w78c31b Winbond Electronics Corp America, w78c31b Datasheet - Page 4

• Manufacturer Part Number: w78c31b
• Description: 8-bit Microcontroller
• Manufacturer: Winbond Electronics Corp America

PSEN
Program Store Enable Output, active low. PSEN enables the external ROM onto the Port 0
address/data bus during fetch and MOVC operations. PSEN goes to a high state during reset with a
weak pull-up.
XTAL1
Crystal 1. This is the crystal oscillator input. This pin may be driven by an external clock.
XTAL2
Crystal 2. This is the crystal oscillator output. It is the inversion of XTAL1.
V
Power Supplies. These are the chip ground and positive supplies.
BLOCK DIAGRAM
SS
, V
CC
Bytes
RAM
128
CORE
CPU
- 4 -
Data Bus
Interrupt
SFR
Timer 1
Timer 0
INT 1
INT 0
Serial
Port
Alternate
Port 1
Port 0
Port 2
Port 3
W78C31B