Applies To:
  • CitectSCADA 5.xx, 6.xx
  • CitectHMI 5.xx, 6.xx
Summary:
I am using the PSdirect driver to talk to my Siemens S5 & S7 series PLC. What do I have to configure to enable redundant CitectSCADA IO server? 
 

Solution:
The poll block ST0 -> ST200 must be defined in the driver poll configuration in the back end.
Make sure each device has a ST0 to ST200 IO block as well in the back end

Set the parameter in the Citect.ini file "AlwaysReturnNoError"=0 (this is default) under the [PSdirect] section

The above simply ensures that the frontend driver can correctly sense the Unit status so that the IO Device goes offline when the backend loses comms.

Note:
Because the link between frontend & backend is the IO Device name, these names need to be identical on both servers and the IO Device number the same as per Citect practice. If you need to use different names, set the IO device Address to "S7;ETHERNET;N=xxx" where xxx is the backend name. Using this option you can have multiple citect IO devices connected to one Backend device. 
 
Keywords:
PSdirect, redundancy, Siemens, primary, standby 

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