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Chapter 4 Theory of Operation
SCXI-1141/1142/1143 User Manual 4-16 ni.com
Filter Bypass Mode
You can bypass the filter of any channel through software control, thus
making the unfiltered signal available at the output. The input amplifiers
are not bypassed.
You can use the filter bypass to examine the effect that the filter has on the
input signal. Using this mode, you can examine an input signal without the
added effects of passband ripple and phase nonlinearities.
At power-up and at reset, all the channels of the SCXI-1141/1142/1143
module default to the filter bypass mode.
Rear Connector Analog Outputs
The connector signals A OUT<1..7> and A GND are the outputs of
channels 1 through 7. You can configure the OUTPUT and OUTPUT REF
signals as any channel (0 through 7) of the SCXI-1141/1142/1143 module
or as the output of a channel passed along the SCXIbus from any other
module in the chassis. Thus, the SCXI-1141/1142/1143 modules can
present its outputs in both parallel and multiplexed modes.
Multiplexed Mode (Recommended)
In multiplexed mode, the output signals for channels 1 through 7 are sent
to the rear signal connector but are usually ignored. All samples from the
module are from the OUTPUT signal of the rear signal connector,
which you can configure as the output of any channel of the
SCXI-1141/1142/1143 module or as the output of any other module in
multiplexed mode that is sending its output onto the SCXIbus. You can also
configure the SCXI-1141/1142/1143 module to send any one of its outputs
to the SCXIbus. Thus, in multiplexed mode only, one module in a chassis
needs to be connected to a DAQ device. You can pass signals from the
other modules to the DAQ device through the SCXIbus.
Multiplexed mode is also useful for performing scanning operations with
the SCXI-1141/1142/1143 module. E/M Series devices support scanning.
The SCXI chassis is programmed with a module scan list that dynamically
controls which module sends its output to the SCXIbus during a scan. You
can specify this list to scan the modules in any order, with an arbitrary
number of channels for each module entry in the list. However, you must
scan the channels on the SCXI-1141/1142/1143 module in consecutive,
ascending order. After channel 7 is scanned, the module wraps back to