The LC662304A, LC662306A, LC662308A, LC662312A, and LC662316A are 4-bit CMOS microcontrollers that integrate on a single chip all the functions required in a special-purpose telephone controller, including ROM, RAM, I/O ports, a serial interface, a DTMF generator, timers, and interrupt functions. These microcontrollers are available in a 42-pin package.