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Intf.Enet.Time.Port.PropDlyTh

Last Modified: February 7, 2020

Sets the threshold for the Propagation Delay property.

For IEEE Std 802.1AS, if the Propagation Delay exceeds the threshold in this property, the protocol assumes that a switch or router that is not 802.1AS-capable exists between this clock and the neighboring 802.1AS-capable clock. The resulting asymmetries would have an adverse effect on time synchronization accuracy, so this port sets AS Capable? to False. If Pdelay Enabled? is False, this property is ignored.

Data type: datatype_icon

Long Name: Interface:Ethernet:Time Sync:Port:Propagation Delay Threshold

Class: XNET Session

Permissions: Read/Write

Propagation Delay Threshold uses a double-precision floating-point, and the value is provided in seconds, which is typically used in LabVIEW for relative times. To convert the value to nanoseconds, multiply this property value by 1000000000 (for read).

The propagation speed for copper wires is close to 2 * 10^8 meters/second (5 nanoseconds/meter). Therefore, multiplying this property value by 200000000 provides a close approximation of the cable length in meters. For example, 800 nanoseconds of propagation delay occurs with approximately 160 meters of copper cable.

For the Protocol of IEEE Std 802.1AS-2011, this property corresponds to the neighborPropDelayThresh parameter, specified in 14.6.8 of IEEE Std 802.1AS-2011. The default value is specified in IEEE Std 802.1AS-2011/Cor1-2013. When an XNET session is started on a port that is set to Tap mode, this property becomes read only and its value cannot be modified.

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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