MC68HC908GR8 MC68HC908GR4 Data Sheet M68HC08 Microcontrollers MC68HC908GR8 Rev. 7 10/2006 freescale.com MC68HC908GR8 MC68HC908GR4 Data Sheet To provide the most up-to-date information, the revision of our documents on the World Wide Web will be the most current. Your printed copy may be an earlier revision. To verify you have the latest information available, refer to: http://freescale.com/ Freescale™ and the Freescale logo are trademarks of Freescale Semiconductor, Inc. This product incorporates SuperFlash® technology licensed from SST. © Freescale Semiconductor, Inc., 2006. All rights reserved. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 3 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 4 Freescale Semiconductor List of Chapters Chapter 1 General Description. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Chapter 2 Memory Map. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Chapter 3 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37 Chapter 4 Resets and Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Chapter 5 Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 Chapter 6 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 Chapter 7 Clock Generator Module (CGMC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 Chapter 8 Configuration Register (CONFIG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Chapter 9 Computer Operating Properly (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 Chapter 10 Central Processing Unit (CPU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 Chapter 11 Flash Memory. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 Chapter 12 External Interrupt (IRQ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 Chapter 13 Keyboard Interrupt (KBI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 Chapter 14 Low-Voltage Inhibit (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 Chapter 15 Monitor ROM (MON) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 Chapter 16 Input/Output Ports (I/O). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 Chapter 17 Random-Access Memory (RAM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Chapter 18 Serial Communications Interface (SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 Chapter 19 System Integration Module (SIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 Chapter 20 Serial Peripheral Interface (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Chapter 21 Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 Chapter 22 Timer Interface Module (TIM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 Chapter 23 Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 Chapter 24 Mechanical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 Chapter 25 Ordering Information. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 5 List of Chapters MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 6 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 of the MC68HC908GR8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 (CGMXFC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analog 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–PTC0) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port D I/O Pins (PTD6/T2CH0–PTD0/SS) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Port E I/O Pins (PTE1/RxD–PTE0/TxD) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19 19 19 20 21 22 24 24 24 24 24 24 25 25 25 25 25 25 26 Chapter 2 Memory Map 2.1 2.2 2.3 2.4 2.5 2.6 2.7 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Unimplemented Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reserved Memory Locations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Input/Output (I/O) Section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Memory Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Register Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vector Addresses. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 27 27 27 28 29 36 Chapter 3 Low-Power Modes 3.1 3.1.1 3.1.2 3.2 3.2.1 3.2.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Analog-to-Digital Converter (ADC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37 37 37 37 37 37 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 7 Table of Contents 3.3 3.3.1 3.3.2 3.4 3.4.1 3.4.2 3.5 3.5.1 3.5.2 3.6 3.6.1 3.6.2 3.7 3.7.1 3.7.2 3.8 3.8.1 3.8.2 3.9 3.9.1 3.9.2 3.10 3.10.1 3.10.2 3.11 3.11.1 3.11.2 3.12 3.12.1 3.12.2 3.13 3.13.1 3.13.2 3.14 Break Module (BRK) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Central Processor Unit (CPU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clock Generator Module (CGM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Computer Operating Properly Module (COP) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Interrupt Module (IRQ). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Interrupt Module (KBI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Voltage Inhibit Module (LVI). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Serial Communications Interface Module (SCI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Serial Peripheral Interface Module (SPI) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timer Interface Module (TIM1 and TIM2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timebase Module (TBM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exiting Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38 38 38 38 38 38 38 38 38 39 39 39 39 39 39 39 39 39 39 39 40 40 40 40 40 40 40 40 40 41 41 41 41 41 Chapter 4 Resets and Interrupts 4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 Resets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.1 Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.2 External Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3 Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3.1 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3.2 COP Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3.3 Low-Voltage Inhibit Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3.4 Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.3.5 Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2.4 SIM Reset Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 43 43 43 43 44 44 45 45 45 45 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 8 Freescale Semiconductor 4.3 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.1 Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2 Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.1 SWI Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.2 Break Interrupt . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.3 IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.4 CGM (Clock Generator Module). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.5 TIM1 (Timer Interface Module 1) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.6 TIM2 (Timer Interface Module 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.7 SPI (Serial Peripheral Interface). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.8 SCI (Serial Communications Interface) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.9 KBD0–KBD4 Pins. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.10 ADC (Analog-to-Digital Converter) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.2.11 TBM (Timebase Module) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3 Interrupt Status Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3.1 Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3.2 Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3.3.3 Interrupt Status Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 47 49 50 51 51 51 51 51 51 52 53 53 53 53 54 54 54 Chapter 5 Analog-to-Digital Converter (ADC) 5.1 5.2 5.3 5.3.1 5.3.2 5.3.3 5.3.4 5.3.5 5.4 5.5 5.5.1 5.5.2 5.6 5.6.1 5.6.2 5.6.3 5.7 5.7.1 5.7.2 5.7.3 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 Power Pin (VDDAD)/ADC Voltage Reference High Pin (VREFH) . . . . . . . . . . . ADC Analog Ground Pin (VSSAD)/ADC Voltage Reference Low Pin (VREFL) . . . . . . . . . . . ADC Voltage In (VADIN) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Data Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Clock Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55 55 55 55 56 56 57 57 57 57 57 57 58 58 58 58 58 58 60 60 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 9 Table of Contents Chapter 6 Break Module (BRK) 6.1 6.2 6.3 6.3.1 6.3.2 6.3.3 6.3.4 6.4 6.4.1 6.4.2 6.5 6.5.1 6.5.2 6.5.3 6.5.4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Flag Protection During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . TIMI and TIM2 During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Module Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Address Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Flag Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63 63 63 63 64 65 65 65 65 65 65 65 66 66 67 Chapter 7 Clock Generator Module (CGMC) 7.1 7.2 7.3 7.3.1 7.3.2 7.3.3 7.3.4 7.3.5 7.3.6 7.3.7 7.3.8 7.3.9 7.4 7.4.1 7.4.2 7.4.3 7.4.4 7.4.5 7.4.6 7.4.7 7.4.8 7.4.9 7.4.10 7.5 7.5.1 7.5.2 7.5.3 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGMC 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) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGMC Base Clock Output (CGMOUT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGMC CPU Interrupt (CGMINT) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGMC Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Bandwidth Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Multiplier Select Register High . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69 69 69 71 71 71 72 72 73 76 76 76 77 77 77 77 78 78 78 78 78 78 78 79 80 82 83 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 10 Freescale Semiconductor 7.5.4 7.5.5 7.5.6 7.6 7.7 7.7.1 7.7.2 7.7.3 7.8 7.8.1 7.8.2 7.8.3 PLL Multiplier Select Register Low . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL VCO Range Select Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PLL Reference Divider Select Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Special Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGMC During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition/Lock Time Specifications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acquisition/Lock Time Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Parametric Influences on Reaction Time . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Choosing a Filter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83 84 84 85 85 85 86 86 86 86 87 87 Chapter 8 Configuration Register (CONFIG) 8.1 8.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89 Chapter 9 Computer Operating Properly (COP) 9.1 9.2 9.3 9.3.1 9.3.2 9.3.3 9.3.4 9.3.5 9.3.6 9.3.7 9.3.8 9.4 9.5 9.6 9.7 9.7.1 9.7.2 9.8 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGMXCLK . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . STOP Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPCTL Write . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power-On Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Internal Reset. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Reset Vector Fetch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPD (COP Disable). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COPRS (COP Rate Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Monitor Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . COP Module During Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 93 94 94 94 94 94 94 94 95 95 95 95 95 95 95 95 96 Chapter 10 Central Processing Unit (CPU) 10.1 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2 CPU Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.1 Accumulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.2 Index Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10.2.3 Stack Pointer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97 97 98 98 99 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 11 Table of Contents 10.2.4 10.2.5 10.3 10.4 10.4.1 10.4.2 10.5 10.6 10.7 Program Counter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99 Condition Code Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100 Arithmetic/Logic Unit (ALU) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 CPU During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101 Instruction Set Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102 Opcode Map . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107 Chapter 11 Flash Memory 11.1 11.2 11.3 11.4 11.5 11.6 11.7 11.7.1 11.8 11.9 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109 109 110 110 111 111 114 114 115 115 Chapter 12 External Interrupt (IRQ) 12.1 12.2 12.3 12.4 12.5 12.6 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IRQ Pin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IRQ Module During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IRQ Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117 117 117 119 119 120 Chapter 13 Keyboard Interrupt (KBI) 13.1 13.2 13.3 13.4 13.5 13.5.1 13.5.2 13.6 13.7 13.7.1 13.7.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Module During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Status and Control Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Keyboard Interrupt Enable Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121 121 121 123 123 123 123 123 124 124 125 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 12 Freescale Semiconductor Chapter 14 Low-Voltage Inhibit (LVI) 14.1 14.2 14.3 14.3.1 14.3.2 14.3.3 14.3.4 14.4 14.5 14.6 14.6.1 14.6.2 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 127 127 128 128 128 129 129 129 129 129 129 Chapter 15 Monitor ROM (MON) 15.1 15.2 15.3 15.3.1 15.3.2 15.3.3 15.3.4 15.3.5 15.4 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Entering Monitor Mode. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Break Signal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baud Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Commands. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131 131 131 133 136 136 136 137 140 Chapter 16 Input/Output Ports (I/O) 16.1 16.2 16.2.1 16.2.2 16.2.3 16.3 16.3.1 16.3.2 16.4 16.4.1 16.4.2 16.4.3 16.5 16.5.1 16.5.2 16.5.3 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 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 143 146 146 146 147 148 148 149 150 150 150 152 152 152 153 155 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 13 Table of Contents 16.6 Port E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 16.6.1 Port E Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155 16.6.2 Data Direction Register E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156 Chapter 17 Random-Access Memory (RAM) 17.1 17.2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159 Chapter 18 Serial Communications Interface (SCI) 18.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.2 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.3 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.1 Data Format . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.2 Transmitter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.2.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.2.2 Character Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.2.3 Break Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.2.4 Idle Characters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.2.5 Inversion of Transmitted Output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.2.6 Transmitter Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3 Receiver . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.1 Character Length . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.2 Character Reception. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.3 Data Sampling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.4 Framing Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.5 Baud Rate Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.6 Slow Data Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.7 Fast Data Tolerance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.8 Receiver Wakeup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.9 Receiver Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.4.3.10 Error Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.5 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.5.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.5.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.6 SCI During Break Module Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.7 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.7.1 PE2/TxD (Transmit Data). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.7.2 PE1/RxD (Receive Data) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8.1 SCI Control Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8.2 SCI Control Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8.3 SCI Control Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8.4 SCI Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18.8.5 SCI Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 161 161 162 162 164 165 166 166 166 167 167 167 167 168 169 169 170 171 171 172 172 173 173 174 174 174 174 174 174 175 175 175 177 179 180 182 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 14 Freescale Semiconductor 18.8.6 18.8.7 SCI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 SCI Baud Rate Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183 Chapter 19 System Integration Module (SIM) 19.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2 SIM Bus Clock Control and Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.1 Bus Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.2 Clock Startup from POR or LVI Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.2.3 Clocks in Stop Mode and Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3 Reset and System Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.1 External Pin Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2 Active Resets from Internal Sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2.1 Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2.2 Computer Operating Properly (COP) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2.3 Illegal Opcode Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2.4 Illegal Address Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2.5 Low-Voltage Inhibit (LVI) Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.3.2.6 Monitor Mode Entry Module Reset (MODRST) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4 SIM Counter. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4.1 SIM Counter During Power-On Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4.2 SIM Counter During Stop Mode Recovery. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.4.3 SIM Counter and Reset States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5 Exception Control. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1.1 Hardware Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1.2 SWI Instruction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1.3 Interrupt Status Registers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1.4 Interrupt Status Register 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1.5 Interrupt Status Register 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.1.6 Interrupt Status Register 3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.2 Reset . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.3 Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.5.4 Status Flag Protection in Break Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.7 SIM Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.7.1 SIM Break Status Register. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.7.2 SIM Reset Status Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19.7.3 SIM Break Flag Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187 189 190 190 190 190 190 191 192 192 193 193 193 193 193 193 193 194 194 194 196 196 197 197 198 198 198 198 199 199 199 200 201 201 202 203 Chapter 20 Serial Peripheral Interface (SPI) 20.1 20.2 20.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205 Pin Name Conventions and I/O Register Addresses . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 15 Table of Contents 20.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4.1 Master Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.4.2 Slave Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5 Transmission Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.1 Clock Phase and Polarity Controls. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.2 Transmission Format When CPHA = 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.3 Transmission Format When CPHA = 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.5.4 Transmission Initiation Latency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.6 Queuing Transmission Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.7 Error Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.7.1 Overflow Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.7.2 Mode Fault Error . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.8 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.9 Resetting the SPI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.10 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.10.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.10.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.11 SPI During Break Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.12 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.12.1 MISO (Master In/Slave Out). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.12.2 MOSI (Master Out/Slave In). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.12.3 SPSCK (Serial Clock) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.12.4 SS (Slave Select) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.13 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.13.1 SPI Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.13.2 SPI Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20.13.3 SPI Data Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206 208 208 209 209 209 210 211 213 214 214 215 217 218 218 218 218 219 219 219 219 220 220 221 221 222 224 Chapter 21 Timebase Module (TBM) 21.1 21.2 21.3 21.4 21.5 21.5.1 21.5.2 21.6 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timebase Register Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225 225 225 225 226 226 226 227 Chapter 22 Timer Interface Module (TIM) 22.1 22.2 22.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 Features. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 Pin Name Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 16 Freescale Semiconductor 22.4 Functional Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.1 TIM Counter Prescaler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.2 Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.3 Output Compare. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.3.1 Unbuffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.3.2 Buffered Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.4 Pulse Width Modulation (PWM) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.4.1 Unbuffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.4.2 Buffered PWM Signal Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4.4.3 PWM Initialization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.5 Interrupts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.6 Low-Power Modes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.6.1 Wait Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.6.2 Stop Mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.7 TIM During Break Interrupts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.8 I/O Signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.9 I/O Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.9.1 TIM Status and Control Register . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.9.2 TIM Counter Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.9.3 TIM Counter Modulo Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.9.4 TIM Channel Status and Control Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.9.5 TIM Channel Registers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230 230 230 230 234 234 234 235 236 236 237 237 237 237 238 238 238 238 240 241 241 244 Chapter 23 Electrical Specifications 23.1 23.2 23.3 23.4 23.5 23.6 23.7 23.8 23.8.1 23.8.2 23.9 23.10 23.11 23.12 23.13 23.14 23.15 23.16 Absolute Maximum Ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Functional Operating Range . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Thermal Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 V DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 V DC Electrical Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 V Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 V Control Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Clock Generation Module Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Component Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . CGM Electrical Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output High-Voltage Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output Low-Voltage Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Typical Supply Currents. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ADC Characteristics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.0 V SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.0 V SPI Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Timer Interface Module Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Memory Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247 248 248 249 251 253 254 255 255 255 256 259 261 263 264 265 268 268 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 17 Table of Contents Chapter 24 Mechanical Specifications 24.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 269 Chapter 25 Ordering Information 25.1 25.2 25.3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 MC Order Numbers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281 Development Tools . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 282 Revision History Revision History. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 283 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 18 Freescale Semiconductor Chapter 1 General Description 1.1 Introduction The MC68HC908GR8 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 MC68HC908GR4. The MC68HC908GR4 is a device identical to the MC68HC908GR8 except that it has less Flash memory. Only when there are differences from the MC68HC908GR8 is the MC68HC908GR4 specifically mentioned in the text. 1.2 Features For convenience, features have been organized to reflect: • Standard features of the MC68HC908GR8 • Features of the CPU08 1.2.1 Standard Features of the MC68HC908GR8 • • • • • • • • • • High-performance M68HC08 architecture optimized for C-compilers Fully upward-compatible object code with M6805, M146805, and M68HC05 Families 8-MHz internal bus frequency 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 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 Master reset pin and power-on reset (POR) 1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 19 General Description • • • • • • • • • • • • • • • • • • 7680 bytes of on-chip FLASH memory on the MC68HC908GR8 and 4096 bytes of on-chip FLASH memory on the MC68HC908GR4 with in-circuit programming capabilities of FLASH program memory 384 bytes of on-chip random-access memory (RAM) Serial peripheral interface module (SPI) Serial communications interface module (SCI) One 16-bit, 2-channel timer (TIM1) and one 16-bit, 1-channel timer (TIM2) interface modules with selectable input capture, output compare, and PWM capability on each channel 6-channel, 8-bit successive approximation analog-to-digital converter (ADC) BREAK module (BRK) to allow single breakpoint setting during in-circuit debugging Internal pullups on IRQ and RST to reduce customer system cost Clock generator module with on-chip 32-kHz crystal compatible PLL (phase-lock loop) Up to 21 general-purpose input/output (I/O) pins, including: – 19 shared-function I/O pins – Up to two dedicated I/O pins, depending on package choice Selectable pullups on inputs only on ports A, C, and D. Selection is on an individual port bit basis. During output mode, pullups are disengaged. High current 10-mA sink/10-mA source capability on all port pins Higher current 15-mA sink/source capability on PTC0–PTC1 Timebase module 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 32-kHz crystal Oscillator stop mode enable bit (OSCSTOPENB) in the CONFIG register to allow user selection of having the oscillator enabled or disabled during stop mode 4-bit keyboard wakeup port 42-pin shrink dual in-line package (SDIP), 32-pin quad flat pack (QFP), 28-pin plastic dual-in-line package (DIP), or 28-pin small outline integrated circuit (SOIC) Specific features of the MC68HC908GR8 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 × 8 multiply instruction • Fast 16/8 divide instruction • Binary-coded decimal (BCD) instructions • Optimization for controller applications • Efficient C language support MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 20 Freescale Semiconductor MCU Block Diagram 1.3 MCU Block Diagram Figure 1-1 shows the structure of the MC68HC908GR8. INTERNAL BUS DDRA PORTA DDRB PORTB PTB5/AD5– PTB0/AD0 DDRC PTC1–PTC0 † ‡ PORTD MC68HC908GR8 USER FLASH — 7680 BYTES MC68HC908GR4 USER FLASH — 4096BYTES SINGLE BRKPT BREAK MODULE PTA3/KBD3– PTA0/KBD0 † PORTC CONTROL AND STATUS REGISTERS — 64 BYTES PROGR. TIMEBASE MODULE DDRD ARITHMETIC/LOGIC UNIT (ALU) PTD6/T2CH0 † PTD5/T1CH1 † PTD4/T1CH0 † PTD3/SPSCK † PTD2/MOSI † PTD1/MISO † PTD0/SS † DDRE CPU REGISTERS PORTE M68HC08 CPU PTE1/RxD PTE0/TxD DUAL V. LOW-VOLTAGE INHIBIT MODULE USER RAM — 384 BYTES 4-BIT KEYBOARD INTERRUPT MODULE MONITOR ROM — 310 BYTES FLASH PROGRAMMING (BURN-IN) ROM — 544 BYTES 2-CHANNEL TIMER INTERFACE MODULE 1 USER FLASH VECTOR SPACE — 36 BYTES 1-CHANNEL TIMER INTERFACE MODULE 2 CLOCK GENERATOR MODULE OSC1 OSC2 CGMXFC 32-kHz OSCILLATOR SERIAL COMMUNICATIONS INTERFACE MODULE COMPUTER OPERATING PROPERLY MODULE PHASE-LOCKED LOOP SERIAL PERIPHERAL INTERFACE MODULE * RST 24 INTR SYSTEM INTEGRATION MODULE * IRQ SINGLE EXTERNAL IRQ MODULE MONITOR MODULE VDDAD / VREFH VSSAD / VREFL DATA BUS SWITCH MODULE 8-BIT ANALOG-TO-DIGITAL CONVERTER MODULE VDD VSS VDDA VSSA POWER MEMORY MAP MODULE MASK OPTION REGISTER1 MODULE MASK OPTION REGISTER2 MODULE POWER-ON RESET MODULE SECURITY MODULE MONITOR MODE ENTRY MODULE † Ports are software configurable with pullup device if input port. ‡ Higher current drive port pins * Pin contains integrated pullup device Figure 1-1. MCU Block Diagram MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 21 General Description 1.4 Pin Assignments VDDA 1 42 PTC1 VSSA 2 41 PTC0 CGMXFC 3 40 N.C. OSC2 4 39 VSS OSC1 5 38 N.C. VSS 6 37 PTA3/KBD3 RST 7 36 PTA2/KBD2 PTE0/TxD 8 35 PTA1/KBD1 PTE1/RxD 9 34 PTA0/KBD0 N.C. 10 33 VSSAD/VREFL IRQ 11 32 VDDAD/VREFH N.C. 12 31 N.C. PTD0/SS 13 30 N.C. PTD1/MISO 14 29 PTB5/AD5 PTD2/MOSI 15 28 PTB4/AD4 PTD3/SPSCK 16 27 PTB3/AD3 VSS 17 26 VSS VSS 18 25 PTB2/AD2 VDD 19 24 PTB1/AD1 PTD4/T1CH0 20 23 PTB0/AD0 PTD5/T1CH1 21 22 PTD6/T2CH0 Figure 1-2. SDIP Pin Assignments MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 22 Freescale Semiconductor OSC2 CGMXFC VSSA VDDA PTC1 PTC0 PTA3/KBD3 31 30 29 28 27 26 25 32 OSC1 Pin Assignments RST 1 24 PTA2/KBD2 VDDAD/VREFH PTD1/MISO 6 19 PTB5/AD5 PTD2/MOSI 7 18 PTB4/AD4 PTD3/SPSCK 8 17 PTB3/AD3 PTB0/AD0 16 20 PTB2/AD2 5 15 PTD0/SS PTB1/AD1 VSSAD/VREFL 14 21 13 4 PTD6/T2CH0 IRQ 12 PTA0/KBD0 PTD5/T1CH1 22 11 3 PTD4/T1CH0 PTE1/RxD 10 PTA1/KBD1 VDD 23 9 2 VSS PTE0/TxD NOTE: Ports PTB4, PTB5, PTC0, and PTC1 are available only with the QFP. Figure 1-3. QFP Pin Assignments CGMXFC 1 28 VSSA OSC2 2 27 VDDA OSC1 3 26 PTA3/KBD3 RST 4 25 PTA2/KBD2 PTE0/TxD 5 24 PTA1/KBD1 PTE1/RxD 6 23 PTA0/KBD0 IRQ 7 22 VSSAD/VREFL PTD0/SS 8 21 VDDAD/VREFH PTD1/MISO 9 20 PTB3/AD3 PTD2/MOSI 10 19 PTB2/AD2 PTD3/SPSCK 11 18 PTB1/AD1 VSS 12 17 PTB0/AD0 VDD 13 16 PTD6/T2CH0 PTD4/T1CH0 14 15 PTD5/T1CH1 OTE: Ports PTB4, PTB5, PTC0, and PTC1 are available only with the QFP. Figure 1-4. DIP And SOIC Pin Assignments MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 23 General Description 1.5 Pin Functions Descriptions of the pin functions are provided here. 1.5.1 Power Supply Pins (VDD and VSS) VDD and VSS are the power supply and ground pins. The MCU operates from a single power supply. Fast signal transitions on MCU pins place high, short-duration current demands on the power supply. To prevent noise problems, take special care to provide power supply bypassing at the MCU as Figure 1-5 shows. Place the C1 bypass capacitor as close to the MCU as possible. Use a high-frequency-response ceramic capacitor for C1. C2 is an optional bulk current bypass capacitor for use in applications that require the port pins to source high current levels. MCU VSS VDD C1 0.1 μF + C2 VDD NOTE: Component values shown represent typical applications. Figure 1-5. Power Supply Bypassing 1.5.2 Oscillator Pins (OSC1 and OSC2) The OSC1 and OSC2 pins are the connections for the on-chip oscillator circuit. See Chapter 7 Clock Generator Module (CGMC). 1.5.3 External Reset Pin (RST) A logic 0 on the RST pin forces the MCU to a known startup state. RST is bidirectional, allowing a reset of the entire system. It is driven low when any internal reset source is asserted. This pin contains an internal pullup resistor that is always activated, even when the reset pin is pulled low. See Chapter 4 Resets and Interrupts. 1.5.4 External Interrupt Pin (IRQ) IRQ is an asynchronous external interrupt pin. This pin contains an internal pullup resistor that is always activated, even when the reset pin is pulled low. See Chapter 12 External Interrupt (IRQ). 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 7 Clock Generator Module (CGMC). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 24 Freescale Semiconductor Pin Functions 1.5.6 External Filter Capacitor Pin (CGMXFC) CGMXFC is an external filter capacitor connection for the CGM. See Chapter 7 Clock Generator Module (CGMC). 1.5.7 Analog Power Supply/Reference Pins (VDDAD/VREFH and VSSAD/VREFL) VDDAD and VSSAD are the power supply pins for the analog-to-digital converter. Decoupling of these pins should be as per the digital supply. NOTE VREFH is the high reference supply for the ADC. The VREFH signal is internally connected with VDDAD and have the same potential as VDDAD. VDDAD should be tied to the same potential as VDD via separate traces. VREFL is the low reference supply for the ADC. The VREFL pin is internally connected with VSSAD and has the same potential as VSSAD. VSSAD should be tied to the same potential as VSS via separate traces. See Chapter 5 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 16 Input/Output Ports (I/O) and See Chapter 12 External Interrupt (IRQ). 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. When the port pins are configured for special-function mode (KBI), pullups will be automatically engaged. As long as the port pins are in special-function mode, the pullups will always be on. 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 16 Input/Output Ports (I/O) and See Chapter 5 Analog-to-Digital Converter (ADC). There are no pullups associated with this port. 1.5.10 Port C I/O Pins (PTC1–PTC0) PTC1–PTC0 are general-purpose, bidirectional I/O port pins. See Chapter 16 Input/Output Ports (I/O). PTC0 and PTC1 are only available on 32-pin QFP packages. 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 22 Timer Interface Module (TIM), Chapter 20 Serial Peripheral Interface (SPI), and See Chapter 16 Input/Output Ports (I/O). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 25 General Description 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. When the port pins are configured for special-function mode (SPI, TIM1, TIM2), pullups can be selectable on an individual port pin basis. 1.5.12 Port E I/O Pins (PTE1/RxD–PTE0/TxD) PTE1–PTE0 are special-function, bidirectional I/O port pins. These pins can also be programmed to be serial communications interface (SCI) pins. See Chapter 18 Serial Communications Interface (SCI) and See Chapter 16 Input/Output Ports (I/O). 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 MC68HC908GR8 do not require termination, termination is recommended to reduce the possibility of electro-static discharge damage. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 26 Freescale Semiconductor Chapter 2 Memory Map 2.1 Introduction The CPU08 can address 64K bytes of memory space. The memory map, shown in Figure 2-1, includes: • 8K bytes of FLASH memory, 7680 bytes of user space on the MC68HC908GR8 or 4K bytes of FLASH memory, 4096 bytes of user space on the MC68HC908GR4 • 384 bytes of random-access memory (RAM) • 36 bytes of user-defined vectors • 310 bytes of monitor routines in read-only memory (ROM) • 544 bytes of integrated FLASH burn-in routines in ROM 2.2 Unimplemented Memory Locations Accessing an unimplemented location can cause an illegal address reset if illegal address resets are enabled. In the memory map (Figure 2-1) and in register figures in this document, unimplemented locations are shaded. 2.3 Reserved Memory Locations Accessing a reserved location can have unpredictable effects on MCU operation. In the Figure 2-1 and in register figures in this document, reserved locations are marked with the word Reserved or with the letter R. 2.4 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; SIM break status register, SBSR • $FE01; SIM reset status register, SRSR • $FE03; SIM 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 FLASH test control register, FLTCR • $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, and Table 2-1 is a list of vector locations. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 27 Memory Map 2.5 Memory Map $0000 I/O Registers 64 Bytes ↓ $003F $0040 RAM 384 Bytes ↓ $01BF $01C0 Unimplemented 6720 Bytes ↓ $1BFF $1C00 ↓ Reserved for Integrated FLASH Burn-in Routines 544 Bytes $1E1F $1E20 Unimplemented 49,632 Bytes ↓ $DFFF $E000 MC68HC908GR4 Unimplemented 3584 Bytes ↓ $EDFF $EE00 MC68HC908GR8 FLASH Memory 7680 Bytes MC68HC908GR4 FLASH Memory 4096 Bytes ↓ $FDFF $FE00 SIM Break Status Register (SBSR) $FE01 SIM Reset Status Register (SRSR) $FE02 Reserved $FE03 SIM 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 for FLASH Test Control Register (FLTCR) $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) Continued on next page Figure 2-1. Memory Map MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 28 Freescale Semiconductor Register Summary $FE0D Reserved 3 Bytes ↓ $FE0F Unimplemented 16 Bytes Reserved for Compatibility with Monitor Code for A-Family Parts $FE10 ↓ $FE1F $FE20 Monitor ROM 310 Bytes ↓ $FF55 $FF56 Unimplemented 40 Bytes ↓ $FF7D $FF7E FLASH Block Protect Register (FLBPR) $FF7F Unimplemented 93 Bytes ↓ $FFDB Note: $FFF6–$FFFD contains 8 security bytes $FFDC FLASH Vectors (36 Bytes including $FFFF) ↓ $FFFE Low byte of reset vector when read COP Control Register (COPCTL) $FFFF Figure 2-1. Memory Map (Continued) 2.6 Register Summary Addr. $0000 $0001 $0002 $0003 Register Name Bit 7 6 5 4 Read: Port A Data Register Write: (PTA) Reset: 0 0 0 0 Read: Port B Data Register Write: (PTB) Reset: 0 0 Read: 0 0 2 1 Bit 0 PTA3 PTA2 PTA1 PTA0 PTB2 PTB1 PTB0 PTC1 PTC0 PTD1 PTD0 Unaffected by reset PTB5 PTB4 PTB3 Unaffected by reset 0 Port C Data Register Write: (PTC) Reset: Read: Port D Data Register Write: (PTD) Reset: 3 0 0 0 Unaffected by reset 0 PTD6 PTD5 PTD4 PTD3 PTD2 Unaffected by reset = Unimplemented R = Reserved U = Unaffected Figure 2-2. Control, Status, and Data Registers (Sheet 1 of 7) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 29 Memory Map Addr. $0004 $0005 $0006 $0007 $0008 Register Name Bit 7 6 5 4 Read: 0 0 0 0 3 2 1 Bit 0 Data Direction Register A Write: (DDRA) Reset: DDRA3 DDRA2 DDRA1 DDRA0 0 0 0 0 0 0 0 0 Read: Data Direction Register B Write: (DDRB) Reset: 0 0 DDRB5 DDRB4 DDRB3 DDRB2 DDRB1 DDRB0 0 0 0 0 0 0 0 0 Read: Data Direction Register C Write: (DDRC) Reset: 0 0 0 0 0 0 DDRC1 DDRC0 0 0 0 0 0 0 0 0 Read: Data Direction Register D Write: (DDRD) Reset: 0 DDRD6 DDRD5 DDRD4 DDRD3 DDRD2 DDRD1 DDRD0 Read: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 PTE1 PTE0 0 0 DDRE1 DDRE0 Port E Data Register Write: (PTE) Reset: Unaffected by reset Read: $0009 ↓ $000B Unimplemented Write: Reset: 0 0 0 0 0 0 0 0 0 0 0 0 $000C Read: Data Direction Register E Write: (DDRE) Reset: 0 0 0 0 0 0 0 0 Read: Port A Input Pullup Enable Write: Register (PTAPUE) Reset: 0 0 0 0 PTAPUE3 PTAPUE2 PTAPUE1 PTAPUE0 0 0 0 0 0 0 0 0 Read: 0 0 0 0 0 0 Port C Input Pullup Enable Write: Register (PTCPUE) Reset: PTCPUE1 PTCPUE0 0 0 0 0 0 0 0 0 PTDPUE6 PTDPUE5 PTDPUE4 PTDPUE3 PTDPUE2 PTDPUE1 PTDPUE0 0 0 0 0 0 0 0 0 SPRIE R SPMSTR CPOL CPHA SPWOM SPE SPTIE 0 0 1 0 1 0 0 0 OVRF MODF SPTE MODFEN SPR1 SPR0 0 1 0 0 0 $000D $000E $000F $0010 $0011 Read: Port D Input Pullup Enable Write: Register (PTDPUE) Reset: Read: SPI Control Register Write: (SPCR) Reset: Read: SPI Status and Control Write: Register (SPSCR) Reset: 0 SPRF 0 ERRIE 0 = Unimplemented 0 R = Reserved U = Unaffected Figure 2-2. Control, Status, and Data Registers (Sheet 2 of 7) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 30 Freescale Semiconductor Register Summary Addr. Register Name Read: $0012 $0013 $0014 $0015 SPI Data Register Write: (SPDR) Reset: Read: SCI Control Register 1 Write: (SCC1) Reset: Read: SCI Control Register 2 Write: (SCC2) Reset: Read: SCI Control Register 3 Write: (SCC3) Reset: Bit 7 6 5 4 3 2 1 Bit 0 R7 R6 R5 R4 R3 R2 R1 R0 T7 T6 T5 T4 T3 T2 T1 T0 Unaffected by reset LOOPS ENSCI TXINV M WAKE ILTY PEN PTY 0 0 0 0 0 0 0 0 SCTIE TCIE SCRIE ILIE TE RE RWU SBK 0 0 0 0 0 0 0 0 T8 R R ORIE NEIE FEIE PEIE R8 U U 0 0 0 0 0 0 SCTE TC SCRF IDLE OR NF FE PE 1 1 0 0 0 0 0 0 Read: SCI Status Register 2 Write: (SCS2) Reset: 0 0 0 0 0 0 BKF RPF 0 0 0 0 0 0 0 0 Read: SCI Data Register Write: (SCDR) Reset: R7 R6 R5 R4 R3 R2 R1 R0 T7 T6 T5 T4 T3 T2 T1 T0 0 0 $0019 Read: SCI Baud Rate Register Write: (SCBR) Reset: R SCR2 SCR1 SCR0 0 0 0 0 $001A Keyboard Status Read: and Control Register Write: (INTKBSCR) Reset: IMASKK MODEK 0 0 0 0 Read: Keyboard Interrupt Enable Write: Register (INTKBIER) Reset: 0 0 0 0 Read: Time Base Module Control Write: Register (TBCR) Reset: TBIF Read: $0016 $0017 $0018 $001B $001C $001D SCI Status Register 1 Write: (SCS1) Reset: Read: IRQ Status and Control Write: Register (INTSCR) Reset: Unaffected by reset SCP1 SCP0 0 0 0 0 0 0 0 0 KEYF 0 ACKK 0 0 0 0 KBIE3 KBIE2 KBIE1 KBIE0 0 0 0 0 TBIE TBON R 0 0 IMASK1 MODE1 0 0 0 TBR2 TBR1 TBR0 0 0 0 0 0 0 0 0 0 0 IRQF1 0 TACK ACK1 0 0 = Unimplemented 0 0 0 R = Reserved 0 U = Unaffected Figure 2-2. Control, Status, and Data Registers (Sheet 3 of 7) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 31 Memory Map Addr. $001E $001F $0020 $0021 $0022 $0023 $0024 $0025 Register Name Bit 7 6 5 4 3 2 Configuration Register 2 Read: (CONFIG2)† Write: 0 0 0 0 0 0 Reset: 0 0 0 0 0 0 0 0 COPRS LVISTOP LVIRSTD LVIPWRD LVI5OR3† SSREC STOP COPD 0 0 0 0 0 0 0 0 TOIE TSTOP 0 0 PS2 PS1 PS0 Read: Configuration Register 1 Write: (CONFIG1)† Reset: $0027 Bit 0 OSCSCIBDSRC STOPENB Read: Timer 1 Status and Control Write: Register (T1SC) Reset: TOF 0 0 1 0 0 0 0 0 Read: Timer 1 Counter Register Write: High (T1CNTH) Reset: Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Read: Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 1 1 1 1 1 1 1 1 Bit 7 6 5 4 3 2 1 Bit 0 1 1 1 1 1 1 1 1 CH0IE MS0B MS0A ELS0B ELS0A TOV0 CH0MAX 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 2 1 Bit 0 Timer 1 Counter Register Write: Low (T1CNTL) Reset: Read: Timer 1 Counter Modulo Write: Register High (T1MODH) Reset: Read: Timer 1 Counter Modulo Write: Register Low (T1MODL) Reset: Timer 1 Channel 0 Status Read: and Control Register Write: (T1SC0) Reset: Read: $0026 1 Timer 1 Channel 0 Write: Register High (T1CH0H) Reset: Read: Timer 1 Channel 0 Write: Register Low (T1CH0L) Reset: 0 CH0F 0 TRST Indeterminate after reset Bit 7 6 5 4 3 Indeterminate after reset † One-time writeable register after each reset, except LVI5OR3 bit. LVI5OR3 bit is only reset via POR (power-on reset). $0028 $0029 Read: Timer 1 Channel 1 Status and Write: Control Register (T1SC1) Reset: Read: Timer 1 Channel 1 Write: Register High (T1CH1H) Reset: CH1F 0 0 CH1IE MS1A ELS1B ELS1A TOV1 CH1MAX 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 Indeterminate after reset = Unimplemented R = Reserved U = Unaffected Figure 2-2. Control, Status, and Data Registers (Sheet 4 of 7) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 32 Freescale Semiconductor Register Summary Addr. Register Name Bit 7 6 5 4 3 2 1 Bit 0 Timer 1 Channel 1 Write: Register Low (T1CH1L) Reset: Bit 7 6 5 4 3 2 1 Bit 0 Read: Timer 2 Status and Control Write: Register (T2SC) Reset: TOF PS2 PS1 PS0 Read: $002A $002B $002C $002D $002F $0030 $0031 $0033 ↓ $0035 $0036 $0037 0 TSTOP 0 0 1 0 0 0 0 0 Read: Timer 2 Counter Register Write: High (T2CNTH) Reset: Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Read: Timer 2 Counter Register Write: Low (T2CNTL) Reset: Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 1 1 1 1 1 1 1 1 Bit 7 6 5 4 3 2 1 Bit 0 1 1 1 1 1 1 1 1 CH0IE MS0B MS0A ELS0B ELS0A TOV0 CH0MAX 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 2 1 Bit 0 Timer 2 Counter Modulo Write: Register High (T2MODH) Reset: Read: Timer 2 Counter Modulo Write: Register Low (T2MODL) Reset: Timer 2 Channel 0 Status Read: and Control Register Write: (T2SC0) Reset: Read: Timer 2 Channel 0 Write: Register High (T2CH0H) Reset: Read: $0032 0 TOIE Read: $002E Indeterminate after reset Timer 2 Channel 0 Write: Register Low (T2CH0L) Reset: Unimplemented 0 CH0F 0 TRST Indeterminate after reset Bit 7 6 5 4 3 Indeterminate after reset Read: Write: Reset: Read: PLL Control Register Write: (PCTL) Reset: Read: PLL Bandwidth Control Write: Register (PBWC) Reset: 0 PLLIE 0 AUTO 0 0 PLLF 0 0 0 0 0 0 PLLON BCS PRE1 PRE0 VPR1 VPR0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 LOCK ACQ 0 = Unimplemented 0 R = Reserved R 0 U = Unaffected Figure 2-2. Control, Status, and Data Registers (Sheet 5 of 7) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 33 Memory Map Addr. $0038 $0039 $003A Register Name Bit 7 6 5 4 Read: 0 0 0 0 PLL Multiplier Select High Write: Register (PMSH) Reset: 0 0 0 MUL7 MUL6 0 Read: PLL Multiplier Select Low Write: Register (PMSL) Reset: Read: PLL VCO Select Range Write: Register (PMRS) Reset: $003B Read: PLL Reference Divider Write: Select Register (PMDS) Reset: $003C Analog-to-Digital Status and Read: Control Register Write: (ADSCR) Reset: $003D $003E Read: Analog-to-Digital Data Write: Register (ADR) Reset: Read: Analog-to-Digital Input Clock Write: Register (ADCLK) Reset: 3 2 1 Bit 0 MUL11 MUL10 MUL9 MUL8 0 0 0 0 0 MUL5 MUL4 MUL3 MUL2 MUL1 MUL0 1 0 0 0 0 0 0 VRS7 VRS6 VRS5 VRS4 VRS3 VRS2 VRS1 VRS0 0 1 0 0 0 0 0 0 0 0 0 0 RDS3 RDS2 RDS1 RDS0 0 0 0 0 0 0 0 1 AIEN ADCO ADCH4 ADCH3 ADCH2 ADCH1 ADCH0 0 0 0 1 1 1 1 1 AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0 0 0 0 0 COCO R Indeterminate after reset ADIV2 ADIV1 ADIV0 ADICLK R R R R 0 0 0 0 0 0 0 0 R R R R R R 0 0 0 0 0 0 0 0 POR PIN COP ILOP ILAD MODRST LVI 0 1 0 0 0 0 0 0 0 BCFE R R R R R R R Read: $003F Unimplemented Write: Reset: $FE00 Read: SIM Break Status Register Write: (SBSR) Reset: BW NOTE R Note: Writing a logic 0 clears SBSW. $FE01 Read: SIM Reset Status Register Write: (SRSR) POR: Read: $FE02 Unimplemented Write: Reset: $FE03 Read: SIM Break Flag Control Write: Register (SBFCR) Reset: 0 = Unimplemented R = Reserved U = Unaffected Figure 2-2. Control, Status, and Data Registers (Sheet 6 of 7) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 34 Freescale Semiconductor Register Summary Addr. Register Name Bit 7 6 5 4 3 2 1 Bit 0 IF6 IF5 IF4 IF3 IF2 IF1 0 0 R R R R R R R R 0 0 0 0 0 0 0 0 Read: Interrupt Status Register 2 Write: (INT2) Reset: IF14 IF13 IF12 IF11 IF10 IF9 IF8 IF7 R R R R R R R R 0 0 0 0 0 0 0 0 Read: Interrupt Status Register 3 Write: (INT3) Reset: 0 0 0 0 0 0 IF16 IF15 R R R R R R R R 0 0 0 0 0 0 0 0 R R R R R R R R 0 0 0 0 HVEN MASS ERASE PGM Read: $FE04 $FE05 $FE06 $FE07 $FE08 $FE09 Interrupt Status Register 1 Write: (INT1) Reset: Read: FLASH Test Control Write: Register (FLTCR) Reset: 0 0 0 0 Read: 0 0 0 0 FLASH Control Register Write: (FLCR) Reset: 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 BRKE BRKA 0 0 0 0 0 0 Read: Break Address Register High Write: (BRKH) Reset: Read: Break Address Register Low $FE0A Write: (BRKL) Reset: $FE0B Read: Break Status and Control Write: Register (BRKSCR) Reset: Read: $FE0C $FFFF 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 BPR7 BPR6 BPR5 BPR4 BPR3 BPR2 BPR1 BPR0 U U U U U U U U LVI Status Register (LVISR) Write: Reset: $FF7E 0 LVIOUT Read: FLASH Block Protect Write: Register (FLBPR)† Reset: Read: COP Control Register Write: (COPCTL) Reset: Low byte of reset vector Writing clears COP counter (any value) Unaffected by reset † Non-volatile FLASH register = Unimplemented R = Reserved U = Unaffected Figure 2-2. Control, Status, and Data Registers (Sheet 7 of 7) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 35 Memory Map 2.7 Vector Addresses . Table 2-1. Vector Addresses Vector Priority Lowest Vector IF16 IF15 IF14 IF13 IF12 IF11 IF10 IF9 IF8 IF7 IF6 IF5 IF4 IF3 IF2 IF1 — Highest — Address Vector $FFDC Timebase Vector (High) $FFDD Timebase Vector (Low) $FFDE ADC Conversion Complete Vector (High) $FFDF ADC Conversion Complete Vector (Low) $FFE0 Keyboard Vector (High) $FFE1 Keyboard Vector (Low) $FFE2 SCI Transmit Vector (High) $FFE3 SCI Transmit Vector (Low) $FFE4 SCI Receive Vector (High) $FFE5 SCI Receive Vector (Low) $FFE6 SCI Error Vector (High) $FFE7 SCI Error Vector (Low) $FFE8 SPI Transmit Vector (High) $FFE9 SPI Transmit Vector (Low) $FFEA SPI Receive Vector (High) $FFEB SPI Receive Vector (Low) $FFEC TIM2 Overflow Vector (High) $FFED TIM2 Overflow Vector (Low) $FFEE Reserved $FFEF Reserved $FFF0 TIM2 Channel 0 Vector (High) $FFF1 TIM2 Channel 0 Vector (Low) $FFF2 TIM1 Overflow Vector (High) $FFF3 TIM1 Overflow Vector (Low) $FFF4 TIM1 Channel 1 Vector (High) $FFF5 TIM1 Channel 1 Vector (Low) $FFF6 TIM1 Channel 0 Vector (High) $FFF7 TIM1 Channel 0 Vector (Low) $FFF8 PLL Vector (High) $FFF9 PLL Vector (Low) $FFFA IRQ Vector (High) $FFFB IRQ Vector (Low) $FFFC SWI Vector (High) $FFFD SWI Vector (Low) $FFFE Reset Vector (High) $FFFF Reset Vector (Low) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 36 Freescale Semiconductor Chapter 3 Low-Power Modes 3.1 Introduction The 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. 3.1.1 Wait Mode The WAIT instruction puts the MCU in a low-power standby mode in which the CPU clock is disabled but the bus clock continues to run. Power consumption can be further reduced by disabling the LVI module and/or the timebase module through bits in the CONFIG register. (See Chapter 8 Configuration Register (CONFIG).) 3.1.2 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 CONFIG register is at a logic 0. (See Chapter 8 Configuration Register (CONFIG).) 3.2 Analog-to-Digital Converter (ADC) 3.2.1 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. 3.2.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 37 Low-Power Modes 3.3 Break Module (BRK) 3.3.1 Wait Mode If enabled, the break module is active in wait mode. In the break routine, the user can subtract one from the return address on the stack if the BW bit in the break status register is set. 3.3.2 Stop Mode The break module is inactive in stop mode. The STOP instruction does not affect break module register states. 3.4 Central Processor Unit (CPU) 3.4.1 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 3.4.2 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. 3.5 Clock Generator Module (CGM) 3.5.1 Wait Mode The 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. 3.5.2 Stop Mode If the OSCSTOPEN 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 OSCSTOPEN 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 38 Freescale Semiconductor Computer Operating Properly Module (COP) 3.6 Computer Operating Properly Module (COP) 3.6.1 Wait Mode The COP remains active in wait mode. To prevent a COP reset during wait mode, periodically clear the COP counter in a CPU interrupt routine. 3.6.2 Stop Mode Stop mode turns off the COPCLK input to the COP and clears the SIM counter. Service the COP immediately before entering or after exiting stop mode to ensure a full COP timeout period after entering or exiting stop mode. The STOP bit in the configuration register (CONFIG) enables the STOP instruction. To prevent inadvertently turning off the COP with a STOP instruction, disable the STOP instruction by clearing the STOP bit. 3.7 External Interrupt Module (IRQ) 3.7.1 Wait Mode The 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. 3.7.2 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. 3.8 Keyboard Interrupt Module (KBI) 3.8.1 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. 3.8.2 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. 3.9 Low-Voltage Inhibit Module (LVI) 3.9.1 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 39 Low-Power Modes 3.9.2 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. 3.10 Serial Communications Interface Module (SCI) 3.10.1 Wait Mode The 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. 3.10.2 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. 3.11 Serial Peripheral Interface Module (SPI) 3.11.1 Wait Mode The 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. 3.11.2 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. 3.12 Timer Interface Module (TIM1 and TIM2) 3.12.1 Wait Mode The TIM remains 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 40 Freescale Semiconductor Timebase Module (TBM) 3.12.2 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. 3.13 Timebase Module (TBM) 3.13.1 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 enabling the WAIT instruction. 3.13.2 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 OSCSTOPEN bit in the CONFIG 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. 3.14 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 – $FFDE and $FFDF; keyboard interrupt pins • Low-voltage inhibit (LVI) reset — A power supply voltage below the LVItripf voltage resets the MCU and loads the program counter with the contents of locations $FFFE and $FFFF. • Break interrupt — A break interrupt loads the program counter with the contents of locations $FFFC and $FFFD. • 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 41 Low-Power Modes The short stop recovery bit, SSREC, in the configuration 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 42 Freescale Semiconductor Chapter 4 Resets and Interrupts 4.1 Introduction Resets and interrupts are responses to exceptional events during program execution. A reset re-initializes the MCU to its startup condition. An interrupt vectors the program counter to a service routine. 4.2 Resets A reset immediately returns the MCU to a known startup condition and begins program execution from a user-defined memory location. 4.2.1 Effects A reset: • Immediately stops the operation of the instruction being executed • Initializes certain control and status bits • Loads the program counter with a user-defined reset vector address from locations $FFFE and $FFFF, $FEFE and $FFFF in monitor mode • Selects CGMXCLK divided by four as the bus clock 4.2.2 External Reset A logic 0 applied to the RST pin for a time, tIRL, generates an external reset. An external reset sets the PIN bit in the SIM reset status register. 4.2.3 Internal Reset Sources: • Power-on reset (POR) • Computer operating properly (COP) • Low-power reset circuits • Illegal opcode • Illegal address All internal reset sources pull the RST pin low for 32 CGMXCLK cycles to allow resetting of external devices. The MCU is held in reset for an additional 32 CGMXCLK cycles after releasing the RST pin. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 43 Resets and Interrupts 4.2.3.1 Power-On Reset A power-on reset is an internal reset caused by a positive transition on the VDD pin. VDD at the POR must go completely to 0 V to reset the MCU. This distinguishes between a reset and a POR. The POR is not a brown-out detector, low-voltage detector, or glitch detector. A power-on reset: • Holds the clocks to the CPU and modules inactive for an oscillator stabilization delay of 4096 CGMXCLK cycles • Drives the RST pin low during the oscillator stabilization delay • Releases the RST pin 32 CGMXCLK cycles after the oscillator stabilization delay • Releases the CPU to begin the reset vector sequence 64 CGMXCLK cycles after the oscillator stabilization delay • Sets the POR bit in the SIM reset status register and clears all other bits in the register OSC1 PORRST(1) 4096 CYCLES 32 CYCLES 32 CYCLES CGMXCLK CGMOUT RST PIN INTERNAL RESET 1. PORRST is an internally generated power-on reset pulse. Figure 4-1. Power-On Reset Recovery 4.2.3.2 COP Reset A COP reset is an internal reset caused by an overflow of the COP counter. A COP reset sets the COP bit in the system integration module (SIM) reset status register. To clear the COP counter and prevent a COP reset, write any value to the COP control register at location $FFFF. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 44 Freescale Semiconductor Resets 4.2.3.3 Low-Voltage Inhibit Reset A low-voltage inhibit (LVI) reset is an internal reset caused by a drop in the power supply voltage to the LVI trip voltage, VTRIPF. An LVI reset: • Holds the clocks to the CPU and modules inactive for an oscillator stabilization delay of 4096 CGMXCLK cycles after the power supply voltage rises to VTRIPF • Drives the RST pin low for as long as VDD is below VTRIPF and during the oscillator stabilization delay • Releases the RST pin 32 CGMXCLK cycles after the oscillator stabilization delay • Releases the CPU to begin the reset vector sequence 64 CGMXCLK cycles after the oscillator stabilization delay • Sets the LVI bit in the SIM reset status register 4.2.3.4 Illegal Opcode Reset An illegal opcode reset is an internal reset caused by an opcode that is not in the instruction set. An illegal opcode reset sets the ILOP bit in the SIM reset status register. If the stop enable bit, STOP, in the mask option register is a logic 0, the STOP instruction causes an illegal opcode reset. 4.2.3.5 Illegal Address Reset An illegal address reset is an internal reset caused by opcode fetch from an unmapped address. An illegal address reset sets the ILAD bit in the SIM reset status register. A data fetch from an unmapped address does not generate a reset. 4.2.4 SIM Reset Status Register This read-only register contains flags to show reset sources. All flag bits are automatically cleared following a read of the register. Reset service can read the SIM reset status register to clear the register after power-on reset and to determine the source of any subsequent reset. The register is initialized on powerup as shown with the POR bit set and all other bits cleared. During a POR or any other internal reset, the RST pin is pulled low. After the pin is released, it will be sampled 32 XCLK cycles later. If the pin is not above a VIH at that time, then the PIN bit in the SRSR may be set in addition to whatever other bits are set. NOTE Only a read of the SIM reset status register clears all reset flags. After multiple resets from different sources without reading the register, multiple flags remain set. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 45 Resets and Interrupts Address: Read: $FE01 Bit 7 6 5 4 3 2 1 Bit 0 POR PIN COP ILOP ILAD MODRST LVI 0 0 0 0 0 0 0 0 Write: POR: 1 = Unimplemented Figure 4-2. SIM Reset Status Register (SRSR) POR — Power-On Reset Flag 1 = Power-on reset since last read of SRSR 0 = Read of SRSR since last power-on reset PIN — External Reset Flag 1 = External reset via RST pin since last read of SRSR 0 = POR or read of SRSR since last external reset COP — Computer Operating Properly Reset Bit 1 = Last reset caused by timeout of 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 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 low-power supply voltage 0 = POR or read of SRSR 4.3 Interrupts An interrupt temporarily changes the sequence of program execution to respond to a particular event. An interrupt does not stop the operation of the instruction being executed, but begins when the current instruction completes its operation. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 46 Freescale Semiconductor Interrupts 4.3.1 Effects An interrupt: • Saves the CPU registers on the stack. At the end of the interrupt, the RTI instruction recovers the CPU registers from the stack so that normal processing can resume. • Sets the interrupt mask (I bit) to prevent additional interrupts. Once an interrupt is latched, no other interrupt can take precedence, regardless of its priority. • Loads the program counter with a user-defined vector address • • • 5 CONDITION CODE REGISTER 1 4 ACCUMULATOR 2 INDEX REGISTER (LOW BYTE)* STACKING 3 ORDER 2 PROGRAM COUNTER (HIGH BYTE) 3 UNSTACKING ORDER 4 1 PROGRAM COUNTER (LOW BYTE) 5 • • • $00FF DEFAULT ADDRESS ON RESET *High byte of index register is not stacked. Figure 4-3. Interrupt Stacking Order MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 47 Resets and Interrupts After every instruction, the CPU checks all pending interrupts if the I bit is not set. If more than one interrupt is pending when an instruction is done, the highest priority interrupt is serviced first. In the example shown in Figure 4-4, if an interrupt is pending upon exit from the interrupt service routine, the pending interrupt is serviced before the LDA instruction is executed. CLI BACKGROUND ROUTINE LDA #$FF INT1 PSHH INT1 INTERRUPT SERVICE ROUTINE PULH RTI INT2 PSHH INT2 INTERRUPT SERVICE ROUTINE PULH RTI Figure 4-4. Interrupt Recognition Example The LDA opcode is prefetched by both the INT1 and INT2 RTI instructions. However, in the case of the INT1 RTI prefetch, this is a redundant operation. NOTE To maintain compatibility with the M6805 Family, the H register is not pushed on the stack during interrupt entry. If the interrupt service routine modifies the H register or uses the indexed addressing mode, save the H register and then restore it prior to exiting the routine. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 48 Freescale Semiconductor Interrupts 4.3.2 Sources The sources in Table 4-1 can generate CPU interrupt requests. Table 4-1. Interrupt Sources Flag Mask(1) INT Register Flag Priority(2) Vector Address Reset None None None 0 $FFFE–$FFFF SWI instruction None None None 0 $FFFC–$FFFD IRQ pin IRQF IMASK1 IF1 1 $FFFA–$FFFB CGM (PLL) PLLF PLLIE IF2 2 $FFF8–$FFF9 TIM1 channel 0 CH0F CH0IE IF3 3 $FFF6–$FFF7 TIM1 channel 1 CH1F CH1IE IF4 4 $FFF4–$FFF5 TOF TOIE IF5 5 $FFF2–$FFF3 CH0F CH0IE IF6 6 $FFF0–$FFF1 TOF TOIE IF8 8 $FFEC–$FFED SPI receiver full SPRF SPRIE SPI overflow OVRF ERRIE IF9 9 $FFEA–$FFEB SPI mode fault MODF ERRIE SPI transmitter empty SPTE SPTIE IF10 10 $FFE8–$FFE9 SCI receiver overrun OR ORIE SCI noise fag NF NEIE IF11 11 $FFE6–$FFE7 SCI framing error FE FEIE SCI parity error PE PEIE SCI receiver full SCRF SCRIE IF12 12 $FFE4–$FFE5 SCI input idle IDLE ILIE SCI transmitter empty SCTE SCTIE IF13 13 $FFE2–$FFE3 TC TCIE Keyboard pin KEYF IMASKK IF14 14 $FFDE–$FFDF ADC conversion complete COCO AIEN IF15 15 $FFDE–$FFDF TBIF TBIE IF16 16 $FFDC–$FFDD Source TIM1 overflow TIM2 channel 0 TIM2 overflow SCI transmission complete Timebase 1. The I bit in the condition code register is a global mask for all interrupt sources except the SWI instruction. 2. 0 = highest priority MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 49 Resets and Interrupts 4.3.2.1 SWI Instruction The software interrupt instruction (SWI) causes a non-maskable interrupt. NOTE A software interrupt pushes PC onto the stack. An SWI does not push PC – 1, as a hardware interrupt does. FROM RESET BREAK INTERRUPT ? NO YES YES BIT SET? SET? II BIT NO IRQ INTERRUPT ? NO YES CGM INTERRUPT ? NO YES OTHER INTERRUPTS ? YES NO STACK CPU REGISTERS SET I BIT LOAD PC WITH INTERRUPT VECTOR FETCH NEXT INSTRUCTION SWI YES INSTRUCTION ? NO RTI YES INSTRUCTION ? UNSTACK CPU REGISTERS NO EXECUTE INSTRUCTION Figure 4-5. Interrupt Processing MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 50 Freescale Semiconductor Interrupts 4.3.2.2 Break Interrupt The break module causes the CPU to execute an SWI instruction at a software-programmable break point. 4.3.2.3 IRQ Pin A logic 0 on the IRQ1 pin latches an external interrupt request. 4.3.2.4 CGM (Clock Generator Module) The CGM can generate a CPU interrupt request every time the phase-locked loop circuit (PLL) enters or leaves the locked state. When the LOCK bit changes state, the PLL flag (PLLF) is set. The PLL interrupt enable bit (PLLIE) enables PLLF CPU interrupt requests. LOCK is in the PLL bandwidth control register. PLLF is in the PLL control register. 4.3.2.5 TIM1 (Timer Interface Module 1) TIM1 CPU interrupt sources: • TIM1 overflow flag (TOF) — The TOF bit is set when the TIM1 counter value rolls over to $0000 after matching the value in the TIM1 counter modulo registers. The TIM1 overflow interrupt enable bit, TOIE, enables TIM1 overflow CPU interrupt requests. TOF and TOIE are in the TIM1 status and control register. • TIM1 channel flags (CH1F–CH0F) — The CHxF bit is set when an input capture or output compare occurs on channel x. The channel x interrupt enable bit, CHxIE, enables channel x TIM1 CPU interrupt requests. CHxF and CHxIE are in the TIM1 channel x status and control register. 4.3.2.6 TIM2 (Timer Interface Module 2) TIM2 CPU interrupt sources: • TIM2 overflow flag (TOF) — The TOF bit is set when the TIM2 counter value rolls over to $0000 after matching the value in the TIM2 counter modulo registers. The TIM2 overflow interrupt enable bit, TOIE, enables TIM2 overflow CPU interrupt requests. TOF and TOIE are in the TIM2 status and control register. • TIM2 channel flag (CH0F) — The CH0F bit is set when an input capture or output compare occurs on channel 0. The channel 0 interrupt enable bit, CH0IE, enables channel 0 TIM2 CPU interrupt requests. CH0F and CH0IE are in the TIM2 channel 0 status and control register. 4.3.2.7 SPI (Serial Peripheral Interface) SPI CPU interrupt sources: • SPI receiver full bit (SPRF) — The SPRF bit is set every time a byte transfers from the shift register to the receive data register. The SPI receiver interrupt enable bit, SPRIE, enables SPRF CPU interrupt requests. SPRF is in the SPI status and control register and SPRIE is in the SPI control register. • SPI transmitter empty (SPTE) — The SPTE bit is set every time a byte transfers from the transmit data register to the shift register. The SPI transmit interrupt enable bit, SPTIE, enables SPTE CPU interrupt requests. SPTE is in the SPI status and control register and SPTIE is in the SPI control register. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 51 Resets and Interrupts • • Mode fault bit (MODF) — The MODF bit is set in a slave SPI if the SS pin goes high during a transmission with the mode fault enable bit (MODFEN) set. In a master SPI, the MODF bit is set if the SS pin goes low at any time with the MODFEN bit set. The error interrupt enable bit, ERRIE, enables MODF CPU interrupt requests. MODF, MODFEN, and ERRIE are in the SPI status and control register. Overflow bit (OVRF) — The OVRF bit is set if software does not read the byte in the receive data register before the next full byte enters the shift register. The error interrupt enable bit, ERRIE, enables OVRF CPU interrupt requests. OVRF and ERRIE are in the SPI status and control register. 4.3.2.8 SCI (Serial Communications Interface) SCI CPU interrupt sources: • SCI transmitter empty bit (SCTE) — SCTE is set when the SCI data register transfers a character to the transmit shift register. The SCI transmit interrupt enable bit, SCTIE, enables transmitter CPU interrupt requests. SCTE is in SCI status register 1. SCTIE is in SCI control register 2. • Transmission complete bit (TC) — TC is set when the transmit shift register and the SCI data register are empty and no break or idle character has been generated. The transmission complete interrupt enable bit, TCIE, enables transmitter CPU interrupt requests. TC is in SCI status register 1. TCIE is in SCI control register 2. • SCI receiver full bit (SCRF) — SCRF is set when the receive shift register transfers a character to the SCI data register. The SCI receive interrupt enable bit, SCRIE, enables receiver CPU interrupts. SCRF is in SCI status register 1. SCRIE is in SCI control register 2. • Idle input bit (IDLE) — IDLE is set when 10 or 11 consecutive logic 1s shift in from the RxD pin. The idle line interrupt enable bit, ILIE, enables IDLE CPU interrupt requests. IDLE is in SCI status register 1. ILIE is in SCI control register 2. • Receiver overrun bit (OR) — OR is set when the receive shift register shifts in a new character before the previous character was read from the SCI data register. The overrun interrupt enable bit, ORIE, enables OR to generate SCI error CPU interrupt requests. OR is in SCI status register 1. ORIE is in SCI control register 3. • Noise flag (NF) — NF is set when the SCI detects noise on incoming data or break characters, including start, data, and stop bits. The noise error interrupt enable bit, NEIE, enables NF to generate SCI error CPU interrupt requests. NF is in SCI status register 1. NEIE is in SCI control register 3. • Framing error bit (FE) — FE is set when a logic 0 occurs where the receiver expects a stop bit. The framing error interrupt enable bit, FEIE, enables FE to generate SCI error CPU interrupt requests. FE is in SCI status register 1. FEIE is in SCI control register 3. • Parity error bit (PE) — PE is set when the SCI detects a parity error in incoming data. The parity error interrupt enable bit, PEIE, enables PE to generate SCI error CPU interrupt requests. PE is in SCI status register 1. PEIE is in SCI control register 3. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 52 Freescale Semiconductor Interrupts 4.3.2.9 KBD0–KBD4 Pins A 0 on a keyboard interrupt pin latches an external interrupt request. 4.3.2.10 ADC (Analog-to-Digital Converter) When the AIEN bit is set, the ADC module is capable of generating a CPU interrupt after each ADC conversion. The COCO/IDMAS bit is not used as a conversion complete flag when interrupts are enabled. 4.3.2.11 TBM (Timebase Module) The timebase module can interrupt the CPU on a regular basis with a rate defined by TBR2–TBR0. When the timebase counter chain rolls over, the TBIF flag is set. If the TBIE bit is set, enabling the timebase interrupt, the counter chain overflow will generate a CPU interrupt request. Interrupts must be acknowledged by writing a logic 1 to the TACK bit. 4.3.3 Interrupt Status Registers The flags in the interrupt status registers identify maskable interrupt sources. Table 4-2 summarizes the interrupt sources and the interrupt status register flags that they set. The interrupt status registers can be useful for debugging. Table 4-2. Interrupt Source Flags Interrupt Source Reset Interrupt Status Register Flag — SWI instruction — IRQ pin IF1 CGM (PLL) IF2 TIM1 channel 0 IF3 TIM1 channel 1 IF4 TIM1 overflow IF5 TIM2 channel 0 IF6 Reserved IF7 TIM2 overflow IF8 SPI receive IF9 SPI transmit IF10 SCI error IF11 SCI receive IF12 SCI transmit IF13 Keyboard IF14 ADC conversion complete IF15 Timebase IF16 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 53 Resets and Interrupts 4.3.3.1 Interrupt Status Register 1 Address: $FE04 Bit 7 6 5 4 3 2 1 Bit 0 Read: IF6 IF5 IF4 IF3 IF2 IF1 0 0 Write: R R R R R R R R Reset: 0 0 0 0 0 0 0 0 R = Reserved Figure 4-6. Interrupt Status Register 1 (INT1) IF6–IF1 — Interrupt Flags 6–1 These flags indicate the presence of interrupt requests from the sources shown in Table 4-2. 1 = Interrupt request present 0 = No interrupt request present Bit 1 and Bit 0 — Always read 0 4.3.3.2 Interrupt Status Register 2 Address: $FE05 Bit 7 6 5 4 3 2 1 Read: IF14 IF13 IF12 IF11 IF10 IF9 IF8 0 Write: R R R R R R R R 0 0 0 0 0 0 0 0 Reset: Bit 0 R = Reserved Figure 4-7. Interrupt Status Register 2 (INT2) IF14–IF8 — Interrupt Flags 14–7 These flags indicate the presence of interrupt requests from the sources shown in Table 4-2. 1 = Interrupt request present 0 = No interrupt request present Bit 0 — Always reads 0 4.3.3.3 Interrupt Status Register 3 Address: $FE06 Bit 7 6 5 4 3 2 1 Bit 0 Read: 0 0 0 0 0 0 IF16 IF15 Write: R R R R R R R R Reset: 0 0 0 0 0 0 0 0 R = Reserved Figure 4-8. Interrupt Status Register 3 (INT3) IF16–IF15 — Interrupt Flags 16–15 This flag indicates the presence of an interrupt request from the source shown in Table 4-2. 1 = Interrupt request present 0 = No interrupt request present Bits 7–2 — Always read 0 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 54 Freescale Semiconductor Chapter 5 Analog-to-Digital Converter (ADC) 5.1 Introduction This section describes the 8-bit analog-to-digital converter (ADC). For further information regarding analog-to-digital converters on Freescale microcontrollers, please consult the HC08 ADC Reference Manual, ADCRM/AD. 5.2 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 5.3 Functional Description The ADC provides six pins for sampling external sources at pins PTB5/ATD5–PTB0/ATD0. 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 5-1. 5.3.1 ADC Port I/O Pins PTB5/ATD5–PTB0/ATD0 are general-purpose I/O (input/output) pins that share with the ADC channels. The channel select bits define which ADC channel/port pin will be used as the input signal. The ADC overrides the port I/O logic by forcing that pin as input to the ADC. The remaining ADC channels/port pins are controlled by the port I/O logic and can be used as general-purpose I/O. Writes to the port register or DDR will not have any affect on the port pin that is selected by the ADC. Read of a port pin in use by the ADC will return a 0 if the corresponding DDR bit is a 0. If the DDR bit is a 1, the value in the port data latch is read. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 55 Analog-to-Digital Converter (ADC) INTERNAL DATA BUS READ DDRBx WRITE DDRBx DISABLE DDRBx RESET WRITE PTBx PTBx PTBx ADC CHANNEL x READ PTBx ADC DATA REGISTER INTERRUPT LOGIC DISABLE ADC VOLTAGE IN (VADIN) CONVERSION COMPLETE ADC CHANNEL SELECT ADCH4–ADCH0 ADC CLOCK AIEN COCO CGMXCLK BUS CLOCK CLOCK GENERATOR ADIV2–ADIV0 ADICLK Figure 5-1. ADC Block Diagram 5.3.2 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. All other input voltages will result in $FF, if greater than VREFH. NOTE Inside the ADC module, the reference voltage, VREFH is connected to the ADC analog power VDDAD; and VREFL is connected to the ADC analog ground VDDAD. Therefore, the ADC input voltage should not exceed the analog supply voltages For operation, VDDAD should be tied to the same potential as VDD via separate traces 5.3.3 Conversion Time Sixteen ADC internal clocks are required to perform one conversion. The ADC starts a conversion on the first rising edge of the ADC internal clock immediately following a write to the ADSCR. If the ADC internal clock is selected to run at 1 MHz, then one conversion will take 16 μs to complete. But since the ADC can run almost completely asynchronously to the bus clock, (for example, the ADC is configured to derive its internal clock from CGMXCLK and the bus clock is being derived from the PLL within the CGM MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 56 Freescale Semiconductor Interrupts [CGMOUT]), this 16-μs conversion can take up to 17 μs to complete. This worst-case could occur if the write to the ADSCR happened directly after the rising edge of the ADC internal clock causing the conversion to wait until the next rising edge of the ADC internal clock. With a 1-MHz ADC internal clock, the maximum sample rate is 59 kHz to 62 kHz. Refer to 23.12 ADC Characteristics. 16 to 17 ADC Clock Cycles Conversion Time = ⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯⎯ ADC Clock Frequency Number of Bus Cycles = Conversion Time x Bus Frequency 5.3.4 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 write of the ADC status and control register or the next read of the ADC data register. In single conversion mode, conversion begins with a write to the ADSCR. Only one conversion occurs between writes to the ADSCR. 5.3.5 Accuracy and Precision The conversion process is monotonic and has no missing codes. See Chapter 23 Electrical Specifications for accuracy information. 5.4 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 logic 0. The COCO bit is not used as a conversion complete flag when interrupts are enabled. 5.5 Low-Power Modes The WAIT and STOP instruction can put the MCU in low power-consumption standby modes. 5.5.1 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. 5.5.2 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. Allow one conversion cycle to stabilize the analog circuitry before attempting a new ADC conversion after exiting stop mode. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 57 Analog-to-Digital Converter (ADC) 5.6 I/O Signals The ADC module has six pins shared with port B, PTB5/AD5–PTB0/ATD0. 5.6.1 ADC Analog Power Pin (VDDAD)/ADC Voltage Reference High Pin (VREFH) The ADC analog portion uses VDDAD as its power pin. Connect the VDDAD pin to the same voltage potential as VDD. External filtering may be necessary to ensure clean VDDAD for good results. NOTE For maximum noise immunity, route VDDAD carefully and place bypass capacitors as close as possible to the package. 5.6.2 ADC Analog Ground Pin (VSSAD)/ADC Voltage Reference Low Pin (VREFL) The ADC analog portion uses VSSAD as its ground pin. Connect the VSSAD pin to the same voltage potential as VSS. 5.6.3 ADC Voltage In (VADIN) VADIN is the input voltage signal from one of the six ADC channels to the ADC module. 5.7 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) 5.7.1 ADC Status and Control Register Function of the ADC status and control register (ADSCR) is described here. Address: Read: Write: Reset: $0003C Bit 7 6 5 4 3 2 1 Bit 0 COCO AIEN ADCO ADCH4 ADCH3 ADCH2 ADCH1 ADCH0 0 0 0 1 1 1 1 1 Figure 5-2. ADC Status and Control Register (ADSCR) COCO — Conversions Complete Bit When the AIEN bit is a logic 0, the COCO is a read-only bit which is set each time a conversion is completed except in the continuous conversion mode where it is set after the first conversion. This bit is cleared whenever the ADSCR is written or whenever the ADR is read. If the AIEN bit is a logic 1, the COCO is a read/write bit which selects the CPU to service the ADC interrupt request. Reset clears this bit. 1 = Conversion completed (AIEN = 0) 0 = Conversion not completed (AIEN = 0), or CPU interrupt (AIEN = 1) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 58 Freescale Semiconductor I/O Registers 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 this bit is set, the ADC will convert samples continuously and update the ADR register at the end of each conversion. Only one conversion is allowed when this bit is cleared. Reset clears the ADCO bit. 1 = Continuous ADC conversion 0 = One ADC conversion 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 5-1. 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 5-1. 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 5-1, are used to verify the operation of the ADC converter both in production test and for user applications. Table 5-1. Mux Channel Select ADCH4 ADCH3 ADCH2 ADCH1 ADCH0 Input Select 0 0 0 0 0 PTB0/ATD0 0 0 0 0 1 PTB1/ATD1 0 0 0 1 0 PTB2/ATD2 0 0 0 1 1 PTB3/ATD3 0 0 1 0 0 PTB4/ATD4 0 0 1 0 1 PTB5/ATD5 0 0 1 1 0 Reserved 0 0 1 1 1 Reserved ↓ ↓ ↓ ↓ ↓ Reserved 1 1 0 1 1 Reserved 1 1 1 0 0 Reserved 1 1 1 0 1 VREFH 1 1 1 1 0 VREFL 1 1 1 1 1 ADC power off NOTE: If an unknown channel is selected it should be made clear what value the user will read from the ADC Data Register, unknown or reserved is not specific enough. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 59 Analog-to-Digital Converter (ADC) 5.7.2 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: $0003D Bit 7 6 5 4 3 2 1 Bit 0 AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0 0 0 0 0 0 0 0 0 Write: Reset: = Unimplemented Figure 5-3. ADC Data Register (ADR) 5.7.3 ADC Clock Register The ADC clock register (ADCLK) selects the clock frequency for the ADC. Address: $0003E Bit 7 6 5 4 ADIV2 ADIV1 ADIV0 ADICLK 0 0 0 0 Read: 3 2 1 Bit 0 0 0 0 0 0 0 0 0 Write: Reset: = Unimplemented Figure 5-4. 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 5-2 shows the available clock configurations. The ADC clock should be set to approximately 1 MHz. Table 5-2. ADC Clock Divide Ratio ADIV2 ADIV1 ADIV0 ADC Clock Rate 0 0 0 ADC input clock ÷ 1 0 0 1 ADC input clock ÷ 2 0 1 0 ADC input clock ÷ 4 0 1 1 ADC input clock ÷ 8 1 X X ADC input clock ÷ 16 X = don’t care MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 60 Freescale Semiconductor I/O Registers ADICLK — ADC Input Clock Select Bit ADICLK selects either the bus clock or CGMXCLK as the input clock source to generate the internal ADC clock. Reset selects CGMXCLK as the ADC clock source. If the external clock (CGMXCLK) is equal to or greater than 1 MHz, CGMXCLK can be used as the clock source for the ADC. If CGMXCLK is less than 1 MHz, use the PLL-generated bus clock as the clock source. As long as the internal ADC clock is at approximately 1 MHz, correct operation can be guaranteed. 1 = Internal bus clock 0 = External clock (CGMXCLK) fxclk or bus frequency = 1 MHz ADIV2–ADIV0 NOTE During the conversion process, changing the ADC clock will result in an incorrect conversion. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 61 Analog-to-Digital Converter (ADC) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 62 Freescale Semiconductor Chapter 6 Break Module (BRK) 6.1 Introduction This section describes the break module. The break module can generate a break interrupt that stops normal program flow at a defined address to enter a background program. 6.2 Features Features of the break module include: • Accessible input/output (I/O) registers during the break interrupt • CPU-generated break interrupts • Software-generated break interrupts • COP disabling during break interrupts 6.3 Functional Description When the internal address bus matches the value written in the break address registers, the break module issues a breakpoint signal to the 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 logic 1 to the BRKA bit in the break status and control register. When a CPU-generated address matches the contents of the break address registers, the break interrupt is generated. A return-from-interrupt instruction (RTI) in the break routine ends the break interrupt and returns the MCU to normal operation. Figure 6-1 shows the structure of the break module. 6.3.1 Flag Protection During Break Interrupts The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 63 Break Module (BRK) IAB15–IAB8 BREAK ADDRESS REGISTER HIGH 8-BIT COMPARATOR IAB15–IAB0 CONTROL BREAK 8-BIT COMPARATOR BREAK ADDRESS REGISTER LOW IAB7–IAB0 Figure 6-1. Break Module Block Diagram Addr. $FE00 $FE03 Register Name Read: SIM Break Status Register Write: (SBSR) Reset: Read: SIM Break Flag Control Write: Register (SBFCR) Reset: Read: $FE09 $FE0A $FE0B Break Address Register High Write: (BRKH) Reset: Read: Break Address Register Low Write: (BRKL) Reset: Read: Break Status and Control Write: Register (BRKSCR) Reset: Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 1 0 0 BW 0 R R R R R R NOTE R 0 0 0 1 0 0 0 0 BCFE R R R R R R R Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 BRKE BRKA 0 0 0 0 0 0 0 0 0 0 0 0 0 0 R = Reserved 0 = Unimplemented Note: Writing a logic 0 clears BW. Figure 6-2. I/O Register Summary 6.3.2 CPU During Break Interrupts The CPU starts a break interrupt by: • Loading the instruction register with the SWI instruction • Loading the program counter with $FFFC and $FFFD ($FEFC and $FEFD in monitor mode) The break interrupt begins after completion of the CPU instruction in progress. If the break address register match occurs on the last cycle of a CPU instruction, the break interrupt begins immediately. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 64 Freescale Semiconductor Low-Power Modes 6.3.3 TIMI and TIM2 During Break Interrupts A break interrupt stops the timer counters and inhibits input captures. 6.3.4 COP During Break Interrupts The COP is disabled during a break interrupt when VTST is present on the RST pin. 6.4 Low-Power Modes The WAIT and STOP instructions put the MCU in low power-consumption standby modes. 6.4.1 Wait Mode If enabled, the break module is active in wait mode. In the break routine, the user can subtract one from the return address on the stack if SBSW is set. See Chapter 3 Low-Power Modes. Clear the BW bit by writing logic 0 to it. 6.4.2 Stop Mode A break interrupt causes exit from stop mode and sets the SBSW bit in the break status register. 6.5 Break Module Registers These registers control and monitor operation of the break module: • Break status and control register (BRKSCR) • Break address register high (BRKH) • Break address register low (BRKL) • SIM break status register (SBSR) • SIM break flag control register (SBFCR) 6.5.1 Break Status and Control Register The break status and control register (BRKSCR) contains break module enable and status bits. Address: Read: Write: Reset: $FE0E Bit 7 6 BRKE BRKA 0 0 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 0 0 0 0 = Unimplemented Figure 6-3. Break Status and Control Register (BRKSCR) BRKE — Break Enable Bit This read/write bit enables breaks on break address register matches. Clear BRKE by writing a logic 0 to bit 7. Reset clears the BRKE bit. 1 = Breaks enabled on 16-bit address match 0 = Breaks disabled on 16-bit address match MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 65 Break Module (BRK) BRKA — Break Active Bit This read/write status and control bit is set when a break address match occurs. Writing a logic 1 to BRKA generates a break interrupt. Clear BRKA by writing a logic 0 to it before exiting the break routine. Reset clears the BRKA bit. 1 = (When read) Break address match 0 = (When read) No break address match 6.5.2 Break Address Registers The break address registers (BRKH and BRKL) contain the high and low bytes of the desired breakpoint address. Reset clears the break address registers. Address: $FE09 Read: Write: Reset: Bit 7 6 5 4 3 2 1 Bit 0 Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Figure 6-4. Break Address Register High (BRKH) Address: Read: Write: Reset: $FE0A Bit 7 6 5 4 3 2 1 Bit 0 Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 Figure 6-5. Break Address Register Low (BRKL) 6.5.3 Break Status Register The break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode. The flag is useful in applications requiring a return to wait mode after exiting from a break interrupt. Address: $FE00 Bit 7 6 5 4 3 2 1 Bit 0 Read: 0 0 0 1 0 0 BW 0 Write: R R R R R R NOTE R Reset: 0 0 0 1 0 0 0 0 Note: Writing a logic 0 clears BW. R = Reserved Figure 6-6. SIM Break Status Register (SBSR) BW — Break Wait Bit This read/write bit is set when a break interrupt causes an exit from wait mode. Clear BW by writing a logic 0 to it. Reset clears BW. 1 = Break interrupt during wait mode 0 = No break interrupt during wait mode BW can be read within the break interrupt routine. The user can modify the return address on the stack by subtracting 1 from it. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 66 Freescale Semiconductor Break Module Registers 6.5.4 Break Flag Control Register The break flag control register (SBFCR) contains a bit that enables software to clear status bits while the MCU is in a break state. Address: Read: Write: Reset: $FE03 Bit 7 6 5 4 3 2 1 Bit 0 BCFE R R R R R R R 0 R = Reserved Figure 6-7. SIM Break Flag Control Register (SBFCR) BCFE — Break Clear Flag Enable Bit This read/write bit enables software to clear status bits by accessing status registers while the MCU is in a break state. To clear status bits during the break state, the BCFE bit must be set. 1 = Status bits clearable during break 0 = Status bits not clearable during break MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 67 Break Module (BRK) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 68 Freescale Semiconductor Chapter 7 Clock Generator Module (CGMC) 7.1 Introduction This section describes the clock generator module. The CGMC generates the crystal clock signal, CGMXCLK, which operates at the frequency of the crystal. The CGMC 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. In monitor mode, PTC3 determines the bus clock. 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 32-kHz crystal. 7.2 Features Features of the CGMC include: • Phase-locked loop with output frequency in integer multiples of an integer dividend of the crystal reference • Low-frequency crystal operation with low-power operation and high-output frequency resolution • Programmable prescaler for power-of-two increases in frequency • 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 7.3 Functional Description The CGMC 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 7-1 shows the structure of the CGMC. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 69 Clock Generator Module (CGMC) OSCILLATOR (OSC) OSC2 CGMXCLK (TO: SIM, TIMEBASE, ADC) OSC1 SIMOSCEN (FROM SIM) OSCSTOPENB (FROM CONFIG) PHASE-LOCKED LOOP (PLL) CGMRDV REFERENCE DIVIDER CGMRCLK CLOCK SELECT CIRCUIT BCS RDS3–RDS0 VDDA CGMXFC CGMOUT ³2 (TO SIM) VSSA VPR1–VPR0 VRS7–VRS0 VOLTAGE CONTROLLED OSCILLATOR LOOP FILTER PHASE DETECTOR CGMVCLK PLL ANALOG AUTOMATIC MODE CONTROL LOCK DETECTOR LOCK CGMVDV AUTO ACQ INTERRUPT CONTROL PLLIE MUL11–MUL0 PRE1–PRE0 FREQUENCY DIVIDER FREQUENCY DIVIDER CGMINT (TO SIM) PLLF Figure 7-1. CGMC Block Diagram MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 70 Freescale Semiconductor Functional Description 7.3.1 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. 7.3.2 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. 7.3.3 PLL Circuits The PLL consists of these circuits: • Voltage-controlled oscillator (VCO) • Reference divider • Frequency prescaler • 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 × 2E)fNOM. CGMRCLK is the PLL reference clock, a buffered version of CGMXCLK. CGMRCLK runs at a frequency, fRCLK, and is fed to the PLL through a programmable modulo reference divider, which divides fRCLK by a factor, R. The divider’s output is the final reference clock, CGMRDV, running at a frequency, fRDV = fRCLK/R. With an external crystal (30 kHz–100 kHz), always set R = 1 for specified performance. With an external high-frequency clock source, use R to divide the external frequency to between 30 kHz and 100 kHz. 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 × 2P). (See 7.3.6 Programming the PLL for more information.) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 71 Clock Generator Module (CGMC) 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 7.3.4 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 final reference clock, CGMRDV. Therefore, the speed of the lock detector is directly proportional to the final reference frequency, fRDV. The circuit determines the mode of the PLL and the lock condition based on this comparison. 7.3.4 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 7.5.2 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 7.3.8 Base Clock Selector Circuit.) The PLL is automatically in tracking mode when not in acquisition mode or when the ACQ bit is set. 7.3.5 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 7.5.2 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 7.3.8 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 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 7.5.2 PLL Bandwidth Control Register) is a read-only indicator of the mode of the filter. (See 7.3.4 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 7.8 Acquisition/Lock Time Specifications for more information.) • The LOCK bit is a read-only indicator of the locked state of the PLL. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 72 Freescale Semiconductor Functional Description • • 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 7.8 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 7.5.1 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. 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 7.8 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 CGMC are disabled. 7.3.6 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 × f BUSDES 3. Choose a practical PLL (crystal) reference frequency, fRCLK, and the reference clock divider, R. Typically, the reference crystal is 32.768 kHz 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 P 2 N f VCLK = ----------- ( f RCLK ) R 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 23 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 73 Clock Generator Module (CGMC) 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 × ⎨ ⎜ --------------------------⎟ – integer ⎜ --------------------------⎟ ⎬ ⎝ f RCLK ⎠ ⎭ ⎩ ⎝ f RCLK ⎠ 4. Select a VCO frequency multiplier, N. ⎛ R × f VCLKDES⎞ N = round ⎜ -------------------------------------⎟ f RCLK ⎝ ⎠ Reduce N/R to the lowest possible R. 5. If N is < Nmax, use P = 0. If N > Nmax, choose P using this table: Current N Value P 0 < N ≤ N max 0 N max < N ≤ N max × 2 1 N max × 2 < N ≤ N max × 4 2 N max × 4 < N ≤ N max × 8 3 Then recalculate N: ⎛ R × f VCLKDES⎞ N = round ⎜ -------------------------------------⎟ P ⎝ f ×2 ⎠ RCLK 6. Calculate and verify the adequacy of the VCO and bus frequencies fVCLK and fBUS. P f VCLK = ( 2 × N ⁄ R ) × f RCLK f BUS = ( f VCLK ) ⁄ 4 7. Select the VCO’s power-of-two range multiplier E, according to this table: Frequency Range E 0 < fVCLK < 8 MHz 0 9,830,400 ≤ fVCLK < 16 MHz 1 19,660,800 ≤ fVCLK < 32 MHz 2 NOTE: Do not program E to a value of 3. 8. Select a VCO linear range multiplier, L, where fNOM = 38.4 kHz ⎛ f VCLK ⎞ L = round ⎜ --------------------------⎟ ⎝ 2E × f ⎠ NOM MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 74 Freescale Semiconductor Functional Description 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. E f VRS = ( L × 2 )f NOM For proper operation, E f NOM × 2 f VRS – f VCLK ≤ -------------------------2 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 7-1 provides numeric examples (numbers are in hexadecimal notation): Table 7-1. Numeric Example fBUS fRCLK R N P E L 2.0 MHz 32.768 kHz 1 F5 0 0 D1 2.4576 MHz 32.768 kHz 1 12C 0 1 80 2.5 MHz 32.768 kHz 1 132 0 1 83 4.0 MHz 32.768 kHz 1 1E9 0 1 D1 4.9152 MHz 32.768 kHz 1 258 0 2 80 5.0 MHz 32.768 kHz 1 263 0 2 82 7.3728 MHz 32.768 kHz 1 384 0 2 C0 8.0 MHz 32.768 kHz 1 3D1 0 2 D0 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 75 Clock Generator Module (CGMC) 7.3.7 Special Programming Exceptions The programming method described in 7.3.6 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 7.3.8 Base Clock Selector Circuit.) 7.3.8 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. 7.3.9 CGMC External Connections In its typical configuration, the CGMC 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 7-2. Figure 7-2 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 7-2 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 23.8.1 CGM Component Specifications for capacitor and resistor values. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 76 Freescale Semiconductor I/O Signals SIMOSCEN OSCSTOPENB (FROM CONFIG) CGMXCLK OSC1 CGMXFC OSC2 VSSA VDDA VDD RB RF1 RS CF2 CBYP 0.1 μF CF1 X1 C1 C2 Note: Filter network in box can be replaced with a 0.47 μF capacitor, but will degrade stability. Figure 7-2. CGMC External Connections 7.4 I/O Signals The following paragraphs describe the CGMC I/O signals. 7.4.1 Crystal Amplifier Input Pin (OSC1) The OSC1 pin is an input to the crystal oscillator amplifier. 7.4.2 Crystal Amplifier Output Pin (OSC2) The OSC2 pin is the output of the crystal oscillator inverting amplifier. 7.4.3 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 7-2.) 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 77 Clock Generator Module (CGMC) 7.4.4 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. 7.4.5 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. 7.4.6 Oscillator Enable Signal (SIMOSCEN) The SIMOSCEN signal comes from the system integration module (SIM) and enables the oscillator and PLL. 7.4.7 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. 7.4.8 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 7-2 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. 7.4.9 CGMC Base Clock Output (CGMOUT) CGMOUT is the clock output of the CGMC. 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. 7.4.10 CGMC CPU Interrupt (CGMINT) CGMINT is the interrupt signal generated by the PLL lock detector. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 78 Freescale Semiconductor CGMC Registers 7.5 CGMC Registers These registers control and monitor operation of the CGMC: • PLL control register (PCTL) (See 7.5.1 PLL Control Register.) • PLL bandwidth control register (PBWC) (See 7.5.2 PLL Bandwidth Control Register.) • PLL multiplier select register high (PMSH) (See 7.5.3 PLL Multiplier Select Register High.) • PLL multiplier select register low (PMSL) (See 7.5.4 PLL Multiplier Select Register Low.) • PLL VCO range select register (PMRS) (See 7.5.5 PLL VCO Range Select Register.) • PLL reference divider select register (PMDS) (See 7.5.6 PLL Reference Divider Select Register.) Figure 7-3 is a summary of the CGMC registers. Addr. $0036 $0037 $0038 Register Name Bit 7 Read: PLL Control Register Write: (PCTL) Reset: Read: PLL Bandwidth Control Write: Register (PBWC) Reset: Read: PLL Multiplier Select High Write: Register (PMSH) Reset: Read: $0039 $003A $003B PLL Multiplier Select Low Write: Register (PMSL) Reset: Read: PLL VCO Select Range Write: Register (PMRS) Reset: Read: PLL Reference Divider Write: Select Register (PMDS) Reset: PLLIE 0 AUTO 6 PLLF 5 4 3 2 1 Bit 0 PLLON BCS PRE1 PRE0 VPR1 VPR0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 MUL11 MUL10 MUL9 MUL8 0 LOCK ACQ R 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 MUL7 MUL6 MUL5 MUL4 MUL3 MUL2 MUL1 MUL0 0 1 0 0 0 0 0 0 VRS7 VRS6 VRS5 VRS4 VRS3 VRS2 VRS1 VRS0 0 1 0 0 0 0 0 0 0 0 0 0 RDS3 RDS2 RDS1 RDS0 0 0 0 0 0 0 0 1 R = Reserved = 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 7-3. CGMC I/O Register Summary MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 79 Clock Generator Module (CGMC) 7.5.1 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 5 4 3 2 1 Bit 0 PLLON BCS PRE1 PRE0 VPR1 VPR0 1 0 0 0 0 0 0 = Unimplemented Figure 7-4. 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 7.3.8 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 CGMC 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 7.3.8 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 80 Freescale Semiconductor CGMC 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 7.3.8 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 7.3.3 PLL Circuits and 7.3.6 Programming the PLL.) PRE1 and PRE0 cannot be written when the PLLON bit is set. Reset clears these bits. NOTE The value of P is normally 0 when using a 32.768-kHz crystal as the reference. Table 7-2. PRE 1 and PRE0 Programming PRE1 and PRE0 P Prescaler Multiplier 00 0 1 01 1 2 10 2 4 11 3 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 7.3.3 PLL Circuits, 7.3.6 Programming the PLL, and 7.5.5 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 7-3. VPR1 and VPR0 Programming VPR1 and VPR0 E VCO Power-of-Two Range Multiplier 00 0 1 01 1 2 10 2 4 11 (1) 8 3 1. Do not program E to a value of 3. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 81 Clock Generator Module (CGMC) 7.5.2 PLL Bandwidth Control Register The PLL bandwidth control register (PBWC): • Selects automatic or manual (software-controlled) bandwidth control mode • Indicates when the PLL is locked • In automatic bandwidth control mode, indicates when the PLL is in acquisition or tracking mode • In manual operation, forces the PLL into acquisition or tracking mode Address: $0037 Bit 7 Read: Write: Reset: AUTO 0 6 LOCK 5 ACQ 0 = Unimplemented 0 4 3 2 1 0 0 0 0 0 0 0 0 R Bit 0 R 0 = Reserved Figure 7-5. PLL Bandwidth Control Register (PBWC) AUTO — Automatic Bandwidth Control Bit This read/write bit selects automatic or manual bandwidth control. When initializing the PLL for manual operation (AUTO = 0), clear the ACQ bit before turning on the PLL. Reset clears the AUTO bit. 1 = Automatic bandwidth control 0 = Manual bandwidth control LOCK — Lock Indicator Bit When the AUTO bit is set, LOCK is a read-only bit that becomes set when the VCO clock, CGMVCLK, is locked (running at the programmed frequency). When the AUTO bit is clear, LOCK reads as 0 and has no meaning. The write one function of this bit is reserved for test, so this bit must always be written 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 82 Freescale Semiconductor CGMC Registers 7.5.3 PLL Multiplier Select Register High The PLL multiplier select register high (PMSH) contains the programming information for the high byte of the modulo feedback divider. Address: Read: $0038 Bit 7 6 5 4 0 0 0 0 0 0 0 0 Write: Reset: 3 2 1 Bit 0 MUL11 MUL10 MUL9 MUL8 0 0 0 0 = Unimplemented Figure 7-6. 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 7.3.3 PLL Circuits and 7.3.6 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 logic 0s. 7.5.4 PLL Multiplier Select Register Low The PLL multiplier select register low (PMSL) contains the programming information for the low byte of the modulo feedback divider. Address: Read: Write: Reset: $0038 Bit 7 6 5 4 3 2 1 Bit 0 MUL7 MUL6 MUL5 MUL4 MUL3 MUL2 MUL1 MUL0 0 1 0 0 0 0 0 0 Figure 7-7. PLL Multiplier Select Register Low (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 7.3.3 PLL Circuits and 7.3.6 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). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 83 Clock Generator Module (CGMC) 7.5.5 PLL VCO Range Select Register NOTE PMRS may be called PVRS on other HC08 derivatives. The PLL VCO range select register (PMRS) contains the programming information required for the hardware configuration of the VCO. Address: Read: Write: Reset: $003A Bit 7 6 5 4 3 2 1 Bit 0 VRS7 VRS6 VRS5 VRS4 VRS3 VRS2 VRS1 VRS0 0 1 0 0 0 0 0 0 Figure 7-8. 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 7.3.3 PLL Circuits, 7.3.6 Programming the PLL, and 7.5.1 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 7.3.7 Special Programming Exceptions.) A value of $00 in the VCO range select register disables the PLL and clears the BCS bit in the PLL control register (PCTL). (See 7.3.8 Base Clock Selector Circuit and 7.3.7 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. 7.5.6 PLL Reference Divider Select Register NOTE PMDS may be called PRDS on other HC08 derivatives. The PLL reference divider select register (PMDS) contains the programming information for the modulo reference divider. Address: Read: $003B Bit 7 6 5 4 0 0 0 0 0 0 0 0 Write: Reset: 3 2 1 Bit 0 RDS3 RDS2 RDS1 RDS0 0 0 0 1 = Unimplemented Figure 7-9. PLL Reference Divider Select Register (PMDS) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 84 Freescale Semiconductor Interrupts RDS3–RDS0 — Reference Divider Select Bits These read/write bits control the modulo reference divider that selects the reference division factor, R. (See 7.3.3 PLL Circuits and 7.3.6 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 7.3.7 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. PMDS7–PMDS4 — Unimplemented Bits These bits have no function and always read as logic 0s. 7.6 Interrupts When the AUTO bit is set in the PLL bandwidth control register (PBWC), the PLL can generate a CPU interrupt request every time the LOCK bit changes state. The PLLIE bit in the PLL control register (PCTL) enables CPU interrupts from the PLL. PLLF, the interrupt flag in the PCTL, becomes set whether interrupts are enabled or not. When the AUTO bit is clear, CPU interrupts from the PLL are disabled and PLLF reads as logic 0. Software should read the LOCK bit after a PLL interrupt request to see if the request was due to an entry into lock or an exit from lock. When the PLL enters lock, the VCO clock, CGMVCLK, divided by two can be selected as the CGMOUT source by setting BCS in the PCTL. When the PLL exits lock, the VCO clock frequency is corrupt, and appropriate precautions should be taken. If the application is not frequency sensitive, interrupts should be disabled to prevent PLL interrupt service routines from impeding software performance or from exceeding stack limitations. NOTE Software can select the CGMVCLK divided by two as the CGMOUT source even if the PLL is not locked (LOCK = 0). Therefore, software should make sure the PLL is locked before setting the BCS bit. 7.7 Special Modes The WAIT instruction puts the MCU in low power-consumption standby modes. 7.7.1 Wait Mode The WAIT instruction does not affect the CGMC. 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 85 Clock Generator Module (CGMC) 7.7.2 Stop Mode If the OSCSTOPENB bit in the CONFIG register is cleared (default), then the STOP instruction disables the CGMC (oscillator and phase locked loop) and holds low all CGMC 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. 7.7.3 CGMC During Break Interrupts The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. (See 19.7.3 SIM Break Flag Control 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. 7.8 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. 7.8.1 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 86 Freescale Semiconductor Acquisition/Lock Time Specifications 7.8.2 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 7.3.3 PLL Circuits, 7.3.6 Programming the PLL, and 7.5.6 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 7.8.3 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. 7.8.3 Choosing a Filter As described in 7.8.2 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 7-10 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 of Figure 7-10 (B) can be replaced by a single capacitor, CF, shown in Figure 7-10 (A). Refer to Table 7-4 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 87 Clock Generator Module (CGMC) CGMXFC CGMXFC RF1 CF2 CF CF1 VSSA VSSA (A) (B) Figure 7-10. PLL Filter Table 7-4. Example Filter Component Values fRCLK CF1 CF2 RF1 CF 32 kHz 0.15 μF 15 nF 2K 0.22 μF 40 kHz 0.12 μF 12 nF 2K 0.18 μF 50 kHz 0.10 μF 10 nF 2K 0.18 μF 60 kHz 82 nF 8.2 nF 2K 0.12 μF 70 kHz 68 nF 6.8 nF 2K 0.12 μF 80 kHz 56 nF 5.6 nF 2K 0.1 μF 90 kHz 56 nF 5.6 nF 2K 0.1 μF 100 kHz 47 nF 4.7 nF 2K 82 nF MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 88 Freescale Semiconductor Chapter 8 Configuration Register (CONFIG) 8.1 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 8.2 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 MCU, it is recommended that these registers be written immediately after reset. The configuration registers are located at $001E and $001F. The configuration register may be read at anytime. NOTE To ensure correct operation of the MCU under all operating conditions, the user must write data $1C to address $0033 immediately after reset. This is to ensure proper termination of an unused module within the MCU. NOTE On a FLASH device, the options except LVI5OR3 are one-time writeable by the user after each reset. The LVI5OR3 bit is one-time writeable 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 writeable latches after each reset. Upon a reset, the CONFIG registers default to predetermined settings as shown in Figure 8-1 and Figure 8-2. Address: Read: $001E Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 OSCSTOPENB SCIBDSRC 0 0 0 0 0 0 0 0 Write: Reset: = Unimplemented Figure 8-1. Configuration Register 2 (CONFIG2) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 89 Configuration Register (CONFIG) Address: Read: Write: Reset: $001F Bit 7 6 5 4 3 2 1 Bit 0 COPRS LVISTOP LVIRSTD LVIPWRD LVI5OR3 SSREC STOP COPD 0 0 0 0 See Note 0 0 0 Note: LVI5OR3 bit is only reset via POR (power-on reset) Figure 8-2. Configuration Register 1 (CONFIG1) OSCSTOPENB— Oscillator Stop Mode Enable Bar Bit OSCSTOPENB enables the oscillator to continue operating during stop mode. Setting the OSCSTOPENB bit allows the oscillator to operate continuously even during stop mode. This is useful for driving the timebase module to allow it to generate periodic wakeup while in stop mode. (See Clock Generator Module (CGM) subsection 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 SCI. The setting of this bit affects the frequency at which the SCI operates. 1 = Internal data 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 9 Computer Operating Properly (COP). 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. See Stop Mode. 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 14 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 14 Low-Voltage Inhibit (LVI). 1 = LVI module power disabled 0 = LVI module power enabled LVI5OR3 — LVI 5V or 3V Operating Mode Bit LVI5OR3 selects the voltage operating mode of the LVI module. See Chapter 14 Low-Voltage Inhibit (LVI). The voltage mode selected for the LVI should match the operating VDD. See Chapter 23 Electrical Specifications for the LVI’s voltage trip points for each of the modes. 1 = LVI operates in 5V mode. 0 = LVI operates in 3V mode. SSREC — Short Stop Recovery Bit MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 90 Freescale Semiconductor Functional Description 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 CGMXCLKC cycles NOTE Exiting stop mode by pulling reset will result in the long stop recovery. If using an external crystal oscillator, do not set the SSREC bit. When the LVISTOP is enabled, the system stabilization time for power on reset and long stop recovery (both 4096 CGMXCLK cycles) gives a delay longer than the enable time for the LVI. 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 is less than the LVI’s turn-on time and there exists 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 9 Computer Operating Properly (COP) 1 = COP module disabled 0 = COP module enabled MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 91 Configuration Register (CONFIG) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 92 Freescale Semiconductor Chapter 9 Computer Operating Properly (COP) 9.1 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. 9.2 Functional Description Figure 9-1 shows the structure of the COP module. RESET STATUS REGISTER COP TIMEOUT CLEAR STAGES 5–12 STOP INSTRUCTION INTERNAL RESET SOURCES RESET VECTOR FETCH RESET CIRCUIT 12-BIT COP PRESCALER CLEAR ALL STAGES CGMXCLK COPCTL WRITE COP CLOCK COP MODULE 6-BIT COP COUNTER COPEN (FROM SIM) COP DISABLE (FROM CONFIG) RESET COPCTL WRITE CLEAR COP COUNTER COP RATE SEL (FROM CONFIG) Figure 9-1. COP Block Diagram MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 93 Computer Operating Properly (COP) 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 8176 CGMXCLK cycle overflow option, a 32.768-kHz crystal gives a COP timeout period of 250 ms. Writing any value to location $FFFF before an overflow occurs prevents a COP reset by clearing the COP counter and stages 12 through 5 of the prescaler. NOTE Service the COP immediately after reset and before entering or after exiting stop mode to guarantee the maximum time before the first COP counter overflow. 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. 9.3 I/O Signals The following paragraphs describe the signals shown in Figure 9-1. 9.3.1 CGMXCLK CGMXCLK is the crystal oscillator output signal. CGMXCLK frequency is equal to the crystal frequency. 9.3.2 STOP Instruction The STOP instruction clears the COP prescaler. 9.3.3 COPCTL Write Writing any value to the COP control register (COPCTL) (see COP Control Register) clears the COP counter and clears bits 12 through 5 of the prescaler. Reading the COP control register returns the low byte of the reset vector. 9.3.4 Power-On Reset The power-on reset (POR) circuit clears the COP prescaler 4096 CGMXCLK cycles after power-up. 9.3.5 Internal Reset An internal reset clears the COP prescaler and the COP counter. 9.3.6 Reset Vector Fetch A reset vector fetch occurs when the vector address appears on the data bus. A reset vector fetch clears the COP prescaler. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 94 Freescale Semiconductor COP Control Register 9.3.7 COPD (COP Disable) The COPD signal reflects the state of the COP disable bit (COPD) in the configuration register. See Chapter 8 Configuration Register (CONFIG). 9.3.8 COPRS (COP Rate Select) The COPRS signal reflects the state of the COP rate select bit (COPRS) in the configuration register. See Chapter 8 Configuration Register (CONFIG). 9.4 COP Control Register The COP control register is located at address $FFFF and overlaps the reset vector. Writing any value to $FFFF clears the COP counter and starts a new timeout period. Reading location $FFFF returns the low byte of the reset vector. Address: $FFFF Bit 7 6 5 4 3 Read: Low byte of reset vector Write: Clear COP counter Reset: Unaffected by reset 2 1 Bit 0 Figure 9-2. COP Control Register (COPCTL) 9.5 Interrupts The COP does not generate CPU interrupt requests. 9.6 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. 9.7 Low-Power Modes The WAIT and STOP instructions put the MCU in low power-consumption standby modes. 9.7.1 Wait Mode The COP remains active during wait mode. If COP is enabled, a reset will occur at COP timeout. 9.7.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 95 Computer Operating Properly (COP) 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. 9.8 COP Module During Break Mode The COP is disabled during a break interrupt when VTST is present on the RST pin. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 96 Freescale Semiconductor Chapter 10 Central Processing Unit (CPU) 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. 10.1 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 10.2 CPU Registers Figure 10-1 shows the five CPU registers. CPU registers are not part of the memory map. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 97 Central Processing Unit (CPU) 0 7 ACCUMULATOR (A) 0 15 H X INDEX REGISTER (H:X) 15 0 STACK POINTER (SP) 15 0 PROGRAM COUNTER (PC) 7 0 V 1 1 H I N Z C CONDITION CODE REGISTER (CCR) CARRY/BORROW FLAG ZERO FLAG NEGATIVE FLAG INTERRUPT MASK HALF-CARRY FLAG TWO’S COMPLEMENT OVERFLOW FLAG Figure 10-1. CPU Registers 10.2.1 Accumulator The accumulator is a general-purpose 8-bit register. The CPU uses the accumulator to hold operands and the results of arithmetic/logic operations. Bit 7 6 5 4 3 2 1 Bit 0 Read: Write: Reset: Unaffected by reset Figure 10-2. Accumulator (A) 10.2.2 Index Register The 16-bit index register allows indexed addressing of a 64-Kbyte memory space. H is the upper byte of the index register, and X is the lower byte. H:X is the concatenated 16-bit index register. In the indexed addressing modes, the CPU uses the contents of the index register to determine the conditional address of the operand. The index register can serve also as a temporary data storage location. Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 X X X X X X X X Read: Write: Reset: X = Indeterminate Figure 10-3. Index Register (H:X) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 98 Freescale Semiconductor CPU Registers 10.2.3 Stack Pointer The stack pointer is a 16-bit register that contains the address of the next location on the stack. During a reset, the stack pointer is preset to $00FF. The reset stack pointer (RSP) instruction sets the least significant byte to $FF and does not affect the most significant byte. The stack pointer decrements as data is pushed onto the stack and increments as data is pulled from the stack. In the stack pointer 8-bit offset and 16-bit offset addressing modes, the stack pointer can function as an index register to access data on the stack. The CPU uses the contents of the stack pointer to determine the conditional address of the operand. Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 Read: Write: Reset: Figure 10-4. 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. 10.2.4 Program Counter The program counter is a 16-bit register that contains the address of the next instruction or operand to be fetched. Normally, the program counter automatically increments to the next sequential memory location every time an instruction or operand is fetched. Jump, branch, and interrupt operations load the program counter with an address other than that of the next sequential location. During reset, the program counter is loaded with the reset vector address located at $FFFE and $FFFF. The vector address is the address of the first instruction to be executed after exiting the reset state. Bit 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 Bit 0 Read: Write: Reset: Loaded with vector from $FFFE and $FFFF Figure 10-5. Program Counter (PC) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 99 Central Processing Unit (CPU) 10.2.5 Condition Code Register The 8-bit condition code register contains the interrupt mask and five flags that indicate the results of the instruction just executed. Bits 6 and 5 are set permanently to 1. The following paragraphs describe the functions of the condition code register. Read: Write: Reset: Bit 7 6 5 4 3 2 1 Bit 0 V 1 1 H I N Z C X 1 1 X 1 X X X X = Indeterminate Figure 10-6. 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 100 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 10.3 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. 10.4 Low-Power Modes The WAIT and STOP instructions put the MCU in low power-consumption standby modes. 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 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 101 Central Processing Unit (CPU) 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. 10.6 Instruction Set Summary Table 10-1 provides a summary of the M68HC08 instruction set. ADC #opr ADC opr ADC opr ADC opr,X ADC opr,X ADC ,X ADC opr,SP ADC opr,SP ADD #opr ADD opr ADD opr ADD opr,X ADD opr,X ADD ,X ADD opr,SP ADD opr,SP V H I N Z C A ← (A) + (M) + (C) Add with Carry A ← (A) + (M) Add without Carry IMM DIR EXT – IX2 IX1 IX SP1 SP2 A9 B9 C9 D9 E9 F9 9EE9 9ED9 ii dd hh ll ee ff ff IMM DIR EXT IX2 – IX1 IX SP1 SP2 AB BB CB DB EB FB 9EEB 9EDB ii dd hh ll ee ff ff ff ee ff Cycles Effect on CCR Description Operand Operation Opcode Source Form Address Mode Table 10-1. Instruction Set Summary (Sheet 1 of 6) 2 3 4 4 3 2 4 5 ff ee ff 2 3 4 4 3 2 4 5 AIS #opr Add Immediate Value (Signed) to SP SP ← (SP) + (16 « M) – – – – – – IMM A7 ii 2 AIX #opr Add Immediate Value (Signed) to H:X H:X ← (H:X) + (16 « M) – – – – – – IMM AF ii 2 A ← (A) & (M) IMM DIR EXT IX2 0 – – – IX1 IX SP1 SP2 A4 B4 C4 D4 E4 F4 9EE4 9ED4 ii dd hh ll ee ff ff 2 3 4 4 3 2 4 5 0 DIR INH INH – – IX1 IX SP1 38 dd 48 58 68 ff 78 9E68 ff 4 1 1 4 3 5 C DIR INH INH – – IX1 IX SP1 37 dd 47 57 67 ff 77 9E67 ff 4 1 1 4 3 5 AND #opr AND opr AND opr AND opr,X AND opr,X AND ,X AND opr,SP AND opr,SP ASL opr ASLA ASLX ASL opr,X ASL ,X ASL opr,SP Logical AND Arithmetic Shift Left (Same as LSL) C b7 ASR opr ASRA ASRX ASR opr,X ASR opr,X ASR opr,SP Arithmetic Shift Right BCC rel Branch if Carry Bit Clear b0 b7 BCLR n, opr Clear Bit n in M b0 PC ← (PC) + 2 + rel ? (C) = 0 Mn ← 0 ff ee ff – – – – – – REL 24 rr 3 DIR (b0) DIR (b1) DIR (b2) DIR (b3) – – – – – – DIR (b4) DIR (b5) DIR (b6) DIR (b7) 11 13 15 17 19 1B 1D 1F dd dd dd dd dd dd dd dd 4 4 4 4 4 4 4 4 BCS rel Branch if Carry Bit Set (Same as BLO) PC ← (PC) + 2 + rel ? (C) = 1 – – – – – – REL 25 rr 3 BEQ rel Branch if Equal PC ← (PC) + 2 + rel ? (Z) = 1 – – – – – – REL 27 rr 3 BGE opr Branch if Greater Than or Equal To (Signed Operands) PC ← (PC) + 2 + rel ? (N ⊕ V) = 0 – – – – – – REL 90 rr 3 BGT opr Branch if Greater Than (Signed Operands) PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 0 – – – – – – REL 92 rr 3 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 102 Freescale Semiconductor Instruction Set Summary Effect on CCR V H I N Z C Cycles Description Operand Operation Opcode Source Form Address Mode Table 10-1. Instruction Set Summary (Sheet 2 of 6) BHCC rel Branch if Half Carry Bit Clear PC ← (PC) + 2 + rel ? (H) = 0 – – – – – – REL 28 rr BHCS rel Branch if Half Carry Bit Set PC ← (PC) + 2 + rel ? (H) = 1 – – – – – – REL 29 rr PC ← (PC) + 2 + rel ? (C) | (Z) = 0 – – – – – – REL 22 rr 3 PC ← (PC) + 2 + rel ? (C) = 0 – – – – – – REL 24 rr 3 3 BHI rel Branch if Higher BHS rel Branch if Higher or Same (Same as BCC) 3 3 BIH rel Branch if IRQ Pin High PC ← (PC) + 2 + rel ? IRQ = 1 – – – – – – REL 2F rr BIL rel Branch if IRQ Pin Low PC ← (PC) + 2 + rel ? IRQ = 0 – – – – – – REL 2E rr 3 (A) & (M) IMM DIR EXT 0 – – – IX2 IX1 IX SP1 SP2 A5 B5 C5 D5 E5 F5 9EE5 9ED5 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 rr 3 BIT #opr BIT opr BIT opr BIT opr,X BIT opr,X BIT ,X BIT opr,SP BIT opr,SP Bit Test BLE opr Branch if Less Than or Equal To (Signed Operands) PC ← (PC) + 2 + rel ? (Z) | (N ⊕ V) = 1 – – – – – – REL 93 BLO rel Branch if Lower (Same as BCS) PC ← (PC) + 2 + rel ? (C) = 1 – – – – – – REL 25 rr 3 BLS rel Branch if Lower or Same PC ← (PC) + 2 + rel ? (C) | (Z) = 1 – – – – – – REL 23 rr 3 BLT opr Branch if Less Than (Signed Operands) PC ← (PC) + 2 + rel ? (N ⊕ V) =1 – – – – – – REL 91 rr 3 BMC rel Branch if Interrupt Mask Clear PC ← (PC) + 2 + rel ? (I) = 0 – – – – – – REL 2C rr 3 BMI rel Branch if Minus PC ← (PC) + 2 + rel ? (N) = 1 – – – – – – REL 2B rr 3 BMS rel Branch if Interrupt Mask Set PC ← (PC) + 2 + rel ? (I) = 1 – – – – – – REL 2D rr 3 3 BNE rel Branch if Not Equal PC ← (PC) + 2 + rel ? (Z) = 0 – – – – – – REL 26 rr BPL rel Branch if Plus PC ← (PC) + 2 + rel ? (N) = 0 – – – – – – REL 2A rr 3 BRA rel Branch Always PC ← (PC) + 2 + rel – – – – – – REL 20 rr 3 DIR (b0) DIR (b1) DIR (b2) DIR (b3) – – – – – DIR (b4) DIR (b5) DIR (b6) DIR (b7) 01 03 05 07 09 0B 0D 0F dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr 5 5 5 5 5 5 5 5 BRCLR n,opr,rel Branch if Bit n in M Clear BRN rel PC ← (PC) + 3 + rel ? (Mn) = 0 PC ← (PC) + 2 Branch Never BRSET n,opr,rel Branch if Bit n in M Set BSET n,opr Set Bit n in M BSR rel Branch to Subroutine – – – – – – REL 21 rr 3 PC ← (PC) + 3 + rel ? (Mn) = 1 DIR (b0) DIR (b1) DIR (b2) DIR (b3) – – – – – DIR (b4) DIR (b5) DIR (b6) DIR (b7) 00 02 04 06 08 0A 0C 0E dd rr dd rr dd rr dd rr dd rr dd rr dd rr dd rr 5 5 5 5 5 5 5 5 Mn ← 1 DIR (b0) DIR (b1) DIR (b2) – – – – – – DIR (b3) DIR (b4) DIR (b5) DIR (b6) DIR (b7) 10 12 14 16 18 1A 1C 1E dd dd dd dd dd dd dd dd 4 4 4 4 4 4 4 4 – – – – – – REL AD rr 4 PC ← (PC) + 2; push (PCL) SP ← (SP) – 1; push (PCH) SP ← (SP) – 1 PC ← (PC) + rel MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 103 Central Processing Unit (CPU) Effect on CCR V H I N Z C CBEQ opr,rel CBEQA #opr,rel CBEQX #opr,rel CBEQ opr,X+,rel Compare and Branch if Equal CBEQ X+,rel CBEQ opr,SP,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 DIR IMM IMM – – – – – – IX1+ IX+ SP1 31 41 51 61 71 9E61 Cycles Description Operand Operation Opcode Source Form Address Mode Table 10-1. Instruction Set Summary (Sheet 3 of 6) dd rr ii rr ii rr ff rr rr ff rr 5 4 4 5 4 6 CLC Clear Carry Bit C←0 – – – – – 0 INH 98 1 CLI Clear Interrupt Mask I←0 – – 0 – – – INH 9A 2 M ← $00 A ← $00 X ← $00 H ← $00 M ← $00 M ← $00 M ← $00 DIR INH INH 0 – – 0 1 – INH IX1 IX SP1 3F dd 4F 5F 8C 6F ff 7F 9E6F ff 3 1 1 1 3 2 4 (A) – (M) IMM DIR EXT IX2 – – IX1 IX SP1 SP2 A1 B1 C1 D1 E1 F1 9EE1 9ED1 2 3 4 4 3 2 4 5 DIR INH INH 0 – – 1 IX1 IX SP1 33 dd 43 53 63 ff 73 9E63 ff CLR opr CLRA CLRX CLRH CLR opr,X CLR ,X CLR opr,SP CMP #opr CMP opr CMP opr CMP opr,X CMP opr,X CMP ,X CMP opr,SP CMP opr,SP Clear Compare A with M COM opr COMA COMX COM opr,X COM ,X COM opr,SP Complement (One’s Complement) CPHX #opr CPHX opr Compare H:X with M CPX #opr CPX opr CPX opr CPX ,X CPX opr,X CPX opr,X CPX opr,SP CPX opr,SP Compare X with M DAA Decimal Adjust A Decrement DIV Divide EOR #opr EOR opr EOR opr EOR opr,X EOR opr,X EOR ,X EOR opr,SP EOR opr,SP (H:X) – (M:M + 1) (X) – (M) (A)10 DBNZ opr,rel DBNZA rel DBNZX rel Decrement and Branch if Not Zero DBNZ opr,X,rel DBNZ X,rel DBNZ opr,SP,rel DEC opr DECA DECX DEC opr,X DEC ,X DEC opr,SP M ← (M) = $FF – (M) A ← (A) = $FF – (M) X ← (X) = $FF – (M) M ← (M) = $FF – (M) M ← (M) = $FF – (M) M ← (M) = $FF – (M) Exclusive OR M with A ff ee ff 4 1 1 4 3 5 65 75 ii ii+1 dd 3 4 IMM DIR EXT – – IX2 IX1 IX SP1 SP2 A3 B3 C3 D3 E3 F3 9EE3 9ED3 ii dd hh ll ee ff ff 2 3 4 4 3 2 4 5 U – – INH 72 – – IMM DIR ii dd hh ll ee ff ff A ← (A) – 1 or M ← (M) – 1 or X ← (X) – 1 PC ← (PC) + 3 + rel ? (result) ≠ 0 DIR PC ← (PC) + 2 + rel ? (result) ≠ 0 INH PC ← (PC) + 2 + rel ? (result) ≠ 0 – – – – – – INH PC ← (PC) + 3 + rel ? (result) ≠ 0 IX1 PC ← (PC) + 2 + rel ? (result) ≠ 0 IX PC ← (PC) + 4 + rel ? (result) ≠ 0 SP1 3B 4B 5B 6B 7B 9E6B M ← (M) – 1 A ← (A) – 1 X ← (X) – 1 M ← (M) – 1 M ← (M) – 1 M ← (M) – 1 DIR INH INH – – – IX1 IX SP1 A ← (H:A)/(X) H ← Remainder – – – – INH 52 A ← (A ⊕ M) IMM DIR EXT IX2 0 – – – IX1 IX SP1 SP2 A8 B8 C8 D8 E8 F8 9EE8 9ED8 ff ee ff 2 dd rr rr rr ff rr rr ff rr 3A dd 4A 5A 6A ff 7A 9E6A ff 5 3 3 5 4 6 4 1 1 4 3 5 7 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 104 Freescale Semiconductor Instruction Set Summary INC opr INCA INCX INC opr,X INC ,X INC opr,SP JMP opr JMP opr JMP opr,X JMP opr,X JMP ,X JSR opr JSR opr JSR opr,X JSR opr,X JSR ,X LDHX #opr LDHX opr Load H:X from M PC ← Jump Address DIR EXT – – – – – – IX2 IX1 IX BC CC DC EC FC dd hh ll ee ff ff 2 3 4 3 2 PC ← (PC) + n (n = 1, 2, or 3) Push (PCL); SP ← (SP) – 1 Push (PCH); SP ← (SP) – 1 PC ← Unconditional Address DIR EXT – – – – – – IX2 IX1 IX BD CD DD ED FD dd hh ll ee ff ff 4 5 6 5 4 A ← (M) IMM DIR EXT 0 – – – IX2 IX1 IX SP1 SP2 A6 B6 C6 D6 E6 F6 9EE6 9ED6 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 ii jj dd 3 4 ii dd hh ll ee ff ff 2 3 4 4 3 2 4 5 H:X ← (M:M + 1) Logical Shift Left (Same as ASL) Logical Shift Right MOV opr,opr MOV opr,X+ MOV #opr,opr MOV X+,opr Move MUL Unsigned multiply 0 – – – C b7 b7 0 DIR INH – – INH IX1 IX SP1 38 dd 48 58 68 ff 78 9E68 ff 4 1 1 4 3 5 C DIR INH INH – – 0 IX1 IX SP1 34 dd 44 54 64 ff 74 9E64 ff 4 1 1 4 3 5 b0 H:X ← (H:X) + 1 (IX+D, DIX+) DD 0 – – – DIX+ IMD IX+D X:A ← (X) × (A) – 0 – – – 0 INH M ← –(M) = $00 – (M) A ← –(A) = $00 – (A) X ← –(X) = $00 – (X) M ← –(M) = $00 – (M) M ← –(M) = $00 – (M) DIR INH INH – – IX1 IX SP1 (M)Destination ← (M)Source Negate (Two’s Complement) 45 55 4 1 1 4 3 5 AE BE CE DE EE FE 9EEE 9EDE b0 0 IMM DIR 3C dd 4C 5C 6C ff 7C 9E6C ff IMM DIR EXT 0 – – – IX2 IX1 IX SP1 SP2 X ← (M) Load X from M LSR opr LSRA LSRX LSR opr,X LSR ,X LSR opr,SP NEG opr NEGA NEGX NEG opr,X NEG ,X NEG opr,SP DIR INH INH – – – IX1 IX SP1 Jump Load A from M LSL opr LSLA LSLX LSL opr,X LSL ,X LSL opr,SP M ← (M) + 1 A ← (A) + 1 X ← (X) + 1 M ← (M) + 1 M ← (M) + 1 M ← (M) + 1 Increment Jump to Subroutine Cycles V H I N Z C LDA #opr LDA opr LDA opr LDA opr,X LDA opr,X LDA ,X LDA opr,SP LDA opr,SP LDX #opr LDX opr LDX opr LDX opr,X LDX opr,X LDX ,X LDX opr,SP LDX opr,SP Effect on CCR Description Operand Operation Opcode Source Form Address Mode Table 10-1. Instruction Set Summary (Sheet 4 of 6) 4E 5E 6E 7E ff ee ff dd dd dd ii dd dd 42 30 dd 40 50 60 ff 70 9E60 ff 5 4 4 4 5 4 1 1 4 3 5 NOP No Operation None – – – – – – INH 9D 1 NSA Nibble Swap A A ← (A[3:0]:A[7:4]) – – – – – – INH 62 3 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 105 Central Processing Unit (CPU) ORA #opr ORA opr ORA opr ORA opr,X ORA opr,X ORA ,X ORA opr,SP ORA opr,SP V H I N Z C IMM DIR EXT IX2 0 – – – IX1 IX SP1 SP2 A ← (A) | (M) Inclusive OR A and M AA BA CA DA EA FA 9EEA 9EDA ii dd hh ll ee ff ff ff ee ff Cycles Effect on CCR Description Operand Operation Opcode Source Form Address Mode Table 10-1. Instruction Set Summary (Sheet 5 of 6) 2 3 4 4 3 2 4 5 PSHA Push A onto Stack Push (A); SP ← (SP) – 1 – – – – – – INH 87 2 PSHH Push H onto Stack Push (H); SP ← (SP) – 1 – – – – – – INH 8B 2 PSHX Push X onto Stack Push (X); SP ← (SP) – 1 – – – – – – INH 89 2 PULA Pull A from Stack SP ← (SP + 1); Pull (A) – – – – – – INH 86 2 PULH Pull H from Stack SP ← (SP + 1); Pull (H) – – – – – – INH 8A 2 PULX Pull X from Stack SP ← (SP + 1); Pull (X) – – – – – – INH C DIR INH INH – – IX1 IX SP1 39 dd 49 59 69 ff 79 9E69 ff 4 1 1 4 3 5 DIR INH INH – – IX1 IX SP1 36 dd 46 56 66 ff 76 9E66 ff 4 1 1 4 3 5 ROL opr ROLA ROLX ROL opr,X ROL ,X ROL opr,SP Rotate Left through Carry b7 b0 88 2 ROR opr RORA RORX ROR opr,X ROR ,X ROR opr,SP Rotate Right through Carry RSP Reset Stack Pointer SP ← $FF – – – – – – INH 9C 1 RTI Return from Interrupt SP ← (SP) + 1; Pull (CCR) SP ← (SP) + 1; Pull (A) SP ← (SP) + 1; Pull (X) SP ← (SP) + 1; Pull (PCH) SP ← (SP) + 1; Pull (PCL) INH 80 7 RTS Return from Subroutine SP ← SP + 1; Pull (PCH) SP ← SP + 1; Pull (PCL) – – – – – – INH 81 4 A ← (A) – (M) – (C) IMM DIR EXT IX2 – – IX1 IX SP1 SP2 A2 B2 C2 D2 E2 F2 9EE2 9ED2 SBC #opr SBC opr SBC opr SBC opr,X SBC opr,X SBC ,X SBC opr,SP SBC opr,SP C b7 Subtract with Carry b0 ii dd hh ll ee ff ff ff ee ff 2 3 4 4 3 2 4 5 SEC Set Carry Bit C←1 – – – – – 1 INH 99 1 SEI Set Interrupt Mask I←1 – – 1 – – – INH 9B 2 M ← (A) DIR EXT IX2 0 – – – IX1 IX SP1 SP2 B7 C7 D7 E7 F7 9EE7 9ED7 (M:M + 1) ← (H:X) 0 – – – DIR 35 I ← 0; Stop Processing – – 0 – – – INH 8E M ← (X) DIR EXT IX2 0 – – – IX1 IX SP1 SP2 BF CF DF EF FF 9EEF 9EDF STA opr STA opr STA opr,X STA opr,X STA ,X STA opr,SP STA opr,SP Store A in M STHX opr Store H:X in M STOP Enable Interrupts, Stop Processing, Refer to MCU Documentation STX opr STX opr STX opr,X STX opr,X STX ,X STX opr,SP STX opr,SP Store X in M dd hh ll ee ff ff ff ee ff 3 4 4 3 2 4 5 dd 4 1 dd hh ll ee ff ff ff ee ff 3 4 4 3 2 4 5 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 106 Freescale Semiconductor Opcode Map SUB #opr SUB opr SUB opr SUB opr,X SUB opr,X SUB ,X SUB opr,SP SUB opr,SP SWI A0 B0 C0 D0 E0 F0 9EE0 9ED0 Software Interrupt PC ← (PC) + 1; Push (PCL) SP ← (SP) – 1; Push (PCH) SP ← (SP) – 1; Push (X) SP ← (SP) – 1; Push (A) SP ← (SP) – 1; Push (CCR) SP ← (SP) – 1; I ← 1 PCH ← Interrupt Vector High Byte PCL ← Interrupt Vector Low Byte – – 1 – – – INH 83 9 CCR ← (A) INH 84 2 X ← (A) – – – – – – INH 97 1 A ← (CCR) – – – – – – INH 85 (A) – $00 or (X) – $00 or (M) – $00 DIR INH 0 – – – INH IX1 IX SP1 H:X ← (SP) + 1 – – – – – – INH 95 2 A ← (X) – – – – – – INH 9F 1 (SP) ← (H:X) – 1 – – – – – – INH 94 2 I bit ← 0; Inhibit CPU clocking until interrupted – – 0 – – – INH 8F 1 A ← (A) – (M) Subtract Transfer A to CCR Transfer A to X TPA Transfer CCR to A Test for Negative or Zero TSX Transfer SP to H:X TXA Transfer X to A TXS Transfer H:X to SP 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 2 3 4 4 3 2 4 5 IMM DIR EXT IX2 – – IX1 IX SP1 SP2 TAP WAIT ii dd hh ll ee ff ff Cycles V H I N Z C TAX TST opr TSTA TSTX TST opr,X TST ,X TST opr,SP Effect on CCR Description Operand Operation Opcode Source Form Address Mode Table 10-1. Instruction Set Summary (Sheet 6 of 6) Enable Interrupts; Wait for Interrupt Accumulator Carry/borrow bit Condition code register Direct address of operand Direct address of operand and relative offset of branch instruction Direct to direct addressing mode Direct addressing mode Direct to indexed with post increment addressing mode High and low bytes of offset in indexed, 16-bit offset addressing Extended addressing mode Offset byte in indexed, 8-bit offset addressing Half-carry bit Index register high byte High and low bytes of operand address in extended addressing Interrupt mask Immediate operand byte Immediate source to direct destination addressing mode Immediate addressing mode Inherent addressing mode Indexed, no offset addressing mode Indexed, no offset, post increment addressing mode Indexed with post increment to direct addressing mode Indexed, 8-bit offset addressing mode Indexed, 8-bit offset, post increment addressing mode Indexed, 16-bit offset addressing mode Memory location Negative bit n opr PC PCH PCL REL rel rr SP1 SP2 SP U V X Z & | ⊕ () –( ) # « ← ? : — ff ee ff 3D dd 4D 5D 6D ff 7D 9E6D ff 1 3 1 1 3 2 4 Any bit Operand (one or two bytes) Program counter Program counter high byte Program counter low byte Relative addressing mode Relative program counter offset byte Relative program counter offset byte Stack pointer, 8-bit offset addressing mode Stack pointer 16-bit offset addressing mode Stack pointer Undefined Overflow bit Index register low byte Zero bit Logical AND Logical OR Logical EXCLUSIVE OR Contents of Negation (two’s complement) Immediate value Sign extend Loaded with If Concatenated with Set or cleared Not affected 10.7 Opcode Map See Table 10-2. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 107 MSB Branch REL DIR INH 3 4 0 1 2 5 BRSET0 3 DIR 5 BRCLR0 3 DIR 5 BRSET1 3 DIR 5 BRCLR1 3 DIR 5 BRSET2 3 DIR 5 BRCLR2 3 DIR 5 BRSET3 3 DIR 5 BRCLR3 3 DIR 5 BRSET4 3 DIR 5 BRCLR4 3 DIR 5 BRSET5 3 DIR 5 BRCLR5 3 DIR 5 BRSET6 3 DIR 5 BRCLR6 3 DIR 5 BRSET7 3 DIR 5 BRCLR7 3 DIR 4 BSET0 2 DIR 4 BCLR0 2 DIR 4 BSET1 2 DIR 4 BCLR1 2 DIR 4 BSET2 2 DIR 4 BCLR2 2 DIR 4 BSET3 2 DIR 4 BCLR3 2 DIR 4 BSET4 2 DIR 4 BCLR4 2 DIR 4 BSET5 2 DIR 4 BCLR5 2 DIR 4 BSET6 2 DIR 4 BCLR6 2 DIR 4 BSET7 2 DIR 4 BCLR7 2 DIR 3 BRA 2 REL 3 BRN 2 REL 3 BHI 2 REL 3 BLS 2 REL 3 BCC 2 REL 3 BCS 2 REL 3 BNE 2 REL 3 BEQ 2 REL 3 BHCC 2 REL 3 BHCS 2 REL 3 BPL 2 REL 3 BMI 2 REL 3 BMC 2 REL 3 BMS 2 REL 3 BIL 2 REL 3 BIH 2 REL Read-Modify-Write INH IX1 5 6 1 NEGX 1 INH 4 CBEQX 3 IMM 7 DIV 1 INH 1 COMX 1 INH 1 LSRX 1 INH 4 LDHX 2 DIR 1 RORX 1 INH 1 ASRX 1 INH 1 LSLX 1 INH 1 ROLX 1 INH 1 DECX 1 INH 3 DBNZX 2 INH 1 INCX 1 INH 1 TSTX 1 INH 4 MOV 2 DIX+ 1 CLRX 1 INH 4 NEG 2 IX1 5 CBEQ 3 IX1+ 3 NSA 1 INH 4 COM 2 IX1 4 LSR 2 IX1 3 CPHX 3 IMM 4 ROR 2 IX1 4 ASR 2 IX1 4 LSL 2 IX1 4 ROL 2 IX1 4 DEC 2 IX1 5 DBNZ 3 IX1 4 INC 2 IX1 3 TST 2 IX1 4 MOV 3 IMD 3 CLR 2 IX1 SP1 IX 9E6 7 Control INH INH 8 9 Register/Memory IX2 SP2 IMM DIR EXT A B C D 9ED 4 SUB 3 EXT 4 CMP 3 EXT 4 SBC 3 EXT 4 CPX 3 EXT 4 AND 3 EXT 4 BIT 3 EXT 4 LDA 3 EXT 4 STA 3 EXT 4 EOR 3 EXT 4 ADC 3 EXT 4 ORA 3 EXT 4 ADD 3 EXT 3 JMP 3 EXT 5 JSR 3 EXT 4 LDX 3 EXT 4 STX 3 EXT 4 SUB 3 IX2 4 CMP 3 IX2 4 SBC 3 IX2 4 CPX 3 IX2 4 AND 3 IX2 4 BIT 3 IX2 4 LDA 3 IX2 4 STA 3 IX2 4 EOR 3 IX2 4 ADC 3 IX2 4 ORA 3 IX2 4 ADD 3 IX2 4 JMP 3 IX2 6 JSR 3 IX2 4 LDX 3 IX2 4 STX 3 IX2 5 SUB 4 SP2 5 CMP 4 SP2 5 SBC 4 SP2 5 CPX 4 SP2 5 AND 4 SP2 5 BIT 4 SP2 5 LDA 4 SP2 5 STA 4 SP2 5 EOR 4 SP2 5 ADC 4 SP2 5 ORA 4 SP2 5 ADD 4 SP2 IX1 SP1 IX E 9EE F LSB 0 1 2 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 3 4 5 6 7 8 9 A B C D E Freescale Semiconductor F 4 1 NEG NEGA 2 DIR 1 INH 5 4 CBEQ CBEQA 3 DIR 3 IMM 5 MUL 1 INH 4 1 COM COMA 2 DIR 1 INH 4 1 LSR LSRA 2 DIR 1 INH 4 3 STHX LDHX 2 DIR 3 IMM 4 1 ROR RORA 2 DIR 1 INH 4 1 ASR ASRA 2 DIR 1 INH 4 1 LSL LSLA 2 DIR 1 INH 4 1 ROL ROLA 2 DIR 1 INH 4 1 DEC DECA 2 DIR 1 INH 5 3 DBNZ DBNZA 3 DIR 2 INH 4 1 INC INCA 2 DIR 1 INH 3 1 TST TSTA 2 DIR 1 INH 5 MOV 3 DD 3 1 CLR CLRA 2 DIR 1 INH INH Inherent REL Relative IMM Immediate IX Indexed, No Offset DIR Direct IX1 Indexed, 8-Bit Offset EXT Extended IX2 Indexed, 16-Bit Offset DD Direct-Direct IMD Immediate-Direct IX+D Indexed-Direct DIX+ Direct-Indexed *Pre-byte for stack pointer indexed instructions 5 3 NEG NEG 3 SP1 1 IX 6 4 CBEQ CBEQ 4 SP1 2 IX+ 2 DAA 1 INH 5 3 COM COM 3 SP1 1 IX 5 3 LSR LSR 3 SP1 1 IX 4 CPHX 2 DIR 5 3 ROR ROR 3 SP1 1 IX 5 3 ASR ASR 3 SP1 1 IX 5 3 LSL LSL 3 SP1 1 IX 5 3 ROL ROL 3 SP1 1 IX 5 3 DEC DEC 3 SP1 1 IX 6 4 DBNZ DBNZ 4 SP1 2 IX 5 3 INC INC 3 SP1 1 IX 4 2 TST TST 3 SP1 1 IX 4 MOV 2 IX+D 4 2 CLR CLR 3 SP1 1 IX SP1 Stack Pointer, 8-Bit Offset SP2 Stack Pointer, 16-Bit Offset IX+ Indexed, No Offset with Post Increment IX1+ Indexed, 1-Byte Offset with Post Increment 7 3 RTI BGE 1 INH 2 REL 4 3 RTS BLT 1 INH 2 REL 3 BGT 2 REL 9 3 SWI BLE 1 INH 2 REL 2 2 TAP TXS 1 INH 1 INH 1 2 TPA TSX 1 INH 1 INH 2 PULA 1 INH 2 1 PSHA TAX 1 INH 1 INH 2 1 PULX CLC 1 INH 1 INH 2 1 PSHX SEC 1 INH 1 INH 2 2 PULH CLI 1 INH 1 INH 2 2 PSHH SEI 1 INH 1 INH 1 1 CLRH RSP 1 INH 1 INH 1 NOP 1 INH 1 STOP * 1 INH 1 1 WAIT TXA 1 INH 1 INH 2 SUB 2 IMM 2 CMP 2 IMM 2 SBC 2 IMM 2 CPX 2 IMM 2 AND 2 IMM 2 BIT 2 IMM 2 LDA 2 IMM 2 AIS 2 IMM 2 EOR 2 IMM 2 ADC 2 IMM 2 ORA 2 IMM 2 ADD 2 IMM 3 SUB 2 DIR 3 CMP 2 DIR 3 SBC 2 DIR 3 CPX 2 DIR 3 AND 2 DIR 3 BIT 2 DIR 3 LDA 2 DIR 3 STA 2 DIR 3 EOR 2 DIR 3 ADC 2 DIR 3 ORA 2 DIR 3 ADD 2 DIR 2 JMP 2 DIR 4 4 BSR JSR 2 REL 2 DIR 2 3 LDX LDX 2 IMM 2 DIR 2 3 AIX STX 2 IMM 2 DIR MSB 0 3 SUB 2 IX1 3 CMP 2 IX1 3 SBC 2 IX1 3 CPX 2 IX1 3 AND 2 IX1 3 BIT 2 IX1 3 LDA 2 IX1 3 STA 2 IX1 3 EOR 2 IX1 3 ADC 2 IX1 3 ORA 2 IX1 3 ADD 2 IX1 3 JMP 2 IX1 5 JSR 2 IX1 5 3 LDX LDX 4 SP2 2 IX1 5 3 STX STX 4 SP2 2 IX1 4 SUB 3 SP1 4 CMP 3 SP1 4 SBC 3 SP1 4 CPX 3 SP1 4 AND 3 SP1 4 BIT 3 SP1 4 LDA 3 SP1 4 STA 3 SP1 4 EOR 3 SP1 4 ADC 3 SP1 4 ORA 3 SP1 4 ADD 3 SP1 2 SUB 1 IX 2 CMP 1 IX 2 SBC 1 IX 2 CPX 1 IX 2 AND 1 IX 2 BIT 1 IX 2 LDA 1 IX 2 STA 1 IX 2 EOR 1 IX 2 ADC 1 IX 2 ORA 1 IX 2 ADD 1 IX 2 JMP 1 IX 4 JSR 1 IX 4 2 LDX LDX 3 SP1 1 IX 4 2 STX STX 3 SP1 1 IX High Byte of Opcode in Hexadecimal LSB Low Byte of Opcode in Hexadecimal 0 5 Cycles BRSET0 Opcode Mnemonic 3 DIR Number of Bytes / Addressing Mode Central Processing Unit (CPU) 108 Table 10-2. Opcode Map Bit Manipulation DIR DIR Chapter 11 Flash Memory 11.1 Introduction This section describes the operation of the embedded FLASH memory. This memory can be read, programmed, and erased from a single external supply. The program, erase, and read operations are enabled through the use of an internal charge pump. 11.2 Functional Description The FLASH memory is an array of 7,680 bytes for the MC68HC908GR8 or 4,096 bytes for the MC68HC908GR4 with an additional 36 bytes of user vectors and one byte used for block protection. An erased bit reads as 1 and a programmed bit reads as a 0. The program and erase operations are facilitated through control bits in the Flash Control Register (FLCR). Details for these operations appear later in this section. The FLASH is organized internally as a 8192-word by 8-bit CMOS page erase, byte (8-bit) program Embedded Flash Memory. Each page consists of 64 bytes. The page erase operation erases all words within a page. A page is composed of two adjacent rows. The address ranges for the user memory and vectors are as follows: • $E000–$FDFF; user memory for the MC68HC908GR8 $EE00–$FDFF; user memory for the MC68HC908GR4. • $FF7E; FLASH block protect register. • $FE08; FLASH control 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 109 Flash Memory 11.3 FLASH Control Register The FLASH control register (FLCR) controls FLASH program and erase operations. Address: Read: $FE08 Bit 7 6 5 4 0 0 0 0 0 0 0 0 Write: Reset: 3 2 1 Bit 0 HVEN MASS ERASE PGM 0 0 0 0 = Unimplemented Figure 11-1. FLASH Control Register (FLCR) HVEN — High-Voltage Enable Bit This read/write bit enables the charge pump to drive high voltages for program and erase operations in the array. HVEN can only be set if either PGM = 1 or ERASE = 1 and the proper sequence for program or erase is followed. 1 = High voltage enabled to array and charge pump on 0 = High voltage disabled to array and charge pump off MASS — Mass Erase Control Bit Setting this read/write bit configures the 8K byte FLASH array for mass erase operation. 1 = MASS erase operation selected 0 = MASS erase operation unselected ERASE — Erase Control Bit This read/write bit configures the memory for erase operation. ERASE is interlocked with the PGM bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = Erase operation selected 0 = Erase operation unselected PGM — Program Control Bit This read/write bit configures the memory for program operation. PGM is interlocked with the ERASE bit such that both bits cannot be equal to 1 or set to 1 at the same time. 1 = Program operation selected 0 = Program operation unselected 11.4 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 user interrupt vector 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 address within the page address range desired. 4. Wait for a time, tnvs (min. 10μs) 5. Set the HVEN bit. 6. Wait for a time, tErase (min. 1ms) 7. Clear the ERASE bit. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 110 Freescale Semiconductor FLASH Mass Erase Operation 8. Wait for a time, tnvh (min. 5μs) 9. Clear the HVEN bit. 10. After a time, trcv (typ. 1μs), the memory can be accessed again in read mode. NOTE While these operations must be performed in the order shown, other unrelated operations may occur between the steps. 11.5 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 from 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 (min. 10μs) 5. Set the HVEN bit. 6. Wait for a time, tMErase (min. 4ms) 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 (min. 100μs) 9. Clear the HVEN bit. 10. After a time, trcv (typical 1μs), the memory can be accessed again in read mode. NOTE Programming and erasing of FLASH locations cannot be performed by code being executed from the FLASH memory. While these operations must be performed in the order shown, other unrelated operations may occur between the steps. 11.6 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 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 11-2 is a flowchart representation): NOTE Only bytes which are currently $FF may be programmed. 1. When in Monitor mode, with security sequence failed see Chapter 15 Monitor ROM (MON), write to the FLASH block protect register instead of any FLASH address. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 111 Flash Memory 1. Set the PGM bit. This configures the memory for program operation and enables the latching of address and data for programming. 2. Read from the FLASH block protect register. 3. Write any data to any FLASH address within the row address range desired. 4. Wait for a time, tnvs (min. 10μs). 5. Set the HVEN bit. 6. Wait for a time, tpgs (min. 5μs). 7. Write data to the FLASH address to be programmed. 8. Wait for a time, tPROG (min. 30μs). 9. Repeat step 7 and 8 until all the bytes within the row are programmed. 10. Clear the PGM bit.* 11. Wait for a time, tnvh (min. 5μs). 12. Clear the HVEN bit. 13. After time, trcv (typical 1μs), 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 cannot be performed by code being executed from the FLASH memory. While these operations must be performed in the order shown, other unrelated operations may occur between the steps. 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. 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 23.16 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 112 Freescale Semiconductor FLASH Program/Read Operation 1 Algorithm for programming a row (32 bytes) of FLASH memory 2 3 4 5 6 7 8 Set PGM bit Read the FLASH block protect register Write any data to any FLASH address within the row address range desired Wait for a time, tnvs Set HVEN bit Wait for a time, tpgs Write data to the FLASH address to be programmed Wait for a time, tPROG Completed programming this row? Y N NOTE: The time between each FLASH address change (step 7 to step 7), or the time between the last FLASH address programmed to clearing PGM bit (step 7 to step 10) must not exceed the maximum programming time, tPROG max. 10 Clear PGM bit 11 Wait for a time, tnvh 12 Clear HVEN bit 13 Wait for a time, trcv This row program algorithm assumes the row/s to be programmed are initially erased. End of programming Figure 11-2. FLASH Programming Flowchart MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 113 Flash Memory 11.7 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 programmed with all 0s, the entire memory is protected from being programmed and erased. When all the bits are erased (all 1s), the entire memory is accessible for program and erase. When bits within the FLBPR are programmed, they lock a block of memory with address ranges as shown in FLASH Block Protect Register. Once the FLBPR is programmed with a value other than $FF, any erase or program of the FLBPR or the protected block of FLASH memory is prohibited. Mass erase is disabled whenever any block is protected (FLBPR does not equal $FF). The 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 operation. 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. 11.7.1 FLASH Block Protect Register The FLASH block protect register (FLBPR) is implemented as a byte within the FLASH memory, and therefore can only be written during a programming sequence of the FLASH memory. The value in this register determines the starting location of the protected range within the FLASH memory. Address: Read: Write: Reset: $FF7E Bit 7 6 5 4 3 2 1 Bit 0 BPR7 BPR6 BPR5 BPR4 BPR3 BPR2 BPR1 BPR0 U U U U U U U U U = Unaffected by reset. Initial value from factory is 1. Write to this register is by a programming sequence to the FLASH memory. Figure 11-3. 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. Bits [15:14] are 1s and bits [5:0] are 0s. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 114 Freescale Semiconductor Wait Mode 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 block protect 1 1 FLBPR value 0 0 0 0 0 0 Figure 11-4. FLASH Block Protect Start Address Examples of protect start address: Table 11-1. Examples of Protect Start Address BPR[7:0] Start of Address of Protect Range $80 The entire FLASH memory is protected. $81 (1000 0001) $E040 (1110 0000 0100 0000) $82 (1000 0010) $E080 (1110 0000 1000 0000) and so on... $FE (1111 1110) $FF80 (1111 1111 1000 0000) $FF The entire FLASH memory is not protected. Note: The end address of the protected range is always $FFFF. 11.8 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. 11.9 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 115 Flash Memory MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 116 Freescale Semiconductor Chapter 12 External Interrupt (IRQ) 12.1 Introduction The IRQ (external interrupt) module provides a maskable interrupt input. 12.2 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 12.3 Functional Description A logic 0 applied to the external interrupt pin can latch a CPU interrupt request. Figure 12-1 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 logic 1 to the ACK bit clears the IRQ latch. • Reset — A reset automatically clears the interrupt latch. The external interrupt pin is falling-edge-triggered 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 117 External Interrupt (IRQ) ACK RESET TO CPU FOR BIL/BIH INSTRUCTIONS INTERNAL ADDRESS BUS VECTOR FETCH DECODER VDD INTERNAL PULLUP DEVICE VDD IRQF D IRQ CLR Q CK SYNCHRONIZER IRQ INTERRUPT REQUEST HIGH VOLTAGE DETECT TO MODE SELECT LOGIC IRQ FF IMASK MODE Figure 12-1. IRQ Module Block Diagram Addr. Register Name Bit 7 6 5 4 3 2 0 0 0 0 IRQF 0 Read: $001D IRQ Status and Control Write: Register (INTSCR) Reset: ACK 0 0 0 0 0 0 1 Bit 0 IMASK MODE 0 0 = Unimplemented Figure 12-2. IRQ I/O Register Summary When an interrupt pin is both falling-edge and low-level-triggered, the interrupt remains set until both of the following occur: • Vector fetch or software clear • Return of the interrupt pin to high level The vector fetch or software clear may occur before or after the interrupt pin returns to 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 mask 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 118 Freescale Semiconductor IRQ Pin 12.4 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 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 at a low level, 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. 12.5 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 6 Break Module (BRK). 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 119 External Interrupt (IRQ) 12.6 IRQ Status and Control Register The IRQ status and control register (INTSCR) controls and monitors operation of the IRQ module. The INTSCR: • Shows the state of the IRQ flag • Clears the IRQ latch • Masks IRQ interrupt request • Controls triggering sensitivity of the IRQ interrupt pin Address: Read: $001D Bit 7 6 5 4 3 2 0 0 0 0 IRQF 0 Write: Reset: ACK 0 0 0 0 0 0 1 Bit 0 IMASK MODE 0 0 = Unimplemented Figure 12-3. 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 logic 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 120 Freescale Semiconductor Chapter 13 Keyboard Interrupt (KBI) 13.1 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. 13.2 Features • • • • • 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) 13.3 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. INTERNAL BUS KBD0 ACKK VDD VECTOR FETCH DECODER KEYF RESET . TO PULLUP ENABLE D CLR Q SYNCHRONIZER . CK KB0IE KEYBOARD INTERRUPT REQUEST . KEYBOARD INTERRUPT FF KBD3 IMASKK MODEK TO PULLUP ENABLE KB3IE Figure 13-1. Keyboard Module Block Diagram MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 121 Keyboard Interrupt (KBI) Addr. $001A $001B Register Name Bit 7 6 5 4 3 2 Read: Keyboard Status and Control Register Write: (INTKBSCR) Reset: 0 0 0 0 KEYF 0 0 0 0 0 Read: Keyboard Interrupt Enable Write: Register (INTKBIER) Reset: 0 0 0 0 1 Bit 0 IMASKK MODEK ACKK 0 0 0 0 KBIE3 KBIE2 KBIE1 KBIE0 0 0 0 0 = Unimplemented Figure 13-2. I/O Register Summary 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. 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. The vector fetch or software clear and the return of all enabled keyboard interrupt pins to a high level may occur in any order. If the MODEK bit is clear, the keyboard interrupt pin is falling-edge-sensitive only. With MODEK clear, a vector fetch or software clear immediately clears the keyboard interrupt request. Reset clears the keyboard interrupt request and the MODEK bit, clearing the interrupt request even if a keyboard interrupt pin stays low. The keyboard flag bit (KEYF) in the keyboard status and control register can be used to see if a pending interrupt exists. The KEYF bit is not affected by the keyboard interrupt mask bit (IMASKK) which makes it useful in applications where polling is preferred. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 122 Freescale Semiconductor Keyboard Initialization 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. 13.4 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 is: 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. 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 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. 13.5.2 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. 13.6 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 SIM break flag control register (SBFCR) enables software to clear status bits during the break state. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 123 Keyboard Interrupt (KBI) 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 logic 0 to the BCFE bit. With BCFE at logic 0 (its default state), writing to the keyboard acknowledge bit (ACKK) in the keyboard status and control register during the break state has no effect. See 13.7.1 Keyboard Status and Control Register. 13.7 I/O Registers These registers control and monitor operation of the keyboard module: • Keyboard status and control register (INTKBSCR) • Keyboard interrupt enable register (INTKBIER) 13.7.1 Keyboard Status and Control Register The keyboard status and control register: • Flags keyboard interrupt requests • Acknowledges keyboard interrupt requests • Masks keyboard interrupt requests • Controls keyboard interrupt triggering sensitivity Address: $001A Read: Bit 7 6 5 4 3 0 0 0 0 KEYF Write: Reset: 2 0 ACKK 0 0 0 0 0 0 1 Bit 0 IMASKK MODEK 0 0 = Unimplemented Figure 13-3. Keyboard Status and Control Register (INTKBSCR) Bits 7–4 — Not used These read-only bits always read as logic 0s. KEYF — Keyboard Flag Bit This read-only bit is set when a keyboard interrupt is pending. Reset clears the KEYF bit. 1 = Keyboard interrupt pending 0 = No keyboard interrupt pending ACKK — Keyboard Acknowledge Bit Writing a 1 to this write-only bit clears the keyboard interrupt request. ACKK always reads as logic 0. Reset clears ACKK. IMASKK — Keyboard Interrupt Mask Bit Writing a 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 124 Freescale Semiconductor I/O Registers 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 13.7.2 Keyboard Interrupt Enable Register The keyboard interrupt enable register enables or disables each port A pin to operate as a keyboard interrupt pin. Address: $001B Read: Bit 7 6 5 4 0 0 0 0 Write: Reset: 3 2 1 Bit 0 KBIE3 KBIE2 KBIE1 KBIE0 0 0 0 0 = Unimplemented Figure 13-4. 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 125 Keyboard Interrupt (KBI) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 126 Freescale Semiconductor Chapter 14 Low-Voltage Inhibit (LVI) 14.1 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. 14.2 Features Features of the LVI module include: • Programmable LVI reset • Selectable LVI trip voltage • Programmable stop mode operation 14.3 Functional Description Figure 14-1 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 the trip point voltage, VTRIPF. Setting the LVI enable in stop mode bit, LVISTOP, enables the LVI to operate in stop mode. Setting the LVI 5V or 3V trip point bit, LVI5OR3, enables VTRIPF to be configured for 5V operation. Clearing the LVI5OR3 bit enables VTRIPF to be configured for 3V operation. The actual trip points are shown in Chapter 23 Electrical Specifications. NOTE After a power-on reset (POR) the LVI’s default mode of operation is 3 V. If a 5V system is used, the user must set the LVI5OR3 bit to raise the trip point to 5V operation. Note that this must be done after every POR since the default will revert back to 3V mode after each POR. If the VDD supply is below the 5V mode trip voltage but above the 3V mode trip voltage when POR is released, the part will operate because VTRIPF defaults to 3V mode after a POR. So, in a 5V system care must be taken to ensure that VDD is above the 5V mode trip voltage after POR is released. If the user requires 5V mode and sets the LVI5OR3 bit after a POR while the VDD supply is not above the VTRIPR for 5V mode, the MCU will immediately go into reset. The LVI in this case will hold the part in reset until either VDD goes above the rising 5V trip point, VTRIPR, which will release reset or VDD decreases to approximately 0 V which will re-trigger the POR and reset the trip point to 3V operation. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 127 Low-Voltage Inhibit (LVI) LVISTOP, LVIPWRD, LVI5OR3, and LVIRSTD are in the configuration register (CONFIG). See Chapter 8 Configuration Register (CONFIG) for details of the LVI’s configuration bits. Once an LVI reset occurs, the MCU remains in reset until VDD rises above a voltage, VTRIPR, which causes the MCU to exit reset. See 19.3.2.5 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 CONFIG FROM CONFIG LVIRSTD LVIPWRD FROM CONFIG VDD > LVITrip = 0 LOW VDD DETECTOR LVI RESET VDD ≤ LVITrip = 1 LVIOUT LVI5OR3 FROM CONFIG Figure 14-1. LVI Module Block Diagram Addr. $FE0C Register Name Read: LVI Status Register Write: (LVISR) Reset: Bit 7 LVIOUT 0 6 0 5 0 4 0 3 0 2 0 1 0 Bit 0 0 0 0 0 0 0 0 0 = Unimplemented Figure 14-2. LVI I/O Register Summary 14.3.1 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 1 to disable LVI resets. 14.3.2 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. 14.3.3 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 128 Freescale Semiconductor LVI Status Register 14.3.4 LVI Trip Selection The LVI5OR3 bit in the configuration register selects whether the LVI is configured for 5V or 3V 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 23 Electrical Specifications for the actual trip point voltages.) 14.4 LVI Status Register The LVI status register (LVISR) indicates if the VDD voltage was detected below the VTRIPF level. Address: $FE0C Bit 7 6 5 4 3 2 1 Bit 0 Read: LVIOUT 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 Write: Reset: = Unimplemented Figure 14-3. 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 14-1. Reset clears the LVIOUT bit. Table 14-1. LVIOUT Bit Indication VDD LVIOUT VDD > VTRIPR 0 VDD < VTRIPF 1 VTRIPF < VDD < VTRIPR Previous value 14.5 LVI Interrupts The LVI module does not generate interrupt requests. 14.6 Low-Power Modes The STOP and WAIT instructions put the MCU in low power-consumption standby modes. 14.6.1 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. 14.6.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 129 Low-Voltage Inhibit (LVI) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 130 Freescale Semiconductor Chapter 15 Monitor ROM (MON) 15.1 Introduction This section describes the monitor ROM (MON) and the monitor mode entry methods. The monitor ROM allows complete testing of the 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 $FFFF are blank, thus reducing the hardware requirements for in-circuit programming. 15.2 Features Features of the monitor ROM include: • Normal user-mode pin functionality • One pin dedicated to serial communication between monitor ROM and host computer • Standard mark/space non-return-to-zero (NRZ) communication with host computer • Execution of code in RAM or FLASH • FLASH memory security feature(1) • FLASH memory programming interface • Enhanced PLL (phase-locked loop) option to allow use of external 32.768-kHz crystal to generate internal frequency of 2.4576 MHz • 310 byte monitor ROM code size ($FE20 to $FF55) • Monitor mode entry without high voltage, VTST, if reset vector is blank ($FFFE and $FFFF contain $FF) • Standard monitor mode entry if high voltage, VTST, is applied to IRQ 15.3 Functional Description The monitor ROM receives and executes commands from a host computer. Figure 15-1 shows an example circuit used to enter monitor mode and communicate with a host computer via a standard RS-232 interface. Simple monitor commands can access any memory address. In monitor mode, the MCU can execute 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. 1. No security feature is absolutely secure. However, Freescale’s strategy is to make reading or copying the FLASH difficult for unauthorized users. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 131 Monitor ROM (MON) 68HC08 RST 0.1 μF (SEE NOTE 3) VTST 10 kΩ C SW2 (SEE NOTES 2 AND 3) IRQ VDDA D VDDA CGMXFC 0.01 μF 10 k 0.033 μF SW3 (SEE NOTE 2) C 10 μF + 3 MC145407 20 + 10 μF 18 C 32.768 kHz XTAL 4 10 μF 17 330 kΩ + + 2 19 DB-25 2 5 16 3 6 15 10 μF VDD OSC1 D 10 MΩ 1 6–30 pF D OSC2 PTA1 SW4 (SEE NOTE 2) 10 kΩ VSS 6–30 pF VSSAD/VREFL VSSA VDD VDD VDDAD/VREFH 0.1 μF 7 VDD 1 MC74HC125 14 2 3 6 5 VDD 10 kΩ PTA0 4 7 VDD 10 kΩ PTB0 PTB1 10 kΩ Notes: 1. SW2, SW3, and SW4: Position C — Enter monitor mode using external oscillator. SW2, SW3, and SW4: Position D — Enter monitor mode using external XTAL and internal PLL. 2. See Table 15-1. Monitor Mode Signal Requirements and Options for IRQ voltage level requirements. Figure 15-1. Monitor Mode Circuit MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 132 Freescale Semiconductor Functional Description The monitor code has been updated from previous versions to allow enabling the PLL to generate the internal clock, provided the reset vector is blank, when the device is being clocked by a low-frequency crystal. This addition, which is enabled when IRQ is held low out of rest, is intended to support serial communication/ programming at 9600 baud in monitor mode by stepping up the external frequency (assumed to be 32.768 kHz) by a fixed amount to generate the desired internal frequency (2.4576 MHz). Since this feature is enabled only when IRQ is held low out of reset, it cannot be used when the reset vector is not blank because entry into monitor mode in this case requires VTST on IRQ. 15.3.1 Entering Monitor Mode Table 15-1 shows the pin conditions for entering monitor mode. As specified in the table, monitor mode may 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: 1. If $FFFE and $FFFF contain values not cared: – The external clock is 9.8304 MHz – IRQ = VTST (PLL off) 2. If $FFFE and $FFFF contain $FF, blank state: – The external clock is 9.8304 MHz – IRQ = VDD (this can be implemented through the internal IRQ pullup; PLL off) 3. If $FFFE and $FFFF contain $FF, blank state: – The external clock is 32.768 kHz (crystal) – IRQ = VSS (this setting initiates the PLL to boost the external 32.768 kHz to an internal bus frequency of 2.4576 MHz) If entering monitor mode with VTST applied on IRQ (condition set 1), the CGMOUT frequency is equal to the CGMXCLK frequency and the OSC1 input directly generates internal bus clocks. In this case, the OSC1 signal must have a 50% duty cycle at maximum bus frequency. If entering monitor mode without high voltage applied on IRQ (condition set 2 or 3, where applied voltage is either VDD or VSS), then 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 POR reset. Once the part has been programmed, the traditional method of applying a voltage, VTST, to IRQ must be used to enter monitor mode. The COP module is disabled in monitor mode based on these conditions: • If monitor mode was entered as a result of the reset vector being blank (condition set 2 or 3), the COP is always disabled regardless of the state of IRQ or RST. • If monitor mode was entered with VTST on IRQ (condition set 1), then the COP is disabled as long as VTST is applied to either IRQ or RST. The second 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 133 Monitor ROM (MON) Table 15-1. Monitor Mode Signal Requirements and Options IRQ $FFFE/ RESET $FFFF X PLL X GND X VTST VDD or VTST X OFF VDD VDD $FFFF GND VDD $FFFF PTB0 PTB1 X External Clock(1) CGMOUT Bus Freq 0 For Serial Communication COP PTA0 PTA1 X X 0 Disabled 1 0 9.8304 MHz 4.9152 MHz 2.4576 Disabled MHz OFF X X 9.8304 MHz 4.9152 MHz 2.4576 Disabled MHz ON X X 32.768 kHz 4.9152 MHz 2.4576 Disabled MHz Baud Comment Rate(2) (3) X X 0 1 0 9600 X 1 DNA 1 0 9600 X 1 DNA 1 0 9600 X 1 DNA No operation until reset goes high PTB0 and PTB1 voltages only required if IRQ = VTST External frequency always divided by 4 PLL enabled (BCS set) in monitor code VDD or GND VTST $FFFF OFF X X X — — Enabled X X — Enters user mode — will encounter an illegal address reset VDD or GND VDD or VTST Not $FFFF OFF X X X — — Enabled X X — Enters user mode 1. External clock is derived by a 32.768 kHz crystal or a 9.8304 MHz off-chip oscillator 2. PTA0 = 1 if serial communication; PTA0 = X if parallel communication 3. PTA1 = 0 → serial, PTA1 = 1 → parallel communication for security code entry 4. DNA = does not apply, X = don’t care Figure 15-2 shows a simplified diagram of the monitor mode entry when the reset vector is blank and just 1 x VDD voltage is applied to the IRQ pin. 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. Enter monitor mode with pin configuration shown in Figure 15-1 by pulling RST low and then high. The rising edge of RST latches monitor mode. Once monitor mode is latched, the values on the specified pins can change. Once out of reset, the MCU waits for the host to send eight security bytes. (See Security.) After the security bytes, the MCU sends a break signal (10 consecutive logic 0s) to the host, indicating that it is ready to receive a command. NOTE The PTA1 pin must remain at logic 0 for 24 bus cycles after the RST pin goes high to enter monitor mode properly. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 134 Freescale Semiconductor Functional Description POR RESET IS VECTOR BLANK? NO NORMAL USER MODE YES MONITOR MODE EXECUTE MONITOR CODE POR TRIGGERED? NO YES Figure 15-2. Low-Voltage Monitor Mode Entry Flowchart 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. NOTE Exiting monitor mode after it has been initiated by having a blank reset vector requires a power-on reset. Pulling RST low will not exit monitor mode in this situation. Table 15-2 summarizes the differences between user mode and monitor mode. Table 15-2. Mode Differences Functions Modes Reset Vector High Reset Vector Low Break Vector High Break Vector Low SWI Vector High SWI Vector Low User $FFFE $FFFF $FFFC $FFFD $FFFC $FFFD Monitor $FEFE $FEFF $FEFC $FEFD $FEFC $FEFD MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 135 Monitor ROM (MON) 15.3.2 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 0 BIT BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 BIT 6 BIT 7 NEXT START STOP BIT BIT Figure 15-3. Monitor Data Format 15.3.3 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 two bits and then echoes back the break signal. MISSING STOP BIT 2-STOP BIT DELAY BEFORE ZERO ECHO 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Figure 15-4. Break Transaction 15.3.4 Baud Rate The communication baud rate is controlled by the crystal frequency upon entry into monitor mode. The divide by ratio is 1024. If monitor mode was entered with VDD on IRQ, then the divide by ratio is also set at 1024. If monitor mode was entered with VSS on IRQ, then the internal PLL steps up the external frequency, presumed to be 32.768 kHz, to 2.4576 MHz. These latter two conditions for monitor mode entry require that the reset vector is blank. Table 15-3 lists external frequencies required to achieve a standard baud rate of 9600 BPS. Other standard baud rates can be accomplished using proportionally higher or lower frequency generators. If using a crystal as the clock source, be aware of the upper frequency limit that the internal clock module can handle. See 23.6 5.0 V Control Timing and 23.7 3.0 V Control Timing for this limit. Table 15-3. Monitor Baud Rate Selection External Frequency IRQ Internal Frequency Baud Rate (BPS) 9.8304 MHz VTST 2.4576 MHz 9600 9.8304 MHz VDD 2.4576 MHz 9600 32.768 kHz VSS 2.4576 MHz 9600 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 136 Freescale Semiconductor Functional Description 15.3.5 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. FROM HOST READ 4 ADDRESS HIGH READ 4 1 ADDRESS HIGH 1 ADDRESS LOW 4 ADDRESS LOW DATA 1 3, 2 4 ECHO RETURN Notes: 1 = Echo delay, 2 bit times 2 = Data return delay, 2 bit times 3 = Cancel command delay, 11 bit times 4 = Wait 1 bit time before sending next byte. Figure 15-5. Read Transaction FROM HOST 3 ADDRESS HIGH WRITE WRITE 1 3 ADDRESS HIGH 1 ADDRESS LOW 3 ADDRESS LOW 1 DATA DATA 3 1 2, 3 ECHO Notes: 1 = Echo delay, 2 bit times 2 = Cancel command delay, 11 bit times 3 = Wait 1 bit time before sending next byte. Figure 15-6. Write Transaction MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 137 Monitor ROM (MON) A brief description of each monitor mode command is given in Table 15-4 through Table 15-9. Table 15-4. READ (Read Memory) Command Description Operand Read byte from memory 2-byte address in high-byte:low-byte order Data Returned Opcode Returns contents of specified address $4A Command Sequence SENT TO MONITOR READ ADDRESS HIGH READ ADDRESS HIGH ADDRESS LOW ADDRESS LOW DATA ECHO RETURN Table 15-5. WRITE (Write Memory) Command Description Operand Write byte to memory 2-byte address in high-byte:low-byte order; low byte followed by data byte Data Returned Opcode None $49 Command Sequence FROM HOST WRITE WRITE ADDRESS HIGH ADDRESS HIGH ADDRESS LOW ADDRESS LOW DATA DATA ECHO Table 15-6. IREAD (Indexed Read) Command Description Operand Data Returned Opcode Read next 2 bytes in memory from last address accessed 2-byte address in high byte:low byte order Returns contents of next two addresses $1A Command Sequence FROM HOST IREAD ECHO IREAD DATA DATA RETURN MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 138 Freescale Semiconductor Functional Description Table 15-7. IWRITE (Indexed Write) Command Description Write to last address accessed + 1 Operand Single data byte Data Returned Opcode None $19 Command Sequence FROM HOST IWRITE IWRITE DATA DATA ECHO A sequence of IREAD or IWRITE commands can access a block of memory sequentially over the full 64K byte memory map. Table 15-8. READSP (Read Stack Pointer) Command Description Reads stack pointer Operand None Data Returned Opcode Returns incremented stack pointer value (SP + 1) in high-byte:low-byte order $0C Command Sequence FROM HOST READSP SP HIGH READSP ECHO SP LOW RETURN Table 15-9. RUN (Run User Program) Command Description Executes PULH and RTI instructions Operand None Data Returned None Opcode $28 Command Sequence FROM HOST RUN RUN ECHO MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 139 Monitor ROM (MON) The MCU executes the SWI and PSHH instructions when it enters monitor mode. The RUN command tells the MCU to execute the PULH and RTI instructions. Before sending the RUN command, the host can modify the stacked CPU registers to prepare to run the host program. The READSP command returns the incremented stack pointer value, SP + 1. The high and low bytes of the program counter are at addresses SP + 5 and SP + 6. SP HIGH BYTE OF INDEX REGISTER SP + 1 CONDITION CODE REGISTER SP + 2 ACCUMULATOR SP + 3 LOW BYTE OF INDEX REGISTER SP + 4 HIGH BYTE OF PROGRAM COUNTER SP + 5 LOW BYTE OF PROGRAM COUNTER SP + 6 SP + 7 Figure 15-7. Stack Pointer at Monitor Mode Entry 15.4 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, they should be programmed 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 15-8.) Upon power-on reset, if the received bytes of the security code do not match the data at locations $FFF6–$FFFD, the host fails to bypass the security feature. The MCU remains in monitor mode, but reading a FLASH location returns an invalid value and trying to execute code from FLASH causes an illegal address reset. After receiving the eight security bytes from the host, the MCU transmits a break character, signifying that it is ready to receive a command. NOTE The MCU does not transmit a break character until after the host sends the eight security bytes. To determine whether the security code entered is correct, check to see if bit 6 of RAM address $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 can be reset by a power-on reset and brought up in monitor mode to attempt another entry. After failing the security sequence, the FLASH mode can also be bulk erased by executing an erase routine that was downloaded into internal RAM. The bulk erase operation clears the security code locations so that all eight security bytes become $FF (blank). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 140 Freescale Semiconductor Security VDD 4096 + 32 CGMXCLK CYCLES COMMAND BYTE 8 BYTE 2 BYTE 1 RST FROM HOST PA0 4 BYTE 8 ECHO 2 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 COMMAND ECHO 1 BREAK 1 BYTE 2 ECHO FROM MCU 4 1 BYTE 1 ECHO 5 Figure 15-8. Monitor Mode Entry Timing MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 141 Monitor ROM (MON) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 142 Freescale Semiconductor Chapter 16 Input/Output Ports (I/O) 16.1 Introduction Twenty one (21) 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 should be taken to make any unbonded port pins an output to prevent them from being floating inputs. Addr. $0000 $0001 $0002 $0003 $0004 Register Name Bit 7 6 5 4 Read: Port A Data Register Write: (PTA) Reset: 0 0 0 0 Read: Port B Data Register Write: (PTB) Reset: 0 Read: Port C Data Register Write: (PTC) Reset: 0 Read: Port D Data Register Write: (PTD) Reset: 0 Read: Data Direction Register A Write: (DDRA) Reset: 0 3 2 1 Bit 0 PTA3 PTA2 PTA1 PTA0 PTB2 PTB1 PTB0 PTC1 PTC0 PTD2 PTD1 PTD0 DDRA3 DDRA2 DDRA1 DDRA0 0 0 0 0 Unaffected by reset 0 PTB5 PTB4 PTB3 Unaffected by reset 0 0 0 0 0 Unaffected by reset PTD6 PTD5 PTD4 PTD3 Unaffected by reset 0 0 0 0 0 0 0 = Unimplemented Figure 16-1. I/O Port Register Summary MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 143 Input/Output Ports (I/O) Addr. $0005 $0006 $0007 $0008 $000C $000D $000E $000F Register Name Bit 7 6 Read: Data Direction Register B Write: (DDRB) Reset: 0 0 0 Read: Data Direction Register C Write: (DDRC) Reset: 0 Read: Data Direction Register D Write: (DDRD) Reset: 0 0 5 4 3 2 1 Bit 0 DDRB5 DDRB4 DDRB3 DDRB2 DDRB1 DDRB0 0 0 0 0 0 0 0 0 0 0 0 0 DDRC1 DDRC0 0 0 0 0 0 0 0 DDRD6 DDRD5 DDRD4 DDRD3 DDRD2 DDRD1 DDRD0 0 0 0 0 0 0 0 0 Read: Port E Data Register Write: (PTE) Reset: 0 0 0 0 0 0 PTE1 PTE0 Read: Data Direction Register E Write: (DDRE) Reset: 0 DDRE1 DDRE0 0 0 0 0 Read: Port A Input Pullup Enable Write: Register (PTAPUE) Reset: 0 0 0 0 0 0 0 Read: Port C Input Pullup Enable Write: Register (PTCPUE) Reset: 0 0 0 Read: Port D Input Pullup Enable Write: Register (PTDPUE) Reset: 0 Unaffected by reset 0 0 0 0 0 0 0 0 0 0 0 PTAPUE3 PTAPUE2 PTAPUE1 PTAPUE0 0 0 0 0 0 0 0 0 PTCPUE1 PTCPUE0 0 0 0 0 0 0 0 PTDPUE6 PTDPUE5 PTDPUE4 PTDPUE3 PTDPUE2 PTDPUE1 PTDPUE0 0 0 0 0 0 0 0 = Unimplemented Figure 16-1. I/O Port Register Summary (Continued) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 144 Freescale Semiconductor Introduction Table 16-1. Port Control Register Bits Summary Port Bit DDR 0 DDRA0 KBIE0 PTA0/KBD0 1 DDRA1 KBIE1 PTA1/KBD1 2 DDRA2 KBIE2 PTA2/KBD2 3 DDRA3 KBIE3 PTA3/KBD3 A Pin KBD — — — — — — — — — — — — — — — — 0 DDRB0 CH0 PTB0/ATD0 1 DDRB1 CH1 PTB1/ATD1 2 DDRB2 CH2 PTB2/ATD2 3 DDRB3 CH3 PTB3/ATD3 B C Module Control ADC 4 DDRB4 CH4 PTB4/ATD4 5 DDRB5 CH5 PTB5/ATD5 — — — — — — — — 0 DDRC0 PTC0 1 DDRC1 PTC1 — — — — — — — — — — — — — — — 0 DDRD0 PTD0/SS 1 DDRD1 PTD1/MISO SPI SPE 2 DDRD2 PTD2/MOSI 3 DDRD3 PTD3/SPSCK 4 DDRD4 D ELS0B:ELS0A PTD4/T1CH0 ELS1B:ELS1A PTD5/T1CH1 ELS0B:ELS0A PTD6/T2CH0 TIM1 5 DDRD5 6 DDRD6 TIM2 — — 0 DDRE0 E — PTE0/TxD SCI 1 ENSCI DDRE1 PTE1/RxD MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 145 Input/Output Ports (I/O) 16.2 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. 16.2.1 Port A Data Register The port A data register (PTA) contains a data latch for each of the four port A pins. Address: $0000 Bit 7 6 5 4 0 0 0 0 Read: Write: 3 2 1 Bit 0 PTA3 PTA2 PTA1 PTA0 KBD2 KBD1 KBD0 Reset: Unaffected by reset Alternative Function: KBD3 = Unimplemented Figure 16-2. Port A Data Register (PTA) 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 13 Keyboard Interrupt (KBI). 16.2.2 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: $0004 Bit 7 6 5 4 0 0 0 0 0 0 0 0 Write: Reset: 3 2 1 Bit 0 DDRA3 DDRA2 DDRA1 DDRA0 0 0 0 0 = Unimplemented Figure 16-3. 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 16-4 shows the port A I/O logic. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 146 Freescale Semiconductor Port A VDD PTAPUEx READ DDRA ($0004) INTERNAL PULLUP DEVICE WRITE DDRA ($0004) DDRAx INTERNAL DATA BUS RESET WRITE PTA ($0000) PTAx PTAx READ PTA ($0000) Figure 16-4. Port A I/O Circuit When bit DDRAx is a 1, reading address $0000 reads the PTAx data latch. When bit DDRAx is a 0, reading address $0000 reads the voltage level on the pin. The data latch can always be written, regardless of the state of its data direction bit. Table 16-2 summarizes the operation of the port A pins. Table 16-2. Port A Pin Functions PTAPUE Bit DDRA Bit PTA Bit 1 0 X(1) 0 0 X 1 I/O Pin Mode Accesses to DDRA Accesses to PTA Read/Write Read Write (4) DDRA3–DDRA0 Pin PTA3–PTA0(3) X Input, Hi-Z(2) DDRA3–DDRA0 Pin PTA3–PTA0(3) X Output DDRA3–DDRA0 PTA3–PTA0 PTA3–PTA0 Input, VDD NOTES: 1. X = Don’t care 2. Hi-Z = High impedance 3. Writing affects data register, but does not affect input. 4. I/O pin pulled up to VDD by internal pullup device 16.2.3 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 147 Input/Output Ports (I/O) Address: $000D Read: Bit 7 6 5 4 0 0 0 0 0 0 0 Write: Reset: 0 3 2 1 Bit 0 PTAPUE3 PTAPUE2 PTAPUE1 PTAPUE0 0 0 0 0 = Unimplemented Figure 16-5. 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 16.3 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. 16.3.1 Port B Data Register The port B data register (PTB) contains a data latch for each of the six port pins. Address: Read: Write: $0001 Bit 7 6 0 0 5 4 3 2 1 Bit 0 PTB5 PTB4 PTB3 PTB2 PTB1 PTB0 AD2 AD1 AD0 Reset: Alternative Function: Unaffected by reset AD5 AD4 AD3 = Unimplemented Figure 16-6. 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 5 are not available in a 28-pin DIP and SOIC package MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 148 Freescale Semiconductor Port B 16.3.2 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: $0005 Bit 7 6 0 0 0 0 Write: Reset: 5 4 3 2 1 Bit 0 DDRB5 DDRB4 DDRB3 DDRB2 DDRB1 DDRB0 0 0 0 0 0 0 = Unimplemented Figure 16-7. Data Direction Register B (DDRB) 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. NOTE 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 16-8 shows the port B I/O logic. INTERNAL DATA BUS READ DDRB ($0005) WRITE DDRB ($0005) RESET DDRBx WRITE PTB ($0001) PTBx PTBx READ PTB ($0001) Figure 16-8. 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 16-3 summarizes the operation of the port B pins. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 149 Input/Output Ports (I/O) Table 16-3. Port B Pin Functions DDRB Bit PTB Bit (1) 0 (2) Input, Hi-Z X 1 Accesses to DDRB I/O Pin Mode X Output Accesses to PTB Read/Write Read Write DDRB5–DDRB0 Pin PTB5–PTB0(3) DDRB5–DDRB0 PTB5–PTB0 PTB5–PTB0 Notes: 1. X = Don’t care 2. Hi-Z = High impedance 3. Writing affects data register, but does not affect input. 16.4 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. 16.4.1 Port C Data Register The port C data register (PTC) contains a data latch for each of the two port C pins. Address: Read: $0002 Bit 7 6 5 4 3 2 0 0 0 0 0 0 Write: Reset: 1 Bit 0 PTC1 PTC0 Unaffected by reset = Unimplemented Figure 16-9. 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 and SOIC package 16.4.2 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: $0006 Bit 7 6 5 4 3 2 0 0 0 0 0 0 0 0 0 0 0 Write: Reset: 0 1 Bit 0 DDRC1 DDRC0 0 0 = Unimplemented Figure 16-10. Data Direction Register C (DDRC) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 150 Freescale Semiconductor Port C 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. Figure 16-11 shows the port C I/O logic. NOTE For those devices packaged in a 28-pin DIP and SOIC package, PTC1,0 are not connected. Set DDRC1,0 to a 1 to configure PTC1,0 as outputs. VDD PTCPUEx READ DDRC ($0006) INTERNAL PULLUP DEVICE INTERNAL DATA BUS WRITE DDRC ($0006) DDRCx RESET WRITE PTC ($0002) PTCx PTCx READ PTC ($0002) Figure 16-11. 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 16-4 summarizes the operation of the port C pins. Table 16-4. Port C Pin Functions PTCPUE Bit DDRC Bit PTC Bit 1 0 X(1) 0 0 X 1 I/O Pin Mode Accesses to DDRC Accesses to PTC Read/Write Read Write (4) DDRC1–DDRC0 Pin PTC1–PTC0(3) X Input, Hi-Z(2) DDRC1–DDRC0 Pin PTC1–PTC0(3) X Output DDRC1–DDRC0 PTC1–PTC0 PTC1–PTC0 Input, VDD Notes: 1. X = Don’t care 2. Hi-Z = High impedance 3. Writing affects data register, but does not affect input. 4. I/O pin pulled up to VDD by internal pullup device. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 151 Input/Output Ports (I/O) 16.4.3 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: $000E Bit 7 6 5 4 3 2 0 0 0 0 0 0 0 0 0 0 0 Read: Write: Reset: 0 1 Bit 0 PTCPUE1 PTCPUE0 0 0 = Unimplemented Figure 16-12. 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 16.5 Port D Port D is an 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. 16.5.1 Port D Data Register The port D data register (PTD) contains a data latch for each of the seven port D pins. Address: $0003 Bit 7 Read: Write: 0 6 5 4 3 2 1 Bit 0 PTD6 PTD5 PTD4 PTD3 PTD2 PTD1 PTD0 MOSI MISO SS Reset: Alternative Function: Unaffected by reset T2CH0 T1CH1 T1CH0 SPSCK = Unimplemented Figure 16-13. 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 Bits The PTD6/T2CH0 pin is the 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 22 Timer Interface Module (TIM). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 152 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 22 Timer Interface Module (TIM). 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 16-5. 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. 16.5.2 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: $0007 Bit 7 Read: 0 Write: Reset: 0 6 5 4 3 2 1 Bit 0 DDRD6 DDRD5 DDRD4 DDRD3 DDRD2 DDRD1 DDRD0 0 0 0 0 0 0 0 = Unimplemented Figure 16-14. 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 153 Input/Output Ports (I/O) Figure 16-15 shows the port D I/O logic. VDD PTDPUEx READ DDRD ($0007) INTERNAL PULLUP DEVICE WRITE DDRD ($0007) DDRDx INTERNAL DATA BUS RESET WRITE PTD ($0003) PTDx PTDx READ PTD ($0003) Figure 16-15. 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 16-5 summarizes the operation of the port D pins. Table 16-5. Port D Pin Functions PTDPUE Bit 1. 2. 3. 4. DDRD Bit PTD Bit 1 0 X(1) 0 0 X 1 I/O Pin Mode Accesses to DDRD Accesses to PTD Read/Write Read Write (4) DDRD6–DDRD0 Pin PTD6–PTD0(3) X Input, Hi-Z(2) DDRD6–DDRD0 Pin PTD6–PTD0(3) X Output DDRD6–DDRD0 PTD6–PTD0 PTD6–PTD0 Input, VDD X = Don’t care Hi-Z = High impedance Writing affects data register, but does not affect input. I/O pin pulled up to VDD by internal pullup device. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 154 Freescale Semiconductor Port E 16.5.3 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: $000F Bit 7 Read: 0 Write: Reset: 6 5 4 3 2 1 Bit 0 PTDPUE6 PTDPUE5 PTDPUE4 PTDPUE3 PTDPUE2 PTDPUE1 PTDPUE0 0 0 0 0 0 0 0 0 = Unimplemented Figure 16-16. Port D Input Pullup Enable Register (PTDPUE) PTDPUE6–PTDPUE0 — Port D Input Pullup Enable Bits These writeable 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 16.6 Port E Port E is a 2-bit special-function port that shares two of its pins with the serial communications interface (SCI) module. 16.6.1 Port E Data Register The port E data register contains a data latch for each of the two port E pins. Address: Read: $0008 Bit 7 6 5 4 3 2 0 0 0 0 0 0 Write: Reset: 1 Bit 0 PTE1 PTE0 RxD TxD Unaffected by reset Alternative Function: = Unimplemented Figure 16-17. Port E Data Register (PTE) PTE1 and PTE0 — Port E Data Bits PTE1 and PTE0 are read/write, software programmable bits. Data direction of each port E pin is under the control of the corresponding bit in data direction register E. NOTE Data direction register E (DDRE) does not affect the data direction of port E pins that are being used by the SCI module. However, the DDRE bits always determine whether reading port E returns the states of the latches or the states of the pins. See Table 16-6. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 155 Input/Output Ports (I/O) RxD — SCI Receive Data Input The PTE1/RxD pin is the receive data input for the SCI module. When the enable SCI bit, ENSCI, is clear, the SCI module is disabled, and the PTE1/RxD pin is available for general-purpose I/O. See Chapter 18 Serial Communications Interface (SCI). TxD — SCI Transmit Data Output The PTE0/TxD pin is the transmit data output for the SCI module. When the enable SCI bit, ENSCI, is clear, the SCI module is disabled, and the PTE0/TxD pin is available for general-purpose I/O. See Chapter 18 Serial Communications Interface (SCI). 16.6.2 Data Direction Register E Data direction register E (DDRE) determines whether each port E pin is an input or an output. Writing a 1 to a DDRE bit enables the output buffer for the corresponding port E pin; a 0 disables the output buffer. Address: Read: $000C Bit 7 6 5 4 3 2 0 0 0 0 0 0 0 0 0 0 0 0 Write: Reset: 1 Bit 0 DDRE1 DDRE0 0 0 = Unimplemented Figure 16-18. Data Direction Register E (DDRE) DDRE1 and DDRE0 — Data Direction Register E Bits These read/write bits control port E data direction. Reset clears DDRE1 and 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 16-19 shows the port E I/O logic. INTERNAL DATA BUS READ DDRE ($000C) WRITE DDRE ($000C) RESET DDREx WRITE PTE ($0008) PTEx PTEx READ PTE ($0008) Figure 16-19. Port E I/O Circuit MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 156 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 16-6 summarizes the operation of the port E pins. Table 16-6. Port E Pin Functions DDRE Bit PTE Bit I/O Pin Mode 0 X(1) 1 X Accesses to DDRE Accesses to PTE Read/Write Read Write Input, Hi-Z(2) DDRE1–DDRE0 Pin PTE1–PTE0(3) Output DDRE1–DDRE0] PTE1–PTE0 PTE1–PTE0 Notes: 1. X = Don’t care 2. Hi-Z = High impedance 3. Writing affects data register, but does not affect input. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 157 Input/Output Ports (I/O) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 158 Freescale Semiconductor Chapter 17 Random-Access Memory (RAM) 17.1 Introduction This section describes the 384 bytes of RAM (random-access memory). 17.2 Functional Description 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 64K byte 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 159 Random-Access Memory (RAM) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 160 Freescale Semiconductor Chapter 18 Serial Communications Interface (SCI) 18.1 Introduction This section describes the serial communications interface (SCI) module, which allows high-speed asynchronous communications with peripheral devices and other MCUs. 18.2 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 • Configuration register bit, SCIBDSRC, to allow selection of baud rate clock source MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 161 Serial Communications Interface (SCI) 18.3 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 18-1 shows the full names and the generic names of the SCI I/O pins. The generic pin names appear in the text of this chapter. Table 18-1. Pin Name Conventions Generic Pin Names: RxD TxD Full Pin Names: PE1/RxD PE0/TxD 18.4 Functional Description Figure 18-1 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). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 162 Freescale Semiconductor Functional Description INTERNAL BUS SCI DATA REGISTER ERROR INTERRUPT CONTROL RECEIVER INTERRUPT CONTROL DMA INTERRUPT CONTROL RECEIVE SHIFT REGISTER PE1/RxD TRANSMITTER INTERRUPT CONTROL SCI DATA REGISTER TRANSMIT SHIFT REGISTER PE2/TxD TXINV SCTIE R8 TCIE T8 SCRIE ILIE DMARE TE SCTE RE DMATE TC RWU SBK SCRF OR ORIE IDLE NF NEIE FE FEIE PE PEIE LOOPS LOOPS SCIBDSRC FROM CONFIG FLAG CONTROL RECEIVE CONTROL WAKEUP CONTROL ENSCI ENSCI TRANSMIT CONTROL BKF M RPF WAKE ILTY SL CGMXCLK A X B IT12 SL = 0 => X = A SL = 1 => X = B ÷4 PRESCALER BAUD DIVIDER ∏ ÷ 16 PEN PTY DATA SELECTION CONTROL Figure 18-1. SCI Module Block Diagram MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 163 Serial Communications Interface (SCI) Addr. $0013 $0014 $0015 $0016 $0017 $0018 $0019 Register Name Read: SCI Control Register 1 Write: (SCC1) Reset: Read: SCI Control Register 2 Write: (SCC2) Reset: Bit 7 6 5 4 3 2 1 Bit 0 LOOPS ENSCI TXINV M WAKE ILTY PEN PTY 0 0 0 0 0 0 0 0 SCTIE TCIE SCRIE ILIE TE RE RWU SBK 0 0 0 0 0 0 0 0 T8 R R ORIE NEIE FEIE PEIE Read: SCI Control Register 3 Write: (SCC3) Reset: R8 U U 0 0 0 0 0 0 Read: SCI Status Register 1 Write: (SCS1) Reset: SCTE TC SCRF IDLE OR NF FE PE 1 1 0 0 0 0 0 0 Read: SCI Status Register 2 Write: (SCS2) Reset: 0 0 0 0 0 0 BKF RPF 0 0 0 0 0 0 0 0 Read: SCI Data Register Write: (SCDR) Reset: R7 R6 R5 R4 R3 R2 R1 R0 T7 T6 T5 T4 T3 T2 T1 T0 Read: SCI Baud Rate Register Write: (SCBR) Reset: 0 Unaffected by reset 0 0 SCP1 SCP0 R SCR2 SCR1 SCR0 0 0 0 0 0 0 0 = Unimplemented R = Reserved U = Unaffected Figure 18-2. SCI I/O Register Summary 18.4.1 Data Format The SCI uses the standard non-return-to-zero mark/space data format illustrated in Figure 18-3. 8-BIT DATA FORMAT BIT M IN SCC1 CLEAR START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 PARITY BIT BIT 6 BIT 7 9-BIT DATA FORMAT BIT M IN SCC1 SET START BIT BIT 0 BIT 1 BIT 2 BIT 3 BIT 4 BIT 5 STOP BIT NEXT START BIT PARITY BIT BIT 6 BIT 7 BIT 8 STOP BIT NEXT START BIT Figure 18-3. SCI Data Formats MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 164 Freescale Semiconductor Functional Description 18.4.2 Transmitter Figure 18-4 shows the structure of the SCI transmitter. The baud rate clock source for the SCI can be selected via the configuration bit, SCIBDSRC. SCIBDSRC FROM CONFIG2 SL A CGMXCLK X B IT12 SL = 0 => X = A SL = 1 => X = B INTERNAL BUS BAUD DIVIDER ÷ 16 SCI DATA REGISTER SCP1 11-BIT TRANSMIT SHIFT REGISTER STOP SCP0 SCR1 H SCR2 8 7 6 5 4 3 2 START PRESCALER ÷4 1 0 L PE2/TxD MSB TXINV PARITY GENERATION T8 DMATE DMATE SCTIE SCTE DMATE SCTE SCTIE TC TCIE BREAK ALL 0s PTY PREAMBLE ALL 1s PEN SHIFT ENABLE M LOAD FROM SCDR TRANSMITTER DMA SERVICE REQUEST TRANSMITTER CPU INTERRUPT REQUEST SCR0 TRANSMITTER CONTROL LOGIC SCTE SBK LOOPS SCTIE ENSCI TC TE TCIE Figure 18-4. SCI Transmitter MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 165 Serial Communications Interface (SCI) 18.4.2.1 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). 18.4.2.2 Character Transmission During an SCI transmission, the transmit shift register shifts a character out to the PE2/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. For 9-bit data, also write the T8 bit in SCC3. 4. Repeat step 3 for each subsequent transmission. At the start of a transmission, transmitter control 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 PE2/TxD pin goes to the idle condition, high. 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. 18.4.2.3 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 at 1, transmitter logic continuously loads break characters into the transmit shift register. After software clears the SBK bit, the shift register finishes transmitting the last break character and then transmits at least one 1. The automatic 1 at the end of a break character guarantees the recognition of the start bit of the next character. 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 166 Freescale Semiconductor Functional Description 18.4.2.4 Idle Characters For TXINV = 0, (output not inverted) a transmitted idle character contains all logic 1s and has no start, stop, or parity bit. Idle character length depends on the M bit in SCC1. The preamble is a synchronizing idle character that begins every transmission. If the TE bit is cleared during a transmission, the PE2/TxD pin becomes idle after completion of the transmission in progress. Clearing and then setting the TE bit during a transmission queues an idle character to be sent after the character currently being transmitted. NOTE When a break sequence is followed immediately by an idle character, this SCI design exhibits a condition in which the break character length is reduced by one half bit time. In this instance, the break sequence will consist of a valid start bit, eight or nine data bits (as defined by the M bit in SCC1) of 0 and one half data bit length of 0 in the stop bit position followed immediately by the idle character. To ensure a break character of the proper length is transmitted, always queue up a byte of data to be transmitted while the final break sequence is in progress. When queueing an idle character, return the TE bit to 1 before the stop bit of the current character shifts out to the TxD pin. Setting TE after the stop bit appears on TxD causes data previously written to the SCDR to be lost. A good time to toggle the TE bit for a queued idle character is when the SCTE bit becomes set and just before writing the next byte to the SCDR. 18.4.2.5 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 at logic 1. See 18.8.1 SCI Control Register 1. 18.4.2.6 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. 18.4.3 Receiver Figure 18-5 shows the structure of the SCI receiver. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 167 Serial Communications Interface (SCI) INTERNAL BUS SCIBDSRC FROM CONFIG2 SCR1 SCR0 PRESCALER BAUD DIVIDER ÷ 16 DATA RECOVERY PE1/RxD CPU INTERRUPT REQUEST 11-BIT RECEIVE SHIFT REGISTER 8 7 6 5 M WAKE ILTY PEN PTY 4 3 2 1 0 L ALL 0s RPF ERROR CPU INTERRUPT REQUEST DMA SERVICE REQUEST H ALL 1s BKF STOP ÷4 SCI DATA REGISTER START SCR2 SCP0 MSB SL CGMXCLK A X B IT12 SL = 0 => X = A SL = 1 => X = B SCP1 SCRF WAKEUP LOGIC PARITY CHECKING IDLE ILIE DMARE SCRF SCRIE DMARE SCRF SCRIE DMARE OR ORIE NF NEIE FE FEIE PE PEIE RWU IDLE R8 ILIE SCRIE DMARE OR ORIE NF NEIE FE FEIE PE PEIE Figure 18-5. SCI Receiver Block Diagram 18.4.3.1 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 3 (SCC3) is the ninth bit (bit 8). When receiving 8-bit data, bit R8 is a copy of the eighth bit (bit 7). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 168 Freescale Semiconductor Functional Description 18.4.3.2 Character Reception During an SCI reception, the receive shift register shifts characters in from the PE1/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. 18.4.3.3 Data Sampling The receiver samples the PE1/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 18-6): • 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 does an asynchronous search for a 0 preceded by three 1s. When the falling edge of a possible start bit occurs, the RT clock begins to count to 16. START BIT LSB PE1/RxD START BIT QUALIFICATION SAMPLES START BIT VERIFICATION DATA SAMPLING RT4 RT3 RT2 RT16 RT1 RT15 RT14 RT13 RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT1 RT CLOCK STATE RT1 RT CLOCK RT CLOCK RESET Figure 18-6. Receiver Data Sampling To verify the start bit and to detect noise, data recovery logic takes samples at RT3, RT5, and RT7. Table 18-2 summarizes the results of the start bit verification samples. Table 18-2. Start Bit Verification RT3, RT5, and RT7 Samples 000 001 010 011 100 Start Bit Verification Yes Yes Yes No Yes Noise Flag 0 1 1 0 1 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 169 Serial Communications Interface (SCI) Table 18-2. Start Bit Verification (Continued) RT3, RT5, and RT7 Samples 101 110 111 Start Bit Verification No No No Noise Flag 0 0 0 If start bit verification is not successful, the RT clock is reset and a new search for a start bit begins. To determine the value of a data bit and to detect noise, recovery logic takes samples at RT8, RT9, and RT10. Table 18-3 summarizes the results of the data bit samples. Table 18-3. 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 18-4 summarizes the results of the stop bit samples. Table 18-4. 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 18.4.3.4 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 170 Freescale Semiconductor Functional Description 18.4.3.5 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. 18.4.3.6 Slow Data Tolerance Figure 18-7 shows how much a slow received character can be misaligned without causing a noise error or a framing error. The slow stop bit begins at RT8 instead of RT1 but arrives in time for the stop bit data samples at RT8, RT9, and RT10. RT16 RT15 RT14 RT13 RT12 RT11 RT10 RT9 RT8 RT7 RT6 STOP RT5 RT4 RT3 RT2 RECEIVER RT CLOCK RT1 MSB DATA SAMPLES Figure 18-7. Slow Data For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 18-7, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 9 bit times × 16 RT cycles + 3 RT cycles = 147 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a slow 8-bit character with no errors is 154 – 147 × 100 = 4.54% -------------------------154 For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 18-7, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 10 bit times × 16 RT cycles + 3 RT cycles = 163 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a slow 9-bit character with no errors is 170 – 163 × 100 = 4.12% -------------------------170 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 171 Serial Communications Interface (SCI) 18.4.3.7 Fast Data Tolerance Figure 18-8 shows how much a fast received character can be misaligned without causing a noise error or a framing error. The fast stop bit ends at RT10 instead of RT16 but is still there for the stop bit data samples at RT8, RT9, and RT10. STOP IDLE OR NEXT CHARACTER RT16 RT15 RT14 RT13 RT12 RT11 RT10 RT9 RT8 RT7 RT6 RT5 RT4 RT3 RT2 RT1 RECEIVER RT CLOCK DATA SAMPLES Figure 18-8. Fast Data For an 8-bit character, data sampling of the stop bit takes the receiver 9 bit times × 16 RT cycles + 10 RT cycles = 154 RT cycles. With the misaligned character shown in Figure 18-8, the receiver counts 154 RT cycles at the point when the count of the transmitting device is 10 bit times × 16 RT cycles = 160 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 8-bit character with no errors is · 154 – 160 × 100 = 3.90% -------------------------154 For a 9-bit character, data sampling of the stop bit takes the receiver 10 bit times × 16 RT cycles + 10 RT cycles = 170 RT cycles. With the misaligned character shown in Figure 18-8, the receiver counts 170 RT cycles at the point when the count of the transmitting device is 11 bit times × 16 RT cycles = 176 RT cycles. The maximum percent difference between the receiver count and the transmitter count of a fast 9-bit character with no errors is 170 – 176 × 100 = 3.53% -------------------------170 18.4.3.8 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 PE1/RxD pin can bring the receiver out of the standby state: • Address mark — An address mark is a logic 1 in the most significant bit position of a received character. When the WAKE bit is set, an address mark wakes the receiver from the standby state by clearing the RWU bit. The address mark also sets the SCI receiver full bit, SCRF. Software can then compare the character containing the address mark to the user-defined address of the MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 172 Freescale Semiconductor Functional Description • receiver. If they are the same, the receiver remains awake and processes the characters that follow. If they are not the same, software can set the RWU bit and put the receiver back into the standby state. Idle input line condition — When the WAKE bit is clear, an idle character on the PE1/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 logic 1s as idle character bits after the start bit or after the stop bit. NOTE With the WAKE bit clear, setting the RWU bit after the RxD pin has been idle may cause the receiver to wake up immediately. 18.4.3.9 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 PE1/RxD pin. The idle line interrupt enable bit, ILIE, in SCC2 enables the IDLE bit to generate CPU interrupt requests. 18.4.3.10 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 173 Serial Communications Interface (SCI) 18.5 Low-Power Modes The WAIT and STOP instructions put the MCU in low power-consumption standby modes. 18.5.1 Wait Mode The SCI module remains active after the execution of a WAIT instruction. Any enabled CPU interrupt request from the SCI module can bring the MCU out of wait mode. If SCI module functions are not required during wait mode, reduce power consumption by disabling the module before executing the WAIT instruction. Refer to Chapter 3 Low-Power Modes for information on exiting wait mode. 18.5.2 Stop Mode The SCI module is inactive in stop mode. The STOP instruction does not affect SCI register states. SCI module operation resumes when 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. Refer to Chapter 3 Low-Power Modes for information on exiting stop mode. 18.6 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. 18.7 I/O Signals Port E shares two of its pins with the SCI module. The two SCI I/O pins are: • PE2/TxD — Transmit data • PE1/RxD — Receive data 18.7.1 PE2/TxD (Transmit Data) The PE2/TxD pin is the serial data output from the SCI transmitter. The SCI shares the PE2/TxD pin with port E. When the SCI is enabled, the PE2/TxD pin is an output regardless of the state of the DDRE0 bit in data direction register E (DDRE). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 174 Freescale Semiconductor I/O Registers 18.7.2 PE1/RxD (Receive Data) The PE1/RxD pin is the serial data input to the SCI receiver. The SCI shares the PE1/RxD pin with port E. When the SCI is enabled, the PE1/RxD pin is an input regardless of the state of the DDRE1 bit in data direction register E (DDRE). 18.8 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) 18.8.1 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 6 5 4 3 2 1 Bit 0 LOOPS ENSCI TXINV M WAKE ILTY PEN PTY 0 0 0 0 0 0 0 0 Figure 18-9. SCI Control Register 1 (SCC1) LOOPS — Loop Mode Select Bit This read/write bit enables loop mode operation. In loop mode the PE1/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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 175 Serial Communications Interface (SCI) ENSCI — Enable SCI Bit This read/write bit enables the SCI and the SCI baud rate generator. Clearing ENSCI sets the SCTE and TC bits in SCI status register 1 and disables transmitter interrupts. Reset clears the ENSCI bit. 1 = SCI enabled 0 = SCI disabled TXINV — Transmit Inversion Bit This read/write bit reverses the polarity of transmitted data. Reset clears the TXINV bit. 1 = Transmitter output inverted 0 = Transmitter output not inverted NOTE Setting the TXINV bit inverts all transmitted values, including idle, break, start, and stop bits. M — Mode (Character Length) Bit This read/write bit determines whether SCI characters are eight or nine bits long. See Table 18-5. 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 PE1/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 18-5. When enabled, the parity function inserts a parity bit in the most significant bit position. See Figure 18-3. 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 18-5. 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 176 Freescale Semiconductor I/O Registers Table 18-5. Character Format Selection Control Bits Character Format M PEN and PTY Start Bits Data Bits Parity Stop Bits Character Length 0 0X 1 8 None 1 10 bits 1 0X 1 9 None 1 11 bits 0 10 1 7 Even 1 10 bits 0 11 1 7 Odd 1 10 bits 1 10 1 8 Even 1 11 bits 1 11 1 8 Odd 1 11 bits 18.8.2 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 6 5 4 3 2 1 Bit 0 SCTIE TCIE SCRIE ILIE TE RE RWU SBK 0 0 0 0 0 0 0 0 Figure 18-10. SCI Control Register 2 (SCC2) SCTIE — SCI Transmit Interrupt Enable Bit This read/write bit enables the SCTE bit to generate SCI transmitter CPU interrupt requests. Reset clears the SCTIE bit. 1 = SCTE enabled to generate CPU interrupt 0 = SCTE not enabled to generate CPU interrupt TCIE — Transmission Complete Interrupt Enable Bit This read/write bit enables the TC bit to generate SCI transmitter CPU interrupt requests. Reset clears the TCIE bit. 1 = TC enabled to generate CPU interrupt requests 0 = TC not enabled to generate CPU interrupt requests SCRIE — SCI Receive Interrupt Enable Bit This read/write bit enables the SCRF bit to generate SCI receiver CPU interrupt requests. Reset clears the SCRIE bit. 1 = SCRF enabled to generate CPU interrupt 0 = SCRF not enabled to generate CPU interrupt MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 177 Serial Communications Interface (SCI) 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 PE2/TxD pin. If software clears the TE bit, the transmitter completes any transmission in progress before the PE2/TxD returns to the idle condition (1). Clearing and then setting TE during a transmission queues an idle character to be sent after the character currently being transmitted. Reset clears the TE bit. 1 = Transmitter enabled 0 = Transmitter disabled NOTE Writing to the TE bit is not allowed when the enable 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 178 Freescale Semiconductor I/O Registers 18.8.3 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: $0015 Bit 7 Read: R8 Write: Reset: U 6 5 4 3 2 1 Bit 0 T8 R R ORIE NEIE FEIE PEIE U 0 0 0 0 0 0 R = Reserved = Unimplemented U = Unaffected Figure 18-11. SCI Control Register 3 (SCC3) R8 — Received Bit 8 When the SCI is receiving 9-bit characters, R8 is the read-only ninth bit (bit 8) of the received character. R8 is received at the same time that the SCDR receives the other 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 clears 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 18.8.4 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 179 Serial Communications Interface (SCI) 18.8.4 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 Address: Read: $0016 Bit 7 6 5 4 3 2 1 Bit 0 SCTE TC SCRF IDLE OR NF FE PE 1 1 0 0 0 0 0 0 Write: Reset: = Unimplemented Figure 18-12. SCI Status Register 1 (SCS1) SCTE — SCI Transmitter Empty Bit This clearable, read-only bit is set when the SCDR transfers a character to the transmit shift register. SCTE can generate an SCI transmitter CPU interrupt request. When the SCTIE bit in SCC2 is set, SCTE generates an SCI transmitter CPU interrupt request. In normal operation, clear the SCTE bit by reading SCS1 with SCTE set and then writing to SCDR. Reset sets the SCTE bit. 1 = SCDR data transferred to transmit shift register 0 = SCDR data not transferred to transmit shift register 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 180 Freescale Semiconductor I/O Registers IDLE — Receiver Idle Bit This clearable, read-only bit is set when 10 or 11 consecutive logic 1s appear on the receiver input. IDLE generates an SCI 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 Software latency may allow an overrun to occur between reads of SCS1 and SCDR in the flag-clearing sequence. Figure 18-13 shows the normal flag-clearing sequence and an example of an overrun caused by a delayed flag-clearing sequence. The delayed read of SCDR does not clear the OR bit because OR was not set when SCS1 was read. Byte 2 caused the overrun and is lost. The next 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. NF — Receiver Noise Flag Bit This clearable, read-only bit is set when the SCI detects noise on the PE1/RxD pin. NF generates an NF CPU interrupt request if the NEIE bit in SCC3 is also set. Clear the NF bit by reading SCS1 and then reading the SCDR. Reset clears the NF bit. 1 = Noise detected 0 = No noise detected FE — Receiver Framing Error Bit This clearable, read-only bit is set when a logic 0 is accepted as the stop bit. FE generates an SCI error CPU interrupt request if the FEIE bit in SCC3 also is set. Clear the FE bit by reading SCS1 with FE set and then reading the SCDR. Reset clears the FE bit. 1 = Framing error detected 0 = No framing error detected PE — Receiver Parity Error Bit This clearable, read-only bit is set when the SCI detects a parity error in incoming data. PE generates a PE CPU interrupt request if the PEIE bit in SCC3 is also set. Clear the PE bit by reading SCS1 with PE set and then reading the SCDR. Reset clears the PE bit. 1 = Parity error detected 0 = No parity error detected MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 181 Serial Communications Interface (SCI) BYTE 1 BYTE 2 SCRF = 0 SCRF = 1 SCRF = 0 SCRF = 1 SCRF = 0 SCRF = 1 NORMAL FLAG CLEARING SEQUENCE BYTE 3 BYTE 4 READ SCS1 SCRF = 1 OR = 0 READ SCS1 SCRF = 1 OR = 0 READ SCS1 SCRF = 1 OR = 0 READ SCDR BYTE 1 READ SCDR BYTE 2 READ SCDR BYTE 3 BYTE 1 BYTE 2 SCRF = 0 OR = 0 SCRF = 1 OR = 1 SCRF = 0 OR = 1 SCRF = 1 OR = 1 SCRF = 1 DELAYED FLAG CLEARING SEQUENCE BYTE 3 BYTE 4 READ SCS1 SCRF = 1 OR = 0 READ SCS1 SCRF = 1 OR = 1 READ SCDR BYTE 1 READ SCDR BYTE 3 Figure 18-13. Flag Clearing Sequence 18.8.5 SCI Status Register 2 SCI status register 2 contains flags to signal the following conditions: • Break character detected • Incoming data Address: Read: Write: Reset: $0017 Bit 7 0 0 6 0 5 0 4 0 3 0 2 0 1 BKF Bit 0 RPF 0 0 = Unimplemented 0 0 0 0 0 Figure 18-14. SCI Status Register 2 (SCS2) BKF — Break Flag Bit This clearable, read-only bit is set when the SCI detects a break character on the PE1/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 PE1/RxD pin followed by another break character. Reset clears the BKF bit. 1 = Break character detected 0 = No break character detected MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 182 Freescale Semiconductor I/O Registers 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 18.8.6 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: $0018 Bit 7 6 5 4 3 2 1 Bit 0 Read: R7 R6 R5 R4 R3 R2 R1 R0 Write: T7 T6 T5 T4 T3 T2 T1 T0 Reset: Unaffected by reset Figure 18-15. SCI Data Register (SCDR) R7/T7–R0/T0 — Receive/Transmit Data Bits Reading address $0018 accesses the read-only received data bits, R7:R0. Writing to address $0018 writes the data to be transmitted, T7:T0. Reset has no effect on the SCI data register. NOTE Do not use read/modify/write instructions on the SCI data register. 18.8.7 SCI Baud Rate Register The baud rate register (SCBR) selects the baud rate for both the receiver and the transmitter. Address: Read: $0019 Bit 7 6 0 0 0 0 Write: Reset: 5 4 3 2 1 Bit 0 SCP1 SCP0 R SCR2 SCR1 SCR0 0 0 0 0 0 0 R = Reserved = Unimplemented Figure 18-16. SCI Baud Rate Register (SCBR) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 183 Serial Communications Interface (SCI) SCP1 and SCP0 — SCI Baud Rate Prescaler Bits These read/write bits select the baud rate prescaler divisor as shown in Table 18-6. Reset clears SCP1 and SCP0. Table 18-6. SCI Baud Rate Prescaling SCP1 and SCP0 Prescaler Divisor (PD) 00 1 01 3 10 4 11 13 SCR2–SCR0 — SCI Baud Rate Select Bits These read/write bits select the SCI baud rate divisor as shown in Table 18-7. Reset clears SCR2–SCR0. Table 18-7. SCI Baud Rate Selection SCR2, SCR1, and SCR0 Baud Rate Divisor (BD) 000 1 001 2 010 4 011 8 100 16 101 32 110 64 111 128 Use this formula to calculate the SCI baud rate: f BUS baud rate = ----------------------------------64 × PD × BD where: fBUS = bus frequency PD = prescaler divisor BD = baud rate divisor SCIBDSRC from the configuration register is an input to the SCI. With SCIBDSRC = 1 to select the bus clock as the clock source, this makes the formula: f BUS baud rate = ----------------------------------64 × PD × BD Table 18-8 shows the SCI baud rates that can be generated with a 4.9152-MHz bus clock. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 184 Freescale Semiconductor I/O Registers Table 18-8. SCI Baud Rate Selection Examples SCP1 and SCP0 Prescaler Divisor (PD) SCR2, SCR1, and SCR0 Baud Rate Divisor (BD) Baud Rate (fBUS = 4.9152 MHz) 00 1 000 1 76,800 00 1 001 2 38,400 00 1 010 4 19,200 00 1 011 8 9600 00 1 100 16 4800 00 1 101 32 2400 00 1 110 64 1200 00 1 111 128 600 01 3 000 1 25,600 01 3 001 2 12,800 01 3 010 4 6400 01 3 011 8 3200 01 3 100 16 1600 01 3 101 32 800 01 3 110 64 400 01 3 111 128 200 10 4 000 1 19,200 10 4 001 2 9600 10 4 010 4 4800 10 4 011 8 2400 10 4 100 16 1200 10 4 101 32 600 10 4 110 64 300 10 4 111 128 150 11 13 000 1 5908 11 13 001 2 2954 11 13 010 4 1477 11 13 011 8 739 11 13 100 16 369 11 13 101 32 185 11 13 110 64 92 11 13 111 128 46 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 185 Serial Communications Interface (SCI) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 186 Freescale Semiconductor Chapter 19 System Integration Module (SIM) 19.1 Introduction This section describes the system integration module (SIM). Together with the CPU, the SIM controls all MCU activities. A block diagram of the SIM is shown in Figure 19-1. Table 19-1 is a summary of the SIM input/output (I/O) registers. The SIM is a system state controller that coordinates CPU and exception timing. The SIM is responsible for: • Bus clock generation and control for CPU and peripherals: – Stop/wait/reset/break entry and recovery – Internal clock control • Master reset control, including power-on reset (POR) and COP timeout • Interrupt arbitration: Table 19-1 shows the internal signal names used in this section. Table 19-1. Signal Name Conventions Signal Name Description CGMXCLK Buffered version of OSC1 from clock generator module (CGM) CGMVCLK PLL output CGMOUT PLL-based or OSC1-based clock output from CGM module (Bus clock = CGMOUT divided by two) IAB IDB PORRST Internal address bus Internal data bus Signal from the power-on reset module to the SIM IRST Internal reset signal R/W Read/write signal MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 187 System Integration Module (SIM) MODULE STOP MODULE WAIT CPU STOP (FROM CPU) CPU WAIT (FROM CPU) STOP/WAIT CONTROL SIMOSCEN (TO CGM) SIM COUNTER COP CLOCK CGMXCLK (FROM CGM) CGMOUT (FROM CGM) ÷2 CLOCK CONTROL VDD INTERNAL CLOCKS CLOCK GENERATORS INTERNAL PULLUP DEVICE RESET PIN LOGIC LVI (FROM LVI MODULE) POR CONTROL MASTER RESET CONTROL RESET PIN CONTROL ILLEGAL OPCODE (FROM CPU) ILLEGAL ADDRESS (FROM ADDRESS MAP DECODERS) COP (FROM COP MODULE) SIM RESET STATUS REGISTER RESET INTERRUPT SOURCES INTERRUPT CONTROL AND PRIORITY DECODE CPU INTERFACE Figure 19-1. SIM Block Diagram Addr. $FE00 Register Name Read: SIM Break Status Register Write: (SBSR) Reset: Bit 7 6 5 4 3 2 1 R R R R R R 0 0 0 0 0 0 0 0 POR PIN COP ILOP ILAD MODRST LVI 0 1 0 0 0 0 0 0 0 BCFE R R R R R R R SBSW NOTE Bit 0 R Note: Writing a logic 0 clears SBSW. $FE01 Read: SIM Reset Status Register Write: (SRSR) POR: Read: SIM Break Flag Control Reg$FE03 Write: ister (SBFCR) Reset: 0 = Unimplemented Figure 19-2. SIM I/O Register Summary MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 188 Freescale Semiconductor SIM Bus Clock Control and Generation Addr. Register Name Bit 7 6 5 4 3 2 1 Bit 0 IF6 IF5 IF4 IF3 IF2 IF1 0 0 R R R R R R R R 0 0 0 0 0 0 0 0 Read: Interrupt Status Register 2 Write: (INT2) Reset: IF14 IF13 IF12 IF11 IF10 IF9 IF8 IF7 R R R R R R R R 0 0 0 0 0 0 0 0 Read: Interrupt Status Register 3 Write: (INT3) Reset: 0 0 0 0 0 0 IF16 IF15 R R R R R R R R 0 0 0 0 0 0 0 0 Read: $FE04 $FE05 $FE06 Interrupt Status Register 1 Write: (INT1) Reset: = Unimplemented Figure 19-2. SIM I/O Register Summary (Continued) 19.2 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 19-3. This clock can come from either an external oscillator or from the on-chip PLL. See Chapter 7 Clock Generator Module. OSC2 OSCILLATOR (OSC) CGMXCLK TO TIMTB15A, ADC OSC1 SIM OSCSTOPENB FROM CONFIG SIM COUNTER CGMRCLK CGMOUT ³2 PHASE-LOCKED LOOP (PLL) BUS CLOCK GENERATORS SIMOSCEN IT12 TO REST OF CHIP IT23 TO REST OF CHIP Figure 19-3. CGM Clock Signals MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 189 System Integration Module (SIM) 19.2.1 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. 19.2.2 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. 19.2.3 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 19.6.2 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. 19.3 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 19.4 SIM Counter), but an external reset does not. Each of the resets sets a corresponding bit in the SIM reset status register (SRSR). See 19.7 SIM Registers. 19.3.1 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 19-2 for details. Figure 19-4 shows the relative timing. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 190 Freescale Semiconductor Reset and System Initialization CGMOUT RST IAB VECT H PC VECT L Figure 19-4. External Reset Timing 19.3.2 Active Resets from Internal Sources All internal reset sources actively pull the RST pin low for 32 CGMXCLK cycles to allow resetting of external peripherals. The internal reset signal IRST continues to be asserted for an additional 32 cycles at which point the reset vector will be fetched. See Figure 19-5. An internal reset can be caused by an illegal address, illegal opcode, COP timeout, LVI, or POR. See Figure 19-6. 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 19-5. IRST RST RST PULLED LOW BY MCU 32 CYCLES 32 CYCLES CGMXCLK IAB VECTOR HIGH Figure 19-5. Internal Reset Timing The COP reset is asynchronous to the bus clock. ILLEGAL ADDRESS RST ILLEGAL OPCODE RST COPRST LVI POR MODRST INTERNAL RESET Figure 19-6. Sources of Internal Reset Table 19-2. PIN Bit Set Timing Reset Recovery Actual Number of Cycles POR/LVI 4163 (4096 + 64 + 3) All others 67 (64 + 3) The active reset feature allows the part to issue a reset to peripherals and other chips within a system built around the MCU. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 191 System Integration Module (SIM) 19.3.2.1 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. OSC1 PORRST 4096 CYCLES 32 CYCLES 32 CYCLES CGMXCLK CGMOUT RST IRST $FFFE IAB $FFFF Figure 19-7. POR Recovery 19.3.2.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 192 Freescale Semiconductor SIM Counter 19.3.2.3 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 CONFIG 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. 19.3.2.4 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. 19.3.2.5 Low-Voltage Inhibit (LVI) Reset The low-voltage inhibit module (LVI) asserts its output to the SIM when the VDD voltage falls to the LVITRIPF voltage. The LVI bit in the SIM reset status register (SRSR) is set, and the external reset pin (RST) is held low while the SIM counter counts out 4096 + 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. 19.3.2.6 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 15.3.1 Entering Monitor Mode.) When MODRST gets asserted, an internal reset occurs. The SIM actively pulls down the RST pin for all internal reset sources. 19.4 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 overflow supplies the clock for the COP module. The SIM counter is 12 bits long. 19.4.1 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. 19.4.2 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 CONFIG 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, that is, with SSREC cleared. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 193 System Integration Module (SIM) 19.4.3 SIM Counter and Reset States External reset has no effect on the SIM counter. (See 19.6.2 Stop Mode for details.) The SIM counter is free-running after all reset states. (See 19.3.2 Active Resets from Internal Sources for counter control and internal reset recovery sequences.) 19.5 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 19.5.1 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 19-8 shows interrupt entry timing. Figure 19-9 shows interrupt recovery timing. Interrupts are latched, and arbitration is performed in the SIM at the start of interrupt processing. The arbitration result is a constant that the CPU uses to determine which vector to fetch. Once an interrupt is latched by the SIM, no other interrupt can take precedence, regardless of priority, until the latched interrupt is serviced (or the I bit is cleared). See Figure 19-10. MODULE INTERRUPT I BIT IAB IDB DUMMY DUMMY SP SP – 1 PC – 1[7:0] SP – 2 PC–1[15:8] SP – 3 SP – 4 X A VECT H CCR VECT L V DATA H START ADDR V DATA L OPCODE R/W Figure 19-8. Interrupt Entry Timing MODULE INTERRUPT I BIT IAB IDB SP – 4 SP – 3 CCR SP – 2 A SP – 1 X PC – 1 [7:0] SP PC PC–1[15:8] PC + 1 OPCODE OPERAND R/W Figure 19-9. Interrupt Recovery Timing MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 194 Freescale Semiconductor Exception Control FROM RESET BREAK I BIT SET? INTERRUPT? YES NO YES I BIT SET? NO IRQ INTERRUPT? YES NO AS MANY INTERRUPTS AS EXIST ON CHIP STACK CPU REGISTERS SET I BIT LOAD PC WITH INTERRUPT VECTOR FETCH NEXT INSTRUCTION SWI INSTRUCTION? YES NO RTI INSTRUCTION? YES UNSTACK CPU REGISTERS NO EXECUTE INSTRUCTION Figure 19-10. Interrupt Processing MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 195 System Integration Module (SIM) 19.5.1.1 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 19-11 demonstrates what happens when two interrupts are pending. If an interrupt is pending upon exit from the original interrupt service routine, the pending interrupt is serviced before the LDA instruction is executed. CLI LDA #$FF INT1 BACKGROUND ROUTINE PSHH INT1 INTERRUPT SERVICE ROUTINE PULH RTI INT2 PSHH INT2 INTERRUPT SERVICE ROUTINE PULH RTI Figure 19-11. 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. 19.5.1.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 196 Freescale Semiconductor Exception Control 19.5.1.3 Interrupt Status Registers The flags in the interrupt status registers identify maskable interrupt sources. Table 19-3 summarizes the interrupt sources and the interrupt status register flags that they set. The interrupt status registers can be useful for debugging. Table 19-3. Interrupt Sources Priority Interrupt Source Interrupt Status Register Flag Highest Reset — SWI instruction — IRQ pin I1 PLL I2 TIM1 channel 0 I3 TIM1 channel 1 I4 TIM1 overflow I5 TIM2 channel 0 I6 Reserved I7 TIM2 overflow I8 SPI receiver full I9 SPI transmitter empty I10 SCI receive error I11 SCI receive I12 SCI transmit I13 Keyboard I14 ADC conversion complete I15 Timebase module I16 Lowest 19.5.1.4 Interrupt Status Register 1 Address: $FE04 Bit 7 6 5 4 3 2 1 Bit 0 Read: I6 I5 I4 I3 I2 I1 0 0 Write: R R R R R R R R Reset: 0 0 0 0 0 0 0 0 R = Reserved Figure 19-12. 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 19-3. 1 = Interrupt request present 0 = No interrupt request present Bit 0 and Bit 1 — Always read 0 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 197 System Integration Module (SIM) 19.5.1.5 Interrupt Status Register 2 Address: $FE05 Bit 7 6 5 4 3 2 1 Bit 0 Read: IF14 IF13 IF12 IF11 IF10 IF9 IF8 0 Write: R R R R R R R R Reset: 0 0 0 0 0 0 0 0 R = Reserved Figure 19-13. Interrupt Status Register 2 (INT2) IF14–IF8 — Interrupt Flags 14–7 These flags indicate the presence of interrupt requests from the sources shown in Table 19-3. 1 = Interrupt request present 0 = No interrupt request present Bit 0 — Always reads 0 19.5.1.6 Interrupt Status Register 3 Address: $FE06 Bit 7 6 5 4 3 2 1 Bit 0 Read: 0 0 0 0 0 0 I16 I15 Write: R R R R R R R R Reset: 0 0 0 0 0 0 0 0 R = Reserved Figure 19-14. Interrupt Status Register 3 (INT3) Bits 7–2 — Always read 0 I16–I15 — Interrupt Flags 16–15 These flags indicate the presence of an interrupt request from the source shown in Table 19-3. 1 = Interrupt request present 0 = No interrupt request present 19.5.2 Reset All reset sources always have equal and highest priority and cannot be arbitrated. 19.5.3 Break Interrupts The break module can stop normal program flow at a software-programmable break point by asserting its break interrupt output. See Chapter 22 Timer Interface Module (TIM). 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 198 Freescale Semiconductor Low-Power Modes 19.5.4 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). 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. 19.6 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. 19.6.1 Wait Mode In wait mode, the CPU clocks are inactive while the peripheral clocks continue to run. Figure 19-15 shows the timing for wait mode entry. A module that is active during wait mode can wake up the CPU with an interrupt if the interrupt is enabled. Stacking for the interrupt begins one cycle after the WAIT instruction during which the interrupt occurred. In wait mode, the CPU clocks are inactive. Refer to the wait mode subsection of each module to see if the module is active or inactive in wait mode. Some modules can be programmed to be active in wait mode. Wait mode 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 CONFIG register is 0, then the computer operating properly module (COP) is enabled and remains active in wait mode. IAB IDB WAIT ADDR WAIT ADDR + 1 PREVIOUS DATA NEXT OPCODE SAME SAME SAME SAME R/W Note: Previous data can be operand data or the WAIT opcode, depending on the last instruction. Figure 19-15. Wait Mode Entry Timing MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 199 System Integration Module (SIM) Figure 19-16 and Figure 19-17 show the timing for WAIT recovery. IAB $6E0B $A6 IDB $A6 $6E0C $A6 $01 $00FF $00FE $0B $00FD $00FC $6E EXITSTOPWAIT Note: EXITSTOPWAIT = RST pin, CPU interrupt, or break interrupt Figure 19-16. Wait Recovery from Interrupt or Break 32 CYCLES IAB IDB $6E0B $A6 $A6 32 CYCLES RST VCT H RST VCT L $A6 RST CGMXCLK Figure 19-17. Wait Recovery from Internal Reset 19.6.2 Stop Mode In stop mode, the SIM counter is reset and the system clocks are disabled. An interrupt request from a module can cause an exit from stop mode. Stacking for interrupts begins after the selected stop recovery time has elapsed. Reset or break also causes an exit from stop mode. The SIM disables the clock generator module outputs (CGMOUT and CGMXCLK) in stop mode, stopping the CPU and peripherals. Stop recovery time is selectable using the SSREC bit in the CONFIG register (MOR). 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 the configuration register. 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 19-18 shows stop mode entry timing. NOTE To minimize stop current, all pins configured as inputs should be driven to a 1 or 0. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 200 Freescale Semiconductor SIM Registers CPUSTOP IAB STOP ADDR + 1 STOP ADDR IDB PREVIOUS DATA SAME SAME NEXT OPCODE SAME SAME R/W Note : Previous data can be operand data or the STOP opcode, depending on the last instruction. Figure 19-18. Stop Mode Entry Timing STOP RECOVERY PERIOD CGMXCLK INT/BREAK IAB STOP + 2 STOP +1 STOP + 2 SP SP – 1 SP – 2 SP – 3 Figure 19-19. Stop Mode Recovery from Interrupt or Break 19.7 SIM Registers The SIM has three memory-mapped registers. Table 19-4 shows the mapping of these registers. Table 19-4. SIM Registers Address Register Access Mode $FE00 SBSR User $FE01 SRSR User $FE03 SBFCR User 19.7.1 SIM Break Status Register The SIM break status register (SBSR) contains a flag to indicate that a break caused an exit from wait mode Address: Read: Write: Reset: $FE00 Bit 7 6 5 4 3 2 R R R R R R 0 0 0 0 0 0 R = Reserved 1 BW Note(1) 0 Bit 0 R 0 Note: 1. Writing a logic 0 clears SBSW. Figure 19-20. SIM Break Status Register (SBSR) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 201 System Integration Module (SIM) BW — SIM Break Wait Clear BW by writing a 0 to it. Reset clears BW. BW can be read within the break state SWI routine. The user can modify the return address on the stack by subtracting one from it. 1 = Wait mode was exited by break interrupt. 0 = Wait mode was not exited by break interrupt. 19.7.2 SIM Reset Status Register The SRSR register contains flags that show the source of the last reset. The status register will automatically clear after reading SRSR. A power-on reset sets the POR bit and clears all other bits in the register. All other reset sources set the individual flag bits but do not clear the register. More than one reset source can be flagged at any time depending on the conditions at the time of the internal or external reset. For example, the POR and LVI bit can both be set if the power supply has a slow rise time. Address: Read: $FE01 Bit 7 6 5 4 3 2 1 Bit 0 POR PIN COP ILOP ILAD MODRST LVI 0 1 0 0 0 0 0 0 0 Write: Reset: = Unimplemented Figure 19-21. 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 202 Freescale Semiconductor SIM Registers 19.7.3 SIM Break Flag Control Register The SIM break control register contains a bit that enables software to clear status bits while the MCU is in a break state. Address: Read: Write: Reset: $FE03 Bit 7 6 5 4 3 2 1 Bit 0 BCFE R R R R R R R 0 R = Reserved Figure 19-22. SIM Break Flag Control Register (SBFCR) BCFE — Break Clear Flag Enable Bit This read/write bit enables software to clear status bits by accessing status registers while the MCU is in a break state. To clear status bits during the break state, the BCFE bit must be set. 1 = Status bits clearable during break 0 = Status bits not clearable during break MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 203 System Integration Module (SIM) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 204 Freescale Semiconductor Chapter 20 Serial Peripheral Interface (SPI) 20.1 Introduction This section describes the serial peripheral interface (SPI) module, which allows full-duplex, synchronous, serial communications with peripheral devices. 20.2 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) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 205 Serial Peripheral Interface (SPI) 20.3 Pin Name Conventions and I/O Register Addresses The text that follows describes the SPI. The SPI I/O pin names are SS (slave select), SPSCK (SPI serial clock), MOSI (master out slave in), and MISO (master in/slave out). The SPI shares four I/O pins with four parallel I/O ports. The full names of the SPI I/O pins are shown in Table 20-1. The generic pin names appear in the text that follows. Table 20-1. Pin Name Conventions SPI Generic Pin Names: Full SPI Pin Names: SPI MISO MOSI SS SPSCK CGND PTD1/ATD9 PTD2/ATD10 PTD0/ATD8 PTD3/ATD11 VSS 20.4 Functional Description Figure 20-1 summarizes the SPI I/O registers and Figure 20-2 shows the structure of the SPI module. Addr. $0010 Register Name Read: SPI Control Register Write: (SPCR) Reset: Read: $0011 $0012 SPI Status and Control Write: Register (SPSCR) Reset: Read: SPI Data Register Write: (SPDR) Reset: Bit 7 6 5 4 3 2 1 Bit 0 SPRIE R SPMSTR CPOL CPHA SPWOM SPE SPTIE 0 0 0 0 0 MODFEN SPR1 SPR0 SPRF ERRIE 1 0 1 OVRF MODF SPTE 0 0 0 0 1 0 0 0 R7 R6 R5 R4 R3 R2 R1 R0 T7 T6 T5 T4 T3 T2 T1 T0 Unaffected by reset = Unimplemented R = Reserved Figure 20-1. SPI I/O Register Summary 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. See 16.5.3 Port D Input Pullup Enable Register. The following paragraphs describe the operation of the SPI module. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 206 Freescale Semiconductor Functional Description INTERNAL BUS TRANSMIT DATA REGISTER CGMOUT ³ 2 FROM SIM SHIFT REGISTER 7 6 5 4 3 2 1 MISO 0 ÷2 CLOCK DIVIDER MOSI ÷8 RECEIVE DATA REGISTER ÷ 32 PIN CONTROL LOGIC ÷ 128 SPMSTR SPE CLOCK SELECT SPR1 SPSCK M CLOCK LOGIC S SS SPR0 SPMSTR TRANSMITTER CPU INTERRUPT REQUEST CPHA CPOL MODFEN SPWOM ERRIE SPI CONTROL SPTIE SPRIE RECEIVER/ERROR CPU INTERRUPT REQUEST DMAS SPE SPRF SPTE OVRF MODF Figure 20-2. SPI Module Block Diagram MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 207 Serial Peripheral Interface (SPI) 20.4.1 Master Mode The SPI operates in master mode when the SPI master bit, SPMSTR, is set. NOTE Configure the SPI modules as master or slave before enabling them. Enable the master SPI before enabling the slave SPI. Disable the slave SPI before disabling the master SPI. See 20.13.1 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 20-3. MASTER MCU SHIFT REGISTER SLAVE MCU MISO MISO MOSI MOSI SPSCK BAUD RATE GENERATOR SS SHIFT REGISTER SPSCK VDD SS Figure 20-3. Full-Duplex Master-Slave Connections The SPR1 and SPR0 bits control the baud rate generator and determine the speed of the shift register. See 20.13.2 SPI Status and Control Register. Through the SPSCK pin, the baud rate generator of the master also controls the shift register of the slave peripheral. As the byte shifts out on the MOSI pin of the master, another byte shifts in from the slave on the master’s MISO pin. The transmission ends when the receiver full bit, SPRF, becomes set. At the same time that SPRF becomes set, the byte from the slave transfers to the receive data register. In normal operation, SPRF signals the end of a transmission. Software clears SPRF by reading the SPI status and control register with SPRF set and then reading the SPI data register. Writing to the SPI data register clears the SPTE bit. 20.4.2 Slave Mode The SPI operates in slave mode when the SPMSTR bit is clear. In slave mode, the SPSCK pin is the input for the serial clock from the master MCU. Before a data transmission occurs, the SS pin of the slave SPI must be at logic 0. SS must remain low until the transmission is complete. See 20.7.2 Mode Fault Error. In a slave SPI module, data enters the shift register under the control of the serial clock from the master SPI module. After a byte enters the shift register of a slave SPI, it transfers to the receive data register, and the SPRF bit is set. To prevent an overflow condition, slave software then must read the receive data register before another full byte enters the shift register. The maximum frequency of the SPSCK for an SPI configured as a slave is the bus clock speed (which is twice as fast as the fastest master SPSCK clock that can be generated). The frequency of the SPSCK for an SPI configured as a slave does not have to correspond to any SPI baud rate. The baud rate only MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 208 Freescale Semiconductor Transmission Formats 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 20.5 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. 20.5 Transmission Formats During an SPI transmission, data is simultaneously transmitted (shifted out serially) and received (shifted in serially). A serial clock synchronizes shifting and sampling on the two serial data lines. A slave select line allows selection of an individual slave SPI device; slave devices that are not selected do not interfere with SPI bus activities. On a master SPI device, the slave select line can optionally be used to indicate multiple-master bus contention. 20.5.1 Clock Phase and Polarity Controls Software can select any of four combinations of serial clock (SPSCK) phase and polarity using two bits in the SPI control register (SPCR). The clock polarity is specified by the CPOL control bit, which selects an active high or low clock and has no significant effect on the transmission format. 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). 20.5.2 Transmission Format When CPHA = 0 Figure 20-4 shows an SPI transmission in which CPHA is logic 0. The figure should not be used as a replacement for data sheet parametric information. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 209 Serial Peripheral Interface (SPI) SPSCK CYCLE # FOR REFERENCE 1 2 3 4 5 6 7 8 MSB BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB SPSCK; CPOL = 0 SPSCK; CPOL =1 MOSI FROM MASTER MISO FROM SLAVE MSB SS; TO SLAVE CAPTURE STROBE Figure 20-4. Transmission Format (CPHA = 0) MISO/MOSI BYTE 1 BYTE 2 BYTE 3 MASTER SS SLAVE SS CPHA = 0 SLAVE SS CPHA = 1 Figure 20-5. CPHA/SS Timing Two waveforms are shown for SPSCK: one for CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins are directly connected between the master and the slave. The MISO signal is the output from the slave, and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The slave SPI drives its MISO output only when its slave select input (SS) is at 0, so that only the selected slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. See 20.7.2 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 20-5. 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. 20.5.3 Transmission Format When CPHA = 1 Figure 20-6 shows an SPI transmission in which CPHA is logic 1. The figure should not be used as a replacement for data sheet parametric information. Two waveforms are shown for SPSCK: one for CPOL = 0 and another for CPOL = 1. The diagram may be interpreted as a master or slave timing diagram since the serial clock (SPSCK), master in/slave out (MISO), and master out/slave in (MOSI) pins are directly connected between the master and the slave. The MISO signal is the output from the slave, and the MOSI signal is the output from the master. The SS line is the slave select input to the slave. The MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 210 Freescale Semiconductor Transmission Formats slave SPI drives its MISO output only when its slave select input (SS) is at logic 0, so that only the selected slave drives to the master. The SS pin of the master is not shown but is assumed to be inactive. The SS pin of the master must be high or must be reconfigured as general-purpose I/O not affecting the SPI. See 20.7.2 Mode Fault Error. When CPHA = 1, the master begins driving its MOSI pin on the first SPSCK edge. Therefore, the slave uses the first SPSCK edge as a start transmission signal. The SS pin can remain low between transmissions. This format may be preferable in systems having only one master and only one slave driving the MISO data line. SPSCK CYCLE # FOR REFERENCE 1 2 3 4 5 6 7 8 MOSI FROM MASTER MSB BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 LSB MISO FROM SLAVE MSB BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 SPSCK; CPOL = 0 SPSCK; CPOL =1 LSB SS; TO SLAVE CAPTURE STROBE Figure 20-6. Transmission Format (CPHA = 1) 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. 20.5.4 Transmission Initiation Latency When the SPI is configured as a master (SPMSTR = 1), writing to the SPDR starts a transmission. CPHA has no effect on the delay to the start of the transmission, but it does affect the initial state of the SPSCK signal. When CPHA = 0, the SPSCK signal remains inactive for the first half of the first SPSCK cycle. 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 20-7. The internal SPI clock in the master is a free-running derivative of the internal MCU clock. To conserve power, it is enabled only when both the SPE and SPMSTR bits are set. 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 20-7. This delay is no longer than a single SPI bit time. That is, the maximum delay is two MCU bus cycles for DIV2, eight MCU bus cycles for DIV8, 32 MCU bus cycles for DIV32, and 128 MCU bus cycles for DIV128. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 211 Serial Peripheral Interface (SPI) WRITE TO SPDR INITIATION DELAY BUS CLOCK MOSI MSB BIT 5 BIT 6 SPSCK CPHA = 1 SPSCK CPHA = 0 SPSCK CYCLE NUMBER 1 2 3 INITIATION DELAY FROM WRITE SPDR TO TRANSFER BEGIN ⎧ ⎨ ⎮ ⎮ ⎩ ⎮ ⎮ ⎮ WRITE TO SPDR BUS CLOCK EARLIEST WRITE TO SPDR LATEST SPSCK = INTERNAL CLOCK ³ 2; 2 POSSIBLE START POINTS BUS CLOCK EARLIEST WRITE TO SPDR SPSCK = INTERNAL CLOCK ³ 8; 8 POSSIBLE START POINTS LATEST SPSCK = INTERNAL CLOCK ³ 32; 32 POSSIBLE START POINTS LATEST SPSCK = INTERNAL CLOCK ³ 128; 128 POSSIBLE START POINTS LATEST BUS CLOCK EARLIEST WRITE TO SPDR BUS CLOCK EARLIEST Figure 20-7. Transmission Start Delay (Master) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 212 Freescale Semiconductor Queuing Transmission Data 20.6 Queuing Transmission Data The double-buffered transmit data register allows a data byte to be queued and transmitted. For an SPI configured as a master, a queued data byte is transmitted immediately after the previous transmission has completed. The SPI transmitter empty flag (SPTE) indicates when the transmit data buffer is ready to accept new data. Write to the transmit data register only when the SPTE bit is high. Figure 20-8 shows the timing associated with doing back-to-back transmissions with the SPI (SPSCK has CPHA: CPOL = 1:0). WRITE TO SPDR SPTE 1 3 2 8 5 10 SPSCK CPHA:CPOL = 1:0 MOSI MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT BIT BIT BIT LSB MSB BIT BIT BIT 6 5 4 6 5 4 3 2 1 6 5 4 3 2 1 BYTE 1 BYTE 2 BYTE 3 4 SPRF 9 6 READ SPSCR 11 7 READ SPDR 12 1 CPU WRITES BYTE 1 TO SPDR, CLEARING SPTE BIT. 7 CPU READS SPDR, CLEARING SPRF BIT. 2 BYTE 1 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 8 CPU WRITES BYTE 3 TO SPDR, QUEUEING BYTE 3 AND CLEARING SPTE BIT. 9 SECOND INCOMING BYTE TRANSFERS FROM SHIFT REGISTER TO RECEIVE DATA REGISTER, SETTING SPRF BIT. 10 BYTE 3 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 11 CPU READS SPSCR WITH SPRF BIT SET. 3 CPU WRITES BYTE 2 TO SPDR, QUEUEING BYTE 2 AND CLEARING SPTE BIT. FIRST INCOMING BYTE TRANSFERS FROM SHIFT REGISTER TO RECEIVE DATA REGISTER, SETTING SPRF BIT. 5 BYTE 2 TRANSFERS FROM TRANSMIT DATA REGISTER TO SHIFT REGISTER, SETTING SPTE BIT. 6 CPU READS SPSCR WITH SPRF BIT SET. 4 12 CPU READS SPDR, CLEARING SPRF BIT. Figure 20-8. SPRF/SPTE CPU Interrupt Timing The transmit data buffer allows back-to-back transmissions without the slave precisely timing its writes between transmissions as in a system with a single data buffer. Also, if no new data is written to the data buffer, the last value contained in the shift register is the next data word to be transmitted. For an idle master or idle slave that has no data loaded into its transmit buffer, the SPTE is set again no more than two bus cycles after the transmit buffer empties into the shift register. This allows the user to queue up a 16-bit value to send. For an already active slave, the load of the shift register cannot occur until the transmission is completed. This implies that a back-to-back write to the transmit data register is not possible. The SPTE indicates when the next write can occur. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 213 Serial Peripheral Interface (SPI) 20.7 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. 20.7.1 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 20-4 and Figure 20-6.) If an overflow occurs, all data received after the overflow and before the OVRF bit is cleared does not transfer to the receive data register and does not set the SPI receiver full bit (SPRF). The unread data that transferred to the receive data register before the overflow occurred can still be read. Therefore, an overflow error always indicates the loss of data. Clear the overflow flag by reading the SPI status and control register and then reading the SPI data register. OVRF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector. See Figure 20-11. It is not possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low prevents MODF from being set. If the CPU SPRF interrupt is enabled and the OVRF interrupt is not, watch for an overflow condition. Figure 20-9 shows how it is possible to miss an overflow. The first part of Figure 20-9 shows how it is possible to read the SPSCR and SPDR to clear the SPRF without problems. However, as illustrated by the second transmission example, the OVRF bit can be set in between the time that SPSCR and SPDR are read. BYTE 1 BYTE 2 BYTE 3 BYTE 4 1 4 6 8 SPRF OVRF READ SPSCR 2 READ SPDR 5 3 1 BYTE 1 SETS SPRF BIT. 2 CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. CPU READS BYTE 1 IN SPDR, CLEARING SPRF BIT. BYTE 2 SETS SPRF BIT. 3 4 7 5 CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. 6 BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST. 7 CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT, BUT NOT OVRF BIT. 8 BYTE 4 FAILS TO SET SPRF BIT BECAUSE OVRF BIT IS NOT CLEARED. BYTE 4 IS LOST. Figure 20-9. Missed Read of Overflow Condition MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 214 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 20-10 illustrates this process. Generally, to avoid this second SPSCR read, enable the OVRF to the CPU by setting the ERRIE bit. BYTE 1 SPI RECEIVE COMPLETE BYTE 2 5 1 BYTE 3 7 BYTE 4 11 SPRF OVRF READ SPSCR 2 READ SPDR 4 3 1 BYTE 1 SETS SPRF BIT. 2 CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. CPU READS BYTE 1 IN SPDR, CLEARING SPRF BIT. 3 6 9 8 12 10 14 13 8 CPU READS BYTE 2 IN SPDR, CLEARING SPRF BIT. 9 CPU READS SPSCR AGAIN TO CHECK OVRF BIT. 10 CPU READS BYTE 2 SPDR, CLEARING OVRF BIT. 4 CPU READS SPSCR AGAIN TO CHECK OVRF BIT. 11 BYTE 4 SETS SPRF BIT. 5 BYTE 2 SETS SPRF BIT. 12 CPU READS SPSCR. 6 CPU READS SPSCR WITH SPRF BIT SET AND OVRF BIT CLEAR. 13 CPU READS BYTE 4 IN SPDR, CLEARING SPRF BIT. 7 BYTE 3 SETS OVRF BIT. BYTE 3 IS LOST. 14 CPU READS SPSCR AGAIN TO CHECK OVRF BIT. Figure 20-10. Clearing SPRF When OVRF Interrupt Is Not Enabled 20.7.2 Mode Fault Error Setting the SPMSTR bit selects master mode and configures the SPSCK and MOSI pins as outputs and the MISO pin as an input. Clearing SPMSTR selects slave mode and configures the SPSCK and MOSI pins as inputs and the MISO pin as an output. The mode fault bit, MODF, becomes set any time the state of the slave select pin, SS, is inconsistent with the mode selected by SPMSTR. To prevent SPI pin contention and damage to the MCU, a mode fault error occurs if: • The SS pin of a slave SPI goes high during a transmission • The SS pin of a master SPI goes low at any time For the MODF flag to be set, the mode fault error enable bit (MODFEN) must be set. Clearing the MODFEN bit does not clear the MODF flag but does prevent MODF from being set again after MODF is cleared. MODF generates a receiver/error CPU interrupt request if the error interrupt enable bit (ERRIE) is also set. The SPRF, MODF, and OVRF interrupts share the same CPU interrupt vector. See Figure 20-11. It is not possible to enable MODF or OVRF individually to generate a receiver/error CPU interrupt request. However, leaving MODFEN low prevents MODF from being set. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 215 Serial Peripheral Interface (SPI) In a master SPI with the mode fault enable bit (MODFEN) set, the mode fault flag (MODF) is set if SS goes to logic 0. A mode fault in a master SPI causes the following events to occur: • 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 20.5 Transmission Formats. NOTE Setting the MODF flag does not clear the SPMSTR bit. The SPMSTR bit has no function when SPE = 0. Reading SPMSTR when MODF = 1 shows the difference between a MODF occurring when the SPI is a master and when it is a slave. When CPHA = 0, a MODF occurs if a slave is selected (SS is 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), the MODF bit generates an SPI receiver/error CPU interrupt request if the ERRIE bit is set. The MODF bit does not clear the SPE bit or reset the SPI in any way. Software can abort the SPI transmission by clearing the SPE bit of the slave. NOTE A 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 216 Freescale Semiconductor Interrupts 20.8 Interrupts Four SPI status flags can be enabled to generate CPU interrupt requests. Table 20-2. SPI Interrupts Flag Request SPTE Transmitter empty SPI transmitter CPU interrupt request (SPTIE = 1, SPE = 1) SPRF Receiver full SPI receiver CPU interrupt request (SPRIE = 1) OVRF Overflow SPI receiver/error interrupt request (ERRIE = 1) MODF Mode fault SPI receiver/error interrupt request (ERRIE = 1) Reading the SPI status and control register with SPRF set and then reading the receive data register clears SPRF. The clearing mechanism for the SPTE flag is always just a write to the transmit data register. The SPI transmitter interrupt enable bit (SPTIE) enables the SPTE flag to generate transmitter CPU interrupt requests, provided that the SPI is enabled (SPE = 1). The SPI receiver interrupt enable bit (SPRIE) enables the SPRF bit to generate receiver CPU interrupt requests, regardless of the state of the SPE bit. See Figure 20-11. The error interrupt enable bit (ERRIE) enables both the MODF and OVRF bits to generate a receiver/error CPU interrupt request. The mode fault enable bit (MODFEN) can prevent the MODF flag from being set so that only the OVRF bit is enabled by the ERRIE bit to generate receiver/error CPU interrupt requests. SPTE SPTIE SPE SPI TRANSMITTER CPU INTERRUPT REQUEST SPRIE SPRF SPI RECEIVER/ERROR ERRIE CPU INTERRUPT REQUEST MODF OVRF Figure 20-11. SPI Interrupt Request Generation MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 217 Serial Peripheral Interface (SPI) The following sources in the SPI status and control register can generate CPU interrupt requests: • SPI receiver full bit (SPRF) — The SPRF bit becomes set every time a byte transfers from the shift register to the receive data register. If the SPI receiver interrupt enable bit, SPRIE, is also set, SPRF generates an SPI receiver/error CPU interrupt request. • SPI transmitter empty (SPTE) — The SPTE bit becomes set every time a byte transfers from the transmit data register to the shift register. If the SPI transmit interrupt enable bit, SPTIE, is also set, SPTE generates an SPTE CPU interrupt request. 20.9 Resetting the SPI Any system reset completely resets the SPI. Partial resets occur whenever the SPI enable bit (SPE) is 0. Whenever SPE is low, the following occurs: • The SPTE flag is set. • Any transmission currently in progress is aborted. • The shift register is cleared. • The SPI state counter is cleared, making it ready for a new complete transmission. • All the SPI port logic is defaulted back to being general-purpose I/O. These items are reset only by a system reset: • All control bits in the SPCR register • All control bits in the SPSCR register (MODFEN, ERRIE, SPR1, and SPR0) • The status flags SPRF, OVRF, and MODF By not resetting the control bits when SPE is low, the user can clear SPE between transmissions without having to set all control bits again when SPE is set back high for the next transmission. 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. 20.10 Low-Power Modes The WAIT and STOP instructions put the MCU in low power-consumption standby modes. 20.10.1 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 20.8 Interrupts. 20.10.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 218 Freescale Semiconductor SPI During Break Interrupts 20.11 SPI During Break Interrupts The system integration module (SIM) controls whether status bits in other modules can be cleared during the break state. The BCFE bit in the SIM break flag control register (SBFCR) enables software to clear status bits during the break state. See Chapter 19 System Integration Module (SIM). 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. Since the SPTE bit cannot be cleared during a break with the BCFE bit cleared, a write to the transmit data register in break mode does not initiate a transmission nor is this data transferred into the shift register. Therefore, a write to the SPDR in break mode with the BCFE bit cleared has no effect. 20.12 I/O Signals The SPI module has four I/O pins and shares four of them with a parallel I/O port. They are: • MISO — Data received • MOSI — Data transmitted • SPSCK — Serial clock • SS — Slave select 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. 20.12.1 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. 20.12.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 219 Serial Peripheral Interface (SPI) 20.12.3 SPSCK (Serial Clock) The serial clock synchronizes data transmission between master and slave devices. In a master MCU, the SPSCK pin is the clock output. In a slave MCU, the SPSCK pin is the clock input. In full-duplex operation, the master and slave MCUs exchange a byte of data in eight serial clock cycles. When enabled, the SPI controls data direction of the SPSCK pin regardless of the state of the data direction register of the shared I/O port. 20.12.4 SS (Slave Select) The SS pin has various functions depending on the current state of the SPI. For an SPI configured as a slave, the SS is used to select a slave. For CPHA = 0, the SS is used to define the start of a transmission. See 20.5 Transmission Formats. Since it is used to indicate the start of a transmission, the SS must be toggled high and low between each byte transmitted for the CPHA = 0 format. However, it can remain low between transmissions for the CPHA = 1 format. See Figure 20-12. MISO/MOSI BYTE 1 BYTE 2 BYTE 3 MASTER SS SLAVE SS CPHA = 0 SLAVE SS CPHA = 1 Figure 20-12. CPHA/SS Timing When an SPI is configured as a slave, the SS pin is always configured as an input. It cannot be used as a general-purpose I/O regardless of the state of the MODFEN control bit. However, the MODFEN bit can still prevent the state of the SS from creating a MODF error. See 20.13.2 SPI Status and Control Register. NOTE A high voltage on the SS pin of a slave SPI puts the MISO pin in a high-impedance state. The slave SPI ignores all incoming SPSCK clocks, even if it was already in the middle of a transmission. When an SPI is configured as a master, the SS input can be used in conjunction with the MODF flag to prevent multiple masters from driving MOSI and SPSCK. See 20.7.2 Mode Fault Error. For the state of the SS pin to set the MODF flag, the MODFEN bit in the SPSCK register must be set. If the MODFEN bit is low for an SPI master, the SS pin can be used as a general-purpose I/O under the control of the data direction register of the shared I/O port. With MODFEN high, it is an input-only pin to the SPI regardless of the state of the data direction register of the shared I/O port. The CPU can always read the state of the SS pin by configuring the appropriate pin as an input and reading the port data register. See Table 20-3. Table 20-3. SPI Configuration SPE SPMSTR MODFEN SPI Configuration State of SS Logic 0 X(1) X Not enabled General-purpose I/O; SS ignored by SPI 1 0 X Slave Input-only to SPI 1 1 0 Master without MODF General-purpose I/O; SS ignored by SPI 1 1 1 Master with MODF Input-only to SPI Note 1. X = Don’t care MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 220 Freescale Semiconductor I/O Registers 20.13 I/O Registers Three registers control and monitor SPI operation: • SPI control register (SPCR) • SPI status and control register (SPSCR) • SPI data register (SPDR) 20.13.1 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: SPRIE Write: Reset: 0 R 6 5 4 3 2 1 Bit 0 R SPMSTR CPOL CPHA SPWOM SPE SPTIE 0 = Reserved 1 0 1 0 0 0 Figure 20-13. SPI Control Register (SPCR) SPRIE — SPI Receiver Interrupt Enable Bit This read/write bit enables CPU interrupt requests generated by the SPRF bit. The SPRF bit is set when a byte transfers from the shift register to the receive data register. Reset clears the SPRIE bit. 1 = SPRF CPU interrupt requests enabled 0 = SPRF CPU interrupt requests disabled 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 20-4 and Figure 20-6.) To transmit data between SPI modules, the SPI modules must have identical CPOL values. Reset clears the CPOL bit. CPHA — Clock Phase Bit This read/write bit controls the timing relationship between the serial clock and SPI data. (See Figure 20-4 and Figure 20-6.) To transmit data between SPI modules, the SPI modules must have identical CPHA values. When CPHA = 0, the SS pin of the slave SPI module must be set to logic 1 between bytes. See Figure 20-12. Reset sets the CPHA bit. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 221 Serial Peripheral Interface (SPI) SPWOM — SPI Wired-OR Mode Bit This read/write bit disables the pullup devices on pins SPSCK, MOSI, and MISO so that those pins become open-drain outputs. 1 = Wired-OR SPSCK, MOSI, and MISO pins 0 = Normal push-pull SPSCK, MOSI, and MISO pins SPE — SPI Enable This read/write bit enables the SPI module. Clearing SPE causes a partial reset of the SPI. See 20.9 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 20.13.2 SPI Status and Control Register The SPI status and control register contains flags to signal these conditions: • Receive data register full • Failure to clear SPRF bit before next byte is received (overflow error) • Inconsistent logic level on SS pin (mode fault error) • Transmit data register empty The SPI status and control register also contains bits that perform these functions: • Enable error interrupts • Enable mode fault error detection • Select master SPI baud rate Address: $0011 Bit 7 Read: SPRF Write: Reset: 0 6 ERRIE 5 OVRF 0 0 = Unimplemented 4 MODF 3 SPTE 0 1 2 1 Bit 0 MODFEN SPR1 SPR0 0 0 0 Figure 20-14. SPI Status and Control Register (SPSCR) SPRF — SPI Receiver Full Bit This clearable, read-only flag is set each time a byte transfers from the shift register to the receive data register. SPRF generates a CPU interrupt request if the SPRIE bit in the SPI control register is set also. During an SPRF CPU interrupt, the CPU clears SPRF by reading the SPI status and control register with SPRF set and then reading the SPI data register. Reset clears the SPRF bit. 1 = Receive data register full 0 = Receive data register not full 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 222 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 the MODFEN bit set. In a master SPI, the MODF flag is set if the SS pin goes low at any time with the MODFEN bit set. Clear the MODF bit by reading the SPI status and control register (SPSCR) with MODF set and then writing to the SPI data register (SPDR). Reset clears the MODF bit. 1 = SS pin at inappropriate logic level 0 = SS pin at appropriate logic level SPTE — SPI Transmitter Empty Bit This clearable, read-only flag is set each time the transmit data register transfers a byte into the shift register. SPTE generates an SPTE CPU interrupt request if the SPTIE bit in the SPI control register is set also. NOTE Do not write to the SPI data register unless the SPTE bit is high. During an SPTE CPU interrupt, the CPU clears the SPTE bit by writing to the transmit data register. Reset sets the SPTE bit. 1 = Transmit data register empty 0 = Transmit data register not empty MODFEN — Mode Fault Enable Bit This read/write bit, when set to 1, allows the MODF flag to be set. If the MODF flag is set, clearing the MODFEN does not clear the MODF flag. If the SPI is enabled as a master and the MODFEN bit is 0, then the SS pin is available as a general-purpose I/O. If the MODFEN bit is set, then this pin is not available as a general-purpose I/O. When the SPI is enabled as a slave, the SS pin is not available as a general-purpose I/O regardless of the value of MODFEN. See 20.12.4 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 20.7.2 Mode Fault Error. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 223 Serial Peripheral Interface (SPI) 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 20-4. SPR1 and SPR0 have no effect in slave mode. Reset clears SPR1 and SPR0. Table 20-4. SPI Master Baud Rate Selection SPR1 and SPR0 Baud Rate Divisor (BD) 00 2 01 8 10 32 11 128 Use this formula to calculate the SPI baud rate: Baud rate = BUSCLK BD where: BD = baud rate divisor 20.13.3 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 20-2. Address: $0012 Bit 7 6 5 4 3 2 1 Bit 0 Read: R7 R6 R5 R4 R3 R2 R1 R0 Write: T7 T6 T5 T4 T3 T2 T1 T0 Reset: Indeterminate after reset Figure 20-15. SPI Data Register (SPDR) R7–R0/T7–T0 — Receive/Transmit Data Bits NOTE Do not use read-modify-write instructions on the SPI data register since the register read is not the same as the register written. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 224 Freescale Semiconductor Chapter 21 Timebase Module (TBM) 21.1 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 crystal clock. This TBM version uses 15 divider stages, eight of which are user selectable. For further information regarding timers on M68HC08 family devices, please consult the HC08 Timer Reference Manual, TIM08RM/AD. 21.2 Features Features of the TBM module include: • Software programmable 1 Hz, 4 Hz, 16 Hz, 256 Hz, 512 Hz, 1024 Hz, 2048 Hz, and 4096 Hz periodic interrupt using external 32.768 kHz crystal • User selectable oscillator clock source enable during stop mode to allow periodic wakeup from stop 21.3 Functional Description NOTE This module is designed for a 32.768 kHz oscillator. This module can generate a periodic interrupt by dividing the crystal frequency, CGMXCLK. The counter is initialized to all 0s when TBON bit is cleared. The counter, shown in Figure 21-1, 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 periodic wakeup from stop mode. 21.4 Interrupts The timebase module can periodically interrupt the CPU with a rate defined by TBR2:TBR0. When the timebase counter chain rolls over, the TBIF flag is set. If the TBIE bit is set, enabling the timebase interrupt, the counter chain overflow will generate a CPU interrupt request. NOTE Interrupts must be acknowledged by writing a 1 to the TACK bit. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 225 Timebase Module (TBM) TBON ÷2 ÷2 ÷ 128 ÷2 ÷ 64 ÷2 ÷ 32 ÷2 ÷8 ÷2 ÷ 16 ÷2 CGMXCLK ÷2 ÷2 TACK ÷2 TBR0 ÷2 TBR1 ÷2 ÷ 32,768 ÷2 ÷ 8192 ÷2 ÷ 2048 ÷2 TBR2 TBMINT TBIF 000 TBIE R 001 010 100 SEL 011 101 110 111 Figure 21-1. Timebase Block Diagram 21.5 Low-Power Modes The WAIT and STOP instructions put the MCU in low power-consumption standby modes. 21.5.1 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 enabling the WAIT instruction. 21.5.2 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 OSCSTOPEN bit in the CONFIG 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 226 Freescale Semiconductor Timebase Register Description If the timebase functions are not required during stop mode, reduce the power consumption by stopping the timebase before enabling the STOP instruction. 21.6 Timebase Register Description The timebase has one register, the TBCR, which is used to enable the timebase interrupts and set the rate. Address: $001C Bit 7 Read: 6 TBIF Write: Reset: 0 5 4 3 0 TBR2 TBR1 TBR0 0 0 0 0 = Unimplemented R = Reserved TACK 2 1 Bit 0 TBIE TBON R 0 0 0 Figure 21-2. 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 Rate Selection These read/write bits are used to select the rate of timebase interrupts as shown in Table 21-1. Table 21-1. Timebase Rate Selection for OSC1 = 32.768 kHz Timebase Interrupt Rate TBR2 TBR1 TBR0 Divider Hz ms 0 0 0 32,768 1 1000 0 0 1 8192 4 250 0 1 0 2048 16 62.5 0 1 1 128 256 ~ 3.9 1 0 0 64 512 ~2 1 0 1 32 1024 ~1 1 1 0 16 2048 ~0.5 1 1 1 8 4096 ~0.24 NOTE Do not change TBR2–TBR0 bits while the timebase is enabled (TBON = 1). TACK— Timebase ACKnowledge 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 227 Timebase Module (TBM) TBIE — Timebase Interrupt Enabled This read/write bit enables the timebase interrupt when the TBIF bit becomes set. Reset clears the TBIE bit. 1 = Timebase interrupt enabled 0 = Timebase interrupt disabled TBON — Timebase Enabled 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 enabled 0 = Timebase disabled and the counter initialized to 0s MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 228 Freescale Semiconductor Chapter 22 Timer Interface Module (TIM) 22.1 Introduction This section describes the timer interface (TIM) module. The TIM on this part is a 2-channel and a1-channel timer that provides a timing reference with input capture, output compare, and pulse-width-modulation functions. Figure 22-1 is a block diagram of the TIM. This particular MCU has two timer interface modules which are denoted as TIM1 and TIM2. For further information regarding timers on M68HC08 family devices, please consult the HC08 Timer Reference Manual, TIM08RM/AD. 22.2 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 22.3 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 1 channel 0, timer 2 channel 0) and T[1]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 22-1. The generic pin names appear in the text that follows. Table 22-1. Pin Name Conventions TIM Generic Pin Names: Full TIM Pin Names: T[1,2]CH0 T[1,2]CH1 TIM1 PTD4/ATD12/T1CH0 PTD5/T1CH1 TIM2 PTD6/ATD14/T2CH0 — MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 229 Timer Interface Module (TIM) NOTE References to either timer 1 or timer 2 may be made in the following text by omitting the timer number. For example, TCH0 may refer generically to T1CH0 and T2CH0, and TCH1 will refer to T1CH1. NOTE The Timer Interface Module in MC68HC908GR8 is constructed by TIM1 which contains channel 0 and 1, and TIM2 which contains channel 0 only. 22.4 Functional Description Figure 22-1 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 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 Port D Input Pullup Enable Register. In Figure 22-1, channel1 will only be available in TIM1 while channel 0 will be available in both TIM1 and TIM2. Figure 22-2 summarizes the timer registers. 22.4.1 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. 22.4.2 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. 22.4.3 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 230 Freescale Semiconductor Functional Description INTERNAL BUS CLOCK PRESCALER SELECT PRESCALER TSTOP PS2 TRST PS1 PS0 16-BIT COUNTER TOF TOIE INTERRUPT LOGIC 16-BIT COMPARATOR TMODH:TMODL TOV0 CHANNEL 0 ELS0B ELS0A CH0MAX PORT LOGIC T[1,2]CH0 16-BIT COMPARATOR TCH0H:TCH0L CH0F 16-BIT LATCH MS0A CH0IE INTERRUPT LOGIC MS0B INTERNAL BUS TOV1 CHANNEL 1 ELS1B ELS1A CH1MAX PORT LOGIC T[1]CH1 16-BIT COMPARATOR TCH1H:TCH1L CH1F 16-BIT LATCH MS1A CH1IE INTERRUPT LOGIC Figure 22-1. TIM Block Diagram 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 231 Timer Interface Module (TIM) Addr. Register Name Bit 7 Read: $0020 $0021 $0022 $0026 $0027 $0029 $002A $002B 4 3 0 0 2 1 Bit 0 PS2 PS1 PS0 0 0 1 0 0 0 0 0 Read: Timer 1 Counter Register Write: High (T1CNTH) Reset: Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Read: Timer 1 Counter Register Write: Low (T1CNTL) Reset: Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 1 1 1 1 1 1 1 1 Timer 1 Counter Modulo Write: Register Low (T1MODL) Reset: Bit 7 6 5 4 3 2 1 Bit 0 1 1 1 1 1 1 1 1 Read: Timer 1 Channel 0 Status and Write: Control Register (T1SC0) Reset: CH0F CH0IE MS0B MS0A ELS0B ELS0A TOV0 CH0MAX 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 2 1 Bit 0 Read: Timer 1 Channel 0 Write: Register High (T1CH0H) Reset: Read: Timer 1 Channel 0 Write: Register Low (T1CH0L) Reset: Read: $0028 5 TSTOP Read: $0025 6 TOIE Timer 1 Status and Control Write: Register (T1SC) Reset: Read: Timer 1 Counter Modulo RegWrite: $0023 ister High (T1MODH) Reset: $0024 TOF Timer 1 Channel 1 Status and Write: Control Register (T1SC1) Reset: Read: Timer 1 Channel 1 Write: Register High (T1CH1H) Reset: Read: Timer 1 Channel 1 Write: Register Low (T1CH1L) Reset: Read: Timer 2 Status and Control Write: Register (T2SC) Reset: 0 0 TRST Indeterminate after reset Bit 7 6 5 4 3 Indeterminate after reset CH1F 0 0 CH1IE MS1A ELS1B ELS1A TOV1 CH1MAX 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 2 1 Bit 0 PS2 PS1 PS0 0 0 0 Indeterminate after reset Bit 7 6 5 4 3 Indeterminate after reset TOF 0 0 TOIE TSTOP 0 1 0 0 TRST 0 0 = Unimplemented Figure 22-2. TIM I/O Register Summary (Sheet 1 of 2) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 232 Freescale Semiconductor Functional Description Addr. Register Name Read: $002C $002D Timer 2 Counter Register Write: High (T2CNTH) Reset: Read: Timer 2 Counter Register Write: Low (T2CNTL) Reset: Read: Timer 2 Counter Modulo Reg$002E Write: ister High (T2MODH) Reset: $002F Read: Timer 2 Counter Modulo Write: Register Low (T2MODL) Reset: Read: $0030 $0031 $0032 Timer 2 Channel 0 Status and Write: Control Register (T2SC0) Reset: Read: Timer 2 Channel 0 Write: Register High (T2CH0H) Reset: Read: Timer 2 Channel 0 Write: Register Low (T2CH0L) Reset: Bit 7 6 5 4 3 2 1 Bit 0 Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 1 1 1 1 1 1 1 1 Bit 7 6 5 4 3 2 1 Bit 0 1 1 1 1 1 1 1 1 CH0IE MS0B MS0A ELS0B ELS0A TOV0 CH0MAX 0 0 0 0 0 0 0 0 Bit 15 14 13 12 11 10 9 Bit 8 2 1 Bit 0 0 0 0 CH0F 0 Indeterminate after reset Bit 7 6 5 4 3 Indeterminate after reset Read: $0033 Unimplemented Write: Reset: 0 0 0 0 0 Read: $0034 Unimplemented Write: Reset: Indeterminate after reset Read: $0035 Unimplemented Write: Reset: Indeterminate after reset = Unimplemented Figure 22-2. TIM I/O Register Summary (Sheet 2 of 2) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 233 Timer Interface Module (TIM) 22.4.3.1 Unbuffered Output Compare Any output compare channel can generate unbuffered output compare pulses as described in 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. 22.4.3.2 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. 22.4.4 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 22-3 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 234 Freescale Semiconductor Functional Description to clear the channel pin on output compare if the state of the PWM pulse is 1. Program the TIM to set the pin if the state of the PWM pulse is 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 TIM Status and Control Register. OVERFLOW OVERFLOW OVERFLOW PERIOD POLARITY = 1 (ELSxA = 0) TCHx PULSE WIDTH POLARITY = 0 (ELSxA = 1) TCHx OUTPUT COMPARE OUTPUT COMPARE OUTPUT COMPARE Figure 22-3. PWM Period and Pulse Width 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%. 22.4.4.1 Unbuffered PWM Signal Generation Any output compare channel can generate unbuffered PWM pulses as described in 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. • 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 235 Timer Interface Module (TIM) 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. 22.4.4.2 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. 22.4.4.3 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 22-3. b. Write 1 to the toggle-on-overflow bit, TOVx. c. Write 1:0 (polarity 1 — to clear output on compare) or 1:1 (polarity 0 — to set out 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 22-3.) 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 236 Freescale Semiconductor Interrupts 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 TIM Channel Status and Control Registers.) 22.5 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. 22.6 Low-Power Modes The WAIT and STOP instructions put the MCU in low power- consumption standby modes. 22.6.1 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. 22.6.2 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 237 Timer Interface Module (TIM) 22.7 TIM During Break Interrupts A break interrupt stops the TIM counter and inhibits input captures. 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 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. 22.8 I/O Signals Port D shares three of its pins with the TIM. The three TIM channel I/O pins are T1CH0, T1CH1 and T2CH0 as described in 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. 22.9 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 control registers (TCNTH:TCNTL) • TIM counter modulo registers (TMODH:TMODL) • TIM channel status and control registers (TSC0, TSC1) • TIM channel registers (TCH0H:TCH0L, TCH1H:TCH1L) 22.9.1 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 238 Freescale Semiconductor I/O Registers Address: T1SC, $0020 and T2SC, $002B Bit 7 Read: TOF Write: 0 Reset: 0 6 5 TOIE TSTOP 0 1 4 3 0 0 TRST 0 0 2 1 Bit 0 PS2 PS1 PS0 0 0 0 = Unimplemented Figure 22-4. 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 logic 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. PS2–PS0 — Prescaler Select Bits These read/write bits select either the TCLK pin or one of the seven prescaler outputs as the input to the TIM counter as Table 22-2 shows. Reset clears the PS[2:0] bits. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 239 Timer Interface Module (TIM) Table 22-2. Prescaler Selection PS2–PS0 TIM Clock Source 000 Internal bus clock ÷1 001 Internal bus clock ÷ 2 010 Internal bus clock ÷ 4 011 Internal bus clock ÷ 8 100 Internal bus clock ÷ 16 101 Internal bus clock ÷ 32 110 Internal bus clock ÷ 64 111 Not available 22.9.2 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: Read: T1CNTH, $0021 and T2CNTH, $002C Bit 7 6 5 4 3 2 1 Bit 0 Bit 15 14 13 12 11 10 9 Bit 8 0 0 0 0 0 0 0 0 Write: Reset: = Unimplemented Figure 22-5. TIM Counter Registers High (TCNTH) Address: Read: T1CNTL, $0022 and T2CNTL, $002D Bit 7 6 5 4 3 2 1 Bit 0 Bit 7 6 5 4 3 2 1 Bit 0 0 0 0 0 0 0 0 Write: Reset: 0 = Unimplemented Figure 22-6. TIM Counter Registers Low (TCNTL) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 240 Freescale Semiconductor I/O Registers 22.9.3 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. Address: Read: Write: Reset: T1MODH, $0023 and T2MODH, $002E Bit 7 6 5 4 3 2 1 Bit 0 Bit 15 14 13 12 11 10 9 Bit 8 1 1 1 1 1 1 1 1 Figure 22-7. TIM Counter Modulo Register High (TMODH) Address: Read: Write: Reset: T1MODL, $0024 and T2MODL, $002F Bit 7 6 5 4 3 2 1 Bit 0 Bit 15 14 13 12 11 10 9 Bit 8 1 1 1 1 1 1 1 1 Figure 22-8. TIM Counter Modulo Register Low (TMODL) NOTE Reset the TIM counter before writing to the TIM counter modulo registers. 22.9.4 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 241 Timer Interface Module (TIM) Address: T1SC0, $0025 and T2SC0, $0030 Bit 7 Read: CH0F Write: 0 Reset: 0 6 5 4 3 2 1 Bit 0 CH0IE MS0B MS0A ELS0B ELS0A TOV0 CH0MAX 0 0 0 0 0 0 0 Figure 22-9. TIM Channel 0 Status and Control Register (TSC0) Address: T1SC1, $0028 Bit 7 Read: CH1F Write: 0 Reset: 0 6 CH1IE 0 5 0 0 4 3 2 1 Bit 0 MS1A ELS1B ELS1A TOV1 CH1MAX 0 0 0 0 0 = Unimplemented Figure 22-10. TIM Channel 1 Status and Control Register (TSC1) 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 service requests enabled 0 = Channel x CPU interrupt service 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 22-3. 1 = Unbuffered output compare/PWM operation 0 = Input capture operation MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 242 Freescale Semiconductor I/O Registers When ELSxB:A = 00, this read/write bit selects the initial output level of the TCHx pin. See Table 22-3. 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 22-3 shows how ELSxB and ELSxA work. Reset clears the ELSxB and ELSxA bits. Table 22-3. Mode, Edge, and Level Selection MSxB MSxA ELSxB ELSxA X 0 0 0 X 1 0 0 0 0 0 1 0 0 1 0 0 0 1 1 Capture on rising or falling edge 0 1 0 0 Software compare only 0 1 0 1 0 1 1 0 0 1 1 1 1 X 0 1 1 X 1 0 1 X 1 1 Mode Output preset Configuration Pin under port control; initial output level high Pin under port control; initial output level low Capture on rising edge only Input capture Output compare or PWM Capture on falling edge only Toggle output on compare Clear output on compare Set output on compare Buffered output compare or buffered PWM Toggle output on compare Clear output on compare Set output on compare NOTE Before enabling a TIM channel register for input capture operation, make sure that the PTD/TCHx pin is stable for at least two bus clocks. TOVx — Toggle On Overflow Bit When channel x is an output compare channel, this read/write bit controls the behavior of the channel x output when the TIM counter overflows. When channel x is an input capture channel, TOVx has no effect. Reset clears the TOVx bit. 1 = Channel x pin toggles on TIM counter overflow. 0 = Channel x pin does not toggle on TIM counter overflow. NOTE When TOVx is set, a TIM counter overflow takes precedence over a channel x output compare if both occur at the same time. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 243 Timer Interface Module (TIM) 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 . CHxMAX Latency 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. OVERFLOW OVERFLOW OVERFLOW OVERFLOW OVERFLOW PERIOD PTEx/TCHx OUTPUT COMPARE OUTPUT COMPARE OUTPUT COMPARE OUTPUT COMPARE CHxMAX Figure 22-11. CHxMAX Latency 22.9.5 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. Address: Read: Write: T1CH0H, $0026 and T2CH0H, $0031 Bit 7 6 5 4 3 2 1 Bit 0 Bit 15 14 13 12 11 10 9 Bit 8 Reset: Indeterminate after reset Figure 22-12. TIM Channel 0 Register High (TCH0H) Address: Read: Write: Reset: T1CH0L, $0027 and T2CH0L $0032 Bit 7 6 5 4 3 2 1 Bit 0 Bit 7 6 5 4 3 2 1 Bit 0 Indeterminate after reset Figure 22-13. TIM Channel 0 Register Low (TCH0L) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 244 Freescale Semiconductor I/O Registers Address: Read: Write: T1CH1H, $0029 Bit 7 6 5 4 3 2 1 Bit 0 Bit 15 14 13 12 11 10 9 Bit 8 Reset: Indeterminate after reset Figure 22-14. TIM Channel 1 Register High (TCH1H) Address: Read: Write: Reset: T1CH1L, $002A Bit 7 6 5 4 3 2 1 Bit 0 Bit 7 6 5 4 3 2 1 Bit 0 Indeterminate after reset Figure 22-15. TIM Channel 1 Register Low (TCH1L) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 245 Timer Interface Module (TIM) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 246 Freescale Semiconductor Chapter 23 Electrical Specifications 23.1 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) Symbol Value Unit Supply voltage VDD –0.3 to + 6.0 V Input voltage VIn VSS – 0.3 to VDD + 0.3 V I ± 15 mA IPTC0–PTC1 ± 25 mA Maximum current into VDD Imvdd 150 mA Maximum current out of VSS Imvss 150 mA Tstg –55 to +150 °C Maximum current per pin excluding VDD, VSS , and PTC0–PTC1 Maximum current for pins PTC0–PTC1 Storage temperature 1. Voltages referenced to VSS NOTE This device contains circuitry to protect the inputs against damage due to high static voltages or electric fields; however, it is advised that normal precautions be taken to avoid application of any voltage higher than maximum-rated voltages to this high-impedance circuit. For proper operation, it is recommended that VIn and VOut be constrained to the range VSS ≤ (VIn or VOut) ≤ VDD. Reliability of operation is enhanced if unused inputs are connected to an appropriate logic voltage level (for example, either VSS or VDD). MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 247 Electrical Specifications 23.2 Functional Operating Range Characteristic Operating temperature range Operating voltage range Symbol Value Unit TA –40 to +125 °C VDD 3.0 ±10% 5.0 ±10% V NOTE To ensure correct operation of the MCU under all operating conditions, the user must write data $1C to address $0033 immediately after reset. This is to ensure proper termination of an unused module within the MCU. 23.3 Thermal Characteristics Characteristic Symbol Value Unit Thermal resistance PDIP (28-pin) SOIC (28-pin) QFP (32-pin) SDIP (42-pin) θJA I/O pin power dissipation PI/O User-Determined W Power dissipation(1) PD PD = (IDD × VDD) + PI/O = K/(TJ + 273 °C) W Constant(2) K Average junction temperature Maximum junction temperature 60 60 95 57 PD x (TA + 273 °C) °C/W + PD2 × θJA W/°C TJ TA + (PD × θJA) °C TJM 140 °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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 248 Freescale Semiconductor 5.0 V DC Electrical Characteristics 23.4 5.0 V DC Electrical Characteristics Symbol Min Typ(2) Max Unit VOH VOH VOH IOH1 VDD – 0.8 VDD – 1.5 VDD – 0.8 — — — — — — — — 50 V V V mA IOH2 — — 50 mA IOHT — — 100 mA VOL VOL VOL IOL1 — — — — — — — — 0.4 1.5 1.0 50 V V V mA IOL2 — — 50 mA IOLT — — 100 mA Input high voltage All ports, IRQs, RESET OSC1 VIH 0.7 x VDD 0.8 x VDD — VDD V Input low voltage All ports, IRQs, RESET, OSC1 VIL VSS — 0.2 x VDD V — — — — — — 15 4 3 5 20 300 20 8 5 10 35 500 mA mA μA μA μA μA 0 0 — — 2 –0.2 mA 0 0 — — 25 –5 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 VDD supply current Run(3) Wait(4) Stop(5) (<85 °C) Stop (>85 °C) Stop with TBM enabled(6) Stop with LVI and TBM enabled(6) IDD DC injection current(7), (8), (9), (10) Single pin limit VIN > VDD VIN < VSS Total MCU limit, includes sum of all stressed pins VIN > VDD VIN < VSS IIC I/O ports Hi-Z leakage current(11) IIL — — ±10 μA Input current IIn — — 1 μA RPU 20 45 65 kΩ Pullup resistors (as input only) Ports PTA3/KBD3–PTA0/KBD0, PTC1–PTC0, PTD6/T2CH0–PTD0/SS Continued on next page MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 249 Electrical Specifications Symbol Min Typ(2) Max Unit Capacitance Ports (as input or output) COut CIn — — — — 12 8 pF Monitor mode entry voltage VTST VDD +2.5 — 8.5 V Low-voltage inhibit, trip falling voltage – target VTRIPF 3.85 4.25 4.50 V Low-voltage inhibit, trip rising voltage – target VTRIPR 3.95 4.35 4.60 V VHYS — 100 — mV VInHYS 0.06 x VDD — — V VPOR 0 — 100 mV VPORRST 0 700 800 mV RPOR 0.035 — — V/ms Characteristic(1) Low-voltage inhibit reset/recover hysteresis – target (VTRIPF + VHYS = VTRIPR) Input hysteresis (alternative input functions only)(7), (12) POR rearm voltage(7), (13) POR reset voltage(14) POR rise time ramp rate(7), (15) 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 square wave clock source (fOSC = 32.8 KHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. All ports configured as inputs. 7. This parameter is characterized and not tested on each device. 8. All functional non-supply pins are internally clamped to VSS and VDD. 9. Input must be current limited to the value specified. To determine the value of the required current-limiting resistor, calculate resistance values for positive and negative clamp voltages, then use the larger of the two values. 10. Power supply must maintain regulation within operating VDD range during instantaneous and operating maximum current conditions. If positive injection current (VIN > VDD) is greater than IDD, the injection current may flow out of VDD and could result in external power supply going out of regulation. Ensure external VDD load will shunt current greater than maximum injection current. This will be the greatest risk when the MCU is not consuming power. Examples are: if no system clock is present, or if clock rate is very low (which would reduce overall power consumption). 11. Pullups and pulldowns are disabled. Port B leakage is specified in 23.12 ADC Characteristics. 12. Digital inputs have hysteresis whenever they are configured for any alternative peripheral input function other than as a general-purpose input. 13. Maximum is highest voltage that POR is guaranteed. 14. Maximum is highest voltage that POR is possible. 15. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum VDD is reached. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 250 Freescale Semiconductor 3.0 V DC Electrical Characteristics 23.5 3.0 V DC Electrical Characteristics Symbol Min Typ(2) Max Unit VOH VOH VOH IOH1 VDD – 0.3 VDD – 1.0 VDD – 0.5 — — — — — — — — 30 V V V mA IOH2 — — 30 mA IOHT — — 60 mA VOL VOL VOL IOL1 — — — — — — — — 0.3 1.0 0.8 30 V V V mA IOL2 — — 30 mA IOLT — — 60 mA Input high voltage All ports, IRQs, RESET OSC1 VIH 0.7 x VDD 0.8 x VDD — VDD V Input low voltage All ports, IRQs, RESET OSC1 VIL VSS — 0.3 x VDD 0.2 x VDD V — — — — — — 4.5 1.65 1 3 12 200 8 4 3 6 20 300 mA mA μA μA μA μA 0 0 — — 2 –0.2 mA 0 0 — — 25 –5 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 VDD supply current Run(3) Wait(4) Stop(5)(<85 °C) Stop (>85 °C) Stop with TBM enabled(6) Stop with LVI and TBM enabled(6) IDD DC injection current(7), (8), (9), (10) Single pin limit VIN > VDD VIN < VSS Total MCU limit, includes sum of all stressed pins VIN > VDD VIN < VSS IIC I/O ports Hi-Z leakage current(11) IIL — — ±10 μA Input current IIn — — 1 μA Continued on next page MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 251 Electrical Specifications Symbol Min Typ(2) Max Unit RPU 20 45 65 kΩ Capacitance Ports (as input or output) COut CIn — — — — 12 8 pF Monitor mode entry voltage VTST VDD +2.5 — VDD +4.0 V Low-voltage inhibit, trip falling voltage – target VTRIPF 2.35 2.60 2.70 V Low-voltage inhibit, trip rising voltage – target VTRIPR 2.45 2.66 2.80 V VHYS — 60 — mV VInHYS 0.06 x VDD — — V VPOR 0 — 100 mV VPORRST 0 700 800 mV RPOR 0.035 — — V/ms Characteristic(1) Pullup resistors (as input only) Ports PTA3/KBD37–PTA0/KBD0, PTC1–PTC0, PTD6/T2CH0–PTD0/SS Low-voltage inhibit reset/recover hysteresis – target (VTRIPF + VHYS = VTRIPR) Input hysteresis (alternative input functions only)(7), (12) POR rearm voltage(7), (13) POR reset voltage (14) POR rise time ramp rate(7), (15) 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 square wave clock source (fOSC = 32.8 KHz). All inputs 0.2 V from rail. No dc loads. Less than 100 pF on all outputs. All ports configured as inputs. 7. This parameter is characterized and not tested on each device. 8. All functional non-supply pins are internally clamped to VSS and VDD. 9. Input must be current limited to the value specified. To determine the value of the required current-limiting resistor, calculate resistance values for positive and negative clamp voltages, then use the larger of the two values. 10. Power supply must maintain regulation within operating VDD range during instantaneous and operating maximum current conditions. If positive injection current (VIN > VDD) is greater than IDD, the injection current may flow out of VDD and could result in external power supply going out of regulation. Ensure external VDD load will shunt current greater than maximum injection current. This will be the greatest risk when the MCU is not consuming power. Examples are: if no system clock is present, or if clock rate is very low (which would reduce overall power consumption). 11. Pullups and pulldowns are disabled. 12. Digital inputs have hysteresis whenever they are configured for any alternative peripheral input function other than as a general-purpose input. 13. Maximum is highest voltage that POR is guaranteed. 14. Maximum is highest voltage that POR is possible. 15. If minimum VDD is not reached before the internal POR reset is released, RST must be driven low externally until minimum VDD is reached. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 252 Freescale Semiconductor 5.0 V Control Timing 23.6 5.0 V Control Timing Symbol Min Max Unit Frequency of operation(2) Crystal option External clock option(3) fosc 32 dc(4) 100 32.8 kHz MHz Internal operating frequency fop — 8.2 MHz Internal clock period (1/fOP) tcyc 122 — ns tIRL 50 — ns IRQ interrupt pulse width low(6) (edge-triggered) tILIH 50 — ns IRQ interrupt pulse period tILIL Note 8 — tcyc 16-bit timer(7) Input capture pulse width Input capture period tTH,tTL tTLTL Note 8 — — ns tcyc Characteristic(1) RST input pulse width low (5) 1. VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VSS unless otherwise noted. 2. See 23.8 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 253 Electrical Specifications 23.7 3.0 V Control Timing Symbol Min Max Unit Frequency of operation(2) Crystal option External clock option(3) fosc 32 dc(4) 100 16.4 kHz MHz Internal operating frequency fop — 4.1 MHz Internal clock period (1/fOP) tcyc 244 — ns tIRL 125 — ns IRQ interrupt pulse width low(6) (edge-triggered) tILIH 125 — ns IRQ interrupt pulse period tILIL Note 8 — tcyc 16-bit timer(7) Input capture pulse width Input capture period tTH,tTL tTLTL Note 8 — — ns tcyc Characteristic(1) RST input pulse width low (5) 1. VSS = 0 Vdc; timing shown with respect to 20% VDD and 70% VSS unless otherwise noted. 2. See 23.8 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. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 254 Freescale Semiconductor Clock Generation Module Characteristics 23.8 Clock Generation Module Characteristics 23.8.1 CGM Component Specifications Characteristic Symbol Min Typ Max Unit fXCLK 30 32.768 100 kHz (1) Crystal load capacitance CL — 12.5 — pF Crystal fixed capacitance(2) C1 — 15 — pF Crystal tuning capacitance(2) C2 — 15 — pF Feedback bias resistor RB 1 10 22 MΩ Series resistor(3) RS 100 330 470 kΩ Crystal reference frequency 1. Crystal manufacturer value. 2. Capacitor on OSC1 pin. Does not include parasitic capacitance due to package, pin, and board. 3. Capacitor on OSC2 pin. Does not include parasitic capacitance due to package, pin, and board. 23.8.2 CGM Electrical Specifications Description Symbol Min Typ Max Unit VDD 2.7 — 5.5 V T –40 25 125 oC Crystal reference frequency fRCLK 30 32.768 100 kHz Range nominal multiplier fNOM — 38.4 — kHz fVRS 38.4 k — 40.0 M Hz fVRS 38.4 k — 40.0 M Hz VCO range linear range multiplier L 1 — 255 VCO power-of-two range multiplier 2E 1 — 4 VCO multiply factor N 1 — 4095 VCO prescale multiplier 2P 1 1 8 Reference divider factor R 1 1 15 VCO operating frequency fVCLK 38.4 k — 40.0 M Hz Bus operating frequency(1) fBUS — — 8.2 MHz Bus frequency @ medium voltage(2) fBUS — — 4.1 MHz Manual acquisition time tLock — — 50 ms Automatic lock time tLock — — 50 ms fJ 0 — fRCLK x 0.025% x 2P N/4 Hz External clock input frequency PLL disabled fOSC dc — 32.8 M Hz External clock input frequency PLL enabled fOSC 30 k — 1.5 M Hz Operating voltage Operating temperature VCO center-of-range frequency(1) Medium-voltage VCO center-of-range frequency (2) PLL jitter(3) 1. 5.0 V ± 10% VDD 2. 3.0 V ± 10% VDD 3. Deviation of average bus frequency over 2 ms. N = VCO multiplier. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 255 Electrical Specifications 23.9 Output High-Voltage Characteristics 0 –5 IOH (mA) –10 –40 0 25 85 –15 –20 –25 –30 –35 –40 3 3.2 3.4 3.6 VOH (V) 3.8 4.0 4.2 VOH > VDD –0.8 V @ IOH = –2.0 mA VOH > VDD –1.5 V @ IOH = –10.0 mA Figure 23-1. Typical High-Side Driver Characteristics – Port PTA3–PTA0 (VDD = 4.5 Vdc) 0 IOH (mA) –5 –40 0 25 85 –10 –15 –20 –25 1.3 1.5 1.7 1.9 VOH (V) 2.1 2.3 2.5 VOH > VDD –0.3 V @ IOH = –0.6 mA VOH > VDD –1.0 V @ IOH = –4.0 mA Figure 23-2. Typical High-Side Driver Characteristics – Port PTA3–PTA0 (VDD = 2.7 Vdc) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 256 Freescale Semiconductor Output High-Voltage Characteristics 0 –5 IOH (mA) –10 –40 0 25 85 –15 –20 –25 –30 –35 –40 3 3.2 3.4 3.6 VOH (V) 3.8 4.0 4.2 VOH > VDD –0.8 V @ IOH = –10.0 mA Figure 23-3. Typical High-Side Driver Characteristics – Port PTC1–PTC0 (VDD = 4.5 Vdc) 0 IOH (mA) –5 –40 0 25 85 –10 –15 –20 –25 1.3 1.5 1.7 1.9 VOH (V) 2.1 2.3 2.5 VOH > VDD –0.5 V @ IOH = –4.0 mA Figure 23-4. Typical High-Side Driver Characteristics – Port PTC1–PTC0 (VDD = 2.7 Vdc) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 257 Electrical Specifications 0 –10 –20 –40 0 25 85 IOH (mA) –30 –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 VOH > VDD –0.8 V @ IOH = –2.0 mA VOH > VDD –1.5 V @ IOH = –10.0 mA Figure 23-5. Typical High-Side Driver Characteristics – Ports PTB5–PTB0, PTD6–PTD0, and PTE1–PTE0 (VDD = 5.5 Vdc) 0 IOH (mA) –5 –40 0 25 85 –10 –15 –20 –25 1.3 1.5 1.7 1.9 VOH (V) 2.1 2.3 2.5 VOH > VDD –0.3 V @ IOH = –0.6 mA VOH > VDD –1.0 V @ IOH = –4.0 mA Figure 23-6. Typical High-Side Driver Characteristics – Ports PTB5–PTB0, PTD6–PTD0, and PTE1–PTE0 (VDD = 2.7 Vdc) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 258 Freescale Semiconductor Output Low-Voltage Characteristics 23.10 Output Low-Voltage Characteristics 35 30 –40 0 25 85 IOL (mA) 25 20 15 10 5 0 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 VOL < 0.4 V @ IOL = 1.6 mA VOL < 1.5 V @ IOL = 10.0 mA Figure 23-7. Typical Low-Side Driver Characteristics – Port PTA3–PTA0 (VDD = 5.5 Vdc) 14 12 –40 0 25 85 IOL (mA) 10 8 6 4 2 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 VOL < 0.3 V @ IOL = 0.5 mA VOL < 1.0 V @ IOL = 6.0 mA Figure 23-8. Typical Low-Side Driver Characteristics – Port PTA3–PTA0 (VDD = 2.7 Vdc) 60 IOL (mA) 50 40 –40 0 25 85 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 Figure 23-9. Typical Low-Side Driver Characteristics – Port PTC1–PTC0 (VDD = 4.5 Vdc) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 259 Electrical Specifications 30 IOL (mA) 25 –40 0 25 85 20 15 10 5 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.6 1.4 VOL < 0.8 V @ IOL = 10 mA Figure 23-10. Typical Low-Side Driver Characteristics – Port PTC1–PTC0 (VDD = 2.7 Vdc) 35 30 –40 0 25 85 IOL (mA) 25 20 15 10 5 0 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.6 1.4 VOL < 0.4 V @ IOL = 1.6 mA VOL < 1.5 V @ IOL = 10.0 mA Figure 23-11. Typical Low-Side Driver Characteristics – Ports PTB5–PTB0, PTD6–PTD0, and PTE1–PTE0 (VDD = 5.5 Vdc) 14 12 –40 0 25 85 IOL (mA) 10 8 6 4 2 0 0 0.2 0.4 0.6 0.8 1.0 VOL (V) 1.2 1.4 1.6 VOL < 0.3 V @ IOL = 0.5 mA VOL < 1.0 V @ IOL = 6.0 mA Figure 23-12. Typical Low-Side Driver Characteristics – Ports PTB5–PTB0, PTD6–PTD0, and PTE1–PTE0 (VDD = 2.7 Vdc) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 260 Freescale Semiconductor Typical Supply Currents 23.11 Typical Supply Currents 16 14 12 IDD (mA) 10 8 6 4 5.5 V 3.6 V 2 0 0 1 2 3 4 5 fbus (MHz) 6 7 8 9 Figure 23-13. Typical Operating IDD, with All Modules Turned On (–40 °C to 125 °C) 5.0 4.5 4.0 IDD (mA) 3.5 3.0 2.5 2.0 1.5 1.0 5.5 V 3.6 V 0.5 0 0 1 2 3 4 fbus (MHz) 5 6 7 8 Figure 23-14. Typical Wait Mode IDD, with all Modules Disabled (–40 °C to 125 °C) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 261 Electrical Specifications 1.35 1.30 IDD (μA) 1.25 1.20 1.15 1.10 5.5 V 3.6 V 1.05 1 0 1 2 3 4 5 fbus (MHz) 6 7 8 9 Figure 23-15. Typical Stop Mode IDD, with all Modules Disabled (–40 °C to 125 °C) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 262 Freescale Semiconductor ADC Characteristics 23.12 ADC Characteristics Characteristic(1) Symbol Min Max Unit Comments Supply voltage VDDAD 2.7 (VDD min) 5.5 (VDD max) V VDDAD should be tied to the same potential as VDD via separate traces. Input voltages VADIN 0 VDDAD V VADIN <= VREFH Resolution BAD 8 8 Bits Absolute accuracy (VREFL = 0 V, VDDAD = VREFH = 5 V ± 10%) AAD −− ±1 LSB Includes quantization ADC internal clock fADIC 0.5 1.048 MHz tAIC = 1/fADIC, tested only at 1 MHz Conversion range RAD VREFL VREFH V VREFH = VDDAD VREFL = VSSAD Power-up time tADPU 16 Conversion time tADC 16 17 tAIC cycles Sample time(2) tADS 5 — tAIC cycles Zero input reading(3) ZADI 00 01 Hex VIN = VREFL Full-scale reading(3) FADI FE FF Hex VIN = VREFH Input capacitance CADI — 20 pF Not tested — — ±1 μA Input leakage(4) Port B tAIC cycles 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 kΩ adversely affect internal RC charging time during input sampling. 3. Zero-input/full-scale reading requires sufficient decoupling measures for accurate conversions. 4. The external system error caused by input leakage current is approximately equal to the product of R source and input current. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 263 Electrical Specifications 23.13 5.0 V SPI Characteristics Diagram Number(1) Characteristic(2) Symbol Min Max Unit Operating frequency Master Slave fOP(M) fOP(S) fOP/128 DC fOP/2 fOP MHz MHz 1 Cycle time Master Slave tCYC(M) tCYC(S) 2 1 128 — tcyc tcyc 2 Enable lead time tLead(S) 1 — tcyc 3 Enable lag time tLag(S) 1 — tcyc 4 Clock (SPSCK) high time Master Slave tSCKH(M) tSCKH(S) tcyc –25 1/2 tcyc –25 64 tcyc — ns ns 5 Clock (SPSCK) low time Master Slave tSCKL(M) tSCKL(S) tcyc –25 1/2 tcyc –25 64 tcyc — ns ns 6 Data setup time (inputs) Master Slave tSU(M) tSU(S) 30 30 — — ns ns 7 Data hold time (inputs) Master Slave tH(M) tH(S) 30 30 — — ns ns 8 Access time, slave(3) CPHA = 0 CPHA = 1 tA(CP0) tA(CP1) 0 0 40 40 ns ns 9 Disable time, slave(4) tDIS(S) — 40 ns 10 Data valid time, after enable edge Master Slave(5) tV(M) tV(S) — — 50 50 ns ns 11 Data hold time, outputs, after enable edge Master Slave tHO(M) tHO(S) 0 0 — — ns ns 1. Numbers refer to dimensions in Figure 23-16 and Figure 23-17. 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 264 Freescale Semiconductor 3.0 V SPI Characteristics 23.14 3.0 V SPI Characteristics Diagram Number(1) Characteristic(2) Symbol Min Max Unit Operating frequency Master Slave fOP(M) fOP(S) fOP/128 DC fOP/2 fOP MHz MHz 1 Cycle time Master Slave tCYC(M) tCYC(S) 2 1 128 — tcyc tcyc 2 Enable lead time tLead(s) 1 — tcyc 3 Enable lag time tLag(s) 1 — tcyc 4 Clock (SPSCK) high time Master Slave tSCKH(M) tSCKH(S) tcyc –35 1/2 tcyc –35 64 tcyc — ns ns 5 Clock (SPSCK) low time Master Slave tSCKL(M) tSCKL(S) tcyc –35 1/2 tcyc –35 64 tcyc — ns ns 6 Data setup time (inputs) Master Slave tSU(M) tSU(S) 40 40 — — ns ns 7 Data hold time (inputs) Master Slave tH(M) tH(S) 40 40 — — ns ns 8 Access time, slave(3) CPHA = 0 CPHA = 1 tA(CP0) tA(CP1) 0 0 50 50 ns ns 9 Disable time, slave(4) tDIS(S) — 50 ns 10 Data valid time, after enable edge Master Slave(5) tV(M) tV(S) — — 60 60 ns ns 11 Data hold time, outputs, after enable edge Master Slave tHO(M) tHO(S) 0 0 — — ns ns 1. Numbers refer to dimensions in Figure 23-16 and Figure 23-17. 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 MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 265 Electrical Specifications SS INPUT SS PIN OF MASTER HELD HIGH 1 SPSCK OUTPUT CPOL = 0 NOTE SPSCK OUTPUT CPOL = 1 NOTE 5 4 5 4 6 MISO INPUT MSB IN BITS 6–1 11 MOSI OUTPUT MASTER MSB OUT 7 LSB IN 10 11 BITS 6–1 MASTER LSB OUT Note: This first clock edge is generated internally, but is not seen at the SPSCK pin. a) SPI Master Timing (CPHA = 0) SS INPUT SS PIN OF MASTER HELD HIGH 1 SPSCK OUTPUT CPOL = 0 5 NOTE 4 SPSCK OUTPUT CPOL = 1 5 NOTE 4 6 MISO INPUT MSB IN 10 MOSI OUTPUT BITS 6–1 11 MASTER MSB OUT 7 LSB IN 10 BITS 6–1 MASTER LSB OUT Note: This last clock edge is generated internally, but is not seen at the SPSCK pin. b) SPI Master Timing (CPHA = 1) Figure 23-16. SPI Master Timing MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 266 Freescale Semiconductor 3.0 V SPI Characteristics SS INPUT 3 1 SPSCK INPUT CPOL = 0 5 4 2 SPSCK INPUT CPOL = 1 5 4 9 8 MISO INPUT SLAVE MSB OUT 6 BITS 6–1 7 MOSI OUTPUT NOTE 11 11 10 MSB IN SLAVE LSB OUT BITS 6–1 LSB IN Note: Not defined but normally MSB of character just received a) SPI Slave Timing (CPHA = 0) SS INPUT 1 SPSCK INPUT CPOL = 0 5 4 2 3 SPSCK INPUT CPOL = 1 8 MISO OUTPUT MOSI INPUT 5 4 10 NOTE 9 SLAVE MSB OUT 6 7 BITS 6–1 11 10 MSB IN SLAVE LSB OUT BITS 6–1 LSB IN Note: Not defined but normally LSB of character previously transmitted b) SPI Slave Timing (CPHA = 1) Figure 23-17. SPI Slave Timing MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 267 Electrical Specifications 23.15 Timer Interface Module Characteristics Characteristic Symbol Min Max Unit Input capture pulse width tTIH, tTIL 2 — tcyc Timer input capture period tTLTL See Note(1) — tcyc 1. The minimum period is the number of cycles it takes to execute the interrupt service routine plus 1 tcyc. 23.16 Memory Characteristics Characteristic Symbol Min Typ Max Unit VRDR 1.3 — — V — 1 — — MHz fRead(1) 32k — 8.4M Hz tErase 0.9 3.6 1 4 1.1 5.5 ms tMErase 4 — — ms FLASH PGM/ERASE to HVEN set up time tnvs 10 — — μs FLASH high-voltage hold time tnvh 5 — — μs FLASH high-voltage hold time (mass erase) tnvhl 100 — — μs FLASH program hold time tpgs 5 — — μs FLASH program time tPROG 30 — 40 μs FLASH return to read time trcv(2) 1 — — μs FLASH cumulative program HV period tHV(3) — — 4 ms FLASH endurance(4) — 10k 100k — Cycles FLASH data retention time(5) — 15 100 — Years 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 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 × 64) ≤ tHV max. 4. Typical endurance was evaluated for this product family. For additional information on how Freescale defines typical Endurance, please refer to Engineering Bulletin EB619. 5. Typical data retention values are based on intrinsic capability of the technology measured at high temperature and de-rated to 25°C using the Arrhenius equation. For additional information on how Freescale defines Typical Data Retention, please refer to Engineering Bulletin EB618. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 268 Freescale Semiconductor Chapter 24 Mechanical Specifications 24.1 Introduction The MC68HC908GR8 and MC68HC908GR4 are available in these packages: • 42-pin shrink dual in-line package (SDIP) • 32-pin low-profile quad flat pack (LQFP) • 28-pin dual in-line package (PDIP) • 28-pin small outline package (SOIC) The package information contained in this section is the latest available at the time of this publication. To make sure that you have the latest package specifications, please visit the Freescale web site at: http://freescale.com Follow World Wide Web on-line instructions to retrieve the current mechanical specifications. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 269 Mechanical Specifications MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 280 Freescale Semiconductor Chapter 25 Ordering Information 25.1 Introduction This section contains instructions for ordering the MC68HC908GR8 and MC68HC908GR4. 25.2 MC Order Numbers Table 25-1. MC Order Numbers MC Order Number(1) Production Parts Tape and Reel Operating Temperature Range (°C) MC68HC908GR8CP MC68HC908GR8CFA MC68HC908GR8CDW MC68HC908GR8VFA MC68HC908GR8VP MC68HC908GR8VDW MC68HC908GR8MFA MC68HC908GR8MP MC68HC908GR8MDW – 40 to + 85 – 40 to + 85 – 40 to + 85 – 40 to + 105 – 40 to + 105 – 40 to + 105 – 40 to + 125 – 40 to + 125 – 40 to + 125 MC68HC908GR4CP MC68HC908GR4CFA MC68HC908GR4CDW MC68HC908GR4VFA MC68HC908GR4VP MC68HC908GR4VDW MC68HC908GR4MFA MC68HC908GR4MP MC68HC908GR4MDW – 40 to + 85 – 40 to + 85 – 40 to + 85 – 40 to + 105 – 40 to + 105 – 40 to + 105 – 40 to + 125 – 40 to + 125 – 40 to + 125 MC908GR8CFAR2 MC908GR8CDWR2 MC908GR8VFAR2 MC908GR8VDWR2 MC908GR8MFAR2 MC908GR8MDWR2 – 40 to + 85 – 40 to + 85 – 40 to + 105 – 40 to + 105 – 40 to + 125 – 40 to + 125 MC908GR4CFAR2 MC908GR4CDWR2 MC908GR4VFAR2 MC908GR4VDWR2 MC908GR4MFAR2 MC908GR4MDWR2 – 40 to + 85 – 40 to + 85 – 40 to + 105 – 40 to + 105 – 40 to + 125 – 40 to + 125 1. FA = quad flat pack P = plastic dual in line package DW = Small outline integrated circuit (SOIC) package MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 281 Ordering Information 25.3 Development Tools Table 25-2. Development Tool Kits Ordering Part Number Description M68ICS08GR HC908GR8 ICS KIT includes: M68ICS08GR programmer board, Windows-based IDE, 68HC908GR8 sample, ICS Board & IDE documentation, Universal Power Supply, Serial cable KITMMEVS08GR HC908GR8 EVS KIT includes: M68MMPFB0508, M68EML08GP32, M68CBL05C, M68TC08GR8P28, M68TC08GR8FA32, M68TQS032SAG1, M68TQP032SA1, M68ICS08GR Kit KITMMDS08GR HC908GR8 MMDS KIT includes: M68MMDS0508, M68EML08GP32, M68CBL05C, M68TC08GR8P28, M68TC08GR8FA32, M68TQS032SAG1, M68TQP032SA1, M68ICS08GR Kit Table 25-3. Development Tool Components Ordering Part Number Description M68MMDS0508 High performance emulator M68MMPFB0508 MMEVS Platform Board M68EML08GP32 HC908GP32 Emulator Board M68CBL05C Used for HC908GR8/GR4 emulation Low noise flex-cable M68TC08GR8P28 28-pin DIP target head adapter M68TC08GR8FA32 32-pin QFP target head adapter M68TQS032SAG1 32-pin TQ socket with guides M68TQP032SA1 Comments 32-pin TQPACK MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 282 Freescale Semiconductor Revision History Changes from Rev 6.0 published in April 2006 to Rev 7.0 published in October 2006 Section Page (in Rev 6.0) Mechanical Specifications 272 Description of change Corrected cas outline for 32-pin LQFP. Changes from Rev 5.0 published in August 2005 to Rev 6.0 published in April 2006 Section General Description Low-Power Modes Page (in Rev 6.0) Added 42-pin SDIP to standard feature list. 22 Added pin assignment drawing for the 42-pin SDIP. 38 Updated description of clock generator module in stop mode to remove erroneous information. 255 Electrical Specifications Mechanical Specifications Description of change 20 249 251 Updated to reflect correct values. Added DC injection current and input hysteresis values to: 5.0 V DC Electrical Characteristics 3.0 V DC Electrical Characteristics 270 Added case outline drawing for the 42-pin SDIP. Changes from Rev 4.0 published in February 2002 to Rev 5.0 published in August 2005 Section Memory Map System Integration Module (SIM) Throughout Page (in Rev 5.0) Description of change 27 In 4th, 5th and 6th bullets 28 Near bottom of memory map 35 In bottom two registers 35 In top register 185 In last three registers Address of Interrupt Status Register 1 (INT1) corrected to $FE04 Address of Interrupt Status Register 2 (INT2) corrected to $FE05 Address of Interrupt Status Register 3 (INT3) corrected to $FE06 Updated to meet Freescale Identity guidelines. MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 Freescale Semiconductor 283 Changes from Rev 3.0 published in February 2002 to Rev 4.0 published in June 2002 Changes from Rev 3.0 published in February 2002 to Rev 4.0 published in June 2002 Section Page (in Rev 4.0) Description of change All references to the ROM MC68HC08GR8 removed. Appendix A removed. Electrical Specifications 363 Maximum junction temperature increased to 140°C 364 Input High Voltage for OSC1 changed Stop IDD for temperatures >85°C added 366 Input High Voltage for OSC1 changed Input Low Voltage for OSC1 changed Stop IDD for temperatures >85°C added Changes from Rev 2.0 published in January 2002 to Rev 3.0 published in February 2002 Section Page (in Rev 3.0) Description of change All references to the ROM MC68HC08GR8 removed. Appendix A removed. 363 Maximum operating temperature increased to 125°C Electrical Specifications 376-377 383 Maximum operating temperature increased to 125°C Ordering Information 391 New section added Maximum temperature increased to 125°C in titles of figures 23-13, 23-14 and 23-15 Changes from Rev 1.0 published in April 2001 to Rev 2.0 published in December 2001 Section Page (in Rev 2.0) Description of change The blank state of the reset vectors, $FFFE and $FFFF, was incorrectly defined as $00 and is now $FF. This affects several places in the Monitor ROM (MON) section. The information was previously described in an addendum. See details below: 190 Penultimate bullet of features list 192 Final sentence of first paragraph Each list item in Entering Monitor Mode section 193 Third column of Table 15-1 Timebase Module (TBM) 329 Several changes for clarification Timer Interface Module (TIM) 335 Several changes for clarification Electrical Specifications 385 Typical column added to table. Typical values added for FLASH row program endurance and FLASH data retention time Monitor ROM (MON) MC68HC908GR8 • MC68HC908GR4 Data Sheet, Rev. 7 284 Freescale Semiconductor How to Reach Us: Home Page: www.freescale.com E-mail: [email protected] USA/Europe or Locations Not Listed: Freescale Semiconductor Technical Information Center, CH370 1300 N. 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