CHAPTER 4 PORT FUNCTIONS
Preliminary User’s Manual U16846EJ1V0UD
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4.2.4 Port 3
Port 3 is a 4-bit I/O port with an output latch. Port 3 can be set to the input mode or output mode in 1-bit units
using port mode register 3 (PM3). When the P30 to P33 pins are used as an input port, use of an on-chip pull-up
resistor can be specified in 1-bit units by pull-up resistor option register 3 (PU3).
This port can also be used for external interrupt request input.
RESET input sets port 3 to input mode.
Figure 4-11 shows a block diagram of port 3.
Figure 4-11. Block Diagram of P30 to P33
P30/INTP1 to
P33/INTP4
WR
PU
RD
WR
PORT
WR
PM
PU30 to PU33
Alternate
function
Output latch
(P30 to P33)
PM30 to PM33
PU3
PM3
V
DD
P-ch
Selector
Internal bus
PU3:
Pull-up resistor option register 3
PM3:
Port mode register 3
RD: Read
signal
WR
××
: Write
signal
