IBM nec pd78081(a) User Manual

CHAPTER 2 PIN FUNCTION

2.2.3 P30 to P37 (Port 3)

These are 8-bit input/output ports. Beside serving as input/output ports, they function as clock output and buzzer

output.

The following operating modes can be specified bit-wise.

(1) Port mode

These ports function as 8-bit input/output ports. They can be specified bit-wise as input or output ports with

port mode register 3 (PM3). When they are used as input ports, on-chip pull-up resistors can be used by

defining the pull-up resistor option register L (PUOL).

(2) Control mode

These ports function as clock output, and buzzer output.

(a) PCL

Clock output pin.

(b) BUZ

Buzzer output pin.

2.2.4 P50 to P57 (Port 5)

These are 8-bit input/output ports. They can be specified bit-wise as input/output ports with port mode register

5 (PM5). When they are used as input ports, on-chip pull-up resistors can be used by defining the pull-up resistor

option register L (PUOL). A maximum of 7 out of 8 ports can drive LEDs directly.