Change Detection Event; Change Detection Acquisition; Digital Output; Buffered Change Detection Acquisition - National Instruments cRIO-904 Series User Manual

• Finite acquisition
• Continuous acquisition
For more information about programming digital input applications and triggers in software,
refer to the NI-DAQmx Help or the LabVIEW Help for more information.

Change Detection Event

The Change Detection Event is the signal generated when a change on the rising or falling
edge lines is detected by the change detection task.
Routing Change Detection Event to an Output Terminal
You can route ChangeDetectionEvent to any output PFI terminal.

Change Detection Acquisition

You can configure lines on parallel digital modules to detect rising or falling edges. When one
or more of these lines sees the edge specified for that line, the cRIO controller samples all the
lines in the task. The rising and falling edge lines do not necessarily have to be in the task.
Change detection acquisitions can only be buffered:
• Buffered Change Detection Acquisition—A buffer is a temporary storage in computer
memory for acquired samples. In a buffered acquisition, data is stored in the cRIO
controller onboard FIFO then transferred to a PC buffer. Buffered acquisitions typically
allow for much faster transfer rates than nonbuffered acquisitions because data
accumulates and is transferred in blocks, rather than one sample at a time.

Digital Output

To generate digital output, install a digital output C Series module in any slot on the cRIO
controller. The generation specifications, such as the number of channels, channel
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).
With parallel digital output modules (formerly known as hardware-timed modules), you can do
multiple software-timed tasks on a single module, as well as mix hardware-timed and
software-timed digital output tasks on a single module. On serial digital output modules
(formerly known as static digital output modules), you cannot mix hardware-timed and
software-timed tasks, but you can run multiple software-timed tasks.
You may have a hardware-timed task or a software-timed task include channels from multiple
modules, but a hardware-timed task may not include a mix of channels from both parallel and
serial modules. Multiple timing engines allow the cRIO controller to run up to eight hardware-
timed digital output tasks simultaneously, each using independent timing and triggering
configurations. The eight output timing engines are ot0, ot1,...ot7. All eight of the output
timing engines are shared between analog output and digital output tasks, allowing up to 8
hardware-timed output tasks.
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