155
1. Port data register 4 (PDR4)
Bit
Initial value
Read/Write
7
—
1
—
6
—
1
—
5
—
1
—
4
—
1
—
3
P4
1
R
0
P4
0
R/W
2
P4
0
R/W
1
P4
0
R/W
3
2
1
0
PDR4 is an 8-bit register that stores data for port 4 pins P4
2
to P4
0
. If port 4 is read while PCR4
bits are set to 1, the values stored in PDR4 are read, regardless of the actual pin states. If port 4 is
read while PCR4 bits are cleared to 0, the pin states are read.
Upon reset, PDR4 is initialized to H'F8.
2. Port control register 4 (PCR4)
Bit
Initial value
Read/Write
7
—
1
—
6
—
1
—
5
—
1
—
4
—
1
—
3
—
1
—
0
PCR4
0
W
2
PCR4
0
W
1
PCR4
0
W
2
1
0
PCR4 is an 8-bit register for controlling whether each of port 4 pins P4
2
to P4
0
functions as an
input pin or output pin. Setting a PCR4 bit to 1 makes the corresponding pin an output pin, while
clearing the bit to 0 makes the pin an input pin. PCR4 and PDR4 settings are valid when the
corresponding pins are designated for general-purpose input/output by SCR3-2.
Upon reset, PCR4 is initialized to H'F8.
PCR4 is a write-only register, which always reads all 1s.
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