CHAPTER 4 PORT FUNCTIONS
User’s Manual U16899EJ2V0UD
97
4.2.5 Port 4
Port 4 is a 4-bit I/O port with an output latch. Port 4 can be set to the input mode or output mode in 1-bit units
using port mode register 4 (PM4). Use of an on-chip pull-up resistor can be specified in 1-bit units with pull-up resistor
option register 4 (PU4).
RESET input sets port 4 to input mode.
Figure 4-14 shows a block diagram of port 4.
Figure 4-14. Block Diagram of P40 to P43
RD
P-ch
WR
PU
WR
PORT
WR
PM
EV
DD
P40 to P43
PU40 to PU43
Output latch
(P40 to P43)
PM40 to PM43
Selector
Internal bus
PU4
PM4
PU4:
Pull-up resistor option register 4
PM4:
Port mode register 4
RD: Read
signal
WR
××
: Write
signal