI receiver full bit, SCRF. The idle line type bit,
ILTY, determines whether the receiver begins counting 1s as idle character bits after the start bit
or after the stop bit.
MC68HC908GR16A Data Sheet, Rev. 1.0
154
Freescale Semiconductor
Low-Power Modes
NOTE
With the WAKE bit clear, setting the RWU bit after the RxD pin has been
idle will cause the receiver to wake up.
14.4.3.7 Receiver Interrupts
These sources can generate CPU interrupt requests from the ESCI receiver:
• ESCI 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 ESCI 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 1s shifted in from the
RxD pin. The idle line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate CPU
interrupt requests.
14.4.3.8 Error Interrupts
These receiver error flags in SCS1 can generate CPU interrupt requests:
• Receiver overrun (OR) — The OR bit indicates that the receive shift register shifted in a new
character before the previous character was read from the SCDR. The previous character remains
in the SCDR, and the new character is lost. The overrun interrupt enable bit, ORIE, in SCC3
enables OR to generate ESCI error CPU interrupt requests.
• Noise flag (NF) — The NF bit is set when the ESCI 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 ESCI error CPU interrupt requests.
• Framing error (FE) — The FE bit in SCS1 is set when a 0 occurs where the receiver expects a stop
bit. The framing error interrupt enable bit, FEIE, in SCC3 enables FE to generate ESCI error CPU
interrupt requests.
• Parity error (PE) — The PE bit in SCS1 is set when the ESCI detects a parity error in incoming
data. The parity error interrupt enable bit, PEIE, in SCC3 enables PE to generate ESCI error CPU
interrupt requests.
14.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
14.5.1 Wait Mode
The ESCI module remains active in wait mode. Any enabled CPU interrupt request from the ESCI module
can bring the MCU out of wait mode.
If ESCI module functions are not required during wait mode, reduce power consumption by disabling the
module before executing the WAIT instruction.
14.5.2 Stop Mode
The ESCI module is inactive in stop mode. The STOP instruction does not affect ESCI register states.
ESCI module operation resumes after the MCU exits stop mode.
Because the internal clock is inactive during stop mode, entering stop mode during an ESCI transmission
or reception results in invalid data.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
155
Enhanced Serial Communications Interface (ESCI) Module
14.6 ESCI During Break Module Interrupts
The BCFE bit in the break flag control register (SBFCR) enables software to clear status bits during the
break state. See Chapter 19 Development Support.
To allow software to clear status bits during a break interrupt, write a 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 0 to the BCFE bit. With BCFE at 0 (its default state),
software can read and write I/O registers during the break state without affecting status bits. Some status
bits have a two-step read/write clearing procedure. If software does the first step on such a bit before the
break, the bit cannot change during the break state as long as BCFE is at 0. After the break, doing the
second step clears the status bit.
14.7 I/O Signals
Port E shares two of its pins with the ESCI module. The two ESCI I/O pins are:
• PTE0/TxD — transmit data
• PTE1/RxD — receive data
14.7.1 PTE0/TxD (Transmit Data)
The PTE0/TxD pin is the serial data output from the ESCI transmitter. The ESCI shares the PTE0/TxD
pin with port E. When the ESCI is enabled, the PTE0/TxD pin is an output regardless of the state of the
DDRE0 bit in data direction register E (DDRE).
14.7.2 PTE1/RxD (Receive Data)
The PTE1/RxD pin is the serial data input to the ESCI receiver. The ESCI shares the PTE1/RxD pin with
port E. When the ESCI is enabled, the PTE1/RxD pin is an input regardless of the state of the DDRE1 bit
in data direction register E (DDRE).
14.8 I/O Registers
These I/O registers control and monitor ESCI operation:
• ESCI control register 1, SCC1
• ESCI control register 2, SCC2
• ESCI control register 3, SCC3
• ESCI status register 1, SCS1
• ESCI status register 2, SCS2
• ESCI data register, SCDR
• ESCI baud rate register, SCBR
• ESCI prescaler register, SCPSC
• ESCI arbiter control register, SCIACTL
• ESCI arbiter data register, SCIADAT
MC68HC908GR16A Data Sheet, Rev. 1.0
156
Freescale Semiconductor
I/O Registers
14.8.1 ESCI Control Register 1
ESCI control register 1 (SCC1):
• Enables loop mode operation
• Enables the ESCI
• Controls output polarity
• Controls character length
• Controls ESCI wakeup method
• Controls idle character detection
• Enables parity function
• Controls parity type
Address: $0013
Read:
Write:
Reset:
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 14-10. ESCI Control Register 1 (SCC1)
LOOPS — Loop Mode Select Bit
This read/write bit enables loop mode operation. In loop mode the RxD pin is disconnected from the
ESCI, 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 ESCI Bit
This read/write bit enables the ESCI and the ESCI baud rate generator. Clearing ENSCI sets the SCTE
and TC bits in ESCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit.
1 = ESCI enabled
0 = ESCI 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.
M — Mode (Character Length) Bit
This read/write bit determines whether ESCI characters are eight or nine bits long (See
Table 14-5).The ninth bit can serve as a receiver wakeup signal or as a parity bit. Reset clears the
M bit.
1 = 9-bit ESCI characters
0 = 8-bit ESCI characters
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
157
Enhanced Serial Communications Interface (ESCI) Module
Table 14-5. Character Format Selection
Control Bits
Character Format
M
PEN:PTY
Start Bits
Data Bits
Parity
Stop Bits
Character Length
0
0 X
1
8
None
1
10 bits
1
0 X
1
9
None
1
11 bits
0
1 0
1
7
Even
1
10 bits
0
1 1
1
7
Odd
1
10 bits
1
1 0
1
8
Even
1
11 bits
1
1 1
1
8
Odd
1
11 bits
WAKE — Wakeup Condition Bit
This read/write bit determines which condition wakes up the ESCI: a 1 (address mark) in the MSB
position of a received character or an idle condition on the RxD pin. Reset clears the WAKE bit.
1 = Address mark wakeup
0 = Idle line wakeup
ILTY — Idle Line Type Bit
This read/write bit determines when the ESCI starts counting 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 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 ESCI parity function (see Table 14-5). When enabled, the parity
function inserts a parity bit in the MSB position (see Table 14-3). Reset clears the PEN bit.
1 = Parity function enabled
0 = Parity function disabled
PTY — Parity Bit
This read/write bit determines whether the ESCI generates and checks for odd parity or even parity
(see Table 14-5). 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.
14.8.2 ESCI Control Register 2
ESCI control register 2 (SCC2):
• Enables these CPU interrupt requests:
– SCTE bit to generate transmitter CPU interrupt requests
– TC bit to generate transmitter CPU interrupt requests
– SCRF bit to generate receiver CPU interrupt requests
– IDLE bit to generate receiver CPU interrupt requests
MC68HC908GR16A Data Sheet, Rev. 1.0
158
Freescale Semiconductor
I/O Registers
•
•
•
•
Enables the transmitter
Enables the receiver
Enables ESCI wakeup
Transmits ESCI break characters
Address: $0014
Read:
Write:
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
Figure 14-11. ESCI Control Register 2 (SCC2)
SCTIE — ESCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate ESCI transmitter CPU interrupt requests. Setting
the SCTIE bit in SCC2 enables the SCTE bit to generate 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 ESCI 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 — ESCI Receive Interrupt Enable Bit
This read/write bit enables the SCRF bit to generate ESCI receiver CPU interrupt requests. Setting the
SCRIE bit in SCC2 enables the SCRF bit to generate CPU interrupt requests. Reset clears the
SCRIE bit.
1 = SCRF enabled to generate CPU interrupt
:
0 = SCRF not enabled to generate CPU interrupt
ILIE — Idle Line Interrupt Enable Bit
This read/write bit enables the IDLE bit to generate ESCI receiver CPU interrupt requests. Reset clears
the ILIE bit.
1 = IDLE enabled to generate CPU interrupt requests
0 = IDLE not enabled to generate CPU interrupt requests
TE — Transmitter Enable Bit
Setting this read/write bit begins the transmission by sending a preamble of 10 or 11 1s from the
transmit shift register to the TxD pin. If software clears the TE bit, the transmitter completes any
transmission in progress before the TxD returns to the idle condition (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 ESCI bit (ENSCI) is
clear. ENSCI is in ESCI control register 1.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
159
Enhanced Serial Communications Interface (ESCI) Module
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 ESCI bit (ENSCI) is
clear. ENSCI is in ESCI control register 1.
RWU — Receiver Wakeup Bit
This read/write bit puts the receiver in a standby state during which receiver interrupts are disabled.
The WAKE bit in SCC1 determines whether an idle input or an address mark brings the receiver out
of the standby state and clears the RWU bit. Reset clears the RWU bit.
1 = Standby state
0 = Normal operation
SBK — Send Break Bit
Setting and then clearing this read/write bit transmits a break character followed by a 1. The 1 after the
break character guarantees recognition of a valid start bit. If SBK remains set, the transmitter
continuously transmits break characters with no 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 ESCI to send a break
character instead of a preamble.
14.8.3 ESCI Control Register 3
ESCI control register 3 (SCC3):
• Stores the ninth ESCI data bit received and the ninth ESCI data bit to be transmitted.
• Enables these interrupts:
– Receiver overrun
– Noise error
– Framing error
– Parity error
Address:
$0015
Bit 7
Read:
R8
Write:
Reset:
U
6
5
4
3
2
1
Bit 0
T8
R
R
ORIE
NEIE
FEIE
PEIE
0
0
0
0
0
0
0
R
= Reserved
= Unimplemented
U = Unaffected
Figure 14-12. ESCI Control Register 3 (SCC3)
R8 — Received Bit 8
When the ESCI 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
160
Freescale Semiconductor
I/O Registers
When the ESCI 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 ESCI 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 clears the T8 bit.
ORIE — Receiver Overrun Interrupt Enable Bit
This read/write bit enables ESCI error CPU interrupt requests generated by the receiver overrun bit,
OR. Reset clears ORIE.
1 = ESCI error CPU interrupt requests from OR bit enabled
0 = ESCI error CPU interrupt requests from OR bit disabled
NEIE — Receiver Noise Error Interrupt Enable Bit
This read/write bit enables ESCI error CPU interrupt requests generated by the noise error bit, NE.
Reset clears NEIE.
1 = ESCI error CPU interrupt requests from NE bit enabled
0 = ESCI error CPU interrupt requests from NE bit disabled
FEIE — Receiver Framing Error Interrupt Enable Bit
This read/write bit enables ESCI error CPU interrupt requests generated by the framing error bit, FE.
Reset clears FEIE.
1 = ESCI error CPU interrupt requests from FE bit enabled
0 = ESCI error CPU interrupt requests from FE bit disabled
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables ESCI receiver CPU interrupt requests generated by the parity error bit, PE.
Reset clears PEIE.
1 = ESCI error CPU interrupt requests from PE bit enabled
0 = ESCI error CPU interrupt requests from PE bit disabled
14.8.4 ESCI Status Register 1
ESCI 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:
$0016
Bit 7
6
5
4
3
2
1
Bit 0
Read:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
1
1
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 14-13. ESCI Status Register 1 (SCS1)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
161
Enhanced Serial Communications Interface (ESCI) Module
SCTE — ESCI 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 ESCI transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set,
SCTE generates an ESCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit
by reading SCS1 with SCTE set and then writing to SCDR. Reset sets the SCTE bit.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
TC — Transmission Complete Bit
This read-only bit is set when the SCTE bit is set, and no data, preamble, or break character is being
transmitted. TC generates an ESCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also
set. TC is cleared automatically when data, preamble, or break is queued and ready to be sent. There
may be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the
transmission actually starting. Reset sets the TC bit.
1 = No transmission in progress
0 = Transmission in progress
SCRF — ESCI Receiver Full Bit
This clearable, read-only bit is set when the data in the receive shift register transfers to the ESCI data
register. SCRF can generate an ESCI receiver CPU interrupt request. When the SCRIE bit in SCC2 is
set the 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 1s appear on the receiver input. IDLE
generates an ESCI receiver CPU interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE
bit by reading SCS1 with IDLE set and then reading the SCDR. After the receiver is enabled, it must
receive a valid character that sets the SCRF bit before an idle condition can set the IDLE bit. Also, after
the IDLE bit has been cleared, a valid character must again set the SCRF bit before an idle condition
can set the IDLE bit. Reset clears the IDLE bit.
1 = Receiver input idle
0 = Receiver input active (or idle since the IDLE bit was cleared)
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 ESCI error CPU interrupt request if the
ORIE bit in SCC3 is also set. The data in the shift register is lost, but the data already in the SCDR is
not affected. Clear the OR bit by reading SCS1 with OR set and then reading the SCDR. Reset clears
the OR bit.
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
Software latency may allow an overrun to occur between reads of SCS1 and SCDR in the flag-clearing
sequence. Figure 14-14 shows the normal flag-clearing sequence and an example of an overrun
caused by a delayed flag-clearing sequence. The delayed read of SCDR does not clear the OR bit
because OR was not set when SCS1 was read. Byte 2 caused the overrun and is lost. The next
flag-clearing sequence reads byte 3 in the SCDR instead of byte 2.
MC68HC908GR16A Data Sheet, Rev. 1.0
162
Freescale Semiconductor
I/O Registers
In applications that are subject to software latency or in which it is important to know which byte is lost
due to an overrun, the flag-clearing routine can check the OR bit in a second read of SCS1 after
reading the data register.
BYTE 1
BYTE 2
BYTE 3
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
NORMAL FLAG CLEARING SEQUENCE
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCDR
BYTE 1
READ SCDR
BYTE 2
READ SCDR
BYTE 3
BYTE 1
BYTE 2
BYTE 3
SCRF = 0
OR = 0
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 1
SCRF = 1
OR = 1
DELAYED FLAG CLEARING SEQUENCE
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 1
READ SCDR
BYTE 3
Figure 14-14. Flag Clearing Sequence
NF — Receiver Noise Flag Bit
This clearable, read-only bit is set when the ESCI detects noise on the 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 0 is accepted as the stop bit. FE generates an ESCI error
CPU interrupt request if the FEIE bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set
and then reading the SCDR. Reset clears the FE bit.
1 = Framing error detected
0 = No framing error detected
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the ESCI 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
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
163
Enhanced Serial Communications Interface (ESCI) Module
14.8.5 ESCI Status Register 2
ESCI status register 2 (SCS2) contains flags to signal these conditions:
• Break character detected
• Incoming data
Address:
Read:
$0017
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
BKF
RPF
0
0
0
0
0
0
0
Write:
Reset:
0
= Unimplemented
Figure 14-15. ESCI Status Register 2 (SCS2)
BKF — Break Flag Bit
This clearable, read-only bit is set when the ESCI detects a break character on the RxD pin. In SCS1,
the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in SCC3 is cleared. BKF
does not generate a CPU interrupt request. Clear BKF by reading SCS2 with BKF set and then reading
the SCDR. Once cleared, BKF can become set again only after 1s again appear on the RxD pin
followed by another break character. Reset clears the BKF bit.
1 = Break character detected
0 = No break character detected
RPF — Reception in Progress Flag Bit
This read-only bit is set when the receiver detects a 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 ESCI module or entering stop mode can show whether a reception is in
progress.
1 = Reception in progress
0 = No reception in progress
14.8.6 ESCI Data Register
The ESCI 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 ESCI 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 14-16. ESCI 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 ESCI data register.
NOTE
Do not use read-modify-write instructions on the ESCI data register.
MC68HC908GR16A Data Sheet, Rev. 1.0
164
Freescale Semiconductor
I/O Registers
14.8.7 ESCI Baud Rate Register
The ESCI baud rate register (SCBR) together with the ESCI prescaler register selects the baud rate for
both the receiver and the transmitter.
NOTE
There are two prescalers available to adjust the baud rate. One in the ESCI
baud rate register and one in the ESCI prescaler register.
Address:
Read:
Write:
Reset:
$0019
Bit 7
6
5
4
3
2
1
Bit 0
LINT
LINR
SCP1
SCP0
R
SCR2
SCR1
SCR0
0
0
0
0
0
0
0
0
R
= Reserved
Figure 14-17. ESCI Baud Rate Register (SCBR)
LINT — LIN Break Symbol Transmit Enable
This read/write bit selects the enhanced ESCI features for master nodes in the local interconnect
network (LIN) protocol (version 1.2) as shown in Table 14-6. Reset clears LINT.
Table 14-6. ESCI LIN Master Node Control Bits
LINT
M
Functionality
0
X
Normal ESCI functionality
1
0
13-bit break generation enabled for LIN transmitter
1
1
14-bit break generation enabled for LIN transmitter
NOTE
LIN master nodes require significantly tighter timing tolerances than slave
nodes. Be sure to consult the current LIN specification to ensure that timing
requirements are met properly. Generally, these timing tolerances require
crystals or oscillators to be used, rather than internal clocking circuits.
LINR — LIN Break Symbol Receiver Bits
This read/write bit selects the enhanced ESCI features for slave nodes in the local interconnect
network (LIN) protocol as shown in Table 14-7. Reset clears LINR.
Table 14-7. ESCI LIN Slave Node Control Bits
LINR
M
Functionality
0
X
Normal ESCI functionality
1
0
11-bit break detect enabled for LIN receiver
1
1
12-bit break detect enabled for LIN receiver
In LIN (version 1.2) systems, the master node transmits a break character which will appear as
11.05–14.95 dominant bits to the slave node. A data character of 0x00 sent from the master might
appear as 7.65–10.35 dominant bit times. This is due to the oscillator tolerance requirement that the
slave node must be within ±15% of the master node's oscillator. Since a slave node cannot know if it
is running faster or slower than the master node (prior to synchronization), the LINR bit allows the slave
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
165
Enhanced Serial Communications Interface (ESCI) Module
node to differentiate between a 0x00 character of 10.35 bits and a break character of 11.05 bits. The
break symbol length must be verified in software in any case, but the LINR bit serves as a filter,
preventing false detections of break characters that are really 0x00 data characters.
SCP1 and SCP0 — ESCI Baud Rate Register Prescaler Bits
These read/write bits select the baud rate register prescaler divisor as shown in Table 14-8. Reset
clears SCP1 and SCP0.
Table 14-8. ESCI Baud Rate Prescaling
SCP[1:0]
Baud Rate Register
Prescaler Divisor (BPD)
0 0
1
0 1
3
1 0
4
1 1
13
SCR2–SCR0 — ESCI Baud Rate Select Bits
These read/write bits select the ESCI baud rate divisor as shown in Table 14-9. Reset clears
SCR2–SCR0.
Table 14-9. ESCI Baud Rate Selection
SCR[2:1:0]
Baud Rate Divisor (BD)
0 0 0
1
0 0 1
2
0 1 0
4
0 1 1
8
1 0 0
16
1 0 1
32
1 1 0
64
1 1 1
128
14.8.8 ESCI Prescaler Register
The ESCI prescaler register (SCPSC) together with the ESCI baud rate register selects the baud rate for
both the receiver and the transmitter.
NOTE
There are two prescalers available to adjust the baud rate. One in the ESCI
baud rate register and one in the ESCI prescaler register.
Address:
Read:
Write:
Reset:
$0009
Bit 7
6
5
4
3
2
1
Bit 0
PDS2
PDS1
PDS0
PSSB4
PSSB3
PSSB2
PSSB1
PSSB0
0
0
0
0
0
0
0
0
Figure 14-18. ESCI Prescaler Register (SCPSC)
MC68HC908GR16A Data Sheet, Rev. 1.0
166
Freescale Semiconductor
I/O Registers
PDS2–PDS0 — Prescaler Divisor Select Bits
These read/write bits select the prescaler divisor as shown in Table 14-10. Reset clears PDS2–PDS0.
NOTE
The setting of ‘000’ will bypass not only this prescaler but also the prescaler
divisor fine adjust (PDFA). It is not recommended to bypass the prescaler
while ENSCI is set, because the switching is not glitch free.
Table 14-10. ESCI Prescaler Division Ratio
PS[2:1:0]
Prescaler Divisor (PD)
0 0 0
Bypass this prescaler
0 0 1
2
0 1 0
3
0 1 1
4
1 0 0
5
1 0 1
6
1 1 0
7
1 1 1
8
PSSB4–PSSB0 — Clock Insertion Select Bits
These read/write bits select the number of clocks inserted in each 32 output cycle frame to achieve
more timing resolution on the average prescaler frequency as shown in Table 14-11. Reset clears
PSSB4–PSSB0.
Table 14-11. ESCI Prescaler Divisor Fine Adjust
PSSB[4:3:2:1:0]
Prescaler Divisor Fine Adjust (PDFA)
0 0 0 0 0
0/32 = 0
0 0 0 0 1
1/32 = 0.03125
0 0 0 1 0
2/32 = 0.0625
0 0 0 1 1
3/32 = 0.09375
0 0 1 0 0
4/32 = 0.125
0 0 1 0 1
5/32 = 0.15625
0 0 1 1 0
6/32 = 0.1875
0 0 1 1 1
7/32 = 0.21875
0 1 0 0 0
8/32 = 0.25
0 1 0 0 1
9/32 = 0.28125
0 1 0 1 0
10/32 = 0.3125
0 1 0 1 1
11/32 = 0.34375
0 1 1 0 0
12/32 = 0.375
0 1 1 0 1
13/32 = 0.40625
0 1 1 1 0
14/32 = 0.4375
0 1 1 1 1
15/32 = 0.46875
Continued on next page
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
167
Enhanced Serial Communications Interface (ESCI) Module
Table 14-11. ESCI Prescaler Divisor Fine Adjust (Continued)
PSSB[4:3:2:1:0]
Prescaler Divisor Fine Adjust (PDFA)
1 0 0 0 0
16/32 = 0.5
1 0 0 0 1
17/32 = 0.53125
1 0 0 1 0
18/32 = 0.5625
1 0 0 1 1
19/32 = 0.59375
1 0 1 0 0
20/32 = 0.625
1 0 1 0 1
21/32 = 0.65625
1 0 1 1 0
22/32 = 0.6875
1 0 1 1 1
23/32 = 0.71875
1 1 0 0 0
24/32 = 0.75
1 1 0 0 1
25/32 = 0.78125
1 1 0 1 0
26/32 = 0.8125
1 1 0 1 1
27/32 = 0.84375
1 1 1 0 0
28/32 = 0.875
1 1 1 0 1
29/32 = 0.90625
1 1 1 1 0
30/32 = 0.9375
1 1 1 1 1
31/32 = 0.96875
Use the following formula to calculate the ESCI baud rate:
Baud rate =
Frequency of the SCI clock source
64 x BPD x BD x (PD + PDFA)
where:
Frequency of the SCI clock source = fBus or CGMXCLK (selected by
ESCIBDSRC in the CONFIG2 register)
BPD = Baud rate register prescaler divisor
BD = Baud rate divisor
PD = Prescaler divisor
PDFA = Prescaler divisor fine adjust
Table 14-12 shows the ESCI baud rates that can be generated with a 4.9152-MHz bus frequency.
MC68HC908GR16A Data Sheet, Rev. 1.0
168
Freescale Semiconductor
I/O Registers
Table 14-12. ESCI Baud Rate Selection Examples
PS[2:1:0]
PSSB[4:3:2:1:0]
SCP[1:0]
Prescaler
Divisor
(BPD)
SCR[2:1:0]
Baud Rate
Divisor
(BD)
0 0 0
X X X X X
0 0
1
0 0 0
1
76,800
1 1 1
0 0 0 0 0
0 0
1
0 0 0
1
9600
1 1 1
0 0 0 0 1
0 0
1
0 0 0
1
9562.65
1 1 1
0 0 0 1 0
0 0
1
0 0 0
1
9525.58
1 1 1
1 1 1 1 1
0 0
1
0 0 0
1
8563.07
0 0 0
X X X X X
0 0
1
0 0 1
2
38,400
0 0 0
X X X X X
0 0
1
0 1 0
4
19,200
0 0 0
X X X X X
0 0
1
0 1 1
8
9600
0 0 0
X X X X X
0 0
1
1 0 0
16
4800
0 0 0
X X X X X
0 0
1
1 0 1
32
2400
0 0 0
X X X X X
0 0
1
1 1 0
64
1200
0 0 0
X X X X X
0 0
1
1 1 1
128
600
0 0 0
X X X X X
0 1
3
0 0 0
1
25,600
0 0 0
X X X X X
0 1
3
0 0 1
2
12,800
0 0 0
X X X X X
0 1
3
0 1 0
4
6400
0 0 0
X X X X X
0 1
3
0 1 1
8
3200
0 0 0
X X X X X
0 1
3
1 0 0
16
1600
0 0 0
X X X X X
0 1
3
1 0 1
32
800
0 0 0
X X X X X
0 1
3
1 1 0
64
400
0 0 0
X X X X X
0 1
3
1 1 1
128
200
0 0 0
X X X X X
1 0
4
0 0 0
1
19,200
0 0 0
X X X X X
1 0
4
0 0 1
2
9600
0 0 0
X X X X X
1 0
4
0 1 0
4
4800
0 0 0
X X X X X
1 0
4
0 1 1
8
2400
0 0 0
X X X X X
1 0
4
1 0 0
16
1200
0 0 0
X X X X X
1 0
4
1 0 1
32
600
0 0 0
X X X X X
1 0
4
1 1 0
64
300
0 0 0
X X X X X
1 0
4
1 1 1
128
150
0 0 0
X X X X X
1 1
13
0 0 0
1
5908
0 0 0
X X X X X
1 1
13
0 0 1
2
2954
0 0 0
X X X X X
1 1
13
0 1 0
4
1477
0 0 0
X X X X X
1 1
13
0 1 1
8
739
0 0 0
X X X X X
1 1
13
1 0 0
16
369
0 0 0
X X X X X
1 1
13
1 0 1
32
185
0 0 0
X X X X X
1 1
13
1 1 0
64
92
0 0 0
X X X X X
1 1
13
1 1 1
128
46
Baud Rate
(fBus= 4.9152 MHz)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
169
Enhanced Serial Communications Interface (ESCI) Module
14.9 ESCI Arbiter
The ESCI module comprises an arbiter module designed to support software for communication tasks as
bus arbitration, baud rate recovery and break time detection. The arbiter module consists of an 9-bit
counter with 1-bit overflow and control logic. The CPU can control operation mode via the ESCI arbiter
control register (SCIACTL).
14.9.1 ESCI Arbiter Control Register
Address:
$000A
Bit 7
Read:
Write:
Reset:
AM1
6
ALOST
0
0
5
4
AM0
ACLK
0
0
3
2
1
Bit 0
AFIN
ARUN
AROVFL
ARD8
0
0
0
0
= Unimplemented
Figure 14-19. ESCI Arbiter Control Register (SCIACTL)
AM1 and AM0 — Arbiter Mode Select Bits
These read/write bits select the mode of the arbiter module as shown in
Table 14-13. Reset clears AM1 and AM0.
Table 14-13. ESCI Arbiter Selectable Modes
AM[1:0]
ESCI Arbiter Mode
0 0
Idle / counter reset
0 1
Bit time measurement
1 0
Bus arbitration
1 1
Reserved / do not use
ALOST — Arbitration Lost Flag
This read-only bit indicates loss of arbitration. Clear ALOST by writing a 0 to AM1. Reset clears
ALOST.
ACLK — Arbiter Counter Clock Select Bit
This read/write bit selects the arbiter counter clock source. Reset clears ACLK.
1 = Arbiter counter is clocked with one half of the ESCI input clock generated by the ESCI prescaler
0 = Arbiter counter is clocked with the bus clock divided by four
NOTE
For ACLK = 1, the arbiter input clock is driven from the ESCI prescaler. The
prescaler can be clocked by either the bus clock or CGMXCLK depending
on the state of the ESCIBDSRC bit in CONFIG2.
AFIN— Arbiter Bit Time Measurement Finish Flag
This read-only bit indicates bit time measurement has finished. Clear AFIN by writing any value to
SCIACTL. Reset clears AFIN.
1 = Bit time measurement has finished
0 = Bit time measurement not yet finished
ARUN— Arbiter Counter Running Flag
This read-only bit indicates the arbiter counter is running. Reset clears ARUN.
1 = Arbiter counter running
0 = Arbiter counter stopped
MC68HC908GR16A Data Sheet, Rev. 1.0
170
Freescale Semiconductor
ESCI Arbiter
AROVFL— Arbiter Counter Overflow Bit
This read-only bit indicates an arbiter counter overflow. Clear AROVFL by writing any value to
SCIACTL. Writing 0s to AM1 and AM0 resets the counter keeps it in this idle state. Reset clears
AROVFL.
1 = Arbiter counter overflow has occurred
0 = No arbiter counter overflow has occurred
ARD8— Arbiter Counter MSB
This read-only bit is the MSB of the 9-bit arbiter counter. Clear ARD8 by writing any value to SCIACTL.
Reset clears ARD8.
14.9.2 ESCI Arbiter Data Register
Address: $000B
Read:
Bit 7
6
5
4
3
2
1
Bit 0
ARD7
ARD6
ARD5
ARD4
ARD3
ARD2
ARD1
ARD0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 14-20. ESCI Arbiter Data Register (SCIADAT)
ARD7–ARD0 — Arbiter Least Significant Counter Bits
These read-only bits are the eight LSBs of the 9-bit arbiter counter. Clear ARD7–ARD0 by writing any
value to SCIACTL. Writing 0s to AM1 and AM0 permanently resets the counter and keeps it in this idle
state. Reset clears ARD7–ARD0.
14.9.3 Bit Time Measurement
Two bit time measurement modes, described here, are available according to the state of ACLK.
1. ACLK = 0 — The counter is clocked with one half of the bus clock. The counter is started when a
falling edge on the RxD pin is detected. The counter will be stopped on the next falling edge. ARUN
is set while the counter is running, AFIN is set on the second falling edge on RxD (for instance, the
counter is stopped). This mode is used to recover the received baud rate. See Figure 14-21.
2. ACLK = 1 — The counter is clocked with one half of the ESCI input clock generated by the ESCI
prescaler. The counter is started when a 0 is detected on RxD (see Figure 14-22). A 0 on RxD on
enabling the bit time measurement with ACLK = 1 leads to immediate start of the counter (see
Figure 14-23). The counter will be stopped on the next rising edge of RxD. This mode is used to
measure the length of a received break.
14.9.4 Arbitration Mode
If AM[1:0] is set to 10, the arbiter module operates in arbitration mode. On every rising edge of SCI_TxD
(output of the ESCI module, internal chip signal), the counter is started. When the counter reaches $38
(ACLK = 0) or $08 (ACLK = 1), RxD is statically sensed. If in this case, RxD is sensed low (for example,
another bus is driving the bus dominant) ALOST is set. As long as ALOST is set, the TxD pin is forced
to 1, resulting in a seized transmission.
If SCI_TxD senses a 0 without having sensed a 0 before on RxD, the counter will be reset, arbitration
operation will be restarted after the next rising edge of SCI_TxD.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
171
Enhanced Serial Communications Interface (ESCI) Module
MEASURED TIME
CPU READS RESULT
OUT OF SCIADAT
COUNTER STOPS,
AFIN = 1
COUNTER STARTS,
ARUN = 1
CPU WRITES SCIACTL
WITH $20
RXD
Figure 14-21. Bit Time Measurement with ACLK = 0
MEASURED TIME
CPU READS RESULT OUT
OF SCIADAT
COUNTER STOPS, AFIN = 1
CPU WRITES SCIACTL WITH $30
COUNTER STARTS, ARUN = 1
RXD
Figure 14-22. Bit Time Measurement with ACLK = 1, Scenario A
MEASURED TIME
CPU READS RESULT
OUT OF SCIADAT
COUNTER STOPS,
AFIN = 1
COUNTER STARTS,
ARUN = 1
CPU WRITES SCIACTL
WITH $30
RXD
Figure 14-23. Bit Time Measurement with ACLK = 1, Scenario B
MC68HC908GR16A Data Sheet, Rev. 1.0
172
Freescale Semiconductor
Chapter 15
System Integration Module (SIM)
15.1 Introduction
This section describes the system integration module (SIM). Together with the central processor unit
(CPU), the SIM controls all microcontroller unit (MCU) activities. A block diagram of the SIM is shown in
Figure 15-1. Table 15-1 is a summary of the SIM input/output (I/O) registers. The SIM is a system state
controller that coordinates CPU and exception timing.
MODULE STOP
MODULE WAIT
CPU STOP (FROM CPU)
CPU WAIT (FROM CPU)
STOP/WAIT
CONTROL
SIMOSCEN (TO CGM)
SIM
COUNTER
CGMXCLK (FROM CGM)
CGMOUT (FROM CGM)
÷2
CLOCK
CONTROL
VDD
CLOCK GENERATORS
INTERNAL
PULLUP
DEVICE
RESET
PIN LOGIC
INTERNAL CLOCKS
FORCED MONITOR MODE ENTRY
LVI (FROM LVI MODULE)
POR CONTROL
MASTER
RESET
CONTROL
RESET PIN CONTROL
SIM RESET STATUS REGISTER
ILLEGAL OPCODE (FROM CPU)
ILLEGAL ADDRESS (FROM ADDRESS
MAP DECODERS)
COP (FROM COP MODULE)
RESET
INTERRUPT CONTROL
AND PRIORITY DECODE
INTERRUPT SOURCES
CPU INTERFACE
Figure 15-1. SIM Block Diagram
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
173
System Integration Module (SIM)
The SIM is responsible for:
• Bus clock generation and control for CPU and peripherals:
– Stop/wait/reset/break entry and recovery
– Internal clock control
• Master reset control, including power-on reset (POR) and computer operating properly (COP)
timeout
• Interrupt arbitration
Table 15-1 shows the internal signal names used in this section.
Table 15-1. Signal Name Conventions
Signal Name
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
IDB
PORRST
Addr.
$FE00
$FE01
$FE03
$FE04
$FE05
$FE06
Description
Internal address bus
Internal data bus
Signal from the power-on reset module to the SIM
IRST
Internal reset signal
R/W
Read/write signal
Register Name
SIM Break Status Register Read:
(SBSR) Write:
See page 187. Reset:
SIM Reset Status Register Read:
(SRSR) Write:
See page 188. POR:
SIM Break Flag Control Read:
Register (SBFCR) Write:
See page 189. Reset:
Interrupt Status Read:
Register 1 (INT1) Write:
See page 183. Reset:
Interrupt Status Read:
Register 2 (INT2) Write:
See page 184. Reset:
Interrupt Status Read:
Register 3 (INT3) Write:
See page 184. Reset:
Bit 7
6
5
4
3
2
R
R
R
R
R
R
0
0
0
0
0
1. Writing a 0 clears SBSW.
Bit 0
0
1
SBSW
Note(1)
0
R
0
POR
PIN
COP
ILOP
ILAD
MODRST
LVI
0
1
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
IF3
R
0
IF11
R
0
IF19
R
0
R
IF2
R
0
IF10
R
0
IF18
R
0
= Reserved
IF1
R
0
IF9
R
0
IF17
R
0
0
R
0
IF8
R
0
IF16
R
0
0
R
0
IF7
R
0
IF15
R
0
0
IF6
R
0
IF14
R
0
0
R
0
IF5
IF4
R
R
0
0
IF13
IF12
R
R
0
0
0
IF20
R
R
0
0
= Unimplemented
Figure 15-2. SIM I/O Register Summary
MC68HC908GR16A Data Sheet, Rev. 1.0
174
Freescale Semiconductor
SIM Bus Clock Control and Generation
15.2 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and peripherals on the MCU. The
system clocks are generated from an incoming clock, CGMOUT, as shown in Figure 15-3. This clock
originates from either an external oscillator or from the on-chip PLL.
15.2.1 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.
15.2.2 Clock Startup 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 completed. The RST pin is driven low by the SIM during this entire period. The bus clocks
start upon completion of the timeout.
OSC2
OSCILLATOR (OSC)
CGMXCLK
OSC1
TO TBM,TIM1,TIM2, ADC
SIM
OSCENINSTOP
FROM
CONFIG2
SIM COUNTER
CGMRCLK
CGMOUT
÷2
PHASE-LOCKED LOOP (PLL)
BUS CLOCK
GENERATORS
SIMOSCEN
IT12
TO REST
OF CHIP
IT23
TO REST
OF CHIP
Figure 15-3. System Clock Signals
15.2.3 Clocks in Stop Mode and Wait Mode
Upon exit from stop mode by an interrupt 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 15.6.2 Stop Mode.
In wait mode, the CPU clocks are inactive. The SIM also produces two sets of clocks for other modules.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
175
System Integration Module (SIM)
15.3 Reset and System Initialization
The MCU has these reset sources:
• Power-on reset module (POR)
• External reset pin (RST)
• Computer operating properly module (COP)
• Low-voltage inhibit module (LVI)
• Illegal opcode
• Illegal address
• Forced monitor mode entry reset (MODRST)
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 15.4 SIM Counter), but an external reset does not. Each of
the resets sets a corresponding bit in the SIM reset status register (SRSR). See 15.7 SIM Registers.
15.3.1 External Pin Reset
The RST pin circuit includes an internal pullup device. Pulling the asynchronous RST pin low halts all
processing. The PIN bit of the SIM reset status register (SRSR) is set as long as RST is held low for a
minimum of 67 CGMXCLK cycles, assuming that neither the POR nor the LVI was the source of the reset.
See Table 15-2 for details. Figure 15-4 shows the relative timing.
CGMOUT
RST
IAB
VECT H
PC
VECT L
Figure 15-4. External Reset Timing
15.3.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 CGMXCLK cycles to allow resetting of
external peripherals. The internal reset continues to be asserted for an additional 32 cycles at which point
the reset vector will be fetched. See Figure 15-5. An internal reset can be caused by an illegal address,
illegal opcode, COP timeout, LVI, or POR. See Figure 15-6.
NOTE
For LVI or POR resets, the SIM cycles through 4096 + 32 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 shown in Figure 15-5.
The COP reset is asynchronous to the bus clock.
The active reset feature allows the part to issue a reset to peripherals and other chips within a system
built around the MCU.
MC68HC908GR16A Data Sheet, Rev. 1.0
176
Freescale Semiconductor
Reset and System Initialization
IRST
RST PULLED LOW BY MCU
RST
32 CYCLES
32 CYCLES
CGMXCLK
IAB
VECTOR HIGH
Figure 15-5. Internal Reset Timing
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
POR
MODRST
INTERNAL RESET
Figure 15-6. Sources of Internal Reset
Table 15-2. Reset Recovery Type
Reset Recovery Type
Actual Number of Cycles
POR/LVI
4163 (4096 + 64 + 3)
All others
67 (64 + 3)
15.3.2.1 Power-On Reset
When power is first applied to the MCU, the power-on reset module (POR) generates a pulse to indicate
that power-on has occurred. The external reset pin (RST) is held low while the SIM counter counts out
4096 + 32 CGMXCLK cycles. Thirty-two CGMXCLK cycles later, the CPU and memories are released
from reset to allow the reset vector sequence to occur.
At power-on, these events occur:
• A POR pulse is generated.
• The internal reset signal is asserted.
• The SIM enables CGMOUT.
• Internal clocks to the CPU and modules are held inactive for 4096 CGMXCLK cycles to allow
stabilization of the oscillator.
• The RST pin is driven low during the oscillator stabilization time.
• The POR bit of the SIM reset status register (SRSR) is set and all other bits in the register are
cleared.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
177
System Integration Module (SIM)
OSC1
PORRST
4096
CYCLES
32
CYCLES
32
CYCLES
CGMXCLK
CGMOUT
RST
IRST
$FFFE
IAB
$FFFF
Figure 15-7. POR Recovery
15.3.2.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of the COP counter causes an
internal reset and sets the COP bit in the SIM reset status register (SRSR). The SIM actively pulls down
the RST pin for all internal reset sources.
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.
15.3.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP
bit in the SIM reset status register (SRSR) and causes a reset.
If the stop enable bit, STOP, in the CONFIG1 register is 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.
15.3.2.4 Illegal Address Reset
An opcode fetch from an unmapped address generates an illegal address reset. The SIM verifies that the
CPU is fetching an opcode prior to asserting the ILAD bit in the SIM reset status register (SRSR) and
resetting the MCU. A data fetch from an unmapped address does not generate a reset. The SIM actively
pulls down the RST pin for all internal reset sources.
15.3.2.5 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit module (LVI) asserts its output to the SIM when the VDD voltage falls to the VTRIPF
voltage. The LVI bit in the SIM reset status register (SRSR) is set, and the external reset pin (RST) is held
MC68HC908GR16A Data Sheet, Rev. 1.0
178
Freescale Semiconductor
SIM Counter
low while the SIM counter counts out 4096 + 32 CGMXCLK cycles. Thirty-two 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.
15.3.2.6 Monitor Mode Entry Module Reset (MODRST)
The monitor mode entry module reset (MODRST) asserts its output to the SIM when monitor mode is
entered in the condition where the reset vectors are erased ($FF) (see 19.3.1.1 Normal Monitor Mode).
When MODRST gets asserted, an internal reset occurs. The SIM actively pulls down the RST pin for all
internal reset sources.
15.4 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 module (COP). The SIM counter is 12 bits long.
15.4.1 SIM Counter During Power-On Reset
The power-on reset module (POR) detects power applied to the MCU. At power-on, the POR circuit
asserts the signal PORRST. Once the SIM is initialized, it enables the clock generation module (CGM) to
drive the bus clock state machine.
15.4.2 SIM Counter During Stop Mode Recovery
The SIM counter also is used for stop mode recovery. The STOP instruction clears the SIM counter. After
an interrupt, break, or reset, the SIM senses the state of the short stop recovery bit, SSREC, in the
CONFIG1 register. If the SSREC bit is a 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 crystals with
the OSCENINSTOP bit set. External crystal applications should use the full stop recovery time, SSREC
cleared, if the OSCENINSTOP bit is cleared.
15.4.3 SIM Counter and Reset States
External reset has no effect on the SIM counter. See 15.6.2 Stop Mode for details. The SIM counter is
free-running after all reset states. See 15.3.2 Active Resets from Internal Sources for counter control and
internal reset recovery sequences.
15.5 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
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
179
System Integration Module (SIM)
15.5.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register contents on the stack and sets the
interrupt mask (I bit) to prevent additional interrupts. At the end of an interrupt, the RTI instruction recovers
the CPU register contents from the stack so that normal processing can resume. Figure 15-8 shows
interrupt entry timing. Figure 15-9 shows interrupt recovery timing.
MODULE
INTERRUPT
I BIT
IAB
IDB
DUMMY
SP
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 15-8. Interrupt Entry Timing
MODULE
INTERRUPT
I BIT
IAB
IDB
SP – 4
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 15-9. Interrupt Recovery Timing
MC68HC908GR16A Data Sheet, Rev. 1.0
180
Freescale Semiconductor
Exception Control
Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The
arbitration result is a constant that the CPU uses to determine which vector to fetch. Once an interrupt is
latched by the SIM, no other interrupt can take precedence, regardless of priority, until the latched
interrupt is serviced (or the I bit is cleared). See Figure 15-10.
FROM RESET
BREAK
I BIT
SET?
INTERRUPT?
YES
NO
YES
I BIT SET?
NO
IRQ
INTERRUPT?
YES
NO
AS MANY INTERRUPTS
AS EXIST ON CHIP
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION?
YES
NO
RTI
INSTRUCTION?
YES
UNSTACK CPU REGISTERS
NO
EXECUTE INSTRUCTION
Figure 15-10. Interrupt Processing
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
181
System Integration Module (SIM)
15.5.1.1 Hardware Interrupts
A hardware interrupt does not stop the current instruction. Processing of a hardware interrupt begins after
completion of the current instruction. When the current instruction is complete, the SIM checks all pending
hardware interrupts. If interrupts are not masked (I bit clear in the condition code register) and if the
corresponding interrupt enable bit is set, the SIM proceeds with interrupt processing; otherwise, the next
instruction is fetched and executed.
If more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is
serviced first. Figure 15-11 demonstrates what happens when two interrupts are pending. If an interrupt
is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the
LDA instruction is executed.
CLI
BACKGROUND
ROUTINE
LDA #$FF
INT1
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 15-11. 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.
15.5.1.2 SWI Instruction
The SWI instruction is a non-maskable instruction that causes an interrupt regardless of the state of the
interrupt mask (I bit) in the condition code register.
NOTE
A software interrupt pushes PC onto the stack. A software interrupt does
not push PC – 1, as a hardware interrupt does.
MC68HC908GR16A Data Sheet, Rev. 1.0
182
Freescale Semiconductor
Exception Control
15.5.1.3 Interrupt Status Registers
The flags in the interrupt status registers identify maskable interrupt sources.
Table 15-3 summarizes the interrupt sources and the interrupt status register flags that they set. The
interrupt status registers can be useful for debugging.
Table 15-3. Interrupt Sources
Priority
Interrupt Source
Interrupt Status
Register Flag
Highest
Reset
—
SWI instruction
—
IRQ pin
I1
CGM clock monitor
I2
TIM1 channel 0
I3
TIM1 channel 1
I4
TIM1 overflow
I5
TIM2 channel 0
I6
TIM2 channel 1
I7
TIM2 overflow
I8
SPI receiver full
I9
SPI transmitter empty
I10
SCI receive error
I11
SCI receive
I12
SCI transmit
I13
Keyboard
I14
ADC conversion complete
I15
Timebase module
I16
Lowest
Interrupt Status Register 1
Address:
$FE04
Bit 7
6
5
4
3
2
1
Bit 0
Read:
I6
I5
I4
I3
I2
I1
0
0
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 15-12. Interrupt Status Register 1 (INT1)
I6–I1 — Interrupt Flags 1–6
These flags indicate the presence of interrupt requests from the sources shown in Table 15-3.
1 = Interrupt request present
0 = No interrupt request present
Bit 0 and Bit 1 — Always read 0
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
183
System Integration Module (SIM)
Interrupt Status Register 2
Address:
$FE05
Bit 7
6
5
4
3
2
1
Bit 0
Read:
I14
I13
I12
I11
I10
I9
I8
I7
Write:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
= Reserved
Reset:
Figure 15-13. Interrupt Status Register 2 (INT2)
I14–I7 — Interrupt Flags 14–7
These flags indicate the presence of interrupt requests from the sources shown in Table 15-3.
1 = Interrupt request present
0 = No interrupt request present
Interrupt Status Register 3
Address:
$FE06
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
I20
I19
I18
I17
I16
I15
Write:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
= Reserved
Reset:
Figure 15-14. Interrupt Status Register 3 (INT3)
Bits 7–6 — Always read 0
I20–I15 — Interrupt Flags 20–15
These flags indicate the presence of an interrupt request from the source shown in Table 15-3.
1 = Interrupt request present
0 = No interrupt request present
15.5.2 Reset
All reset sources always have equal and highest priority and cannot be arbitrated.
15.5.3 Break Interrupts
The break module can stop normal program flow at a software-programmable break point by asserting its
break interrupt output (see Chapter 18 Timer Interface Module (TIM1 and TIM2)). 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.
15.5.4 Status Flag Protection in Break Mode
The SIM controls whether status flags contained in other modules can be cleared during break mode. The
user can select whether flags are protected from being cleared by properly initializing the break clear flag
enable bit (BCFE) in the SIM break flag control register (SBFCR).
MC68HC908GR16A Data Sheet, Rev. 1.0
184
Freescale Semiconductor
Low-Power Modes
Protecting flags in break mode ensures that set flags will not be cleared while in break mode. This
protection allows registers to be freely read and written during break mode without losing status flag
information.
Setting the BCFE bit enables the clearing mechanisms. Once cleared in break mode, a flag remains
cleared even when break mode is exited. Status flags with a 2-step clearing mechanism — for example,
a read of one register followed by the read or write of another — are protected, even when the first step
is accomplished prior to entering break mode. Upon leaving break mode, execution of the second step
will clear the flag as normal.
15.6 Low-Power Modes
Executing the WAIT or STOP instruction puts the MCU in a low power- consumption mode for standby
situations. The SIM holds the CPU in a non-clocked state. The operation of each of these modes is
described in the following subsections. Both STOP and WAIT clear the interrupt mask (I) in the condition
code register, allowing interrupts to occur.
15.6.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks continue to run. Figure 15-15 shows
the timing for wait mode entry.
A module that is active during wait mode can wakeup the CPU with an interrupt if the interrupt is enabled.
Stacking for the interrupt begins one cycle after the WAIT instruction during which the interrupt occurred.
In wait mode, the CPU clocks are inactive. Refer to the wait mode subsection of each module to see if the
module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode.
Wait mode also can be exited by a reset (or break in emulation mode). 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 CONFIG1 register is 0, then the computer operating properly module (COP) is enabled and
remains active in wait mode.
IAB
IDB
WAIT ADDR
WAIT ADDR + 1
PREVIOUS DATA
NEXT OPCODE
SAME
SAME
SAME
SAME
R/W
Note:
Previous data can be operand data or the WAIT opcode, depending on the
last instruction.
Figure 15-15. Wait Mode Entry Timing
Figure 15-16 and Figure 15-17 show the timing for WAIT recovery.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
185
System Integration Module (SIM)
IAB
$6E0B
$A6
IDB
$A6
$6E0C
$A6
$00FF
$01
$0B
$00FE
$00FD
$00FC
$6E
EXITSTOPWAIT
Note: EXITSTOPWAIT = RST pin or CPU interrupt
Figure 15-16. Wait Recovery from Interrupt
32
CYCLES
IAB
IDB
$6E0B
$A6
$A6
32
CYCLES
RSTVCT H
RSTVCTL
$A6
RST
CGMXCLK
Figure 15-17. Wait Recovery from Internal Reset
15.6.2 Stop Mode
In stop mode, the SIM counter is reset and the system clocks are disabled. An interrupt request from a
module can cause an exit from stop mode. Stacking for interrupts begins after the selected stop recovery
time has elapsed. Reset 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 CONFIG1 register.
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 startup times from stop
mode.
NOTE
External crystal applications should use the full stop recovery time by
clearing the SSREC bit unless the OSCENINSTOP bit is set in CONFIG2.
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 15-18 shows stop mode entry timing.
Figure 15-19 shows stop mode recovery time from interrupt.
NOTE
To minimize stop current, all pins configured as inputs should be driven to
a 1 or 0.
MC68HC908GR16A Data Sheet, Rev. 1.0
186
Freescale Semiconductor
SIM Registers
CPUSTOP
IAB
STOP ADDR + 1
STOP ADDR
IDB
PREVIOUS DATA
SAME
SAME
NEXT OPCODE
SAME
SAME
R/W
Note: Previous data can be operand data or the STOP opcode, depending
on the last instruction.
Figure 15-18. Stop Mode Entry Timing
STOP RECOVERY PERIOD
CGMXCLK
INT/BREAK
IAB
STOP + 2
STOP +1
STOP + 2
SP
SP – 1
SP – 2
SP – 3
Figure 15-19. Stop Mode Recovery from Interrupt
15.7 SIM Registers
The SIM has three memory-mapped registers. Table 15-4 shows the mapping of these registers.
Table 15-4. SIM Registers
Address
Register
Access Mode
$FE00
SBSR
User
$FE01
SRSR
User
$FE03
SBFCR
User
15.7.1 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait
mode. This register is only used in emulation mode.
Address:
$FE00
Bit 7
Read:
Write:
Reset:
6
5
4
3
2
R
R
R
R
R
R
0
0
0
0
0
0
R
= Reserved
1
SBSW
Note(1)
0
Bit 0
R
0
1. Writing a 0 clears SBSW.
Figure 15-20. Break Status Register (SBSR)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
187
System Integration Module (SIM)
SBSW — SIM Break Stop/Wait
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.
1 = Wait mode was exited by break interrupt.
0 = Wait mode was not exited by break interrupt.
15.7.2 SIM Reset Status Register
The SRSR register contains flags that show the source of the last reset. The status register will
automatically clear after reading SRSR. A power-on reset sets the POR bit and clears all other bits in the
register. All other reset sources set the individual flag bits but do not clear the register. More than one
reset source can be flagged at any time depending on the conditions at the time of the internal or external
reset. For example, the POR and LVI bit can both be set if the power supply has a slow rise time.
Address:
Read:
$FE01
Bit 7
6
5
4
3
2
1
Bit 0
POR
PIN
COP
ILOP
ILAD
MODRST
LVI
0
1
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 15-21. SIM Reset Status Register (SRSR)
POR — Power-On Reset Bit
1 = Last reset caused by POR circuit
0 = Read of SRSR
PIN — External Reset Bit
1 = Last reset caused by external reset pin (RST)
0 = POR or read of SRSR
COP — Computer Operating Properly Reset Bit
1 = Last reset caused by COP counter
0 = POR or read of SRSR
ILOP — Illegal Opcode Reset Bit
1 = Last reset caused by an illegal opcode
0 = POR or read of SRSR
ILAD — Illegal Address Reset Bit (opcode fetches only)
1 = Last reset caused by an opcode fetch from an illegal address
0 = POR or read of SRSR
MODRST — Monitor Mode Entry Module Reset Bit
1 = Last reset caused by monitor mode entry when vector locations $FFFE and $FFFF are $FF after
POR while IRQ ≠ VTST
0 = POR or read of SRSR
LVI — Low-Voltage Inhibit Reset Bit
1 = Last reset caused by the LVI circuit
0 = POR or read of SRSR
MC68HC908GR16A Data Sheet, Rev. 1.0
188
Freescale Semiconductor
SIM Registers
15.7.3 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 15-22. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing status registers while the MCU is
in a break state. To clear status bits during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
189
System Integration Module (SIM)
MC68HC908GR16A Data Sheet, Rev. 1.0
190
Freescale Semiconductor
Chapter 16
Serial Peripheral Interface (SPI) Module
16.1 Introduction
This section describes the serial peripheral interface (SPI) module, which allows full-duplex, synchronous,
serial communications with peripheral devices.
The text that follows describes the SPI. The SPI I/O pin names are SS (slave select), SPSCK (SPI serial
clock), MOSI (master out slave in), and MISO (master in/slave out). The SPI shares four I/O pins with four
parallel I/O ports.
16.2 Features
Features of the SPI module include:
• 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
• I/O (input/output) port bit(s) software configurable with pullup device(s) if configured as input port
bit(s)
16.3 Functional Description
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 interrupt
driven.
If a port bit is configured for input, then an internal pullup device may be enabled for that port bit.
The following paragraphs describe the operation of the SPI module. Refer to Figure 16-3 for a summary
of the SPI I/O registers.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
191
Serial Peripheral Interface (SPI) Module
INTERNAL BUS
DDRA
PORTA
PTB7/AD7
PTB6/AD6
PTB5/AD5
PTB4/AD4
PTB3/AD3
PTB2/AD2
PTB1/AD1
PTB0/AD0
PTC6(1)
PTC5(1)
PTC4(1), (2)
PTC3(1), (2)
PTC2(1), (2)
PTC1(1), (2)
PTC0(1), (2)
PTD7/T2CH1(1)
PTD6/T2CH0(1)
PTD5/T1CH1(1)
PTD4/T1CH0(1)
PTD3/SPSCK(1)
PTD2/MOSI(1)
PTD1/MISO(1)
PTD0/SS(1)
PTE5–PTE2
PTE1/RxD
PTE0/TxD
DDRB
SINGLE BREAKPOINT
BREAK MODULE
DUAL VOLTAGE
LOW-VOLTAGE INHIBIT
MODULE
USER FLASH — 15,872 BYTES
PTA7/KBD7–
PTA0/KBD0(1)
PORTB
CONTROL AND STATUS REGISTERS — 64 BYTES
PROGRAMMABLE TIMEBASE
MODULE
PORTC
ARITHMETIC/LOGIC
UNIT (ALU)
PORTD
CPU
REGISTERS
PORTE
M68HC08 CPU
USER RAM — 1024 BYTES
FLASH PROGRAMMING ROUTINES ROM — 406 BYTES
USER FLASH VECTOR SPACE — 36 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 1
DDRC
8-BIT KEYBOARD
INTERRUPT MODULE
MONITOR ROM — 350 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 2
CLOCK GENERATOR MODULE
PHASE LOCKED LOOP
COMPUTER OPERATING
PROPERLY MODULE
RST(3)
SYSTEM INTEGRATION
MODULE
IRQ(3)
SINGLE EXTERNAL
INTERRUPT MODULE
SERIAL PERIPHERAL
INTERFACE MODULE
MONITOR MODULE
VDDAD/VREFH
VSSAD/VREFL
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
POWER-ON RESET
MODULE
VDD
VSS
VDDA
VSSA
DDRD
CGMXFC
ENHANCED SERIAL
COMUNICATIONS
INTERFACE MODULE
1–8 MHz OSCILLATOR
DDRE
OSC1
OSC2
MEMORY MAP
MODULE
SECURITY
MODULE
CONFIGURATION
REGISTER 1–2
MODULE
POWER
MONITOR MODE ENTRY
MODULE
1. Ports are software configurable with pullup device if input port.
2. Higher current drive port pins
3. Pin contains integrated pullup device
Figure 16-1. Block Diagram Highlighting SPI Block and Pins
MC68HC908GR16A Data Sheet, Rev. 1.0
192
Freescale Semiconductor
Functional Description
INTERNAL BUS
TRANSMIT DATA REGISTER
SHIFT REGISTER
BUSCLK
7
6
5
4
3
2
1
MISO
0
÷2
MOSI
÷8
CLOCK
DIVIDER
RECEIVE DATA REGISTER
÷ 32
PIN
CONTROL
LOGIC
÷ 128
SPMSTR
SPE
CLOCK
SELECT
SPR1
SPSCK
M
CLOCK
LOGIC
S
SS
SPR0
SPMSTR
TRANSMITTER CPU INTERRUPT REQUEST
CPHA
CPOL
MODFEN
SPWOM
ERRIE
SPI
CONTROL
SPTIE
RECEIVER/ERROR CPU INTERRUPT REQUEST
SPRIE
SPE
SPRF
SPTE
OVRF
MODF
Figure 16-2. SPI Module Block Diagram
Addr.
$0010
Register Name
SPI Control Register Read:
(SPCR) Write:
See page 207. Reset:
$0011
SPI Status and Control Read:
Register (SPSCR) Write:
See page 208. Reset:
$0012
SPI Data Register Read:
(SPDR) Write:
See page 210. 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
R
= Reserved
= Unimplemented
Figure 16-3. SPI I/O Register Summary
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
193
Serial Peripheral Interface (SPI) Module
16.3.1 Master Mode
The SPI operates in master mode when the SPI master bit, SPMSTR, is set.
NOTE
In a multi-SPI system, 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 16.12.1 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 16-4.
MASTER MCU
SHIFT REGISTER
SLAVE MCU
MISO
MISO
MOSI
MOSI
SPSCK
BAUD RATE
GENERATOR
SS
SHIFT REGISTER
SPSCK
VDD
SS
Figure 16-4. Full-Duplex Master-Slave Connections
The SPR1 and SPR0 bits control the baud rate generator and determine the speed of the shift register.
(See 16.12.2 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 (SPDR)
clears SPTE.
16.3.2 Slave Mode
The SPI operates in slave mode when SPMSTR 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 low. SS must remain low until the transmission is complete. See 16.6.2 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
194
Freescale Semiconductor
Transmission Formats
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.
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 16.4 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.
16.4 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
multiple-master bus contention.
16.4.1 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.
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).
16.4.2 Transmission Format When CPHA = 0
Figure 16-5 shows an SPI transmission in which CPHA = 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
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
195
Serial Peripheral Interface (SPI) Module
input (SS) is low, 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 16.6.2 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 16-6.
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 16-5. Transmission Format (CPHA = 0)
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 16-6. 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.
16.4.3 Transmission Format When CPHA = 1
Figure 16-7 shows an SPI transmission in which CPHA = 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 low, 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
MC68HC908GR16A Data Sheet, Rev. 1.0
196
Freescale Semiconductor
Transmission Formats
pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. (See
16.6.2 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.
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.
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 16-7. Transmission Format (CPHA = 1)
16.4.4 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 16-8.) 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. 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 16-8. 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
197
Serial Peripheral Interface (SPI) Module
WRITE
TO SPDR
INITIATION DELAY
BUS
CLOCK
MOSI
MSB
BIT 6
BIT 5
SPSCK
CPHA = 1
SPSCK
CPHA = 0
SPSCK CYCLE
NUMBER
1
2
3
INITIATION DELAY FROM WRITE SPDR TO TRANSFER BEGIN
WRITE
TO SPDR
BUS
CLOCK
EARLIEST
LATEST
WRITE
TO SPDR
SPSCK = BUS CLOCK ÷ 2;
2 POSSIBLE START POINTS
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
SPSCK = BUS CLOCK ÷ 8;
8 POSSIBLE START POINTS
LATEST
SPSCK = BUS CLOCK ÷ 32;
32 POSSIBLE START POINTS
LATEST
SPSCK = BUS CLOCK ÷ 128;
128 POSSIBLE START POINTS
LATEST
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
BUS
CLOCK
EARLIEST
Figure 16-8. Transmission Start Delay (Master)
MC68HC908GR16A Data Sheet, Rev. 1.0
198
Freescale Semiconductor
Queuing Transmission Data
16.5 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 SPTE is high. Figure 16-9 shows the
timing associated with doing back-to-back transmissions with the SPI (SPSCK has CPHA: CPOL = 1:0).
WRITE TO SPDR
SPTE
1
3
2
8
5
10
SPSCK
CPHA:CPOL = 1:0
MOSI
MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT
6 5 4
6 5 4 3 2 1
6 5 4 3 2 1
BYTE 1
BYTE 2
BYTE 3
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 16-9. 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.
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. SPTE indicates when the next write can occur.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
199
Serial Peripheral Interface (SPI) Module
16.6 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.
16.6.1 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 16-5 and Figure 16-7.) 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 interrupts share the same CPU interrupt vector (see Figure 16-12.) 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 16-10 shows how it is possible to miss an overflow. The first part of Figure 16-10 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
7
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
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 16-10. Missed Read of Overflow Condition
MC68HC908GR16A Data Sheet, Rev. 1.0
200
Freescale Semiconductor
Error Conditions
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 16-11 illustrates this process. Generally, to avoid this second
SPSCR read, enable the OVRF to the CPU by setting the ERRIE bit.
BYTE 1
SPI RECEIVE
COMPLETE
BYTE 2
5
1
BYTE 3
7
BYTE 4
11
SPRF
OVRF
READ
SPSCR
2
READ
SPDR
4
3
1
BYTE 1 SETS SPRF BIT.
2
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
3
6
9
8
12
10
14
13
8
CPU READS BYTE 2 IN SPDR,
CLEARING SPRF BIT.
9
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
10 CPU READS BYTE 2 SPDR,
CLEARING OVRF BIT.
4
CPU READS SPSCR AGAIN
TO CHECK OVRF BIT.
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 16-11. Clearing SPRF When OVRF Interrupt Is Not Enabled
16.6.2 Mode Fault Error
Setting SPMSTR 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.
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 16-12.)
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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
201
Serial Peripheral Interface (SPI) Module
In a master SPI with the mode fault enable bit (MODFEN) set, the mode fault flag (MODF) is set if SS
goes low. A mode fault in a master SPI causes the following events to occur:
• 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.
NOTE
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 16.4 Transmission Formats.
NOTE
Setting the MODF flag does not clear the SPMSTR bit. SPMSTR 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.
NOTE
When CPHA = 0, a MODF occurs if a slave is selected (SS is low) and later
unselected (SS is high) even if no SPSCK is sent to that slave. This
happens because SS low 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), MODF 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 high 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.
16.7 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt requests. See Table 16-1.
MC68HC908GR16A Data Sheet, Rev. 1.0
202
Freescale Semiconductor
Interrupts
Table 16-1. 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)
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 SPRF to generate receiver CPU interrupt requests,
regardless of the state of SPE. See Figure 16-12.
The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error
CPU interrupt request.
SPTE
SPTIE
SPE
SPI TRANSMITTER
CPU INTERRUPT REQUEST
SPRIE
SPRF
SPI RECEIVER/ERROR
ERRIE
CPU INTERRUPT REQUEST
MODF
OVRF
Figure 16-12. SPI Interrupt Request Generation
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.
• The following sources in the SPI status and control register can generate CPU interrupt requests:
• SPI receiver full bit (SPRF) — SPRF 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) — SPTE 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
203
Serial Peripheral Interface (SPI) Module
16.8 Resetting the SPI
Any system reset completely resets the SPI. Partial resets occur whenever the SPI enable bit (SPE) is 0.
Whenever SPE is 0, 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.
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.
16.9 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
16.9.1 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 16.7 Interrupts.
16.9.2 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.
16.10 SPI During Break Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during
the break state. BCFE in the SIM break flag control register (SBFCR) enables software to clear status bits
during the break state. See Chapter 15 System Integration Module (SIM).
To allow software to clear status bits during a break interrupt, write a 1 to BCFE. If a status bit is cleared
during the break state, it remains cleared when the MCU exits the break state.
MC68HC908GR16A Data Sheet, Rev. 1.0
204
Freescale Semiconductor
I/O Signals
To protect status bits during the break state, write a 0 to BCFE. With BCFE at 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 0. After the break, doing the second step
clears the status bit.
Since the SPTE bit cannot be cleared during a break with BCFE 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 BCFE cleared has no effect.
16.11 I/O Signals
The SPI module has four I/O pins:
• MISO — Master input/slave output
• MOSI — Master output/slave input
• SPSCK — Serial clock
• SS — Slave select
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.
16.11.1 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 0 and its SS pin is low. To support a multiple-slave system,
a high on the SS pin puts the MISO pin in a high-impedance 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.
16.11.2 MOSI (Master Out/Slave In)
MOSI is one of the two SPI module pins that transmits serial data. In full-duplex 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.
16.11.3 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
205
Serial Peripheral Interface (SPI) Module
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.
16.11.4 SS (Slave Select)
The SS pin has various functions depending on the current state of the SPI. For an SPI configured as a
slave, SS is used to select a slave. For CPHA = 0, SS is used to define the start of a transmission. (See
16.4 Transmission Formats.) Since it is used to indicate the start of a transmission, 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 16-13.
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 16-13. 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 SS from creating a MODF error. See 16.12.2 SPI Status and Control Register.
NOTE
A high on the SS pin of a slave SPI puts the MISO pin in a high-impedance
state. The slave SPI ignores all incoming SPSCK clocks, even if it was
already in the middle of a transmission.
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 16.6.2 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 MODFEN is 0 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. When MODFEN is 1, SS 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 16-2.
Table 16-2. SPI Configuration
SPE
SPMSTR
MODFEN
SPI Configuration
Function of SS Pin
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
1. X = Don’t care
MC68HC908GR16A Data Sheet, Rev. 1.0
206
Freescale Semiconductor
I/O Registers
16.12 I/O Registers
Three registers control and monitor SPI operation:
• SPI control register (SPCR)
• SPI status and control register (SPSCR)
• SPI data register (SPDR)
16.12.1 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
R
= Reserved
Figure 16-14. 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
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 16-5 and Figure 16-7.) 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 16-5 and Figure 16-7.) 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 high between
bytes. (See Figure 16-13.) 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
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
207
Serial Peripheral Interface (SPI) Module
SPE — SPI Enable
This read/write bit enables the SPI module. Clearing SPE causes a partial reset of the SPI. (See 16.8
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
16.12.2 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 16-15. 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
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
MC68HC908GR16A Data Sheet, Rev. 1.0
208
Freescale Semiconductor
I/O Registers
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
MODFEN 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 MODF 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 SPTIE in the SPI control register is set
also.
NOTE
Do not write to the SPI data register unless SPTE is high.
During an SPTE CPU interrupt, the CPU clears SPTE bit writing to the transmit data register. Reset
sets the SPTE bit.
1 = Transmit data register empty
0 = Transmit data register not empty
MODFEN — Mode Fault Enable Bit
This read/write bit, when set, allows the MODF flag to be set. If the MODF flag is set, clearing MODFEN
does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is 0, then the SS
pin is available as a general-purpose I/O.
If the MODFEN bit is 1, then the SS is not available as a general-purpose 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 16.11.4 SS (Slave Select).
If the MODFEN bit is 0, 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 16.6.2 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 16-3. SPR1 and
SPR0 have no effect in slave mode. Reset clears SPR1 and SPR0.
Table 16-3. SPI Master Baud Rate Selection
SPR1 and SPR0
Baud Rate Divisor (BD)
00
2
01
8
10
32
11
128
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
209
Serial Peripheral Interface (SPI) Module
Use this formula to calculate the SPI baud rate:
Baud rate =
BUSCLK
BD
16.12.3 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 16-16. 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
210
Freescale Semiconductor
Chapter 17
Timebase Module (TBM)
17.1 Introduction
This section describes the timebase module (TBM). The TBM will generate periodic interrupts at user
selectable rates using a counter clocked by the external clock source. This TBM version uses 15 divider
stages, eight of which are user selectable. A configuration option bit to select an additional 128 divide of
the external clock source can be selected. See Chapter 5 Configuration Register (CONFIG)
17.2 Features
Features of the TBM module include:
• External clock or an additional divide-by-128 selected by configuration option bit as clock source
• Software configurable periodic interrupts with divide-by: 8, 16, 32, 64, 128, 2048, 8192, and 32768
taps of the selected clock source
• Configurable for operation during stop mode to allow periodic wakeup from stop
17.3 Functional Description
This module can generate a periodic interrupt by dividing the clock source supplied from the clock
generator module, CGMXCLK.
The counter is initialized to all 0s when TBON bit is cleared. The counter, shown in Figure 17-1, starts
counting when the TBON bit is set. When the counter overflows at the tap selected by TBR2–TBR0, the
TBIF bit gets set. If the TBIE bit is set, an interrupt request is sent to the CPU. The TBIF flag is cleared
by writing a 1 to the TACK bit. The first time the TBIF flag is set after enabling the timebase module, the
interrupt is generated at approximately half of the overflow period. Subsequent events occur at the exact
period.
The timebase module may remain active after execution of the STOP instruction if the crystal oscillator
has been enabled to operate during stop mode through the OSCENINSTOP bit in the configuration
register. The timebase module can be used in this mode to generate a periodic wakeup from stop mode.
17.4 Interrupts
The timebase module can periodically interrupt the CPU with a rate defined by the selected TBMCLK and
the select bits TBR2–TBR0. When the timebase counter chain rolls over, the TBIF flag is set. If the TBIE
bit is set, enabling the timebase interrupt, the counter chain overflow will generate a CPU interrupt
request.
NOTE
Interrupts must be acknowledged by writing a 1 to the TACK bit.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
211
Timebase Module (TBM)
TBMCLKSEL
FROM CONFIG2
CGMXCLK
FROM CGM MODULE
TBMCLK
0
1
DIVIDE BY 128
PRESCALER
TBON
÷2
÷2
÷2
÷2
÷2
÷2
÷2
÷2
÷2
÷2
÷2
÷2
TACK
÷2
TBR0
÷2
TBR1
÷2
TBR2
TBMINT
TBIF
000
TBIE
R
001
010
100
SEL
011
101
110
111
Figure 17-1. Timebase Block Diagram
17.5 TBM Interrupt Rate
The interrupt rate is determined by the equation:
Divider
t TBMRATE = --------------------------f CGMXCLK
where:
fCGMXCLK = Frequency supplied from the clock generator (CGM) module
Divider = Divider value as determined by TBR2–TBR0 settings and TBMCLKSEL, see Table 17-1
MC68HC908GR16A Data Sheet, Rev. 1.0
212
Freescale Semiconductor
Low-Power Modes
Table 17-1. Timebase Divider Selection
Divider
TBR2
TBR1
TBR0
TBMCLKSEL
0
1
0
0
0
32,768
4,194,304
0
0
1
8192
1,048,576
0
1
0
2048
262144
0
1
1
128
16,384
1
0
0
64
8192
1
0
1
32
4096
1
1
0
16
2048
1
1
1
8
1024
As an example, the divider is 16,384 with a 4.9152 MHz crystal, the TBMCLKSEL set for divide-by-128,
and TBR2–TBR0 set to {011}. The interrupt period is:
16,384/4.9152 x 106 = 3.33 ms
NOTE
Do not change TBR2–TBR0 bits while the timebase is enabled (TBON = 1).
17.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
17.6.1 Wait Mode
The timebase module remains active after execution of the WAIT instruction. In wait mode the timebase
register is not accessible by the CPU.
If the timebase functions are not required during wait mode, reduce the power consumption by stopping
the timebase before executing the WAIT instruction.
17.6.2 Stop Mode
The timebase module may remain active after execution of the STOP instruction if the internal clock
generator has been enabled to operate during stop mode through the OSCENINSTOP bit in the
configuration register. The timebase module can be used in this mode to generate a periodic wakeup from
stop mode.
If the internal clock generator has not been enabled to operate in stop mode, the timebase module will
not be active during stop mode. In stop mode, the timebase register is not accessible by the CPU.
If the timebase functions are not required during stop mode, reduce power consumption by disabling the
timebase module before executing the STOP instruction.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
213
Timebase Module (TBM)
17.7 Timebase Control Register
The timebase has one register, the timebase control register (TBCR), which is used to enable the
timebase interrupts and set the rate.
Address: $001C
Bit 7
Read:
TBIF
Write:
Reset:
0
6
5
4
TBR2
TBR1
TBR0
0
0
0
= Unimplemented
3
2
1
Bit 0
TBIE
TBON
R
0
0
0
0
R
= Reserved
0
TACK
Figure 17-2. Timebase Control Register (TBCR)
TBIF — Timebase Interrupt Flag
This read-only flag bit is set when the timebase counter has rolled over.
1 = Timebase interrupt pending
0 = Timebase interrupt not pending
TBR2–TBR0 — Timebase Divider Selection Bits
These read/write bits select the tap in the counter to be used for timebase interrupts as shown in
Table 17-1.
NOTE
Do not change TBR2–TBR0 bits while the timebase is enabled (TBON = 1).
TACK— Timebase Acknowledge Bit
The TACK bit is a write-only bit and always reads as 0. Writing a 1 to this bit clears TBIF, the timebase
interrupt flag bit. Writing a 0 to this bit has no effect.
1 = Clear timebase interrupt flag
0 = No effect
TBIE — Timebase Interrupt Enabled Bit
This read/write bit enables the timebase interrupt when the TBIF bit becomes set. Reset clears the
TBIE bit.
1 = Timebase interrupt is enabled.
0 = Timebase interrupt is disabled.
TBON — Timebase Enabled Bit
This read/write bit enables the timebase. Timebase may be turned off to reduce power consumption
when its function is not necessary. The counter can be initialized by clearing and then setting this bit.
Reset clears the TBON bit.
1 = Timebase is enabled.
0 = Timebase is disabled and the counter initialized to 0s.
MC68HC908GR16A Data Sheet, Rev. 1.0
214
Freescale Semiconductor
Chapter 18
Timer Interface Module (TIM1 and TIM2)
18.1 Introduction
This section describes the timer interface (TIM) module. The TIM is a two-channel timer that provides a
timing reference with input capture, output compare, and pulse-width-modulation functions. Figure 18-1
is a block diagram of the TIM.
This particular MCU has two timer interface modules which are denoted as TIM1 and TIM2.
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
INTERRUPT
LOGIC
16-BIT COMPARATOR
TMODH:TMODL
TOV0
INTERNAL BUS
CHANNEL 0
ELS0B
ELS0A
CH0MAX
PORT
LOGIC
T[1,2]CH0
16-BIT COMPARATOR
TCH0H:TCH0L
CH0F
16-BIT LATCH
CH0IE
MS0A
INTERRUPT
LOGIC
MS0B
TOV1
CHANNEL 1
ELS1B
ELS1A
CH1MAX
PORT
LOGIC
T[1,2]CH1
16-BIT COMPARATOR
TCH1H:TCH1L
CH1F
16-BIT LATCH
MS1A
CH1IE
INTERRUPT
LOGIC
Figure 18-1. TIM Block Diagram
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
215
Timer Interface Module (TIM1 and TIM2)
INTERNAL BUS
DDRA
PORTA
PTB7/AD7
PTB6/AD6
PTB5/AD5
PTB4/AD4
PTB3/AD3
PTB2/AD2
PTB1/AD1
PTB0/AD0
PTC6(1)
PTC5(1)
PTC4(1), (2)
PTC3(1), (2)
PTC2(1), (2)
PTC1(1), (2)
PTC0(1), (2)
PTD7/T2CH1(1)
PTD6/T2CH0(1)
PTD5/T1CH1(1)
PTD4/T1CH0(1)
PTD3/SPSCK(1)
PTD2/MOSI(1)
PTD1/MISO(1)
PTD0/SS(1)
PTE5–PTE2
PTE1/RxD
PTE0/TxD
DDRB
SINGLE BREAKPOINT
BREAK MODULE
DUAL VOLTAGE
LOW-VOLTAGE INHIBIT
MODULE
USER FLASH — 15,872 BYTES
PTA7/KBD7–
PTA0/KBD0(1)
PORTB
CONTROL AND STATUS REGISTERS — 64 BYTES
PROGRAMMABLE TIMEBASE
MODULE
PORTC
ARITHMETIC/LOGIC
UNIT (ALU)
PORTD
CPU
REGISTERS
PORTE
M68HC08 CPU
USER RAM — 1024 BYTES
FLASH PROGRAMMING ROUTINES ROM — 406 BYTES
USER FLASH VECTOR SPACE — 36 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 1
DDRC
8-BIT KEYBOARD
INTERRUPT MODULE
MONITOR ROM — 350 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 2
CLOCK GENERATOR MODULE
PHASE LOCKED LOOP
COMPUTER OPERATING
PROPERLY MODULE
RST(3)
SYSTEM INTEGRATION
MODULE
IRQ(3)
SINGLE EXTERNAL
INTERRUPT MODULE
SERIAL PERIPHERAL
INTERFACE MODULE
MONITOR MODULE
VDDAD/VREFH
VSSAD/VREFL
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
POWER-ON RESET
MODULE
VDD
VSS
VDDA
VSSA
DDRD
CGMXFC
ENHANCED SERIAL
COMUNICATIONS
INTERFACE MODULE
1–8 MHz OSCILLATOR
DDRE
OSC1
OSC2
MEMORY MAP
MODULE
SECURITY
MODULE
CONFIGURATION
REGISTER 1–2
MODULE
POWER
MONITOR MODE ENTRY
MODULE
1. Ports are software configurable with pullup device if input port.
2. Higher current drive port pins
3. Pin contains integrated pullup device
Figure 18-2. Block Diagram Highlighting TIM Block and Pins
MC68HC908GR16A Data Sheet, Rev. 1.0
216
Freescale Semiconductor
Features
18.2 Features
Features of the TIM include:
• Two input capture/output compare channels:
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
• Buffered and unbuffered pulse-width-modulation (PWM) signal generation
• Programmable TIM clock input with 7-frequency internal bus clock prescaler selection
• Free-running or modulo up-count operation
• Toggle any channel pin on overflow
• TIM counter stop and reset bits
18.3 Pin Name Conventions
The text that follows describes both timers, TIM1 and TIM2. The TIM input/output (I/O) pin names are
T[1,2]CH0 (timer channel 0) and T[1,2]CH1 (timer channel 1), where “1” is used to indicate TIM1 and “2” is
used to indicate TIM2. The two TIMs share four I/O pins with four port D I/O port pins. The full names of
the TIM I/O pins are listed in Table 18-1. The generic pin names appear in the text that follows.
Table 18-1. Pin Name Conventions
TIM Generic Pin Names:
T[1,2]CH0
T[1,2]CH1
TIM1
PTD4/T1CH0
PTD5/T1CH1
TIM2
PTD6/T2CH0
PTD7/T2CH1
Full TIM Pin Names:
NOTE
References to either timer 1 or timer 2 may be made in the following text by
omitting the timer number. For example, TCH0 may refer generically to
T1CH0 and T2CH0, and TCH1 may refer to T1CH1 and T2CH1.
18.4 Functional Description
Figure 18-1 shows the structure of the TIM. The central component of the TIM is the 16-bit TIM counter
that can operate as a free-running counter or a modulo up-counter. The TIM counter provides the timing
reference for the input capture and output compare functions. The TIM counter modulo registers,
TMODH:TMODL, control the modulo value of the TIM counter. Software can read the TIM counter value
at any time without affecting the counting sequence.
The two TIM channels (per timer) are programmable independently as input capture or output compare
channels. If a channel is configured as input capture, then an internal pullup device may be enabled for
that channel. See 12.5.3 Port D Input Pullup Enable Register.
Figure 18-3 summarizes the timer registers.
NOTE
References to either timer 1 or timer 2 may be made in the following text by
omitting the timer number. For example, TSC may generically refer to both
T1SC and T2SC.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
217
Timer Interface Module (TIM1 and TIM2)
Addr.
$0020
$0021
$0022
Register Name
Bit 7
Timer 1 Status and Control Read:
Register (T1SC) Write:
See page 225. Reset:
TOF
$002B
1
Bit 0
PS2
PS1
PS0
1
0
0
0
0
0
Timer 1 Counter Read:
Register High (T1CNTH) Write:
See page 226. Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Timer 1 Counter Read:
Register Low (T1CNTL) Write:
See page 226. 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
Timer 1 Channel 0 Status and Read:
Control Register (T1SC0) Write:
See page 227. Reset:
Timer 1 Channel 0 Read:
Register High (T1CH0H) Write:
See page 230. Reset:
Timer 1 Channel 0 Read:
Register Low (T1CH0L) Write:
See page 230. Reset:
Timer 1 Channel 1 Status and Read:
$0028
Control Register (T1SC1) Write:
See page 227. Reset:
$002A
2
0
$0024
$0029
3
0
0
Timer 1 Counter Modulo Read:
Register Low (T1MODL) Write:
See page 227. Reset:
$0027
4
0
TSTOP
$0023
$0026
5
TOIE
Timer 1 Counter Modulo Read:
Register High (T1MODH) Write:
See page 227. Reset:
$0025
6
Timer 1 Channel 1 Read:
Register High (T1CH1H) Write:
See page 230. Reset:
Timer 1 Channel 1 Read:
Register Low (T1CH1L) Write:
See page 230. Reset:
Timer 2 Status and Control Read:
Register (T2SC) Write:
See page 225. Reset:
0
CH0F
0
TRST
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH1F
0
0
CH1IE
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
PS2
PS1
PS0
0
0
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
TOF
0
0
TOIE
TSTOP
0
1
0
0
TRST
0
0
= Unimplemented
Figure 18-3. TIM I/O Register Summary (Sheet 1 of 2)
MC68HC908GR16A Data Sheet, Rev. 1.0
218
Freescale Semiconductor
Functional Description
Addr.
$002C
$002D
$002E
$002F
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
Timer 2 Counter Read:
Register High (T2CNTH) Write:
See page 226. Reset:
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Timer 2 Counter Read:
Register Low (T2CNTL) Write:
See page 226. 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
Timer 2 Counter Modulo Read:
Register High (T2MODH) Write:
See page 227. Reset:
Timer 2 Counter Modulo Read:
Register Low (T2MODL) Write:
See page 227. Reset:
Timer 2 Channel 0 Status and Read:
$0030
Control Register (T2SC0) Write:
See page 227. Reset:
$0031
$0032
Timer 2 Channel 0 Read:
Register High (T2CH0H) Write:
See page 230. Reset:
Timer 2 Channel 0 Read:
Register Low (T2CH0L) Write:
See page 230. Reset:
Timer 2 Channel 1 Status and Read:
$0033
Control Register (T2SC1) Write:
See page 227. Reset:
$0034
$0035
Timer 2 Channel 1 Read:
Register High (T2CH1H) Write:
See page 230. Reset:
Timer 2 Channel 1 Read:
Register Low (T2CH1L) Write:
See page 230. Reset:
CH0F
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH1F
0
0
CH1IE
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
= Unimplemented
Figure 18-3. TIM I/O Register Summary (Sheet 2 of 2)
18.4.1 TIM Counter Prescaler
The TIM clock source can be one of the seven prescaler outputs. The prescaler generates seven clock
rates from the internal bus clock. The prescaler select bits, PS[2:0], in the TIM status and control register
select the TIM clock source.
18.4.2 Input Capture
With the input capture function, the TIM can capture the time at which an external event occurs. When an
active edge occurs on the pin of an input capture channel, the TIM latches the contents of the TIM counter
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
219
Timer Interface Module (TIM1 and TIM2)
into the TIM channel registers, TCHxH:TCHxL. The polarity of the active edge is programmable. Input
captures can generate TIM CPU interrupt requests.
18.4.3 Output Compare
With the output compare function, the TIM can generate a periodic pulse with a programmable polarity,
duration, and frequency. When the counter reaches the value in the registers of an output compare
channel, the TIM can set, clear, or toggle the channel pin. Output compares can generate TIM CPU
interrupt requests.
18.4.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare pulses as described in 18.4.3
Output Compare. The pulses are unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIM channel registers.
An unsynchronized write to the TIM channel registers to change an output compare value could cause
incorrect operation for up to two counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new value prevents any compare during
that counter overflow period. Also, using a TIM overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIM may pass the new value before it is written.
Use the following methods to synchronize unbuffered changes in the output compare value on channel x:
• When changing to a smaller value, enable channel x output compare interrupts and write the new
value in the output compare interrupt routine. The output compare interrupt occurs at the end of
the current output compare pulse. The interrupt routine has until the end of the counter overflow
period to write the new value.
• When changing to a larger output compare value, enable TIM overflow interrupts and write the new
value in the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the
current counter overflow period. Writing a larger value in an output compare interrupt routine (at
the end of the current pulse) could cause two output compares to occur in the same counter
overflow period.
18.4.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the
TCH0 pin. The TIM channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1.
The output compare value in the TIM channel 0 registers initially controls the output on the TCH0 pin.
Writing to the TIM channel 1 registers enables the TIM channel 1 registers to synchronously control the
output after the TIM overflows. At each subsequent overflow, the TIM channel registers (0 or 1) that
control the output are the ones written to last. TSC0 controls and monitors the buffered output compare
function, and TIM channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the
channel 1 pin, TCH1, is available as a general-purpose I/O pin.
NOTE
In buffered output compare operation, do not write new output compare
values to the currently active channel registers. User software should track
the currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered output compares.
MC68HC908GR16A Data Sheet, Rev. 1.0
220
Freescale Semiconductor
Functional Description
18.4.4 Pulse Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIM can generate a PWM
signal. The value in the TIM counter modulo registers determines the period of the PWM signal. The
channel pin toggles when the counter reaches the value in the TIM counter modulo registers. The time
between overflows is the period of the PWM signal.
As Figure 18-4 shows, the output compare value in the TIM channel registers determines the pulse width
of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIM
to clear the channel pin on output compare if the polarity of the PWM pulse is 1 (ELSxA = 0). Program the
TIM to set the pin if the polarity of the PWM pulse is 0 (ELSxA = 1).
The value in the TIM counter modulo registers and the selected prescaler output determines the
frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIM counter modulo registers produces a PWM period of 256 times the internal bus
clock period if the prescaler select value is $000. See 18.9.1 TIM Status and Control Register.
The value in the TIM channel registers determines the pulse width of the PWM output. The pulse width of
an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIM channel registers
produces a duty cycle of 128/256 or 50%.
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
POLARITY = 1
(ELSxA = 0)
TCHx
PULSE
WIDTH
POLARITY = 0
(ELSxA = 1)
TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 18-4. PWM Period and Pulse Width
18.4.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as described in 18.4.4 Pulse Width
Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new
pulse width value over the old value currently in the TIM channel registers.
An unsynchronized write to the TIM channel registers to change a pulse width value could cause incorrect
operation for up to two PWM periods. For example, writing a new value before the counter reaches the
old value but after the counter reaches the new value prevents any compare during that PWM period.
Also, using a TIM overflow interrupt routine to write a new, smaller pulse width value may cause the
compare to be missed. The TIM may pass the new value before it is written.
Use the following methods to synchronize unbuffered changes in the PWM pulse width on channel x:
• 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.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
221
Timer Interface Module (TIM1 and TIM2)
•
When changing to a longer pulse width, enable TIM overflow interrupts and write the new value in
the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the current PWM
period. Writing a larger value in an output compare interrupt routine (at the end of the current pulse)
could cause two output compares to occur in the same PWM period.
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 self-correct in the
event of software error or noise. Toggling on output compare also can
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
18.4.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the TCH0 pin.
The TIM channel registers of the linked pair alternately control the pulse width of the output.
Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1.
The TIM channel 0 registers initially control the pulse width on the TCH0 pin. Writing to the TIM channel 1
registers enables the TIM channel 1 registers to synchronously control the pulse width at the beginning
of the next PWM period. At each subsequent overflow, the TIM channel registers (0 or 1) that control the
pulse width are the ones written to last. TSC0 controls and monitors the buffered PWM function, and TIM
channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin,
TCH1, is available as a general-purpose I/O pin.
NOTE
In buffered PWM signal generation, do not write new pulse width values to
the currently active channel registers. User software should track the
currently active channel to prevent writing a new value to the active
channel. Writing to the active channel registers is the same as generating
unbuffered PWM signals.
18.4.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered PWM signals, use the following
initialization procedure:
1. In the TIM status and control register (TSC):
a. Stop the TIM counter by setting the TIM stop bit, TSTOP.
b. Reset the TIM counter and prescaler by setting the TIM reset bit, TRST.
2. In the TIM counter modulo registers (TMODH:TMODL), write the value for the required PWM
period.
3. In the TIM channel x registers (TCHxH:TCHxL), write the value for the required pulse width.
4. In TIM channel x status and control register (TSCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or 1:0 (for buffered output compare
or PWM signals) to the mode select bits, MSxB:MSxA. See Table 18-3.
b. Write 1 to the toggle-on-overflow bit, TOVx.
MC68HC908GR16A Data Sheet, Rev. 1.0
222
Freescale Semiconductor
Interrupts
c. Write 1:0 (polarity 1 — to clear output on compare) or 1:1 (polarity 0 — 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 18-3.
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 self-correct in the
event of software error or noise. Toggling on output compare can also
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
5. In the TIM status control register (TSC), clear the TIM stop bit, TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIM
channel 0 registers (TCH0H:TCH0L) initially control the buffered PWM output. TIM status control
register 0 (TSCR0) controls and monitors the PWM signal from the linked channels.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIM overflows. Subsequent output
compares try to force the output to a state it is already in and have no effect. The result is a 0% duty cycle
output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a 100% duty
cycle output. See 18.9.4 TIM Channel Status and Control Registers.
18.5 Interrupts
The following TIM sources can generate interrupt requests:
• TIM overflow flag (TOF) — The TOF bit is set when the TIM counter reaches the modulo value
programmed in the TIM counter modulo registers. The TIM overflow interrupt enable bit, TOIE,
enables TIM overflow CPU interrupt requests. TOF and TOIE are in the TIM status and control
register.
• TIM channel flags (CH1F:CH0F) — The CHxF bit is set when an input capture or output compare
occurs on channel x. Channel x TIM CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE. Channel x TIM CPU interrupt requests are enabled when CHxIE = 1.
CHxF and CHxIE are in the TIM channel x status and control register.
18.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
18.6.1 Wait Mode
The TIM remains active after the execution of a WAIT instruction. In wait mode, the TIM registers are not
accessible by the CPU. Any enabled CPU interrupt request from the TIM can bring the MCU out of wait
mode.
If TIM functions are not required during wait mode, reduce power consumption by stopping the TIM before
executing the WAIT instruction.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
223
Timer Interface Module (TIM1 and TIM2)
18.6.2 Stop Mode
The TIM is inactive after the execution of a STOP instruction. The STOP instruction does not affect
register conditions or the state of the TIM counter. TIM operation resumes when the MCU exits stop mode
after an external interrupt.
18.7 TIM During Break Interrupts
A break interrupt stops the TIM counter.
The system integration module (SIM) controls whether status bits in other modules can be cleared during
the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear
status bits during the break state. See 15.7.3 SIM Break Flag Control Register.
To allow software to clear status bits during a break interrupt, write a 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 0 to the BCFE bit. With BCFE at 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 0. After the break, doing the
second step clears the status bit.
18.8 I/O Signals
Port D shares four of its pins with the TIM. The four TIM channel I/O pins are T1CH0, T1CH1, T2CH0,
and T2CH1 as described in 18.3 Pin Name Conventions.
Each channel I/O pin is programmable independently as an input capture pin or an output compare pin.
T1CH0 and T2CH0 can be configured as buffered output compare or buffered PWM pins.
18.9 I/O Registers
NOTE
References to either timer 1 or timer 2 may be made in the following text by
omitting the timer number. For example, TSC may generically refer to both
T1SC AND T2SC.
These I/O registers control and monitor operation of the TIM:
• TIM status and control register (TSC)
• TIM counter registers (TCNTH:TCNTL)
• TIM counter modulo registers (TMODH:TMODL)
• TIM channel status and control registers (TSC0 and TSC1)
• TIM channel registers (TCH0H:TCH0L, TCH1H:TCH1L)
18.9.1 TIM Status and Control Register
The TIM status and control register (TSC):
• Enables TIM overflow interrupts
• Flags TIM overflows
• Stops the TIM counter
• Resets the TIM counter
• Prescales the TIM counter clock
MC68HC908GR16A Data Sheet, Rev. 1.0
224
Freescale Semiconductor
I/O Registers
Address: T1SC, $002 and T2SC, $002B
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 18-5. TIM Status and Control Register (TSC)
TOF — TIM Overflow Flag Bit
This read/write flag is set when the TIM counter reaches the modulo value programmed in the TIM
counter modulo registers. Clear TOF by reading the TIM status and control register when TOF is set
and then writing a 0 to TOF. If another TIM overflow occurs before the clearing sequence is complete,
then writing 0 to TOF has no effect. Therefore, a TOF interrupt request cannot be lost due to
inadvertent clearing of TOF. Reset clears the TOF bit. Writing a 1 to TOF has no effect.
1 = TIM counter has reached modulo value
0 = TIM counter has not reached modulo value
TOIE — TIM Overflow Interrupt Enable Bit
This read/write bit enables TIM overflow interrupts when the TOF bit becomes set. Reset clears the
TOIE bit.
1 = TIM overflow interrupts enabled
0 = TIM overflow interrupts disabled
TSTOP — TIM Stop Bit
This read/write bit stops the TIM counter. Counting resumes when TSTOP is cleared. Reset sets the
TSTOP bit, stopping the TIM counter until software clears the TSTOP bit.
1 = TIM counter stopped
0 = TIM counter active
NOTE
Do not set the TSTOP bit before entering wait mode if the TIM is required
to exit wait mode. Also, when the TSTOP bit is set and the timer is
configured for input capture operation, input captures are inhibited until the
TSTOP bit is cleared.
TRST — TIM Reset Bit
Setting this write-only bit resets the TIM counter and the TIM prescaler. Setting TRST has no effect on
any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIM
counter is reset and always reads as 0. Reset clears the TRST bit.
1 = Prescaler and TIM counter cleared
0 = No effect
NOTE
Setting the TSTOP and TRST bits simultaneously stops the TIM counter at
a value of $0000.
PS[2:0] — Prescaler Select Bits
These read/write bits select one of the seven prescaler outputs as the input to the TIM counter as
Table 18-2 shows. Reset clears the PS[2:0] bits.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
225
Timer Interface Module (TIM1 and TIM2)
Table 18-2. 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
Not available
18.9.2 TIM Counter Registers
The two read-only TIM counter registers contain the high and low bytes of the value in the TIM counter.
Reading the high byte (TCNTH) latches the contents of the low byte (TCNTL) into a buffer. Subsequent
reads of TCNTH do not affect the latched TCNTL value until TCNTL is read. Reset clears the TIM counter
registers. Setting the TIM reset bit (TRST) also clears the TIM counter registers.
NOTE
If you read TCNTH during a break interrupt, be sure to unlatch TCNTL by
reading TCNTL before exiting the break interrupt. Otherwise, TCNTL
retains the value latched during the break.
Address: T1CNTH, $0021 and T2CNTH, $002C
Read:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
Write:
Reset:
0
= Unimplemented
Figure 18-6. TIM Counter Registers High (TCNTH)
Address: T1CNTL, $0022 and T2CNTL, $002D
Read:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 18-7. TIM Counter Registers Low (TCNTL)
18.9.3 TIM Counter Modulo Registers
The read/write TIM modulo registers contain the modulo value for the TIM counter. When the TIM counter
reaches the modulo value, the overflow flag (TOF) becomes set, and the TIM counter resumes counting
from $0000 at the next timer clock. Writing to the high byte (TMODH) inhibits the TOF bit and overflow
interrupts until the low byte (TMODL) is written. Reset sets the TIM counter modulo registers.
MC68HC908GR16A Data Sheet, Rev. 1.0
226
Freescale Semiconductor
I/O Registers
Address: T1MODH, $0023 and T2MODH, $002E
Read:
Write:
Reset:
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 18-8. TIM Counter Modulo Register High (TMODH)
Address: T1MODL, $0024 and T2MODL, $002F
Read:
Write:
Reset:
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 18-9. TIM Counter Modulo Register Low (TMODL)
NOTE
Reset the TIM counter before writing to the TIM counter modulo registers.
18.9.4 TIM Channel Status and Control Registers
Each of the TIM channel status and control registers:
• Flags input captures and output compares
• Enables input capture and output compare interrupts
• Selects input capture, output compare, or PWM operation
• Selects high, low, or toggling output on output compare
• Selects rising edge, falling edge, or any edge as the active input capture trigger
• Selects output toggling on TIM overflow
• Selects 0% and 100% PWM duty cycle
• Selects buffered or unbuffered output compare/PWM operation
Address: T1SC0, $0025 and T2SC0, $0030
Bit 7
Read:
CH0F
Write:
0
Reset:
0
6
5
4
3
2
1
Bit 0
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
Figure 18-10. TIM Channel 0 Status and Control Register (TSC0)
Address: T1SC1, $0028 and T2SC1, $0033
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 18-11. TIM Channel 1 Status and Control Register (TSC1)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
227
Timer Interface Module (TIM1 and TIM2)
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set when an active edge occurs on
the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the
TIM counter registers matches the value in the TIM channel x registers.
When TIM CPU interrupt requests are enabled (CHxIE = 1), clear CHxF by reading TIM channel x
status and control register with CHxF set and then writing a 0 to CHxF. If another interrupt request
occurs before the clearing sequence is complete, then writing 0 to CHxF has no effect. Therefore, an
interrupt request cannot be lost due to inadvertent clearing of CHxF.
Reset clears the CHxF bit. Writing a 1 to CHxF has no effect.
1 = Input capture or output compare on channel x
0 = No input capture or output compare on channel x
CHxIE — Channel x Interrupt Enable Bit
This read/write bit enables TIM CPU interrupt service requests on channel x.
Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation. MSxB exists only in the TIM1
channel 0 and TIM2 channel 0 status and control registers.
Setting MS0B disables the channel 1 status and control register and reverts TCH1 to general-purpose
I/O.
Reset clears the MSxB bit.
1 = Buffered output compare/PWM operation enabled
0 = Buffered output compare/PWM operation disabled
MSxA — Mode Select Bit A
When ELSxB:A ≠ 00, this read/write bit selects either input capture operation or unbuffered output
compare/PWM operation. See Table 18-3.
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 TCHx pin. See Table 18-3.
Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE
Before changing a channel function by writing to the MSxB or MSxA bit, set
the TSTOP and TRST bits in the TIM status and control register (TSC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits control the active edge-sensing logic
on channel x.
When channel x is an output compare channel, ELSxB and ELSxA control the channel x output
behavior when an output compare occurs.
When ELSxB and ELSxA are both clear, channel x is not connected to port D, and pin PTDx/TCHx is
available as a general-purpose I/O pin. Table 18-3 shows how ELSxB and ELSxA work. Reset clears
the ELSxB and ELSxA bits.
MC68HC908GR16A Data Sheet, Rev. 1.0
228
Freescale Semiconductor
I/O Registers
Table 18-3. Mode, Edge, and Level Selection
MSxB
MSxA
ELSxB
ELSxA
X
0
0
0
X
1
0
0
0
0
0
1
0
0
1
0
0
0
1
1
Capture on rising or falling edge
0
1
0
0
Software compare only
0
1
0
1
0
1
1
0
0
1
1
1
1
X
0
1
1
X
1
0
1
X
1
1
Mode
Output preset
Configuration
Pin under port control; initial output level high
Pin under port control; initial output level low
Capture on rising edge only
Input capture
Output compare
or PWM
Capture on falling edge only
Toggle output on compare
Clear output on compare
Set output on compare
Buffered output
compare or
buffered PWM
Toggle output on compare
Clear output on compare
Set output on compare
NOTE
Before enabling a TIM channel register for input capture operation, make
sure that the PTD/TCHx 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 TIM counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIM counter overflow.
0 = Channel x pin does not toggle on TIM counter overflow.
NOTE
When TOVx is set, a TIM counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx bit is at 1, setting the CHxMAX bit forces the duty cycle of buffered and unbuffered
PWM signals to 100%. As Figure 18-12 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.
NOTE
The 100% PWM duty cycle is defined as a continuous high level if the PWM
polarity is 1 and a continuous low level if the PWM polarity is 0. Conversely,
a 0% PWM duty cycle is defined as a continuous low level if the PWM
polarity is 1 and a continuous high level if the PWM polarity is 0.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
Figure 18-12. CHxMAX Latency
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
229
Timer Interface Module (TIM1 and TIM2)
18.9.5 TIM Channel Registers
These read/write registers contain the captured TIM counter value of the input capture function or the
output compare value of the output compare function. The state of the TIM channel registers after reset
is unknown.
In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the TIM channel x registers (TCHxH)
inhibits input captures until the low byte (TCHxL) is read.
In output compare mode (MSxB:MSxA ≠ 0:0), writing to the high byte of the TIM channel x registers
(TCHxH) inhibits output compares until the low byte (TCHxL) is written.
See Figure 18-13 through Figure 18-16.
Address: T1CH0H, $0026 and T2CH0H, $0031
Read:
Write:
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 18-13. TIM Channel 0 Register High (TCH0H)
Address: T1CH0L, $0027 and T2CH0L $0032
Read:
Write:
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 18-14. TIM Channel 0 Register Low (TCH0L)
Address: T1CH1H, $0029 and T2CH1H, $0034
Read:
Write:
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 18-15. TIM Channel 1 Register High (TCH1H)
Address: T1CH1L, $002A and T2CH1L, $0035
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
Indeterminate after reset
Figure 18-16. TIM Channel 1 Register Low (TCH1L)
MC68HC908GR16A Data Sheet, Rev. 1.0
230
Freescale Semiconductor
Chapter 19
Development Support
19.1 Introduction
This section describes the break module, the monitor module (MON), and the monitor mode entry
methods.
19.2 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.
Features of the break module include:
• Accessible input/output (I/O) registers during the break Interrupt
• Central processor unit (CPU) generated break interrupts
• Software-generated break interrupts
• Computer operating properly (COP) disabling during break interrupts
19.2.1 Functional Description
When the internal address bus matches the value written in the break address registers, the break module
issues a breakpoint signal (BKPT) to the system integration module (SIM). The SIM then causes the CPU
to load the instruction register with a software interrupt instruction (SWI). 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 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
is generated. A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and
returns the microcontroller unit (MCU) to normal operation.
Figure 19-2 shows the structure of the break module.
Figure 19-3 provides a summary of the I/O registers.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
231
Development Support
INTERNAL BUS
DDRA
PORTA
PTB7/AD7
PTB6/AD6
PTB5/AD5
PTB4/AD4
PTB3/AD3
PTB2/AD2
PTB1/AD1
PTB0/AD0
PTC6(1)
PTC5(1)
PTC4(1), (2)
PTC3(1), (2)
PTC2(1), (2)
PTC1(1), (2)
PTC0(1), (2)
PTD7/T2CH1(1)
PTD6/T2CH0(1)
PTD5/T1CH1(1)
PTD4/T1CH0(1)
PTD3/SPSCK(1)
PTD2/MOSI(1)
PTD1/MISO(1)
PTD0/SS(1)
PTE5–PTE2
PTE1/RxD
PTE0/TxD
DDRB
SINGLE BREAKPOINT
BREAK MODULE
DUAL VOLTAGE
LOW-VOLTAGE INHIBIT
MODULE
USER FLASH — 15,872 BYTES
PTA7/KBD7–
PTA0/KBD0(1)
PORTB
CONTROL AND STATUS REGISTERS — 64 BYTES
PROGRAMMABLE TIMEBASE
MODULE
PORTC
ARITHMETIC/LOGIC
UNIT (ALU)
PORTD
CPU
REGISTERS
PORTE
M68HC08 CPU
USER RAM — 1024 BYTES
FLASH PROGRAMMING ROUTINES ROM — 406 BYTES
USER FLASH VECTOR SPACE — 36 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 1
DDRC
8-BIT KEYBOARD
INTERRUPT MODULE
MONITOR ROM — 350 BYTES
2-CHANNEL TIMER
INTERFACE MODULE 2
CLOCK GENERATOR MODULE
PHASE LOCKED LOOP
COMPUTER OPERATING
PROPERLY MODULE
RST(3)
SYSTEM INTEGRATION
MODULE
IRQ(3)
SINGLE EXTERNAL
INTERRUPT MODULE
SERIAL PERIPHERAL
INTERFACE MODULE
MONITOR MODULE
VDDAD/VREFH
VSSAD/VREFL
10-BIT ANALOG-TO-DIGITAL
CONVERTER MODULE
POWER-ON RESET
MODULE
VDD
VSS
VDDA
VSSA
DDRD
CGMXFC
ENHANCED SERIAL
COMUNICATIONS
INTERFACE MODULE
1–8 MHz OSCILLATOR
DDRE
OSC1
OSC2
MEMORY MAP
MODULE
SECURITY
MODULE
CONFIGURATION
REGISTER 1–2
MODULE
POWER
MONITOR MODE ENTRY
MODULE
1. Ports are software configurable with pullup device if input port.
2. Higher current drive port pins
3. Pin contains integrated pullup device
Figure 19-1. Block Diagram Highlighting BRK and MON Blocks
MC68HC908GR16A Data Sheet, Rev. 1.0
232
Freescale Semiconductor
Break Module (BRK)
ADDRESS BUS[15:8]
BREAK ADDRESS REGISTER HIGH
8-BIT COMPARATOR
ADDRESS BUS[15:0]
BKPT
(TO SIM)
CONTROL
8-BIT COMPARATOR
BREAK ADDRESS REGISTER LOW
ADDRESS BUS[7:0]
Figure 19-2. Break Module Block Diagram
Addr.
$FE00
Register Name
SIM Break Status Register Read:
(SBSR) Write:
See page 236. Reset:
Read:
Reserved Write:
$FE02
Reset:
$FE03
$FE09
SIM Break Flag Control Read:
Register (SBFCR) Write:
See page 236. Reset:
Break Address High Read:
Register (BRKH) Write:
See page 235. Reset:
$FE0A
Break Address Low Read:
Register (BRKL) Write:
See page 235. Reset:
$FE0B
Break Status and Control Read:
Register (BRKSCR) Write:
See page 235. Reset:
1. Writing a 0 clears SBSW.
Bit 7
6
5
4
3
2
R
R
R
R
R
R
1
SBSW
Note(1)
Bit 0
R
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
Bit15
Bit14
Bit13
Bit12
Bit11
Bit10
Bit9
Bit8
0
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
BRKE
BRKA
0
0
= Unimplemented
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
R
= Reserved
Figure 19-3. Break I/O Register Summary
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
233
Development Support
When the internal address bus matches the value written in the break address registers or when software
writes a 1 to the BRKA bit in the break status and control register, 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 timing is:
• When a break address is placed at the address of the instruction opcode, the instruction is not
executed until after completion of the break interrupt routine.
• When a break address is placed at an address of an instruction operand, the instruction is executed
before the break interrupt.
• When software writes a 1 to the BRKA bit, the break interrupt occurs just before the next instruction
is executed.
By updating a break address and clearing the BRKA bit in a break interrupt routine, a break interrupt can
be generated continuously.
CAUTION
A break address should be placed at the address of the instruction opcode. When software does not
change the break address and clears the BRKA bit in the first break interrupt routine, the next break
interrupt will not be generated after exiting the interrupt routine even when the internal address bus
matches the value written in the break address registers.
19.2.1.1 Flag Protection During Break Interrupts
The system integration module (SIM) controls whether or not module status bits can be cleared during
the break state. The BCFE bit in the break flag control register (SBFCR) enables software to clear status
bits during the break state. See 15.7.3 SIM Break Flag Control Register and the Break Interrupts
subsection for each module.
19.2.1.2 TIM During Break Interrupts
A break interrupt stops the timer counter.
19.2.1.3 COP During Break Interrupts
The COP is disabled during a break interrupt when VTST is present on the RST pin.
19.2.2 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)
• Break status register (SBSR)
• Break flag control register (SBFCR)
MC68HC908GR16A Data Sheet, Rev. 1.0
234
Freescale Semiconductor
Break Module (BRK)
19.2.2.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module enable and status bits.
Address: $FE0B
Read:
Write:
Reset:
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 19-4. 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 0 to bit
7. Reset clears the BRKE bit.
1 = Breaks enabled on 16-bit address match
0 = Breaks disabled
BRKA — Break Active Bit
This read/write status and control bit is set when a break address match occurs. Writing a 1 to BRKA
generates a break interrupt. Clear BRKA by writing a 0 to it before exiting the break routine. Reset
clears the BRKA bit.
1 = Break address match
0 = No break address match
19.2.2.2 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: $FE09
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
Figure 19-5. Break Address Register High (BRKH)
Address: $FE0A
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Figure 19-6. Break Address Register Low (BRKL)
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
235
Development Support
19.2.2.3 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait
mode. This register is only used in emulation mode.
Address: $FE00
Read:
Write:
Bit 7
6
5
4
3
2
R
R
R
R
R
R
1
SBSW
Note(1)
Reset:
Bit 0
R
0
R
= Reserved
1. Writing a 0 clears SBSW.
Figure 19-7. SIM Break Status Register (SBSR)
SBSW — SIM Break Stop/Wait
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.
1 = Wait mode was exited by break interrupt
0 = Wait mode was not exited by break interrupt
19.2.2.4 SIM Break Flag Control Register
The SIM break control register (SBFCR) contains a bit that enables software to clear status bits while the
MCU is in a break state.
Address: $FE03
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
BCFE
R
R
R
R
R
R
R
0
R
= Reserved
Figure 19-8. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing status registers while the MCU is
in a break state. To clear status bits during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
19.2.3 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes. If enabled,
the break module will remain enabled in wait and stop modes. However, since the internal address bus
does not increment in these modes, a break interrupt will never be triggered.
MC68HC908GR16A Data Sheet, Rev. 1.0
236
Freescale Semiconductor
Monitor Module (MON)
19.3 Monitor Module (MON)
The monitor module allows debugging and programming of the microcontroller unit (MCU) through a
single-wire interface with a host computer. Monitor mode entry can be achieved without use of the higher
test voltage, VTST, as long as vector addresses $FFFE and $FFFF are blank, thus reducing the hardware
requirements for in-circuit programming.
Features of the monitor module include:
• Normal user-mode pin functionality
• One pin dedicated to serial communication between MCU and host computer
• Standard non-return-to-zero (NRZ) communication with host computer
• Standard communication baud rate (7200 @ 2-MHz bus frequency)
• Execution of code in random-access memory (RAM) or FLASH
• FLASH memory security feature(1)
• FLASH memory programming interface
• Monitor mode entry without high voltage, VTST, if reset vector is blank ($FFFE and $FFFF contain
$FF)
• Normal monitor mode entry if VTST is applied to IRQ
19.3.1 Functional Description
Figure 19-9 shows a simplified diagram of the monitor mode.
The monitor module receives and executes commands from a host computer.
Figure 19-10 and Figure 19-11 show example circuits used to enter monitor mode and communicate with
a host computer via a standard RS-232 interface.
Simple monitor commands can access any memory address. In monitor mode, the MCU can execute
code downloaded into RAM by a host computer while most MCU pins retain normal operating mode
functions. All communication between the host computer and the MCU is through the PTA0 pin. A
level-shifting and multiplexing interface is required between PTA0 and the host computer. PTA0 is used
in a wired-OR configuration and requires a pullup resistor.
Table 19-1 shows the pin conditions for entering monitor mode. As specified in the table, monitor mode
must be entered after a power-on reset (POR) and will allow communication at 7200 baud provided one
of the following sets of conditions is met:
• If $FFFE and $FFFF does not contain $FF (programmed state):
– The external clock is 4.0 MHz (7200 baud)
– PTB4 = low
– IRQ = VTST
• If $FFFE and $FFFF do not contain $FF (programmed state):
– The external clock is 8.0 MHz (7200 baud)
– PTB4 = high
– IRQ = VTST
• If $FFFE and $FFFF contain $FF (erased state):
– The external clock is 8.0 MHz (7200 baud)
– IRQ = VDD (this can be implemented through the internal IRQ pullup) or VSS
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
237
Development Support
POR RESET
NO
CONDITIONS
FROM Table 19-1
PTA0 = 1,
PTA1 = 0, RESET
VECTOR BLANK?
IRQ = VTST?
YES
PTA0 = 1, PTA1 = 0,
PTB0 = 1, AND
PTB1 = 0?
NO
NO
YES
YES
FORCED
MONITOR MODE
NORMAL
USER MODE
NORMAL
MONITOR MODE
INVALID
USER MODE
HOST SENDS
8 SECURITY BYTES
IS RESET
POR?
YES
NO
YES
ARE ALL
SECURITY BYTES
CORRECT?
ENABLE FLASH
NO
DISABLE FLASH
MONITOR MODE ENTRY
DEBUGGING
AND FLASH
PROGRAMMING
(IF FLASH
IS ENABLED)
EXECUTE
MONITOR CODE
YES
DOES RESET
OCCUR?
NO
Figure 19-9. Simplified Monitor Mode Entry Flowchart
MC68HC908GR16A Data Sheet, Rev. 1.0
238
Freescale Semiconductor
Monitor Module (MON)
MC68HC908GR16A
N.C.
RST
VDD
47 pF
VDDA
OSC2
MAX232
1
1 µF
+
4
1 µF
+
10 k
1 kΩ
IRQ
3
10 k
1 µF
74HC125
3
2
9
PTA1
10 kΩ
74HC125
5
6
10
8
10 k
PTB1
9.1 V
DB9
7
PTB0
VDD
+
2
PTB4
V– 6
5 C2–
10 k
1 µF
V+ 2
C2+
+
VDD
OSC1
8 MHz
GND 15
C1–
0.1 µF
10 MΩ
27 pF
+
3
1 µF
VDD
VCC 16
C1+
VDD
PTA0
VSSA
VSS
4
1
5
Figure 19-10. Normal Monitor Mode Circuit
MC68HC908GR16A
N.C.
RST
47 pF
OSC2
MAX232
1
1 µF
+
4
GND 15
C2+
V+ 2
5 C2–
1 µF
1 µF
N.C.
3
8
9
5
PTB4
N.C.
PTB0
N.C.
PTB1
N.C.
10 k
1 µF
74HC125
5
6
DB9
10
IRQ
VDD
V– 6
7
0.1 µF
OSC1
8 MHz
+
+
2
VDDA
10 MΩ
27 pF
VCC 16
C1–
+
VDD
VDD
+
3
1 µF
C1+
VDD
74HC125
3
2
PTA1
10 kΩ
4
PTA0
VSSA
VSS
1
Figure 19-11. Forced Monitor Mode
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
239
Development Support
Table 19-1. Monitor Mode Signal Requirements and Options
Mode
IRQ
Serial
Mode
Divider
Communication
Selection
Reset
RST
PLL
Vector
PTA0
PTA1 PTB0 PTB1 PTB4
VTST
VDD
or
VTST
X
1
0
1
0
0
OFF Disabled
4 MHz
2 MHz
7200
VTST
VDD
or
VTST
X
1
0
1
0
1
OFF Disabled
8 MHz
2 MHz
7200
VDD
or
GND
VDD
$FF
(blank)
1
0
X
X
X
OFF Disabled
8 MHz
2 MHz
7200
X
X
X
X
X
X
Enabled
X
X
X
COM
[8]
SSEL
[10]
DIV4
[16]
—
—
OSC1
[13]
—
—
Normal
Monitor
Forced
Monitor
User
VDD VDD
or
or
GND VTST
MON08
VTST RST
Function
[4]
[6]
[Pin No.]
Not
$FF
—
MOD0 MOD1
[12]
[14]
COP
Communication
Speed
Bus
External
Clock Frequency
Baud
Rate
1. PTA0 must have a pullup resistor to VDD in monitor mode.
2. Communication speed in the table is an example to obtain a baud rate of 7200. Baud rate using external oscillator is bus
frequency / 278.
3. External clock is an 4.0 MHz or 8.0 MHz crystal on OSC1 and OSC2 or a canned oscillator on OSC1.
4. X = don’t care
5. MON08 pin refers to P&E Microcomputer Systems’ MON08-Cyclone 2 by 8-pin connector.
NC
1
2
GND
NC
3
4
RST
NC
5
6
IRQ
NC
7
8
PTA0
NC
9
10
PTA1
NC
11
12
PTB0
OSC1
13
14
PTB1
VDD
15
16
PTB4
MC68HC908GR16A Data Sheet, Rev. 1.0
240
Freescale Semiconductor
Monitor Module (MON)
Enter monitor mode with pin configuration shown in Table 19-1 with a power-on reset. The rising edge of
RST latches monitor mode. Once monitor mode is latched, the levels on the port pins except PTA0 can
change.
Once out of reset, the MCU waits for the host to send eight security bytes (see 19.3.2 Security). After the
security bytes, the MCU sends a break signal (10 consecutive 0s) to the host, indicating that it is ready to
receive a command.
19.3.1.1 Normal Monitor Mode
If VTST is applied to IRQ and PTB4 is low upon monitor mode entry, the bus frequency is a divide-by-two
of the input clock. If PTB4 is high with VTST applied to IRQ upon monitor mode entry, the bus frequency
will be a divide-by-four of the input clock. Holding the PTB4 pin low when entering monitor mode causes
a bypass of a divide-by-two stage at the oscillator only if VTST is applied to IRQ. In this event, the
CGMOUT frequency is equal to the CGMXCLK frequency, and the OSC1 input directly generates internal
bus clocks. In this case, the OSC1 signal must have a 50% duty cycle at maximum bus frequency.
When monitor mode was entered with VTST on IRQ, the computer operating properly (COP) is disabled
as long as VTST is applied to either IRQ or RST.
This condition states that as long as VTST is maintained on the IRQ pin after entering monitor mode, or if
VTST is applied to RST after the initial reset to get into monitor mode (when VTST was applied to IRQ),
then the COP will be disabled. In the latter situation, after VTST is applied to the RST pin, VTST can be
removed from the IRQ pin in the interest of freeing the IRQ for normal functionality in monitor mode.
19.3.1.2 Forced Monitor Mode
If entering monitor mode without high voltage on IRQ, all port B pin requirements and conditions, including
the PTB4 frequency divisor selection, are not in effect. This is to reduce circuit requirements when
performing in-circuit programming.
NOTE
If the reset vector is blank and monitor mode is entered, the chip will see an
additional reset cycle after the initial power-on reset (POR). Once the reset
vector has been programmed, the traditional method of applying a voltage,
VTST, to IRQ must be used to enter monitor mode.
An external oscillator of 8 MHz is required for a baud rate of 7200, as the internal bus frequency is
automatically set to the external frequency divided by four.
When the forced monitor mode is entered the COP is always disabled regardless of the state of IRQ or
RST.
19.3.1.3 Monitor Vectors
In monitor mode, the MCU uses different vectors for reset, SWI (software interrupt), and break interrupt
than those for user mode. The alternate vectors are in the $FE page instead of the $FF page and allow
code execution from the internal monitor firmware instead of user code.
Table 19-2 summarizes the differences between user mode and monitor mode.
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
241
Development Support
Table 19-2. Mode Differences
Functions
Modes
Reset
Vector High
Reset
Vector Low
Break
Vector High
Break
Vector Low
SWI
Vector High
SWI
Vector Low
User
$FFFE
$FFFF
$FFFC
$FFFD
$FFFC
$FFFD
Monitor
$FEFE
$FEFF
$FEFC
$FEFD
$FEFC
$FEFD
19.3.1.4 Data Format
Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format.
Transmit and receive baud rates must be identical.
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
NEXT
START
BIT
Figure 19-12. Monitor Data Format
19.3.1.5 Break Signal
A start bit (0) followed by nine 0 bits is a break signal. When the monitor receives a break signal, it drives
the PTA0 pin high for the duration of approximately two bits and then echoes back the break signal.
MISSING STOP BIT
0
1
2
3
4
5
6
APPROXIMATELY 2 BITS DELAY
BEFORE ZERO ECHO
7
0
1
2
3
4
5
6
7
Figure 19-13. Break Transaction
19.3.1.6 Baud Rate
The communication baud rate is controlled by the crystal frequency or external clock and the state of the
PTB4 pin (when IRQ is set to VTST) upon entry into monitor mode. If monitor mode was entered with VDD
on IRQ and the reset vector blank, then the baud rate is independent of PTB4.
Table 19-1 also lists external frequencies required to achieve a standard baud rate of 7200 bps. The
effective baud rate is the bus frequency divided by 278. If using a crystal as the clock source, be aware
of the upper frequency limit that the internal clock module can handle. See 20.5 5-Vdc Electrical
Characteristics or 20.6 3.3-Vdc Electrical Characteristics for this limit.
19.3.1.7 Commands
The monitor ROM firmware uses these commands:
• READ (read memory)
• WRITE (write memory)
• IREAD (indexed read)
• IWRITE (indexed write)
• READSP (read stack pointer)
• RUN (run user program)
MC68HC908GR16A Data Sheet, Rev. 1.0
242
Freescale Semiconductor
Monitor Module (MON)
The monitor ROM firmware echoes each received byte back to the PTA0 pin for error checking. An 11-bit
delay at the end of each command allows the host to send a break character to cancel the command. A
delay of two bit times occurs before each echo and before READ, IREAD, or READSP data is returned.
The data returned by a read command appears after the echo of the last byte of the command.
NOTE
Wait one bit time after each echo before sending the next byte.
FROM HOST
READ
4
ADDRESS
HIGH
READ
4
1
ADDRESS
HIGH
ADDRESS
LOW
1
ADDRESS
LOW
4
DATA
1
3, 2
4
ECHO
RETURN
Notes:
1 = Echo delay, approximately 2 bit times
2 = Data return delay, approximately 2 bit times
3 = Cancel command delay, 11 bit times
4 = Wait 1 bit time before sending next byte.
Figure 19-14. Read Transaction
FROM HOST
WRITE
3
ADDRESS
HIGH
WRITE
3
1
ADDRESS
HIGH
1
ADDRESS
LOW
3
ADDRESS
LOW
1
DATA
DATA
3
1
2, 3
ECHO
Notes:
1 = Echo delay, approximately 2 bit times
2 = Cancel command delay, 11 bit times
3 = Wait 1 bit time before sending next byte.
Figure 19-15. Write Transaction
A brief description of each monitor mode command is given in Table 19-3 through Table 19-8.
Table 19-3. READ (Read Memory) Command
Description
Read byte from memory
Operand
2-byte address in high-byte:low-byte order
Data Returned
Returns contents of specified address
Opcode
$4A
Command Sequence
SENT TO MONITOR
READ
READ
ADDRESS
HIGH
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
ECHO
DATA
RETURN
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
243
Development Support
Table 19-4. WRITE (Write Memory) Command
Description
Operand
Data Returned
Opcode
Write byte to memory
2-byte address in high-byte:low-byte order; low byte followed by data byte
None
$49
Command Sequence
FROM HOST
WRITE
ADDRESS
HIGH
WRITE
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
DATA
ECHO
Table 19-5. IREAD (Indexed Read) Command
Description
Operand
Data Returned
Opcode
Read next 2 bytes in memory from last address accessed
None
Returns contents of next two addresses
$1A
Command Sequence
FROM HOST
IREAD
IREAD
DATA
DATA
ECHO
RETURN
Table 19-6. IWRITE (Indexed Write) Command
Description
Operand
Data Returned
Opcode
Write to last address accessed + 1
Single data byte
None
$19
Command Sequence
FROM HOST
IWRITE
IWRITE
DATA
DATA
ECHO
A sequence of IREAD or IWRITE commands can access a block of memory sequentially over the full
64-Kbyte memory map.
MC68HC908GR16A Data Sheet, Rev. 1.0
244
Freescale Semiconductor
Monitor Module (MON)
Table 19-7. READSP (Read Stack Pointer) Command
Description
Operand
Data Returned
Opcode
Reads stack pointer
None
Returns incremented stack pointer value (SP + 1) in high-byte:low-byte order
$0C
Command Sequence
FROM HOST
READSP
SP
HIGH
READSP
SP
LOW
ECHO
RETURN
Table 19-8. RUN (Run User Program) Command
Description
Executes PULH and RTI instructions
Operand
None
Data Returned
None
Opcode
$28
Command Sequence
FROM HOST
RUN
RUN
ECHO
The MCU executes the SWI and PSHH instructions when it enters monitor mode. The RUN command
tells the MCU to execute the PULH and RTI instructions. Before sending the RUN command, the host can
modify the stacked CPU registers to prepare to run the host program. The READSP command returns
the incremented stack pointer value, SP + 1. The high and low bytes of the program counter are at
addresses SP + 5 and SP + 6.
SP
HIGH BYTE OF INDEX REGISTER
SP + 1
CONDITION CODE REGISTER
SP + 2
ACCUMULATOR
SP + 3
LOW BYTE OF INDEX REGISTER
SP + 4
HIGH BYTE OF PROGRAM COUNTER
SP + 5
LOW BYTE OF PROGRAM COUNTER
SP + 6
SP + 7
Figure 19-16. Stack Pointer at Monitor Mode Entry
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
245
Development Support
19.3.2 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 user-defined data.
NOTE
Do not leave locations $FFF6–$FFFD blank. For security reasons, program
locations $FFF6–$FFFD even if they are not used for vectors.
During monitor mode entry, the MCU waits after the power-on reset for the host to send the eight security
bytes on pin 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 19-17.
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.
NOTE
The MCU does not transmit a break character until after the host sends the
eight security bytes.
VDD
4096 + 32 CGMXCLK CYCLES
COMMAND
BYTE 8
BYTE 2
BYTE 1
RST
FROM HOST
PA0
4
BREAK
2
1
COMMAND ECHO
1
BYTE 8 ECHO
Notes:
1 = Echo delay, approximately 2 bit times
2 = Data return delay, approximately 2 bit times
4 = Wait 1 bit time before sending next byte
5 = Wait until the monitor ROM runs
1
BYTE 2 ECHO
FROM MCU
4
1
BYTE 1 ECHO
5
Figure 19-17. Monitor Mode Entry Timing
To determine whether the security code entered is correct, check to see if bit 6 of RAM address $40 is
set. If it is, then the correct security code has been entered and FLASH can be accessed.
If the security sequence fails, the device should be reset by a power-on reset and brought up in monitor
mode to attempt another entry. After failing the security sequence, the FLASH module can also be mass
erased by executing an erase routine that was downloaded into internal RAM. The mass erase operation
clears the security code locations so that all eight security bytes become $FF (blank).
MC68HC908GR16A Data Sheet, Rev. 1.0
246
Freescale Semiconductor
Chapter 20
Electrical Specifications
20.1 Introduction
This section contains electrical and timing specifications.
20.2 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the MCU can be exposed without permanently
damaging it.
NOTE
This device is not guaranteed to operate properly at the maximum ratings. Refer to 20.5 5-Vdc Electrical
Characteristics and 20.6 3.3-Vdc 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
I
± 15
mA
IPTC0–PTC4
± 25
mA
Maximum current into VDD
IMVDD
150
mA
Maximum current out of VSS
IMVSS
150
mA
Tstg
–55 to +150
°C
Maximum current per pin excluding those specified below
Maximum current for pins PTC0–PTC4
Storage temperature
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).
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
247
Electrical Specifications
20.3 Functional Operating Range
Characteristic
Symbol
Value
Unit
TA
–40 to +125
°C
VDD
5.0 ±10%
3.3 ±10%
V
Symbol
Value
Unit
Thermal resistance
32-pin LQFP
48-pin LQFP
θJA
95
95
°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
PD × (TA + 273 °C)
+ PD2 × θJA
W/°C
Average junction temperature
TJ
TA + (PD × θJA)
°C
Operating temperature range
Operating voltage range
20.4 Thermal Characteristics
Characteristic
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.
MC68HC908GR16A Data Sheet, Rev. 1.0
248
Freescale Semiconductor
5-Vdc Electrical Characteristics
20.5 5-Vdc Electrical Characteristics
Typ(2)
Max
Unit
—
—
—
—
—
—
V
V
V
—
50
mA
—
50
mA
—
100
mA
—
—
—
—
—
—
0.4
1.5
1.5
V
V
V
—
—
50
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
—
0.2 × VDD
V
—
—
20
6
30
12
mA
mA
—
—
—
—
—
3
20
300
50
500
—
—
—
—
—
µA
µA
µA
µA
µA
Characteristic(1)
Output high voltage
(ILoad = –2.0 mA) all I/O pins
(ILoad = –10.0 mA) all I/O pins
(ILoad = –20.0 mA) pins PTC0–PTC4 only
Maximum combined IOH for port PTA7–PTA3,
port PTC0–PTC1, port E, port PTD0–PTD3
Maximum combined IOH for port PTA2–PTA0,
port B, port PTC2-PTC6, port PTD4–PTD7
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 = 20mA) pins PTC0–PTC4 only
Maximum combined IOH for port PTA7–PTA3,
port PTC0-PTC1, port E, port PTD0–PTD3
Maximum combined IOH for port PTA2–PTA0,
port B, port PTC2–PTC6, port PTD4–PTD7
Maximum total IOL for all port pins
Symbol
Min
VOH
VOH
VOH
IOH1
VDD – 0.8
VDD – 1.5
VDD – 1.5
—
IOH2
—
IOHT
—
VOL
VOL
VOL
IOL1
VDD supply current
Run(3)
Wait(4)
Stop(5)
25°C
25°C with TBM enabled(6)
25°C with LVI and TBM enabled(6)
–40°C to 125°C with TBM enabled(6)
–40°C to 125°C with LVI and TBM enabled(6)
IDD
DC injection current, all ports
IINJ
–2
—
+2
mA
IINJTOT
–25
—
+25
mA
I/O ports Hi-Z leakage current(7)
IIL
–10
—
+10
µA
Input current
IIn
–1
—
+1
µA
RPU
20
45
65
kΩ
Total dc current injection (sum of all I/O)
Pullup resistors (as input only)
Ports PTA7/KBD7–PTA0/KBD0, PTC6–PTC0,
PTD7/T2CH1–PTD0/SS
Continued on next page
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
249
Electrical Specifications
Symbol
Min
Typ(2)
Max
Unit
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
Monitor mode entry voltage
VTST
VDD + 2.5
—
VDD + 4.0
V
Low-voltage inhibit, trip falling voltage
VTRIPF
3.90
4.25
4.50
V
Low-voltage inhibit, trip rising voltage
VTRIPR
4.20
4.35
4.60
V
Low-voltage inhibit reset/recover hysteresis
(VTRIPF + VHYS = VTRIPR)
VHYS
—
100
—
mV
POR rearm voltage(8)
VPOR
0
—
100
mV
POR reset voltage(9)
VPORRST
0
700
800
mV
RPOR
0.035
—
—
V/ms
Characteristic(1)
POR rise time ramp rate(10)
1. VDD = 5.0 Vdc ± 10%, VSS = 0 Vdc, TA = TA (min) to TA (max), unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using external square wave clock source (fOSC = 32 MHz). All inputs 0.2 V from rail. No dc
loads. Less than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly
affects run IDD. Measured with all modules enabled.
4. Wait IDD measured using external square wave clock source (fOSC = 32 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 CGM and LVI enabled.
5. Stop IDD is measured with OSC1 = VSS. All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. All ports
configured as inputs. Typical values at midpoint of voltage range, 25°C only.
6. Stop IDD with TBM enabled is measured using an external square wave clock source (fOSC = 32 MHz). All inputs 0.2 V
from rail. No dc loads. Less than 100 pF on all outputs. All inputs configured as inputs.
7. Pullups and pulldowns are disabled. Port B leakage is specified in 20.10 5.0-Volt ADC Characteristics.
8. Maximum is highest voltage that POR is guaranteed.
9. Maximum is highest voltage that POR is possible.
10. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum
VDD is reached.
MC68HC908GR16A Data Sheet, Rev. 1.0
250
Freescale Semiconductor
3.3-Vdc Electrical Characteristics
20.6 3.3-Vdc Electrical Characteristics
Typ(2)
Max
Unit
—
—
—
—
—
—
V
V
V
—
30
mA
—
30
mA
—
60
mA
—
—
—
—
—
—
0.3
1.0
0.8
V
V
V
—
—
30
mA
IOL2
—
—
30
mA
IOLT
—
—
60
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
—
—
8
3
12
6
mA
mA
—
—
—
—
—
2
12
200
30
300
—
—
—
—
—
µA
µA
µA
µA
µA
Characteristic(1)
Output high voltage
(ILoad = –0.6 mA) all I/O pins
(ILoad = –4.0 mA) all I/O pins
(ILoad = –10.0 mA) pins PTC0–PTC4 only
Maximum combined IOH for port PTA7–PTA3,
port PTC0–PTC1, port E, port PTD0–PTD3
Maximum combined IOH for port PTA2–PTA0,
port B, port PTC2–PTC6, port PTD4–PTD7
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 = 20 mA) pins PTC0–PTC4 only
Maximum combined IOH for port PTA7–PTA3,
port PTC0–PTC1, port E, port PTD0–PTD3
Maximum combined IOH for port PTA2–PTA0,
port B, port PTC2–PTC6, port PTD4–PTD7
Maximum total IOL for all port pins
Symbol
Min
VOH
VOH
VOH
IOH1
VDD – 0.3
VDD – 1.0
VDD – 1.0
—
IOH2
—
IOHT
—
VOL
VOL
VOL
IOL1
VDD supply current
Run(3)
Wait(4)
Stop(5)
25°C
25°C with TBM enabled(6)
25°C with LVI and TBM enabled(6)
–40°C to 125°C with TBM enabled(6)
–40°C to 125°C with LVI and TBM enabled(6)
IDD
DC injection current, all ports
IINJ
–2
—
+2
mA
IINJTOT
–25
—
+25
mA
I/O ports Hi-Z leakage current(7)
IIL
–10
—
+10
µA
Input current
IIn
–1
—
+1
µA
RPU
20
45
65
kΩ
Total dc current injection (sum of all I/O)
Pullup resistors (as input only)
Ports PTA7/KBD7–PTA0/KBD0, PTC6–PTC0,
PTD7/T2CH1–PTD0/SS
Continued on next page
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
251
Electrical Specifications
Symbol
Min
Typ(2)
Max
Unit
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
Monitor mode entry voltage
VTST
VDD + 2.5
—
VDD + 4.0
V
Low-voltage inhibit, trip falling voltage
VTRIPF
2.35
2.6
2.7
V
Low-voltage inhibit, trip rising voltage
VTRIPR
2.4
2.66
2.8
V
Low-voltage inhibit reset/recover hysteresis
(VTRIPF + VHYS = VTRIPR)
VHYS
—
100
—
mV
POR rearm voltage(8)
VPOR
0
—
100
mV
POR reset voltage(9)
VPORRST
0
700
800
mV
RPOR
0.035
—
—
V/ms
Characteristic(1)
POR rise time ramp rate(10)
1. VDD = 3.3 Vdc ± 10%, VSS = 0 Vdc, TA = TA (min) to TA (max), unless otherwise noted
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using external square wave clock source (fOSC = 16 MHz). All inputs 0.2 V from rail. No dc
loads. Less than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly
affects run IDD. Measured with all modules enabled.
4. Wait IDD measured using external square wave clock source (fOSC = 16 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 CGM and LVI enabled.
5. Stop IDD is measured with OSC1 = VSS. All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. All ports
configured as inputs. Typical values at midpoint of voltage range, 25°C only.
6. Stop IDD with TBM enabled is measured using an external square wave clock source (fOSC = 16 MHz). All inputs 0.2 V
from rail. No dc loads. Less than 100 pF on all outputs. All inputs configured as inputs.
7. Pullups and pulldowns are disabled.
8. Maximum is highest voltage that POR is guaranteed.
9. Maximum is highest voltage that POR is possible.
10. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum
VDD is reached.
MC68HC908GR16A Data Sheet, Rev. 1.0
252
Freescale Semiconductor
5.0-Volt Control Timing
20.7 5.0-Volt Control Timing
Symbol
Min
Max
Unit
fOSC
1
dc
8
32
MHz
Internal operating frequency
fOP (fBus)
—
8
MHz
Internal clock period (1/fOP)
tCYC
125
—
ns
RST input pulse width low
tRL
50
—
ns
IRQ interrupt pulse width low (edge-triggered)
tILIH
50
—
ns
IRQ interrupt pulse period
tILIL
Note(3)
—
tCYC
Characteristic(1)
Frequency of operation
Crystal option
External clock option(2)
1. VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD unless otherwise noted.
2. No more than 10% duty cycle deviation from 50%.
3. The minimum period is the number of cycles it takes to execute the interrupt service routine plus 1 tCYC.
20.8 3.3-Volt Control Timing
Symbol
Min
Max
Unit
fOSC
1
dc
8
16
MHz
Internal operating frequency
fOP (fBus)
—
4
MHz
Internal clock period (1/fOP)
tCYC
250
—
ns
RST input pulse width low
tRL
125
—
ns
IRQ interrupt pulse width low (edge-triggered)
tILIH
125
—
ns
tILIL
Note(3)
—
tCYC
Characteristic(1)
Frequency of operation
Crystal option
External clock option(2)
IRQ interrupt pulse period
1. VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD unless otherwise noted.
2. No more than 10% duty cycle deviation from 50%.
3. The minimum period is the number of cycles it takes to execute the interrupt service routine plus 1 tCYC.
tRL
RST
tILIL
tILIH
IRQ
Figure 20-1. RST and IRQ Timing
MC68HC908GR16A Data Sheet, Rev. 1.0
Freescale Semiconductor
253
Electrical Specifications
20.9 Clock Generation Module (CGM) Characteristics
20.9.1 CGM Component Specifications
Characteristic
Symbol
Min
Typ
Max
Unit
fXCLK
1
4
8
MHz
Crystal load capacitance(1)
CL
—
20
—
pF
Crystal fixed capacitance
C1
—
(2 x CL) –5
—
pF
Crystal tuning capacitance
C2
—
(2 x CL) –5
—
pF
Feedback bias resistor
RB
0.5
1
10
MΩ
Series resistor
RS
—
0
—
Ω
Symbol
Min
Typ
Max
Unit
Reference frequency (for PLL operation)
fRCLK
1
4
8
MHz
Range nominal multiplier
fNOM
—
71.42
—
KHz
Programmed VCO center-of-range frequency(1)
fVRS
—
(Lx2E)fNOM
—
MHz
Crystal frequency
1. Consult crystal manufacturer’s data.
20.9.2 CGM Electrical Specifications
Characteristic
1. See 4.3.6 Programming the PLL for detailed instruction on selecting appropriate values for L and E.
MC68HC908GR16A Data Sheet, Rev. 1.0
254
Freescale Semiconductor
5.0-Volt ADC Characteristics
20.10 5.0-Volt ADC Characteristics
Characteristic(1)
Symbol
Min
Max
Unit
Comments
Supply voltage
VDDAD
4.5
5.5
V
VDDAD should be tied to
the same potential as VDD
via separate traces.
Input voltages
VADIN
0
VDDAD
V
VADIN
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