Programming instructions

Chapter 20 Special Programming Considerations for SCXI
LabVIEW Data Acquisition Basics Manual 20-2
© National Instruments Corporation
the data from the first cabled chassis. If you use VXI-SC submodules,
LabVIEW ignores the onboard channel, since VXI-DAQ provides a special
channel for retrieving data from submodules.
The
channel
input for DAQ VIs is either a string (with the Easy I/O VIs)
or an array of strings. Each string value can only list the channels for one
module. With the array structure for channel values, you can list the
channels for several modules. In other words for one scanning operation,
you can scan several modules. You can scan an arbitrary number of
channels for each module, but the channels of each module must be
scanned in consecutive, ascending order.
Note
You do not need the SCXI channel string syntax to access channels on the
SCXI-1200 module. Use
0 for channel 0, 1 for channel 1, and so on. The
SCXI-1200 module is identified by its logical device number.
Note
When you connect any type of SCXI module to a DAQ device, certain analog input
and digital lines on the DAQ device are reserved for SCXI control. On MIO Series
devices, lines 0, 1, and 2 are unavailable. On MIO-E Series devices, lines 0, 1, 2,
and 4 are unavailable. For more channel information refer to the LabVIEW
Online Reference, by selecting Help»Online Reference….
For the fastest performance in parallel mode on digital modules, you can
use the appropriate onboard port numbers instead of the SCXI channel
string syntax in the digital VIs.
Channel List Element Channel Specified
OBz!SCx!MDy!a Channel
a
on the module in slot
y
of the
chassis with ID
x
is multiplexed into
onboard channel
z
.
OBz!SCx!MDy!a:b Channels
a
through
b
inclusive on the
module in slot
y
of the chassis with ID
x
are multiplexed into onboard channel
z
.