The Z89135/136 is a fully integrated, dual processor controller designed for low-cost digital telephone answering machines. The I/O control processor is a Z8 MCU with 24 KB of program memory, two 8-bit counter/timers, and up to 47 I/O pins. The DSP is a 16-bit processor with a 24-bit ALU and accumulator, 512 x 16 bits of RAM, single cycle instructions, and 6K word program ROM plus constants memory. The chip also contains a half-flash 8-bit A/D converter with up to 128 kHz sample rate and 10-bit PWM D/A converter. The sampling rates for the converters are programmable. The precision of the 8-bit A/D may be extended by resampling the data at a lower rate in software.