User manual

Chapter 3 Signal Connections
PC-DIO-96/PnP User Manual 3-4 © National Instruments Corporation
Port C Pin Assignments
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.
Warning: During programming, note that each time a port is configured, output
ports A and C are reset to 0, and output port B is undefined.
Cable Assembly Connectors
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.
Table 3-1. Port C Signal Assignments
Programming
Mode
Group A Group B
PC7 PC6 PC5 PC4 PC3 PC2 PC1 PC0
Mode 0
I/O I/O I/O I/O I/O I/O I/O I/O
Mode 1 Input
I/O I/O IBF
A
STB
A
* INTR
A
STB
B
* IBFB
B
INTR
B
Mode 1 Output
OBF
A
* ACK
A
* I/O I/O INTR
A
ACK
B
* OBF
B
* INTR
B
Mode 2
OBF
A
* ACK
A
* IBF
A
STB
A
* INTR
A
I/O I/O I/O
* Indicates that the signal is active low