How to timestamp events with BMXERT1604 module when the NTP clock time is changing backward comparated with the last timestamped event
When the NTP server time is moved forward, the ERT module correctly updates event timestamps.When the NTP server time is set backward, the ERT stops updating event timestamps entirely. Timestamp updates only resume once the NTP time naturally reaches the last accepted timestamp value. During the entire process, the CPU clock continues to synchronize correctly.
When the new time provided by NTP is lower than the timestamp of the last event, the new time is rejected and the last event time is kept.
This situation can occur when NTP time updates and internal timer drifts accumulate.
This “blocking” mechanism is necessary; otherwise, SCADA systems could flush or mishandle events stamped with a lower timestamp than previous ones.
As a result:
- The ERT intentionally blocks timestamp updates until time exceeds the last valid event timestamp.
- This prevents timestamp regression, which could corrupt event sequencing in SCADA systems.
The anomaly can be cleared by one of the following actions:
- Resetting the CPU or CRA rack where the BMXERT1604 module is present
- Performing a hot swap of the BMXERT1604 module
These actions reinitialize the time logic used by the ERT.
Released for: Schneider Electric Ireland
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