PD64A_15 Datasheet, PDF (17/66 Pages) Renesas Technology Corp – 4-BIT SINGLE-CHIP MICROCONTROLLERS FOR INFRARED REMOTE CONTROL TRANSMISSION

µPD64A, 65
3.1 KI/O Port (P0)
The KI/O port is an 8-bit I/O port for key scan output.
Input/output mode is set by bit 1 of the P4 register.
If a read instruction is executed, the pin state can be read in input mode, whereas the output latch contents can
be read in output mode.
If a write instruction is executed, data can be written to the output latch regardless of input or output mode.
After reset, the port enters output mode, and the value of the output latch (P0) becomes 1111 1111B.
The KI/O port includes a pull-down resistor, which functions in input mode only.
Caution Because during double pressing of a key, a high-level output and a low-level output may conflict
with each other at the KI/O port, the low-level output current of the KI/O port is held low. Therefore,
be careful when using the KI/O port for purposes other than key scan output.
The KI/O port is designed so that, even when connected directly to VDD within the normal supply
voltage range (VDD = 2.0 to 3.6 V), no problem may occur.
Bit
Name
Table 3-2. KI/O Port (P0)
b7
KI/O7
b6
KI/O6
b5
KI/O5
b4
KI/O4
b3
KI/O3
b2
KI/O2
b1
KI/O1
b0
KI/O0
b0 to b7: When reading: In input mode, state of the KI/O pin is read.
In output mode, the KI/O pin’s output latch contents are read.
When writing: Data is written to the KI/O pin’s output latch regardless of input or output mode.
Data Sheet U14380EJ3V0DS00
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