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ABWCR and P4DDR are not initialized in software standby mode. Therefore, if a transition is
made to software standby mode while port 4 is functioning as an input/output port and a P4DDR
bit is set to 1, the corresponding pin maintains its output state.
Port 4 Data Register (P4DR): P4DR is an 8-bit readable/writable register that stores output data
for port 4. When port 4 functions as an output port, the value of this register is output. When a bit
in P4DDR is set to 1, if port 4 is read the value of the corresponding P4DR bit is returned. When a
bit in P4DDR is cleared to 0, if port 4 is read the corresponding pin logic level is read.
Bit
Initial value
Read/Write
R/W
P4DR is initialized to H'00 by a reset and in hardware standby mode. In software standby mode it
retains its previous setting.
Port 4 Input Pull-Up MOS Control Register (P4PCR): P4PCR is an 8-bit readable/writable
register that controls the MOS input pull-up transistors in port 4.
Bit
P4 PCR
Initial value
Read/Write
R/W
In modes 6 and 7 (single-chip mode), and in 8-bit bus mode in modes 1 to 5 (expanded modes),
when a P4DDR bit is cleared to 0 (selecting generic input), if the corresponding P4PCR bit is set
to 1, the input pull-up transistor is turned on.
P4PCR is initialized to H'00 by a reset and in hardware standby mode. In software standby mode it
retains its previous setting.
Table 7.7 summarizes the states of the input pull-up MOS in each operating mode.
176
7
6
P4
P4
7
6
0
0
R/W
R/W
7
6
P4 PCR
P4 PCR
7
6
0
0
R/W
R/W
Port 4 input pull-up MOS control 7 to 0
These bits control input pull-up transistors built into port 4
5
4
P4
P4
5
4
0
0
R/W
R/W
Port 4 data 7 to 0
These bits store data for port 4 pins
5
4
P4 PCR
P4 PCR
5
4
0
0
R/W
R/W
3
2
P4
P4
3
2
0
0
R/W
R/W
3
2
P4 PCR
P4 PCR
3
2
0
0
R/W
R/W
1
0
P4
P4
1
0
0
0
R/W
1
0
P4 PCR
1
0
0
0
R/W
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