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Port 3 Data Direction Register (P3DDR): P3DDR is an 8-bit write-only register that can select
input or output for each pin in port 3.
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Bit
7
P3 DDR
7
Initial value
0
Read/Write
W
Modes 1 to 6 (Expanded Modes): Port 3 functions as a data bus. P3DDR is ignored.
Mode 7 (Single-Chip Mode): Port 3 functions as an input/output port. A pin in port 3 becomes an
output port if the corresponding P3DDR bit is set to 1, and an input port if this bit is cleared to 0.
P3DDR is a write-only register. Its value cannot be read. All bits return 1 when read.
P3DDR is initialized to H'00 by a reset and in hardware standby mode. In software standby mode
it retains its previous setting. If a P3DDR bit is set to 1, the corresponding pin maintains its output
state in software standby mode.
Port 3 Data Register (P3DR): P3DR is an 8-bit readable/writable register that stores output data
for pins P3
to P3
. When a bit in P3DDR is set to 1, if port 3 is read the value of the
7
0
corresponding P3DR bit is returned. When a bit in P3DDR is cleared to 0, if port 3 is read the
corresponding pin level is read.
Bit
7
P3
7
Initial value
0
Read/Write
R/W
P3DR is initialized to H'00 by a reset and in hardware standby mode. In software standby mode it
retains its previous setting.
6
5
4
P3 DDR
P3 DDR
P3 DDR
6
5
4
0
0
0
W
W
W
Port 3 data direction 7 to 0
These bits select input or output for port 3 pins
6
5
4
P3
P3
P3
6
5
0
0
0
R/W
R/W
R/W
Port 3 data 7 to 0
These bits store data for port 3 pins
254
3
2
P3 DDR
P3 DDR
3
2
0
0
W
W
3
2
P3
P3
4
3
2
0
0
R/W
R/W
1
0
P3 DDR
P3 DDR
1
0
0
0
W
W
1
0
P3
P3
1
0
0
0
R/W
R/W
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