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Chapter 3
Signal Connections
Port C Pin Assignments
Warning: During programming, note that each time a port is configured, output
Programming
Mode
Mode 0
I/O
Mode 1 Input
I/O
Mode 1 Output
OBF A *
Mode 2
OBF A *
* Indicates that the signal is active low
Cable Assembly Connectors
PC-DIO-96/PnP User Manual
The signals assigned to port C depend on the mode in which the
82C55A is programmed. In mode 0, port C is considered as two 4-bit
I/O ports. In modes 1 and 2, port C is used for status and handshaking
signals with zero, two, or three lines available for general-purpose
input/output. The following table summarizes the signal assignments of
port C for each programmable mode. Consult Appendix D, Register-
Level Programming, for programming information.
ports A and C are reset to 0, and output port B is undefined.
Table 3-1.
Group A
PC7
PC6
PC5
I/O
I/O
I/O
IBF A
ACK A *
I/O
ACK A *
IBF A
The cable assembly referred to in Optional Equipment in Chapter 1,
Introduction, is an assembly of two 50-pin cables and three connectors.
Both cables are joined to a single connector on one end and to
individual connectors on the free ends. The 100-pin connector that joins
the two cables plugs into the I/O connector of the PC-DIO-96/PnP. The
other two connectors are 50-pin connectors, one of which is connected
to pins 1 through 50 and the other is connected to pins 51 through 100
of the PC-DIO-96/PnP I/O connector. The cable with the label on it is
connected to pins 1 through 50. Figures 3-2 and 3-3 show the pin
assignments for the 50-pin connectors on the cable assembly.
Port C Signal Assignments
PC4
PC3
I/O
I/O
STB A *
INTR A
I/O
INTR A
STB A *
INTR A
3-4
Group B
PC2
PC1
I/O
I/O
STB B *
IBFB B
ACK B *
OBF B *
I/O
I/O
© National Instruments Corporation
PC0
I/O
INTR B
INTR B
I/O
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