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6.2.5 Port 3
Port 3 is an 8-bit input/output port with output latch. P30 to P37 pins can be set to the input mode/output mode
bit-wise with the port mode register (PM3). When P30 to P37 pins are used as input ports, an on-chip pull-up resistor
can be connected to them in 8-bit units with a pull-up resistor option register (PUO).
Alternate functions include timer input/output, clock output and buzzer output.
RESET input sets port 3 to input mode.
Figure 6-10 shows a block diagram of port 3.
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Figure 6-10. P30 to P37 Block Diagrams
WR
PUO
PUO3
RD
WR
PORT
Output Latch
(P30 to P37)
WR
PM
PM30 to PM37
Alternate
Function
PUO : Pull-up resistor option register
PM
: Port mode register
RD
: Port 3 read signal
WR : Port 3 write signal
CHAPTER 6 PORT FUNCTIONS
Selector
V
DD
P-ch
P30/TO0,
P31/TO1,
P32/TO2,
P33/TI1,
P34/TI2,
P35/PCL,
P36/BUZ,
P37
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