NEC PD78F9488 Manuale Utente

User’s Manual  U15331EJ4V1UD

This is an 8-bit I/O port with an output latch.  Port 0 can be specified in the input or output mode in 1-bit units by 

using port mode register 0 (PM0).  When the P00 to P07 pins are used as input port pins, on-chip pull-up resistors can 
be connected in 1-bit units by using pull-up resistor option register B0 (PUB0). 

This port is also used for key return signal input. 
RESET input sets this port to input mode. 
Figure 4-2 shows a block diagram of port 0. 
 

WR

KRM00

V

DD

P00/KR0 to
P07/KR7

or
P00/KR00 to
P07/KR07

WR

PUO

RD

WR

PORT

W

RPM

PUB00 to PUB07

PM00 to PM07

KRM000,

KRM004 to KRM007

P-ch

Internal bus

Selector

Output latch

(P00 to P07)

Alternate function

 

 

KRM00: Key return mode register 00 
PUB0:  Pull-up resistor option register B0 
PM: 

Port mode register 

RD: 

Port 0 read signal 

WR: 

Port 0 write signal 

 
Notes 1. When 

µ

PD789488, 78F9488 is used 

 

2. When 

µ

PD789489, 78F9489 is used