Intermittent Online Device (Xenta function via the DI-block) errors

Issue

Online Device shows "0" for one scan, but the device is still online from TAC Vista. This is enough for the unit to stop and close dampers.

Product Line

TAC Vista

Environment

  • TAC Vista
  • TAC Xenta 280, TAC Xenta 300, TAC Xenta 401
  • Menta
  • Device Status Digital Input

Cause

The Online Device function depends on your network. If two controllers are within the same TAC Xenta group, there should be no extra traffic and the asking device could just check in the online table if the other device has sent out its poll lately.

If it is outside the actual TAC Xenta group, it will be like a TACNV connection, within the limits for TACNV. However, there are no re-sends. A single missed message will result in an Offline status.

If there is a lot of traffic, there could be a collision on the network traffic and this could result in an Offline status. The next scan time, the messages might working correctly again, and resulting in an online status.

Resolution

The best solution is to have a Delay block in the Menta code, to get a delay off (when the value goes from Online (1), to Offline (0)). Make sure the device is offline for at least a few program cycles before taking any action in the logic.