Applies To:
  • CitectSCADA 6.10
  • CitectHMI 6.10
Summary:
When using the Melsec A-Series PLCs using the MelsecNet protocol the following may occur.  After running for some time Citect tags return #COM and require Citect to be restarted many times before Communications operate correctly again.   

Solution:
The PLC program for A'series Ethernet requires in the logic if a connection is opened and no communications occurs within 30sec then close the connection for 2sec then open again

The reasons for this are unexplained, it is as if the PLC Ethernet module goes to sleep waiting for data RX as well as the citect default retry of only 2.

 
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