CHAPTER 4 PORT FUNCTIONS
4.2.4 Port 3
This is a 4-bit I/O port with an output latch. Port 3 can be specified in the input or output mode in 1-bit units by
using port mode register 3 (PM3). When using the P30 to P33 pins as input port pins, on-chip pull-up resistors can
be connected in 1-bit units by using pull-up resistor option register B3 (PUB3).
This port is also used as an external interrupt input, capture input, and timer I/O.
This port is set in the input mode when the RESET signal is input.
Figures 4-11 and 4-12 show block diagrams of port 3.
Figure 4-11. Block Diagram of P30
VDD
WRPUB3
PUB30
P-ch
Alternate
function
RD
WRPORT
Output latch
(P30)
P30/INTP0/CPT90
WRPM
PM30
PUB3: Pull-up resistor option register B3
PM:
RD:
WR:
Port mode register
Port 3 read signal
Port 3 write signal
User’s Manual U15075EJ1V0UM00
89
NEC [ NEC ]
