173
8.11
Port A
8.11.1
Overview
Port A is a 4-bit I/O port, configured as shown in figure 8-10.
PA
3
PA
2
PA
1
PA
0
Port A
Figure 8-10 Port A Pin Configuration
8.11.2
Register Configuration and Description
Table 8-29 shows the port A register configuration.
Table 8-29 Port A Registers
Name
Abbrev.
R/W
Initial Value
Address
Port data register A
PDRA
R/W
H'F0
H'FFDD
Port control register A
PCRA
W
H'F0
H'FFED
1. Port data register A (PDRA)
Bit
Initial value
Read/Write
7
—
1
—
6
—
1
—
5
—
1
—
4
—
1
—
3
PA
0
R/W
0
PA
0
R/W
2
PA
0
R/W
1
PA
0
R/W
3
2
1
0
PDRA is an 8-bit register that stores data for port A pins PA
3
to PA
0
. 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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