Programming instructions

© National Instruments Corporation 20-1 LabVIEW Data Acquisition Basics Manual
20
Special Programming
Considerations for SCXI
When you want LabVIEW to acquire data from SCXI analog input
channels, you use the analog input VIs in the same way that you acquire
data from onboard channels. You also read and write to your SCXI relays
and digital channels using the digital VIs in the same way that you read and
write to onboard digital channels. You can write voltages to your SCXI
analog output channels using the analog output VIs. The following sections
describe special programming considerations for SCXI in LabVIEW which
include channel addressing, gains (limit settings), and settling time.
Note
This chapter does not apply if you use the DAQ Channel Wizard to configure
your channels. If you use the DAQ Channel Wizard, you address SCXI
channels the same way you address on-board channels—by specifying the
channel name(s). LabVIEW configures your hardware by selecting the best
input limits and gain for the named channel based on the channel
configuration. For more information about using the DAQ Channel Wizard to
configure your channels, see the Configuring Your Channels in NI-DAQ 5.x, 6.0
section of Chapter 2, Installing and Configuring Your Data Acquisition Hardware.
For more information about using channel names, refer to the Channel Name
Addressing section of Chapter 3, Basic LabVIEW Data Acquisition Concepts.
SCXI Channel Addressing
If you operate a module in parallel mode, you can specify an SCXI channel
either by specifying the corresponding onboard channels or by using the
SCXI channel syntax described in this section. If you operate the modules
in multiplexed mode, you must use the SCXI channel syntax.
An SCXI channel number has four parts: the onboard channel (optional),
the chassis ID, the module number, and the module channel.
In the following table of examples,
x
is any chassis ID,
y
is any module
number,
a
is any module channel, and
b
is any module channel greater
than
a
.
z
is the onboard channel from which the conditioned data is
retrieved. If you operate in multiplexed mode, analog input channel 0 reads