NEC PD78F9488 - Manual (Page 77)

CHAPTER 4 PORT FUNCTIONS
User’s Manual U15331EJ4V1UD
77
4.2.1 Port 0
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.
Figure 4-2. Block Diagram of P00 to P07
WR
KRM00
V DD
P00/KR0 to
P07/KR7
Note 1
or
P00/KR00 to
P07/KR07
Note 2
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
µPD789488, 78F9488 is used
2. When µPD789489, 78F9489 is used