IBM uPD78082 - Manual (Page 41)

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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.