NI cDAQ-9172 User Guide and Specifications 22 ni.com
a continuous generation continues until you stop the operation. There are
three different continuous generation modes that control how the data
is written. These modes are regeneration, onboard regeneration, and
non-regeneration.
In regeneration mode, you define a buffer in host memory. The data from
the buffer is continually downloaded to the FIFO to be written out. New
data can be written to the host buffer at any time without disrupting the
output.
With onboard regeneration, the entire buffer is downloaded to the FIFO and
regenerated from there. After the data is downloaded, new data cannot be
written to the FIFO. To use onboard regeneration, the entire buffer must fit
within the FIFO size. The advantage of using onboard regeneration is that
it does not require communication with the main host memory once the
operation is started, which prevents problems that may occur due to
excessive bus traffic or operating system latency.
With non-regeneration, old data is not repeated. New data must continually
be written to the buffer. If the program does not write new data to the buffer
at a fast enough rate to keep up with the generation, the buffer underflows
and causes an error.
Analog Output Triggering
Analog output supports two different triggering actions:
• Start trigger
• Pause trigger
An analog or digital trigger can initiate these actions. Any C Series
correlated digital module in slots 5 and/or 6 can supply a digital trigger, and
some C Series analog modules can supply an analog trigger. For more
information refer to the AO Start Trigger Signal section of this document
or to the documentation included with your C Series I/O module(s).
Analog Output Timing Signals
The NI cDAQ-9172 chassis features the following AO (waveform
generation) timing signals:
• AO Sample Clock
•AO Start Trigger
• AO Pause Trigger