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Rev. 1.00, 05/04, page 125 of 544
7.10 Port A
Port A is an 8-bit I/O port. Port A pins also function as keyboard buffer controller I/O pins, and
key-sense interrupt input pins. Port A input/output operates by VccB power independent from the
Vcc power. Up to 5 V can be applied to port A pins if VccB power is 5 V. Port A has the
following registers. PADDR and PAPIN have the same address.
• Port A data direction register (PADDR)
• Port A output data register (PAODR)
• Port A input data register (PAPIN)
7.10.1 Port A Data Direction Register (PADDR)
PADDR specifies input or output for the pins of port A on a bit-by-bit basis.
Bit Bit Name
Initial
Value
R/W Description
7 PA7DDR 0 W
6 PA6DDR 0 W
5 PA5DDR 0 W
4 PA4DDR 0 W
3 PA3DDR 0 W
2 PA2DDR 0 W
1 PA1DDR 0 W
0 PA0DDR 0 W
The corresponding port A pins are output ports when
PADDR bits are set to 1, and input ports when
cleared to 0.
PA7 to PA2 pins are used as the keyboard buffer
controller I/O pins by setting the KBIOE bit to 1, while
the I/O direction according to PA7DDR to PA2DDR is
ignored.
PADDR has the same address as PAPIN, if read, port
A state is returned.
7.10.2 Port A Output Data Register (PAODR)
PAODR stores output data for port A.
Bit Bit Name
Initial
Value R/W Description
7 PA7ODR 0 R/W
6 PA6ODR 0 R/W
5 PA5ODR 0 R/W
4 PA4ODR 0 R/W
3 PA3ODR 0 R/W
2 PA2ODR 0 R/W
1 PA1ODR 0 R/W
0 PA0ODR 0 R/W
PAODR can always be read or written to, regardless
of the contents of PADDR.