NEC 78K0 Series User Manual page 116

5.2.5 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). When the P40 to P43 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 4 (PU4).
Reset signal generation sets port 4 to input mode.
Figure 5-16 shows a block diagram of port 4.
WR
PU
RD
WR
PORT
WR
PM
P4: Port register 4
PU4: Pull-up resistor option register 4
PM4: Port mode register 4
RD: Read signal
WR××: Write signal
116
CHAPTER 5 PORT FUNCTIONS
Figure 5-16. Block Diagram of P40 to P43
PU4
PU40 to PU43
Selector
P4
Output latch
(P40 to P43)
PM4
PM40 to PM43
Preliminary User's Manual U17260EJ3V1UD
EV
DD
P-ch
P40 to P43