General Description

Introduction

The MC68HC908GR8A is a member of the low-cost, high-performance M68HC08 Family of 8-bit microcontroller units (MCUs). All MCUs in the family use the enhanced M68HC08 central processor unit (CPU08) and are available with a variety of modules, memory sizes and types, and package types.

This document also describes the MC68HC908GR4A. The MC68HC908GR4A is a device identical to the MC68HC908GR8A except that it has less FLASH memory. Only when there are differences from the MC68HC908GR8A is the MC68HC908GR4A specifically mentioned in the text.

Features

For convenience, features have been organized to reflect:

• Standard features

• Features of the CPU08

Standard Features

Features include:

• High-performance M68HC08 architecture optimized for C-compilers

• Fully upward-compatible object code with M6805, M146805, and M68HC05 Families

• 8-MHz internal bus frequency

• Clock generation module supporting 1-MHz to 8-MHz crystals

• FLASH program memory security(1)

• On-chip programming firmware for use with host personal computer which does not require high voltage for entry

• In-system programming (ISP)

• System protection features:

– Optional computer operating properly (COP) reset

– Low-voltage detection with optional reset and selectable trip points for 3.0-V and 5.0-V operation

– Illegal opcode detection with reset

– Illegal address detection with reset

• Low-power design; fully static with stop and wait modes

• Standard low-power modes of operation:

– Wait mode

– Stop mode

• Master reset pin and power-on reset (POR)

• 7680 bytes of on-chip FLASH memory on the MC68HC908GR8A and 4096 byes of on-chip FLASH memory on the MC68HC908GR4A with in-circuit programming capabilities of FLASH program memory.

• 384 bytes of on-chip random-access memory (RAM)

• 544 bytes of FLASH programming routines read-only memory (ROM)

• Serial peripheral interface (SPI) module

• Serial communications interface (SCI) module

• One 16-bit, 2-channel timer (TIM1) and one 16-bit, 1-channel timer (TIM2) interface modules with selectable input capture, output compare, and pulse-width modulation (PWM) capability on each channel

• Up to 6-channel, 8-bit successive approximation analog-to-digital converter (ADC) depending on package choice

• BREAK (BRK) module to allow single breakpoint setting during in-circuit debugging

• Internal pullups on IRQ and RST to reduce system cost

• Up to 21 general-purpose input/output (I/O) pins

• Selectable pullups on inputs only on ports A, C, and D. Selection is on an individual port bit basis.

During output mode, pullups are disengaged.

• High current 10-mA sink/source capability on all port pins

• Higher current 15-mA sink/source capability on PTC0–PTC1

• Timebase module (TBM) with clock prescaler circuitry for eight user selectable periodic real-time interrupts with optional active clock source during stop mode for periodic wakeup from stop using an external crystal

• User selection of having the oscillator enabled or disabled during stop mode

• 4-bit keyboard wakeup port

• Available packages:

– 32-pin low-profile quad flat pack (LQFP)

– 28-pin plastic dual in-line package (DIP)

– 28-pin small outline integrated circuit (SOIC)

• Specific features of the MC68HC908GR8A in 28-pin DIP and 28-pin SOIC are:

– Port B is only 4 bits: PTB0–PTB3; 4-channel ADC module

– No port C bits

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