Freescale MC68HC908MR32 M68hc08 microcontroller Datasheet

MC68HC908MR32
MC68HC908MR16
Data Sheet
M68HC08
Microcontrollers
MC68HC908MR32
Rev. 6.1
07/2005
freescale.com
MC68HC908MR32
MC68HC908MR16
Data Sheet
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This product incorporates SuperFlash® technology licensed from SST.
© Freescale Semiconductor, Inc., 2005. All rights reserved.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
3
Revision History
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
August,
2001
3.0
October,
2001
4.0
December,
2001
5.0
Page
Number(s)
Description
Figure 2-1. MC68HC908MR32 Memory Map — Added FLASH Block Protect
Register (FLBPR) at address location $FF7E
29
Figure A-1. MC68HC908MR16 Memory Map — Added FLASH Block Protect
Register (FLBPR) at address location $FF7E
306
3.3.3 Conversion Time — Reworked equations and text for clarity.
50
Figure 18-8. Monitor Mode Circuit — PTA7 and connecting circuitry added
279
Table 18-2. Monitor Mode Signal Requirements and Options — Switch locations
added to column headings for clarity
281
Section 16. Timer Interface A (TIMA) — Timer discrepancies corrected throughout
this section.
233
Section 17. Timer Interface B (TIMB) — Timer discrepancies corrected throughout
this section.
255
Reformatted to meet current publication standards
November,
2003
July,
2005
6.0
6.1
Throughout
2.8.2 FLASH Page Erase Operation — Procedure reworked for clarity
42
2.8.3 FLASH Mass Erase Operation — Procedure reworked for clarity
42
2.8.4 FLASH Program Operation — Procedure reworked for clarity
43
Figure 14-14. SIM Break Status Register (SBSR) — Clarified definition of SBSW bit.
207
19.5 DC Electrical Characteristics — Corrected maximum value for monitor mode
entry voltage (on IRQ)
291
19.6 FLASH Memory Characteristics — Updated table entries
292
Updated to meet Freescale identity guidelines.
Throughout
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
4
Freescale Semiconductor
List of Chapters
Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Chapter 2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Chapter 3 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Chapter 4 Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Chapter 5 Configuration Register (CONFIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Chapter 6 Computer Operating Properly (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 7 Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
Chapter 8 External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Chapter 9 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Chapter 10 Input/Output (I/O) Ports (PORTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
Chapter 11 Power-On Reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC) . . . . . . . . . . . . . . . . . . . 115
Chapter 13 Serial Communications Interface Module (SCI) . . . . . . . . . . . . . . . . . . . . . . .157
Chapter 14 System Integration Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Chapter 15 Serial Peripheral Interface Module (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
Chapter 16 Timer Interface A (TIMA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
Chapter 17 Timer Interface B (TIMB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
Chapter 18 Development Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
Chapter 19 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
Chapter 20 Ordering Information and Mechanical Specifications . . . . . . . . . . . . . . . . . . 275
Appendix A MC68HC908MR16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
5
List of Chapters
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
6
Freescale Semiconductor
Table of Contents
Chapter 1
General Description
1.1
1.2
1.3
1.4
1.4.1
1.4.2
1.4.3
1.4.4
1.4.5
1.4.6
1.4.7
1.4.8
1.4.9
1.4.10
1.4.11
1.4.12
1.4.13
1.4.14
1.4.15
1.4.16
1.4.17
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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 VSSAD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Analog Power Supply Pins (VDDAD and VSSAD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Voltage Decoupling Capacitor Pin (VREFH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port A Input/Output (I/O) Pins (PTA7–PTA0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port B I/O Pins (PTB7/ATD7–PTB0/ATD0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port C I/O Pins (PTC6–PTC2 and PTC1/ATD9–PTC0/ATD8). . . . . . . . . . . . . . . . . . . . . . .
Port D Input-Only Pins (PTD6/IS3–PTD4/IS1 and PTD3/FAULT4–PTD0/FAULT1) . . . . . .
PWM Pins (PWM6–PWM1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PWM Ground Pin (PWMGND) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port E I/O Pins (PTE7/TCH3A–PTE3/TCLKA and PTE2/TCH1B–PTE0/TCLKB) . . . . . . . .
Port F I/O Pins (PTF5/TxD–PTF4/RxD and PTF3/MISO–PTF0/SPSCK) . . . . . . . . . . . . . .
17
17
18
20
22
22
22
22
22
23
23
23
23
23
23
23
23
23
24
24
24
Chapter 2
Memory
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
2.8.1
2.8.2
2.8.3
2.8.4
2.8.5
2.8.6
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Monitor ROM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Program Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Block Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
25
25
25
26
26
37
37
38
38
39
40
41
43
43
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
7
Table of Contents
2.8.7
2.8.8
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
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
Continuous Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.5
Result Justification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.3.6
Monotonicity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.4
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.5
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.1
ADC Analog Power Pin (VDDAD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.2
ADC Analog Ground Pin (VSSAD). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.3
ADC Voltage Reference Pin (VREFH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.4
ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.5
ADC Voltage In (ADVIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.6
ADC External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.6.1
VREFH and VREFL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.6.2
ANx. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.6.6.3
Grounding. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7
I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.1
ADC Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.2
ADC Data Register High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.3
ADC Data Register Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
3.7.4
ADC Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
45
45
45
47
47
48
48
48
49
50
50
50
50
50
50
50
51
51
51
51
51
51
52
54
54
55
Chapter 4
Clock Generator Module (CGM)
4.1
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.2
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.1
Crystal Oscillator Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2
Phase-Locked Loop Circuit (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2.1
PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2.2
Acquisition and Tracking Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2.3
Manual and Automatic PLL Bandwidth Modes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2.4
Programming the PLL. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.2.5
Special Programming Exceptions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.3
Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
4.3.4
CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
57
57
57
59
59
59
60
60
61
62
62
63
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
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
4.5
4.5.1
4.5.2
4.5.3
4.6
4.7
4.8
4.8.1
4.8.2
4.8.3
4.8.4
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Oscillator Enable Signal (SIMOSCEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Crystal Output Frequency Signal (CGMXCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Base Clock Output (CGMOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
PLL Programming Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acquisition/Lock Time Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Acquisition/Lock Time Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Parametric Influences on Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Choosing a Filter Capacitor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reaction Time Calculation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64
64
64
64
64
64
65
65
65
65
66
67
68
69
69
70
70
70
71
71
Chapter 5
Configuration Register (CONFIG)
5.1
5.2
5.3
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
Configuration Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 74
Chapter 6
Computer Operating Properly (COP)
6.1
6.2
6.3
6.3.1
6.3.2
6.3.3
6.3.4
6.3.5
6.3.6
6.4
6.5
6.6
6.7
6.8
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Reset Vector Fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
75
75
76
76
76
76
76
76
77
77
77
77
77
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Table of Contents
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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
79
79
79
80
80
81
81
82
83
83
83
83
83
84
89
Chapter 8
External Interrupt (IRQ)
8.1
8.2
8.3
8.4
8.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
IRQ Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
91
91
91
92
94
Chapter 9
Low-Voltage Inhibit (LVI)
9.1
9.2
9.3
9.3.1
9.3.2
9.3.3
9.3.4
9.4
9.5
9.6
9.7
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
False Reset Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
LVI Trip Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
LVI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
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Chapter 10
Input/Output (I/O) Ports (PORTS)
10.1
10.2
10.2.1
10.2.2
10.3
10.3.1
10.3.2
10.4
10.4.1
10.4.2
10.5
10.6
10.6.1
10.6.2
10.7
10.7.1
10.7.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port C Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port E Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Port F Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Data Direction Register F . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
101
103
103
103
104
104
105
106
106
106
107
108
108
109
110
110
110
Chapter 11
Power-On Reset (POR)
11.1
11.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC)
12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3 Timebase . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3.1
Resolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.3.2
Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4 PWM Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.1
Load Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.4.2
PWM Data Overflow and Underflow Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5 Output Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5.1
Selecting Six Independent PWMs or Three Complementary PWM Pairs . . . . . . . . . . . . .
12.5.2
Dead-Time Insertion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5.3
Top/Bottom Correction with Motor Phase Current Polarity Sensing . . . . . . . . . . . . . . . . .
12.5.4
Output Polarity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.5.5
PWM Output Port Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6 Fault Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6.1
Fault Condition Input Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6.1.1
Fault Pin Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6.1.2
Automatic Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6.1.3
Manual Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
115
115
120
120
122
122
122
125
126
126
127
130
133
135
137
137
139
139
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12.6.2
Software Output Disable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.6.3
Output Port Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.7 Initialization and the PWMEN Bit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.8 PWM Operation in Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9 Control Logic Block . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.1
PWM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.2
PWM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.3
PWMx Value Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.4
PWM Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.5
PWM Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.6
Dead-Time Write-Once Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.7
PWM Disable Mapping Write-Once Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.8
Fault Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.9
Fault Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.10
Fault Acknowledge Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.9.11
PWM Output Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
12.10 PWM Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
141
141
142
143
143
143
144
145
146
148
150
150
150
152
153
154
155
Chapter 13
Serial Communications Interface Module (SCI)
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.1
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2
Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.2
Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.3
Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.4
Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.5
Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.2.6
Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3
Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.1
Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.2
Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.3
Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.4
Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.5
Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.6
Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.3.3.7
Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.4 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.5 SCI During Break Module Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.6.1
PTF5/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.6.2
PTF4/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7.1
SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
13.7.2
SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
157
157
159
160
161
162
162
162
163
163
163
163
164
165
165
167
167
167
167
168
168
168
168
169
169
169
171
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13.7.3
13.7.4
13.7.5
13.7.6
13.7.7
SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
173
174
176
177
177
Chapter 14
System Integration Module (SIM)
14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2 SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.1
Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.2
Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.2.3
Clocks in Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.1
External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.2
Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.2.1
Power-On Reset (POR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.2.2
Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.2.3
Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.2.4
Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.2.5
Forced Monitor Mode Entry Reset (MENRST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.3.2.6
Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4 SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.1
SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.4.2
SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.5 Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.5.1
Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.5.1.1
Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.5.1.2
Software Interrupt (SWI) Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.5.2
Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.6 Low-Power Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.6.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.6.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.7 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.7.1
SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.7.2
SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
14.7.3
SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
181
182
182
182
183
183
183
184
185
185
186
186
186
186
186
186
186
187
187
189
190
190
190
190
191
191
191
192
193
Chapter 15
Serial Peripheral Interface Module (SPI)
15.1
15.2
15.3
15.4
15.4.1
15.4.2
15.5
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
195
195
195
197
198
199
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Table of Contents
15.5.1
Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.2
Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.3
Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.5.4
Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.6 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.6.1
Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.6.2
Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.7 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.8 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.9 Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.10 Low-Power Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.11 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.11.1
MISO (Master In/Slave Out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.11.2
MOSI (Master Out/Slave In). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.11.3
SPSCK (Serial Clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.11.4
SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.11.5
VSS (Clock Ground) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.12 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.12.1
SPI Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.12.2
SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
15.12.3
SPI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
199
200
201
201
203
203
204
206
207
207
208
208
209
209
209
209
210
210
210
212
214
Chapter 16
Timer Interface A (TIMA)
16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.1
TIMA Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.2
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.3
Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.4
Pulse-Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.3.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.5 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.6.1
TIMA Clock Pin (PTE3/TCLKA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.6.2
TIMA Channel I/O Pins (PTE4/TCH0A–PTE7/TCH3A) . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7.1
TIMA Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7.2
TIMA Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7.3
TIMA Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7.4
TIMA Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
16.7.5
TIMA Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
215
215
219
219
219
220
220
221
221
222
223
223
224
224
225
225
225
225
225
227
228
228
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Chapter 17
Timer Interface B (TIMB)
17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.1
TIMB Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.2
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.3
Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.3.1
Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.3.2
Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.4
Pulse-Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.4.1
Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.4.2
Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.3.4.3
PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.5 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6.1
TIMB Clock Pin (PTE0/TCLKB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.6.2
TIMB Channel I/O Pins (PTE1/TCH0B–PTE2/TCH1B) . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7.1
TIMB Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7.2
TIMB Counter Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7.3
TIMB Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7.4
TIMB Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
17.7.5
TIMB Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
235
235
235
238
238
239
239
240
240
241
241
242
243
243
243
243
243
244
244
246
246
247
250
Chapter 18
Development Support
18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.1.1
Flag Protection During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.1.2
CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.1.3
TIM1 and TIM2 During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.1.4
COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.2
Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.2.1
Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.2.2
Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.3
Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.3.1
Break Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.3.2
Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.3.3
Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.2.3.4
Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
251
251
251
251
253
253
253
253
253
253
253
254
254
255
255
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
15
Table of Contents
18.3 Monitor ROM (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1
Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.1
Entering Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.2
Normal Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.3
Forced Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.4
Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.5
Echoing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.6
Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.7
Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.1.8
Baud Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
18.3.2
Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
255
256
256
256
259
259
260
260
260
263
263
Chapter 19
Electrical Specifications
19.1
19.2
19.3
19.4
19.5
19.6
19.7
19.8
19.9
19.10
19.11
19.12
19.13
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
FLASH Memory Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Serial Peripheral Interface Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
TImer Interface Module Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Clock Generation Module Component Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
CGM Acquisition/Lock Time Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Analog-to-Digital Converter (ADC) Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
265
265
266
266
267
268
268
269
272
272
272
273
274
Chapter 20
Ordering Information and Mechanical Specifications
20.1
20.2
20.3
20.4
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
64-Pin Plastic Quad Flat Pack (QFP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
56-Pin Shrink Dual In-Line Package (SDIP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
275
275
276
277
Appendix A
MC68HC908MR16
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
16
Freescale Semiconductor
Chapter 1
General Description
1.1 Introduction
The MC68HC908MR32 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.
The information contained in this document pertains to the MC68HC908MR16 with the exceptions shown
in Appendix A MC68HC908MR16.
1.2 Features
Features include:
• High-performance M68HC08 architecture
• Fully upward-compatible object code with M6805, M146805, and M68HC05 Families
• 8-MHz internal bus frequency
• On-chip FLASH memory with in-circuit programming capabilities of FLASH program memory:
MC68HC908MR32 — 32 Kbytes
MC68HC908MR16 — 16 Kbytes
• On-chip programming firmware for use with host personal computer
• FLASH data security(1)
• 768 bytes of on-chip random-access memory (RAM)
• 12-bit, 6-channel center-aligned or edge-aligned pulse-width modulator (PWMMC)
• Serial peripheral interface module (SPI)
• Serial communications interface module (SCI)
• 16-bit, 4-channel timer interface module (TIMA)
• 16-bit, 2-channel timer interface module (TIMB)
• Clock generator module (CGM)
• Low-voltage inhibit (LVI) module with software selectable trip points
• 10-bit, 10-channel analog-to-digital converter (ADC)
• System protection features:
– Optional computer operating properly (COP) reset
– Low-voltage detection with optional reset
– Illegal opcode or address detection with optional reset
– Fault detection with optional PWM disabling
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
17
General Description
•
•
•
•
•
Available packages:
– 64-pin plastic quad flat pack (QFP)
– 56-pin shrink dual in-line package (SDIP)
Low-power design, fully static with wait mode
Master reset pin (RST) and power-on reset (POR)
Stop mode as an option
Break module (BRK) supports setting the in-circuit simulator (ICS) single break point
Features of the CPU08 include:
• Enhanced M68HC05 programming model
• Extensive loop control functions
• 16 addressing modes (eight more than the M68HC05)
• 16-bit index register and stack pointer
• Memory-to-memory data transfers
• Fast 8 × 8 multiply instruction
• Fast 16/8 divide instruction
• Binary-coded decimal (BCD) instructions
• Optimization for controller applications
• C language support
1.3 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908MR32.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
18
Freescale Semiconductor
Freescale Semiconductor
PTA
PTA7–PTA0
PTB
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
PTC
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1/ATD9(1)
PTC0/ATD8
PTD
CONTROL AND STATUS REGISTERS — 112 BYTES
DDRA
ARITHMETIC/LOGIC
UNIT
PTD6/IS3
PTD5/IS2
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
DDRB
CPU
REGISTERS
PTE
INTERNAL BUS
M68HC08 CPU
USER FLASH — 32,256 BYTES
USER RAM — 768 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VDDAD
VSSAD(3)
VREFL(3)
VREFH
PWMGND
PWM6–PWM1
VDDAD
VSSAD
PULSE-WIDTH MODULATOR
MODULE
DDRC
SERIAL PERIPHERAL INTERFACE
MODULE(2)
POWER-ON RESET
MODULE
SINGLE BREAK
MODULE
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PTF1/SS(1)
PTF0/SPSCK(1)
POWER
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
19
Figure 1-1. MCU Block Diagram
MCU Block Diagram
VSS
VDD
ANALOG-TO-DIGITAL CONVERTER
MODULE
SERIAL COMMUNICATIONS INTERFACE
MODULE
DDRE
USER FLASH VECTOR SPACE — 46 BYTES
TIMER INTERFACE
MODULE B
PTF
MONITOR ROM — 240 BYTES
DDRF
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
TIMER INTERFACE
MODULE A
General Description
1.4 Pin Assignments
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
VSSAD
OSC2
OSC1
CGMXFC
VDDAD
62
61
60
59
58
57
56
55
54
53
52
51
50
PTB2/ATD2
1
49
RST
PTB0/ATD0
63
64
PTB1/ATD1
Figure 1-2 shows the 64-pin QFP pin assignments and Figure 1-3 shows the 56-pin SDIP pin
assignments.
48
IRQ
VDDAD
9
40
VDD
VSSAD
10
39
PTE7/TCH3A
VREFL
11
38
PTE6/TCH2A
VREFH
12
37
PTE5/TCH1A
PTC2
13
36
PTE4/TCH0A
PTC3
14
35
PTE3/TCLKA
PTC4
15
34
PTE2/TCH1B
33
PTE1/TCH0B
PTE0/TCLKB 32
16
PTC6 17
PTC5
31
VSS
PWM6
41
30
8
PWM5
PTC1/ATD9
29
PTF0/SPSCK
PWMGND
42
28
7
PWM4
PTC0/ATD8
27
PTF1/SS
PWM3
43
26
6
PWM2
PTB7/ATD7
25
PTF2/MOSI
PWM1
44
24
5
PTD6/IS3
PTB6/ATD6
23
PTF3/MISO
PTD5/IS2
45
22
4
PTD4/IS1
PTB5/ATD5
21
PTF4/RxD
PTD3/FAULT4
46
20
3
PTD2/FAULT3
PTB4/ATD4
19
PTF5/TxD
PTD1/FAULT2
47
18
2
PTD0/FAULT1
PTB3/ATD3
Figure 1-2. 64-Pin QFP Pin Assignments
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
20
Freescale Semiconductor
Pin Assignments
PTA2
1
56
PTA1
PTA3
2
55
PTA0
PTA4
3
54
VSSA
PTA5
4
53
OSC2
PTA6
5
52
OSC1
PTA7
6
51
CGMXFC
PTB0/ATD0
7
50
VDDA
PTB1/ATD1
8
49
RST
PTB2/ATD2
9
48
IRQ
PTB3/ATD3
10
47
PTF5/TxD
PTB4/ATD4
11
46
PTF4/RxD
PTB5/ATD5
12
45
VSS
PTB6/ATD5
13
44
VDD
PTB7/ATD7
14
43
PTE7/TCH3A
PTC0/ATD8
15
42
PTE6/TCH2A
VDDAD
16
41
PTE5/TCH1A
VSSAD/VREFL
17
40
PTE4/TCH0A
VREFH
18
39
PTE3/TCLKA
PTC2
19
38
NC
PTC3
20
37
PWM6
PTC4
21
36
PWM5
PTC5
22
35
PWMGND
PTC6
23
34
PWM4
PTD0/FAULT1
24
33
PWM3
PTD1/FAULT2
25
32
PWM2
PTD2/FAULT3
26
31
PWM1
PTD3/FAULT4
27
30
PTD6/IS3
PTD4/IS1
28
29
PTD5/IS2
Note:
PTC1, PTE0, PTE1, PTE2, PTF0, PTF1, PTF2, and PTF3
are removed from this package.
Figure 1-3. 56-Pin SDIP Pin Assignments
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
21
General Description
1.4.1 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
1–10 µF
VDD
Note: Component values shown represent typical applications.
Figure 1-4. Power Supply Bypassing
1.4.2 Oscillator Pins (OSC1 and OSC2)
The OSC1 and OSC2 pins are the connections for the on-chip oscillator circuit. For more detailed
information, see Chapter 4 Clock Generator Module (CGM).
1.4.3 External Reset Pin (RST)
A logic 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset
of the entire system. It is driven low when any internal reset source is asserted. See Chapter 14 System
Integration Module (SIM).
1.4.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. See Chapter 8 External Interrupt (IRQ).
1.4.5 CGM Power Supply Pins (VDDA and VSSAD)
VDDA and VSSAD are the power supply pins for the analog portion of the clock generator module (CGM).
Decoupling of these pins should be per the digital supply. See Chapter 4 Clock Generator Module (CGM).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
22
Freescale Semiconductor
Pin Assignments
1.4.6 External Filter Capacitor Pin (CGMXFC)
CGMXFC is an external filter capacitor connection for the CGM. See Chapter 4 Clock Generator Module
(CGM).
1.4.7 Analog Power Supply Pins (VDDAD and VSSAD)
VDDAD and VSSAD are the power supply pins for the analog-to-digital converter. Decoupling of these pins
should be per the digital supply. See Chapter 3 Analog-to-Digital Converter (ADC).
1.4.8 ADC Voltage Decoupling Capacitor Pin (VREFH)
VREFH is the power supply for setting the reference voltage. Connect the VREFH pin to the same voltage
potential as VDDAD. See Chapter 3 Analog-to-Digital Converter (ADC).
1.4.9 ADC Voltage Reference Low Pin (VREFL)
VREFL is the lower reference supply for the ADC. Connect the VREFL pin to the same voltage potential as
VSSAD. See Chapter 3 Analog-to-Digital Converter (ADC).
1.4.10 Port A Input/Output (I/O) Pins (PTA7–PTA0)
PTA7–PTA0 are general-purpose bidirectional input/output (I/O) port pins. See Chapter 10 Input/Output
(I/O) Ports (PORTS).
1.4.11 Port B I/O Pins (PTB7/ATD7–PTB0/ATD0)
Port B is an 8-bit special function port that shares all eight pins with the analog-to-digital converter (ADC).
See Chapter 3 Analog-to-Digital Converter (ADC) and Chapter 10 Input/Output (I/O) Ports (PORTS).
1.4.12 Port C I/O Pins (PTC6–PTC2 and PTC1/ATD9–PTC0/ATD8)
PTC6–PTC2 are general-purpose bidirectional I/O port pins Chapter 10 Input/Output (I/O) Ports
(PORTS). PTC1/ATD9–PTC0/ATD8 are special function port pins that are shared with the
analog-to-digital converter (ADC). See Chapter 3 Analog-to-Digital Converter (ADC) and Chapter 10
Input/Output (I/O) Ports (PORTS).
1.4.13 Port D Input-Only Pins (PTD6/IS3–PTD4/IS1 and PTD3/FAULT4–PTD0/FAULT1)
PTD6/IS3–PTD4/IS1 are special function input-only port pins that also serve as current sensing pins for
the pulse-width modulator module (PWMMC). PTD3/FAULT4–PTD0/FAULT1 are special function port
pins that also serve as fault pins for the PWMMC. See Chapter 12 Pulse-Width Modulator for Motor
Control (PWMMC) and Chapter 10 Input/Output (I/O) Ports (PORTS).
1.4.14 PWM Pins (PWM6–PWM1)
PWM6–PWM1 are dedicated pins used for the outputs of the pulse-width modulator module (PWMMC).
These are high-current sink pins. See Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC)
and Chapter 19 Electrical Specifications.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
23
General Description
1.4.15 PWM Ground Pin (PWMGND)
PWMGND is the ground pin for the pulse-width modulator module (PWMMC). This dedicated ground pin
is used as the ground for the six high-current PWM pins. See Chapter 12 Pulse-Width Modulator for Motor
Control (PWMMC).
1.4.16 Port E I/O Pins (PTE7/TCH3A–PTE3/TCLKA and PTE2/TCH1B–PTE0/TCLKB)
Port E is an 8-bit special function port that shares its pins with the two timer interface modules (TIMA and
TIMB). See Chapter 16 Timer Interface A (TIMA), Chapter 17 Timer Interface B (TIMB), and Chapter 10
Input/Output (I/O) Ports (PORTS).
1.4.17 Port F I/O Pins (PTF5/TxD–PTF4/RxD and PTF3/MISO–PTF0/SPSCK)
Port F is a 6-bit special function port that shares two of its pins with the serial communications interface
module (SCI) and four of its pins with the serial peripheral interface module (SPI). See Chapter 15 Serial
Peripheral Interface Module (SPI), Chapter 13 Serial Communications Interface Module (SCI), and
Chapter 10 Input/Output (I/O) Ports (PORTS).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
24
Freescale Semiconductor
Chapter 2
Memory
2.1 Introduction
The central processor unit (CPU08) can address 64 Kbytes of memory space. The memory map, shown
in Figure 2-1, includes:
• 32 Kbytes of FLASH
• 768 bytes of random-access memory (RAM)
• 46 bytes of user-defined vectors
• 240 bytes of monitor read-only memory (ROM)
2.2 Unimplemented Memory Locations
Some addresses are unimplemented. Accessing an unimplemented address can cause an illegal address
reset. In the memory map and in the input/output (I/O) register summary, unimplemented addresses are
shaded.
Some I/O bits are read only; the write function is unimplemented. Writing to a read-only I/O bit has no
effect on microcontroller unit (MCU) operation. In register figures, the write function of read-only bits is
shaded.
Similarly, some I/O bits are write only; the read function is unimplemented. Reading of write-only I/O bits
has no effect on MCU operation. In register figures, the read function of write-only bits is shaded.
2.3 Reserved Memory Locations
Some addresses are reserved. Writing to a reserved address can have unpredictable effects on MCU
operation. In the memory map (Figure 2-1) and in the I/O register summary (Figure 2-2) reserved
addresses are marked with the word reserved.
Some I/O bits are reserved. Writing to a reserved bit can have unpredictable effects on MCU operation.
In register figures, reserved bits are marked with the letter R.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
25
Memory
2.4 I/O Section
Addresses $0000–$005F, shown in Figure 2-2, contain most of the control, status, and data registers.
Additional I/O registers have these addresses:
• $FE00, SIM break status register (SBSR)
• $FE01, SIM reset status register (SRSR)
• $FE03, SIM break flag control register (SBFCR)
• $FE07, FLASH control register (FLCR)
• $FE0C, Break address register high (BRKH)
• $FE0D, Break address register low (BRKL)
• $FE0E, Break status and control register (BRKSCR)
• $FE0F, LVI status and control register (LVISCR)
• $FF7E, FLASH block protect register (FLBPR)
• $FFFF, COP control register (COPCTL)
2.5 Memory Map
Figure 2-1 shows the memory map for the MC68HC908MR32 while the memory map for the
MC68HC908MR16 is shown in Appendix A MC68HC908MR16
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
26
Freescale Semiconductor
Memory Map
$0000
↓
I/O REGISTERS — 96 BYTES
$005F
$0060
↓
RAM — 768 BYTES
$035F
$0360
↓
UNIMPLEMENTED — 31,904 BYTES
$7FFF
$8000
↓
FLASH — 32,256 BYTES
$FDFF
$FE00
SIM BREAK STATUS REGISTER (SBSR)
$FE01
SIM RESET STATUS REGISTER (SRSR)
$FE02
RESERVED
$FE03
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
$FE04
RESERVED
$FE05
RESERVED
$FE06
RESERVED
$FE07
RESERVED
$FE08
FLASH CONTROL REGISTER (FLCR)
$FE09
UNIMPLEMENTED
$FE0A
UNIMPLEMENTED
$FE0B
UNIMPLEMENTED
$FE0C
SIM BREAK ADDRESS REGISTER HIGH (BRKH)
$FE0D
SIM BREAK ADDRESS REGISTER LOW (BRKL)
$FE0E
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
$FE0F
LVI STATUS AND CONTROL REGISTER (LVISCR)
$FE10
↓
MONITOR ROM — 240 BYTES
$FEFF
$FF00
↓
$FF7D
UNIMPLEMENTED — 126 BYTES
$FF7E
FLASH BLOCK PROTECT REGISTER (FLBPR)
$FF7F
↓
$FFD1
UNIMPLEMENTED — 83 BYTES
$FFD2
↓
VECTORS — 46 BYTES
$FFFF
Figure 2-1. MC68HC908MR32 Memory Map
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
27
Memory
Addr.
$0000
$0001
$0002
$0003
$0004
$0005
Register Name
Port A Data Register Read:
(PTA) Write:
See page 103. Reset:
Port B Data Register Read:
(PTB) Write:
See page 104. Reset:
Port D Data Register
(PTD) Write:
See page 107. Reset:
2
1
Bit 0
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
PTC2
PTC1
PTC0
Unaffected by reset
PTB7
Port E Data Register Read:
(PTE) Write:
See page 108. Reset:
Port F Data Register Read:
(PTF) Write:
See page 110. Reset:
Unimplemented
$000B
Unimplemented
PTB6
PTB5
PTB4
PTB3
Unaffected by reset
0
PTC6
PTC5
PTC4
0
PTD6
PTD5
PTD4
PTC3
PTD3
PTD2
PTD1
PTD0
R
R
R
R
R
R
R
R
Unaffected by reset
Unaffected by reset
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
0
0
PTE7
PTE6
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
PTF2
PTF1
PTF0
Data Direction Register B Read: DDRB7
(DDRB) Write:
See page 105. Reset:
0
$000A
U = Unaffected
3
Data Direction Register A Read: DDRA7
(DDRA) Write:
See page 103. Reset:
0
Unimplemented
$000D
4
Read:
$0007
$000C
5
R
$0006
$0009
6
Port C Data Register Read:
(PTC) Write:
See page 106. Reset:
Data Direction Register C Read:
(DDRC) Write:
See page 106. Reset:
$0008
Bit 7
0
R
Unaffected by reset
0
0
R
R
PTF5
PTF4
PTF3
Unaffected by reset
Data Direction Register E Read: DDRE7
(DDRE) Write:
See page 109. Reset:
0
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
DDRF5
DDRF4
DDRF3
DDRF2
DDRF1
DDRF0
0
0
0
0
0
0
Bold
= Buffered
Data Direction Register F Read:
(DDRF) Write:
See page 110. Reset:
0
0
R
R
X = Indeterminate
R
= Reserved
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 1 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
28
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
Read:
$000E
TIMA Status/Control Register
(TASC) Write:
See page 226. Reset:
TOF
$0019
Bit 0
PS2
PS1
PS0
0
0
0
0
0
TIMA Counter Register High Read:
(TACNTH) Write:
See page 227. Reset:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
TIMA Counter Register Low Read:
(TACNTL) Write:
See page 227. Reset:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
1
1
1
1
1
1
1
1
TIMA Counter Modulo
Register Low (TAMODL) Write:
See page 228. Reset:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
TIMA Channel 0 Status/Control Read:
Register (TASC0) Write:
See page 229. Reset:
CH0F
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
TIMA Counter Modulo Read:
Register High (TAMODH) Write:
See page 228. Reset:
TIMA Channel 0 Register High Read:
(TACH0H) Write:
See page 232. Reset:
TIMA Channel 0 Register Low Read:
(TACH0L) Write:
See page 232. Reset:
Read:
$0018
R
1
1
$0012
$0017
TRST
2
0
Read:
$0016
3
0
0
$0011
$0015
4
0
TSTOP
$0010
$0014
5
TOIE
$000F
$0013
6
TIMA Channel 1 Status/Control
Register (TASC1) Write:
See page 232. Reset:
TIMA Channel 1 Register High Read:
(TACH1H) Write:
See page 232. Reset:
TIMA Channel 1 Register Low Read:
(TACH1L) Write:
See page 232. Reset:
TIMA Channel 2 Status/Control Read:
Register (TASC2) Write:
See page 229. Reset:
U = Unaffected
X = Indeterminate
0
0
Indeterminate after reset
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
CH1F
0
CH1IE
0
R
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
Bold
= Buffered
Indeterminate after reset
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
CH2F
0
0
R
CH2IE
MS2B
0
0
= Reserved
MS2A
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 2 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
29
Memory
Addr.
Register Name
Read:
$001A
$001B
$001C
$001D
TIMA Channel 2 Register High
(TACH2H) Write:
See page 232. Reset:
TIMA Channel 2 Register Low Read:
(TACH2L) Write:
See page 232. Reset:
TIMA Channel 3 Status/Control Read:
Register (TASC3) Write:
See page 229. Reset:
TIMA Channel 3 Register High Read:
(TACH3H) Write:
See page 232. Reset:
Read:
$001E
TIMA Channel 3 Register Low
(TACH3L) Write:
See page 232. Reset:
Configuration Register Read:
(CONFIG) Write:
See page 74. Reset:
$001F
PWM Control Register 1 Read:
(PCTL1) Write:
See page 146. Reset:
$0020
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Bit 7
Read:
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
CH3F
0
CH3IE
0
R
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
EDGE
BOTNEG
TOPNEG
INDEP
LVIRST
LVIPWR
STOPE
COPD
0
0
0
0
1
1
0
0
DISX
DISY
PWMINT
PWMF
ISENS1
ISENS0
LDOK
PWMEN
0
0
0
0
0
0
0
0
IPOL1
IPOL2
IPOL3
PRSC1
PRSC0
PWM Control Register 2 Read: LDFQ1
(PCTL2) Write:
See page 148. Reset:
0
$0021
LDFQ0
0
0
0
0
0
0
0
0
Fault Control Register
(FCR) Write:
See page 150. Reset:
FINT4
FMODE4
FINT3
FMODE3
FINT2
FMODE2
FINT1
FMODE1
0
0
0
0
0
0
0
0
Fault Status Register Read:
(FSR) Write:
See page 152. Reset:
FPIN4
FFLAG4
FPIN3
FFLAG3
FPIN2
FFLAG2
FPIN1
FFLAG1
U
0
U
0
U
0
U
0
Fault Acknowledge Register Read:
(FTACK) Write:
See page 153. Reset:
0
0
DT6
DT5
DT4
DT3
DT2
DT1
PWM Output Control Register Read:
(PWMOUT) Write:
See page 154. Reset:
0
$0022
$0023
$0024
$0025
Bit 7
U = Unaffected
X = Indeterminate
FTACK4
0
0
R
FTACK3
FTACK2
FTACK1
0
0
0
0
0
0
0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
0
0
0
0
0
0
Bold
= Buffered
= Reserved
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 3 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
30
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
PWM Counter Register High
(PCNTH) Write:
See page 143. Reset:
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
PWM Counter Register Low Read:
(PCNTL) Write:
See page 143. Reset:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
X
X
X
X
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
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
0
0
0
0
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
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
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
0
0
0
0
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
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
Bold
= Buffered
Read:
$0026
$0027
$0028
$0029
PWM Counter Modulo Register Read:
High (PMODH) Write:
See page 144. Reset:
PWM Counter Modulo Register Read:
Low (PMODL) Write:
See page 144. Reset:
Read:
$002A
$002B
$002C
$002D
PWM 1 Value Register High
(PVAL1H) Write:
See page 145. Reset:
PWM 1 Value Register Low Read:
(PVAL1L) Write:
See page 145. Reset:
PWM 2 Value Register High Read:
(PVAL2H) Write:
See page 145. Reset:
PWM 2 Value Register Low Read:
(PVAL2L) Write:
See page 145. Reset:
Read:
$002E
$002F
$0030
$0031
U = Unaffected
PWM 3 Value Register High
(PVAL3H) Write:
See page 145. Reset:
PWM 3 Value Register Low Read:
(PVAL3L) Write:
See page 145. Reset:
PWM 4 Value Register High Read:
(PVAL4H) Write:
See page 145. Reset:
PWM 4 Value Register Low Read:
(PVAL4L) Write:
See page 145. Reset:
X = Indeterminate
0
R
= Reserved
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 4 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
31
Memory
Addr.
Register Name
Read:
PWM 5 Value Register High
(PMVAL5H) Write:
See page 145. Reset:
$0032
PWM 5 Value Register Low Read:
(PVAL5L) Write:
See page 145. Reset:
$0033
PWM 6 Value Register High Read:
(PVAL6H) Write:
See page 145. Reset:
$0034
PWM 6 Value Register Low Read:
(PMVAL6L) Write:
See page 145. Reset:
$0035
Read:
Dead-Time Write-Once
Register (DEADTM) Write:
See page 150. Reset:
$0036
$0037
PWM Disable Mapping Read:
Write-Once Register (DISMAP) Write:
See page 137. Reset:
$0038
$0039
$003B
$003C
$003D
U = Unaffected
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
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
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
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
ENSCI
TXINV
M
WAKE
ILTY
PEN
PTY
0
0
0
0
0
0
0
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
0
0
0
0
0
0
0
0
0
R
R
ORIE
NEIE
FEIE
PEIE
SCI Control Register 1 Read: LOOPS
(SCC1) Write:
See page 169. Reset:
0
SCI Control Register 2 Read: SCTIE
(SCC2) Write:
See page 171. Reset:
0
Read:
$003A
Bit 7
SCI Control Register 3
(SCC3) Write:
See page 173. Reset:
R8
U
U
0
0
0
0
0
0
SCI Status Register 1 Read:
(SCS1) Write:
See page 174. Reset:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
R
R
R
R
R
R
R
R
1
1
0
0
0
0
0
0
SCI Status Register 2 Read:
(SCS2) Write:
See page 176. Reset:
0
0
0
0
0
0
BKF
RPF
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
SCI Data Register Read:
(SCDR) Write:
See page 177. Reset:
X = Indeterminate
R
T8
Unaffected by reset
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 5 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
32
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
6
SCI Baud Rate Register
(SCBR) Write:
See page 177. Reset:
0
0
R
R
0
0
IRQ Status/Control Register Read:
(ISCR) Write:
See page 94. Reset:
0
0
R
R
0
0
0
0
0
AIEN
ADCO
ADCH4
0
0
0
0
R
Read:
$003E
$003F
$0040
$0041
ADC Data Register High Read:
Right Justified Mode (ADRH) Write:
See page 54. Reset:
Read:
ADC Data Register Low
Right Justified Mode (ADRL) Write:
See page 54. Reset:
$0042
ADC Clock Register Read:
(ADCLK) Write:
See page 55. Reset:
$0043
1
Bit 0
SCR2
SCR1
SCR0
0
0
0
IMASK1
MODE1
0
0
0
ADCH3
ADCH2
ADCH1
ADCH0
1
1
1
1
1
0
0
0
0
AD9
AD8
R
R
R
R
R
R
R
AD7
AD6
AD5
AD4
SPI Status and Control Read:
Register (SPSCR) Write:
See page 212. Reset:
$0045
Read:
SPI Data Register
(SPDR) Write:
See page 214. Reset:
$0046
$0047
↓
$0050
4
3
AD3
AD2
AD1
AD0
R
R
R
R
R
R
R
R
0
SCP1
SCP0
0
0
0
0
0
IRQF
R
R
R
0
ACK1
Unaffected by reset
Unaffected by reset
0
ADIV2
ADIV1
ADIV0
ADICLK
MODE1
MODE0
0
0
0
0
0
0
1
0
0
R
SPMSTR
CPOL
CPHA
SPWOM
SPE
SPTIE
0
1
0
1
0
0
0
OVRF
MODF
SPTE
R
R
R
MODFEN
SPR1
SPR0
SPI Control Register Read: SPRIE
(SPCR) Write:
See page 211. Reset:
0
$0044
$0051
2
ADC Status and Control Read: COCO
R
Register (ADSCR) Write:
See page 52. Reset:
0
5
SPRF
R
ERRIE
R
0
0
0
0
1
0
0
0
R7
R6
R5
R4
R3
R2
R1
R0
T7
T6
T5
T4
T3
T2
T1
T0
PS2
PS1
PS0
Unaffected by reset
Unimplemented
TIMB Status/Control Register Read:
(TBSC) Write:
See page 244. Reset:
TOF
TIMB Counter Register High Read:
(TBCNTH) Write:
See page 246. Reset:
$0052
U = Unaffected
X = Indeterminate
0
0
TRST
R
1
0
0
0
0
0
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bold
= Buffered
TOIE
TSTOP
0
0
Bit 15
0
R
= Reserved
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 6 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
33
Memory
Addr.
Register Name
Read:
TIMB Counter Register Low
(TBCNTL) Write:
See page 246. Reset:
$0053
$0054
$0055
$0056
TIMB Counter Modulo Register Read:
High (TBMODH) Write:
See page 246. Reset:
TIMB Counter Modulo Register Read:
Low (TBMODL) Write:
See page 246. Reset:
TIMB Channel 0 Status/Control Read:
Register (TBSC0) Write:
See page 247. Reset:
Read:
$0057
$0058
$0059
$005A
TIMB Channel 0 Register High
(TBCH0H) Write:
See page 250. Reset:
TIMB Channel 0 Register Low Read:
(TBCH0L) Write:
See page 250. Reset:
TIMB Channel 1 Status/Control Read:
Register (TBSC1) Write:
See page 247. Reset:
TIMB Channel 1 Register High Read:
(TBCH1H) Write:
See page 250. Reset:
Read:
$005B
TIMB Channel 1 Register Low
(TBCH1L) Write:
See page 250. Reset:
$005C
$005D
$005E
$005F
U = Unaffected
PLL Control Register Read:
(PCTL) Write:
See page 66. Reset:
PLL Bandwidth Control Read:
Register (PBWC) Write:
See page 67. Reset:
PLL Programming Register Read:
(PPG) Write:
See page 68. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
CH0F
0
Indeterminate after reset
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
CH1F
0
CH1IE
0
R
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
PLLIE
0
AUTO
PLLF
R
0
LOCK
R
PLLON
BCS
1
0
ACQ
XLD
1
1
1
1
R
R
R
R
1
1
1
1
0
0
0
0
R
R
R
R
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
Bold
= Buffered
Unimplemented
X = Indeterminate
R
= Reserved
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 7 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
34
Freescale Semiconductor
Memory Map
Addr.
Register Name
Bit 7
6
5
4
3
2
1
Bit 0
SIM Break Status Register
(SBSR) Write:
See page 191. Reset:
R
R
R
R
R
R
BW
R
SIM Reset Status Register Read:
(SRSR) Write:
See page 192. Reset:
POR
PIN
COP
ILOP
ILAD
MENRST
LVI
0
R
R
R
R
R
R
R
R
1
0
0
0
0
0
0
0
BCFE
R
R
R
R
R
R
R
0
0
0
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
0
0
0
0
0
Read:
$FE00
$FE01
SIM Break Flag Control Read:
Register (SBFCR) Write:
See page 193. Reset:
$FE03
FLASH Control Register
(FLCR)
See page 38.
$FE08
Read:
Break Address Register High Read:
(BRKH) Write:
See page 254. Reset:
Read:
Break Address Register Low
(BRKL) Write:
See page 254. Reset:
$FE0D
Break Status and Control Read:
Register (BRKSCR) Write:
See page 254. Reset:
$FE0E
$FE0F
$FF7E
0
Write:
Reset:
$FE0C
0
LVI Status and Control Register Read: LVIOUT
(LVISCR) Write:
R
See page 99. Reset:
0
FLASH Block Protect Register Read:
(FLBPR) Write:
See page 43. Reset:
$FFFF
U = Unaffected
0
R
R
R
R
R
R
0
0
0
0
0
0
0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
0
0
0
0
0
0
0
0
COP Control Register Read:
(COPCTL) Write:
See page 77. Reset:
X = Indeterminate
TRPSEL
Low byte of reset vector
Clear COP counter
Unaffected by reset
R
= Reserved
Bold
= Buffered
= Unimplemented
Figure 2-2. Control, Status, and Data Registers Summary (Sheet 8 of 8)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
35
Memory
Table 2-1 is a list of vector locations.
Table 2-1. Vector Addresses
Priority
Low
Address
Vector
$FFD2
SCI transmit vector (high)
$FFD3
SCI transmit vector (low)
$FFD4
SCI receive vector (high)
$FFD5
SCI receive vector (low)
$FFD6
SCI error vector (high)
$FFD7
SCI error vector (low)
$FFD8
SPI transmit vector (high)(1)
$FFD9
SPI transmit vector (low)(1)
$FFDA
SPI receive vector (high)(1)
$FFDB
SPI receive vector (low)(1)
$FFDC
A/D vector (high)
$FFDD
A/D vector (low)
$FFDE
TIMB overflow vector (high)
$FFDF
TIMB overflow vector (low)
$FFE0
TIMB channel 1 vector (high)
$FFE1
TIMB channel 1 vector (low)
$FFE2
TIMB channel 0 vector (high)
$FFE3
TIMB channel 0 vector (low)
$FFE4
TIMA overflow vector (high)
$FFE5
TIMA overflow vector (low)
$FFE6
TIMA channel 3 vector (high)
$FFE7
TIMA channel 3 vector (low)
$FFE8
TIMA channel 2 vector (high)
$FFE9
TIMA channel 2 vector (low)
$FFEA
TIMA channel 1 vector (high)
$FFEB
TIMA channel 1 vector (low)
$FFEC
TIMA channel 0 vector (high)
$FFED
TIMA channel 0 vector (low)
1. The SPI module is not available in the 56-pin SDIP package.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
36
Freescale Semiconductor
Monitor ROM
Table 2-1. Vector Addresses (Continued)
High
Priority
Address
Vector
$FFEE
PWMMC vector (high)
$FFEF
PWMMC vector (low)
$FFF0
FAULT 4 (high)
$FFF1
FAULT 4 (low)
$FFF2
FAULT 3 (high)
$FFF3
FAULT 3 (low)
$FFF4
FAULT 2 (high)
$FFF5
FAULT 2 (low)
$FFF6
FAULT 1 (high)
$FFF7
FAULT 1 (low)
$FFF8
PLL vector (high)
$FFF9
PLL vector (low)
$FFFA
IRQ vector (high)
$FFFB
IRQ vector (low)
$FFFC
SWI vector (high)
$FFFD
SWI vector (low)
$FFFE
Reset vector (high)
$FFFF
Reset vector (low)
2.6 Monitor ROM
The 240 bytes at addresses $FE10–$FEFF are reserved ROM addresses that contain the instructions for
the monitor functions. See 18.3 Monitor ROM (MON).
2.7 Random-Access Memory (RAM)
Addresses $0060–$035F are RAM locations. The location of the stack RAM is programmable. The 16-bit
stack pointer allows the stack to be anywhere in the 64-Kbyte memory space.
NOTE
For correct operation, the stack pointer must point only to RAM locations.
Within page zero are 160 bytes of RAM. Because the location of the stack RAM is programmable, all page
zero RAM locations can be used for input/output (I/O) control and user data or code. When the stack
pointer is moved from its reset location at $00FF, direct addressing mode instructions can access
efficiently all page zero RAM locations. Page zero RAM, therefore, provides ideal locations for frequently
accessed global variables.
Before processing an interrupt, the central processor unit (CPU) uses five bytes of the stack to save the
contents of the CPU registers.
NOTE
For M68HC05 and M1468HC05 compatibility, the H register is not stacked.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
37
Memory
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.
2.8 FLASH Memory (FLASH)
The FLASH memory is an array of 32,256 bytes with an additional 46 bytes of user vectors and one byte
of block protection.
NOTE
An erased bit reads as a 1 and a programmed bit reads as a 0.
Program and erase operations are facilitated through control bits in a memory mapped register. Details
for these operations appear later in this section.
Memory in the FLASH array is organized into two rows per page. The page size is 128 bytes per page.
The minimum erase page size is 128 bytes. Programming is performed on a row basis, 64 bytes at a time.
The address ranges for the user memory and vectors are:
• $8000–$FDFF, user memory
• $FF7E, block protect register (FLBPR)
• $FE08, FLASH control register (FLCR)
• $FFD2–$FFFF, reserved for user-defined interrupt and reset vectors
Programming tools are available from Freescale. Contact a local Freescale representative for more
information.
NOTE
A security feature prevents viewing of the FLASH contents.(1)
2.8.1 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
Write:
Reset:
0
3
2
1
Bit 0
HVEN
MASS
ERASE
PGM
0
0
0
0
= Unimplemented
Figure 2-3. FLASH Control Register (FLCR)
1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for
unauthorized users.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
38
Freescale Semiconductor
FLASH Memory (FLASH)
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 32-Kbyte FLASH array for mass erase operation. Mass erase
is disabled if any FLASH block is protected
1 = MASS erase operation selected
0 = MASS erase operation unselected
ERASE — Erase Control Bit
This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit
such that both bits cannot be equal to 1 or set to 1 at the same time.
1 = Erase operation selected
0 = Erase operation unselected
PGM — Program Control Bit
This read/write bit configures the memory for program operation. PGM is interlocked with the ERASE
bit such that both bits cannot be equal to 1 or set to 1 at the same time.
1 = Program operation selected
0 = Program operation unselected
2.8.2 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (128 bytes) of FLASH memory.
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 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 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 the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps.
In applications that require 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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
39
Memory
2.8.3 FLASH Mass Erase Operation
Use this step-by-step procedure to erase the 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 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 the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps.
1. When in monitor mode, with security sequence failed (see 18.3.2 Security), write to the FLASH block protect register instead
of any FLASH address.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
40
Freescale Semiconductor
FLASH Memory (FLASH)
2.8.4 FLASH Program Operation
Use the following step-by-step procedure to program a row of FLASH memory. Figure 2-4 shows a
flowchart of the programming algorithm.
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 location within the 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 being programmed(1).
8. Wait for time, tPROG (minimum 30 µs).
9. Repeat step 7 and 8 until all desired bytes within the row are programmed.
10. Clear the PGM bit(1).
11. Wait for 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.
NOTE
The COP register at location $FFFF should not be written between steps
5-12, when the HVEN bit is set. Since this register is located at a valid
FLASH address, unpredictable behavior may occur if this location is written
while HVEN is set.
This program sequence is repeated throughout the memory until all data is programmed.
NOTE
Programming and erasing of FLASH locations cannot be performed by
code being executed from the FLASH memory. While these operations
must be performed in the order shown, other unrelated operations may
occur between the steps. Do not exceed tPROG maximum, see 19.6 FLASH
Memory Characteristics.
1. The time between each FLASH address change, or the time between the last FLASH address programmed to clearing PGM
bit, must not exceed the maximum programming time, tPROG maximum.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
41
Memory
ALGORITHM FOR PROGRAMMING
A ROW (64 BYTES) OF FLASH MEMORY
1
2
3
4
5
6
7
8
SET PGM BIT
READ THE FLASH BLOCK PROTECT REGISTER
WRITE ANY DATA TO ANY FLASH ADDRESS
WITHIN THE ROW ADDRESS RANGE DESIRED
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?
YES
NO
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
42
Freescale Semiconductor
FLASH Memory (FLASH)
2.8.5 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 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 programmed with all 0s, the entire memory is protected from being programmed and
erased. When all the bits are erased (all 1s), the entire memory is accessible for program and erase.
When bits within the FLBPR are programmed, they lock a block of memory, whose address ranges are
shown in 2.8.6 FLASH Block Protect Register. Once the FLBPR is programmed with a value other than
$FF, any erase or program of the FLBPR or the protected block of FLASH memory is prohibited. Mass
erase is disabled whenever any block is protected (FLBPR does not equal $FF). The FLBPR itself can be
erased or programmed only with an external voltage, VTST, present on the IRQ pin. This voltage also
allows entry from reset into the monitor mode.
2.8.6 FLASH Block Protect Register
The FLASH block protect register (FLBPR) is implemented as a byte within the FLASH memory, and
therefore can be written only during a programming sequence of the FLASH memory. The value in this
register determines the starting location of the protected range within the FLASH memory.
Address:
Read:
Write:
Reset:
$FF7E
Bit 7
6
5
4
3
2
1
Bit 0
BPR7
BPR6
BPR5
BPR4
BPR3
BPR2
BPR1
BPR0
0
0
0
0
0
0
0
0
U = Unaffected by reset. Initial value from factory is 1.
Write to this register 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 [14:7] of a 16-bit memory address. Bit 15 is 1 and bits [6:0] 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 and XX80 (128 bytes page boundaries)
within the FLASH memory.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
43
Memory
16-BIT MEMORY ADDRESS
START ADDRESS OF FLASH
BLOCK PROTECT
1
FLBPR VALUE
0
0
0
0
0
0
0
Figure 2-6. FLASH Block Protect Start Address
Refer to Table 2-2 for examples of the protect start address.
Table 2-2. Examples of Protect Start Address
BPR[7:0]
Start of Address of Protect Range
$00
The entire FLASH memory is protected.
$01 (0000 0001)
$8080 (1000 0000 1000 0000)
$02 (0000 0010)
$8100 (1000 0001 0000 0000)
and so on...
$FE (1111 1110)
$FF00 (1111 1111 0000 0000)
$FF
The entire FLASH memory is not protected.
Note: The end address of the protected range is always $FFFF.
2.8.7 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.
2.8.8 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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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:
• 10 channels with multiplexed input
• Linear successive approximation
• 10-bit resolution, 8-bit accuracy
• Single or continuous conversion
• Conversion complete flag or conversion complete interrupt
• Selectable ADC clock
• Left or right justified result
• Left justified sign data mode
• High impedance buffered ADC input
3.3 Functional Description
Ten ADC channels are available for sampling external sources at pins PTC1/ATD9:PTC0/ATD8 and
PTB7/ATD7:PTB0/ATD0. To achieve the best possible accuracy, these pins are implemented as
input-only pins when the analog-to-digital (A/D) feature is enabled. An analog multiplexer allows the single
ADC to select one of the 10 ADC channels as ADC voltage IN (ADCVIN). ADCVIN is converted by the
successive approximation algorithm. When the conversion is completed, the ADC places the result in the
ADC data register (ADRH and ADRL) and sets a flag or generates an interrupt. See Figure 3-2.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
45
PTA
PTA7–PTA0
PTB
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
PTC
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1/ATD9(1)
PTC0/ATD8
PTD
PTD6/IS3
PTD5/IS2
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
PTE
CONTROL AND STATUS REGISTERS — 112 BYTES
DDRA
ARITHMETIC/LOGIC
UNIT
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
DDRB
CPU
REGISTERS
USER FLASH — 32,256 BYTES
USER RAM — 768 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VDDA
VSSA(3)
VREFL(3)
VREFH
PWMGND
PWM6–PWM1
Freescale Semiconductor
VSS
VDD
VDDAD
VSSAD
ANALOG-TO-DIGITAL CONVERTER
MODULE
PULSE-WIDTH MODULATOR
MODULE
DDRC
SERIAL COMMUNICATIONS INTERFACE
MODULE
SERIAL PERIPHERAL INTERFACE
MODULE(2)
POWER-ON RESET
MODULE
SINGLE BREAK
MODULE
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PTF1/SS(1)
DDRE
USER FLASH VECTOR SPACE — 46 BYTES
TIMER INTERFACE
MODULE B
PTF
MONITOR ROM — 240 BYTES
DDRF
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
TIMER INTERFACE
MODULE A
PTF0/SPSCK(1)
POWER
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 3-1. Block Diagram Highlighting ADC Block and Pins
Analog-to-Digital Converter (ADC)
46
INTERNAL BUS
M68HC08 CPU
Functional Description
INTERNAL
DATA BUS
PTB/Cx
ADC CHANNEL x
READ PTB/PTC
DISABLE
ADC DATA REGISTERS
INTERRUPT
LOGIC
AIEN
CONVERSION
COMPLETE
ADC VOLTAGE IN
ADVIN
ADC
CHANNEL
SELECT
ADCH[4:0]
COCO
ADC CLOCK
CGMXCLK
BUS CLOCK
CLOCK
GENERATOR
ADIV[2:0]
ADICLK
Figure 3-2. ADC Block Diagram
3.3.1 ADC Port I/O Pins
PTC1/ATD9:PTC0/ATD8 and PTB7/ATD7:PTB0/ATD0 are general-purpose I/O pins that are shared with
the ADC channels.
The channel select bits define which ADC channel/port pin will be used as the input signal. The ADC
overrides the port logic when that port is selected by the ADC multiplexer. The remaining ADC
channels/port pins are controlled by the port logic and can be used as general-purpose input/output (I/O)
pins. Writes to the port register or DDR will not have any effect on the port pin that is selected by the ADC.
Read of a port pin which is in use by the ADC will return a 0.
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
straight-line linear conversions. All other input voltages will result in $3FF if greater than VREFH and $000
if less than VREFL.
NOTE
Input voltage should not exceed the analog supply voltages. See
19.13 Analog-to-Digital Converter (ADC) Characteristics.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
47
Analog-to-Digital Converter (ADC)
3.3.3 Conversion Time
Conversion starts after a write to the ADSCR. A conversion is between 16 and 17 ADC clock cycles,
therefore:
16 to17 ADC Cycles
Conversion time =
ADC Frequency
Number of Bus Cycles = Conversion Time x CPU Bus Frequency
The ADC conversion time is determined by the clock source chosen and the divide ratio selected. The
clock source is either the bus clock or CGMXCLK and is selectable by ADICLK located in the ADC clock
register. For example, if CGMXCLK is 4 MHz and is selected as the ADC input clock source, the ADC
input clock divide-by-4 prescale is selected and the CPU bus frequency is 8 MHz:
Conversion Time =
16 to 17 ADC Cycles
= 16 to 17 µs
4 MHz/4
Number of bus cycles = 16 µs x 8 MHz = 128 to 136 cycles
NOTE
The ADC frequency must be between fADIC minimum and fADIC maximum
to meet A/D specifications. See 19.13 Analog-to-Digital Converter (ADC)
Characteristics.
Since an ADC cycle may be comprised of several bus cycles (eight, 136 minus 128, in the previous
example) and the start of a conversion is initiated by a bus cycle write to the ADSCR, from zero to eight
additional bus cycles may occur before the start of the initial ADC cycle. This results in a fractional ADC
cycle and is represented as the 17th cycle.
3.3.4 Continuous Conversion
In continuous conversion mode, the ADC data registers ADRH and ADRL will be filled with new data after
each conversion. Data from the previous conversion will be overwritten whether that data has been read
or not. Conversions will continue until the ADCO bit is cleared. The COCO bit is set after each conversion
and will stay set until the next read of the ADC data register.
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 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
(ADCR).
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
48
Freescale Semiconductor
Functional Description
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 ADC data register low, ADRL. The two LSBs are dropped. This mode of operation is
used when compatibility with 8-bit ADC designs are required. No interlocking between ADRH and ADRL
is present.
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. 8-Bit Truncation Mode Error
3.3.6 Monotonicity
The conversion process is monotonic and has no missing codes.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
49
Analog-to-Digital Converter (ADC)
3.4 Interrupts
When the AIEN bit is set, the ADC module is capable of generating a CPU interrupt after each ADC
conversion. A CPU interrupt is generated if the COCO bit is at 0. The COCO bit is not used as a
conversion complete flag when interrupts are enabled.
3.5 Wait Mode
The WAIT instruction can put the MCU in low power-consumption standby mode.
The ADC continues normal operation during wait mode. Any enabled CPU interrupt request from the ADC
can bring the MCU out of wait mode. If the ADC is not required to bring the MCU out of wait mode, power
down the ADC by setting ADCH[4:0] in the ADC status and control register before executing the WAIT
instruction.
3.6 I/O Signals
The ADC module has 10 input signals that are shared with port B and port C.
3.6.1 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
Route VDDAD carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
3.6.2 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.
3.6.3 ADC Voltage Reference Pin (VREFH)
VREFH is the power supply for setting the reference voltage VREFH. Connect the VREFH pin to the same
voltage potential as VDDAD. There will be a finite current associated with VREFH. See Chapter 19 Electrical
Specifications.
NOTE
Route VREFH carefully for maximum noise immunity and place bypass
capacitors as close as possible to the package.
3.6.4 ADC Voltage Reference Low Pin (VREFL)
VREFL is the lower reference supply for the ADC. Connect the VREFL pin to the same voltage potential as
VSSAD. A finite current will be associated with VREFL. See Chapter 19 Electrical Specifications.
NOTE
In the 56-pin shrink dual in-line package (SDIP), VREFL and VSSAD are tied
together.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
50
Freescale Semiconductor
I/O Registers
3.6.5 ADC Voltage In (ADVIN)
ADVIN is the input voltage signal from one of the 10 ADC channels to the ADC module.
3.6.6 ADC External Connections
This section describes the ADC external connections: VREFH and VREFL, ANx, and grounding.
3.6.6.1 VREFH and VREFL
Both ac and dc current are drawn through the VREFH and VREFL loop. The AC current is in the form of
current spikes required to supply charge to the capacitor array at each successive approximation step.
The current flows through the internal resistor string. The best external component to meet both these
current demands is a capacitor in the 0.01 µF to 1 µF range with good high frequency characteristics. This
capacitor is connected between VREFH and VREFL and must be placed as close as possible to the
package pins. Resistance in the path is not recommended because the dc current will cause a voltage
drop which could result in conversion errors.
3.6.6.2 ANx
Empirical data shows that capacitors from the analog inputs to VREFL improve ADC performance. 0.01-µF
and 0.1-µF capacitors with good high-frequency characteristics are sufficient. These capacitors must be
placed as close as possible to the package pins.
3.6.6.3 Grounding
In cases where separate power supplies are used for analog and digital power, the ground connection
between these supplies should be at the VSSAD pin. This should be the only ground connection between
these supplies if possible. The VSSA pin makes a good single point ground location. Connect the VREFL
pin to the same potential as VSSAD at the single point ground location.
3.7 I/O Registers
These I/O registers control and monitor operation of the ADC:
• ADC status and control register, ADSCR
• ADC data registers, ADRH and ARDL
• ADC clock register, ADCLK
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
51
Analog-to-Digital Converter (ADC)
3.7.1 ADC Status and Control Register
This section describes the function of the ADC status and control register (ADSCR). Writing ADSCR
aborts the current conversion and initiates a new conversion.
Address: $0040
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.
AIEN — ADC Interrupt Enable Bit
When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is
cleared when the data register is read or the status/control register is written. Reset clears the AIEN bit.
1 = ADC interrupt enabled
0 = ADC interrupt disabled
ADCO — ADC Continuous Conversion Bit
When set, the ADC will convert samples continuously and update the ADR register at the end of each
conversion. Only one conversion is allowed when this bit is cleared. Reset clears the ADCO bit.
1 = Continuous ADC conversion
0 = One ADC conversion
ADCH[4:0] — ADC Channel Select Bits
ADCH4, ADCH3, ADCH2, ADCH1, and ADCH0 form a 5-bit field which is used to select one of 10 ADC
channels. The ADC channels are detailed in Table 3-1.
NOTE
Take care to prevent switching noise from corrupting the analog signal
when simultaneously using a port pin as both an analog and digital input.
The ADC subsystem is turned off when the channel select bits are all set to 1. This feature allows for
reduced power consumption for the MCU when the ADC is not used.
NOTE
Recovery from the disabled state requires one conversion cycle to stabilize.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
52
Freescale Semiconductor
I/O Registers
The voltage levels supplied from internal reference nodes as specified in Table 3-1 are used to verify
the operation of the ADC both in production test and for user applications.
Table 3-1. Mux Channel Select
ADCH4
ADCH3
ADCH2
ADCH1
ADCH0
Input Select
0
0
0
0
0
PTB0/ATD0
0
0
0
0
1
PTB1/ATD1
0
0
0
1
0
PTB2/ATD2
0
0
0
1
1
PTB3/ATD3
0
0
1
0
0
PTB4/ATD4
0
0
1
0
1
PTB5/ATD5
0
0
1
1
0
PTB6/ATD6
0
0
1
1
1
PTB7/ATD7
0
1
0
0
0
PTC0/ATD8
0
1
0
0
1
PTC1/ATD9(1)
0
1
0
1
0
Unused(2)
0
1
0
1
1
Ø
0
1
1
0
0
Ø
0
1
1
0
1
Ø
0
1
1
1
0
Ø
0
1
1
1
1
Ø
1
0
0
0
0
Ø
1
1
0
1
0
Unused(2)
1
1
0
1
1
Reserved(3)
1
1
1
0
0
Unused(2)
1
1
1
0
1
VREFH
1
1
1
1
0
VREFL
1
1
1
1
1
ADC power off
1. ATD9 is not available in the 56-pin SDIP package.
2. Used for factory testing.
3. If any unused channels are selected, the resulting ADC conversion will be unknown.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
53
Analog-to-Digital Converter (ADC)
3.7.2 ADC Data Register High
In left justified mode, this 8-bit result register holds the eight MSBs of the 10-bit result. This register is
updated each time an ADC single channel conversion completes. Reading ADRH latches the contents of
ADRL until ADRL is read. Until ADRL is read, all subsequent ADC results will be lost.
Address:
$0041
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by reset
R
= Reserved
Figure 3-5. ADC Data Register High (ADRH) Left Justified Mode
In right justified mode, this 8-bit result register holds the two MSBs of the 10-bit result. All other bits read
as 0. This register is updated each time a single channel ADC conversion completes. Reading ADRH
latches the contents of ADRL until ADRL is read. Until ADRL is read, all subsequent ADC results will be
lost.
Address:
$0041
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
0
0
AD9
AD8
Write:
R
R
R
R
R
R
R
R
R
= Reserved
Reset:
Unaffected by reset
Figure 3-6. ADC Data Register High (ADRH) Right Justified Mode
3.7.3 ADC Data Register Low
In left justified mode, this 8-bit result register holds the two LSBs of the 10-bit result. All other bits read as
0. This register is updated each time a single channel ADC conversion completes. Reading ADRH latches
the contents of ADRL until ADRL is read. Until ADRL is read, all subsequent ADC results will be lost.
Address:
$0042
Bit 7
6
Read:
AD1
AD0
0
0
0
0
0
0
Write:
R
R
R
R
R
R
R
R
Reset:
5
4
3
2
1
Bit 0
Unaffected by reset
R
= Reserved
Figure 3-7. ADC Data Register Low (ADRL) Left Justified Mode
In right justified mode, this 8-bit result register holds the eight LSBs of the 10-bit result. This register is
updated each time an ADC conversion completes. Reading ADRH latches the contents of ADRL until
ADRL is read. Until ADRL is read, all subsequent ADC results will be lost.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
54
Freescale Semiconductor
I/O Registers
Address:
$0042
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD7
AD6
AD5
AD4
AD3
AD2
AD1
AD0
Write:
R
R
R
R
R
R
R
R
R
= Reserved
Reset:
Unaffected by reset
Figure 3-8. ADC Data Register Low (ADRL) Right Justified Mode
In 8-bit mode, this 8-bit result register holds the eight MSBs of the 10-bit result. This register is updated
each time an ADC conversion completes. In 8-bit mode, this register contains no interlocking with ADRH.
Address:
$0042
Bit 7
6
5
4
3
2
1
Bit 0
Read:
AD9
AD8
AD7
AD6
AD5
AD4
AD3
AD2
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by reset
R
= Reserved
Figure 3-9. ADC Data Register Low (ADRL) 8-Bit Mode
3.7.4 ADC Clock Register
This register selects the clock frequency for the ADC, selecting between modes of operation.
Address:
Read:
Write:
Reset:
$0043
Bit 7
6
5
4
3
2
1
ADIV2
ADIV1
ADIV0
ADICLK
MODE1
MODE0
0
0
0
0
0
0
1
0
R
= Reserved
Bit 0
0
R
0
Figure 3-10. ADC Clock Register (ADCLK)
ADIV2:ADIV0 — ADC Clock Prescaler Bits
ADIV2, ADIV1, and ADIV0 form a 3-bit field which selects the divide ratio used by the ADC to generate
the internal ADC clock. Table 3-2 shows the available clock configurations.
Table 3-2. ADC Clock Divide Ratio
ADIV2
ADIV1
ADIV0
0
0
0
ADC input clock ÷ 1
ADC Clock Rate
0
0
1
ADC input clock ÷ 2
0
1
0
ADC input clock ÷ 4
0
1
1
ADC input clock ÷ 8
1
X
X
ADC input clock ÷ 16
X = don’t care
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
55
Analog-to-Digital Converter (ADC)
ADICLK — ADC Input Clock Select Bit
ADICLK selects either bus clock or CGMXCLK as the input clock source to generate the internal ADC
clock. Reset selects CGMXCLK as the ADC clock source.
If the external clock (CGMXCLK) is equal to or greater than 1 MHz, CGMXCLK can be used as the
clock source for the ADC. If CGMXCLK is less than 1 MHz, use the PLL-generated bus clock as the
clock source. As long as the internal ADC clock is at fADIC, correct operation can be guaranteed. See
19.13 Analog-to-Digital Converter (ADC) Characteristics.
1 = Internal bus clock
0 = External clock, CGMXCLK
CGMXCLK or bus frequency
fADIC =
ADIV[2:0]
MODE1:MODE0 — Modes of Result Justification Bits
MODE1:MODE0 selects among four modes of operation. The manner in which the ADC conversion
results will be placed in the ADC data registers is controlled by these modes of operation. Reset returns
right-justified mode.
00 = 8-bit truncation mode
01 = Right justified mode
10 = Left justified mode
11 = Left justified sign data mode
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
56
Freescale Semiconductor
Chapter 4
Clock Generator Module (CGM)
4.1 Introduction
This section describes the clock generator module (CGM, version A). The CGM generates the crystal
clock signal, CGMXCLK, which operates at the frequency of the crystal. The CGM also generates the
base clock signal, CGMOUT, from which the system integration module (SIM) derives the system clocks.
CGMOUT is based on either the crystal clock divided by two or the phase-locked loop (PLL) clock,
CGMVCLK, divided by two. The PLL is a frequency generator designed for use with crystals or ceramic
resonators. The PLL can generate an 8-MHz bus frequency without using a 32-MHz external clock.
4.2 Features
Features of the CGM include:
• PLL with output frequency in integer multiples of the crystal reference
• Programmable hardware voltage-controlled oscillator (VCO) for low-jitter operation
• Automatic bandwidth control mode for low-jitter operation
• Automatic frequency lock detector
• Central processor unit (CPU) interrupt on entry or exit from locked condition
4.3 Functional Description
The CGM consists of three major submodules:
1. Crystal oscillator circuit — The crystal oscillator circuit generates the constant crystal frequency
clock, CGMXCLK.
2. Phase-locked loop (PLL) — The PLL generates the programmable VCO frequency clock,
CGMVCLK.
3. Base clock selector circuit — This software-controlled circuit selects either CGMXCLK divided by
two or the VCO clock, CGMVCLK, divided by two as the base clock, CGMOUT. The SIM derives
the system clocks from CGMOUT.
Figure 4-1 shows the structure of the CGM.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
57
Clock Generator Module (CGM)
CRYSTAL OSCILLATOR
OSC2
CGMXCLK
CLOCK
SELECT
CIRCUIT
OSC1
A
÷2
CGMOUT
B S*
TO SIM
TO SIM
*WHEN S = 1, CGMOUT = B
SIMOSCEN
CGMRDV
CGMRCLK
VDDA
BCS
CGMXFC
USER MODE
VSS
PTC2
VRS[7:4]
MONITOR MODE
VOLTAGE
CONTROLLED
OSCILLATOR
LOOP
FILTER
PHASE
DETECTOR
PLL ANALOG
LOCK
DETECTOR
LOCK
AUTO
CGMINT
INTERRUPT
CONTROL
BANDWIDTH
CONTROL
ACQ
PLLIE
PLLF
MUL[7:4]
CGMVDV
CGMVCLK
FREQUENCY
DIVIDER
Figure 4-1. CGM Block Diagram
Addr.
Register Name
Bit 7
$005C
PLL Control Register Read:
(PCTL) Write:
See page 66. Reset:
$005D
PLL Bandwidth Control Register Read:
(PBWC) Write:
See page 67. Reset:
$005E
PLL Programming Register Read:
(PPG) Write:
See page 68. Reset:
PLLIE
0
AUTO
6
PLLF
R
0
LOCK
4
PLLON
BCS
1
0
ACQ
XLD
3
2
1
Bit 0
1
1
1
1
R
R
R
R
1
1
1
1
0
0
0
0
R
R
R
R
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
R
R
5
= Reserved
Figure 4-2. CGM I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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) enables the crystal oscillator circuit.
The CGMXCLK signal is the output of the crystal oscillator circuit and runs at a rate equal to the crystal
frequency. CGMXCLK is then buffered to produce CGMRCLK, the PLL reference clock.
CGMXCLK can be used by other modules which require precise timing for operation. The duty cycle of
CGMXCLK is not guaranteed to be 50 percent and depends on external factors, including the crystal and
related external components.
An externally generated clock also can feed the OSC1 pin of the crystal oscillator circuit. Connect the
external clock to the OSC1 pin and let the OSC2 pin float.
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.
4.3.2.1 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, (4.9152 MHz) times a linear factor, L or (L) fNOM.
CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK. CGMRCLK runs at a frequency,
fRCLK, and is fed to the PLL through a buffer. The buffer output is the final reference clock, CGMRDV,
running at a frequency, fRDV = fRCLK.
The VCO’s output clock, CGMVCLK, running at a frequency, fVCLK, is fed back through a programmable
modulo divider. The modulo divider reduces the VCO clock by a factor, N. The divider’s output is the VCO
feedback clock, CGMVDV, running at a frequency, fVDV = fVCLK/N. (See 4.3.2.4 Programming the PLL for
more information.)
The phase detector then compares the VCO feedback clock, CGMVDV, with the final reference clock,
CGMRDV. A correction pulse is generated based on the phase difference between the two signals. The
loop filter then slightly alters the dc voltage on the external capacitor connected to CGMXFC based on
the width and direction of the correction pulse. The filter can make fast or slow corrections depending on
its mode, described in 4.3.2.2 Acquisition and Tracking Modes. The value of the external capacitor and
the reference frequency determines the speed of the corrections and the stability of the PLL.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
59
Clock Generator Module (CGM)
The lock detector compares the frequencies of the VCO feedback clock, CGMVDV, and the final
reference clock, CGMRDV. Therefore, the speed of the lock detector is directly proportional to the final
reference frequency, fRDV. The circuit determines the mode of the PLL and the lock condition based on
this comparison.
4.3.2.2 Acquisition and Tracking Modes
The PLL filter is manually or automatically configurable into one of two operating modes:
1. Acquisition mode — In acquisition mode, the filter can make large frequency corrections to the
VCO. This mode is used at PLL startup or when the PLL has suffered a severe noise hit and the
VCO frequency is far off the desired frequency. When in acquisition mode, the ACQ bit is clear in
the PLL bandwidth control register. See 4.5.2 PLL Bandwidth Control Register.
2. 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 4.3.3 Base Clock Selector Circuit. The PLL is automatically in
tracking mode when not in acquisition mode or when the ACQ bit is set.
4.3.2.3 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter manually or automatically.
In automatic bandwidth control mode (AUTO = 1), the lock detector automatically switches between
acquisition and tracking modes. Automatic bandwidth control mode also is used to determine when the
VCO clock, CGMVCLK, is safe to use as the source for the base clock, CGMOUT. 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 (during PLL startup, usually) or at periodic intervals. In either case, when the LOCK bit is set,
the VCO clock is safe to use as the source for the base clock. See 4.3.3 Base Clock Selector Circuit. If
the VCO is selected as the source for the base clock and the LOCK bit is clear, the PLL has suffered a
severe noise hit and the software must take appropriate action, depending on the application. See 4.6
Interrupts for information and precautions on using interrupts.
These 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. For more information, see 4.3.2.2 Acquisition and Tracking Modes.
• The ACQ bit is set when the VCO frequency is within a certain tolerance, ∆TRK, and is cleared when
the VCO frequency is out of a certain tolerance, ∆UNT. For more information, see 4.8
Acquisition/Lock Time Specifications.
• The LOCK bit is a read-only indicator of the locked state of the PLL.
• The LOCK bit is set when the VCO frequency is within a certain tolerance, ∆Lock, and is cleared
when the VCO frequency is out of a certain tolerance, ∆UNL. For more information, see 4.8
Acquisition/Lock Time Specifications.
• CPU interrupts can occur if enabled (PLLIE = 1) when the PLL’s lock condition changes, toggling
the LOCK bit. For more information, see 4.5.1 PLL Control Register.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
60
Freescale Semiconductor
Functional Description
The PLL also may operate in manual mode (AUTO = 0). Manual mode is used by systems that do not
require an indicator of the lock condition for proper operation. Such systems typically operate well below
fBUSMAX and require fast startup. These conditions apply when in manual mode:
• ACQ is a writable control bit that controls the mode of the filter. Before turning on the PLL in manual
mode, the ACQ bit must be clear.
• Before entering tracking mode (ACQ = 1), software must wait a given time, tACQ (see 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.
4.3.2.4 Programming the PLL
Use this 9-step procedure to program the PLL. Table 4-1 lists the variables used and their meaning.
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
Shifted FCO center frequency
1. Choose the desired bus frequency, fBUSDES.
Example: fBUSDES = 8 MHz
2. Calculate the desired VCO frequency, fVCLKDES.
fVCLKDES = 4 x fBUSDES
Example: fVCLKDES = 4 x 8 MHz = 32 MHz
3. Using a reference frequency, fRCLK, equal to the crystal frequency, calculate the VCO frequency
multiplier, N. Round the result to the nearest integer.
fVCLKDES
N=
fRCLK
Example: N =
32 MHz
= 8 MHz
4 MHz
4. Calculate the VCO frequency, fVCLK.
fVCLK = N x fRCLK
Example: fVCLK = 8 x 4 MHz = 32 MHz
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
61
Clock Generator Module (CGM)
5. Calculate the bus frequency, fBUS, and compare fBUS with fBUSDES.
fBUS =
Example: N =
fVCLK
4
32 MHz
= 8 MHz
4 MHz
6. If the calculated fBUS is not within the tolerance limits of the application, select another fBUSDES or
another fRCLK.
7. Using the value 4.9152 MHz for fNOM, calculate the VCO linear range multiplier, L. The linear range
multiplier controls the frequency range of the PLL.
fVCLK
)
L = round ( f
NOM
Example: L =
32 MHz
= 7 MHz
4.9152 MHz
8. Calculate the VCO center-of-range frequency, fVRS. The center-or-range frequency is the midpoint
between the minimum and maximum frequencies attainable by the PLL.
fVRS = L x fNOM
Example: fVRS = 7 x 4.9152 MHz = 34.4 MHz
For proper operation,
fNOM
fVRS – fVCLK | ≤
2
CAUTION
Exceeding the recommended maximum bus frequency or VCO frequency can crash the MCU.
9. Program the PLL registers accordingly:
a. In the upper four bits of the PLL programming register (PPG), program the binary equivalent
of N.
b. In the lower four bits of the PLL programming register (PPG), program the binary equivalent
of L.
4.3.2.5 Special Programming Exceptions
The programming method described in 4.3.2.4 Programming the PLL does not account for possible
exceptions. A value of 0 for N or L is meaningless when used in the equations given. To account for these
exceptions:
• A 0 value for N is interpreted exactly the same as a value of 1.
• A 0 value for L disables the PLL and prevents its selection as the source for the base clock. See
4.3.3 Base Clock Selector Circuit.
4.3.3 Base Clock Selector Circuit
This circuit is used to select either the crystal clock, CGMXCLK, or the VCO clock, CGMVCLK, as the
source of the base clock, CGMOUT. The two input clocks go through a transition control circuit that waits
up to three CGMXCLK cycles and three CGMVCLK cycles to change from one clock source to the other.
During this time, CGMOUT is held in stasis. The output of the transition control circuit is then divided by
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
62
Freescale Semiconductor
Functional Description
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.
4.3.4 CGM External Connections
In its typical configuration, the CGM requires seven external components. Five of these are for the crystal
oscillator and two are for the PLL.
The crystal oscillator is normally connected in a Pierce oscillator configuration, as shown in Figure 4-3.
Figure 4-3 shows only the logical representation of the internal components and may not represent actual
circuitry.
SIMOSCEN
CGMXCLK
OSC1
OSC2
VSS
R S*
CGMXFC
VDDA
VDD
CF
CBYP
RB
X1
C1
C2
*RS can be 0 (shorted) when used with
higher frequency crystals. Refer to
manufacturer’s data.
Figure 4-3. CGM External Connections
The oscillator configuration uses five components:
1. Crystal, X1
2. Fixed capacitor, C1
3. Tuning capacitor, C2 (can also be a fixed capacitor)
4. Feedback resistor, RB
5. Series resistor, RS (optional)
The series resistor (RS) is included in the diagram to follow strict Pierce oscillator guidelines and may not
be required for all ranges of operation, especially with high-frequency crystals. Refer to the crystal
manufacturer’s data for more information.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
63
Clock Generator Module (CGM)
Figure 4-3 also shows the external components for the PLL:
• Bypass capacitor, CBYP
• Filter capacitor, CF
NOTE
Routing should be done with great care to minimize signal cross talk and
noise. (See 4.8 Acquisition/Lock Time Specifications for routing information
and more information on the filter capacitor’s value and its effects on PLL
performance.)
4.4 I/O Signals
This section describes the CGM input/output (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. A small external capacitor is
connected to this pin.
NOTE
To prevent noise problems, CF should be placed as close to the CGMXFC
pin as possible, with minimum routing distances and no routing of other
signals across the CF connection.
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 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM) and enables the oscillator and
PLL.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
64
Freescale Semiconductor
CGM Registers
4.4.6 Crystal Output Frequency Signal (CGMXCLK)
CGMXCLK is the crystal oscillator output signal. It runs at the full speed of the crystal (fXCLK) and comes
directly from the crystal oscillator circuit. Figure 4-3 shows only the logical relation of CGMXCLK to OSC1
and OSC2 and may not represent the actual circuitry. The duty cycle of CGMXCLK is unknown and may
depend on the crystal and other external factors. Also, the frequency and amplitude of CGMXCLK can be
unstable at startup.
4.4.7 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM, which generates the MCU clocks.
CGMOUT is a 50 percent duty cycle clock running at twice the bus frequency. CGMOUT is software
programmable to be either the oscillator output, CGMXCLK, divided by two or the VCO clock, CGMVCLK,
divided by two.
4.4.8 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 programming register (PPG) — see 4.5.3 PLL Programming Register
Figure 4-4 is a summary of the CGM registers.
Addr.
$005C
$005D
$005E
Register Name
Bit 7
PLL Control Register
(PCTL)
See page 66.
PLL Bandwidth Control Register
(PBWC)
See page 67.
PLL Programming Register
(PPG)
See page 68.
Read:
6
Write:
PLLON
BCS
R
0
Read:
0
1
0
ACQ
XLD
LOCK
AUTO
Write:
Reset:
4
PLLF
PLLIE
Reset:
5
R
3
2
1
Bit 0
1
1
1
1
R
R
R
R
1
1
1
1
0
0
0
0
R
R
R
R
0
0
0
0
0
0
0
0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
Read:
Write:
Reset:
R
= Reserved
Notes:
1. When AUTO = 0, PLLIE is forced to logic 0 and is read-only.
2. When AUTO = 0, PLLF and LOCK read as logic 0.
3. When AUTO = 1, ACQ is read-only.
4. When PLLON = 0 or VRS[7:4] = $0, BCS is forced to logic 0 and is read-only.
5. When PLLON = 1, the PLL programming register is read-only.
6. When BCS = 1, PLLON is forced set and is read-only.
Figure 4-4. CGM I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
65
Clock Generator Module (CGM)
4.5.1 PLL Control Register
The PLL control register (PCTL) contains the interrupt enable and flag bits, the on/off switch, and the base
clock selector bit.
Address:
$005C
Bit 7
Read:
Write:
Reset:
PLLIE
6
PLLF
R
0
0
R
= Reserved
5
4
PLLON
BCS
1
0
3
2
1
Bit 0
1
1
1
1
R
R
R
R
1
1
1
1
Figure 4-5. PLL Control Register (PCTL)
PLLIE — PLL Interrupt Enable Bit
This read/write bit enables the PLL to generate an interrupt request when the LOCK bit toggles, setting
the PLL flag, PLLF. When the AUTO bit in the PLL bandwidth control register (PBWC) is clear, PLLIE
cannot be written and reads as logic 0. Reset clears the PLLIE bit.
1 = PLL interrupts enabled
0 = PLL interrupts disabled
PLLF — PLL Interrupt Flag
This read-only bit is set whenever the LOCK bit toggles. PLLF generates an interrupt request if the
PLLIE bit also is set. PLLF always reads as logic 0 when the AUTO bit in the PLL bandwidth control
register (PBWC) is clear. Clear the PLLF bit by reading the PLL control register. Reset clears the PLLF
bit.
1 = Change in lock condition
0 = No change in lock condition
NOTE
Do not inadvertently clear the PLLF bit. Any read or read-modify-write
operation on the PLL control register clears the PLLF bit.
PLLON — PLL On Bit
This read/write bit activates the PLL and enables the VCO clock, CGMVCLK. PLLON cannot be
cleared if the VCO clock is driving the base clock, CGMOUT (BCS = 1). See 4.3.3 Base Clock Selector
Circuit. Reset sets this bit so that the loop can stabilize as the MCU is powering up.
1 = PLL on
0 = PLL off
BCS — Base Clock Select Bit
This read/write bit selects either the crystal oscillator output, CGMXCLK, or the VCO clock,
CGMVCLK, as the source of the CGM output, CGMOUT. CGMOUT frequency is one-half the
frequency of the selected clock. BCS cannot be set while the PLLON bit is clear. After toggling BCS,
it may take up to three CGMXCLK and three CGMVCLK cycles to complete the transition from one
source clock to the other. During the transition, CGMOUT is held in stasis. See 4.3.3 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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
66
Freescale Semiconductor
CGM Registers
if the PLL is off. Therefore, PLLON cannot be cleared when BCS is set, and
BCS cannot be set when PLLON is clear. If the PLL is off (PLLON = 0),
selecting CGMVCLK requires two writes to the PLL control register. See
4.3.3 Base Clock Selector Circuit.
PCTL[3:0] — Unimplemented Bits
These bits provide no function and always read as logic 1s.
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: $005D
Bit 7
Read:
Write:
Reset:
AUTO
6
LOCK
R
0
0
R
= Reserved
5
4
ACQ
XLD
0
0
3
2
1
Bit 0
0
0
0
0
R
R
R
R
0
0
0
0
Figure 4-6. PLL Bandwidth Control Register (PBWC)
AUTO — Automatic Bandwidth Control Bit
This read/write bit selects automatic or manual bandwidth control. When initializing the PLL for manual
operation (AUTO = 0), clear the ACQ bit before turning on the PLL. Reset clears the AUTO bit.
1 = Automatic bandwidth control
0 = Manual bandwidth control
LOCK — Lock Indicator Bit
When the AUTO bit is set, LOCK is a read-only bit that becomes set when the VCO clock, CGMVCLK,
is locked (running at the programmed frequency). When the AUTO bit is clear, LOCK reads as logic 0
and has no meaning. Reset clears the LOCK bit.
1 = VCO frequency correct or locked
0 = VCO frequency incorrect or unlocked
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
67
Clock Generator Module (CGM)
XLD — Crystal Loss Detect Bit
When the VCO output, CGMVCLK, is driving CGMOUT, this read/write bit can indicate whether the
crystal reference frequency is active or not. To check the status of the crystal reference, follow these
steps:
1. Write a logic 1 to XLD.
2. Wait N × 4 cycles. (N is the VCO frequency multiplier.)
3. Read XLD.
The crystal loss detect function works only when the BCS bit is set, selecting CGMVCLK to drive
CGMOUT. When BCS is clear, XLD always reads as logic 0.
1 = Crystal reference is not active.
0 = Crystal reference is active.
PBWC[3:0] — Reserved for Test
These bits enable test functions not available in user mode. To ensure software portability from
development systems to user applications, software should write 0s to PBWC[3:0] whenever writing to
PBWC.
4.5.3 PLL Programming Register
The PLL programming register (PPG) contains the programming information for the modulo feedback
divider and the programming information for the hardware configuration of the VCO.
Address: $005E
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
MUL7
MUL6
MUL5
MUL4
VRS7
VRS6
VRS5
VRS4
0
1
1
0
0
1
1
0
Figure 4-7. PLL Programming Register (PPG)
MUL[7:4] — Multiplier Select Bits
These read/write bits control the modulo feedback divider that selects the VCO frequency multiplier,
N. See 4.3.2.1 PLL Circuits and 4.3.2.4 Programming the PLL. A value of $0 in the multiplier select bits
configures the modulo feedback divider the same as a value of $1. Reset initializes these bits to $6 to
give a default multiply value of 6.
Table 4-2. VCO Frequency Multiplier (N) Selection
MUL7:MUL6:MUL5:MUL4
VCO Frequency Multiplier (N)
0000
1
0001
1
0010
2
0011
3
1101
13
1110
14
1111
15
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
68
Freescale Semiconductor
Interrupts
NOTE
The multiplier select bits have built-in protection that prevents them from
being written when the PLL is on (PLLON = 1).
VRS[7:4] — VCO Range Select Bits
These read/write bits control the hardware center-of-range linear multiplier L, which controls the
hardware center-of-range frequency fVRS. See 4.3.2.1 PLL Circuits, 4.3.2.4 Programming the PLL and
4.5.1 PLL Control Register. VRS[7:4] cannot be written when the PLLON bit in the PLL control register
(PCTL) is set. See 4.3.2.5 Special Programming Exceptions. A value of $0 in the VCO range select
bits disables the PLL and clears the BCS bit in the PCTL. See 4.3.3 Base Clock Selector Circuit and
4.3.2.5 Special Programming Exceptions for more information.
Reset initializes the bits to $6 to give a default range multiply value of 6.
NOTE
The VCO range select bits have built-in protection that prevents them from
being written when the PLL is on (PLLON = 1) and prevents selection of the
VCO clock as the source of the base clock (BCS = 1) if the VCO range
select bits are all clear.
The VCO range select bits must be programmed correctly. Incorrect
programming may result in failure of the PLL to achieve lock.
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 logic 0.
Software should read the LOCK bit after a PLL interrupt request to see if the request was due to an entry
into lock or an exit from lock. When the PLL enters lock, the VCO clock, CGMVCLK, divided by two can
be selected as the CGMOUT source by setting BCS in the PCTL. When the PLL exits lock, the VCO clock
frequency is corrupt, and appropriate precautions should be taken. If the application is not
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 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
The WAIT instruction does not affect the CGM. Before entering wait mode, software can disengage and
turn off the PLL by clearing the BCS and PLLON bits in the PLL control register (PCTL). Less
power-sensitive applications can disengage the PLL without turning it off. Applications that require the
PLL to wake the MCU from wait mode also can deselect the PLL output without turning off the PLL.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
69
Clock Generator Module (CGM)
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.
The discrepancy in these definitions makes it difficult to specify an acquisition or lock time for a typical
PLL. Therefore, the definitions for acquisition and lock times for this module are:
• Acquisition time, tACQ, is the time the PLL takes to reduce the error between the actual output
frequency and the desired output frequency to less than the tracking mode entry tolerance, ∆TRK.
Acquisition time is based on an initial frequency error, (fDES – fORIG)/fDES, of not more than ±100
percent. In automatic bandwidth control mode (see 4.3.2.3 Manual and Automatic PLL Bandwidth
Modes), acquisition time expires when the ACQ bit becomes set in the PLL bandwidth control
register (PBWC).
• Lock time, tLock, is the time the PLL takes to reduce the error between the actual output frequency
and the desired output frequency to less than the lock mode entry tolerance, ∆Lock. Lock time is
based on an initial frequency error, (fDES – fORIG)/fDES, of not more than ±100 percent. In automatic
bandwidth control mode, lock time expires when the LOCK bit becomes set in the PLL bandwidth
control register (PBWC). See 4.3.2.3 Manual and Automatic PLL Bandwidth Modes.
Obviously, the acquisition and lock times can vary according to how large the frequency error is and may
be shorter or longer in many cases.
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.
The most critical parameter which affects the reaction times of the PLL is the reference frequency, fRDV.
This frequency is the input to the phase detector and controls how often the PLL makes corrections. For
stability, the corrections must be small compared to the desired frequency, so several corrections are
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Acquisition/Lock Time Specifications
required to reduce the frequency error. Therefore, the slower the reference the longer it takes to make
these corrections. This parameter is also under user control via the choice of crystal frequency, fXCLK.
Another critical parameter is the external filter capacitor. The PLL modifies the voltage on the VCO by
adding or subtracting charge from this capacitor. Therefore, the rate at which the voltage changes for a
given frequency error (thus change in charge) is proportional to the capacitor size. The size of the
capacitor also is related to the stability of the PLL. If the capacitor is too small, the PLL cannot make small
enough adjustments to the voltage and the system cannot lock. If the capacitor is too large, the PLL may
not be able to adjust the voltage in a reasonable time. See 4.8.3 Choosing a Filter Capacitor.
Also important is the operating voltage potential applied to VDDA. The power supply potential alters the
characteristics of the PLL. A fixed value is best. Variable supplies, such as batteries, are acceptable if
they vary within a known range at very slow speeds. Noise on the power supply is not acceptable,
because it causes small frequency errors which continually change the acquisition time of the PLL.
Temperature and processing also can affect acquisition time because the electrical characteristics of the
PLL change. The part operates as specified as long as these influences stay within the specified limits.
External factors, however, can cause drastic changes in the operation of the PLL. These factors include
noise injected into the PLL through the filter capacitor filter, capacitor leakage, stray impedances on the
circuit board, and even humidity or circuit board contamination.
4.8.3 Choosing a Filter Capacitor
As described in 4.8.2 Parametric Influences on Reaction Time, the external filter capacitor, CF, is critical
to the stability and reaction time of the PLL. The PLL is also dependent on reference frequency and supply
voltage. The value of the capacitor must, therefore, be chosen with supply potential and reference
frequency in mind. For proper operation, the external filter capacitor must be chosen according to this
equation:
⎛ V DDA⎞
C F = C FACT ⎜ ---------------⎟
⎝ f RDV ⎠
For acceptable values of CFACT, see 4.8 Acquisition/Lock Time Specifications. For the value of VDDA,
choose the voltage potential at which the MCU is operating. If the power supply is variable, choose a value
near the middle of the range of possible supply values.
This equation does not always yield a commonly available capacitor size, so round to the nearest
available size. If the value is between two different sizes, choose the higher value for better stability.
Choosing the lower size may seem attractive for acquisition time improvement, but the PLL can become
unstable. Also, always choose a capacitor with a tight tolerance (±20 percent or better) and low
dissipation.
4.8.4 Reaction Time Calculation
The actual acquisition and lock times can be calculated using the equations here. These equations yield
nominal values under these conditions:
• Correct selection of filter capacitor, CF, see 4.8.3 Choosing a Filter Capacitor
• Room temperature operation
• Negligible external leakage on CGMXFC
• Negligible noise
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
71
Clock Generator Module (CGM)
The K factor in the equations is derived from internal PLL parameters. KACQ is the K factor when the PLL
is configured in acquisition mode, and KTRK is the K factor when the PLL is configured in tracking mode.
See 4.3.2.2 Acquisition and Tracking Modes.
⎛ V DDA⎞
8
t ACQ = ⎜ ---------------⎟ ⎛ ---------------⎞
⎝
K
f
⎝ RDV ⎠ ACQ⎠
⎛ V DDA⎞
4
t AL = ⎜ ---------------⎟ ⎛ --------------⎞
⎝ f RDV ⎠ ⎝ K TRK⎠
t Lock = t ACQ + t AL
NOTE
The inverse proportionality between the lock time and the reference
frequency.
In automatic bandwidth control mode, the acquisition and lock times are quantized into units based on the
reference frequency. See 4.3.2.3 Manual and Automatic PLL Bandwidth Modes A certain number of clock
cycles, nACQ, is required to ascertain that the PLL is within the tracking mode entry tolerance, ∆TRK,
before exiting acquisition mode. A certain number of clock cycles, nTRK, is required to ascertain that the
PLL is within the lock mode entry tolerance, ∆Lock. Therefore, the acquisition time, tACQ, is an integer
multiple of nACQ/fRDV, and the acquisition to lock time, tAL, is an integer multiple of nTRK/fRDV. Also, since
the average frequency over the entire measurement period must be within the specified tolerance, the
total time usually is longer than tLock as calculated in the previous example.
In manual mode, it is usually necessary to wait considerably longer than tLock before selecting the PLL
clock (see 4.3.3 Base Clock Selector Circuit) because the factors described in 4.8.2 Parametric
Influences on Reaction Time may slow the lock time considerably.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Chapter 5
Configuration Register (CONFIG)
5.1 Introduction
This section describes the configuration register (CONFIG). This register contains bits that configure
these options:
• Resets caused by the low-voltage inhibit (LVI) module
• Power to the LVI module
• Computer operating properly (COP) module
• Top-side pulse-width modulator (PWM) polarity
• Bottom-side PWM polarity
• Edge-aligned versus center-aligned PWMs
• Six independent PWMs versus three complementary PWM pairs
5.2 Functional Description
The configuration register (CONFIG) is used in the initialization of various options. The configuration
register 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
this register be written immediately after reset. The configuration register is located at $001F and may be
read at anytime.
NOTE
On a FLASH device, the options are one-time writeable by the user after
each reset. The registers are not in the FLASH memory but are special
registers containing one-time writeable latches after each reset. Upon a
reset, the configuration register defaults to predetermined settings as
shown in Figure 5-1.
If the LVI module and the LVI reset signal are enabled, a reset occurs when
VDD falls to a voltage, VLVRx, and remains at or below that level for at least
nine consecutive central processor unit (CPU) cycles. Once an LVI reset
occurs, the MCU remains in reset until VDD rises to a voltage, VLVRX.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
73
Configuration Register (CONFIG)
5.3 Configuration Register
Address:
Read:
Write:
Reset:
$001F
Bit 7
6
5
4
3
2
1
Bit 0
EDGE
BOTNEG
TOPNEG
INDEP
LVIRST
LVIPWR
STOPE
COPD
0
0
0
0
1
1
0
0
Figure 5-1. Configuration Register (CONFIG)
EDGE — Edge-Align Enable Bit
EDGE determines if the motor control PWM will operate in edge-aligned mode or center-aligned mode.
See Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC).
1 = Edge-aligned mode enabled
0 = Center-aligned mode enabled
BOTNEG — Bottom-Side PWM Polarity Bit
BOTNEG determines if the bottom-side PWMs will have positive or negative polarity. See Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC).
1 = Negative polarity
0 = Positive polarity
TOPNEG — Top-Side PWM Polarity Bit
TOPNEG determines if the top-side PWMs will have positive or negative polarity. See Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC).
1 = Negative polarity
0 = Positive polarity
INDEP — Independent Mode Enable Bit
INDEP determines if the motor control PWMs will be six independent PWMs or three complementary
PWM pairs. See Chapter 12 Pulse-Width Modulator for Motor Control (PWMMC).
1 = Six independent PWMs
0 = Three complementary PWM pairs
LVIRST — LVI Reset Enable Bit
LVIRST enables the reset signal from the LVI module. See
Chapter 9 Low-Voltage Inhibit (LVI).
1 = LVI module resets enabled
0 = LVI module resets disabled
LVIPWR — LVI Power Enable Bit
LVIPWR enables the LVI module. Chapter 9 Low-Voltage Inhibit (LVI)
1 = LVI module power enabled
0 = LVI module power disabled
STOPE — Stop Enable Bit
Writing a 0 or a 1 to bit 1 has no effect on MCU operation. Bit 1 operates the same as the other bits
within this write-once register operate.
1 = STOP mode enabled
0 = STOP mode disabled
COPD — COP Disable Bit
COPD disables the COP module. See Chapter 6 Computer Operating Properly (COP).
1 = COP module disabled
0 = COP module enabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Chapter 6
Computer Operating Properly (COP)
6.1 Introduction
This section describes the computer operating properly module, a free-running counter that generates a
reset if allowed to overflow. The computer operating properly (COP) module helps software recover from
runaway code. Prevent a COP reset by periodically clearing the COP counter.
6.2 Functional Description
Figure 6-1 shows the structure of the COP module. A summary of the input/output (I/O) register is shown
in Figure 6-2.
SIM
SIM RESET CIRCUIT
CLEAR BITS 12–4
13-BIT SIM COUNTER
CLEAR ALL BITS
CGMXCLK
SIM RESET STATUS REGISTER
INTERNAL RESET SOURCES(1)
RESET VECTOR FETCH
COPCTL WRITE
COP MODULE
COPD (FROM CONFIG)
RESET
COPCTL WRITE
6-BIT COP COUNTER
CLEAR
COP COUNTER
Note 1. See 14.3.2 Active Resets from Internal Sources.
Figure 6-1. COP Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
75
Computer Operating Properly (COP)
Addr.
$FFFF
Register Name
Bit 7
COP Control Register
(COPCTL)
See page 77.
6
5
4
3
Read:
Low byte of reset vector
Write:
Clear COP counter
Reset:
Unaffected by reset
2
1
Bit 0
Figure 6-2. COP I/O Register Summary
The COP counter is a free-running, 6-bit counter preceded by the 13-bit system integration module (SIM)
counter. If not cleared by software, the COP counter overflows and generates an asynchronous reset after
218–24 CGMXCLK cycles. With a 4.9152-MHz crystal, the COP timeout period is 53.3 ms. Writing any
value to location $FFFF before overflow occurs clears the COP counter and prevents reset.
A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the COP bit in the SIM reset status
register (SRSR). See 14.7.2 SIM Reset Status Register.
NOTE
Place COP clearing instructions in the main program and not in an interrupt
subroutine. Such an interrupt subroutine could keep the COP from
generating a reset even while the main program is not working properly.
6.3 I/O Signals
This section describes 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 COPCTL Write
Writing any value to the COP control register (COPCTL) (see 6.4 COP Control Register) clears the COP
counter and clears bits 12–4 of the SIM counter. Reading the COP control register returns the reset
vector.
6.3.3 Power-On Reset
The power-on reset (POR) circuit in the SIM clears the SIM counter 4096 CGMXCLK cycles after
power-up.
6.3.4 Internal Reset
An internal reset clears the SIM counter and the COP counter.
6.3.5 Reset Vector Fetch
A reset vector fetch occurs when the vector address appears on the data bus. A reset vector fetch clears
the SIM counter.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
COP Control Register
6.3.6 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the configuration register (CONFIG).
See Chapter 5 Configuration Register (CONFIG).
6.4 COP Control Register
The COP control register is located at address $FFFF and overlaps the reset vector. Writing any value to
$FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF returns the low
byte of the reset vector.
Address:
$FFFF
Bit 7
6
5
4
3
Read:
Low byte of reset vector
Write:
Clear COP counter
Reset:
Unaffected by reset
2
1
Bit 0
Figure 6-3. COP Control Register (COPCTL)
6.5 Interrupts
The COP does not generate CPU interrupt requests.
6.6 Monitor Mode
The COP is disabled in monitor mode when VHI is present on the IRQ pin or on the RST pin.
6.7 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
The COP continues to operate during wait mode.
6.8 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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
77
Computer Operating Properly (COP)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
79
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)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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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)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
81
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
83
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
84
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
BRCLR n,opr,rel Branch if Bit n in M Clear
BRN rel
PC ← (PC) + 3 + rel ? (Mn) = 0
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
85
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
Clear
Compare A with M
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
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
INC opr
INCA
INCX
INC opr,X
INC ,X
INC opr,SP
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
Effect
on CCR
V H I N Z C
COM opr
COMA
COMX
COM opr,X
COM ,X
COM opr,SP
EOR #opr
EOR opr
EOR opr
EOR opr,X
EOR opr,X
EOR ,X
EOR opr,SP
EOR opr,SP
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
86
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
0 – – –
Logical Shift Left
(Same as ASL)
C
b7
Logical Shift Right
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
MOV opr,opr
MOV opr,X+
MOV #opr,opr
MOV X+,opr
Move
MUL
Unsigned multiply
b0
0
b7
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
Negate (Two’s Complement)
45
55
IMM
DIR
EXT
IX2
0 – – – IX1
IX
SP1
SP2
X ← (M)
Load X from M
IMM
DIR
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
H:X ← (M:M + 1)
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
87
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
88
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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
89
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
3
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
5
Cycles
BRSET0 Opcode Mnemonic
3 DIR Number of Bytes / Addressing Mode
Central Processor Unit (CPU)
90
Table 7-2. Opcode Map
Bit Manipulation
DIR
DIR
Chapter 8
External Interrupt (IRQ)
8.1 Introduction
This section describes the external interrupt (IRQ) module, which supports external interrupt functions.
8.2 Features
Features of the IRQ module include:
• A dedicated external interrupt pin, IRQ
• Hysteresis buffers
8.3 Functional Description
A logic 0 applied to any of the external interrupt pins can latch a CPU interrupt request. Figure 8-1 shows
the structure of the IRQ module.
ACK1
VDD
D
CLR
Q
CK
IRQ
SYNCHRONIZER
IRQ
INTERRUPT
REQUEST
HIGH
VOLTAGE
DETECT
TO MODE
SELECT
LOGIC
IRQ
LATCH
IMASK1
MODE1
Figure 8-1. IRQ Module Block Diagram
Addr.
$003F
Register Name
IRQ Status/Control Register
(ISCR)
See page 94.
Bit 7
6
5
4
Read:
0
0
0
0
Write:
R
R
R
R
Reset:
0
0
0
0
R
3
IRQF
0
2
0
ACK1
0
1
Bit 0
IMASK1
MODE1
0
0
= Reserved
Figure 8-2. IRQ I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
91
External Interrupt (IRQ)
Interrupt signals on the IRQ pin are latched into the IRQ1 latch. An interrupt latch remains set until one of
the following actions occurs:
• Vector fetch — A vector fetch automatically generates an interrupt acknowledge signal that clears
the latch that caused the vector fetch.
• Software clear — Software can clear an interrupt latch by writing to the appropriate acknowledge
bit in the interrupt status and control register (ISCR). Writing a logic 1 to the ACK1 bit clears the
IRQ1 latch.
• Reset — A reset automatically clears both interrupt latches.
The external interrupt pins are falling-edge-triggered and are software-configurable to be both
falling-edge and low-level-triggered. The MODE1 bit in the ISCR controls the triggering sensitivity of the
IRQ pin.
When the interrupt pin is edge-triggered only, the interrupt latch remains set until a vector fetch, software
clear, or reset occurs.
When the interrupt pin is both falling-edge and low-level-triggered, the interrupt latch remains set until
both of these occur:
• Vector fetch, software clear, or reset
• Return of the interrupt pin to logic 1
The vector fetch or software clear can occur before or after the interrupt pin returns to logic 1. As long as
the pin is low, the interrupt request remains pending.
When set, the IMASK1 bit in the ISCR 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. (See Figure 8-3.)
8.4 IRQ Pin
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch. A vector fetch, software clear,
or reset clears the IRQ latch.
If the MODE1 bit is set, the IRQ pin is both falling-edge-sensitive and low-level- sensitive. With MODE1
set, both of these actions must occur to clear the IRQ1 latch:
• Vector fetch, software clear, or reset — A vector fetch generates an interrupt acknowledge signal
to clear the latch. Software can generate the interrupt acknowledge signal by writing a logic 1 to
the ACK1 bit in the interrupt status and control register (ISCR). The ACK1 bit is useful in
applications that poll the IRQ pin and require software to clear the IRQ1 latch. Writing to the ACK1
bit can also prevent spurious interrupts due to noise. Setting ACK1 does not affect subsequent
transitions on the IRQ pin. A falling edge that occurs after writing to the ACK1 bit latches another
interrupt request. If the IRQ1 mask bit, IMASK1, is clear, the CPU loads the program counter with
the vector address at locations $FFFA and $FFFB.
• Return of the IRQ pin to logic 1 — As long as the IRQ pin is at logic 0, the IRQ1 latch remains set.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
92
Freescale Semiconductor
IRQ Pin
FROM RESET
YES
I BIT SET?
NO
INTERRUPT?
YES
NO
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION?
YES
NO
RTI
INSTRUCTION?
YES
UNSTACK CPU REGISTERS
NO
EXECUTE INSTRUCTION
Figure 8-3. IRQ Interrupt Flowchart
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
93
External Interrupt (IRQ)
A logic 0 on the IRQ pin can latch an interrupt request into the IRQ latch. A vector fetch, software clear,
or reset clears the IRQ latch.
If the MODE1 bit is set, the IRQ pin is both falling-edge-sensitive and low-level- sensitive. With MODE1
set, both of these actions must occur to clear the IRQ1 latch:
• Vector fetch, software clear, or reset — A vector fetch generates an interrupt acknowledge signal
to clear the latch. Software can generate the interrupt acknowledge signal by writing a logic 1 to
the ACK1 bit in the interrupt status and control register (ISCR). The ACK1 bit is useful in
applications that poll the IRQ pin and require software to clear the IRQ1 latch. Writing to the ACK1
bit can also prevent spurious interrupts due to noise. Setting ACK1 does not affect subsequent
transitions on the IRQ pin. A falling edge that occurs after writing to the ACK1 bit latches another
interrupt request. If the IRQ1 mask bit, IMASK1, is clear, the CPU loads the program counter with
the vector address at locations $FFFA and $FFFB.
• Return of the IRQ pin to logic 1 — As long as the IRQ pin is at logic 0, the IRQ1 latch remains set.
The vector fetch or software clear and the return of the IRQ pin to logic 1 can occur in any order. The
interrupt request remains pending as long as the IRQ pin is at logic 0.
If the MODE1 bit is clear, the IRQ pin is falling-edge-sensitive only. With MODE1 clear, a vector fetch or
software clear immediately clears the IRQ1 latch.
Use the branch if IRQ pin high (BIH) or branch if IRQ pin low (BIL) instruction to read the logic level on
the IRQ pin.
NOTE
When using the level-sensitive interrupt trigger, avoid false interrupts by
masking interrupt requests in the interrupt routine.
8.5 IRQ Status and Control Register
The IRQ status and control register (ISCR) has these functions:
• Clears the IRQ interrupt latch
• Masks IRQ interrupt requests
• Controls triggering sensitivity of the IRQ interrupt pin
Address:
$003F
Bit 7
6
5
4
Read:
0
0
0
0
Write:
R
R
R
R
Reset:
0
0
0
0
R
= Reserved
3
IRQF
0
2
0
ACK1
0
1
Bit 0
IMASK1
MODE1
0
0
Figure 8-4. IRQ Status and Control Register (ISCR)
ACK1 — IRQ Interrupt Request Acknowledge Bit
Writing a logic 1 to this write-only bit clears the IRQ latch. ACK1 always reads as logic 0. Reset clears
ACK1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
94
Freescale Semiconductor
IRQ Status and Control Register
IMASK1 — IRQ Interrupt Mask Bit
Writing a logic 1 to this read/write bit disables IRQ interrupt requests. Reset clears IMASK1.
1 = IRQ interrupt requests disabled
0 = IRQ interrupt requests enabled
MODE1 — IRQ Edge/Level Select Bit
This read/write bit controls the triggering sensitivity of the IRQ pin. Reset clears MODE1.
1 = IRQ interrupt requests on falling edges and low levels
0 = IRQ interrupt requests on falling edges only
IRQF — IRQ Flag
This read-only bit acts as a status flag, indicating an IRQ event occurred.
1 = External IRQ event occurred.
0 = External IRQ event did not occur.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
95
External Interrupt (IRQ)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
96
Freescale Semiconductor
Chapter 9
Low-Voltage Inhibit (LVI)
9.1 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 to the LVI trip voltage.
9.2 Features
Features of the LVI module include:
• Programmable LVI reset
• Programmable power consumption
• Digital filtering of VDD pin level
• Selectable LVI trip voltage
9.3 Functional Description
Figure 9-1 shows the structure of the LVI module. The LVI is enabled out of reset. The LVI module
contains a bandgap reference circuit and comparator. The LVI power bit, LVIPWR, enables the LVI to
monitor VDD voltage. The LVI reset bit, LVIRST, enables the LVI module to generate a reset when VDD
falls below a voltage, VLVRX, and remains at or below that level for nine or more consecutive CGMXCLK.
VLVRX and VLVHX are determined by the TRPSEL bit in the LVISCR (see Figure 9-2). LVIPWR and
LVIRST are in the configuration register (CONFIG). See Chapter 5 Configuration Register (CONFIG).
VDD
LVIPWR
FROM CONFIG
FROM CONFIG
CPU CLOCK
LOW VDD
DETECTOR
VDD > LVItrip = 0
LVIRST
VDD
DIGITAL FILTER
LVI RESET
VDD < LVItrip = 1
TRPSEL
FROM LVISCR
ANLGTRIP
LVIOUT
Figure 9-1. LVI Module Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
97
Low-Voltage Inhibit (LVI)
Once an LVI reset occurs, the MCU remains in reset until VDD rises above a voltage, VLVRX + VLVHX.
VDD must be above VLVRX + VLVHX for only one CPU cycle to bring the MCU out of reset. See
14.3.2.6 Low-Voltage Inhibit (LVI) Reset. The output of the comparator controls the state of the LVIOUT
flag in the LVI status register (LVISCR).
An LVI reset also drives the RST pin low to provide low-voltage protection to external peripheral devices.
See 19.5 DC Electrical Characteristics.
Addr.
$FE0F
Register Name
Bit 7
Read: LVIOUT
LVI Status and Control Register
(LVISCR) Write:
R
See page 99.
Reset:
0
R
6
5
0
4
3
2
1
Bit 0
0
0
0
0
0
R
R
R
R
R
0
0
0
0
0
TRPSEL
R
0
0
= Reserved
Figure 9-2. LVI I/O Register Summary
9.3.1 Polled LVI Operation
In applications that can operate at VDD levels below VLVRX, software can monitor VDD by polling the
LVIOUT bit. In the configuration register, the LVIPWR bit must be 1 to enable the LVI module, and the
LVIRST bit must be 0 to disable LVI resets. See Chapter 5 Configuration Register (CONFIG). TRPSEL
in the LVISCR selects VLVRX.
9.3.2 Forced Reset Operation
In applications that require VDD to remain above VLVRX, enabling LVI resets allows the LVI module to
reset the MCU when VDD falls to the VLVRX level and remains at or below that level for nine or more
consecutive CPU cycles. In the CONFIG register, the LVIPWR and LVIRST bits must be 1s to enable the
LVI module and to enable LVI resets. TRPSEL in the LVISCR selects VLVRX.
9.3.3 False Reset Protection
The VDD pin level is digitally filtered to reduce false resets due to power supply noise. In order for the LVI
module to reset the MCU, VDD must remain at or below VLVRX for nine or more consecutive CPU cycles.
VDD must be above VLVRX + VLVHX for only one CPU cycle to bring the MCU out of reset. TRPSEL in the
LVISCR selects VLVRX + VLVHX.
9.3.4 LVI Trip Selection
The TRPSEL bit allows the user to chose between 5 percent and 10 percent tolerance when monitoring
the supply voltage. The 10 percent option is enabled out of reset. Writing a 1 to TRPSEL will enable 5
percent option.
NOTE
The microcontroller is guaranteed to operate at a minimum supply voltage.
The trip point (VLVR1 or VLVR2) may be lower than this. See 19.5 DC
Electrical Characteristics.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
98
Freescale Semiconductor
LVI Status and Control Register
9.4 LVI Status and Control Register
The LVI status register (LVISCR) flags VDD voltages below the VLVRX level.
Address:
$FE0F
Bit 7
6
5
Read:
LVIOUT
0
Write:
R
R
Reset:
0
0
R
= Reserved
TRPSEL
0
4
3
2
1
Bit 0
0
0
0
0
0
R
R
R
R
R
0
0
0
0
0
Figure 9-3. LVI Status and Control Register (LVISCR)
LVIOUT — LVI Output Bit
This read-only flag becomes set when the VDD voltage falls below the VLVRX voltage for 32 to 40
CGMXCLK cycles. See Table 9-1. Reset clears the LVIOUT bit.
Table 9-1. LVIOUT Bit Indication
VDD
LVIOUT
At Level:
For Number of CGMXCLK Cycles:
VDD > VLVRX + VLVHX
Any
0
VDD < VLVRX
< 32 CGMXCLK cycles
0
VDD < VLVRX
Between 32 & 40 CGMXCLK cycles
0 or 1
VDD < VLVRX
> 40 CGMXCLK cycles
1
VLVRX < VDD < VLVRX + VLVHX
Any
Previous value
TRPSEL — LVI Trip Select Bit
This bit selects the LVI trip point. Reset clears this bit.
1 = 5 percent tolerance. The trip point and recovery point are determined by VLVR1 and VLVH1,
respectively.
0 = 10 percent tolerance. The trip point and recovery point are determined by VLVR2 and VLVH2,
respectively.
NOTE
If LVIRST and LVIPWR are 0s, note that when changing the tolerance, LVI
reset will be generated if the supply voltage is below the trip point.
9.5 LVI Interrupts
The LVI module does not generate interrupt requests.
9.6 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
With the LVIPWR bit in the configuration register programmed to 1, the LVI module is active after a WAIT
instruction.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
99
Low-Voltage Inhibit (LVI)
With the LVIRST bit in the configuration register programmed to 1, the LVI module can generate a reset
and bring the MCU out of wait mode.
9.7 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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
100
Freescale Semiconductor
Chapter 10
Input/Output (I/O) Ports (PORTS)
10.1 Introduction
Thirty-seven bidirectional input-output (I/O) pins and seven input pins form six parallel ports. All I/O pins
are programmable as inputs or outputs.
When using the 56-pin package version:
• Set the data direction register bits in DDRC such that bit 1 is written to a logic 1 (along with any
other output bits on port C).
• Set the data direction register bits in DDRE such that bits 0, 1, and 2 are written to a logic 1 (along
with any other output bits on port E).
• Set the data direction register bits in DDRF such that bits 0, 1, 2, and 3 are written to a logic 1 (along
with any other output bits on port F).
NOTE
Connect any unused I/O pins to an appropriate logic level, either VDD or
VSS. Although PWM6–PWM1 do not require termination for proper
operation, termination reduces excess current consumption and the
possibility of electrostatic damage.
Addr.
Register Name
$0000
Port A Data Register
(PTA)
See page 103.
$0001
$0002
$0003
$0004
Port B Data Register
(PTB)
See page 104.
Port C Data Register
(PTC)
See page 106.
Port D Data Register
(PTD)
See page 107.
Data Direction Register A
(DDRA)
See page 103.
Read:
Write:
Bit 7
6
5
4
3
2
1
Bit 0
PTA7
PTA6
PTA5
PTA4
PTA3
PTA2
PTA1
PTA0
PTB2
PTB1
PTB0
PTC2
PTC1
PTC0
Reset:
Read:
Write:
Unaffected by reset
PTB7
PTB6
PTB5
Reset:
PTB4
PTB3
Unaffected by reset
Read:
0
Write:
R
PTC6
PTC5
Reset:
PTC4
PTC3
Unaffected by reset
Read:
0
PTD6
PTD5
PTD4
PTD3
PTD2
PTD1
PTD0
Write:
R
R
R
R
R
R
R
R
Reset:
Read:
Write:
Reset:
Unaffected by reset
DDRA7
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
0
R
= Reserved
= Unimplemented
Figure 10-1. I/O Port Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
101
Input/Output (I/O) Ports (PORTS)
Addr.
$0005
$0006
Register Name
Data Direction Register B
(DDRB)
See page 105.
Data Direction Register C
(DDRC)
See page 106.
Read:
Write:
Reset:
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
PTE2
PTE1
PTE0
PTF2
PTF1
PTF0
Read:
0
Write:
R
Reset:
0
$0007
$0008
$0009
Unimplemented
Port E Data Register
(PTE)
See page 108.
Port F Data Register
(PTF)
See page 110.
$000A
Unimplemented
$000B
Unimplemented
$000C
Data Direction Register E
(DDRE)
See page 109.
$000D
Data Direction Register F
(DDRF)
See page 110.
Read:
Write:
PTE7
PTE6
PTE5
Reset:
0
0
Write:
R
R
PTF5
Reset:
Write:
Reset:
PTE3
Unaffected by reset
Read:
Read:
PTE4
PTF4
PTF3
Unaffected by reset
DDRE7
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
0
DDRF5
DDRF4
DDRF3
DDRF2
DDRF1
DDRF0
0
0
0
0
0
0
Read:
0
0
Write:
R
R
Reset:
R
= Reserved
= Unimplemented
Figure 10-1. I/O Port Register Summary (Continued)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
102
Freescale Semiconductor
Port A
10.2 Port A
Port A is an 8-bit, general-purpose, bidirectional I/O port.
10.2.1 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
Reset:
Unaffected by reset
Figure 10-2. Port A Data Register (PTA)
PTA[7:0] — Port A Data Bits
These read/write bits are software programmable. Data direction of each port A pin is under the control
of the corresponding bit in data direction register A. Reset has no effect on port A data.
10.2.2 Data Direction Register A
Data direction register A (DDRA) determines whether each port A pin is an input or an output. Writing a
logic 1 to a DDRA bit enables the output buffer for the corresponding port A pin; a logic 0 disables the
output buffer.
Address:
Read:
Write:
Reset:
$0004
Bit 7
6
5
4
3
2
1
Bit 0
DDRA7
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
0
0
0
0
0
0
0
0
Figure 10-3. Data Direction Register A (DDRA)
DDRA[7:0] — Data Direction Register A Bits
These read/write bits control port A data direction. Reset clears DDRA[7:0], configuring all port A pins
as inputs.
1 = Corresponding port A pin configured as output
0 = Corresponding port A pin configured as input
NOTE
Avoid glitches on port A pins by writing to the port A data register before
changing data direction register A bits from 0 to 1.
Figure 10-4 shows the port A I/O logic.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
103
Input/Output (I/O) Ports (PORTS)
READ DDRA ($0004)
INTERNAL DATA BUS
WRITE DDRA ($0004)
DDRAx
RESET
WRITE PTA ($0000)
PTAx
PTAx
READ PTA ($0000)
Figure 10-4. Port A I/O Circuit
When bit DDRAx is a logic 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a
logic 0, reading address $0000 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-1 summarizes the operation of the port A pins.
Table 10-1. Port A Pin Functions
DDRA Bit
PTA Bit
(1)
0
Input,
X
1
Accesses to DDRA
I/O Pin Mode
X
Hi-Z(2)
Output
Accesses to PTA
Read/Write
Read
Write
DDRA[7:0]
Pin
PTA[7:0](3)
DDRA[7:0]
PTA[7:0]
PTA[7:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
10.3 Port B
Port B is an 8-bit, general-purpose, bidirectional I/O port that shares its pins with the analog-to-digital
convertor (ADC) module.
10.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the eight port B pins.
Address:
Read:
Write:
Reset:
$0001
Bit 7
6
5
4
3
2
1
Bit 0
PTB7
PTB6
PTB5
PTB4
PTB3
PTB2
PTB1
PTB0
Unaffected by reset
Figure 10-5. Port B Data Register (PTB)
PTB[7:0] — Port B Data Bits
These read/write bits are software-programmable. Data direction of each port B pin is under the control
of the corresponding bit in data direction register B. Reset has no effect on port B data.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
104
Freescale Semiconductor
Port B
10.3.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is an input or an output. Writing a
logic 1 to a DDRB bit enables the output buffer for the corresponding port B pin; a logic 0 disables the
output buffer.
Address:
Read:
Write:
Reset:
$0005
Bit 7
6
5
4
3
2
1
Bit 0
DDRB7
DDRB6
DDRB5
DDRB4
DDRB3
DDRB2
DDRB1
DDRB0
0
0
0
0
0
0
0
0
Figure 10-6. Data Direction Register B (DDRB)
DDRB[7:0] — Data Direction Register B Bits
These read/write bits control port B data direction. Reset clears DDRB[7:0], configuring all port B pins
as inputs.
1 = Corresponding port B pin configured as output
0 = Corresponding port B pin configured as input
NOTE
Avoid glitches on port B pins by writing to the port B data register before
changing data direction register B bits from 0 to 1.
Figure 10-7 shows the port B I/O logic.
READ DDRB ($0005)
INTERNAL DATA BUS
WRITE DDRB ($0005)
RESET
DDRBx
WRITE PTB ($0001)
PTBx
PTBx
READ PTB ($0001)
Figure 10-7. Port B I/O Circuit
When bit DDRBx is a logic 1, reading address $0001 reads the PTBx data latch. When bit DDRBx is a
logic 0, reading address $0001 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-2 summarizes the operation of the port B pins.
Table 10-2. Port B Pin Functions
DDRB Bit
PTB Bit
I/O Pin Mode
0
X(1)
X
Input, Hi-Z(2)
Output
1
Accesses to DDRB
Read/Write
Accesses to PTB
Read
Write
DDRB[7:0]
Pin
DDRB[7:0]
PTB[7:0]
PTB[7:0](3)
PTB[7:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
105
Input/Output (I/O) Ports (PORTS)
10.4 Port C
Port C is a 7-bit, general-purpose, bidirectional I/O port that shares two of its pins with the analog-to-digital
convertor module (ADC).
10.4.1 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:
0
Write:
R
6
5
4
3
2
1
Bit 0
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1
PTC0
Reset:
Unaffected by reset
R
= Reserved
Figure 10-8. Port C Data Register (PTC)
PTC[6:0] — Port C Data Bits
These read/write bits are software-programmable. Data direction of each port C pin is under the control
of the corresponding bit in data direction register C. Reset has no effect on port C data.
10.4.2 Data Direction Register C
Data direction register C (DDRC) determines whether each port C pin is an input or an output. Writing a
logic 1 to a DDRC bit enables the output buffer for the corresponding port C pin; a logic 0 disables the
output buffer.
Address:
$0006
Bit 7
6
5
4
3
2
1
Bit 0
DDRC6
DDRC5
DDRC4
DDRC3
DDRC2
DDRC1
DDRC0
0
0
0
0
0
0
Read:
0
Write:
R
Reset:
0
0
R
= Reserved
Figure 10-9. Data Direction Register C (DDRC)
DDRC[6:0] — Data Direction Register C Bits
These read/write bits control port C data direction. Reset clears DDRC[6:0], configuring all port C pins
as inputs.
1 = Corresponding port C pin configured as output
0 = Corresponding port C pin configured as input
NOTE
Avoid glitches on port C pins by writing to the port C data register before
changing data direction register C bits from 0 to 1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
106
Freescale Semiconductor
Port D
Figure 10-10 shows the port C I/O logic.
READ DDRC ($0006)
INTERNAL DATA BUS
WRITE DDRC ($0006)
DDRCx
RESET
WRITE PTC ($0002)
PTCx
PTCx
READ PTC ($0002)
Figure 10-10. Port C I/O Circuit
When bit DDRCx is a logic 1, reading address $0002 reads the PTCx data latch. When bit DDRCx is a
logic 0, reading address $0002 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-3 summarizes the operation of the port C pins.
Table 10-3. Port C Pin Functions
DDRC Bit
PTC Bit
I/O Pin Mode
Accesses to DDRC
Accesses to PTC
Read/Write
Read
Write
0
X(1)
Input, Hi-Z(2)
DDRC[6:0]
Pin
PTC[6:0](3)
1
X
Output
DDRC[6:0]
PTC[6:0]
PTC[6:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
10.5 Port D
Port D is a 7-bit, input-only port that shares its pins with the pulse width modulator for motor control
module (PMC).
The port D data register (PTD) contains a data latch for each of the seven port pins.
Address:
$0003
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
PTD6
PTD5
PTD4
PTD3
PTD2
PTD1
PTD0
Write:
R
R
R
R
R
R
R
R
Reset:
Unaffected by reset
R
= Reserved
Figure 10-11. Port D Data Register (PTD)
PTD[6:0] — Port D Data Bits
These read/write bits are software programmable. Reset has no effect on port D data.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
107
Input/Output (I/O) Ports (PORTS)
INTERNAL DATA BUS
Figure 10-12 shows the port D input logic.
READ PTD ($0003)
PTDx
Figure 10-12. Port D Input Circuit
Reading address $0003 reads the voltage level on the pin. Table 10-4 summarizes the operation of the
port D pins.
Table 10-4. Port D Pin Functions
PTD Bit
Accesses to PTD
Pin Mode
(1)
Input,
X
Hi-Z(2)
Read
Write
Pin
PTD[6:0](3)
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
10.6 Port E
Port E is an 8-bit, special function port that shares five of its pins with the timer interface module (TIM)
and two of its pins with the serial communications interface module (SCI).
10.6.1 Port E Data Register
The port E data register (PTE) contains a data latch for each of the eight port E pins.
Address:
Read:
Write:
Reset:
$0008
Bit 7
6
5
4
3
2
1
Bit 0
PTE7
PTE6
PTE5
PTE4
PTE3
PTE2
PTE1
PTE0
Unaffected by reset
Figure 10-13. Port E Data Register (PTE)
PTE[7:0] — Port E Data Bits
PTE[7:0] are read/write, software-programmable bits. Data direction of each port E pin is under the
control of the corresponding bit in data direction register E.
NOTE
Data direction register E (DDRE) does not affect the data direction of port
E pins that are being used by the TIMA or TIMB. However, the DDRE bits
always determine whether reading port E returns the states of the latches
or the states of the pins.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
108
Freescale Semiconductor
Port E
10.6.2 Data Direction Register E
Data direction register E (DDRE) determines whether each port E pin is an input or an output. Writing a
logic 1 to a DDRE bit enables the output buffer for the corresponding port E pin; a logic 0 disables the
output buffer.
Address:
Read:
Write:
Reset:
$000C
Bit 7
6
5
4
3
2
1
Bit 0
DDRE7
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
DDRE1
DDRE0
0
0
0
0
0
0
0
0
Figure 10-14. Data Direction Register E (DDRE)
DDRE[7:0] — Data Direction Register E Bits
These read/write bits control port E data direction. Reset clears DDRE[7:0], configuring all port E pins
as inputs.
1 = Corresponding port E pin configured as output
0 = Corresponding port E pin configured as input
NOTE
Avoid glitches on port E pins by writing to the port E data register before
changing data direction register E bits from 0 to 1.
Figure 10-15 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 10-15. Port E I/O Circuit
When bit DDREx is a logic 1, reading address $0008 reads the PTEx data latch. When bit DDREx is a
logic 0, reading address $0008 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-5 summarizes the operation of the port E pins.
Table 10-5. Port E Pin Functions
DDRE Bit
PTE Bit
I/O Pin Mode
0
X(1)
1
X
Accesses to DDRE
Accesses to PTE
Read/Write
Read
Write
Input, Hi-Z(2)
DDRE[7:0]
Pin
PTE[7:0](3)
Output
DDRE[7:0]
PTE[7:0]
PTE[7:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
109
Input/Output (I/O) Ports (PORTS)
10.7 Port F
Port F is a 6-bit, special function port that shares four of its pins with the serial peripheral interface module
(SPI) and two pins with the serial communications interface (SCI).
10.7.1 Port F Data Register
The port F data register (PTF) contains a data latch for each of the six port F pins.
Address:
$0009
Bit 7
6
Read:
0
0
Write:
R
R
R
= Reserved
5
4
3
2
1
Bit 0
PTF5
PTF4
PTF3
PTF2
PTF1
PTF0
Reset:
Unaffected by reset
Figure 10-16. Port F Data Register (PTF)
PTF[5:0] — Port F Data Bits
These read/write bits are software programmable. Data direction of each port F pin is under the control
of the corresponding bit in data direction register F. Reset has no effect on PTF[5:0].
NOTE
Data direction register F (DDRF) does not affect the data direction of port F
pins that are being used by the SPI or SCI module. However, the DDRF bits
always determine whether reading port F returns the states of the latches
or the states of the pins.
10.7.2 Data Direction Register F
Data direction register F (DDRF) determines whether each port F pin is an input or an output. Writing a
logic 1 to a DDRF bit enables the output buffer for the corresponding port F pin; a logic 0 disables the
output buffer.
Address:
$000D
Bit 7
6
Read:
0
0
Write:
R
R
Read:
R
5
4
3
2
1
Bit 0
DDRF5
DDRF4
DDRF3
DDRF2
DDRF1
DDRF0
0
0
0
0
0
0
= Reserved
Figure 10-17. Data Direction Register F (DDRF)
DDRF[5:0] — Data Direction Register F Bits
These read/write bits control port F data direction. Reset clears DDRF[5:0], configuring all port F pins
as inputs.
1 = Corresponding port F pin configured as output
0 = Corresponding port F pin configured as input
NOTE
Avoid glitches on port F pins by writing to the port F data register before
changing data direction register F bits from 0 to 1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
110
Freescale Semiconductor
Port F
Figure 10-18 shows the port F I/O logic.
READ DDRF ($000D)
INTERNAL DATA BUS
WRITE DDRF ($000D)
RESET
DDRFx
WRITE PTF ($0009)
PTFx
PTFx
READ PTF ($0009)
Figure 10-18. Port F I/O Circuit
When bit DDRFx is a logic 1, reading address $0009 reads the PTFx data latch. When bit DDRFx is a
logic 0, reading address $0009 reads the voltage level on the pin. The data latch can always be written,
regardless of the state of its data direction bit. Table 10-6 summarizes the operation of the port F pins.
Table 10-6. Port F Pin Functions
DDRF Bit
PTF Bit
I/O Pin Mode
0
X(1)
1
X
Accesses to DDRF
Accesses to PTF
Read/Write
Read
Write
Input, Hi-Z(2)
DDRF[6:0]
Pin
PTF[6:0](3)
Output
DDRF[6:0]
PTF[6:0]
PTF[6:0]
1. X = don’t care
2. Hi-Z = high impedance
3. Writing affects data register, but does not affect input.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
111
Input/Output (I/O) Ports (PORTS)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
112
Freescale Semiconductor
Chapter 11
Power-On Reset (POR)
11.1 Introduction
This section describes the power-on reset (POR) module.
11.2 Functional Description
The POR module provides a known, stable signal to the microcontroller unit (MCU) at power-on. This
signal tracks VDD until the MCU generates a feedback signal to indicate that it is properly initialized. At
this time, the POR drives its output low.
The POR is not a brown-out detector, low-voltage detector, or glitch detector. VDD at the POR must go
completely to 0 to reset the microcontroller unit (MCU). To detect power-loss conditions, use a low-voltage
inhibit module (LVI) or other suitable circuit.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
113
Power-On Reset (POR)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
114
Freescale Semiconductor
Chapter 12
Pulse-Width Modulator for Motor Control (PWMMC)
12.1 Introduction
This section describes the pulse-width modulator for motor control (PWMMC, version A). The PWM
module can generate three complementary PWM pairs or six independent PWM signals. These
PWM signals can be center-aligned or edge-aligned. A block diagram of the PWM module is shown in
Figure 12-2.
A12-bit timer PWM counter is common to all six channels. PWM resolution is one clock period for
edge-aligned operation and two clock periods for center-aligned operation. The clock period is dependent
on the internal operating frequency (fOP) and a programmable prescaler. The highest resolution for
edge-aligned operation is 125 ns (fOP = 8 MHz). The highest resolution for center-aligned operation is
250 ns (fOP = 8 MHz).
When generating complementary PWM signals, the module features automatic dead-time insertion to the
PWM output pairs and transparent toggling of PWM data based upon sensed motor phase current
polarity.
A summary of the PWM registers is shown in Figure 12-3.
12.2 Features
Features of the PWMMC include:
• Three complementary PWM pairs or six independent PWM signals
• Edge-aligned PWM signals or center-aligned PWM signals
• PWM signal polarity control
• 20-mA current sink capability on PWM pins
• Manual PWM output control through software
• Programmable fault protection
• Complementary mode featuring:
– Dead-time insertion
– Separate top/bottom pulse width correction via current sensing or programmable software bits
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
115
PTA
PTA7–PTA0
PTB
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
PTC
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1/ATD9(1)
PTC0/ATD8
PTD
PTD6/IS3
PTD5/IS2
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
PTE
CONTROL AND STATUS REGISTERS — 112 BYTES
DDRA
ARITHMETIC/LOGIC
UNIT
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
DDRB
CPU
REGISTERS
USER FLASH — 32,256 BYTES
USER RAM — 768 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VDDA
VSSA(3)
VREFL(3)
VREFH
PWMGND
PWM6–PWM1
Freescale Semiconductor
VSS
VDD
VDDAD
VSSAD
ANALOG-TO-DIGITAL CONVERTER
MODULE
PULSE-WIDTH MODULATOR
MODULE
DDRC
SERIAL COMMUNICATIONS INTERFACE
MODULE
SERIAL PERIPHERAL INTERFACE
MODULE(2)
POWER-ON RESET
MODULE
SINGLE BREAK
MODULE
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PTF1/SS(1)
DDRE
USER FLASH VECTOR SPACE — 46 BYTES
TIMER INTERFACE
MODULE B
PTF
MONITOR ROM — 240 BYTES
DDRF
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
TIMER INTERFACE
MODULE A
PTF0/SPSCK(1)
POWER
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 12-1. Block Diagram Highlighting PWMMC Block and Pins
Pulse-Width Modulator for Motor Control (PWMMC)
116
INTERNAL BUS
M68HC08 CPU
Features
8
CPU BUS
PWM1 PIN
PWM2 PIN
PWM CHANNELS 3 AND 4
FAULT PROTECTION
OUTPUT CONTROL
CONTROL LOGIC BLOCK
PWM CHANNELS 1 AND 2
PWM3 PIN
PWM4 PIN
PWM5 PIN
PWM CHANNELS 5 AND 6
PWM6 PIN
FAULT
INTERRUPT
PINS
4
12
TIMEBASE
3
COIL CURRENT
POLARITY PINS
Figure 12-2. PWM Module Block Diagram
Addr.
Register Name
$0020
PWM Control Register 1
(PCTL1)
See page 146.
$0021
$0022
$0023
$0024
PWM Control Register 2
(PCTL2)
See page 148.
Fault Control Register
(FCR)
See page 150.
Fault Status Register
(FSR)
See page 152.
Fault Acknowledge Register
(FTACK)
See page 153.
Bit 7
6
5
4
3
2
1
Bit 0
DISX
DISY
PWMINT
PWMF
ISENS1
ISENS0
LDOK
PWMEN
0
0
0
0
0
0
0
0
LDFQ1
LDFQ0
IPOL1
IPOL2
IPOL3
PRSC1
PRSC0
0
0
0
0
0
0
0
0
FINT4
FMODE4
FINT3
FMODE3
FINT2
FMODE2
FINT1
FMODE1
Reset:
0
0
0
0
0
0
0
0
Read:
FPIN4
FFLAG4
FPIN3
FFLAG3
FPIN2
FFLAG2
FPIN1
FFLAG1
Reset:
U
0
U
0
U
0
U
0
Read:
0
0
DT6
DT5
DT4
DT3
DT2
DT1
Read:
Write:
Reset:
Read:
0
Write:
Reset:
Read:
Write:
Write:
FTACK4
Write:
Reset:
0
R
0
= Reserved
FTACK3
0
FTACK2
0
0
Bold
= Buffered
0
FTACK1
0
0
X = Indeterminate
Figure 12-3. Register Summary (Sheet 1 of 3)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
117
Pulse-Width Modulator for Motor Control (PWMMC)
Addr.
$0025
$0026
$0027
$0028
$0029
$002A
$002B
$002C
$002D
$002E
$002F
Register Name
Bit 7
PWM Output Control
Register (PWMOUT)
See page 154.
PWM Counter Register High
(PCNTH)
See page 143.
PWM Counter Register Low
(PCNTL)
See page 143.
PWM Counter Modulo Register
High (PMODH)
See page 144.
PWM Counter Modulo Register
Low (PMODL)
See page 144.
PWM 1 Value Register High
(PVAL1H)
See page 145.
PWM 1 Value Register Low
(PVAL1L)
See page 145.
PWM 2 Value Register High
(PVAL2H)
See page 145.
PWM 2 Value Register Low
(PVAL2L)
See page 145.
PWM 3 Value Register High
(PVAL3H)
See page 145.
PWM 3 Value Register Low
(PVAL3L)
See page 145.
Read:
6
5
4
3
2
1
Bit 0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
Write:
Reset:
0
0
0
0
0
0
0
0
Read:
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
0
0
0
0
0
0
0
0
Read:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset:
0
0
0
0
0
0
0
0
Read:
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
Write:
Write:
Write:
Reset:
0
0
0
0
X
X
X
X
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
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
0
0
0
0
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
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
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
0
0
0
0
0
Bold
= Buffered
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
R
= Reserved
X = Indeterminate
Figure 12-3. Register Summary (Sheet 2 of 3)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
118
Freescale Semiconductor
Features
Addr.
$0030
$0031
$0032
$0033
$0034
$0035
$0036
$0037
Register Name
PWM 4 Value Register High
(PVAL4H)
See page 145.
PWM 4 Value Register Low
(PVAL4L)
See page 145.
PWM 5 Value Register High
(PVAL5H)
See page 145.
PWM 5 Value Register Low
(PVAL5L)
See page 145.
PWM 6 Value Register High
(PVAL6H)
See page 145.
PWM 6 Value Register Low
(PMVAL6L)
See page 145.
Dead-Time Write-Once
Register (DEADTM)
See page 150.
PWM Disable Mapping
Write-Once Register
(DISMAP) See page 150.
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
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
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
0
0
0
0
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
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Bold
= Buffered
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
Read:
Write:
Reset:
R
= Reserved
X = Indeterminate
Figure 12-3. Register Summary (Sheet 3 of 3)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
119
Pulse-Width Modulator for Motor Control (PWMMC)
12.3 Timebase
This section provides a discussion of the timebase.
12.3.1 Resolution
In center-aligned mode, a 12-bit up/down counter is used to create the PWM period. Therefore, the PWM
resolution in center-aligned mode is two clocks (highest resolution is 250 ns @ fOP = 8 MHz) as shown in
Figure 12-4. The up/down counter uses the value in the timer modulus register to determine its maximum
count. The PWM period will equal:
[(timer modulus) x (PWM clock period) x 2].
UP/DOWN COUNTER
MODULUS = 4
PERIOD = 8 X (PWM CLOCK PERIOD)
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
Figure 12-4. Center-Aligned PWM (Positive Polarity)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
120
Freescale Semiconductor
Timebase
For edge-aligned mode, a 12-bit up-only counter is used to create the PWM period. Therefore, the PWM
resolution in edge-aligned mode is one clock (highest resolution is125 ns @ fOP = 8 MHz) as shown in
Figure 12-5. Again, the timer modulus register is used to determine the maximum count. The PWM period
will equal:
(timer modulus) x (PWM clock period)
Center-aligned operation versus edge-aligned operation is determined by the option EDGE. See 5.2
Functional Description.
UP-ONLY COUNTER
MODULUS = 4
PERIOD = 4 X (PWM
CLOCK PERIOD)
PWM = 0
PWM = 1
PWM = 2
PWM = 3
PWM = 4
Figure 12-5. Edge-Aligned PWM (Positive Polarity)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
121
Pulse-Width Modulator for Motor Control (PWMMC)
12.3.2 Prescaler
To permit lower PWM frequencies, a prescaler is provided which will divide the PWM clock frequency by
1, 2, 4, or 8. Table 12-1 shows how setting the prescaler bits in PWM control register 2 affects the PWM
clock frequency. This prescaler is buffered and will not be used by the PWM generator until the LDOK bit
is set and a new PWM reload cycle begins.
Table 12-1. PWM Prescaler
Prescaler Bits
PRSC1 and PRSC0
PWM Clock Frequency
00
fOP
01
fOP/2
10
fOP/4
11
fOP/8
12.4 PWM Generators
Pulse-width modulator (PWM) generators are discussed in this subsection.
12.4.1 Load Operation
To help avoid erroneous pulse widths and PWM periods, the modulus, prescaler, and PWM value
registers are buffered. New PWM values, counter modulus values, and prescalers can be loaded from
their buffers into the PWM module every one, two, four, or eight PWM cycles. LDFQ1 and LDFQ0 in PWM
control register 2 are used to control this reload frequency, as shown in Table 12-2. When a reload cycle
arrives, regardless of whether an actual reload occurs (as determined by the LDOK bit), the PWM reload
flag bit in PWM control register 1 will be set. If the PWMINT bit in PWM control register 1 is set, a CPU
interrupt request will be generated when PWMF is set. Software can use this interrupt to calculate new
PWM parameters in real time for the PWM module.
Table 12-2. PWM Reload Frequency
Reload Frequency Bits
LDFQ1 and LDFQ0
PWM Reload Frequency
00
Every PWM cycle
01
Every 2 PWM cycles
10
Every 4 PWM cycles
11
Every 8 PWM cycles
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
122
Freescale Semiconductor
PWM Generators
For ease of software, the LDFQx bits are buffered. When the LDFQx bits are changed, the reload
frequency will not change until the previous reload cycle is completed. See Figure 12-6.
NOTE
When reading the LDFQx bits, the value is the buffered value (for example,
not necessarily the value being acted upon).
RELOAD
RELOAD
RELOAD
RELOAD RELOADRELOADRELOAD
CHANGE RELOAD
FREQUENCY TO
EVERY 4 CYCLES
CHANGE RELOAD
FREQUENCY TO
EVERY CYCLE
Figure 12-6. Reload Frequency Change
PWMINT enables CPU interrupt requests as shown in Figure 12-7. When this bit is set, CPU interrupt
requests are generated when the PWMF bit is set. When the PWMINT bit is clear, PWM interrupt requests
are inhibited. PWM reloads will still occur at the reload rate, but no interrupt requests will be generated.
READ PWMF AS 1,
WRITE PWMF AS 0
OR
RESET
VDD
RESET
PWMF
CPU INTERRUPT
REQUEST
D
LATCH
PWM RELOAD
CK
PWMINT
Figure 12-7. PWM Interrupt Requests
To prevent a partial reload of PWM parameters from occurring while the software is still calculating them,
an interlock bit controlled from software is provided. This bit informs the PWM module that all the PWM
parameters have been calculated, and it is “okay” to use them. A new modulus, prescaler, and/or PWM
value cannot be loaded into the PWM module until the LDOK bit in PWM control register 1 is set. When
the LDOK bit is set, these new values are loaded into a second set of registers and used by the PWM
generator at the beginning of the next PWM reload cycle as shown in Figure 12-8, Figure 12-9,
Figure 12-10, and Figure 12-11. After these values are loaded, the LDOK bit is cleared.
NOTE
When the PWM module is enabled (via the PWMEN bit), a load will occur
if the LDOK bit is set. Even if it is not set, an interrupt will occur if the
PWMINT bit is set. To prevent this, the software should clear the PWMINT
bit before enabling the PWM module.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
123
Pulse-Width Modulator for Motor Control (PWMMC)
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP/DOWN
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE = 1
PWMF SET
LDOK = 0
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 1
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 0
MODULUS = 3
PWM VALUE = 1
PWMF SET
PWM
Figure 12-8. Center-Aligned PWM Value Loading
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP/DOWN
COUNTER
LDOK = 1
MODULUS = 2
PWM VALUE = 1
PWMF SET
LDOK = 1
MODULUS = 3
PWM VALUE = 1
PWMF SET
LDOK = 1
LDOK = 1
LDOK = 0
MODULUS = 2 MODULUS = 1 MODULUS = 2
PWMVALUE = 1 PWM VALUE = 1 PWM VALUE = 1
PWMF SET
PWMF SET
PWMF SET
PWM
Figure 12-9. Center-Aligned Loading of Modulus
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
LDOK = 0
LDOK = 1
LDOK = 0
LDOK = 0
MODULUS = 3 MODULUS = 3
MODULUS = 3
MODULUS = 3 MODULUS = 3
PWM VALUE = 1 PWM VALUE = 2 PWM VALUE = 2 PWM VALUE = 1 PWM VALUE = 1
PWMF SET
PWMF SET
PWMF SET
PWMF SET
PWMF SET
PWM
Figure 12-10. Edge-Aligned PWM Value Loading
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
124
Freescale Semiconductor
PWM Generators
LDFQ1:LDFQ0 = 00 (RELOAD EVERY CYCLE)
UP-ONLY
COUNTER
LDOK = 1
MODULUS = 3
PWM VALUE = 2
PWMF SET
LDOK = 1
MODULUS = 4
PWM VALUE = 2
PWMF SET
LDOK = 1
MODULUS = 2
PWM VALUE = 2
PWMF SET
LDOK = 0
MODULUS = 1
PWM VALUE = 2
PWMF SET
PWM
Figure 12-11. Edge-Aligned Modulus Loading
12.4.2 PWM Data Overflow and Underflow Conditions
The PWM value registers are 16-bit registers. Although the counter is only 12 bits, the user may write a
16-bit signed value to a PWM value register. As shown in Figure 12-4 and Figure 12-5, if the PWM value
is less than or equal to zero, the PWM will be inactive for the entire period. Conversely, if the PWM value
is greater than or equal to the timer modulus, the PWM will be active for the entire period. Refer to
Table 12-3.
NOTE
The terms “active” and “inactive” refer to the asserted and negated states
of the PWM signals and should not be confused with the high-impedance
state of the PWM pins.
Table 12-3. PWM Data Overflow and Underflow Conditions
PWMVALxH:PWMVALxL
Condition
PWM Value Used
$0000–$0FFF
Normal
Per register contents
$1000–$7FFF
Overflow
$FFF
$8000–$FFFF
Underflow
$000
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
125
Pulse-Width Modulator for Motor Control (PWMMC)
12.5 Output Control
This subsection discusses output control.
12.5.1 Selecting Six Independent PWMs or Three Complementary PWM Pairs
The PWM outputs can be configured as six independent PWM channels or three complementary channel
pairs. The option INDEP determines which mode is used (see 5.2 Functional Description). If
complementary operation is chosen, the PWM pins are paired as shown in Figure 12-12. Operation of
one pair is then determined by one PWM value register. This type of operation is meant for use in motor
drive circuits such as the one in Figure 12-13.
PWM1 PIN
PWM VALUE REGISTER
PWMS 1 AND 2
PWM VALUE REGISTER
OUTPUT CONTROL
POLARITY & DEAD-TIME INSERTION
PWM2 PIN
PWMS 3 AND 4
PWM3 PIN
PWM4 PIN
PWM5 PIN
PWMS 5 AND 6
PWM VALUE REGISTER
PWM6 PIN
Figure 12-12. Complementary Pairing
PWM
1
PWM
3
PWM
5
TO
AC
MOTOR
INPUTS
PWM
2
PWM
4
PWM
6
Figure 12-13. Typical AC Motor Drive
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
126
Freescale Semiconductor
Output Control
When complementary operation is used, two additional features are provided:
• Dead-time insertion
• Separate top/bottom pulse width correction to correct for distortions caused by the motor drive
characteristics
If independent operation is chosen, each PWM has its own PWM value register.
12.5.2 Dead-Time Insertion
As shown in Figure 12-13, in complementary mode, each PWM pair can be used to drive
top-side/bottom-side transistors.
When controlling dc-to-ac inverters such as this, the top and bottom PWMs in one pair should never be
active at the same time. In Figure 12-13, if PWM1 and PWM2 were on at the same time, large currents
would flow through the two transistors as they discharge the bus capacitor. The IGBTs could be
weakened or destroyed.
Simply forcing the two PWMs to be inversions of each other is not always sufficient. Since a time delay is
associated with turning off the transistors in the motor drive, there must be a dead-time between the
deactivation of one PWM and the activation of the other.
A dead-time can be specified in the dead-time write-once register. This 8-bit value specifies the number
of CPU clock cycles to use for the dead-time. The dead-time is not affected by changes in the PWM period
caused by the prescaler.
Dead-time insertion is achieved by feeding the top PWM outputs of the PWM generator into dead-time
generators, as shown in Figure 12-14. Current sensing determines which PWM value of a PWM generator
pair to use for the top PWM in the next PWM cycle. See 12.5.3 Top/Bottom Correction with Motor Phase
Current Polarity Sensing. When output control is enabled, the odd OUT bits, rather than the PWM
generator outputs, are fed into the dead-time generators. See 12.5.5 PWM Output Port Control.
Whenever an input to a dead-time generator transitions, a dead-time is inserted (for example, both PWMs
in the pair are forced to their inactive state). The bottom PWM signal is generated from the top PWM and
the dead-time. In the case of output control enabled, the odd OUTx bits control the top PWMs, the even
OUTx bits control the bottom PWMs with respect to the odd OUTx bits (see Table 12-6). Figure 12-15
shows the effects of the dead-time insertion.
As seen in Figure 12-15, some pulse width distortion occurs when the dead-time is inserted. The active
pulse widths are reduced. For example, in Figure 12-15, when the PWM value register is equal to two,
the ideal waveform (with no dead-time) has pulse widths equal to four. However, the actual pulse widths
shrink to two after a dead-time of two was inserted. In this example, with the prescaler set to divide by
one and center-aligned operation selected, this distortion can be compensated for by adding or
subtracting half the dead-time value to or from the PWM register value. This correction is further described
in 12.5.3 Top/Bottom Correction with Motor Phase Current Polarity Sensing.
Further examples of dead-time insertion are shown in Figure 12-16 and Figure 12-17. Figure 12-16 shows
the effects of dead-time insertion at the duty cycle boundaries (near 0 percent and 100 percent duty
cycles). Figure 12-17 shows the effects of dead-time insertion on pulse widths smaller than the dead-time.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
127
Pulse-Width Modulator for Motor Control (PWMMC)
PREDT (TOP)
OUTX
SELECT
DEAD-TIME
POSTDT (TOP)
MUX
PWMPAIR56
(TOP)
PWM (TOP)
PREDT (TOP)
OUTX
SELECT
PWM1
BOTTOM
(PWM2)
PWM2
TOP
(PWM3)
BOTTOM
(PWM4)
POLARITY/OUTPUT DRIVE
PWM (TOP)
TOP
(PWM1)
FAULT
DEAD-TIME
POSTDT (TOP)
MUX
PWMPAIR34
(TOP)
TOP/BOTTOM
GENERATION
DEAD-TIME
6
CURRENT SENSING
PWMGEN<1:6>
PWM GENERATOR
PREDT (TOP)
OUTX
SELECT
DEAD-TIME
POSTDT (TOP)
DEAD-TIME
PWM (TOP)
DEAD-TIME
MUX
PWMPAIR12
(TOP)
TOP/BOTTOM
GENERATION
OUT2
OUT4
OUT6
TOP/BOTTOM
GENERATION
OUTCTL
OUT5
OUT3
OUT1
OUTPUT CONTROL
(OUTCTL)
PWM3
PWM4
TOP
(PWM5)
PWM5
BOTTOM
(PWM6)
PWM6
Figure 12-14. Dead-Time Generators
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
128
Freescale Semiconductor
Output Control
UP/DOWN COUNTER
MODULUS = 4
PWM VALUE = 2
PWM VALUE = 2
PWM VALUE = 3
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 2
2
PWM2 W/
DEAD-TIME = 2
2
2
2
2
2
Figure 12-15. Effects of Dead-Time Insertion
UP/DOWN COUNTER
MODULUS = 3
PWM VALUE = 1
PWM VALUE = 1
PWM VALUE = 3
PWM VALUE = 3
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 2
PWM2 W/
DEAD-TIME = 2
2
2
2
2
Figure 12-16. Dead-Time at Duty Cycle Boundaries
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
129
Pulse-Width Modulator for Motor Control (PWMMC)
UP/DOWN COUNTER
MOUDULUS = 3
PWM VALUE = 2
PWM VALUE = 3
PWM VALUE = 2
PWM VALUE = 1
PWM1 W/
NO DEAD-TIME
PWM2 W/
NO DEAD-TIME
PWM1 W/
DEAD-TIME = 3
3
3
PWM2 W/
DEAD-TIME = 3
3
3
3
3
Figure 12-17. Dead-Time and Small Pulse Widths
12.5.3 Top/Bottom Correction with Motor Phase Current Polarity Sensing
Ideally, when complementary pairs are used, the PWM pairs are inversions of each other, as shown in
Figure 12-18. When PWM1 is active, PWM2 is inactive, and vice versa. In this case, the motor terminal
voltage is never allowed to float and is strictly controlled by the PWM waveforms.
UP/DOWN COUNTER
MODULUS = 4
PWM1
PWM VALUE = 1
PWM2
PWM3
PWM VALUE = 2
PWM4
PWM5
PWM VALUE = 3
PWM6
Figure 12-18. Ideal Complementary Operation (Dead-Time = 0)
However, when dead-time is inserted, the motor voltage is allowed to float momentarily during the
dead-time interval, creating a distortion in the motor current waveform. This distortion is aggravated by
dissimilar turn-on and turn-off delays of each of the transistors.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
130
Freescale Semiconductor
Output Control
For a typical motor drive inverter as shown in Figure 12-13, for a given top/bottom transistor pair, only one
of the transistors will be effective in controlling the output voltage at any given time depending on the
direction of the motor current for that pair. To achieve distortion correction, one of two different correction
factors must be added to the desired PWM value, depending on whether the top or bottom transistor is
controlling the output voltage. Therefore, the software is responsible for calculating both compensated
PWM values and placing them in an odd/even PWM register pair. By supplying the PWM module with
information regarding which transistor (top or bottom) is controlling the output voltage at any given time
(for instance, the current polarity for that motor phase), the PWM module selects either the odd or even
numbered PWM value register to be used by the PWM generator.
Current sensing or programmable software bits are then used to determine which PWM value to use. If
the current sensed at the motor for that PWM pair is positive (voltage on current pin ISx is low) or bit IPOLx
in PWM control register 2 is low, the top PWM value is used for the PWM pair. Likewise, if the current
sensed at the motor for that PWM pair is negative (voltage on current pin ISx is high) or bit IPOLx in PWM
control register 2 is high, the bottom PWM value is used. See Table 12-4.
NOTE
This text assumes the user will provide current sense circuitry which causes
the voltage at the corresponding input pin to be low for positive current and
high for negative current. See Figure 12-19 for current convention. In
addition, it assumes the top PWMs are PWMs 1, 3, and 5 while the bottom
PWMs are PWMs 2, 4, and 6.
Table 12-4. Current Sense Pins
Current
Sense Pin
or Bit
Voltage
on Current
Sense Pin
or IPOLx Bit
PWM Value
Register Used
PWMs
Affected
IS1 or IPOL1
Logic 0
PWM value register 1
PWMs 1 and 2
IS1 or IPOL1
Logic 1
PWM value register 2
PWMs 1 and 2
I+
I-
Figure 12-19. Current Convention
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
131
Pulse-Width Modulator for Motor Control (PWMMC)
To allow for correction based on different current sensing methods or correction controlled by software,
the ISENS1 and ISENS0 bits in PWM control register 1 are provided to choose the correction method.
These bits provide correction according to Table 12-5.
Table 12-5. Correction Methods
Current Correction Bits
ISENS1 and ISENS0
Correction Method
00
01
Bits IPOL1, IPOL2, and IPOL3 used for correction
10
Current sensing on pins IS1, IS2, and IS3 occurs during the
dead-time.
11
Current sensing on pins IS1, IS2, and IS3 occurs at the half
cycle in center-aligned mode and at the end of the cycle in
edge-aligned mode.
If correction is to be done in software or is not necessary, setting ISENS1:ISENS0 = 00 or = 01 causes
the correction to be based on bits IPOL1, IPOL2, and IPOL3 in PWM control register 2. If correction is not
required, the user can initialize the IPOLx bits and then only load one PWM value register per PWM pair.
To allow the user to use a current sense scheme based upon sensed phase voltage during dead-time,
setting ISENS1:ISENS0 = 10 causes the polarity of the Ix pin to be latched when both the top and bottom
PWMs are off (for example, during the dead-time). At the 0 percent and 100 percent duty cycle
boundaries, there is no dead-time so no new current value is sensed.
To accommodate other current sensing schemes, setting ISENS1:ISENS0 = 11 causes the polarity of the
current sense pin to be latched half-way into the PWM cycle in center-aligned mode and at the end of the
cycle in edge-aligned mode. Therefore, even at 0 percent and 100 percent duty cycle, the current is
sensed.
Distortion correction is only available in complementary mode. At the beginning of the PWM period, the
PWM uses this latched current value or polarity bit to decide whether the top PWM value or bottom PWM
value is used. Figure 12-20 shows an example of top/bottom correction for PWMs 1 and 2.
NOTE
The IPOLx bits and the values latched on the ISx pins are buffered so that
only one PWM register is used per PWM cycle. If the IPOLx bits or the
current sense values change during a PWM period, this new value will not
be used until the next PWM period. The ISENSx bits are NOT buffered;
therefore, changing the current sensing method could affect the present
PWM cycle.
When the PWM is first enabled by setting PWMEN, PWM value registers 1, 3, and 5 will be used if the
ISENSx bits are configured for current sensing correction. This is because no current will have previously
been sensed.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
132
Freescale Semiconductor
Output Control
PWM VALUE REG. 2 = 2
PWM VALUE REG. 1 = 1
IS1 POSITIVE
PWM = 1
IS1 POSITIVE
PWM = 1
IS1 NEGATIVE
PWM = 2
IS1 NEGATIVE
PWM = 2
PWM1
PWM2
Figure 12-20. Top/Bottom Correction for PWMs 1 and 2
12.5.4 Output Polarity
The output polarity of the PWMs is determined by two options: TOPNEG and BOTNEG. The top polarity
option, TOPNEG, controls the polarity of PWMs 1, 3, and 5. The bottom polarity option, BOTNEG,
controls the polarity of PWMs 2, 4, and 6. Positive polarity means that when the PWM is active, the PWM
output is high. Conversely, negative polarity means that when the PWM is active, PWM output is low. See
Figure 12-21.
NOTE
Both bits are found in the CONFIG register, which is a write-once register.
This reduces the chances of the software inadvertently changing the
polarity of the PWM signals and possibly damaging the motor drive
hardware.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
133
Pulse-Width Modulator for Motor Control (PWMMC)
CENTER-ALIGNED POSITIVE POLARITY
EDGE-ALIGNED POSITIVE POLARITY
UP-ONLY COUNTER
MODULUS = 4
UP/DOWN COUNTER
MODULUS = 4
PWM <= 0
PWM <= 0
PWM = 1
PWM = 1
PWM = 2
PWM = 2
PWM = 3
PWM = 3
PWM >= 4
PWM >= 4
CENTER-ALIGNED NEGATIVE POLARITY
EDGE-ALIGNED NEGATIVE POLARITY
UP-ONLY COUNTER
MODULUS = 4
UP/DOWN COUNTER
MODULUS = 4
PWM <= 0
PWM = 1
PWM <= 0
PWM = 2
PWM = 1
PWM = 3
PWM = 2
PWM = 3
PWM >= 4
PWM >= 4
Figure 12-21. PWM Polarity
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
134
Freescale Semiconductor
Output Control
12.5.5 PWM Output Port Control
Conditions may arise in which the PWM pins need to be individually controlled. This is made possible by
the PWM output control register (PWMOUT) shown in Figure 12-22.
Address:
$0025
Bit 7
Read:
0
Write:
Reset:
0
6
5
4
3
2
1
Bit 0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
0
0
0
0
0
0
= Unimplemented
Figure 12-22. PWM Output Control Register (PWMOUT)
If the OUTCTL bit is set, the PWM pins can be controlled by the OUTx bits. These bits behave according
to Table 12-6.
Table 12-6. OUTx Bits
OUTx Bit
Complementary Mode
Independent Mode
OUT1
1 — PWM1 is active.
0 — PWM1 is inactive.
1 — PWM1 is active.
0 — PWM1 is inactive.
OUT2
1 — PWM2 is complement of PWM 1.
0 — PWM2 is inactive.
1 — PWM2 is active.
0 — PWM2 is inactive.
OUT3
1 — PWM3 is active.
0 — PWM3 is inactive.
1 — PWM3 is active.
0 — PWM3 is inactive.
OUT4
1 — PWM4 is complement of PWM 3.
0 — PWM4 is inactive.
1 — PWM4 is active.
0 — PWM4 is inactive.
OUT5
1 — PWM5 is active.
0 — PWM5 is inactive.
1 — PWM5 is active.
0 — PWM5 is inactive.
OUT6
1 — PWM 6 is complement of PWM 5.
0 — PWM6 is inactive.
1 — PWM6 is active.
0 — PWM6 is inactive.
When OUTCTL is set, the polarity options TOPPOL and BOTPOL will still affect the outputs. In addition,
if complementary operation is in use, the PWM pairs will not be allowed to be active simultaneously, and
dead-time will still not be violated. When OUTCTL is set and complementary operation is in use, the odd
OUTx bits are inputs to the dead-time generators as shown in Figure 12-15. Dead-time is inserted
whenever the odd OUTx bit toggles as shown in Figure 12-23. Although dead-time is not inserted when
the even OUTx bits change, there will be no dead-time violation as shown in Figure 12-24.
Setting the OUTCTL bit does not disable the PWM generator and current sensing circuitry. They continue
to run, but are no longer controlling the output pins. In addition, OUTCTL will control the PWM pins even
when PWMEN = 0. When OUTCTL is cleared, the outputs of the PWM generator become the inputs to
the dead-time and output circuitry at the beginning of the next PWM cycle.
NOTE
To avoid an unexpected dead-time occurrence, it is recommended that the
OUTx bits be cleared prior to entering and prior to exiting individual PWM
output control mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
135
Pulse-Width Modulator for Motor Control (PWMMC)
UP/DOWN COUNTER
MODULUS = 4
DEAD-TIME = 2
PWM VALUE = 3
OUTCTL
OUT1
OUT2
PWM1
PWM2
PWM1/PWM2
DEAD-TIME
2
2
2
DEAD-TIME INSERTED AS PART OF DEAD-TIME INSERTED DUE
NORMAL PWM OPERATION AS
TO SETTING OF OUT1 BIT
CONTROLLED BY CURRENT
SENSING AND PWM GENERATOR
DEAD-TIME INSERTED
DUE TO CLEARING OF
OUT1 BIT
Figure 12-23. Dead-Time Insertion During OUTCTL = 1
UP/DOWN COUNTER
MODULUS = 4
DEAD-TIME = 2
PWM VALUE = 3
OUTCTL
OUT1
OUT2
PWM1
PWM2
PWM1/PWM2
DEAD-TIME
2
2
DEAD-TIME INSERTED BECAUSE
WHEN OUTCTL WAS SET, THE
STATE OF OUT1 WAS SUCH THAT
PWM1 WAS DIRECTED TO TOGGLE
2
2
DEAD-TIME INSERTED
BECAUSE OUT1 TOGGLES,
DIRECTING PWM1 TO
TOGGLE
NO DEAD-TIME INSERTED
BECAUSE OUT1 IS NOT
TOGGLING
Figure 12-24. Dead-Time Insertion During OUTCTL = 1
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
136
Freescale Semiconductor
Fault Protection
12.6 Fault Protection
Conditions may arise in the external drive circuitry which require that the PWM signals become inactive
immediately, such as an overcurrent fault condition. Furthermore, it may be desirable to selectively
disable PWM(s) solely with software.
One or more PWM pins can be disabled (forced to their inactive state) by applying a logic high to any of
the four external fault pins or by writing a logic high to either of the disable bits (DISX and DISY in PWM
control register 1). Figure 12-26 shows the structure of the PWM disabling scheme. While the PWM pins
are disabled, they are forced to their inactive state. The PWM generator continues to run — only the
output pins are disabled.
To allow for different motor configurations and the controlling of more than one motor, the PWM disabling
function is organized as two banks, bank X and bank Y. Bank information combines with information from
the disable mapping register to allow selective PWM disabling. Fault pin 1, fault pin 2, and PWM disable
bit X constitute the disabling function of bank X. Fault pin 3, fault pin 4, and PWM disable bit Y constitute
the disabling function of bank Y. Figure 12-25 and Figure 12-27 show the disable mapping write-once
register and the decoding scheme of the bank which selectively disables PWM(s). When all bits of the
disable mapping register are set, any disable condition will disable all PWMs.
A fault can also generate a CPU interrupt. Each fault pin has its own interrupt vector.
Address: $0037
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
1
1
1
1
1
1
1
1
Figure 12-25. PWM Disable Mapping Write-Once Register (DISMAP)
12.6.1 Fault Condition Input Pins
A logic high level on a fault pin disables the respective PWM(s) determined by the bank and the disable
mapping register. Each fault pin incorporates a filter to assist in rejecting spurious faults. All of the external
fault pins are software-configurable to re-enable the PWMs either with the fault pin (automatic mode) or
with software (manual mode). Each fault pin has an associated FMODE bit to control the PWM
re-enabling method. Automatic mode is selected by setting the FMODEx bit in the fault control register.
Manual mode is selected when FMODEx is clear.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
137
Pulse-Width Modulator for Motor Control (PWMMC)
DISX
CYCLE START
SOFTWARE X DISABLE
S
Q
R
FMODE2
TWO
SAMPLE
FILTER
FAULT
PIN2
AUTO
MODE
FPIN2
LOGIC HIGH FOR FAULT
ONE
SHOT
BANK X
DISABLE
FAULT PIN 2 DISABLE
S
Q FFLAG2
R
S
Q
R
MANUAL
MODE
CLEAR BY WRITING 1 TO FTACK4
INTERRUPT REQUEST
FINT2
The example is of fault pin 2 with DISX. Fault pin 4 with DISY is logically similar and affects BANK Y disable.
Note: In manual mode (FMODE = 0), faults 2 and 4 may be cleared only if a logic level low at the input of the fault
pin is present.
CYCLE START
FMODE1
FAULT PIN 1 DISABLE
AUTO
MODE
FPIN1
LOGIC HIGH FOR FAULT
FAULT
PIN1
TWO
SAMPLE
FILTER
ONE
SHOT
S
R
Q FFLAG1
S
Q
BANK X DISABLE
R
MANUAL
MODE
CLEAR BY WRITING 1 TO FTACK1
FINT1
INTERRUPT REQUEST
The example is of fault pin 1. Fault pin 3 is logically similar and affects BANK Y disable.
Note: In manual mode (FMODE = 0), faults 1 and 3 may be cleared regardless of the logic level at the input of the fault pin.
Figure 12-26. PWM Disabling Scheme
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
138
Freescale Semiconductor
Fault Protection
BIT 7
DISABLE
PWM PIN 1
BIT 6
BANK X
DISABLE
BIT 5
DISABLE
PWM PIN 2
BIT 4
DISABLE
PWM PIN 3
BIT 3
BANK Y
DISABLE
DISABLE
PWM PIN 4
BIT 2
BIT 1
DISABLE
PWM PIN 5
BIT 0
DISABLE
PWM PIN 6
Figure 12-27. PWM Disabling Decode Scheme
12.6.1.1 Fault Pin Filter
Each fault pin incorporates a filter to assist in determining a genuine fault condition. After a fault pin has
been logic low for one CPU cycle, a rising edge (logic high) will be synchronously sampled once per CPU
cycle for two cycles. If both samples are detected logic high, the corresponding FPIN bit and FFLAG bit
will be set. The FPIN bit will remain set until the corresponding fault pin is logic low and synchronously
sampled once in the following CPU cycle.
12.6.1.2 Automatic Mode
In automatic mode, the PWM(s) are disabled immediately once a filtered fault condition is detected (logic
high). The PWM(s) remain disabled until the filtered fault condition is cleared (logic low) and a new PWM
cycle begins as shown in Figure 12-28. Clearing the corresponding FFLAGx event bit will not enable the
PWMs in automatic mode.
The filtered fault pin’s logic state is reflected in the respective FPINx bit. Any write to this bit is overwritten
by the pin state. The FFLAGx event bit is set with each rising edge of the respective fault pin after filtering
has been applied. To clear the FFLAGx bit, the user must write a 1 to the corresponding FTACKx bit.
f the FINTx bit is set, a fault condition resulting in setting the corresponding FFLAG bit will also latch a
CPU interrupt request. The interrupt request latch is not cleared until one of these actions occurs:
• The FFLAGx bit is cleared by writing a 1 to the corresponding FTACKx bit.
• The FINTx bit is cleared. This will not clear the FFLAGx bit.
• A reset automatically clears all four interrupt latches.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
139
Pulse-Width Modulator for Motor Control (PWMMC)
FILTERED FAULT PIN
PWM(S) ENABLED
PWM(S) DISABLED (INACTIVE)
PWM(S) ENABLED
Figure 12-28. PWM Disabling in Automatic Mode
IIf prior to a vector fetch, the interrupt request latch is cleared by one of the actions listed, a CPU interrupt
will no longer be requested. A vector fetch does not alter the state of the PWMs, the FFLAGx event flag,
or FINTx.
NOTE
If the FFLAGx or FINTx bits are not cleared during the interrupt service
routine, the interrupt request latch will not be cleared.
12.6.1.3 Manual Mode
In manual mode, the PWM(s) are disabled immediately once a filtered fault condition is detected (logic
high). The PWM(s) remain disabled until software clears the corresponding FFLAGx event bit and a new
PWM cycle begins. In manual mode, the fault pins are grouped in pairs, each pair sharing common
functionality. A fault condition on pins 1 and 3 may be cleared, allowing the PWM(s) to enable at the start
of a PWM cycle regardless of the logic level at the fault pin. See Figure 12-29. A fault condition on pins 2
and 4 can only be cleared, allowing the PWM(s) to enable, if a logic low level at the fault pin is present at
the start of a PWM cycle. See Figure 12-30.
The function of the fault control and event bits is the same as in automatic mode except that the PWMs
are not re-enabled until the FFLAGx event bit is cleared by writing to the FTACKx bit and the filtered fault
condition is cleared (logic low).
FILTERED FAULT PIN 1 OR 3
PWM(S) ENABLED
PWM(S) DISABLED
PWM(S) ENABLED
FFLAGX CLEARED
Figure 12-29. PWM Disabling in Manual Mode (Example 1)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
140
Freescale Semiconductor
Fault Protection
FILTERED FAULT PIN 2 OR 4
PWM(S) ENABLED
PWM(S) DISABLED
PWM(S) ENABLED
FFLAGX CLEARED
Figure 12-30. PWM Disabling in Manual Mode (Example 2)
12.6.2 Software Output Disable
Setting PWM disable bit DISX or DISY in PWM control register 1 immediately disables the corresponding
PWM pins as determined by the bank and disable mapping register. The PWM pin(s) remain disabled
until the PWM disable bit is cleared and a new PWM cycle begins as shown in Figure 12-31. Setting a
PWM disable bit does not latch a CPU interrupt request, and there are no event flags associated with the
PWM disable bits.
12.6.3 Output Port Control
When operating the PWMs using the OUTx bits (OUTCTL = 1), fault protection applies as described in
this section. Due to the absence of periodic PWM cycles, fault conditions are cleared upon each CPU
cycle and the PWM outputs are re-enabled, provided all fault clearing conditions are satisfied.
DISABLE BIT
PWM(S) ENABLED
PWM(S) DISABLED
PWM(S) ENABLED
Figure 12-31. PWM Software Disable
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
141
Pulse-Width Modulator for Motor Control (PWMMC)
12.7 Initialization and the PWMEN Bit
For proper operation, all registers should be initialized and the LDOK bit should be set before enabling
the PWM via the PWMEN bit. When the PWMEN bit is first set, a reload will occur immediately, setting
the PWMF flag and generating an interrupt if PWMINT is set. In addition, in complementary mode, PWM
value registers 1, 3, and 5 will be used for the first PWM cycle if current sensing is selected.
NOTE
If the LDOK bit is not set when PWMEN is set after a RESET, the prescaler
and PWM values will be 0, but the modulus will be unknown. If the LDOK
bit is not set after the PWMEN bit has been cleared then set (without a
RESET), the modulus value that was last loaded will be used.
If the dead-time register (DEADTM) is changed after PWMEN or OUTCTL
is set, an improper dead-time insertion could occur. However, the
dead-time can never be shorter than the specified value.
Because of the equals-comparator architecture of this PWM, the modulus
= 0 case is considered illegal. Therefore, the modulus register is not reset,
and a modulus value of 0 will result in waveforms inconsistent with the other
modulus waveforms. See 12.9.2 PWM Counter Modulo Registers.
When PWMEN is set, the PWM pins change from high impedance to outputs. At this time, assuming no
fault condition is present, the PWM pins will drive according to the PWM values, polarity, and dead-time.
See the timing diagram in Figure 12-32.
CPU CLOCK
PWMEN
DRIVE ACCORDING TO PWM
VALUE, POLARITY, AND DEAD-TIME
PWM PINS
HI-Z IF OUTCTL = 0
HI-Z IF OUTCTL = 0
Figure 12-32. PWMEN and PWM Pins
When the PWMEN bit is cleared, this will occur:
• PWM pins will be three-stated unless OUTCTL = 1.
• PWM counter is cleared and will not be clocked.
• Internally, the PWM generator will force its outputs to 0 to avoid glitches when the PWMEN is set
again.
When PWMEN is cleared, these features remain active:
• All fault circuitry
• Manual PWM pin control via the PWMOUT register
• Dead-time insertion when PWM pins change via the PWMOUT register
NOTE
The PWMF flag and pending CPU interrupts are NOT cleared when
PWMEN = 0.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
142
Freescale Semiconductor
PWM Operation in Wait Mode
12.8 PWM Operation in Wait Mode
When the microcontroller is put in low-power wait mode via the WAIT instruction, all clocks to the PWM
module will continue to run. If an interrupt is issued from the PWM module (via a reload or a fault), the
microcontroller will exit wait mode.
Clearing the PWMEN bit before entering wait mode will reduce power consumption in wait mode because
the counter, prescaler divider, and LDFQ divider will no longer be clocked. In addition, power will be
reduced because the PWMs will no longer toggle.
12.9 Control Logic Block
This subsection provides a description of the control logic block.
12.9.1 PWM Counter Registers
The PWM counter registers (PCNTH and PCNTL) display the 12-bit up/down or up-only counter. When
the high byte of the counter is read, the lower byte is latched. PCNTL will hold this latched value until it is
read. See Figure 12-33 and Figure 12-34.
Address:
Read:
$0026
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 12-33. PWM Counter Register High (PCNTH)
Address:
Read:
$0027
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
Figure 12-34. PWM Counter Register Low (PCNTL)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
143
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.2 PWM Counter Modulo Registers
The PWM counter modulus registers (PMODH and PMODL) hold a 12-bit unsigned number that
determines the maximum count for the up/down or up-only counter. In center-aligned mode, the PWM
period will be twice the modulus (assuming no prescaler). In edge-aligned mode, the PWM period will
equal the modulus. See Figure 12-35 and Figure 12-36.
Address:
Read:
$0028
Bit 7
6
5
4
0
0
0
0
0
0
0
0
Write:
Reset:
= Unimplemented
3
2
1
Bit 0
Bit 11
Bit 10
Bit 9
Bit 8
X
X
X
X
X = Indeterminate
Figure 12-35. PWM Counter Modulo Register High (PMODH)
Address:
Read:
Write:
Reset:
$0029
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
X
X
X
X
X
X
X
X
X = Indeterminate
Figure 12-36. PWM Counter Modulo Register Low (PMODL)
To avoid erroneous PWM periods, this value is buffered and will not be used by the PWM generator until
the LDOK bit has been set and the next PWM load cycle begins.
NOTE
When reading this register, the value read is the buffer (not necessarily the
value the PWM generator is currently using).
Because of the equals-comparator architecture of this PWM, the
modulus = 0 case is considered illegal. Therefore, the modulus register is
not reset, and a modulus value of 0 will result in waveforms inconsistent
with the other modulus waveforms. If a modulus of 0 is loaded, the counter
will continually count down from $FFF. This operation will not be tested or
guaranteed (the user should consider it illegal). However, the dead-time
constraints and fault conditions will still be guaranteed.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
144
Freescale Semiconductor
Control Logic Block
12.9.3 PWMx Value Registers
Each of the six PWMs has a 16-bit PWM value register.
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
0
0
0
0
0
0
0
0
Bold
= Buffered
Figure 12-37. PWMx Value Registers High (PVALxH)
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
0
0
0
0
0
0
0
0
Bold
= Buffered
Figure 12-38. PWMx Value Registers Low (PVALxL)
The 16-bit signed value stored in this register determines the duty cycle of the PWM. The duty cycle is
defined as: (PWM value/modulus) x 100.
Writing a number less than or equal to 0 causes the PWM to be off for the entire PWM period. Writing a
number greater than or equal to the 12-bit modulus causes the PWM to be on for the entire PWM period.
If the complementary mode is selected, the PWM pairs share PWM value registers.
To avoid erroneous PWM pulses, this value is buffered and will not be used by the PWM generator until
the LDOK bit has been set and the next PWM load cycle begins.
NOTE
When reading these registers, the value read is the buffer (not necessarily
the value the PWM generator is currently using).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
145
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.4 PWM Control Register 1
PWM control register 1 (PCTL1) controls PWM enabling/disabling, the loading of new modulus, prescaler,
PWM values, and the PWM correction method. In addition, this register contains the software disable bits
to force the PWM outputs to their inactive states (according to the disable mapping register).
Address:
Read:
Write:
Reset:
$0020
Bit 7
6
5
4
3
2
1
Bit 0
DISX
DISY
PWMINT
PWMF
ISENS1
ISENS0
LDOK
PWMEN
0
0
0
0
0
0
0
0
Figure 12-39. PWM Control Register 1 (PCTL1)
DISX — Software Disable Bit for Bank X Bit
This read/write bit allows the user to disable one or more PWM pins in bank X. The pins that are
disabled are determined by the disable mapping write-once register.
1 = Disable PWM pins in bank X.
0 = Re-enable PWM pins at beginning of next PWM cycle.
DISY — Software Disable Bit for Bank Y Bit
This read/write bit allows the user to disable one or more PWM pins in bank Y. The pins that are
disabled are determined by the disable mapping write-once register.
1 = Disable PWM pins in bank Y.
0 = Re-enable PWM pins at beginning of next PWM cycle.
PWMINT — PWM Interrupt Enable Bit
This read/write bit allows the user to enable and disable PWM CPU interrupts. If set, a CPU interrupt
will be pending when the PWMF flag is set.
1 = Enable PWM CPU interrupts.
0 = Disable PWM CPU interrupts.
NOTE
When PWMINT is cleared, pending CPU interrupts are inhibited.
PWMF — PWM Reload Flag
This read/write bit is set at the beginning of every reload cycle regardless of the state of the LDOK bit.
This bit is cleared by reading PWM control register 1 with the PWMF flag set, then writing a logic 0 to
PWMF. If another reload occurs before the clearing sequence is complete, then writing logic 0 to
PWMF has no effect.
1 = New reload cycle began.
0 = New reload cycle has not begun.
NOTE
When PWMF is cleared, pending PWM CPU interrupts are cleared (not
including fault interrupts).
ISENS1 and ISENS0 — Current Sense Correction Bits
These read/write bits select the top/bottom correction scheme as shown in Table 12-7.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
146
Freescale Semiconductor
Control Logic Block
Table 12-7. Correction Methods
Current Correction Bits
ISENS1 and ISENS0
Correction Method
00
01
Bits IPOL1, IPOL2, and IPOL3 are used for correction.
10
Current sensing on pins IS1, IS2, and IS3 occurs during the
dead-time.
11
Current sensing on pins IS1, IS2, and IS3 occurs at the half
cycle in center-aligned mode and at the end of the cycle in
edge-aligned mode.
1. The polarity of the ISx pin is latched when both the top and bottom PWMs are off. At
the 0% and 100% duty cycle boundaries, there is no dead-time, so no new current
value is sensed.
2. Current is sensed even with 0% and 100% duty cycle.
NOTE
The ISENSx bits are not buffered. Changing the current sensing method
can affect the present PWM cycle.
LDOK— Load OK Bit
This read/write bit loads the prescaler bits of the PMCTL2 register and the entire PMMODH/L and
PWMVALH/L registers into a set of buffers. The buffered prescaler divisor, PWM counter modulus
value, and PWM pulse will take effect at the next PWM load. Set LDOK by reading it when it is logic 0
and then writing a logic 1 to it. LDOK is automatically cleared after the new values are loaded or can
be manually cleared before a reload by writing a 0 to it. Reset clears LDOK.
1 = Load prescaler, modulus, and PWM values.
0 = Do not load new modulus, prescaler, and PWM values.
NOTE
The user should initialize the PWM registers and set the LDOK bit before
enabling the PWM.
A PWM CPU interrupt request can still be generated when LDOK is 0.
PWMEN — PWM Module Enable Bit
This read/write bit enables and disables the PWM generator and the PWM pins. When PWMEN is
clear, the PWM generator is disabled and the PWM pins are in the high-impedance state (unless
OUTCTL = 1).
When the PWMEN bit is set, the PWM generator and PWM pins are activated.
For more information, see 12.7 Initialization and the PWMEN Bit.
1 = PWM generator and PWM pins enabled
0 = PWM generator and PWM pins disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
147
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.5 PWM Control Register 2
PWM control register 2 (PCTL2) controls the PWM load frequency, the PWM correction method, and the
PWM counter prescaler. For ease of software and to avoid erroneous PWM periods, some of these
register bits are buffered. The PWM generator will not use the prescaler value until the LDOK bit has been
set, and a new PWM cycle is starting. The correction bits are used at the beginning of each PWM cycle
(if the ISENSx bits are configured for software correction). The load frequency bits are not used until the
current load cycle is complete.
See Figure 12-40.
NOTE
The user should initialize this register before enabling the PWM.
Address:
Read:
Write:
Reset:
$0021
Bit 7
6
5
LDFQ1
LDFQ0
0
0
0
0
= Unimplemented
4
3
2
1
Bit 0
IPOL1
IPOL2
IPOL3
PRSC1
PRSC0
0
0
0
0
0
Bold
= Buffered
Figure 12-40. PWM Control Register 2 (PCTL2)
LDFQ1 and LDFQ0 — PWM Load Frequency Bits
These buffered read/write bits select the PWM CPU load frequency according to Table 12-8.
NOTE
When reading these bits, the value read is the buffer value (not necessarily
the value the PWM generator is currently using).
The LDFQx bits take effect when the current load cycle is complete
regardless of the state of the load okay bit, LDOK.
Table 12-8. PWM Reload Frequency
Reload Frequency Bits
LDFQ1 and LDFQ0
PWM Reload Frequency
00
Every PWM cycle
01
Every 2 PWM cycles
10
Every 4 PWM cycles
11
Every 8 PWM cycles
NOTE
Reading the LPFQx bit reads the buffered values and not necessarily the
values currently in effect.
IPOL1 — Top/Bottom Correction Bit for PWM Pair 1 (PWMs 1 and 2)
This buffered read/write bit selects which PWM value register is used if top/bottom correction is to be
achieved without current sensing.
1 = Use PWM value register 2.
0 = Use PWM value register 1.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
148
Freescale Semiconductor
Control Logic Block
NOTE
When reading this bit, the value read is the buffer value (not necessarily the
value the output control block is currently using).
The IPOLx bits take effect at the beginning of the next load cycle,
regardless of the state of the load okay bit, LDOK.
IPOL2 — Top/Bottom Correction Bit for PWM Pair 2 (PWMs 3 and 4)
This buffered read/write bit selects which PWM value register is used if top/bottom correction is to be
achieved without current sensing.
1 = Use PWM value register 4.
0 = Use PWM value register 3.
NOTE
When reading this bit, the value read is the buffer value (not necessarily the
value the output control block is currently using).
IPOL3 — Top/Bottom Correction Bit for PWM Pair 3 (PWMs 5 and 6)
This buffered read/write bit selects which PWM value register is used if top/bottom correction is to be
achieved without current sensing.
1 = Use PWM value register 6.
0 = Use PWM value register 5.
NOTE
When reading this bit, the value read is the buffer value (not necessarily the
value the output control block is currently using).
PRSC1 and PRSC0 — PWM Prescaler Bits
These buffered read/write bits allow the PWM clock frequency to be modified as shown in Table 12-9.
NOTE
When reading these bits, the value read is the buffer value (not necessarily
the value the PWM generator is currently using).
Table 12-9. PWM Prescaler
Prescaler Bits
PRSC1 and PRSC0
PWM Clock Frequency
00
fOP
01
fOP/2
10
fOP/4
11
fOP/8
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
149
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.6 Dead-Time Write-Once Register
The dead-time write-once register (DEADTM) holds an 8-bit value which specifies the number of CPU
clock cycles to use for the dead-time when complementary PWM mode is selected. After this register is
written for the first time, it cannot be rewritten unless a reset occurs. Dead-time is not affected by changes
to the prescaler value.
Address:
Read:
Write:
Reset:
$0036
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 12-41. Dead-Time Write-Once Register (DEADTM)
12.9.7 PWM Disable Mapping Write-Once Register
The PWM disable mapping write-once register (DISMAP) holds an 8-bit value which determines which
PWM pins will be disabled if an external fault or software disable occurs. For a further description of
disable mapping, see 12.6 Fault Protection. After this register is written for the first time, it cannot be
rewritten unless a reset occurs.
Address:
Read:
Write:
Reset:
$0037
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 12-42. PWM Disable Mapping Write-Once Register (DISMAP)
12.9.8 Fault Control Register
The fault control register (FCR) controls the fault-protection circuitry.
Address: $0022
Read:
Write:
Reset:
Bit 7
6
5
4
3
2
1
Bit 0
FINT4
FMODE4
FINT3
FMODE3
FINT2
FMODE2
FINT1
FMODE1
0
0
0
0
0
0
0
0
Figure 12-43. Fault Control Register (FCR)
FINT4 — Fault 4 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 4 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 4 will cause CPU interrupts.
0 = Fault pin 4 will not cause CPU interrupts.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
150
Freescale Semiconductor
Control Logic Block
FMODE4 —Fault Mode Selection for Fault Pin 4 Bit (automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
FINT3 — Fault 3 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 3 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 3 will cause CPU interrupts.
0 = Fault pin 3 will not cause CPU interrupts.
FMODE3 —Fault Mode Selection for Fault Pin 3 Bit (automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
FINT2 — Fault 2 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 2 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 2 will cause CPU interrupts.
0 = Fault pin 2 will not cause CPU interrupts.
FMODE2 —Fault Mode Selection for Fault Pin 2 Bit
(automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
FINT1 — Fault 1 Interrupt Enable Bit
This read/write bit allows the CPU interrupt caused by faults on fault pin 1 to be enabled. The fault
protection circuitry is independent of this bit and will always be active. If a fault is detected, the PWM
pins will still be disabled according to the disable mapping register.
1 = Fault pin 1 will cause CPU interrupts.
0 = Fault pin 1 will not cause CPU interrupts.
FMODE1 —Fault Mode Selection for Fault Pin 1 Bit (automatic versus manual mode)
This read/write bit allows the user to select between automatic and manual mode faults. For further
descriptions of each mode, see 12.6 Fault Protection.
1 = Automatic mode
0 = Manual mode
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
151
Pulse-Width Modulator for Motor Control (PWMMC)
12.9.9 Fault Status Register
The fault status register (FSR) is a read-only register that indicates the current fault status.
Address:
$0023
Bit 7
6
5
4
3
2
1
Bit 0
Read:
FPIN4
FFLAG4
FPIN3
FFLAG3
FPIN2
FFLAG2
FPIN1
FFLAG1
U
0
U
0
U
0
U
0
Write:
Reset:
= Unimplemented
U = Unaffected
Figure 12-44. Fault Status Register (FSR)
FPIN4 — State of Fault Pin 4 Bit
This read-only bit allows the user to read the current state of fault
pin 4.
1 = Fault pin 4 is at logic 1.
0 = Fault pin 4 is at logic 0.
FFLAG4 — Fault Event Flag 4
The FFLAG4 event bit is set within two CPU cycles after a rising edge on fault pin 4. To clear the
FFLAG4 bit, the user must write a 1 to the FTACK4 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 4.
0 = No new fault on fault pin 4
FPIN3 — State of Fault Pin 3 Bit
This read-only bit allows the user to read the current state of fault
pin 3.
1 = Fault pin 3 is at logic 1.
0 = Fault pin 3 is at logic 0.
FFLAG3 — Fault Event Flag 3
The FFLAG3 event bit is set within two CPU cycles after a rising edge on fault pin 3. To clear the
FFLAG3 bit, the user must write a 1 to the FTACK3 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 3.
0 = No new fault on fault pin 3.
FPIN2 — State of Fault Pin 2 Bit
This read-only bit allows the user to read the current state of fault pin 2.
1 = Fault pin 2 is at logic 1.
0 = Fault pin 2 is at logic 0.
FFLAG2 — Fault Event Flag 2
The FFLAG2 event bit is set within two CPU cycles after a rising edge on fault pin 2. To clear the
FFLAG2 bit, the user must write a 1 to the FTACK2 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 2.
0 = No new fault on fault pin 2
FPIN1 — State of Fault Pin 1 Bit
This read-only bit allows the user to read the current state of fault pin 1.
1 = Fault pin 1 is at logic 1.
0 = Fault pin 1 is at logic 0.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
152
Freescale Semiconductor
Control Logic Block
FFLAG1 — Fault Event Flag 1
The FFLAG1 event bit is set within two CPU cycles after a rising edge on fault pin 1. To clear the
FFLAG1 bit, the user must write a 1 to the FTACK1 bit in the fault acknowledge register.
1 = A fault has occurred on fault pin 1.
0 = No new fault on fault pin 1.
12.9.10 Fault Acknowledge Register
The fault acknowledge register (FTACK) is used to acknowledge and clear the FFLAGs. In addition, it is
used to monitor the current sensing bits to test proper operation.
Address: $0024
Read:
Bit 7
6
5
4
3
2
1
Bit 0
0
0
DT6
DT5
DT4
DT3
DT2
DT1
FTACK4
Write:
Reset:
0
0
FTACK3
0
0
FTACK2
0
0
FTACK1
0
0
= Unimplemented
Figure 12-45. Fault Acknowledge Register (FTACK)
FTACK4 — Fault Acknowledge 4 Bit
The FTACK4 bit is used to acknowledge and clear FFLAG4. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG4. Writing a 0 will have no effect.
FTACK3 — Fault Acknowledge 3 Bit
The FTACK3 bit is used to acknowledge and clear FFLAG3. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG3. Writing a 0 will have no effect.
FTACK2 — Fault Acknowledge 2 Bit
The FTACK2 bit is used to acknowledge and clear FFLAG2. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG2. Writing a 0 will have no effect.
FTACK1 — Fault Acknowledge 1 Bit
The FTACK1 bit is used to acknowledge and clear FFLAG1. This bit will always read 0. Writing a 1 to
this bit will clear FFLAG1. Writing a 0 will have no effect.
DT6 — Dead-Time 6 Bit
Current sensing pin IS3 is monitored immediately before dead-time ends due to the assertion of
PWM6.
DT5 — Dead-Time 5 Bit
Current sensing pin IS3 is monitored immediately before dead-time ends due to the assertion of
PWM5.
DT4 — Dead-Time 4 Bit
Current sensing pin IS2 is monitored immediately before dead-time ends due to the assertion of
PWM4.
DT3 — Dead-Time 3 Bit
Current sensing pin IS2 is monitored immediately before dead-time ends due to the assertion of
PWM3.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
153
Pulse-Width Modulator for Motor Control (PWMMC)
DT2 — Dead-Time 2 Bit
Current sensing pin IS1 is monitored immediately before dead-time ends due to the assertion of
PWM2.
DT1 — Dead-Time 1 Bit
Current sensing pin IS1 is monitored immediately before dead-time ends due to the assertion of
PWM1.
12.9.11 PWM Output Control Register
The PWM output control register (PWMOUT) is used to manually control the PWM pins.
Address: $0025
Bit 7
Read:
0
Write:
Reset:
0
6
5
4
3
2
1
Bit 0
OUTCTL
OUT6
OUT5
OUT4
OUT3
OUT2
OUT1
0
0
0
0
0
0
0
= Unimplemented
Figure 12-46. PWM Output Control Register (PWMOUT)
OUTCTL— Output Control Enable Bit
This read/write bit allows the user to manually control the PWM pins. When set, the PWM generator is
no longer the input to the dead-time and output circuitry. The OUTx bits determine the state of the
PWM pins. Setting the OUTCTL bit does not disable the PWM generator. The generator continues to
run, but is no longer the input to the PWM dead-time and output circuitry. When OUTCTL is cleared,
the outputs of the PWM generator immediately become the inputs to the dead-time and output circuitry.
1 = PWM outputs controlled manually
0 = PWM outputs determined by PWM generator
OUT6–OUT1— PWM Pin Output Control Bits
These read/write bits control the PWM pins according to Table 12-10.
Table 12-10. OUTx Bits
OUTx Bit
Complementary Mode
Independent Mode
OUT1
1 — PWM1 is active.
0 — PWM1 is inactive.
1 — PWM1 is active.
0 — PWM1 is inactive.
OUT2
1 — PWM2 is complement of PWM 1.
0 — PWM2 is inactive.
1 — PWM2 is active.
0 — PWM2 is inactive.
OUT3
1 — PWM3 is active.
0 — PWM3 is inactive.
1 — PWM3 is active.
0 — PWM3 is inactive.
OUT4
1 — PWM4 is complement of PWM 3.
0 — PWM4 is inactive.
1 — PWM4 is active.
0 — PWM4 is inactive.
OUT5
1 — PWM5 is active.
0 — PWM5 is inactive.
1 — PWM5 is active.
0 — PWM5 is inactive.
OUT6
1 — PWM 6 is complement of PWM 5.
0 — PWM6 is inactive.
1 — PWM6 is active.
0 — PWM6 is inactive.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
154
Freescale Semiconductor
PWM Glossary
12.10 PWM Glossary
CPU cycle — One internal bus cycle (1/fOP)
PWM clock cycle (or period) — One tick of the PWM counter (1/fOP with no prescaler). See
Figure 12-47.
PWM cycle (or period)
• Center-aligned mode: The time it takes the PWM counter to count up and count down (modulus *
2/fOP assuming no prescaler). See Figure 12-47.
• Edge-aligned mode: The time it takes the PWM counter to count up (modulus/fOP). See Figure
12-47.
Center-Aligned Mode
PWM CLOCK CYCLE
PWM CYCLE (OR PERIOD)
Edge-Aligned Mode
PWM
CLOCK
CYCLE
PWM CYCLE (OR PERIOD)
Figure 12-47. PWM Clock Cycle and PWM Cycle Definitions
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
155
Pulse-Width Modulator for Motor Control (PWMMC)
PWM Load Frequency — Frequency at which new PWM parameters get loaded into the PWM. See
Figure 12-48.
LDFQ1:LDFQ0 = 01 — Reload Every Two Cycles
PWM LOAD CYCLE
(1/PWM LOAD FREQUENCY)
RELOAD NEW
MODULUS,
PRESCALER, &
PWM VALUES IF
LDOK = 1
RELOAD NEW
MODULUS,
PRESCALER, &
PWM VALUES IF
LDOK = 1
Figure 12-48. PWM Load Cycle/Frequency Definition
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
156
Freescale Semiconductor
Chapter 13
Serial Communications Interface Module (SCI)
13.1 Introduction
This section describes the serial communications interface module (SCI, version D), which allows
high-speed asynchronous communications with peripheral devices and other microcontroller units
(MCUs).
13.2 Features
Features of the SCI module include:
• Full-duplex operation
• Standard mark/space non-return-to-zero (NRZ) format
• 32 programmable baud rates
• Programmable 8-bit or 9-bit character length
• Separately enabled transmitter and receiver
• Separate receiver and transmitter CPU interrupt requests
• Separate receiver and transmitter
• Programmable transmitter output polarity
• Two receiver wakeup methods:
– Idle line wakeup
– Address mark wakeup
• 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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
157
PTA
PTA7–PTA0
PTB
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
PTC
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1/ATD9(1)
PTC0/ATD8
PTD
PTD6/IS3
PTD5/IS2
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
PTE
CONTROL AND STATUS REGISTERS — 112 BYTES
DDRA
ARITHMETIC/LOGIC
UNIT
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
DDRB
CPU
REGISTERS
USER FLASH — 32,256 BYTES
USER RAM — 768 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VDDA
VSSA(3)
VREFL(3)
VREFH
PWMGND
PWM6–PWM1
Freescale Semiconductor
VSS
VDD
VDDAD
VSSAD
ANALOG-TO-DIGITAL CONVERTER
MODULE
PULSE-WIDTH MODULATOR
MODULE
DDRC
SERIAL COMMUNICATIONS INTERFACE
MODULE
SERIAL PERIPHERAL INTERFACE
MODULE(2)
POWER-ON RESET
MODULE
SINGLE BREAK
MODULE
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PTF1/SS(1)
DDRE
USER FLASH VECTOR SPACE — 46 BYTES
TIMER INTERFACE
MODULE B
PTF
MONITOR ROM — 240 BYTES
DDRF
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
TIMER INTERFACE
MODULE A
PTF0/SPSCK(1)
POWER
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 13-1. Block Diagram Highlighting SCI Block and Pins
Serial Communications Interface Module (SCI)
158
INTERNAL BUS
M68HC08 CPU
Functional Description
13.3 Functional Description
Figure 13-2 shows the structure of the SCI module. The SCI allows full-duplex, asynchronous, NRZ serial
communication among the MCU and remote devices, including other MCUs. The transmitter and receiver
of the SCI operate independently, although they use the same baud rate generator. During normal
operation, the CPU monitors the status of the SCI, writes the data to be transmitted, and processes
received data.
INTERNAL BUS
ERROR
INTERRUPT
CONTROL
RECEIVE
SHIFT REGISTER
PTF4/RxD
SCI DATA
REGISTER
RECEIVER
INTERRUPT
CONTROL
TRANSMITTER
INTERRUPT
CONTROL
SCI DATA
REGISTER
TRANSMIT
SHIFT REGISTER
PTF5/TxD
TXINV
SCTIE
R8
TCIE
T8
SCRIE
ILIE
TE
SCTE
RE
TC
RWU
SBK
SCRF
OR
ORIE
IDLE
NF
NEIE
FE
FEIE
PE
PEIE
LOOPS
LOOPS
WAKEUP
CONTROL
FLAG
CONTROL
RECEIVE
CONTROL
ENSCI
ENSCI
TRANSMIT
CONTROL
BKF
M
RPF
WAKE
ILTY
fOP
÷4
PRESCALER
BAUD RATE
GENERATOR
÷ 16
PEN
PTY
DATA SELECTION
CONTROL
Figure 13-2. SCI Module Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
159
Serial Communications Interface Module (SCI)
Addr.
$0038
$0039
$003A
$003B
$003C
Register Name
SCI Control Register 1
(SCC1)
See page 169.
SCI Control Register 2
(SCC2)
See page 171.
SCI Control Register 3
(SCC3)
See page 173.
SCI Status Register 1
(SCS1)
See page 174.
SCI Status Register 2
(SCS2)
See page 176.
SCI Data Register
(SCDR)
See page 177.
$003D
$003E
SCI Baud Rate Register
(SCBR)
See page 177.
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
SCTIE
TCIE
SCRIE
ILIE
TE
RE
RWU
SBK
Reset:
0
0
0
0
0
0
0
0
Read:
R8
0
0
Write:
R
R
R
ORIE
NEIE
FEIE
PEIE
Reset:
U
U
0
0
0
0
0
0
Read:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
Write:
R
R
R
R
R
R
R
R
Reset:
1
1
0
0
0
0
0
0
Read:
0
0
0
0
0
0
BKF
RPF
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
Read:
R7
R6
R5
R4
R3
R2
R1
R0
Write:
T7
T6
T5
T4
T3
T2
T1
T0
SCR2
SCR1
SCR0
0
0
0
Read:
Write:
Reset:
Read:
Write:
T8
Reset:
Unaffected by reset
Read:
0
0
Write:
R
R
Reset:
0
0
R
SCP1
SCP0
0
0
= Reserved
0
R
0
U = Unaffected
Figure 13-3. SCI I/O Register Summary
13.3.1 Data Format
The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 13-4.
8-BIT DATA FORMAT
BIT M IN SCC1 CLEAR
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
POSSIBLE
PARITY
BIT
BIT 6
BIT 7
9-BIT DATA FORMAT
BIT M IN SCC1 SET
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
STOP
BIT
NEXT
START
BIT
POSSIBLE
PARITY
BIT
BIT 6
BIT 7
BIT 8
STOP
BIT
NEXT
START
BIT
Figure 13-4. SCI Data Formats
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
160
Freescale Semiconductor
Functional Description
13.3.2 Transmitter
Figure 13-5 shows the structure of the SCI transmitter.
INTERNAL BUS
BAUD
DIVIDER
÷ 16
SCI DATA REGISTER
SCP1
SCP0
11-BIT
TRANSMIT
SHIFT REGISTER
SCR2
H
SCR1
8
7
6
5
4
3
2
START
PRESCALER
STOP
fOP
÷4
1
0
L
PTF5/TxD
MSB
SCR0
TXINV
T8
TRANSMITTER CPU
INTERRUPT REQUEST
BREAK
ALL 0s
PARITY
GENERATION
PREAMBLE
ALL 1s
PTY
SHIFT ENABLE
PEN
LOAD FROM SCDR
M
TRANSMITTER
CONTROL LOGIC
SCTE
SCTE
SCTIE
TC
TCIE
SBK
LOOPS
SCTIE
ENSCI
TC
TE
TCIE
Figure 13-5. SCI Transmitter
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
161
Serial Communications Interface Module (SCI)
13.3.2.1 Character Length
The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1
(SCC1) determines character length. When transmitting 9-bit data, bit T8 in SCI control register 3 (SCC3)
is the ninth bit (bit 8).
13.3.2.2 Character Transmission
During an SCI transmission, the transmit shift register shifts a character out to the PTF5/TxD pin. The SCI
data register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register.
To initiate an SCI transmission:
1. Enable the SCI by writing a 1 to the enable SCI bit (ENSCI) in SCI control register 1 (SCC1).
2. Enable the transmitter by writing a 1 to the transmitter enable bit (TE) in SCI control register 2
(SCC2).
3. Clear the SCI transmitter empty bit by first reading SCI status register 1 (SCS1) and then writing
to the SCDR.
4. Repeat step 3 for each subsequent transmission.
At the start of a transmission, transmitter control logic automatically loads the transmit shift register with
a preamble of 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 SCI transmitter empty bit, SCTE, in SCS1 becomes set when the SCDR transfers a byte to the
transmit shift register. The SCTE bit indicates that the SCDR can accept new data from the internal data
bus. If the SCI transmit interrupt enable bit, SCTIE, in SCC2 is also set, the SCTE bit generates a
transmitter CPU interrupt request.
When the transmit shift register is not transmitting a character, the PTF5/TxD pin goes to the idle
condition, logic 1. If at any time software clears the ENSCI bit in SCI control register 1 (SCC1), the
transmitter and receiver relinquish control of the port E pins.
13.3.2.3 Break Characters
Writing a 1 to the send break bit, SBK, in SCC2 loads the transmit shift register with a break character. A
break character contains all 0s and has no start, stop, or parity bit. Break character length depends on
the M bit in SCC1. As long as SBK is at 1, transmitter logic continuously loads break characters into the
transmit shift register. After software clears the SBK bit, the shift register finishes transmitting the last
break character and then transmits at least one logic 1. The automatic logic 1 at the end of a break
character guarantees the recognition of the start bit of the next character.
The SCI recognizes a break character when a start bit is followed by eight or nine logic 0 data bits and a
logic 0 where the stop bit should be.
Receiving a break character has these effects on SCI registers:
• Sets the framing error bit (FE) in SCS1
• Sets the SCI receiver full bit (SCRF) in SCS1
• Clears the SCI data register (SCDR)
• Clears the R8 bit in SCC3
• Sets the break flag bit (BKF) in SCS2
• May set the overrun (OR), noise flag (NF), parity error (PE), or reception-in-progress flag (RPF) bits
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
162
Freescale Semiconductor
Functional Description
13.3.2.4 Idle Characters
An 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 PTF5/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 logic 0 and one half data bit length of logic 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 PTF5/TxD pin. Setting TE after the
stop bit appears on PTF5/TxD causes data previously written to the SCDR
to be lost.
A good time to toggle the TE bit is when the SCTE bit becomes set and just
before writing the next byte to the SCDR.
13.3.2.5 Inversion of Transmitted Output
The transmit inversion bit (TXINV) in SCI control register 1 (SCC1) reverses the polarity of transmitted
data. All transmitted values, including idle, break, start, and stop bits, are inverted when TXINV is at 1.
See 13.7.1 SCI Control Register 1.
13.3.2.6 Transmitter Interrupts
These conditions can generate CPU interrupt requests from the SCI transmitter:
• SCI transmitter empty (SCTE) — The SCTE bit in SCS1 indicates that the SCDR has transferred
a character to the transmit shift register. SCTE can generate a transmitter CPU interrupt request.
Setting the SCI transmit interrupt enable bit, SCTIE, in SCC2 enables the SCTE bit to generate
transmitter CPU interrupt requests.
• Transmission complete (TC) — The TC bit in SCS1 indicates that the transmit shift register and the
SCDR are empty and that no break or idle character has been generated. The transmission
complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to generate transmitter CPU
interrupt requests.
13.3.3 Receiver
Figure 13-6 shows the structure of the SCI receiver.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
163
Serial Communications Interface Module (SCI)
INTERNAL BUS
SCR2
SCR1
SCP0
SCR0
BAUD
PRESCALER DIVIDER
fOP
DATA
RECOVERY
PTF4/RxD
ALL 1s
M
WAKE
ILTY
PEN
PTY
H
11-BIT
RECEIVE SHIFT REGISTER
8
7
6
5
4
3
2
1
0
L
ALL 0s
RPF
CPU INTERRUPT REQUEST
ERROR CPU INTERRUPT REQUEST
BKF
STOP
÷ 16
MSB
÷4
SCI DATA REGISTER
START
SCP1
SCRF
WAKEUP
LOGIC
PARITY
CHECKING
IDLE
ILIE
RWU
IDLE
R8
ILIE
SCRF
SCRIE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
SCRIE
OR
ORIE
NF
NEIE
FE
FEIE
PE
PEIE
Figure 13-6. SCI Receiver Block Diagram
13.3.3.1 Character Length
The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1
(SCC1) determines character length. When receiving 9-bit data, bit R8 in SCI control register 2 (SCC2)
is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
164
Freescale Semiconductor
Functional Description
13.3.3.2 Character Reception
During an SCI reception, the receive shift register shifts characters in from the PTF4/RxD pin. The SCI
data register (SCDR) is the read-only buffer between the internal data bus and the receive shift register.
After a complete character shifts into the receive shift register, the data portion of the character transfers
to the SCDR. The SCI receiver full bit, SCRF, in SCI status register 1 (SCS1) becomes set, indicating that
the received byte can be read. If the SCI receive interrupt enable bit, SCRIE, in SCC2 is also set, the
SCRF bit generates a receiver CPU interrupt request.
13.3.3.3 Data Sampling
The receiver samples the PTF4/RxD pin at the RT clock rate. The RT clock is an internal signal with a
frequency 16 times the baud rate. To adjust for baud rate mismatch, the RT clock is resynchronized at
these times (see Figure 13-7):
• 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 return a valid 1 and the majority of the next RT8, RT9, and RT10 samples
return a valid 0)
LSB
START BIT
PTF4/RxD
START BIT
QUALIFICATION
SAMPLES
START BIT
VERIFICATION
DATA
SAMPLING
RT4
RT3
RT2
RT16
RT1
RT15
RT14
RT13
RT12
RT11
RT10
RT9
RT8
RT7
RT6
RT5
RT4
RT3
RT2
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT1
RT CLOCK
STATE
RT1
RT
CLOCK
RT CLOCK
RESET
Figure 13-7. Receiver Data Sampling
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.
To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7.
Table 13-1 summarizes the results of the start bit verification samples.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
165
Serial Communications Interface Module (SCI)
Table 13-1. Start Bit Verification
RT3, RT5, and RT7
Samples
000
001
010
011
100
101
110
111
Start Bit
Verification
Yes
Yes
Yes
No
Yes
No
No
No
Noise Flag
0
1
1
0
1
0
0
0
If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins.
To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and
RT10. Table 13-2 summarizes the results of the data bit samples.
Table 13-2. Data Bit Recovery
RT8, RT9, and RT10
Samples
000
001
010
011
100
101
110
111
Data Bit
Determination
0
0
0
1
0
1
1
1
Noise Flag
0
1
1
1
1
1
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 13-3
summarizes the results of the stop bit samples.
Table 13-3. Stop Bit Recovery
RT8, RT9, and RT10
Samples
000
001
010
011
100
101
110
111
Framing
Error Flag
1
1
1
0
1
0
0
0
Noise Flag
0
1
1
1
1
1
1
0
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
166
Freescale Semiconductor
Functional Description
13.3.3.4 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. The FE flag is set at the same time that the SCRF bit is set. A break
character that has no stop bit also sets the FE bit.
13.3.3.5 Receiver Wakeup
So that the MCU can ignore transmissions intended only for other receivers in multiple-receiver systems,
the receiver can be put into a standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the
receiver into a standby state during which receiver interrupts are disabled.
Depending on the state of the WAKE bit in SCC1, either of two conditions on the PTF4/RxD pin can bring
the receiver out of the standby state:
• Address mark — An address mark is a 1 in the most significant bit position of a received character.
When the WAKE bit is set, an address mark wakes the receiver from the standby state by clearing
the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can then
compare the character containing the address mark to the user-defined address of the receiver. If
they are the same, the receiver remains awake and processes the characters that follow. If they
are not the same, software can set the RWU bit and put the receiver back into the standby state.
• Idle input line condition — When the WAKE bit is clear, an idle character on the PTF4/RxD pin
wakes the receiver from the standby state by clearing the RWU bit. The idle character that wakes
the receiver does not set the receiver idle bit, IDLE, or the SCI receiver full bit, SCRF. The idle line
type bit, ILTY, determines whether the receiver begins counting 1s as idle character bits after the
start bit or after the stop bit.
NOTE
Clearing the WAKE bit after the PTF4/RxD pin has been idle can cause the
receiver to wake up immediately.
13.3.3.6 Receiver Interrupts
These sources can generate CPU interrupt requests from the SCI receiver:
• SCI receiver full (SCRF) — The SCRF bit in SCS1 indicates that the receive shift register has
transferred a character to the SCDR. SCRF can generate a receiver CPU interrupt request. Setting
the SCI receive interrupt enable bit, SCRIE, in SCC2 enables the SCRF bit to generate receiver
CPU interrupts.
• Idle input (IDLE) — The IDLE bit in SCS1 indicates that 10 or 11 consecutive 1s shifted in from the
PTF4/RxD pin. The idle line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate
CPU interrupt requests.
13.3.3.7 Error Interrupts
These receiver error flags in SCS1 can generate CPU interrupt requests:
• Receiver overrun (OR) — The OR bit indicates that the receive shift register shifted in a new
character before the previous character was read from the SCDR. The previous character remains
in the SCDR, and the new character is lost. The overrun interrupt enable bit, ORIE, in SCC3
enables OR to generate SCI error CPU interrupt requests.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
167
Serial Communications Interface Module (SCI)
•
•
•
Noise flag (NF) — The NF bit is set when the SCI detects noise on incoming data or break
characters, including start, data, and stop bits. The noise error interrupt enable bit, NEIE, in SCC3
enables NF to generate SCI error CPU interrupt requests.
Framing error (FE) — The FE bit in SCS1 is set when a 0 occurs where the receiver expects a stop
bit. The framing error interrupt enable bit, FEIE, in SCC3 enables FE to generate SCI error CPU
interrupt requests.
Parity error (PE) — The PE bit in SCS1 is set when the SCI detects a parity error in incoming data.
The parity error interrupt enable bit, PEIE, in SCC3 enables PE to generate SCI error CPU interrupt
requests.
13.4 Wait Mode
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
The SCI module remains active after the execution of a WAIT instruction. In wait mode the SCI module
registers are not accessible by the CPU. Any enabled CPU interrupt request from the SCI module can
bring the MCU out of wait mode.
If SCI module functions are not required during wait mode, reduce power consumption by disabling the
module before executing the WAIT instruction.
13.5 SCI During Break Module Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during
interrupts generated by the break module. The BCFE bit in the SIM break flag control register (SBFCR)
enables software to clear status bits during the break state.
To allow software to clear status bits during a break interrupt, write a 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.
13.6 I/O Signals
Port F shares two of its pins with the SCI module. The two SCI input/output (I/O) pins are:
• PTF5/TxD — Transmit data
• PTF4/RxD — Receive data
13.6.1 PTF5/TxD (Transmit Data)
The PTF5/TxD pin is the serial data output from the SCI transmitter. The SCI shares the PTF5/TxD pin
with port F. When the SCI is enabled, the PTF5/TxD pin is an output regardless of the state of the DDRF5
bit in data direction register F (DDRF).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
168
Freescale Semiconductor
I/O Registers
13.6.2 PTF4/RxD (Receive Data)
The PTF4/RxD pin is the serial data input to the SCI receiver. The SCI shares the PTF4/RxD pin with
port F. When the SCI is enabled, the PTF4/RxD pin is an input regardless of the state of the DDRF4 bit
in data direction register F (DDRF).
13.7 I/O Registers
These I/O registers control and monitor SCI operation:
• SCI control register 1 (SCC1)
• SCI control register 2 (SCC2)
• SCI control register 3 (SCC3)
• SCI status register 1 (SCS1)
• SCI status register 2 (SCS2)
• SCI data register (SCDR)
• SCI baud rate register (SCBR)
13.7.1 SCI Control Register 1
SCI control register 1 (SCC1):
• Enables loop-mode operation
• Enables the SCI
• Controls output polarity
• Controls character length
• Controls SCI wakeup method
• Controls idle character detection
• Enables parity function
• Controls parity type
Address: $0038
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 13-8. SCI Control Register 1 (SCC1)
LOOPS — Loop Mode Select Bit
This read/write bit enables loop mode operation. In loop mode the PTF4/RxD pin is disconnected from
the SCI, and the transmitter output goes into the receiver input. Both the transmitter and the receiver
must be enabled to use loop mode. Reset clears the
LOOPS bit.
1 = Loop mode enabled
0 = Normal operation enabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
169
Serial Communications Interface Module (SCI)
ENSCI — Enable SCI Bit
This read/write bit enables the SCI and the SCI baud rate generator. Clearing ENSCI sets the SCTE
and TC bits in SCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit.
1 = SCI enabled
0 = SCI disabled
TXINV — Transmit Inversion Bit
This read/write bit reverses the polarity of transmitted data. Reset clears the TXINV bit.
1 = Transmitter output inverted
0 = Transmitter output not inverted
NOTE
Setting the TXINV bit inverts all transmitted values, including idle, break,
start, and stop bits.
M — Mode (Character Length) Bit
This read/write bit determines whether SCI characters are eight or nine bits long. See Table 13-4. The
ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. Reset clears the
M bit.
1 = 9-bit SCI characters
0 = 8-bit SCI characters
WAKE — Wakeup Condition Bit
This read/write bit determines which condition wakes up the SCI: a 1 (address mark) in the most
significant bit (MSB) position of a received character or an idle condition on the PTF4/RxD pin. Reset
clears the WAKE bit.
1 = Address mark wakeup
0 = Idle line wakeup
ILTY — Idle Line Type Bit
This read/write bit determines when the SCI starts counting 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 SCI parity function. See Table 13-4. When enabled, the parity function
inserts a parity bit in the most significant bit position. See Figure 13-4. Reset clears the PEN bit.
1 = Parity function enabled
0 = Parity function disabled
PTY — Parity Bit
This read/write bit determines whether the SCI generates and checks for odd parity or even parity. See
Table 13-4. Reset clears the PTY bit.
1 = Odd parity
0 = Even parity
NOTE
Changing the PTY bit in the middle of a transmission or reception can
generate a parity error.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
170
Freescale Semiconductor
I/O Registers
Table 13-4. Character Format Selection
Control Bits
Character Format
M
PEN:PTY
Start
Bits
Data
Bits
Parity
Stop
Bits
Character
Length
0
0X
1
8
None
1
10 bits
1
0X
1
9
None
1
11 bits
0
10
1
7
Even
1
10 bits
0
11
1
7
Odd
1
10 bits
1
10
1
8
Even
1
11 bits
1
11
1
8
Odd
1
11 bits
13.7.2 SCI Control Register 2
SCI control register 2 (SCC2):
• Enables these CPU interrupt requests:
– Enables the SCTE bit to generate transmitter CPU interrupt requests
– Enables the TC bit to generate transmitter CPU interrupt requests
– Enables the SCRF bit to generate receiver CPU interrupt requests
– Enables the IDLE bit to generate receiver CPU interrupt requests
• Enables the transmitter
• Enables the receiver
• Enables SCI wakeup
• Transmits SCI break characters
Address: $0039
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 13-9. SCI Control Register 2 (SCC2)
SCTIE — SCI Transmit Interrupt Enable Bit
This read/write bit enables the SCTE bit to generate SCI transmitter CPU interrupt requests. Setting
the SCTIE bit in SCC3 enables SCTE CPU interrupt requests. Reset clears the SCTIE bit.
1 = SCTE enabled to generate CPU interrupt
0 = SCTE not enabled to generate CPU interrupt
TCIE — Transmission Complete Interrupt Enable Bit
This read/write bit enables the TC bit to generate SCI transmitter CPU interrupt requests. Reset clears
the TCIE bit.
1 = TC enabled to generate CPU interrupt requests
0 = TC not enabled to generate CPU interrupt requests
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
171
Serial Communications Interface Module (SCI)
SCRIE — SCI Receive Interrupt Enable Bit
This read/write bit enables the SCRF bit to generate SCI receiver CPU interrupt requests. Setting the
SCRIE bit in SCC3 enables the SCRF bit to generate CPU interrupt requests. Reset clears the SCRIE
bit.
1 = SCRF enabled to generate CPU interrupt
0 = SCRF not enabled to generate CPU interrupt
ILIE — Idle Line Interrupt Enable Bit
This read/write bit enables the IDLE bit to generate SCI receiver CPU interrupt requests. Reset clears
the ILIE bit.
1 = IDLE enabled to generate CPU interrupt requests
0 = IDLE not enabled to generate CPU interrupt requests
TE — Transmitter Enable Bit
Setting this read/write bit begins the transmission by sending a preamble of 10 or 11 1s from the
transmit shift register to the PTF5/TxD pin. If software clears the TE bit, the transmitter completes any
transmission in progress before the PTF5/TxD returns to the idle condition (logic 1). Clearing and then
setting TE during a transmission queues an idle character to be sent after the character currently being
transmitted. Reset clears the TE bit.
1 = Transmitter enabled
0 = Transmitter disabled
NOTE
Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is clear.
ENSCI is in SCI control register 1.
RE — Receiver Enable Bit
Setting this read/write bit enables the receiver. Clearing the RE bit disables the receiver but does not
affect receiver interrupt flag bits. Reset clears the RE bit.
1 = Receiver enabled
0 = Receiver disabled
NOTE
Writing to the RE bit is not allowed when the enable SCI bit (ENSCI) is
clear. ENSCI is in SCI control register 1.
RWU — Receiver Wakeup Bit
This read/write bit puts the receiver in a standby state during which receiver interrupts are disabled.
The WAKE bit in SCC1 determines whether an idle input or an address mark brings the receiver out
of the standby state and clears the RWU bit. Reset clears the RWU bit.
1 = Standby state
0 = Normal operation
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 too early causes the SCI to send a break character instead of a
preamble.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
I/O Registers
13.7.3 SCI Control Register 3
SCI control register 3 (SCC3):
• Stores the ninth SCI data bit received and the ninth SCI data bit to be transmitted
• Enables SCI receiver full (SCRF)
• Enables SCI transmitter empty (SCTE)
• Enables the following interrupts:
– Receiver overrun interrupts
– Noise error interrupts
– Framing error interrupts
– Parity error interrupts
Address:
$003A
Bit 7
6
Read:
R8
Write:
R
Reset:
U
U
R
= Reserved
T8
5
4
0
0
R
R
0
0
3
2
1
Bit 0
ORIE
NEIE
FEIE
PEIE
0
0
0
0
U = Unaffected
Figure 13-10. SCI Control Register 3 (SCC3)
R8 — Received Bit 8
When the SCI is receiving 9-bit characters, R8 is the read-only ninth bit (bit 8) of the received character.
R8 is received at the same time that the SCDR receives the other eight bits.
When the SCI is receiving 8-bit characters, R8 is a copy of the eighth bit (bit 7). Reset has no effect on
the R8 bit.
T8 — Transmitted Bit 8
When the SCI is transmitting 9-bit characters, T8 is the read/write ninth bit (bit 8) of the transmitted
character. T8 is loaded into the transmit shift register at the same time that the SCDR is loaded into
the transmit shift register. Reset has no effect on the T8 bit.
ORIE — Receiver Overrun Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the receiver overrun bit, OR.
1 = SCI error CPU interrupt requests from OR bit enabled
0 = SCI error CPU interrupt requests from OR bit disabled
NEIE — Receiver Noise Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the noise error bit, NE.
Reset clears NEIE.
1 = SCI error CPU interrupt requests from NE bit enabled
0 = SCI error CPU interrupt requests from NE bit disabled
FEIE — Receiver Framing Error Interrupt Enable Bit
This read/write bit enables SCI error CPU interrupt requests generated by the framing error bit, FE.
Reset clears FEIE.
1 = SCI error CPU interrupt requests from FE bit enabled
0 = SCI error CPU interrupt requests from FE bit disabled
PEIE — Receiver Parity Error Interrupt Enable Bit
This read/write bit enables SCI receiver CPU interrupt requests generated by the parity error bit, PE.
See 13.7.4 SCI Status Register 1. Reset clears PEIE.
1 = SCI error CPU interrupt requests from PE bit enabled
0 = SCI error CPU interrupt requests from PE bit disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
173
Serial Communications Interface Module (SCI)
13.7.4 SCI Status Register 1
SCI status register 1 (SCS1) contains flags to signal these conditions:
• Transfer of SCDR data to transmit shift register complete
• Transmission complete
• Transfer of receive shift register data to SCDR complete
• Receiver input idle
• Receiver overrun
• Noisy data
• Framing error
• Parity error
Address: $003B
Bit 7
6
5
4
3
2
1
Bit 0
Read:
SCTE
TC
SCRF
IDLE
OR
NF
FE
PE
Write:
R
R
R
R
R
R
R
R
Reset:
1
1
0
0
0
0
0
0
R
= Reserved
Figure 13-11. SCI Status Register 1 (SCS1)
SCTE — SCI Transmitter Empty Bit
This clearable, read-only bit is set when the SCDR transfers a character to the transmit shift register.
SCTE can generate an SCI transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set,
SCTE generates an SCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit by
reading SCS1 with SCTE set and then writing to SCDR. Reset sets the SCTE bit.
1 = SCDR data transferred to transmit shift register
0 = SCDR data not transferred to transmit shift register
TC — Transmission Complete Bit
This read-only bit is set when the SCTE bit is set and no data, preamble, or break character is being
transmitted. TC generates an SCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also set.
TC is cleared automatically when data, preamble, or break is queued and ready to be sent. There may
be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the
transmission actually starting. Reset sets the TC bit.
1 = No transmission in progress
0 = Transmission in progress
SCRF — SCI Receiver Full Bit
This clearable, read-only bit is set when the data in the receive shift register transfers to the SCI data
register. SCRF can generate an SCI receiver CPU interrupt request. When the SCRIE bit in SCC2 is
set, SCRF generates a CPU interrupt request. In normal operation, clear the SCRF bit by reading
SCS1 with SCRF set and then reading the SCDR. Reset clears SCRF.
1 = Received data available in SCDR
0 = Data not available in SCDR
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
I/O Registers
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 SCI error CPU interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE bit by
reading SCS1 with IDLE set and then reading the SCDR. After the receiver is enabled, it must receive
a valid character that sets the SCRF bit before an idle condition can set the IDLE bit. Also, after the
IDLE bit has been cleared, a valid character must again set the SCRF bit before an idle condition can
set the IDLE bit. Reset clears the
IDLE bit.
1 = Receiver input idle
0 = Receiver input active or idle since the IDLE bit was cleared
OR — Receiver Overrun Bit
This clearable, read-only bit is set when software fails to read the SCDR before the receive shift
register receives the next character. The OR bit generates an SCI error CPU interrupt request if the
ORIE bit in SCC3 is also set. The data in the shift register is lost, but the data already in the SCDR is
not affected. Clear the OR bit by reading SCS1 with OR set and then reading the SCDR. Reset clears
the OR bit.
1 = Receive shift register full and SCRF = 1
0 = No receiver overrun
Software latency may allow an overrun to occur between reads of SCS1 and SCDR in the flag-clearing
sequence. Figure 13-12 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.
BYTE 1
BYTE 2
BYTE 3
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
SCRF = 0
SCRF = 1
NORMAL FLAG CLEARING SEQUENCE
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 0
READ SCDR
BYTE 1
READ SCDR
BYTE 2
READ SCDR
BYTE 3
BYTE 1
BYTE 2
BYTE 3
SCRF = 0
OR = 0
SCRF = 1
OR = 1
SCRF = 0
OR = 1
SCRF = 1
SCRF = 1
OR = 1
DELAYED FLAG CLEARING SEQUENCE
BYTE 4
READ SCS1
SCRF = 1
OR = 0
READ SCS1
SCRF = 1
OR = 1
READ SCDR
BYTE 1
READ SCDR
BYTE 3
Figure 13-12. Flag Clearing Sequence
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
175
Serial Communications Interface Module (SCI)
In applications that are subject to software latency or in which it is important to know which byte is lost
due to an overrun, the flag-clearing routine can check the OR bit in a second read of SCS1 after
reading the data register.
NF — Receiver Noise Flag Bit
This clearable, read-only bit is set when the SCI detects noise on the PTF4/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 SCI error CPU
interrupt request if the FEIE bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set and
then reading the SCDR. Reset clears the FE bit.
1 = Framing error detected
0 = No framing error detected
PE — Receiver Parity Error Bit
This clearable, read-only bit is set when the SCI detects a parity error in incoming data. PE generates
a PE CPU interrupt request if the PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with
PE set and then reading the SCDR. Reset clears the PE bit.
1 = Parity error detected
0 = No parity error detected
13.7.5 SCI Status Register 2
SCI status register 2 (SCS2) contains flags to signal these conditions:
• Break character detected
• Incoming data
Address:
$003C
Bit 7
6
5
4
3
2
1
Bit 0
Read:
0
0
0
0
0
0
BKF
RPF
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 13-13. SCI Status Register 2 (SCS2)
BKF — Break Flag
This clearable, read-only bit is set when the SCI detects a break character on the PTF4/RxD pin. In
SCS1, the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in SCC3 is
cleared. BKF does not generate a CPU interrupt request. Clear BKF by reading SCS2 with BKF set
and then reading the SCDR. Once cleared, BKF can become set again only after logic 1s again appear
on the PTF4/RxD pin followed by another break character. Reset clears the BKF bit.
1 = Break character detected
0 = No break character detected
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
176
Freescale Semiconductor
I/O Registers
RPF —Reception-in-Progress Flag
This read-only bit is set when the receiver detects a logic 0 during the RT1 time period of the start bit
search. RPF does not generate an interrupt request. RPF is reset after the receiver detects false start
bits (usually from noise or a baud rate mismatch, or when the receiver detects an idle character. Polling
RPF before disabling the SCI module or entering stop mode can show whether a reception is in
progress.
1 = Reception in progress
0 = No reception in progress
13.7.6 SCI Data Register
The SCI data register (SCDR) is the buffer between the internal data bus and the receive and transmit
shift registers. Reset has no effect on data in the SCI data register.
Address:
$003D
Bit 7
6
5
4
3
2
1
Bit 0
Read:
R7
R6
R5
R4
R3
R2
R1
R0
Write:
T7
T6
T5
T4
T3
T2
T1
T0
Reset:
Unaffected by reset
Figure 13-14. SCI Data Register (SCDR)
R7/T7:R0/T0 — Receive/Transmit Data Bits
Reading address $003D accesses the read-only received data bits, R7:R0. Writing to address $003D
writes the data to be transmitted, T7:T0. Reset has no effect on the SCI data register.
13.7.7 SCI Baud Rate Register
The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter.
Address:
$003E
Bit 7
6
Read:
0
0
Write:
R
R
Reset:
0
0
R
= Reserved
5
4
SCP1
SCP0
0
0
3
0
R
2
1
Bit 0
SCR2
SCR1
SCR0
0
0
0
0
Figure 13-15. SCI Baud Rate Register (SCBR)
SCP1 and SCP0 — SCI Baud Rate Prescaler Bits
These read/write bits select the baud rate prescaler divisor as shown in Table 13-5. Reset clears SCP1
and SCP0.
Table 13-5. SCI Baud Rate Prescaling
SCP1:SCP0
Prescaler Divisor (PD)
00
1
01
3
10
4
11
13
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
177
Serial Communications Interface Module (SCI)
SCR2–SCR0 — SCI Baud Rate Select Bits
These read/write bits select the SCI baud rate divisor as shown in Table 13-6. Reset clears
SCR2–SCR0.
Table 13-6. SCI Baud Rate Selection
SCR2:SCR1:SCR0
Baud Rate Divisor (BD)
000
1
001
2
010
4
011
8
100
16
101
32
110
64
111
128
Use this formula to calculate the SCI baud rate:
f OP
Baud rate = -----------------------------------64 × PD × BD
where:
fOP = internal operating frequency
PD = prescaler divisor
BD = baud rate divisor
Table 13-7 shows the SCI baud rates that can be generated with a 4.9152-MHz crystal with the CGM set
for an fOP of 7.3728 MHz and the CGM set for an fOP of 4.9152 MHz.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
178
Freescale Semiconductor
I/O Registers
Table 13-7. SCI Baud Rate Selection Examples
SCP1:SCP0
Prescaler
Divisor (PD)
SCR2:SCR1:SCR0
Baud Rate
Divisor (BD)
Baud Rate
(fOP = 7.3728 MHz)
Baud Rate
(fOP = 4.9152 MHz)
00
1
000
1
115,200
76,800
00
1
001
2
57,600
38,400
00
1
010
4
28,800
19,200
00
1
011
8
14,400
9600
00
1
100
16
7200
4800
00
1
101
32
3600
2400
00
1
110
64
1800
1200
00
1
111
128
900
600
01
3
000
1
38,400
25,600
01
3
001
2
19,200
12,800
01
3
010
4
9600
6400
01
3
011
8
4800
3200
01
3
100
16
2400
1600
01
3
101
32
1200
800
01
3
110
64
600
400
01
3
111
128
300
200
10
4
000
1
28,800
19,200
10
4
001
2
14,400
9600
10
4
010
4
7200
4800
10
4
011
8
3600
2400
10
4
100
16
1800
1200
10
4
101
32
900
600
10
4
110
64
450
300
10
4
111
128
225
150
11
13
000
1
8861.5
5907.7
11
13
001
2
4430.7
2953.8
11
13
010
4
2215.4
1476.9
11
13
011
8
1107.7
738.5
11
13
100
16
553.8
369.2
11
13
101
32
276.9
184.6
11
13
110
64
138.5
92.3
11
13
111
128
69.2
46.2
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
179
Serial Communications Interface Module (SCI)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
180
Freescale Semiconductor
Chapter 14
System Integration Module (SIM)
14.1 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 14-1.
The SIM is a system state controller that coordinates CPU and exception timing. The SIM is responsible
for:
• Bus clock generation and control for CPU and peripherals:
– Wait/reset/break entry and recovery
– Internal clock control
• Master reset control, including power-on reset (POR) and computer operating properly (COP)
timeout
• Interrupt control:
– Acknowledge timing
– Arbitration control timing
– Vector address generation
• CPU enable/disable timing
• Modular architecture expandable to 128 interrupt sources
Table 14-1 shows the internal signal names used in this section.
Table 14-1. Signal Name Conventions
Signal Name
Description
CGMXCLK
Buffered version of OSC1 from clock generator module (CGM)
CGMVCLK
Phase-locked loop (PLL) circuit output
CGMOUT
PLL-based or OSC1-based clock output from CGM module (bus clock = CGMOUT divided by two)
IAB
Internal address bus
IDB
Internal data bus
PORRST
Signal from the power-on reset module to the SIM
IRST
Internal reset signal
R/W
Read/write signal
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
181
System Integration Module (SIM)
MODULE WAIT
WAIT
CONTROL
CPU WAIT (FROM CPU)
SIMOSCEN (TO CGM)
SIM
COUNTER
COP CLOCK
CGMXCLK (FROM CGM)
CGMOUT (FROM CGM)
÷2
CLOCK
CONTROL
RESET
PIN LOGIC
CLOCK GENERATORS
INTERNAL CLOCKS
LVI (FROM LVI MODULE)
POR CONTROL
MASTER
RESET
CONTROL
RESET PIN CONTROL
SIM RESET STATUS REGISTER
ILLEGAL OPCODE (FROM CPU)
ILLEGAL ADDRESS (FROM ADDRESS
MAP DECODERS)
COP (FROM COP MODULE)
RESET
INTERRUPT CONTROL
AND PRIORITY DECODE
INTERRUPT SOURCES
CPU INTERFACE
Figure 14-1. SIM Block Diagram
14.2 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 14-2. This clock
can come from either an external oscillator or from the on-chip phase-locked loop (PLL) circuit. See
Chapter 4 Clock Generator Module (CGM).
14.2.1 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. See Chapter 4 Clock Generator Module (CGM).
14.2.2 Clock Startup from POR or LVI Reset
When the power-on reset (POR) module or the low-voltage inhibit (LVI) module generates a reset, the
clocks to the CPU and peripherals are inactive and held in an inactive phase until after the 4096
CGMXCLK cycle POR timeout has completed. The RST pin is driven low by the SIM during this entire
period. The internal bus (IBUS) clocks start upon completion of the timeout.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
182
Freescale Semiconductor
Reset and System Initialization
CGMXCLK
OSC1
CLOCK
SELECT
CIRCUIT
CGMVCLK
÷2
A
CGMOUT
B S*
*When S = 1,
CGMOUT = B
BUS CLOCK
GENERATORS
÷2
SIM
BCS
PLL
SIM COUNTER
PTC2
MONITOR MODE
USER MODE
CGM
Figure 14-2. CGM Clock Signals
14.2.3 Clocks in Wait Mode
In wait mode, the CPU clocks are inactive. The SIM also produces two sets of clocks for other modules.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
14.3 Reset and System Initialization
The MCU has these reset sources:
• Power-on reset module (POR)
• External reset pin (RST)
• Computer operating properly (COP) module
• Low-voltage inhibit (LVI) module
• Illegal opcode
• Illegal address
All of these resets produce the vector $FFFE–FFFF ($FEFE–FEFF in monitor mode) and assert the
internal reset signal (IRST). IRST causes all registers to be returned to their default values and all
modules to be returned to their reset states.
An internal reset clears the SIM counter (see 14.4 SIM Counter), but an external reset does not. Each of
the resets sets a corresponding bit in the SIM reset status register (SRSR). See 14.7.2 SIM Reset Status
Register.
14.3.1 External Pin Reset
Pulling the asynchronous RST pin low halts all processing. The PIN bit of the SIM reset status register
(SRSR) is set as long as RST is held low for a minimum of 67 CGMXCLK cycles, assuming that neither
the POR nor the LVI was the source of the reset. See Table 14-2 for details. Figure 14-3 shows the relative
timing.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
183
System Integration Module (SIM)
Table 14-2. PIN Bit Set Timing
Reset Type
Number of Cycles Required to Set PIN
POR/LVI
4163 (4096 + 64 + 3)
All others
67 (64 + 3)
CGMOUT
RST
IAB
VECT H
PC
VECT L
Figure 14-3. External Reset Timing
14.3.2 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 signal (IRST) continues to be asserted for an additional 32 cycles
(see Figure 14-5). An internal reset can be caused by an illegal address, illegal opcode, COP timeout,
LVI, or POR. (See Figure 14-4.)
ILLEGAL ADDRESS RST
ILLEGAL OPCODE RST
COPRST
LVI
POR
INTERNAL RESET
Figure 14-4. Sources of Internal Reset
NOTE
For LVI or POR resets, the SIM cycles through 4096 CGMXCLK cycles
during which the SIM forces the RST pin low. The internal reset signal then
follows the sequence from the falling edge of RST, as shown in Figure 14-5.
IRST
RST
RST PULLED LOW BY MCU
32 CYCLES
32 CYCLES
CGMXCLK
IAB
VECTOR HIGH
Figure 14-5. Internal Reset Timing
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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
184
Freescale Semiconductor
Reset and System Initialization
14.3.2.1 Power-On Reset (POR)
When power is first applied to the MCU, the power-on reset (POR) module generates a pulse to indicate
that power-on has occurred. The external reset pin (RST) is held low while the SIM counter counts out
4096 CGMXCLK cycles. Sixty-four CGMXCLK cycles later, the CPU and memories are released from
reset to allow the reset vector sequence to occur.
OSC1
PORRST
4096
CYCLES
32
CYCLES
32
CYCLES
CGMXCLK
CGMOUT
RST
IAB
$FFFE
$FFFF
Figure 14-6. POR Recovery
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.
14.3.2.2 Computer Operating Properly (COP) Reset
An input to the SIM is reserved for the COP reset signal. The overflow of the COP counter causes an
internal reset and sets the COP bit in the SIM reset status register (SRSR). The SIM actively pulls down
the RST pin for all internal reset sources.
To prevent a COP module timeout, write any value to location $FFFF. Writing to location $FFFF clears
the COP counter and bits 12–4 of the SIM counter. The SIM counter output, which occurs at least every
213–24 CGMXCLK cycles, drives the COP counter. The COP should be serviced as soon as possible out
of reset to guarantee the maximum amount of time before the first timeout.
The COP module is disabled if the RST pin or the IRQ pin is held at VHI while the MCU is in monitor mode.
The COP module can be disabled only through combinational logic conditioned with the high voltage
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
185
System Integration Module (SIM)
signal on the RST or the IRQ pin. This prevents the COP from becoming disabled as a result of external
noise. During a break state, VHI on the RST pin disables the COP module.
14.3.2.3 Illegal Opcode Reset
The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP
bit in the SIM reset status register (SRSR) and causes a reset.
Because the MC68HC908MR32 has stop mode disabled, execution of the STOP instruction will cause
an illegal opcode reset.
14.3.2.4 Illegal Address Reset
An opcode fetch from addresses other than FLASH or RAM addresses generates an illegal address reset
(unimplemented locations within memory map). The SIM verifies that the CPU is fetching an opcode prior
to asserting the ILAD bit in the SIM reset status register (SRSR) and resetting the MCU. A data fetch from
an unmapped address does not generate a reset.
14.3.2.5 Forced Monitor Mode Entry Reset (MENRST)
The MENRST module monitors the reset vector fetches and will assert an internal reset if it detects that
the reset vectors are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode.
14.3.2.6 Low-Voltage Inhibit (LVI) Reset
The low-voltage inhibit (LVI) module asserts its output to the SIM when the VDD voltage falls to the VLVRX
voltage and remains at or below that level for at least nine consecutive CPU cycles (see 19.5 DC Electrical
Characteristics). The LVI bit in the SIM reset status register (SRSR) is set, and the external reset pin
(RST) is held low while the SIM counter counts out 4096 CGMXCLK cycles. Sixty-four CGMXCLK cycles
later, the CPU is released from reset to allow the reset vector sequence to occur. The SIM actively pulls
down the RST pin for all internal reset sources.
14.4 SIM Counter
The SIM counter is used by the power-on reset (POR) module to allow the oscillator time to stabilize
before enabling the internal bus (IBUS) clocks. The SIM counter also serves as a prescaler for the
computer operating properly (COP) module. The SIM counter overflow supplies the clock for the COP
module. The SIM counter is 13 bits long and is clocked by the falling edge of CGMXCLK.
14.4.1 SIM Counter During Power-On Reset
The power-on reset (POR) module detects power applied to the MCU. At power-on, the POR circuit
asserts the signal PORRST. Once the SIM is initialized, it enables the clock generation (CGM) module to
drive the bus clock state machine.
14.4.2 SIM Counter and Reset States
External reset has no effect on the SIM counter. The SIM counter is free-running after all reset states. For
counter control and internal reset recovery sequences, see 14.3.2 Active Resets from Internal Sources.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
186
Freescale Semiconductor
Exception Control
14.5 Exception Control
Normal, sequential program execution can be changed in three different ways:
1. Interrupts:
a. Maskable hardware CPU interrupts
b. Non-maskable software interrupt instruction (SWI)
2. Reset
3. Break interrupts
14.5.1 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 return-from-interrupt
(RTI) instruction recovers the CPU register contents from the stack so that normal processing can
resume. Figure 14-7 shows interrupt entry timing. Figure 14-9 shows interrupt recovery timing.
MODULE
INTERRUPT
I BIT
IAB
SP
DUMMY
IDB
DUMMY
SP – 1
SP – 2
PC – 1[7:0] PC – 1[15:8]
SP – 3
X
SP – 4
A
VECT H
CCR
VECT L
V DATA H
START
ADDR
V DATA L
OPCODE
R/W
Figure 14-7. Interrupt Entry
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 14-8.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
187
System Integration Module (SIM)
FROM RESET
BREAK
OR SWI
I BIT SET?
INTERRUPT?
YES
NO
YES
I BIT SET?
NO
INTERRUPT?
YES
NO
STACK CPU REGISTERS
SET I BIT
LOAD PC WITH INTERRUPT VECTOR
AS MANY INTERRUPTS AS EXIST ON CHIP
FETCH NEXT
INSTRUCTION
SWI
INSTRUCTION?
YES
NO
RTI
INSTRUCTION?
YES
UNSTACK CPU REGISTERS
NO
EXECUTE INSTRUCTION
Figure 14-8. Interrupt Processing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
188
Freescale Semiconductor
Exception Control
MODULE
INTERRUPT
I BIT
IAB
SP – 4
IDB
SP – 3
CCR
SP – 2
A
SP – 1
X
SP
PC
PC + 1
PC – 1[7:0] PC – 1[15:8] OPCODE
OPERAND
R/W
Figure 14-9. Interrupt Recovery
14.5.1.1 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 14-10 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
load-accumulator-from- memory (LDA) instruction is executed.
CLI
LDA#$FF
INT1
BACKGROUND ROUTINE
PSHH
INT1 INTERRUPT SERVICE ROUTINE
PULH
RTI
INT2
PSHH
INT2 INTERRUPT SERVICE ROUTINE
PULH
RTI
Figure 14-10. 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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
189
System Integration Module (SIM)
14.5.1.2 Software Interrupt (SWI) Instruction
The software interrupt (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.
14.5.2 Reset
All reset sources always have equal and highest priority and cannot be arbitrated.
14.6 Low-Power Mode
Executing the WAIT instruction puts the MCU in a low power-consumption mode for standby situations.
The SIM holds the CPU in a non-clocked state. WAIT clears the interrupt mask (I) in the condition code
register, allowing interrupts to occur.
14.6.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks continue to run. Figure 14-11 shows
the timing for wait mode entry.
A module that is active during wait mode can wake up the CPU with an interrupt if the interrupt is enabled.
Stacking for the interrupt begins one cycle after the WAIT instruction during which the interrupt occurred.
Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode.
Some modules can be programmed to be active in wait mode.
Wait mode can also be exited by a reset. If the COP disable bit, COPD, in the configuration register is
logic 0, then the computer operating properly module (COP) is enabled and remains active in wait mode.
IAB
WAIT ADDR
IDB
WAIT ADDR + 1
PREVIOUS DATA
SAME
SAME
NEXT OPCODE
SAME
SAME
R/W
Note: Previous data can be operand data or the WAIT opcode, depending on the
last instruction.
Figure 14-11. Wait Mode Entry Timing
Figure 14-12 and Figure 14-13 show the timing for wait recovery.
IAB
IDB
$6E0B
$A6
$A6
$6E0C
$A6
$01
$00FF
$0B
$00FE
$00FD
$00FC
$6E
EXITSTOPWAIT
Note: EXITSTOPWAIT = RST pin OR CPU interrupt
Figure 14-12. Wait Recovery from Interrupt
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
190
Freescale Semiconductor
SIM Registers
32
CYCLES
IAB
32
CYCLES
$6E0B
IDB
$A6
$A6
RST VCT H RST VCT L
$A6
RST
CGMXCLK
Figure 14-13. Wait Recovery from Internal Reset
14.6.2 Stop Mode
In stop mode, the SIM counter is reset and the system clocks are disabled. An interrupt request from a
module can cause an exit from stop mode. Stacking for interrupts begins after the selected stop recovery
time has elapsed. Reset or break also causes an exit from stop mode.
The SIM disables the clock generator module outputs (CGMOUT and CGMXCLK) in stop mode, stopping
the CPU and peripherals. Stop recovery time is hard wired at the normal delay of 4096 CGMXCLK cycles.
It is important to note that when using the PWM generator, its outputs will stop toggling when stop mode
is entered. The PWM module must be disabled before entering stop mode to prevent external inverter
failure.
14.7 SIM Registers
This subsection describes the SIM registers.
14.7.1 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait
mode.
Address:
Read:
Write:
$FE00
BIt 7
6
5
4
3
2
R
R
R
R
R
R
1
SBSW
Note(1)
Reset:
Bit 0
R
0
R
= Reserved
Note 1. Writing a logic 0 clears SBSW.
Figure 14-14. SIM Break Status Register (SBSR)
SBSW — SIM Break Stop/Wait
This status bit is useful in applications requiring a return to wait mode after exiting from a break
interrupt. Clear SBSW by writing a logic 0 to it. Reset clears SBSW.
1 = Wait mode was exited by break interrupt.
0 = Wait mode was not exited by break interrupt.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
191
System Integration Module (SIM)
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.
14.7.2 SIM Reset Status Register
The SIM reset status register (SRSR) contains six flags that show the source of the last reset. Clear the
SIM reset status register by reading it. A power-on reset sets the POR bit and clears all other bits in the
register.
Address: $FE01
BIt 7
6
5
4
3
2
1
Bit 0
Read:
POR
PIN
COP
ILOP
ILAD
MENRST
LVI
0
Write:
R
R
R
R
R
R
R
R
Reset:
1
0
0
0
0
0
0
0
R
= Reserved
Figure 14-15. 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
MENRST — Forced Monitor Mode Entry Reset Bit
1 = Last reset caused by the MENRST circuit
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
192
Freescale Semiconductor
SIM Registers
14.7.3 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:
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 14-16. 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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
193
System Integration Module (SIM)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
194
Freescale Semiconductor
Chapter 15
Serial Peripheral Interface Module (SPI)
15.1 Introduction
The serial peripheral interface (SPI) module allows full-duplex, synchronous, serial communications with
peripheral devices.
15.2 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 with central processor unit (CPU) service:
– SPRF (SPI receiver full)
– SPTE (SPI transmitter empty)
• Mode fault error flag with CPU interrupt capability
• Overflow error flag with CPU interrupt capability
• Programmable wired-OR mode
• I2C (inter-integrated circuit) compatibility
15.3 Pin Name Conventions
The generic names of the SPI input/output (I/O) pins are:
• SS, slave select
• SPSCK, SPI serial clock
• MOSI, master out/slave in
• MISO, master in/slave out
SPI pins are shared by parallel I/O ports or have alternate functions. The full name of an SPI pin reflects
the name of the shared port pin or the name of an alternate pin function. The generic pin names appear
in the text that follows. Table 15-1 shows the full names of the SPI I/O pins.
Table 15-1. Pin Name Conventions
Generic Pin Names:
Full Pin Names:
MISO
MOSI
SPSCK
SS
PTF3/MISO
PTF2/MOSI
PTF0/SPSCK
PTF1/SS
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
195
PTA
PTA7–PTA0
PTB
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
PTC
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1/ATD9(1)
PTC0/ATD8
PTD
PTD6/IS3
PTD5/IS2
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
PTE
CONTROL AND STATUS REGISTERS — 112 BYTES
DDRA
ARITHMETIC/LOGIC
UNIT
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
DDRB
CPU
REGISTERS
USER FLASH — 32,256 BYTES
USER RAM — 768 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VDDA
VSSA(3)
VREFL(3)
VREFH
PWMGND
PWM6–PWM1
Freescale Semiconductor
VSS
VDD
VDDAD
VSSAD
ANALOG-TO-DIGITAL CONVERTER
MODULE
PULSE-WIDTH MODULATOR
MODULE
DDRC
SERIAL COMMUNICATIONS INTERFACE
MODULE
SERIAL PERIPHERAL INTERFACE
MODULE(2)
POWER-ON RESET
MODULE
SINGLE BREAK
MODULE
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PTF1/SS(1)
DDRE
USER FLASH VECTOR SPACE — 46 BYTES
TIMER INTERFACE
MODULE B
PTF
MONITOR ROM — 240 BYTES
DDRF
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
TIMER INTERFACE
MODULE A
PTF0/SPSCK(1)
POWER
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 15-1. Block Diagram Highlighting SPI Block and Pins
Serial Peripheral Interface Module (SPI)
196
INTERNAL BUS
M68HC08 CPU
Functional Description
15.4 Functional Description
Figure 15-2 shows the structure of the SPI module and Figure 15-3 shows the locations and contents of
the SPI I/O registers.
The SPI module allows full-duplex, synchronous, serial communication between the microcontroller unit
(MCU) and peripheral devices, including other MCUs. Software can poll the SPI status flags or SPI
operation can be interrupt-driven. All SPI interrupts can be serviced by the CPU.
INTERNAL BUS
TRANSMIT DATA REGISTER
CGMOUT ÷ 2
(FROM SIM)
SHIFT REGISTER
7
6
5
4
3
2
1
MISO
0
÷2
CLOCK
DIVIDER
MOSI
÷8
RECEIVE DATA REGISTER
÷ 32
PIN
CONTROL
LOGIC
÷ 128
SPMSTR
SPE
CLOCK
SELECT
SPSCK
M
CLOCK
LOGIC
S
SS
SPR1
SPR0
SPMSTR
CPHA
CPOL
SPWOM
TRANSMITTER CPU INTERRUPT REQUEST
MODFEN
ERRIE
SPI
CONTROL
SPTIE
RECEIVER/ERROR CPU INTERRUPT REQUEST
SPRIE
SPE
SPRF
SPTE
OVRF
MODF
Figure 15-2. SPI Module Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
197
Serial Peripheral Interface Module (SPI)
Addr.
$0044
Register Name
SPI Control Register Read:
(SPCR) Write:
See page 211. Reset:
$0045
SPI Status and Control Read:
Register (SPSCR) Write:
See page 212. Reset:
$0046
SPI Data Register Read:
(SPDR) Write:
See page 214. 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
R
R
R
MODFEN
SPR1
SPR0
SPRF
R
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
Figure 15-3. SPI I/O Register Summary
15.4.1 Master Mode
The SPI operates in master mode when the SPI master bit, SPMSTR, is set.
NOTE
Configure the SPI modules as master or slave before enabling them.
Enable the master SPI before enabling the slave SPI. Disable the slave SPI
before disabling the master SPI. See 15.12.1 SPI Control Register.
Only a master SPI module can initiate transmissions. Software begins the transmission from a master SPI
module by writing to the SPI data register. If the shift register is empty, the byte immediately transfers to
the shift register, setting the SPI transmitter empty bit, SPTE. The byte begins shifting out on the MOSI
pin under the control of the serial clock. See Figure 15-4.
MASTER MCU
SHIFT REGISTER
SLAVE MCU
MISO
MISO
MOSI
MOSI
SPSCK
BAUD RATE
GENERATOR
SS
SHIFT REGISTER
SPSCK
VDD
SS
Figure 15-4. Full-Duplex Master-Slave Connections
The SPR1 and SPR0 bits control the baud rate generator and determine the speed of the shift register.
See 15.12.2 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,
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
198
Freescale Semiconductor
Transmission Formats
SPRF signals the end of a transmission. Software clears SPRF by reading the SPI status and control
register with SPRF set and then reading the SPI data register. Writing to the SPI data register clears the
SPTE bit.
15.4.2 Slave Mode
The SPI operates in slave mode when the SPMSTR bit is clear. In slave mode the SPSCK pin is the input
for the serial clock from the master MCU. Before a data transmission occurs, the SS pin of the slave SPI
must be at logic 0. SS must remain low until the transmission is complete. See 15.6.2 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.
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 15.5 Transmission Formats.
NOTE
If the write to the data register is late, the SPI transmits the data already in
the shift register from the previous transmission.
SPSCK must be in the proper idle state before the slave is enabled to
prevent SPSCK from appearing as a clock edge.
15.5 Transmission Formats
During an SPI transmission, data is simultaneously transmitted (shifted out serially) and received (shifted
in serially). A serial clock synchronizes shifting and sampling on the two serial data lines. A slave select
line allows selection of an individual slave SPI device; slave devices that are not selected do not interfere
with SPI bus activities. On a master SPI device, the slave select line can optionally be used to indicate
multiple-master bus contention.
15.5.1 Clock Phase and Polarity Controls
Software can select any of four combinations of serial clock (SPSCK) phase and polarity using two bits
in the SPI control register (SPCR). The clock polarity is specified by the CPOL control bit, which selects
an active high or low clock and has no significant effect on the transmission format.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
199
Serial Peripheral Interface Module (SPI)
The clock phase (CPHA) control bit selects one of two fundamentally different transmission formats. The
clock phase and polarity should be identical for the master SPI device and the communicating slave
device. In some cases, the phase and polarity are changed between transmissions to allow a master
device to communicate with peripheral slaves having different requirements.
NOTE
Before writing to the CPOL bit or the CPHA bit, disable the SPI by clearing
the SPI enable bit (SPE).
15.5.2 Transmission Format When CPHA = 0
Figure 15-5 shows an SPI transmission in which CPHA is logic 0. The figure should not be used as a
replacement for data sheet parametric information.Two waveforms are shown for SPSCK: one for
CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing
diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins
are directly connected between the master and the slave. The MISO signal is the output from the slave,
and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The
slave SPI drives its MISO output only when its slave select input (SS) is at logic 0, so that only the selected
slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS
pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. (See
15.6.2 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 15-6.
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 15-5. Transmission Format (CPHA = 0)
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 15-6. CPHA/SS Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
200
Freescale Semiconductor
Transmission Formats
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.
15.5.3 Transmission Format When CPHA = 1
Figure 15-7 shows an SPI transmission in which CPHA is logic 1. The figure should not be used as a
replacement for data sheet parametric information. Two waveforms are shown for SPSCK: one for
CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing
diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins
are directly connected between the master and the slave. The MISO signal is the output from the slave,
and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The
slave SPI drives its MISO output only when its slave select input (SS) is at logic 0, so that only the selected
slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS
pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. See
15.6.2 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 15-7. Transmission Format (CPHA = 1)
15.5.4 Transmission Initiation Latency
When the SPI is configured as a master (SPMSTR = 1), writing to the SPDR starts a transmission. CPHA
has no effect on the delay to the start of the transmission, but it does affect the initial state of the SPSCK
signal. When CPHA = 0, the SPSCK signal remains inactive for the first half of the first SPSCK cycle.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
201
Serial Peripheral Interface Module (SPI)
When CPHA = 1, the first SPSCK cycle begins with an edge on the SPSCK line from its inactive to its
active level. The SPI clock rate (selected by SPR1:SPR0) affects the delay from the write to SPDR and
the start of the SPI transmission. See Figure 15-8 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. SPSCK edges occur halfway through the low time of the internal MCU clock. Since
the SPI clock is free-running, it is uncertain where the write to the SPDR occurs relative to the slower
SPSCK. This uncertainty causes the variation in the initiation delay shown in Figure 15-8. 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.
WRITE
TO SPDR
INITIATION DELAY
BUS
CLOCK
MOSI
MSB
BIT 5
BIT 6
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
SPSCK = INTERNAL CLOCK ÷ 2;
2 POSSIBLE START POINTS
WRITE
TO SPDR
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
SPSCK = INTERNAL CLOCK ÷ 8;
8 POSSIBLE START POINTS
LATEST
SPSCK = INTERNAL CLOCK ÷ 32;
32 POSSIBLE START POINTS
LATEST
SPSCK = INTERNAL CLOCK ÷ 128;
128 POSSIBLE START POINTS
LATEST
BUS
CLOCK
EARLIEST
WRITE
TO SPDR
BUS
CLOCK
EARLIEST
Figure 15-8. Transmission Start Delay (Master)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Error Conditions
15.6 Error Conditions
These flags signal SPI error conditions:
• Overflow (OVRF) — Failing to read the SPI data register before the next full byte enters the shift
register sets the OVRF bit. The new byte does not transfer to the receive data register, and the
unread byte still can be read. OVRF is in the SPI status and control register.
• Mode fault error (MODF) — The MODF bit indicates that the voltage on the slave select pin (SS)
is inconsistent with the mode of the SPI. MODF is in the SPI status and control register.
15.6.1 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. 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. MODF and OVRF can generate a receiver/error CPU interrupt request. See Figure 15-11. It is not
possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request.
However, leaving MODFEN low prevents MODF from being set.
If the CPU SPRF interrupt is enabled and the OVRF interrupt is not, watch for an overflow condition.
Figure 15-9 shows how it is possible to miss an overflow. The first part of Figure 15-9 shows how it is
possible to read the SPSCR and SPDR to clear the SPRF without problems. However, as illustrated by
the second transmission example, the OVRF bit can be set in between the time that SPSCR and SPDR
are read.
BYTE 1
BYTE 2
BYTE 3
BYTE 4
1
4
6
8
SPRF
OVRF
READ
SPSCR
2
READ
SPDR
5
3
1
BYTE 1 SETS SPRF BIT.
2
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
CPU READS BYTE 1 IN SPDR,
CLEARING SPRF BIT.
BYTE 2 SETS SPRF BIT.
3
4
7
5
CPU READS SPSCR WITH SPRF BIT SET
AND OVRF BIT CLEAR.
6
BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST.
7
CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT,
BUT NOT OVRF BIT.
8
BYTE 4 FAILS TO SET SPRF BIT BECAUSE
OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST.
Figure 15-9. Missed Read of Overflow Condition
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
203
Serial Peripheral Interface Module (SPI)
In this case, an overflow can easily be missed. Since no more SPRF interrupts can be generated until this
OVRF is serviced, it is not obvious that bytes are being lost as more transmissions are completed. To
prevent this, either enable the OVRF interrupt or do another read of the SPSCR following the read of the
SPDR. This ensures that the OVRF was not set before the SPRF was cleared and that future
transmissions can set the SPRF bit. Figure 15-10 illustrates this process. Generally, to avoid this second
SPSCR read, enable the OVRF interrupt 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 15-10. Clearing SPRF When OVRF Interrupt Is Not Enabled
15.6.2 Mode Fault Error
Setting the SPMSTR bit selects master mode and configures the SPSCK and MOSI pins as outputs and
the MISO pin as an input. Clearing SPMSTR selects slave mode and configures the SPSCK and MOSI
pins as inputs and the MISO pin as an output. The mode fault bit, MODF, becomes set any time the state
of the slave select pin, SS, is inconsistent with the mode selected by SPMSTR.
To prevent SPI pin contention and damage to the MCU, a mode fault error occurs if:
• The SS pin of a slave SPI goes high during a transmission.
• The SS pin of a master SPI goes low at any time.
For the MODF flag to be set, the mode fault error enable bit (MODFEN) must be set. Clearing the
MODFEN bit does not clear the MODF flag but does prevent MODF from being set again after MODF is
cleared.
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. MODF and OVRF can
generate a receiver/error CPU interrupt request. See Figure 15-11. It is not possible to enable MODF or
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
204
Freescale Semiconductor
Error Conditions
OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low
prevents MODF from being set.
In a master SPI with the mode fault enable bit (MODFEN) set, the mode fault flag (MODF) is set if SS
goes to logic 0. A mode fault in a master SPI causes these 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 15.5 Transmission Formats.
NOTE
Setting the MODF flag does not clear the SPMSTR bit. Reading SPMSTR
when MODF = 1 will indicate a mode fault error occurred in either master
mode or slave mode.
When CPHA = 0, a MODF occurs if a slave is selected (SS is at logic 0) and
later unselected (SS is at logic 1) even if no SPSCK is sent to that slave.
This happens because SS at logic 0 indicates the start of the transmission
(MISO driven out with the value of MSB) for CPHA = 0. When CPHA = 1, a
slave can be selected and then later unselected with no transmission
occurring. Therefore, MODF does not occur since a transmission was
never begun.
In a slave SPI (MSTR = 0), the MODF bit generates an SPI receiver/error CPU interrupt request if the
ERRIE bit is set. The MODF bit does not clear the SPE bit or reset the SPI in any way. Software can abort
the SPI transmission by clearing the SPE bit of the slave.
NOTE
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a high
impedance state. Also, the slave SPI ignores all incoming SPSCK clocks,
even if it was already in the middle of a transmission.
To clear the MODF flag, read the SPSCR with the MODF bit set and then write to the SPCR register. This
entire clearing procedure must occur with no MODF condition existing or else the flag is not cleared.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
205
Serial Peripheral Interface Module (SPI)
15.7 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt requests as shown in Table 15-2.
Table 15-2. SPI Interrupts
Flag
Request
SPTE transmitter empty
SPI transmitter CPU interrupt request (SPTIE = 1, SPE = 1)
SPRF receiver full
SPI receiver CPU interrupt request (SPRIE = 1)
OVRF overflow
SPI receiver/error interrupt request (ERRIE = 1)
MODF mode fault
SPI receiver/error interrupt request (ERRIE = 1)
The SPI transmitter interrupt enable bit (SPTIE) enables the SPTE flag to generate transmitter CPU
interrupt requests, provided that the SPI is enabled (SPE = 1).
The SPI receiver interrupt enable bit (SPRIE) enables the SPRF bit to generate receiver CPU interrupt
requests, provided that the SPI is enabled (SPE = 1). (See Figure 15-11.)
SPTE
SPTIE
SPE
SPI TRANSMITTER
CPU INTERRUPT REQUEST
SPRIE
SPRF
SPI RECEIVER/ERROR
ERRIE
CPU INTERRUPT REQUEST
MODF
OVRF
Figure 15-11. SPI Interrupt Request Generation
The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error
CPU interrupt request.
The mode fault enable bit (MODFEN) can prevent the MODF flag from being set so that only the OVRF
bit is enabled by the ERRIE bit to generate receiver/error CPU interrupt requests.
These sources in the SPI status and control register can generate CPU interrupt requests:
• SPI receiver full bit (SPRF) — The SPRF bit becomes set every time a byte transfers from the shift
register to the receive data register. If the SPI receiver interrupt enable bit, SPRIE, is also set,
SPRF can generate either an SPI receiver/error or CPU interrupt.
• SPI transmitter empty (SPTE) — The SPTE bit becomes set every time a byte transfers from the
transmit data register to the shift register. If the SPI transmit interrupt enable bit, SPTIE, is also set,
SPTE can generate either an SPTE or CPU interrupt request.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Resetting the SPI
15.8 Resetting the SPI
Any system reset completely resets the SPI. Partial resets occur whenever the SPI enable bit (SPE) is
low. Whenever SPE is low:
• The 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
• All control bits in the SPSCR (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.
15.9 Queuing Transmission Data
The double-buffered transmit data register allows a data byte to be queued and transmitted. For an SPI
configured as a master, a queued data byte is transmitted immediately after the previous transmission
has completed. The SPI transmitter empty flag (SPTE) indicates when the transmit data buffer is ready
to accept new data. Write to the transmit data register only when the SPTE bit is high. Figure 15-12
shows the timing associated with doing back-to-back transmissions with the SPI (SPSCK has
CPHA:CPOL = 1:0).
For a slave, 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. The SPTE indicates when the next write can occur.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
207
Serial Peripheral Interface Module (SPI)
WRITE TO SPDR
1
SPTE
3
2
8
5
10
SPSCK
CPHA:CPOL = 1:0
MSBBIT BIT BIT BIT BIT BIT LSBMSBBIT BIT BIT BIT BIT BIT LSBMSBBIT BIT BIT
6 5 4
6 5 4 3 2 1
6 5 4 3 2 1
BYTE 1
BYTE 2
BYTE 3
MOSI
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 15-12. SPRF/SPTE CPU Interrupt Timing
15.10 Low-Power Mode
The WAIT instruction puts the MCU in a low power-consumption standby mode.
The SPI module remains active after the execution of a WAIT instruction. In wait mode the SPI module
registers are not accessible by the CPU. Any enabled CPU interrupt request from the SPI module can
bring the MCU out of wait mode.
If SPI module functions are not required during wait mode, reduce power consumption by disabling the
SPI module before executing the WAIT instruction.
To exit wait mode when an overflow condition occurs, enable the OVRF bit to generate CPU interrupt
requests by setting the error interrupt enable bit (ERRIE). See 15.7 Interrupts.
Since the SPTE bit cannot be cleared during a break with the BCFE bit cleared, a write to the transmit
data register in break mode does not initiate a transmission nor is this data transferred into the shift
register. Therefore, a write to the SPDR in break mode with the BCFE bit cleared has no effect.
15.11 I/O Signals
The SPI module has five I/O pins and shares four of them with a parallel I/O port. The pins are:
• MISO — Data received
• MOSI — Data transmitted
• SPSCK — Serial clock
• SS — Slave select
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
I/O Signals
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.
15.11.1 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 logic 0 and its SS pin is at logic 0. To support a
multiple-slave system, a logic 1 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.
15.11.2 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.
15.11.3 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.
When enabled, the SPI controls data direction of the SPSCK pin regardless of the state of the data
direction register of the shared I/O port.
15.11.4 SS (Slave Select)
The SS pin has various functions depending on the current state of the SPI. For an SPI configured as a
slave, the SS is used to select a slave. For CPHA = 0, the SS is used to define the start of a transmission.
See 15.5 Transmission Formats. Since it is used to indicate the start of a transmission, the SS must be
toggled high and low between each byte transmitted for the CPHA = 0 format. However, it can remain low
between transmissions for the CPHA = 1 format. See Figure 15-13.
MISO/MOSI
BYTE 1
BYTE 2
BYTE 3
MASTER SS
SLAVE SS
CPHA = 0
SLAVE SS
CPHA = 1
Figure 15-13. CPHA/SS Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
209
Serial Peripheral Interface Module (SPI)
When an SPI is configured as a slave, the SS pin is always configured as an input. It cannot be used as
a general-purpose I/O regardless of the state of the MODFEN control bit. However, the MODFEN bit can
still prevent the state of the SS from creating a MODF error. See 15.12.2 SPI Status and Control Register.
NOTE
A logic 1 voltage on the SS pin of a slave SPI puts the MISO pin in a
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 15.6.2 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 the MODFEN bit
is low for an SPI master, the SS pin can be used as a general-purpose I/O under the control of the data
direction register of the shared I/O port. With MODFEN high, it is an input-only pin to the SPI regardless
of the state of the data direction register of the shared I/O port.
The CPU can always read the state of the SS pin by configuring the appropriate pin as an input and
reading the port data register. See Table 15-3.
Table 15-3. SPI Configuration
SPE
SPMSTR
MODFEN
SPI Configuration
State of SS Logic
0
X(1)
X
Not enabled
General-purpose I/O; SS ignored by SPI
1
0
X
Slave
Input-only to SPI
1
1
0
Master without MODF
General-purpose I/O; SS ignored by SPI
1
1
1
Master with MODF
Input-only to SPI
1. X = don’t care
15.11.5 VSS (Clock Ground)
VSS is the ground return for the serial clock pin, SPSCK, and the ground for the port output buffers. To
reduce the ground return path loop and minimize radio frequency (RF) emissions, connect the ground pin
of the slave to the VSS pin of the master.
15.12 I/O Registers
Three registers control and monitor SPI operation:
• SPI control register, SPCR
• SPI status and control register, SPSCR
• SPI data register, SPDR
15.12.1 SPI Control Register
The SPI control register (SPCR):
• Enables SPI module interrupt requests
• Selects CPU interrupt requests or DMA service 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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
210
Freescale Semiconductor
I/O Registers
Address: $0044
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 15-14. 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
15-5 and Figure 15-7. 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
15-5 and Figure 15-7. To transmit data between SPI modules, the SPI modules must have identical
CPHA bits. When CPHA = 0, the SS pin of the slave SPI module must be set to logic 1 between bytes.
See Figure 15-13. Reset sets the CPHA bit.
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 data register. Therefore,
the slave data register must be loaded with the desired transmit data before the falling edge of SS. Any
data written after the falling edge is stored in the data register and transferred to the shift register at
the current transmission.
When CPHA = 1 for a slave, the first edge of the SPSCK indicates the beginning of the transmission.
The same applies when SS is high for a slave. The MISO pin is held in a high-impedance state, and
the incoming SPSCK is ignored. In certain cases, it may also cause the MODF flag to be set. See
15.6.2 Mode Fault Error. A logic 1 on the SS pin does not in any way affect the state of the SPI state
machine.
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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
211
Serial Peripheral Interface Module (SPI)
SPE — SPI Enable Bit
This read/write bit enables the SPI module. Clearing SPE causes a partial reset of the SPI. See 15.8
Resetting the SPI. Reset clears the SPE bit.
1 = SPI module enabled
0 = SPI module disabled
SPTIE— SPI Transmit Interrupt Enable Bit
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
15.12.2 SPI Status and Control Register
The SPI status and control register (SPSCR) 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: $0045
Bit 7
6
Read:
SPRF
Write:
R
Reset:
0
0
R
= Reserved
ERRIE
5
4
3
OVRF
MODF
SPTE
R
R
R
0
0
1
2
1
Bit 0
MODFEN
SPR1
SPR0
0
0
0
Figure 15-15. 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 (DMAS = 0), 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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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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
the MODFEN bit set. In a master SPI, the MODF flag is set if the SS pin goes low at any time with the
MODFEN bit set. Clear the MODF bit by reading the SPI status and control register (SPSCR) with
MODF set and then writing to the SPI control register (SPCR). Reset clears the MODF bit.
1 = SS pin at inappropriate logic level
0 = SS pin at appropriate logic level
SPTE — SPI Transmitter Empty Bit
This clearable, read-only flag is set each time the transmit data register transfers a byte into the shift
register. SPTE generates an SPTE CPU interrupt request or an SPTE DMA service request if the
SPTIE bit in the SPI control register is set also.
NOTE
Do not write to the SPI data register unless the SPTE bit is high.
For an idle master of idle slave that has no data loaded into its transmit buffer, the SPTE will be set
again within two bus cycles since the transmit buffer empties into the shift register. This allows the user
to queue up a 16-bit value to send. For an already active slave, the load of the shift register cannot
occur until the transmission is completed. This implies that a back-to-back write to the transmit data
register is not possible. The SPTE indicates when the next write can occur.
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 to 1, allows the MODF flag to be set. If the MODF flag is set, clearing the
MODFEN does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is low,
then the SS pin is available as a general-purpose I/O.
If the MODFEN bit is set, then this pin is not available as a 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 15.11.4 SS (Slave Select).
If the MODFEN bit is low, the level of the SS pin does not affect the operation of an enabled SPI
configured as a master. For an enabled SPI configured as a slave, having MODFEN low only prevents
the MODF flag from being set. It does not affect any other part of SPI operation. See 15.6.2 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 15-4. SPR1 and
SPR0 have no effect in slave mode. Reset clears SPR1 and SPR0.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
213
Serial Peripheral Interface Module (SPI)
Table 15-4. SPI Master Baud Rate Selection
SPR1:SPR0
Baud Rate Divisor (BD)
00
2
01
8
10
32
11
128
Use this formula to calculate the SPI baud rate:
CGMOUT
Baud rate = -------------------------2 × BD
where:
CGMOUT = base clock output of the clock generator module (CGM)
BD = baud rate divisor
15.12.3 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 15-2.
Address: $0046
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:
Indeterminate after reset
Figure 15-16. 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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Chapter 16
Timer Interface A (TIMA)
16.1 Introduction
This section describes the timer interface module A (TIMA). The TIMA is a 4-channel timer that provides:
• Timing reference with input capture
• Output compare
• Pulse-width modulator functions
Figure 16-2 is a block diagram of the TIMA.
16.2 Features
Features of the TIMA include:
• Four input capture/output compare channels:
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
• Buffered and unbuffered pulse-width modulator (PWM) signal generation
• Programmable TIMA clock input:
– 7-frequency internal bus clock prescaler selection
– External TIMA clock input (4-MHz maximum frequency)
• Free-running or modulo up-count operation
• Toggle any channel pin on overflow
• TIMA counter stop and reset bits
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
215
PTA
PTA7–PTA0
PTB
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
PTC
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1/ATD9(1)
PTC0/ATD8
PTD
PTD6/IS3
PTD5/IS2
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
PTE
CONTROL AND STATUS REGISTERS — 112 BYTES
DDRA
ARITHMETIC/LOGIC
UNIT
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
DDRB
CPU
REGISTERS
USER FLASH — 32,256 BYTES
USER RAM — 768 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VDDA
VSSA(3)
VREFL(3)
VREFH
PWMGND
PWM6–PWM1
Freescale Semiconductor
VSS
VDD
VDDAD
VSSAD
ANALOG-TO-DIGITAL CONVERTER
MODULE
PULSE-WIDTH MODULATOR
MODULE
DDRC
SERIAL COMMUNICATIONS INTERFACE
MODULE
SERIAL PERIPHERAL INTERFACE
MODULE(2)
POWER-ON RESET
MODULE
SINGLE BREAK
MODULE
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PTF1/SS(1)
DDRE
USER FLASH VECTOR SPACE — 46 BYTES
TIMER INTERFACE
MODULE B
PTF
MONITOR ROM — 240 BYTES
DDRF
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
TIMER INTERFACE
MODULE A
PTF0/SPSCK(1)
POWER
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 16-1. Block Diagram Highlighting TIMA Block and Pins
Timer Interface A (TIMA)
216
INTERNAL BUS
M68HC08 CPU
Features
TCLK
PTE3/TCLKA
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
INTERRUPT
LOGIC
16-BIT COMPARATOR
TMODH:TMODL
ELS0B
CHANNEL 0
ELS0A
TOV0
CH0MAX
16-BIT COMPARATOR
TCH0H:TCH0L
CH0F
16-BIT LATCH
MS0A
ELS1B
CHANNEL 1
MS0B
ELS1A
TOV1
CH1MAX
16-BIT COMPARATOR
TCH1H:TCH1L
CH0IE
CH1F
16-BIT LATCH
CH1IE
MS1A
ELS2B
CHANNEL 2
ELS2A
TOV2
CH2MAX
16-BIT COMPARATOR
TCH2H:TCH2L
CH2F
16-BIT LATCH
MS2A
ELS3B
CHANNEL 3
MS2B
ELS3A
TOV3
CH3MAX
16-BIT COMPARATOR
TCH3H:TCH3L
CH2IE
CH3F
16-BIT LATCH
MS3A
CH3IE
PTE4
LOGIC
PTE4/TCH0A
INTERRUPT
LOGIC
PTE5
LOGIC
PTE5/TCH1A
INTERRUPT
LOGIC
PTE6
LOGIC
PTE6/TCH2A
INTERRUPT
LOGIC
PTE7
LOGIC
PTE7/TCH3A
INTERRUPT
LOGIC
Figure 16-2. TIMA Block Diagram
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
217
Timer Interface A (TIMA)
Addr.
$000E
$000F
$0010
$0011
$0012
$0013
Register Name
Bit 7
$0015
$0016
$0017
$0019
TOIE
TSTOP
4
3
0
0
TRST
R
2
1
Bit 0
PS2
PS1
PS0
TOF
0
0
1
0
0
0
0
0
TIMA Counter Register High Read:
(TACNTH) Write:
See page 227. Reset:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Read:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bit 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
TIMA Counter Register Low
(TACNTL) Write:
See page 227. Reset:
TIMA Counter Modulo Read:
Register High (TAMODH) Write:
See page 228. Reset:
TIMA Counter Modulo Read:
Register Low (TAMODL) Write:
See page 228. Reset:
TIMA Channel 0 Status/Control Read:
Register (TASC0) Write:
See page 229. Reset:
TIMA Channel 0 Register High
(TACH0H) Write:
See page 232. Reset:
TIMA Channel 0 Register Low Read:
(TACH0L) Write:
See page 232. Reset:
TIMA Channel 1 Status/Control Read:
Register (TASC1) Write:
See page 229. Reset:
TIMA Channel 1 Register High Read:
(TACH1H) Write:
See page 232. Reset:
Read:
$0018
5
TIMA Status/Control Register Read:
(TASC) Write:
See page 226. Reset:
Read:
$0014
6
0
CH0F
0
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
CH1F
0
CH1IE
0
R
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
TIMA Channel 1 Register Low
(TACH1L) Write:
See page 232. Reset:
Bit 7
TIMA Channel 2 Status/Control Read:
Register (TASC2) Write:
See page 229. Reset:
CH2F
6
5
4
3
Indeterminate after reset
0
0
R
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
= Reserved
Figure 16-3. TIM I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Functional Description
Addr.
Register Name
Read:
$001A
$001B
$001C
$001D
TIMA Channel 2 Register High
(TACH2H) Write:
See page 232. Reset:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Indeterminate after reset
TIMA Channel 2 Register Low Read:
(TACH2L) Write:
See page 232. Reset:
TIMA Channel 3 Status/Control Read:
Register (TASC3) Write:
See page 229. Reset:
TIMA Channel 3 Register High Read:
(TACH3H) Write:
See page 232. Reset:
Bit 7
5
4
3
Indeterminate after reset
CH3F
0
CH3IE
0
R
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
0
0
0
0
0
0
0
0
Bit 15
14
13
12
11
10
9
Bit 8
2
1
Bit 0
Read:
$001E
6
TIMA Channel 3 Register Low
(TACH3L) Write:
See page 232. Reset:
Indeterminate after reset
Bit 7
6
5
4
3
Indeterminate after reset
R
= Reserved
Figure 16-3. TIM I/O Register Summary (Continued)
16.3 Functional Description
Figure 16-2 shows the TIMA structure. The central component of the TIMA is the 16-bit TIMA counter that
can operate as a free-running counter or a modulo up-counter. The TIMA counter provides the timing
reference for the input capture and output compare functions. The TIMA counter modulo registers,
TAMODH–TAMODL, control the modulo value of the TIMA counter. Software can read the TIMA counter
value at any time without affecting the counting sequence.
The four TIMA channels are programmable independently as input capture or output compare channels.
16.3.1 TIMA Counter Prescaler
The TIMA clock source can be one of the seven prescaler outputs or the TIMA clock pin, PTE3/TCLKA.
The prescaler generates seven clock rates from the internal bus clock. The prescaler select bits, PS[2:0],
in the TIMA status and control register select the TIMA clock source.
16.3.2 Input Capture
An input capture function has three basic parts:
1. Edge select logic
2. Input capture latch
3. 16-bit counter
Two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the
free-running counter after the corresponding input capture edge detector senses a defined transition. The
polarity of the active edge is programmable. The level transition which triggers the counter transfer is
defined by the corresponding input edge bits (ELSxB and ELSxA in TASC0–TASC3 control registers with
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
219
Timer Interface A (TIMA)
x referring to the active channel number). When an active edge occurs on the pin of an input capture
channel, the TIMA latches the contents of the TIMA counter into the TIMA channel registers,
TACHxH–TACHxL. Input captures can generate TIMA CPU interrupt requests. Software can determine
that an input capture event has occurred by enabling input capture interrupts or by polling the status flag
bit.
The free-running counter contents are transferred to the TIMA channel status and control register
(TACHxH–TACHxL, see 16.7.5 TIMA Channel Registers) on each proper signal transition regardless of
whether the TIMA channel flag (CH0F–CH3F in TASC0–TASC3 registers) is set or clear. When the status
flag is set, a CPU interrupt is generated if enabled. The value of the count latched or “captured” is the time
of the event. Because this value is stored in the input capture register two bus cycles after the actual event
occurs, user software can respond to this event at a later time and determine the actual time of the event.
However, this must be done prior to another input capture on the same pin; otherwise, the previous time
value will be lost.
By recording the times for successive edges on an incoming signal, software can determine the period
and/or pulse width of the signal. To measure a period, two successive edges of the same polarity are
captured. To measure a pulse width, two alternate polarity edges are captured. Software should track the
overflows at the 16-bit module counter to extend its range.
Another use for the input capture function is to establish a time reference. In this case, an input capture
function is used in conjunction with an output compare function. For example, to activate an output signal
a specified number of clock cycles after detecting an input event (edge), use the input capture function to
record the time at which the edge occurred. A number corresponding to the desired delay is added to this
captured value and stored to an output compare register (see
16.7.5 TIMA Channel Registers). Because both input captures and output compares are referenced to
the same 16-bit modulo counter, the delay can be controlled to the resolution of the counter independent
of software latencies.
Reset does not affect the contents of the input capture channel registers.
16.3.3 Output Compare
With the output compare function, the TIMA can generate a periodic pulse with a programmable polarity,
duration, and frequency. When the counter reaches the value in the registers of an output compare
channel, the TIMA can set, clear, or toggle the channel pin. Output compares can generate TIMA CPU
interrupt requests.
16.3.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare pulses as described in 16.3.3
Output Compare. The pulses are unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change an output compare value could cause
incorrect operation for up to two counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new value prevents any compare during
that counter overflow period. Also, using a TIMA overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMA may pass the new value before it is
written.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
220
Freescale Semiconductor
Functional Description
Use this method to synchronize unbuffered changes in the output compare value on channel x:
• When changing to a smaller value, enable channel x output compare interrupts and write the new
value in the output compare interrupt routine. The output compare interrupt occurs at the end of
the current output compare pulse. The interrupt routine has until the end of the counter overflow
period to write the new value.
• When changing to a larger output compare value, enable TIMA overflow interrupts and write the
new value in the TIMA overflow interrupt routine. The TIMA overflow interrupt occurs at the end of
the current counter overflow period. Writing a larger value in an output compare interrupt routine
(at the end of the current pulse) could cause two output compares to occur in the same counter
overflow period.
16.3.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the
PTE4/TCH0A pin. The TIMA channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIMA channel 0 status and control register (TASC0) links channel 0 and
channel 1. The output compare value in the TIMA channel 0 registers initially controls the output on the
PTE4/TCH0A pin. Writing to the TIMA channel 1 registers enables the TIMA channel 1 registers to
synchronously control the output after the TIMA overflows. At each subsequent overflow, the TIMA
channel registers (0 or 1) that control the output are the ones written to last. TASC0 controls and monitors
the buffered output compare function, and TIMA channel 1 status and control register (TASC1) is unused.
While the MS0B bit is set, the channel 1 pin, PTE5/TCH1A, is available as a general-purpose I/O pin.
Channels 2 and 3 can be linked to form a buffered output compare channel whose output appears on the
PTE6/TCH2A pin. The TIMA channel registers of the linked pair alternately control the output.
Setting the MS2B bit in TIMA channel 2 status and control register (TASC2) links channel 2 and
channel 3. The output compare value in the TIMA channel 2 registers initially controls the output on the
PTE6/TCH2A pin. Writing to the TIMA channel 3 registers enables the TIMA channel 3 registers to
synchronously control the output after the TIMA overflows. At each subsequent overflow, the TIMA
channel registers (2 or 3) that control the output are the ones written to last. TASC2 controls and monitors
the buffered output compare function, and TIMA channel 3 status and control register (TASC3) is unused.
While the MS2B bit is set, the channel 3 pin, PTE7/TCH3A, 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.
16.3.4 Pulse-Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIMA can generate a PWM
signal. The value in the TIMA counter modulo registers determines the period of the PWM signal. The
channel pin toggles when the counter reaches the value in the TIMA counter modulo registers. The time
between overflows is the period of the PWM signal.
As Figure 16-4 shows, the output compare value in the TIMA channel registers determines the pulse width
of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIMA
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
221
Timer Interface A (TIMA)
to clear the channel pin on output compare if the polarity of the PWM pulse is 1 (ELSxA = 0). Program the
TIMA to set the pin if the polarity of the PWM pulse is 0 (ELSxA = 1).
The value in the TIMA counter modulo registers and the selected prescaler output determines the
frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMA counter modulo registers produces a PWM period of 256 times the internal bus
clock period if the prescaler select value is $000 (see 16.7.1 TIMA Status and Control Register).
The value in the TIMA channel registers determines the pulse width of the PWM output. The pulse width
of an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIMA channel registers
produces a duty cycle of 128/256 or 50 percent.
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
POLARITY = 1
(ELSxA = 0)
TCHx
PULSE
WIDTH
POLARITY = 0
(ELSxA = 1)
TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 16-4. PWM Period and Pulse Width
16.3.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as described in 16.3.4 Pulse-Width
Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new
pulse width value over the value currently in the TIMA channel registers.
An unsynchronized write to the TIMA channel registers to change a pulse width value could cause
incorrect operation for up to two PWM periods. For example, writing a new value before the counter
reaches the old value but after the counter reaches the new value prevents any compare during that PWM
period. Also, using a TIMA overflow interrupt routine to write a new, smaller pulse width value may cause
the compare to be missed. The TIMA may pass the new value before it is written to the TIMA channel
registers.
Use this method 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.
• When changing to a longer pulse width, enable TIMA overflow interrupts and write the new value
in the TIMA overflow interrupt routine. The TIMA overflow interrupt occurs at the end of the current
PWM period. Writing a larger value in an output compare interrupt routine (at the end of the current
pulse) could cause two output compares to occur in the same PWM period.
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Freescale Semiconductor
Functional Description
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.
16.3.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the
PTE4/TCH0A pin. The TIMA channel registers of the linked pair alternately control the pulse width of the
output.
Setting the MS0B bit in TIMA channel 0 status and control register (TASC0) links channel 0 and
channel 1. The TIMA channel 0 registers initially control the pulse width on the PTE4/TCH0A pin. Writing
to the TIMA channel 1 registers enables the TIMA channel 1 registers to synchronously control the pulse
width at the beginning of the next PWM period. At each subsequent overflow, the TIMA channel registers
(0 or 1) that control the pulse width are the ones written to last. TASC0 controls and monitors the buffered
PWM function, and TIMA channel 1 status and control register (TASC1) is unused. While the MS0B bit is
set, the channel 1 pin, PTE5/TCH1A, is available as a general-purpose
I/O pin.
Channels 2 and 3 can be linked to form a buffered PWM channel whose output appears on the
PTE6/TCH2A pin. The TIMA channel registers of the linked pair alternately control the pulse width of the
output.
Setting the MS2B bit in TIMA channel 2 status and control register (TASC2) links channel 2 and
channel 3. The TIMA channel 2 registers initially control the pulse width on the PTE6/TCH2A pin. Writing
to the TIMA channel 3 registers enables the TIMA channel 3 registers to synchronously control the pulse
width at the beginning of the next PWM period. At each subsequent overflow, the TIMA channel registers
(2 or 3) that control the pulse width are written to last. TASC2 controls and monitors the buffered PWM
function, and TIMA channel 3 status and control register (TASC3) is unused. While the MS2B bit is set,
the channel 3 pin, PTE7/TCH3A, 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.
16.3.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered PWM signals, use this initialization
procedure:
1. In the TIMA status and control register (TASC):
a. Stop the TIMA counter by setting the TIMA stop bit, TSTOP.
b. Reset the TIMA counter and prescaler by setting the TIMA reset bit, TRST.
2. In the TIMA counter modulo registers (TAMODH–TAMODL), write the value for the required PWM
period.
3. In the TIMA channel x registers (TACHxH–TACHxL), write the value for the required pulse width.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
223
Timer Interface A (TIMA)
4. In TIMA 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 16-2.)
b. Write 1 to the toggle-on-overflow bit, TOVx.
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 16-2.)
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare can also
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
5. In the TIMA status control register (TASC), clear the TIMA stop bit, TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIMA
channel 0 registers (TACH0H–TACH0L) initially control the buffered PWM output. TIMA status control
register 0 (TASC0) controls and monitors the PWM signal from the linked channels. MS0B takes priority
over MS0A.
Setting MS2B links channels 2 and 3 and configures them for buffered PWM operation. The TIMA
channel 2 registers (TACH2H–TACH2L) initially control the buffered PWM output. TIMA status control
register 2 (TASC2) controls and monitors the PWM signal from the linked channels. MS2B takes priority
over MS2A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIMA overflows. Subsequent output
compares try to force the output to a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a 100
percent duty cycle output. (See 16.7.4 TIMA Channel Status and Control Registers.)
16.4 Interrupts
These TIMA sources can generate interrupt requests:
• TIMA overflow flag (TOF) — The timer overflow flag (TOF) bit is set when the TIMA counter
reaches the modulo value programmed in the TIMA counter modulo registers. The TIMA overflow
interrupt enable bit, TOIE, enables TIMA overflow interrupt requests. TOF and TOIE are in the
TIMA status and control registers.
• TIMA channel flags (CH3F–CH0F) — The CHxF bit is set when an input capture or output compare
occurs on channel x. Channel x TIMA CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE.
16.5 Wait Mode
The WAIT instruction puts the MCU in low power-consumption standby mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
224
Freescale Semiconductor
I/O Signals
The TIMA remains active after the execution of a WAIT instruction. In wait mode, the TIMA registers are
not accessible by the CPU. Any enabled CPU interrupt request from the TIMA can bring the MCU out of
wait mode.
If TIMA functions are not required during wait mode, reduce power consumption by stopping the TIMA
before executing the WAIT instruction.
16.6 I/O Signals
Port E shares five of its pins with the TIMA:
• PTE3/TCLKA is an external clock input to the TIMA prescaler.
• The four TIMA channel I/O pins are PTE4/TCH0A, PTE5/TCH1A, PTE6/TCH2A, and
PTE7/TCH3A.
16.6.1 TIMA Clock Pin (PTE3/TCLKA)
PTE3/TCLKA is an external clock input that can be the clock source for the TIMA counter instead of the
prescaled internal bus clock. Select the PTE3/TCLKA input by writing logic 1s to the three prescaler select
bits, PS[2:0]. See 16.7.1 TIMA Status and Control Register.
The maximum TCLK frequency is the least: 4 MHz or bus frequency ÷ 2.
PTE3/TCLKA is available as a general-purpose I/O pin when not used as the TIMA clock input. When the
PTE3/TCLKA pin is the TIMA clock input, it is an input regardless of the state of the DDRE3 bit in data
direction register E.
16.6.2 TIMA Channel I/O Pins (PTE4/TCH0A–PTE7/TCH3A)
Each channel I/O pin is programmable independently as an input capture pin or an output compare pin.
PTE2/TCH0 and PTE4/TCH2 can be configured as buffered output compare or buffered PWM pins.
16.7 I/O Registers
These input/output (I/O) registers control and monitor TIMA operation:
• TIMA status and control register (TASC)
• TIMA control registers (TACNTH–TACNTL)
• TIMA counter modulo registers (TAMODH–TAMODL)
• TIMA channel status and control registers (TASC0, TASC1, TASC2, and TASC3)
• TIMA channel registers (TACH0H–TACH0L, TACH1H–TACH1L, TACH2H–TACH2L, and
TACH3H–TACH3L)
16.7.1 TIMA Status and Control Register
The TIMA status and control register:
• Enables TIMA overflow interrupts
• Flags TIMA overflows
• Stops the TIMA counter
• Resets the TIMA counter
• Prescales the TIMA counter clock
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
225
Timer Interface A (TIMA)
Address: $000E
Bit 7
6
5
TOIE
TSTOP
1
Read:
TOF
Write:
0
Reset:
0
0
R
= Reserved
4
3
0
0
TRST
R
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
Figure 16-5. TIMA Status and Control Register (TASC)
TOF — TIMA Overflow Flag
This read/write flag is set when the TIMA counter reaches the modulo value programmed in the TIMA
counter modulo registers. Clear TOF by reading the TIMA status and control register when TOF is set
and then writing a logic 0 to TOF. If another TIMA overflow occurs before the clearing sequence is
complete, then writing logic 0 to TOF has no effect. Therefore, a TOF interrupt request
cannot be lost due to inadvertent clearing of TOF. Reset clears the TOF bit. Writing a logic 1 to TOF
has no effect.
1 = TIMA counter has reached modulo value.
0 = TIMA counter has not reached modulo value.
TOIE — TIMA Overflow Interrupt Enable Bit
This read/write bit enables TIMA overflow interrupts when the TOF bit becomes set. Reset clears the
TOIE bit.
1 = TIMA overflow interrupts enabled
0 = TIMA overflow interrupts disabled
TSTOP — TIMA Stop Bit
This read/write bit stops the TIMA counter. Counting resumes when TSTOP is cleared. Reset sets the
TSTOP bit, stopping the TIMA counter until software clears the TSTOP bit.
1 = TIMA counter stopped
0 = TIMA counter active
NOTE
Do not set the TSTOP bit before entering wait mode if the TIMA is required
to exit wait mode. Also when the TSTOP bit is set and the timer is
configured for input capture operation, input captures are inhibited until the
TSTOP bit is cleared.
TRST — TIMA Reset Bit
Setting this write-only bit resets the TIMA counter and the TIMA prescaler. Setting TRST has no effect
on any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIMA
counter is reset and always reads as logic 0. Reset clears the TRST bit.
1 = Prescaler and TIMA counter cleared
0 = No effect
NOTE
Setting the TSTOP and TRST bits simultaneously stops the TIMA counter
at a value of $0000.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
226
Freescale Semiconductor
I/O Registers
PS[2:0] — Prescaler Select Bits
These read/write bits select either the PTE3/TCLKA pin or one of the seven prescaler outputs as the
input to the TIMA counter as Table 16-1 shows. Reset clears the PS[2:0] bits.
Table 16-1. Prescaler Selection
PS[2:0]
TIMA Clock Source
000
Internal bus clock ÷1
001
Internal bus clock ÷ 2
010
Internal bus clock ÷ 4
011
Internal bus clock ÷ 8
100
Internal bus clock ÷ 16
101
Internal bus clock ÷ 32
110
Internal bus clock ÷ 64
111
PTE3/TCLKA
16.7.2 TIMA Counter Registers
The two read-only TIMA counter registers contain the high and low bytes of the value in the TIMA counter.
Reading the high byte (TACNTH) latches the contents of the low byte (TACNTL) into a buffer. Subsequent
reads of TACNTH do not affect the latched TACNTL value until TACNTL is read. Reset clears the TIMA
counter registers. Setting the TIMA reset bit (TRST) also clears the TIMA counter registers.
NOTE
If TACNTH is read during a break interrupt, be sure to unlatch TACNTL by
reading TACNTL before exiting the break interrupt. Otherwise, TACNTL
retains the value latched during the break.
Register Name and Address:
TACNTH — $000F
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
Register Name and Address:
TACNTL — $0010
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
R
= Reserved
Figure 16-6. TIMA Counter Registers (TACNTH and TACNTL)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
227
Timer Interface A (TIMA)
16.7.3 TIMA Counter Modulo Registers
The read/write TIMA modulo registers contain the modulo value for the TIMA counter. When the TIMA
counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIMA counter resumes
counting from $0000 at the next timer clock. Writing to the high byte (TAMODH) inhibits the TOF bit and
overflow interrupts until the low byte (TAMODL) is written. Reset sets the TIMA counter modulo registers.
Register Name and Address:
Read:
Write:
Reset:
TAMODH — $0011
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
1
Register Name and Address:
Read:
Write:
Reset:
TAMODL — $0012
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 16-7. TIMA Counter Modulo Registers
(TAMODH and TAMODL)
NOTE
Reset the TIMA counter before writing to the TIMA counter modulo registers.
16.7.4 TIMA Channel Status and Control Registers
Each of the TIMA channel status and control registers:
• Flags input captures and output compares
• Enables input capture and output compare interrupts
• Selects input capture, output compare, or PWM operation
• Selects high, low, or toggling output on output compare
• Selects rising edge, falling edge, or any edge as the active input capture trigger
• Selects output toggling on TIMA overflow
• Selects 0 percent and 100 percent PWM duty cycle
• Selects buffered or unbuffered output compare/PWM operation
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
228
Freescale Semiconductor
I/O Registers
Register Name and Address:
Bit 7
Read:
CH0F
Write:
0
Reset:
0
TASC0 — $0013
6
5
4
3
2
1
Bit 0
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
Register Name and Address:
Bit 7
Read:
CH1F
Write:
0
Reset:
0
TASC1 — $0016
6
CH1IE
0
Register Name and Address:
Bit 7
Read:
CH2F
Write:
0
Reset:
0
Read:
CH3F
Write:
0
Reset:
0
R
0
TASC2 — $0019
6
5
4
3
2
1
Bit 0
CH2IE
MS2B
MS2A
ELS2B
ELS2A
TOV2
CH2MAX
0
0
0
0
0
0
0
4
3
2
1
Bit 0
MS3A
ELS3B
ELS3A
TOV3
CH3MAX
0
0
0
0
0
Register Name and Address:
Bit 7
5
TASC3 — $001C
6
CH3IE
0
0
R
= Reserved
5
0
R
0
Figure 16-8. TIMA Channel Status
and Control Registers (TASC0–TASC3)
CHxF — Channel x Flag Bit
When channel x is an input capture channel, this read/write bit is set when an active edge occurs on
the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the
TIMA counter registers matches the value in the TIMA channel x registers.
When CHxIE = 1, clear CHxF by reading TIMA 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 TIMA CPU interrupts on channel x.
Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
229
Timer Interface A (TIMA)
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation. MSxB exists only in the TIMA
channel 0 and TIMA channel 2 status and control registers.
Setting MS0B disables the channel 1 status and control register and reverts TCH1A pin to
general-purpose I/O.
Setting MS2B disables the channel 3 status and control register and reverts TCH3A pin 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 16-2.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level of the TCHxA pin once PWM,
input capture, or output compare operation is enabled. See Table 16-2. Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE
Before changing a channel function by writing to the MSxB or MSxA bit, set
the TSTOP and TRST bits in the TIMA status and control register (TASC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits control the active edge-sensing logic
on channel x.
When channel x is an output compare channel, ELSxB and ELSxA control the channel x output
behavior when an output compare occurs.
When ELSxB and ELSxA are both clear, channel x is not connected to port E, and pin PTEx/TCHxA
is available as a general-purpose I/O pin. However, channel x is at a state determined by these bits
and becomes transparent to the respective pin when PWM, input capture, or output compare mode is
enabled. Table 16-2 shows how ELSxB and ELSxA work. Reset clears the ELSxB and ELSxA bits.
NOTE
Before enabling a TIMA channel register for input capture operation, make
sure that the PTEx/TACHx pin is stable for at least two bus clocks.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
230
Freescale Semiconductor
I/O Registers
Table 16-2. Mode, Edge, and Level Selection
MSxB:MSxA
ELSxB:ELSxA
X0
00
X1
00
00
01
00
10
00
11
01
00
01
01
01
10
01
11
1X
01
1X
10
1X
11
Mode
Configuration
Pin under port control; initialize timer output level high
Output preset
Pin under port control; initialize timer output level low
Capture on rising edge only
Input capture
Capture on falling edge only
Capture on rising or falling edge
Software compare only
Output
compare
or PWM
Toggle output on compare
Clear output on compare
Set output on compare
Toggle output on compare
Buffered
output compare
or buffered PWM
Clear output on compare
Set output on compare
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit controls the behavior of the channel
x output when the TIMA counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMA counter overflow.
0 = Channel x pin does not toggle on TIMA counter overflow.
NOTE
When TOVx is set, a TIMA counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx is 1 and clear output on compare is selected, setting the CHxMAX bit forces the duty
cycle of buffered and unbuffered PWM signals to 100 percent. As Figure 16-9 shows, CHxMAX bit
takes effect in the cycle after it is set or cleared. The output stays at 100 percent duty cycle level until
the cycle after CHxMAX is cleared.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTEx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
TOVx
Figure 16-9. CHxMAX Latency
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
231
Timer Interface A (TIMA)
16.7.5 TIMA Channel Registers
These read/write registers contain the captured TIMA counter value of the input capture function or the
output compare value of the output compare function. The state of the TIMA channel registers after reset
is unknown.
In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the TIMA channel x registers
(TACHxH) inhibits input captures until the low byte (TACHxL) is read.
In output compare mode (MSxB:MSxA ≠ 0:0), writing to the high byte of the TIMA channel x registers
(TACHxH) inhibits output compares until the low byte (TACHxL) is written.
Register Name and Address:
Read:
Write:
TACH0H — $0014
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
TACH0L — $0015
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset:
Indeterminate after reset
Register Name and Address: TACH1H — $0017
Read:
Write:
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
TACH1L — $0018
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
Reset:
TACH2H — $001A
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Indeterminate after reset
Figure 16-10. TIMA Channel Registers
(TACH0H/L–TACH3H/L)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
232
Freescale Semiconductor
I/O Registers
Register Name and Address:
Read:
Write:
TACH2L — $001B
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
TACH3H — $001D
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
Reset:
TACH3L — $001E
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Figure 16-10. TIMA Channel Registers
(TACH0H/L–TACH3H/L) (Continued)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
233
Timer Interface A (TIMA)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
234
Freescale Semiconductor
Chapter 17
Timer Interface B (TIMB)
17.1 Introduction
This section describes the timer interface module B (TIMB). The TIMB is a 2-channel timer that provides:
• Timing reference with input capture
• Output compare
• Pulse-width modulation functions
Figure 17-2 is a block diagram of the TIMB.
NOTE
The TIMB module is not available in the 56-pin shrink dual in-line package
(SDIP).
17.2 Features
Features of the TIMB include:
• Two input capture/output compare channels:
– Rising-edge, falling-edge, or any-edge input capture trigger
– Set, clear, or toggle output compare action
• Buffered and unbuffered pulse-width modulation (PWM) signal generation
• Programmable TIMB clock input:
– 7-frequency internal bus clock prescaler selection
– External TIMB clock input (4-MHz maximum frequency)
• Free-running or modulo up-count operation
• Toggle any channel pin on overflow
• TIMB counter stop and reset bits
17.3 Functional Description
Figure 17-2 shows the TIMB structure. The central component of the TIMB is the 16-bit TIMB counter that
can operate as a free-running counter or a modulo up-counter. The TIMB counter provides the timing
reference for the input capture and output compare functions. The TIMB counter modulo registers,
TBMODH–TBMODL, control the modulo value of the TIMB counter. Software can read the TIMB counter
value at any time without affecting the counting sequence.
The two TIMB channels are programmable independently as input capture or output compare channels.
NOTE
The TIMB module is not available in the 56-pin SDIP.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
235
PTA
PTA7–PTA0
PTB
PTB7/ATD7
PTB6/ATD6
PTB5/ATD5
PTB4/ATD4
PTB3/ATD3
PTB2/ATD2
PTB1/ATD1
PTB0/ATD0
PTC
PTC6
PTC5
PTC4
PTC3
PTC2
PTC1/ATD9(1)
PTC0/ATD8
PTD
PTD6/IS3
PTD5/IS2
PTD4/IS1
PTD3/FAULT4
PTD2/FAULT3
PTD1/FAULT2
PTD0/FAULT1
PTE
CONTROL AND STATUS REGISTERS — 112 BYTES
DDRA
ARITHMETIC/LOGIC
UNIT
PTE7/TCH3A
PTE6/TCH2A
PTE5/TCH1A
PTE4/TCH0A
PTE3/TCLKA
PTE2/TCH1B(1)
PTE1/TCH0B(1)
PTE0/TCLKB(1)
LOW-VOLTAGE INHIBIT
MODULE
COMPUTER OPERATING PROPERLY
MODULE
DDRB
CPU
REGISTERS
USER FLASH — 32,256 BYTES
USER RAM — 768 BYTES
OSC1
OSC2
CGMXFC
CLOCK GENERATOR
MODULE
RST
SYSTEM INTEGRATION
MODULE
IRQ
IRQ
MODULE
VDDA
VSSA(3)
VREFL(3)
VREFH
PWMGND
PWM6–PWM1
Freescale Semiconductor
VSS
VDD
VDDAD
VSSAD
ANALOG-TO-DIGITAL CONVERTER
MODULE
PULSE-WIDTH MODULATOR
MODULE
DDRC
SERIAL COMMUNICATIONS INTERFACE
MODULE
SERIAL PERIPHERAL INTERFACE
MODULE(2)
POWER-ON RESET
MODULE
SINGLE BREAK
MODULE
PTF5/TxD
PTF4/RxD
PTF3/MISO(1)
PTF2/MOSI(1)
PTF1/SS(1)
DDRE
USER FLASH VECTOR SPACE — 46 BYTES
TIMER INTERFACE
MODULE B
PTF
MONITOR ROM — 240 BYTES
DDRF
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
TIMER INTERFACE
MODULE A
PTF0/SPSCK(1)
POWER
Notes:
1. These pins are not available in the 56-pin SDIP package.
2. This module is not available in the 56-pin SDIP package.
3. In the 56-pin SDIP package, these pins are bonded together.
Figure 17-1. Block Diagram Highlighting TIMB Block and Pins
Timer Interface B (TIMB)
236
INTERNAL BUS
M68HC08 CPU
Functional Description
TCLK
PTE0/TCLKB
PRESCALER SELECT
INTERNAL
BUS CLOCK
PRESCALER
TSTOP
PS2
TRST
PS1
PS0
16-BIT COUNTER
TOF
TOIE
INTERRUPT
LOGIC
16-BIT COMPARATOR
TMODH:TMODL
ELS0B
CHANNEL 0
ELS0A
TOV0
CH0MAX
16-BIT COMPARATOR
TCH0H:TCH0L
CH0F
ELS1B
CHANNEL 1
CH0IE
MS0B
ELS1A
TOV1
CH1MAX
16-BIT COMPARATOR
TCH1H:TCH1L
CH1F
PTE2
LOGIC
PTE2/TCH1B
INTERRUPT
LOGIC
16-BIT LATCH
CH1IE
MS1A
PTE1/TCH0B
INTERRUPT
LOGIC
16-BIT LATCH
MS0A
PTE1
LOGIC
Figure 17-2. TIMB Block Diagram
Addr.
$0051
$0052
$0053
$0054
$0055
Register Name
Bit 7
6
5
TOIE
TSTOP
4
3
0
0
TRST
R
2
1
Bit 0
PS2
PS1
PS0
TIMB Status/Control Register Read:
(TBSC) Write:
See page 244. Reset:
TOF
0
0
1
0
0
0
0
0
Read:
TIMB Counter Register High
(TBCNTH) Write:
See page 246. Reset:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
TIMB Counter Register Low Read:
(TBCNTL) Write:
See page 246. Reset:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
1
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
R
= Reserved
TIMB Counter Modulo Register Read:
High (TBMODH) Write:
See page 246. Reset:
TIMB Counter Modulo Register Read:
Low (TBMODL) Write:
See page 246. Reset:
0
Figure 17-3. TIMB I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
237
Timer Interface B (TIMB)
Addr.
Register Name
Bit 7
Read:
$0056
$0057
$0058
$0059
TIMB Channel 0 Status/Control
Register Write:
(TBSC0) See page 247. Reset:
TIMB Channel 0 Register High Read:
(TBCH0H) Write:
See page 250. Reset:
TIMB Channel 0 Register Low Read:
(TBCH0L) Write:
See page 250. Reset:
TIMB Channel 1 Status/Control Read:
Register Write:
(TBSC1) See page 247. Reset:
Read:
$005A
$005B
TIMB Channel 1 Register High
(TBCH1H) Write:
See page 250. Reset:
TIMB Channel 1 Register Low Read:
(TBCH1L) Write:
See page 250. Reset:
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
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
CH0F
0
Indeterminate after reset
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
CH1F
0
CH1IE
0
R
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
0
0
0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Indeterminate after reset
R
= Reserved
Figure 17-3. TIMB I/O Register Summary (Continued)
17.3.1 TIMB Counter Prescaler
The TIMB clock source can be one of the seven prescaler outputs or the TIMB clock pin, PTE0/TCLKB.
The prescaler generates seven clock rates from the internal bus clock. The prescaler select bits, PS[2:0],
in the TIMB status and control register select the TIMB clock source.
17.3.2 Input Capture
An input capture function has three basic parts:
1. Edge select logic
2. Input capture latch
3. 16-bit counter
Two 8-bit registers, which make up the 16-bit input capture register, are used to latch the value of the
free-running counter after the corresponding input capture edge detector senses a defined transition. The
polarity of the active edge is programmable. The level transition which triggers the counter transfer is
defined by the corresponding input edge bits (ELSxB and ELSxA in TBSC0–TBSC1 control registers with
x referring to the active channel number). When an active edge occurs on the pin of an input capture
channel, the TIMB latches the contents of the TIMB counter into the TIMB channel registers,
TCHxH–TCHxL. Input captures can generate TIMB CPU interrupt requests. Software can determine that
an input capture event has occurred by enabling input capture interrupts or by polling the status flag bit.
The free-running counter contents are transferred to the TIMB channel status and control register
(TBCHxH–TBCHxL, see 17.7.5 TIMB Channel Registers) on each proper signal transition regardless of
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
238
Freescale Semiconductor
Functional Description
whether the TIMB channel flag (CH0F–CH1F in TBSC0–TBSC1 registers) is set or clear. When the status
flag is set, a CPU interrupt is generated if enabled. The value of the count latched or “captured” is the time
of the event. Because this value is stored in the input capture register two bus cycles after the actual event
occurs, user software can respond to this event at a later time and determine the actual time of the event.
However, this must be done prior to another input capture on the same pin; otherwise, the previous time
value will be lost.
By recording the times for successive edges on an incoming signal, software can determine the period
and/or pulse width of the signal. To measure a period, two successive edges of the same polarity are
captured. To measure a pulse width, two alternate polarity edges are captured. Software should track the
overflows at the 16-bit module counter to extend its range.
Another use for the input capture function is to establish a time reference. In this case, an input capture
function is used in conjunction with an output compare function. For example, to activate an output signal
a specified number of clock cycles after detecting an input event (edge), use the input capture function to
record the time at which the edge occurred. A number corresponding to the desired delay is added to this
captured value and stored to an output compare register (see 17.7.5 TIMB Channel Registers). Because
both input captures and output compares are referenced to the same 16-bit modulo counter, the delay
can be controlled to the resolution of the counter independent of software latencies.
Reset does not affect the contents of the input capture channel register (TBCHxH–TBCHxL).
17.3.3 Output Compare
With the output compare function, the TIMB can generate a periodic pulse with a programmable polarity,
duration, and frequency. When the counter reaches the value in the registers of an output compare
channel, the TIMB can set, clear, or toggle the channel pin. Output compares can generate TIMB CPU
interrupt requests.
17.3.3.1 Unbuffered Output Compare
Any output compare channel can generate unbuffered output compare pulses as described in 17.3.3
Output Compare. The pulses are unbuffered because changing the output compare value requires writing
the new value over the old value currently in the TIMB channel registers.
An unsynchronized write to the TIMB channel registers to change an output compare value could cause
incorrect operation for up to two counter overflow periods. For example, writing a new value before the
counter reaches the old value but after the counter reaches the new value prevents any compare during
that counter overflow period. Also, using a TIMB overflow interrupt routine to write a new, smaller output
compare value may cause the compare to be missed. The TIMB may pass the new value before it is
written.
Use this method to synchronize unbuffered changes in the output compare value on channel x:
• When changing to a smaller value, enable channel x output compare interrupts and write the new
value in the output compare interrupt routine. The output compare interrupt occurs at the end of
the current output compare pulse. The interrupt routine has until the end of the counter overflow
period to write the new value.
• When changing to a larger output compare value, enable TIMB overflow interrupts and write the
new value in the TIMB overflow interrupt routine. The TIMB overflow interrupt occurs at the end of
the current counter overflow period. Writing a larger value in an output compare interrupt routine
(at the end of the current pulse) could cause two output compares to occur in the same counter
overflow period.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
239
Timer Interface B (TIMB)
17.3.3.2 Buffered Output Compare
Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the
PTE1/TCH0B pin. The TIMB channel registers of the linked pair alternately control the output.
Setting the MS0B bit in TIMB channel 0 status and control register (TBSC0) links channel 0 and channel
1. The output compare value in the TIMB channel 0 registers initially controls the output on the
PTE1/TCH0B pin. Writing to the TIMB channel 1 registers enables the TIMB channel 1 registers to
synchronously control the output after the TIMB overflows. At each subsequent overflow, the TIMB
channel registers (0 or 1) that control the output are the ones written to last. TSC0 controls and monitors
the buffered output compare function, and TIMB channel 1 status and control register (TBSC1) is unused.
While the MS0B bit is set, the channel 1 pin, PTE2/TCH1B, 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.
17.3.4 Pulse-Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIMB can generate a PWM
signal. The value in the TIMB counter modulo registers determines the period of the PWM signal. The
channel pin toggles when the counter reaches the value in the TIMB counter modulo registers. The time
between overflows is the period of the PWM signal.
As Figure 17-4 shows, the output compare value in the TIMB channel registers determines the pulse width
of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIMB
to clear the channel pin on output compare if the polarity of the PWM pulse is 1 (ELSxA = 0). Program the
TIMB to set the pin if the polarity of the PWM pulse is 0 (ELSxA = 1).
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
POLARITY = 1
(ELSxA = 0)
TCHx
PULSE
WIDTH
POLARITY = 0
(ELSxA = 1)
TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
Figure 17-4. PWM Period and Pulse Width
The value in the TIMB counter modulo registers and the selected prescaler output determines the
frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing
$00FF (255) to the TIMB counter modulo registers produces a PWM period of 256 times the internal bus
clock period if the prescaler select value is $000 (see 17.7.1 TIMB Status and Control Register).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
240
Freescale Semiconductor
Functional Description
The value in the TIMB channel registers determines the pulse width of the PWM output. The pulse width
of an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIMB channel registers
produces a duty cycle of 128/256 or 50 percent.
17.3.4.1 Unbuffered PWM Signal Generation
Any output compare channel can generate unbuffered PWM pulses as described in 17.3.4 Pulse-Width
Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new
pulse width value over the value currently in the TIMB channel registers.
An unsynchronized write to the TIMB channel registers to change a pulse width value could cause
incorrect operation for up to two PWM periods. For example, writing a new value before the counter
reaches the old value but after the counter reaches the new value prevents any compare during that PWM
period. Also, using a TIMB overflow interrupt routine to write a new, smaller pulse width value may cause
the compare to be missed. The TIMB may pass the new value before it is written to the TIMB channel
registers.
Use this method 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.
• When changing to a longer pulse width, enable TIMB overflow interrupts and write the new value
in the TIMB overflow interrupt routine. The TIMB overflow interrupt occurs at the end of the current
PWM period. Writing a larger value in an output compare interrupt routine (at the end of the current
pulse) could cause two output compares to occur in the same PWM period.
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare also can
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
17.3.4.2 Buffered PWM Signal Generation
Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the
PTE1/TCH0B pin. The TIMB channel registers of the linked pair alternately control the pulse width of the
output.
Setting the MS0B bit in TIMB channel 0 status and control register (TBSC0) links channel 0 and channel
1. The TIMB channel 0 registers initially control the pulse width on the PTE1/TCH0B pin. Writing to the
TIMB channel 1 registers enables the TIMB channel 1 registers to synchronously control the pulse width
at the beginning of the next PWM period. At each subsequent overflow, the TIMB channel registers
(0 or 1) that control the pulse width are the ones written to last. TBSC0 controls and monitors the buffered
PWM function, and TIMB channel 1 status and control register (TBSC1) is unused. While the MS0B bit is
set, the channel 1 pin, PTE2/TCH1B, 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
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
241
Timer Interface B (TIMB)
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.
17.3.4.3 PWM Initialization
To ensure correct operation when generating unbuffered or buffered PWM signals, use this initialization
procedure:
1. In the TIMB status and control register (TBSC):
a. Stop the TIMB counter by setting the TIMB stop bit, TSTOP.
b. Reset the TIMB counter and prescaler by setting the TIMB reset bit, TRST.
2. In the TIMB counter modulo registers (TBMODH–TBMODL), write the value for the required PWM
period.
3. In the TIMB channel x registers (TBCHxH–TBCHxL), write the value for the required pulse width.
4. In TIMB channel x status and control register (TBSCx):
a. Write 0:1 (for unbuffered output compare or PWM signals) or 1:0 (for buffered output compare
or PWM signals) to the mode select bits, MSxB–MSxA. (See Table 17-2.)
b. Write 1 to the toggle-on-overflow bit, TOVx.
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 17-2.)
NOTE
In PWM signal generation, do not program the PWM channel to toggle on
output compare. Toggling on output compare prevents reliable 0 percent
duty cycle generation and removes the ability of the channel to self-correct
in the event of software error or noise. Toggling on output compare can also
cause incorrect PWM signal generation when changing the PWM pulse
width to a new, much larger value.
5. In the TIMB status control register (TBSC), clear the TIMB stop bit, TSTOP.
Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIMB channel
0 registers (TBCH0H–TBCH0L) initially control the buffered PWM output. TIMB status control register 0
(TBSC0) controls and monitors the PWM signal from the linked channels. MS0B takes priority over MS0A.
Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIMB overflows. Subsequent output
compares try to force the output to a state it is already in and have no effect. The result is a 0 percent duty
cycle output.
Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a
100 percent duty cycle output. (See 17.7.4 TIMB Channel Status and Control Registers.)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
242
Freescale Semiconductor
Interrupts
17.4 Interrupts
These TIMB sources can generate interrupt requests:
• TIMB overflow flag (TOF) — The timer overflow flag (TOF) bit is set when the TIMB counter
reaches the modulo value programmed in the TIMB counter modulo registers. The TIMB overflow
interrupt enable bit, TOIE, enables TIMB overflow interrupt requests. TOF and TOIE are in the
TIMB status and control registers.
• TIMB channel flags (CH1F–CH0F) — The CHxF bit is set when an input capture or output compare
occurs on channel x. Channel x TIMB CPU interrupt requests are controlled by the channel x
interrupt enable bit, CHxIE.
17.5 Wait Mode
The WAIT instruction puts the MCU in low-power standby mode.
The TIMB remains active after the execution of a WAIT instruction. In wait mode, the TIMB registers are
not accessible by the CPU. Any enabled CPU interrupt request from the TIMB can bring the MCU out of
wait mode.
If TIMB functions are not required during wait mode, reduce power consumption by stopping the TIMB
before executing the WAIT instruction.
17.6 I/O Signals
Port E shares three of its pins with the TIMB:
• PTE0/TCLKB is an external clock input to the TIMB prescaler.
• The two TIMB channel I/O pins are PTE1/TCH0B and PTE2/TCH1B.
17.6.1 TIMB Clock Pin (PTE0/TCLKB)
PTE0/TCLKB is an external clock input that can be the clock source for the TIMB counter instead of the
prescaled internal bus clock. Select the PTE0/TCLKB input by writing 1s to the three prescaler select bits,
PS[2:0]. See 17.7.1 TIMB Status and Control Register.
The maximum TCLK frequency is the least: 4 MHz or bus frequency ÷ 2.
PTE0/TCLKB is available as a general-purpose I/O pin or ADC channel when not used as the TIMB clock
input. When the PTE0/TCLKB pin is the TIMB clock input, it is an input regardless of the state of the
DDRE0 bit in data direction register E.
17.6.2 TIMB Channel I/O Pins (PTE1/TCH0B–PTE2/TCH1B)
Each channel I/O pin is programmable independently as an input capture pin or an output compare pin.
PTE1/TCH0B and PTE2/TCH1B can be configured as buffered output compare or buffered PWM pins.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
243
Timer Interface B (TIMB)
17.7 I/O Registers
These input/output (I/O) registers control and monitor TIMB operation:
• TIMB status and control register (TBSC)
• TIMB control registers (TBCNTH–TBCNTL)
• TIMB counter modulo registers (TBMODH–TBMODL)
• TIMB channel status and control registers (TBSC0 and TBSC1)
• TIMB channel registers (TBCH0H–TBCH0L and TBCH1H–TBCH1L)
17.7.1 TIMB Status and Control Register
The TIMB status and control register:
• Enables TIMB overflow interrupts
• Flags TIMB overflows
• Stops the TIMB counter
• Resets the TIMB counter
• Prescales the TIMB counter clock
Address:
$0051
Bit 7
6
5
TOIE
TSTOP
1
Read:
TOF
Write:
0
Reset:
0
0
R
= Reserved
4
3
0
0
TRST
R
0
0
2
1
Bit 0
PS2
PS1
PS0
0
0
0
Figure 17-5. TIMB Status and Control Register (TBSC)
TOF — TIMB Overflow Flag
This read/write flag is set when the TIMB counter reaches the modulo value programmed in the TIMB
counter modulo registers. Clear TOF by reading the TIMB status and control register when TOF is set
and then writing a logic 0 to TOF. If another TIMB overflow occurs before the clearing sequence is
complete, then writing logic 0 to TOF has no effect. Therefore, a TOF interrupt request cannot be lost
due to inadvertent clearing of TOF. Reset clears the TOF bit. Writing a logic 1 to TOF has no effect.
1 = TIMB counter has reached modulo value.
0 = TIMB counter has not reached modulo value.
TOIE — TIMB Overflow Interrupt Enable Bit
This read/write bit enables TIMB overflow interrupts when the TOF bit becomes set. Reset clears the
TOIE bit.
1 = TIMB overflow interrupts enabled
0 = TIMB overflow interrupts disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
244
Freescale Semiconductor
I/O Registers
TSTOP — TIMB Stop Bit
This read/write bit stops the TIMB counter. Counting resumes when TSTOP is cleared. Reset sets the
TSTOP bit, stopping the TIMB counter until software clears the TSTOP bit.
1 = TIMB counter stopped
0 = TIMB counter active
NOTE
Do not set the TSTOP bit before entering wait mode if the TIMB is required
to exit wait mode. Also, when the TSTOP bit is set and the timer is
configured for input capture operation, input captures are inhibited until
TSTOP is cleared.
TRST — TIMB Reset Bit
Setting this write-only bit resets the TIMB counter and the TIMB prescaler. Setting TRST has no effect
on any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIMB
counter is reset and always reads as logic 0. Reset clears the TRST bit.
1 = Prescaler and TIMB counter cleared
0 = No effect
NOTE
Setting the TSTOP and TRST bits simultaneously stops the TIMB counter
at a value of $0000.
PS[2:0] — Prescaler Select Bits
These read/write bits select either the PTE0/TCLKB pin or one of the seven prescaler outputs as the
input to the TIMB counter as Table 17-1 shows. Reset clears the PS[2:0] bits.
Table 17-1. Prescaler Selection
PS[2:0]
TIMB Clock Source
000
Internal bus clock ÷1
001
Internal bus clock ÷ 2
010
Internal bus clock ÷ 4
011
Internal bus clock ÷ 8
100
Internal bus clock ÷ 16
101
Internal bus clock ÷ 32
110
Internal bus clock ÷ 64
111
PTE0/TCLKB
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
245
Timer Interface B (TIMB)
17.7.2 TIMB Counter Registers
The two read-only TIMB counter registers contain the high and low bytes of the value in the TIMB counter.
Reading the high byte (TBCNTH) latches the contents of the low byte (TBCNTL) into a buffer. Subsequent
reads of TBCNTH do not affect the latched TBCNTL value until TBCNTL is read. Reset clears the TIMB
counter registers. Setting the TIMB reset bit (TRST) also clears the TIMB counter registers.
NOTE
If TBCNTH is read during a break interrupt, be sure to unlatch TBCNTL by
reading TBCNTL before exiting the break interrupt. Otherwise, TBCNTL
retains the value latched during the break.
Register Name and Address:
TBCNTH — $0052
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Write:
R
R
R
R
R
R
R
R
Reset:
0
0
0
0
0
0
0
0
Register Name and Address:
TBCNTL — $0053
Bit 7
6
5
4
3
2
1
Bit 0
Read:
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Write:
R
R
R
R
R
R
R
R
0
0
0
0
0
0
0
0
R
= Reserved
Reset:
Figure 17-6. TIMB Counter Registers (TBCNTH and TBCNTL)
17.7.3 TIMB Counter Modulo Registers
The read/write TIMB modulo registers contain the modulo value for the TIMB counter. When the TIMB
counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIMB counter resumes
counting from $0000 at the next timer clock. Writing to the high byte (TBMODH) inhibits the TOF bit and
overflow interrupts until the low byte (TBMODL) is written. Reset sets the TIMB counter modulo registers.
Register Name and Address:
Read:
Write:
Reset:
TBMODH — $0054
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
1
1
1
1
1
1
1
1
Register Name and Address:
Read:
Write:
Reset:
TBMODL — $0055
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
1
1
1
1
1
1
1
1
Figure 17-7. TIMB Counter Modulo Registers (TBMODH and TBMODL)
NOTE
Reset the TIMB counter before writing to the TIMB counter modulo registers.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
246
Freescale Semiconductor
I/O Registers
17.7.4 TIMB Channel Status and Control Registers
Each of the TIMB channel status and control registers:
• Flags input captures and output compares
• Enables input capture and output compare interrupts
• Selects input capture, output compare, or PWM operation
• Selects high, low, or toggling output on output compare
• Selects rising edge, falling edge, or any edge as the active input capture trigger
• Selects output toggling on TIMB overflow
• Selects 0 percent and 100 percent PWM duty cycle
• Selects buffered or unbuffered output compare/PWM operation
Register Name and Address:
Bit 7
Read:
CH0F
Write:
0
Reset:
0
TBSC0 — $0056
6
5
4
3
2
1
Bit 0
CH0IE
MS0B
MS0A
ELS0B
ELS0A
TOV0
CH0MAX
0
0
0
0
0
0
0
4
3
2
1
Bit 0
MS1A
ELS1B
ELS1A
TOV1
CH1MAX
0
0
0
0
0
Register Name and Address:
Bit 7
TBSC1 — $0059
6
Read:
CH1F
Write:
0
Reset:
0
0
R
= Reserved
CH1IE
5
0
R
0
Figure 17-8. TIMB Channel Status and Control Registers (TBSC0–TBSC1)
CHxF — Channel x Flag
When channel x is an input capture channel, this read/write bit is set when an active edge occurs on
the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the
TIMB counter registers matches the value in the TIMB channel x registers.
When CHxIE = 1, clear CHxF by reading TIMB 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 TIMB CPU interrupts on channel x.
Reset clears the CHxIE bit.
1 = Channel x CPU interrupt requests enabled
0 = Channel x CPU interrupt requests disabled
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
247
Timer Interface B (TIMB)
MSxB — Mode Select Bit B
This read/write bit selects buffered output compare/PWM operation. MSxB exists only in the TIMB
channel 0.
Setting MS0B disables the channel 1 status and control register and reverts TCH1B 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 17-2.
1 = Unbuffered output compare/PWM operation
0 = Input capture operation
When ELSxB:A = 00, this read/write bit selects the initial output level of the TCHx pin once PWM, input
capture, or output compare operation is enabled. See Table 17-2. Reset clears the MSxA bit.
1 = Initial output level low
0 = Initial output level high
NOTE
Before changing a channel function by writing to the MSxB or MSxA bit, set
the TSTOP and TRST bits in the TIMB status and control register (TBSC).
ELSxB and ELSxA — Edge/Level Select Bits
When channel x is an input capture channel, these read/write bits control the active edge-sensing logic
on channel x.
When channel x is an output compare channel, ELSxB and ELSxA control the channel x output
behavior when an output compare occurs.
When ELSxB and ELSxA are both clear, channel x is not connected to port E, and pin PTEx/TCHxB
is available as a general-purpose I/O pin. However, channel x is at a state determined by these bits
and becomes transparent to the respective pin when PWM, input capture, or output compare mode is
enabled. Table 17-2 shows how ELSxB and ELSxA work. Reset clears the ELSxB and ELSxA bits.
NOTE
Before enabling a TIMB channel register for input capture operation, make
sure that the PTEx/TBCHx pin is stable for at least two bus clocks.
TOVx — Toggle-On-Overflow Bit
When channel x is an output compare channel, this read/write bit controls the behavior of the channel
x output when the TIMB counter overflows. When channel x is an input capture channel, TOVx has no
effect. Reset clears the TOVx bit.
1 = Channel x pin toggles on TIMB counter overflow.
0 = Channel x pin does not toggle on TIMB counter overflow.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
248
Freescale Semiconductor
I/O Registers
Table 17-2. Mode, Edge, and Level Selection
MSxB:MSxA
ELSxB:ELSxA
X0
00
X1
00
00
01
00
10
00
11
Capture on rising or falling edge
01
00
Softare compare only
01
01
01
10
01
11
1X
01
1X
10
1X
11
Mode
Configuration
Output preset
Pin under port control; initialize timer output level high
Pin under port control; initialize timer output level low
Capture on rising edge only
Input capture
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
When TOVx is set, a TIMB counter overflow takes precedence over a
channel x output compare if both occur at the same time.
CHxMAX — Channel x Maximum Duty Cycle Bit
When the TOVx is 1 and clear output on compare is selected, setting the CHxMAX bit forces the duty
cycle of buffered and unbuffered PWM signals to 100 percent. As Figure 17-9 shows, CHxMAX bit
takes effect in the cycle after it is set or cleared. The output stays at 100 percent duty cycle level until
the cycle after CHxMAX is cleared.
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
OVERFLOW
PERIOD
PTEx/TCHx
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
OUTPUT
COMPARE
CHxMAX
TOVx
Figure 17-9. CHxMAX Latency
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
249
Timer Interface B (TIMB)
17.7.5 TIMB Channel Registers
These read/write registers contain the captured TIMB counter value of the input capture function or the
output compare value of the output compare function. The state of the TIMB channel registers after reset
is unknown.
In input capture mode (MSxB–MSxA = 0:0), reading the high byte of the TIMB channel x registers
(TBCHxH) inhibits input captures until the low byte (TBCHxL) is read.
In output compare mode (MSxB–MSxA ≠ 0:0), writing to the high byte of the TIMB channel x registers
(TBCHxH) inhibits output compares until the low byte (TBCHxL) is written.
Register Name and Address:
Read:
Write:
TBCH0H — $0057
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
TBCH0L — $0058
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
TBCH1H — $005A
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
Bit 14
Bit 13
Bit 12
Bit 11
Bit 10
Bit 9
Bit 8
Reset:
Indeterminate after reset
Register Name and Address:
Read:
Write:
Reset:
TBCH1L — $005B
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
Bit 6
Bit 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
Indeterminate after reset
Figure 17-10. TIMB Channel Registers (TBCH0H/L–TBCH1H/L)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
250
Freescale Semiconductor
Chapter 18
Development Support
18.1 Introduction
This section describes the break module, the monitor read-only memory (MON), and the monitor mode
entry methods.
18.2 Break Module (BRK)
The break module (BRK) can generate a break interrupt that stops normal program flow at a defined
address to enter a background program. Features 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
18.2.1 Functional Description
When the internal address bus matches the value written in the break address registers, the break module
issues a breakpoint signal to the CPU. The CPU then loads the instruction register with a software
interrupt instruction (SWI) after completion of the current CPU instruction. The program counter vectors
to $FFFC and $FFFD ($FEFC and $FEFD in monitor mode).
These events can cause a break interrupt to occur:
• A CPU-generated address (the address in the program counter) matches the contents of the break
address registers.
• Software writes a logic 1 to the BRKA bit in the break status and control register.
When a CPU-generated address matches the contents of the break address registers, the break interrupt
begins after the CPU completes its current instruction. A return-from-interrupt instruction (RTI) in the
break routine ends the break interrupt and returns the microcontroller unit (MCU) to normal operation.
Figure 18-1 shows the structure of the break module.
18.2.1.1 Flag Protection During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during
the break state.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
251
Development Support
IAB15–IAB8
BREAK ADDRESS REGISTER HIGH
8-BIT COMPARATOR
IAB15–IAB0
CONTROL
BREAK
8-BIT COMPARATOR
BREAK ADDRESS REGISTER LOW
IAB7–IAB0
Figure 18-1. Break Module Block Diagram
Addr.
Register Name
$FE00
SIM Break Status Register Read:
(SBSR) Write:
See page 255. Reset:
$FE03
SIM Break Flag Control Read:
Register (SBFCR) Write:
See page 255. Reset:
$FE0C
Break Address Register High Read:
(BRKH) Write:
See page 254. Reset:
Break Address Register Low Read:
$FE0D
(BRKL) Write:
See page 254. Reset:
$FE0E
Break Status and Control Read:
Register (BRKSCR) Write:
See page 254. Reset:
Note: Writing a 0 clears BW.
Bit 7
6
5
4
3
2
1
Bit 0
R
R
R
R
R
R
BW
R
0
BCFE
R
R
R
R
R
R
R
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
BRKE
BRKA
0
0
0
0
0
0
0
0
0
0
0
R
= Reserved
0
0
0
= Unimplemented
0
Figure 18-2. I/O Register Summary
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
252
Freescale Semiconductor
Break Module (BRK)
18.2.1.2 CPU During Break Interrupts
The CPU starts a break interrupt by:
• Loading the instruction register with the SWI instruction
• Loading the program counter with $FFFC and $FFFD ($FEFC and $FEFD in monitor mode)
The break interrupt begins after completion of the CPU instruction in progress. If the break address
register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately.
18.2.1.3 TIM1 and TIM2 During Break Interrupts
A break interrupt stops the timer counters.
18.2.1.4 COP During Break Interrupts
The COP is disabled during a break interrupt when VTST is present on the RST pin.
18.2.2 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes.
18.2.2.1 Wait Mode
If enabled, the break module is active in wait mode. In the break routine, the user can subtract one from
the return address on the stack if SBSW is set. Clear the BW bit by writing logic 0 to it.
18.2.2.2 Stop Mode
The break module is inactive in stop mode. The STOP instruction does not affect break module register
states.
18.2.3 Break Module Registers
These registers control and monitor operation of the break module:
• Break status and control register (BRKSCR)
• Break address register high (BRKH)
• Break address register low (BRKL)
• SIM break status register (SBSR)
• SIM break flag control register (SBFCR)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
253
Development Support
18.2.3.1 Break Status and Control Register
The break status and control register (BRKSCR) contains break module enable and status bits.
Address:
Read:
Write:
Reset:
$FE0E
Bit 7
6
BRKE
BRKA
0
0
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
0
0
0
0
= Unimplemented
Figure 18-3. Break Status and Control Register (BRKSCR)
BRKE — Break Enable Bit
This read/write bit enables breaks on break address register matches. Clear BRKE by writing a logic
0 to bit 7. Reset clears the BRKE bit.
1 = Breaks enabled on 16-bit address match
0 = Breaks disabled on 16-bit address match
BRKA — Break Active Bit
This read/write status and control bit is set when a break address match occurs. Writing a logic 1 to
BRKA generates a break interrupt. Clear BRKA by writing a logic 0 to it before exiting the break routine.
Reset clears the BRKA bit.
1 = When read, break address match
0 = When read, no break address match
18.2.3.2 Break Address Registers
The break address registers (BRKH and BRKL) contain the high and low bytes of the desired breakpoint
address. Reset clears the break address registers.
Address:
Read:
Write:
Reset:
$FE0C
Bit 7
6
5
4
3
2
1
Bit 0
Bit 15
14
13
12
11
10
9
Bit 8
0
0
0
0
0
0
0
0
Figure 18-4. Break Address Register High (BRKH)
Address:
Read:
Write:
Reset:
$FE0D
Bit 7
6
5
4
3
2
1
Bit 0
Bit 7
6
5
4
3
2
1
Bit 0
0
0
0
0
0
0
0
0
Figure 18-5. Break Address Register Low (BRKL)
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
254
Freescale Semiconductor
Monitor ROM (MON)
18.2.3.3 Break Status Register
The break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode.
The flag is useful in applications requiring a return to wait mode after exiting from a break interrupt.
Address:
Read:
Write:
$FE00
Bit 7
6
5
4
3
2
1
Bit 0
R
R
R
R
R
R
BW
R
0
Reset:
Figure 18-6. SIM Break Status Register (SBSR)
BW — Break Wait Bit
This read/write bit is set when a break interrupt causes an exit from wait mode. Clear BW by writing a
logic 0 to it. Reset clears BW.
1 = Break interrupt during wait mode
0 = No break interrupt during wait mode
BW can be read within the break interrupt routine. The user can modify the return address on the stack
by subtracting 1 from it.
18.2.3.4 Break Flag Control Register
The 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 18-7. SIM Break Flag Control Register (SBFCR)
BCFE — Break Clear Flag Enable Bit
This read/write bit enables software to clear status bits by accessing status registers while the MCU is
in a break state. To clear status bits during the break state, the BCFE bit must be set.
1 = Status bits clearable during break
0 = Status bits not clearable during break
18.3 Monitor ROM (MON)
The monitor ROM (MON) allows complete testing of the microcontroller unit (MCU) through a single-wire
interface with a host computer. Monitor mode entry can be achieved without the use of VTST as long as
vector addresses $FFFE and $FFFF are blank, thus reducing the hardware requirements for in-circuit
programming.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
255
Development Support
Features include:
• Normal user-mode pin functionality
• One pin dedicated to serial communication between monitor ROM and host computer
• Standard mark/space non-return-to-zero (NRZ) communication with host computer
• 4800 baud–28.8 Kbaud communication with host computer
• Execution of code in random-access memory (RAM) or ROM
• FLASH programming
18.3.1 Functional Description
The monitor ROM receives and executes commands from a host computer. Figure 18-8 shows a sample
circuit used to enter monitor mode and communicate with a host computer via a standard RS-232
interface.
Simple monitor commands can access any memory address. In monitor mode, the MCU can execute
host-computer code in RAM while all MCU pins retain normal operating mode functions. All
communication between the host computer and the MCU is through the PTA0 pin. A level-shifting and
multiplexing interface is required between PTA0 and the host computer. PTA0 is used in a wired-OR
configuration and requires a pullup resistor.
18.3.1.1 Entering Monitor Mode
There are two methods for entering monitor:
• The first is the traditional M68HC08 method where VDD + VHI is applied to IRQ1 and the mode pins
are configured appropriately.
• A second method, intended for in-circuit programming applications, will force entry into monitor
mode without requiring high voltage on the IRQ1 pin when the reset vector locations of the FLASH
are erased ($FF).
NOTE
For both methods, holding the PTC2 pin low when entering monitor mode
causes a bypass of a divide-by-two stage at the oscillator. The CGMOUT
frequency is equal to the CGMXCLK frequency, and the OSC1 input
directly generates internal bus clocks. In this case, the OSC1 signal must
have a 50 percent duty cycle at maximum bus frequency.
Table 18-1 is a summary of the differences between user mode and monitor mode.
Table 18-1. Mode Differences
Functions
Modes
COP
Rest
Vector High
Reset
Vector Low
Break
Vector High
Break
Vector Low
SWI
Vector High
SWI
Vector Low
User
Enabled
$FFFE
$FFFF
$FFFC
$FFFD
$FFFC
$FFFD
Monitor
Disabled(1)
$FEFE
$FEFF
$FEFC
$FEFD
$FEFC
$FEFD
1. If the high voltage (VDD + VHI) is removed from the IRQ1 pin or the RST pin, the SIM asserts its COP enable output. The
COP is a mask option enabled or disabled by the COPD bit in the configuration register.
18.3.1.2 Normal Monitor Mode
Table 18-2 shows the pin conditions for entering monitor mode.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
256
Freescale Semiconductor
Monitor ROM (MON)
VDD
10 kΩ
MC68HC908MR16/
MC68HC908MR32
S1
RST
0.1 µF
VHI
10 kΩ
IRQ
VDDA
1
10 µF
MC145407
VDDA
20
+
+
3
18
4
17
0.1 µF
10 µF
VDDAD
VDDAD
0.1 µF
10 µF
+
2
19
+
10 µF
VREFH
VDD
VREFH
0.1 µF
CGMXFC
0.02 µF
DB-25
2
5
16
3
6
15
OSC1
X1
4.9152 MHz
20 pF
7
10 MΩ
OSC2
VDD
1
MC74HC125
VREFL
VSSAD
VSSA
PWMGND
VSS
20 pF
14
2
3
6
5
VDD
VDD
4
7
0.1 µF
VDD
VDD
10 kΩ
10 kΩ
A
B
PTA0
PTA7
PTC2
S3
VDD
S2 Position A — Bus clock = CGMXCLK ÷ 4 or CGMVCLK ÷ 4
S2 Position B — Bus clock = CGMXCLK ÷ 2
S3 Position A — Parallel communication
S3 Position B — Serial communication
VDD
10 kΩ
10 kΩ
A
S2
B
PTC3
PTC4
Figure 18-8. Monitor Mode Circuit
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
257
Development Support
258
Table 18-2. Monitor Mode Signal Requirements and Options
For Serial
PTC2 External
Bus
CGMOUT
(S2) Clock(1)
Frequency
Communication(2)
RESET
(S1)
$FFFE
/$FFFF
X
GND
X
X
X
X
X
X
0
0
Disabled
VTST
VDD
or
VTST
X
OFF
1
0
0
4.9152
MHz
4.9152
MHz
2.4576
MHz
Disabled
VTST
VDD
or
VTST
X
9.8304
MHz
4.9152
MHz
2.4576
MHz
Disabled
VDD
VDD
$FFFF
Blank
OFF
9.8304
MHz
4.9152
MHz
2.4576
MHz
Disabled
VDD
or
GND
VTST
$FFFF
Blank
OFF
X
X
X
X
—
—
VDD
or
GND
VDD
or
VTST
Non-$FF
OFF
Programmed
X
X
X
X
—
—
IRQ
PLL PTC3 PTC4
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
OFF
1
X
0
X
1
X
1. External clock is derived by a 32.768 kHz crystal or a 4.9152/9.8304 MHz off-chip oscillator.
2. DNA = does not apply, X = don’t care
3. PAT0 = 1 if serial communication; PTA0 = X if parallel communication
4. PTA7 = 0 → serial, PTA7 = 1 → parallel communication for security code entry
COP
Comment
Baud
PTA7
PTA0
(S3) Rate(3) (4)
X
X
0
No operation until reset goes high
1
0
9600
X
1
DNA
1
0
9600
X
1
DNA
1
0
9600
X
1
DNA
Enabled
X
X
—
Enters user mode — will encounter an
illegal address reset
Enabled
X
X
—
Enters user mode
PTC3 and PTC2 voltages only required if
IRQ = VTST; PTC2 determines frequency
divider
PTC3 and PTC2 voltages only required if
IRQ = VTST; PTC2 determines frequency
divider
External frequency always divided by 4
Freescale Semiconductor
Monitor ROM (MON)
Enter monitor mode by either:
• Executing a software interrupt instruction (SWI) or
• Applying a logic 0 and then a logic 1 to the RST pin
Once out of reset, the MCU waits for the host to send eight security bytes. After receiving the security
bytes, the MCU sends a break signal (10 consecutive logic 0s) to the host computer, indicating that it is
ready to receive a command. The break signal also provides a timing reference to allow the host to
determine the necessary baud rate.
Monitor mode uses alternate vectors for reset and SWI. The alternate vectors are in the $FE page instead
of the $FF page and allow code execution from the internal monitor firmware instead of user code. The
computer operating properly (COP) module is disabled in monitor mode as long as VHI is applied to either
the IRQ pin or the RST pin. (See Chapter 14 System Integration Module (SIM) for more information on
modes of operation.)
18.3.1.3 Forced Monitor Mode
If the voltage applied to the IRQ1 is less than VDD + VHI the MCU will come out of reset in user mode. The
MENRST module is monitoring the reset vector fetches and will assert an internal reset if it detects that
the reset vectors are erased ($FF). When the MCU comes out of reset, it is forced into monitor mode
without requiring high voltage on the IRQ1 pin.
The COP module is disabled in forced monitor mode. Any reset other than a POR reset will automatically
force the MCU to come back to the forced monitor mode.
18.3.1.4 Data Format
Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format.
(See Figure 18-9 and Figure 18-10.)
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
NEXT
START
BIT
Figure 18-9. Monitor Data Format
$A5
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
BREAK
START
BIT
BIT 0
BIT 1
BIT 2
BIT 3
BIT 4
BIT 5
BIT 6
BIT 7
STOP
BIT
STOP
BIT
NEXT
START
BIT
NEXT
START
BIT
Figure 18-10. Sample Monitor Waveforms
The data transmit and receive rate can be anywhere from 4800 baud to 28.8 Kbaud. Transmit and receive
baud rates must be identical.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
259
Development Support
18.3.1.5 Echoing
As shown in Figure 18-11, the monitor ROM immediately echoes each received byte back to the PTA0
pin for error checking.
SENT TO
MONITOR
READ
READ
ADDR. HIGH ADDR. HIGH
ADDR. LOW
ADDR. LOW
ECHO
DATA
RESULT
Figure 18-11. Read Transaction
Any result of a command appears after the echo of the last byte of the command.
18.3.1.6 Break Signal
A start bit followed by nine low bits is a break signal. See Figure 18-12. When the monitor receives a break
signal, it drives the PTA0 pin high for the duration of two bits before echoing the break signal.
MISSING STOP BIT
2--STOP-BIT DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 18-12. Break Transaction
18.3.1.7 Commands
The monitor ROM uses these commands (see Table 18-3–Table 18-8):
• READ, read memory
• WRITE, write memory
• IREAD, indexed read
• IWRITE, indexed write
• READSP, read stack pointer
• RUN, run user program
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
260
Freescale Semiconductor
Monitor ROM (MON)
Table 18-3. 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
ADDRESS
HIGH
READ
ADDRESS
HIGH
ADDRESS
LOW
ADDRESS
LOW
DATA
ECHO
RETURN
Table 18-4. 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 18-5. IREAD (Indexed Read) Command
Description
Operand
Data Returned
Opcode
Read next 2 bytes in memory from last address accessed
2-byte address in high byte:low byte order
Returns contents of next two addresses
$1A
Command Sequence
FROM HOST
IREAD
ECHO
IREAD
DATA
DATA
RETURN
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
261
Development Support
Table 18-6. IWRITE (Indexed Write) Command
Description
Write to last address accessed + 1
Operand
Single data byte
Data Returned
Opcode
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.
Table 18-7. 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
ECHO
SP
LOW
RETURN
Table 18-8. RUN (Run User Program) Command
Description
Operand
Data Returned
Opcode
Executes PULH and RTI instructions
None
None
$28
Command Sequence
FROM HOST
RUN
RUN
ECHO
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
262
Freescale Semiconductor
Monitor ROM (MON)
18.3.1.8 Baud Rate
With a 4.9152-MHz crystal and the PTC2 pin at logic 1 during reset, data is transferred between the
monitor and host at 4800 baud. If the PTC2 pin is at logic 0 during reset, the monitor baud rate is 9600.
See Table 18-9.
Table 18-9. Monitor Baud Rate Selection
VCO Frequency Multiplier (N)
Monitor baud rate
1
2
3
4
5
6
4800
9600
14,400
19,200
24,000
28,800
18.3.2 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 18-13.)
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.
To determine whether the security code entered is correct, check to see if bit 6 of RAM address $60 is
set. If it is, then the correct security code has been entered and FLASH can be accessed.
If the security sequence fails, the device can be reset (via power-pin reset only) and brought up in monitor
mode to attempt another entry. After failing the security sequence, the FLASH mode can also be bulk
erased by executing an erase routine that was downloaded into internal RAM. The bulk erase operation
clears the security code locations so that all eight security bytes become $FF.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
263
Development Support
VDD
4096 + 32 CGMXCLK CYCLES
RST
24 BUS CYCLES
PA7
COMMAND
BYTE 8
BYTE 2
BYTE 1
256 BUS CYCLES (MINIMUM)
FROM HOST
PA0
3
1
1
1
3
2
1
NOTES:
1 = Echo delay, 2 bit times
2 = Data return delay, 2 bit times
3 = Wait 1 bit time before sending next byte.
COMMAND ECHO
BREAK
BYTE 8 ECHO
BYTE 2 ECHO
BYTE 1 ECHO
FROM MCU
Figure 18-13. Monitor Mode Entry Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
264
Freescale Semiconductor
Chapter 19
Electrical Specifications
19.1 Introduction
This section contains electrical and timing specifications.
19.2 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the microcontroller unit (MCU) can be exposed without
permanently damaging it.
NOTE
This device is not guaranteed to operate properly at the maximum ratings. For guaranteed operating
conditions, refer to 19.5 DC Electrical Characteristics.
Characteristic(1)
Symbol
Value
Unit
Supply voltage
VDD
–0.3 to +6.0
V
Input voltage
VIn
VSS –0.3 to
VDD +0.3
V
Input high voltage
VHI
VDD + 4 maximum
V
I
±25
mA
Storage temperature
TSTG
–55 to +150
°C
Maximum current out of VSS
IMVSS
100
mA
Maximum current into VDD
IMVDD
100
mA
Maximum current per pin excluding VDD and VSS
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).
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
265
Electrical Specifications
19.3 Functional Operating Range
Characteristic
Symbol
Value
Unit
TA
–40 to 85
–40 to 105
°C
VDD
5.0 ± 10%
V
Symbol
Value
Unit
Thermal resistance,
64-pin QFP
θJA
76
°C/W
I/O pin power dissipation
PI/O
User determined
W
Power dissipation(1)
PD
PD = (IDD x VDD) + PI/O =
K/(TJ + 273°C)
W
Constant(2)
K
Average junction temperature
Operating temperature range(1)
MC68HC908MR24CFU
MC68HC908MR24VFU
Operating voltage range
1. See Freescale representative for temperature availability.
C = Extended temperature range (–40°C to +85°C)
V = Automotive temperature range (–40°C to +105°C)
19.4 Thermal Characteristics
Characteristic
Maximum junction temperature
PD x (TA + 273°C)
+ PD2 x θJA
W/°C
TJ
TA + (PD x θJA)
°C
TJM
125
°C
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.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
266
Freescale Semiconductor
DC Electrical Characteristics
19.5 DC Electrical Characteristics
Characteristic(1)
Symbol
Min
Typ(2)
Max
Unit
Output high voltage
(ILoad = –2.0 mA) all I/O pins
VOH
VDD –0.8
—
—
V
Output low voltage
(ILoad = 1.6 mA) all I/O pins
VOL
—
—
0.4
V
PWM pin output source current
(VOH = VDD –0.8 V)
IOH
–7
—
—
mA
PWM pin output sink current (VOL = 0.8 V)
IOL
20
—
—
mA
Input high voltage, all ports, IRQs, RESET, OSC1
VIH
0.7 x VDD
—
VDD
V
Input low voltage, all ports, IRQs, RESET, OSC1
VIL
VSS
—
0.3 x VDD
V
—
—
—
—
—
—
30
12
700
mA
mA
µA
VDD supply current
Run(3)
Wait(4)
Stop(5)
IDD
I/O ports high-impedance leakage current
IIL
—
—
±10
µA
Input current (input only pins)
IIn
—
—
±1
µA
Capacitance
Ports (as input or output)
COut
CIn
—
—
—
—
12
8
pF
Low-voltage inhibit reset(6)
VLVR1
4.0
4.35
4.65
V
Low-voltage reset/recover hysteresis
VLVH1
40
90
150
mV
Low-voltage inhibit reset recovery
(VREC1 = VLVR1 + VLVH1)
VREC1
4.04
4.5
4.75
V
Low-voltage inhibit reset
VLVR2
3.85
4.15
4.45
V
Low-voltage reset/recover hysteresis
VLVH2
150
210
250
mV
Low-voltage inhibit reset recovery
(VREC2 = VLVR2 + VLVH2)
VREC2
4.0
4.4
4.6
V
POR re-arm voltage(7)
VPOR
0
—
100
mV
POR rise time ramp rate(8)
RPOR
0.035
—
—
V/ms
VPORRST
0
700
800
V
VHi
VDD + 2.5
—
8.0
V
POR reset
voltage(9)
Monitor mode entry voltage (on IRQ)
1. VDD = 5.0 Vdc ± 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted.
2. Typical values reflect average measurements at midpoint of voltage range, 25°C only.
3. Run (operating) IDD measured using external square wave clock source (fOSC = 8.2 MHz). All inputs 0.2 V from rail; no dc
loads; less than 100 pF on all outputs. CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly
affects run IDD; measured with all modules enabled
4. Wait IDD measured using external square wave clock source (fOSC = 8.2 MHz); all inputs 0.2 V from rail; no dc loads; less
than 100 pF on all outputs. CL = 20 pF on OSC2; all ports configured as inputs; OSC2 capacitance linearly affects wait IDD;
measured with PLL and LVI enabled.
5. Stop IDD measured with PLL and LVI disengaged, OCS1 grounded, no port pins sourcing current. It is measured through
combination of VDD, VDDAD, and VDDA.
6. The low-voltage inhibit reset is software selectable. Refer to Chapter 9 Low-Voltage Inhibit (LVI).
7. Maximum is highest voltage that POR is guaranteed.
8. If minimum VDD is not reached before the internal POR is released, RST must be driven low externally until minimum VDD
is reached.
9. Maximum is highest voltage that POR is possible.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
267
Electrical Specifications
19.6 FLASH Memory Characteristics
Characteristic
Symbol
Min
Typ
Max
Unit
VRDR
1.3
—
—
V
—
1
—
—
MHz
fRead(1)
0
—
8M
Hz
FLASH page erase time
<1 K cycles
>1 K cycles
tErase
0.9
3.6
1
4
1.1
5.5
ms
FLASH mass erase time
tMErase
4
—
—
ms
FLASH PGM/ERASE to HVEN setup time
tNVS
10
—
—
µs
FLASH high-voltage hold time
tNVH
5
—
—
µs
FLASH high-voltage hold time (mass erase)
tNVHL
100
—
—
µs
FLASH program hold time
tPGS
5
—
—
µs
FLASH program time
tPROG
30
—
40
µs
FLASH return to read time
tRCV(2)
1
—
—
µs
FLASH cumulative program HV period
tHV(3)
—
—
4
ms
FLASH endurance(4)
—
10 k
100 k
—
Cycles
FLASH data retention time(5)
—
15
100
—
Years
RAM data retention voltage
FLASH program bus clock frequency
FLASH read bus clock frequency
1. fRead is defined as the frequency range for which the FLASH memory can be read.
2. tRCV is defined as the time it needs before the FLASH can be read after turning off the high voltage charge pump, by
clearing HVEN to 0.
3. 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.
4. Typical endurance was evaluated for this product family. For additional information on how Freescale defines Typical
Endurance, please refer to Engineering Bulletin EB619.
5. Typical data retention values are based on intrinsic capability of the technology measured at high temperature and de-rated
to 25°C using the Arrhenius equation. For additional information on how Freescale defines Typical Data Retention, please
refer to Engineering Bulletin EB618.
19.7 Control Timing
Characteristic(1)
Symbol
Min
Max
Unit
Frequency of operation(2)
Crystal option
External clock option(3)
fOSC
1
dc(4)
8
32.8
MHz
Internal operating frequency
fOP
—
8.2
MHz
RESET input pulse width low(5)
tIRL
50
—
ns
1. VDD = 5.0 Vdc ± 10%, VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VDD, unless otherwise noted
2. See 19.8 Serial Peripheral Interface Characteristics for more information.
3. No more than 10% duty cycle deviation from 50%.
4. Some modules may require a minimum frequency greater than dc for proper operation; see appropriate table for this
information.
5. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause a reset.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
268
Freescale Semiconductor
Serial Peripheral Interface Characteristics
19.8 Serial Peripheral Interface Characteristics
Diagram
Number(1)
Characteristic(2)
Symbol
Min
Max
Unit
Operating frequency
Master
Slave
fOP(M)
fOP(S)
fOP/128
fOP/2
MHz
dc
fOP
1
Cycle time
Master
Slave
tCYC(M)
tCYC(S)
2
1
128
—
tCYC
2
Enable lead time
tLead(S)
15
—
ns
3
Enable lag time
tLag(S)
15
—
ns
4
Clock (SPCK) high time
Master
Slave
tSCKH(M)
tSCKH(S)
100
50
—
—
ns
5
Clock (SPCK) low time
Master
Slave
tSCKL(M)
tSCKL(S)
100
50
—
—
ns
6
Data setup time (inputs)
Master
Slave
tSU(M)
tSU(S)
45
5
—
—
ns
7
Data hold time (inputs)
Master
Slave
tH(M)
tH(S)
0
15
—
—
ns
8
Access time, slave(3)
CPHA = 0
CHPA = 1
tA(CP0)
tA(CP1)
0
0
40
20
ns
9
Disable time, slave(4)
tDIS(S)
—
25
ns
10
Data valid time after enable edge
Master
Slave(5)
tV(M)
tV(S)
—
—
10
40
ns
1. VDD = 5.0 Vdc ± 10%, all timing is shown with respect to 20% VDD and 70% VDD, unless otherwise noted; assumes 100 pF
load on all SPI pins
2. Numbers refer to dimensions in Figure 19-1 and Figure 19-2.
3. Time to data active from high-impedance state
4. Hold time to high-impedance state
5. With 100 pF on all SPI pins
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
269
Electrical Specifications
SS
INPUT
SS PIN OF MASTER HELD HIGH
1
SPCK, CPOL = 0
OUTPUT
NOTE
SPCK, CPOL = 1
OUTPUT
NOTE
5
4
5
4
6
MISO
INPUT
MSB IN
BITS 6–1
10
11
MOSI
OUTPUT
MASTER MSB OUT
7
LSB IN
10
11
BITS 6–1
MASTER LSB OUT
Note: This first clock edge is generated internally, but is not seen at the SCK pin.
a) SPI Master Timing (CPHA = 0)
SS
INPUT
SS PIN OF MASTER HELD HIGH
1
SPCK, CPOL = 0
OUTPUT
SPCK, CPOL = 1
OUTPUT
5
NOTE
4
5
NOTE
4
6
MISO
INPUT
10
MOSI
OUTPUT
MSB IN
BITS 6–1
11
MASTER MSB OUT
7
LSB IN
10
BITS 6–1
11
MASTER LSB OUT
Note: This last clock edge is generated internally, but is not seen at the SCK pin.
b) SPI Master Timing (CPHA = 1)
Figure 19-1. SPI Master Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
270
Freescale Semiconductor
Serial Peripheral Interface Characteristics
SS
INPUT
3
1
SPCK, CPOL = 0
INPUT
11
5
4
2
SPCK, CPOL = 1
INPUT
5
4
9
8
MISO
INPUT
SLAVE
MSB OUT
6
MOSI
OUTPUT
BITS 6–1
7
NOTE
11
11
10
MSB IN
SLAVE LSB OUT
BITS 6–1
LSB IN
Note: Not defined, but normally MSB of character just received
a) SPI Slave Timing (CPHA = 0)
SS
INPUT
1
SPCK, CPOL = 0
INPUT
5
4
2
3
SPCK, CPOL = 1
INPUT
8
MISO
INPUT
MOSI
OUTPUT
5
4
10
NOTE
9
SLAVE
MSB OUT
6
7
BITS 6–1
11
10
MSB IN
SLAVE LSB OUT
BITS 6–1
LSB IN
Note: Not defined, but normally LSB of character previously transmitted
b) SPI Slave Timing (CPHA = 1)
Figure 19-2. SPI Slave Timing
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
271
Electrical Specifications
19.9 TImer Interface Module Characteristics
Characteristic
Input capture pulse width
Input clock pulse width
Symbol
Min
Max
Unit
tTIH, tTIL
125
—
ns
tTCH, tTCL
(1/fOP) + 5
—
ns
19.10 Clock Generation Module Component Specifications
Characteristic
Symbol
Min
Typ
Max
Notes
Crystal load capacitance
CL
—
—
—
Consult crystal
manufacturing data
Crystal fixed capacitance
C1
—
2 * CL
—
Consult crystal
manufacturing data
Crystal tuning capacitance
C2
—
2 * CL
—
Consult crystal
manufacturing data
Feedback bias resistor
RB
—
22 MΩ
—
Series resistor
RS
0
330 kΩ
1 MΩ
Filter capacitor
CF
—
CFACT*
(VDDA/fXCLK)
—
CBYP
Bypass capacitor
0.1 µF
—
Not required
CBYP must provide low ac
impedance from
f = fXCLK/100 to 100*fVCLK, so
series resistance must be
considered
—
19.11 CGM Operating Conditions
Characteristic
Symbol
Min
Typ
Max
Unit
Crystal reference frequency
fXCLK
1
—
8
MHz
Range nominal multiplier
fNOM
—
4.9152
—
MHz
VCO center-of-range frequency
fVRS
4.9152
—
32.8
MHz
VCO frequency multiplier
N
1
—
15
—
VCO center of range multiplier
L
1
—
15
—
fVCLK
fVRSMIN
—
fVRSMAX
—
VCO operating frequency
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
272
Freescale Semiconductor
CGM Acquisition/Lock Time Specifications
19.12 CGM Acquisition/Lock Time Specifications
Description
Symbol
Min
Typ
Max
Notes
Filter capacitor multiply factor
CFACT
—
0.0154
—
F/sV
Acquisition mode time factor
KACQ
—
0.1135
—
V
Tracking mode time factor
KTRK
—
0.0174
—
V
Manual mode time to stable
tACQ
—
(8*VDDA)/
(fXCLK*KACQ)
—
If CF chosen
correctly
tAL
—
(4*VDDA)/
(fXCLK*KTRK)
—
If CF chosen
correctly
Manual acquisition time
tLock
—
tACQ+tAL
—
Tracking mode entry frequency
tolerance
∆TRK
0
—
± 3.6%
Acquisition mode entry frequency
tolerance
∆ACQ
±6.3%
—
± 7.2%
Lock entry frequency tolerance
∆Lock
0
—
± 0.9%
Lock exit frequency tolerance
∆UNL
±0.9%
—
± 1.8%
Reference cycles per acquisition mode
measurement
nACQ
—
32
—
Reference cycles per tracking mode
measurement
nTRK
—
128
—
Automatic mode time to stable
tACQ
nACQ/fXCLK
(8*VDDA)/
(fXCLK*KACQ)
—
If CF chosen
correctly
tAL
nTRK/fXCLK
(4*VDDA)/
(fXCLK*KTRK)
—
If CF chosen
correctly
tLock
—
tACQ+tAL
—
fJ
0
—
± (fXCLK)
*(0.025%)
*(N/4)
Manual stable to lock time
Automatic stable to lock time
Automatic lock time
PLL jitter (deviation of average bus
frequency over 2 ms)
N = VCO
freq. mult.
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
Freescale Semiconductor
273
Electrical Specifications
19.13 Analog-to-Digital Converter (ADC) Characteristics
Characteristic
Symbol
Min
Typ
Max
Unit
Notes
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 <= VDDAD
Resolution
BAD
10
—
10
Bits
Absolute accuracy
AAD
—
—
±4
LSB
Includes quantization
ADC internal clock
fADIC
500 k
—
1.048 M
Hz
tAIC = 1/fADIC
Conversion range
RAD
VSSAD
—
VDDAD
V
Power-up time
tADPU
16
—
—
tAIC cycles
Conversion time
tADC
16
—
17
tAIC cycles
Sample time
tADS
5
—
—
tAIC cycles
Monotonicity
MAD
Zero input reading
ZADI
000
—
003
Hex
VADIN = VSSAD
Full-scale reading
FADI
3FC
—
3FF
Hex
VADIN = VDDAD
Input capacitance
CADI
—
—
30
pF
Not tested
VREFH/VREFL current
IVREF
—
1.6
—
mA
Absolute accuracy
(8-bit truncation mode)
AAD
—
—
±1
LSB
Quantization error
(8-bit truncation mode)
—
—
—
+ 7/8
– 1/8
LSB
Guaranteed
Includes quantization
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
274
Freescale Semiconductor
Chapter 20
Ordering Information and Mechanical Specifications
20.1 Introduction
This section provides ordering information for the MC68HC908MR16 and MC68HC908MR32 along with
the dimensions for:
• 64-lead plastic quad flat pack (QFP)
• 56-pin shrink dual in-line package (SDIP)
The following figures show the latest package drawings at the time of this publication. To make sure that
you have the latest package specifications, contact your local Freescale Sales Office.
20.2 Order Numbers
Table 20-1. Order Numbers
MC Order Number(1)
Operating
Temperature Range
68HC908MR16CFU
68HC908MR16VFU
–40°C to +85°C
–40°C to +105°C
68HC908MR16CB
68HC908MR16VB
–40°C to +85°C
–40°C to +105°C
68HC908MR32CFU
68HC908MR32VFU
–40°C to +85°C
–40°C to +105°C
68HC908MR32CB
68HC908MR32VB
–40°C to +85°C
–40°C to +105°C
1. FU = quad flat pack
B = shrink dual in-line package
MC68HC908MR32XXX
FAMILY
PACKAGE DESIGNATOR
TEMPERATURE RANGE
Figure 20-1. Device Numbering System
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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Ordering Information and Mechanical Specifications
20.3 64-Pin Plastic Quad Flat Pack (QFP)
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56-Pin Shrink Dual In-Line Package (SDIP)
20.4 56-Pin Shrink Dual In-Line Package (SDIP)
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Ordering Information and Mechanical Specifications
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Appendix A
MC68HC908MR16
The information contained in this document pertains to the MC68HC908MR16 with the exception of that
shown in Figure A-1.
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279
MC68HC908MR16
$0000
↓
$005F
I/O REGISTERS — 96 BYTES
$0060
↓
$035F
RAM — 768 BYTES
$0360
↓
$7FFF
UNIMPLEMENTED — 31,904 BYTES
$8000
↓
$BEFF
FLASH — 16,128 BYTES
$BF00
↓
$FDFF
UNIMPLEMENTED — 16,128 BYTES
$FE00
SIM BREAK STATUS REGISTER (SBSR)
$FE01
SIM RESET STATUS REGISTER (SRSR)
$FE02
RESERVED
$FE03
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
$FE04
RESERVED
$FE05
RESERVED
$FE06
RESERVED
$FE07
RESERVED
$FE08
FLASH CONTROL REGISTER (FLCR)
$FE09
UNIMPLEMENTED
$FE0A
UNIMPLEMENTED
$FE0B
UNIMPLEMENTED
$FE0C
SIM BREAK ADDRESS REGISTER HIGH (BRKH)
$FE0D
SIM BREAK ADDRESS REGISTER LOW (BRKL)
$FE0E
SIM BREAK FLAG CONTROL REGISTER (SBFCR)
$FE0F
LVI STATUS AND CONTROL REGISTER (LVISCR)
$FE10
↓
$FEFF
MONITOR ROM — 240 BYTES
$FF00
↓
$FF7D
UNIMPLEMENTED — 126 BYTES
$FF7E
FLASH BLOCK PROTECT REGISTER (FLBPR)
$FF7F
↓
$FFD1
UNIMPLEMENTED — 83 BYTES
$FFD2
↓
$FFFF
VECTORS — 46 BYTES
Figure A-1. MC68HC908MR16 Memory Map
MC68HC908MR32 • MC68HC908MR16 Data Sheet, Rev. 6.1
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MC68HC908MR32
Rev. 6.1, 07/2005
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