Applies To:
  • CitectSCADA 3.00

Citect version 3.x and later supports standby Disk PLCs. To keep the Disk PLC's in sync you must specify the path of both disk PLCs in each of the I/O Device records. The file names are specified in the address filed as two paths separated by a comma ',' as follows:


To make projects independent of the disk structure, path substitution can be used for the file name. eg [RUN]:\MYPLC.DSK. instead of C:\CITECT\USER\DEMO\MYPLC.DSK. However if you specify path substitution for the second file name, Citect will not be able to open the disk PLC file. For example if you entered a path as follows: [RUN]:\MYPLC.DSK,[RUN]:\YOURPLC.DSK Citect would be able to open the first disk PLC but not the second as Citect does not expand the path correctly.


CIT has confirmed this to be a problem in Citect for Windows versions 3.21 and 4.01. This problem has been fixed in versions 3.22 and 4.10.

You may work around this problem by specify the whole physical second path For example: