Wait on Notification from Multiple with Notifier History Function

LabVIEW 2018 Help


Edition Date: March 2018
Part Number: 371361R-01
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Owning Palette: Advanced Notifier Waiting Functions

Requires: Base Development System

Waits until a notifier within an array receives a message. This function tracks the most recent message and timestamp for each individual notifier within an array.

Details  

notifiers is an array of notifier references. Use the Obtain Notifier function to obtain a notifier reference.
ignore previous indicates whether to ignore messages that LabVIEW sends to the notifier before it calls this function. If TRUE and the notifier contains a message before you call this function, this function waits until the notifier receives another message. If FALSE (default) and the notifier contains a message before you call this function, this function continues to execute.
timeout in ms specifies the time, in milliseconds, that the function waits for the notifier to receive a message. The default is –1, which indicates never to time out.

If the function waits timeout in ms and the notifier does not receive a message, timed out? is TRUE.
error in describes error conditions that occur before this node runs. This input provides standard error in functionality.
notifiers out returns an array of the notifier references from which messages were received. The indexes of this array correspond to the indexes of the notifications output array. From the notifiers out array, you can determine which messages came from which notifiers—the first value comes from the first notifier, the second value from the second notifier, and so on. If an error occurs, this array contains references to the notifiers that caused an error.
notifications is an array of the last messages the notifiers receive. This data type changes to match the subtype of notifiers, unless the subtype is an array. If the subtype is an array, the data type becomes a cluster of arrays.
timed out? is TRUE if the notifier does not receive a message before the function times out or if an error occurs.
error out contains error information. This output provides standard error out functionality.

Wait on Notification from Multiple with Notifier History Details

Each unique instance of this function remembers the time stamp of the most recent message for each individual notifier.

Maintaining notifier history prevents dropped messages and other problems when you use this function repeatedly with different notifiers. When one of the notifiers in the array receives a message, this function continues to execute. Use the Send Notification function to send the message. If a notifier reference becomes invalid, such as when another function closes it, this function stops waiting and returns error code 1122. If the notifier does not contain a message, this function waits until a notifier within the array receives a message.

Maintaining notifier history also causes this function to run slower than the Wait on Notification from Multiple function, which does not maintain notifier history and might experience deadlock when you use it repeatedly with different notifiers.

Use the Wait on Notification with Notifier History function for a single notifier reference.

If ignore previous is FALSE, each instance of the Wait on Notification from Multiple with Notifier History function waits if it has not received notification. If one or more of the notifiers have messages newer than the time stamp most recently received by this function, the function returns all messages. Otherwise, the function waits.

When ignore previous is TRUE, this function always waits for a new message, even if the message currently in the notifier is one it has never seen before.

This function does not remove the message from the notifier. Although a specific instance of the function returns a message only once, other instances of the function or the Wait on Notification function repeat the message until you call the Send Notification function with a new message.

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