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Port 9 Data Direction Register (P9DDR): P9DDR is an 8-bit write-only register that can select
input or output for each pin in port 9.
Bits 7 and 6 are reserved. They are fixed at 1, and cannot be modified.
Bit
Initial value
Read/Write
7
—
1
—
6
—
1
—
5
P9 DDR
0
W
5
4
P9 DDR
0
W
4
3
P9 DDR
0
W
3
2
P9 DDR
0
W
2
1
P9 DDR
0
W
1
0
P9 DDR
0
W
0
Reserved bits
Port 9 data direction 5 to 0
These bits select input or
output for port 9 pins
When port 9 functions as an input/output port, a pin in port 9 becomes an output port if the
corresponding P9DDR bit is set to 1, and an input port if this bit is cleared to 0. For the method of
selecting the pin functions, see table 7.10.
P9DDR is a write-only register. Its value cannot be read. All bits return 1 when read.
P9DDR is initialized to H'C0 by a reset and in hardware standby mode. In software standby mode
it retains its previous setting. Therefore, if a transition is made to software standby mode while
port 9 is functioning as an input/output port and a P9DDR bit is set to 1, the corresponding pin
maintains its output state.
Port 9 Data Register (P9DR): P9DR is an 8-bit readable/writable register that stores output data
for port 9. When port 9 functions as an output port, the value of this register is output. When a bit
in P9DDR is set to 1, if port 9 is read the value of the corresponding P9DR bit is returned. When a
bit in P9DDR is cleared to 0, if port 9 is read the corresponding pin logic level is read.
Bits 7 and 6 are reserved. They are fixed at 1, and cannot be modified.
Bit
Initial value
Read/Write
7
—
1
—
6
—
1
—
5
P9
0
R/W
4
P9
0
R/W
4
3
P9
0
R/W
3
2
P9
0
R/W
2
1
P9
0
R/W
1
0
P9
0
R/W
0
Reserved bits
Port 9 data 5 to 0
These bits store data
for port 9 pins
5
P9DR is initialized to H'C0 by a reset and in hardware standby mode. In software standby mode it
retains its previous setting.
Summary of Contents for H8/3008
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