Справочник Пользователя для IBM uPD78P083

Port 3 is an 8-bit input/output port with output latch.  P30 to P37 pins can specify the input mode/output mode in

1-bit units with the port mode register 3 (PM3).  When P30 to P37 pins are used as input ports, an on-chip pull-up

resistor can be used to them in 8-bit units with a pull-up resistor option register L (PUOL).

Dual-functions include clock output and buzzer output.

RESET input sets port 3 to input mode.

Figure 4-5 shows a block diagram of port 3.

PUO :  Pull-up resistor option register

PM

:  Port mode register

RD

:  Port 3 read signal

WR :  Port 3 write signal

P-ch

WR

PM

WR

PORT

RD

WR

PUO

V

DD

Selector

PUO3

Output Latch
(P30 to P37)

PM30-PM37

Internal bus

Alternate Function

P30

P34,
P35/PCL,
P36/BUZ,
P37