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