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Chapter 3
Signal Connections
Port C Pin Assignments
Caution
During programming, be aware that each time a port is configured, output ports A
!
and C are reset to 0, and output port B is undefined.
Programming
Mode
Mode 0
I/O
Mode 1 Input
I/O
Mode 1 Output
OBF
Mode 2
OBF
* Indicates that the signal is active low; refer to Table 3-3 for signal name definitions.
Cable Assembly Connectors
DAQPad-6507/6508 User Manual
The signals assigned to port C depend on the mode in which the 82C55A is
programmed in your application software. 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. Table 3-2 summarizes the signal
assignments of port C for each programmable mode.
Table 3-2. Port C Signal Assignments
Group A
PC7
PC6
PC5
I/O
I/O
I/O
IBF
*
ACK A *
I/O
A
*
ACK
*
IBF
A
A
The cable assembly referred to in the
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 DAQPad-6508. 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
DAQPad-6508 I/O connector. The cables are labelled Position 1-50 and
51-100, respectively. Figures 3-3 and 3-4 show the pin assignments for the
50-pin connectors on the cable assembly.
PC4
PC3
I/O
I/O
STB
*
INTR
A
A
A
I/O
INTR
A
STB
*
INTR
A
A
A
Optional Equipment
3-4
Group B
PC2
PC1
I/O
I/O
I/O
STB
*
IBFB
INTR
B
B
ACK
*
OBF
*
INTR
B
B
I/O
I/O
I/O
section in
© National Instruments Corporation
PC0
B
B
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