GENERAL DESCRIPTION
The W921E880A/W921C880 are 4-bit micro-processor fabricated by CMOS process. With a single channel DTMF generator, an 8-bit D/A converter circuit, a built in four by one channel comparator circuit and four multi-function timers. The excellent memory structure, 8K super EPROM in W921E880A and 8K mask ROM in W921C880 for program code and 1536 x 4 bit RAM minimize the need for external memory devices. The W921E880A/W921C880 provides good solution for consumming application, especially for telecommunication design with few external components. Using the serial transmit/receive function, the W921E880A/W921C880 can interface with the Winbond LCD driver IC using the serial control circuit.

FEATURES
Memory
· ROM (Super EPROM): 8K x 10 bits
· RAM: 1536 x 4 bits
   - 64 x 4 bit Special registers
   - 16 x 4 bit Working registers
   - 128 x 4 bit General registers
   - 304 x 4 bit Multi-purpose registers4 bit serial buffer registers
   - 512 x 4-bit ´ 2 banks

Dual-clock Operation
· Crystal or RC for the main system clock: RC up to 4 MHz
   Crystal for 400 K, 800 K, 2 M, 3.58 M, 4 MHz
· Crystal for subsystem clock: 32.768 KHz

I/O Pins
· 32 bidirectional and individually controllable I/O lines:
   - P0 Port: P0.0-P0.3 large drive current Pins
   - P1 Port: P1.0-P1.3 large drive current Pins
   - P2 Port: P2.0-P2.3 large sink current pins and open drain option
   - P3 Port: P3.0-P3.3 multi-function I/O
   - P4 Port: P4.0-P4.3 open drain and pull high resistor option, multi-function I/O
   - P5 Port: P5.0-P5.3 multi-function I/O
   - P6 Port: P6.0-P6.3 open drain and pull high resistor option, multi-function I/O
   - P7 Port: P7.0-P7.3 large sink current pins and open drain option
· 32 bidirectional I/O lines:
   - P8 Port: P8.0-P8.3 large drive current pins
   - P9 Port: P9.0-P9.3 large sink current pins and open drain option
   - PA Port: PA.0-PA.3 open drain and pull high resistor option
   - PB Port: PB.0-PB.3 open drain and pull high resistor option
   - PC Port: PC.1-PC.3 open drain and pull high resistor option
   - PD Port: PD.0-PD.3 open drain and pull high resistor option
   - PE Port: PE.0-PE.3
   - PF Port: PF.0-PF.3

Interrupt
· Four External sources: INT0 ( P4.3 )
   P4 Port ( P4.0-P4.2 )
· Six Internal sources: Timer 0
   Timer 1
   Timer 2
   Timer 3
   Comparator
   Serial Port
   Timer/Counter
· Timer 0: 2-19 order divider (double source)
   Auto-reload timer
   Watch-dog timer
· Timer 1: 2-19 order divider
   Auto-reload timer
   Arbitrary waveform generator
   External event counter
· Timer 2: 2-19 order divider
   Auto-reload timer
   Arbitrary waveform generator
   Period/Pulse width measurement function
· Timer 3: 2-19 order divider
   Auto-reload timer
   Operating Mode (System Clock)
· Normal mode: System clock operating
· HOLD mode: no operation except for oscillator (System clock stops only)
· STOP mode: no operation including oscillator