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Number of Values Unused

Last Modified: December 6, 2019

Returns the number of values (frames or signals) unused for the session. If you get this property prior to starting the session, it provides the size of the underlying queue(s).

Data type: datatype_icon

Long Name: Number of Values Unused

Class: XNET Session

Permissions: Read

Contrary to the Queue Size property, this value is in number of frames for Frame I/O, not number of bytes; for Signal I/O, it is the number of signal values in both cases. After start, this property returns the queue size minus the Number of Values Pending property.

For input sessions, this is the number of frame/signal values unused in the underlying queue(s).

For output sessions, this is the number of frame/signal values you can provide to a subsequent Write. If you call XNET Write with this number of values and timeout of 0.0, XNET Write should return success.

Stream frame sessions using the FlexRay, CAN FD, or Ethernet protocol may use frames that vary in size. In these cases, this property assumes the largest possible frame size. If you use smaller frames, the real number of pending values might be higher.

The largest possible frames sizes are:

  • CAN FD: 64 byte payload.
  • FlexRay: The higher value of the frame size in the static segment and the maximum frame size in the dynamic segment. The XNET Cluster FlexRay:Payload Length Maximum property provides this value.
  • Ethernet: The Payload Length Maximum property provides this value.

The execution time to read this property is sufficient for use in a high-priority loop on LabVIEW Real-Time (RT).

Where This Property Is Available:

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application


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