Why Is My VxWorks cRIO with NI-TimeSync Installed a PTP Clock Master?

Updated Jun 7, 2018

Reported In


  • CompactRIO Controller


  • NI-TimeSync

Operating System

  • PharLap
  • VxWorks
  • NI Linux Real-Time

Issue Details

I have a network with several VxWorks-based CompactRIOs. They shall synchronize with a dedicated 3rd-party PTP Grandmaster clock device. Whenever the Grandmaster is not reachable due to network issues, the cRIOs take turns in being the master. This while cRIOs can never be a master unless explicitly configured, which I haven't done. What am I missing?


The default configuration of NI-TimeSync (Precision Time Protocol, PTP, IEEE 1588-2008) is different for VxWorks-based and NI Linux RT-based CompactRIOs. On controllers running VxWorks or Phar Laps operating system the default setting is masterslave, whereas on NI Linux RT it is slaveonly.

These settings can be changed in the corresponding configuration files, as described in the article titled "Using NI-TimeSync to Configure IEEE 1588 and 802.1AS Time References".

Additional Information

The setting tokens are:
  • source.ptp.SlaveOnly as found in /ni-rt/system/ni-timesync/ni-timesync-ptp.ini on Phar Laps and VxWorks.
  • ptpengine:preset in /usr/local/natinst/share/TimeSync/TimeReferences/ptp.conf respective bmcaMode in /usr/local/natinst/share/TimeSync/tsm.json for NI Linux Real-Time Operating Systems


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