CHAPTER 4 PORT FUNCTIONS
User's Manual U11919EJ3V0UM00
76
4.2.4 Port 3
This is a 3-bit I/O port with output latch. It can be specified in input or output mode in 1-bit units by using the port
mode register 3 (PM3). When using P30 to P32 pins as input port pins, on-chip pull-up resistors can be connected
in 3-bit units by using the pull-up resistor option register (PUO).
The pins of this port are also used as the external interrupt input and capture edge input.
RESET input sets port 3 to input mode.
Figure 4-7 shows the block diagram of port 3.
Figure 4-7. Block Diagram of P30 to P32
Internal Bus
WR
PUO
RD
WR
PORT
WR
PM
Output Latch
(P30 to P32)
PM30 to PM32
Selector
PUO3
V
DD0
P-ch
P30/INTP0
P31/INTP1
P32/INTP2/
CPT2
Alternate
Function
PUO : Pull-up resistor option register
PM
: Port mode register
RD
: Port 3 read signal
WR : Port 3 write signal
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Summary of Contents for UPD789026 Series
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