How does Vijeo Citect identify the connection with PLC device when it is connected via OPC Factory Server.
The Specific Item are the OPC items which is not the PLC variable but the internal variable of OPC or PLC status that is being used by OPC clients for getting the status of OPC or PLC.
For Vijeo Citect if it is connected to OFS require the status of device whether it is connected to OFS or not then only it start the communication with PLC. In Vijeo Citect Version 1.02.12.001 (or later) of the OFSOPC driver will only use the #PLCQualStatus (part of OPC Specific Items) tag to determine the status of a device.
So looking at the above if you want to read the variable in Vijeo Citect you must Enable OPC extension in OFS configuration tool under Communication section so that Vijeo Citect get the PLC status and start the request and response from OPC device.