NEC PD78078 用户手册

Port 8 is an 8-bit input/output port with output latch.  P80 to P87 pins can specify the input mode/output mode in

1-bit units with the port mode register 8 (PM8).  When pins P80 to P87 are used as input ports, an on-chip pull-up

resistor can be connected to them in 8-bit units with a pull-up resistor option register H (PUOH).

Dual-functions include the address bus function in external memory expansion mode.

RESET input sets port 8 to input mode.

Figure 6-17 shows block diagram of port 8.

PUO :  Pull-up resistor option register

PM

:  Port mode register

RD

:  Port 8 read signal

WR :  Port 8 write signal

P-ch

WR

PM

WR

PORT

RD

WR

PUO

V

DD

Selector

PUO8

Output Latch
(P80 to P87)

PM80 to PM87

Internal bus

P80/A0 to
P87/A7