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How does time sync function in AS-P react with BACnet MSTP devices?

Issue

Customers question the time sync function in AS-P for BACnet devices

Environment

SE8650, Viconic, SBO, AS-P, SmartStruxure, Room Controller, MSTP, 3rd Party BACnet Devices

Cause

It is important to understand what happens when AS-P or Room Controller lose power.

Resolution

SE8650 firmware version 1.7.1-56d and SBO 1.9.3.24 were used in the test.

The testing was done with the fieldbus speed at both 38400 and 76800 baud.

1. The first test was to confirm AS-P sends out time sync signal 38 minutes after each hour periodically.
A review of all the timeSync data packets during the capture reveals that the time sync packets are sent every hour when the time in AS-P is 38 after the hour minutes mark.

 




2. The second test was to confirm that the AS-P will send out a timeSync data packet if a device comes back online after a power outage.

First the time was synchronized between the SE8650 with AS-P.


SE8650 was then powered down and the AS-P server time changed so that the times in the two devices would not match.


 

A review of the time synchronization packets in the packet capture confirms that the AS sends out a time synchronization once the SE8650 is powered and boots up.


3. If the AS-P and SE8650 both lost power the SE8650 will boot up before the AS-P. The AS-P will then sends out a timeSync once the BACnet communication is settled.

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