Port; P30 To P37 Block Diagram - NEC PD78081(A) User Manual

4.2.3 Port 3

Port 3 is an 8-bit input/output port with output latch. P30 to P37 pins can specify the input mode/output mode in
1-bit units with the port mode register 3 (PM3). When P30 to P37 pins are used as input ports, an on-chip pull-up
resistor can be used to them in 8-bit units with a pull-up resistor option register L (PUOL).
Dual-functions include clock output and buzzer output.
RESET input sets port 3 to input mode.
Figure 4-5 shows a block diagram of port 3.
WR
PUO
RD
WR
PORT
WR
PM
PUO : Pull-up resistor option register
PM : Port mode register
RD : Port 3 read signal
WR : Port 3 write signal
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CHAPTER 4 PORT FUNCTIONS
Figure 4-5. P30 to P37 Block Diagram
PUO3
Output Latch
(P30 to P37)
PM30-PM37
Alternate Function
Selector
V
DD
P-ch
P30
P34,
P35/PCL,
P36/BUZ,
P37