Freescale MC68HC908QB8, MC68HC908QB4, MC68HC908QY8 DATA SHEET

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MC68HC908QB8 MC68HC908QB4 MC68HC908QY8

Data Sheet

M68HC08 Microcontrollers

MC68HC908QB8 Rev. 1 6/3/2005

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MC68HC908QB8 MC68HC908QB4 MC68HC908QY8

Data Sheet

To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify you have the latest information available, refer to:

http://freescale.com/

The following revision history table summarizes changes contained in this document. For your convenience, the page number designators have been linked to the appropriate location.

Revision History

Date

June 3,

2005

Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. This product incorporates SuperFlash® technology licensed from SST.

Freescale Semiconductor 3

Revision

Level

1 Initial full release N/A

MC68HC908QB8 Data Sheet, Rev. 1

Description

Page

Number(s)

Revision History

MC68HC908QB8 Data Sheet, Rev. 1

4 Freescale Semiconductor

List of Chapters

Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Chapter 2 Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23

Chapter 3 Analog-to-Digital Converter (ADC10) Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Chapter 4 Auto Wakeup Module (AWU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .51

Chapter 5 Configuration Register (CONFIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .57

Chapter 6 Computer Operating Properly (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .61

Chapter 7 Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .65

Chapter 8 External Interrupt (IRQ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .77

Chapter 9 Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .83

Chapter 10 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

Chapter 11 Oscillator Module (OSC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .93

Chapter 12 Input/Output Ports (PORTS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .103

Chapter 13 Enhanced Serial Communications Interface (ESCI) Module . . . . . . . . . . . . .109

Chapter 14 System Integration Module (SIM). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .139

Chapter 15 Serial Peripheral Interface (SPI) Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . .155

Chapter 16 Timer Interface Module (TIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .175

Chapter 17 Development Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .191

Chapter 18 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .207

Chapter 19 Ordering Information and Mechanical Specifications . . . . . . . . . . . . . . . . . .227

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List of Chapters

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Table of Contents

Chapter 1

General Description

1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

1.3 MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

1.4 Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.5 Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

1.6 Pin Function Priority. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22

Chapter 2

Memory

2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.2 Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.3 Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.4 Direct Page Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

2.5 Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30

2.6 FLASH Memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.6.1 FLASH Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

2.6.2 FLASH Page Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32

2.6.3 FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2.6.4 FLASH Program Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

2.6.5 FLASH Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

2.6.6 FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36

Chapter 3

Analog-to-Digital Converter (ADC10) Module

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

3.3.1 Clock Select and Divide Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

3.3.2 Input Select and Pin Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.3.3 Conversion Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.3.3.1 Initiating Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.3.3.2 Completing Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.3.3.3 Aborting Conversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40

3.3.3.4 Total Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41

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3.3.4 Sources of Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.3.4.1 Sampling Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.3.4.2 Pin Leakage Error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.3.4.3 Noise-Induced Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42

3.3.4.4 Code Width and Quantization Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.3.4.5 Linearity Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.3.4.6 Code Jitter, Non-Monotonicity and Missing Codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43

3.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.6 ADC10 During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

3.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

3.7.1 ADC10 Analog Power Pin (V

3.7.2 ADC10 Analog Ground Pin (V

3.7.3 ADC10 Voltage Reference High Pin (V

3.7.4 ADC10 Voltage Reference Low Pin (V

) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

DDA

). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

SSA

). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

REFH

) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

REFL

3.7.5 ADC10 Channel Pins (ADn). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.8 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.8.1 ADC10 Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46

3.8.2 ADC10 Result High Register (ADRH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.8.3 ADC10 Result Low Register (ADRL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

3.8.4 ADC10 Clock Register (ADCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Chapter 4

Auto Wakeup Module (AWU)

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

4.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

4.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.6 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.6.1 Port A I/O Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53

4.6.2 Keyboard Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

4.6.3 Keyboard Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54

4.6.4 Configuration Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

4.6.5 Configuration Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55

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8 Freescale Semiconductor

Chapter 5

Configuration Register (CONFIG)

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

5.2 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57

Chapter 6

Computer Operating Properly (COP)

6.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6.2 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61

6.3 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.3.1 BUSCLKX4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.3.2 STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.3.3 COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.3.4 Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.3.5 Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.3.6 COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62

6.3.7 COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.5 Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.7 COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

6.8 Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63

Chapter 7

Central Processor Unit (CPU)

7.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7.3 CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

7.3.1 Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

7.3.2 Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

7.3.3 Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

7.3.4 Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67

7.3.5 Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 68

7.4 Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.6 CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

7.7 Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70

7.8 Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75

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Chapter 8

External Interrupt (IRQ)

8.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

8.3.1 MODE = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

8.3.2 MODE = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79

8.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.6 IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

8.7.1 IRQ Input Pins (IRQ

8.8 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81

) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80

Chapter 9

Keyboard Interrupt Module (KBI)

9.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

9.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

9.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

9.3.1 Keyboard Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

9.3.1.1 MODEK = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84

9.3.1.2 MODEK = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 85

9.3.2 Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

9.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

9.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

9.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

9.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

9.6 KBI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86

9.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

9.7.1 KBI Input Pins (KBIx:KBI0). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

9.8 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

9.8.1 Keyboard Status and Control Register (KBSCR). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87

9.8.2 Keyboard Interrupt Enable Register (KBIER). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

9.8.3 Keyboard Interrupt Polarity Register (KBIPR) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

Chapter 10

Low-Voltage Inhibit (LVI)

10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

10.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

10.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

10.3.1 Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

10.3.2 Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

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10.3.3 LVI Hysteresis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

10.3.4 LVI Trip Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 90

10.4 LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

10.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

10.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

10.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

10.6 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Chapter 11

Oscillator Module (OSC)

11.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

11.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

11.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

11.3.1 Internal Signal Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.1.1 Oscillator Enable Signal (SIMOSCEN). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.1.2 XTAL Oscillator Clock (XTALCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.1.3 RC Oscillator Clock (RCCLK). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.1.4 Internal Oscillator Clock (INTCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.1.5 Bus Clock Times 4 (BUSCLKX4) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.1.6 Bus Clock Times 2 (BUSCLKX2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.2 Internal Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95

11.3.2.1 Internal Oscillator Trimming . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

11.3.2.2 Internal to External Clock Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

11.3.2.3 External to Internal Clock Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

11.3.3 External Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96

11.3.4 XTAL Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97

11.3.5 RC Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

11.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

11.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

11.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

11.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98

11.6 OSC During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

11.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

11.7.1 Oscillator Input Pin (OSC1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

11.7.2 Oscillator Output Pin (OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99

11.8 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

11.8.1 Oscillator Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100

11.8.2 Oscillator Trim Register (OSCTRIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

Chapter 12

Input/Output Ports (PORTS)

12.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

12.2 Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103

12.2.1 Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

12.2.2 Data Direction Register A. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104

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12.2.3 Port A Input Pullup Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105

12.2.4 Port A Summary Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

12.3 Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

12.3.1 Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106

12.3.2 Data Direction Register B. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107

12.3.3 Port B Input Pullup Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

12.3.4 Port B Summary Table. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108

Chapter 13

Enhanced Serial Communications Interface (ESCI) Module

13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

13.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109

13.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111

13.3.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

13.3.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112

13.3.2.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

13.3.2.2 Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

13.3.2.3 Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113

13.3.2.4 Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

13.3.2.5 Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

13.3.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

13.3.3.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

13.3.3.2 Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114

13.3.3.3 Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116

13.3.3.4 Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

13.3.3.5 Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

13.3.3.6 Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

13.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119

13.4.1 Transmitter Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

13.4.2 Receiver Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

13.4.3 Error Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

13.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

13.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120

13.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

13.6 ESCI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

13.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

13.7.1 ESCI Transmit Data (TxD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

13.7.2 ESCI Receive Data (RxD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

13.8 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121

13.8.1 ESCI Control Register 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122

13.8.2 ESCI Control Register 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123

13.8.3 ESCI Control Register 3. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

13.8.4 ESCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126

13.8.5 ESCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

13.8.6 ESCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129

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13.8.7 ESCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130

13.8.8 ESCI Prescaler Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131

13.9 ESCI Arbiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

13.9.1 ESCI Arbiter Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 135

13.9.2 ESCI Arbiter Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

13.9.3 Bit Time Measurement. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136

13.9.4 Arbitration Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138

Chapter 14

System Integration Module (SIM)

14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

14.2 RST

14.3 SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 140

14.3.1 Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

14.3.2 Clock Start-Up from POR. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

14.3.3 Clocks in Stop Mode and Wait Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

14.4 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

14.4.1 External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141

14.4.2 Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142

14.4.2.1 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

14.4.2.2 Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

14.4.2.3 Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143

14.4.2.4 Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

14.4.2.5 Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

14.5 SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

14.5.1 SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

14.5.2 SIM Counter During Stop Mode Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

14.5.3 SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144

14.6 Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

14.6.1 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

14.6.1.1 Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

14.6.1.2 SWI Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

14.6.2 Interrupt Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 148

14.6.2.1 Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

14.6.2.2 Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

14.6.2.3 Interrupt Status Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

14.6.3 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

14.6.4 Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

14.6.5 Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

14.7 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

14.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150

14.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 151

14.8 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

14.8.1 SIM Reset Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 152

14.8.2 Break Flag Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153

and IRQ Pins Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139

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Chapter 15

Serial Peripheral Interface (SPI) Module

15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

15.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155

15.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157

15.3.1 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

15.3.2 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 158

15.3.3 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

15.3.3.1 Clock Phase and Polarity Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

15.3.3.2 Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159

15.3.3.3 Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160

15.3.3.4 Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161

15.3.4 Queuing Transmission Data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163

15.3.5 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

15.3.6 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

15.3.6.1 Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 164

15.3.6.2 Mode Fault Error. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166

15.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 167

15.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

15.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

15.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

15.6 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168

15.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

15.7.1 MISO (Master In/Slave Out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

15.7.2 MOSI (Master Out/Slave In). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

15.7.3 SPSCK (Serial Clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

15.7.4 SS

15.8 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170

15.8.1 SPI Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171

15.8.2 SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172

15.8.3 SPI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174

(Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

Chapter 16

Timer Interface Module (TIM)

16.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

16.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

16.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

16.3.1 TIM Counter Prescaler. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175

16.3.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176

16.3.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 177

16.3.3.1 Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

16.3.3.2 Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178

16.3.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

16.3.4.1 Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179

16.3.4.2 Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 180

16.3.4.3 PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181

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16.4 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

16.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

16.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

16.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

16.6 TIM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182

16.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

16.7.1 TIM Channel I/O Pins (TCH3:TCH0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

16.7.2 TIM Clock Pin (TCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

16.8 Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

16.8.1 TIM Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183

16.8.2 TIM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

16.8.3 TIM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185

16.8.4 TIM Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 186

16.8.5 TIM Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 188

Chapter 17

Development Support

17.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

17.2 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

17.2.1 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191

17.2.1.1 Flag Protection During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

17.2.1.2 TIM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

17.2.1.3 COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 193

17.2.2 Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

17.2.2.1 Break Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

17.2.2.2 Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 194

17.2.2.3 Break Auxiliary Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

17.2.2.4 Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

17.2.2.5 Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195

17.2.3 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

17.3 Monitor Module (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

17.3.1 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 196

17.3.1.1 Normal Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 200

17.3.1.2 Forced Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

17.3.1.3 Monitor Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201

17.3.1.4 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

17.3.1.5 Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

17.3.1.6 Baud Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

17.3.1.7 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202

17.3.2 Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206

Chapter 18

Electrical Specifications

18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

18.2 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207

18.3 Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

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Table of Contents

18.4 Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208

18.5 5-V DC Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209

18.6 Typical 5-V Output Drive Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210

18.7 5-V Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211

18.8 3-V DC Electrical Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212

18.9 Typical 3-V Output Drive Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213

18.10 3-V Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214

18.11 Oscillator Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215

18.12 Supply Current Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 217

18.13 ADC10 Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 219

18.14 5.0-Volt SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221

18.15 3.0-Volt SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222

18.16 Timer Interface Module Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225

18.17 Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 226

Chapter 19

Ordering Information and Mechanical Specifications

19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

19.2 MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

19.3 Package Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 227

MC68HC908QB8 Data Sheet, Rev. 1

16 Freescale Semiconductor

Chapter 1 General Description

1.1 Introduction

The MC68HC908QB8 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.

0.4

Table 1-1. Summary of Device Variations

Device

MC68HC908QB8 8K/256 bytes 10 channel, 10 bit 4 Yes Yes 16 pins

MC68HC908QB4 4K/128 bytes 10 channel, 10 bit 4 Yes Yes 16 pins

MC68HC908QY8 8K/256 bytes 4 channel, 10 bit 2 No No 16 pins

FLASH/RAM

Memory Size

ADC

16-Bit Timer

Channels

ESCI SPI

1.2 Features

Features include:

• High-performance M68HC08 CPU core

• Fully upward-compatible object code with M68HC05 Family

• 5-V and 3-V operating voltages (V

• 8-MHz internal bus operation at 5 V, 4-MHz at 3 V

• Trimmable internal oscillator – Software selectable 1 MHz, 2 MHz, or 3.2 MHz internal bus operation – 8-bit trim capability – ± 25% untrimmed – Trimmable to approximately 0.4%

• Software selectable crystal oscillator range, 32–100 kHz, 1–8 MHz, and 8–32 MHz

• Software configurable input clock from either internal or external source

• Auto wakeup from STOP capability using dedicated internal 32-kHz RC or bus clock source

• On-chip in-application programmable FLASH memory – Internal program/erase voltage generation – Monitor ROM containing user callable program/erase routines – FLASH security

(2)

)

(1)

Count

1. See 18.11 Oscillator Characteristics for internal oscillator specifications

2. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for unauthorized users.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 17

General Description

• On-chip random-access memory (RAM)

• Enhanced serial communications interface (ESCI) module

• Serial peripheral interface (SPI) module

• 4-channel, 16-bit timer interface (TIM) module

• 10-channel, 10-bit analog-to-digital converter (ADC) with internal bandgap reference channel (ADC10)

• Up to 13 bidirectional input/output (I/O) lines and one input only: – Six shared with KBI – Ten shared with ADC – Four shared with TIM – Two shared with ESCI – Four shared with SPI – One input only shared with IRQ – High current sink/source capability on all port pins – Selectable pullups on all ports, selectable on an individual bit basis – Three-state ability on all port pins

• 6-bit keyboard interrupt with wakeup feature (KBI) – Programmable for rising/falling or high/low level detect

• Low-voltage inhibit (LVI) module features: – Software selectable trip point

• System protection features: – Computer operating properly (COP) watchdog – Low-voltage detection with reset – Illegal opcode detection with reset – Illegal address detection with reset

• External asynchronous interrupt pin with internal pullup (IRQ

) shared with general-purpose input

• Master asynchronous reset pin with internal pullup (RST

) shared with general-purpose input/output

(I/O) pin

• Memory mapped I/O registers

• Power saving stop and wait modes

• MC68HC908QB8, MC68HC908QB4 and MC68HC908QY8 are available in these packages: – 16-pin plastic dual in-line package (PDIP) – 16-pin small outline integrated circuit (SOIC) package – 16-pin thin shrink small outline packages (TSSOP)

Features of the CPU08 include the following:

• Enhanced HC05 programming model

• Extensive loop control functions

• 16 addressing modes (eight more than the HC05)

• 16-bit index register and stack pointer

• Memory-to-memory data transfers

• Fast 8 × 8 multiply instruction

• Fast 16/8 divide instruction

• Binary-coded decimal (BCD) instructions

• Optimization for controller applications

• Efficient C language support

MC68HC908QB8 Data Sheet, Rev. 1

18 Freescale Semiconductor

1.3 MCU Block Diagram

Figure 1-1 shows the structure of the MC68HC908QB8.

PTA0/TCH0/AD0/KBI0

PTA1/TCH1/AD1/KBI1

PTA2/IRQ

/KBI2/TCLK

PTA

PTA3/RST

PTA4/OSC2/AD2/KBI4

PTA5/OSC1/AD3/KBI5

PTB0/SPSCK/AD4

PTB1/MOSI/AD5 PTB2/MISO/AD6

/KBI3

PTB3/SS

PTB4/RxD/AD8

PTB5/TxD/AD9

/AD7

PTB6/TCH2 PTB7/TCH3

DDRA

M68HC08 CPU

PTB

DDRB

MCU Block Diagram

CLOCK

GENERATOR

KEYBOARD INTERRUPT

MODULE

SINGLE INTERRUPT

MODULE

AUTO WAKEUP

MODULE

LOW-VOLTAGE

INHIBIT

4-CHANNEL 16-BIT

TIMER MODULE

MC68HC908QB8

256 BYTES

USER RAM

POWER SUPPLY

RST, IRQ: Pins have internal pull up device All port pins have programmable pull up device PTA[0:5]: Higher current sink and source capability

Figure 1-1. Block Diagram

MC68HC908QB8

8192 BYTES

USER FLASH

COP

MODULE

10-CHANNEL

10-BIT ADC

ENHANCED SERIAL COMMUNICATIONS

INTERFACE MODULE

SERIAL PERIPHERAL

INTERFACE

DEVELOPMENT SUPPORT

MONITOR ROM

BREAK MODULE

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 19

General Description

1.4 Pin Assignments

The MC68HC908QB8, MC68HC908QB4, and MC68HC908QY8 are available in 16-pin packages.

Figure 1-2 shows the pin assignment for these packages.

PTB7

PTB6

PTA5/OSC1/AD3/KBI5

PTA4/OSC2/AD2/KBI4

PTB5

PTB4

PTA3/RST

PTA5/OSC1/AD3/KBI5

PTA4/OSC2/AD2/KBI4

PTA3/RST

/KBI3

PTB7/TCH3

PTB6/TCH2

PTB5/Tx/AD9

PTB4/Rx/AD8

/KBI3

MC68HC908QB8/MC68HC908QB4 PDIP/SOIC

16-PIN ASSIGNMENT

MC68HC908QY8 PDIP/SOIC

16-PIN ASSIGNMENT

PTB0

PTB1

PTA0/TCH0/AD0/KBI0

PTA1/TCH1/AD1/KBI1

PTB2

PTB3

PTA2/IRQ

/KBI2/TCLK

PTB0/SCK/AD4

PTB1/MOSI/AD5

PTA0/TCH0/AD0/KBI0

PTA1/TCH1/AD1/KBI1

PTB2/MISO/AD6

/AD7

PTB3/SS

/KBI2/TCLK

PTA2/IRQ

PTA0/TCH0/AD0/KBI0

PTB1 PTB0

PTB7 PTB6

PTA5/OSC1/AD3/KBI5

PTA0/TCH0/AD0/KBI0

PTB1/MOSI/AD5

PTB0/SCK/AD4

PTB7/TCH3 PTB6/TCH2

PTA5/OSC1/AD3/KBI5

MC68HC908QB8/MC68HC908QB4 TSSOP

Figure 1-2. MCU Pin Assignments

1 2 3 4 5 6 7 8

16-PIN ASSIGNMENT

MC68HC908QY8 TSSOP

1 2 3 4 5 6 7 8

16-PIN ASSIGNMENT

16 15 14 13 12 11 10

PTA1/TCH1/AD1/KBI1 PTB2 PTB3 PTA2/IRQ PTA3/RST PTB4 PTB5 PTA4/OSC2/AD2/KBI4

/KBI2/TCLK

/KBI3

PTA1/TCH1/AD1/KBI1 PTB2/MISO/AD6

/AD7

PTB3/SS PTA2/IRQ

/KBI2/TCLK PTA3/RST PTB4//Rx/AD8 PTB5/Tx/AD9 PTA4/OSC2/AD2/KBI4

/KBI3

1.5 Pin Functions

Table 1-2 provides a description of the pin functions.

MC68HC908QB8 Data Sheet, Rev. 1

20 Freescale Semiconductor

Table 1-2. Pin Functions

Pin Functions

Name

PTA0

PTA1

PTA2

PTA3

PTA4

PTA5

PTB0

PTB1

PTB2

PTB3

Description Input/Output

Power supply Power

Power supply ground Power

PTA0 — General purpose I/O port Input/Output

TCH0 — Timer Channel 0 I/O Input/Output

AD0 — A/D channel 0 input Input

KBI0 — Keyboard interrupt input 0 Input

PTA1 — General purpose I/O port Input/Output

TCH1 — Timer Channel 1 I/O Input/Output

AD1 — A/D channel 1 input Input

KBI1 — Keyboard interrupt input 1 Input

PTA2 — General purpose input-only port Input

— External interrupt with programmable pullup and Schmitt trigger input Input

IRQ

KBI2 — Keyboard interrupt input 2 Input

TCLK — Timer clock input Input

PTA3 — General purpose I/O port Input/Output

— Reset input, active low with internal pullup and Schmitt trigger Input

RST

KBI3 — Keyboard interrupt input 3 Input

PTA4 — General purpose I/O port Input/Output

OSC2 —XTAL oscillator output (XTAL option only)

RC or internal oscillator output (OSC2EN = 1 in PTAPUE register)

Output Output

AD2 — A/D channel 2 input Input

KBI4 — Keyboard interrupt input 4 Input

PTA5 — General purpose I/O port Input/Output

OSC1 — XTAL, RC, or external oscillator input Input

AD3 — A/D channel 3 input Input

KBI5 — Keyboard interrupt input 5 Input

PTB0 — General-purpose I/O port Input/Output

SPSCK — SPI serial clock Input/Output

AD4 — A/D channel 4 input Input

PTB1 — General-purpose I/O port Input/Output

MOSI — SPI Master out Slave in Input/Output

AD5 — A/D channel 5 input Input

PTB2 — General-purpose I/O port Input/Output

MISO — SPI Master in Slave out Input/Output

AD6 — A/D channel 6 input Input

PTB3 — General-purpose I/O port Input/Output

— SPI slave select Input

AD7 — A/D channel 7 input Input

— Continued on next page

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 21

General Description

Table 1-2. Pin Functions (Continued)

Name

Description Input/Output

PTB4 — General-purpose I/O port Input/Output

PTB4

RxD — ESCI receive data I/O Input/Output

AD8 — A/D channel 8 input Input

PTB5 — General-purpose I/O port Input/Output

PTB5

TxD — ESCI transmit data I/O Output

AD9 — A/D channel 9 input Input

PTB6 — General-purpose I/O port Input/Output

PTB6

TCH2 — Timer channel 2 I/O Input/Output

PTB7 — General-purpose I/O port Input/Output

PTB7

TCH3 — Timer channel 3 I/O Input/Output

1.6 Pin Function Priority

Table 1-3 is meant to resolve the priority if multiple functions are enabled on a single pin.

NOTE

Upon reset all pins come up as input ports regardless of the priority table.

Table 1-3. Function Priority in Shared Pins

Pin Name Highest-to-Lowest Priority Sequence

PTA0

PTA1

(1)

AD0 → TCH0 → KBI0 → PTA0

AD1 → TCH1 → KBI1 → PTA1

PTA2 IRQ → TCLK → KBI2 → PTA2

PTA3 RST

(1)

PTA4

(1)

PTA5

(1)

PTB0

(1)

PTB1

(1)

PTB2

(1)

PTB3

(1)

PTB4

(1)

PTB5

→ KBI3 → PTA3

OSC2 → AD2 → KBI4 → PTA4

OSC1 → AD3 → KBI5 → PTA5

AD4 → SPSCK → PTB0

AD5 → MOSI → PTB1

AD6 → MISO → PTB2

AD7 → SS → PTB3

AD8 → RxD → PTB4

AD9 → TxD → PTB5

PTB6 TCH2 → PTB6 PTB7 TCH3 → PTB7

1. When a pin is to be used as an ADC pin, the I/O port function should be left as an input and all other shared modules should be disabled. The ADC does not override additional modules using the pin.

MC68HC908QB8 Data Sheet, Rev. 1

22 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.

2.2 Unimplemented Memory Locations

Executing code from an unimplemented location will cause an illegal address reset. In Figure 2-1, unimplemented locations are shaded.

2.3 Reserved Memory Locations

Accessing a reserved location can have unpredictable effects on MCU operation. In Figure 2-1, register locations are marked with the word Reserved or with the letter R.

2.4 Direct Page Registers

Figure 2-2 shows the memory mapped registers of the MC68HC908QB8. Registers with addresses

between $0000 and $00FF are considered direct page registers and all instructions including those with direct page addressing modes can access them. Registers between $0100 and $FFFF require non-direct page addressing modes. See Chapter 7 Central Processor Unit (CPU) for more information on addressing modes.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 23

Memory

$0000

↓

$003F

$0040

↓

$013F

$0140

↓

$27FF

$2800

↓

$2A1F

$2A20

↓

$2F7D

$2F7E

↓

$2FFF

$3000

↓

$DDFF

$DE00

↓

$FDFF

$FE00

↓

$FE1F

IDIRECT PAGE REGISTERS

64 BYTES

RAM

256 BYTES

UNIMPLEMENTED

9920 BYTES

AUXILIARY ROM

544 BYTES

UNIMPLEMENTED

1374 BYTES

AUXILIARY ROM

130 BYTES

UNIMPLEMENTED

44,544 BYTES

FLASH MEMORY

8192 BYTES

MISCELLANEOUS REGISTERS

32 BYTES

RESERVED

64 BYTES

RAM

128 BYTES

RESERVED

64 BYTES

RESERVED

4096 BYTES

FLASH MEMORY

4096 BYTES

$0040

↓

$007F

$0080

↓

$00FF

$0100

↓

$013F

$DE00

↓

$EDFF

$EE00

↓

$FDFF

$FE20

↓

$FF7D

$FF7E

↓

$FFAF

$FFB0

↓

$FFBD

$FFBE

↓

$FFC1

$FFC2

↓

$FFCF

$FFD0

↓

$FFFF

MONITOR ROM

350 BYTES

UNIMPLEMENTED

50BYTES

FLASH

14 BYTES

MISCELLANEOUS REGISTERS

4 BYTES

FLASH

14 BYTES

USER VECTORS

48 BYTES

MC68HC908QB8 and MC68HC908QY8

Memory Map

MC68HC908QB4

Memory Map

Figure 2-1. Memory Map

MC68HC908QB8 Data Sheet, Rev. 1

24 Freescale Semiconductor

Direct Page Registers

Addr.Register Name Bit 7654321Bit 0

$0000

$0001

$0002

↓

$0003

Port A Data Register

(PTA)

See page 104.

Port B Data Register

(PTB)

See page 106.

Reserved

Read:

Write:

Reset: Unaffected by reset

Read:

Write:

Reset: Unaffected by reset

PTB7 PTB6 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0

AWUL

PTA5 PTA4 PTA3

PTA2

PTA1 PTA0

$0004

$0005

$0006

↓

$000A

$000B

$000C

$000D

$000E

$000F

$0010

$0011

$0012

$0013

Data Direction Register A

(DDRA)

See page 104.

Data Direction Register B

(DDRB)

See page 107.

Reserved

Port A Input Pullup Enable

See page 105.

Port B Input Pullup Enable

See page 108.

SPI Control Register

(SPCR)

See page 171.

SPI Status and Control

See page 172.

SPI Data Register

(SPDR)

See page 174.

ESCI Control Register 1

(SCC1)

See page 122.

ESCI Control Register 2

(SCC2)

See page 124.

ESCI Control Register 3

(SCC3)

See page 125.

ESCI Status Register 1

(SCS1)

See page 126.

Read:

Write:

Reset:00000000

Read:

Write:

Reset:00000000

Read:

Write:

Reset:00000000

Read:

Write:

Reset:00000000

Read:

Write:

Reset:00101000

Read: SPRF

Write:

Reset:00001000

Read:R7R6R5R4R3R2R1R0

Write: T7 T6 T5 T4 T3 T2 T1 T0

Reset: Unaffected by reset

Read:

Write:

Reset:00000000

Read:

Write:

Reset:00000000

Read: R8

Write:

Reset:U0000000

Read: SCTE TC SCRF IDLE OR NF FE PE

Write:

Reset:11000000

R R DDRA5 DDRA4 DDRA3

DDRB7 DDRB6 DDRB5 DDRB4 DDRB3 DDRB2 DDRB1 DDRB0

OSC2EN

PTBPUE7 PTBPUE6 PTBPUE5 PTBPUE4 PTBPUE3 PTBPUE2 PTBPUE1 PTBPUE0

SPRIE R SPMSTR CPOL CPHA SPWOM SPE SPTIE

LOOPS ENSCI TXINV M WAKE ILTY PEN PTY

SCTIE TCIE SCRIE ILIE TE RE RWU SBK

PTAPUE5 PTAPUE4 PTAPUE3 PTAPUE2 PTAPUE1 PTAPUE0

ERRIE

T8 R R ORIE NEIE FEIE PEIE

= Unimplemented R = Reserved U = Unaffected

OVRF MODF SPTE

MODFEN SPR1 SPR0

DDRA1 DDRA0

Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 5)

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 25

Memory

Addr.Register Name Bit 7654321Bit 0

Read:000000BKFRPF

Write:

Reset:00000000

Read:R7R6R5R4R3R2R1R0

Write: T7 T6 T5 T4 T3 T2 T1 T0

Reset: Unaffected by reset

Read:

Write:

LINT LINR SCP1 SCP0 R SCR2 SCR1 SCR0

Reset:00000000

Read:

Write:

PDS2 PDS1 PDS0 PSSB4 PSSB3 PSSB2 PSSB1 PSSB0

Reset:00000000

Read:

Write:

AM1

ALOST

AM0 ACLK

AFIN ARUN AROVFL ARD8

Reset:00000000

Read: ARD7 ARD6 ARD5 ARD4 ARD3 ARD2 ARD1 ARD0

Write:

Reset:00000000

Read: 0 0 0 0 KEYF 0

Write:

ACKK

IMASKK MODEK

Reset:00000000

Write:

AWUIE KBIE5 KBIE4 KBIE3 KBIE2 KBIE1 KBIE0

Reset:00000000

Write:

KBIP5 KBIP4 KBIP3 KBIP2 KBIP1 KBIP0

Reset:00000000

Read: 0 0 0 0 IRQF 0

Write:

ACK

IMASK MODE

Reset:00000000

Read:

(1)

IRQPUD IRQEN

Write:

RRRESCIBDSRC

Reset:00000000

OSCENIN-

STOP

RSTEN

(2)

$0014

$0015

$0016

$0017

$0018

$0019

$001A

$001B

$001C

$001D

$001E

ESCI Status Register 2

(SCS2)

See page 129.

ESCI Data Register

(SCDR)

See page 129.

ESCI Baud Rate Register

(SCBR)

See page 130.

ESCI Prescaler Register

(SCPSC)

See page 131.

ESCI Arbiter Control

See page 135.

ESCI Arbiter Data Register

(SCIADAT)

See page 136.

Keyboard Status and

Control Register (KBSCR)

See page 87.

Keyboard Interrupt

Enable Register (KBIER)

See page 88.

Keyboard Interrupt Polarity

See page 88.

IRQ Status and Control

See page 81.

Configuration Register 2

(CONFIG2)

See page 57.

1. One-time writable register after each reset.

2. RSTEN reset to 0 by a power-on reset (POR) only.

Read:

(1)

Write:

COPRS LVISTOP LVIRSTD LVIPWRD LVITRIP SSREC STOP COPD

Reset:00000

(2)

000

$001F

Configuration Register 1

(CONFIG1)

See page 58.

1. One-time writable register after each reset.

2. LVITRIP reset to 0 by a power-on reset (POR) only.

$0020

$0021

TIM Status and Control

See page 183.

TIM Counter Register High

(TCNTH)

See page 185.

Read: TOF

Write: 0 TRST

TOIE TSTOP

Reset:00100000

Read: Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Write:

Reset:00000000

PS2 PS1 PS0

= Unimplemented R = Reserved U = Unaffected

Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 5)

MC68HC908QB8 Data Sheet, Rev. 1

26 Freescale Semiconductor

Direct Page Registers

Addr.Register Name Bit 7654321Bit 0

Read: Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Write:

Reset:00000000

Read:

Write:

Reset:11111111

Read:

Write:

Reset:11111111

Read: CH0F

Write: 0

Reset:00000000

Read:

Write:

Reset: Indeterminate after reset

Read:

Write:

Reset: Indeterminate after reset

Read: CH1F

Write: 0

Reset:00000000

Read:

Write:

Reset: Indeterminate after reset

Read:

Write:

Reset: Indeterminate after reset

Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

CH0IE MS0B MS0A ELS0B ELS0A TOV0 CH0MAX

Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

CH1IE

Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

MS1A ELS1B ELS1A TOV1 CH1MAX

$0022

$0023

$0024

$0025

$0026

$0027

$0028

$0029

$002A

$002B

↓

$002F

TIM Counter Register Low

(TCNTL)

See page 185.

TIM Counter Modulo

See page 185.

TIM Counter Modulo

See page 185.

TIM Channel 0 Status and

Control Register (TSC0)

See page 186.

TIM Channel 0

See page 189.

TIM Channel 0

See page 189.

TIM Channel 1 Status and

Control Register (TSC1)

See page 186.

TIM Channel 1

See page 189.

TIM Channel 1

See page 189.

Reserved

$0030

$0031

$0032

$0033

$0034

$0035

TIM Channel 2 Status and

Control Register (TSC2)

See page 186.

TIM Channel 2

See page 189.

TIM Channel 2

See page 189.

TIM Channel 3 Status and

Control Register (TSC3)

See page 186.

TIM Channel 3

See page 189.

TIM Channel 3

See page 189.

Read: CH2F

Write: 0

Reset:00000000

Read:

Write:

Reset: Indeterminate after reset

Read:

Write:

Reset: Indeterminate after reset

Read: CH3F

Write: 0

Reset:00000000

Read:

Write:

Reset: Indeterminate after reset

Read:

Write:

Reset: Indeterminate after reset

Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

CH2IE

CH3IE

= Unimplemented R = Reserved U = Unaffected

MS2A ELS2B ELS2A TOV2 CH2MAX

MS3A ELS3B ELS3A TOV3 CH3MAX

Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 5)

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 27

Memory

Addr.Register Name Bit 7654321Bit 0

Oscillator Status and

$0036

$0037 Reserved

Control Register (OSCSC)

See page 100.

Read:

OSCOPT1 OSCOPT0 ICFS1 ICFS0 ECFS1 ECFS0 ECGON

Write:

Reset:00000000

ECGST

$0038

$0039

↓

$003B

$003C

$003D

$003E

$003F

$FE00

$FE01

$FE02

$FE03

$FE04

$FE05

$FE06

Oscillator Trim Register

(OSCTRIM)

See page 101.

Reserved

ADC10 Status and Control

See page 46.

ADC10 Data Register High

(ADRH)

See page 48.

ADC10 Data Register Low

(ADRL)

See page 48.

ADC10 Clock Register

(ADCLK)

See page 49.

Break Status Register

(BSR)

See page 195.

SIM Reset Status Register

(SRSR)

See page 152.

Break Auxiliary

See page 195.

Break Flag Control

See page 195.

Interrupt Status Register 1

(INT1)

See page 149.

Interrupt Status Register 2

(INT2)

See page 149.

Interrupt Status Register 3

(INT3)

See page 149.

Read:

Write:

Reset:10000000

Read: COCO

Write:

Reset:00011111

Read:000000AD9AD8

Write:RRRRRRRR

Reset:00000000

Read: AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0

Write:RRRRRRRR

Reset:00000000

Read:

Write:

Reset:00000000

Read:

Write: 0

Reset: 0

Read: POR PIN COP ILOP ILAD MODRST LVI 0

Write:

POR:10000000

Write:

Reset:00000000

Read:

Write:

Reset: 0

Read: IF6 IF5 IF4 IF3 IF2 IF1 0 0

Write:RRRRRRRR

Reset:00000000

Read: IF14 IF13 IF12 IF11 IF10 IF9 IF8 IF7

Write:RRRRRRRR

Reset:00000000

Read: IF22 IF21 IF20 IF19 IF18 IF17 IF16 IF15

Write:RRRRRRRR

Reset:00000000

TRIM7 TRIM6 TRIM5 TRIM4 TRIM3 TRIM2 TRIM1 TRIM0

AIEN ADCO ADCH4 ADCH3 ADCH2 ADCH1 ADCH0

ADLPC ADIV1 ADIV0 ADICLK MODE1 MODE0 ADLSMP ACLKEN

RRRRRR

BCFERRRRRRR

= Unimplemented R = Reserved U = Unaffected

SBSW

BDCOP

Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 5)

MC68HC908QB8 Data Sheet, Rev. 1

28 Freescale Semiconductor

Direct Page Registers

Addr.Register Name Bit 7654321Bit 0

$FE07 Reserved

FLASH Control Register

$FE08

Break Address High

$FE09

$FE0A

$FE0B

$FE0C

$FE0D

↓

$FE0F

$FFBE

$FFBF Reserved

Break Address low

Break Status and Control

LVI Status Register

FLASH Block Protect

(FLCR)

See page 31.

See page 194.

(LVISR)

See page 91.

Reserved

See page 36.

Write:

Reset:00000000

Read:

Write:

Reset:00000000

Read:

Write:

Reset:00000000

Read:

Write:

Reset:00000000

Read:LVIOUT000000R

Write:

Reset:00000000

Read:

Write:

Reset: Unaffected by reset

Bit 15 Bit 14 Bit 13 Bit 12 Bit 11 Bit 10 Bit 9 Bit 8

Bit 7 Bit 6 Bit 5 Bit 4 Bit 3 Bit 2 Bit 1 Bit 0

BRKE BRKA

BPR7 BPR6 BPR5 BPR4 BPR3 BPR2 BPR1 BPR0

000000

HVEN MASS ERASE PGM

$FFC0

$FFC1 Reserved

$FFFF

Internal Oscillator

Trim Value

COP Control Register

(COPCTL)

See page 63.

Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 5)

Read:

Write:

Reset: Resets to factory programmed value

Read: LOW BYTE OF RESET VECTOR

Write: WRITING CLEARS COP COUNTER (ANY VALUE)

Reset: Unaffected by reset

TRIM7 TRIM6 TRIM5 TRIM4 TRIM3 TRIM2 TRIM1 TRIM0

= Unimplemented R = Reserved U = Unaffected

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 29

Memory

Table 2-1. Vector Addresses

Vector Priority Vector Address Vector

Lowest

IF22–

IF16

IF15 $FFDE,F ADC conversion complete vector

IF14 $FFE0,1 Keyboard vector

IF13 $FFE2,3 SPI transmit vector

IF12 $FFE4,5 SPI receive vector

IF11 $FFE6,7 ESCI transmit vector

IF10 $FFE8,9 ESCI receive vector

IF9 $FFEA,B ESCI error vector

IF8 — Not used

IF7 $FFEE,F TIM1 Channel 3 vector

IF6 $FFF0,1 TIM1 Channel 2 vector

IF5 $FFF2,3 TIM1 overflow vector

IF4 $FFF4,5 TIM1 Channel 1 vector

IF3 $FFF6,7 TIM1 Channel 0 vector

IF2 — Not used

$FFD0–

$FFDC

Not used

vector

Highest

IF1 $FFFA,B IRQ

— $FFFC,D SWI vector

— $FFFE,F Reset vector

2.5 Random-Access Memory (RAM)

This MCU includes static RAM. The locations in RAM below $0100 can be accessed using the more efficient direct addressing mode, and any single bit in this area can be accessed with the bit manipulation instructions (BCLR, BSET, BRCLR, and BRSET). Locating the most frequently accessed program variables in this area of RAM is preferred.

The RAM retains data when the MCU is in low-power wait or stop mode. At power-on, the contents of RAM are uninitialized. RAM data is unaffected by any reset provided that the supply voltage does not drop below the minimum value for RAM retention.

For compatibility with older M68HC05 MCUs, the HC08 resets the stack pointer to $00FF. In the devices that have RAM above $00FF, it is usually best to reinitialize the stack pointer to the top of the RAM so the direct page RAM can be used for frequently accessed RAM variables and bit-addressable program variables. Include the following 2-instruction sequence in your reset initialization routine (where RamLast is equated to the highest address of the RAM).

LDHX #RamLast+1 ;point one past RAM TXS ;SP<-(H:X-1)

MC68HC908QB8 Data Sheet, Rev. 1

30 Freescale Semiconductor

FLASH Memory (FLASH)

2.6 FLASH Memory (FLASH)

The FLASH memory is intended primarily for program storage. In-circuit programming allows the operating program to be loaded into the FLASH memory after final assembly of the application product. It is possible to program the entire array through the single-wire monitor mode interface. Because no special voltages are needed for FLASH erase and programming operations, in-application programming is also possible through other software-controlled communication paths.

This subsection describes the operation of the embedded FLASH memory. The FLASH memory can be read, programmed, and erased from the internal V enabled through the use of an internal charge pump.

The minimum size of FLASH memory that can be erased is 64 bytes; and the maximum size of FLASH memory that can be programmed in a program cycle is 32 bytes (a row). Program and erase operations are facilitated through control bits in the FLASH control register (FLCR). Details for these operations appear later in this section.

An erased bit reads as a 1 and a programmed bit reads as a 0. A security feature prevents viewing of the FLASH contents.

2.6.1 FLASH Control Register

supply. The program and erase operations are

NOTE

(1)

The FLASH control register (FLCR) controls FLASH program and erase operations.

Bit 7654321Bit 0

Write:

Reset:00000000

= Unimplemented

HVEN MASS ERASE PGM

Figure 2-3. FLASH Control Register (FLCR)

HVEN — High Voltage Enable Bit

This read/write bit enables high voltage from the charge pump to the memory for either program or erase operation. It can only be set if either PGM =1 or ERASE = 1 and the proper sequence for program or erase is followed.

1 = High voltage enabled to array and charge pump on 0 = High voltage disabled to array and charge pump off

MASS — Mass Erase Control Bit

This read/write bit configures the memory for mass erase operation.

1 = Mass erase operation selected 0 = Mass erase operation unselected

1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for unauthorized users.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 31

Memory

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

2.6.2 FLASH Page Erase Operation

Use the following procedure to erase a page of FLASH memory. A page consists of 64 consecutive bytes starting from addresses $XX00, $XX40, $XX80, or $XXC0. The 48-byte user interrupt vectors area also forms a page. Any FLASH memory page can be erased alone.

1. Set the ERASE bit and clear the MASS bit in the FLASH control register.

2. Read the FLASH block protect register.

3. Write any data to any FLASH location within the address range of the block to be erased.

4. Wait for a time, t

5. Set the HVEN bit.

6. Wait for a time, t

7. Clear the ERASE bit.

8. Wait for a time, t

9. Clear the HVEN bit.

10. After time, t

RCV,

The COP register at location $FFFF should not be written between steps 5-9, 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.

NVS

Erase

NVH

the memory can be accessed in read mode again.

NOTE

Programming and erasing of FLASH locations cannot be performed by code being executed from the FLASH memory. While these operations must be performed in the order as shown, other unrelated operations may occur between the steps.

CAUTION

A page erase of the vector page will erase the internal oscillator trim value at $FFC0.

MC68HC908QB8 Data Sheet, Rev. 1

32 Freescale Semiconductor

2.6.3 FLASH Mass Erase Operation

Use the following procedure to erase the entire FLASH memory to read as a 1:

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

4. Wait for a time, t

NVS

5. Set the HVEN bit.

6. Wait for a time, t

MErase

7. Clear the ERASE and MASS bits.

Mass erase is disabled whenever any block is protected (FLBPR does not equal $FF).

(1)

within the FLASH memory address range.

NOTE

FLASH Memory (FLASH)

8. Wait for a time, t

NVHL

9. Clear the HVEN bit.

10. After time, t

the memory can be accessed in read mode again.

RCV,

NOTE

CAUTION

A mass erase will erase the internal oscillator trim value at $FFC0.

2.6.4 FLASH Program Operation

Programming of the FLASH memory is done on a row basis. A row consists of 32 consecutive bytes starting from addresses $XX00, $XX20, $XX40, $XX60, $XX80, $XXA0, $XXC0, or $XXE0. 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

Do not program any byte in the FLASH more than once after a successful erase operation. Reprogramming bits to a byte which is already programmed is not allowed without first erasing the page in which the byte resides or mass erasing the entire FLASH memory. Programming without first erasing may disturb data stored in the FLASH.

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, t

NVS

5. Set the HVEN bit.

1. When in monitor mode, with security sequence failed (see 17.3.2 Security), write to the FLASH block protect register instead of any FLASH address.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 33

Memory

6. Wait for a time, t

7. Write data to the FLASH address being programmed

8. Wait for time, t

PGS

PROG

(1)

9. Repeat step 7 and 8 until all desired bytes within the row are programmed.

NVH

(1)

10. Clear the PGM bit

11. Wait for time, t

12. Clear the HVEN bit.

13. After time, t

, the memory can be accessed in read mode again.

RCV

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 t

maximum, see 18.17

PROG

Memory Characteristics.

2.6.5 FLASH Protection

Due to the ability of the on-board charge pump to erase and program the FLASH memory in the target application, provision is made to protect blocks of memory from unintentional erase or program operations due to system malfunction. This protection is done by use of a FLASH block protect register (FLBPR). The FLBPR determines the range of the FLASH memory which is to be protected. The range of the protected area starts from a location defined by FLBPR and ends to the bottom of the FLASH memory ($FFFF). When the memory is protected, the HVEN bit cannot be set in either ERASE or PROGRAM operations.

NOTE

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 0 s, the entire memory is protected from being programmed and erased. When all the bits are erased (all 1’s), the entire memory is accessible for program and erase.

When bits within the FLBPR are programmed, they lock a block of memory. The address ranges are shown in 2.6.6 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, V allows entry from reset into the monitor mode.

, present on the IRQ pin. This voltage also

TST

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, t

MC68HC908QB8 Data Sheet, Rev. 1

34 Freescale Semiconductor

PROG

maximum.

FLASH Memory (FLASH)

Algorithm for Programming a Row (32 Bytes) of FLASH Memory

READ THE FLASH BLOCK PROTECT REGISTER

WRITE ANY DATA TO ANY FLASH ADDRESS

WITHIN THE ROW ADDRESS RANGE DESIRED

WRITE DATA TO THE FLASH ADDRESS

SET PGM BIT

WAIT FOR A TIME, t

SET HVEN BIT

WAIT FOR A TIME, t

TO BE PROGRAMMED

WAIT FOR A TIME, t

NVS

PGS

PROG

PROGRAMMING

NOTES:

The time between each FLASH address change (step 7 to step 7 loop), or the time between the last FLASH address programmed to clearing PGM bit (step 7 to step 10) must not exceed the maximum programming

PROG

max.

time, t

This row program algorithm assumes the row/s to be programmed are initially erased.

Figure 2-4. FLASH Programming Flowchart

COMPLETED

THIS ROW?

CLEAR PGM BIT

WAIT FOR A TIME, t

CLEAR HVEN BIT

WAIT FOR A TIME, t

END OF PROGRAMMING

NVH

RCV

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 35

Memory

2.6.6 FLASH Block Protect Register

The FLASH block protect register is implemented as a byte within the FLASH memory, and therefore can only be written during a programming sequence of the FLASH memory. The value in this register determines the starting address of the protected range within the FLASH memory.

Bit 7654321Bit 0

Read:

Write:

Reset: Unaffected by reset. Initial value from factory is 1.

Write to this register is by a programming sequence to the FLASH memory.

BPR[7:0] — FLASH Protection Register Bits [7:0]

These eight bits in FLBPR represent bits [13:6] of a 16-bit memory address. Bits [15:14] are 1s and bits [5:0] are 0s. The resultant 16-bit address is used for specifying the start address of the FLASH memory for block protection. The FLASH is protected from this start address to the end of FLASH memory, at $FFFF. With this mechanism, the protect start address can be XX00, XX40, XX80, or XXC0 within the FLASH memory. See Figure 2-6 and Table 2-2.

BPR7 BPR6 BPR5 BPR4 BPR3 BPR2 BPR1 BPR0

Figure 2-5. FLASH Block Protect Register (FLBPR)

16-BIT MEMORY ADDRESS

START ADDRESS OF

FLASH BLOCK PROTECT

FLBPR VALUE

Figure 2-6. FLASH Block Protect Start Address

Table 2-2. Examples of Protect Start Address

BPR[7:0] Start of Address of Protect Range

$00–$77 The entire FLASH memory is protected.

$78 (0111 1000)$DE00 (1101 1110 0000 0000)

$79 (0111 1001)$DE40 (1101 1110 0100 0000)

$7A (0111 1010)$DE80 (1101 1110 1000 0000)

$7B (0111 1011)$DFC0 (1101 1110 1100 0000)

and so on...

$DE (1101 1110)$F780 (1111 0111 1000 0000)

$DF (1101 1111)$F7C0 (1111 0111 1100 0000)

$FE (1111 1110)

$FF The entire FLASH memory is not protected.

FLBPR, OSCTRIM, and vectors are protected

$FF80 (1111 1111 1000 0000)

00011

MC68HC908QB8 Data Sheet, Rev. 1

36 Freescale Semiconductor

Chapter 3 Analog-to-Digital Converter (ADC10) Module

3.1 Introduction

This section describes the 10-bit successive approximation analog-to-digital converter (ADC10).

The ADC10 module shares its pins with general-purpose input/output (I/O) port pins. See Figure 3-1 for port location of these shared pins. The ADC10 on this MCU uses V pins. This MCU uses BUSCLKX4 as its alternate clock source for the ADC. This MCU does not have a hardware conversion trigger.

3.2 Features

Features of the ADC10 module include:

• Linear successive approximation algorithm with 10-bit resolution

• Output formatted in 10- or 8-bit right-justified format

• Single or continuous conversion (automatic power-down in single conversion mode)

• Configurable sample time and conversion speed (to save power)

• Conversion complete flag and interrupt

• Input clock selectable from up to three sources

• Operation in wait and stop modes for lower noise operation

• Selectable asynchronous hardware conversion trigger

and VSS as its supply and reference

3.3 Functional Description

The ADC10 uses successive approximation to convert the input sample taken from ADVIN to a digital representation. The approximation is taken and then rounded to the nearest 10- or 8-bit value to provide greater accuracy and to provide a more robust mechanism for achieving the ideal code-transition voltage.

Figure 3-2 shows a block diagram of the ADC10

For proper conversion, the voltage on ADVIN must fall between V or exceeds V a 8-bit representation. If ADVIN is equal to or less than V Input voltages between V

Freescale Semiconductor 37

, the converter circuit converts the signal to $3FF for a 10-bit representation or $FF for

REFH

the converter circuit converts it to $000.

REFL,

and V

REFH

Input voltage must not exceed the analog supply voltages.

are straight-line linear conversions.

REFL

NOTE

MC68HC908QB8 Data Sheet, Rev. 1

REFH

and V

. If ADVIN is equal to

REFL

Analog-to-Digital Converter (ADC10) Module

PTA0/TCH0/AD0/KBI0

PTA1/TCH1/AD1/KBI1

PTA2/IRQ

/KBI2/TCLK

PTA

PTA3/RST

PTA4/OSC2/AD2/KBI4

PTA5/OSC1/AD3/KBI5

PTB0/SCK/AD4 PTB1/MOSI/AD5 PTB2/MISO/AD6

PTB4/RxD/AD8

/KBI3

PTB3/SS

/AD7

PTB5/TxD/AD9

PTB6/TCH2 PTB7/TCH3

DDRA

PTB

DDRB

M68HC08 CPU

CLOCK

GENERATOR

KEYBOARD INTERRUPT

MODULE

EXTERNAL INTERRUPT

MODULE

AUTO WAKEUP

MODULE

LOW-VOLTAGE

INHIBIT

4-CHANNEL 16-BIT

TIMER MODULE

MC68HC908QB8

256 BYTES

USER RAM

POWER SUPPLY

RST, IRQ: Pins have internal pull up device All port pins have programmable pull up device PTA[0:5]: Higher current sink and source capability

Figure 3-1. Block Diagram Highlighting ADC10 Block and Pins

MC68HC908QB8

8192 BYTES

USER FLASH

COP

MODULE

10-CHANNEL

10-BIT ADC

ENHANCED SERIAL

COMMUNICATIONS

INTERFACE MODULE

SERIAL PERIPHERAL

INTERFACE

DEVELOPMENT SUPPORT

MONITOR ROM

BREAK MODULE

MC68HC908QB8 Data Sheet, Rev. 1

38 Freescale Semiconductor

Functional Description

ADCLK

ADLPC

ADCK

ADIV

CLOCK DIVIDE

AIEN

COCO

ADICLK

ACLKEN

ACLK

ASYNC CLOCK

GENERATOR

BUS CLOCK

ALTERNATE CLOCK SOURCE

INTERRUPT

MCU STOP

ADHWT

AD0

ADn

REFH

REFL

ADCSC

AIEN

1 2

ADCH

• • •

ADVIN

ADCO

COCO

COMPLETE

CONTROL SEQUENCER

INITIALIZE

MODE

ADLSMP

SAMPLE

DATA REGISTERS ADRH:ADRL

ABORT

CONVERT

TRANSFER

SAR CONVERTER

Figure 3-2. ADC10 Block Diagram

The ADC10 can perform an analog-to-digital conversion on one of the software selectable channels. The output of the input multiplexer (ADVIN) is converted by a successive approximation algorithm into a 10-bit digital result. When the conversion is completed, the result is placed in the data registers (ADRH and ADRL). In 8-bit mode, the result is rounded to 8 bits and placed in ADRL. The conversion complete flag is then set and an interrupt is generated if the interrupt has been enabled.

3.3.1 Clock Select and Divide Circuit

The clock select and divide circuit selects one of three clock sources and divides it by a configurable value to generate the input clock to the converter (ADCK). The clock can be selected from one of the following sources:

• The asynchronous clock source (ACLK) — This clock source is generated from a dedicated clock source which is enabled when the ADC10 is converting and the clock source is selected by setting the ACLKEN bit. When the ADLPC bit is clear, this clock operates from 1–2 MHz; when ADLPC is set it operates at 0.5–1 MHz. This clock is not disabled in STOP and allows conversions in stop mode for lower noise operation.

• Alternate Clock Source — This clock source is equal to the external oscillator clock or a four times the bus clock. The alternate clock source is MCU specific, see 3.1 Introduction to determine source and availability of this clock source option. This clock is selected when ADICLK and ACLKEN are both low.

• The bus clock — This clock source is equal to the bus frequency. This clock is selected when ADICLK is high and ACLKEN is low.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 39

Analog-to-Digital Converter (ADC10) Module

Whichever clock is selected, its frequency must fall within the acceptable frequency range for ADCK. If the available clocks are too slow, the ADC10 will not perform according to specifications. If the available clocks are too fast, then the clock must be divided to the appropriate frequency. This divider is specified by the ADIV[1:0] bits and can be divide-by 1, 2, 4, or 8.

3.3.2 Input Select and Pin Control

Only one analog input may be used for conversion at any given time. The channel select bits in ADCSC are used to select the input signal for conversion.

3.3.3 Conversion Control

Conversions can be performed in either 10-bit mode or 8-bit mode as determined by the MODE bits. Conversions can be initiated by either a software or hardware trigger. In addition, the ADC10 module can be configured for low power operation, long sample time, and continuous conversion.

3.3.3.1 Initiating Conversions

A conversion is initiated:

• Following a write to ADCSC (with ADCH bits not all 1s) if software triggered operation is selected.

• Following a hardware trigger event if hardware triggered operation is selected.

• Following the transfer of the result to the data registers when continuous conversion is enabled.

If continuous conversions are enabled a new conversion is automatically initiated after the completion of the current conversion. In software triggered operation, continuous conversions begin after ADCSC is written and continue until aborted. In hardware triggered operation, continuous conversions begin after a hardware trigger event and continue until aborted.

3.3.3.2 Completing Conversions

A conversion is completed when the result of the conversion is transferred into the data result registers, ADRH and ADRL. This is indicated by the setting of the COCO bit. An interrupt is generated if AIEN is high at the time that COCO is set.

A blocking mechanism prevents a new result from overwriting previous data in ADRH and ADRL if the previous data is in the process of being read while in 10-bit mode (ADRH has been read but ADRL has not). In this case the data transfer is blocked, COCO is not set, and the new result is lost. When a data transfer is blocked, another conversion is initiated regardless of the state of ADCO (single or continuous conversions enabled). If single conversions are enabled, this could result in several discarded conversions and excess power consumption. To avoid this issue, the data registers must not be read after initiating a single conversion until the conversion completes.

3.3.3.3 Aborting Conversions

Any conversion in progress will be aborted when:

• A write to ADCSC occurs (the current conversion will be aborted and a new conversion will be initiated, if ADCH are not all 1s).

• A write to ADCLK occurs.

• The MCU is reset.

• The MCU enters stop mode with ACLK not enabled.

MC68HC908QB8 Data Sheet, Rev. 1

40 Freescale Semiconductor

Functional Description

When a conversion is aborted, the contents of the data registers, ADRH and ADRL, are not altered but continue to be the values transferred after the completion of the last successful conversion. In the case that the conversion was aborted by a reset, ADRH and ADRL return to their reset states.

Upon reset or when a conversion is otherwise aborted, the ADC10 module will enter a low power, inactive state. In this state, all internal clocks and references are disabled. This state is entered asynchronously and immediately upon aborting of a conversion.

3.3.3.4 Total Conversion Time

The total conversion time depends on many factors such as sample time, bus frequency, whether ACLKEN is set, and synchronization time. The total conversion time is summarized in Table 3-1.

Table 3-1. Total Conversion Time versus Control Conditions

Conversion Mode ACLKEN Maximum Conversion Time

8-Bit Mode (short sample — ADLSMP = 0):

Single or 1st continuous Single or 1st continuous Subsequent continuous (f

8-Bit Mode (long sample — ADLSMP = 1):

Single or 1st continuous Single or 1st continuous Subsequent continuous (f

10-Bit Mode (short sample — ADLSMP = 0):

Single or 1st continuous Single or 1st continuous Subsequent continuous (f

10-Bit Mode (long sample — ADLSMP = 1):

Single or 1st continuous Single or 1st continuous Subsequent continuous (f

Bus

≥ f

ADCK

)

0 1

0 1 X

18 ADCK + 3 bus clock

18 ADCK + 3 bus clock + 5 µs

16 ADCK

38 ADCK + 3 bus clock

38 ADCK + 3 bus clock + 5 µs

36 ADCK

21 ADCK + 3 bus clock

21 ADCK + 3 bus clock + 5 µs

19 ADCK

41 ADCK + 3 bus clock

41 ADCK + 3 bus clock + 5 µs

39 ADCK

The maximum total conversion time for a single conversion or the first conversion in continuous conversion mode is determined by the clock source chosen and the divide ratio selected. The clock source is selectable by the ADICLK and ACLKEN bits, and the divide ratio is specified by the ADIV bits. For example, if the alternate clock source is 16 MHz and is selected as the input clock source, the input clock divide-by-8 ratio is selected and the bus frequency is 4 MHz, then the conversion time for a single 10-bit conversion is:

Maximum Conversion time =

21 ADCK cycles

16 MHz/8

3 bus cycles

4 MHz

= 11.25 µs

Number of bus cycles = 11.25 µs x 4 MHz = 45 cycles

NOTE

The ADCK frequency must be between f

minimum and f

ADCK

maximum to meet A/D specifications.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 41

Analog-to-Digital Converter (ADC10) Module

3.3.4 Sources of Error

Several sources of error exist for ADC conversions. These are discussed in the following sections.

3.3.4.1 Sampling Error

For proper conversions, the input must be sampled long enough to achieve the proper accuracy. Given the maximum input resistance of approximately 15 kΩ and input capacitance of approximately 10 pF, sampling to within 1/4 (3.5 cycles / 2 MHz maximum ADCK frequency) provided the resistance of the external analog source (R

) is kept below 10 kΩ. Higher source resistances or higher-accuracy sampling is possible by setting

ADLSMP (to increase the sample window to 23.5 cycles) or decreasing ADCK frequency to increase sample time.

3.3.4.2 Pin Leakage Error

LSB (at 10-bit resolution) can be achieved within the minimum sample window

Leakage on the I/O pins can cause conversion error if the external analog source resistance (R If this error cannot be tolerated by the application, keep R

LSB leakage error (at 10-bit resolution).

1/4

lower than V

ADVIN

/ (4096*I

Leak

) is high.

) for less than

3.3.4.3 Noise-Induced Errors

System noise which occurs during the sample or conversion process can affect the accuracy of the conversion. The ADC10 accuracy numbers are guaranteed as specified only if the following conditions are met:

• There is a 0.1µF low-ESR capacitor from V

REFH

DDA

to V

(if available).

REFL

(if available).

SSA

• If inductive isolation is used from the primary supply, an additional 1µF capacitor is placed from V

DDA

•V

SSA

to V

and V

(if available).

SSA

(if available) is connected to VSS at a quiet point in the ground plane.

REFL

• The MCU is placed in wait mode immediately after initiating the conversion (next instruction after write to ADCSC).

• There is no I/O switching, input or output, on the MCU during the conversion.

There are some situations where external system activity causes radiated or conducted noise emissions or excessive V

noise is coupled into the ADC10. In these cases, or when the MCU cannot be placed

in wait or I/O activity cannot be halted, the following recommendations may reduce the effect of noise on the accuracy:

• Place a 0.01 µF capacitor on the selected input channel to V

REFL

or V

(if available). This will

SSA

improve noise issues but will affect sample rate based on the external analog source resistance.

• Operate the ADC10 in stop mode by setting ACLKEN, selecting the channel in ADCSC, and executing a STOP instruction. This will reduce V

noise but will increase effective conversion time

due to stop recovery.

• Average the input by converting the output many times in succession and dividing the sum of the results. Four samples are required to eliminate the effect of a 1

LSB, one-time error.

• Reduce the effect of synchronous noise by operating off the asynchronous clock (ACLKEN=1) and averaging. Noise that is synchronous to the ADCK cannot be averaged out.

MC68HC908QB8 Data Sheet, Rev. 1

42 Freescale Semiconductor

Functional Description

3.3.4.4 Code Width and Quantization Error

The ADC10 quantizes the ideal straight-line transfer function into 1024 steps (in 10-bit mode). Each step ideally has the same height (1 code) and width. The width is defined as the delta between the transition points from one code to the next. The ideal code width for an N bit converter (in this case N can be 8 or

10), defined as 1

LSB, is:

LSB = (V

REFH–VREFL

) / 2

Because of this quantization, there is an inherent quantization error. Because the converter performs a conversion and then rounds to 8 or 10 bits, the code will transition when the voltage is at the midpoint between the points where the straight line transfer function is exactly represented by the actual transfer function. Therefore, the quantization error will be ± 1/2 however, the code width of the first ($000) conversion is only 1/2 or $3FF) is 1.5

LSB.

LSB in 8- or 10-bit mode. As a consequence,

LSB and the code width of the last ($FF

3.3.4.5 Linearity Errors

The ADC10 may also exhibit non-linearity of several forms. Every effort has been made to reduce these errors but the user should be aware of them because they affect overall accuracy. These errors are:

• Zero-Scale Error (E the actual code width of the first conversion and the ideal code width (1/2 conversion is $001, then the difference between the actual $001 code width and its ideal (1

) (sometimes called offset) — This error is defined as the difference between

LSB). Note, if the first

LSB) is

used.

• Full-Scale Error (E the last conversion and the ideal code width (1.5 difference between the actual $3FE code width and its ideal (1

) — This error is defined as the difference between the actual code width of

LSB). Note, if the last conversion is $3FE, then the

LSB) is used.

• Differential Non-Linearity (DNL) — This error is defined as the worst-case difference between the actual code width and the ideal code width for all conversions.

• Integral Non-Linearity (INL) — This error is defined as the highest-value the (absolute value of the) running sum of DNL achieves. More simply, this is the worst-case difference of the actual transition voltage to a given code and its corresponding ideal transition voltage, for all codes.

• Total Unadjusted Error (TUE) — This error is defined as the difference between the actual transfer function and the ideal straight-line transfer function, and therefore includes all forms of error.

3.3.4.6 Code Jitter, Non-Monotonicity and Missing Codes

Analog-to-digital converters are susceptible to three special forms of error. These are code jitter, non-monotonicity, and missing codes.

• Code jitter is when, at certain points, a given input voltage converts to one of two values when sampled repeatedly. Ideally, when the input voltage is infinitesimally smaller than the transition voltage, the converter yields the lower code (and vice-versa). However, even very small amounts of system noise can cause the converter to be indeterminate (between two codes) for a range of input voltages around the transition voltage. This range is normally around ±1/2

LSB but will

increase with noise.

• Non-monotonicity is defined as when, except for code jitter, the converter converts to a lower code for a higher input voltage.

• Missing codes are those which are never converted for any input value. In 8-bit or 10-bit mode, the ADC10 is guaranteed to be monotonic and to have no missing codes.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 43

Analog-to-Digital Converter (ADC10) Module

3.4 Interrupts

When AIEN is set, the ADC10 is capable of generating a CPU interrupt after each conversion. A CPU interrupt is generated when the conversion completes (indicated by COCO being set). COCO will set at the end of a conversion regardless of the state of AIEN.

3.5 Low-Power Modes

The WAIT and STOP instructions put the MCU in low power-consumption standby modes.

3.5.1 Wait Mode

The ADC10 will continue the conversion process and will generate an interrupt following a conversion if AIEN is set. If the ADC10 is not required to bring the MCU out of wait mode, ensure that the ADC10 is not in continuous conversion mode by clearing ADCO in the ADC10 status and control register before executing the WAIT instruction. In single conversion mode the ADC10 automatically enters a low-power state when the conversion is complete. It is not necessary to set the channel select bits (ADCH[4:0]) to all 1s to enter a low power state.

3.5.2 Stop Mode

If ACLKEN is clear, executing a STOP instruction will abort the current conversion and place the ADC10 in a low-power state. Upon return from stop mode, a write to ADCSC is required to resume conversions, and the result stored in ADRH and ADRL will represent the last completed conversion until the new conversion completes.

If ACLKEN is set, the ADC10 continues normal operation during stop mode. The ADC10 will continue the conversion process and will generate an interrupt following a conversion if AIEN is set. If the ADC10 is not required to bring the MCU out of stop mode, ensure that the ADC10 is not in continuous conversion mode by clearing ADCO in the ADC10 status and control register before executing the STOP instruction. In single conversion mode the ADC10 automatically enters a low-power state when the conversion is complete. It is not necessary to set the channel select bits (ADCH[4:0]) to all 1s to enter a low-power state.

If ACLKEN is set, a conversion can be initiated while in stop using the external hardware trigger ADEXTCO when in external convert mode. The ADC10 will operate in a low-power mode until the trigger is asserted, at which point it will perform a conversion and assert the interrupt when complete (if AIEN is set).

3.6 ADC10 During Break Interrupts

The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. BCFE in the break flag control register (BFCR) enables software to clear status bits during the break state. See BFCR in the SIM section of this data sheet.

To allow software to clear status bits during a break interrupt, write a 1 to BCFE. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state.

MC68HC908QB8 Data Sheet, Rev. 1

44 Freescale Semiconductor

I/O Signals

break, the bit cannot change during the break state as long as BCFE is cleared. After the break, doing the second step clears the status bit.

3.7 I/O Signals

and VSS as its supply and reference

3.7.1 ADC10 Analog Power Pin (V

The ADC10 analog portion uses V to V

. If externally available, connect the V

may be necessary to ensure clean V

DDA

)

DDA

as its power pin. In some packages, V

pin to the same voltage potential as VDD. External filtering

DDA

for good results.

is connected internally

DDA

NOTE

If externally available, route V

carefully for maximum noise immunity

DDA

and place bypass capacitors as near as possible to the package.

3.7.2 ADC10 Analog Ground Pin (V

The ADC10 analog portion uses V to V

. If externally available, connect the V

as its ground pin. In some packages, V

SSA

)

SSA

pin to the same voltage potential as VSS.

SSA

is connected internally

SSA

In cases where separate power supplies are used for analog and digital power, the ground connection between these supplies should be at the V these supplies if possible. The V

pin makes a good single point ground location.

SSA

3.7.3 ADC10 Voltage Reference High Pin (V

V V potential as V the V

is the power supply for setting the high-reference voltage for the converter. In some packages,

REFH

is connected internally to V

REFH

, or may be driven by an external source that is between the minimum V

DDA

potential (V

DDA

REFH

must never exceed V

. If externally available, V

DDA

pin. This should be the only ground connection between

SSA

)

REFH

may be connected to the same

REFH

spec and

DDA

NOTE

Route V

carefully for maximum noise immunity and place bypass

REFH

capacitors as near as possible to the package.

AC current in the form of current spikes required to supply charge to the capacitor array at each successive approximation step is drawn through the V

REFH

and V

loop. The best external component

REFL

to meet this current demand is a 0.1 µF capacitor with good high frequency characteristics. This capacitor is connected between V

REFH

and V

and must be placed as close as possible to the package pins.

REFL

Resistance in the path is not recommended because the current will cause a voltage drop which could result in conversion errors. Inductance in this path must be minimum (parasitic only).

3.7.4 ADC10 Voltage Reference Low Pin (V

is the power supply for setting the low-reference voltage for the converter. In some packages,

REFL

is connected internally to V

REFL

potential as V

Freescale Semiconductor 45

. There will be a brief current associated with V

SSA

. If externally available, connect the V

SSA

MC68HC908QB8 Data Sheet, Rev. 1

REFL

)

pin to the same voltage

REFL

when the sampling capacitor is

REFL

Analog-to-Digital Converter (ADC10) Module

charging. If externally available, connect the V

pin to the same potential as V

REFL

at the single point

SSA

ground location.

3.7.5 ADC10 Channel Pins (ADn)

The ADC10 has multiple input channels. Empirical data shows that capacitors on the analog inputs improve performance in the presence of noise or when the source impedance is high. 0.01 µF capacitors with good high-frequency characteristics are sufficient. These capacitors are not necessary in all cases, but when used they must be placed as close as possible to the package pins and be referenced to V

SSA

3.8 Registers

These registers control and monitor operation of the ADC10:

• ADC10 status and control register, ADCSC

• ADC10 data registers, ADRH and ADRL

• ADC10 clock register, ADCLK

3.8.1 ADC10 Status and Control Register

This section describes the function of the ADC10 status and control register (ADCSC). Writing ADCSC aborts the current conversion and initiates a new conversion (if the ADCH[4:0] bits are equal to a value other than all 1s).

Bit 7654321Bit 0

Read: COCO

Write:

Reset:00011111

AIEN ADCO ADCH4 ADCH3 ADCH2 ADCH1 ADCH0

= Unimplemented

Figure 3-3. ADC10 Status and Control Register (ADCSC)

COCO — Conversion Complete Bit

COCO is a read-only bit which is set each time a conversion is completed. This bit is cleared whenever the status and control register is written or whenever the data register (low) is read.

1 = Conversion completed 0 = Conversion not completed

AIEN — ADC10 Interrupt Enable Bit

When this bit is set, an interrupt is generated at the end of a conversion. The interrupt signal is cleared when the data register is read or the status/control register is written.

1 = ADC10 interrupt enabled 0 = ADC10 interrupt disabled

ADCO — ADC10 Continuous Conversion Bit

When this bit is set, the ADC10 will begin to convert samples continuously (continuous conversion mode) and update the result registers at the end of each conversion, provided the ADCH[4:0] bits do not decode to all 1s. The ADC10 will continue to convert until the MCU enters reset, the MCU enters stop mode (if ACLKEN is clear), ADCLK is written, or until ADCSC is written again. If stop is entered

MC68HC908QB8 Data Sheet, Rev. 1

46 Freescale Semiconductor

Registers

(with ACLKEN low), continuous conversions will cease and can be restarted only with a write to ADCSC. Any write to ADCSC with ADCO set and the ADCH bits not all 1s will abort the current conversion and begin continuous conversions.

If the bus frequency is less than the ADCK frequency, precise sample time for continuous conversions cannot be guaranteed in short-sample mode (ADLSMP = 0). If the bus frequency is less than 1/11th of the ADCK frequency, precise sample time for continuous conversions cannot be guaranteed in long-sample mode (ADLSMP = 1).

When clear, the ADC10 will perform a single conversion (single conversion mode) each time ADCSC is written (assuming the ADCH[4:0] bits do not decode all 1s).

1 = Continuous conversion following a write to ADCSC 0 = One conversion following a write to ADCSC

ADCH[4:0] — Channel Select Bits

The ADCH[4:0] bits form a 5-bit field that is used to select one of the input channels. The input channels are detailed in Table 3-2. The successive approximation converter subsystem is turned off when the channel select bits are all set to 1. This feature allows explicit disabling of the ADC10 and isolation of the input channel from the I/O pad. Terminating continuous conversion mode this way will prevent an additional, single conversion from being performed. It is not necessary to set the channel select bits to all 1s to place the ADC10 in a low-power state, however, because the module is automatically placed in a low-power state when a conversion completes.

Table 3-2. Input Channel Select

ADCH4 ADCH3 ADCH2 ADCH1 ADCH0

00000 AD0

00001 AD1

00010 AD2

00011 AD3

00100 AD4

00101 AD5

00110 AD6

00111 AD7

01000 Unused

Continuing through Unused

10111 Unused

11000 AD8

11001 AD9

11010

11011 Reserved

11100 Reserved

11101

11110

11111Low-power state

Input Select

BANDGAP REF

(1)

(2)

REFH

REFL

1. If any unused or reserved channels are selected, the resulting conversion will be unknown.

2. Requires LVI to be powered (LVIPWRD =0, in CONFIG1)

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 47

Analog-to-Digital Converter (ADC10) Module

3.8.2 ADC10 Result High Register (ADRH)

This register holds the MSBs of the result and is updated each time a conversion completes. All other bits read as 0s. Reading ADRH prevents the ADC10 from transferring subsequent conversion results into the result registers until ADRL is read. If ADRL is not read until the after next conversion is completed, then the intermediate conversion result will be lost. In 8-bit mode, this register contains no interlocking with ADRL.

Bit 7654321Bit 0

Write:

Reset:00000000

= Unimplemented

Figure 3-4. ADC10 Data Register High (ADRH), 8-Bit Mode

Bit 7654321Bit 0

Read:000000AD9AD8

Write:

Reset:00000000

= Unimplemented

Figure 3-5. ADC10 Data Register High (ADRH), 10-Bit Mode

3.8.3 ADC10 Result Low Register (ADRL)

This register holds the LSBs of the result. This register is updated each time a conversion completes. Reading ADRH prevents the ADC10 from transferring subsequent conversion results into the result registers until ADRL is read. If ADRL is not read until the after next conversion is completed, then the intermediate conversion result will be lost. In 8-bit mode, there is no interlocking with ADRH.

Bit 7654321Bit 0

Read: AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0

Write:

Reset:00000000

= Unimplemented

Figure 3-6. ADC10 Data Register Low (ADRL)

MC68HC908QB8 Data Sheet, Rev. 1

48 Freescale Semiconductor

Registers

3.8.4 ADC10 Clock Register (ADCLK)

This register selects the clock frequency for the ADC10 and the modes of operation.

Bit 7654321Bit 0

Read:

Write:

Reset:00000000

ADLPC — ADC10 Low-Power Configuration Bit

ADLPC controls the speed and power configuration of the successive approximation converter. This is used to optimize power consumption when higher sample rates are not required.

1 = Low-power configuration: The power is reduced at the expense of maximum clock speed. 0 = High-speed configuration

ADIV[1:0] — ADC10 Clock Divider Bits

ADIV1 and ADIV0 select the divide ratio used by the ADC10 to generate the internal clock ADCK.

Table 3-3 shows the available clock configurations.

ADLPC ADIV1 ADIV0 ADICLK MODE1 MODE0 ADLSMP ACLKEN

Figure 3-7. ADC10 Clock Register (ADCLK)

Table 3-3. ADC10 Clock Divide Ratio

ADIV1 ADIV0 Divide Ratio (ADIV) Clock Rate

0 0 1 Input clock ÷ 1

0 1 2 Input clock ÷ 2

1 0 4 Input clock ÷ 4

1 1 8 Input clock ÷ 8

ADICLK — Input Clock Select Bit

If ACLKEN is clear, ADICLK selects either the bus clock or an alternate clock source as the input clock source to generate the internal clock ADCK. If the alternate clock source is less than the minimum clock speed, use the internally-generated bus clock as the clock source. As long as the internal clock ADCK, which is equal to the selected input clock divided by ADIV, is at a frequency (f

ADCK

) between

the minimum and maximum clock speeds (considering ALPC), correct operation can be guaranteed.

1 = The internal bus clock is selected as the input clock source 0 = The alternate clock source IS SELECTED

MODE[1:0] — 10- or 8-Bit or Hardware Triggered Mode Selection

These bits select 10- or 8-bit operation. The successive approximation converter generates a result that is rounded to 8- or 10-bit value based on the mode selection. This rounding process sets the transfer function to transition at the midpoint between the ideal code voltages, causing a quantization error of ± 1/2

LSB.

Reset returns 8-bit mode.

00 = 8-bit, right-justified, ADCSC software triggered mode enabled 01 = 10-bit, right-justified, ADCSC software triggered mode enabled 10 = Reserved 11 = 10-bit, right-justified, hardware triggered mode enabled

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 49

Analog-to-Digital Converter (ADC10) Module

ADLSMP — Long Sample Time Configuration

This bit configures the sample time of the ADC10 to either 3.5 or 23.5 ADCK clock cycles. This adjusts the sample period to allow higher impedance inputs to be accurately sampled or to maximize conversion speed for lower impedance inputs. Longer sample times can also be used to lower overall power consumption in continuous conversion mode if high conversion rates are not required.

1 = Long sample time (23.5 cycles) 0 = Short sample time (3.5 cycles)

ACLKEN — Asynchronous Clock Source Enable

This bit enables the asynchronous clock source as the input clock to generate the internal clock ADCK, and allows operation in stop mode. The asynchronous clock source will operate between 1 MHz and 2 MHz if ADLPC is clear, and between 0.5 MHz and 1 MHz if ADLPC is set.

1 = The asynchronous clock is selected as the input clock source (the clock generator is only

enabled during the conversion)

0 = ADICLK specifies the input clock source and conversions will not continue in stop mode

MC68HC908QB8 Data Sheet, Rev. 1

50 Freescale Semiconductor

Chapter 4 Auto Wakeup Module (AWU)

4.1 Introduction

This section describes the auto wakeup module (AWU). The AWU generates a periodic interrupt during stop mode to wake the part up without requiring an external signal. Figure 4-1 is a block diagram of the AWU.

COPRS (FROM CONFIG1)

OSCENINSTOP (FROM CONFIG2)

BUSCLKX4

EN 32 kHz

INT RC OSC

CLRLOGIC

(CGMXCLK)

BUSCLKX4

RESET

CLK

RST

Figure 4-1. Auto Wakeup Interrupt Request Generation Logic

CLEAR

M U X

RESET

AUTOW UGEN

SHORT

CLK

AWUI E

1 = DIV 2 0 = DIV 2

OVERFLOW

RST

ISTOP

9 14

RESET

ACKK

TO PTA READ, BIT 6

AWUL

AWUIREQ

TO KBI INTERRUPT LOGIC (SEE Figure 9-2)

4.2 Features

Features of the auto wakeup module include:

• One internal interrupt with separate interrupt enable bit, sharing the same keyboard interrupt vector and keyboard interrupt mask bit

• Exit from low-power stop mode without external signals

• Selectable timeout periods

• Dedicated low-power internal oscillator separate from the main system clock sources

• Option to allow bus clock source to run the AWU if enabled in STOP

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 51

Auto Wakeup Module (AWU)

4.3 Functional Description

The function of the auto wakeup logic is to generate periodic wakeup requests to bring the microcontroller unit (MCU) out of stop mode. The wakeup requests are treated as regular keyboard interrupt requests, with the difference that instead of a pin, the interrupt signal is generated by an internal logic.

Writing the AWUIE bit in the keyboard interrupt enable register enables or disables the auto wakeup interrupt input (see Figure 4-1). A 1 applied to the AWUIREQ input with auto wakeup interrupt request enabled, latches an auto wakeup interrupt request.

Auto wakeup latch, AWUL, can be read directly from the bit 6 position of port A data register (PTA). This is a read-only bit which is occupying an empty bit position on PTA. No PTA associated registers, such as PTA6 data direction or PTA6 pullup exist for this bit.

There exists two clock sources for the AWU. An internal RC oscillator (exclusive for the auto wakeup feature, AWU oscillator) drives the wakeup request generator provided the OSCENINSTOP bit in the CONFIG2 register Figure 4-1is cleared. If the application employs a crystal, for example, by setting the OSCENINSTOP bit the BUSCLKX4 will drive the wakeup request generator to allow a more accurate wakeup.

Entering stop mode will enable the auto wakeup generation logic.

Once the overflow count is reached in the generator counter, a wakeup request, AWUIREQ, is latched and sent to the KBI logic. See Figure 4-1.

Wakeup interrupt requests will only be serviced if the associated interrupt enable bit, AWUIE, in KBIER is set. The AWU shares the keyboard interrupt vector.

The overflow count can be selected from two options defined by the COPRS bit in CONFIG1. This bit was “borrowed” from the computer operating properly (COP) using the fact that the COP feature is idle (no MCU clock available) in stop mode.

The auto wakeup RC oscillator is highly dependent on operating voltage and temperature. This feature is not recommended for use as a time-keeping function.

The wakeup request is latched to allow the interrupt source identification. The latched value, AWUL, can be read directly from the bit 6 position of PTA data register. This is a read-only bit which is occupying an empty bit position on PTA. No PTA associated registers, such as PTA6 data, PTA6 direction, and PTA6 pullup exist for this bit. The latch can be cleared by writing to the ACKK bit in the KBSCR register. Reset also clears the latch. AWUIE bit in KBI interrupt enable register (see Figure 4-1) has no effect on AWUL reading.

The AWU oscillator and counters are inactive in normal operating mode and become active only upon entering stop mode.

4.4 Interrupts

The AWU can generate an interrupt requests:.

AWU Latch (AWUL) — The AWUL bit is set when the AWU counter overflows. The auto wakeup interrupt mask bit, AWUIE, is used to enable or disable AWU interrupt requests.

The AWU shares its interrupt with the KBI vector.

MC68HC908QB8 Data Sheet, Rev. 1

52 Freescale Semiconductor

Low-Power Modes

4.5 Low-Power Modes

The WAIT and STOP instructions put the MCU in low power-consumption standby modes.

4.5.1 Wait Mode

The AWU module remains inactive in wait mode.

4.5.2 Stop Mode

When the AWU module is enabled (AWUIE = 1 in the keyboard interrupt enable register) it is activated automatically upon entering stop mode. Clearing the IMASKK bit in the keyboard status and control register enables keyboard interrupt requests to bring the MCU out of stop mode. The AWU counters start from 0 each time stop mode is entered.

4.6 Registers

The AWU shares registers with the keyboard interrupt (KBI) module, the port A I/O module and configuration register 2. The following I/O registers control and monitor operation of the AWU:

• Port A data register (PTA)

• Keyboard interrupt status and control register (KBSCR)

• Keyboard interrupt enable register (KBIER)

• Configuration register 1 (CONFIG1)

• Configuration register 2 (CONFIG2)

4.6.1 Port A I/O Register

The port A data register (PTA) contains a data latch for the state of the AWU interrupt request, in addition to the data latches for port A.

Bit 7654321Bit 0

Read: 0 AWUL

Write:

Reset: 0 0 Unaffected by reset

= Unimplemented

PTA5 PTA4 PTA3

Figure 4-2. Port A Data Register (PTA)

AWUL — Auto Wakeup Latch

This is a read-only bit which has the value of the auto wakeup interrupt request latch. The wakeup request signal is generated internally. There is no PTA6 port or any of the associated bits such as PTA6 data direction or pullup bits.

1 = Auto wakeup interrupt request is pending 0 = Auto wakeup interrupt request is not pending

NOTE

PTA5–PTA0 bits are not used in conjuction with the auto wakeup feature. To see a description of these bits, see 12.2.1 Port A Data Register.

PTA2

PTA1 PTA0

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 53

Auto Wakeup Module (AWU)

4.6.2 Keyboard Status and Control Register

The keyboard status and control register (KBSCR):

• Flags keyboard/auto wakeup interrupt requests

• Acknowledges keyboard/auto wakeup interrupt requests

• Masks keyboard/auto wakeup interrupt requests

Bit 7654321Bit 0

Read:0000KEYF 0

Write:

Reset:00000000

= Unimplemented

ACKK

Figure 4-3. Keyboard Status and Control Register (KBSCR)

Bits 7–4 — Not used

These read-only bits always read as 0s.

KEYF — Keyboard Flag Bit

This read-only bit is set when a keyboard interrupt is pending on port A or auto wakeup. Reset clears the KEYF bit.

1 = Keyboard/auto wakeup interrupt pending 0 = No keyboard/auto wakeup interrupt pending

IMASKK MODEK

ACKK — Keyboard Acknowledge Bit

Writing a 1 to this write-only bit clears the keyboard/auto wakeup interrupt request on port A and auto wakeup logic. ACKK always reads as 0. Reset clears ACKK.

IMASKK— Keyboard Interrupt Mask Bit

Writing a 1 to this read/write bit prevents the output of the keyboard interrupt mask from generating interrupt requests on port A or auto wakeup. Reset clears the IMASKK bit.

1 = Keyboard/auto wakeup interrupt requests masked 0 = Keyboard/auto wakeup interrupt requests not masked

NOTE

MODEK is not used in conjuction with the auto wakeup feature. To see a description of this bit, see 9.8.1 Keyboard Status and Control Register

(KBSCR).

4.6.3 Keyboard Interrupt Enable Register

The keyboard interrupt enable register (KBIER) enables or disables the auto wakeup to operate as a keyboard/auto wakeup interrupt input.

Bit 7654321Bit 0

Write:

Reset:00000000

AWUIE KBIE5 KBIE4 KBIE3 KBIE2 KBIE1 KBIE0

= Unimplemented

Figure 4-4. Keyboard Interrupt Enable Register (KBIER)

MC68HC908QB8 Data Sheet, Rev. 1

54 Freescale Semiconductor

Registers

AWUIE — Auto Wakeup Interrupt Enable Bit

This read/write bit enables the auto wakeup interrupt input to latch interrupt requests. Reset clears AWUIE.

1 = Auto wakeup enabled as interrupt input 0 = Auto wakeup not enabled as interrupt input

NOTE

KBIE5–KBIE0 bits are not used in conjuction with the auto wakeup feature. To see a description of these bits, see 9.8.2 Keyboard Interrupt Enable

4.6.4 Configuration Register 2

The configuration register 2 (CONFIG2), is used to allow the bus clock source to run in STOP. In this case, the clock, BUSCLKX4 will be used to drive the AWU request generator.

Bit 76543 2 1 Bit 0

Read:

IRQPUD IRQEN RRRESCI-BDSRC OSCENINSTOP RSTEN

Write:

Reset:00000 0 0 0

Figure 4-5. Configuration Register 2 (CONFIG2)

OSCENINSTOP — Oscillator Enable in Stop Mode Bit

OSCENINSTOP, when set, will allow the bus clock source (BUSCLKX4) to generate clocks for the AWU in stop mode. See 11.8.1 Oscillator Status and Control Register for information on enabling the external clock sources.

1 = Oscillator enabled to operate during stop mode 0 = Oscillator disabled during stop mode

NOTE

IRQPUD, IRQEN, ESCIBDSRC, and RSTEN bits are not used in conjuction with the auto wakeup feature. To see a description of these bits, see

Chapter 5 Configuration Register (CONFIG).

4.6.5 Configuration Register 1

The configuration register 1 (CONFIG1), is used to select the period for the AWU. The timeout will be based on the COPRS bit along with the clock source for the AWU.

Bit 7654321Bit 0

Read:

Write:

Reset: POR:

COPRS LVISTOP LVIRSTD LVIPWRD LVITRIP SSREC STOP COPD

0 0

U = Unaffected

0 0

U 0

0 0

Figure 4-6. Configuration Register 1 (CONFIG1)

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 55

Auto Wakeup Module (AWU)

COPRS (In Stop Mode) — Auto Wakeup Period Selection Bit, depends on OSCSTOPEN in CONFIG2 and bus clock source (BUSCLKX4).

1 = Auto wakeup short cycle = 512 × (INTRCOSC or BUSCLKX4) 0 = Auto wakeup long cycle = 16,384 × (INTRCOSC or BUSCLKX4)

NOTE

LVISTOP, LVIRST, LVIPWRD, LVITRIP, SSREC and COPD bits are not used in conjuction with the auto wakeup feature. To see a description of these bits, see Chapter 5 Configuration Register (CONFIG)

MC68HC908QB8 Data Sheet, Rev. 1

56 Freescale Semiconductor

Chapter 5 Configuration Register (CONFIG)

5.1 Introduction

This section describes the configuration registers (CONFIG1 and CONFIG2). The configuration registers enable or disable the following options:

• Stop mode recovery time (32 × BUSCLKX4 cycles or 4096 × BUSCLKX4 cycles)

•STOP instruction

• Computer operating properly module (COP)

• COP reset period (COPRS): 8176 × BUSCLKX4 or 262,128 × BUSCLKX4

• Low-voltage inhibit (LVI) enable and trip voltage selection

• Auto wakeup timeout period

• Allow clock source to remain enabled in STOP

• Enable IRQ

• Disable IRQ

• Enable RST

• Clock source selection for the enhanced serial communication interface (ESCI) module

5.2 Functional Description

pin pullup device pin

The configuration registers are used in the initialization of various options. The configuration registers can be written once after each reset. Most 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 registers are located at $001E and $001F, and may be read at anytime.

NOTE

The CONFIG registers are one-time writable by the user after each reset. Upon a reset, the CONFIG registers default to predetermined settings as shown in Figure 5-1 and Figure 5-2.

Bit 7 6 5 4 3 2 1 Bit 0

Read:

IRQPUD IRQEN R R R ESCIBDSRC OSCENINSTOP RSTEN

Write:

Reset:000 0 0 0 0 U

POR:000 0 0 0 0 0

= Reserved U = Unaffected

Figure 5-1. Configuration Register 2 (CONFIG2)

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 57

Configuration Register (CONFIG)

IRQPUD — IRQ Pin Pullup Control Bit

1 = Internal pullup is disconnected 0 = Internal pullup is connected between IRQ

pin and V

IRQEN — IRQ Pin Function Selection Bit

1 = Interrupt request function active in pin 0 = Interrupt request function inactive in pin

ESCIBDSRC — ESCI Baud Rate Clock Source Bit

ESCIBDSRC controls the clock source used for the ESCI. The setting of the bit affects the frequency at which the ESCI operates.

1 = Internal data bus clock used as clock source for ESCI 0 = CGMXCLK used as clock source for ESCI

OSCENINSTOP— Oscillator Enable in Stop Mode Bit

OSCENINSTOP, when set, will allow the clock source to continue to generate clocks in stop mode. This function can be used to keep the auto-wakeup running while the rest of the microcontroller stops. When clear, the clock source is disabled when the microcontroller enters stop mode.

1 = Oscillator enabled to operate during stop mode 0 = Oscillator disabled during stop mode

RSTEN — RST

Pin Function Selection

1 = Reset function active in pin 0 = Reset function inactive in pin

NOTE

The RSTEN bit is cleared by a power-on reset (POR) only. Other resets will leave this bit unaffected.

Bit 7 6 5 4 3 2 1 Bit 0

Read:

Write:

Reset:0000U000

COPRS LVISTOP LVIRSTD LVIPWRD LVITRIP SSREC STOP COPD

POR:000 00000

U = Unaffected

Figure 5-2. Configuration Register 1 (CONFIG1)

COPRS (Out of Stop Mode) — COP Reset Period Selection Bit

1 = COP reset short cycle = 8176 × BUSCLKX4 0 = COP reset long cycle = 262,128 × BUSCLKX4

COPRS (In Stop Mode) — Auto Wakeup Period Selection Bit, depends on OSCSTOPEN in CONFIG2 and external clock source

1 = Auto wakeup short cycle = 512 × (INTRCOSC or BUSCLKX4) 0 = Auto wakeup long cycle = 16,384 × (INTRCOSC or BUSCLKX4)

LVISTOP — LVI Enable in Stop Mode Bit

When the LVIPWRD bit is clear, setting the LVISTOP bit enables the LVI to operate during stop mode. Reset clears LVISTOP.

1 = LVI enabled during stop mode 0 = LVI disabled during stop mode

MC68HC908QB8 Data Sheet, Rev. 1

58 Freescale Semiconductor

Functional Description

LVIRSTD — LVI Reset Disable Bit

LVIRSTD disables the reset signal from the LVI module.

1 = LVI module resets disabled 0 = LVI module resets enabled

LVIPWRD — LVI Power Disable Bit

LVIPWRD disables the LVI module.

1 = LVI module power disabled 0 = LVI module power enabled

LVITRIP — LVI Trip Point Selection Bit

LVITRIP selects the voltage operating mode of the LVI module. The voltage mode selected for the LVI should match the operating V

for the LVI’s voltage trip points for each of the modes.

1 = LVI operates for a 5-V protection 0 = LVI operates for a 3-V protection

NOTE

The LVITRIP bit is cleared by a power-on reset (POR) only. Other resets will leave this bit unaffected.

SSREC — Short Stop Recovery Bit

SSREC enables the CPU to exit stop mode with a delay of 32 BUSCLKX4 cycles instead of a 4096 BUSCLKX4 cycle delay.

1 = Stop mode recovery after 32 BUSCLKX4 cycles 0 = Stop mode recovery after 4096 BUSCLKX4 cycles

NOTE

Exiting stop mode by an LVI reset will result in the long stop recovery.

When using the LVI during normal operation but disabling during stop mode, the LVI will have an enable time of t

. The system stabilization time for power-on reset and long stop recovery (both 4096

BUSCLKX4 cycles) gives a delay longer than the LVI enable time for these startup scenarios. There is no period where the MCU is not protected from a low-power condition. However, when using the short stop recovery configuration option, the 32 BUSCLKX4 delay must be greater than the LVI’s turn on time to avoid a period in startup where the LVI is not protecting the MCU.

STOP — STOP Instruction Enable Bit

STOP enables the STOP instruction.

1 = STOP instruction enabled 0 = STOP instruction treated as illegal opcode

COPD — COP Disable Bit

COPD disables the COP module.

1 = COP module disabled 0 = COP module enabled

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 59

Configuration Register (CONFIG)

MC68HC908QB8 Data Sheet, Rev. 1

60 Freescale Semiconductor

Chapter 6 Computer Operating Properly (COP)

6.1 Introduction

The computer operating properly (COP) module contains a free-running counter that generates a reset if allowed to overflow. The COP module helps software recover from runaway code. Prevent a COP reset by clearing the COP counter periodically. The COP module can be disabled through the COPD bit in the configuration 1 (CONFIG1) register.

6.2 Functional Description

SIM MODULE

BUSCLKX4

INTERNAL RESET SOURCES

STOP INSTRUCTION

COPCTL WRITE

COPEN (FROM SIM)

COPD (FROM CONFIG1)

RESET

COPCTL WRITE

COP RATE SELECT

(COPRS FROM CONFIG1)

12-BIT SIM COUNTER

(1)

CLEAR ALL STAGES

COP CLOCK

CLEAR STAGES 5–12

COP TIMEOUT

COP MODULE

6-BIT COP COUNTER

CLEAR

COP COUNTER

SIM RESET CIRCUIT

RESET STATUS REGISTER

1. See Chapter 14 System Integration Module (SIM) for more details.

Figure 6-1. COP Block Diagram

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 61

Computer Operating Properly (COP)

The COP counter is a free-running 6-bit counter preceded by the 12-bit system integration module (SIM) counter. If not cleared by software, the COP counter overflows and generates an asynchronous reset after 8176 or 262,128 BUSCLKX4 cycles; depending on the state of the COP rate select bit, COPRS, in configuration register 1. With a 262,128 BUSCLKX4 cycle overflow option, the internal 12.8-MHz oscillator gives a COP timeout period of 20.48 ms. Writing any value to location $FFFF before an overflow occurs prevents a COP reset by clearing the COP counter and stages 12–5 of the SIM counter.

NOTE

Service the COP immediately after reset and before entering or after exiting stop mode to guarantee the maximum time before the first COP counter overflow.

A COP reset pulls the RST cycles and sets the COP bit in the reset status register (RSR). See 14.8.1 SIM Reset Status Register.

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.

pin low (if the RSTEN bit is set in the CONFIG1 register) for 32 × BUSCLKX4

NOTE

6.3 I/O Signals

The following paragraphs describe the signals shown in Figure 6-1.

6.3.1 BUSCLKX4

BUSCLKX4 is the oscillator output signal. BUSCLKX4 frequency is equal to the internal oscillator frequency, the crystal frequency, or the RC-oscillator frequency.

6.3.2 STOP Instruction

The STOP instruction clears the SIM counter.

6.3.3 COPCTL Write

Writing any value to the COP control register (COPCTL) (see Figure 6-2) clears the COP counter and clears stages 12–5 of the SIM counter. Reading the COP control register returns the low byte of the reset vector.

6.3.4 Power-On Reset

The power-on reset (POR) circuit in the SIM clears the SIM counter 4096 × BUSCLKX4 cycles after power up.

6.3.5 Internal Reset

An internal reset clears the SIM counter and the COP counter.

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).

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62 Freescale Semiconductor

Interrupts

6.3.7 COPRS (COP Rate Select)

The COPRS signal reflects the state of the COP rate select bit (COPRS) in the configuration register 1 (CONFIG1). See Chapter 5 Configuration Register (CONFIG).

6.4 Interrupts

The COP does not generate CPU interrupt requests.

6.5 Monitor Mode

The COP is disabled in monitor mode when V

is present on the IRQ pin.

TST

6.6 Low-Power Modes

The WAIT and STOP instructions put the MCU in low power-consumption standby modes.

6.6.1 Wait Mode

The COP continues to operate during wait mode. To prevent a COP reset during wait mode, periodically clear the COP counter.

6.6.2 Stop Mode

Stop mode turns off the BUSCLKX4 input to the COP and clears the SIM counter. Service the COP immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering or exiting stop mode.

6.7 COP Module During Break Mode

The COP is disabled during a break interrupt with monitor mode when BDCOP bit is set in break auxiliary register (BRKAR).

6.8 Register

The COP control register (COPCTL) is located at address $FFFF and overlaps the reset vector. Writing any value to $FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF returns the low byte of the reset vector.

Bit 7654321Bit 0

Read: LOW BYTE OF RESET VECTOR

Write: CLEAR COP COUNTER

Reset: Unaffected by reset

Figure 6-2. COP Control Register (COPCTL)

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 63

Computer Operating Properly (COP)

MC68HC908QB8 Data Sheet, Rev. 1

64 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.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 65

Central Processor Unit (CPU)

H X

V11H I NZC

ACCUMULATOR (A)

INDEX REGISTER (H:X)

STACK POINTER (SP)

PROGRAM COUNTER (PC)

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 7654321Bit 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 151413121110987654321

Read:

Write:

Reset:00000000XXXXXXXX

X = Indeterminate

Figure 7-3. Index Register (H:X)

Bit

MC68HC908QB8 Data Sheet, Rev. 1

66 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 151413121110987654321

Read:

Write:

Reset:0000000011111111

Bit

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 151413121110987654321

Read:

Write:

Reset: Loaded with vector from $FFFE and $FFFF

Bit

Figure 7-5. Program Counter (PC)

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 67

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.

Bit 7654321Bit 0

Read:

Write:

Reset:X11X1XXX

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

V11H I NZC

X = Indeterminate

Figure 7-6. Condition Code Register (CCR)

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

MC68HC908QB8 Data Sheet, Rev. 1

68 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.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 69

Central Processor Unit (CPU)

7.7 Instruction Set Summary

Table 7-1 provides a summary of the M68HC08 instruction set.

Table 7-1. Instruction Set Summary (Sheet 1 of 6)

Effect

Source

Form

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

AIS #

opr Add Immediate Value (Signed) to SP

AIX #opr Add Immediate Value (Signed) to H:X

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

ASR opr ASRA ASRX ASR opr,X ASR opr,X ASR opr,SP

BCC rel Branch if Carry Bit Clear PC ← (PC) + 2 + rel ? (C) = 0 ––––––REL 24 rr 3

BCLR n, opr Clear Bit n in M Mn ← 0 ––––––

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

BGT opr

BHCC rel Branch if Half Carry Bit Clear PC ← (PC) + 2 + rel ? (H) = 0 ––––––REL 28 rr 3 BHCS rel Branch if Half Carry Bit Set PC ← (PC) + 2 + rel ? (H) = 1 ––––––REL 29 rr 3 BHI rel Branch if Higher PC ← (PC) + 2 + rel ? (C) | (Z) = 0 ––––––REL 22 rr 3

Add with Carry A ← (A) + (M) + (C) – 

Add without Carry A ← (A) + (M) – 

Logical AND A ← (A) & (M) 0 – – –

Arithmetic Shift Left (Same as LSL)

Arithmetic Shift Right  ––

Branch if Greater Than or Equal To (Signed Operands)

Branch if Greater Than (Signed Operands)

Operation Description

SP ← (SP) + (16

H:X ← (H:X) + (16

PC ← (PC) + 2 + rel ? (N

PC ← (PC) + 2 + rel ? (Z) | (N

« M)

⊕ V) = 0

on CCR

VH I NZC

––––––IMM A7 ii 2

––––––IMM AF ii 2

 ––



––––––REL 90 rr 3

––––––REL 92 rr 3

Address

Mode

IMM DIR EXT IX2 IX1 IX SP1 SP2

DIR INH INH IX1 IX SP1

DIR (b0) DIR (b1) DIR (b2) DIR (b3) DIR (b4) DIR (b5) DIR (b6) DIR (b7)

A9 B9 C9 D9 E9

F9 9EE9 9ED9

FB 9EEB

9EDB

9EE4 9ED4

78 9E68

77 9E67

Opcode

ii dd hh ll ee ff ff

ff ee ff

ii dd hh ll ee ff ff

ff ee ff

ii dd hh ll ee ff ff

ff ee ff

ff dd

dd dd dd dd dd dd dd dd

Operand

Cycles

2 3 4 4 3 2 4 5

4 1 1 4 3 5

4 4 4 4 4 4 4 4

MC68HC908QB8 Data Sheet, Rev. 1

70 Freescale Semiconductor

Instruction Set Summary

Table 7-1. Instruction Set Summary (Sheet 2 of 6)

Effect

Source

Form

BHS rel

BIH rel Branch if IRQ BIL rel Branch if IRQ BIT #opr

BIT opr BIT opr BIT opr,X BIT opr,X BIT ,X BIT opr,SP BIT opr,SP

BLE opr

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) BMC rel Branch if Interrupt Mask Clear PC ← (PC) + 2 + rel ? (I) = 0 ––––––REL 2C rr 3

BMI rel Branch if Minus PC ← (PC) + 2 + rel ? (N) = 1 ––––––REL 2B rr 3 BMS rel Branch if Interrupt Mask Set PC ← (PC) + 2 + rel ? (I) = 1 ––––––REL 2D rr 3 BNE rel Branch if Not Equal PC ← (PC) + 2 + rel ? (Z) = 0 ––––––REL 26 rr 3 BPL rel Branch if Plus PC ← (PC) + 2 + rel ? (N) = 0 ––––––REL 2A rr 3 BRA rel Branch Always PC ← (PC) + 2 + rel ––––––REL 20 rr 3

BRCLR n,opr,rel Branch if Bit n in M Clear PC ← (PC) + 3 + rel ? (Mn) = 0 –––––

BRN rel Branch Never PC ← (PC) + 2 ––––––REL 21 rr 3

BRSET n,opr,rel Branch if Bit n in M Set PC ← (PC) + 3 +

BSET n,opr Set Bit n in M Mn ← 1 ––––––

BSR rel Branch to Subroutine

CBEQ opr,rel CBEQA #opr,rel CBEQX #opr,rel CBEQ opr,X+,rel CBEQ X+,rel CBEQ opr,SP,rel

CLC Clear Carry Bit C ← 0 –––––0INH 98 1 CLI Clear Interrupt Mask I ← 0 ––0–––INH 9A 2

Branch if Higher or Same (Same as BCC)

Bit Test (A) & (M) 0 – – –

Branch if Less Than or Equal To (Signed Operands)

Compare and Branch if Equal

Operation Description

PC ← (PC) + 2 + rel ? (C) = 0 ––––––REL 24 rr 3

Pin High PC ← (PC) + 2 + rel ? IRQ = 1 ––––––REL 2F rr 3 Pin Low PC ← (PC) + 2 + rel ? IRQ = 0 ––––––REL 2E rr 3

PC ← (PC) + 2 + rel ? (Z) | (N

PC ← (PC) + 2 + rel ? (N

rel ? (Mn) = 1 –––––

PC ← (PC) + 2; push (PCL) SP ← (SP) – 1; push (PCH)

SP ← (SP) – 1

PC ← (PC) + rel

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

⊕ V) = 1

⊕ V) =1

on CCR

VH I NZC

––––––REL 93 rr 3

––––––REL 91 rr 3

––––––REL AD rr 4

––––––

Address

Mode

IMM DIR EXT IX2 IX1 IX SP1 SP2

DIR (b0) DIR (b1) DIR (b2) DIR (b3) DIR (b4) DIR (b5) DIR (b6) DIR (b7)

DIR IMM IMM IX1+ IX+ SP1

9EE5 9ED5

71 9E61

Opcode

ii dd hh ll ee ff ff

ff ee ff

dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr

dd dd dd dd dd dd dd dd

dd rr ii rr ii rr ff rr rr ff rr

Operand

2 3 4 4 3 2 4 5

5 5 5 5 5 5 5 5

4 4 4 4 4 4 4 4

5 4 4 5 4 6

Cycles

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 71

Central Processor Unit (CPU)

Source

Form

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

COM

opr

COMA COMX COM opr,X COM ,X COM opr,SP

CPHX #opr CPHX opr

CPX #opr CPX opr CPX opr CPX ,X CPX opr,X CPX opr,X CPX opr,SP CPX opr,SP

DAA Decimal Adjust A

DBNZ opr,rel DBNZA rel DBNZX rel DBNZ opr,X,rel DBNZ X,rel DBNZ opr,SP,rel

DEC opr DECA DECX DEC opr,X DEC ,X DEC opr,SP

DIV Divide

EOR #opr EOR opr EOR opr EOR opr,X EOR opr,X EOR ,X EOR opr,SP EOR opr,SP

INC opr INCA INCX INC opr,X INC ,X INC opr,SP

Clear

Compare A with M (A) – (M)  ––

Complement (One’s Complement)

Compare H:X with M (H:X) – (M:M + 1)  ––

Compare X with M (X) – (M)  ––

Decrement and Branch if Not Zero

Decrement

Exclusive OR M with A

Increment

Operation Description

Table 7-1. Instruction Set Summary (Sheet 3 of 6)

Effect

on CCR

VH I NZC

M ← $00 A ← $00 X ← $00 H ← $00 M ← $00 M ← $00 M ← $00

M ← (M

) = $FF – (M)

A ← (A

) = $FF – (M)

X ← (X) = $FF – (M)

M ← (M

) = $FF – (M)

M ← (M) = $FF – (M) M ← (M) = $FF – (M)

(A)

A ← (A) – 1 or M ← (M) – 1 or X ← (X) – 1

PC ← (PC) + 3 + rel ? (result) ≠ 0 PC ← (PC) + 2 + rel ? (result) ≠ 0 PC ← (PC) + 2 + rel ? (result) ≠ 0 PC ← (PC) + 3 + rel ? (result) ≠ 0 PC ← (PC) + 2 + rel ? (result) ≠ 0 PC ← (PC) + 4 + rel ? (result) ≠ 0

← (M) – 1 A ← (A) – 1 X ← (X) – 1

M ← (M) – 1 M ← (M) – 1 M ← (M) – 1

A ← (H:A)/(X)

H ← Remainder

A ← (A

⊕ M)

M ← (M) + 1

A ← (A) + 1 X ← (X) + 1

M ← (M) + 1 M ← (M) + 1 M ← (M) + 1

0––01–

0––1

U–– INH 72 2

––––––

 –––

––––INH 52 7

0–––

 –––

DIR INH INH INH IX1 IX SP1

IMM DIR EXT IX2 IX1 IX SP1 SP2

DIR INH INH IX1 IX SP1

IMM DIR

IMM DIR EXT IX2 IX1 IX SP1 SP2

DIR INH INH IX1 IX SP1

IMM DIR EXT IX2 IX1 IX SP1 SP2

DIR INH INH IX1 IX SP1

Address

Mode

Opcode

Operand

dd 4F 5F 8C 6F

ff 7F

9E6F

hh ll

ee ff

E1 F1

9EE1

ee ff

9ED1

dd 43 53 63

ff 73

9E63

ff 6575ii ii+1dd3

ii B3

dd C3

hh ll D3

ee ff E3

ff F3

9EE3

9ED3

ee ff

dd rr 4B

rr 5B

rr 6B

ff rr 7B

9E6B

ff rr 3A

dd 4A 5A 6A

ff 7A

9E6A

ii B8

dd C8

hh ll D8

ee ff E8

ff F8

9EE8

9ED8

ee ff 3C

dd 4C 5C 6C

ff 7C

9E6C

Cycles

3 1 1 1 3 2 4

2 3 4 4 3 2 4 5

4 1 1 4 3 5

4 2

3 4 4 3 2 4 5

5 3 3 5 4 6

4 1 1 4 3 5

2 3 4 4 3 2 4 5

4 1 1 4 3 5

MC68HC908QB8 Data Sheet, Rev. 1

72 Freescale Semiconductor

Instruction Set Summary

Table 7-1. Instruction Set Summary (Sheet 4 of 6)

Effect

Source

Form

JMP opr JMP opr JMP opr,X JMP opr,X JMP ,X

JSR opr JSR opr JSR opr,X JSR opr,X JSR ,X

LDA #opr LDA opr LDA opr LDA opr,X LDA opr,X LDA ,X LDA opr,SP LDA opr,SP

LDHX #opr LDHX opr

LDX #opr LDX opr LDX opr LDX opr,X LDX opr,X LDX ,X LDX opr,SP LDX opr,SP

LSL opr LSLA LSLX LSL opr,X LSL ,X LSL opr,SP

LSR opr LSRA LSRX LSR opr,X LSR ,X LSR opr,SP

MOV opr,opr MOV opr,X+ MOV #opr,opr MOV X+,opr

MUL Unsigned multiply X:A ← (X) × (A) –0–––0INH 42 5 NEG opr

NEGA NEGX NEG opr,X NEG ,X NEG opr,SP

NOP No Operation None ––––––INH 9D 1 NSA Nibble Swap A A ← (A[3:0]:A[7:4]) ––––––INH 62 3 ORA #opr

ORA opr ORA opr ORA opr,X ORA opr,X ORA ,X ORA opr,SP ORA opr,SP

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

Jump PC ← Jump Address ––––––

Jump to Subroutine

Load A from M A ← (M) 0–––

Load H:X from M H:X ← (M:M + 1) 0–––

Load X from M X ← (M) 0–––

Logical Shift Left (Same as ASL)

Logical Shift Right  ––0

Move

Negate (Two’s Complement)

Inclusive OR A and M A ← (A) | (M) 0 – – –

Operation Description

PC ← (PC) + n (n = 1, 2, or 3)

Push (PCL); SP ← (SP) – 1

Push (PCH); SP ← (SP) – 1

PC ← Unconditional Address

(M)

Destination

H:X ← (H:X) + 1 (IX+D, DIX+)

M ← –(M) = $00 – (M)

A ← –(A) = $00 – (A)

X ← –(X) = $00 – (X) M ← –(M) = $00 – (M) M ← –(M) = $00 – (M)

← (M)

Source

on CCR

VH I NZC

––––––

 ––

0–––

 ––

DIR EXT IX2 IX1 IX

IMM DIR EXT IX2 IX1 IX SP1 SP2

IMM DIR

IMM DIR EXT IX2 IX1 IX SP1 SP2

DIR INH INH IX1 IX SP1

DD DIX+ IMD IX+D

DIR INH INH IX1 IX SP1

IMM DIR EXT IX2 IX1 IX SP1 SP2

Address

Mode

Opcode

Operand

hh ll

ee ff

FC BD

hh ll

ee ff

hh ll

ee ff

9EE6

9ED6

ee ff

4555ii jjdd3

hh ll

ee ff

9EEE

9EDE

ee ff

dd 48 58 68

ff 78

9E68

ff 34

dd 44 54 64

ff 74

9E64

ff 4E

dd dd 5E

dd 6E

ii dd 7E

dd 40 50 60

ff 70

9E60

hh ll

ee ff

9EEA

ee ff

9EDA

2 3 4 3 2

4 5 6 5 4

2 3 4 4 3 2 4 5

4 2

3 4 4 3 2 4 5

4 1 1 4 3 5

5 4 4 4

4 1 1 4 3 5

2 3 4 4 3 2 4 5

Cycles

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 73

Central Processor Unit (CPU)

Table 7-1. Instruction Set Summary (Sheet 5 of 6)

Effect

Source

Form

PULA Pull A from Stack SP ← (SP + 1); Pull (A) ––––––INH 86 2 PULH Pull H from Stack SP ← (SP + 1); Pull (H) ––––––INH 8A 2 PULX Pull X from Stack SP ← (SP + 1); Pull (X) ––––––INH 88 2 ROL opr

ROLA ROLX ROL opr,X ROL ,X ROL opr,SP

ROR opr RORA RORX ROR opr,X ROR ,X ROR opr,SP

RSP Reset Stack Pointer SP ← $FF ––––––INH 9C 1

RTI Return from Interrupt

RTS Return from Subroutine

SBC #opr SBC opr SBC opr SBC opr,X SBC opr,X SBC ,X SBC opr,SP SBC opr,SP

SEC Set Carry Bit C ← 1 –––––1INH 99 1 SEI Set Interrupt Mask I ← 1 ––1–––INH 9B 2 STA opr

STA opr STA opr,X STA opr,X STA ,X STA opr,SP STA opr,SP

STHX opr Store H:X in M (M:M + 1) ← (H:X) 0 – – – DIR 35 dd 4

STOP

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

Rotate Left through Carry  ––

Rotate Right through Carry  ––

Subtract with Carry A ← (A) – (M) – (C)  ––

Store A in M M ← (A) 0–––

Enable Interrupts, Stop Processing, Refer to MCU Documentation

Store X in M M ← (X) 0–––

Subtract A ← (A) – (M)  ––

Operation Description

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)

SP ← SP + 1; Pull (PCH) SP ← SP + 1; Pull (PCL)

I ← 0; Stop Processing ––0–––INH 8E 1

on CCR

VH I NZC

INH 80 7

––––––INH 81 4



DIR INH INH IX1 IX SP1

IMM DIR EXT IX2 IX1 IX SP1 SP2

DIR EXT IX2 IX1 IX SP1 SP2

IMM DIR EXT IX2 IX1 IX SP1 SP2

Address

Mode

9E69

9E66

9EE2 9ED2

9EE7 9ED7

9EEF 9EDF

9EE0 9ED0

39 49 59 69 79

36 46 56 66 76

A2 B2

C2 D2

E2 F2

C7 D7

E7 F7

BF CF DF EF

A0 B0

C0 D0

E0 F0

Opcode

hh ll

ee ff

hh ll

ee ff

hh ll

ee ff

hh ll

ee ff

Operand

Cycles

4 1 1 4 3 5

2 3 4 4 3 2 4 5

3 4 4 3 2 4 5

2 3 4 4 3 2 4 5

MC68HC908QB8 Data Sheet, Rev. 1

74 Freescale Semiconductor

Opcode Map

Table 7-1. Instruction Set Summary (Sheet 6 of 6)

Effect

Source

Form

SWI Software Interrupt

TAP Transfer A to CCR CCR ← (A) INH 84 2 TAX Transfer A to X X ← (A) ––––––INH 97 1 TPA Transfer CCR to A A ← (CCR) ––––––INH 85 1 TST opr

TSTA TSTX TST opr,X TST ,X TST opr,SP

TSX Transfer SP to H:X H:X ← (SP) + 1 ––––––INH 95 2 TXA Transfer X to A A ← (X) ––––––INH 9F 1 TXS Transfer H:X to SP (SP) ← (H:X) – 1 ––––––INH 94 2

WAIT Enable Interrupts; Wait for Interrupt

A Accumulator n Any bit C Carry/borrow bit opr Operand (one or two bytes) CCR Condition code register PC Program counter dd Direct address of operand PCH Program counter high byte dd rr Direct address of operand and relative offset of branch instruction PCL Program counter low byte DD Direct to direct addressing mode REL Relative addressing mode DIR Direct addressing mode rel Relative program counter offset byte DIX+ Direct to indexed with post increment addressing mode rr Relative program counter offset byte ee ff High and low bytes of offset in indexed, 16-bit offset addressing SP1 Stack pointer, 8-bit offset addressing mode EXT Extended addressing mode SP2 Stack pointer 16-bit offset addressing mode ff Offset byte in indexed, 8-bit offset addressing SP Stack pointer H Half-carry bit U Undefined H Index register high byte V Overflow bit hh ll High and low bytes of operand address in extended addressing X Index register low byte I Interrupt mask Z Zero bit ii Immediate operand byte & Logical AND IMD Immediate source to direct destination addressing mode | Logical OR

IMM Immediate addressing mode INH Inherent addressing mode ( ) Contents of IX Indexed, no offset addressing mode –( ) Negation (two’s complement) IX+ Indexed, no offset, post increment addressing mode # Immediate value IX+D Indexed with post increment to direct addressing mode IX1 Indexed, 8-bit offset addressing mode ← Loaded with IX1+ Indexed, 8-bit offset, post increment addressing mode ? If IX2 Indexed, 16-bit offset addressing mode : Concatenated with M Memory location  Set or cleared N Negative bit — Not affected

Test for Negative or Zero (A) – $00 or (X) – $00 or (M) – $00 0 – – –

Operation Description

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

I bit ← 0; Inhibit CPU clocking

until interrupted

⊕ Logical EXCLUSIVE OR

« Sign extend

on CCR

VH I NZC

––1–––INH 83 9

––0–––INH 8F 1

DIR INH INH IX1 IX SP1

Address

Mode

9E6D

3D 4D 5D 6D 7D

Opcode

Operand

3 1 1 3 2 4

Cycles

7.8 Opcode Map

See Table 7-2.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 75

Central Processor Unit (CPU)

SUB

1IX

SUB

3 SP1

SUB

2IX1

SUB

4 SP2

SUB

3IX2

SUB

3EXT

SUB

2DIR

SUB

2IMM

BGE

2REL

RTI

1INH

NEG

1IX

NEG

3 SP1

NEG

2IX1

NEGX

1INH

NEGA

1INH

NEG

2DIR

BRA

2REL

BSET0

2DIR

Table 7-2. Opcode Map

CMP

BLT

RTS

CBEQ

CBEQX

CBEQA

CBEQ

BRN

BCLR0

1IX

3 SP1

2IX1

4 SP2

3IX2

3EXT

2DIR

2IMM

2REL

1INH

2IX+

4 SP1

3IX1+

3IMM

3DIR

2REL

2DIR

SBC

BGT

DAA

NSA

DIV

MUL

BHI

BSET1

1IX

3 SP1

2IX1

4 SP2

3IX2

3EXT

2DIR

2IMM

2REL

1INH

2REL

2DIR

CPX

BLE

SWI

COM

COMX

COMA

COM

BLS

BCLR1

1IX

3 SP1

2IX1

4 SP2

3IX2

3EXT

2DIR

2IMM

2REL

1INH

1IX

3 SP1

2IX1

1INH

2DIR

2REL

2DIR

AND

1IX

AND

3 SP1

AND

2IX1

AND

4 SP2

AND

3IX2

AND

3EXT

AND

2DIR

AND

2IMM

TXS

1INH

TA P

1INH

LSR

1IX

LSR

3 SP1

LSR

2IX1

LSRX

1INH

LSRA

1INH

LSR

2DIR

BCC

2REL

BSET2

2DIR

BIT

TSX

TPA

CPHX

LDHX

STHX

BCS

BCLR2

1IX

3 SP1

2IX1

4 SP2

3IX2

3EXT

2DIR

2IMM

1INH

2DIR

3IMM

2DIR

3IMM

2DIR

2REL

2DIR

LDA

1IX

LDA

3 SP1

LDA

2IX1

LDA

4 SP2

LDA

3IX2

LDA

3EXT

LDA

2DIR

LDA

2IMM

PULA

1INH

ROR

1IX

ROR

3 SP1

ROR

2IX1

RORX

1INH

RORA

1INH

ROR

2DIR

BNE

2REL

BSET3

2DIR

STA

1IX

STA

3 SP1

STA

2IX1

STA

4 SP2

STA

3IX2

STA

3EXT

STA

2DIR

AIS

2IMM

TA X

1INH

PSHA

1INH

ASR

1IX

ASR

3 SP1

ASR

2IX1

ASRX

1INH

ASRA

1INH

ASR

2DIR

BEQ

2REL

BCLR3

2DIR

EOR

1IX

EOR

3 SP1

EOR

2IX1

EOR

4 SP2

EOR

3IX2

EOR

3EXT

EOR

2DIR

EOR

2IMM

CLC

1INH

PULX

1INH

LSL

1IX

LSL

3 SP1

LSL

2IX1

LSLX

1INH

LSLA

1INH

LSL

2DIR

BHCC

2REL

BSET4

2DIR

ADC

1IX

ADC

3 SP1

ADC

2IX1

ADC

4 SP2

ADC

3IX2

ADC

3EXT

ADC

2DIR

ADC

2IMM

SEC

1INH

PSHX

1INH

ROL

1IX

ROL

3 SP1

ROL

2IX1

ROLX

1INH

ROLA

1INH

ROL

2DIR

BHCS

2REL

BCLR4

2DIR

ORA

1IX

ORA

3 SP1

ORA

2IX1

ORA

4 SP2

ORA

3IX2

ORA

3EXT

ORA

2DIR

ORA

2IMM

CLI

1INH

PULH

1INH

DEC

1IX

DEC

3 SP1

DEC

2IX1

DECX

1INH

DECA

1INH

DEC

2DIR

BPL

2REL

BSET5

2DIR

ADD

SEI

PSHH

DBNZ

DBNZX

DBNZA

DBNZ

BMI

BCLR5

1IX

3 SP1

2IX1

4 SP2

3IX2

3EXT

2DIR

2IMM

1INH

2IX

4 SP1

3IX1

2INH

3DIR

2REL

2DIR

JMP

1IX

JMP

2IX1

JMP

3IX2

JMP

3EXT

JMP

2DIR

RSP

1INH

CLRH

1INH

INC

1IX

INC

3 SP1

INC

2IX1

INCX

1INH

INCA

1INH

INC

2DIR

BMC

2REL

BSET6

2DIR

JSR

1IX

JSR

2IX1

JSR

3IX2

JSR

3EXT

JSR

2DIR

BSR

2REL

NOP

1INH

TST

1IX

TST

3 SP1

TST

2IX1

TSTX

1INH

TSTA

1INH

TST

2DIR

BMS

2REL

BCLR6

2DIR

STX

LDX

1IX

STX

LDX

3 SP1

STX

LDX

2IX1

STX

LDX

4 SP2

STX

LDX

3IX2

STX

LDX

3EXT

STX

LDX

2DIR

AIX

LDX

2IMM

TXA

1INH

WAIT

STOP

1INH

CLR

MOV

1IX

2IX+D

CLR

3 SP1

CLR

MOV

2IX1

3IMD

MOV

CLRX

1INH

2DIX+

MOV

CLRA

1INH

3DD

CLR

2DIR

BIL

BIH

2REL

BSET7

BCLR7

2DIR

MSB

0 High Byte of Opcode in Hexadecimal

LSB

Cycles

Opcode Mnemonic

Number of Bytes / Addressing Mode

BRSET0

3DIR

Low Byte of Opcode in Hexadecimal 0

0 1 2 3 4 5 6 9E6 7 8 9 A B C D 9ED E 9EE F

DIR DIR REL DIR INH INH IX1 SP1 IX INH INH IMM DIR EXT IX2 SP2 IX1 SP1 IX

Bit Manipulation Branch Read-Modify-Write Control Register/Memory

MSB

BRSET0

3DIR

LSB

BRSET1

BRCLR0

3DIR

BRSET2

3DIR

BRCLR1

3DIR

BRSET3

3DIR

BRCLR2

3DIR

BRSET4

3DIR

BRCLR3

3DIR

BRSET5

3DIR

BRSET6

BRCLR5

3DIR

BRCLR6

3DIR

BRCLR4

3DIR

BRSET7

BRCLR7

3DIR

INH Inherent REL Relative SP1 Stack Pointer, 8-Bit Offset

IMM Immediate IX Indexed, No Offset SP2 Stack Pointer, 16-Bit Offset

DIR Direct IX1 Indexed, 8-Bit Offset IX+ Indexed, No Offset with

EXT Extended IX2 Indexed, 16-Bit Offset Post Increment

DD Direct-Direct IMD Immediate-Direct IX1+ Indexed, 1-Byte Offset with

IX+D Indexed-Direct DIX+ Direct-Indexed Post Increment

*Pre-byte for stack pointer indexed instructions

MC68HC908QB8 Data Sheet, Rev. 1

76 Freescale Semiconductor

Chapter 8 External Interrupt (IRQ)

8.1 Introduction

The IRQ (external interrupt) module provides a maskable interrupt input.

functionality is enabled by setting configuration register 2 (CONFIG2) IRQEN bit accordingly. A zero

IRQ disables the IRQ function and IRQ function. See Chapter 5 Configuration Register (CONFIG) for more information on enabling the IRQ pin.

The IRQ pin shares its pin with general-purpose input/output (I/O) port pins. See Figure 8-1 for port location of this shared pin.

8.2 Features

Features of the IRQ module include:

• A dedicated external interrupt pin IRQ

• IRQ interrupt control bits

• Programmable edge-only or edge and level interrupt sensitivity

• Automatic interrupt acknowledge

• Internal pullup device

will assume the other shared functionalities. A one enables the IRQ

8.3 Functional Description

A low level applied to the external interrupt request (IRQ) pin can latch a CPU interrupt request. Figure 8-2 shows the structure of the IRQ module.

Interrupt signals on the IRQ following actions occurs:

• IRQ vector fetch. An IRQ vector fetch automatically generates an interrupt acknowledge signal that clears the latch that caused the vector fetch.

• Software clear. Software can clear the IRQ latch by writing a 1 to the ACK bit in the interrupt status and control register (INTSCR).

• Reset. A reset automatically clears the IRQ latch.

The external IRQ edge or falling edge and low level sensitive. The MODE bit in INTSCR controls the triggering sensitivity of the IRQ

pin.

pin is falling edge sensitive out of reset and is software-configurable to be either falling

pin are latched into the IRQ latch. The IRQ latch remains set until one of the

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 77

External Interrupt (IRQ)

PTA0/TCH0/AD0/KBI0

PTA1/TCH1/AD1/KBI1

PTA2/IRQ

PTA4/OSC2/AD2/KBI4

PTA5/OSC1/AD3/KBI5

/KBI2/TCLK

PTA3/RST

PTB0/SCK/AD4 PTB1/MOSI/AD5 PTB2/MISO/AD6

/KBI3

PTB3/SS

PTB4/RxD/AD8

PTB5/TxD/AD9

/AD7

PTB6/TCH2 PTB7/TCH3

PTA

PTB

DDRA

DDRB

M68HC08 CPU

CLOCK

GENERATOR

KEYBOARD INTERRUPT

MODULE

EXTERNAL INTERRUPT

MODULE

AUTO WAKEUP

MODULE

LOW-VOLTAGE

INHIBIT

4-CHANNEL 16-BIT

TIMER MODULE

MC68HC908QB8

256 BYTES

USER RAM

POWER SUPPLY

RST, IRQ: Pins have internal pull up device All port pins have programmable pull up device PTA[0:5]: Higher current sink and source capability

MC68HC908QB8

8192 BYTES

USER FLASH

Figure 8-1. Block Diagram Highlighting IRQ Block and Pin

When set, the IMASK bit in INTSCR masks the IRQ

interrupt request. A latched interrupt request is not

presented to the interrupt priority logic unless IMASK is clear.

COP

MODULE

10-CHANNEL

10-BIT ADC

ENHANCED SERIAL

COMMUNICATIONS

INTERFACE MODULE

SERIAL PERIPHERAL

INTERFACE

DEVELOPMENT SUPPORT

MONITOR ROM

BREAK MODULE

NOTE

The interrupt mask (I) in the condition code register (CCR) masks all interrupt requests, including the IRQ

A falling edge on the IRQ

pin can latch an interrupt request into the IRQ latch. An IRQ vector fetch,

interrupt request.

software clear, or reset clears the IRQ latch.

MC68HC908QB8 Data Sheet, Rev. 1

78 Freescale Semiconductor

RESET

ACK

Functional Description

IRQ VECTOR

FETCH

DECODER

INTERNAL ADDRESS BUS

IRQ

INTERNAL PULLUP DEVICE

IRQ LATCH

MODE

CLR

SYNCHRONIZER

IMASK

HIGH

VOLTAGE

DETECT

IRQF

TO CPU FOR BIL/BIH INSTRUCTIONS

IRQ INTERRUPT REQUEST

TO MODE SELECT LOGIC

Figure 8-2. IRQ Module Block Diagram

8.3.1 MODE = 1

If the MODE bit is set, the IRQ pin is both falling edge sensitive and low level sensitive. With MODE set, both of the following actions must occur to clear the IRQ

• Return of the IRQ

pin to a high level. As long as the IRQ pin is low, the IRQ request remains active.

• IRQ vector fetch or software clear. An IRQ vector fetch generates an interrupt acknowledge signal to clear the IRQ latch. Software generates the interrupt acknowledge signal by writing a 1 to ACK in INTSCR. The ACK bit is useful in applications that poll the IRQ the IRQ latch. Writing to ACK prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. Setting ACK does not affect subsequent transitions on the IRQ edge that occurs after writing to ACK latches another interrupt request. If the IRQ mask bit, IMASK, is clear, the CPU loads the program counter with the IRQ vector address.

interrupt request:

pin and require software to clear

pin. A falling

The IRQ vector fetch or software clear and the return of the IRQ The interrupt request remains pending as long as the IRQ

pin to a high level may occur in any order.

pin is low. A reset will clear the IRQ latch and

the MODE control bit, thereby clearing the interrupt even if the pin stays low.

Use the BIH or BIL instruction to read the logic level on the IRQ

pin.

8.3.2 MODE = 0

If the MODE bit is clear, the IRQ pin is falling edge sensitive only. With MODE clear, an IRQ vector fetch or software clear immediately clears the IRQ latch.

The IRQF bit in INTSCR can be read to check for pending interrupts. The IRQF bit is not affected by IMASK, which makes it useful in applications where polling is preferred.

NOTE

When using the level-sensitive interrupt trigger, avoid false IRQ interrupts by masking interrupt requests in the interrupt routine.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 79

External Interrupt (IRQ)

8.4 Interrupts

The following IRQ source can generate interrupt requests:

• Interrupt flag (IRQF) — The IRQF bit is set when the IRQ The IRQ interrupt mask bit, IMASK, is used to enable or disable IRQ interrupt requests.

pin is asserted based on the IRQ mode..

8.5 Low-Power Modes

The WAIT and STOP instructions put the MCU in low power-consumption standby modes.

8.5.1 Wait Mode

The IRQ module remains active in wait mode. Clearing IMASK in INTSCR enables IRQ interrupt requests to bring the MCU out of wait mode.

8.5.2 Stop Mode

The IRQ module remains active in stop mode. Clearing IMASK in INTSCR enables IRQ interrupt requests to bring the MCU out of stop mode.

8.6 IRQ Module During Break Interrupts

The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the break flag control register (BFCR) enables software to clear status bits during the break state. See BFCR in the SIM section of this data sheet.

To allow software to clear status bits during a break interrupt, write a 1 to BCFE. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state.

To protect status bits during the break state, write a 0 to BCFE. With BCFE cleared (its default state), software can read and write registers during the break state without affecting status bits. Some status bits have a two-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is cleared. After the break, doing the second step clears the status bit.

8.7 I/O Signals

The IRQ module does not share its pin with any module on this MCU.

8.7.1 IRQ Input Pins (IRQ)

The IRQ pin provides a maskable external interrupt source. The IRQ pin contains an internal pullup device.

MC68HC908QB8 Data Sheet, Rev. 1

80 Freescale Semiconductor

Registers

8.8 Registers

The IRQ status and control register (INTSCR) controls and monitors operation of the IRQ module. The INTSCR:

• Shows the state of the IRQ flag

• Clears the IRQ latch

• Masks the IRQ interrupt request

• Controls triggering sensitivity of the IRQ

Bit 7654321Bit 0

Read:0000IRQF0

Write:

Reset:00000000

= Unimplemented

Figure 8-3. IRQ Status and Control Register (INTSCR)

IRQF — IRQ Flag Bit

This read-only status bit is set when the IRQ interrupt is pending.

1 = IRQ 0 = IRQ

interrupt pending interrupt not pending

interrupt pin

ACK

IMASK MODE

ACK — IRQ Interrupt Request Acknowledge Bit

Writing a 1 to this write-only bit clears the IRQ latch. ACK always reads 0.

IMASK — IRQ Interrupt Mask Bit

Writing a 1 to this read/write bit disables the IRQ interrupt request.

1 = IRQ interrupt request disabled 0 = IRQ interrupt request enabled

MODE — IRQ Edge/Level Select Bit

This read/write bit controls the triggering sensitivity of the IRQ

1 = IRQ 0 = IRQ

interrupt request on falling edges and low levels interrupt request on falling edges only

pin.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 81

External Interrupt (IRQ)

MC68HC908QB8 Data Sheet, Rev. 1

82 Freescale Semiconductor

Chapter 9 Keyboard Interrupt Module (KBI)

9.1 Introduction

The keyboard interrupt module (KBI) provides independently maskable external interrupts.

The KBI shares its pins with general-purpose input/output (I/O) port pins. See Figure 9-1 for port location of these shared pins.

9.2 Features

Features of the keyboard interrupt module include:

• Keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard interrupt mask

• Programmable edge-only or edge and level interrupt sensitivity

• Edge sensitivity programmable for rising or falling edge

• Level sensitivity programmable for high or low level

• Pullup or pulldown device automatically enabled based on the polarity of edge or level detect

• Exit from low-power modes

9.3 Functional Description

The keyboard interrupt module controls the enabling/disabling of interrupt functions on the KBI pins. These pins can be enabled/disabled independently of each other. See Figure 9-2.

9.3.1 Keyboard Operation

Writing to the KBIEx bits in the keyboard interrupt enable register (KBIER) independently enables or disables each KBI pin. The polarity of the keyboard interrupt is controlled using the KBIPx bits in the keyboard interrupt polarity register (KBIPR). Edge-only or edge and level sensitivity is controlled using the MODEK bit in the keyboard status and control register (KBISCR).

Enabling a keyboard interrupt pin also enables its internal pullup or pulldown device based on the polarity enabled. On falling edge or low level detection, a pullup device is configured. On rising edge or high level detection, a pulldown device is configured.

The keyboard interrupt latch is set when one or more enabled keyboard interrupt inputs are asserted.

• If the keyboard interrupt sensitivity is edge-only, for KBIPx = 0, a falling (for KBIPx = 1, a rising) edge on a keyboard interrupt input does not latch an interrupt request if another enabled keyboard pin is already asserted. To prevent losing an interrupt request on one input because another input remains asserted, software can disable the latter input while it is asserted.

• If the keyboard interrupt is edge and level sensitive, an interrupt request is present as long as any enabled keyboard interrupt input is asserted.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 83

Keyboard Interrupt Module (KBI)

PTA0/TCH0/AD0/KBI0

PTA1/TCH1/AD1/KBI1

PTA2/IRQ

PTA4/OSC2/AD2/KBI4

PTA5/OSC1/AD3/KBI5

/KBI2/TCLK

PTA3/RST

PTB1/MOSI/AD5 PTB2/MISO/AD6

/KBI3

PTB0/SCK/AD4

PTB3/SS

PTB4/RxD/AD8

/AD7

PTB5/TxD/AD9

PTB6/TCH2 PTB7/TCH3

PTA

PTB

DDRA

DDRB

M68HC08 CPU

CLOCK

GENERATOR

KEYBOARD INTERRUPT

MODULE

EXTERNAL INTERRUPT

MODULE

AUTO WAKEUP

MODULE

LOW-VOLTAGE

INHIBIT

4-CHANNEL 16-BIT

TIMER MODULE

MC68HC908QB8

256 BYTES

USER RAM

POWER SUPPLY

RST, IRQ: Pins have internal pull up device All port pins have programmable pull up device PTA[0:5]: Higher current sink and source capability

MC68HC908QB8

8192 BYTES

USER FLASH

DEVELOPMENT SUPPORT

COP

MODULE

10-CHANNEL

10-BIT ADC

ENHANCED SERIAL COMMUNICATIONS

INTERFACE MODULE

SERIAL PERIPHERAL

INTERFACE

MONITOR ROM

BREAK MODULE

Figure 9-1. Block Diagram Highlighting KBI Block and Pins

9.3.1.1 MODEK = 1

If the MODEK bit is set, the keyboard interrupt inputs are both edge and level sensitive. The KBIPx bit will determine whether a edge sensitive pin detects rising or falling edges and on level sensitive pins whether the pin detects low or high levels. With MODEK set, both of the following actions must occur to clear a keyboard interrupt request:

• Return of all enabled keyboard interrupt inputs to a deasserted level. As long as any enabled keyboard interrupt pin is asserted, the keyboard interrupt remains active.

MC68HC908QB8 Data Sheet, Rev. 1

84 Freescale Semiconductor

INTERNAL BUS

VECTOR FETCH

DECODER

Functional Description

ACKK

RESET

AWUIREQ

KBIE0

TO PULLUP/ PULLDOWN ENABLE

KBIEx

TO PULLUP/ PULLDOWN ENABLE

MODEK

KBI LATCH

CLR

SYNCHRONIZER

IMASKK

KEYF

KEYBOARD INTERRUPT REQUEST

KBI0

KBIP0

KBIx

KBIPx

(SEE Figure 4-1)

Figure 9-2. Keyboard Interrupt Block Diagram

• Vector fetch or software clear. A KBI vector fetch generates an interrupt acknowledge signal to clear the KBI latch. Software generates the interrupt acknowledge signal by writing a 1 to ACKK in KBSCR. The ACKK bit is useful in applications that poll the keyboard interrupt inputs and require software to clear the KBI latch. Writing to ACKK prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. Setting ACKK does not affect subsequent transitions on the keyboard interrupt inputs. An edge detect that occurs after writing to ACKK latches another interrupt request. If the keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the program counter with the KBI vector address.

The KBI vector fetch or software clear and the return of all enabled keyboard interrupt pins to a deasserted level may occur in any order.

Reset clears the keyboard interrupt request and the MODEK bit, clearing the interrupt request even if a keyboard interrupt input stays asserted.

9.3.1.2 MODEK = 0

If the MODEK bit is clear, the keyboard interrupt inputs are edge sensitive. The KBIPx bit will determine whether an edge sensitive pin detects rising or falling edges. A KBI vector fetch or software clear immediately clears the KBI latch.

The keyboard flag bit (KEYF) in KBSCR can be read to check for pending interrupts. The KEYF bit is not affected by IMASKK, which makes it useful in applications where polling is preferred.

NOTE

Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding keyboard interrupt pin to be an input, overriding the data direction register. However, the data direction register bit must be a 0 for software to read the pin.

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 85

Keyboard Interrupt Module (KBI)

9.3.2 Keyboard Initialization

When a keyboard interrupt pin is enabled, it takes time for the internal pullup or pulldown device to pull the pin to its deasserted level. Therefore a false interrupt can occur as soon as the pin is enabled.

To prevent a false interrupt on keyboard initialization:

1. Mask keyboard interrupts by setting IMASKK in KBSCR.

2. Enable the KBI polarity by setting the appropriate KBIPx bits in KBIPR.

3. Enable the KBI pins by setting the appropriate KBIEx bits in KBIER.

4. Write to ACKK in KBSCR to clear any false interrupts.

5. Clear IMASKK.

An interrupt signal on an edge sensitive pin can be acknowledged immediately after enabling the pin. An interrupt signal on an edge and level sensitive pin must be acknowledged after a delay that depends on the external load.

9.4 Interrupts

The following KBI source can generate interrupt requests:

• Keyboard flag (KEYF) — The KEYF bit is set when any enabled KBI pin is asserted based on the KBI mode and pin polarity. The keyboard interrupt mask bit, IMASKK, is used to enable or disable KBI interrupt requests.

9.5 Low-Power Modes

The WAIT and STOP instructions put the MCU in low power-consumption standby modes.

9.5.1 Wait Mode

The KBI module remains active in wait mode. Clearing IMASKK in KBSCR enables keyboard interrupt requests to bring the MCU out of wait mode.

9.5.2 Stop Mode

The KBI module remains active in stop mode. Clearing IMASKK in KBSCR enables keyboard interrupt requests to bring the MCU out of stop mode.

9.6 KBI During Break Interrupts

To allow software to clear status bits during a break interrupt, write a 1 to BCFE. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state.

MC68HC908QB8 Data Sheet, Rev. 1

86 Freescale Semiconductor

I/O Signals

9.7 I/O Signals

The KBI module can share its pins with the general-purpose I/O pins. See Figure 9-1 for the port pins that are shared.

9.7.1 KBI Input Pins (KBIx:KBI0)

Each KBI pin is independently programmable as an external interrupt source. KBI pin polarity can be controlled independently. Each KBI pin when enabled will automatically configure the appropriate pullup/pulldown device based on polarity.

9.8 Registers

The following registers control and monitor operation of the KBI module:

• KBSCR (keyboard interrupt status and control register)

• KBIER (keyboard interrupt enable register)

• KBIPR (keyboard interrupt polarity register)

9.8.1 Keyboard Status and Control Register (KBSCR)

Features of the KBSCR:

• Flags keyboard interrupt requests

• Acknowledges keyboard interrupt requests

• Masks keyboard interrupt requests

• Controls keyboard interrupt triggering sensitivity

Bit 7654321Bit 0

Read:0000KEYF 0

Write:

Reset:00000000

= Unimplemented

ACKK

IMASKK MODEK

Figure 9-3. Keyboard Status and Control Register (KBSCR)

Bits 7–4 — Not used

KEYF — Keyboard Flag Bit

This read-only bit is set when a keyboard interrupt is pending.

1 = Keyboard interrupt pending 0 = No keyboard interrupt pending

ACKK — Keyboard Acknowledge Bit

Writing a 1 to this write-only bit clears the KBI request. ACKK always reads 0.

IMASKK— Keyboard Interrupt Mask Bit

Writing a 1 to this read/write bit prevents the output of the KBI latch from generating interrupt requests.

1 = Keyboard interrupt requests disabled 0 = Keyboard interrupt requests enabled

MODEK — Keyboard Triggering Sensitivity Bit

This read/write bit controls the triggering sensitivity of the keyboard interrupt pins.

1 = Keyboard interrupt requests on edge and level 0 = Keyboard interrupt requests on edge only

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 87

Keyboard Interrupt Module (KBI)

9.8.2 Keyboard Interrupt Enable Register (KBIER)

KBIER enables or disables each keyboard interrupt pin.

Bit 7654321Bit 0

Write:

Reset:00000000

Figure 9-4. Keyboard Interrupt Enable Register (KBIER)

KBIE5–KBIE0 — Keyboard Interrupt Enable Bits

Each of these read/write bits enables the corresponding keyboard interrupt pin to latch KBI interrupt requests.

1 = KBIx pin enabled as keyboard interrupt pin 0 = KBIx pin not enabled as keyboard interrupt pin

AWUIE bit is not used in conjunction with the keyboard interrupt feature. To see a description of this bit, see Chapter 4 Auto Wakeup Module (AWU)

AWUIE KBIE5 KBIE4 KBIE3 KBIE2 KBIE1 KBIE0

= Unimplemented

NOTE

9.8.3 Keyboard Interrupt Polarity Register (KBIPR)

KBIPR determines the polarity of the enabled keyboard interrupt pin and enables the appropriate pullup or pulldown device.

Bit 7654321Bit 0

Write:

Reset:00000000

= Unimplemented

Figure 9-5. Keyboard Interrupt Polarity Register (KBIPR)

KBIP5–KBIP0 — Keyboard Interrupt Polarity Bits

Each of these read/write bits enables the polarity of the keyboard interrupt detection.

1 = Keyboard polarity is high level and/or rising edge 0 = Keyboard polarity is low level and/or falling edge

KBIP5 KBIP4 KBIP3 KBIP2 KBIP1 KBIP0

MC68HC908QB8 Data Sheet, Rev. 1

88 Freescale Semiconductor

Chapter 10 Low-Voltage Inhibit (LVI)

10.1 Introduction

The low-voltage inhibit (LVI) module is provided as a system protection mechanism to prevent the MCU from operating below a certain operating supply voltage level. The module has several configuration options to allow functionality to be tailored to different system level demands.

The configuration registers (see Chapter 5 Configuration Register (CONFIG)) contain control bits for this module.

10.2 Features

Features of the LVI module include:

• Programmable LVI reset

• Selectable LVI trip voltage

• Programmable stop mode operation

10.3 Functional Description

Figure 10-1 shows the structure of the LVI module. LVISTOP, LVIPWRD, LVITRIP, and LVIRSTD are

user selectable options found in the configuration register.

STOP INSTRUCTION

LVISTOP

FROM CONFIGURATION REGISTER

LVIRSTD

LVIPWRD

FROM CONFIGURATION REGISTER

0 IF V

> V

1 IF V

≤ V

LOW V

DETECTOR

LVITRIP

FROM CONFIGURATION REGISTER

TRIPR

TRIPF

LVIOUT

LVI RESET

Figure 10-1. LVI Module Block Diagram

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 89

Low-Voltage Inhibit (LVI)

The LVI module contains a bandgap reference circuit and comparator. When the LVITRIP bit is cleared, the default state at power-on reset, V

is configured for the lower VDD operating range. The actual

TRIPF

trip points are specified in 18.5 5-V DC Electrical Characteristics and 18.8 3-V DC Electrical

Characteristics.

Because the default LVI trip point after power-on reset is configured for low voltage operation, a system requiring high voltage LVI operation must set the LVITRIP bit during system initialization. V above the LVI trip rising voltage, V

, for the high voltage operating range or the MCU will immediately

TRIPR

must be

go into LVI reset.

After an LVI reset occurs, the MCU remains in reset until V

rises above V

. See Chapter 14 System

TRIPR

Integration Module (SIM) for the reset recovery sequence.

The output of the comparator controls the state of the LVIOUT flag in the LVI status register (LVISR) and can be used for polling LVI operation when the LVI reset is disabled.

The LVI is enabled out of reset. The following bits located in the configuration register can alter the default conditions.

• Setting the LVI power disable bit, LVIPWRD, disables the LVI.

• Setting the LVI reset disable bit, LVIRSTD, prevents the LVI module from generating a reset.

• Setting the LVI enable in stop mode bit, LVISTOP, enables the LVI to operate in stop mode.

• Setting the LVI trip point bit, LVITRIP, configures the trip point voltage (V

) for the higher VDD

TRIPF

operating range.

10.3.1 Polled LVI Operation

In applications that can operate at VDD levels below the V the LVIOUT bit. In the configuration register, LVIPWRD must be cleared to enable the LVI module, and LVIRSTD must be set to disable LVI resets.

level, software can monitor VDD by polling

TRIPF

10.3.2 Forced Reset Operation

In applications that require VDD to remain above the V module to reset the MCU when V

falls below the V

TRIPF

and LVIRSTD must be cleared to enable the LVI module and to enable LVI resets.

level, enabling LVI resets allows the LVI

TRIPF

level. In the configuration register, LVIPWRD

10.3.3 LVI Hysteresis

The LVI has hysteresis to maintain a stable operating condition. After the LVI has triggered (by having V

fall below V

. This prevents a condition in which the MCU is continually entering and exiting reset if VDD is

TRIPR

approximately equal to V

), the MCU will remain in reset until VDD rises above the rising trip point voltage,

TRIPF

. V

is greater than V

TRIPR

by the typical hysteresis voltage, V

TRIPF

HYS

10.3.4 LVI Trip Selection

LVITRIP in the configuration register selects the LVI protection range. The default setting out of reset is for the low voltage range. Because LVITRIP is in a write-once configuration register, the protection range cannot be changed after initialization.

NOTE

The MCU is guaranteed to operate at a minimum supply voltage. The trip point (V section for the actual trip point voltages.

90 Freescale Semiconductor

) may be lower than this. See the Electrical Characteristics

TRIPF

MC68HC908QB8 Data Sheet, Rev. 1

LVI Interrupts

10.4 LVI Interrupts

The LVI module does not generate interrupt requests.

10.5 Low-Power Modes

The STOP and WAIT instructions put the MCU in low power-consumption standby modes.

10.5.1 Wait Mode

If enabled, the LVI module remains active in wait mode. If enabled to generate resets, the LVI module can generate a reset and bring the MCU out of wait mode.

10.5.2 Stop Mode

If the LVIPWRD bit in the configuration register is cleared and the LVISTOP bit in the configuration register is set, the LVI module remains active. If enabled to generate resets, the LVI module can generate a reset and bring the MCU out of stop mode.

10.6 Registers

The LVI status register (LVISR) contains a status bit that is useful when the LVI is enabled and LVI reset is disabled.

Bit 76 5 4 3 2 1Bit 0

Read:LVIOUT000000R

Write:

Reset:00000000

= Unimplemented R = Reserved

Figure 10-2. LVI Status Register (LVISR)

LVIOUT — LVI Output Bit

This read-only flag becomes set when the V when V

voltage rises above V

TRIPR

Table 10-1. LVIOUT Bit Indication

VDD > V

< V

< VDD < V

TRIPF

MC68HC908QB8 Data Sheet, Rev. 1

voltage falls below the V

. (See Table 10-1).

TRIPR

TRIPF

TRIPR

LVIOUT

Previous value

trip voltage and is cleared

TRIPF

Freescale Semiconductor 91

Low-Voltage Inhibit (LVI)

MC68HC908QB8 Data Sheet, Rev. 1

92 Freescale Semiconductor

Chapter 11 Oscillator Module (OSC)

11.1 Introduction

The oscillator (OSC) module is used to provide a stable clock source for the MCU system and bus.

The OSC shares its pins with general-purpose input/output (I/O) port pins. See Figure 11-1 for port location of these shared pins. The OSC2EN bit is located in the port A pull enable register (PTAPUEN) on this MCU. See Chapter 12 Input/Output Ports (PORTS) for information on PTAPUEN register.

11.2 Features

The bus clock frequency is one fourth of any of these clock source options:

1. Internal oscillator: An internally generated, fixed frequency clock, trimmable to ± 0.4%. There are

three choices for the internal oscillator,12.8 MHz, 8 MHz, or 4 MHz. The 4-MHz internal oscillator is the default option out of reset.

2. External oscillator: An external clock that can be driven directly into OSC1.

3. External RC: A built-in oscillator module (RC oscillator) that requires an external R connection only. The capacitor is internal to the chip.

4. External crystal: A built-in XTAL oscillator that requires an external crystal or ceramic-resonator. There are three crystal frequency ranges supported, 8–32 MHz, 1–8 MHz, and 32–100 kHz.

11.3 Functional Description

The oscillator contains these major subsystems:

• Internal oscillator circuit

• Internal or external clock switch control

• External clock circuit

• External crystal circuit

• External RC clock circuit

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 93

Oscillator Module (OSC)

PTA0/TCH0/AD0/KBI0

PTA1/TCH1/AD1/KBI1

PTA2/IRQ

/KBI2/TCLK

PTA3/RST

PTA4/OSC2/AD2/KBI4

PTA5/OSC1/AD3/KBI5

PTB1/MOSI/AD5 PTB2/MISO/AD6

/KBI3

PTB0/SCK/AD4

PTB3/SS

PTB4/RxD/AD8

PTB5/TxD/AD9

/AD7

PTB6/TCH2 PTB7/TCH3

PTA

PTB

DDRA

DDRB

M68HC08 CPU

CLOCK

GENERATOR

KEYBOARD INTERRUPT

MODULE

EXTERNAL INTERRUPT

MODULE

AUTO WAKEUP

MODULE

LOW-VOLTAGE

INHIBIT

4-CHANNEL 16-BIT

TIMER MODULE

MC68HC908QB8

256 BYTES

USER RAM

POWER SUPPLY

RST, IRQ: Pins have internal pull up device All port pins have programmable pull up device PTA[0:5]: Higher current sink and source capability

Figure 11-1. Block Diagram Highlighting OSC Block and Pins

MC68HC908QB8

8192 BYTES

USER FLASH

COP

MODULE

10-CHANNEL

10-BIT ADC

ENHANCED SERIAL COMMUNICATIONS

INTERFACE MODULE

SERIAL PERIPHERAL

INTERFACE

DEVELOPMENT SUPPORT

MONITOR ROM

BREAK MODULE

MC68HC908QB8 Data Sheet, Rev. 1

94 Freescale Semiconductor

Functional Description

11.3.1 Internal Signal Definitions

The following signals and clocks are used in the functional description and figures of the OSC module.

11.3.1.1 Oscillator Enable Signal (SIMOSCEN)

The SIMOSCEN signal comes from the system integration module (SIM) and disables the XTAL oscillator circuit, the RC oscillator, or the internal oscillator in stop mode. OSCENINSTOP in the configuration register can be used to override this signal.

11.3.1.2 XTAL Oscillator Clock (XTALCLK)

XTALCLK is the XTAL oscillator output signal. It runs at the full speed of the crystal (f

) and comes

XCLK

directly from the crystal oscillator circuit. Figure 11-2 shows only the logical relation of XTALCLK to OSC1 and OSC2 and may not represent the actual circuitry. The duty cycle of XTALCLK is unknown and may depend on the crystal and other external factors. The frequency of XTALCLK can be unstable at start up.

11.3.1.3 RC Oscillator Clock (RCCLK)

RCCLK is the RC oscillator output signal. Its frequency is directly proportional to the time constant of the external R (R

) and internal C. Figure 11-3 shows only the logical relation of RCCLK to OSC1 and may

EXT

not represent the actual circuitry.

11.3.1.4 Internal Oscillator Clock (INTCLK)

INTCLK is the internal oscillator output signal. INTCLK is software selectable to be nominally 12.8 MHz,

8.0 MHz, or 4.0 MHz. INTCLK can be digitally adjusted using the oscillator trimming feature of the OSCTRIM register (see 11.3.2.1 Internal Oscillator Trimming).

11.3.1.5 Bus Clock Times 4 (BUSCLKX4)

BUSCLKX4 is the same frequency as the input clock (XTALCLK, RCCLK, or INTCLK). This signal is driven to the SIM module and is used during recovery from reset and stop and is the clock source for the COP module.

11.3.1.6 Bus Clock Times 2 (BUSCLKX2)

The frequency of this signal is equal to half of the BUSCLKX4. This signal is driven to the SIM for generation of the bus clocks used by the CPU and other modules on the MCU. BUSCLKX2 will be divided by two in the SIM. The internal bus frequency is one fourth of the XTALCLK, RCCLK, or INTCLK frequency.

11.3.2 Internal Oscillator

The internal oscillator circuit is designed for use with no external components to provide a clock source with a tolerance of less than ±25% untrimmed. An 8-bit register (OSCTRIM) allows the digital adjustment to a tolerance of ACC

The internal oscillator is capable of generating clocks of 12.8 MHz, 8.0 MHz, or 4.0 MHz (INTCLK) resulting in a bus frequency (INTCLK divided by 4) of 3.2 MHz, 2.0 MHz, or 1.0 MHz respectively. The bus clock is software selectable and defaults to the 1.0-MHz bus out of reset. Users can increase the bus frequency based on the voltage range of their application.

Freescale Semiconductor 95

. See the oscillator characteristics in the Electrical section of this data sheet.

INT

MC68HC908QB8 Data Sheet, Rev. 1

Oscillator Module (OSC)

Figure 11-3 shows how BUSCLKX4 is derived from INTCLK and OSC2 can output BUSCLKX4 by setting

OSC2EN.

11.3.2.1 Internal Oscillator Trimming

OSCTRIM allows a clock period adjustment of +127 and –128 steps. Increasing the OSCTRIM value increases the clock period, which decreases the clock frequency. Trimming allows the internal clock frequency to be fine tuned to the target frequency.

All devices are factory programmed with a trim value that is stored in FLASH memory at location $FFC0. This trim value is not automatically loaded into OSCTRIM register. User software must copy the trim value from $FFC0 into OSCTRIM if needed. The factory trim value provides the accuracy required for communication using force monitor mode. Trimming the device in the user application board will provide the most accurate trim value. See Oscillator Characteristics in the Electrical Chapter of this data book for additional information on factory trim.

11.3.2.2 Internal to External Clock Switching

When external clock source (external OSC, RC, or XTAL) is desired, the user must perform the following steps:

1. For external crystal circuits only, configure OSCOPT[1:0] to external crystal. To help precharge an external crystal oscillator, momentarily configure OSC2 as an output and drive it high for several cycles. This can help the crystal circuit start more robustly.

2. Configure OSCOPT[1:0] and ECFS[1:0] according to 11.8.1 Oscillator Status and Control Register. The oscillator module control logic will then enable OSC1 as an external clock input and, if the external crystal option is selected, OSC2 will also be enabled as the clock output. If RC oscillator option is selected, enabling the OSC2 output may change the bus frequency.

3. Create a software delay to provide the stabilization time required for the selected clock source (crystal, resonator, RC). A good rule of thumb for crystal oscillators is to wait 4096 cycles of the crystal frequency; i.e., for a 4-MHz crystal, wait approximately 1 ms.

4. After the stabilization delay has elapsed, set ECGON.

After ECGON set is detected, the OSC module checks for oscillator activity by waiting two external clock rising edges. The OSC module then switches to the external clock. Logic provides a coherent transition. The OSC module first sets ECGST and then stops the internal oscillator.

11.3.2.3 External to Internal Clock Switching

After following the procedures to switch to an external clock source, it is possible to go back to the internal source. By clearing the OSCOPT[1:0] bits and clearing the ECGON bit, the external circuit will be disengaged. The bus clock will be derived from the selected internal clock source based on the ICFS[1:0] bits.

11.3.3 External Oscillator

The external oscillator option is designed for use when a clock signal is available in the application to provide a clock source to the MCU. The OSC1 pin is enabled as an input by the oscillator module. The clock signal is used directly to create BUSCLKX4 and also divided by two to create BUSCLKX2.

In this configuration, the OSC2 pin cannot output BUSCLKX4. The OSC2EN bit will be forced clear to enable alternative functions on the pin.

MC68HC908QB8 Data Sheet, Rev. 1

96 Freescale Semiconductor

Functional Description

11.3.4 XTAL Oscillator

The XTAL oscillator circuit is designed for use with an external crystal or ceramic resonator to provide an accurate clock source. In this configuration, the OSC2 pin is dedicated to the external crystal circuit. The OSC2EN bit has no effect when this clock mode is selected.

In its typical configuration, the XTAL oscillator is connected in a Pierce oscillator configuration, as shown in Figure 11-2. This figure shows only the logical representation of the internal components and may not represent actual circuitry.

The oscillator configuration uses five components:

•Crystal, X

• Fixed capacitor, C

• Tuning capacitor, C2 (can also be a fixed capacitor)

• Feedback resistor, R

• Series resistor, RS (optional)

NOTE

The series resistor (R

) 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 oscillator characteristics table in the Electricals section for more information.

SIMOSCEN (INTERNAL SIGNAL) OR

OSCENINSTOP (BIT LOCATED IN

CONFIGURATION REGISTER)

MCU

XTALCLK

OSC2OSC1

See the electrical section for details.

BUSCLKX2BUSCLKX4

÷ 2

Figure 11-2. XTAL Oscillator External Connections

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 97

Oscillator Module (OSC)

11.3.5 RC Oscillator

The RC oscillator circuit is designed for use with an external resistor (R

) to provide a clock source with

EXT

a tolerance within 25% of the expected frequency. See Figure 11-3.

The capacitor (C) for the RC oscillator is internal to the MCU. The R

value must have a tolerance of

EXT

1% or less to minimize its effect on the frequency.

In this configuration, the OSC2 pin can be used as general-purpose input/output (I/O) port pins or other alternative pin function. The OSC2EN bit can be set to enable the OSC2 output function on the pin. Enabling the OSC2 output can affect the external RC oscillator frequency, f

SIMOSCEN (INTERNAL SIGNAL) OR

OSCENINSTOP (BIT LOCATED IN

CONFIGURATION REGISTER)

EXTERNAL RC

OSCILLATOR

MCU

INTCLK

RCCLK

OSCOPT = EXTERNAL RC SELECTED

BUSCLKX4

÷ 2

ALTERNATIVE

PIN FUNTION

RCCLK

BUSCLKX2

OSC2EN

OSC1

EXT

OSC2 — AVAILABLE FOR ALTERNATIVE PIN FUNCTION

See the electricals section for component value.

Figure 11-3. RC Oscillator External Connections

11.4 Interrupts

There are no interrupts associated with the OSC module.

11.5 Low-Power Modes

The WAIT and STOP instructions put the MCU in low power-consumption standby modes.

11.5.1 Wait Mode

The OSC module remains active in wait mode.

11.5.2 Stop Mode

The OSC module can be configured to remain active in stop mode by setting OSCENINSTOP located in a configuration register.

MC68HC908QB8 Data Sheet, Rev. 1

98 Freescale Semiconductor

OSC During Break Interrupts

11.6 OSC During Break Interrupts

There are no status flags associated with the OSC module.

To allow software to clear status bits during a break interrupt, write a 1 to BCFE. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state.

11.7 I/O Signals

The OSC shares its pins with general-purpose input/output (I/O) port pins. See Figure 11-1 for port location of these shared pins.

11.7.1 Oscillator Input Pin (OSC1)

The OSC1 pin is an input to the crystal oscillator amplifier, an input to the RC oscillator circuit, or an input from an external clock source.

When the OSC is configured for internal oscillator, the OSC1 pin can be used as a general-purpose input/output (I/O) port pin or other alternative pin function.

11.7.2 Oscillator Output Pin (OSC2)

For the XTAL oscillator option, the OSC2 pin is the output of the crystal oscillator amplifier.

When the OSC is configured for internal oscillator, external clock, or RC, the OSC2 pin can be used as a general-purpose I/O port pin or other alternative pin function. When the oscillator is configured for internal or RC, the OSC2 pin can be used to output BUSCLKX4.

Table 11-1. OSC2 Pin Function

Option OSC2 Pin Function

XTAL oscillator Inverting OSC1

External clock General-purpose I/O or alternative pin function

Internal oscillator

RC oscillator

Controlled by OSC2EN bit

OSC2EN = 0: General-purpose I/O or alternative pin function OSC2EN = 1: BUSCLKX4 output

MC68HC908QB8 Data Sheet, Rev. 1

Freescale Semiconductor 99

Oscillator Module (OSC)

11.8 Registers

The oscillator module contains two registers:

• Oscillator status and control register (OSCSC)

• Oscillator trim register (OSCTRIM)

11.8.1 Oscillator Status and Control Register

The oscillator status and control register (OSCSC) contains the bits for switching between internal and external clock sources. If the application uses an external crystal, bits in this register are used to select the crystal oscillator amplifier necessary for the desired crystal. While running off the internal clock source, the user can use bits in this register to select the internal clock source frequency.

Bit 7654321Bit 0

Read:

OSCOPT1 OSCOPT0 ICFS1 ICFS0 ECFS1 ECFS0 ECGON

Write:

Reset:0 0000000

= Unimplemented

Figure 11-4. Oscillator Status and Control Register (OSCSC)

ECGST

OSCOPT1:OSCOPT0 — OSC Option Bits

These read/write bits allow the user to change the clock source for the MCU. The default reset condition has the bus clock being derived from the internal oscillator. See 11.3.2.2 Internal to External

Clock Switching for information on changing clock sources.

OSCOPT1 OSCOPT0 Oscillator Modes

0 0 Internal oscillator (frequency selected using ICFSx bits)

0 1 External oscillator clock

10External RC

1 1 External crystal (range selected using ECFSx bits)

ICFS1:ICFS0 — Internal Clock Frequency Select Bits

These read/write bits enable the frequency to be increased for applications requiring a faster bus clock when running off the internal oscillator. The WAIT instruction has no effect on the oscillator logic. BUSCLKX2 and BUSCLKX4 continue to drive to the SIM module.

ICFS1 ICFS0 Internal Clock Frequency

0 0 4.0 MHz — default reset condition

0 1 8.0 MHz

1 0 12.8 MHz

11Reserved

MC68HC908QB8 Data Sheet, Rev. 1

100 Freescale Semiconductor

Freescale MC68HC908QB8, MC68HC908QB4, MC68HC908QY8 DATA SHEET

Specifications and Main Features

Frequently Asked Questions

User Manual