General Description
The APU429 is an embedded high performance 4-bit micro-computer with an on-chip LCD driver. It contains all the necessary functions in a single chip: 4-bit parallel processing ALU, ROM, RAM, I/O ports, timer, clock generator, dual clock, RFC, EL-light, LCD driver, look-up table, watchdog timer and keyboard scanning. The instruction set includes not only 4-bit operation and manipulation instructions but also various conditional branch instructions and LCD driver data transfer instructions which are powerful and easy to use.

Features
• Low power and low voltage operation
• Powerful instruction set (150 instructions)
• Memory capacity
   - Instruction ROM capacity 4096 x 16 bits
   - Index ROM capacity 256 x 8 bits
   - Internal RAM capacity 384 or 256 x 4 bits
• Input/Output ports of up to 20 pins
• 8-level subroutine nesting
• Built-in LCD driver, 8 x 42 = 336 segments
• Built-in EL driver, frequency or melody generator
• Built-in Resistance-to-Frequency Converter
• Built-in 2-channel 6/8-bit PWM output
• Built-in key strobe function
   (Shared with segment pin)
• Built-in voltage doubler, halver, tripler quadrupler charge pump circuit
• Two 6-bit programmable timers with programmable clock source
• Watchdog timer
• 4 external & 3 internal interrupt resources
   - External: INT, RFC, IOA/IOC/S port, keystrobe
   - Internal: TM1, TM2, Predivider
• Dual clock operation
• HALT and STOP function