Hitachi H8/3937 Series Hardware Manual page 167

1. Port data register 4 (PDR4)
Bit 7
—
Initial value 1
Read/Write —
PDR4 is an 8-bit register that stores data for port 4 pins P4
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 7
—
Initial value 1
Read/Write —
PCR4 is an 8-bit register for controlling whether each of port 4 pins P4
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.
6 5 4
— — —
1 1 1
— — —
6 5 4
— — —
1 1 1
— — —
3 2
P4 P4 P4
3 2
1 0
R R/W R/W
to P4 . If port 4 is read while PCR4
2 0
3 2
— PCR4 PCR4
2
1 0
— W
to P4 functions as an
2 0
1 0
P4
1 0
0 0
R/W
1 0
PCR4
1 0
0 0
W W
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