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8. I/O Ports
Port Data Register 3 (PDR3)
Bit
P3
Initial value
Read/Write
R/W
PDR3 is an 8-bit register that stores data for port 3 pins P3
bits are set to 1, the values stored in PDR3 are read, regardless of the actual pin states. If port 3 is
read while PCR3 bits are cleared to 0, the pin states are read.
Upon reset, PDR3 is initialized to H'00.
Port Control Register 3 (PCR3)
Bit
PCR3
Initial value
Read/Write
PCR3 is an 8-bit register for controlling whether each of the port 3 pins P3
input pin or output pin. Setting a PCR3 bit to 1 makes the corresponding pin an output pin, while
clearing the bit to 0 makes the pin an input pin. The settings in PCR3 and in PDR3 are valid only
when the corresponding pin is designated in PMR3 as a general I/O pin.
Upon reset, PCR3 is initialized to H'00.
PCR3 is a write-only register. All bits are read as 1.
Port Pull-Up Control Register 3 (PUCR3)
Bit
PUCR3
Initial value
Read/Write
R/W
PUCR3 bits control the on/off state of pin P3
0, setting the corresponding PUCR3 bit to 1 turns on the MOS pull-up for the corresponding pin,
while clearing the bit to 0 turns off the MOS pull-up.
Rev.3.00 Jul. 19, 2007 page 190 of 532
REJ09B0397-0300
7
6
5
P3
P3
7
6
0
0
0
R/W
R/W
7
6
5
PCR3
PCR3
7
6
0
0
0
W
W
W
7
6
5
PUCR3
PUCR3
7
6
0
0
0
R/W
R/W
4
3
P3
P3
5
4
3
0
0
R/W
R/W
to P3
7
4
3
PCR3
PCR3
5
4
0
0
W
W
4
3
PUCR3
PUCR3
5
4
0
0
R/W
R/W
–P3
MOS pull-ups. When a PCR3 bit is cleared to
7
0
2
1
P3
P3
2
1
0
0
R/W
R/W
. If port 3 is read while PCR3
0
2
1
PCR3
PCR3
3
2
0
0
W
W
to P3
functions as an
7
0
2
1
PUCR3
PUCR3
3
2
0
0
R/W
R/W
0
P3
0
0
R/W
0
PCR3
1
0
0
W
0
PUCR3
1
0
0
R/W
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