National Instruments DAQ AT-MIO-16X, User Manual, Page: 179 / 330

Chapter 5 Programming
AT-MIO-16X User Manual 5-10
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National Instruments Corporation
Programming Data Acquisition Sequences with Channel Scanning
The preceding data acquisition programming sequence programs
the AT-MIO-16X for multiple A/D conversions on a single input
channel. The AT-MIO-16X can also be programmed for scanning
multiple-analog input channels with different gain, mode, and range
settings during the data acquisition operation. The sequence of A/D
channels and configuration settings, called the scan sequence, is
programmed into the channel configuration memory.
There are two types of multiple A/D conversions with channel
scanning: continuous channel scanning and interval-channel scanning.
Continuous channel scanning cycles through the scan sequence in the
channel configuration memory and repeats the scan sequence until the
sample counter terminates the data acquisition. There is no delay
between the cycles of the scan sequence. Continuous channel scanning
can be thought of as a round-robin approach to scanning multiple
channels.
Interval-channel scanning gives each scan sequence a programmed
time interval called a scan interval. Each cycle of the scan sequence
begins at the time interval determined by the scan interval. If the
sample-interval counter is programmed for the minimum time required
to complete an A/D conversion, interval-channel scanning can be
thought of as a pseudo-simultaneous scanning of multiple channels; that
is, all channels in the scan sequence are read as quickly as possible at
the beginning of each scan interval.
Continuous Channel Scanning Data Acquisition
Use the programming steps listed in Figure 5-4 to program continuous
scanning of multiple A/D conversions for posttrigger and pretrigger
modes, as well as internal and external timing. The instructions in
the blocks of the following flow chart are enumerated in the Data
Acquisition Programming Functions section later in this chapter.