User's Manual

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.