CHAPTER 4 PORT FUNCTIONS
User’s Manual U15075EJ1V0UM00
89
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
P30/INTP0/CPT90
WR
PUB3
RD
WR
PORT
WR
PM
PUB30
PM30
V
DD
P-ch
Internal bus
Alternate
function
Selector
Output latch
(P30)
PUB3:
Pull-up resistor option register B3
PM:
Port mode register
RD:
Port 3 read signal
WR:
Port 3 write signal
Содержание mPD789425
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