Rainbow Electronics W78C32C - Manual (Page 4)

W78C32C
- 4 -
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 SS , V CC
Power Supplies. These are the chip ground and positive supplies.
BLOCK DIAGRAM
SFR
Port 0
Port 1
Port 2
CPU
Data Bus
Port 3
Alternate
Serial
Port
Timer 0
CORE
Interrupt Timer 1
RAM
256
Bytes
Alternate
Timer 2
INT 1
INT 0