Digital Input; Digital Input Triggering Signals - National Instruments NI cRIO-905x Series User Manual

individually configured as a digital input (DI) or digital output (DO), if the C Series module
being used allows such configuration.
All samples of static DI lines and updates of static DO lines are software-timed.

Digital Input

You can acquire digital waveforms using either parallel or serial digital modules. The DI
waveform acquisition FIFO stores the digital samples. The cRIO controller samples the DIO
lines on each rising or falling edge of the DI Sample Clock signal.
Multiple input timing engines allow the cRIO controller to run up to eight hardware-timed
digital input tasks simultaneously, each using independent timing and triggering
configurations. The eight input timing engines are it0, it1,...it7. All eight of the input timing
engines are shared between analog input and digital input tasks, allowing up to 8 hardware-
timed input tasks.
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.
Use HWTSP mode if you need to know if a loop executes in a given amount of time, such as
in a control application. Because there is no buffer, if you use HWTSP mode, ensure that reads
or writes execute fast enough to keep up with hardware timing. If a read or write executes late,
it returns a warning.
Note
DSA modules do not support HWTSP mode.

Digital Input Triggering Signals

A trigger is a signal that causes an action, such as starting or stopping the acquisition of data.
When you configure a trigger, you must decide how you want to produce the trigger and the
action you want the trigger to cause. The cRIO controller supports internal software triggering,
external digital triggering, analog triggering, and internal time triggering.
Three triggers are available: Start Trigger, Reference Trigger, and Pause Trigger. An analog or
digital trigger can initiate these three trigger actions. C Series parallel digital input modules
and the controller's integrated PFI trigger line can be used in any controller slot to supply a
digital trigger. To find your module triggering options, refer to the documentation included
with your C Series modules. For more information about using analog modules for triggering,
refer to the Analog Input Triggering Signal and Analog Output Triggering Signals sections.
Refer to the DI Start Trigger Signal, DI Reference Trigger Signal, and DI Pause Trigger
Signal sections in Digital Input Timing Signals for more information about the digital input
trigger signals.
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