Port 4 - NEC mPD780065 Series Preliminary User's Manual

4.2.4 Port 4

Port 4 is an 8-bit input/output port with output latch. Input mode/output mode can be specified for pins P40 to P47
in 1-bit units with port mode register 4 (PM4). For pins P40 to P47, a pull-up resistor can be specified in 1-bit units
with pull-up resistor option register 4 (PU4).
This port can also be used as an address/data bus in external memory expansion mode.
RESET input sets port 4 to input mode.
Figure 4-5 shows a block diagram of port 4.
WR
PU
RD
WR
PORT
WR
PM
PUO: Pull-up resistor option register
PM: Port mode register
RD: Port 4 read signal
WR: Port 4 write signal
CHAPTER 4 PORT FUNCTIONS
Figure 4-5. Block Diagram of P40 to P47
PU40 to PU47
Selector
Output latch
(P40 to P47)
PM40 to PM47
Preliminary User's Manual U13420EJ2V0UM00
V
DD0
P-ch
P40/AD0 to
P47/AD7
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