Introduction
The MC68HC908RF2 MCU is a member of the low-cost, high-performance M68HC08 Family of 8-bit microcontroller units (MCUs). Optimized for low-power operation and available in a small 32-pin low-profile quad flat pack (LQFP), this MCU is well suited for remote keyless entry (RKE) transmitter designs. The M68HC08 Family is based on the customer-specified integrated circuit (CSIC) design strategy. 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
Features of the MC68HC908RF2 MCU include:
• High-performance M68HC08 architecture
• Fully upward-compatible object code with M6805, M146805, and M68HC05 Families
• Maximum internal bus frequency of 4 MHz at 3.3 volts
• Maximum internal bus frequency of 2 MHz at 1.8 volts
• Internal oscillator requiring no external components:
   – Software selectable bus frequencies
   – ± 25 percent accuracy with trim capability to ±2 percent
   – Option to allow use of external clock source or external crystal/ceramic resonator
• 2 Kbytes of on-chip FLASH memory
• FLASH program memory security(1)
• 128 bytes of on-chip RAM
• 16-bit, 2-channel timer interface module (TIM)
• 12 general-purpose input/output (I/O) ports:
   – Six shared with keyboard wakeup function
   – Two shared with the timer module
   – Port A pins have 3-mA sink capabilities
• Low-voltage inhibit (LVI) module:
   – 1.85-V detection forces MCU into reset
   – 2.0-V detection sets indicator flag
• 6-bit keyboard interrupt with wakeup feature
• External asynchronous interrupt pin with internal pullup (IRQ1)
• Ultra high frequency (UHF) transmitter
• System protection features:
   – Computer operating properly (COP) reset
   – Low-voltage detection with reset
   – Illegal opcode detection with reset
   – Illegal address detection with reset
• 32-pin plastic LQFP package
• Low-power design with stop and wait modes
• Master reset pin and power-on reset (POR)
• –40° to 85° Celsius operation

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
• Third party C language support