General Description
The APExx24 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) or D/A current outputs, 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: 64k x 10 bits
(3) 1 set of 16-bits DPR can access up to 64k x 10 bits melody data memory space, and 1 set of 20-bits VPR can access up to 1024k x 10 bits voice data memory space.
(4) Data Registers:
   a). 128 x 4-bits data RAM (00-7Fh)
   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)
   b). PRB: 4-bits I/O Port B (13h) can be configured to input/output individually. (Mask option)
   c). PRC: 4-bits I/O Port C (14h) can be programmed to input/output individually. (Register control)
   d). PRD: 4-bits I/O Port D (15h) can be programmed to input/output individually. (Register control)
   e). PRE: 4-bits I/O Port E (17h) can be programmed to input/output individually. (Register control)
   f). PRF: 4-bits I/O Port F (18h) can be programmed to input/output individually. (Register control)
(6) On-chip clock generator: Resistive Clock Drive (RM) or Crystal oscillator (HM)
(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 8 Level DAC Current Control can be configured. (Mask option)
(11) Built-in IR Carry Output: Port B[1] can be configured as IR pin by 38k / 56kHz. (Mask option)
(12) External Reset: Port B[3] can be configured as reset pin. (Mask opton)
(13) HALT and Release from HALT function to reduce power consumption
(14) Watch Dog Timer (WDT)
(15) Instruction: 1-cycle instruction except for table read and program branches which are 2-cycles
(16) Number of instruction: 27
(17) DAC: 1 channel voice and dual tone melody synthesizer (One 9-bits Cout or 8-bits PWM output).