GENERAL DESCRIPTION
The W742E81A/W742C81A is a high-performance 4-bit microcontroller (mC) 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 ´ 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 W742E81A/W742C81A 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.

FEATURES
· Operating voltage: 2.4V-3.8V
· Dual-clock operation or single-clock operation (By option)
· Main-oscillator
   - Connect to 3.58 MHz crystal or 400 KHz that can be selected by option code
   - Crystal or RC oscillator can be selected by code option (W742E81A)
   - Connect to 2 MHz typical RC oscillator (W742C81A)
· Sub-oscillator
   - Connect to 32768 Hz crystal only
· Memory
   - 16384 x 16 bits program flash EEPROM (including 64K x 4 bit look-up table)
   - 2048 x 4 bits data RAM (including 16 nibbles x 16 pages working registers)
   - 40 x 4 LCD data RAM
· 24 input/output pins
   - Port for input only: 1 ports/4 pins(RC)
   - Input/output ports: 3 ports/12 pins(RA, RB & RD)
   - High sink current output port for LED driving: 1 port /4 pins(RE)
   - Port for output only: 1 port/ 4 pins(RF)
· Power-down mode
   - Hold function: no operation (main-oscillator and sub-oscillator still operate)
   - Stop function: no operation (main-oscillator and sub-oscillator are stopped)
   - Dual-clock slow operation mode: system is operated by the sub-oscillator (FOSC=Fs and Fm is stopped)
· Five types of interrupts
   - Four internal interrupts (Divider0, Divider1, Timer 0, Timer 1)
   - One external interrupts (RC Port)
· LCD driver output
   - 40 segments x 4 commons
   - 1/4 duty 1/3 bias driving mode
   - Clock source should be the sub-oscillator clock in the dual-clock operation mode
· MFP output pin
   - Output is software selectable as modulating or nonmodulating frequency
   - Works as frequency output specified by Timer 1
· DTMF output pin
   - Output is one channel Dual Tone Multi-Frequency signal for dialling
· Two built-in 14-bit frequency dividers
   - Divider0: the clock source is the output of the main-oscillator
   - Divider1: the clock source is the output of the sub-oscillator (dual-clock mode) or the Fosc/128 (single-clock mode)
· Two built-in 8-bit programmable countdown timers
   - Timer 0: one of two internal clock frequencies (FOSC/4 or FOSC/1024) can be selected
   - Timer 1: with auto-reload function and one of three internal clock frequencies (FOSC, FOSC/64 or Fs) can be selected by MR1 register; and the specified frequency can be delivered to MFP pin
· Built-in 18/15-bit watchdog timer selectable for system reset; enable the watch dog timer or not is determined by code option
· Powerful instruction set: 142 instructions
· 16-levels subroutine (include interrupt) nesting