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7.10.2 Register Descriptions
Table 7-15 summarizes the registers of port A.
Table 7-15 Port A Registers
Initial Value
Address
*
Name
Abbreviation
R/W
Modes 1, 5, and 7
Modes 3 and 6
H'FFD1
Port A data
direction register
PADDR
W
H'00
H'80
H'FFD3
Port A data register
PADR
R/W
H'00
H'00
Note:
*
Lower 16 bits of the address.
Port A Data Direction Register (PADDR): PADDR is an 8-bit write-only register that can select
input or output for each pin in port A. The corresponding PADDR bit should also be set when a
pin is used as a TPC output.
7
PA DDR
1
—
0
W
Port A data direction 7 to 0
These bits select input or output for port A pins
7
6
PA DDR
0
W
0
W
6
5
PA DDR
0
W
0
W
5
4
PA DDR
0
W
0
W
4
3
PA DDR
0
W
0
W
3
2
PA DDR
0
W
0
W
2
1
PA DDR
0
W
0
W
1
0
PA DDR
0
W
0
W
0
Bit
Initial value
Read/Write
Initial value
Read/Write
Modes
1, 5, and 7
Modes 3
and 6
A pin in port A becomes an output pin if the corresponding PADDR bit is set to 1, and an input
pin if this bit is cleared to 0. However, in modes 3 and 6, PA
7
DDR is fixed at 1, and PA7
functions as an address output pin.
PADDR is a write-only register. Its value cannot be read. All bits return 1 when read.
PADDR is initialized to H'00 in modes 1, 5 and 7 and to H'80 in modes 3 and 6 by a reset and in
hardware standby mode. In software standby mode it retains its previous setting. If a PADDR bit
is set to 1, the corresponding pin maintains its output state in software standby mode.