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9.6
Port A
Port A is a 4-bit I/O port that also has other functions. Port A has the following registers.
• Port A data direction register (PADDR)
• Port A data register (PADR)
• Port A register (PORTA)
• Port A pull-up MOS control register (PAPCR)
• Port A open-drain control register (PAODR)
9.6.1
Port A Data Direction Register (PADDR)
PADDR is an 8-bit write-only register, the individual bits of which specify whether the pins of
port A are used for input or output.
Bit
Bit Name
Initial Value
7 to
Undefined
4
3
PA3DDR
0
2
PA2DDR
0
1
PA1DDR
0
0
PA0DDR
0
Rev. 1.0, 09/02, page 138 of 568
R/W
Description
Reserved
These bits are read as undefined value and cannot
be modified.
W
When a pin is specified as a general purpose I/O
port, setting this bit to 1 makes the corresponding
W
port A pin an output pin. Clearing this bit to 0 makes
W
the pin an input pin.
W
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