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DIO PORT C DATA
BADR3 + 6
PORT C may be configured as an 8-bit port of either input or output, or it may be split into two independent 4-bit ports of
input or output. When split into two 4-bit I/O ports, D[3:0]
make up the lower nibble, D[7:4] comprise the upper nibble. Although it may be split, every
write to Port C is a byte operation. Unwanted information must be ANDed out during reads
and writes must be ORd with current value of the other 4-bit port.
READ/WRITE
7
6
D7
D6
DIO CONTROL REGISTER
BADR3 + 7
The DIO Control register is used configure Ports A,B and C as inputs or outputs. Operation is identical to that of the 8255
in Mode 0.
WRITE
7
6
D7
D6
The following table summarizes the possible I/O Port configurations for the PCI-DAS1000
DIO operatin in MODE 0:
D4
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
5
4
D5
D4
5
4
D5
D4
D3
D1
D0
PORT A
0
0
0
OUT
0
0
1
OUT
0
1
0
OUT
0
1
1
OUT
1
0
0
OUT
1
0
1
OUT
1
1
0
OUT
1
1
1
OUT
0
0
0
IN
0
0
1
IN
0
1
0
IN
0
1
1
IN
1
0
0
IN
1
0
1
IN
1
1
0
IN
1
1
1
IN
2
3
D3
D2
2
3
D3
D2
PORT C
PORT B
UPPER
OUT
OUT
OUT
OUT
OUT
IN
OUT
IN
IN
OUT
IN
OUT
IN
IN
IN
IN
OUT
OUT
OUT
OUT
OUT
IN
OUT
IN
IN
OUT
IN
OUT
IN
IN
IN
IN
28
1
0
D1
D0
1
0
D1
D0
PORT C
LOWER
OUT
IN
OUT
IN
OUT
IN
OUT
IN
OUT
IN
OUT
IN
OUT
IN
OUT
IN
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