General Description

Introduction

The MC68HC908GR8B 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.

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 reset and trip points for 3.0-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 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 MC68HC908GR8B 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