General Description
The APExx04 series are very low cost voice and melody synthesizer with 4-bits CPU. They have various features including 4-bits ALU, ROM, RAM, I/O ports, timers, clock generator, voice and melody synthesizer, and PWM (Direct drive) output, etc. The audio synthesizer contains one voice-channel and two melody-channels. Furthermore, they consist of 27 instructions in these devices. With CMOS technology and halt function can minimize power dissipation. Their architectures are similar to RISC, with two stages of instruction pipeline. They allow all instructions to be executed in a single cycle, except for program branches and data table read instructions (which need two instruction cycles).

FEATUREs
(1) Single power supply can operate from 2.4V to 5.5V at 4MHz or 8MHz.
(2) Program ROM: 8k x 10 bits
(3) 1 set of 15-bits DPR can access up to 32k x 10 bits melody data memory space, and 1 set of 15-bits
   VPR can access up to 32k x 10 bits voice data memory space.
(4) Data Registers:
   a). 96 x 4-bits data RAM (00-5Fh)
   b). Unbanked special function registers (SFR) range: 00h-2Fh
(5) I/O Ports:
   a). PRA: 4-bits I/O Port A (10h) can be programmed to input/output individually. (Register control)
(6) On-chip clock generator: Resistive Clock Drive (RM)
(7) Timer: 1-set Voice Interrupt (Timer0: a 9-bits auto-reload timer/counter).
(8) Stack: 2-level subroutine nesting.
(9) Built-in 4 Level Volume Control can be programmed.
(10) Built-in IR Carry Output: Port A[1] can be configured as IR pin by 38k / 56kHz. (Mask option)
(11) External Reset: Port A[3] can be configured as reset pin. (Mask opton)
(12) HALT and Release from HALT function to reduce power consumption
(13) Watch Dog Timer (WDT)
(14) Instruction: 1-cycle instruction except for table read and program branches which are 2-cycles
(15) Number of instruction: 27
(16) DAC: 1 channel voice and dual tone melody synthesizer (One 8-bits PWM output).