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.
●Features
●For convenience, features have been organized to reflect:
●• Standard features of the MC68HC908GR8
●• Features of the CPU08
●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)
●• 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
●• 32-pin quad flat pack (QFP) or 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
●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
