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Specify the callback function to execute when the output buffer is empty


You configure OutputEmptyFcn to execute a callback function when an output-empty event occurs. An output-empty event is generated when the last byte is sent from the output buffer to the device.


An output-empty event can be generated only for asynchronous write operations.

If the RecordStatus property value is on, and an output-empty event occurs, the record file records this information:

  • The event type as OutputEmpty

  • The time the event occurred using the format day-month-year hour:minute:second:millisecond

To learn how to create a callback function, see Create and Execute Callback Functions.


Read only


Data type

Callback function


The default value is an empty string.