available frequencies; by default, the fastest available is used. The sample rate of all modules
in the task is an integer divisor of the frequency of the AI Sample Clock Timebase.
When one or more delta-sigma modules are in an analog input task, the delta-sigma modules
also provide the signal used as the AI Sample Clock. This signal is used to cause A/D
conversion for other modules in the system, just as the AI Sample Clock does when a delta-
sigma module is not being used.
When delta-sigma modules are in an AI task, the controller automatically issues a
synchronization pulse to each delta-sigma module so that their ADCs are reset at the same
time. Because of the filtering used in delta-sigma A/D converters, these modules usually
exhibit a fixed input delay relative to non-delta-sigma modules in the system. This input delay
is specified in the C Series module documentation.
When channels from delta-sigma C Series modules are included in a multi-chassis task, please
ensure that the first channel in your channel list is from a delta-sigma module.
Note DSA modules do not support HWTSP mode.
Slow Sample Rate Modules
Some C Series analog input modules are specifically designed for measuring signals that vary
slowly, such as temperature. Because of their slow rate, it is not appropriate for these modules
to constrain the AI Sample Clock to operate at or slower than their maximum rate. When using
such a module in the cRIO controller mixed with a non-slow sample module in the same task,
exceeding the maximum sampling rate of the slow sample module results in the most recently
acquired sample being read multiple times. In this scenario, the first sample of a hardware-
timed acquisition with a slow sampled C Series module is sampled when the task is
committed.
For more information about which C Series modules are compatible with the cRIO controller,
go to ni.com/info and enter the Info Code rdcdaq.
Getting Started with AI Applications in Software
You can use the cRIO controller in the following analog input applications:
• Single-point acquisition
• Hardware-Timed Single Point acquisition
• Finite acquisition
• Continuous acquisition
For more information about programming analog input applications and triggers in software,
refer to the NI-DAQmx Help or the LabVIEW Help for more information.
Analog Output with NI-DAQmx
To generate analog output, install an analog output C Series module in any slot on the cRIO
controller. The generation specifications, such as the number of channels, channel
44 | ni.com | NI cRIO-905x User Manual
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