configuration, update rate, and output range, are determined by the type of C Series module
used. For more information, refer to the documentation included with your C Series module(s).
The cRIO controller has eight output timing engines, which means that up to eight hardware-
timed analog output tasks can be running at a time on the controller. On a single analog output
C Series module, you can assign any number of channels to either a hardware-timed task or a
software-timed (single-point) task. However, you cannot assign some channels to a hardware-
timed task and other channels (on the same module) to a software-timed task.
Multiple timing engines allow the cRIO controller to run up to eight analog output tasks
simultaneously, each using independent timing and triggering configurations. The eight timing
engines are ot0, ot1,… ot7.
Analog Output Data Generation Methods
When performing an analog output operation, you either can perform software-timed
generations or hardware-timed generations.
Software-Timed Generations
With a software-timed generation, software controls the rate at which data is generated.
Software sends a separate command to the hardware to initiate each DAC conversion. In NI-
DAQmx, software-timed generations are referred to as on-demand timing. Software-timed
generations are also referred to as immediate or static operations. They are typically used for
writing out a single value, such as a constant DC voltage.
The following considerations apply to software-timed generations:
•
If any AO channel on a module is used in a hardware-timed (waveform) task, no channels
on that module can be used in a software-timed task
•
You can configure software-timed generations to simultaneously update
•
Only one simultaneous update task can run at a time
•
A hardware-timed AO task and a simultaneous update AO task cannot run at the same
time
Hardware-Timed Generations
With a hardware-timed generation, a digital hardware signal controls the rate of the generation.
This signal can be generated internally on the controller or provided externally.
Hardware-timed generations have several advantages over software-timed acquisitions:
•
The time between samples can be much shorter
•
The timing between samples is deterministic
•
Hardware-timed acquisitions can use hardware triggering
Hardware-Timed Single Point (HWTSP) Mode
In HWTSP mode, samples are acquired or generated continuously using hardware timing and
no buffer. You must use the sample clock or change detection timing types. No other timing
types are supported.
NI cRIO-905x User Manual
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© National Instruments
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