CHAPTER 4 PORT FUNCTIONS
4.2.9 Port 9 (µPD789426, 789436 Subseries only)
This is an 8-bit I/O port with an output latch. Port 9 can be specified in the input or output mode in 1-bit units by
using port mode register 9 (PM9). When using the pins of this port as input port pins, on-chip pull-up resistors can be
connected in 1-bit units by using pull-up resistor option register B9 (PUB9).
This port is set in the input mode when the RESET signal is input.
Figure 4-17 shows a block diagram of port 9.
Figure 4-17. Block Diagram of P90 to P97
VDD
WRPUB9
PUB90 to PUB97
P-ch
RD
WRPORT
Output latch
(P90 to P97)
P90 to P97
WRPM
PM90 to PM97
PUB9: Pull-up resistor option register B9
PM: Port mode register
RD: Port 9 read signal
WR: Port 9 write signal
User’s Manual U15075EJ1V0UM00
95
NEC [ NEC ]
