Applies To:
  • CitectSCADA 3.xx, 4.xx, 5.xx
Summary:
I wish to have redundant communications to a PLC, but I want different primary and secondary communications methods. For example, I want to communicate to the device via TCP/IP from the primary IO Server, but I want to communicate to the device via standard serial communications from the secondary I/O Server. The reason for this may be that it saves on the cost of the Ethernet communications. 

Solution:
It is NOT recommended to have two different physical protocols for Citect redundancy. This is known to cause performance problems and under some conditions the redundancy will not operate correctly. You must use the same physical protocols and hardware on the standby link to the I/O Device.

See also Q1800. 

 
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