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

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


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


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


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


SE8650 firmware version 1.7.1-56d and SBO 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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