The W742S81A is a high-performance 4-bit microcontroller (C) that provides an LCD driver. The device contains a 4-bit ALU, two 8-bit timers, two dividers (for two oscillators) in dual-clock operation, a 40 x 4 LCD driver, six 4-bit I/O ports (including 1 output port for LED driving), and one channel DTMF generator. There are also five interrupt sources and 16-levels subroutine nesting for interrupt applications. The W742S81A operates on very low current and has two power reduction modes, that is the dual-clock slow operation and STOP mode, which help to minimize power dissipation.