Port 9 ( Μ Pd789426, 789436 Subseries Only); Block Diagram Of P90 To P97 - NEC UPD789426 Series User Manual

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4.2.9 Port 9 ( PD789426, 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 setting 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.
WR
PUB9
RD
WR
PORT
WR
PM
PUB9: Pull-up resistor option register B9
PM: Port mode register
RD: Port 9 read signal
WR: Port 9 write signal
94
CHAPTER 4 PORT FUNCTIONS
Figure 4-17. Block Diagram of P90 to P97
PUB90 to PUB97
Output latch
(P90 to P97)
PM90 to PM97
User's Manual U15075EJ2V1UD
V
DD
P-ch
P90 to P97