Applies To:
  • CitectSCADA 5.xx
  • CitectHMI 5.xx

Citect is set up to communicate with RSLinx v2.40.01 using the OPC protocol, but it won't communicate reliably or won't communicate at all. 

This may be caused by problems in the RSLinx OPC server v2.40.01. Rockwell has released v2.40.01 Build 16.6 hotfix that seems to correct the problem. See Rockwell knowledge base article R49647774 at This article lists the corrections made and has a link to download the update.

It was found that Citect may not be able to connect using OPC2 after installing this update. Make sure you do NOT have the following citect.ini parameter: