Session Control

You can use session control to release any current references to tags on the ControlLogix PLCs. This is required if you want to modify or delete any of your PLC tags, as the Logix5000 software cannot access a tag if Plant SCADA is currently subscribed to it. You can also use session control to load a refreshed tag list from a PLC.

Session control is achieved by using the SessionDisable:x tag. This tag needs to be configured on a virtual device on a virtual channel. The virtual channel is specified by entering 0.0.0.0 as the IP address in the Special Options field of the Ports form. There should be a single virtual port and virtual device configured for each I/O server, and the virtual devices should not be configured for redundancy; i.e., the network numbers for the virtual units should not be the same. Otherwise it is not possible to communicate with a specific virtual unit from a Plant SCADA client.

Where:

x = the address entered for the specified device in the I/O Devices form. It needs to be unique across all systems.

If this tag is written to with a 1, the session is disabled. Writing a 0 to this tag will re-enable the session.