General Description
Introduction
The MC68HC908GT16, MC68HC908GT8, and MC68HC08GT16 are members 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 of the MC68HC908GT16/MC68HC908GT8
• Features of the CPU08

Standard Features of the MC68HC908GT16/MC68HC908GT8
• High-performance M68HC08 architecture optimized for C-compilers
• Fully upward-compatible object code with M6805, M146805, and M68HC05 Families
• 8-MHz internal bus frequency
• Internal oscillator requiring no external components:
   – Software selectable bus frequencies
   – ±25 percent accuracy with trim capability to ±4 percent
   – Clock monitor
   – Option to allow use of external clock source or external crystal/ceramic resonator
• 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)
• 16 Kbytes of on-chip 100k cycle write/erase capable Flash memory (8 Kbytes on MC68HC908GT8)
• 512 bytes of on-chip random-access memory (RAM)
• 720 bytes of Flash programming routines ROM
• Serial peripheral interface module (SPI)
• Serial communications interface module (SCI)
• Two 16-bit, 2-channel timer interface modules (TIM1 and TIM2) with selectable input capture, output compare, and pulse-width modulation (PWM) capability on each channel
• 8-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
• Up to 36 general-purpose input/output (I/O) pins, including:
   – 28 shared-function I/O pins
   – Six or eight 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 20-mA sink/source capability on PTC0–PTC4
• 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 or internal oscillator
• User selection of having the oscillator enabled or disabled during stop mode
• 8-bit keyboard wakeup port
• Available packages:
   – 42-pin shrink dual in-line package (SDIP)
   – 44-pin quad flat pack (QFP)
• Specific features of the MC68HC908GT16 in 42-pin SDIP are:
   – Port C is only 5 bits: PTC0–PTC4
   – Port D is 8 bits: PTD0–PTD7; dual 2-channel TIM modules
• Specific features of the MC68HC908GT16 in 44-pin QFP are:
   – Port C is 7 bits: PTC0–PTC6
   – Port D is 8 bits: PTD0–PTD7; dual 2-channel TIM modules