Appendix B
Register-Level Programming — Port C Status-Word Bit Definitions for Output (Ports A and B)
PCI-DIO-96/PXI-6508/PCI-6503 User Manual
B-26
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Mode 2—Bidirectional Bus
Note
For mode 2 examples, you must configure the don’t care bits appropriately in the
control word if you want to use the other ports in combination with the example.
Mode 2 has an 8-bit bus that can transfer both input and output data without changing the
configuration. The data transfers are synchronized with handshaking lines in port C. This
mode uses only port A; however, port B can be used in either mode 0 or mode 1 while port A
is configured for mode 2.
Figure B-10 shows the control word written to the Configuration Register to configure port A
as a bidirectional data bus in mode 2. If port B is configured for mode 0, you can use PC2,
PC1, and PC0 of port C as extra input or output lines.
Figure B-10.
Control Word to Configure Port A as Mode 2 Bidirectional Data Bus
During a mode 2 data transfer, you can obtain the status of the handshaking lines and interrupt
signals by reading port C. The following sections show the port C status-word bit definitions
for a mode 2 transfer.
Port C
PC <2..0>
1 = Input
0 = Output
D7
D6
D5
D4
D3
D2
D1
D0
1
1
X
X
X
1/0
1/0
1/0
Port B
1 = Input
0 = Output
Group B Mode
0 = Mode 0
1 = Mode 1