Read Multiple Event Registration Endpoint

LabVIEW 2018 Help


Edition Date: March 2018
Part Number: 371361R-01
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Requires: Base Development System

Reads multiple event registration refnums for an Event Messenger channel and makes the refnums available to one or more Event structures.

You can drop this endpoint on the block diagram by right-clicking an Event Messenger channel terminal or wire and selecting Create»Channel Reader»Event Messenger»Read Multiple Event Registration.

Details  Example

channel is the channel wire that connects this endpoint to a writer endpoint.
number of event structures specifies the number of Event structures that read event registration information from this endpoint. number of event structures must match the number of Event structures that read from this endpoint to avoid undefined errors.
event registration refnums returns an array of event registration refnums for an Event Messenger channel. The number of elements in the array equals number of event structures. Each refnum in the array is a unique refnum intended for one specific Event structure that reads from this endpoint, and each Event structure triggers on all of the events from the channel.

Read Multiple Event Registration Details

Unlike the reader endpoints of other channel templates, this reader endpoint must be placed outside the While Loop and can execute only once.

Use one Event structure to handle events whenever possible. Use the Build Array or Bundle functions to combine multiple event registration refnums for a single Event structure.

To allow multiple Event structures to read event registration refnums from this endpoint, you must use the Index Array function to index the event registration refnums and wire each refnum to the dynamic event terminal of each Event structure so that each Event structure receives its own copy of the events from the channel.

Do not fork the event registration refnums to multiple Event structures. Doing so creates undefined behavior that may result in race conditions or deadlocks in your application.

Related Information

Write

Caveats and Recommendations when Using Events in LabVIEW

Example

Refer to the Channel - Event Messenger.lvproj in the labview\examples\Channels\Event Messenger directory for an example of using the Read Multiple Event Registration endpoint.

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