Chapter 1
Introduction to SCXI
1-18
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Figure 1-7.
SCXI Signal Routing
With multichannel scanning, the DAQ device programs SCXI Slot 0 with a
list of modules and the number of channels to scan from each module. Each
module in the list is programmed with the channel on which to start the
scan. The DAQ device or module then begins the multichannel scan. The
SCANCLK signal from the AI or MIO device synchronizes the SCXI
multiplexing with the internal clock that triggers the A/D conversions on
the DAQ device. SCXI Slot 0 enables and disables the modules according
to the preprogrammed list. In this way, the system multiplexes channels
from several modules to an analog input channel of the DAQ device at very
high rates. NI-DAQ contains high-level functions you can use for
multichannel scanning operations.
Analog
Input
Signals
Module 1
Module
n
Slot 0
Analog Bus
DIO Lines
(program the chassis
and modules)
Input Channel 0
Multiplexing
and
Conditioning
Circuitry
SCXI Chassis
Plug-In DAQ Device
Multiplexing
and
Conditioning
Circuitry
