Chapter 3
Connecting the Signals
©
National Instruments Corporation
3-17
DAQCard-1200 User Manual
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.
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.
Table 3-4.
Port C Signal Assignments
Configuration Terminology
Signal Assignments
82C55A/
DAQCard-1200
User Manual
NI-DAQ/
LabVIEW
PC7
PC6
PC5
PC4
PC3
PC2
PC1
PC0
Mode 0
(Basic I/O)
No
Handshaking
I/O
I/O
I/O
I/O
I/O
I/O
I/O
I/O
Mode 1
(Strobed Input)
Handshaking
I/O
I/O
IBF
A
STB
A
*
INTR
A
STB
B
*
IBFB
B
INTR
B
Mode 1
(Strobed Output)
Handshaking
OBF
A
*
ACK
A
*
I/O
I/O
INTR
A
ACK
B
*
OBF
B
*
INTR
B
Mode 2
(Bidirectional Bus)
Handshaking
OBF
A
*
ACK
A
*
IBF
A
STB
A
*
INTR
A
I/O
I/O
I/O
* Indicates that the signal is active low.
Subscripts A and B denote port A or port B handshaking signals.
