Programming instructions

Chapter 21 Common SCXI Applications
LabVIEW Data Acquisition Basics Manual 21-18
© National Instruments Corporation
lines on your DAQ device. The DIO-32F device can access all 32 lines of
the SCXI modules at once by using the SCXI-1348 cable assembly. The
DIO-24 and the DIO-96 devices can only access the first 24 lines of these
modules when configured in parallel mode. For the fastest performance in
parallel mode, you can use the appropriate onboard port numbers instead of
the SCXI channel string syntax.
Use the iteration input to optimize your digital operation. When
iteration
is
0
(default), LabVIEW calls the DIO Port Config VI (an Advanced VI) to
configure the port. If
iteration
is greater than zero, LabVIEW bypasses
reconfiguration and remembers the last configuration, which improves
performance. You can wire this input to an iteration terminal of a loop. With
the DIO-24 and DIO-96 devices, every time you call the DIO Port Config
VI, the digital line values are reset to default values. If you want to maintain
the integrity of the digital values from one loop iteration to another, do not
set
iteration
to
0
except for the first iteration of the loop.
For an example on SCXI digital input, refer to SCXI-1162/1162HV Digital
Input VI located in
labview\examples\daq\scxi\scxi_dig.llb
.
Even though this VI uses Advanced VIs, it is functionally equivalent to the
Easy I/O Digital VI, Read from Digital Port.
Note
The DIO Port Config VI resets output lines on adjacent ports on the same
8255 chip for DIO-24, DIO-96, AT-MIO-16D, AT-MIO-16DE, and Lab and
1200 Series devices.
Note
If you are also using SCXI analog input modules, make sure your cabling
DAQ device is cabled to one of them.