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9.2.2 Register Descriptions
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Table 9-2 summarizes the registers of port 1.
Table 9-2 Port 1 Registers
Address*
Name
H'FFC0
Port 1 data direction register
H'FFC2
Port 1 data register
Note: * Lower 16 bits of the address.
Port 1 Data Direction Register (P1DDR): P1DDR is an 8-bit write-only register that can select
input or output for each pin in port 1.
Bit
Initial value
Modes
1 to 4
Read/Write
Initial value
Modes
5 to 7
Read/Write
Modes 1 to 4 (Expanded Modes with On-Chip ROM Disabled): P1DDR values are fixed at 1
and cannot be modified. Port 1 functions as an address bus.
Modes 5 and 6 (Expanded Modes with On-Chip ROM Enabled): A pin in port 1 becomes an
address output pin if the corresponding P1DDR bit is set to 1, and a generic input pin if this bit is
cleared to 0.
Mode 7 (Single-Chip Mode): Port 1 functions as an input/output port. A pin in port 1 becomes an
output pin if the corresponding P1DDR bit is set to 1, and an input pin if this bit is cleared to 0.
7
6
5
P1 DDR
P1 DDR
P1 DDR
7
6
5
1
1
1
—
—
—
0
0
0
W
W
W
Abbreviation
R/W
Modes 1 to 4
P1DDR
W
H'FF
P1DR
R/W
H'00
4
3
P1 DDR
P1 DDR
P1 DDR
4
3
1
1
—
—
0
0
W
W
Port 1 data direction 7 to 0
These bits select input or
output for port 1 pins
247
Initial Value
Modes 5 to 7
H'00
H'00
2
1
0
P1 DDR
P1 DDR
2
1
0
1
1
1
—
—
—
0
0
0
W
W
W
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