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MC68HC908GR8A MC68HC908GR4A Data Sheet
M68HC08 Microcontrollers
MC68HC908GR8A Rev. 5 04/2007
freescale.com
MC68HC908GR8A MC68HC908GR4A
Data Sheet
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FreescaleTM and the Freescale logo are trademarks of Freescale Semiconductor, Inc. This product incorporates SuperFlash(R) technology licensed from SST. (c) Freescale Semiconductor, Inc., 2005, 2007. All rights reserved. MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 3
Revision History
The following revision history table summarizes changes contained in this document. For your convenience, the page number designators have been linked to the appropriate location.
Revision History
Date April, 2003 Revision Level 0 Initial release Module construction and style updated to meet current publications standards. IRQ1 changed to IRQ Mask option register changed to configuration register Deleted references to DMA module and bits FLASH memory operation details updated 3.3.4 Conversion -- Clarified ADC details 3.7.1 ADC Status and Control Register -- Corrected COCO bit functionality Table 4-1. Numeric Example -- Corrected and improved examples Table 4-4. Example Filter Component Values -- Added more values Chapter 5 Configuration Register (CONFIG) -- Updated COP timeout selections 6.2 Functional Description -- Updated block diagram and timeout values Table 7-1. Instruction Set Summary -- Corrected STOP and added WAIT instruction 8.3 Functional Description -- Updated IRQ description 8.4 IRQ Pin -- Updated IRQ description October, 2004 1 Chapter 12 Input/Output (I/O) Ports -- Corrected Figures 12-4, 12-11, 12-15 Figure 13-3. SCI Module Block Diagram -- Corrected diagram Figure 13-5. SCI Transmitter -- Updated diagram Figure 13-6. SCI Receiver Block Diagram -- Updated Diagram Chapter 14 System Integration Module (SIM) -- Clarified SIM features and functionality 16.3 Functional Description -- Updated TBM description Table 17-3. Mode, Edge, and Level Selection -- Added software compare condition Chapter 18 Development Support -- Combined Break and Monitor Mode modules 18.2.1 Functional Description -- Corrected Break description 18.3 Monitor Module (MON) -- Reworked for clarity 19.5 5.0 V DC Electrical Characteristics -- Changed VTST max to 8.5 V 19.6 3.0 V DC Electrical Characteristics -- Changed VTST max to 8.5 V 19.15.1 CGM Component Specifications -- Corrected and updated values 19.15.2 CGM Electrical Specifications -- Corrected and updated values 19.17 Memory Characteristics -- Updated memory characteristics table Description Page Number(s) N/A Throughout Throughout Throughout Throughout 40--42 50 51 61 73 75, 76 79, 80 92, 93 95 97 118, 123, 126 134 136 139 157--173 195 213 215--230 215 221 233 234 247 247 248
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 4 Freescale Semiconductor
Revision History
Date October, 2004 Revision Level 2 Description 19.17 Memory Characteristics -- Corrected values for FLASH read bus clock frequency. 19.2 Absolute Maximum Ratings -- Corrected value for supply voltage June, 2005 19.5 5.0 V DC Electrical Characteristics -- Corrected stop IDD and I/O ports Hi-Z leakage current values. 19.6 3.0 V DC Electrical Characteristics -- Corrected stop IDD and I/O ports Hi-Z leakage current values. 20.3 Package Dimensions -- Updated package information. March, 2006 April, 2007 4 10.5 Clock Generator Module (CGM) -- Updated description to remove erroneous information. Chapter 5 Configuration Register (CONFIG) -- Replaced COPCLK with CGMXCLK and corrected what set and cleared indicate for bit CONFIG1_COPRS 10.6.2 Stop Mode -- Replaced COPCLK with CGMXCLK Page Number(s) 248 229 231 232 247 106
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Revision History
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 6 Freescale Semiconductor
List of Chapters
Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Chapter 2 Memory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Chapter 3 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Chapter 4 Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Chapter 5 Configuration Register (CONFIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Chapter 6 Computer Operating Properly (COP) Module . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 Chapter 7 Central Processor Unit (CPU). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Chapter 8 External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 Chapter 9 Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Chapter 10 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105 Chapter 11 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 Chapter 12 Input/Output (I/O) Ports. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 Chapter 13 Serial Communications Interface (SCI) Module . . . . . . . . . . . . . . . . . . . . . . .131 Chapter 14 System Integration Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157 Chapter 15 Serial Peripheral Interface (SPI) Module . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 Chapter 16 Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 Chapter 17 Timer Interface Module (TIM1 and TIM2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Chapter 18 Development Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215 Chapter 19 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 Chapter 20 Ordering Information and Mechanical Specifications . . . . . . . . . . . . . . . . . . 249
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 7
List of Chapters
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 8 Freescale Semiconductor
Table of Contents
Chapter 1 General Description
1.1 1.2 1.2.1 1.2.2 1.3 1.4 1.5 1.5.1 1.5.2 1.5.3 1.5.4 1.5.5 1.5.6 1.5.7 1.5.8 1.5.9 1.5.10 1.5.11 1.5.12 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Standard Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features of the CPU08 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MCU Block Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin Assignments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pin Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power Supply Pins (VDD and VSS). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator Pins (OSC1 and OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Reset Pin (RST). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Interrupt Pin (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Power Supply Pins (VDDA and VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Filter Capacitor Pin (VCGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Power Supply/Reference Pins (VDDAD/VREFH and VSSAD/VREFL). . . . . . . . . . . . . . . . Port A Input/Output (I/O) Pins (PTA3/KBD3-PTA0/KBD0) . . . . . . . . . . . . . . . . . . . . . . . . . Port B I/O Pins (PTB5/AD5-PTB0/AD0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port C I/O Pins (PTC1 and PTC0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port D I/O Pins (PTD6/T2CH0-PTD0/SS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port E I/O Pins (PTE1/RxD and PTE0/TxD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 19 19 20 21 22 23 23 23 23 23 24 24 24 24 24 24 24 25
Chapter 2 Memory
2.1 2.2 2.3 2.4 2.5 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.6.6 2.6.7 2.6.8 2.6.9 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input/Output (I/O) Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Memory (FLASH) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Page Erase Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Mass Erase Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Program/Read Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Block Protection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FLASH Block Protect Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 27 27 27 38 38 38 39 40 40 41 42 44 45 45
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Table of Contents
Chapter 3 Analog-to-Digital Converter (ADC)
3.1 3.2 3.3 3.3.1 3.3.2 3.3.3 3.3.4 3.3.5 3.4 3.5 3.5.1 3.5.2 3.6 3.6.1 3.6.2 3.6.3 3.7 3.7.1 3.7.2 3.7.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Port I/O Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Voltage Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conversion Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accuracy and Precision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Analog Ground Pin (VSSAD)/ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . ADC Analog Power Pin (VDDAD)/ADC Voltage Reference High Pin (VREFH) . . . . . . . . . . . ADC Voltage In (VADIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 47 47 47 49 50 50 50 50 50 50 50 51 51 51 51 51 51 53 53
Chapter 4 Clock Generator Module (CGM)
4.1 4.2 4.3 4.3.1 4.3.2 4.3.3 4.3.4 4.3.5 4.3.6 4.3.7 4.3.8 4.3.9 4.4 4.4.1 4.4.2 4.4.3 4.4.4 4.4.5 4.4.6 4.4.7 4.4.8 4.4.9 4.4.10 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crystal Oscillator Circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phase-Locked Loop Circuit (PLL) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition and Tracking Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Manual and Automatic PLL Bandwidth Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Programming the PLL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Programming Exceptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Base Clock Selector Circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM External Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crystal Amplifier Input Pin (OSC1). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crystal Amplifier Output Pin (OSC2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Filter Capacitor Pin (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Analog Power Pin (VDDA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Analog Ground Pin (VSSA) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator Enable Signal (SIMOSCEN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Oscillator Stop Mode Enable Bit (OSCSTOPENB) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Crystal Output Frequency Signal (CGMXCLK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Base Clock Output (CGMOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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55 55 55 57 57 57 58 58 59 62 62 62 63 63 63 63 64 64 64 64 64 64 64
4.5 4.5.1 4.5.2 4.5.3 4.5.4 4.5.5 4.5.6 4.6 4.7 4.7.1 4.7.2 4.7.3 4.8 4.8.1 4.8.2 4.8.3
CGM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Multiplier Select Register High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Multiplier Select Register Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL VCO Range Select Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Reference Divider Select Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition/Lock Time Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition/Lock Time Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parametric Influences on Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Choosing a Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
65 66 67 68 69 69 70 70 71 71 71 71 71 72 72 73
Chapter 5 Configuration Register (CONFIG)
5.1 5.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
Chapter 6 Computer Operating Properly (COP) Module
6.1 6.2 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.3.5 6.3.6 6.3.7 6.4 6.5 6.6 6.7 6.7.1 6.7.2 6.8 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79 79 80 80 80 80 80 80 81 81 81 81 81 81 81 81 82
Chapter 7 Central Processor Unit (CPU)
7.1 7.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83
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7.3 7.3.1 7.3.2 7.3.3 7.3.4 7.3.5 7.4 7.5 7.5.1 7.5.2 7.6 7.7 7.8
CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
83 84 84 85 85 86 87 87 87 87 87 88 93
Chapter 8 External Interrupt (IRQ)
8.1 8.2 8.3 8.4 8.5 8.6 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IRQ Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95 95 95 97 97 98
Chapter 9 Keyboard Interrupt Module (KBI)
9.1 9.2 9.3 9.4 9.5 9.5.1 9.5.2 9.6 9.7 9.7.1 9.7.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Keyboard Module During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Keyboard Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 Keyboard Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
Chapter 10 Low-Power Modes
10.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.1.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.3.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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105 105 105 105 105 105 106 106 106
10.4 Central Processor Unit (CPU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.4.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5 Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6 Computer Operating Properly Module (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7 External Interrupt Module (IRQ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.7.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.8 Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.8.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.8.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.9 Low-Voltage Inhibit Module (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.9.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.9.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.10 Serial Communications Interface Module (SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.10.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.10.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.11 Serial Peripheral Interface Module (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.11.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.11.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.12 Timer Interface Module (TIM1 and TIM2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.12.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.12.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.13 Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.13.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.13.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.14 Exiting Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
106 106 106 106 106 106 107 107 107 107 107 107 107 107 107 108 108 108 108 108 108 108 108 108 109 109 109 109 109 109 109
Chapter 11 Low-Voltage Inhibit (LVI)
11.1 11.2 11.3 11.3.1 11.3.2 11.3.3 11.3.4 11.4 11.5 11.6 11.6.1 11.6.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Polled LVI Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Forced Reset Operation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Voltage Hysteresis Protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LVI Trip Selection. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LVI Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LVI Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111 111 111 112 112 113 113 113 113 113 114 114
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Chapter 12 Input/Output (I/O) Ports
12.1 12.2 12.2.1 12.2.2 12.2.3 12.3 12.3.1 12.3.2 12.4 12.4.1 12.4.2 12.4.3 12.5 12.5.1 12.5.2 12.5.3 12.6 12.6.1 12.6.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port A Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port A Input Pullup Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port B Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register B . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port C. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port C Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register C . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port C Input Pullup Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port D. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port D Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register D . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port D Input Pullup Enable Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port E Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Direction Register E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 117 117 118 119 120 120 120 122 122 122 124 124 124 125 127 127 127 128
Chapter 13 Serial Communications Interface (SCI) Module
13.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2.2 Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2.3 Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2.4 Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2.5 Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.2.6 Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.2 Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.3 Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.4 Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.5 Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.6 Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.7 Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.4.3.8 Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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131 131 133 133 133 135 135 137 137 138 138 138 138 138 138 140 141 142 143 144 144 144 144 145
13.6 SCI During Break Module Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7.1 PTE0/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.7.2 PTE1/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8.4 SCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8.5 SCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8.6 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.8.7 SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
145 145 145 145 146 146 148 149 150 153 154 154
Chapter 14 System Integration Module (SIM)
14.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2 SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.1 Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.2 Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.2.3 Clocks in Stop Mode and Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.1 External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2 Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2.1 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2.2 Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2.3 Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2.4 Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2.5 Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.3.2.6 Monitor Mode Entry Module Reset (MODRST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4 SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.1 SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.2 SIM Counter During Stop Mode Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.4.3 SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5 Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.1 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.1.1 Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.1.2 SWI Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.1.3 Interrupt Status Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.2 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.3 Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.5.4 Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7.1 SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7.2 SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14.7.3 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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157 159 159 159 159 160 160 160 161 162 162 162 162 163 163 163 163 163 163 164 166 166 167 168 168 168 169 169 170 171 171 172 173
Table of Contents
Chapter 15 Serial Peripheral Interface (SPI) Module
15.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3.1 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.3.2 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4.1 Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4.2 Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4.3 Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.4.4 Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.5 Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.6 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.6.1 Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.6.2 Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.7 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.8 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.9.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.10 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.11 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.11.1 MISO (Master In/Slave Out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.11.2 MOSI (Master Out/Slave In). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.11.3 SPSCK (Serial Clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.11.4 SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.12 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.12.1 SPI Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.12.2 SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15.12.3 SPI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175 175 175 178 178 179 179 179 180 181 183 184 184 185 186 188 188 188 188 188 189 189 189 189 190 191 191 192 194
Chapter 16 Timebase Module (TBM)
16.1 16.2 16.3 16.4 16.5 16.5.1 16.5.2 16.6 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timebase Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195 195 195 195 196 196 196 197
Chapter 17 Timer Interface Module (TIM1 and TIM2)
17.1 17.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 201
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 16 Freescale Semiconductor
17.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.1 TIM Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.3.1 Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.3.2 Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.4.1 Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.4.2 Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.4.4.3 PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.5 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.7 TIM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9.1 TIM Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9.2 TIM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9.3 TIM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9.4 TIM Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17.9.5 TIM Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
201 201 203 203 204 204 204 205 205 206 206 207 207 207 208 208 208 208 208 210 210 211 214
Chapter 18 Development Support
18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1.1 Flag Protection During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1.2 TIM During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.1.3 COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.2 Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.2.1 Break Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.2.2 Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.2.3 SIM Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.2.4 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2.3 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3 Monitor Module (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1.1 Normal Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1.2 Forced Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1.3 Monitor Vectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1.4 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1.5 Break Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1.6 Baud Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.1.7 Commands . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3.2 Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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215 215 215 218 218 218 218 219 219 220 220 220 221 221 225 225 225 226 226 226 226 230
Table of Contents
Chapter 19 Electrical Specifications
19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3 Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4 Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5 5.0 V DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 3.0 V DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.7 5.0 V Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.8 3.0 V Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.9 Output High-Voltage Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.10 Output Low-Voltage Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.11 Typical Supply Currents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.12 ADC Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.13 5.0 V SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.14 3.0 V SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.15 Clock Generation Module Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.15.1 CGM Component Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.15.2 CGM Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.16 Timer Interface Module Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.17 Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231 231 232 232 233 234 236 236 237 239 241 242 243 244 247 247 247 248 248
Chapter 20 Ordering Information and Mechanical Specifications
20.1 20.2 20.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249 Package Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 18 Freescale Semiconductor
Chapter 1 General Description
1.1 Introduction
The MC68HC908GR8A 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. This document also describes the MC68HC908GR4A. The MC68HC908GR4A is a device identical to the MC68HC908GR8A except that it has less FLASH memory. Only when there are differences from the MC68HC908GR8A is the MC68HC908GR4A specifically mentioned in the text.
1.2 Features
For convenience, features have been organized to reflect: * Standard features * Features of the CPU08
1.2.1 Standard Features
Features include: * High-performance M68HC08 architecture optimized for C-compilers * Fully upward-compatible object code with M6805, M146805, and M68HC05 Families * 8-MHz internal bus frequency * Clock generation module supporting 1-MHz to 8-MHz crystals * FLASH program memory security(1) * On-chip programming firmware for use with host personal computer which does not require high voltage for entry * In-system programming (ISP) * System protection features: - Optional computer operating properly (COP) reset - Low-voltage detection with optional reset and selectable trip points for 3.0-V and 5.0-V operation - Illegal opcode detection with reset - Illegal address detection with reset * Low-power design; fully static with stop and wait modes * Standard low-power modes of operation: - Wait mode - Stop mode
1. No security feature is absolutely secure. However, Freescale's strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 19
General Description
* *
* * * * *
* * * * * * * *
* * *
*
Master reset pin and power-on reset (POR) 7680 bytes of on-chip FLASH memory on the MC68HC908GR8A and 4096 byes of on-chip FLASH memory on the MC68HC908GR4A with in-circuit programming capabilities of FLASH program memory. 384 bytes of on-chip random-access memory (RAM) 544 bytes of FLASH programming routines read-only memory (ROM) Serial peripheral interface (SPI) module Serial communications interface (SCI) module One 16-bit, 2-channel timer (TIM1) and one 16-bit, 1-channel timer (TIM2) interface modules with selectable input capture, output compare, and pulse-width modulation (PWM) capability on each channel Up to 6-channel, 8-bit successive approximation analog-to-digital converter (ADC) depending on package choice BREAK (BRK) module to allow single breakpoint setting during in-circuit debugging Internal pullups on IRQ and RST to reduce system cost Up to 21 general-purpose input/output (I/O) pins Selectable pullups on inputs only on ports A, C, and D. Selection is on an individual port bit basis. During output mode, pullups are disengaged. High current 10-mA sink/source capability on all port pins Higher current 15-mA sink/source capability on PTC0-PTC1 Timebase module (TBM) with clock prescaler circuitry for eight user selectable periodic real-time interrupts with optional active clock source during stop mode for periodic wakeup from stop using an external crystal User selection of having the oscillator enabled or disabled during stop mode 4-bit keyboard wakeup port Available packages: - 32-pin low-profile quad flat pack (LQFP) - 28-pin plastic dual in-line package (DIP) - 28-pin small outline integrated circuit (SOIC) Specific features of the MC68HC908GR8A in 28-pin DIP and 28-pin SOIC are: - Port B is only 4 bits: PTB0-PTB3; 4-channel ADC module - No port C bits
1.2.2 Features of the CPU08
Features of the CPU08 include: * Enhanced HC05 programming model * Extensive loop control functions * 16 addressing modes (eight more than the HC05) * 16-bit index register and stack pointer * Memory-to-memory data transfers * Fast 8 x 8 multiply instruction * Fast 16/8 divide instruction * Binary-coded decimal (BCD) instructions * Optimization for controller applications * Efficient C language support
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 20 Freescale Semiconductor
MCU Block Diagram
1.3 MCU Block Diagram
Figure 1-1 shows the structure of the MC68HC908GR8A.
INTERNAL BUS M68HC08 CPU PORTA DDRA CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) PROGRAMMABLE TIMEBASE MODULE SINGLE BREAKPOINT BREAK MODULE DUAL VOLTAGE LOW-VOLTAGE INHIBIT MODULE 4-BIT KEYBOARD INTERRUPT MODULE DDRC 2-CHANNEL TIMER INTERFACE MODULE 1 1-CHANNEL TIMER INTERFACE MODULE 2 SERIAL COMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE RST(3) IRQ(3) VDDAD/VREFH VSSAD/VREFL SYSTEM INTEGRATION MODULE SINGLE EXTERNAL INTERRUPT MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE POWER-ON RESET MODULE VDD VSS VDDA VSSA SERIAL PERIPHERAL INTERFACE MODULE MONITOR MODULE MEMORY MAP MODULE CONFIGURATION REGISTER 1 MODULE CONFIGURATION REGISTER 2 MODULE PORTC PORTB DDRB PTA3/KBD3- PTA0/KBD0(1)
CONTROL AND STATUS REGISTERS -- 64 BYTES MC68HC908GR8A USER FLASH -- 7680 BYTES MC68HC908GR4A USER FLASH -- 4096 BYTES USER RAM -- 384 BYTES MONITOR ROM -- 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM -- 544 BYTES USER FLASH VECTOR SPACE -- 36 BYTES CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 1-8-MHz OSCILLATOR PHASE LOCKED LOOP
PTB5/AD5 PTB4/AD4 PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0
PTC1(1), (2) PTC0(1), (2)
PTD6/T2CH0(1) PTD5/T1CH1(1) PTD4/T1CH0(1) PTD3/SPSCK(1) PTD2/MOSI(1) PTD1/MISO(1) PTD0/SS(1)
PORTE
PORTD
DDRD
PTE1/RxD PTE0/TxD
DDRE
SECURITY MODULE
POWER
MONITOR MODE ENTRY MODULE
1. Ports are software configurable with pullup device if input port. 2. Higher current drive port pins 3. Pin contains integrated pullup device
Figure 1-1. MCU Block Diagram
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 21
General Description
1.4 Pin Assignments
Figure 1-2 illustrations the pin assignments for the 32-pin LQFP. Figure 1-3 illustrate the pin assignments for the 28-pin DIP and 28-pin SOIC.
PTA3/KBD3 25
32 OSC1
CGMXFC
OSC2
PTC1 27
31
30
29
28
RST PTE0/TxD PTE1/RxD IRQ PTD0/SS PTD1/MISO PTD2/MOSI PTD3/SPSCK
1 2 3 4 5 6 7
26
PTC0
VDDA
VSSA
24 23 22 21 20 19 18
PTA2/KBD2 PTA1/KBD1 PTA0/KBD0 VSSAD/VREFL VDDAD/VREFH PTB5/AD5 PTB4/AD4 PTB3/AD3
10
11
12
13
14
PTD4/T1CH0
PTD5/T1CH1
PTD6/T2CH0
PTB0/AD0
PTB1/AD1
VDD
VSS
15
9
Figure 1-2. 32-Pin LQFP Pin Assignments
CGMXFC OSC2 OSC1 RST PTE0/TxD PTE1/RxD IRQ PTD0/SS PTD1/MISO PTD2/MOSI PTD3/SPSCK VSS VDD PTD4/T1CH0
1 2 3 4 5 6 7 8 9 10 11 12 13 14
28 27 26 25 24 23 22 21 20 19 18 17 16 15
VSSA VDDA PTA3/KBD3 PTA2/KBD2 PTA1/KBD1 PTA0/KBD0 VSSAD/VREFL VDDAD/VREFH PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0 PTD6/T2CH0 PTD5/T1CH1
NOTE: Ports PTB4, PTB5, PTC0, and PTC1 are available only with the LQFP.
Figure 1-3. 28-Pin DIP and SOIC Pin Assignments
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 22 Freescale Semiconductor
PTB2/AD2
16
8
17
Pin Functions
1.5 Pin Functions
Descriptions of the pin functions are provided here.
1.5.1 Power Supply Pins (VDD and VSS)
VDD and VSS are the power supply and ground pins. The MCU operates from a single power supply. Fast signal transitions on MCU pins place high, short-duration current demands on the power supply. To prevent noise problems, take special care to provide power supply bypassing at the MCU as Figure 1-4 shows. Place the C1 bypass capacitor as close to the MCU as possible. Use a high-frequency-response ceramic capacitor for C1. C2 is an optional bulk current bypass capacitor for use in applications that require the port pins to source high current levels.
MCU VDD VSS
C1 0.1 F + C2
VDD Note: Component values shown represent typical applications.
Figure 1-4. Power Supply Bypassing
1.5.2 Oscillator Pins (OSC1 and OSC2)
OSC1 and OSC2 are the connections for an external crystal, resonator, or clock circuit. See Chapter 4 Clock Generator Module (CGM).
1.5.3 External Reset Pin (RST)
A 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset of the entire system. It is driven low when any internal reset source is asserted. This pin contains an internal pullup resistor. See Chapter 14 System Integration Module (SIM).
1.5.4 External Interrupt Pin (IRQ)
IRQ is an asynchronous external interrupt pin. This pin contains an internal pullup resistor. See Chapter 8 External Interrupt (IRQ).
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 23
General Description
1.5.5 CGM Power Supply Pins (VDDA and VSSA)
VDDA and VSSA are the power supply pins for the analog portion of the clock generator module (CGM). Decoupling of these pins should be as per the digital supply. See Chapter 4 Clock Generator Module (CGM).
1.5.6 External Filter Capacitor Pin (VCGMXFC)
CGMXFC is an external filter capacitor connection for the CGM. See Chapter 4 Clock Generator Module (CGM).
1.5.7 ADC Power Supply/Reference Pins (VDDAD/VREFH and VSSAD/VREFL)
VDDAD and VSSAD are the power supply pins to the analog-to-digital converter (ADC). VREFH and VREFL are the reference voltage pins for the ADC. VREFH is the high reference supply for the ADC, and by default the VDDAD/VREFH pin should be externally filtered and connected to the same voltage potential as VDD. VREFL is the low reference supply for the ADC, and by default the VSSAD/VREFL pin should be connected to the same voltage potential as VSS. See Chapter 3 Analog-to-Digital Converter (ADC).
1.5.8 Port A Input/Output (I/O) Pins (PTA3/KBD3-PTA0/KBD0)
PTA3-PTA0 are special-function, bidirectional I/O port pins. Any or all of the port A pins can be programmed to serve as keyboard interrupt pins. See Chapter 12 Input/Output (I/O) Ports and Chapter 9 Keyboard Interrupt Module (KBI). These port pins also have selectable pullups when configured for input mode. The pullups are disengaged when configured for output mode. The pullups are selectable on an individual port bit basis.
1.5.9 Port B I/O Pins (PTB5/AD5-PTB0/AD0)
PTB5-PTB0 are special-function, bidirectional I/O port pins that can also be used for analog-to-digital converter (ADC) inputs. See Chapter 12 Input/Output (I/O) Ports and Chapter 3 Analog-to-Digital Converter (ADC).
1.5.10 Port C I/O Pins (PTC1 and PTC0)
PTC1 and PTC0 are general-purpose, bidirectional I/O port pins. PTC1-PTC0 are only available on the 32-pin LQFP package. See Chapter 12 Input/Output (I/O) Ports. These port pins also have selectable pullups when configured for input mode. The pullups are disengaged when configured for output mode. The pullups are selectable on an individual port bit basis.
1.5.11 Port D I/O Pins (PTD6/T2CH0-PTD0/SS)
PTD6-PTD0 are special-function, bidirectional I/O port pins. PTD3-PTD0 can be programmed to be serial peripheral interface (SPI) pins, while PTD6-PTD4 can be individually programmed to be timer interface module (TIM1 and TIM2) pins. See Chapter 17 Timer Interface Module (TIM1 and TIM2), Chapter 15 Serial Peripheral Interface (SPI) Module, and Chapter 12 Input/Output (I/O) Ports. These port pins also have selectable pullups when configured for input mode. The pullups are disengaged when configured for output mode. The pullups are selectable on an individual port bit basis.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 24 Freescale Semiconductor
Pin Functions
1.5.12 Port E I/O Pins (PTE1/RxD and PTE0/TxD)
PTE1 and PTE0 are special-function, bidirectional I/O port pins. These pins can also be programmed to be serial communications interface (SCI) pins. See Chapter 13 Serial Communications Interface (SCI) Module and Chapter 12 Input/Output (I/O) Ports. NOTE Any unused inputs and I/O ports should be tied to an appropriate logic level (either VDD or VSS). Although the I/O ports of the MC68HC908GR8A do not require termination, termination is recommended to reduce the possibility of static damage.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 25
General Description
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 26 Freescale Semiconductor
Chapter 2 Memory
2.1 Introduction
The CPU08 can address 64 Kbytes of memory space. The memory map, shown in Figure 2-1, includes: * 7680 bytes of user FLASH memory on the MC68HC908GR8A or 4096 bytes of user FLASH memory on the MC68HC908GR4A * 384 bytes of random-access memory (RAM) * 544 bytes of FLASH burn-in routines in ROM * 36 bytes of user-defined vectors * 310 bytes of monitor ROM
2.2 Unimplemented Memory Locations
Accessing an unimplemented location can cause an illegal address reset. In the memory map (Figure 2-1) and in register figures in this document, unimplemented locations are shaded.
2.3 Reserved Memory Locations
Accessing a reserved location can have unpredictable effects on microcontroller (MCU) operation. In the Figure 2-1 and in register figures in this document, reserved locations are marked with the word Reserved or with the letter R.
2.4 Input/Output (I/O) Section
Most of the control, status, and data registers are in the zero page area of $0000-$003F. Additional I/O registers have these addresses: * $FE00; break status register, SBSR * $FE01; SIM reset status register, SRSR * $FE02; reserved * $FE03; break flag control register, SBFCR * $FE04; interrupt status register 1, INT1 * $FE05; interrupt status register 2, INT2 * $FE06; interrupt status register 3, INT3 * $FE07; reserved * $FE08; FLASH control register, FLCR * $FE09; break address register high, BRKH * $FE0A; break address register low, BRKL * $FE0B; break status and control register, BRKSCR * $FE0C; LVI status register, LVISR * $FF7E; FLASH block protect register, FLBPR Data registers are shown in Figure 2-2. Table 2-1 is a list of vector locations.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 27
Memory
$0000 $003F $0040 $01BF $01C0 $1BFF $1C00 $1E1F $1E20 $DFFF $E000 $EDFF $EE00 $FDFF $FE00 $FE01 $FE02 $FE03 $FE04 $FE05 $FE06 $FE07 MC68HC908GR8A FLASH MEMORY 7680 BYTES MC68HC908GR4A RESERVED 3584 BYTES MC68HC908GR4A FLASH MEMORY 4096 BYTES UNIMPLEMENTED 49,632 BYTES RESERVED FOR INTEGRATED FLASH BURN-IN ROUTINES 544 BYTES UNIMPLEMENTED 6720 BYTES RAM 384 BYTES I/O REGISTERS 64 BYTES
SIM BREAK STATUS REGISTER (SBSR) SIM RESET STATUS REGISTER (SRSR) RESERVED SIM BREAK FLAG CONTROL REGISTER (SBFCR) INTERRUPT STATUS REGISTER 1 (INT1) INTERRUPT STATUS REGISTER 2 (INT2) INTERRUPT STATUS REGISTER 3 (INT3) Reserved for FLASH Test Control Register (FLTCR)
Figure 2-1. Memory Map
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 28 Freescale Semiconductor
Input/Output (I/O) Section
$FE08 $FE09 $FE0A $FE0B $FE0C $FE0D $FE0F $FE10 $FE1F $FE20 $FF55 $FF56 $FF7D $FF7E $FF7F $FFDB Note: $FFF6-$FFFD contains 8 security bytes $FFDC $FFFE $FFFF
FLASH CONTROL REGISTER (FLCR) BREAK ADDRESS REGISTER HIGH (BRKH) BREAK ADDRESS REGISTER LOW (BRKL) BREAK STATUS AND CONTROL REGISTER (BRKSCR) LVI STATUS REGISTER (LVISR) RESERVED 3 BYTES UNIMPLEMENTED 16 BYTES RESERVED FOR COMPATIBILITY WITH MONITOR CODE FOR A-FAMILY PARTS MONITOR ROM 310 BYTES
UNIMPLEMENTED 40 BYTES FLASH BLOCK PROTECT REGISTER (FLBPR) UNIMPLEMENTED 93 BYTES
FLASH VECTORS (36 BYTES INCLUDING $FFFF) LOW BYTE OF RESET VECTOR WHEN READ COP CONTROL REGISTER (COPCTL)
Figure 2-1. Memory Map (Continued)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 29
Memory Addr. Register Name Read: Port A Data Register (PTA) Write: See page 117. Reset: Read: Port B Data Register (PTB) Write: See page 120. Reset: Read: Port C Data Register (PTC) Write: See page 122. Reset: Read: Port D Data Register (PTD) Write: See page 124. Reset: Read: Data Direction Register A (DDRA) Write: See page 118. Reset: Read: Data Direction Register B (DDRB) Write: See page 120. Reset: Read: Data Direction Register C (DDRC) Write: See page 122. Reset: Read: Data Direction Register D (DDRD) Write: See page 125. Reset: Read: Port E Data Register (PTE) Write: See page 127. Reset: Read: Reserved Write: Reset: Read: Data Direction Register E (DDRE) Write: See page 128. Reset: Bit 7 0 6 0 5 0 4 0 3 PTA3 2 PTA2 1 PTA1 Bit 0 PTA0
$0000
Unaffected by reset 0 0 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0
$0001
Unaffected by reset 0 0 0 0 0 0 PTC1 PTC0
$0002
Unaffected by reset 0 PTD6 PTD5 PTD4 PTD3 PTD2 PTD1 PTD0
$0003
Unaffected by reset 0 0 0 0 DDRA3 0 DDRB3 0 0 DDRA2 0 DDRB2 0 0 DDRA1 0 DDRB1 0 DDRC1 0 DDRD1 0 PTE1 DDRA0 0 DDRB0 0 DDRC0 0 DDRD0 0 PTE0
$0004
0 0
0 0
0 DDRB5 0 0
0 DDRB4 0 0
$0005
0 0
0 0
$0006
0 0
0 DDRD6 0 0
0 DDRD5 0 0
0 DDRD4 0 0
0 DDRD3 0 0
0 DDRD2 0 0
$0007
0 0
$0008
Unaffected by reset R 0 0 R 0 0 R 0 0 R 0 0 R 0 0 R 0 0 R 0 DDRE1 0 R 0 DDRE0 0
$0009 $000B
$000C
0
0 = Unimplemented
0
0 R = Reserved
0
0 U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 7)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 30 Freescale Semiconductor
Input/Output (I/O) Section Addr. Register Name Read: Port A Input Pullup Enable Register (PTAPUE) Write: See page 119. Reset: Read: Port C Input Pullup Enable Register (PTCPUE) Write: See page 124. Reset: Read: Port D Input Pullup Enable Register (PTDPUE) Write: See page 127. Reset: Read: SPI Control Register (SPCR) Write: See page 191. Reset: Read: SPI Status and Control Register (SPSCR) Write: See page 192. Reset: Read: SPI Data Register (SPDR) Write: See page 194. Reset: Read: SCI Control Register 1 (SCC1) Write: See page 146. Reset: Read: SCI Control Register 2 (SCC2) Write: See page 148. Reset: Read: SCI Control Register 3 (SCC3) Write: See page 149. Reset: Read: SCI Status Register 1 (SCS1) Write: See page 151. Reset: Read: SCI Status Register 2 (SCS2) Write: See page 153. Reset: Bit 7 0 6 0 5 0 4 0 3 PTAPUE3 0 0 2 PTAPUE2 0 0 1 PTAPUE1 0 PTCPUE1 0 PTDPUE1 0 SPE 0 SPR1 0 R1 T1 Bit 0 PTAPUE0 0 PTCPUE0 0 PTDPUE0 0 SPTIE 0 SPR0 0 R0 T0
$000D
0 0
0 0
0 0
0 0
$000E
0 0
0 PTDPUE6 0 R 0 ERRIE 0 R6 T6
0 PTDPUE5 0 SPMSTR 1 OVRF
0 PTDPUE4 0 CPOL 0 MODF
0 PTDPUE3 0 CPHA 1 SPTE
0 PTDPUE2 0 SPWOM 0 MODFEN 0 R2 T2
$000F
0 SPRIE 0 SPRF
$0010
$0011
0 R7 T7
0 R5 T5
0 R4 T4
1 R3 T3
$0012
Unaffected by reset LOOPS 0 SCTIE 0 R8 ENSCI 0 TCIE 0 T8 0 TC TXINV 0 SCRIE 0 R 0 SCRF M 0 ILIE 0 R 0 IDLE WAKE 0 TE 0 ORIE 0 OR ILTY 0 RE 0 NEIE 0 NF PEN 0 RWU 0 FEIE 0 FE PTY 0 SBK 0 PEIE 0 PE
$0013
$0014
$0015
U SCTE
$0016
1 0
1 0
0 0
0 0
0 0
0 0
0 BKF
0 RPF
$0017
0
0 = Unimplemented
0
0 R = Reserved
0
0 U = Unaffected
0
0
Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 7)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 31
Memory Addr. Register Name Read: SCI Data Register (SCDR) Write: See page 154. Reset: Read: SCI Baud Rate Register (SCBR) Write: See page 154. Reset: Keyboard Status Read: and Control Register Write: (INTKBSCR) See page 103. Reset: Read: Keyboard Interrupt Enable Register (INTKBIER) Write: See page 104. Reset: Read: Timebase Module Control Register (TBCR) Write: See page 197. Reset: Read: IRQ Status and Control Register (INTSCR) Write: See page 98. Reset: Configuration Register 2 Read: (CONFIG2)(1) Write: See page 75. Reset: Read: Configuration Register 1 (CONFIG1)(1) Write: See page 76. Reset: Bit 7 R7 T7 6 R6 T6 5 R5 T5 4 R4 T4 3 R3 T3 2 R2 T2 1 R1 T1 Bit 0 R0 T0
$0018
Unaffected by reset SCP1 0 0 0 0 0 0 SCP0 0 0 R 0 KEYF SCR2 0 0 ACKK 0 0 0 0 0 KBIE3 0 TBIF 0 TBR2 0 0 0 TBR1 0 0 0 TBR0 0 0 0 0 TACK 0 IRQF 0 KBIE2 0 TBIE 0 0 ACK 0 0 0 0 0 0 0 0 0 0 0 0 SCR1 0 IMASKK 0 KBIE1 0 TBON 0 IMASK 0 SCR0 0 MODEK 0 KBIE0 0 R 0 MODE 0
$0019
$001A
$001B
$001C
0 0
$001D
$001E
OSCSCIBDSRC STOPENB 0 STOP 0 0 COPD 0
0 COPRS 0
0 LVISTOP 0
0 LVIRSTD 0
0 LVIPWRD 0
0 LVI5OR3 (Note 1) 0
0 SSREC 0
$001F
1. One-time writable register after each reset, except LVI5OR3 bit. LVI5OR3 bit is only reset via POR (power-on reset). Read: Timer 1 Status and Control Register (T1SC) Write: See page 209. Reset: Read: Timer 1 Counter Register High (T1CNTH) Write: See page 210. Reset: TOF 0 0 Bit 15 0 TRST 0 12 0 11 0
$0020
TOIE 0 14
TSTOP 1 13
PS2 0 10
PS1 0 9
PS0 0 Bit 8
$0021
0
0 = Unimplemented
0
0 R = Reserved
0
0 U = Unaffected
0
0
Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 7)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 32 Freescale Semiconductor
Input/Output (I/O) Section Addr. Register Name Read: Timer 1 Counter Register Low (T1CNTL) Write: See page 210. Reset: Read: Timer 1 Counter Modulo Register High (T1MODH) Write: See page 211. Reset: Read: Timer 1 Counter Modulo Register Low (T1MODL) Write: See page 211. Reset: Bit 7 Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
$0022
0 Bit 15 1 Bit 7 1 CH0F 0 0 Bit 15
0 14 1 6 1 CH0IE 0 14
0 13 1 5 1 MS0B 0 13
0 12 1 4 1 MS0A 0 12
0 11 1 3 1 ELS0B 0 11
0 10 1 2 1 ELS0A 0 10
0 9 1 1 1 TOV0 0 9
0 Bit 8 1 Bit 0 1 CH0MAX 0 Bit 8
$0023
$0024
Read: Timer 1 Channel 0 Status and $0025 Control Register (T1SC0) Write: See page 214. Reset: Read: Timer 1 Channel 0 Register High (T1CH0H) Write: See page 214. Reset: Read: Timer 1 Channel 0 Register Low (T1CH0L) Write: See page 214. Reset:
$0026
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$0027
Indeterminate after reset CH1F 0 0 Bit 15 CH1IE 0 14 0 MS1A 0 12 ELS1B 0 11 ELS1A 0 10 TOV1 0 9 CH1MAX 0 Bit 8
Read: Timer 1 Channel 1 Status and $0028 Control Register (T1SC1) Write: See page 214. Reset: Read: Timer 1 Channel 1 Register High (T1CH1H) Write: See page 214. Reset: Read: Timer 1 Channel 1 Register Low (T1CH1L) Write: See page 214. Reset: Read: Timer 2 Status and Control Register (T2SC) Write: See page 211. Reset: Read: Timer 2 Counter Register High (T2CNTH) Write: See page 210. Reset:
0 13
$0029
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$002A
Indeterminate after reset TOF 0 0 Bit 15 TOIE 0 14 TSTOP 1 13 0 TRST 0 12 0 11 0 PS2 0 10 PS1 0 9 PS0 0 Bit 8
$002B
$002C
0
0 = Unimplemented
0
0 R = Reserved
0
0 U = Unaffected
0
0
Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 7)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 33
Memory Addr. Register Name Read: Timer 2 Counter Register Low (T2CNTL) Write: See page 210. Reset: Read: Timer 2 Counter Modulo Register High (T2MODH) Write: See page 211. Reset: Read: Timer 2 Counter Modulo Register Low (T2MODL) Write: See page 211. Reset: Bit 7 Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
$002D
0 Bit 15 1 Bit 7 1 CH0F 0 0 Bit 15
0 14 1 6 1 CH0IE 0 14
0 13 1 5 1 MS0B 0 13
0 12 1 4 1 MS0A 0 12
0 11 1 3 1 ELS0B 0 11
0 10 1 2 1 ELS0A 0 10
0 9 1 1 1 TOV0 0 9
0 Bit 8 1 Bit 0 1 CH0MAX 0 Bit 8
$002E
$002F
Read: Timer 2 Channel 0 Status and $0030 Control Register (T2SC0) Write: See page 211. Reset: Read: Timer 2 Channel 0 Register High (T2CH0H) Write: See page 211. Reset: Read: Timer 2 Channel 0 Register Low (T2CH0L) Write: See page 214. Reset: Read: Reserved Write: Reset: Read: PLL Control Register (PCTL) Write: See page 66. Reset: Read: PLL Bandwidth Control Register (PBWC) Write: See page 67. Reset: Read: PLL Multiplier Select High Register (PMSH) Write: See page 68. Reset: Read: PLL Multiplier Select Low Register (PMSL) Write: See page 69. Reset:
$0031
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$0032
Indeterminate after reset R 0 PLLIE 0 AUTO 0 0 R 0 PLLF R 0 PLLON 1 ACQ 0 0 R 0 BCS 0 0 R 0 PRE1 0 0 R 0 PRE0 0 0 R 0 VPR1 0 0 R 0 VPR0 0 R 0 MUL8 0 MUL0 0
$0033 $0035
$0036
0 LOCK
$0037
0 0
0 0
0 MUL11 0 MUL3 0
0 MUL10 0 MUL2 0 U = Unaffected
0 MUL9 0 MUL1 0
$0038
0 MUL7 0
0 MUL6 1 = Unimplemented
0 MUL5 0
0 MUL4 0 R = Reserved
$0039
Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 7)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 34 Freescale Semiconductor
Input/Output (I/O) Section Addr. Register Name Read: PLL VCO Select Range Register (PMRS) Write: See page 69. Reset: Bit 7 VRS7 0 0 6 VRS6 1 0 5 VRS5 0 0 4 VRS4 0 0 3 VRS3 0 RDS3 0 ADCH3 1 A3 2 VRS2 0 RDS2 0 ADCH2 1 AD2 1 VRS1 0 RDS1 0 ADCH1 1 AD1 Bit 0 VRS0 0 RDS0 1 ADCH0 1 AD0
$003A
Read: PLL Reference Divider Select $003B Register (PMDS) Write: See page 70. Reset: Read: ADC Status and Control Register (ADSCR) Write: See page 51. Reset: Read: ADC Data Register (ADR) Write: See page 53. Reset: Read: ADC Clock Register (ADCLK) Write: See page 53. Reset: Reserved
0 COCO R 0 AD7
0 AIEN 0 AD6
0 ADCO 0 AD5
0 ADCH4 1 AD4
$003C
$003D
Unaffected by reset ADIV2 0 R ADIV1 0 R ADIV0 0 R ADICLK 0 R 0 0 0 0
$003E
0 R
0 R
0 R
0 R
$003F
$FE00
Read: SIM Break Status Register (SBSR) Write: See page 220. Reset:
R 0
R 0
R 0
R 0
R 0
R 0
SBSW (Note 1) 0
R 0
1. Writing a 0 clears SBSW. Read: SIM Reset Status Register (SRSR) Write: See page 172. POR: Read: $FE02 Reserved Write: Reset: Read: SIM Break Flag Control Register (SBFCR) Write: See page 220. Reset: Read: Interrupt Status Register 1 (INT1) Write: See page 167. Reset: POR PIN COP ILOP ILAD MODRST LVI 0
$FE01
1 R 0 BCFE 0 IF6 R 0
0 R 0 R 0 IF5 R 0 = Unimplemented
0 R 0 R 0 IF4 R 0
0 R 0 R 0 IF3 R 0 R = Reserved
0 R 0 R 0 IF2 R 0
0 R 0 R 0 IF1 R 0 U = Unaffected
0 R 0 R 0 0 R 0
0 R 0 R 0 0 R 0
$FE03
$FE04
Figure 2-2. Control, Status, and Data Registers (Sheet 6 of 7)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 35
Memory Addr. Register Name Read: Interrupt Status Register 2 (INT2) Write: See page 168. Reset: Read: Interrupt Status Register 3 (INT3) Write: See page 168. Reset: Read: $FE07 Reserved Write: Reset: Read: FLASH Control Register (FLCR) Write: See page 39. Reset: Bit 7 IF14 R 0 0 R 0 R 0 0 6 IF13 R 0 0 R 0 R 0 0 5 IF12 R 0 0 R 0 R 0 0 4 IF11 R 0 0 R 0 R 0 0 3 IF10 R 0 0 R 0 R 0 HVEN 0 11 0 3 0 0 2 IF9 R 0 0 R 0 R 0 MASS 0 10 0 2 0 0 1 IF8 R 0 IF16 R 0 R 0 ERASE 0 9 0 1 0 0 Bit 0 IF7 R 0 IF15 R 0 R 0 PGM 0 Bit 8 0 Bit 0 0 0
$FE05
$FE06
$FE08
0 Bit 15 0 Bit 7 0 BRKE 0 LVIOUT
0 14 0 6 0 BRKA 0 0
0 13 0 5 0 0
0 12 0 4 0 0
Read: Break Address Register High $FE09 (BRKH) Write: See page 219. Reset: Read: Break Address Register Low $FE0A (BRKL) Write: See page 219. Reset: Read: Break Status and Control Register (BRKSCR) Write: See page 219. Reset: Read: LVI Status Register (LVISR) Write: See page 113. Reset: Read: FLASH Block Protect (1) Register (FLBPR) Write: See page 44. Reset:
$FE0B
0 0
0 0
0 0
0 0
0 0
0 0
$FE0C
0 BPR7
0 BPR6
0 BPR5
0 BPR4
0 BPR3
0 BPR2
0 BPR1
0 BPR0
$FF7E
Unaffected by reset
1. Non-volatile FLASH register
$FFFF
Read: COP Control Register (COPCTL) Write: See page 81. Reset: = Unimplemented
Low byte of reset vector Writing clears COP counter (any value) Unaffected by reset R = Reserved U = Unaffected
Figure 2-2. Control, Status, and Data Registers (Sheet 7 of 7)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 36 Freescale Semiconductor
Input/Output (I/O) Section
Table 2-1. Vector Addresses
Vector Priority Lowest Vector IF16 Address $FFDC $FFDD $FFDE $FFDF $FFE0 $FFE1 $FFE2 $FFE3 $FFE4 $FFE5 $FFE6 $FFE7 $FFE8 $FFE9 $FFEA $FFEB $FFEC $FFED $FFEE $FFEF $FFF0 $FFF1 $FFF2 $FFF3 $FFF4 $FFF5 $FFF6 $FFF7 $FFF8 $FFF9 $FFFA $FFFB $FFFC $FFFD $FFFE $FFFF Vector Timebase Vector (High) Timebase Vector (Low) ADC Conversion Complete Vector (High) ADC Conversion Complete Vector (Low) Keyboard Vector (High) Keyboard Vector (Low) SCI Transmit Vector (High) SCI Transmit Vector (Low) SCI Receive Vector (High) SCI Receive Vector (Low) SCI Error Vector (High) SCI Error Vector (Low) SPI Transmit Vector (High) SPI Transmit Vector (Low) SPI Receive Vector (High) SPI Receive Vector (Low) TIM2 Overflow Vector (High) TIM2 Overflow Vector (Low) Reserved Reserved TIM2 Channel 0 Vector (High) TIM2 Channel 0 Vector (Low) TIM1 Overflow Vector (High) TIM1 Overflow Vector (Low) TIM1 Channel 1 Vector (High) TIM1 Channel 1 Vector (Low) TIM1 Channel 0 Vector (High) TIM1 Channel 0 Vector (Low) PLL Vector (High) PLL Vector (Low) IRQ Vector (High) IRQ Vector (Low) SWI Vector (High) SWI Vector (Low) Reset Vector (High) Reset Vector (Low)
.
IF15
IF14
IF13
IF12
IF11
IF10
IF9
IF8
IF7
IF6
IF5
IF4
IF3
IF2
IF1
--
Highest
--
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 37
Memory
2.5 Random-Access Memory (RAM)
Addresses $0040 through $01BF are RAM locations. The location of the stack RAM is programmable. The 16-bit stack pointer allows the stack to be anywhere in the 64-Kbyte memory space. NOTE For correct operation, the stack pointer must point only to RAM locations. Within page zero are 192 bytes of RAM. Because the location of the stack RAM is programmable, all page zero RAM locations can be used for I/O control and user data or code. When the stack pointer is moved from its reset location at $00FF out of page zero, direct addressing mode instructions can efficiently access all page zero RAM locations. Page zero RAM, therefore, provides ideal locations for frequently accessed global variables. Before processing an interrupt, the CPU uses five bytes of the stack to save the contents of the CPU registers. NOTE For M6805 compatibility, the H register is not stacked. During a subroutine call, the CPU uses two bytes of the stack to store the return address. The stack pointer decrements during pushes and increments during pulls. NOTE Be careful when using nested subroutines. The CPU may overwrite data in the RAM during a subroutine or during the interrupt stacking operation.
2.6 FLASH Memory (FLASH)
This subsection describes the operation of the embedded FLASH memory. This memory can be read, programmed, and erased from a single external supply. The program, erase, and read operations are enabled through the use of an internal charge pump.
2.6.1 Functional Description
The FLASH memory is an array of 7,680 bytes for the MC68HC908GR8A or 4,096 bytes for the MC68HC908GR4A with an additional 36 bytes of user vectors and one byte of block protection. An erased bit reads as 1 and a programmed bit reads as a 0. Memory in the FLASH array is organized into two rows per page basis. The page size is 64 bytes per page and the row size is 32 bytes per row. Hence the minimum erase page size is 64 bytes and the minimum program row size is 32 bytes. Program and erase operation operations are facilitated through control bits in FLASH control register (FLCR). Details for these operations appear later in this section. The address ranges for the user memory and vectors are: * $E000-$FDFF; user memory for the MC68HC908GR8A $EE00-$FDFF; user memory for the MC68HC908GR4A * $FE08; FLASH control register * $FF7E; FLASH block protect register * $FFDC-$FFFF; these locations are reserved for user-defined interrupt and reset vectors NOTE A security feature prevents viewing of the FLASH contents.(1)
1. No security feature is absolutely secure. However, Freescale's strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 38 Freescale Semiconductor
FLASH Memory (FLASH)
2.6.2 FLASH Control Register
The FLASH control register (FLCR) controls FLASH program and erase operations.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 $FE08 Bit 7 0 6 0 5 0 4 0 3 HVEN 0 2 MASS 0 1 ERASE 0 Bit 0 PGM 0
Figure 2-3. FLASH Control Register (FLCR) HVEN -- High-Voltage Enable Bit This read/write bit enables the charge pump to drive high voltages for program and erase operations in the array. HVEN can only be set if either PGM = 1 or ERASE = 1 and the proper sequence for program or erase is followed. 1 = High voltage enabled to array and charge pump on 0 = High voltage disabled to array and charge pump off MASS -- Mass Erase Control Bit Setting this read/write bit configures the FLASH array for mass erase operation. 1 = MASS erase operation selected 0 = PAGE erase operation selected ERASE -- Erase Control Bit This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = Erase operation selected 0 = Erase operation unselected PGM -- Program Control Bit This read/write bit configures the memory for program operation. PGM is interlocked with the ERASE bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = Program operation selected 0 = Program operation unselected
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 39
Memory
2.6.3 FLASH Page Erase Operation
Use this step-by-step procedure to erase a page (64 bytes) of FLASH memory. A page consists of 64 consecutive bytes starting from addresses $XX00, $XX40, $XX80, or $XXC0. The 36-byte user interrupt vectors area also forms a page. Any FLASH memory page can be erased alone. 1. Set the ERASE bit, and clear the MASS bit in the FLASH control register. 2. Read the FLASH block protect register. 3. Write any data to any FLASH location within the page address range of the block to be erased. 4. Wait for a time, tNVS (minimum 10 s) 5. Set the HVEN bit. 6. Wait for a time, tErase (minimum 1 ms or 4 ms) 7. Clear the ERASE bit. 8. Wait for a time, tNVH (minimum 5 s) 9. Clear the HVEN bit. 10. After a time, tRCV (typical 1 s), the memory can be accessed in read mode again. NOTE Programming and erasing of FLASH locations cannot be performed by code being executed from FLASH memory. While these operations must be performed in the order shown, other unrelated operations may occur between the steps. In applications that need more than 1000 program/erase cycles, use the 4-ms page erase specification to get improved long-term reliability. Any application can use this 4-ms page erase specification. However, in applications where a FLASH location will be erased and reprogrammed less than 1000 times, and speed is important, use the 1-ms page erase specification to get a shorter cycle time.
2.6.4 FLASH Mass Erase Operation
Use this step-by-step procedure to erase entire FLASH memory: 1. Set both the ERASE bit, and the MASS bit in the FLASH control register. 2. Read the FLASH block protect register. 3. Write any data to any FLASH address(1) within the FLASH memory address range. 4. Wait for a time, tNVS (minimum 10 s) 5. Set the HVEN bit. 6. Wait for a time, tMErase (minimum 4 ms) 7. Clear the ERASE and MASS bits. NOTE Mass erase is disabled whenever any block is protected (FLBPR does not equal $FF). 8. Wait for a time, tNVHL (minimum 100 s) 9. Clear the HVEN bit. 10. After a time, tRCV (typical 1 s), the memory can be accessed in read mode again.
1. When in monitor mode, with security sequence failed (see 18.3.2 Security), write to the FLASH block protect register instead of any FLASH address. MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 40 Freescale Semiconductor
FLASH Memory (FLASH)
NOTE Programming and erasing of FLASH locations cannot be performed by code being executed from FLASH memory. While these operations must be performed in the order shown, other unrelated operations may occur between the steps.
2.6.5 FLASH Program/Read Operation
Programming of the FLASH memory is done on a row basis. A row consists of 32 consecutive bytes starting from addresses $XX00, $XX20, $XX40, $XX60, $XX80, $XXA0, $XXC0, and $XXE0. During the programming cycle, make sure that all addresses being written to fit within one of the ranges specified above. Attempts to program addresses in different row ranges in one programming cycle will fail. Use this step-by-step procedure to program a row of FLASH memory (Figure 2-4 is a flowchart representation). NOTE Only bytes which are currently $FF may be programmed. 1. Set the PGM bit. This configures the memory for program operation and enables the latching of address and data for programming. 2. Read the FLASH block protect register. 3. Write any data to any FLASH address within the row address range desired. 4. Wait for a time, tNVS (minimum 10 s). 5. Set the HVEN bit. 6. Wait for a time, tPGS (minimum 5 s). 7. Write data to the FLASH address to be programmed. 8. Wait for a time, tPROG (minimum 30 s). 9. Repeat step 7 and 8 until all the bytes within the row are programmed. 10. Clear the PGM bit.(1) 11. Wait for a time, tNVH (minimum 5 s). 12. Clear the HVEN bit. 13. After time, tRCV (typical 1 s), the memory can be accessed in read mode again. This program sequence is repeated throughout the memory until all data is programmed. NOTE Programming and erasing of FLASH locations can not be performed by code being executed from the same FLASH array. NOTE While these operations must be performed in the order shown, other unrelated operations may occur between the steps. Care must be taken within the FLASH array memory space such as the COP control register (COPCTL) at $FFFF. NOTE It is highly recommended that interrupts be disabled during program/ erase operations.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 41
Memory
NOTE Do not exceed tPROG maximum or tHV maximum. tHV is defined as the cumulative high voltage programming time to the same row before next erase. tHV must satisfy this condition: tNVS + tNVH + tPGS + (tPROG x 32) tHV maximum Refer to 19.17 Memory Characteristics. NOTE The time between programming the FLASH address change (step 7 to step 7), or the time between the last FLASH programmed to clearing the PGM bit (step 7 to step 10) must not exceed the maximum programming time, tPROG maximum. CAUTION Be cautious when programming the FLASH array to ensure that non-FLASH locations are not used as the address that is written to when selecting either the desired row address range in step 3 of the algorithm or the byte to be programmed in step 7 of the algorithm. This applies particularly to $FFD4-$FFDF.
2.6.6 FLASH Block Protection
Due to the ability of the on-board charge pump to erase and program the FLASH memory in the target application, provision is made for protecting a block of memory from unintentional erase or program operations due to system malfunction. This protection is done by using of a FLASH block protect register (FLBPR). The FLBPR determines the range of the FLASH memory which is to be protected. The range of the protected area starts from a location defined by FLBPR and ends at the bottom of the FLASH memory ($FFFF). When the memory is protected, the HVEN bit cannot be set in either ERASE or PROGRAM operations. NOTE In performing a program or erase operation, the FLASH block protect register must be read after setting the PGM or ERASE bit and before asserting the HVEN bit When the FLBPR is program with all 0's, the entire memory is protected from being programmed and erased. When all the bits are erased (all 1's), the entire memory is accessible for program and erase. When bits within the FLBPR are programmed, they lock a block of memory, address ranges as shown in 2.6.7 FLASH Block Protect Register. Once the FLBPR is programmed with a value other than $FF or $FE, any erase or program of the FLBPR or the protected block of FLASH memory is prohibited. Mass erase is disabled whenever any block is protected (FLBPR does not equal $FF). The presence of a VTST on the IRQ pin will bypass the block protection so that all of the memory included in the block protect register is open for program and erase operations. NOTE The FLASH block protect register is not protected with special hardware or software. Therefore, if this page is not protected by FLBPR the register is erased by either a page or mass erase operation.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 42 Freescale Semiconductor
FLASH Memory (FLASH)
Algorithm for programming a row (32 bytes) of FLASH memory
1
SET PGM BIT
2
READ THE FLASH BLOCK PROTECT REGISTER
3
WRITE ANY DATA TO ANY FLASH ADDRESS WITHIN THE ROW ADDRESS RANGE DESIRED
4
WAIT FOR A TIME, tNVS
5
SET HVEN BIT
6
WAIT FOR A TIME, tPGS
7
WRITE DATA TO THE FLASH ADDRESS TO BE PROGRAMMED
8
WAIT FOR A TIME, tPROG
COMPLETED PROGRAMMING THIS ROW? N 10
Y
CLEAR PGM BIT
11
WAIT FOR A TIME, tNVH
Note: The time between each FLASH address change (step 7 to step 7), or the time between the last FLASH address programmed to clearing PGM bit (step 7 to step 10) must not exceed the maximum programming time, tPROG max. This row program algorithm assumes the row/s to be programmed are initially erased.
12 CLEAR HVEN BIT
13
WAIT FOR A TIME, tRCV
END OF PROGRAMMING
Figure 2-4. FLASH Programming Flowchart
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 43
Memory
2.6.7 FLASH Block Protect Register
The FLASH block protect register (FLBPR) is implemented as a byte within the FLASH memory, and therefore can only be written during a programming sequence of the FLASH memory. The value in this register determines the starting location of the protected range within the FLASH memory.
Address: Read: Write: Reset: $FF7E Bit 7 BPR7 6 BPR6 5 BPR5 4 BPR4 3 BPR3 2 BPR2 1 BPR1 Bit 0 BPR0
Unaffected by reset. Initial value from factory is 1. Write to this register is by a programming sequence to the FLASH memory.
Figure 2-5. FLASH Block Protect Register (FLBPR) BPR[7:0] -- FLASH Block Protect Bits These eight bits represent bits [13:6] of a 16-bit memory address. Bit 15 and Bit 14 are 1s and bits [5:0] are 0s. The resultant 16-bit address is used for specifying the start address of the FLASH memory for block protection. The FLASH is protected from this start address to the end of FLASH memory, at $FFFF. With this mechanism, the protect start address can be $XX00, $XX40, $XX80, and $XXC0 (64 bytes page boundaries) within the FLASH memory.
16-BIT MEMORY ADDRESS START ADDRESS OF FLASH 1 BLOCK PROTECT
1
FLBPR VALUE
0
0
0
0
0
0
Figure 2-6. FLASH Block Protect Start Address Table 2-2. Examples of Protect Address Ranges
BPR[7:0] $00 $81 (1000 0001) $82 (1000 0010) Addresses of Protect Range The entire FLASH memory is protected. $E040 (1110 0000 0100 0000) -- $FFFF $E080 (1110 0000 1000 0000) -- $FFFF and so on... $FC (1111 1100) $FD (1111 1101) $FE (1111 1110) $FF $FF00 (1111 1111 0000 0000) -- FFFF $FF40 (1111 1111 0100 0000) -- $FFFF FLBPR and vectors are protected $FF80 (1111 1111 1000 0000) -- FFFF Vectors are protected The entire FLASH memory is not protected.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 44 Freescale Semiconductor
FLASH Memory (FLASH)
2.6.8 Wait Mode
Putting the MCU into wait mode while the FLASH is in read mode does not affect the operation of the FLASH memory directly, but there will not be any memory activity since the CPU is inactive. The WAIT instruction should not be executed while performing a program or erase operation on the FLASH, otherwise the operation will discontinue, and the FLASH will be on standby mode.
2.6.9 Stop Mode
Putting the MCU into stop mode while the FLASH is in read mode does not affect the operation of the FLASH memory directly, but there will not be any memory activity since the CPU is inactive. The STOP instruction should not be executed while performing a program or erase operation on the FLASH, otherwise the operation will discontinue, and the FLASH will be on standby mode NOTE Standby mode is the power saving mode of the FLASH module in which all internal control signals to the FLASH are inactive and the current consumption of the FLASH is at a minimum.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 45
Memory
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 46 Freescale Semiconductor
Chapter 3 Analog-to-Digital Converter (ADC)
3.1 Introduction
This section describes the 8-bit analog-to-digital converter (ADC).
3.2 Features
Features of the ADC module include: * Six channels with multiplexed input * Linear successive approximation with monotonicity * 8-bit resolution * Single or continuous conversion * Conversion complete flag or conversion complete interrupt * Selectable ADC clock
3.3 Functional Description
The ADC provides six pins for sampling external sources at pins PTB5/AD5-PTB0/KBD0. An analog multiplexer allows the single ADC converter to select one of six ADC channels as ADC voltage in (VADIN). VADIN is converted by the successive approximation register-based analog-to-digital converter. When the conversion is completed, ADC places the result in the ADC data register and sets a flag or generates an interrupt. See Figure 3-2.
3.3.1 ADC Port I/O Pins
PTB5/AD5-PTB0/KBD0 are general-purpose I/O (input/output) pins that share with the ADC channels. The channel select bits define which ADC channel/port pin will be used as the input signal. The ADC overrides the port I/O logic by forcing that pin as input to the ADC. The remaining ADC channels/port pins are controlled by the port I/O logic and can be used as general-purpose I/O. Writes to the port register or data direction register (DDR) will not have any affect on the port pin that is selected by the ADC. Read of a port pin in use by the ADC will return a 0.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 47
Analog-to-Digital Converter (ADC)
INTERNAL BUS M68HC08 CPU PORTA DDRA CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) PROGRAMMABLE TIMEBASE MODULE SINGLE BREAKPOINT BREAK MODULE DUAL VOLTAGE LOW-VOLTAGE INHIBIT MODULE 4-BIT KEYBOARD INTERRUPT MODULE PORTC DDRC 2-CHANNEL TIMER INTERFACE MODULE 1 1-CHANNEL TIMER INTERFACE MODULE 2 SERIAL COMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE RST(3) IRQ(3) VDDAD/VREFH VSSAD/VREFL SYSTEM INTEGRATION MODULE SINGLE EXTERNAL INTERRUPT MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE POWER-ON RESET MODULE VDD VSS VDDA VSSA SERIAL PERIPHERAL INTERFACE MODULE MONITOR MODULE MEMORY MAP MODULE CONFIGURATION REGISTER 1 MODULE CONFIGURATION REGISTER 2 MODULE PORTB DDRB PTA3/KBD3- PTA0/KBD0(1)
CONTROL AND STATUS REGISTERS -- 64 BYTES MC68HC908GR8A USER FLASH -- 7680 BYTES MC68HC908GR4A USER FLASH -- 4096 BYTES USER RAM -- 384 BYTES MONITOR ROM -- 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM -- 544 BYTES USER FLASH VECTOR SPACE -- 36 BYTES CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 1-8-MHz OSCILLATOR PHASE LOCKED LOOP
PTB5/AD5 PTB4/AD4 PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0
PTC1(1), (2) PTC0(1), (2)
PTD6/T2CH0(1) PTD5/T1CH1(1) PTD4/T1CH0(1) PTD3/SPSCK(1) PTD2/MOSI(1) PTD1/MISO(1) PTD0/SS(1)
PORTE
PORTD
DDRD
PTE1/RxD PTE0/TxD
DDRE
SECURITY MODULE
POWER
MONITOR MODE ENTRY MODULE
1. Ports are software configurable with pullup device if input port. 2. Higher current drive port pins 3. Pin contains integrated pullup device
Figure 3-1. Block Diagram Highlighting ADC Block and Pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 48 Freescale Semiconductor
Functional Description
INTERNAL DATA BUS READ DDRBx WRITE DDRBx RESET WRITE PTBx DDRBx PTBx PTBx ADC CHANNEL x DISABLE
READ PTBx
DISABLE ADC DATA REGISTER ADC VOLTAGE IN (VADIN) ADC VREFH VREFL AIEN COCO CGMXCLK BUS CLOCK ADC CLOCK CLOCK GENERATOR
INTERRUPT LOGIC
CONVERSION COMPLETE
CHANNEL SELECT
ADCH4-ADCH0
ADIV2-ADIV0
ADICLK
Figure 3-2. ADC Block Diagram
3.3.2 Voltage Conversion
When the input voltage to the ADC equals VREFH, the ADC converts the signal to $FF (full scale). If the input voltage equals VREFL, the ADC converts it to $00. Input voltages between VREFH and VREFL are a straight-line linear conversion. NOTE The ADC input voltage must always be greater than VSSA and less than VDDA. VREFH must always be greater than or equal to VREFL. NOTE Connect the VDDA pin to the same voltage potential as the VDD pin, and connect the VSSA pin to the same voltage potential as the VSS pin. The VDDA pin should be routed carefully for maximum noise immunity.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 49
Analog-to-Digital Converter (ADC)
3.3.3 Conversion Time
Conversion starts after a write to the ADC status and control register (ADSCR). One conversion will take between 16 and 17 ADC clock cycles. The ADIVx and ADICLK bits should be set to provide a 1-MHz ADC clock frequency. Conversion time = 16 to 17 ADC cycles ADC frequency
Number of bus cycles = conversion time x bus frequency
3.3.4 Conversion
In continuous conversion mode, the ADC data register will be filled with new data after each conversion. Data from the previous conversion will be overwritten whether that data has been read or not. Conversions will continue until the ADCO bit is cleared. The COCO bit is set after the first conversion and will stay set until the next read of the ADC data register. In single conversion mode, conversion begins with a write to the ADSCR. Only one conversion occurs between writes to the ADSCR. When a conversion is in process and the ADSCR is written, the current conversion data should be discarded to prevent an incorrect reading.
3.3.5 Accuracy and Precision
The conversion process is monotonic and has no missing codes.
3.4 Interrupts
When the AIEN bit is set, the ADC module is capable of generating CPU interrupts after each ADC conversion. A CPU interrupt is generated if the COCO bit is at 0. The COCO bit is not used as a conversion complete flag when interrupts are enabled.
3.5 Low-Power Modes
The WAIT and STOP instruction can put the MCU in low power-consumption standby modes.
3.5.1 Wait Mode
The ADC continues normal operation during wait mode. Any enabled CPU interrupt request from the ADC can bring the MCU out of wait mode. If the ADC is not required to bring the MCU out of wait mode, power down the ADC by setting ADCH4-ADCH0 bits in the ADC status and control register before executing the WAIT instruction.
3.5.2 Stop Mode
The ADC module is inactive after the execution of a STOP instruction. Any pending conversion is aborted. ADC conversions resume when the MCU exits stop mode after an external interrupt. Allow one conversion cycle to stabilize the analog circuitry.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 50 Freescale Semiconductor
I/O Signals
3.6 I/O Signals
The ADC module has six pins shared with port B, PTB5/AD5-PTB0/KBD0.
3.6.1 ADC Analog Ground Pin (VSSAD)/ADC Voltage Reference Low Pin (VREFL)
The ADC analog portion uses VSSAD as its ground pin and VREFL as its lower voltage reference pin. Connect the VSSAD/VREFL pin to the same voltage potential as VSS. NOTE For maximum noise immunity, route VSSAD/VREFL carefully and place bypass capacitors as close as possible to the package. Routing VREFH close and parallel to VREFL may improve common mode noise rejection. 3.6.2 ADC Analog Power Pin (VDDAD)/ADC Voltage Reference High Pin (VREFH) The ADC analog portion uses VDDAD as its power pin and VREFH as its upper voltage reference pin. Connect the VDDAD/ VREFH pin to the same voltage potential as VDD. NOTE For maximum noise immunity, route VDDAD/VREFH carefully and place bypass capacitors as close as possible to the package. Routing VREFH close and parallel to VREFL may improve common mode noise rejection.
3.6.3 ADC Voltage In (VADIN)
VADIN is the input voltage signal from one of the six ADC channels to the ADC module.
3.7 I/O Registers
These I/O registers control and monitor ADC operation: * ADC status and control register (ADSCR) * ADC data register (ADR) * ADC clock register (ADCLK)
3.7.1 ADC Status and Control Register
Function of the ADC status and control register (ADSCR) is described here.
Address: Read: Write: Reset: $003C Bit 7 COCO R 0 R 6 AIEN 0 = Reserved 5 ADCO 0 4 ADCH4 1 3 ADCH3 1 2 ADCH2 1 1 ADCH1 1 Bit 0 ADCH0 1
Figure 3-3. ADC Status and Control Register (ADSCR) COCO -- Conversions Complete Bit In non-interrupt mode (AIEN = 0), COCO is a read-only bit that is set at the end of each conversion. COCO will stay set until cleared by a read of the ADC data register. Reset clears this bit.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 51
Analog-to-Digital Converter (ADC)
In interrupt mode (AIEN = 1), COCO is a read-only bit that is not set at the end of a conversion. It always reads as a 0. 1 = Conversion completed (AIEN = 0) 0 = Conversion not completed (AIEN = 0) or CPU interrupt enabled (AIEN = 1) NOTE The write function of the COCO bit is reserved. When writing to the ADSCR register, always have a 0 in the COCO bit position. AIEN -- ADC Interrupt Enable Bit When this bit is set, an interrupt is generated at the end of an ADC conversion. The interrupt signal is cleared when the data register is read or the status/control register is written. Reset clears the AIEN bit. 1 = ADC interrupt enabled 0 = ADC interrupt disabled ADCO -- ADC Continuous Conversion Bit When set, the ADC will convert samples continuously and update the ADR register at the end of each conversion. Only one conversion is completed between writes to the ADSCR when this bit is cleared. Reset clears the ADCO bit. 1 = Continuous ADC conversion 0 = One ADC conversion ADCH4-ADCH0 -- ADC Channel Select Bits ADCH4-ADCH0 form a 5-bit field which is used to select one of 16 ADC channels. Only six channels, AD5-AD0, are available on this MCU. The channels are detailed in Table 3-1. Care should be taken when using a port pin as both an analog and digital input simultaneously to prevent switching noise from corrupting the analog signal. See Table 3-1. The ADC subsystem is turned off when the channel select bits are all set to 1. This feature allows for reduced power consumption for the MCU when the ADC is not being used. NOTE Recovery from the disabled state requires one conversion cycle to stabilize. The voltage levels supplied from internal reference nodes, as specified in Table 3-1, are used to verify the operation of the ADC converter both in production test and for user applications. Table 3-1. Mux Channel Select(1)
ADCH4 0 0 0 0 0 0 0 1 1 1 1 ADCH3 0 0 0 0 0 0 0 1 1 1 1 ADCH2 0 0 0 0 1 1 1 1 1 1 1 ADCH1 0 0 1 1 0 0 1 0 0 1 1 ADCH0 0 1 0 1 0 1 0 0 1 0 1 Input Select PTB0/KBD0 PTB1/AD1 PTB1/AD2 PTB2/AD3 PTB4/AD4 PTB5/AD5 Reserved VREFH VREFL ADC power off
1. If any unused channels are selected, the resulting ADC conversion will be unknown or reserved. MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 52 Freescale Semiconductor
I/O Registers
3.7.2 ADC Data Register
One 8-bit result register, ADC data register (ADR), is provided. This register is updated each time an ADC conversion completes.
Address: Read: Write: Reset: 0 0 0 0 0 0 0 0 = Unimplemented $003D Bit 7 AD7 6 AD6 5 AD5 4 AD4 3 AD3 2 AD2 1 AD1 Bit 0 AD0
Figure 3-4. ADC Data Register (ADR)
3.7.3 ADC Clock Register
The ADC clock register (ADCLK) selects the clock frequency for the ADC.
Address: Read: Write: Reset: $003E Bit 7 ADIV2 0 6 ADIV1 0 5 ADIV0 0 4 ADICLK 0 3 0 0 2 0 0 1 0 0 Bit 0 0 0
= Unimplemented
Figure 3-5. ADC Clock Register (ADCLK) ADIV2-ADIV0 -- ADC Clock Prescaler Bits ADIV2-ADIV0 form a 3-bit field which selects the divide ratio used by the ADC to generate the internal ADC clock. Table 3-2 shows the available clock configurations. The ADC clock should be set to approximately 1 MHz. Table 3-2. ADC Clock Divide Ratio
ADIV2 0 0 0 0 1 ADIV1 0 0 1 1 X
(1)
ADIV0 0 1 0 1 X
(1)
ADC Clock Rate ADC input clock / 1 ADC input clock / 2 ADC input clock / 4 ADC input clock / 8 ADC input clock / 16
1. X = Don't care
ADICLK -- ADC Input Clock Select Bit ADICLK selects either the bus clock or the oscillator output clock (CGMXCLK) as the input clock source to generate the internal ADC clock. Reset selects CGMXCLK as the ADC clock source. 1 = Internal bus clock 0 = Oscillator output clock (CGMXCLK)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 53
Analog-to-Digital Converter (ADC)
The ADC requires a clock rate of approximately 1 MHz for correct operation. If the selected clock source is not fast enough, the ADC will generate incorrect conversions. See 19.12 ADC Characteristics. fADIC = fCGMXCLK or bus frequency ADIV[2:0] 1 MHz
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 54 Freescale Semiconductor
Chapter 4 Clock Generator Module (CGM)
4.1 Introduction
This section describes the clock generator module. The CGM generates the crystal clock signal, CGMXCLK, which operates at the frequency of the crystal. The CGM also generates the base clock signal, CGMOUT, which is based on either the crystal clock divided by two or the phase-locked loop (PLL) clock, CGMVCLK, divided by two. In user mode, CGMOUT is the clock from which the SIM derives the system clocks, including the bus clock, which is at a frequency of CGMOUT/2. The PLL is a fully functional frequency generator designed for use with crystals or ceramic resonators. The PLL can generate an 8-MHz bus frequency using a 1-8 MHz crystal or external clock source.
4.2 Features
Features of the CGM include: * Phase-locked loop with output frequency in integer multiples of an integer dividend of the crystal reference * High-frequency crystal operation with low-power operation and high-output frequency resolution * Programmable hardware voltage-controlled oscillator (VCO) for low-jitter operation * Automatic bandwidth control mode for low-jitter operation * Automatic frequency lock detector * CPU interrupt on entry or exit from locked condition * Configuration register bit to allow oscillator operation during stop mode
4.3 Functional Description
The CGM consists of three major submodules: * Crystal oscillator circuit -- The crystal oscillator circuit generates the constant crystal frequency clock, CGMXCLK. * Phase-locked loop (PLL) -- The PLL generates the programmable VCO frequency clock, CGMVCLK. * Base clock selector circuit -- This software-controlled circuit selects either CGMXCLK divided by two or the VCO clock, CGMVCLK, divided by two as the base clock, CGMOUT. The SIM derives the system clocks from either CGMOUT or CGMXCLK. Figure 4-1 shows the structure of the CGM.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 55
Clock Generator Module (CGM)
OSCILLATOR (OSC) OSC2 CGMXCLK (TO: SIM, TIM, ADC) OSC1 SIMOSCEN (FROM SIM) OSCSTOPENB (FROM CONFIG)
PHASE-LOCKED LOOP (PLL)
CGMRDV
REFERENCE DIVIDER
CGMRCLK BCS CLOCK SELECT CIRCUIT /2 CGMOUT (TO SIM)
RDS3-RDS0
VDDA
CGMXFC
VSSA VPR1-VPR0 VRS7-VRS0
PHASE DETECTOR
LOOP FILTER PLL ANALOG
VOLTAGE CONTROLLED OSCILLATOR
CGMVCLK
LOCK DETECTOR
AUTOMATIC MODE CONTROL
INTERRUPT CONTROL
PLLIREQ (TO SIM)
LOCK MUL11-MUL0
AUTO
ACQ
PLLIE PRE1-PRE0
PLLF
CGMVDV
FREQUENCY DIVIDER
FREQUENCY DIVIDER
Figure 4-1. CGM Block Diagram
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 56 Freescale Semiconductor
Functional Description
4.3.1 Crystal Oscillator Circuit
The crystal oscillator circuit consists of an inverting amplifier and an external crystal. The OSC1 pin is the input to the amplifier and the OSC2 pin is the output. The SIMOSCEN signal from the system integration module (SIM) or the OSCSTOPENB bit in the CONFIG register enable the crystal oscillator circuit. The CGMXCLK signal is the output of the crystal oscillator circuit and runs at a rate equal to the crystal frequency. CGMXCLK is then buffered to produce CGMRCLK, the PLL reference clock. CGMXCLK can be used by other modules which require precise timing for operation. The duty cycle of CGMXCLK is not guaranteed to be 50% and depends on external factors, including the crystal and related external components. An externally generated clock also can feed the OSC1 pin of the crystal oscillator circuit. Connect the external clock to the OSC1 pin and let the OSC2 pin float.
4.3.2 Phase-Locked Loop Circuit (PLL)
The PLL is a frequency generator that can operate in either acquisition mode or tracking mode, depending on the accuracy of the output frequency. The PLL can change between acquisition and tracking modes either automatically or manually.
4.3.3 PLL Circuits
The PLL consists of these circuits: * Voltage-controlled oscillator (VCO) * Modulo VCO frequency divider * Phase detector * Loop filter * Lock detector The operating range of the VCO is programmable for a wide range of frequencies and for maximum immunity to external noise, including supply and CGM/XFC noise. The VCO frequency is bound to a range from roughly one-half to twice the center-of-range frequency, fVRS. Modulating the voltage on the CGM/XFC pin changes the frequency within this range. By design, fVRS is equal to the nominal center-of-range frequency, fNOM, (38.4 kHz) times a linear factor, L, and a power-of-two factor, E, or (L x 2E)fNOM. CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK. CGMRCLK runs at a frequency, fRCLK. The VCO's output clock, CGMVCLK, running at a frequency, fVCLK, is fed back through a programmable prescale divider and a programmable modulo divider. The prescaler divides the VCO clock by a power-of-two factor P and the modulo divider reduces the VCO clock by a factor, N. The dividers' output is the VCO feedback clock, CGMVDV, running at a frequency, fVDV = fVCLK/(N x 2P). (See 4.3.6 Programming the PLL for more information.) The phase detector then compares the VCO feedback clock, CGMVDV, with the final reference clock, CGMRDV. A correction pulse is generated based on the phase difference between the two signals. The loop filter then slightly alters the DC voltage on the external capacitor connected to CGM/XFC based on the width and direction of the correction pulse. The filter can make fast or slow corrections depending on its mode, described in 4.3.4 Acquisition and Tracking Modes. The value of the external capacitor and the reference frequency determine the speed of the corrections and the stability of the PLL. The lock detector compares the frequencies of the VCO feedback clock, CGMVDV, and the reference clock, CGMRCLK. Therefore, the speed of the lock detector is directly proportional to the reference
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 57
Clock Generator Module (CGM)
frequency, fRCLK. The circuit determines the mode of the PLL and the lock condition based on this comparison.
4.3.4 Acquisition and Tracking Modes
The PLL filter is manually or automatically configurable into one of two operating modes: * Acquisition mode -- In acquisition mode, the filter can make large frequency corrections to the VCO. This mode is used at PLL startup or when the PLL has suffered a severe noise hit and the VCO frequency is far off the desired frequency. When in acquisition mode, the ACQ bit is clear in the PLL bandwidth control register. (See 4.5.2 PLL Bandwidth Control Register.) * Tracking mode -- In tracking mode, the filter makes only small corrections to the frequency of the VCO. PLL jitter is much lower in tracking mode, but the response to noise is also slower. The PLL enters tracking mode when the VCO frequency is nearly correct, such as when the PLL is selected as the base clock source. (See 4.3.8 Base Clock Selector Circuit.) The PLL is automatically in tracking mode when not in acquisition mode or when the ACQ bit is set.
4.3.5 Manual and Automatic PLL Bandwidth Modes
The PLL can change the bandwidth or operational mode of the loop filter manually or automatically. Automatic mode is recommended for most users. In automatic bandwidth control mode (AUTO = 1), the lock detector automatically switches between acquisition and tracking modes. Automatic bandwidth control mode also is used to determine when the VCO clock, CGMVCLK, is safe to use as the source for the base clock, CGMOUT. (See 4.5.2 PLL Bandwidth Control Register.) If PLL interrupts are enabled, the software can wait for a PLL interrupt request and then check the LOCK bit. If interrupts are disabled, software can poll the LOCK bit continuously (during PLL startup, usually) or at periodic intervals. In either case, when the LOCK bit is set, the VCO clock is safe to use as the source for the base clock. (See 4.3.8 Base Clock Selector Circuit.) If the VCO is selected as the source for the base clock and the LOCK bit is clear, the PLL has suffered a severe noise hit and the software must take appropriate action, depending on the application. (See 4.6 Interrupts for information and precautions on using interrupts.) The following conditions apply when the PLL is in automatic bandwidth control mode: * The ACQ bit (see 4.5.2 PLL Bandwidth Control Register) is a read-only indicator of the mode of the filter. (See 4.3.4 Acquisition and Tracking Modes.) * The ACQ bit is set when the VCO frequency is within a certain tolerance and is cleared when the VCO frequency is out of a certain tolerance. (See 4.8 Acquisition/Lock Time Specifications for more information.) * The LOCK bit is a read-only indicator of the locked state of the PLL. * The LOCK bit is set when the VCO frequency is within a certain tolerance and is cleared when the VCO frequency is out of a certain tolerance. (See 4.8 Acquisition/Lock Time Specifications for more information.) * CPU interrupts can occur if enabled (PLLIE = 1) when the PLL's lock condition changes, toggling the LOCK bit. (See 4.5.1 PLL Control Register.) The PLL also may operate in manual mode (AUTO = 0). Manual mode is used by systems that do not require an indicator of the lock condition for proper operation. Such systems typically operate well below fBUSMAX.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 58 Freescale Semiconductor
Functional Description
The following conditions apply when in manual mode: * ACQ is a writable control bit that controls the mode of the filter. Before turning on the PLL in manual mode, the ACQ bit must be clear. * Before entering tracking mode (ACQ = 1), software must wait a given time, tACQ (see 4.8 Acquisition/Lock Time Specifications), after turning on the PLL by setting PLLON in the PLL control register (PCTL). * Software must wait a given time, tAL, after entering tracking mode before selecting the PLL as the clock source to CGMOUT (BCS = 1). * The LOCK bit is disabled. * CPU interrupts from the CGM are disabled.
4.3.6 Programming the PLL
The following procedure shows how to program the PLL. NOTE The round function in the following equations means that the real number should be rounded to the nearest integer number. 1. Choose the desired bus frequency, fBUSDES. 2. Calculate the desired VCO frequency (four times the desired bus frequency).
f VCLKDES = 4 x f BUSDES
3. Choose a practical PLL (crystal) reference frequency, fRCLK, and the reference divider, R. Typically, the reference crystal is 4 MHz and R = 1. Frequency errors to the PLL are corrected at a rate of fRCLK/R. For stability and lock time reduction, this rate must be as fast as possible. The VCO frequency must be an integer multiple of this rate. The relationship between the VCO frequency, fVCLK, and the reference frequency, fRCLK, is
2N f VCLK = ----------- ( f RCLK ) R
P
P, the power of two multiplier, and N, the range multiplier, are integers. In cases where desired bus frequency has some tolerance, choose fRCLK to a value determined either by other module requirements (such as modules which are clocked by CGMXCLK), cost requirements, or ideally, as high as the specified range allows. See Chapter 19 Electrical Specifications. Choose the reference divider, R = 1. After choosing N and P, the actual bus frequency can be determined using equation in 2 above. When the tolerance on the bus frequency is tight, choose fRCLK to an integer divisor of fBUSDES, and R = 1. If fRCLK cannot meet this requirement, use the following equation to solve for R with practical choices of fRCLK, and choose the fRCLK that gives the lowest R.
f VCLKDES f VCLKDES R = round R MAX x ------------------------- - integer ------------------------- f RCLK f RCLK
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 59
Clock Generator Module (CGM)
4. Select a VCO frequency multiplier, N.
R x f VCLKDES N = round ------------------------------------ f RCLK
5. If N is < Nmax, use P = 0. If N > Nmax, choose P using this table:
Current N Value 0 < N N max N max < N N max x 2 N max x 2 < N N max x 4 N max x 4 < N N max x 8 P 0 1 2 3
Then recalculate N:
R x f VCLKDES N = round ------------------------------------ P f x2
RCLK
6. Calculate and verify the adequacy of the VCO and bus frequencies fVCLK and fBUS.
f VCLK f P = (2 x N R) x f = (f VCLK RCLK
BUS
)4
7. Select the VCO's power-of-two range multiplier E, according to this table:
Frequency Range 0 < fVCLK < 8MHz 8MHz fVCLK < 16MHz 16MHz fVCLK < 32MHz NOTE: Do not program E to a value of 3. E 0 1 2
8. Select a VCO linear range multiplier, L, where fNOM = 38.4 kHz
f VCLK L = round -------------------------- 2E x f NOM
9. Calculate and verify the adequacy of the VCO programmed center-of-range frequency, fVRS. The center-of-range frequency is the midpoint between the minimum and maximum frequencies attainable by the PLL.
f VRS = ( L x 2 )f NOM
E
For proper operation,
f NOM x 2 f VRS - f VCLK -------------------------2
E
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 60 Freescale Semiconductor
Functional Description
10. Verify the choice of P, R, N, E, and L by comparing fVCLK to fVRS and fVCLKDES. For proper operation, fVCLK must be within the application's tolerance of fVCLKDES, and fVRS must be as close as possible to fVCLK. NOTE Exceeding the recommended maximum bus frequency or VCO frequency can crash the MCU. 11. Program the PLL registers accordingly: a. In the PRE bits of the PLL control register (PCTL), program the binary equivalent of P. b. In the VPR bits of the PLL control register (PCTL), program the binary equivalent of E. c. In the PLL multiplier select register low (PMSL) and the PLL multiplier select register high (PMSH), program the binary equivalent of N. d. In the PLL VCO range select register (PMRS), program the binary coded equivalent of L. e. In the PLL reference divider select register (PMDS), program the binary coded equivalent of R. Table 4-1 provides numeric examples (numbers are in hexadecimal notation):
Table 4-1. Numeric Example
fBUS (MHz) 2.0 4.0 8.0 2.0 4.0 8.0 2.4576 4.9152 7.3728 2.0 4.0 8.0 fRCLK (MHz) 8.0 8.0 8.0 4.0 4.0 4.0 4.9152 4.9152 4.9152 8.0 8.0 8.0 PCTL P 0 0 0 0 0 0 0 0 0 0 0 0 E 0 1 2 0 1 2 1 2 2 0 1 2 PMSH,L N 008 010 020 002 004 008 002 004 006 001 002 004 PMRS L D0 D0 D0 D0 D0 D0 80 80 C0 D0 D0 D0 PMDS R 8 8 8 1 1 1 1 1 1 1 1 1
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 61
Clock Generator Module (CGM)
4.3.7 Special Programming Exceptions
The programming method described in 4.3.6 Programming the PLL does not account for three possible exceptions. A value of 0 for R, N, or L is meaningless when used in the equations given. To account for these exceptions: * A 0 value for R or N is interpreted exactly the same as a value of 1. * A 0 value for L disables the PLL and prevents its selection as the source for the base clock. (See 4.3.8 Base Clock Selector Circuit.)
4.3.8 Base Clock Selector Circuit
This circuit is used to select either the crystal clock, CGMXCLK, or the VCO clock, CGMVCLK, as the source of the base clock, CGMOUT. The two input clocks go through a transition control circuit that waits up to three CGMXCLK cycles and three CGMVCLK cycles to change from one clock source to the other. During this time, CGMOUT is held in stasis. The output of the transition control circuit is then divided by two to correct the duty cycle. Therefore, the bus clock frequency, which is one-half of the base clock frequency, is one-fourth the frequency of the selected clock (CGMXCLK or CGMVCLK). The BCS bit in the PLL control register (PCTL) selects which clock drives CGMOUT. The VCO clock cannot be selected as the base clock source if the PLL is not turned on. The PLL cannot be turned off if the VCO clock is selected. The PLL cannot be turned on or off simultaneously with the selection or deselection of the VCO clock. The VCO clock also cannot be selected as the base clock source if the factor L is programmed to a 0. This value would set up a condition inconsistent with the operation of the PLL, so that the PLL would be disabled and the crystal clock would be forced as the source of the base clock.
4.3.9 CGM External Connections
In its typical configuration, the CGM requires up to nine external components. Five of these are for the crystal oscillator and two or four are for the PLL. The crystal oscillator is normally connected in a Pierce oscillator configuration, as shown in Figure 4-2. Figure 4-2 shows only the logical representation of the internal components and may not represent actual circuitry. The oscillator configuration uses five components: * Crystal, X1 * Fixed capacitor, C1 * Tuning capacitor, C2 (can also be a fixed capacitor) * Feedback resistor, RB * Series resistor, RS The series resistor (RS) is included in the diagram to follow strict Pierce oscillator guidelines. Refer to the crystal manufacturer's data for more information regarding values for C1 and C2. Figure 4-2 also shows the external components for the PLL: * Bypass capacitor, CBYP * Filter network Routing should be done with great care to minimize signal cross talk and noise. See 19.15 Clock Generation Module Characteristics for capacitor and resistor values.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 62 Freescale Semiconductor
I/O Signals
SIMOSCEN OSCSTOPENB (FROM CONFIG)
CGMXCLK
OSC1
OSC2
CGMXFC
VSSA
VDDA
VDD
RB RF1 RS CF1 X1 C1 C2 CF2 CBYP 0.1 F
Note: Filter network in box can be replaced with CF but will degrade stability.
Figure 4-2. CGM External Connections
4.4 I/O Signals
The following paragraphs describe the CGM I/O signals.
4.4.1 Crystal Amplifier Input Pin (OSC1)
The OSC1 pin is an input to the crystal oscillator amplifier.
4.4.2 Crystal Amplifier Output Pin (OSC2)
The OSC2 pin is the output of the crystal oscillator inverting amplifier.
4.4.3 External Filter Capacitor Pin (CGMXFC)
The CGMXFC pin is required by the loop filter to filter out phase corrections. An external filter network is connected to this pin. (See Figure 4-2.) NOTE To prevent noise problems, the filter network should be placed as close to the CGMXFC pin as possible, with minimum routing distances and no routing of other signals across the network.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 63
Clock Generator Module (CGM)
4.4.4 PLL Analog Power Pin (VDDA)
VDDA is a power pin used by the analog portions of the PLL. Connect the VDDA pin to the same voltage potential as the VDD pin. NOTE Route VDDA carefully for maximum noise immunity and place bypass capacitors as close as possible to the package.
4.4.5 PLL Analog Ground Pin (VSSA)
VSSA is a ground pin used by the analog portions of the PLL. Connect the VSSA pin to the same voltage potential as the VSS pin. NOTE Route VSSA carefully for maximum noise immunity and place bypass capacitors as close as possible to the package.
4.4.6 Oscillator Enable Signal (SIMOSCEN)
The SIMOSCEN signal comes from the system integration module (SIM) and enables the oscillator and PLL.
4.4.7 Oscillator Stop Mode Enable Bit (OSCSTOPENB)
OSCSTOPENB is a bit in the CONFIG register that enables the oscillator to continue operating during stop mode. If this bit is set, the Oscillator continues running during stop mode. If this bit is not set (default), the oscillator is controlled by the SIMOSCEN signal which will disable the oscillator during stop mode.
4.4.8 Crystal Output Frequency Signal (CGMXCLK)
CGMXCLK is the crystal oscillator output signal. It runs at the full speed of the crystal (fXCLK) and comes directly from the crystal oscillator circuit. Figure 4-2 shows only the logical relation of CGMXCLK to OSC1 and OSC2 and may not represent the actual circuitry. The duty cycle of CGMXCLK is unknown and may depend on the crystal and other external factors. Also, the frequency and amplitude of CGMXCLK can be unstable at startup.
4.4.9 CGM Base Clock Output (CGMOUT)
CGMOUT is the clock output of the CGM. This signal goes to the SIM, which generates the MCU clocks. CGMOUT is a 50 percent duty cycle clock running at twice the bus frequency. CGMOUT is software programmable to be either the oscillator output, CGMXCLK, divided by two or the VCO clock, CGMVCLK, divided by two.
4.4.10 CGM CPU Interrupt (CGMINT)
CGMINT is the interrupt signal generated by the PLL lock detector.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 64 Freescale Semiconductor
CGM Registers
4.5 CGM Registers
These registers control and monitor operation of the CGM: * PLL control register (PCTL) (See 4.5.1 PLL Control Register.) * PLL bandwidth control register (PBWC) (See 4.5.2 PLL Bandwidth Control Register.) * PLL multiplier select register high (PMSH) (See 4.5.3 PLL Multiplier Select Register High.) * PLL multiplier select register low (PMSL) (See 4.5.4 PLL Multiplier Select Register Low.) * PLL VCO range select register (PMRS) (See 4.5.5 PLL VCO Range Select Register.) * PLL reference divider select register (PMDS) (See 4.5.6 PLL Reference Divider Select Register.) Figure 4-3 is a summary of the CGM registers.
Addr. $0036
Register Name PLL Control Register (PCTL) PLL Bandwidth Control Register (PBWC) PLL Multiplier Select High Register (PMSH) PLL Multiplier Select Low Register (PMSL) PLL VCO Select Range Register (PMRS) PLL Reference Divider Select Register (PMDS) Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset: Read: Write: Reset:
Bit 7 PLLIE 0 AUTO 0 0 0 MUL7 0 VRS7 0 0 0
6 PLLF 0 LOCK 0 0 0 MUL6 1 VRS6 1 0
5 PLLON 1 ACQ 0 0 0 MUL5 0 VRS5 0 0
4 BCS 0 0 0 0 0 MUL4 0 VRS4 0 0 0 R
3 PRE1 0 0 0 MUL11 0 MUL3 0 VRS3 0 RDS3 0 = Reserved
2 PRE0 0 0 0 MUL10 0 MUL2 0 VRS2 0 RDS2 0
1 VPR1 0 0 0 MUL9 0 MUL1 0 VRS1 0 RDS1 0
Bit 0 VPR0 0 R 0 MUL8 0 MUL0 0 VRS0 0 RDS0 1
$0037
$0038
$0039
$003A
$003B
0 0 = Unimplemented
NOTES: 1. When AUTO = 0, PLLIE is forced clear and is read-only. 2. When AUTO = 0, PLLF and LOCK read as clear. 3. When AUTO = 1, ACQ is read-only. 4. When PLLON = 0 or VRS7:VRS0 = $0, BCS is forced clear and is read-only. 5. When PLLON = 1, the PLL programming register is read-only. 6. When BCS = 1, PLLON is forced set and is read-only.
Figure 4-3. CGM I/O Register Summary
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 65
Clock Generator Module (CGM)
4.5.1 PLL Control Register
The PLL control register (PCTL) contains the interrupt enable and flag bits, the on/off switch, the base clock selector bit, the prescaler bits, and the VCO power-of-two range selector bits.
Address: $0036 Bit 7 Read: Write: Reset: PLLIE 0 6 PLLF 0 = Unimplemented 5 PLLON 1 4 BCS 0 3 PRE1 0 2 PRE0 0 1 VPR1 0 Bit 0 VPR0 0
Figure 4-4. PLL Control Register (PCTL)
PLLIE -- PLL Interrupt Enable Bit This read/write bit enables the PLL to generate an interrupt request when the LOCK bit toggles, setting the PLL flag, PLLF. When the AUTO bit in the PLL bandwidth control register (PBWC) is clear, PLLIE cannot be written and reads as logic 0. Reset clears the PLLIE bit. 1 = PLL interrupts enabled 0 = PLL interrupts disabled PLLF -- PLL Interrupt Flag Bit This read-only bit is set whenever the LOCK bit toggles. PLLF generates an interrupt request if the PLLIE bit also is set. PLLF always reads as logic 0 when the AUTO bit in the PLL bandwidth control register (PBWC) is clear. Clear the PLLF bit by reading the PLL control register. Reset clears the PLLF bit. 1 = Change in lock condition 0 = No change in lock condition NOTE Do not inadvertently clear the PLLF bit. Any read or read-modify-write operation on the PLL control register clears the PLLF bit. PLLON -- PLL On Bit This read/write bit activates the PLL and enables the VCO clock, CGMVCLK. PLLON cannot be cleared if the VCO clock is driving the base clock, CGMOUT (BCS = 1). (See 4.3.8 Base Clock Selector Circuit.) Reset sets this bit so that the loop can stabilize as the MCU is powering up. 1 = PLL on 0 = PLL off BCS -- Base Clock Select Bit This read/write bit selects either the crystal oscillator output, CGMXCLK, or the VCO clock, CGMVCLK, as the source of the CGM output, CGMOUT. CGMOUT frequency is one-half the frequency of the selected clock. BCS cannot be set while the PLLON bit is clear. After toggling BCS, it may take up to three CGMXCLK and three CGMVCLK cycles to complete the transition from one source clock to the other. During the transition, CGMOUT is held in stasis. (See 4.3.8 Base Clock Selector Circuit.) Reset clears the BCS bit. 1 = CGMVCLK divided by two drives CGMOUT 0 = CGMXCLK divided by two drives CGMOUT NOTE PLLON and BCS have built-in protection that prevents the base clock selector circuit from selecting the VCO clock as the source of the base clock
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 66 Freescale Semiconductor
CGM Registers
if the PLL is off. Therefore, PLLON cannot be cleared when BCS is set, and BCS cannot be set when PLLON is clear. If the PLL is off (PLLON = 0), selecting CGMVCLK requires two writes to the PLL control register. (See 4.3.8 Base Clock Selector Circuit.) PRE1 and PRE0 -- Prescaler Program Bits These read/write bits control a prescaler that selects the prescaler power-of-two multiplier, P. (See PLL Circuits and Programming the PLL.) PRE1 and PRE0 cannot be written when the PLLON bit is set. Reset clears these bits.
Table 4-2. PRE 1 and PRE0 Programming
PRE1 and PRE0 00 01 10 11 P 0 1 2 3 Prescaler Multiplier 1 2 4 8
VPR1 and 0 -- VCO Power-of-Two Range Select Bits These read/write bits control the VCO's hardware power-of-two range multiplier E that, in conjunction with L (See 4.3.3 PLL Circuits, 4.3.6 Programming the PLL, and 4.5.5 PLL VCO Range Select Register.) controls the hardware center-of-range frequency, fVRS. VPR1:VPR0 cannot be written when the PLLON bit is set. Reset clears these bits.
Table 4-3. VPR1 and VPR0 Programming
VPR1 and VPR0 00 01 10 11
1. Do not program E to a value of 3.
E 0 1 2 3(1)
VCO Power-of-Two Range Multiplier 1 2 4 8
4.5.2 PLL Bandwidth Control Register
The PLL bandwidth control register (PBWC): * Selects automatic or manual (software-controlled) bandwidth control mode * Indicates when the PLL is locked * In automatic bandwidth control mode, indicates when the PLL is in acquisition or tracking mode * In manual operation, forces the PLL into acquisition or tracking mode
Address: $0037 Bit 7 Read: Write: Reset: AUTO 0 6 LOCK 0 = Unimplemented 5 ACQ 0 4 0 0 R 3 0 0 = Reserved 2 0 0 1 0 0 Bit 0 R 0
Figure 4-5. PLL Bandwidth Control Register (PBWC)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 67
Clock Generator Module (CGM)
AUTO -- Automatic Bandwidth Control Bit This read/write bit selects automatic or manual bandwidth control. When initializing the PLL for manual operation (AUTO = 0), clear the ACQ bit before turning on the PLL. Reset clears the AUTO bit. 1 = Automatic bandwidth control 0 = Manual bandwidth control LOCK -- Lock Indicator Bit When the AUTO bit is set, LOCK is a read-only bit that becomes set when the VCO clock, CGMVCLK, is locked (running at the programmed frequency). When the AUTO bit is clear, LOCK reads as logic 0 and has no meaning. The write one function of this bit is reserved for test, so this bit must always be written a 0. Reset clears the LOCK bit. 1 = VCO frequency correct or locked 0 = VCO frequency incorrect or unlocked ACQ -- Acquisition Mode Bit When the AUTO bit is set, ACQ is a read-only bit that indicates whether the PLL is in acquisition mode or tracking mode. When the AUTO bit is clear, ACQ is a read/write bit that controls whether the PLL is in acquisition or tracking mode. In automatic bandwidth control mode (AUTO = 1), the last-written value from manual operation is stored in a temporary location and is recovered when manual operation resumes. Reset clears this bit, enabling acquisition mode. 1 = Tracking mode 0 = Acquisition mode
4.5.3 PLL Multiplier Select Register High
The PLL multiplier select register high (PMSH) contains the programming information for the high byte of the modulo feedback divider.
Address: $0038 Bit 7 Read: Write: Reset: 0 0 = Unimplemented 0 0 0 6 0 5 0 4 0 3 MUL11 0 2 MUL10 0 1 MUL9 0 Bit 0 MUL8 0
Figure 4-6. PLL Multiplier Select Register High (PMSH)
MUL11-MUL8 -- Multiplier Select Bits These read/write bits control the high byte of the modulo feedback divider that selects the VCO frequency multiplier N. (See 4.3.3 PLL Circuits and 4.3.6 Programming the PLL.) A value of $0000 in the multiplier select registers configures the modulo feedback divider the same as a value of $0001. Reset initializes the registers to $0040 for a default multiply value of 64. NOTE The multiplier select bits have built-in protection such that they cannot be written when the PLL is on (PLLON = 1). PMSH[7:4] -- Unimplemented Bits These bits have no function and always read as 0s.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 68 Freescale Semiconductor
CGM Registers
4.5.4 PLL Multiplier Select Register Low
The PLL multiplier select register low (PMSL) contains the programming information for the low byte of the modulo feedback divider.
Address: $0038 Bit 7 Read: Write: Reset: MUL7 0 6 MUL6 1 5 MUL5 0 4 MUL4 0 3 MUL3 0 2 MUL2 0 1 MUL1 0 Bit 0 MUL0 0
Figure 4-7. PLL Multiplier Select Register Low (PMSL)
NOTE For applications using 1-8 MHz reference frequencies, this register must be reprogrammed before enabling the PLL. The reset value of this register will cause applications using 1-8 MHz reference frequencies to become unstable if the PLL is enabled without programming an appropriate value. The programmed value must not allow the VCO clock to exceed 32 MHz. See 4.3.6 Programming the PLL for detailed instructions on choosing the proper value for PMSL. MUL7-MUL0 -- Multiplier Select Bits These read/write bits control the low byte of the modulo feedback divider that selects the VCO frequency multiplier, N. (See 4.3.3 PLL Circuits and 4.3.6 Programming the PLL.) MUL7-MUL0 cannot be written when the PLLON bit in the PCTL is set. A value of $0000 in the multiplier select registers configures the modulo feedback divider the same as a value of $0001. Reset initializes the register to $40 for a default multiply value of 64. NOTE The multiplier select bits have built-in protection such that they cannot be written when the PLL is on (PLLON = 1).
4.5.5 PLL VCO Range Select Register
The PLL VCO range select register (PMRS) contains the programming information required for the hardware configuration of the VCO.
Address: $003A Bit 7 Read: Write: Reset: VRS7 0 6 VRS6 1 5 VRS5 0 4 VRS4 0 3 VRS3 0 2 VRS2 0 1 VRS1 0 Bit 0 VRS0 0
Figure 4-8. PLL VCO Range Select Register (PMRS)
VRS7-VRS0 -- VCO Range Select Bits These read/write bits control the hardware center-of-range linear multiplier L which, in conjunction with E (see 4.3.3 PLL Circuits, 4.3.6 Programming the PLL, and 4.5.1 PLL Control Register), controls the hardware center-of-range frequency, fVRS. VRS7-VRS0 cannot be written when the PLLON bit in the PCTL is set. (See 4.3.7 Special Programming Exceptions.) A value of $00 in the VCO range select
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 69
Clock Generator Module (CGM)
register disables the PLL and clears the BCS bit in the PLL control register (PCTL). (See 4.3.8 Base Clock Selector Circuit and 4.3.7 Special Programming Exceptions.). Reset initializes the register to $40 for a default range multiply value of 64. NOTE The VCO range select bits have built-in protection such that they cannot be written when the PLL is on (PLLON = 1) and such that the VCO clock cannot be selected as the source of the base clock (BCS = 1) if the VCO range select bits are all clear. The PLL VCO range select register must be programmed correctly. Incorrect programming can result in failure of the PLL to achieve lock.
4.5.6 PLL Reference Divider Select Register
The PLL reference divider select register (PMDS) contains the programming information for the modulo reference divider.
Address: $003B Bit 7 Read: Write: Reset: 0 0 = Unimplemented 0 0 0 6 0 5 0 4 0 3 RDS3 0 2 RDS2 0 1 RDS1 0 Bit 0 RDS0 1
Figure 4-9. PLL Reference Divider Select Register (PMDS)
RDS3-RDS0 -- Reference Divider Select Bits These read/write bits control the modulo reference divider that selects the reference division factor, R. (See 4.3.3 PLL Circuits and 4.3.6 Programming the PLL.) RDS7-RDS0 cannot be written when the PLLON bit in the PCTL is set. A value of $00 in the reference divider select register configures the reference divider the same as a value of $01. (See 4.3.7 Special Programming Exceptions.) Reset initializes the register to $01 for a default divide value of 1. NOTE The reference divider select bits have built-in protection such that they cannot be written when the PLL is on (PLLON = 1). The default divide value of 1 is recommended for all applications.
4.6 Interrupts
When the AUTO bit is set in the PLL bandwidth control register (PBWC), the PLL can generate a CPU interrupt request every time the LOCK bit changes state. The PLLIE bit in the PLL control register (PCTL) enables CPU interrupts from the PLL. PLLF, the interrupt flag in the PCTL, becomes set whether interrupts are enabled or not. When the AUTO bit is clear, CPU interrupts from the PLL are disabled and PLLF reads as logic 0. Software should read the LOCK bit after a PLL interrupt request to see if the request was due to an entry into lock or an exit from lock. When the PLL enters lock, the VCO clock, CGMVCLK, divided by two can be selected as the CGMOUT source by setting BCS in the PCTL. When the PLL exits lock, the VCO clock frequency is corrupt, and appropriate precautions should be taken. If the application is not frequency
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 70 Freescale Semiconductor
Special Modes
sensitive, interrupts should be disabled to prevent PLL interrupt service routines from impeding software performance or from exceeding stack limitations. NOTE Software can select the CGMVCLK divided by two as the CGMOUT source even if the PLL is not locked (LOCK = 0). Therefore, software should make sure the PLL is locked before setting the BCS bit.
4.7 Special Modes
The WAIT instruction puts the MCU in low power-consumption standby modes.
4.7.1 Wait Mode
The WAIT instruction does not affect the CGM. Before entering wait mode, software can disengage and turn off the PLL by clearing the BCS and PLLON bits in the PLL control register (PCTL) to save power. Less power-sensitive applications can disengage the PLL without turning it off, so that the PLL clock is immediately available at WAIT exit. This would be the case also when the PLL is to wake the MCU from wait mode, such as when the PLL is first enabled and waiting for LOCK or LOCK is lost.
4.7.2 Stop Mode
If the OSCSTOPENB bit in the CONFIG register is cleared (default), then the STOP instruction disables the CGM (oscillator and phase locked loop) and holds low all CGM outputs (CGMXCLK, CGMOUT, and CGMINT). If the STOP instruction is executed with the VCO clock, CGMVCLK, divided by two driving CGMOUT, the PLL automatically clears the BCS bit in the PLL control register (PCTL), thereby selecting the crystal clock, CGMXCLK, divided by two as the source of CGMOUT. When the MCU recovers from STOP, the crystal clock divided by two drives CGMOUT and BCS remains clear. If the OSCSTOPENB bit in the CONFIG register is set, then the phase locked loop is shut off but the oscillator will continue to operate in stop mode.
4.7.3 CGM During Break Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. (See 14.7.1 SIM Break Status Register.) To allow software to clear status bits during a break interrupt, write a logic 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect the PLLF bit during the break state, write a logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), software can read and write the PLL control register during the break state without affecting the PLLF bit.
4.8 Acquisition/Lock Time Specifications
The acquisition and lock times of the PLL are, in many applications, the most critical PLL design parameters. Proper design and use of the PLL ensures the highest stability and lowest acquisition/lock times.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 71
Clock Generator Module (CGM)
4.8.1 Acquisition/Lock Time Definitions
Typical control systems refer to the acquisition time or lock time as the reaction time, within specified tolerances, of the system to a step input. In a PLL, the step input occurs when the PLL is turned on or when it suffers a noise hit. The tolerance is usually specified as a percentage of the step input or when the output settles to the desired value plus or minus a percentage of the frequency change. Therefore, the reaction time is constant in this definition, regardless of the size of the step input. For example, consider a system with a 5 percent acquisition time tolerance. If a command instructs the system to change from 0 Hz to 1 MHz, the acquisition time is the time taken for the frequency to reach 1 MHz 50 kHz. Fifty kHz = 5% of the 1-MHz step input. If the system is operating at 1 MHz and suffers a -100-kHz noise hit, the acquisition time is the time taken to return from 900 kHz to 1 MHz 5 kHz. Five kHz = 5% of the 100-kHz step input. Other systems refer to acquisition and lock times as the time the system takes to reduce the error between the actual output and the desired output to within specified tolerances. Therefore, the acquisition or lock time varies according to the original error in the output. Minor errors may not even be registered. Typical PLL applications prefer to use this definition because the system requires the output frequency to be within a certain tolerance of the desired frequency regardless of the size of the initial error.
4.8.2 Parametric Influences on Reaction Time
Acquisition and lock times are designed to be as short as possible while still providing the highest possible stability. These reaction times are not constant, however. Many factors directly and indirectly affect the acquisition time. The most critical parameter which affects the reaction times of the PLL is the reference frequency, fRDV. This frequency is the input to the phase detector and controls how often the PLL makes corrections. For stability, the corrections must be small compared to the desired frequency, so several corrections are required to reduce the frequency error. Therefore, the slower the reference the longer it takes to make these corrections. This parameter is under user control via the choice of crystal frequency fXCLK and the R value programmed in the reference divider. (See 4.3.3 PLL Circuits, 4.3.6 Programming the PLL, and 4.5.6 PLL Reference Divider Select Register.) Another critical parameter is the external filter network. The PLL modifies the voltage on the VCO by adding or subtracting charge from capacitors in this network. Therefore, the rate at which the voltage changes for a given frequency error (thus change in charge) is proportional to the capacitance. The size of the capacitor also is related to the stability of the PLL. If the capacitor is too small, the PLL cannot make small enough adjustments to the voltage and the system cannot lock. If the capacitor is too large, the PLL may not be able to adjust the voltage in a reasonable time. (See 4.8.3 Choosing a Filter.) Also important is the operating voltage potential applied to VDDA. The power supply potential alters the characteristics of the PLL. A fixed value is best. Variable supplies, such as batteries, are acceptable if they vary within a known range at very slow speeds. Noise on the power supply is not acceptable, because it causes small frequency errors which continually change the acquisition time of the PLL. Temperature and processing also can affect acquisition time because the electrical characteristics of the PLL change. The part operates as specified as long as these influences stay within the specified limits. External factors, however, can cause drastic changes in the operation of the PLL. These factors include noise injected into the PLL through the filter capacitor, filter capacitor leakage, stray impedances on the circuit board, and even humidity or circuit board contamination.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 72 Freescale Semiconductor
Acquisition/Lock Time Specifications
4.8.3 Choosing a Filter
As described in 4.8.2 Parametric Influences on Reaction Time, the external filter network is critical to the stability and reaction time of the PLL. The PLL is also dependent on reference frequency and supply voltage. Figure 4-10 shows two types of filter circuits. In low-cost applications, where stability and reaction time of the PLL are not critical, the three component filter network shown in Figure 4-10(B) can be replaced by a single capacitor, CF, as shown in Figure 4-10(A). Refer to Table 4-4 for recommended filter components at various reference frequencies. For reference frequencies between the values listed in the table, extrapolate to the nearest common capacitor value. In general, a slightly larger capacitor provides more stability at the expense of increased lock time.
(A)
CGMXFC
(B)
CGMXFC
CF
RF1 CF1
CF2
VSSA
VSSA
Figure 4-10. PLL Filter Table 4-4. Example Filter Component Values
fRCLK 1 MHz 2 MHz 3 MHz 4 MHz 5 MHz 6 MHz 7 MHz 8 MHz CF1 8.2 nF 4.7 nF 3.3 nF 2.2 nF 1.8 nF 1.5 nF 1.2 nF 1 nF CF2 820 pF 470 pF 330 pF 220 pF 180 pF 150 pF 120 pF 100 pF RF1 2k 2k 2k 2k 2k 2k 2k 2k CF 18 nF 6.8 nF 5.6 nF 4.7 nF 3.9 nF 3.3 nF 2.7 nF 2.2 nF
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 73
Clock Generator Module (CGM)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 74 Freescale Semiconductor
Chapter 5 Configuration Register (CONFIG)
5.1 Introduction
This section describes the configuration registers, CONFIG1 and CONFIG2. The configuration registers enable or disable these options: * Stop mode recovery time (32 CGMXCLK cycles or 4096 CGMXCLK cycles) * COP timeout period (262,128 or 8176 CGMXCLK cycles) * STOP instruction * Computer operating properly module (COP) * Low-voltage inhibit (LVI) module control and voltage trip point selection * Enable/disable the oscillator (OSC) during stop mode
5.2 Functional Description
The configuration registers are used in the initialization of various options. The configuration registers can be written once after each reset. All of the configuration register bits are cleared during reset. Since the various options affect the operation of the microcontroller unit (MCU), it is recommended that these registers be written immediately after reset. The configuration registers are located at $001E and $001F and may be read at anytime. NOTE On a FLASH device, the options except LVI5OR3 are one-time writable by the user after each reset. The LVI5OR3 bit is one-time writable by the user only after each POR (power-on reset). The CONFIG registers are not in the FLASH memory but are special registers containing one-time writable latches after each reset. Upon a reset, the CONFIG registers default to predetermined settings as shown in Figure 5-1 and Figure 5-2.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 R 0 = Reserved 0 $001E Bit 7 0 6 0 5 0 4 0 3 0 2 0 1 OSCSTOPENB 0 Bit 0 SCIBDSRC 0
Figure 5-1. Configuration Register 2 (CONFIG2)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 75
Configuration Register (CONFIG) Address: Read: Write: Reset: $001F Bit 7 COPRS 0 6 LVISTOP 0 5 LVIRSTD 0 4 LVIPWRD 0 3 LVI5OR3 See note 2 SSREC 0 1 STOP 0 Bit 0 COPD 0
Note: LVI5OR3 bit is only reset via POR (power-on reset).
Figure 5-2. Configuration Register 1 (CONFIG1) OSCSTOPENB -- Oscillator Stop Mode Enable Bar Bit OSCSTOPENB, when set, will enable the oscillator to continue to generate clocks in stop mode. See Chapter 4 Clock Generator Module (CGM). This function is used to keep the timebase running while the rest of the MCU stops. See Chapter 16 Timebase Module (TBM). When clear, the oscillator will cease to generate clocks while in stop mode. The default state for this option is clear, disabling the oscillator in stop mode. 1 = Oscillator enabled to operate during stop mode 0 = Oscillator disabled during stop mode (default) SCIBDSRC -- SCI Baud Rate Clock Source Bit SCIBDSRC controls the clock source used for the serial communications interface (SCI). The setting of this bit affects the frequency at which the SCI operates.See Chapter 13 Serial Communications Interface (SCI) Module. 1 = Internal bus clock used as clock source for SCI 0 = External oscillator used as clock source for SCI COPRS -- COP Rate Select Bit COPRS selects the COP timeout period. Reset clears COPRS. See Chapter 6 Computer Operating Properly (COP) Module 1 = COP timeout period = 8176 CGMXCLK cycles 0 = COP timeout period = 262,128 CGMXCLK cycles LVISTOP -- LVI Enable in Stop Mode Bit When the LVIPWRD bit is clear, setting the LVISTOP bit enables the LVI to operate during stop mode. Reset clears LVISTOP. 1 = LVI enabled during stop mode 0 = LVI disabled during stop mode LVIRSTD -- LVI Reset Disable Bit LVIRSTD disables the reset signal from the LVI module. See Chapter 11 Low-Voltage Inhibit (LVI). 1 = LVI module resets disabled 0 = LVI module resets enabled LVIPWRD -- LVI Power Disable Bit LVIPWRD disables the LVI module. See Chapter 11 Low-Voltage Inhibit (LVI). 1 = LVI module power disabled 0 = LVI module power enabled
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 76 Freescale Semiconductor
Functional Description
LVI5OR3 -- LVI 5-V or 3-V Operating Mode Bit LVI5OR3 selects the voltage operating mode of the LVI module (see Chapter 11 Low-Voltage Inhibit (LVI)). The voltage mode selected for the LVI should match the operating VDD (see Chapter 19 Electrical Specifications) for the LVI's voltage trip points for each of the modes. 1 = LVI operates in 5-V mode 0 = LVI operates in 3-V mode NOTE The LVI5OR3 bit is cleared by a power-on reset (POR) only. Other resets will leave this bit unaffected. SSREC -- Short Stop Recovery Bit SSREC enables the CPU to exit stop mode with a delay of 32 CGMXCLK cycles instead of a 4096-CGMXCLK cycle delay. 1 = Stop mode recovery after 32 CGMXCLK cycles 0 = Stop mode recovery after 4096 CGMXCLCK cycles NOTE Exiting stop mode by an LVI reset will result in the long stop recovery. If the system clock source is an external crystal and the OSCSTOPENB configuration bit is not set, the oscillator will be disabled during stop mode. The short stop recovery does not provide enough time for oscillator stabilization and for this reason the SSREC bit should not be set. The system stabilization time for power-on reset and long stop recovery (both 4096 CGMXCLK cycles) gives a delay longer than the LVI enable time for these startup scenarios. There is no period where the MCU is not protected from a low-power condition. However, when using the short stop recovery configuration option, the 32-CGMXCLK delay must be greater than the LVI's turn on time to avoid a period in startup where the LVI is not protecting the MCU. STOP -- STOP Instruction Enable Bit STOP enables the STOP instruction. 1 = STOP instruction enabled 0 = STOP instruction treated as illegal opcode COPD -- COP Disable Bit COPD disables the COP module. See Chapter 6 Computer Operating Properly (COP) Module. 1 = COP module disabled 0 = COP module enabled
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 77
Configuration Register (CONFIG)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 78 Freescale Semiconductor
Chapter 6 Computer Operating Properly (COP) Module
6.1 Introduction
The computer operating properly (COP) module contains a free-running counter that generates a reset if allowed to overflow. The COP module helps software recover from runaway code. Prevent a COP reset by clearing the COP counter periodically. The COP module can be disabled through the COPD bit in the CONFIG register.
6.2 Functional Description
Figure 6-1 shows the structure of the COP module.
SIM MODULE CGMXCLK 12-BIT SIM COUNTER SIM RESET CIRCUIT RESET STATUS REGISTER
CLEAR ALL STAGES
CLEAR STAGES 5-12
INTERNAL RESET SOURCES(1) STOP INSTRUCTION COPCTL WRITE
COP CLOCK COP MODULE COPEN (FROM SIM) COPD (FROM CONFIG1) RESET COPCTL WRITE COP RATE SELECT (COPRS FROM CONFIG1)
6-BIT COP COUNTER CLEAR COP COUNTER
1. See Chapter 14 System Integration Module (SIM) for more details.
Figure 6-1. COP Block Diagram
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 79
COP TIMEOUT
Computer Operating Properly (COP) Module
The COP counter is a free-running 6-bit counter preceded by a 12-bit prescaler counter. If not cleared by software, the COP counter overflows and generates an asynchronous reset after 262,128 or 8176 CGMXCLK cycles, depending on the state of the COP rate select bit, COPRS, in the configuration register. With a 262,128 CGMXCLK cycle overflow option, a 4.9152-MHz crystal gives a COP timeout period of 53.3 ms. Writing any value to location $FFFF before an overflow occurs prevents a COP reset by clearing the COP counter and stages 12-5 of the prescaler. NOTE Service the COP immediately after reset and before entering or after exiting stop mode to guarantee the maximum time before the first COP counter overflow. A COP reset pulls the RST pin low for 32 CGMXCLK cycles and sets the COP bit in the reset status register (RSR). In monitor mode, the COP is disabled if the RST pin or the IRQ is held at VTST. During the break state, VTST on the RST pin disables the COP. NOTE Place COP clearing instructions in the main program and not in an interrupt subroutine. Such an interrupt subroutine could keep the COP from generating a reset even while the main program is not working properly.
6.3 I/O Signals
The following paragraphs describe the signals shown in Figure 6-1.
6.3.1 CGMXCLK
CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency is equal to the crystal frequency.
6.3.2 STOP Instruction
The STOP instruction clears the COP prescaler.
6.3.3 COPCTL Write
Writing any value to the COP control register (COPCTL) clears the COP counter and clears bits 12-5 of the prescaler. Reading the COP control register returns the low byte of the reset vector. See 6.4 COP Control Register.
6.3.4 Power-On Reset
The power-on reset (POR) circuit clears the COP prescaler 4096 CGMXCLK cycles after power-up.
6.3.5 Internal Reset
An internal reset clears the COP prescaler and the COP counter.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 80 Freescale Semiconductor
COP Control Register
6.3.6 COPD (COP Disable)
The COPD signal reflects the state of the COP disable bit (COPD) in the configuration register. See Chapter 5 Configuration Register (CONFIG).
6.3.7 COPRS (COP Rate Select)
The COPRS signal reflects the state of the COP rate select bit (COPRS) in the configuration register. See Chapter 5 Configuration Register (CONFIG).
6.4 COP Control Register
The COP control register (COPCTL) is located at address $FFFF and overlaps the reset vector. Writing any value to $FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF returns the low byte of the reset vector.
Address: $FFFF Bit 7 Read: Write: Reset: 6 5 4 3 2 1 Bit 0 Low byte of reset vector Clear COP counter Unaffected by reset
Figure 6-2. COP Control Register (COPCTL)
6.5 Interrupts
The COP does not generate central processor unit (CPU) interrupt requests.
6.6 Monitor Mode
When monitor mode is entered with VTST on the IRQ pin, the COP is disabled as long as VTST remains on the IRQ pin or the RST pin. When monitor mode is entered by having blank reset vectors and not having VTST on the IRQ pin, the COP is automatically disabled until a POR occurs.
6.7 Low-Power Modes
The WAIT and STOP instructions put the microcontroller unit (MCU) in low power-consumption standby modes.
6.7.1 Wait Mode
The COP remains active during wait mode. If COP is enabled, a reset will occur at COP timeout.
6.7.2 Stop Mode
Stop mode turns off the CGMXCLK input to the COP and clears the COP prescaler. Service the COP immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering or exiting stop mode.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 81
Computer Operating Properly (COP) Module
To prevent inadvertently turning off the COP with a STOP instruction, a configuration option is available that disables the STOP instruction. When the STOP bit in the configuration register has the STOP instruction disabled, execution of a STOP instruction results in an illegal opcode reset.
6.8 COP Module During Break Mode
The COP is disabled during a break interrupt when VTST is present on the RST pin.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 82 Freescale Semiconductor
Chapter 7 Central Processor Unit (CPU)
7.1 Introduction
The M68HC08 CPU (central processor unit) is an enhanced and fully object-code-compatible version of the M68HC05 CPU. The CPU08 Reference Manual (document order number CPU08RM/AD) contains a description of the CPU instruction set, addressing modes, and architecture.
7.2 Features
Features of the CPU include: * Object code fully upward-compatible with M68HC05 Family * 16-bit stack pointer with stack manipulation instructions * 16-bit index register with x-register manipulation instructions * 8-MHz CPU internal bus frequency * 64-Kbyte program/data memory space * 16 addressing modes * Memory-to-memory data moves without using accumulator * Fast 8-bit by 8-bit multiply and 16-bit by 8-bit divide instructions * Enhanced binary-coded decimal (BCD) data handling * Modular architecture with expandable internal bus definition for extension of addressing range beyond 64 Kbytes * Low-power stop and wait modes
7.3 CPU Registers
Figure 7-1 shows the five CPU registers. CPU registers are not part of the memory map.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 83
Central Processor Unit (CPU)
7 15 H 15 15 X 0 STACK POINTER (SP) 0 PROGRAM COUNTER (PC) 7 0 V11HINZC CONDITION CODE REGISTER (CCR) 0 ACCUMULATOR (A) 0 INDEX REGISTER (H:X)
CARRY/BORROW FLAG ZERO FLAG NEGATIVE FLAG INTERRUPT MASK HALF-CARRY FLAG TWO'S COMPLEMENT OVERFLOW FLAG
Figure 7-1. CPU Registers
7.3.1 Accumulator
The accumulator is a general-purpose 8-bit register. The CPU uses the accumulator to hold operands and the results of arithmetic/logic operations.
Bit 7 Read: Write: Reset: Unaffected by reset 6 5 4 3 2 1 Bit 0
Figure 7-2. Accumulator (A)
7.3.2 Index Register
The 16-bit index register allows indexed addressing of a 64-Kbyte memory space. H is the upper byte of the index register, and X is the lower byte. H:X is the concatenated 16-bit index register. In the indexed addressing modes, the CPU uses the contents of the index register to determine the conditional address of the operand. The index register can serve also as a temporary data storage location.
Bit 15 Read: Write: Reset: 0 0 0 0 0 0 0 0 X X X X X X X X X = Indeterminate 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0
Figure 7-3. Index Register (H:X)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 84 Freescale Semiconductor
CPU Registers
7.3.3 Stack Pointer
The stack pointer is a 16-bit register that contains the address of the next location on the stack. During a reset, the stack pointer is preset to $00FF. The reset stack pointer (RSP) instruction sets the least significant byte to $FF and does not affect the most significant byte. The stack pointer decrements as data is pushed onto the stack and increments as data is pulled from the stack. In the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an index register to access data on the stack. The CPU uses the contents of the stack pointer to determine the conditional address of the operand.
Bit 15 Read: Write: Reset: 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0
Figure 7-4. Stack Pointer (SP) NOTE The location of the stack is arbitrary and may be relocated anywhere in random-access memory (RAM). Moving the SP out of page 0 ($0000 to $00FF) frees direct address (page 0) space. For correct operation, the stack pointer must point only to RAM locations.
7.3.4 Program Counter
The program counter is a 16-bit register that contains the address of the next instruction or operand to be fetched. Normally, the program counter automatically increments to the next sequential memory location every time an instruction or operand is fetched. Jump, branch, and interrupt operations load the program counter with an address other than that of the next sequential location. During reset, the program counter is loaded with the reset vector address located at $FFFE and $FFFF. The vector address is the address of the first instruction to be executed after exiting the reset state.
Bit 15 Read: Write: Reset: Loaded with vector from $FFFE and $FFFF 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0
Figure 7-5. Program Counter (PC)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 85
Central Processor Unit (CPU)
7.3.5 Condition Code Register
The 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the instruction just executed. Bits 6 and 5 are set permanently to 1. The following paragraphs describe the functions of the condition code register.
Bit 7 Read: Write: Reset: V X X = Indeterminate 6 1 1 5 1 1 4 H X 3 I 1 2 N X 1 Z X Bit 0 C X
Figure 7-6. Condition Code Register (CCR) V -- Overflow Flag The CPU sets the overflow flag when a two's complement overflow occurs. The signed branch instructions BGT, BGE, BLE, and BLT use the overflow flag. 1 = Overflow 0 = No overflow H -- Half-Carry Flag The CPU sets the half-carry flag when a carry occurs between accumulator bits 3 and 4 during an add-without-carry (ADD) or add-with-carry (ADC) operation. The half-carry flag is required for binary-coded decimal (BCD) arithmetic operations. The DAA instruction uses the states of the H and C flags to determine the appropriate correction factor. 1 = Carry between bits 3 and 4 0 = No carry between bits 3 and 4 I -- Interrupt Mask When the interrupt mask is set, all maskable CPU interrupts are disabled. CPU interrupts are enabled when the interrupt mask is cleared. When a CPU interrupt occurs, the interrupt mask is set automatically after the CPU registers are saved on the stack, but before the interrupt vector is fetched. 1 = Interrupts disabled 0 = Interrupts enabled NOTE To maintain M6805 Family compatibility, the upper byte of the index register (H) is not stacked automatically. If the interrupt service routine modifies H, then the user must stack and unstack H using the PSHH and PULH instructions. After the I bit is cleared, the highest-priority interrupt request is serviced first. A return-from-interrupt (RTI) instruction pulls the CPU registers from the stack and restores the interrupt mask from the stack. After any reset, the interrupt mask is set and can be cleared only by the clear interrupt mask software instruction (CLI). N -- Negative Flag The CPU sets the negative flag when an arithmetic operation, logic operation, or data manipulation produces a negative result, setting bit 7 of the result. 1 = Negative result 0 = Non-negative result
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 86 Freescale Semiconductor
Arithmetic/Logic Unit (ALU)
Z -- Zero Flag The CPU sets the zero flag when an arithmetic operation, logic operation, or data manipulation produces a result of $00. 1 = Zero result 0 = Non-zero result C -- Carry/Borrow Flag The CPU sets the carry/borrow flag when an addition operation produces a carry out of bit 7 of the accumulator or when a subtraction operation requires a borrow. Some instructions -- such as bit test and branch, shift, and rotate -- also clear or set the carry/borrow flag. 1 = Carry out of bit 7 0 = No carry out of bit 7
7.4 Arithmetic/Logic Unit (ALU)
The ALU performs the arithmetic and logic operations defined by the instruction set. Refer to the CPU08 Reference Manual (document order number CPU08RM/AD) for a description of the instructions and addressing modes and more detail about the architecture of the CPU.
7.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
7.5.1 Wait Mode
The WAIT instruction: * Clears the interrupt mask (I bit) in the condition code register, enabling interrupts. After exit from wait mode by interrupt, the I bit remains clear. After exit by reset, the I bit is set. * Disables the CPU clock
7.5.2 Stop Mode
The STOP instruction: * Clears the interrupt mask (I bit) in the condition code register, enabling external interrupts. After exit from stop mode by external interrupt, the I bit remains clear. After exit by reset, the I bit is set. * Disables the CPU clock After exiting stop mode, the CPU clock begins running after the oscillator stabilization delay.
7.6 CPU During Break Interrupts
If a break module is present on the MCU, the CPU starts a break interrupt by: * Loading the instruction register with the SWI instruction * Loading the program counter with $FFFC:$FFFD or with $FEFC:$FEFD in monitor mode The break interrupt begins after completion of the CPU instruction in progress. If the break address register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately. A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and returns the MCU to normal operation if the break interrupt has been deasserted.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 87
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)
Address Mode Opcode 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 AIX #opr 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
Operation
Description
VH I NZC
Add with Carry
A (A) + (M) + (C)
-
IMM DIR EXT IX2 IX1 IX SP1 SP2 IMM DIR EXT IX2 IX1 IX SP1 SP2
A9 B9 C9 D9 E9 F9 9EE9 9ED9 AB BB CB DB EB FB 9EEB 9EDB A7 AF A4 B4 C4 D4 E4 F4 9EE4 9ED4
ii dd hh ll ee ff ff ff ee ff ii dd hh ll ee ff ff ff ee ff ii ii ii dd hh ll ee ff ff ff ee ff
Add without Carry
A (A) + (M)
-
Add Immediate Value (Signed) to SP Add Immediate Value (Signed) to H:X
SP (SP) + (16 M) H:X (H:X) + (16 M)
- - - - - - IMM - - - - - - IMM IMM DIR EXT IX2 - IX1 IX SP1 SP2 DIR INH INH IX1 IX SP1
Logical AND
A (A) & (M)
0--
Arithmetic Shift Left (Same as LSL)
C b7 b0
0
--
38 dd 48 58 68 ff 78 9E68 ff 37 47 57 67 77 9E67 24 11 13 15 17 19 1B 1D 1F 25 27 90 92 28 29 22 dd ff ff rr dd dd dd dd dd dd dd dd rr rr rr rr rr rr rr
Arithmetic Shift Right
b7 b0
C
Branch if Carry Bit Clear
PC (PC) + 2 + rel ? (C) = 0
DIR INH INH -- IX1 IX SP1 - - - - - - REL DIR (b0) DIR (b1) DIR (b2) - - - - - - DIR (b3) DIR (b4) DIR (b5) DIR (b6) DIR (b7) - - - - - - REL - - - - - - REL
BCLR n, opr
Clear Bit n in M
Mn 0
BCS rel BEQ rel BGE opr BGT opr BHCC rel BHCS rel BHI rel
Branch if Carry Bit Set (Same as BLO) Branch if Equal
PC (PC) + 2 + rel ? (C) = 1 PC (PC) + 2 + rel ? (Z) = 1
Branch if Greater Than or Equal To - - - - - - REL PC (PC) + 2 + rel ? (N V) = 0 (Signed Operands) Branch if Greater Than (Signed PC (PC) + 2 + rel ? (Z) | (N V) = 0 - - - - - - REL Operands) Branch if Half Carry Bit Clear Branch if Half Carry Bit Set Branch if Higher PC (PC) + 2 + rel ? (H) = 0 PC (PC) + 2 + rel ? (H) = 1 PC (PC) + 2 + rel ? (C) | (Z) = 0 - - - - - - REL - - - - - - REL - - - - - - REL
3 3
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 88 Freescale Semiconductor
Cycles
2 3 4 4 3 2 4 5 2 3 4 4 3 2 4 5 2 2 2 3 4 4 3 2 4 5 4 1 1 4 3 5 4 1 1 4 3 5 3 4 4 4 4 4 4 4 4 3 3 3 3 3
Effect on CCR
Operand
Instruction Set Summary
Table 7-1. Instruction Set Summary (Sheet 2 of 6)
Address Mode Opcode Source Form
BHS rel BIH rel BIL rel BIT #opr BIT opr BIT opr BIT opr,X BIT opr,X BIT ,X BIT opr,SP BIT opr,SP BLE opr BLO rel BLS rel BLT opr BMC rel BMI rel BMS rel BNE rel BPL rel BRA rel
Operation
Branch if Higher or Same (Same as BCC) Branch if IRQ Pin High Branch if IRQ Pin Low
Description
PC (PC) + 2 + rel ? (C) = 0 PC (PC) + 2 + rel ? IRQ = 1 PC (PC) + 2 + rel ? IRQ = 0
VH I NZC
- - - - - - REL - - - - - - REL - - - - - - REL IMM DIR EXT - IX2 IX1 IX SP1 SP2
24 2F 2E A5 B5 C5 D5 E5 F5 9EE5 9ED5 93 25 23 91 2C 2B 2D 26 2A 20 01 03 05 07 09 0B 0D 0F 21 00 02 04 06 08 0A 0C 0E 10 12 14 16 18 1A 1C 1E AD 31 41 51 61 71 9E61 98 9A
rr rr rr ii dd hh ll ee ff ff ff ee ff rr rr rr rr rr rr rr rr rr rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd dd dd dd dd dd dd dd rr dd rr ii rr ii rr ff rr rr ff rr
Bit Test
(A) & (M)
0--
Branch if Less Than or Equal To (Signed Operands) Branch if Lower (Same as BCS) Branch if Lower or Same Branch if Less Than (Signed Operands) Branch if Interrupt Mask Clear Branch if Minus Branch if Interrupt Mask Set Branch if Not Equal Branch if Plus Branch Always
PC (PC) + 2 + rel ? (Z) | (N V) = 1 - - - - - - REL PC (PC) + 2 + rel ? (C) = 1 PC (PC) + 2 + rel ? (C) | (Z) = 1 PC (PC) + 2 + rel ? (N V) =1 PC (PC) + 2 + rel ? (I) = 0 PC (PC) + 2 + rel ? (N) = 1 PC (PC) + 2 + rel ? (I) = 1 PC (PC) + 2 + rel ? (Z) = 0 PC (PC) + 2 + rel ? (N) = 0 PC (PC) + 2 + rel - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL - - - - - - REL DIR (b0) DIR (b1) DIR (b2) DIR (b3) DIR (b4) DIR (b5) DIR (b6) DIR (b7)
BRCLR n,opr,rel Branch if Bit n in M Clear
PC (PC) + 3 + rel ? (Mn) = 0
-----
BRN rel
Branch Never
PC (PC) + 2
BRSET n,opr,rel Branch if Bit n in M Set
PC (PC) + 3 + rel ? (Mn) = 1
- - - - - - REL DIR (b0) DIR (b1) DIR (b2) DIR (b3) ----- DIR (b4) DIR (b5) DIR (b6) DIR (b7) DIR (b0) DIR (b1) DIR (b2) - - - - - - DIR (b3) DIR (b4) DIR (b5) DIR (b6) DIR (b7) - - - - - - REL DIR IMM - - - - - - IMM IX1+ IX+ SP1 - - - - - 0 INH - - 0 - - - INH
BSET n,opr
Set Bit n in M
Mn 1
BSR rel
Branch to Subroutine
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 C0 I0
CBEQ opr,rel CBEQA #opr,rel CBEQX #opr,rel Compare and Branch if Equal CBEQ opr,X+,rel CBEQ X+,rel CBEQ opr,SP,rel CLC Clear Carry Bit CLI Clear Interrupt Mask
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 89
Cycles
3 3 3 2 3 4 4 3 2 4 5 3 3 3 3 3 3 3 3 3 3 5 5 5 5 5 5 5 5 3 5 5 5 5 5 5 5 5 4 4 4 4 4 4 4 4 4 5 4 4 5 4 6 1 2
Effect on CCR
Operand
Central Processor Unit (CPU)
Table 7-1. Instruction Set Summary (Sheet 3 of 6)
Address Mode Opcode 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
Operation
Description
M $00 A $00 X $00 H $00 M $00 M $00 M $00
VH I NZC
Clear
DIR INH INH 0 - - 0 1 - INH IX1 IX SP1 IMM DIR EXT IX2 IX1 IX SP1 SP2 DIR INH INH 1 IX1 IX SP1 IMM DIR IMM DIR EXT IX2 IX1 IX SP1 SP2 INH
3F dd 4F 5F 8C 6F ff 7F 9E6F ff A1 B1 C1 D1 E1 F1 9EE1 9ED1 33 43 53 63 73 9E63 65 75 A3 B3 C3 D3 E3 F3 9EE3 9ED3 72 3B 4B 5B 6B 7B 9E6B dd rr rr rr ff rr rr ff rr ii dd hh ll ee ff ff ff ee ff dd ff ff ii ii+1 dd ii dd hh ll ee ff ff ff ee ff
Compare A with M
(A) - (M)
--
Complement (One's Complement)
M (M) = $FF - (M) A (A) = $FF - (M) X (X) = $FF - (M) M (M) = $FF - (M) M (M) = $FF - (M) M (M) = $FF - (M) (H:X) - (M:M + 1)
0--
Compare H:X with M
--
Compare X with M
(X) - (M)
--
Decimal Adjust A
(A)10
U--
DBNZ opr,rel DBNZA rel DBNZX rel Decrement and Branch if Not Zero DBNZ opr,X,rel DBNZ X,rel DBNZ opr,SP,rel DEC opr DECA DECX DEC opr,X DEC ,X DEC opr,SP DIV 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
A (A) - 1 or M (M) - 1 or X (X) - 1 PC (PC) + 3 + rel ? (result) 0 DIR PC (PC) + 2 + rel ? (result) 0 INH PC (PC) + 2 + rel ? (result) 0 - - - - - - INH PC (PC) + 3 + rel ? (result) 0 IX1 PC (PC) + 2 + rel ? (result) 0 IX PC (PC) + 4 + rel ? (result) 0 SP1 M (M) - 1 A (A) - 1 X (X) - 1 M (M) - 1 M (M) - 1 M (M) - 1 A (H:A)/(X) H Remainder DIR INH INH - IX1 IX SP1 INH IMM DIR EXT - IX2 IX1 IX SP1 SP2 DIR INH - INH IX1 IX SP1
Decrement
--
3A dd 4A 5A 6A ff 7A 9E6A ff 52 A8 B8 C8 D8 E8 F8 9EE8 9ED8 ii dd hh ll ee ff ff ff ee ff
Divide
----
Exclusive OR M with A
A (A M)
0--
Increment
M (M) + 1 A (A) + 1 X (X) + 1 M (M) + 1 M (M) + 1 M (M) + 1
--
3C dd 4C 5C 6C ff 7C 9E6C ff
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 90 Freescale Semiconductor
Cycles
3 1 1 1 3 2 4 2 3 4 4 3 2 4 5 4 1 1 4 3 5 3 4 2 3 4 4 3 2 4 5 2 5 3 3 5 4 6 4 1 1 4 3 5 7 2 3 4 4 3 2 4 5 4 1 1 4 3 5
Effect on CCR
Operand
Instruction Set Summary
Table 7-1. Instruction Set Summary (Sheet 4 of 6)
Address Mode Opcode 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 NEG opr NEGA NEGX NEG opr,X NEG ,X NEG opr,SP NOP NSA ORA #opr ORA opr ORA opr ORA opr,X ORA opr,X ORA ,X ORA opr,SP ORA opr,SP PSHA PSHH PSHX
Operation
Description
VH I NZC
PC Jump Address
Jump
DIR EXT - - - - - - IX2 IX1 IX 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 DIR INH INH IX1 IX SP1 DD DIX+ - IMD IX+D DIR INH INH IX1 IX SP1
BC CC DC EC FC BD CD DD ED FD A6 B6 C6 D6 E6 F6 9EE6 9ED6 45 55 AE BE CE DE EE FE 9EEE 9EDE
dd hh ll ee ff ff dd hh ll ee ff ff ii dd hh ll ee ff ff ff ee ff ii jj dd ii dd hh ll ee ff ff ff ee ff
Jump to Subroutine
PC (PC) + n (n = 1, 2, or 3) Push (PCL); SP (SP) - 1 Push (PCH); SP (SP) - 1 PC Unconditional Address
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)
C b7 b0
0
--
38 dd 48 58 68 ff 78 9E68 ff 34 44 54 64 74 9E64 4E 5E 6E 7E 42 30 dd 40 50 60 ff 70 9E60 ff 9D 62 AA BA CA DA EA FA 9EEA 9EDA 87 8B 89 ii dd hh ll ee ff ff ff ee ff dd
Logical Shift Right
0 b7 b0
C
--0
Move Unsigned multiply
(M)Destination (M)Source H:X (H:X) + 1 (IX+D, DIX+) X:A (X) x (A) M -(M) = $00 - (M) A -(A) = $00 - (A) X -(X) = $00 - (X) M -(M) = $00 - (M) M -(M) = $00 - (M) None A (A[3:0]:A[7:4])
0--
4 1 1 ff 4 3 ff 5 dd dd 5 dd 4 ii dd 4 dd 4 5 4 1 1 4 3 5 1 3 2 3 4 4 3 2 4 5 2 2 2
- 0 - - - 0 INH
Negate (Two's Complement)
--
No Operation Nibble Swap A
- - - - - - INH - - - - - - INH IMM DIR EXT IX2 - IX1 IX SP1 SP2
Inclusive OR A and M
A (A) | (M)
0--
Push A onto Stack Push H onto Stack Push X onto Stack
Push (A); SP (SP) - 1 Push (H); SP (SP) - 1 Push (X); SP (SP) - 1
- - - - - - INH - - - - - - INH - - - - - - INH
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 91
Cycles
2 3 4 3 2 4 5 6 5 4 2 3 4 4 3 2 4 5 3 4 2 3 4 4 3 2 4 5 4 1 1 4 3 5
Effect on CCR
Operand
Central Processor Unit (CPU)
Table 7-1. Instruction Set Summary (Sheet 5 of 6)
Address Mode Opcode Source Form
PULA PULH PULX 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
Operation
Pull A from Stack Pull H from Stack Pull X from Stack
Description
SP (SP + 1); Pull (A) SP (SP + 1); Pull (H) SP (SP + 1); Pull (X)
VH I NZC
- - - - - - INH - - - - - - INH - - - - - - INH DIR INH INH IX1 IX SP1 DIR INH INH IX1 IX SP1
86 8A 88 39 dd 49 59 69 ff 79 9E69 ff 36 dd 46 56 66 ff 76 9E66 ff 9C
Rotate Left through Carry
C b7 b0
--
Rotate Right through Carry
b7 b0
C
--
Reset Stack Pointer
SP $FF 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)
- - - - - - INH
RTI
Return from Interrupt
INH
80
RTS SBC #opr SBC opr SBC opr SBC opr,X SBC opr,X SBC ,X SBC opr,SP SBC opr,SP SEC SEI STA opr STA opr STA opr,X STA opr,X STA ,X STA opr,SP STA opr,SP STHX opr 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
Return from Subroutine
- - - - - - INH IMM DIR EXT IX2 IX1 IX SP1 SP2
81 A2 B2 C2 D2 E2 F2 9EE2 9ED2 99 9B B7 C7 D7 E7 F7 9EE7 9ED7 35 8E BF CF DF EF FF 9EEF 9EDF A0 B0 C0 D0 E0 F0 9EE0 9ED0 dd hh ll ee ff ff ff ee ff ii dd hh ll ee ff ff ff ee ff dd hh ll ee ff ff ff ee ff dd ii dd hh ll ee ff ff ff ee ff
Subtract with Carry
A (A) - (M) - (C)
--
Set Carry Bit Set Interrupt Mask
C1 I1
- - - - - 1 INH - - 1 - - - INH DIR EXT IX2 - IX1 IX SP1 SP2 - DIR
Store A in M
M (A)
0--
Store H:X in M Enable Interrupts, Stop Processing, Refer to MCU Documentation
(M:M + 1) (H:X) I 0; Stop Processing
0--
- - 0 - - - INH DIR EXT IX2 - IX1 IX SP1 SP2 IMM DIR EXT IX2 IX1 IX SP1 SP2
Store X in M
M (X)
0--
Subtract
A (A) - (M)
--
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 92 Freescale Semiconductor
Cycles
2 2 2 4 1 1 4 3 5 4 1 1 4 3 5 1 7 4 2 3 4 4 3 2 4 5 1 2 3 4 4 3 2 4 5 4 1 3 4 4 3 2 4 5 2 3 4 4 3 2 4 5
Effect on CCR
Operand
Opcode Map
Table 7-1. Instruction Set Summary (Sheet 6 of 6)
Address Mode Opcode Source Form 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 CCR (A) X (A) A (CCR)
VH I NZC
SWI
Software Interrupt
- - 1 - - - INH
83
TAP TAX TPA TST opr TSTA TSTX TST opr,X TST ,X TST opr,SP TSX TXA TXS WAIT A C CCR dd dd rr DD DIR DIX+ ee ff EXT ff H H hh ll I ii IMD IMM INH IX IX+ IX+D IX1 IX1+ IX2 M N
Transfer A to CCR Transfer A to X Transfer CCR to A
INH - - - - - - INH - - - - - - INH DIR INH INH - IX1 IX SP1
84 97 85 3D dd 4D 5D 6D ff 7D 9E6D ff 95 9F 94 8F
Test for Negative or Zero
(A) - $00 or (X) - $00 or (M) - $00
0--
Transfer SP to H:X Transfer X to A Transfer H:X to SP Enable Interrupts; Wait for Interrupt
H:X (SP) + 1 A (X) (SP) (H:X) - 1 I bit 0; Inhibit CPU clocking until interrupted n opr PC PCH PCL REL rel rr SP1 SP2 SP U V X Z & |
- - - - - - INH - - - - - - INH - - - - - - INH - - 0 - - - INH
Accumulator Carry/borrow bit Condition code register Direct address of operand Direct address of operand and relative offset of branch instruction Direct to direct addressing mode Direct addressing mode Direct to indexed with post increment addressing mode High and low bytes of offset in indexed, 16-bit offset addressing Extended addressing mode Offset byte in indexed, 8-bit offset addressing Half-carry bit Index register high byte High and low bytes of operand address in extended addressing Interrupt mask Immediate operand byte Immediate source to direct destination addressing mode Immediate addressing mode Inherent addressing mode Indexed, no offset addressing mode Indexed, no offset, post increment addressing mode Indexed with post increment to direct addressing mode Indexed, 8-bit offset addressing mode Indexed, 8-bit offset, post increment addressing mode Indexed, 16-bit offset addressing mode Memory location Negative bit
() -( ) #
? : --
Any bit Operand (one or two bytes) Program counter Program counter high byte Program counter low byte Relative addressing mode Relative program counter offset byte Relative program counter offset byte Stack pointer, 8-bit offset addressing mode Stack pointer 16-bit offset addressing mode Stack pointer Undefined Overflow bit Index register low byte Zero bit Logical AND Logical OR Logical EXCLUSIVE OR Contents of Negation (two's complement) Immediate value Sign extend Loaded with If Concatenated with Set or cleared Not affected
7.8 Opcode Map
See Table 7-2.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 93
Cycles
9 2 1 1 3 1 1 3 2 4 2 1 2 1
Effect on CCR
Operand
94
Bit Manipulation DIR DIR
MSB LSB
Central Processor Unit (CPU)
Table 7-2. Opcode Map
Branch REL 2 3 BRA 2 REL 3 BRN 2 REL 3 BHI 2 REL 3 BLS 2 REL 3 BCC 2 REL 3 BCS 2 REL 3 BNE 2 REL 3 BEQ 2 REL 3 BHCC 2 REL 3 BHCS 2 REL 3 BPL 2 REL 3 BMI 2 REL 3 BMC 2 REL 3 BMS 2 REL 3 BIL 2 REL 3 BIH 2 REL DIR 3 INH 4 Read-Modify-Write INH IX1 5 1 NEGX 1 INH 4 CBEQX 3 IMM 7 DIV 1 INH 1 COMX 1 INH 1 LSRX 1 INH 4 LDHX 2 DIR 1 RORX 1 INH 1 ASRX 1 INH 1 LSLX 1 INH 1 ROLX 1 INH 1 DECX 1 INH 3 DBNZX 2 INH 1 INCX 1 INH 1 TSTX 1 INH 4 MOV 2 DIX+ 1 CLRX 1 INH 6 4 NEG 2 IX1 5 CBEQ 3 IX1+ 3 NSA 1 INH 4 COM 2 IX1 4 LSR 2 IX1 3 CPHX 3 IMM 4 ROR 2 IX1 4 ASR 2 IX1 4 LSL 2 IX1 4 ROL 2 IX1 4 DEC 2 IX1 5 DBNZ 3 IX1 4 INC 2 IX1 3 TST 2 IX1 4 MOV 3 IMD 3 CLR 2 IX1 SP1 9E6 IX 7 Control INH INH 8 9 IMM A 2 SUB 2 IMM 2 CMP 2 IMM 2 SBC 2 IMM 2 CPX 2 IMM 2 AND 2 IMM 2 BIT 2 IMM 2 LDA 2 IMM 2 AIS 2 IMM 2 EOR 2 IMM 2 ADC 2 IMM 2 ORA 2 IMM 2 ADD 2 IMM DIR B EXT C 4 SUB 3 EXT 4 CMP 3 EXT 4 SBC 3 EXT 4 CPX 3 EXT 4 AND 3 EXT 4 BIT 3 EXT 4 LDA 3 EXT 4 STA 3 EXT 4 EOR 3 EXT 4 ADC 3 EXT 4 ORA 3 EXT 4 ADD 3 EXT 3 JMP 3 EXT 5 JSR 3 EXT 4 LDX 3 EXT 4 STX 3 EXT Register/Memory IX2 SP2 D 4 SUB 3 IX2 4 CMP 3 IX2 4 SBC 3 IX2 4 CPX 3 IX2 4 AND 3 IX2 4 BIT 3 IX2 4 LDA 3 IX2 4 STA 3 IX2 4 EOR 3 IX2 4 ADC 3 IX2 4 ORA 3 IX2 4 ADD 3 IX2 4 JMP 3 IX2 6 JSR 3 IX2 4 LDX 3 IX2 4 STX 3 IX2 9ED 5 SUB 4 SP2 5 CMP 4 SP2 5 SBC 4 SP2 5 CPX 4 SP2 5 AND 4 SP2 5 BIT 4 SP2 5 LDA 4 SP2 5 STA 4 SP2 5 EOR 4 SP2 5 ADC 4 SP2 5 ORA 4 SP2 5 ADD 4 SP2 IX1 E SP1 9EE 4 SUB 3 SP1 4 CMP 3 SP1 4 SBC 3 SP1 4 CPX 3 SP1 4 AND 3 SP1 4 BIT 3 SP1 4 LDA 3 SP1 4 STA 3 SP1 4 EOR 3 SP1 4 ADC 3 SP1 4 ORA 3 SP1 4 ADD 3 SP1 IX F
0 5 BRSET0 3 DIR 5 BRCLR0 3 DIR 5 BRSET1 3 DIR 5 BRCLR1 3 DIR 5 BRSET2 3 DIR 5 BRCLR2 3 DIR 5 BRSET3 3 DIR 5 BRCLR3 3 DIR 5 BRSET4 3 DIR 5 BRCLR4 3 DIR 5 BRSET5 3 DIR 5 BRCLR5 3 DIR 5 BRSET6 3 DIR 5 BRCLR6 3 DIR 5 BRSET7 3 DIR 5 BRCLR7 3 DIR
1 4 BSET0 2 DIR 4 BCLR0 2 DIR 4 BSET1 2 DIR 4 BCLR1 2 DIR 4 BSET2 2 DIR 4 BCLR2 2 DIR 4 BSET3 2 DIR 4 BCLR3 2 DIR 4 BSET4 2 DIR 4 BCLR4 2 DIR 4 BSET5 2 DIR 4 BCLR5 2 DIR 4 BSET6 2 DIR 4 BCLR6 2 DIR 4 BSET7 2 DIR 4 BCLR7 2 DIR
0 1 2
3 4 5 6 7 8 9 A B C D E
F
4 1 NEG NEGA 2 DIR 1 INH 5 4 CBEQ CBEQA 3 DIR 3 IMM 5 MUL 1 INH 4 1 COM COMA 2 DIR 1 INH 4 1 LSR LSRA 2 DIR 1 INH 4 3 STHX LDHX 2 DIR 3 IMM 4 1 ROR RORA 2 DIR 1 INH 4 1 ASR ASRA 2 DIR 1 INH 4 1 LSL LSLA 2 DIR 1 INH 4 1 ROL ROLA 2 DIR 1 INH 4 1 DEC DECA 2 DIR 1 INH 5 3 DBNZ DBNZA 3 DIR 2 INH 4 1 INC INCA 2 DIR 1 INH 3 1 TST TSTA 2 DIR 1 INH 5 MOV 3 DD 3 1 CLR CLRA 2 DIR 1 INH
5 3 NEG NEG 3 SP1 1 IX 6 4 CBEQ CBEQ 4 SP1 2 IX+ 2 DAA 1 INH 5 3 COM COM 3 SP1 1 IX 5 3 LSR LSR 3 SP1 1 IX 4 CPHX 2 DIR 5 3 ROR ROR 3 SP1 1 IX 5 3 ASR ASR 3 SP1 1 IX 5 3 LSL LSL 3 SP1 1 IX 5 3 ROL ROL 3 SP1 1 IX 5 3 DEC DEC 3 SP1 1 IX 6 4 DBNZ DBNZ 4 SP1 2 IX 5 3 INC INC 3 SP1 1 IX 4 2 TST TST 3 SP1 1 IX 4 MOV 2 IX+D 4 2 CLR CLR 3 SP1 1 IX
7 3 RTI BGE 1 INH 2 REL 4 3 RTS BLT 1 INH 2 REL 3 BGT 2 REL 9 3 SWI BLE 1 INH 2 REL 2 2 TAP TXS 1 INH 1 INH 1 2 TPA TSX 1 INH 1 INH 2 PULA 1 INH 2 1 PSHA TAX 1 INH 1 INH 2 1 PULX CLC 1 INH 1 INH 2 1 PSHX SEC 1 INH 1 INH 2 2 PULH CLI 1 INH 1 INH 2 2 PSHH SEI 1 INH 1 INH 1 1 CLRH RSP 1 INH 1 INH 1 NOP 1 INH 1 STOP * 1 INH 1 1 WAIT TXA 1 INH 1 INH
3 SUB 2 DIR 3 CMP 2 DIR 3 SBC 2 DIR 3 CPX 2 DIR 3 AND 2 DIR 3 BIT 2 DIR 3 LDA 2 DIR 3 STA 2 DIR 3 EOR 2 DIR 3 ADC 2 DIR 3 ORA 2 DIR 3 ADD 2 DIR 2 JMP 2 DIR 4 4 BSR JSR 2 REL 2 DIR 2 3 LDX LDX 2 IMM 2 DIR 2 3 AIX STX 2 IMM 2 DIR
MSB LSB
3 SUB 2 IX1 3 CMP 2 IX1 3 SBC 2 IX1 3 CPX 2 IX1 3 AND 2 IX1 3 BIT 2 IX1 3 LDA 2 IX1 3 STA 2 IX1 3 EOR 2 IX1 3 ADC 2 IX1 3 ORA 2 IX1 3 ADD 2 IX1 3 JMP 2 IX1 5 JSR 2 IX1 5 3 LDX LDX 4 SP2 2 IX1 5 3 STX STX 4 SP2 2 IX1
2 SUB 1 IX 2 CMP 1 IX 2 SBC 1 IX 2 CPX 1 IX 2 AND 1 IX 2 BIT 1 IX 2 LDA 1 IX 2 STA 1 IX 2 EOR 1 IX 2 ADC 1 IX 2 ORA 1 IX 2 ADD 1 IX 2 JMP 1 IX 4 JSR 1 IX 4 2 LDX LDX 3 SP1 1 IX 4 2 STX STX 3 SP1 1 IX
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor
Inherent REL Relative Immediate IX Indexed, No Offset Direct IX1 Indexed, 8-Bit Offset Extended IX2 Indexed, 16-Bit Offset Direct-Direct IMD Immediate-Direct Indexed-Direct DIX+ Direct-Indexed *Pre-byte for stack pointer indexed instructions
INH IMM DIR EXT DD IX+D
SP1 Stack Pointer, 8-Bit Offset SP2 Stack Pointer, 16-Bit Offset IX+ Indexed, No Offset with Post Increment IX1+ Indexed, 1-Byte Offset with Post Increment
0
High Byte of Opcode in Hexadecimal
Low Byte of Opcode in Hexadecimal
0
5 Cycles BRSET0 Opcode Mnemonic 3 DIR Number of Bytes / Addressing Mode
Chapter 8 External Interrupt (IRQ)
8.1 Introduction
The IRQ (external interrupt) module provides a maskable interrupt input.
8.2 Features
Features of the IRQ module include: * A dedicated external interrupt pin (IRQ) * IRQ interrupt control bits * Hysteresis buffer * Programmable edge-only or edge and level interrupt sensitivity * Automatic interrupt acknowledge * Internal pullup resistor
8.3 Functional Description
A falling edge applied to the external interrupt pin can latch a central processor unit (CPU) interrupt request. Figure 8-1 shows the structure of the IRQ module. Interrupt signals on the IRQ pin are latched into the IRQ latch. An interrupt latch remains set until one of the following actions occurs: * Vector fetch -- A vector fetch automatically generates an interrupt acknowledge signal that clears the latch that caused the vector fetch. * Software clear -- Software can clear an interrupt latch by writing to the appropriate acknowledge bit in the interrupt status and control register (INTSCR). Writing a 1 to the ACK bit clears the IRQ latch. * Reset -- A reset automatically clears the interrupt latch. The external interrupt pin is falling-edge triggered out of reset and is software-configurable to be either falling-edge or falling-edge and low-level triggered. The MODE bit in the INTSCR controls the triggering sensitivity of the IRQ pin. When an interrupt pin is edge-triggered only (MODE = 0), the interrupt remains set until a vector fetch, software clear, or reset occurs.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 95
External Interrupt (IRQ)
RESET ACK INTERNAL ADDRESS BUS VECTOR FETCH DECODER VDD INTERNAL PULLUP DEVICE IRQ VDD D CLR Q IRQF SYNCHRONIZER IRQ INTERRUPT REQUEST TO CPU FOR BIL/BIH INSTRUCTIONS
CK
IMASK
MODE HIGH VOLTAGE DETECT TO MODE SELECT LOGIC
Figure 8-1. IRQ Module Block Diagram When an interrupt pin is both falling-edge and low-level triggered (MODE = 1), the interrupt remains set until both of these events occur: * Vector fetch or software clear * Return of the interrupt pin to a high level The vector fetch or software clear may occur before or after the interrupt pin returns to a high level. As long as the pin is low, the interrupt request remains pending. A reset will clear the latch and the MODE control bit, thereby clearing the interrupt even if the pin stays low. When set, the IMASK bit in the INTSCR masks all external interrupt requests. A latched interrupt request is not presented to the interrupt priority logic unless the IMASK bit is clear. NOTE The interrupt mask (I) in the condition code register (CCR) masks all interrupt requests, including external interrupt requests.
Addr. Register Name Read: IRQ Status and Control Register (INTSCR) Write: See page 98. Reset: Bit 7 0 6 0 5 0 4 0 3 IRQF 2 0 ACK 0 0 = Unimplemented 0 0 0 0 1 IMASK 0 Bit 0 MODE 0
$001D
Figure 8-2. IRQ I/O Register Summary
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 96 Freescale Semiconductor
IRQ Pin
8.4 IRQ Pin
A falling edge on the IRQ pin can latch an interrupt request into the IRQ latch. A vector fetch, software clear, or reset clears the IRQ latch. If the MODE bit is set, the IRQ pin is both falling-edge-sensitive and low-level sensitive. With MODE set, both of the following actions must occur to clear IRQ: * Vector fetch or software clear -- A vector fetch generates an interrupt acknowledge signal to clear the latch. Software may generate the interrupt acknowledge signal by writing a 1 to the ACK bit in the interrupt status and control register (INTSCR). The ACK bit is useful in applications that poll the IRQ pin and require software to clear the IRQ latch. Writing to the ACK bit prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. Setting ACK does not affect subsequent transitions on the IRQ pin. A falling edge that occurs after writing to the ACK bit latches another interrupt request. If the IRQ mask bit, IMASK, is clear, the CPU loads the program counter with the vector address at locations $FFFA and $FFFB. * Return of the IRQ pin to a high level -- As long as the IRQ pin is low, IRQ remains active. The vector fetch or software clear and the return of the IRQ pin to a high level may occur in any order. The interrupt request remains pending as long as the IRQ pin is low. A reset will clear the latch and the MODE control bit, thereby clearing the interrupt even if the pin stays low. If the MODE bit is clear, the IRQ pin is falling-edge-sensitive only. With MODE clear, a vector fetch or software clear immediately clears the IRQ latch. The IRQF bit in the INTSCR register can be used to check for pending interrupts. The IRQF bit is not affected by the IMASK bit, which makes it useful in applications where polling is preferred. Use the BIH or BIL instruction to read the logic level on the IRQ pin. NOTE When using the level-sensitive interrupt trigger, avoid false interrupts by masking interrupt requests in the interrupt routine.
8.5 IRQ Module During Break Interrupts
The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear the latch during the break state. See Chapter 18 Development Support. To allow software to clear the IRQ latch during a break interrupt, write a 1 to the BCFE bit. If a latch is cleared during the break state, it remains cleared when the MCU exits the break state. To protect CPU interrupt flags during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default state), writing to the ACK bit in the IRQ status and control register during the break state has no effect on the IRQ interrupt flags.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 97
External Interrupt (IRQ)
8.6 IRQ Status and Control Register
The IRQ status and control register (INTSCR) controls and monitors operation of the IRQ module. The INTSCR: * Shows the state of the IRQ flag * Clears the IRQ latch * Masks IRQ interrupt request * Controls triggering sensitivity of the IRQ interrupt pin
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 0 $001D Bit 7 0 6 0 5 0 4 0 3 IRQF 2 0 ACK 0 1 IMASK 0 Bit 0 MODE 0
Figure 8-3. IRQ Status and Control Register (INTSCR) IRQF -- IRQ Flag Bit This read-only status bit is high when the IRQ interrupt is pending. 1 = IRQ interrupt pending 0 = IRQ interrupt not pending ACK -- IRQ Interrupt Request Acknowledge Bit Writing a 1 to this write-only bit clears the IRQ latch. ACK always reads as 0. Reset clears ACK. IMASK -- IRQ Interrupt Mask Bit Writing a 1 to this read/write bit disables IRQ interrupt requests. Reset clears IMASK. 1 = IRQ interrupt requests disabled 0 = IRQ interrupt requests enabled MODE -- IRQ Edge/Level Select Bit This read/write bit controls the triggering sensitivity of the IRQ pin. Reset clears MODE. 1 = IRQ interrupt requests on falling edges and low levels 0 = IRQ interrupt requests on falling edges only
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 98 Freescale Semiconductor
Chapter 9 Keyboard Interrupt Module (KBI)
9.1 Introduction
The keyboard interrupt module (KBI) provides four independently maskable external interrupts which are accessible via PTA0-PTA3. When a port pin is enabled for keyboard interrupt function, an internal pullup device is also enabled on the pin.
9.2 Features
Features include: * Four keyboard interrupt pins with separate keyboard interrupt enable bits and one keyboard interrupt mask * Hysteresis buffers * Programmable edge-only or edge- and level- interrupt sensitivity * Exit from low-power modes * I/O (input/output) port bit(s) software configurable with pullup device(s) if configured as input port bit(s)
9.3 Functional Description
Writing to the KBIE3-KBIE0 bits in the keyboard interrupt enable register independently enables or disables each port A pin as a keyboard interrupt pin. Enabling a keyboard interrupt pin also enables its internal pullup device. A low level applied to an enabled keyboard interrupt pin latches a keyboard interrupt request. A keyboard interrupt is latched when one or more keyboard pins goes low after all were high. The MODEK bit in the keyboard status and control register controls the triggering mode of the keyboard interrupt. * If the keyboard interrupt is edge-sensitive only, a falling edge on a keyboard pin does not latch an interrupt request if another keyboard pin is already low. To prevent losing an interrupt request on one pin because another pin is still low, software can disable the latter pin while it is low. * If the keyboard interrupt is falling edge- and low-level sensitive, an interrupt request is present as long as any keyboard interrupt pin is low and the pin is keyboard interrupt enabled.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 99
Keyboard Interrupt Module (KBI)
INTERNAL BUS M68HC08 CPU PORTA DDRA CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) PROGRAMMABLE TIMEBASE MODULE SINGLE BREAKPOINT BREAK MODULE DUAL VOLTAGE LOW-VOLTAGE INHIBIT MODULE 4-BIT KEYBOARD INTERRUPT MODULE PORTC DDRC 2-CHANNEL TIMER INTERFACE MODULE 1 1-CHANNEL TIMER INTERFACE MODULE 2 SERIAL COMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE RST(3) IRQ(3) VDDAD/VREFH VSSAD/VREFL SYSTEM INTEGRATION MODULE SINGLE EXTERNAL INTERRUPT MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE POWER-ON RESET MODULE VDD VSS VDDA VSSA SERIAL PERIPHERAL INTERFACE MODULE MONITOR MODULE MEMORY MAP MODULE CONFIGURATION REGISTER 1 MODULE CONFIGURATION REGISTER 2 MODULE PORTB DDRB PTA3/KBD3- PTA0/KBD0(1)
CONTROL AND STATUS REGISTERS -- 64 BYTES MC68HC908GR8A USER FLASH -- 7680 BYTES MC68HC908GR4A USER FLASH -- 4096 BYTES USER RAM -- 384 BYTES MONITOR ROM -- 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM -- 544 BYTES USER FLASH VECTOR SPACE -- 36 BYTES CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 1-8-MHz OSCILLATOR PHASE LOCKED LOOP
PTB5/AD5 PTB4/AD4 PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0
PTC1(1), (2) PTC0(1), (2)
PTD6/T2CH0(1) PTD5/T1CH1(1) PTD4/T1CH0(1) PTD3/SPSCK(1) PTD2/MOSI(1) PTD1/MISO(1) PTD0/SS(1)
PORTE
PORTD
DDRD
PTE1/RxD PTE0/TxD
DDRE
SECURITY MODULE
POWER
MONITOR MODE ENTRY MODULE
1. Ports are software configurable with pullup device if input port. 2. Higher current drive port pins 3. Pin contains integrated pullup device
Figure 9-1. Block Diagram Highlighting KBI Block and Pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 100 Freescale Semiconductor
Functional Description
INTERNAL BUS
VECTOR FETCH DECODER
ACKK RESET
KBD0 VDD TO PULLUP ENABLE KBIE0 . . . KBD3 IMASKK D CLR Q KEYF SYNCHRONIZER KEYBOARD INTERRUPT REQUEST
CK
TO PULLUP ENABLE KBIE3
MODEK
Figure 9-2. Keyboard Module Block Diagram
Addr. $001A Register Name Keyboard Status Read: and Control Register Write: (INTKBSCR) See page 103. Reset: Keyboard Interrupt Enable Read: Register Write: (INTKBIER) See page 104. Reset: Bit 7 0 0 6 0 0 5 0 0 4 0 0 3 KEYF 0 KBIE3 0 0 = Unimplemented 0 0 0 2 0 ACKK 0 KBIE2 0 1 IMASKK 0 KBIE1 0 Bit 0 MODEK 0 KBIE0 0
$001B
Figure 9-3. I/O Register Summary If the MODEK bit is set, the keyboard interrupt pins are both falling edge- and low-level sensitive, and both of the following actions must occur to clear a keyboard interrupt request: * Vector fetch or software clear -- A vector fetch generates an interrupt acknowledge signal to clear the interrupt request. Software may generate the interrupt acknowledge signal by writing a 1 to the ACKK bit in the keyboard status and control register (INTKBSCR). The ACKK bit is useful in applications that poll the keyboard interrupt pins and require software to clear the keyboard interrupt request. Writing to the ACKK bit prior to leaving an interrupt service routine can also prevent spurious interrupts due to noise. Setting ACKK does not affect subsequent transitions on the keyboard interrupt pins. A falling edge that occurs after writing to the ACKK bit latches another interrupt request. If the keyboard interrupt mask bit, IMASKK, is clear, the CPU loads the program counter with the vector address at locations $FFE0 and $FFE1. * Return of all enabled keyboard interrupt pins to a high level -- As long as any enabled keyboard interrupt pin is low, the keyboard interrupt remains set.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 101
Keyboard Interrupt Module (KBI)
The vector fetch or software clear and the return of all enabled keyboard interrupt pins to a high level may occur in any order. If the MODEK bit is clear, the keyboard interrupt pin is falling-edge-sensitive only. With MODEK clear, a vector fetch or software clear immediately clears the keyboard interrupt request. Reset clears the keyboard interrupt request and the MODEK bit, clearing the interrupt request even if a keyboard interrupt pin stays at low. The keyboard flag bit (KEYF) in the keyboard status and control register can be used to see if a pending interrupt exists. The KEYF bit is not affected by the keyboard interrupt mask bit (IMASKK) which makes it useful in applications where polling is preferred. To determine the logic level on a keyboard interrupt pin, use the data direction register to configure the pin as an input and read the data register. NOTE Setting a keyboard interrupt enable bit (KBIEx) forces the corresponding keyboard interrupt pin to be an input, overriding the data direction register. However, the data direction register bit must be a 0 for software to read the pin.
9.4 Keyboard Initialization
When a keyboard interrupt pin is enabled, it takes time for the internal pullup to reach a 1. Therefore, a false interrupt can occur as soon as the pin is enabled. To prevent a false interrupt on keyboard initialization: 1. Mask keyboard interrupts by setting the IMASKK bit in the keyboard status and control register. 2. Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard interrupt enable register. 3. Write to the ACKK bit in the keyboard status and control register to clear any false interrupts. 4. Clear the IMASKK bit. An interrupt signal on an edge-triggered pin can be acknowledged immediately after enabling the pin. An interrupt signal on an edge- and level-triggered interrupt pin must be acknowledged after a delay that depends on the external load. Another way to avoid a false interrupt: 1. Configure the keyboard pins as outputs by setting the appropriate DDRA bits in data direction register A. 2. Write 1s to the appropriate port A data register bits. 3. Enable the KBI pins by setting the appropriate KBIEx bits in the keyboard interrupt enable register.
9.5 Low-Power Modes
The WAIT and STOP instructions put the microcontroller unit (MCU) in low power-consumption standby modes.
9.5.1 Wait Mode
The keyboard module remains active in wait mode. Clearing the IMASKK bit in the keyboard status and control register enables keyboard interrupt requests to bring the MCU out of wait mode.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 102 Freescale Semiconductor
Keyboard Module During Break Interrupts
9.5.2 Stop Mode
The keyboard module remains active in stop mode. Clearing the IMASKK bit in the keyboard status and control register enables keyboard interrupt requests to bring the MCU out of stop mode.
9.6 Keyboard Module During Break Interrupts
The system integration module (SIM) controls whether the keyboard interrupt latch can be cleared during the break state. The BCFE bit in the break flag control register (SBFCR) enables software to clear status bits during the break state. To allow software to clear the keyboard interrupt latch during a break interrupt, write a 1 to the BCFE bit. If a latch is cleared during the break state, it remains cleared when the MCU exits the break state. To protect the latch during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default state), writing to the keyboard acknowledge bit (ACKK) in the keyboard status and control register during the break state has no effect. See 9.7.1 Keyboard Status and Control Register.
9.7 I/O Registers
These registers control and monitor operation of the keyboard module: * Keyboard status and control register (INTKBSCR) * Keyboard interrupt enable register (INTKBIER)
9.7.1 Keyboard Status and Control Register
The keyboard status and control register: * Flags keyboard interrupt requests * Acknowledges keyboard interrupt requests * Masks keyboard interrupt requests * Controls keyboard interrupt triggering sensitivity
Address: $001A Bit 7 Read: Write: Reset: 0 0 0 0 0 = Unimplemented 0 6 0 5 0 4 0 3 KEYF 2 0 ACKK 0 1 IMASKK 0 Bit 0 MODEK 0
Figure 9-4. Keyboard Status and Control Register (INTKBSCR) Bits 7-4 -- Not used These read-only bits always read as 0s. KEYF -- Keyboard Flag Bit This read-only bit is set when a keyboard interrupt is pending. Reset clears the KEYF bit. 1 = Keyboard interrupt pending 0 = No keyboard interrupt pending ACKK -- Keyboard Acknowledge Bit Writing a 1 to this write-only bit clears the keyboard interrupt request. ACKK always reads as 0. Reset clears ACKK.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 103
Keyboard Interrupt Module (KBI)
IMASKK -- Keyboard Interrupt Mask Bit Writing a 1 to this read/write bit prevents the output of the keyboard interrupt mask from generating interrupt requests. Reset clears the IMASKK bit. 1 = Keyboard interrupt requests masked 0 = Keyboard interrupt requests not masked MODEK -- Keyboard Triggering Sensitivity Bit This read/write bit controls the triggering sensitivity of the keyboard interrupt pins. Reset clears MODEK. 1 = Keyboard interrupt requests on falling edges and low levels 0 = Keyboard interrupt requests on falling edges only
9.7.2 Keyboard Interrupt Enable Register
The keyboard interrupt enable register enables or disables each port A pin to operate as a keyboard interrupt pin.
Address: $001B Bit 7 Read: Write: Reset: 0 0 = Unimplemented 0 0 6 5 4 3 KBIE3 0 2 KBIE2 0 1 KBIE1 0 Bit 0 KBIE0 0
Figure 9-5. Keyboard Interrupt Enable Register (INTKBIER) KBIE3-KBIE0 -- Keyboard Interrupt Enable Bits Each of these read/write bits enables the corresponding keyboard interrupt pin to latch interrupt requests. Reset clears the keyboard interrupt enable register. 1 = PTAx pin enabled as keyboard interrupt pin 0 = PTAx pin not enabled as keyboard interrupt pin
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 104 Freescale Semiconductor
Chapter 10 Low-Power Modes
10.1 Introduction
The microcontroller (MCU) may enter two low-power modes: wait mode and stop mode. They are common to all HC08 MCUs and are entered through instruction execution. This section describes how each module acts in the low-power modes.
10.1.1 Wait Mode
The WAIT instruction puts the MCU in a low-power standby mode in which the central processor unit (CPU) clock is disabled but the bus clock continues to run. Power consumption can be further reduced by disabling the low-voltage inhibit (LVI) module through bits in the CONFIG1 register. See Chapter 5 Configuration Register (CONFIG).
10.1.2 Stop Mode
Stop mode is entered when a STOP instruction is executed. The CPU clock is disabled and the bus clock is disabled if the OSCSTOPENB bit in the CONFIG2 register is a 0. See Chapter 5 Configuration Register (CONFIG).
10.2 Analog-to-Digital Converter (ADC)
10.2.1 Wait Mode
The analog-to-digital converter (ADC) continues normal operation during wait mode. Any enabled CPU interrupt request from the ADC can bring the MCU out of wait mode. If the ADC is not required to bring the MCU out of wait mode, power down the ADC by setting ADCH4-ADCH0 bits in the ADC status and control register before executing the WAIT instruction.
10.2.2 Stop Mode
The ADC module is inactive after the execution of a STOP instruction. Any pending conversion is aborted. ADC conversions resume when the MCU exits stop mode after an external interrupt. Allow one conversion cycle to stabilize the analog circuitry.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 105
Low-Power Modes
10.3 Break Module (BRK)
10.3.1 Wait Mode
The break (BRK) module is active in wait mode. In the break routine, the user can subtract one from the return address on the stack if the SBSW bit in the break status register is set.
10.3.2 Stop Mode
The break module is inactive in stop mode. The STOP instruction does not affect break module register states.
10.4 Central Processor Unit (CPU)
10.4.1 Wait Mode
The WAIT instruction: * Clears the interrupt mask (I bit) in the condition code register, enabling interrupts. After exit from wait mode by interrupt, the I bit remains clear. After exit by reset, the I bit is set. * Disables the CPU clock
10.4.2 Stop Mode
The STOP instruction: * Clears the interrupt mask (I bit) in the condition code register, enabling external interrupts. After exit from stop mode by external interrupt, the I bit remains clear. After exit by reset, the I bit is set. * Disables the CPU clock After exiting stop mode, the CPU clock begins running after the oscillator stabilization delay.
10.5 Clock Generator Module (CGM)
10.5.1 Wait Mode
The clock generator module (CGM) remains active in wait mode. Before entering wait mode, software can disengage and turn off the PLL by clearing the BCS and PLLON bits in the PLL control register (PCTL). Less power-sensitive applications can disengage the PLL without turning it off. Applications that require the PLL to wake the MCU from wait mode also can deselect the PLL output without turning off the PLL.
10.5.2 Stop Mode
If the OSCSTOPENB bit in the CONFIG2 register is cleared (default), then the STOP instruction disables the CGM (oscillator and phase-locked loop) and holds low all CGM outputs (CGMXCLK, CGMOUT, and CGMINT). If the OSCSTOPENB bit in the CONFIG2 register is set, then the phase locked loop is shut off, but the oscillator will continue to operate in stop mode.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 106 Freescale Semiconductor
Computer Operating Properly Module (COP)
10.6 Computer Operating Properly Module (COP)
10.6.1 Wait Mode
The COP remains active during wait mode. If COP is enabled, a reset will occur at COP timeout.
10.6.2 Stop Mode
Stop mode turns off the CGMXCLK input to the COP and clears the SIM counter. Service the COP immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering or exiting stop mode. The STOP bit in the CONFIG1 register enables the STOP instruction. To prevent inadvertently turning off the COP with a STOP instruction, disable the STOP instruction by clearing the STOP bit.
10.7 External Interrupt Module (IRQ)
10.7.1 Wait Mode
The external interrupt (IRQ) module remains active in wait mode. Clearing the IMASK bit in the IRQ status and control register enables IRQ CPU interrupt requests to bring the MCU out of wait mode.
10.7.2 Stop Mode
The IRQ module remains active in stop mode. Clearing the IMASK bit in the IRQ status and control register enables IRQ CPU interrupt requests to bring the MCU out of stop mode.
10.8 Keyboard Interrupt Module (KBI)
10.8.1 Wait Mode
The keyboard interrupt (KBI) module remains active in wait mode. Clearing the IMASKK bit in the keyboard status and control register enables keyboard interrupt requests to bring the MCU out of wait mode.
10.8.2 Stop Mode
The keyboard module remains active in stop mode. Clearing the IMASKK bit in the keyboard status and control register enables keyboard interrupt requests to bring the MCU out of stop mode.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 107
Low-Power Modes
10.9 Low-Voltage Inhibit Module (LVI)
10.9.1 Wait Mode
If enabled, the low-voltage inhibit (LVI) module remains active in wait mode. If enabled to generate resets, the LVI module can generate a reset and bring the MCU out of wait mode.
10.9.2 Stop Mode
If enabled, the LVI module remains active in stop mode. If enabled to generate resets, the LVI module can generate a reset and bring the MCU out of stop mode.
10.10 Serial Communications Interface Module (SCI)
10.10.1 Wait Mode
The serial communications interface (SCI) module remains active in wait mode. Any enabled CPU interrupt request from the SCI module can bring the MCU out of wait mode. If SCI module functions are not required during wait mode, reduce power consumption by disabling the module before executing the WAIT instruction.
10.10.2 Stop Mode
The SCI module is inactive in stop mode. The STOP instruction does not affect SCI register states. SCI module operation resumes after the MCU exits stop mode. Because the internal clock is inactive during stop mode, entering stop mode during an SCI transmission or reception results in invalid data.
10.11 Serial Peripheral Interface Module (SPI)
10.11.1 Wait Mode
The serial peripheral interface (SPI) module remains active in wait mode. Any enabled CPU interrupt request from the SPI module can bring the MCU out of wait mode. If SPI module functions are not required during wait mode, reduce power consumption by disabling the SPI module before executing the WAIT instruction.
10.11.2 Stop Mode
The SPI module is inactive in stop mode. The STOP instruction does not affect SPI register states. SPI operation resumes after an external interrupt. If stop mode is exited by reset, any transfer in progress is aborted, and the SPI is reset.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 108 Freescale Semiconductor
Timer Interface Module (TIM1 and TIM2)
10.12 Timer Interface Module (TIM1 and TIM2)
10.12.1 Wait Mode
The timer interface modules (TIM) remain active in wait mode. Any enabled CPU interrupt request from the TIM can bring the MCU out of wait mode. If TIM functions are not required during wait mode, reduce power consumption by stopping the TIM before executing the WAIT instruction.
10.12.2 Stop Mode
The TIM is inactive in stop mode. The STOP instruction does not affect register states or the state of the TIM counter. TIM operation resumes when the MCU exits stop mode after an external interrupt.
10.13 Timebase Module (TBM)
10.13.1 Wait Mode
The timebase module (TBM) remains active after execution of the WAIT instruction. In wait mode, the timebase register is not accessible by the CPU. If the timebase functions are not required during wait mode, reduce the power consumption by stopping the timebase before enabling the WAIT instruction.
10.13.2 Stop Mode
The timebase module may remain active after execution of the STOP instruction if the oscillator has been enabled to operate during stop mode through the OSCSTOPENB bit in the CONFIG2 register. The timebase module can be used in this mode to generate a periodic wakeup from stop mode. If the oscillator has not been enabled to operate in stop mode, the timebase module will not be active during stop mode. In stop mode, the timebase register is not accessible by the CPU. If the timebase functions are not required during stop mode, reduce the power consumption by stopping the timebase before enabling the STOP instruction.
10.14 Exiting Stop Mode
These events restart the system clocks and load the program counter with the reset vector or with an interrupt vector: * External reset -- A 0 on the RST pin resets the MCU and loads the program counter with the contents of locations $FFFE and $FFFF. * External interrupt -- A high-to-low transition on an external interrupt pin loads the program counter with the contents of locations: - $FFFA and $FFFB; IRQ pin - $FFE0 and $FFE1; keyboard interrupt pins * Low-voltage inhibit (LVI) reset -- A power supply voltage below the VTRIPF voltage resets the MCU and loads the program counter with the contents of locations $FFFE and $FFFF.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 109
Low-Power Modes
*
Timebase module (TBM) interrupt -- A TBM interrupt loads the program counter with the contents of locations $FFDC and $FFDD when the timebase counter has rolled over. This allows the TBM to generate a periodic wakeup from stop mode.
Upon exit from stop mode, the system clocks begin running after an oscillator stabilization delay. A 12-bit stop recovery counter inhibits the system clocks for 4096 CGMXCLK cycles after the reset or external interrupt. The short stop recovery bit, SSREC, in the CONFIG1 register controls the oscillator stabilization delay during stop recovery. Setting SSREC reduces stop recovery time from 4096 CGMXCLK cycles to 32 CGMXCLK cycles. NOTE Use the full stop recovery time (SSREC = 0) in applications that use an external crystal unless the OSCSTOPENB bit is set.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 110 Freescale Semiconductor
Chapter 11 Low-Voltage Inhibit (LVI)
11.1 Introduction
This section describes the low-voltage inhibit (LVI) module, which monitors the voltage on the VDD pin and can force a reset when the VDD voltage falls below the LVI trip falling voltage, VTRIPF.
11.2 Features
Features of the LVI module include: * Programmable LVI reset * Selectable LVI trip voltage * Programmable stop mode operation
11.3 Functional Description
Figure 11-1 shows the structure of the LVI module. The LVI is enabled out of reset. The LVI module contains a bandgap reference circuit and comparator. Clearing the LVI power disable bit, LVIPWRD, enables the LVI to monitor VDD voltage. Clearing the LVI reset disable bit, LVIRSTD, enables the LVI module to generate a reset when VDD falls below a voltage, VTRIPF. Setting the LVI enable in stop mode bit, LVISTOP, enables the LVI to operate in stop mode. Setting the LVI 5-V or 3-V trip point bit, LVI5OR3, enables the trip point voltage, VTRIPF, to be configured for 5-V operation. Clearing the LVI5OR3 bit enables the trip point voltage, VTRIPF, to be configured for 3-V operation. The actual trip points are shown in Chapter 19 Electrical Specifications. NOTE After a power-on reset (POR) the LVI's default mode of operation is 3 V. If a 5-V system is used, the user must set the LVI5OR3 bit to raise the trip point to 5-V operation. Note that this must be done after every power-on reset since the default will revert back to 3-V mode after each power-on reset. If the VDD supply is below the 5-V mode trip voltage but above the 3-V mode trip voltage when POR is released, the part will operate because VTRIPF defaults to 3-V mode after a POR. So, in a 5-V system care must be taken to ensure that VDD is above the 5-V mode trip voltage after POR is released. If the user requires 5-V mode and sets the LVI5OR3 bit after a power-on reset while the VDD supply is not above the VTRIPR for 5-V mode, the microcontroller unit (MCU) will immediately go into reset. The LVI in this case will hold the part in reset until either VDD goes above the rising 5-V trip point, VTRIPR, which will release reset or VDD decreases to approximately 0 V which will re-trigger the power-on reset and reset the trip point to 3-V operation.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 111
Low-Voltage Inhibit (LVI)
LVISTOP, LVIPWRD, LVI5OR3, and LVIRSTD are in the configuration register (CONFIG1). See Figure 5-2. Configuration Register 1 (CONFIG1) for details of the LVI's configuration bits. Once an LVI reset occurs, the MCU remains in reset until VDD rises above a voltage, VTRIPR, which causes the MCU to exit reset. See 14.3.2.5 Low-Voltage Inhibit (LVI) Reset for details of the interaction between the SIM and the LVI. The output of the comparator controls the state of the LVIOUT flag in the LVI status register (LVISR). An LVI reset also drives the RST pin low to provide low-voltage protection to external peripheral devices.
VDD STOP INSTRUCTION LVISTOP FROM CONFIG1 FROM CONFIG1 LVIRSTD LVIPWRD FROM CONFIG LOW VDD DETECTOR VDD > LVITrip = 0 VDD LVITrip = 1 LVIOUT LVI5OR3 FROM CONFIG1 LVI RESET
Figure 11-1. LVI Module Block Diagram
Addr. Register Name Read: LVI Status Register (LVISR) Write: See page 113. Reset: Bit 7 LVIOUT 6 0 5 0 4 0 3 0 2 0 1 0 Bit 0 0
$FE0C
0
0
0
0
0
0
0
0
= Unimplemented
Figure 11-2. LVI I/O Register Summary
11.3.1 Polled LVI Operation
In applications that can operate at VDD levels below the VTRIPF level, software can monitor VDD by polling the LVIOUT bit. In the configuration register, the LVIPWRD bit must be 0 to enable the LVI module, and the LVIRSTD bit must be at 1 to disable LVI resets.
11.3.2 Forced Reset Operation
In applications that require VDD to remain above the VTRIPF level, enabling LVI resets allows the LVI module to reset the MCU when VDD falls below the VTRIPF level. In the configuration register, the LVIPWRD and LVIRSTD bits must be cleared to enable the LVI module and to enable LVI resets.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 112 Freescale Semiconductor
LVI Status Register
11.3.3 Voltage Hysteresis Protection
Once the LVI has triggered (by having VDD fall below VTRIPF), the LVI will maintain a reset condition until VDD rises above the rising trip point voltage, VTRIPR. This prevents a condition in which the MCU is continually entering and exiting reset if VDD is approximately equal to VTRIPF. VTRIPR is greater than VTRIPF by the hysteresis voltage, VHYS.
11.3.4 LVI Trip Selection
The LVI5OR3 bit in the configuration register selects whether the LVI is configured for 5-V or 3-V protection. NOTE The microcontroller is guaranteed to operate at a minimum supply voltage. The trip point (VTRIPF [5 V] or VTRIPF [3 V]) may be lower than this. See Chapter 19 Electrical Specifications for the actual trip point voltages.
11.4 LVI Status Register
The LVI status register (LVISR) indicates if the VDD voltage was detected below the VTRIPF level.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 0 0 $FE0C Bit 7 LVIOUT 6 0 5 0 4 0 3 0 2 0 1 0 Bit 0 0
Figure 11-3. LVI Status Register (LVISR) LVIOUT -- LVI Output Bit This read-only flag becomes set when the VDD voltage falls below the VTRIPF trip voltage (see Table 11-1). Reset clears the LVIOUT bit. Table 11-1. LVIOUT Bit Indication
VDD VDD > VTRIPR VDD < VTRIPF VTRIPF < VDD < VTRIPR LVIOUT 0 1 Previous value
11.5 LVI Interrupts
The LVI module does not generate interrupt requests.
11.6 Low-Power Modes
The STOP and WAIT instructions put the MCU in low power-consumption standby modes.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 113
Low-Voltage Inhibit (LVI)
11.6.1 Wait Mode
If enabled, the LVI module remains active in wait mode. If enabled to generate resets, the LVI module can generate a reset and bring the MCU out of wait mode.
11.6.2 Stop Mode
If enabled in stop mode (LVISTOP bit in the configuration register is set), the LVI module remains active in stop mode. If enabled to generate resets, the LVI module can generate a reset and bring the MCU out of stop mode.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 114 Freescale Semiconductor
Chapter 12 Input/Output (I/O) Ports
12.1 Introduction
Bidirectional input-output (I/O) pins form five parallel ports. All I/O pins are programmable as inputs or outputs. All individual bits within port A, port C, and port D are software configurable with pullup devices if configured as input port bits. The pullup devices are automatically and dynamically disabled when a port bit is switched to output mode. NOTE Connect any unused I/O pins to an appropriate logic level, either VDD or VSS. Although the I/O ports do not require termination for proper operation, termination reduces excess current consumption and the possibility of electrostatic damage. Not all port pins are bonded out in all packages. Care sure be taken to make any unbonded port pins an output to prevent them from being floating inputs.
Addr. Register Name Read: Port A Data Register (PTA) Write: See page 117. Reset: Read: Port B Data Register (PTB) Write: See page 120. Reset: Read: Port C Data Register (PTC) Write: See page 122. Reset: Read: Port D Data Register (PTD) Write: See page 124. Reset: Read: Data Direction Register A (DDRA) Write: See page 118. Reset: Bit 7 0 6 0 5 0 4 0 3 PTA3 2 PTA2 1 PTA1 Bit 0 PTA0
$0000
Unaffected by reset 0 0 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0
$0001
Unaffected by reset 0 0 0 0 0 0 PTC1 PTC0
$0002
Unaffected by reset 0 PTD6 PTD5 PTD4 PTD3 PTD2 PTD1 PTD0
$0003
Unaffected by reset 0 0 0 0 DDRA3 0 DDRA2 0 DDRA1 0 DDRA0 0
$0004
0
0 = Unimplemented
0
0
Figure 12-1. I/O Port Register Summary
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 115
Input/Output (I/O) Ports Addr. Register Name Read: Data Direction Register B (DDRB) Write: See page 120. Reset: Read: Data Direction Register C (DDRC) Write: See page 122. Reset: Read: Data Direction Register D (DDRD) Write: See page 125. Reset: Read: Port E Data Register (PTE) Write: See page 127. Reset: Read: Data Direction Register E (DDRE) Write: See page 128. Reset: Read: Port A Input Pullup Enable Register (PTAPUE) Write: See page 119. Reset: Read: Port C Input Pullup Enable Register (PTCPUE) Write: See page 124. Reset: Read: Port D Input Pullup Enable Register (PTDPUE) Write: See page 127. Reset: Bit 7 0 6 0 5 DDRB5 0 0 4 DDRB4 0 0 3 DDRB3 0 0 2 DDRB2 0 0 1 DDRB1 0 DDRC1 0 DDRD1 0 PTE1 Bit 0 DDRB0 0 DDRC0 0 DDRD0 0 PTE0
$0005
0 0
0 0
$0006
0 0
0 DDRD6 0 0
0 DDRD5 0 0
0 DDRD4 0 0
0 DDRD3 0 0
0 DDRD2 0 0
$0007
0 0
$0008
Unaffected by reset 0 0 0 0 0 0 DDRE1 0 PTAPUE1 0 PTCPUE1 0 PTDPUE1 0 DDRE0 0 PTAPUE0 0 PTCPUE0 0 PTDPUE0 0
$000C
0 0
0 0
0 0
0 0
0 PTAPUE3 0 0
0 PTAPUE2 0 0
$000D
0 0
0 0
0 0
0 0
$000E
0 0
0 PTDPUE6 0 = Unimplemented
0 PTDPUE5 0
0 PTDPUE4 0
0 PTDPUE3 0
0 PTDPUE2 0
$000F
0
Figure 12-1. I/O Port Register Summary (Continued)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 116 Freescale Semiconductor
Port A
Table 12-1. Port Control Register Bits Summary
Port Bit 0 A 1 2 3 0 1 B 2 3 4 5 C 0 1 0 1 2 D 3 4 5 6 E 0 1 DDR DDRA0 DDRA1 DDRA2 DDRA3 DDRB0 DDRB1 DDRB2 DDRB3 DDRB4 DDRB5 DDRC0 DDRC1 DDRD0 DDRD1 DDRD2 DDRD3 DDRD4 DDRD5 DDRD6 DDRE0 DDRE1 TIM1 TIM2 SCI ELS0B:ELS0A ELS1B:ELS1A ELS0B:ELS0A ENSCI SPI SPE ADC KBD Module Control KBIE0 KBIE1 KBIE2 KBIE3 ADCH4:0 ADCH4:0 ADCH4:0 ADCH4:0 ADCH4:0 ADCH4:0 Pin PTA0/KBD0 PTA1/KBD1 PTA2/KBD2 PTA3/KBD3 PTB0/AD0 PTB1/AD1 PTB2/AD2 PTB3/AD3 PTB4/AD4 PTB5/AD5 PTC0 PTC1 PTD0/SS PTD1/MISO PTD2/MOSI PTD3/SPSCK PTD4/T1CH0 PTD5/T1CH1 PTD6/T2CH0 PTE0/TxD PTE1/RxD
12.2 Port A
Port A is an 4-bit special-function port that shares all four of its pins with the keyboard interrupt (KBI) module. Port A also has software configurable pullup devices if configured as an input port.
12.2.1 Port A Data Register
The port A data register (PTA) contains a data latch for each of the four port A pins.
Address: Read: Write: Reset: Alternative Function: = Unimplemented $0000 Bit 7 0 6 0 5 0 4 0 3 PTA3 2 PTA2 1 PTA1 Bit 0 PTA0
Unaffected by reset KBD3 KBD2 KBD1 KBD0
Figure 12-2. Port A Data Register (PTA)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 117
Input/Output (I/O) Ports
PTA3-PTA0 -- Port A Data Bits These read/write bits are software programmable. Data direction of each port A pin is under the control of the corresponding bit in data direction register A. Reset has no effect on port A data. KBD3-KBD0 -- Keyboard Inputs The keyboard interrupt enable bits, KBIE3-KBIE0, in the keyboard interrupt control register (KBICR) enable the port A pins as external interrupt pins. See Chapter 9 Keyboard Interrupt Module (KBI).
12.2.2 Data Direction Register A
Data direction register A (DDRA) determines whether each port A pin is an input or an output. Writing a 1 to a DDRA bit enables the output buffer for the corresponding port A pin; a 0 disables the output buffer.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 $0004 Bit 7 0 6 0 5 0 4 0 3 DDRA3 0 2 DDRA2 0 1 DDRA1 0 Bit 0 DDRA0 0
Figure 12-3. Data Direction Register A (DDRA) DDRA3-DDRA0 -- Data Direction Register A Bits These read/write bits control port A data direction. Reset clears DDRA3-DDRA0, configuring all port A pins as inputs. 1 = Corresponding port A pin configured as output 0 = Corresponding port A pin configured as input NOTE Avoid glitches on port A pins by writing to the port A data register before changing data direction register A bits from 0 to 1. Figure 12-4 shows the port A I/O logic.
VDD PTAPUEx
READ DDRA ($0004) WRITE DDRA ($0004) RESET WRITE PTA ($0000) DDRAx
INTERNAL PULLUP DEVICE
INTERNAL DATA BUS
PTAx
PTAx
READ PTA ($0000)
Figure 12-4. Port A I/O Circuit
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 118 Freescale Semiconductor
Port A
When bit DDRAx is a 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a 0, reading address $0000 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 12-2 summarizes the operation of the port A pins. Table 12-2. Port A Pin Functions
PTAPUE Bit 1 0 X DDRA Bit 0 0 1 PTA Bit X(1) X X I/O Pin Mode Input, VDD
(2)
Accesses to DDRA Read/Write DDRA3-DDRA0 DDRA3-DDRA0 DDRA3-DDRA0
Accesses to PTA Read Pin Pin PTA3-PTA0 Write PTA3-PTA0(3) PTA3-PTA0(3) PTA3-PTA0
Input, Hi-Z(4) Output
1. X = Don't care 2. I/O pin pulled up to VDD by internal pullup device 3. Writing affects data register, but does not affect input. 4. Hi-Z = High impedance
12.2.3 Port A Input Pullup Enable Register
The port A input pullup enable register (PTAPUE) contains a software configurable pullup device for each of the four port A pins. Each bit is individually configurable and requires that the data direction register, DDRA, bit be configured as an input. Each pullup is automatically and dynamically disabled when a port bit's DDRA is configured for output mode.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 $000D Bit 7 0 6 0 5 0 4 0 3 PTAPUE3 0 2 PTAPUE2 0 1 PTAPUE1 0 Bit 0 PTAPUE0 0
Figure 12-5. Port A Input Pullup Enable Register (PTAPUE) PTAPUE3-PTAPUE0 -- Port A Input Pullup Enable Bits These writeable bits are software programmable to enable pullup devices on an input port bit. 1 = Corresponding port A pin configured to have internal pullup 0 = Corresponding port A pin has internal pullup disconnected
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 119
Input/Output (I/O) Ports
12.3 Port B
Port B is a 6-bit special-function port that shares all six of its pins with the analog-to-digital converter (ADC) module.
12.3.1 Port B Data Register
The port B data register (PTB) contains a data latch for each of the six port pins.
Address: Read: Write: Reset: Alternative Function: AD5 = Unimplemented $0001 Bit 7 0 6 0 5 PTB5 4 PTB4 3 PTB3 2 PTB2 1 PTB1 Bit 0 PTB0
Unaffected by reset AD4 AD3 AD2 AD1 AD0
Figure 12-6. Port B Data Register (PTB) PTB5-PTB0 -- Port B Data Bits These read/write bits are software-programmable. Data direction of each port B pin is under the control of the corresponding bit in data direction register B. Reset has no effect on port B data. AD5-AD0 -- Analog-to-Digital Input Bits AD5-AD0 are pins used for the input channels to the analog-to-digital converter module. The channel select bits in the ADC status and control register define which port B pin will be used as an ADC input and overrides any control from the port I/O logic by forcing that pin as the input to the analog circuitry. NOTE Care must be taken when reading port B while applying analog voltages to AD5-AD0 pins. If the appropriate ADC channel is not enabled, excessive current drain may occur if analog voltages are applied to the PTBx/ADx pin, while PTB is read as a digital input. Those ports not selected as analog input channels are considered digital I/O ports. PTB4 and PTB5 are not available in 28-pin DIP and SOIC packages.
12.3.2 Data Direction Register B
Data direction register B (DDRB) determines whether each port B pin is an input or an output. Writing a 1 to a DDRB bit enables the output buffer for the corresponding port B pin; a 0 disables the output buffer.
Address: Read: Write: Reset: 0 0 = Unimplemented $0005 Bit 7 0 6 0 5 DDRB5 0 4 DDRB4 0 3 DDRB3 0 2 DDRB2 0 1 DDRB1 0 Bit 0 DDRB0 0
Figure 12-7. Data Direction Register B (DDRB)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 120 Freescale Semiconductor
Port B
DDRB5-DDRB0 -- Data Direction Register B Bits These read/write bits control port B data direction. Reset clears DDRB5-DDRB0, configuring all port B pins as inputs. 1 = Corresponding port B pin configured as output 0 = Corresponding port B pin configured as input NOTE Avoid glitches on port B pins by writing to the port B data register before changing data direction register B bits from 0 to 1. For those devices packaged in a 28-pin DIP and SOIC package, PTB5,4 are not connected. Set DDRB5,4 to a 1 to configure PTB5,4 as outputs. Figure 12-8 shows the port B I/O logic.
READ DDRB ($0005) WRITE DDRB ($0005) INTERNAL DATA BUS RESET WRITE PTB ($0001) DDRBx
PTBx
PTBx
READ PTB ($0001)
Figure 12-8. Port B I/O Circuit When bit DDRBx is a 1, reading address $0001 reads the PTBx data latch. When bit DDRBx is a 0, reading address $0001 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 12-3 summarizes the operation of the port B pins. Table 12-3. Port B Pin Functions
DDRB Bit 0 1 PTB Bit X(1) X I/O Pin Mode Input, Hi-Z(2) Output Accesses to DDRB Read/Write DDRB5-DDRB0 DDRB5-DDRB0 Read Pin PTB5-PTB0 Accesses to PTB Write PTB5-PTB0(3) PTB5-PTB0
1. X = Don't care 2. Hi-Z = High impedance 3. Writing affects data register, but does not affect input.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 121
Input/Output (I/O) Ports
12.4 Port C
Port C is a 2-bit, general-purpose bidirectional I/O port. Port C also has software configurable pullup devices if configured as an input port.
12.4.1 Port C Data Register
The port C data register (PTC) contains a data latch for each of the two port C pins.
Address: Read: Write: Reset: = Unimplemented Unaffected by reset $0002 Bit 7 0 6 0 5 0 4 0 3 0 2 0 1 PTC1 Bit 0 PTC0
Figure 12-9. Port C Data Register (PTC) PTC1-PTC0 -- Port C Data Bits These read/write bits are software-programmable. Data direction of each port C pin is under the control of the corresponding bit in data direction register C. Reset has no effect on port C data. NOTE PTC is not available in a 28-pin DIP or SOIC package.
12.4.2 Data Direction Register C
Data direction register C (DDRC) determines whether each port C pin is an input or an output. Writing a 1 to a DDRC bit enables the output buffer for the corresponding port C pin; a 0 disables the output buffer.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 $0006 Bit 7 0 6 0 5 0 4 0 3 0 2 0 1 DDRC1 0 Bit 0 DDRC0 0
Figure 12-10. Data Direction Register C (DDRC) DDRC1-DDRC0 -- Data Direction Register C Bits These read/write bits control port C data direction. Reset clears DDRC1-DDRC0, configuring all port C pins as inputs. 1 = Corresponding port C pin configured as output 0 = Corresponding port C pin configured as input NOTE Avoid glitches on port C pins by writing to the port C data register before changing data direction register C bits from 0 to 1. For those devices packaged in a 28-pin DIP or SOIC package, PTC1-PTC0 are not connected. Set DDRC1 and DDRC0 to a 1 to configure PTC1-PTC0 as outputs.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 122 Freescale Semiconductor
Port C
Figure 12-11 shows the port C I/O logic.
VDD PTCPUEx
READ DDRC ($0006) WRITE DDRC ($0006) INTERNAL DATA BUS RESET WRITE PTC ($0002) DDRCx
INTERNAL PULLUP DEVICE
PTCx
PTCx
READ PTC ($0002)
Figure 12-11. Port C I/O Circuit When bit DDRCx is a 1, reading address $0002 reads the PTCx data latch. When bit DDRCx is a 0, reading address $0002 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 12-4 summarizes the operation of the port C pins. Table 12-4. Port C Pin Functions
PTCPUE Bit 1 0 X DDRC Bit 0 0 1 PTC Bit X(1) X X I/O Pin Mode Input, VDD
(2)
Accesses to DDRC Read/Write DDRC1-DDRC0 DDRC1-DDRC0 DDRC1-DDRC0
Accesses to PTC Read Pin Pin PTC1-PTC0 Write PTC1-PTC0(3) PTC1-PTC0(3) PTC1-PTC0
Input, Hi-Z(4) Output
1. X = Don't care 2. I/O pin pulled up to VDD by internal pullup device. 3. Writing affects data register, but does not affect input. 4. Hi-Z = High impedance
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 123
Input/Output (I/O) Ports
12.4.3 Port C Input Pullup Enable Register
The port C input pullup enable register (PTCPUE) contains a software configurable pullup device for each of the two port C pins. Each bit is individually configurable and requires that the data direction register, DDRC, bit be configured as an input. Each pullup is automatically and dynamically disabled when a port bit's DDRC is configured for output mode.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 $000E Bit 7 0 6 0 5 0 4 0 3 0 2 0 1 PTCPUE1 0 Bit 0 PTCPUE0 0
Figure 12-12. Port C Input Pullup Enable Register (PTCPUE) PTCPUE1-PTCPUE0 -- Port C Input Pullup Enable Bits These writeable bits are software programmable to enable pullup devices on an input port bit. 1 = Corresponding port C pin configured to have internal pullup 0 = Corresponding port C pin internal pullup disconnected
12.5 Port D
Port D is a 7-bit special-function port that shares four of its pins with the serial peripheral interface (SPI) module and three of its pins with two timer interface (TIM1 and TIM2) modules. Port D also has software configurable pullup devices if configured as an input port.
12.5.1 Port D Data Register
The port D data register (PTD) contains a data latch for each of the seven port D pins.
Address: Read: Write: Reset: Alternative Function: T2CH0 T1CH1 $0003 Bit 7 0 6 PTD6 5 PTD5 4 PTD4 3 PTD3 2 PTD2 1 PTD1 Bit 0 PTD0
Unaffected by reset T1CH0 SPSCK MOSI MISO SS
= Unimplemented
Figure 12-13. Port D Data Register (PTD) PTD6-PTD0 -- Port D Data Bits These read/write bits are software-programmable. Data direction of each port D pin is under the control of the corresponding bit in data direction register D. Reset has no effect on port D data. T2CH0 -- Timer 2 Channel I/O Bit The PTD6/T2CH0 pin is a TIM2 input capture/output compare pin. The edge/level select bits, ELSxB:ELSxA, determine whether the PTD6/T2CH0 pin is a timer channel I/O pin or a general-purpose I/O pin. See Chapter 17 Timer Interface Module (TIM1 and TIM2).
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 124 Freescale Semiconductor
Port D
T1CH1 and T1CH0 -- Timer 1 Channel I/O Bits The PTD5/T1CH1-PTD4/T1CH0 pins are the TIM1 input capture/output compare pins. The edge/level select bits, ELSxB and ELSxA, determine whether the PTD5/T1CH1-PTD4/T1CH0 pins are timer channel I/O pins or general-purpose I/O pins. See Chapter 17 Timer Interface Module (TIM1 and TIM2). SPSCK -- SPI Serial Clock The PTD3/SPSCK pin is the serial clock input of the SPI module. When the SPE bit is clear, the PTD3/SPSCK pin is available for general-purpose I/O. MOSI -- Master Out/Slave In The PTD2/MOSI pin is the master out/slave in terminal of the SPI module. When the SPE bit is clear, the PTD2/MOSI pin is available for general-purpose I/O. MISO -- Master In/Slave Out The PTD1/MISO pin is the master in/slave out terminal of the SPI module. When the SPI enable bit, SPE, is clear, the SPI module is disabled, and the PTD0/SS pin is available for general-purpose I/O. Data direction register D (DDRD) does not affect the data direction of port D pins that are being used by the SPI module. However, the DDRD bits always determine whether reading port D returns the states of the latches or the states of the pins. See Table 12-5. SS -- Slave Select The PTD0/SS pin is the slave select input of the SPI module. When the SPE bit is clear, or when the SPI master bit, SPMSTR, is set, the PTD0/SS pin is available for general-purpose I/O. When the SPI is enabled, the DDRB0 bit in data direction register B (DDRB) has no effect on the PTD0/SS pin.
12.5.2 Data Direction Register D
Data direction register D (DDRD) determines whether each port D pin is an input or an output. Writing a 1 to a DDRD bit enables the output buffer for the corresponding port D pin; a 0 disables the output buffer.
Address: Read: Write: Reset: 0 $0007 Bit 7 0 6 DDRD6 0 = Unimplemented 5 DDRD5 0 4 DDRD4 0 3 DDRD3 0 2 DDRD2 0 1 DDRD1 0 Bit 0 DDRD0 0
Figure 12-14. Data Direction Register D (DDRD) DDRD6-DDRD0 -- Data Direction Register D Bits These read/write bits control port D data direction. Reset clears DDRD6-DDRD0, configuring all port D pins as inputs. 1 = Corresponding port D pin configured as output 0 = Corresponding port D pin configured as input NOTE Avoid glitches on port D pins by writing to the port D data register before changing data direction register D bits from 0 to 1.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 125
Input/Output (I/O) Ports
Figure 12-15 shows the port D I/O logic.
VDD PTDPUEx
READ DDRD ($0007) WRITE DDRD ($0007) RESET INTERNAL DATA BUS WRITE PTD ($0003) DDRDx
INTERNAL PULLUP DEVICE
PTDx
PTDx
READ PTD ($0003)
Figure 12-15. Port D I/O Circuit When bit DDRDx is a 1, reading address $0003 reads the PTDx data latch. When bit DDRDx is a 0, reading address $0003 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 12-5 summarizes the operation of the port D pins. Table 12-5. Port D Pin Functions
PTDPUE Bit 1 0 X DDRD Bit 0 0 1 PTD Bit X(1) X X I/O Pin Mode Input, VDD(2) Input, Hi-Z(4) Output Accesses to DDRD Read/Write DDRD6-DDRD0 DDRD6-DDRD0 DDRD6-DDRD0 Accesses to PTD Read Pin Pin PTD6-PTD0 Write PTD6-PTD0(3) PTD6-PTD0(3) PTD6-PTD0
1. X = Don't care 2. I/O pin pulled up to VDD by internal pullup device. 3. Writing affects data register, but does not affect input. 4. Hi-Z = High impedance
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 126 Freescale Semiconductor
Port E
12.5.3 Port D Input Pullup Enable Register
The port D input pullup enable register (PTDPUE) contains a software configurable pullup device for each of the seven port D pins. Each bit is individually configurable and requires that the data direction register, DDRD, bit be configured as an input. Each pullup is automatically and dynamically disabled when a port bit's DDRD is configured for output mode.
Address: Read: Write: Reset: 0 $000F Bit 7 0 6 PTDPUE6 0 5 PTDPUE5 0 4 PTDPUE4 0 3 PTDPUE3 0 2 PTDPUE2 0 1 PTDPUE1 0 Bit 0 PTDPUE0 0
Figure 12-16. Port D Input Pullup Enable Register (PTDPUE) PTDPUE6-PTDPUE0 -- Port D Input Pullup Enable Bits These writable bits are software programmable to enable pullup devices on an input port bit. 1 = Corresponding port D pin configured to have internal pullup 0 = Corresponding port D pin has internal pullup disconnected
12.6 Port E
Port E is a 2-bit special-function port that shares two of its pins with the serial communications interface (SCI) module.
12.6.1 Port E Data Register
The port E data register contains a data latch for each of the two port E pins.
Address: Read: Write: Reset: Alternative Function: = Unimplemented Unaffected by reset RxD TxD $0008 Bit 7 0 6 0 5 0 4 0 3 0 2 0 1 PTE1 Bit 0 PTE0
Figure 12-17. Port E Data Register (PTE) PTE1-PTE0 -- Port E Data Bits These read/write bits are software-programmable. Data direction of each port E pin is under the control of the corresponding bit in data direction register E. Reset has no effect on port E data. NOTE Data direction register E (DDRE) does not affect the data direction of port E pins that are being used by the ESCI module. However, the DDRE bits always determine whether reading port E returns the states of the latches or the states of the pins. See Table 12-6.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 127
Input/Output (I/O) Ports
RxD -- SCI Receive Data Input The PTE1/RxD pin is the receive data input for the ESCI module. When the enable SCI bit, ENSCI, is clear, the ESCI module is disabled, and the PTE1/RxD pin is available for general-purpose I/O. See Chapter 13 Serial Communications Interface (SCI) Module. TxD -- SCI Transmit Data Output The PTE0/TxD pin is the transmit data output for the ESCI module. When the enable SCI bit, ENSCI, is clear, the ESCI module is disabled, and the PTE0/TxD pin is available for general-purpose I/O. See Chapter 13 Serial Communications Interface (SCI) Module.
12.6.2 Data Direction Register E
Data direction register E (DDRE) determines whether each port E pin is an input or an output. Writing a 1 to a DDRE bit enables the output buffer for the corresponding port E pin; a 0 disables the output buffer.
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 $000C Bit 7 0 6 0 5 0 4 0 3 0 2 0 1 DDRE1 0 Bit 0 DDRE0 0
Figure 12-18. Data Direction Register E (DDRE) DDRE1-DDRE0 -- Data Direction Register E Bits These read/write bits control port E data direction. Reset clears DDRE1-DDRE0, configuring all port E pins as inputs. 1 = Corresponding port E pin configured as output 0 = Corresponding port E pin configured as input NOTE Avoid glitches on port E pins by writing to the port E data register before changing data direction register E bits from 0 to 1. Figure 12-19 shows the port E I/O logic.
READ DDRE ($000C) WRITE DDRE ($000C) INTERNAL DATA BUS RESET WRITE PTE ($0008) DDREx
PTEx
PTEx
READ PTE ($0008)
Figure 12-19. Port E I/O Circuit
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 128 Freescale Semiconductor
Port E
When bit DDREx is a 1, reading address $0008 reads the PTEx data latch. When bit DDREx is a 0, reading address $0008 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 12-6 summarizes the operation of the port E pins. Table 12-6. Port E Pin Functions
DDRE Bit 0 1 PTE Bit X(1) X I/O Pin Mode Input, Hi-Z(2) Output Accesses to DDRE Read/Write DDRE1-DDRE0 DDRE1-DDRE0 Read Pin PTE1-PTE0 Accesses to PTE Write PTE1-PTE0(3) PTE1-PTE0
1. X = Don't care 2. Hi-Z = High impedance 3. Writing affects data register, but does not affect input.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 129
Input/Output (I/O) Ports
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 130 Freescale Semiconductor
Chapter 13 Serial Communications Interface (SCI) Module
13.1 Introduction
This section describes the serial communications interface (SCI) module, which allows high-speed asynchronous communications with peripheral devices and other MCUs.
13.2 Features
Features of the SCI module include: * Full-duplex operation * Standard mark/space non-return-to-zero (NRZ) format * 32 programmable baud rates * Programmable 8-bit or 9-bit character length * Separately enabled transmitter and receiver * Separate receiver and transmitter CPU interrupt requests * Programmable transmitter output polarity * Two receiver wakeup methods: - Idle line wakeup - Address mark wakeup * Interrupt-driven operation with eight interrupt flags: - Transmitter empty - Transmission complete - Receiver full - Idle receiver input - Receiver overrun - Noise error - Framing error - Parity error * Receiver framing error detection * Hardware parity checking * 1/16 bit-time noise detection * Mask option register bit, SCIBDSRC, to allow selection of baud rate clock source
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 131
Serial Communications Interface (SCI) Module
INTERNAL BUS M68HC08 CPU PORTA DDRA CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) PROGRAMMABLE TIMEBASE MODULE SINGLE BREAKPOINT BREAK MODULE DUAL VOLTAGE LOW-VOLTAGE INHIBIT MODULE 4-BIT KEYBOARD INTERRUPT MODULE PORTC DDRC 2-CHANNEL TIMER INTERFACE MODULE 1 1-CHANNEL TIMER INTERFACE MODULE 2 SERIAL COMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE RST(3) IRQ(3) VDDAD/VREFH VSSAD/VREFL SYSTEM INTEGRATION MODULE SINGLE EXTERNAL INTERRUPT MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE POWER-ON RESET MODULE VDD VSS VDDA VSSA SERIAL PERIPHERAL INTERFACE MODULE MONITOR MODULE MEMORY MAP MODULE CONFIGURATION REGISTER 1 MODULE CONFIGURATION REGISTER 2 MODULE PORTB DDRB PTA3/KBD3- PTA0/KBD0(1)
CONTROL AND STATUS REGISTERS -- 64 BYTES MC68HC908GR8A USER FLASH -- 7680 BYTES MC68HC908GR4A USER FLASH -- 4096 BYTES USER RAM -- 384 BYTES MONITOR ROM -- 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM -- 544 BYTES USER FLASH VECTOR SPACE -- 36 BYTES CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 1-8-MHz OSCILLATOR PHASE LOCKED LOOP
PTB5/AD5 PTB4/AD4 PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0
PTC1(1), (2) PTC0(1), (2)
PTD6/T2CH0(1) PTD5/T1CH1(1) PTD4/T1CH0(1) PTD3/SPSCK(1) PTD2/MOSI(1) PTD1/MISO(1) PTD0/SS(1)
PORTE
PORTD
DDRD
PTE1/RxD PTE0/TxD
DDRE
SECURITY MODULE
POWER
MONITOR MODE ENTRY MODULE
1. Ports are software configurable with pullup device if input port. 2. Higher current drive port pins 3. Pin contains integrated pullup device
Figure 13-1. Block Diagram Highlighting SCI Block and Pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 132 Freescale Semiconductor
Pin Name Conventions
13.3 Pin Name Conventions
The generic names of the SCI I/O pins are: * RxD (receive data) * TxD (transmit data) SCI I/O (input/output) lines are implemented by sharing parallel I/O port pins. The full name of an SCI input or output reflects the name of the shared port pin. Table 13-1 shows the full names and the generic names of the SCI I/O pins. The generic pin names appear in the text of this section. Table 13-1. Pin Name Conventions
Generic Pin Names: Full Pin Names: RxD PTE1/RxD TxD PTE0/TxD
13.4 Functional Description
Figure 13-3 shows the structure of the SCI module. The SCI allows full-duplex, asynchronous, NRZ serial communication among the MCU and remote devices, including other MCUs. The transmitter and receiver of the SCI operate independently, although they use the same baud rate generator. During normal operation, the CPU monitors the status of the SCI, writes the data to be transmitted, and processes received data. The baud rate clock source for the SCI can be selected via the configuration bit, SCIBDSRC, of the CONFIG2 register ($001E). Source selection values are shown in Figure 13-3. 13.4.1 Data Format The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 13-2.
8-BIT DATA FORMAT BIT M IN SCC1 CLEAR START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 PARITY BIT BIT 7 STOP BIT
NEXT START BIT
START BIT
9-BIT DATA FORMAT BIT M IN SCC1 SET BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7
PARITY BIT BIT 8 STOP BIT
NEXT START BIT
Figure 13-2. SCI Data Formats
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 133
Serial Communications Interface (SCI) Module
INTERNAL BUS
SCI DATA REGISTER TRANSMITTER INTERRUPT CONTROL RECEIVE SHIFT REGISTER ERROR INTERRUPT CONTROL RECEIVER INTERRUPT CONTROL
SCI DATA REGISTER TRANSMIT SHIFT REGISTER TXINV
PTE1/RxD
PTE0/TxD
SCTIE TCIE SCRIE ILIE TE RE RWU SBK SCTE TC SCRF IDLE OR NF FE PE LOOPS LOOPS WAKEUP CONTROL SCIBDSRC FROM CONFIG2 A SL X B RECEIVE CONTROL BKF RPF BAUD DIVIDER FLAG CONTROL M WAKE ILTY CGMXCLK BUS CLOCK /4 PRESCALER PEN PTY DATA SELECTION CONTROL ENSCI
R8 T8
ORIE NEIE FEIE PEIE
TRANSMIT CONTROL
ENSCI
SL = 0 => SCICLK = CGMXCLK SL = 1 => SCICLK = BUS CLOCK
/16
Figure 13-3. SCI Module Block Diagram
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 134 Freescale Semiconductor
Functional Description Addr. $0013 Register Name SCI Control Register 1 Read: (SCC1) Write: See page 146. Reset: SCI Control Register 2 Read: (SCC2) Write: See page 148. Reset: SCI Control Register 3 Read: (SCC3) Write: See page 149. Reset: SCI Status Register 1 Read: (SCS1) Write: See page 151. Reset: SCI Status Register 2 Read: (SCS2) Write: See page 153. Reset: SCI Data Register Read: (SCDR) Write: See page 154. Reset: SCI Baud Rate Register Read: (SCBR) Write: See page 154. Reset: Bit 7 LOOPS 0 SCTIE 0 R8 U SCTE 1 6 ENSCI 0 TCIE 0 T8 U TC 1 5 TXINV 0 SCRIE 0 R 0 SCRF 0 4 M 0 ILIE 0 R 0 IDLE 0 3 WAKE 0 TE 0 ORIE 0 OR 0 2 ILTY 0 RE 0 NEIE 0 NF 0 1 PEN 0 RWU 0 FEIE 0 FE 0 BKF 0 R7 T7 0 R6 T6 0 R5 T5 0 R4 T4 0 R3 T3 0 R2 T2 0 R1 T1 Bit 0 PTY 0 SBK 0 PEIE 0 PE 0 RPF 0 R0 T0
$0014
$0015
$0016
$0017
$0018
Unaffected by reset SCP1 0 0 = Unimplemented 0 SCP0 0 R R 0 = Reserved SCR2 0 SCR1 0 U = Unaffected SCR0 0
$0019
Figure 13-4. SCI I/O Register Summary 13.4.2 Transmitter Figure 13-5 shows the structure of the SCI transmitter. The baud rate clock source for the SCI can be selected via the configuration bit, SCIBDSRC. Source selection values are shown in Figure 13-5. 13.4.2.1 Character Length The transmitter can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1 (SCC1) determines character length. When transmitting 9-bit data, bit T8 in SCI control register 3 (SCC3) is the ninth bit (bit 8).
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 135
Serial Communications Interface (SCI) Module
SCIBDSRC FROM CONFIG2
CGMXCLK BUS CLOCK SL X INTERNAL BUS
SL = 0 => SCICLK = CGMXCLK SL = 1 => SCICLK = BUS CLOCK
/4 SCP1 SCP0 SCR2 SCR1 SCR0
PRESCALER
BAUD DIVIDER
/ 16
SCI DATA REGISTER
11-BIT TRANSMIT SHIFT REGISTER 8 7 6 5 4 3 2 1 0
H
START L
STOP
PTE0/TxD
TXINV M
MSB
PREAMBLE ALL 1s
PTY
SHIFT ENABLE
PEN
PARITY GENERATION
LOAD FROM SCDR
TRANSMITTER CPU INTERRUPT REQUEST
T8
TRANSMITTER CONTROL LOGIC SCTE SCTIE TC TCIE
SCTE SCTIE TC TCIE
LOOPS ENSCI TE
Figure 13-5. SCI Transmitter
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 136 Freescale Semiconductor
BREAK ALL 0s SBK
Functional Description
13.4.2.2 Character Transmission During an SCI transmission, the transmit shift register shifts a character out to the PTE0/TxD pin. The SCI data register (SCDR) is the write-only buffer between the internal data bus and the transmit shift register. To initiate an SCI transmission: 1. Enable the SCI by writing a 1 to the enable SCI bit (ENSCI) in SCI control register 1 (SCC1). 2. Enable the transmitter by writing a 1 to the transmitter enable bit (TE) in SCI control register 2 (SCC2). 3. Clear the SCI transmitter empty bit by first reading SCI status register 1 (SCS1) and then writing to the SCDR. 4. Repeat step 3 for each subsequent transmission. At the start of a transmission, transmitter control logic automatically loads the transmit shift register with a preamble of 1s. After the preamble shifts out, control logic transfers the SCDR data into the transmit shift register. A 0 start bit automatically goes into the least significant bit position of the transmit shift register. A 1 stop bit goes into the most significant bit position. The SCI transmitter empty bit, SCTE, in SCS1 becomes set when the SCDR transfers a byte to the transmit shift register. The SCTE bit indicates that the SCDR can accept new data from the internal data bus. If the SCI transmit interrupt enable bit, SCTIE, in SCC2 is also set, the SCTE bit generates a transmitter CPU interrupt request. When the transmit shift register is not transmitting a character, the PTE0/TxD pin goes to the idle condition, 1. If at any time software clears the ENSCI bit in SCI control register 1 (SCC1), the transmitter and receiver relinquish control of the port E pins. 13.4.2.3 Break Characters Writing a 1 to the send break bit, SBK, in SCC2 loads the transmit shift register with a break character. A break character contains all 0s and has no start, stop, or parity bit. Break character length depends on the M bit in SCC1. As long as SBK is 1, transmitter logic continuously loads break characters into the transmit shift register. After software clears the SBK bit, the shift register finishes transmitting the last break character and then transmits at least one 1. The automatic 1 at the end of a break character guarantees the recognition of the start bit of the next character. The SCI recognizes a break character when a start bit is followed by eight or nine 0 data bits and a 0 where the stop bit should be. Receiving a break character has these effects on SCI registers: * Sets the framing error bit (FE) in SCS1 * Sets the SCI receiver full bit (SCRF) in SCS1 * Clears the SCI data register (SCDR) * Clears the R8 bit in SCC3 * Sets the break flag bit (BKF) in SCS2 * May set the overrun (OR), noise flag (NF), parity error (PE), or reception in progress flag (RPF) bits
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 137
Serial Communications Interface (SCI) Module
13.4.2.4 Idle Characters An idle character contains all 1s and has no start, stop, or parity bit. Idle character length depends on the M bit in SCC1. The preamble is a synchronizing idle character that begins every transmission. If the TE bit is cleared during a transmission, the PTE0/TxD pin becomes idle after completion of the transmission in progress. Clearing and then setting the TE bit during a transmission queues an idle character to be sent after the character currently being transmitted. NOTE When queueing an idle character, return the TE bit to 1 before the stop bit of the current character shifts out to the TxD pin. Setting TE after the stop bit appears on TxD causes data previously written to the SCDR to be lost. Toggle the TE bit for a queued idle character when the SCTE bit becomes set and just before writing the next byte to the SCDR. 13.4.2.5 Inversion of Transmitted Output The transmit inversion bit (TXINV) in SCI control register 1 (SCC1) reverses the polarity of transmitted data. All transmitted values, including idle, break, start, and stop bits, are inverted when TXINV is 1. See 13.8.1 SCI Control Register 1. 13.4.2.6 Transmitter Interrupts These conditions can generate CPU interrupt requests from the SCI transmitter: * SCI transmitter empty (SCTE) -- The SCTE bit in SCS1 indicates that the SCDR has transferred a character to the transmit shift register. SCTE can generate a transmitter CPU interrupt request. Setting the SCI transmit interrupt enable bit, SCTIE, in SCC2 enables the SCTE bit to generate transmitter CPU interrupt requests. * Transmission complete (TC) -- The TC bit in SCS1 indicates that the transmit shift register and the SCDR are empty and that no break or idle character has been generated. The transmission complete interrupt enable bit, TCIE, in SCC2 enables the TC bit to generate transmitter CPU interrupt requests. 13.4.3 Receiver Figure 13-6 shows the structure of the SCI receiver. 13.4.3.1 Character Length The receiver can accommodate either 8-bit or 9-bit data. The state of the M bit in SCI control register 1 (SCC1) determines character length. When receiving 9-bit data, bit R8 in SCI control register 2 (SCC2) is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7). 13.4.3.2 Character Reception During an SCI reception, the receive shift register shifts characters in from the PTE1/RxD pin. The SCI data register (SCDR) is the read-only buffer between the internal data bus and the receive shift register. After a complete character shifts into the receive shift register, the data portion of the character transfers to the SCDR. The SCI receiver full bit, SCRF, in SCI status register 1 (SCS1) becomes set, indicating that the received byte can be read. If the SCI receive interrupt enable bit, SCRIE, in SCC2 is also set, the SCRF bit generates a receiver CPU interrupt request.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 138 Freescale Semiconductor
Functional Description
INTERNAL BUS SCR2 SCP1 SCP0 CGMXCLK BUS CLOCK SL X /4 PRESCALER BAUD DIVIDER SCR1 SCR0 START 0 L RWU / 16 DATA RECOVERY ALL 0s MSB SCI DATA REGISTER
SCIBDSRC FROM CONFIG2
SL = 0 => SCICLK = CGMXCLK SL = 1 => SCICLK = BUS CLOCK
11-BIT RECEIVE SHIFT REGISTER 8 7 6 5 4 3 2 1
PTE1/RxD
BKF RPF
M WAKE ILTY PEN ERROR CPU INTERRUPT REQUEST PTY WAKEUP LOGIC PARITY CHECKING
STOP H
SCRF IDLE R8
OR ORIE NF NEIE FE FEIE PE PEIE
OR ORIE NF NEIE FE FEIE PE PEIE
Figure 13-6. SCI Receiver Block Diagram
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 139
Serial Communications Interface (SCI) Module
13.4.3.3 Data Sampling The receiver samples the PTE1/RxD pin at the RT clock rate. The RT clock is an internal signal with a frequency 16 times the baud rate. To adjust for baud rate mismatch, the RT clock is resynchronized at the following times (see Figure 13-7): * After every start bit * After the receiver detects a data bit change from 1 to 0 (after the majority of data bit samples at RT8, RT9, and RT10 returns a valid 1 and the majority of the next RT8, RT9, and RT10 samples returns a valid 0) To locate the start bit, data recovery logic does an asynchronous search for a 0 preceded by three 1s. When the falling edge of a possible start bit occurs, the RT clock begins to count to 16.
PTE1/RxD START BIT LSB
SAMPLES
START BIT QUALIFICATION
START BIT VERIFICATION
DATA SAMPLING
RT CLOCK RT10 RT11 RT12 RT13 RT14 RT15 RT CLOCK STATE RT CLOCK RESET RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT2 RT3 RT4 RT5 RT6 RT7 RT8 RT9 RT16 RT1 RT2 RT3 RT4
Figure 13-7. Receiver Data Sampling To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7. Table 13-2 summarizes the results of the start bit verification samples. Table 13-2. Start Bit Verification
RT3, RT5, and RT7 Samples 000 001 010 011 100 101 110 111 Start Bit Verification Yes Yes Yes No Yes No No No Noise Flag 0 1 1 0 1 0 0 0
Start bit verification is not successful if any two of the three verification samples are 1s. If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 140 Freescale Semiconductor
Functional Description
To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 13-3 summarizes the results of the data bit samples. Table 13-3. Data Bit Recovery
RT8, RT9, and RT10 Samples 000 001 010 011 100 101 110 111 Data Bit Determination 0 0 0 1 0 1 1 1 Noise Flag 0 1 1 1 1 1 1 0
NOTE The RT8, RT9, and RT10 samples do not affect start bit verification. If any or all of the RT8, RT9, and RT10 start bit samples are 1s following a successful start bit verification, the noise flag (NF) is set and the receiver assumes that the bit is a start bit. To verify a stop bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 13-4 summarizes the results of the stop bit samples. Table 13-4. Stop Bit Recovery
RT8, RT9, and RT10 Samples 000 001 010 011 100 101 110 111 Framing Error Flag 1 1 1 0 1 0 0 0 Noise Flag 0 1 1 1 1 1 1 0
13.4.3.4 Framing Errors If the data recovery logic does not detect a 1 where the stop bit should be in an incoming character, it sets the framing error bit, FE, in SCS1. A break character also sets the FE bit because a break character has no stop bit. The FE bit is set at the same time that the SCRF bit is set.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 141
Serial Communications Interface (SCI) Module
13.4.3.5 Baud Rate Tolerance A transmitting device may be operating at a baud rate below or above the receiver baud rate. Accumulated bit time misalignment can cause one of the three stop bit data samples to fall outside the actual stop bit. Then a noise error occurs. If more than one of the samples is outside the stop bit, a framing error occurs. In most applications, the baud rate tolerance is much more than the degree of misalignment that is likely to occur. As the receiver samples an incoming character, it resynchronizes the RT clock on any valid falling edge within the character. Resynchronization within characters corrects misalignments between transmitter bit times and receiver bit times. Slow Data Tolerance Figure 13-8 shows how much a slow received character can be misaligned without causing a noise error or a framing error. The slow stop bit begins at RT8 instead of RT1 but arrives in time for the stop bit data samples at RT8, RT9, and RT10. For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times x 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 13-8, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 9 bit times x 16 RT cycles + 3 RT cycles = 147 RT cycles.
MSB RECEIVER RT CLOCK RT10 RT11 RT12 RT13 RT14 RT15 RT16 RT1 RT2 RT3 RT4 RT5 RT6 RT7 RT8 RT9 STOP
DATA SAMPLES
Figure 13-8. Slow Data The maximum percent difference between the receiver count and the transmitter count of a slow 8-bit character with no errors is
154 - 147 ------------------------- x 100 = 4.54% 154
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 13-8, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 10 bit times x 16 RT cycles + 3 RT cycles = 163 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit character with no errors is
170 - 163 ------------------------- x 100 = 4.12% 170
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 142 Freescale Semiconductor
Functional Description
Fast Data Tolerance Figure 13-9 shows how much a fast received character can be misaligned without causing a noise error or a framing error. The fast stop bit ends at RT10 instead of RT16 but is still there for the stop bit data samples at RT8, RT9, and RT10.
STOP RECEIVER RT CLOCK RT10 RT11 RT12 RT13 RT14 RT15 RT16 RT1 RT2 RT3 RT4 RT5 RT6 RT7 RT8 RT9 IDLE OR NEXT CHARACTER
DATA SAMPLES
Figure 13-9. Fast Data For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times x 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 13-9, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 10 bit times x 16 RT cycles = 160 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit character with no errors is
* 154 - 160 ------------------------- x 100 = 3.90% 154
For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times x 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 13-9, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 11 bit times x 16 RT cycles = 176 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 9-bit character with no errors is
170 - 176 x 100 = 3.53% ------------------------170
13.4.3.6 Receiver Wakeup So that the MCU can ignore transmissions intended only for other receivers in multiple-receiver systems, the receiver can be put into a standby state. Setting the receiver wakeup bit, RWU, in SCC2 puts the receiver into a standby state during which receiver interrupts are disabled. Depending on the state of the WAKE bit in SCC1, either of two conditions on the PTE1/RxD pin can bring the receiver out of the standby state: * Address mark -- An address mark is a 1 in the most significant bit position of a received character. When the WAKE bit is set, an address mark wakes the receiver from the standby state by clearing the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can then compare the character containing the address mark to the user-defined address of the receiver. If they are the same, the receiver remains awake and processes the characters that follow. If they are not the same, software can set the RWU bit and put the receiver back into the standby state.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 143
Serial Communications Interface (SCI) Module
*
Idle input line condition -- When the WAKE bit is clear, an idle character on the PTE1/RxD pin wakes the receiver from the standby state by clearing the RWU bit. The idle character that wakes the receiver does not set the receiver idle bit, IDLE, or the SCI receiver full bit, SCRF. The idle line type bit, ILTY, determines whether the receiver begins counting 1s as idle character bits after the start bit or after the stop bit. NOTE With the WAKE bit clear, setting the RWU bit after the RxD pin has been idle may cause the receiver to wake up immediately.
13.4.3.7 Receiver Interrupts The following sources can generate CPU interrupt requests from the SCI receiver: * SCI receiver full (SCRF) -- The SCRF bit in SCS1 indicates that the receive shift register has transferred a character to the SCDR. SCRF can generate a receiver CPU interrupt request. Setting the SCI receive interrupt enable bit, SCRIE, in SCC2 enables the SCRF bit to generate receiver CPU interrupts. * Idle input (IDLE) -- The IDLE bit in SCS1 indicates that 10 or 11 consecutive 1s shifted in from the PTE1/RxD pin. The idle line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate CPU interrupt requests. 13.4.3.8 Error Interrupts The following receiver error flags in SCS1 can generate CPU interrupt requests: * Receiver overrun (OR) -- The OR bit indicates that the receive shift register shifted in a new character before the previous character was read from the SCDR. The previous character remains in the SCDR, and the new character is lost. The overrun interrupt enable bit, ORIE, in SCC3 enables OR to generate SCI error CPU interrupt requests. * Noise flag (NF) -- The NF bit is set when the SCI detects noise on incoming data or break characters, including start, data, and stop bits. The noise error interrupt enable bit, NEIE, in SCC3 enables NF to generate SCI error CPU interrupt requests. * Framing error (FE) -- The FE bit in SCS1 is set when a 0 occurs where the receiver expects a stop bit. The framing error interrupt enable bit, FEIE, in SCC3 enables FE to generate SCI error CPU interrupt requests. * Parity error (PE) -- The PE bit in SCS1 is set when the SCI detects a parity error in incoming data. The parity error interrupt enable bit, PEIE, in SCC3 enables PE to generate SCI error CPU interrupt requests.
13.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes. 13.5.1 Wait Mode The SCI module remains active after the execution of a WAIT instruction. In wait mode, the SCI module registers are not accessible by the CPU. Any enabled CPU interrupt request from the SCI module can bring the MCU out of wait mode. If SCI module functions are not required during wait mode, reduce power consumption by disabling the module before executing the WAIT instruction.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 144 Freescale Semiconductor
SCI During Break Module Interrupts
Refer to Chapter 10 Low-Power Modes for information on exiting wait mode. 13.5.2 Stop Mode The SCI module is inactive after the execution of a STOP instruction. The STOP instruction does not affect SCI register states. SCI module operation resumes after an external interrupt. Because the internal clock is inactive during stop mode, entering stop mode during an SCI transmission or reception results in invalid data. Refer to Chapter 10 Low-Power Modes for information on exiting stop mode.
13.6 SCI During Break Module Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. To allow software to clear status bits during a break interrupt, write a 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect status bits during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default state), software can read and write I/O registers during the break state without affecting status bits. Some status bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is at 0. After the break, doing the second step clears the status bit.
13.7 I/O Signals
Port E shares two of its pins with the SCI module. The two SCI I/O pins are: * PTE0/TxD -- Transmit data * PTE1/RxD -- Receive data 13.7.1 PTE0/TxD (Transmit Data) The PTE0/TxD pin is the serial data output from the SCI transmitter. The SCI shares the PTE0/TxD pin with port E. When the SCI is enabled, the PTE0/TxD pin is an output regardless of the state of the DDRE0 bit in data direction register E (DDRE). 13.7.2 PTE1/RxD (Receive Data) The PTE1/RxD pin is the serial data input to the SCI receiver. The SCI shares the PTE1/RxD pin with port E. When the SCI is enabled, the PTE1/RxD pin is an input regardless of the state of the DDRE1 bit in data direction register E (DDRE).
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 145
Serial Communications Interface (SCI) Module
13.8 I/O Registers
These I/O registers control and monitor SCI operation: * SCI control register 1 (SCC1) * SCI control register 2 (SCC2) * SCI control register 3 (SCC3) * SCI status register 1 (SCS1) * SCI status register 2 (SCS2) * SCI data register (SCDR) * SCI baud rate register (SCBR) 13.8.1 SCI Control Register 1 SCI control register 1: * Enables loop mode operation * Enables the SCI * Controls output polarity * Controls character length * Controls SCI wakeup method * Controls idle character detection * Enables parity function * Controls parity type
Address: Read: Write: Reset: $0013 Bit 7 LOOPS 0 6 ENSCI 0 5 TXINV 0 4 M 0 3 WAKE 0 2 ILTY 0 1 PEN 0 Bit 0 PTY 0
Figure 13-10. SCI Control Register 1 (SCC1) LOOPS -- Loop Mode Select Bit This read/write bit enables loop mode operation. In loop mode the PTE1/RxD pin is disconnected from the SCI, and the transmitter output goes into the receiver input. Both the transmitter and the receiver must be enabled to use loop mode. Reset clears the LOOPS bit. 1 = Loop mode enabled 0 = Normal operation enabled ENSCI -- Enable SCI Bit This read/write bit enables the SCI and the SCI baud rate generator. Clearing ENSCI sets the SCTE and TC bits in SCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit. 1 = SCI enabled 0 = SCI disabled TXINV -- Transmit Inversion Bit This read/write bit reverses the polarity of transmitted data. Reset clears the TXINV bit. 1 = Transmitter output inverted 0 = Transmitter output not inverted NOTE Setting the TXINV bit inverts all transmitted values, including idle, break, start, and stop bits.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 146 Freescale Semiconductor
I/O Registers
M -- Mode (Character Length) Bit This read/write bit determines whether SCI characters are eight or nine bits long. See Table 13-5. The ninth bit can serve as an extra stop bit, as a receiver wakeup signal, or as a parity bit. Reset clears the M bit. 1 = 9-bit SCI characters 0 = 8-bit SCI characters WAKE -- Wakeup Condition Bit This read/write bit determines which condition wakes up the SCI: a 1 (address mark) in the most significant bit position of a received character or an idle condition on the PTE1/RxD pin. Reset clears the WAKE bit. 1 = Address mark wakeup 0 = Idle line wakeup ILTY -- Idle Line Type Bit This read/write bit determines when the SCI starts counting 1s as idle character bits. The counting begins either after the start bit or after the stop bit. If the count begins after the start bit, then a string of 1s preceding the stop bit may cause false recognition of an idle character. Beginning the count after the stop bit avoids false idle character recognition, but requires properly synchronized transmissions. Reset clears the ILTY bit. 1 = Idle character bit count begins after stop bit 0 = Idle character bit count begins after start bit PEN -- Parity Enable Bit This read/write bit enables the SCI parity function. See Table 13-5. When enabled, the parity function inserts a parity bit in the most significant bit position. See Figure 13-2. Reset clears the PEN bit. 1 = Parity function enabled 0 = Parity function disabled PTY -- Parity Bit This read/write bit determines whether the SCI generates and checks for odd parity or even parity. See Table 13-5. Reset clears the PTY bit. : 1 = Odd parity 0 = Even parity NOTE Changing the PTY bit in the middle of a transmission or reception can generate a parity error. Table 13-5. Character Format Selection
Control Bits M 0 1 0 0 1 1 PEN and PTY 0X 0X 10 11 10 11 Start Bits 1 1 1 1 1 1 Data Bits 8 9 7 7 8 8 Character Format Parity None None Even Odd Even Odd Stop Bits 1 1 1 1 1 1 Character Length 10 bits 11 bits 10 bits 10 bits 11 bits 11 bits
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 147
Serial Communications Interface (SCI) Module
13.8.2 SCI Control Register 2 SCI control register 2: * Enables the following CPU interrupt requests: - Enables the SCTE bit to generate transmitter CPU interrupt requests - Enables the TC bit to generate transmitter CPU interrupt requests - Enables the SCRF bit to generate receiver CPU interrupt requests - Enables the IDLE bit to generate receiver CPU interrupt requests * Enables the transmitter * Enables the receiver * Enables SCI wakeup * Transmits SCI break characters
Address: Read: Write: Reset: $0014 Bit 7 SCTIE 0 6 TCIE 0 5 SCRIE 0 4 ILIE 0 3 TE 0 2 RE 0 1 RWU 0 Bit 0 SBK 0
Figure 13-11. SCI Control Register 2 (SCC2) SCTIE -- SCI Transmit Interrupt Enable Bit This read/write bit enables the SCTE bit to generate SCI transmitter CPU interrupt requests. Reset clears the SCTIE bit. 1 = SCTE enabled to generate CPU interrupt 0 = SCTE not enabled to generate CPU interrupt TCIE -- Transmission Complete Interrupt Enable Bit This read/write bit enables the TC bit to generate SCI transmitter CPU interrupt requests. Reset clears the TCIE bit. 1 = TC enabled to generate CPU interrupt requests 0 = TC not enabled to generate CPU interrupt requests SCRIE -- SCI Receive Interrupt Enable Bit This read/write bit enables the SCRF bit to generate SCI receiver CPU interrupt requests. Reset clears the SCRIE bit. 1 = SCRF enabled to generate CPU interrupt 0 = SCRF not enabled to generate CPU interrupt ILIE -- Idle Line Interrupt Enable Bit This read/write bit enables the IDLE bit to generate SCI receiver CPU interrupt requests. Reset clears the ILIE bit. 1 = IDLE enabled to generate CPU interrupt requests 0 = IDLE not enabled to generate CPU interrupt requests TE -- Transmitter Enable Bit Setting this read/write bit begins the transmission by sending a preamble of 10 or 11 1s from the transmit shift register to the PTE0/TxD pin. If software clears the TE bit, the transmitter completes any transmission in progress before the PTE0/TxD returns to the idle condition (1). Clearing and then setting TE during a transmission queues an idle character to be sent after the character currently being transmitted. Reset clears the TE bit. 1 = Transmitter enabled 0 = Transmitter disabled
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 148 Freescale Semiconductor
I/O Registers
NOTE Writing to the TE bit is not allowed when the enable SCI bit (ENSCI) is clear. ENSCI is in SCI control register 1. RE -- Receiver Enable Bit Setting this read/write bit enables the receiver. Clearing the RE bit disables the receiver but does not affect receiver interrupt flag bits. Reset clears the RE bit. 1 = Receiver enabled 0 = Receiver disabled NOTE Writing to the RE bit is not allowed when the enable SCI bit (ENSCI) is clear. ENSCI is in SCI control register 1. RWU -- Receiver Wakeup Bit This read/write bit puts the receiver in a standby state during which receiver interrupts are disabled. The WAKE bit in SCC1 determines whether an idle input or an address mark brings the receiver out of the standby state and clears the RWU bit. Reset clears the RWU bit. 1 = Standby state 0 = Normal operation SBK -- Send Break Bit Setting and then clearing this read/write bit transmits a break character followed by a 1. The 1 after the break character guarantees recognition of a valid start bit. If SBK remains set, the transmitter continuously transmits break characters with no 1s between them. Reset clears the SBK bit. 1 = Transmit break characters 0 = No break characters being transmitted NOTE Do not toggle the SBK bit immediately after setting the SCTE bit. Toggling SBK before the preamble begins causes the SCI to send a break character instead of a preamble. 13.8.3 SCI Control Register 3 SCI control register 3: * Stores the ninth SCI data bit received and the ninth SCI data bit to be transmitted * Enables these interrupts: - Receiver overrun interrupts - Noise error interrupts - Framing error interrupts * Parity error interrupts
Address: Read: Write: Reset: U $0015 Bit 7 R8 6 T8 U = Unimplemented 5 R 0 4 R 0 R 3 ORIE 0 = Reserved 2 NEIE 0 1 FEIE 0 U = Unaffected Bit 0 PEIE 0
Figure 13-12. SCI Control Register 3 (SCC3)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 149
Serial Communications Interface (SCI) Module
R8 -- Received Bit 8 When the SCI is receiving 9-bit characters, R8 is the read-only ninth bit (bit 8) of the received character. R8 is received at the same time that the SCDR receives the other 8 bits. When the SCI is receiving 8-bit characters, R8 is a copy of the eighth bit (bit 7). Reset has no effect on the R8 bit. T8 -- Transmitted Bit 8 When the SCI is transmitting 9-bit characters, T8 is the read/write ninth bit (bit 8) of the transmitted character. T8 is loaded into the transmit shift register at the same time that the SCDR is loaded into the transmit shift register. Reset has no effect on the T8 bit. ORIE -- Receiver Overrun Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the receiver overrun bit, OR. 1 = SCI error CPU interrupt requests from OR bit enabled 0 = SCI error CPU interrupt requests from OR bit disabled NEIE -- Receiver Noise Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the noise error bit, NE. Reset clears NEIE. 1 = SCI error CPU interrupt requests from NE bit enabled 0 = SCI error CPU interrupt requests from NE bit disabled FEIE -- Receiver Framing Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the framing error bit, FE. Reset clears FEIE. 1 = SCI error CPU interrupt requests from FE bit enabled 0 = SCI error CPU interrupt requests from FE bit disabled PEIE -- Receiver Parity Error Interrupt Enable Bit This read/write bit enables SCI error CPU interrupt requests generated by the parity error bit, PE. See 13.8.4 SCI Status Register 1. Reset clears PEIE. 1 = SCI error CPU interrupt requests from PE bit enabled 0 = SCI error CPU interrupt requests from PE bit disabled 13.8.4 SCI Status Register 1 SCI status register 1 (SCS1) contains flags to signal these conditions: * Transfer of SCDR data to transmit shift register complete * Transmission complete * Transfer of receive shift register data to SCDR complete * Receiver input idle * Receiver overrun * Noisy data * Framing error * Parity error
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 150 Freescale Semiconductor
I/O Registers Address: Read: Write: Reset: 1 1 = Unimplemented 0 0 0 0 0 0 $0016 Bit 7 SCTE 6 TC 5 SCRF 4 IDLE 3 OR 2 NF 1 FE Bit 0 PE
Figure 13-13. SCI Status Register 1 (SCS1) SCTE -- SCI Transmitter Empty Bit This clearable, read-only bit is set when the SCDR transfers a character to the transmit shift register. SCTE can generate an SCI transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set, SCTE generates an SCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit by reading SCS1 with SCTE set and then writing to SCDR. Reset sets the SCTE bit. 1 = SCDR data transferred to transmit shift register 0 = SCDR data not transferred to transmit shift register TC -- Transmission Complete Bit This read-only bit is set when the SCTE bit is set, and no data, preamble, or break character is being transmitted. TC generates an SCI transmitter CPU interrupt request if the TCIE bit in SCC2 is also set. TC is automatically cleared when data, preamble or break is queued and ready to be sent. There may be up to 1.5 transmitter clocks of latency between queueing data, preamble, and break and the transmission actually starting. Reset sets the TC bit. 1 = No transmission in progress 0 = Transmission in progress SCRF -- SCI Receiver Full Bit This clearable, read-only bit is set when the data in the receive shift register transfers to the SCI data register. SCRF can generate an SCI receiver CPU interrupt request. When the SCRIE bit in SCC2 is set, SCRF generates a CPU interrupt request. In normal operation, clear the SCRF bit by reading SCS1 with SCRF set and then reading the SCDR. Reset clears SCRF. 1 = Received data available in SCDR 0 = Data not available in SCDR IDLE -- Receiver Idle Bit This clearable, read-only bit is set when 10 or 11 consecutive 1s appear on the receiver input. IDLE generates an SCI receiver CPU interrupt request if the ILIE bit in SCC2 is also set. Clear the IDLE bit by reading SCS1 with IDLE set and then reading the SCDR. After the receiver is enabled, it must receive a valid character that sets the SCRF bit before an idle condition can set the IDLE bit. Also, after the IDLE bit has been cleared, a valid character must again set the SCRF bit before an idle condition can set the IDLE bit. Reset clears the IDLE bit. 1 = Receiver input idle 0 = Receiver input active (or idle since the IDLE bit was cleared) OR -- Receiver Overrun Bit This clearable, read-only bit is set when software fails to read the SCDR before the receive shift register receives the next character. The OR bit generates an SCI error CPU interrupt request if the ORIE bit in SCC3 is also set. The data in the shift register is lost, but the data already in the SCDR is not affected. Clear the OR bit by reading SCS1 with OR set and then reading the SCDR. Reset clears the OR bit. 1 = Receive shift register full and SCRF = 1 0 = No receiver overrun
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 151
Serial Communications Interface (SCI) Module
Software latency may allow an overrun to occur between reads of SCS1 and SCDR in the flag-clearing sequence. Figure 13-14 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearing sequence. The delayed read of SCDR does not clear the OR bit because OR was not set when SCS1 was read. Byte 2 caused the overrun and is lost. The next flag-clearing sequence reads byte 3 in the SCDR instead of byte 2. In applications that are subject to software latency or in which it is important to know which byte is lost due to an overrun, the flag-clearing routine can check the OR bit in a second read of SCS1 after reading the data register.
NORMAL FLAG CLEARING SEQUENCE SCRF = 1 SCRF = 0 SCRF = 1 SCRF = 0 SCRF = 1 SCRF = 0 BYTE 4 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 3 BYTE 4 READ SCS1 SCRF = 1 OR = 1 READ SCDR BYTE 3
BYTE 1 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 1
BYTE 2 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 2
BYTE 3
DELAYED FLAG CLEARING SEQUENCE SCRF = 1 SCRF = 1 OR = 1 SCRF = 0 OR = 1 SCRF = 1 OR = 1 SCRF = 0 OR = 0
BYTE 1
BYTE 2 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 1
BYTE 3
Figure 13-14. Flag Clearing Sequence
NF -- Receiver Noise Flag Bit This clearable, read-only bit is set when the SCI detects noise on the PTE1/RxD pin. NF generates an SCI error CPU interrupt request if the NEIE bit in SCC3 is also set. Clear the NF bit by reading SCS1 and then reading the SCDR. Reset clears the NF bit. 1 = Noise detected 0 = No noise detected FE -- Receiver Framing Error Bit This clearable, read-only bit is set when a 0 is accepted as the stop bit. FE generates an SCI error CPU interrupt request if the FEIE bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set and then reading the SCDR. Reset clears the FE bit. 1 = Framing error detected 0 = No framing error detected
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 152 Freescale Semiconductor
I/O Registers
PE -- Receiver Parity Error Bit This clearable, read-only bit is set when the SCI detects a parity error in incoming data. PE generates an SCI error CPU interrupt request if the PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with PE set and then reading the SCDR. Reset clears the PE bit. 1 = Parity error detected 0 = No parity error detected 13.8.5 SCI Status Register 2 SCI status register 2 contains flags to signal the following conditions: * Break character detected * Incoming data
Address: Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 0 0 $0017 Bit 7 6 5 4 3 2 1 BKF Bit 0 RPF
Figure 13-15. SCI Status Register 2 (SCS2) BKF -- Break Flag Bit This clearable, read-only bit is set when the SCI detects a break character on the PTE1/RxD pin. In SCS1, the FE and SCRF bits are also set. In 9-bit character transmissions, the R8 bit in SCC3 is cleared. BKF does not generate a CPU interrupt request. Clear BKF by reading SCS2 with BKF set and then reading the SCDR. Once cleared, BKF can become set again only after 1s again appear on the PTE1/RxD pin followed by another break character. Reset clears the BKF bit. 1 = Break character detected 0 = No break character detected RPF -- Reception in Progress Flag Bit This read-only bit is set when the receiver detects a 0 during the RT1 time period of the start bit search. RPF does not generate an interrupt request. RPF is reset after the receiver detects false start bits (usually from noise or a baud rate mismatch) or when the receiver detects an idle character. Polling RPF before disabling the SCI module or entering stop mode can show whether a reception is in progress. 1 = Reception in progress 0 = No reception in progress
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 153
Serial Communications Interface (SCI) Module
13.8.6 SCI Data Register The SCI data register (SCDR) is the buffer between the internal data bus and the receive and transmit shift registers. Reset has no effect on data in the SCI data register.
Address: Read: Write: Reset: $0018 Bit 7 R7 T7 6 R6 T6 5 R5 T5 4 R4 T4 3 R3 T3 2 R2 T2 1 R1 T1 Bit 0 R0 T0
Unaffected by reset
Figure 13-16. SCI Data Register (SCDR) R7/T7-R0/T0 -- Receive/Transmit Data Bits Reading the SCDR accesses the read-only received data bits, R7:R0. Writing to the SCDR writes the data to be transmitted, T7:T0. Reset has no effect on the SCDR. NOTE Do not use read/modify/write instructions on the SCI data register. 13.8.7 SCI Baud Rate Register The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter.
Address: Read: Write: Reset: 0 0 = Unimplemented $0019 Bit 7 6 5 SCP1 0 4 SCP0 0 3 R 0 R 2 SCR2 0 = Reserved 1 SCR1 0 Bit 0 SCR0 0
Figure 13-17. SCI Baud Rate Register (SCBR) SCP1 and SCP0 -- SCI Baud Rate Prescaler Bits These read/write bits select the baud rate prescaler divisor as shown in Table 13-6. Reset clears SCP1 and SCP0. Table 13-6. SCI Baud Rate Prescaling
SCP1 and SCP0 00 01 10 11 Prescaler Divisor (PD) 1 3 4 13
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 154 Freescale Semiconductor
I/O Registers
SCR2-SCR0 -- SCI Baud Rate Select Bits These read/write bits select the SCI baud rate divisor as shown in Table 13-7. Reset clears SCR2-SCR0. Table 13-7. SCI Baud Rate Selection
SCR2, SCR1, and SCR0 000 001 010 011 100 101 110 111 Baud Rate Divisor (BD) 1 2 4 8 16 32 64 128
Use this formula to calculate the SCI baud rate:
SCI clock source Baud rate = -------------------------------------------64 x PD x BD
where: SCI clock source = fBUS or CGMXCLK (selected by SCIBDSRC bit in CONFIG2) PD = prescaler divisor BD = baud rate divisor Table 13-8 shows the SCI baud rates that can be generated with a 4.9152-MHz bus clock when fBUS is selected as SCI clock source.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 155
Serial Communications Interface (SCI) Module
Table 13-8. SCI Baud Rate Selection Examples
SCP1 and SCP0 00 00 00 00 00 00 00 00 01 01 01 01 01 01 01 01 10 10 10 10 10 10 10 10 11 11 11 11 11 11 11 11 Prescaler Divisor (PD) 1 1 1 1 1 1 1 1 3 3 3 3 3 3 3 3 4 4 4 4 4 4 4 4 13 13 13 13 13 13 13 13 SCR2, SCR1, and SCR0 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 000 001 010 011 100 101 110 111 Baud Rate Divisor (BD) 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 1 2 4 8 16 32 64 128 Baud Rate (fBUS = 4.9152 MHz) 76,800 38,400 19,200 9600 4800 2400 1200 600 25,600 12,800 6400 3200 1600 800 400 200 19,200 9600 4800 2400 1200 600 300 150 5908 2954 1477 739 369 185 92 46
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 156 Freescale Semiconductor
Chapter 14 System Integration Module (SIM)
14.1 Introduction
This section describes the system integration module (SIM). Together with the central processor unit (CPU), the SIM controls all microcontroller unit (MCU) activities. A block diagram of the SIM is shown in Figure 14-1. Table 14-1 is a summary of the SIM input/output (I/O) registers. The SIM is a system state controller that coordinates CPU and exception timing.
MODULE STOP MODULE WAIT STOP/WAIT CONTROL CPU STOP (FROM CPU) CPU WAIT (FROM CPU) SIMOSCEN (TO CGM) SIM COUNTER CGMXCLK (FROM CGM)
CGMOUT (FROM CGM) /2
VDD INTERNAL PULLUP DEVICE RESET PIN LOGIC
CLOCK CONTROL
CLOCK GENERATORS
INTERNAL CLOCKS
FORCED MONITOR MODE ENTRY POR CONTROL RESET PIN CONTROL SIM RESET STATUS REGISTER LVI (FROM LVI MODULE) MASTER RESET CONTROL ILLEGAL OPCODE (FROM CPU) ILLEGAL ADDRESS (FROM ADDRESS MAP DECODERS) COP (FROM COP MODULE)
RESET
INTERRUPT CONTROL AND PRIORITY DECODE
INTERRUPT SOURCES CPU INTERFACE
Figure 14-1. SIM Block Diagram
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 157
System Integration Module (SIM)
The SIM is responsible for: * Bus clock generation and control for CPU and peripherals: - Stop/wait/reset/break entry and recovery - Internal clock control * Master reset control, including power-on reset (POR) and computer operating properly (COP) timeout * Interrupt arbitration Table 14-1 shows the internal signal names used in this section. Table 14-1. Signal Name Conventions
Signal Name CGMXCLK CGMVCLK CGMOUT IAB IDB PORRST IRST R/W PLL output PLL-based or OSC1-based clock output from CGM module (Bus clock = CGMOUT divided by two) Internal address bus Internal data bus Signal from the power-on reset module to the SIM Internal reset signal Read/write signal Description Buffered version of OSC1 from clock generator module (CGM)
Addr. $FE00
Register Name SIM Break Status Register Read: (SBSR) Write: See page 171. Reset:
Bit 7 R
6 R
5 R 0
4 R 0
3 R 0
2 R 0
0 0 1. Writing a 0 clears SBSW. POR 1 BCFE 0 IF6 R 0 IF14 R 0 0 R 0 PIN 0 R
1 SBSW Note(1) 0
Bit 0 R 0
$FE01
$FE03
$FE04
$FE05
$FE06
SIM Reset Status Register Read: (SRSR) Write: See page 172. POR: SIM Break Flag Control Read: Register (SBFCR) Write: See page 173. Reset: Interrupt Status Read: Register 1 (INT1) Write: See page 167. Reset: Interrupt Status Read: Register 2 (INT2) Write: See page 168. Reset: Interrupt Status Read: Register 3 (INT3) Write: See page 168. Reset:
COP 0 R
ILOP 0 R IF3 R 0 IF11 R 0 0 R 0 R
ILAD 0 R IF2 R 0 IF10 R 0 0 R 0 = Reserved
MODRST 0 R IF1 R 0 IF9 R 0 0 R 0
LVI 0 R 0 R 0 IF8 R 0 IF16 R 0
0 0 R 0 R 0 IF7 R 0 IF15 R 0
IF5 IF4 R R 0 0 IF13 IF12 R R 0 0 0 0 R R 0 0 = Unimplemented
Figure 14-2. SIM I/O Register Summary
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 158 Freescale Semiconductor
SIM Bus Clock Control and Generation
14.2 SIM Bus Clock Control and Generation
The bus clock generator provides system clock signals for the CPU and peripherals on the MCU. The system clocks are generated from an incoming clock, CGMOUT, as shown in Figure 14-3. This clock originates from either an external oscillator or from the on-chip PLL.
14.2.1 Bus Timing
In user mode, the internal bus frequency is either the crystal oscillator output (CGMXCLK) divided by four or the PLL output (CGMVCLK) divided by four.
14.2.2 Clock Startup from POR or LVI Reset
When the power-on reset module or the low-voltage inhibit module generates a reset, the clocks to the CPU and peripherals are inactive and held in an inactive phase until after the 4096 CGMXCLK cycle POR timeout has completed. The RST pin is driven low by the SIM during this entire period. The bus clocks start upon completion of the timeout.
OSC2
OSCILLATOR (OSC) CGMXCLK
OSC1
TO TBM,TIM1,TIM2, ADC
SIM OSCSTOPENB FROM CONFIG2
SIMOSCEN IT12 TO REST OF CHIP IT23 TO REST OF CHIP
CGMRCLK CGMOUT PHASE-LOCKED LOOP (PLL)
SIM COUNTER BUS CLOCK GENERATORS
/2
Figure 14-3. System Clock Signals
14.2.3 Clocks in Stop Mode and Wait Mode
Upon exit from stop mode by an interrupt or reset, the SIM allows CGMXCLK to clock the SIM counter. The CPU and peripheral clocks do not become active until after the stop delay timeout. This timeout is selectable as 4096 or 32 CGMXCLK cycles. See 14.6.2 Stop Mode. In wait mode, the CPU clocks are inactive. The SIM also produces two sets of clocks for other modules. Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 159
System Integration Module (SIM)
14.3 Reset and System Initialization
The MCU has these reset sources: * Power-on reset module (POR) * External reset pin (RST) * Computer operating properly module (COP) * Low-voltage inhibit module (LVI) * Illegal opcode * Illegal address * Forced monitor mode entry reset (MODRST) All of these resets produce the vector $FFFE:$FFFF ($FEFE:$FEFF in monitor mode) and assert the internal reset signal (IRST). IRST causes all registers to be returned to their default values and all modules to be returned to their reset states. An internal reset clears the SIM counter (see 14.4 SIM Counter), but an external reset does not. Each of the resets sets a corresponding bit in the SIM reset status register (SRSR). See 14.7 SIM Registers.
14.3.1 External Pin Reset
The RST pin circuit includes an internal pullup device. Pulling the asynchronous RST pin low halts all processing. The PIN bit of the SIM reset status register (SRSR) is set as long as RST is held low for a minimum of 67 CGMXCLK cycles, assuming that neither the POR nor the LVI was the source of the reset. See Table 14-2 for details. Figure 14-4 shows the relative timing.
CGMOUT RST IAB PC VECT H VECT L
Figure 14-4. External Reset Timing
14.3.2 Active Resets from Internal Sources
All internal reset sources actively pull the RST pin low for 32 CGMXCLK cycles to allow resetting of external peripherals. The internal reset continues to be asserted for an additional 32 cycles at which point the reset vector will be fetched. See Figure 14-5. An internal reset can be caused by an illegal address, illegal opcode, COP timeout, LVI, or POR. See Figure 14-6. NOTE For LVI or POR resets, the SIM cycles through 4096 + 32 CGMXCLK cycles during which the SIM forces the RST pin low. The internal reset signal then follows the sequence from the falling edge of RST shown in Figure 14-5. The COP reset is asynchronous to the bus clock. The active reset feature allows the part to issue a reset to peripherals and other chips within a system built around the MCU.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 160 Freescale Semiconductor
Reset and System Initialization
IRST RST CGMXCLK RST PULLED LOW BY MCU 32 CYCLES 32 CYCLES
IAB
VECTOR HIGH
Figure 14-5. Internal Reset Timing
ILLEGAL ADDRESS RST ILLEGAL OPCODE RST COPRST LVI POR MODRST
INTERNAL RESET
Figure 14-6. Sources of Internal Reset Table 14-2. Reset Recovery Type
Reset Recovery Type POR/LVI All others Actual Number of Cycles 4163 (4096 + 64 + 3) 67 (64 + 3)
14.3.2.1 Power-On Reset When power is first applied to the MCU, the power-on reset module (POR) generates a pulse to indicate that power-on has occurred. The external reset pin (RST) is held low while the SIM counter counts out 4096 + 32 CGMXCLK cycles. Thirty-two CGMXCLK cycles later, the CPU and memories are released from reset to allow the reset vector sequence to occur. At power-on, these events occur: * A POR pulse is generated. * The internal reset signal is asserted. * The SIM enables CGMOUT. * Internal clocks to the CPU and modules are held inactive for 4096 CGMXCLK cycles to allow stabilization of the oscillator. * The RST pin is driven low during the oscillator stabilization time. * The POR bit of the SIM reset status register (SRSR) is set and all other bits in the register are cleared.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 161
System Integration Module (SIM)
OSC1 PORRST 4096 CYCLES CGMXCLK CGMOUT RST IRST 32 CYCLES 32 CYCLES
IAB
$FFFE
$FFFF
Figure 14-7. POR Recovery 14.3.2.2 Computer Operating Properly (COP) Reset An input to the SIM is reserved for the COP reset signal. The overflow of the COP counter causes an internal reset and sets the COP bit in the SIM reset status register (SRSR). The SIM actively pulls down the RST pin for all internal reset sources. The COP module is disabled if the RST pin or the IRQ pin is held at VTST while the MCU is in monitor mode. The COP module can be disabled only through combinational logic conditioned with the high voltage signal on the RST or the IRQ pin. This prevents the COP from becoming disabled as a result of external noise. During a break state, VTST on the RST pin disables the COP module. 14.3.2.3 Illegal Opcode Reset The SIM decodes signals from the CPU to detect illegal instructions. An illegal instruction sets the ILOP bit in the SIM reset status register (SRSR) and causes a reset. If the stop enable bit, STOP, in the CONFIG1 register is 0, the SIM treats the STOP instruction as an illegal opcode and causes an illegal opcode reset. The SIM actively pulls down the RST pin for all internal reset sources. 14.3.2.4 Illegal Address Reset An opcode fetch from an unmapped address generates an illegal address reset. The SIM verifies that the CPU is fetching an opcode prior to asserting the ILAD bit in the SIM reset status register (SRSR) and resetting the MCU. A data fetch from an unmapped address does not generate a reset. The SIM actively pulls down the RST pin for all internal reset sources. 14.3.2.5 Low-Voltage Inhibit (LVI) Reset The low-voltage inhibit module (LVI) asserts its output to the SIM when the VDD voltage falls to the VTRIPF voltage. The LVI bit in the SIM reset status register (SRSR) is set, and the external reset pin (RST) is held
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 162 Freescale Semiconductor
SIM Counter
low while the SIM counter counts out 4096 + 32 CGMXCLK cycles. Thirty-two CGMXCLK cycles later, the CPU is released from reset to allow the reset vector sequence to occur. The SIM actively pulls down the RST pin for all internal reset sources. 14.3.2.6 Monitor Mode Entry Module Reset (MODRST) The monitor mode entry module reset (MODRST) asserts its output to the SIM when monitor mode is entered in the condition where the reset vectors are erased ($FF) (see 18.3.1.1 Normal Monitor Mode). When MODRST gets asserted, an internal reset occurs. The SIM actively pulls down the RST pin for all internal reset sources.
14.4 SIM Counter
The SIM counter is used by the power-on reset module (POR) and in stop mode recovery to allow the oscillator time to stabilize before enabling the internal bus (IBUS) clocks. The SIM counter also serves as a prescaler for the computer operating properly module (COP). The SIM counter is 12 bits long.
14.4.1 SIM Counter During Power-On Reset
The power-on reset module (POR) detects power applied to the MCU. At power-on, the POR circuit asserts the signal PORRST. Once the SIM is initialized, it enables the clock generation module (CGM) to drive the bus clock state machine.
14.4.2 SIM Counter During Stop Mode Recovery
The SIM counter also is used for stop mode recovery. The STOP instruction clears the SIM counter. After an interrupt, break, or reset, the SIM senses the state of the short stop recovery bit, SSREC, in the CONFIG1 register. If the SSREC bit is a 1, then the stop recovery is reduced from the normal delay of 4096 CGMXCLK cycles down to 32 CGMXCLK cycles. This is ideal for applications using crystals with the OSCSTOPENB bit set. External crystal applications should use the full stop recovery time, SSREC cleared, if the OSCSTOPENB bit is cleared.
14.4.3 SIM Counter and Reset States
External reset has no effect on the SIM counter. See 14.6.2 Stop Mode for details. The SIM counter is free-running after all reset states. See 14.3.2 Active Resets from Internal Sources for counter control and internal reset recovery sequences.
14.5 Exception Control
Normal, sequential program execution can be changed in three different ways: * Interrupts: - Maskable hardware CPU interrupts - Non-maskable software interrupt instruction (SWI) * Reset * Break interrupts
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 163
System Integration Module (SIM)
14.5.1 Interrupts
At the beginning of an interrupt, the CPU saves the CPU register contents on the stack and sets the interrupt mask (I bit) to prevent additional interrupts. At the end of an interrupt, the RTI instruction recovers the CPU register contents from the stack so that normal processing can resume. Figure 14-8 shows interrupt entry timing. Figure 14-9 shows interrupt recovery timing.
MODULE INTERRUPT
I BIT IAB IDB R/W DUMMY DUMMY SP SP - 1 SP - 2 X SP - 3 A SP - 4 CCR VECT H VECT L START ADDR OPCODE
PC - 1[7:0] PC - 1[15:8]
V DATA H
V DATA L
Figure 14-8. Interrupt Entry Timing
MODULE INTERRUPT
I BIT IAB IDB R/W SP - 4 CCR SP - 3 A SP - 2 X SP - 1 SP PC PC + 1 OPERAND
PC - 1 [7:0] PC - 1 [15:8] OPCODE
Figure 14-9. Interrupt Recovery Timing
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 164 Freescale Semiconductor
Exception Control
Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The arbitration result is a constant that the CPU uses to determine which vector to fetch. Once an interrupt is latched by the SIM, no other interrupt can take precedence, regardless of priority, until the latched interrupt is serviced (or the I bit is cleared). See Figure 14-10.
FROM RESET
BREAK I BIT SET? INTERRUPT? NO YES
YES
I BIT SET? NO IRQ INTERRUPT? NO YES
AS MANY INTERRUPTS AS EXIST ON CHIP STACK CPU REGISTERS SET I BIT LOAD PC WITH INTERRUPT VECTOR
FETCH NEXT INSTRUCTION
SWI INSTRUCTION? NO RTI INSTRUCTION? NO
YES
YES
UNSTACK CPU REGISTERS
EXECUTE INSTRUCTION
Figure 14-10. Interrupt Processing
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 165
System Integration Module (SIM)
14.5.1.1 Hardware Interrupts A hardware interrupt does not stop the current instruction. Processing of a hardware interrupt begins after completion of the current instruction. When the current instruction is complete, the SIM checks all pending hardware interrupts. If interrupts are not masked (I bit clear in the condition code register) and if the corresponding interrupt enable bit is set, the SIM proceeds with interrupt processing; otherwise, the next instruction is fetched and executed. If more than one interrupt is pending at the end of an instruction execution, the highest priority interrupt is serviced first. Figure 14-11 demonstrates what happens when two interrupts are pending. If an interrupt is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the LDA instruction is executed.
CLI LDA #$FF BACKGROUND ROUTINE
INT1
PSHH INT1 INTERRUPT SERVICE ROUTINE PULH RTI
INT2
PSHH INT2 INTERRUPT SERVICE ROUTINE PULH RTI
Figure 14-11. Interrupt Recognition Example The LDA opcode is prefetched by both the INT1 and INT2 RTI instructions. However, in the case of the INT1 RTI prefetch, this is a redundant operation. NOTE To maintain compatibility with the M6805 Family, the H register is not pushed on the stack during interrupt entry. If the interrupt service routine modifies the H register or uses the indexed addressing mode, software should save the H register and then restore it prior to exiting the routine. 14.5.1.2 SWI Instruction The SWI instruction is a non-maskable instruction that causes an interrupt regardless of the state of the interrupt mask (I bit) in the condition code register. NOTE A software interrupt pushes PC onto the stack. A software interrupt does not push PC - 1, as a hardware interrupt does.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 166 Freescale Semiconductor
Exception Control
14.5.1.3 Interrupt Status Registers The flags in the interrupt status registers identify maskable interrupt sources. Table 14-3 summarizes the interrupt sources and the interrupt status register flags that they set. The interrupt status registers can be useful for debugging. Table 14-3. Interrupt Sources
Priority Highest Interrupt Source Reset SWI instruction IRQ pin CGM clock monitor TIM1 channel 0 TIM1 channel 1 TIM1 overflow TIM2 channel 0 TIM2 channel 1 TIM2 overflow SPI receiver full SPI transmitter empty SCI receive error SCI receive SCI transmit Keyboard ADC conversion complete Lowest Timebase module Interrupt Status Register Flag -- -- I1 I2 I3 I4 I5 I6 I7 I8 I9 I10 I11 I12 I13 I14 I15 I16
Interrupt Status Register 1
Address: Read: Write: Reset: $FE04 Bit 7 I6 R 0 R 6 I5 R 0 = Reserved 5 I4 R 0 4 I3 R 0 3 I2 R 0 2 I1 R 0 1 0 R 0 Bit 0 0 R 0
Figure 14-12. Interrupt Status Register 1 (INT1) I6-I1 -- Interrupt Flags 1-6 These flags indicate the presence of interrupt requests from the sources shown in Table 14-3. 1 = Interrupt request present 0 = No interrupt request present Bit 0 and Bit 1 -- Always read 0
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 167
System Integration Module (SIM)
Interrupt Status Register 2
Address: Read: Write: Reset: $FE05 Bit 7 I14 R 0 R 6 I13 R 0 = Reserved 5 I12 R 0 4 I11 R 0 3 I10 R 0 2 I9 R 0 1 I8 R 0 Bit 0 I7 R 0
Figure 14-13. Interrupt Status Register 2 (INT2) I14-I7 -- Interrupt Flags 14-7 These flags indicate the presence of interrupt requests from the sources shown in Table 14-3. 1 = Interrupt request present 0 = No interrupt request present Interrupt Status Register 3
Address: Read: Write: Reset: $FE06 Bit 7 0 R 0 R 6 0 R 0 = Reserved 5 0 R 0 4 0 R 0 3 0 R 0 2 0 R 0 1 I16 R 0 Bit 0 I15 R 0
Figure 14-14. Interrupt Status Register 3 (INT3) Bits 7-6 -- Always read 0 I16 and I15 -- Interrupt Flags 16 and 15 These flags indicate the presence of an interrupt request from the source shown in Table 14-3. 1 = Interrupt request present 0 = No interrupt request present
14.5.2 Reset
All reset sources always have equal and highest priority and cannot be arbitrated.
14.5.3 Break Interrupts
The break module can stop normal program flow at a software-programmable break point by asserting its break interrupt output (see Chapter 17 Timer Interface Module (TIM1 and TIM2)). The SIM puts the CPU into the break state by forcing it to the SWI vector location. Refer to the break interrupt subsection of each module to see how each module is affected by the break state.
14.5.4 Status Flag Protection in Break Mode
The SIM controls whether status flags contained in other modules can be cleared during break mode. The user can select whether flags are protected from being cleared by properly initializing the break clear flag enable bit (BCFE) in the SIM break flag control register (SBFCR).
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 168 Freescale Semiconductor
Low-Power Modes
Protecting flags in break mode ensures that set flags will not be cleared while in break mode. This protection allows registers to be freely read and written during break mode without losing status flag information. Setting the BCFE bit enables the clearing mechanisms. Once cleared in break mode, a flag remains cleared even when break mode is exited. Status flags with a 2-step clearing mechanism -- for example, a read of one register followed by the read or write of another -- are protected, even when the first step is accomplished prior to entering break mode. Upon leaving break mode, execution of the second step will clear the flag as normal.
14.6 Low-Power Modes
Executing the WAIT or STOP instruction puts the MCU in a low power- consumption mode for standby situations. The SIM holds the CPU in a non-clocked state. The operation of each of these modes is described in the following subsections. Both STOP and WAIT clear the interrupt mask (I) in the condition code register, allowing interrupts to occur.
14.6.1 Wait Mode
In wait mode, the CPU clocks are inactive while the peripheral clocks continue to run. Figure 14-15 shows the timing for wait mode entry. A module that is active during wait mode can wakeup the CPU with an interrupt if the interrupt is enabled. Stacking for the interrupt begins one cycle after the WAIT instruction during which the interrupt occurred. In wait mode, the CPU clocks are inactive. Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode. Wait mode also can be exited by a reset (or break in emulation mode). A break interrupt during wait mode sets the SIM break stop/wait bit, SBSW, in the SIM break status register (SBSR). If the COP disable bit, COPD, in the CONFIG1 register is 0, then the computer operating properly module (COP) is enabled and remains active in wait mode.
IAB IDB R/W WAIT ADDR WAIT ADDR + 1 NEXT OPCODE SAME SAME SAME SAME
PREVIOUS DATA
Note:
Previous data can be operand data or the WAIT opcode, depending on the last instruction.
Figure 14-15. Wait Mode Entry Timing Figure 14-16 and Figure 14-17 show the timing for WAIT recovery.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 169
System Integration Module (SIM)
IAB IDB EXITSTOPWAIT $A6
$6E0B $A6 $A6
$6E0C $01
$00FF $0B
$00FE $6E
$00FD
$00FC
Note: EXITSTOPWAIT = RST pin or CPU interrupt
Figure 14-16. Wait Recovery from Interrupt
32 CYCLES IAB IDB RST CGMXCLK $A6 $6E0B $A6 $A6 32 CYCLES RSTVCT H RSTVCTL
Figure 14-17. Wait Recovery from Internal Reset
14.6.2 Stop Mode
In stop mode, the SIM counter is reset and the system clocks are disabled. An interrupt request from a module can cause an exit from stop mode. Stacking for interrupts begins after the selected stop recovery time has elapsed. Reset causes an exit from stop mode. The SIM disables the clock generator module outputs (CGMOUT and CGMXCLK) in stop mode, stopping the CPU and peripherals. Stop recovery time is selectable using the SSREC bit in the CONFIG1 register. If SSREC is set, stop recovery is reduced from the normal delay of 4096 CGMXCLK cycles down to 32. This is ideal for applications using canned oscillators that do not require long startup times from stop mode. NOTE External crystal applications should use the full stop recovery time by clearing the SSREC bit unless the OSCSTOPENB bit is set in CONFIG2. The SIM counter is held in reset from the execution of the STOP instruction until the beginning of stop recovery. It is then used to time the recovery period. Figure 14-18 shows stop mode entry timing. Figure 14-19 shows stop mode recovery time from interrupt. NOTE To minimize stop current, all pins configured as inputs should be driven to a 1 or 0.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 170 Freescale Semiconductor
SIM Registers
CPUSTOP IAB IDB R/W Note: Previous data can be operand data or the STOP opcode, depending on the last instruction. STOP ADDR STOP ADDR + 1 NEXT OPCODE SAME SAME SAME SAME
PREVIOUS DATA
Figure 14-18. Stop Mode Entry Timing
STOP RECOVERY PERIOD CGMXCLK INT/BREAK IAB STOP +1 STOP + 2 STOP + 2 SP SP - 1 SP - 2 SP - 3
Figure 14-19. Stop Mode Recovery from Interrupt
14.7 SIM Registers
The SIM has three memory-mapped registers. Table 14-4 shows the mapping of these registers. Table 14-4. SIM Registers
Address $FE00 $FE01 $FE03 Register SBSR SRSR SBFCR Access Mode User User User
14.7.1 SIM Break Status Register
The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode. This register is only used in emulation mode.
Address: Read: Write: Reset: $FE00 Bit 7 R 0 R 6 R 0 = Reserved 5 R 0 4 R 0 3 R 0 2 R 0 1 SBSW Note(1) 0 Bit 0 R 0
1. Writing a 0 clears SBSW.
Figure 14-20. Break Status Register (SBSR)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 171
System Integration Module (SIM)
SBSW -- SIM Break Stop/Wait SBSW can be read within the break state SWI routine. The user can modify the return address on the stack by subtracting one from it. 1 = Wait mode was exited by break interrupt. 0 = Wait mode was not exited by break interrupt.
14.7.2 SIM Reset Status Register
The SRSR register contains flags that show the source of the last reset. The status register will automatically clear after reading SRSR. A power-on reset sets the POR bit and clears all other bits in the register. All other reset sources set the individual flag bits but do not clear the register. More than one reset source can be flagged at any time depending on the conditions at the time of the internal or external reset. For example, the POR and LVI bit can both be set if the power supply has a slow rise time.
Address: Read: Write: Reset: 1 0 = Unimplemented 0 0 0 0 0 0 $FE01 Bit 7 POR 6 PIN 5 COP 4 ILOP 3 ILAD 2 MODRST 1 LVI Bit 0 0
Figure 14-21. SIM Reset Status Register (SRSR) POR -- Power-On Reset Bit 1 = Last reset caused by POR circuit 0 = Read of SRSR PIN -- External Reset Bit 1 = Last reset caused by external reset pin (RST) 0 = POR or read of SRSR COP -- Computer Operating Properly Reset Bit 1 = Last reset caused by COP counter 0 = POR or read of SRSR ILOP -- Illegal Opcode Reset Bit 1 = Last reset caused by an illegal opcode 0 = POR or read of SRSR ILAD -- Illegal Address Reset Bit (opcode fetches only) 1 = Last reset caused by an opcode fetch from an illegal address 0 = POR or read of SRSR MODRST -- Monitor Mode Entry Module Reset Bit 1 = Last reset caused by monitor mode entry when vector locations $FFFE and $FFFF are $FF after POR while IRQ = VDD 0 = POR or read of SRSR LVI -- Low-Voltage Inhibit Reset Bit 1 = Last reset caused by the LVI circuit 0 = POR or read of SRSR
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 172 Freescale Semiconductor
SIM Registers
14.7.3 SIM Break Flag Control Register
The SIM break flag control register (SBFCR) contains a bit that enables software to clear status bits while the MCU is in a break state.
Address: Read: Write: Reset: $FE03 Bit 7 BCFE 0 R = Reserved 6 R 5 R 4 R 3 R 2 R 1 R Bit 0 R
Figure 14-22. SIM Break Flag Control Register (BFCR) BCFE -- Break Clear Flag Enable Bit This read/write bit enables software to clear status bits by accessing status registers while the MCU is in a break state. To clear status bits during the break state, the BCFE bit must be set. 1 = Status bits clearable during break 0 = Status bits not clearable during break
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 173
System Integration Module (SIM)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 174 Freescale Semiconductor
Chapter 15 Serial Peripheral Interface (SPI) Module
15.1 Introduction
This section describes the serial peripheral interface (SPI) module, which allows full-duplex, synchronous, serial communications with peripheral devices. The text that follows describes the SPI. The SPI I/O pin names are SS (slave select), SPSCK (SPI serial clock), MOSI (master out slave in), and MISO (master in/slave out). The SPI shares four I/O pins with four parallel I/O ports.
15.2 Features
Features of the SPI module include: * Full-duplex operation * Master and slave modes * Double-buffered operation with separate transmit and receive registers * Four master mode frequencies (maximum = bus frequency / 2) * Maximum slave mode frequency = bus frequency * Serial clock with programmable polarity and phase * Two separately enabled interrupts: - SPRF (SPI receiver full) - SPTE (SPI transmitter empty) * Mode fault error flag with CPU interrupt capability * Overflow error flag with CPU interrupt capability * Programmable wired-OR mode * I/O (input/output) port bit(s) software configurable with pullup device(s) if configured as input port bit(s)
15.3 Functional Description
The SPI module allows full-duplex, synchronous, serial communication between the MCU and peripheral devices, including other MCUs. Software can poll the SPI status flags or SPI operation can be interrupt driven. If a port bit is configured for input, then an internal pullup device may be enabled for that port bit. The following paragraphs describe the operation of the SPI module. Refer to Figure 15-3 for a summary of the SPI I/O registers.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 175
Serial Peripheral Interface (SPI) Module
INTERNAL BUS M68HC08 CPU PORTA DDRA CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) PROGRAMMABLE TIMEBASE MODULE SINGLE BREAKPOINT BREAK MODULE DUAL VOLTAGE LOW-VOLTAGE INHIBIT MODULE 4-BIT KEYBOARD INTERRUPT MODULE PORTC DDRC 2-CHANNEL TIMER INTERFACE MODULE 1 1-CHANNEL TIMER INTERFACE MODULE 2 SERIAL COMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE RST(3) IRQ(3) VDDAD/VREFH VSSAD/VREFL SYSTEM INTEGRATION MODULE SINGLE EXTERNAL INTERRUPT MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE POWER-ON RESET MODULE VDD VSS VDDA VSSA SERIAL PERIPHERAL INTERFACE MODULE MONITOR MODULE MEMORY MAP MODULE CONFIGURATION REGISTER 1 MODULE CONFIGURATION REGISTER 2 MODULE PORTB DDRB PTA3/KBD3- PTA0/KBD0(1)
CONTROL AND STATUS REGISTERS -- 64 BYTES MC68HC908GR8A USER FLASH -- 7680 BYTES MC68HC908GR4A USER FLASH -- 4096 BYTES USER RAM -- 384 BYTES MONITOR ROM -- 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM -- 544 BYTES USER FLASH VECTOR SPACE -- 36 BYTES CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 1-8-MHz OSCILLATOR PHASE LOCKED LOOP
PTB5/AD5 PTB4/AD4 PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0
PTC1(1), (2) PTC0(1), (2)
PTD6/T2CH0(1) PTD5/T1CH1(1) PTD4/T1CH0(1) PTD3/SPSCK(1) PTD2/MOSI(1) PTD1/MISO(1) PTD0/SS(1)
PORTE
PORTD
DDRD
PTE1/RxD PTE0/TxD
DDRE
SECURITY MODULE
POWER
MONITOR MODE ENTRY MODULE
1. Ports are software configurable with pullup device if input port. 2. Higher current drive port pins 3. Pin contains integrated pullup device
Figure 15-1. Block Diagram Highlighting SPI Block and Pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 176 Freescale Semiconductor
Functional Description
INTERNAL BUS
TRANSMIT DATA REGISTER SHIFT REGISTER 7 /2 CLOCK DIVIDER /8 / 32 / 128 CLOCK SELECT RECEIVE DATA REGISTER PIN CONTROL LOGIC SPSCK CLOCK LOGIC M S SS 6 5 4 3 2 1 0 MISO
BUSCLK
MOSI
SPMSTR
SPE
SPR1
SPR0 SPMSTR CPHA CPOL
TRANSMITTER CPU INTERRUPT REQUEST SPI CONTROL RECEIVER/ERROR CPU INTERRUPT REQUEST
MODFEN ERRIE SPTIE SPRIE SPE SPRF SPTE OVRF MODF
SPWOM
Figure 15-2. SPI Module Block Diagram
Addr. $0010 Register Name SPI Control Register Read: (SPCR) Write: See page 191. Reset: SPI Status and Control Read: Register (SPSCR) Write: See page 192. Reset: SPI Data Register Read: (SPDR) Write: See page 194. Reset: Bit 7 SPRIE 0 SPRF 0 R7 T7 R 6 R 0 ERRIE 0 R6 T6 = Reserved 5 SPMSTR 1 OVRF 0 R5 T5 4 CPOL 0 MODF 0 R4 T4 3 CPHA 1 SPTE 1 R3 T3 2 SPWOM 0 MODFEN 0 R2 T2 1 SPE 0 SPR1 0 R1 T1 Bit 0 SPTIE 0 SPR0 0 R0 T0
$0011
$0012
Unaffected by reset = Unimplemented
Figure 15-3. SPI I/O Register Summary
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 177
Serial Peripheral Interface (SPI) Module
15.3.1 Master Mode
The SPI operates in master mode when the SPI master bit, SPMSTR, is set. NOTE In a multi-SPI system, configure the SPI modules as master or slave before enabling them. Enable the master SPI before enabling the slave SPI. Disable the slave SPI before disabling the master SPI. See 15.12.1 SPI Control Register. Only a master SPI module can initiate transmissions. Software begins the transmission from a master SPI module by writing to the transmit data register. If the shift register is empty, the byte immediately transfers to the shift register, setting the SPI transmitter empty bit, SPTE. The byte begins shifting out on the MOSI pin under the control of the serial clock. See Figure 15-4.
MASTER MCU MISO MOSI SPSCK BAUD RATE GENERATOR SS MISO MOSI SPSCK SS SLAVE MCU
SHIFT REGISTER
SHIFT REGISTER
VDD
Figure 15-4. Full-Duplex Master-Slave Connections The SPR1 and SPR0 bits control the baud rate generator and determine the speed of the shift register. (See 15.12.2 SPI Status and Control Register.) Through the SPSCK pin, the baud rate generator of the master also controls the shift register of the slave peripheral. As the byte shifts out on the MOSI pin of the master, another byte shifts in from the slave on the master's MISO pin. The transmission ends when the receiver full bit, SPRF, becomes set. At the same time that SPRF becomes set, the byte from the slave transfers to the receive data register. In normal operation, SPRF signals the end of a transmission. Software clears SPRF by reading the SPI status and control register with SPRF set and then reading the SPI data register. Writing to the SPI data register (SPDR) clears SPTE.
15.3.2 Slave Mode
The SPI operates in slave mode when SPMSTR is clear. In slave mode, the SPSCK pin is the input for the serial clock from the master MCU. Before a data transmission occurs, the SS pin of the slave SPI must be low. SS must remain low until the transmission is complete. See 15.6.2 Mode Fault Error. In a slave SPI module, data enters the shift register under the control of the serial clock from the master SPI module. After a byte enters the shift register of a slave SPI, it transfers to the receive data register, and the SPRF bit is set. To prevent an overflow condition, slave software then must read the receive data register before another full byte enters the shift register.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 178 Freescale Semiconductor
Transmission Formats
The maximum frequency of the SPSCK for an SPI configured as a slave is the bus clock speed (which is twice as fast as the fastest master SPSCK clock that can be generated). The frequency of the SPSCK for an SPI configured as a slave does not have to correspond to any SPI baud rate. The baud rate only controls the speed of the SPSCK generated by an SPI configured as a master. Therefore, the frequency of the SPSCK for an SPI configured as a slave can be any frequency less than or equal to the bus speed. When the master SPI starts a transmission, the data in the slave shift register begins shifting out on the MISO pin. The slave can load its shift register with a new byte for the next transmission by writing to its transmit data register. The slave must write to its transmit data register at least one bus cycle before the master starts the next transmission. Otherwise, the byte already in the slave shift register shifts out on the MISO pin. Data written to the slave shift register during a transmission remains in a buffer until the end of the transmission. When the clock phase bit (CPHA) is set, the first edge of SPSCK starts a transmission. When CPHA is clear, the falling edge of SS starts a transmission. See 15.4 Transmission Formats. NOTE SPSCK must be in the proper idle state before the slave is enabled to prevent SPSCK from appearing as a clock edge.
15.4 Transmission Formats
During an SPI transmission, data is simultaneously transmitted (shifted out serially) and received (shifted in serially). A serial clock synchronizes shifting and sampling on the two serial data lines. A slave select line allows selection of an individual slave SPI device; slave devices that are not selected do not interfere with SPI bus activities. On a master SPI device, the slave select line can optionally be used to indicate multiple-master bus contention.
15.4.1 Clock Phase and Polarity Controls
Software can select any of four combinations of serial clock (SPSCK) phase and polarity using two bits in the SPI control register (SPCR). The clock polarity is specified by the CPOL control bit, which selects an active high or low clock and has no significant effect on the transmission format. The clock phase (CPHA) control bit selects one of two fundamentally different transmission formats. The clock phase and polarity should be identical for the master SPI device and the communicating slave device. In some cases, the phase and polarity are changed between transmissions to allow a master device to communicate with peripheral slaves having different requirements. NOTE Before writing to the CPOL bit or the CPHA bit, disable the SPI by clearing the SPI enable bit (SPE).
15.4.2 Transmission Format When CPHA = 0
Figure 15-5 shows an SPI transmission in which CPHA = 0. The figure should not be used as a replacement for data sheet parametric information. Two waveforms are shown for SPSCK: one for CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins are directly connected between the master and the slave. The MISO signal is the output from the slave, and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The slave SPI drives its MISO output only when its slave select
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 179
Serial Peripheral Interface (SPI) Module
input (SS) is low, so that only the selected slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. (See 15.6.2 Mode Fault Error.) When CPHA = 0, the first SPSCK edge is the MSB capture strobe. Therefore, the slave must begin driving its data before the first SPSCK edge, and a falling edge on the SS pin is used to start the slave data transmission. The slave's SS pin must be toggled back to high and then low again between each byte transmitted as shown in Figure 15-6.
SPSCK CYCLE # FOR REFERENCE SPSCK; CPOL = 0 SPSCK; CPOL =1 MOSI FROM MASTER MISO FROM SLAVE SS; TO SLAVE CAPTURE STROBE MSB MSB BIT 6 BIT 6 BIT 5 BIT 5 BIT 4 BIT 4 BIT 3 BIT 3 BIT 2 BIT 2 BIT 1 BIT 1 LSB LSB 1 2 3 4 5 6 7 8
Figure 15-5. Transmission Format (CPHA = 0)
MISO/MOSI MASTER SS SLAVE SS CPHA = 0 SLAVE SS CPHA = 1
BYTE 1
BYTE 2
BYTE 3
Figure 15-6. CPHA/SS Timing When CPHA = 0 for a slave, the falling edge of SS indicates the beginning of the transmission. This causes the SPI to leave its idle state and begin driving the MISO pin with the MSB of its data. Once the transmission begins, no new data is allowed into the shift register from the transmit data register. Therefore, the SPI data register of the slave must be loaded with transmit data before the falling edge of SS. Any data written after the falling edge is stored in the transmit data register and transferred to the shift register after the current transmission.
15.4.3 Transmission Format When CPHA = 1
Figure 15-7 shows an SPI transmission in which CPHA = 1. The figure should not be used as a replacement for data sheet parametric information. Two waveforms are shown for SPSCK: one for CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins are directly connected between the master and the slave. The MISO signal is the output from the slave, and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The slave SPI drives its MISO output only when its slave select input (SS) is low, so that only the selected slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 180 Freescale Semiconductor
Transmission Formats
pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. (See 15.6.2 Mode Fault Error.) When CPHA = 1, the master begins driving its MOSI pin on the first SPSCK edge. Therefore, the slave uses the first SPSCK edge as a start transmission signal. The SS pin can remain low between transmissions. This format may be preferable in systems having only one master and only one slave driving the MISO data line. When CPHA = 1 for a slave, the first edge of the SPSCK indicates the beginning of the transmission. This causes the SPI to leave its idle state and begin driving the MISO pin with the MSB of its data. Once the transmission begins, no new data is allowed into the shift register from the transmit data register. Therefore, the SPI data register of the slave must be loaded with transmit data before the first edge of SPSCK. Any data written after the first edge is stored in the transmit data register and transferred to the shift register after the current transmission.
SPSCK CYCLE # FOR REFERENCE SPSCK; CPOL = 0 SPSCK; CPOL =1 MOSI FROM MASTER MISO FROM SLAVE SS; TO SLAVE CAPTURE STROBE MSB MSB BIT 6 BIT 6 BIT 5 BIT 5 BIT 4 BIT 4 BIT 3 BIT 3 BIT 2 BIT 2 BIT 1 BIT 1 LSB LSB 1 2 3 4 5 6 7 8
Figure 15-7. Transmission Format (CPHA = 1)
15.4.4 Transmission Initiation Latency
When the SPI is configured as a master (SPMSTR = 1), writing to the SPDR starts a transmission. CPHA has no effect on the delay to the start of the transmission, but it does affect the initial state of the SPSCK signal. When CPHA = 0, the SPSCK signal remains inactive for the first half of the first SPSCK cycle. When CPHA = 1, the first SPSCK cycle begins with an edge on the SPSCK line from its inactive to its active level. The SPI clock rate (selected by SPR1:SPR0) affects the delay from the write to SPDR and the start of the SPI transmission. (See Figure 15-8.) The internal SPI clock in the master is a free-running derivative of the internal MCU clock. To conserve power, it is enabled only when both the SPE and SPMSTR bits are set. Since the SPI clock is free-running, it is uncertain where the write to the SPDR occurs relative to the slower SPSCK. This uncertainty causes the variation in the initiation delay shown in Figure 15-8. This delay is no longer than a single SPI bit time. That is, the maximum delay is two MCU bus cycles for DIV2, eight MCU bus cycles for DIV8, 32 MCU bus cycles for DIV32, and 128 MCU bus cycles for DIV128.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 181
Serial Peripheral Interface (SPI) Module
WRITE TO SPDR BUS CLOCK MOSI SPSCK CPHA = 1 SPSCK CPHA = 0 SPSCK CYCLE NUMBER 1 2 3 MSB BIT 6 BIT 5
INITIATION DELAY
INITIATION DELAY FROM WRITE SPDR TO TRANSFER BEGIN
WRITE TO SPDR BUS CLOCK EARLIEST WRITE TO SPDR LATEST SPSCK = BUS CLOCK / 2; 2 POSSIBLE START POINTS
BUS CLOCK
EARLIEST WRITE TO SPDR
SPSCK = BUS CLOCK / 8; 8 POSSIBLE START POINTS
LATEST
BUS CLOCK
EARLIEST WRITE TO SPDR
SPSCK = BUS CLOCK / 32; 32 POSSIBLE START POINTS
LATEST
BUS CLOCK
EARLIEST
SPSCK = BUS CLOCK / 128; 128 POSSIBLE START POINTS
LATEST
Figure 15-8. Transmission Start Delay (Master)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 182 Freescale Semiconductor
Queuing Transmission Data
15.5 Queuing Transmission Data
The double-buffered transmit data register allows a data byte to be queued and transmitted. For an SPI configured as a master, a queued data byte is transmitted immediately after the previous transmission has completed. The SPI transmitter empty flag (SPTE) indicates when the transmit data buffer is ready to accept new data. Write to the transmit data register only when SPTE is high. Figure 15-9 shows the timing associated with doing back-to-back transmissions with the SPI (SPSCK has CPHA: CPOL = 1:0).
WRITE TO SPDR SPTE SPSCK CPHA:CPOL = 1:0 MOSI SPRF READ SPSCR READ SPDR 1 CPU WRITES BYTE 1 TO SPDR, CLEARING SPTE BIT. 2 BYTE 1 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 3 CPU WRITES BYTE 2 TO SPDR, QUEUEING BYTE 2 AND CLEARING SPTE BIT. 4 FIRST INCOMING BYTE TRANSFERS FROM SHIFT REGISTER TO RECEIVE DATA REGISTER, SETTING SPRF BIT. 5 BYTE 2 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 6 CPU READS SPSCR WITH SPRF BIT SET. MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT 654 654321 654321 BYTE 1 BYTE 2 BYTE 3 4 6 7 7 CPU READS SPDR, CLEARING SPRF BIT. 8 CPU WRITES BYTE 3 TO SPDR, QUEUEING BYTE 3 AND CLEARING SPTE BIT. 9 SECOND INCOMING BYTE TRANSFERS FROM SHIFT REGISTER TO RECEIVE DATA REGISTER, SETTING SPRF BIT. 10 BYTE 3 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 11 CPU READS SPSCR WITH SPRF BIT SET. 12 CPU READS SPDR, CLEARING SPRF BIT. 9 11 12 1 2 3 5 8 10
Figure 15-9. SPRF/SPTE CPU Interrupt Timing The transmit data buffer allows back-to-back transmissions without the slave precisely timing its writes between transmissions as in a system with a single data buffer. Also, if no new data is written to the data buffer, the last value contained in the shift register is the next data word to be transmitted. For an idle master or idle slave that has no data loaded into its transmit buffer, the SPTE is set again no more than two bus cycles after the transmit buffer empties into the shift register. This allows the user to queue up a 16-bit value to send. For an already active slave, the load of the shift register cannot occur until the transmission is completed. This implies that a back-to-back write to the transmit data register is not possible. SPTE indicates when the next write can occur.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 183
Serial Peripheral Interface (SPI) Module
15.6 Error Conditions
The following flags signal SPI error conditions: * Overflow (OVRF) -- Failing to read the SPI data register before the next full byte enters the shift register sets the OVRF bit. The new byte does not transfer to the receive data register, and the unread byte still can be read. OVRF is in the SPI status and control register. * Mode fault error (MODF) -- The MODF bit indicates that the voltage on the slave select pin (SS) is inconsistent with the mode of the SPI. MODF is in the SPI status and control register.
15.6.1 Overflow Error
The overflow flag (OVRF) becomes set if the receive data register still has unread data from a previous transmission when the capture strobe of bit 1 of the next transmission occurs. The bit 1 capture strobe occurs in the middle of SPSCK cycle 7 (see Figure 15-5 and Figure 15-7.) If an overflow occurs, all data received after the overflow and before the OVRF bit is cleared does not transfer to the receive data register and does not set the SPI receiver full bit (SPRF). The unread data that transferred to the receive data register before the overflow occurred can still be read. Therefore, an overflow error always indicates the loss of data. Clear the overflow flag by reading the SPI status and control register and then reading the SPI data register. OVRF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector (see Figure 15-12.) It is not possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low prevents MODF from being set. If the CPU SPRF interrupt is enabled and the OVRF interrupt is not, watch for an overflow condition. Figure 15-10 shows how it is possible to miss an overflow. The first part of Figure 15-10 shows how it is possible to read the SPSCR and SPDR to clear the SPRF without problems. However, as illustrated by the second transmission example, the OVRF bit can be set in between the time that SPSCR and SPDR are read.
BYTE 1 1 SPRF OVRF READ SPSCR READ SPDR 1 2 3 4 2 5 BYTE 2 4 BYTE 3 6 BYTE 4 8
3 BYTE 1 SETS SPRF BIT. CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. CPU READS BYTE 1 IN SPDR, CLEARING SPRF BIT. BYTE 2 SETS SPRF BIT. 5 6 7 8
7 CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST. CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT, BUT NOT OVRF BIT. BYTE 4 FAILS TO SET SPRF BIT BECAUSE OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST.
Figure 15-10. Missed Read of Overflow Condition
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 184 Freescale Semiconductor
Error Conditions
In this case, an overflow can be missed easily. Since no more SPRF interrupts can be generated until this OVRF is serviced, it is not obvious that bytes are being lost as more transmissions are completed. To prevent this, either enable the OVRF interrupt or do another read of the SPSCR following the read of the SPDR. This ensures that the OVRF was not set before the SPRF was cleared and that future transmissions can set the SPRF bit. Figure 15-11 illustrates this process. Generally, to avoid this second SPSCR read, enable the OVRF to the CPU by setting the ERRIE bit.
BYTE 1 SPI RECEIVE COMPLETE SPRF OVRF READ SPSCR READ SPDR 1 2 3 4 5 6 7 2 3 BYTE 1 SETS SPRF BIT. CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. CPU READS BYTE 1 IN SPDR, CLEARING SPRF BIT. CPU READS SPSCR AGAIN TO CHECK OVRF BIT. BYTE 2 SETS SPRF BIT. CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST. 4 6 8 8 9 9 10 12 13 14 1 BYTE 2 5 BYTE 3 7 BYTE 4 11
CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT. CPU READS SPSCR AGAIN TO CHECK OVRF BIT.
10 CPU READS BYTE 2 SPDR, CLEARING OVRF BIT. 11 BYTE 4 SETS SPRF BIT. 12 CPU READS SPSCR. 13 CPU READS BYTE 4 IN SPDR, CLEARING SPRF BIT. 14 CPU READS SPSCR AGAIN TO CHECK OVRF BIT.
Figure 15-11. Clearing SPRF When OVRF Interrupt Is Not Enabled
15.6.2 Mode Fault Error
Setting SPMSTR selects master mode and configures the SPSCK and MOSI pins as outputs and the MISO pin as an input. Clearing SPMSTR selects slave mode and configures the SPSCK and MOSI pins as inputs and the MISO pin as an output. The mode fault bit, MODF, becomes set any time the state of the slave select pin, SS, is inconsistent with the mode selected by SPMSTR. To prevent SPI pin contention and damage to the MCU, a mode fault error occurs if: * The SS pin of a slave SPI goes high during a transmission * The SS pin of a master SPI goes low at any time For the MODF flag to be set, the mode fault error enable bit (MODFEN) must be set. Clearing the MODFEN bit does not clear the MODF flag but does prevent MODF from being set again after MODF is cleared. MODF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector. (See Figure 15-12.) It is not possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low prevents MODF from being set.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 185
Serial Peripheral Interface (SPI) Module
In a master SPI with the mode fault enable bit (MODFEN) set, the mode fault flag (MODF) is set if SS goes low. A mode fault in a master SPI causes the following events to occur: * If ERRIE = 1, the SPI generates an SPI receiver/error CPU interrupt request. * The SPE bit is cleared. * The SPTE bit is set. * The SPI state counter is cleared. * The data direction register of the shared I/O port regains control of port drivers. NOTE To prevent bus contention with another master SPI after a mode fault error, clear all SPI bits of the data direction register of the shared I/O port before enabling the SPI. When configured as a slave (SPMSTR = 0), the MODF flag is set if SS goes high during a transmission. When CPHA = 0, a transmission begins when SS goes low and ends once the incoming SPSCK goes back to its idle level following the shift of the eighth data bit. When CPHA = 1, the transmission begins when the SPSCK leaves its idle level and SS is already low. The transmission continues until the SPSCK returns to its idle level following the shift of the last data bit. See 15.4 Transmission Formats. NOTE Setting the MODF flag does not clear the SPMSTR bit. SPMSTR has no function when SPE = 0. Reading SPMSTR when MODF = 1 shows the difference between a MODF occurring when the SPI is a master and when it is a slave. NOTE When CPHA = 0, a MODF occurs if a slave is selected (SS is low) and later unselected (SS is high) even if no SPSCK is sent to that slave. This happens because SS low indicates the start of the transmission (MISO driven out with the value of MSB) for CPHA = 0. When CPHA = 1, a slave can be selected and then later unselected with no transmission occurring. Therefore, MODF does not occur since a transmission was never begun. In a slave SPI (MSTR = 0), MODF generates an SPI receiver/error CPU interrupt request if the ERRIE bit is set. The MODF bit does not clear the SPE bit or reset the SPI in any way. Software can abort the SPI transmission by clearing the SPE bit of the slave. NOTE A high on the SS pin of a slave SPI puts the MISO pin in a high impedance state. Also, the slave SPI ignores all incoming SPSCK clocks, even if it was already in the middle of a transmission. To clear the MODF flag, read the SPSCR with the MODF bit set and then write to the SPCR register. This entire clearing mechanism must occur with no MODF condition existing or else the flag is not cleared.
15.7 Interrupts
Four SPI status flags can be enabled to generate CPU interrupt requests. See Table 15-1.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 186 Freescale Semiconductor
Interrupts
Table 15-1. SPI Interrupts
Flag SPTE Transmitter empty SPRF Receiver full OVRF Overflow MODF Mode fault Request SPI transmitter CPU interrupt request (SPTIE = 1, SPE = 1) SPI receiver CPU interrupt request (SPRIE = 1) SPI receiver/error interrupt request (ERRIE = 1) SPI receiver/error interrupt request (ERRIE = 1)
Reading the SPI status and control register with SPRF set and then reading the receive data register clears SPRF. The clearing mechanism for the SPTE flag is always just a write to the transmit data register. The SPI transmitter interrupt enable bit (SPTIE) enables the SPTE flag to generate transmitter CPU interrupt requests, provided that the SPI is enabled (SPE = 1). The SPI receiver interrupt enable bit (SPRIE) enables SPRF to generate receiver CPU interrupt requests, regardless of the state of SPE. See Figure 15-12. The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error CPU interrupt request.
SPTE SPTIE SPE SPI TRANSMITTER CPU INTERRUPT REQUEST
SPRIE
SPRF
SPI RECEIVER/ERROR ERRIE MODF OVRF CPU INTERRUPT REQUEST
Figure 15-12. SPI Interrupt Request Generation The mode fault enable bit (MODFEN) can prevent the MODF flag from being set so that only the OVRF bit is enabled by the ERRIE bit to generate receiver/error CPU interrupt requests. * The following sources in the SPI status and control register can generate CPU interrupt requests: * SPI receiver full bit (SPRF) -- SPRF becomes set every time a byte transfers from the shift register to the receive data register. If the SPI receiver interrupt enable bit, SPRIE, is also set, SPRF generates an SPI receiver/error CPU interrupt request. * SPI transmitter empty (SPTE) -- SPTE becomes set every time a byte transfers from the transmit data register to the shift register. If the SPI transmit interrupt enable bit, SPTIE, is also set, SPTE generates an SPTE CPU interrupt request.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 187
Serial Peripheral Interface (SPI) Module
15.8 Resetting the SPI
Any system reset completely resets the SPI. Partial resets occur whenever the SPI enable bit (SPE) is 0. Whenever SPE is 0, the following occurs: * The SPTE flag is set. * Any transmission currently in progress is aborted. * The shift register is cleared. * The SPI state counter is cleared, making it ready for a new complete transmission. * All the SPI port logic is defaulted back to being general-purpose I/O. These items are reset only by a system reset: * All control bits in the SPCR register * All control bits in the SPSCR register (MODFEN, ERRIE, SPR1, and SPR0) * The status flags SPRF, OVRF, and MODF By not resetting the control bits when SPE is low, the user can clear SPE between transmissions without having to set all control bits again when SPE is set back high for the next transmission. By not resetting the SPRF, OVRF, and MODF flags, the user can still service these interrupts after the SPI has been disabled. The user can disable the SPI by writing 0 to the SPE bit. The SPI can also be disabled by a mode fault occurring in an SPI that was configured as a master with the MODFEN bit set.
15.9 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
15.9.1 Wait Mode
The SPI module remains active after the execution of a WAIT instruction. In wait mode the SPI module registers are not accessible by the CPU. Any enabled CPU interrupt request from the SPI module can bring the MCU out of wait mode. If SPI module functions are not required during wait mode, reduce power consumption by disabling the SPI module before executing the WAIT instruction. To exit wait mode when an overflow condition occurs, enable the OVRF bit to generate CPU interrupt requests by setting the error interrupt enable bit (ERRIE). See 15.7 Interrupts.
15.9.2 Stop Mode
The SPI module is inactive after the execution of a STOP instruction. The STOP instruction does not affect register conditions. SPI operation resumes after an external interrupt. If stop mode is exited by reset, any transfer in progress is aborted, and the SPI is reset.
15.10 SPI During Break Interrupts
The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. BCFE in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. See Chapter 14 System Integration Module (SIM). To allow software to clear status bits during a break interrupt, write a 1 to BCFE. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 188 Freescale Semiconductor
I/O Signals
To protect status bits during the break state, write a 0 to BCFE. With BCFE at 0 (its default state), software can read and write I/O registers during the break state without affecting status bits. Some status bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is 0. After the break, doing the second step clears the status bit. Since the SPTE bit cannot be cleared during a break with BCFE cleared, a write to the transmit data register in break mode does not initiate a transmission nor is this data transferred into the shift register. Therefore, a write to the SPDR in break mode with BCFE cleared has no effect.
15.11 I/O Signals
The SPI module has four I/O pins: * MISO -- Master input/slave output * MOSI -- Master output/slave input * SPSCK -- Serial clock * SS -- Slave select The SPI has limited inter-integrated circuit (I2C) capability (requiring software support) as a master in a single-master environment. To communicate with I2C peripherals, MOSI becomes an open-drain output when the SPWOM bit in the SPI control register is set. In I2C communication, the MOSI and MISO pins are connected to a bidirectional pin from the I2C peripheral and through a pullup resistor to VDD.
15.11.1 MISO (Master In/Slave Out)
MISO is one of the two SPI module pins that transmits serial data. In full duplex operation, the MISO pin of the master SPI module is connected to the MISO pin of the slave SPI module. The master SPI simultaneously receives data on its MISO pin and transmits data from its MOSI pin. Slave output data on the MISO pin is enabled only when the SPI is configured as a slave. The SPI is configured as a slave when its SPMSTR bit is 0 and its SS pin is low. To support a multiple-slave system, a high on the SS pin puts the MISO pin in a high-impedance state. When enabled, the SPI controls data direction of the MISO pin regardless of the state of the data direction register of the shared I/O port.
15.11.2 MOSI (Master Out/Slave In)
MOSI is one of the two SPI module pins that transmits serial data. In full-duplex operation, the MOSI pin of the master SPI module is connected to the MOSI pin of the slave SPI module. The master SPI simultaneously transmits data from its MOSI pin and receives data on its MISO pin. When enabled, the SPI controls data direction of the MOSI pin regardless of the state of the data direction register of the shared I/O port.
15.11.3 SPSCK (Serial Clock)
The serial clock synchronizes data transmission between master and slave devices. In a master MCU, the SPSCK pin is the clock output. In a slave MCU, the SPSCK pin is the clock input. In full-duplex operation, the master and slave MCUs exchange a byte of data in eight serial clock cycles.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 189
Serial Peripheral Interface (SPI) Module
When enabled, the SPI controls data direction of the SPSCK pin regardless of the state of the data direction register of the shared I/O port.
15.11.4 SS (Slave Select)
The SS pin has various functions depending on the current state of the SPI. For an SPI configured as a slave, SS is used to select a slave. For CPHA = 0, SS is used to define the start of a transmission. (See 15.4 Transmission Formats.) Since it is used to indicate the start of a transmission, SS must be toggled high and low between each byte transmitted for the CPHA = 0 format. However, it can remain low between transmissions for the CPHA = 1 format. See Figure 15-13.
MISO/MOSI MASTER SS SLAVE SS CPHA = 0 SLAVE SS CPHA = 1 BYTE 1 BYTE 2 BYTE 3
Figure 15-13. CPHA/SS Timing When an SPI is configured as a slave, the SS pin is always configured as an input. It cannot be used as a general-purpose I/O regardless of the state of the MODFEN control bit. However, the MODFEN bit can still prevent the state of SS from creating a MODF error. See 15.12.2 SPI Status and Control Register. NOTE A high on the SS pin of a slave SPI puts the MISO pin in a high-impedance state. The slave SPI ignores all incoming SPSCK clocks, even if it was already in the middle of a transmission. When an SPI is configured as a master, the SS input can be used in conjunction with the MODF flag to prevent multiple masters from driving MOSI and SPSCK. (See 15.6.2 Mode Fault Error.) For the state of the SS pin to set the MODF flag, the MODFEN bit in the SPSCK register must be set. If MODFEN is 0 for an SPI master, the SS pin can be used as a general-purpose I/O under the control of the data direction register of the shared I/O port. When MODFEN is 1, SS is an input-only pin to the SPI regardless of the state of the data direction register of the shared I/O port. The CPU can always read the state of the SS pin by configuring the appropriate pin as an input and reading the port data register. See Table 15-2. Table 15-2. SPI Configuration
SPE 0 1 1 1 SPMSTR X(1)) 0 1 1 MODFEN X X 0 1 SPI Configuration Not enabled Slave Master without MODF Master with MODF Function of SS Pin General-purpose I/O; SS ignored by SPI Input-only to SPI General-purpose I/O; SS ignored by SPI Input-only to SPI
1. X = Don't care
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 190 Freescale Semiconductor
I/O Registers
15.12 I/O Registers
Three registers control and monitor SPI operation: * SPI control register (SPCR) * SPI status and control register (SPSCR) * SPI data register (SPDR)
15.12.1 SPI Control Register
The SPI control register: * Enables SPI module interrupt requests * Configures the SPI module as master or slave * Selects serial clock polarity and phase * Configures the SPSCK, MOSI, and MISO pins as open-drain outputs * Enables the SPI module
Address: $0010 Bit 7 Read: Write: Reset: SPRIE 0 R 6 R 0 = Reserved 5 SPMSTR 1 4 CPOL 0 3 CPHA 1 2 SPWOM 0 1 SPE 0 Bit 0 SPTIE 0
Figure 15-14. SPI Control Register (SPCR) SPRIE -- SPI Receiver Interrupt Enable Bit This read/write bit enables CPU interrupt requests generated by the SPRF bit. The SPRF bit is set when a byte transfers from the shift register to the receive data register. Reset clears the SPRIE bit. 1 = SPRF CPU interrupt requests enabled 0 = SPRF CPU interrupt requests disabled SPMSTR -- SPI Master Bit This read/write bit selects master mode operation or slave mode operation. Reset sets the SPMSTR bit. 1 = Master mode 0 = Slave mode CPOL -- Clock Polarity Bit This read/write bit determines the logic state of the SPSCK pin between transmissions. (See Figure 15-5 and Figure 15-7.) To transmit data between SPI modules, the SPI modules must have identical CPOL values. Reset clears the CPOL bit. CPHA -- Clock Phase Bit This read/write bit controls the timing relationship between the serial clock and SPI data. (See Figure 15-5 and Figure 15-7.) To transmit data between SPI modules, the SPI modules must have identical CPHA values. When CPHA = 0, the SS pin of the slave SPI module must be high between bytes. (See Figure 15-13.) Reset sets the CPHA bit. SPWOM -- SPI Wired-OR Mode Bit This read/write bit disables the pullup devices on pins SPSCK, MOSI, and MISO so that those pins become open-drain outputs. 1 = Wired-OR SPSCK, MOSI, and MISO pins 0 = Normal push-pull SPSCK, MOSI, and MISO pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 191
Serial Peripheral Interface (SPI) Module
SPE -- SPI Enable This read/write bit enables the SPI module. Clearing SPE causes a partial reset of the SPI. (See 15.8 Resetting the SPI.) Reset clears the SPE bit. 1 = SPI module enabled 0 = SPI module disabled SPTIE-- SPI Transmit Interrupt Enable This read/write bit enables CPU interrupt requests generated by the SPTE bit. SPTE is set when a byte transfers from the transmit data register to the shift register. Reset clears the SPTIE bit. 1 = SPTE CPU interrupt requests enabled 0 = SPTE CPU interrupt requests disabled
15.12.2 SPI Status and Control Register
The SPI status and control register contains flags to signal these conditions: * Receive data register full * Failure to clear SPRF bit before next byte is received (overflow error) * Inconsistent logic level on SS pin (mode fault error) * Transmit data register empty The SPI status and control register also contains bits that perform these functions: * Enable error interrupts * Enable mode fault error detection * Select master SPI baud rate
Address: $0011 Bit 7 Read: Write: Reset: 0 SPRF 6 ERRIE 0 5 OVRF 0 4 MODF 0 3 SPTE 1 2 MODFEN 0 1 SPR1 0 Bit 0 SPR0 0
= Unimplemented
Figure 15-15. SPI Status and Control Register (SPSCR) SPRF -- SPI Receiver Full Bit This clearable, read-only flag is set each time a byte transfers from the shift register to the receive data register. SPRF generates a CPU interrupt request if the SPRIE bit in the SPI control register is set also. During an SPRF CPU interrupt, the CPU clears SPRF by reading the SPI status and control register with SPRF set and then reading the SPI data register. Reset clears the SPRF bit. 1 = Receive data register full 0 = Receive data register not full ERRIE -- Error Interrupt Enable Bit This read/write bit enables the MODF and OVRF bits to generate CPU interrupt requests. Reset clears the ERRIE bit. 1 = MODF and OVRF can generate CPU interrupt requests 0 = MODF and OVRF cannot generate CPU interrupt requests
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 192 Freescale Semiconductor
I/O Registers
OVRF -- Overflow Bit This clearable, read-only flag is set if software does not read the byte in the receive data register before the next full byte enters the shift register. In an overflow condition, the byte already in the receive data register is unaffected, and the byte that shifted in last is lost. Clear the OVRF bit by reading the SPI status and control register with OVRF set and then reading the receive data register. Reset clears the OVRF bit. 1 = Overflow 0 = No overflow MODF -- Mode Fault Bit This clearable, read-only flag is set in a slave SPI if the SS pin goes high during a transmission with MODFEN set. In a master SPI, the MODF flag is set if the SS pin goes low at any time with the MODFEN bit set. Clear MODF by reading the SPI status and control register (SPSCR) with MODF set and then writing to the SPI control register (SPCR). Reset clears the MODF bit. 1 = SS pin at inappropriate logic level 0 = SS pin at appropriate logic level SPTE -- SPI Transmitter Empty Bit This clearable, read-only flag is set each time the transmit data register transfers a byte into the shift register. SPTE generates an SPTE CPU interrupt request if SPTIE in the SPI control register is set also. NOTE Do not write to the SPI data register unless SPTE is high. During an SPTE CPU interrupt, the CPU clears SPTE bit writing to the transmit data register. Reset sets the SPTE bit. 1 = Transmit data register empty 0 = Transmit data register not empty MODFEN -- Mode Fault Enable Bit This read/write bit, when set, allows the MODF flag to be set. If the MODF flag is set, clearing MODFEN does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is 0, then the SS pin is available as a general-purpose I/O. If the MODFEN bit is 1, then the SS is not available as a general-purpose I/O. When the SPI is enabled as a slave, the SS pin is not available as a general-purpose I/O regardless of the value of MODFEN. See 15.11.4 SS (Slave Select). If the MODFEN bit is 0, the level of the SS pin does not affect the operation of an enabled SPI configured as a master. For an enabled SPI configured as a slave, having MODFEN low only prevents the MODF flag from being set. It does not affect any other part of SPI operation. See 15.6.2 Mode Fault Error. SPR1 and SPR0 -- SPI Baud Rate Select Bits In master mode, these read/write bits select one of four baud rates as shown in Table 15-3. SPR1 and SPR0 have no effect in slave mode. Reset clears SPR1 and SPR0. Table 15-3. SPI Master Baud Rate Selection
SPR1 and SPR0 00 01 10 11 Baud Rate Divisor (BD) 2 8 32 128
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 193
Serial Peripheral Interface (SPI) Module
Use this formula to calculate the SPI baud rate: Baud rate = BUSCLK BD
15.12.3 SPI Data Register
The SPI data register consists of the read-only receive data register and the write-only transmit data register. Writing to the SPI data register writes data into the transmit data register. Reading the SPI data register reads data from the receive data register. The transmit data and receive data registers are separate registers that can contain different values. See Figure 15-2.
Address: $0012 Bit 7 Read: Write: Reset: R7 T7 6 R6 T6 5 R5 T5 4 R4 T4 3 R3 T3 2 R2 T2 1 R1 T1 Bit 0 R0 T0
Unaffected by reset
Figure 15-16. SPI Data Register (SPDR) R7-R0/T7-T0 -- Receive/Transmit Data Bits NOTE Do not use read-modify-write instructions on the SPI data register since the register read is not the same as the register written.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 194 Freescale Semiconductor
Chapter 16 Timebase Module (TBM)
16.1 Introduction
This section describes the timebase module (TBM). The TBM will generate periodic interrupts at user selectable rates using a counter clocked by the external clock source. This TBM version uses 15 divider stages, eight of which are user selectable.
16.2 Features
Features of the TBM module include: * Software configurable periodic interrupts with divide-by: 8, 16, 32, 64, 128, 2048, 8192, and 32768 taps of the selected clock source * Configurable for operation during stop mode to allow periodic wakeup from stop
16.3 Functional Description
This module can generate a periodic interrupt by dividing the clock source supplied from the clock generator module, CGMXCLK. The counter is initialized to all 0s when TBON bit is cleared. The counter, shown in Figure 16-1, starts counting when the TBON bit is set. When the counter overflows at the tap selected by TBR2-TBR0, the TBIF bit gets set. If the TBIE bit is set, an interrupt request is sent to the CPU. The TBIF flag is cleared by writing a 1 to the TACK bit. The first time the TBIF flag is set after enabling the timebase module, the interrupt is generated at approximately half of the overflow period. Subsequent events occur at the exact period. The timebase module may remain active after execution of the STOP instruction if the crystal oscillator has been enabled to operate during stop mode through the OSCSTOPENB bit in the configuration register. The timebase module can be used in this mode to generate a periodic wakeup from stop mode.
16.4 Interrupts
The timebase module can periodically interrupt the CPU with a rate defined by the selected TBMCLK and the select bits TBR2-TBR0. When the timebase counter chain rolls over, the TBIF flag is set. If the TBIE bit is set, enabling the timebase interrupt, the counter chain overflow will generate a CPU interrupt request. NOTE Interrupts must be acknowledged by writing a 1 to the TACK bit.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 195
Timebase Module (TBM)
TBON
CGMXCLK
/2
/2
/2
/2
/2
/2
/2
TBMINT
/2
/2
/2
/2
/2
/2
/2
/2
TACK
TBR2
TBR1
TBR0
TBIF 000 001 010 011 100 101 110 111 SEL R
TBIE
Figure 16-1. Timebase Block Diagram
16.5 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
16.5.1 Wait Mode
The timebase module remains active after execution of the WAIT instruction. In wait mode the timebase register is not accessible by the CPU. If the timebase functions are not required during wait mode, reduce the power consumption by stopping the timebase before executing the WAIT instruction.
16.5.2 Stop Mode
The timebase module may remain active after execution of the STOP instruction if the internal clock generator has been enabled to operate during stop mode through the OSCSTOPENB bit in the configuration register. The timebase module can be used in this mode to generate a periodic wakeup from stop mode. If the internal clock generator has not been enabled to operate in stop mode, the timebase module will not be active during stop mode. In stop mode, the timebase register is not accessible by the CPU.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 196 Freescale Semiconductor
Timebase Control Register
If the timebase functions are not required during stop mode, reduce power consumption by disabling the timebase module before executing the STOP instruction.
16.6 Timebase Control Register
The timebase has one register, the timebase control register (TBCR), which is used to enable the timebase interrupts and set the rate.
Address: $001C Bit 7 Read: Write: Reset: 0 TBIF 6 TBR2 0 5 TBR1 0 4 TBR0 0 3 0 TACK 0 R 2 TBIE 0 = Reserved 1 TBON 0 Bit 0 R 0
= Unimplemented
Figure 16-2. Timebase Control Register (TBCR) TBIF -- Timebase Interrupt Flag This read-only flag bit is set when the timebase counter has rolled over. 1 = Timebase interrupt pending 0 = Timebase interrupt not pending TBR2-TBR0 -- Timebase Divider Selection Bits These read/write bits select the tap in the counter to be used for timebase interrupts as shown in Table 16-1. Table 16-1. Timebase Divider Selection
TBR2 0 0 0 0 1 1 1 1 TBR1 0 0 1 1 0 0 1 1 TBR0 0 1 0 1 0 1 0 1 Divider 32,768 8192 2048 128 64 32 16 8
NOTE Do not change TBR2-TBR0 bits while the timebase is enabled (TBON = 1). TACK-- Timebase Acknowledge Bit The TACK bit is a write-only bit and always reads as 0. Writing a 1 to this bit clears TBIF, the timebase interrupt flag bit. Writing a 0 to this bit has no effect. 1 = Clear timebase interrupt flag 0 = No effect
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 197
Timebase Module (TBM)
TBIE -- Timebase Interrupt Enabled Bit This read/write bit enables the timebase interrupt when the TBIF bit becomes set. Reset clears the TBIE bit. 1 = Timebase interrupt is enabled. 0 = Timebase interrupt is disabled. TBON -- Timebase Enabled Bit This read/write bit enables the timebase. Timebase may be turned off to reduce power consumption when its function is not necessary. The counter can be initialized by clearing and then setting this bit. Reset clears the TBON bit. 1 = Timebase is enabled. 0 = Timebase is disabled and the counter initialized to 0s.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 198 Freescale Semiconductor
Chapter 17 Timer Interface Module (TIM1 and TIM2)
17.1 Introduction
This section describes the timer interface (TIM) module. The timer on this part consists of a 2-channel and a 1-channel timer that provides a timing reference with input capture, output compare, and pulse-width-modulation functions. Figure 17-1 is a block diagram of the TIM. This particular MCU has two timer interface modules which are denoted as TIM1 and TIM2.
INTERNAL BUS CLOCK TSTOP TRST
PRESCALER SELECT PRESCALER
PS2
PS1
PS0
16-BIT COUNTER 16-BIT COMPARATOR TMODH:TMODL
TOF TOIE
INTERRUPT LOGIC
TOV0 CHANNEL 0 INTERNAL BUS 16-BIT COMPARATOR TCH0H:TCH0L 16-BIT LATCH MS0A MS0B TOV1 CHANNEL 1 16-BIT COMPARATOR TCH1H:TCH1L 16-BIT LATCH MS1A CH1IE CH1F INTERRUPT LOGIC ELS1B ELS1A CH1MAX PORT LOGIC T1CH1 CH0F CH0IE INTERRUPT LOGIC ELS0B ELS0A CH0MAX PORT LOGIC T[1,2]CH0
Figure 17-1. TIM Block Diagram
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 199
Timer Interface Module (TIM1 and TIM2)
INTERNAL BUS M68HC08 CPU PORTA DDRA CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) PROGRAMMABLE TIMEBASE MODULE SINGLE BREAKPOINT BREAK MODULE DUAL VOLTAGE LOW-VOLTAGE INHIBIT MODULE 4-BIT KEYBOARD INTERRUPT MODULE PORTC DDRC 2-CHANNEL TIMER INTERFACE MODULE 1 1-CHANNEL TIMER INTERFACE MODULE 2 SERIAL COMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE RST(3) IRQ(3) VDDAD/VREFH VSSAD/VREFL SYSTEM INTEGRATION MODULE SINGLE EXTERNAL INTERRUPT MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE POWER-ON RESET MODULE VDD VSS VDDA VSSA SERIAL PERIPHERAL INTERFACE MODULE MONITOR MODULE MEMORY MAP MODULE CONFIGURATION REGISTER 1 MODULE CONFIGURATION REGISTER 2 MODULE PORTB DDRB PTA3/KBD3- PTA0/KBD0(1)
CONTROL AND STATUS REGISTERS -- 64 BYTES MC68HC908GR8A USER FLASH -- 7680 BYTES MC68HC908GR4A USER FLASH -- 4096 BYTES USER RAM -- 384 BYTES MONITOR ROM -- 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM -- 544 BYTES USER FLASH VECTOR SPACE -- 36 BYTES CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 1-8-MHz OSCILLATOR PHASE LOCKED LOOP
PTB5/AD5 PTB4/AD4 PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0
PTC1(1), (2) PTC0(1), (2)
PTD6/T2CH0(1) PTD5/T1CH1(1) PTD4/T1CH0(1) PTD3/SPSCK(1) PTD2/MOSI(1) PTD1/MISO(1) PTD0/SS(1)
PORTE
PORTD
DDRD
PTE1/RxD PTE0/TxD
DDRE
SECURITY MODULE
POWER
MONITOR MODE ENTRY MODULE
1. Ports are software configurable with pullup device if input port. 2. Higher current drive port pins 3. Pin contains integrated pullup device
Figure 17-2. Block Diagram Highlighting TIM Block and Pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 200 Freescale Semiconductor
Features
17.2 Features
Features of the TIM include: * Three input capture/output compare channels: - Rising-edge, falling-edge, or any-edge input capture trigger - Set, clear, or toggle output compare action * Buffered and unbuffered pulse-width-modulation (PWM) signal generation * Programmable TIM clock input with 7-frequency internal bus clock prescaler selection * Free-running or modulo up-count operation * Toggle any channel pin on overflow * TIM counter stop and reset bits
17.3 Pin Name Conventions
The text that follows describes both timers, TIM1 and TIM2. The TIM input/output (I/O) pin names are T[1,2]CH0 (timer channel 0) and T[1,2]CH1 (timer channel 1), where "1" is used to indicate TIM1 and "2" is used to indicate TIM2. The two TIMs share three I/O pins with three port D I/O port pins. The full names of the TIM I/O pins are listed in Table 17-1. The generic pin names appear in the text that follows. Table 17-1. Pin Name Conventions
TIM Generic Pin Names: TIM1 Full TIM Pin Names: TIM2 PTD6/T2CH0 -- T[1,2]CH0 PTD4/T1CH0 T[1,2]CH1 PTD5/T1CH1
NOTE References to either timer 1 or timer 2 may be made in the following text by omitting the timer number. For example, TCH0 may refer generically to T1CH0 and T2CH0.
17.4 Functional Description
Figure 17-1 shows the structure of the TIM. The central component of the TIM is the 16-bit TIM counter that can operate as a free-running counter or a modulo up-counter. The TIM counter provides the timing reference for the input capture and output compare functions. The TIM counter modulo registers, TMODH:TMODL, control the modulo value of the TIM counter. Software can read the TIM counter value at any time without affecting the counting sequence. The two TIM channels (per timer) are programmable independently as input capture or output compare channels. If a channel is configured as input capture, then an internal pullup device may be enabled for that channel. See 12.5.3 Port D Input Pullup Enable Register. Figure 17-3 summarizes the timer registers. NOTE References to either timer 1 or timer 2 may be made in the following text by omitting the timer number. For example, TSC may generically refer to both T1SC and T2SC.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 201
Timer Interface Module (TIM1 and TIM2) Addr. $0020 Register Name Timer 1 Status and Control Read: Register (T1SC) Write: See page 209. Reset: Timer 1 Counter Read: Register High (T1CNTH) Write: See page 210. Reset: Timer 1 Counter Read: Register Low (T1CNTL) Write: See page 210. Reset: Timer 1 Counter Modulo Read: Register High (T1MODH) Write: See page 211. Reset: Timer 1 Counter Modulo Read: Register Low (T1MODL) Write: See page 211. Reset: Timer 1 Channel 0 Status and Read: Control Register (T1SC0) Write: See page 211. Reset: Timer 1 Channel 0 Read: Register High (T1CH0H) Write: See page 214. Reset: Timer 1 Channel 0 Read: Register Low (T1CH0L) Write: See page 214. Reset: Bit 7 TOF 0 0 Bit 15 0 Bit 7 0 Bit 15 1 Bit 7 1 CH0F 0 0 Bit 15 6 TOIE 0 14 0 6 0 14 1 6 1 CH0IE 0 14 5 TSTOP 1 13 0 5 0 13 1 5 1 MS0B 0 13 4 0 TRST 0 12 0 4 0 12 1 4 1 MS0A 0 12 0 11 0 3 0 11 1 3 1 ELS0B 0 11 3 0 2 PS2 0 10 0 2 0 10 1 2 1 ELS0A 0 10 1 PS1 0 9 0 1 0 9 1 1 1 TOV0 0 9 Bit 0 PS0 0 Bit 8 0 Bit 0 0 Bit 8 1 Bit 0 1 CH0MAX 0 Bit 8
$0021
$0022
$0023
$0024
$0025
$0026
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$0027
Indeterminate after reset CH1F 0 0 Bit 15 CH1IE 0 14 0 0 13 MS1A 0 12 ELS1B 0 11 ELS1A 0 10 TOV1 0 9 CH1MAX 0 Bit 8
Timer 1 Channel 1 Status and Read: $0028 Control Register (T1SC1) Write: See page 211. Reset: $0029 Timer 1 Channel 1 Read: Register High (T1CH1H) Write: See page 214. Reset: Timer 1 Channel 1 Read: Register Low (T1CH1L) Write: See page 214. Reset: Timer 2 Status and Control Read: Register (T2SC) Write: See page 209. Reset:
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$002A
Indeterminate after reset TOF 0 0 TOIE 0 = Unimplemented TSTOP 1 0 TRST 0 0 0 PS2 0 PS1 0 PS0 0
$002B
Figure 17-3. TIM I/O Register Summary (Sheet 1 of 2)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 202 Freescale Semiconductor
Functional Description Addr. $002C Register Name Timer 2 Counter Read: Register High (T2CNTH) Write: See page 210. Reset: Timer 2 Counter Read: Register Low (T2CNTL) Write: See page 210. Reset: Timer 2 Counter Modulo Read: Register High (T2MODH) Write: See page 211. Reset: Timer 2 Counter Modulo Read: Register Low (T2MODL) Write: See page 211. Reset: Bit 7 Bit 15 0 Bit 7 0 Bit 15 1 Bit 7 1 CH0F 0 0 Bit 15 6 14 0 6 0 14 1 6 1 CH0IE 0 14 5 13 0 5 0 13 1 5 1 MS0B 0 13 4 12 0 4 0 12 1 4 1 MS0A 0 12 3 11 0 3 0 11 1 3 1 ELS0B 0 11 2 10 0 2 0 10 1 2 1 ELS0A 0 10 1 9 0 1 0 9 1 1 1 TOV0 0 9 Bit 0 Bit 8 0 Bit 0 0 Bit 8 1 Bit 0 1 CH0MAX 0 Bit 8
$002D
$002E
$002F
Timer 2 Channel 0 Status and Read: $0030 Control Register (T2SC0) Write: See page 211. Reset: $0031 Timer 2 Channel 0 Read: Register High (T2CH0H) Write: See page 214. Reset: Timer 2 Channel 0 Read: Register Low (T2CH0L) Write: See page 214. Reset: Read: $0033 Reserved Write: Reset: $0034 $0035 Read: Reserved Write: Reset:
Indeterminate after reset Bit 7 6 5 4 3 2 1 Bit 0
$0032
Indeterminate after reset R 0 R R 0 R R 0 R R 0 R R 0 R R 0 R R 0 R R 0 R
Indeterminate after reset = Unimplemented
Figure 17-3. TIM I/O Register Summary (Sheet 2 of 2)
17.4.1 TIM Counter Prescaler
The TIM clock source can be one of the seven prescaler outputs. The prescaler generates seven clock rates from the internal bus clock. The prescaler select bits, PS[2:0], in the TIM status and control register select the TIM clock source.
17.4.2 Input Capture
With the input capture function, the TIM can capture the time at which an external event occurs. When an active edge occurs on the pin of an input capture channel, the TIM latches the contents of the TIM counter into the TIM channel registers, TCHxH:TCHxL. The polarity of the active edge is programmable. Input captures can generate TIM CPU interrupt requests.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 203
Timer Interface Module (TIM1 and TIM2)
17.4.3 Output Compare
With the output compare function, the TIM can generate a periodic pulse with a programmable polarity, duration, and frequency. When the counter reaches the value in the registers of an output compare channel, the TIM can set, clear, or toggle the channel pin. Output compares can generate TIM CPU interrupt requests. 17.4.3.1 Unbuffered Output Compare Any output compare channel can generate unbuffered output compare pulses as described in 17.4.3 Output Compare. The pulses are unbuffered because changing the output compare value requires writing the new value over the old value currently in the TIM channel registers. An unsynchronized write to the TIM channel registers to change an output compare value could cause incorrect operation for up to two counter overflow periods. For example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that counter overflow period. Also, using a TIM overflow interrupt routine to write a new, smaller output compare value may cause the compare to be missed. The TIM may pass the new value before it is written. Use the following methods to synchronize unbuffered changes in the output compare value on channel x: * When changing to a smaller value, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. The output compare interrupt occurs at the end of the current output compare pulse. The interrupt routine has until the end of the counter overflow period to write the new value. * When changing to a larger output compare value, enable TIM overflow interrupts and write the new value in the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the current counter overflow period. Writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same counter overflow period. 17.4.3.2 Buffered Output Compare Channels 0 and 1 can be linked to form a buffered output compare channel whose output appears on the TCH0 pin. The TIM channel registers of the linked pair alternately control the output. Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1. The output compare value in the TIM channel 0 registers initially controls the output on the TCH0 pin. Writing to the TIM channel 1 registers enables the TIM channel 1 registers to synchronously control the output after the TIM overflows. At each subsequent overflow, the TIM channel registers (0 or 1) that control the output are the ones written to last. TSC0 controls and monitors the buffered output compare function, and TIM channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin, TCH1, is available as a general-purpose I/O pin. NOTE In buffered output compare operation, do not write new output compare values to the currently active channel registers. User software should track the currently active channel to prevent writing a new value to the active channel. Writing to the active channel registers is the same as generating unbuffered output compares.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 204 Freescale Semiconductor
Functional Description
17.4.4 Pulse Width Modulation (PWM)
By using the toggle-on-overflow feature with an output compare channel, the TIM can generate a PWM signal. The value in the TIM counter modulo registers determines the period of the PWM signal. The channel pin toggles when the counter reaches the value in the TIM counter modulo registers. The time between overflows is the period of the PWM signal. As Figure 17-4 shows, the output compare value in the TIM channel registers determines the pulse width of the PWM signal. The time between overflow and output compare is the pulse width. Program the TIM to clear the channel pin on output compare if the polarity of the PWM pulse is 1 (ELSxA = 0). Program the TIM to set the pin if the polarity of the PWM pulse is 0 (ELSxA = 0). The value in the TIM counter modulo registers and the selected prescaler output determines the frequency of the PWM output. The frequency of an 8-bit PWM signal is variable in 256 increments. Writing $00FF (255) to the TIM counter modulo registers produces a PWM period of 256 times the internal bus clock period if the prescaler select value is $000. See 17.9.1 TIM Status and Control Register. The value in the TIM channel registers determines the pulse width of the PWM output. The pulse width of an 8-bit PWM signal is variable in 256 increments. Writing $0080 (128) to the TIM channel registers produces a duty cycle of 128/256 or 50%.
OVERFLOW PERIOD POLARITY = 1 (ELSxA = 0) TCHx PULSE WIDTH POLARITY = 0 (ELSxA = 1) TCHx OVERFLOW OVERFLOW
OUTPUT COMPARE
OUTPUT COMPARE
OUTPUT COMPARE
Figure 17-4. PWM Period and Pulse Width 17.4.4.1 Unbuffered PWM Signal Generation Any output compare channel can generate unbuffered PWM pulses as described in 17.4.4 Pulse Width Modulation (PWM). The pulses are unbuffered because changing the pulse width requires writing the new pulse width value over the old value currently in the TIM channel registers. An unsynchronized write to the TIM channel registers to change a pulse width value could cause incorrect operation for up to two PWM periods. For example, writing a new value before the counter reaches the old value but after the counter reaches the new value prevents any compare during that PWM period. Also, using a TIM overflow interrupt routine to write a new, smaller pulse width value may cause the compare to be missed. The TIM may pass the new value before it is written. Use the following methods to synchronize unbuffered changes in the PWM pulse width on channel x: * When changing to a shorter pulse width, enable channel x output compare interrupts and write the new value in the output compare interrupt routine. The output compare interrupt occurs at the end of the current pulse. The interrupt routine has until the end of the PWM period to write the new value.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 205
Timer Interface Module (TIM1 and TIM2)
*
When changing to a longer pulse width, enable TIM overflow interrupts and write the new value in the TIM overflow interrupt routine. The TIM overflow interrupt occurs at the end of the current PWM period. Writing a larger value in an output compare interrupt routine (at the end of the current pulse) could cause two output compares to occur in the same PWM period. NOTE In PWM signal generation, do not program the PWM channel to toggle on output compare. Toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self-correct in the event of software error or noise. Toggling on output compare also can cause incorrect PWM signal generation when changing the PWM pulse width to a new, much larger value.
17.4.4.2 Buffered PWM Signal Generation Channels 0 and 1 can be linked to form a buffered PWM channel whose output appears on the TCH0 pin. The TIM channel registers of the linked pair alternately control the pulse width of the output. Setting the MS0B bit in TIM channel 0 status and control register (TSC0) links channel 0 and channel 1. The TIM channel 0 registers initially control the pulse width on the TCH0 pin. Writing to the TIM channel 1 registers enables the TIM channel 1 registers to synchronously control the pulse width at the beginning of the next PWM period. At each subsequent overflow, the TIM channel registers (0 or 1) that control the pulse width are the ones written to last. TSC0 controls and monitors the buffered PWM function, and TIM channel 1 status and control register (TSC1) is unused. While the MS0B bit is set, the channel 1 pin, TCH1, is available as a general-purpose I/O pin. NOTE In buffered PWM signal generation, do not write new pulse width values to the currently active channel registers. User software should track the currently active channel to prevent writing a new value to the active channel. Writing to the active channel registers is the same as generating unbuffered PWM signals. 17.4.4.3 PWM Initialization To ensure correct operation when generating unbuffered or buffered PWM signals, use the following initialization procedure: 1. In the TIM status and control register (TSC): a. Stop the TIM counter by setting the TIM stop bit, TSTOP. b. Reset the TIM counter and prescaler by setting the TIM reset bit, TRST. 2. In the TIM counter modulo registers (TMODH:TMODL), write the value for the required PWM period. 3. In the TIM channel x registers (TCHxH:TCHxL), write the value for the required pulse width. 4. In TIM channel x status and control register (TSCx): a. Write 0:1 (for unbuffered output compare or PWM signals) or 1:0 (for buffered output compare or PWM signals) to the mode select bits, MSxB:MSxA. See Table 17-3. b. Write 1 to the toggle-on-overflow bit, TOVx.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 206 Freescale Semiconductor
Interrupts
c. Write 1:0 (polarity 1 -- to clear output on compare) or 1:1 (polarity 0 -- to set output on compare) to the edge/level select bits, ELSxB:ELSxA. The output action on compare must force the output to the complement of the pulse width level. See Table 17-3. NOTE In PWM signal generation, do not program the PWM channel to toggle on output compare. Toggling on output compare prevents reliable 0% duty cycle generation and removes the ability of the channel to self-correct in the event of software error or noise. Toggling on output compare can also cause incorrect PWM signal generation when changing the PWM pulse width to a new, much larger value. 5. In the TIM status control register (TSC), clear the TIM stop bit, TSTOP. Setting MS0B links channels 0 and 1 and configures them for buffered PWM operation. The TIM channel 0 registers (TCH0H:TCH0L) initially control the buffered PWM output. TIM status control register 0 (TSCR0) controls and monitors the PWM signal from the linked channels. Clearing the toggle-on-overflow bit, TOVx, inhibits output toggles on TIM overflows. Subsequent output compares try to force the output to a state it is already in and have no effect. The result is a 0% duty cycle output. Setting the channel x maximum duty cycle bit (CHxMAX) and setting the TOVx bit generates a 100% duty cycle output. See 17.9.4 TIM Channel Status and Control Registers.
17.5 Interrupts
The following TIM sources can generate interrupt requests: * TIM overflow flag (TOF) -- The TOF bit is set when the TIM counter reaches the modulo value programmed in the TIM counter modulo registers. The TIM overflow interrupt enable bit, TOIE, enables TIM overflow CPU interrupt requests. TOF and TOIE are in the TIM status and control register. * TIM channel flags (CH1F:CH0F) -- The CHxF bit is set when an input capture or output compare occurs on channel x. Channel x TIM CPU interrupt requests are controlled by the channel x interrupt enable bit, CHxIE. Channel x TIM CPU interrupt requests are enabled when CHxIE = 1. CHxF and CHxIE are in the TIM channel x status and control register.
17.6 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power-consumption standby modes.
17.6.1 Wait Mode
The TIM remains active after the execution of a WAIT instruction. In wait mode, the TIM registers are not accessible by the CPU. Any enabled CPU interrupt request from the TIM can bring the MCU out of wait mode. If TIM functions are not required during wait mode, reduce power consumption by stopping the TIM before executing the WAIT instruction.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 207
Timer Interface Module (TIM1 and TIM2)
17.6.2 Stop Mode
The TIM is inactive after the execution of a STOP instruction. The STOP instruction does not affect register conditions or the state of the TIM counter. TIM operation resumes when the MCU exits stop mode after an external interrupt.
17.7 TIM During Break Interrupts
A break interrupt stops the TIM counter. The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. See 14.7.3 SIM Break Flag Control Register. To allow software to clear status bits during a break interrupt, write a 1 to the BCFE bit. If a status bit is cleared during the break state, it remains cleared when the MCU exits the break state. To protect status bits during the break state, write a 0 to the BCFE bit. With BCFE at 0 (its default state), software can read and write I/O registers during the break state without affecting status bits. Some status bits have a 2-step read/write clearing procedure. If software does the first step on such a bit before the break, the bit cannot change during the break state as long as BCFE is at 0. After the break, doing the second step clears the status bit.
17.8 I/O Signals
Port D shares four of its pins with the TIM. The four TIM channel I/O pins are T1CH0, T1CH1, T2CH0, and T2CH1 as described in 17.3 Pin Name Conventions. Each channel I/O pin is programmable independently as an input capture pin or an output compare pin. T1CH0 and T2CH0 can be configured as buffered output compare or buffered PWM pins.
17.9 I/O Registers
NOTE References to either timer 1 or timer 2 may be made in the following text by omitting the timer number. For example, TSC may generically refer to both T1SC AND T2SC. These I/O registers control and monitor operation of the TIM: * TIM status and control register (TSC) * TIM counter registers (TCNTH:TCNTL) * TIM counter modulo registers (TMODH:TMODL) * TIM channel status and control registers (TSC0 and TSC1) * TIM channel registers (TCH0H:TCH0L, TCH1H:TCH1L)
17.9.1 TIM Status and Control Register
The TIM status and control register (TSC): * Enables TIM overflow interrupts * Flags TIM overflows * Stops the TIM counter * Resets the TIM counter * Prescales the TIM counter clock
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 208 Freescale Semiconductor
I/O Registers Address: T1SC, $002 and T2SC, $002B Bit 7 Read: Write: Reset: TOF 0 0 6 TOIE 0 = Unimplemented 5 TSTOP 1 4 0 TRST 0 0 3 0 2 PS2 0 1 PS1 0 Bit 0 PS0 0
Figure 17-5. TIM Status and Control Register (TSC) TOF -- TIM Overflow Flag Bit This read/write flag is set when the TIM counter reaches the modulo value programmed in the TIM counter modulo registers. Clear TOF by reading the TIM status and control register when TOF is set and then writing a 0 to TOF. If another TIM overflow occurs before the clearing sequence is complete, then writing 0 to TOF has no effect. Therefore, a TOF interrupt request cannot be lost due to inadvertent clearing of TOF. Reset clears the TOF bit. Writing a 1 to TOF has no effect. 1 = TIM counter has reached modulo value 0 = TIM counter has not reached modulo value TOIE -- TIM Overflow Interrupt Enable Bit This read/write bit enables TIM overflow interrupts when the TOF bit becomes set. Reset clears the TOIE bit. 1 = TIM overflow interrupts enabled 0 = TIM overflow interrupts disabled TSTOP -- TIM Stop Bit This read/write bit stops the TIM counter. Counting resumes when TSTOP is cleared. Reset sets the TSTOP bit, stopping the TIM counter until software clears the TSTOP bit. 1 = TIM counter stopped 0 = TIM counter active NOTE Do not set the TSTOP bit before entering wait mode if the TIM is required to exit wait mode. Also, when the TSTOP bit is set and the timer is configured for input capture operation, input captures are inhibited until the TSTOP bit is cleared. TRST -- TIM Reset Bit Setting this write-only bit resets the TIM counter and the TIM prescaler. Setting TRST has no effect on any other registers. Counting resumes from $0000. TRST is cleared automatically after the TIM counter is reset and always reads as 0. Reset clears the TRST bit. 1 = Prescaler and TIM counter cleared 0 = No effect NOTE Setting the TSTOP and TRST bits simultaneously stops the TIM counter at a value of $0000. PS[2:0] -- Prescaler Select Bits These read/write bits select one of the seven prescaler outputs as the input to the TIM counter as Table 17-2 shows. Reset clears the PS[2:0] bits.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 209
Timer Interface Module (TIM1 and TIM2)
Table 17-2. Prescaler Selection
PS2 0 0 0 0 1 1 1 1 PS1 0 0 1 1 0 0 1 1 PS0 0 1 0 1 0 1 0 1 TIM Clock Source Internal bus clock / 1 Internal bus clock / 2 Internal bus clock / 4 Internal bus clock / 8 Internal bus clock / 16 Internal bus clock / 32 Internal bus clock / 64 Not available
17.9.2 TIM Counter Registers
The two read-only TIM counter registers contain the high and low bytes of the value in the TIM counter. Reading the high byte (TCNTH) latches the contents of the low byte (TCNTL) into a buffer. Subsequent reads of TCNTH do not affect the latched TCNTL value until TCNTL is read. Reset clears the TIM counter registers. Setting the TIM reset bit (TRST) also clears the TIM counter registers. NOTE If you read TCNTH during a break interrupt, be sure to unlatch TCNTL by reading TCNTL before exiting the break interrupt. Otherwise, TCNTL retains the value latched during the break.
Address: T1CNTH, $0021 and T2CNTH, $002C Bit 7 Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 0 0 Bit 15 6 14 5 13 4 12 3 11 2 10 1 9 Bit 0 Bit 8
Figure 17-6. TIM Counter Registers High (TCNTH)
Address: T1CNTL, $0022 and T2CNTL, $002D Bit 7 Read: Write: Reset: 0 0 = Unimplemented 0 0 0 0 0 0 Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
Figure 17-7. TIM Counter Registers Low (TCNTL)
17.9.3 TIM Counter Modulo Registers
The read/write TIM modulo registers contain the modulo value for the TIM counter. When the TIM counter reaches the modulo value, the overflow flag (TOF) becomes set, and the TIM counter resumes counting from $0000 at the next timer clock. Writing to the high byte (TMODH) inhibits the TOF bit and overflow interrupts until the low byte (TMODL) is written. Reset sets the TIM counter modulo registers.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 210 Freescale Semiconductor
I/O Registers Address: T1MODH, $0023 and T2MODH, $002E Bit 7 Read: Write: Reset: Bit 15 1 6 14 1 5 13 1 4 12 1 3 11 1 2 10 1 1 9 1 Bit 0 Bit 8 1
Figure 17-8. TIM Counter Modulo Register High (TMODH)
Address: T1MODL, $0024 and T2MODL, $002F Bit 7 Read: Write: Reset: Bit 7 1 6 6 1 5 5 1 4 4 1 3 3 1 2 2 1 1 1 1 Bit 0 Bit 0 1
Figure 17-9. TIM Counter Modulo Register Low (TMODL) NOTE Reset the TIM counter before writing to the TIM counter modulo registers.
17.9.4 TIM Channel Status and Control Registers
Each of the TIM channel status and control registers: * Flags input captures and output compares * Enables input capture and output compare interrupts * Selects input capture, output compare, or PWM operation * Selects high, low, or toggling output on output compare * Selects rising edge, falling edge, or any edge as the active input capture trigger * Selects output toggling on TIM overflow * Selects 0% and 100% PWM duty cycle * Selects buffered or unbuffered output compare/PWM operation
Address: T1SC0, $0025 and T2SC0, $0030 Bit 7 Read: Write: Reset: CH0F 0 0 6 CH0IE 0 5 MS0B 0 4 MS0A 0 3 ELS0B 0 2 ELS0A 0 1 TOV0 0 Bit 0 CH0MAX 0
Figure 17-10. TIM Channel 0 Status and Control Register (TSC0)
Address: T1SC1, $0028 Bit 7 Read: Write: Reset: CH1F 0 0 6 CH1IE 0 5 0 0 4 MS1A 0 3 ELS1B 0 2 ELS1A 0 1 TOV1 0 Bit 0 CH1MAX 0
Figure 17-11. TIM Channel 1 Status and Control Register (TSC1)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 211
Timer Interface Module (TIM1 and TIM2)
CHxF -- Channel x Flag Bit When channel x is an input capture channel, this read/write bit is set when an active edge occurs on the channel x pin. When channel x is an output compare channel, CHxF is set when the value in the TIM counter registers matches the value in the TIM channel x registers. When TIM CPU interrupt requests are enabled (CHxIE = 1), clear CHxF by reading TIM channel x status and control register with CHxF set and then writing a 0 to CHxF. If another interrupt request occurs before the clearing sequence is complete, then writing 0 to CHxF has no effect. Therefore, an interrupt request cannot be lost due to inadvertent clearing of CHxF. Reset clears the CHxF bit. Writing a 1 to CHxF has no effect. 1 = Input capture or output compare on channel x 0 = No input capture or output compare on channel x CHxIE -- Channel x Interrupt Enable Bit This read/write bit enables TIM CPU interrupt service requests on channel x. Reset clears the CHxIE bit. 1 = Channel x CPU interrupt requests enabled 0 = Channel x CPU interrupt requests disabled MSxB -- Mode Select Bit B This read/write bit selects buffered output compare/PWM operation. MSxB exists only in the TIM1 channel 0 and TIM2 channel 0 status and control registers. Setting MS0B disables the channel 1 status and control register and reverts TCH1 to general-purpose I/O. Reset clears the MSxB bit. 1 = Buffered output compare/PWM operation enabled 0 = Buffered output compare/PWM operation disabled MSxA -- Mode Select Bit A When ELSxB:A 00, this read/write bit selects either input capture operation or unbuffered output compare/PWM operation. See Table 17-3. 1 = Unbuffered output compare/PWM operation 0 = Input capture operation When ELSxB:A = 00, this read/write bit selects the initial output level of the TCHx pin. See Table 17-3. Reset clears the MSxA bit. 1 = Initial output level low 0 = Initial output level high NOTE Before changing a channel function by writing to the MSxB or MSxA bit, set the TSTOP and TRST bits in the TIM status and control register (TSC). ELSxB and ELSxA -- Edge/Level Select Bits When channel x is an input capture channel, these read/write bits control the active edge-sensing logic on channel x. When channel x is an output compare channel, ELSxB and ELSxA control the channel x output behavior when an output compare occurs. When ELSxB and ELSxA are both clear, channel x is not connected to port D, and pin PTDx/TCHx is available as a general-purpose I/O pin. Table 17-3 shows how ELSxB and ELSxA work. Reset clears the ELSxB and ELSxA bits.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 212 Freescale Semiconductor
I/O Registers
Table 17-3. Mode, Edge, and Level Selection
MSxB X X 0 0 0 0 0 0 0 1 1 1 MSxA 0 1 0 0 0 1 1 1 1 X X X ELSxB 0 0 0 1 1 0 0 1 1 0 1 1 ELSxA 0 0 1 0 1 0 1 0 1 1 0 1 Buffered output compare or buffered PWM Output compare or PWM Input capture Mode Output preset Configuration Pin under port control; initial output level high Pin under port control; initial output level low Capture on rising edge only Capture on falling edge only Capture on rising or falling edge Software compare only Toggle output on compare Clear output on compare Set output on compare Toggle output on compare Clear output on compare Set output on compare
NOTE Before enabling a TIM channel register for input capture operation, make sure that the PTD/TCHx pin is stable for at least two bus clocks. TOVx -- Toggle On Overflow Bit When channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the TIM counter overflows. When channel x is an input capture channel, TOVx has no effect. Reset clears the TOVx bit. 1 = Channel x pin toggles on TIM counter overflow. 0 = Channel x pin does not toggle on TIM counter overflow. NOTE When TOVx is set, a TIM counter overflow takes precedence over a channel x output compare if both occur at the same time. CHxMAX -- Channel x Maximum Duty Cycle Bit When the TOVx bit is at 1, setting the CHxMAX bit forces the duty cycle of buffered and unbuffered PWM signals to 100%. As Figure 17-12 shows, the CHxMAX bit takes effect in the cycle after it is set or cleared. The output stays at the 100% duty cycle level until the cycle after CHxMAX is cleared. NOTE The 100% PWM duty cycle is defined as a continuous high level if the PWM polarity is 1 and a continuous low level if the PWM polarity is 0. Conversely, a 0% PWM duty cycle is defined as a continuous low level if the PWM polarity is 1 and a continuous high level if the PWM polarity is 0.
OVERFLOW PERIOD TCHx OVERFLOW OVERFLOW OVERFLOW OVERFLOW
OUTPUT COMPARE CHxMAX
OUTPUT COMPARE
OUTPUT COMPARE
OUTPUT COMPARE
Figure 17-12. CHxMAX Latency
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 213
Timer Interface Module (TIM1 and TIM2)
17.9.5 TIM Channel Registers
These read/write registers contain the captured TIM counter value of the input capture function or the output compare value of the output compare function. The state of the TIM channel registers after reset is unknown. In input capture mode (MSxB:MSxA = 0:0), reading the high byte of the TIM channel x registers (TCHxH) inhibits input captures until the low byte (TCHxL) is read. In output compare mode (MSxB:MSxA 0:0), writing to the high byte of the TIM channel x registers (TCHxH) inhibits output compares until the low byte (TCHxL) is written. See Figure 17-13 through Figure 17-16.
Address: T1CH0H, $0026 and T2CH0H, $0031 Bit 7 Read: Write: Reset: Bit 15 6 14 5 13 4 12 3 11 2 10 1 9 Bit 0 Bit 8
Indeterminate after reset
Figure 17-13. TIM Channel 0 Register High (TCH0H)
Address: T1CH0L, $0027 and T2CH0L $0032 Bit 7 Read: Write: Reset: Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
Indeterminate after reset
Figure 17-14. TIM Channel 0 Register Low (TCH0L)
Address: T1CH1H, $0029 Bit 7 Read: Write: Reset: Bit 15 6 14 5 13 4 12 3 11 2 10 1 9 Bit 0 Bit 8
Indeterminate after reset
Figure 17-15. TIM Channel 1 Register High (TCH1H)
Address: T1CH1L, $002A Bit 7 Read: Write: Reset: Bit 7 6 6 5 5 4 4 3 3 2 2 1 1 Bit 0 Bit 0
Indeterminate after reset
Figure 17-16. TIM Channel 1 Register Low (TCH1L)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 214 Freescale Semiconductor
Chapter 18 Development Support
18.1 Introduction
This section describes the break module, the monitor module (MON), and the monitor mode entry methods.
18.2 Break Module (BRK)
The break module can generate a break interrupt that stops normal program flow at a defined address to enter a background program. Features of the break module include: * Accessible input/output (I/O) registers during the break Interrupt * Central processor unit (CPU) generated break interrupts * Software-generated break interrupts * Computer operating properly (COP) disabling during break interrupts
18.2.1 Functional Description
When the internal address bus matches the value written in the break address registers, the break module issues a breakpoint signal (BKPT) to the system integration module (SIM). The SIM then causes the CPU to load the instruction register with a software interrupt instruction (SWI). The program counter vectors to $FFFC and $FFFD ($FEFC and $FEFD in monitor mode). The following events can cause a break interrupt to occur: * A CPU generated address (the address in the program counter) matches the contents of the break address registers. * Software writes a 1 to the BRKA bit in the break status and control register. When a CPU generated address matches the contents of the break address registers, the break interrupt is generated. A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and returns the microcontroller unit (MCU) to normal operation. Figure 18-2 shows the structure of the break module. Figure 18-3 provides a summary of the I/O registers.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 215
Development Support
INTERNAL BUS M68HC08 CPU PORTA DDRA CPU REGISTERS ARITHMETIC/LOGIC UNIT (ALU) PROGRAMMABLE TIMEBASE MODULE SINGLE BREAKPOINT BREAK MODULE DUAL VOLTAGE LOW-VOLTAGE INHIBIT MODULE 4-BIT KEYBOARD INTERRUPT MODULE DDRC 2-CHANNEL TIMER INTERFACE MODULE 1 1-CHANNEL TIMER INTERFACE MODULE 2 SERIAL COMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE RST(3) IRQ(3) VDDAD/VREFH VSSAD/VREFL SYSTEM INTEGRATION MODULE SINGLE EXTERNAL INTERRUPT MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE POWER-ON RESET MODULE VDD VSS VDDA VSSA SERIAL PERIPHERAL INTERFACE MODULE MONITOR MODULE MEMORY MAP MODULE CONFIGURATION REGISTER 1 MODULE CONFIGURATION REGISTER 2 MODULE PORTC PORTB DDRB PTA3/KBD3- PTA0/KBD0(1)
CONTROL AND STATUS REGISTERS -- 64 BYTES MC68HC908GR8A USER FLASH -- 7680 BYTES MC68HC908GR4A USER FLASH -- 4096 BYTES USER RAM -- 384 BYTES MONITOR ROM -- 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM -- 544 BYTES USER FLASH VECTOR SPACE -- 36 BYTES CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 1-8-MHz OSCILLATOR PHASE LOCKED LOOP
PTB5/AD5 PTB4/AD4 PTB3/AD3 PTB2/AD2 PTB1/AD1 PTB0/AD0
PTC1(1), (2) PTC0(1), (2)
PTD6/T2CH0(1) PTD5/T1CH1(1) PTD4/T1CH0(1) PTD3/SPSCK(1) PTD2/MOSI(1) PTD1/MISO(1) PTD0/SS(1)
PORTE
PORTD
DDRD
PTE1/RxD PTE0/TxD
DDRE
SECURITY MODULE
POWER
MONITOR MODE ENTRY MODULE
1. Ports are software configurable with pullup device if input port. 2. Higher current drive port pins 3. Pin contains integrated pullup device
Figure 18-1. Block Diagram Highlighting BRK and MON Blocks
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 216 Freescale Semiconductor
Break Module (BRK)
ADDRESS BUS[15:8]
BREAK ADDRESS REGISTER HIGH 8-BIT COMPARATOR CONTROL 8-BIT COMPARATOR BREAK ADDRESS REGISTER LOW BKPT (TO SIM)
ADDRESS BUS[15:0]
ADDRESS BUS[7:0]
Figure 18-2. Break Module Block Diagram
Addr. $FE00
Register Name SIM Break Status Register Read: (SBSR) Write: See page 220. Reset: Read: Reserved Write: Reset: SIM Break Flag Control Read: Register (SBFCR) Write: See page 220. Reset: Break Address High Read: Register (BRKH) Write: See page 219. Reset: Break Address Low Read: Register (BRKL) Write: See page 219. Reset: Break Status and Control Read: Register (BRKSCR) Write: See page 219. Reset:
Bit 7 R
6 R
5 R
4 R
3 R
2 R
1 SBSW Note(1) 0
Bit 0 R
$FE02
R 0 BCFE 0 Bit15 0 Bit 7 0 BRKE 0
R 0 R
R 0 R
R 0 R
R 0 R
R 0 R
R 0 R
R 0 R
$FE03
$FE09
Bit14 0 Bit 6 0 BRKA 0
Bit13 0 Bit 5 0 0 0
Bit12 0 Bit 4 0 0 0 R
Bit11 0 Bit 3 0 0 0 = Reserved
Bit10 0 Bit 2 0 0 0
Bit9 0 Bit 1 0 0 0
Bit8 0 Bit 0 0 0 0
$FE0A
$FE0B
1. Writing a 0 clears SBSW.
= Unimplemented
Figure 18-3. Break I/O Register Summary
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 217
Development Support
When the internal address bus matches the value written in the break address registers or when software writes a 1 to the BRKA bit in the break status and control register, the CPU starts a break interrupt by: * Loading the instruction register with the SWI instruction * Loading the program counter with $FFFC and $FFFD ($FEFC and $FEFD in monitor mode) The break interrupt timing is: * When a break address is placed at the address of the instruction opcode, the instruction is not executed until after completion of the break interrupt routine. * When a break address is placed at an address of an instruction operand, the instruction is executed before the break interrupt. * When software writes a 1 to the BRKA bit, the break interrupt occurs just before the next instruction is executed. By updating a break address and clearing the BRKA bit in a break interrupt routine, a break interrupt can be generated continuously. CAUTION A break address should be placed at the address of the instruction opcode. When software does not change the break address and clears the BRKA bit in the first break interrupt routine, the next break interrupt will not be generated after exiting the interrupt routine even when the internal address bus matches the value written in the break address registers. 18.2.1.1 Flag Protection During Break Interrupts The system integration module (SIM) controls whether or not module status bits can be cleared during the break state. The BCFE bit in the break flag control register (SBFCR) enables software to clear status bits during the break state. See 14.7.3 SIM Break Flag Control Register and the Break Interrupts subsection for each module. 18.2.1.2 TIM During Break Interrupts A break interrupt stops the timer counter. 18.2.1.3 COP During Break Interrupts The COP is disabled during a break interrupt when VTST is present on the RST pin.
18.2.2 Break Module Registers
These registers control and monitor operation of the break module: * Break status and control register (BRKSCR) * Break address register high (BRKH) * Break address register low (BRKL) * Break status register (SBSR) * Break flag control register (SBFCR)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 218 Freescale Semiconductor
Break Module (BRK)
18.2.2.1 Break Status and Control Register The break status and control register (BRKSCR) contains break module enable and status bits.
Address: $FE0B Bit 7 Read: Write: Reset: BRKE 0 6 BRKA 0 5 0 0 4 0 0 3 0 0 2 0 0 1 0 0 Bit 0 0 0
= Unimplemented
Figure 18-4. Break Status and Control Register (BRKSCR) BRKE -- Break Enable Bit This read/write bit enables breaks on break address register matches. Clear BRKE by writing a 0 to bit 7. Reset clears the BRKE bit. 1 = Breaks enabled on 16-bit address match 0 = Breaks disabled BRKA -- Break Active Bit This read/write status and control bit is set when a break address match occurs. Writing a 1 to BRKA generates a break interrupt. Clear BRKA by writing a 0 to it before exiting the break routine. Reset clears the BRKA bit. 1 = Break address match 0 = No break address match 18.2.2.2 Break Address Registers The break address registers (BRKH and BRKL) contain the high and low bytes of the desired breakpoint address. Reset clears the break address registers.
Address: $FE09 Bit 7 Read: Write: Reset: Bit 15 0 6 Bit 14 0 5 Bit 13 0 4 Bit 12 0 3 Bit 11 0 2 Bit 10 0 1 Bit 9 0 Bit 0 Bit 8 0
Figure 18-5. Break Address Register High (BRKH)
Address: $FE0A Bit 7 Read: Write: Reset: Bit 7 0 6 Bit 6 0 5 Bit 5 0 4 Bit 4 0 3 Bit 3 0 2 Bit 2 0 1 Bit 1 0 Bit 0 Bit 0 0
Figure 18-6. Break Address Register Low (BRKL)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 219
Development Support
18.2.2.3 SIM Break Status Register The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode. This register is only used in emulation mode.
Address: $FE00 Bit 7 Read: Write: Reset: R = Reserved 1. Writing a 0 clears SBSW. R 6 R 5 R 4 R 3 R 2 R 1 SBSW Note(1) 0 Bit 0 R
Figure 18-7. SIM Break Status Register (SBSR) SBSW -- SIM Break Stop/Wait SBSW can be read within the break state SWI routine. The user can modify the return address on the stack by subtracting one from it. 1 = Wait mode was exited by break interrupt 0 = Wait mode was not exited by break interrupt 18.2.2.4 SIM Break Flag Control Register The SIM break control register (SBFCR) contains a bit that enables software to clear status bits while the MCU is in a break state.
Address: $FE03 Bit 7 Read: Write: Reset: BCFE 0 R = Reserved 6 R 5 R 4 R 3 R 2 R 1 R Bit 0 R
Figure 18-8. SIM Break Flag Control Register (SBFCR) BCFE -- Break Clear Flag Enable Bit This read/write bit enables software to clear status bits by accessing status registers while the MCU is in a break state. To clear status bits during the break state, the BCFE bit must be set. 1 = Status bits clearable during break 0 = Status bits not clearable during break
18.2.3 Low-Power Modes
The WAIT and STOP instructions put the MCU in low power- consumption standby modes. If enabled, the break module will remain enabled in wait and stop modes. However, since the internal address bus does not increment in these modes, a break interrupt will never be triggered.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 220 Freescale Semiconductor
Monitor Module (MON)
18.3 Monitor Module (MON)
The monitor module allows debugging and programming of the microcontroller unit (MCU) through a single-wire interface with a host computer. Monitor mode entry can be achieved without use of the higher test voltage, VTST, as long as vector addresses $FFFE and $FFFF are blank, thus reducing the hardware requirements for in-circuit programming. Features of the monitor module include: * Normal user-mode pin functionality * One pin dedicated to serial communication between MCU and host computer * Standard non-return-to-zero (NRZ) communication with host computer * Standard communication baud rate * Execution of code in random-access memory (RAM) or FLASH * FLASH memory security feature(1) * FLASH memory programming interface * Monitor mode entry without high voltage, VTST, if reset vector is blank ($FFFE and $FFFF contain $FF) * Normal monitor mode entry if VTST is applied to IRQ
18.3.1 Functional Description
Figure 18-9 shows a simplified diagram of the monitor mode. The monitor module receives and executes commands from a host computer. Figure 18-10 and Figure 18-11 show example circuits used to enter monitor mode and communicate with a host computer via a standard RS-232 interface. Simple monitor commands can access any memory address. In monitor mode, the MCU can execute code downloaded into RAM by a host computer while most MCU pins retain normal operating mode functions. All communication between the host computer and the MCU is through the PTA0 pin. A level-shifting and multiplexing interface is required between PTA0 and the host computer. PTA0 is used in a wired-OR configuration and requires a pullup resistor. Table 18-1 shows the pin conditions for entering monitor mode. As specified in the table, monitor mode must be entered after a power-on reset (POR) and will allow communication at 9600 baud provided one of the following sets of conditions is met: * If $FFFE and $FFFF do not contain $FF (programmed state): - The external clock is 9.8304 MHz - IRQ = VTST * If $FFFE and $FFFF contain $FF (erased state): - The external clock is 9.8304 MHz - IRQ = VDD (this can be implemented through the internal IRQ pullup)
1. No security feature is absolutely secure. However, Freescale's strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 221
Development Support
POR RESET
NO
IRQ = VTST?
YES
CONDITIONS FROM Table 18-1
PTA0 = 1, PTA1 = 0, RESET VECTOR BLANK? YES FORCED MONITOR MODE
NO
PTA0 = 1, PTA1 = 0, PTB0 = 1, AND PTB1 = 0? YES NORMAL USER MODE NORMAL MONITOR MODE
NO
INVALID USER MODE
HOST SENDS 8 SECURITY BYTES
IS RESET POR? NO
YES
YES
ARE ALL SECURITY BYTES CORRECT?
NO
ENABLE FLASH
DISABLE FLASH
MONITOR MODE ENTRY
DEBUGGING AND FLASH PROGRAMMING (IF FLASH IS ENABLED)
EXECUTE MONITOR CODE
YES
DOES RESET OCCUR?
NO
Figure 18-9. Simplified Monitor Mode Entry Flowchart
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 222 Freescale Semiconductor
Monitor Module (MON)
MC68HC908GR8A N.C. 33 pF MAX232 1 1 F + 3 4 1 F + C1+ C1- C2+ VCC 16 GND 15 V+ 2 V- 6 + 7 8 10 9 74HC125 3 2 1 1 F 74HC125 5 6 4 VDD 10 k PTA0 OSC2 VDD 33 pF + 1 F + 1 F 1 k IRQ 8.5 V PTB1 PTA1 VSSA VSS PTB0 9.8304 MHz 10 M OSC1 10 k RST VDD VDDA 0.1 F VDD
VDD
10 k 10 k
5 C2- DB9 2 3 5
Figure 18-10. Normal Monitor Mode Circuit
MC68HC908GR8A N.C. 33 pF MAX232 1 1 F + 3 4 1 F + C1+ C1- C2+ VCC 16 GND 15 V+ 2 V- 6 + 7 8 10 9 74HC125 3 2 1 1 F 74HC125 5 6 4 VDD 10 k PTA0 OSC2 VDD 33 pF + 1 F + 1 F PTB0 IRQ PTB1 10 k PTA1 VSSA VSS N.C. N.C. 9.8304 MHz 10 M OSC1 RST VDD VDDA 0.1 F VDD
N.C.
5 C2- DB9 2 3 5
Figure 18-11. Forced Monitor Mode
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 223
Development Support
Table 18-1. Monitor Mode Signal Requirements and Options
Serial Communication PTA0 Normal Monitor Forced Monitor User MON08 Function [Pin No.] VDD or VTST VDD VDD or VTST RST [4] PTA1 Mode Selection PTB0 PTB1 Communication Speed External Clock OFF Disabled 9.8304 MHz 9.8304 MHz X Bus Frequency 2.4576 MHz 2.4576 MHz X Baud Rate 9600
Mode
IRQ
RST
Reset Vector
PLL
COP
VTST
X $FFFF (blank) Not $FFFF
1
0
1
0
VDD VDD or VSS VTST [6]
1
0
X
X
OFF
Disabled
9600
X
X
X
X
X
Enabled
X
--
COM [8]
SSEL [10]
MOD0 [12]
MOD1 [14]
--
--
OSC1 [13]
--
--
1. PTA0 must have a pullup resistor to VDD in monitor mode. 2. Communication speed in the table is an example to obtain a baud rate of 9600. Baud rate using external oscillator is bus frequency / 256. 3. External clock is an 9.8304 MHz crystal on OSC1 and OSC2 or a 9.8304 MHz canned oscillator on OSC1. 4. X = don't care 5. MON08 pin refers to P&E Microcomputer Systems' MON08-Cyclone 2 by 8-pin connector.
NC NC NC NC NC NC OSC1 VDD
1 3 5 7 9 11 13 15
2 4 6 8 10 12 14 16
GND RST IRQ PTA0 PTA1 PTB0 PTB1 NC
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 224 Freescale Semiconductor
Monitor Module (MON)
Enter monitor mode with pin configuration shown in Table 18-1 with a power-on reset. The rising edge of RST latches monitor mode. Once monitor mode is latched, the levels on the port pins except PTA0 can change. Once out of reset, the MCU waits for the host to send eight security bytes (see 18.3.2 Security). After the security bytes, the MCU sends a break signal (10 consecutive 0s) to the host, indicating that it is ready to receive a command. 18.3.1.1 Normal Monitor Mode When monitor mode is entered with VTST on IRQ, the computer operating properly (COP) is disabled as long as VTST is applied to either IRQ or RST. This condition states that as long as VTST is maintained on the IRQ pin after entering monitor mode, or if VTST is applied to RST after the initial reset to get into monitor mode (when VTST was applied to IRQ), then the COP will be disabled. In the latter situation, after VTST is applied to the RST pin, VTST can be removed from the IRQ pin in the interest of freeing the IRQ for normal functionality in monitor mode. 18.3.1.2 Forced Monitor Mode If entering monitor mode without high voltage on IRQ, all port B pin requirements and conditions are not in effect. This is to reduce circuit requirements when performing in-circuit programming. NOTE If the reset vector is blank and monitor mode is entered, the chip will see an additional reset cycle after the initial power-on reset (POR). Once the reset vector has been programmed, the traditional method of applying a voltage, VTST, to IRQ must be used to enter monitor mode. An external oscillator of 9.8304 MHz is required for a baud rate of 9600, as the internal bus frequency is automatically set to the external frequency divided by four. When the forced monitor mode is entered the COP is always disabled regardless of the state of IRQ or RST. 18.3.1.3 Monitor Vectors In monitor mode, the MCU uses different vectors for reset, SWI (software interrupt), and break interrupt than those for user mode. The alternate vectors are in the $FE page instead of the $FF page and allow code execution from the internal monitor firmware instead of user code. Table 18-2 summarizes the differences between user mode and monitor mode. Table 18-2. Mode Differences
Functions Modes User Monitor Reset Vector High $FFFE $FEFE Reset Vector Low $FFFF $FEFF Break Vector High $FFFC $FEFC Break Vector Low $FFFD $FEFD SWI Vector High $FFFC $FEFC SWI Vector Low $FFFD $FEFD
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 225
Development Support
18.3.1.4 Data Format Communication with the monitor ROM is in standard non-return-to-zero (NRZ) mark/space data format. Transmit and receive baud rates must be identical.
START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 STOP BIT NEXT START BIT
Figure 18-12. Monitor Data Format 18.3.1.5 Break Signal A start bit (0) followed by nine 0 bits is a break signal. When the monitor receives a break signal, it drives the PTA0 pin high for the duration of approximately two bits and then echoes back the break signal.
MISSING STOP BIT APPROXIMATELY 2 BITS DELAY BEFORE ZERO ECHO
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
Figure 18-13. Break Transaction 18.3.1.6 Baud Rate The communication baud rate is controlled by the crystal frequency or external clock and the state of the PTB4 pin (when IRQ is set to VTST) upon entry into monitor mode. If monitor mode was entered with VDD on IRQ and the reset vector blank, then the baud rate is independent of PTB4. Table 18-1 also lists external frequencies required to achieve a standard baud rate of 9600 bps. The effective baud rate is the bus frequency divided by 256. If using a crystal as the clock source, be aware of the upper frequency limit that the internal clock module can handle. See 19.5 5.0 V DC Electrical Characteristics or 19.6 3.0 V DC Electrical Characteristics for this limit. 18.3.1.7 Commands The monitor ROM firmware uses these commands: * READ (read memory) * WRITE (write memory) * IREAD (indexed read) * IWRITE (indexed write) * READSP (read stack pointer) * RUN (run user program) The monitor ROM firmware echoes each received byte back to the PTA0 pin for error checking. An 11-bit delay at the end of each command allows the host to send a break character to cancel the command. A delay of two bit times occurs before each echo and before READ, IREAD, or READSP data is returned. The data returned by a read command appears after the echo of the last byte of the command. NOTE Wait one bit time after each echo before sending the next byte.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 226 Freescale Semiconductor
Monitor Module (MON)
FROM HOST
READ
READ
ADDRESS HIGH
ADDRESS HIGH
ADDRESS LOW
ADDRESS LOW
DATA
4 ECHO
1
4
1
4
1
3, 2
4 RETURN
Notes: 1 = Echo delay, approximately 2 bit times 2 = Data return delay, approximately 2 bit times 3 = Cancel command delay, 11 bit times 4 = Wait 1 bit time before sending next byte.
Figure 18-14. Read Transaction
FROM HOST
WRITE 3 ECHO 1
WRITE 3
ADDRESS HIGH
ADDRESS HIGH
ADDRESS LOW
ADDRESS LOW
DATA
DATA
1
3
1
3
1
2, 3
Notes: 1 = Echo delay, approximately 2 bit times 2 = Cancel command delay, 11 bit times 3 = Wait 1 bit time before sending next byte.
Figure 18-15. Write Transaction A brief description of each monitor mode command is given in Table 18-3 through Table 18-8. Table 18-3. READ (Read Memory) Command
Description Operand Data Returned Opcode
SENT TO MONITOR
Read byte from memory 2-byte address in high-byte:low-byte order Returns contents of specified address $4A Command Sequence
READ
READ
ADDRESS HIGH
ADDRESS HIGH
ADDRESS LOW
ADDRESS LOW
DATA
ECHO
RETURN
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 227
Development Support
Table 18-4. WRITE (Write Memory) Command
Description Operand Data Returned Opcode
FROM HOST
Write byte to memory 2-byte address in high-byte:low-byte order; low byte followed by data byte None $49 Command Sequence
WRITE
WRITE
ADDRESS HIGH
ADDRESS
HIGH
ADDRESS LOW
ADDRESS LOW
DATA
DATA
ECHO
Table 18-5. IREAD (Indexed Read) Command
Description Operand Data Returned Opcode Read next 2 bytes in memory from last address accessed None Returns contents of next two addresses $1A Command Sequence
FROM HOST
IREAD
IREAD
DATA
DATA
ECHO
RETURN
Table 18-6. IWRITE (Indexed Write) Command
Description Operand Data Returned Opcode Write to last address accessed + 1 Single data byte None $19 Command Sequence
FROM HOST
IWRITE
IWRITE
DATA
DATA
ECHO
A sequence of IREAD or IWRITE commands can access a block of memory sequentially over the full 64-Kbyte memory map.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 228 Freescale Semiconductor
Monitor Module (MON)
Table 18-7. READSP (Read Stack Pointer) Command
Description Operand Data Returned Opcode Reads stack pointer None Returns incremented stack pointer value (SP + 1) in high-byte:low-byte order $0C Command Sequence
FROM HOST
READSP
READSP
SP HIGH
SP LOW
ECHO
RETURN
Table 18-8. RUN (Run User Program) Command
Description Operand Data Returned Opcode Executes PULH and RTI instructions None None $28 Command Sequence
FROM HOST
RUN
RUN
ECHO
The MCU executes the SWI and PSHH instructions when it enters monitor mode. The RUN command tells the MCU to execute the PULH and RTI instructions. Before sending the RUN command, the host can modify the stacked CPU registers to prepare to run the host program. The READSP command returns the incremented stack pointer value, SP + 1. The high and low bytes of the program counter are at addresses SP + 5 and SP + 6.
SP HIGH BYTE OF INDEX REGISTER CONDITION CODE REGISTER ACCUMULATOR LOW BYTE OF INDEX REGISTER HIGH BYTE OF PROGRAM COUNTER LOW BYTE OF PROGRAM COUNTER SP + 1 SP + 2 SP + 3 SP + 4 SP + 5 SP + 6 SP + 7
Figure 18-16. Stack Pointer at Monitor Mode Entry
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 229
Development Support
18.3.2 Security
A security feature discourages unauthorized reading of FLASH locations while in monitor mode. The host can bypass the security feature at monitor mode entry by sending eight security bytes that match the bytes at locations $FFF6-$FFFD. Locations $FFF6-$FFFD contain user-defined data. NOTE Do not leave locations $FFF6-$FFFD blank. For security reasons, program locations $FFF6-$FFFD even if they are not used for vectors. During monitor mode entry, the MCU waits after the power-on reset for the host to send the eight security bytes on pin PTA0. If the received bytes match those at locations $FFF6-$FFFD, the host bypasses the security feature and can read all FLASH locations and execute code from FLASH. Security remains bypassed until a power-on reset occurs. If the reset was not a power-on reset, security remains bypassed and security code entry is not required. See Figure 18-17. Upon power-on reset, if the received bytes of the security code do not match the data at locations $FFF6-$FFFD, the host fails to bypass the security feature. The MCU remains in monitor mode, but reading a FLASH location returns an invalid value and trying to execute code from FLASH causes an illegal address reset. After receiving the eight security bytes from the host, the MCU transmits a break character, signifying that it is ready to receive a command. NOTE The MCU does not transmit a break character until after the host sends the eight security bytes.
VDD 4096 + 32 CGMXCLK CYCLES RST COMMAND 1 BYTE 2 ECHO BYTE 8 ECHO 2 BREAK 4 1 COMMAND ECHO
BYTE 1
BYTE 2
FROM HOST PA0 5 FROM MCU Notes: 1 = Echo delay, approximately 2 bit times 2 = Data return delay, approximately 2 bit times 4 = Wait 1 bit time before sending next byte 5 = Wait until the monitor ROM runs
1 BYTE 1 ECHO
4
1
Figure 18-17. Monitor Mode Entry Timing To determine whether the security code entered is correct, check to see if bit 6 of RAM address $40 is set. If it is, then the correct security code has been entered and FLASH can be accessed. If the security sequence fails, the device should be reset by a power-on reset and brought up in monitor mode to attempt another entry. After failing the security sequence, the FLASH module can also be mass erased by executing an erase routine that was downloaded into internal RAM. The mass erase operation clears the security code locations so that all eight security bytes become $FF (blank).
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 230 Freescale Semiconductor
BYTE 8
Chapter 19 Electrical Specifications
19.1 Introduction
This chapter contains electrical and timing specifications
19.2 Absolute Maximum Ratings
Maximum ratings are the extreme limits to which the microcontroller unit (MCU) can be exposed without permanently damaging it. NOTE This device is not guaranteed to operate properly beyond the maximum ratings. Refer to 5.0 V DC Electrical Characteristics for guaranteed operating conditions.
Characteristic(1) Supply voltage Input voltage Maximum current per pin excluding VDD, VSS , and PTC0-PTC Maximum current for pins PTC0-PTC1 Maximum current into VDD Maximum current out of VSS Storage temperature 1. Voltages referenced to VSS Symbol VDD VIn I IPTC0-PTC1 Imvdd Imvss Tstg Value -0.3 to + 6.0 VSS - 0.3 to VDD + 0.3 15 25 150 150 -55 to +150 Unit V V mA mA mA mA C
NOTE This device contains circuitry to protect the inputs against damage due to high static voltages or electric fields; however, it is advised that normal precautions be taken to avoid application of any voltage higher than maximum-rated voltages to this high-impedance circuit. For proper operation, it is recommended that VIn and VOut be constrained to the range VSS (VIn or VOut) VDD. Reliability of operation is enhanced if unused inputs are connected to an appropriate logic voltage level (for example, either VSS or VDD).
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 231
Electrical Specifications
19.3 Functional Operating Range
Characteristic Operating temperature range Operating voltage range Symbol TA VDD Value -40 to +125 3.0 10% 5.0 10% Unit C V
19.4 Thermal Characteristics
Characteristic Thermal resistance PDIP (28-pin) SOIC (28-pin) QFP (32-pin) I/O pin power dissipation Power dissipation(1) Constant(2) Average junction temperature Maximum junction temperature Symbol JA PI/O PD K TJ TJM Value 60 60 95 User-Determined PD = (IDD x VDD) + PI/O = K/(TJ + 273 C) PD x (TA + 273 C) + PD2 x JA TA + (PD x JA) 140 Unit C/W
W W W/C C C
1. Power dissipation is a function of temperature. 2. K is a constant unique to the device. K can be determined for a known TA and measured PD. With this value of K, PD and TJ can be determined for any value of TA.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 232 Freescale Semiconductor
5.0 V DC Electrical Characteristics
19.5 5.0 V DC Electrical Characteristics
Characteristic(1) Output high voltage (ILoad = -2.0 mA) all I/O pins (ILoad = -10.0 mA) all I/O pins (ILoad = -10.0 mA) pins PTC0-PTC1 only Maximum combined IOH for port C, port E, port PTD0-PTD3 Maximum combined IOH for port PTD4-PTD6, port A, port B Maximum total IOH for all port pins Output low voltage (ILoad = 1.6 mA) all I/O pins (ILoad = 10 mA) all I/O pins (ILoad = 15 mA) pins PTC0-PTC1 only Maximum combined IOL for port C, port E, port PTD0-PTD3 Maximum combined IOL for port PTD4-PTD6, port A, port B Maximum total IOL for all port pins Input high voltage All ports, IRQs, RESET OSC1 Input low voltage All ports, IRQs, RESET, OSC1 VDD supply current Run(3) Wait(4) Stop(5) Stop with TBM enabled(6) Stop with LVI and TBM enabled(6) Stop with LVI I/O ports Hi-Z leakage current(7) Input current Pullup resistors (as input only) Ports PTA3/KBD3-PTA0/KBD0, PTC1-PTC0, PTD6/T2CH0-PTD0/SS Capacitance Ports (as input or output) Monitor mode entry voltage Low-voltage inhibit, trip falling voltage - target Low-voltage inhibit, trip rising voltage - target Low-voltage inhibit reset/recover hysteresis - target (VTRIPF + VHYS = VTRIPR) Symbol VOH VOH VOH IOH1 IOH2 IOHT VOL VOL VOL IOL1 IOL2 IOLT VIH Min VDD - 0.8 VDD - 1.5 VDD - 0.8 -- -- -- -- -- -- -- -- -- 0.7 x VDD 0.8 x VDD VSS Typ(2) -- -- -- -- -- -- -- -- -- -- -- -- -- Max -- -- -- 50 50 100 0.4 1.5 1.0 50 50 100 VDD Unit V V V mA mA mA V V V mA mA mA V
VIL
--
0.2 x VDD
V
IDD
-- -- -- -- -- -- -- -- 20 -- -- VDD +2.5 3.85 3.95 --
15 4 3 1 1.25 250 10 -- 45 -- -- -- 4.25 4.35 100
20 8 10 1.25 1.6 350 10 1 65 12 8 8.5 4.50 4.60 --
mA mA A mA mA A A A k
IIL IIn RPU COut CIn VTST VTRIPF VTRIPR VHYS
pF V V V mV
Continued on next page
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 233
Electrical Specifications Typ(2) 700 --
Characteristic(1) POR reset voltage(8) POR rise time ramp rate(9)
Symbol VPORRST RPOR
Min 0 0.035
Max 800 --
Unit mV V/ms
1. VDD = 5.0 Vdc 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted 2. Typical values reflect average measurements at midpoint of voltage range, 25 C only. 3. Run (operating) IDD measured using external square wave clock source (fosc = 32.8 MHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly affects run IDD. Measured with all modules enabled. 4. Wait IDD measured using external square wave clock source (fosc = 32.8 MHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly affects wait IDD. Measured with PLL and LVI enabled. 5. Stop IDD is measured with OSC1 = VSS. 6. Stop IDD with TBM enabled is measured using an external crystal clock source (fOSC = 8 MHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. All inputs configured as inputs. 7. Pullups and pulldowns are disabled. Port B leakage is specified in 19.12 ADC Characteristics. 8. Maximum is highest voltage that POR is possible. 9. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum VDD is reached.
19.6 3.0 V DC Electrical Characteristics
Characteristic(1) Output high voltage (ILoad = -0.6 mA) all I/O pins (ILoad = -4.0 mA) all I/O pins (ILoad = -4.0 mA) pins PTC0-PTC1 only Maximum combined IOH for port C, port E, port PTD0-PTD3 Maximum combined IOH for port PTD4-PTD6, port A, port B Maximum total IOH for all port pins Output low voltage (ILoad = 0.5 mA) all I/O pins (ILoad = 6.0 mA) all I/O pins (ILoad = 10.0 mA) pins PTC0-PTC1 only Maximum combined IOL for port C, port E, port PTD0-PTD3 Maximum combined IOL for port PTD4-PTD6, port A, port B Maximum total IOL for all port pins Input high voltage All ports, IRQs, RESET OSC1 Input low voltage All ports, IRQs, RESET OSC1 Symbol VOH VOH VOH IOH1 IOH2 IOHT VOL VOL VOL IOL1 IOL2 IOLT VIH Min VDD - 0.3 VDD - 1.0 VDD - 0.5 -- -- -- -- -- -- -- -- -- 0.7 x VDD 0.8 x VDD VSS Typ(2) -- -- -- -- -- -- -- -- -- -- -- -- -- Max -- -- -- 30 30 60 0.3 1.0 0.8 30 30 60 VDD Unit V V V mA mA mA V V V mA mA mA V
VIL
--
0.3 x VDD 0.2 x VDD
V
Continued on next page
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 234 Freescale Semiconductor
3.0 V DC Electrical Characteristics Typ(2) 4.5 1.65 1 300 500 200 10 -- 45 -- -- -- 2.60 2.66 60 -- 700 --
Characteristic(1) VDD supply current Run(3) Wait(4) Stop(5) Stop with TBM enabled(6) Stop with LVI and TBM enabled(6) Stop with LVI I/O ports Hi-Z leakage current(7) Input current Pullup resistors (as input only) Ports PTA3/KBD37-PTA0/KBD0, PTC1-PTC0, PTD6/T2CH0-PTD0/SS Capacitance Ports (as input or output) Monitor mode entry voltage Low-voltage inhibit, trip falling voltage - target Low-voltage inhibit, trip rising voltage - target Low-voltage inhibit reset/recover hysteresis - target (VTRIPF + VHYS = VTRIPR) POR rearm voltage(8) POR reset voltage(9) POR rise time ramp rate(10)
Symbol
Min -- -- -- -- -- -- -- -- 20 -- -- VDD +2.5 2.35 2.45 -- 0 0 0.02
Max 8 4 6 500 700 300 10 1 65 12 8 8.5 2.70 2.80 -- 100 800 --
Unit mA mA A A A A A A k
IDD
IIL IIn RPU COut CIn VTST VTRIPF VTRIPR VHYS VPOR VPORRST RPOR
pF V V V mV mV mV V/ms
1. VDD = 3.0 Vdc 10%, VSS = 0 Vdc, TA = TL to TH, unless otherwise noted 2. Typical values reflect average measurements at midpoint of voltage range, 25 C only. 3. Run (operating) IDD measured using external square wave clock source (fosc = 16.4 MHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly affects run IDD. Measured with all modules enabled. 4. Wait IDD measured using external square wave clock source (fosc = 16.4 MHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. CL = 20 pF on OSC2. All ports configured as inputs. OSC2 capacitance linearly affects wait IDD. Measured with PLL and LVI enabled. 5. Stop IDD is measured with OSC1 = VSS. 6. Stop IDD with TBM enabled is measured using an external crystal clock source (fOSC = 4 MHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. All inputs configured as inputs. 7. Pullups and pulldowns are disabled. 8. Maximum is highest voltage that POR is guaranteed. 9. Maximum is highest voltage that POR is possible. 10. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum VDD is reached.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 235
Electrical Specifications
19.7 5.0 V Control Timing
Characteristic(1) Frequency of operation(2) Crystal option External clock option(3) Internal operating frequency Internal clock period (1/fOP) RESET input pulse width low(5) IRQ interrupt pulse width low(6) (edge-triggered) IRQ interrupt pulse period 16-bit Input capture pulse width Input capture period timer(7) Symbol fosc fop tcyc tIRL tILIH tILIL tTH,tTL tTLTL Min 1 dc(4) -- 122 50 50 Note 8 Max 8 32.8 8.2 -- -- -- -- -- -- Unit MHz MHz MHz ns ns ns tcyc ns tcyc
Note 8
1. VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VSS unless otherwise noted. 2. See 19.15 Clock Generation Module Characteristics for more information. 3. No more than 10% duty cycle deviation from 50% 4. Some modules may require a minimum frequency greater than dc for proper operation. See appropriate table for this information. 5. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause a reset. 6. Minimum pulse width is for guaranteed interrupt. It is possible for a smaller pulse width to be recognized. 7. Minimum pulse width is for guaranteed interrupt. It is possible for a smaller pulse width to be recognized. 8. The minimum period, tILIL or tTLTL, should not be less than the number of cycles it takes to execute the interrupt service routine plus tcyc.
19.8 3.0 V Control Timing
Characteristic(1) Frequency of Crystal option External clock option(3) operation(2) fosc fop tcyc tIRL (edge-triggered) tILIH tILIL tTH,tTL tTLTL 1 dc(4) -- 244 125 125 Note 8 8 16.4 4.1 -- -- -- -- -- -- MHz MHz MHz ns ns ns tcyc ns tcyc Symbol Min Max Unit
Internal operating frequency Internal clock period (1/fOP) RESET input pulse width IRQ interrupt pulse width low(5) low(6)
IRQ interrupt pulse period 16-bit timer(7) Input capture pulse width Input capture period
Note 8
1. VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VSS unless otherwise noted. 2. See 19.15 Clock Generation Module Characteristics for more information. 3. No more than 10% duty cycle deviation from 50% 4. Some modules may require a minimum frequency greater than dc for proper operation. See appropriate table for this information. 5. Minimum pulse width reset is guaranteed to be recognized. It is possible for a smaller pulse width to cause a reset. 6. Minimum pulse width is for guaranteed interrupt. It is possible for a smaller pulse width to be recognized. 7. Minimum pulse width is for guaranteed interrupt. It is possible for a smaller pulse width to be recognized. 8. The minimum period, tILIL or tTLTL, should not be less than the number of cycles it takes to execute the interrupt service routine plus tcyc.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 236 Freescale Semiconductor
Output High-Voltage Characteristics
19.9 Output High-Voltage Characteristics
0 -5 -10 IOH (mA) -15 -20 -25 -30 -35 -40 3 3.2 3.4 3.6 VOH (V) 3.8 4.0 4.2 -40 0 25 85
VOH > VDD -0.8 V @ IOH = -2.0 mA VOH > VDD -1.5 V @ IOH = -10.0 mA
Figure 19-1. Typical High-Side Driver Characteristics -- Port PTA3-PTA0 (VDD = 4.5 Vdc)
0 -5 -10 -15 -20 -25 1.3 1.5 1.7 1.9 VOH (V) 2.1 2.3 2.5 -40 0 25 85 IOH (mA)
VOH > VDD -0.3 V @ IOH = -0.6 mA VOH > VDD -1.0 V @ IOH = -4.0 mA
Figure 19-2. Typical High-Side Driver Characteristics -- Port PTA3-PTA0 (VDD = 2.7 Vdc)
0 -5 -10 IOH (mA) -15 -20 -25 -30 -35 -40 3 3.2 3.4 3.6 VOH (V) 3.8 4.0 4.2 -40 0 25 85
VOH > VDD -0.8 V @ IOH = -10.0 mA
Figure 19-3. Typical High-Side Driver Characteristics -- Port PTC1-PTC0 (VDD = 4.5 Vdc)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 237
Electrical Specifications
0 -5 -10 -15 -20 -25 1.9 VOH (V) VOH > VDD -0.5 V @ IOH = -4.0 mA 1.3 1.5 1.7 2.1 2.3 2.5 -40 0 25 85 IOH (mA) 0 -10 -20 -30 IOH (mA) -40 -50 -60 -70 -80 -90 3 3.2 3.4 3.6 3.8 VOH (V) 4.0 4.2 4.4 4.6 -40 0 25 85
Figure 19-4. Typical High-Side Driver Characteristics -- Port PTC1-PTC0 (VDD = 2.7 Vdc)
VOH > VDD -0.8 V @ IOH = -2.0 mA VOH > VDD -1.5 V @ IOH = -10.0 mA
Figure 19-5. Typical High-Side Driver Characteristics -- Ports PTB5-PTB0, PTD6-PTD0, and PTE1-PTE0 (VDD = 5.5 Vdc)
0 -5 -10 -15 -20 -25 1.9 VOH (V) VOH > VDD -0.3 V @ IOH = -0.6 mA VOH > VDD -1.0 V @ IOH = -4.0 mA 1.3 1.5 1.7 2.1 2.3 2.5 -40 0 25 85 IOH (mA)
Figure 19-6. Typical High-Side Driver Characteristics -- Ports PTB5-PTB0, PTD6-PTD0, and PTE1-PTE0 (VDD = 2.7 Vdc)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 238 Freescale Semiconductor
Output Low-Voltage Characteristics
19.10 Output Low-Voltage Characteristics
35 30 25 IOL (mA) 20 15 10 5 0 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 -40 0 25 85
VOL < 0.4 V @ IOL = 1.6 mA VOL < 1.5 V @ IOL = 10.0 mA
Figure 19-7. Typical Low-Side Driver Characteristics -- Port PTA3-PTA0 (VDD = 5.5 Vdc)
14 12 10 IOL (mA) 8 6 4 2 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 -40 0 25 85
VOL < 0.3 V @ IOL = 0.5 mA VOL < 1.0 V @ IOL = 6.0 mA
Figure 19-8. Typical Low-Side Driver Characteristics -- Port PTA3-PTA0 (VDD = 2.7 Vdc)
60 50 IOL (mA) 40 30 20 10 0 0.4 0.6 0.8 1.0 1.2 1.4 1.6 VOL (V) VOL < 1.0 V @ IOL = 15 mA -40 0 25 85
Figure 19-9. Typical Low-Side Driver Characteristics -- Port PTC1-PTC0 (VDD = 4.5 Vdc)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 239
Electrical Specifications
30 25 IOL (mA) 20 15 10 5 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 -40 0 25 85
VOL < 0.8 V @ IOL = 10 mA
Figure 19-10. Typical Low-Side Driver Characteristics -- Port PTC1-PTC0 (VDD = 2.7 Vdc)
35 30 25 IOL (mA) 20 15 10 5 0 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 -40 0 25 85
VOL < 0.4 V @ IOL = 1.6 mA VOL < 1.5 V @ IOL = 10.0 mA
Figure 19-11. Typical Low-Side Driver Characteristics -- Ports PTB5-PTB0, PTD6-PTD0, and PTE1-PTE0 (VDD = 5.5 Vdc)
14 12 10 IOL (mA) 8 6 4 2 0 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 -40 0 25 85
VOL < 0.3 V @ IOL = 0.5 mA VOL < 1.0 V @ IOL = 6.0 mA
Figure 19-12. Typical Low-Side Driver Characteristics -- Ports PTB5-PTB0, PTD6-PTD0, and PTE1-PTE0 (VDD = 2.7 Vdc)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 240 Freescale Semiconductor
Typical Supply Currents
19.11 Typical Supply Currents
16 14 12 IDD (mA) 10 8 6 4 2 0 0 1 2 3 4 5 fbus (MHz) 6 7 8 9 5.5 V 3.6 V
Figure 19-13. Typical Operating IDD, with All Modules Turned On (-40 C to 125 C)
5.0 4.5 4.0 3.5 IDD (mA) 3.0 2.5 2.0 1.5 1.0 0.5 0 0 1 2 3 4 fbus (MHz) 5 6 7 8 5.5 V 3.6 V
Figure 19-14. Typical Wait Mode IDD, with all Modules Disabled (-40 C to 125 C)
1.35 1.30 1.25 IDD (A) 1.20 1.15 1.10 1.05 1 0 1 2 3 4 5 fbus (MHz) 6 7 8 9 5.5 V 3.6 V
Figure 19-15. Typical Stop Mode IDD, with all Modules Disabled (-40 C to 125 C)
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 241
Electrical Specifications
19.12 ADC Characteristics
Characteristic(1) Symbol Min 2.7 (VDD min) 0 8 -- 0.5 VREFL 16 16 5 00 FE -- -- 17 -- 01 FF (20) 8 1 Max 5.5 (VDD max) VDDAD 8 1 1.048 VREFH Unit Comments VDDAD should be tied to the same potential as VDD via separate traces. VADIN <= VREFH
Supply voltage
VDDAD
V
Input voltages Resolution Absolute accuracy (VREFL = 0 V, VDDAD = VREFH = 5 V 10%) ADC internal clock Conversion range Power-up time Conversion time Sample time(2) Zero input reading(3) Full-scale reading(3)
VADIN BAD AAD fADIC RAD tADPU tADC tADS ZADI FADI CADI --
V Bits LSB MHz V tAIC cycles tAIC cycles tAIC cycles Hex Hex pF A
Includes quantization tAIC = 1/fADIC, tested only at 1 MHz VREFH = VDDAD VREFL = VSSAD
VIN = VREFL VIN = VREFH Not tested
Input capacitance Input leakage(4) Port B
1. VDD = 5.0 Vdc 10%, VSS = 0 Vdc, VDDAD = 5.0 Vdc 10%, VSSAD = 0 Vdc, VREFH = 5.0 Vdc 10%, VREFL = 0 2. Source impedances greater than 10 k adversely affect internal RC charging time during input sampling. 3. Zero-input/full-scale reading requires sufficient decoupling measures for accurate conversions. 4. The external system error caused by input leakage current is approximately equal to the product of R source and input current.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 242 Freescale Semiconductor
5.0 V SPI Characteristics
19.13 5.0 V SPI Characteristics
Diagram Number(1) Characteristic(2) Operating frequency Master Slave 1 2 3 4 Cycle time Master Slave Enable lead time Enable lag time Clock (SPSCK) high time Master Slave Clock (SPSCK) low time Master Slave Data setup time (inputs) Master Slave Data hold time (inputs) Master Slave Access time, slave(3) CPHA = 0 CPHA = 1 Disable time, slave(4) Data valid time, after enable edge Master Slave(5) Data hold time, outputs, after enable edge Master Slave Symbol Min Max Unit
fOP(M) fOP(S) tCYC(M) tCYC(S) tLead(S) tLag(S) tSCKH(M) tSCKH(S) tSCKL(M) tSCKL(S) tSU(M) tSU(S) tH(M) tH(S) tA(CP0) tA(CP1) tDIS(S) tV(M) tV(S) tHO(M) tHO(S)
fOP/128 DC 2 1 1 1 tcyc -25 1/2 tcyc -25 tcyc -25 1/2 tcyc -25 30 30 30 30 0 0 -- -- -- 0 0
fOP/2 fOP 128 -- -- -- 64 tcyc -- 64 tcyc -- -- -- -- -- 40 40 40 50 50 -- --
MHz MHz tcyc tcyc tcyc tcyc ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
5
6
7
8 9 10
11
1. Numbers refer to dimensions in Figure 19-16 and Figure 19-17. 2. All timing is shown with respect to 20% VDD and 70% VDD, unless noted; 100 pF load on all SPI pins. 3. Time to data active from high-impedance state 4. Hold time to high-impedance state 5. With 100 pF on all SPI pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 243
Electrical Specifications
19.14 3.0 V SPI Characteristics
Diagram Number(1) Characteristic(2) Operating frequency Master Slave 1 2 3 4 Cycle time Master Slave Enable lead time Enable lag time Clock (SPSCK) high time Master Slave Clock (SPSCK) low time Master Slave Data setup time (inputs) Master Slave Data hold time (inputs) Master Slave Access time, slave(3) CPHA = 0 CPHA = 1 Disable time, slave(4) Data valid time, after enable edge Master Slave(5) Data hold time, outputs, after enable edge Master Slave Symbol Min Max Unit
fOP(M) fOP(S) tCYC(M) tCYC(S) tLead(s) tLag(s) tSCKH(M) tSCKH(S) tSCKL(M) tSCKL(S) tSU(M) tSU(S) tH(M) tH(S) tA(CP0) tA(CP1) tDIS(S) tV(M) tV(S) tHO(M) tHO(S)
fOP/128 DC 2 1 1 1 tcyc -35 1/2 tcyc -35 tcyc -35 1/2 tcyc -35 40 40 40 40 0 0 -- -- -- 0 0
fOP/2 fOP 128 -- -- -- 64 tcyc -- 64 tcyc -- -- -- -- -- 50 50 50 60 60 -- --
MHz MHz tcyc tcyc tcyc tcyc ns ns ns ns ns ns ns ns ns ns ns ns ns ns ns
5
6
7
8 9 10
11
1. Numbers refer to dimensions in Figure 19-16 and Figure 19-17. 2. All timing is shown with respect to 20% VDD and 70% VDD, unless noted; 100 pF load on all SPI pins. 3. Time to data active from high-impedance state 4. Hold time to high-impedance state 5. With 100 pF on all SPI pins
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 244 Freescale Semiconductor
3.0 V SPI Characteristics
SS INPUT
SS PIN OF MASTER HELD HIGH 1
SPSCK OUTPUT CPOL = 0
NOTE
5 4 5 4 6 7 LSB IN 10 BITS 6-1 11 MASTER LSB OUT
SPSCK OUTPUT CPOL = 1
NOTE
MISO INPUT
MSB IN 11
BITS 6-1
MOSI OUTPUT
MASTER MSB OUT
Note: This first clock edge is generated internally, but is not seen at the SPSCK pin.
a) SPI Master Timing (CPHA = 0)
SS INPUT
SS PIN OF MASTER HELD HIGH 1
SPSCK OUTPUT CPOL = 0
5 4 5 4 6 7 LSB IN 10 BITS 6-1 MASTER LSB OUT
NOTE
SPSCK OUTPUT CPOL = 1
NOTE
MISO INPUT 10 MOSI OUTPUT
MSB IN 11 MASTER MSB OUT
BITS 6-1
Note: This last clock edge is generated internally, but is not seen at the SPSCK pin.
b) SPI Master Timing (CPHA = 1)
Figure 19-16. SPI Master Timing
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 245
Electrical Specifications
SS INPUT 1 SPSCK INPUT CPOL = 0 2 SPSCK INPUT CPOL = 1 8 MISO INPUT SLAVE 6 MOSI OUTPUT MSB IN MSB OUT 7 10 BITS 6-1 BITS 6-1 11 LSB IN SLAVE LSB OUT 11 5 4 9 NOTE 5 4 3
Note: Not defined but normally MSB of character just received
a) SPI Slave Timing (CPHA = 0)
SS INPUT 1 SPSCK INPUT CPOL = 0 2 SPSCK INPUT CPOL = 1 8 MISO OUTPUT 5 4 10 NOTE SLAVE 6 MOSI INPUT MSB IN MSB OUT 7 10 BITS 6-1 BITS 6-1 11 LSB IN 9 SLAVE LSB OUT 5 4 3
Note: Not defined but normally LSB of character previously transmitted
b) SPI Slave Timing (CPHA = 1)
Figure 19-17. SPI Slave Timing
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 246 Freescale Semiconductor
Clock Generation Module Characteristics
19.15 Clock Generation Module Characteristics
19.15.1 CGM Component Specifications
Characteristic Crystal reference frequency Crystal load capacitance
(2) (2) (2) (1)
Symbol fXCLK CL C1 C2 RB RS
Min 1 -- -- -- 0.5 --
Typ 4 20 2 x CL 2 x CL 1 0
Max 8 -- -- -- 10 --
Unit MHz pF pF pF M
Crystal fixed capacitance
Crystal tuning capacitance Feedback bias resistor Series resistor
1. Fundamental mode crystals only 2. Consult crystal manufacturer's data.
19.15.2 CGM Electrical Specifications
Description Operating voltage Operating temperature Crystal reference frequency Range nominal multiplier VCO center-of-range frequency VCO range linear range multiplier VCO power-of-two range multiplier VCO multiply factor VCO prescale multiplier Reference divider factor VCO operating frequency Bus operating frequency (5-V operation) Bus frequency (3-V operation) Manual acquisition time Automatic lock time PLL jitter(1) External clock input frequency PLL disabled External clock input frequency PLL enabled Symbol VDD TA fRCLK fNOM fVRS L 2
E
Min 2.7 -40 1 -- 4 1 1 1 1 1 4 -- -- -- -- 0 dc 1
Typ -- 25 4 38.4 -- -- -- -- 1 1 -- -- -- -- -- -- -- 4
Max 5.5 125 8 -- 40 255 4 4095 8 15 40 8.2 4.1 5 5 fRCLK x 0.025% x 2P N/4 32.8 M 8
Unit V
oC
MHz kHz MHz
N 2P R fVCLK fBUS fBUS tLock tLock fJ fOSC fOSC
MHz MHz MHz ms ms Hz Hz MHz
1. Deviation of average bus frequency over 2 ms. N = VCO multiplier.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 247
Electrical Specifications
19.16 Timer Interface Module Characteristics
Characteristic Input capture pulse width Symbol tTIH, tTIL Min 1 Max -- Unit tcyc
19.17 Memory Characteristics
Characteristic RAM data retention voltage FLASH program bus clock frequency FLASH read bus clock frequency FLASH page erase time Limited endurance (<1 K cycles) Maximum endurance (>1 K cycles) FLASH mass erase time FLASH PGM/ERASE to HVEN setup time FLASH high-voltage hold time FLASH high-voltage hold time (mass erase) FLASH program hold time FLASH program time FLASH return to read time FLASH cumulative program hv period FLASH endurance(4) Symbol VRDR -- fRead(1) tErase tMErase tNVS tNVH tNVHL tPGS tPROG tRCV(2) tHV(3) -- -- Min 1.3 1 -- 0.9 3.6 4 10 5 100 5 30 1 -- 10 k 15 Typ -- -- -- 1 4 -- -- -- -- -- -- -- -- 100 k 100 Max -- -- 8.2 1.1 5.5 -- -- -- -- -- 40 -- 4 -- -- Unit V MHz MHz ms ms s s s s s s ms Cycles Years
FLASH data retention time(5)
1. fRead is defined as the frequency range for which the FLASH memory can be read. 2. tRCV is defined as the time it needs before the FLASH can be read after turning off the high voltage charge pump, by clearing HVEN to 0. 3. tHV is defined as the cumulative high voltage programming time to the same row before next erase. tHV must satisfy this condition: tNVS + tNVH + tPGS + (tPROG x 32) tHV maximum. 4. Typical endurance was evaluated for this product family. For additional information on how Freescale defines Typical Endurance, please refer to Engineering Bulletin EB619. 5. Typical data retention values are based on intrinsic capability of the technology measured at high temperature and de-rated to 25C using the Arrhenius equation. For additional information on how Freescale defines Typical Data Retention, please refer to Engineering Bulletin EB618.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 248 Freescale Semiconductor
Chapter 20 Ordering Information and Mechanical Specifications
20.1 Introduction
This section provides ordering information for the MC68HC908GR8A and MC68HC908GR4A along with the dimensions for: * 32-pin low-profile quad flat pack package (case 873A) * 28-pin dual in-line package (case 710) * 28-pin small outline package (case 751F) The following figures show the latest package drawings at the time of this publication. To make sure that you have the latest package specifications, contact your local Freescale Semiconductor Sales Office.
20.2 MC Order Numbers
Table 20-1. MC Order Numbers
MC Order Number MC68HC908GR8ACFA MC68HC908GR4ACFA MC68HC908GR8AVFA MC68HC908GR8AMFA MC68HC908GR8ACP MC68HC908GR4ACP MC68HC908GR8ACDW MC68HC908GR4ACDW Temperature designators: C = -40C to +85C V = -40C to +105C M = -40C to +125C Operating Temperature Range -40C to +85C -40C to +85C -40C to +105C -40C to +125C -40C to +85C -40C to +85C -40C to +85C -40C to +85C 28-pin dual in-ine package (PDIP) 28-pin small outout package (SOIC 32-pin low-profile quad flat package (LQFP) Package
MC908GR8A X XX E
FAMILY Pb FREE PACKAGE DESIGNATOR TEMPERATURE RANGE
Figure 20-1. Device Numbering System
20.3 Package Dimensions
Refer to the following pages for detailed package dimensions.
MC68HC908GR8A * MC68HC908GR4A Data Sheet, Rev. 5 Freescale Semiconductor 249
How to Reach Us:
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MC68HC908GR8A Rev. 5, 04/2007

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