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Last Modified: February 7, 2020

Indicates whether the clock using the time synchronization protocol is successfully synchronized to other clocks in the network.


Time synchronization occurs independently from start of the interface. For example, you can read and write Ethernet frames when time sync is not enabled, or when the time sync protocol is not synced.

Data type: datatype_icon

Long Name: Interface:Ethernet:Time Sync:Port:Synced?

Class: XNET Session

Permissions: Read

For the Protocol of IEEE Std 802.1AS-2011, this property is True when AS Capable is True and the following conditions apply:

  • If Port State is Slave, XNET clock adjustment algorithm (servo) is in its final stage (calibrated). Sufficient messages have been exchanged such that synchronization quality (e.g., Offset From Master) is unlikely to improve significantly, but no fixed metric is applied as a threshold.
  • If Port State is Master and best master clock algorithm (BMCA) is enabled, at least two announce intervals have elapsed. Master state means that the XNET port is acting as grandmaster (the source of time in the network), so Synced? would normally be true immediately. When using the BMCA, the XNET port initializes assuming that it is a potential grandmaster (Master), but when it receives an announce message from a better grandmaster, the Port State changes to Slave. By waiting up to two announce intervals, the XNET port avoids reporting a false-positive from Synced? (i.e., true because it was Master upon initialization, then false when a better grandmaster is detected, and then true again after slave calibration).
  • If Port State is Master and BMCA is disabled, Synced? is true immediately. As BMCA is disabled, this XNET port will act as the Master (grandmaster) indefinitely.

In the IEEE 1588-2008 standard (on which IEEE Std 802.1AS-2011 is based), this Synced? flag is analogous to transition out of the UNCALIBRATED state. For 802.1AS, behavior similar to this property is specified as the AVB_Sync state of the Avnu Automotive Ethernet AVB Functional and Interoperability Specification.

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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