8.11
Port A
8.11.1
Overview
Port A is a 4-bit I/O port, configured as shown in figure 8-10.
PA3/COM4
PA2/COM3
PA1/COM2
PA0/COM1
Port A
Figure 8-10 Port A Pin Configuration
Register Configuration and Description
8.11.2
Table 8-29 shows the port A register configuration.
Table 8-29 Port A Registers
Name
Abbrev.
PDRA
R/W
R/W
W
Initial Value
H'F0
Address
H'FFDD
H'FFED
Port data register A
Port control register A
PCRA
H'F0
1. Port data register A (PDRA)
Bit
7
—
1
6
—
1
5
—
1
4
—
1
3
2
1
0
PA3
0
PA2
0
PA1
0
PA 0
0
Initial value
Read/Write
—
—
—
—
R/W
R/W
R/W
R/W
PDRA is an 8-bit register that stores data for port A pins PA3 to PA0. If port A is read while
PCRA bits are set to 1, the values stored in PDRA are read, regardless of the actual pin states. If
port A is read while PCRA bits are cleared to 0, the pin states are read.
Upon reset, PDRA is initialized to H'F0.
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