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Note
Table 3-4 shows both the port C signal assignments and the terminology correlation
between different documentation sources. The 82C55A terminology refers to the different
82C55A configurations as modes, whereas NI-DAQ and LabVIEW documentation refers
to them as handshaking and no handshaking. These signal assignments are the same for all
four 82C55A PPIs.
Configuration Terminology
82C55A/
DAQCard-1200
NI-DAQ/
User Manual
LabVIEW
Mode 0
No
(Basic I/O)
Handshaking
Mode 1
Handshaking
(Strobed Input)
Mode 1
Handshaking
(Strobed Output)
Mode 2
Handshaking
(Bidirectional Bus)
* Indicates that the signal is active low.
Subscripts A and B denote port A or port B handshaking signals.
© National Instruments Corporation
Port C Pin Connections
The signals assigned to port C depend on how the 82C55A is configured.
In mode 0, or no-handshaking configuration, port C is configured as
two 4-bit I/O ports. In modes 1 or 2, or handshaking configuration, port C
is used for status and handshaking signals with zero, two, or three lines
available for general-purpose I/O. Table 3-4 summarizes the port C signal
assignments for each configuration.
Table 3-4. Port C Signal Assignments
PC7
PC6
I/O
I/O
I/O
I/O
OBF
*
ACK
*
A
A
OBF
*
ACK
*
A
A
Signal Assignments
PC5
PC4
PC3
I/O
I/O
I/O
IBF
STB
*
INTR
A
A
I/O
I/O
INTR
IBF
STB
*
INTR
A
A
3-17
Chapter 3
Connecting the Signals
PC2
PC1
I/O
I/O
STB
*
IBFB
A
B
B
ACK
*
OBF
*
A
B
B
I/O
I/O
A
DAQCard-1200 User Manual
PC0
I/O
INTR
B
INTR
B
I/O
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