Leased Scan Class
Tags set to the Leased scan class execute/poll the PLC at the fast polling rate when they are subscribed and visible in a Client window, that is, when a Client needs the value. If the tags are not subscribed and the window or client is closed, the scan class runs at the slow polling rate.
To add a leased scan class
Let's add a new leased scan class that updates the tag at a 1 second rate when a client needs the tag and doesn't poll when the client is closed.
-
On the Scan Class Editor, click on the green + icon to add a new scan class.
-
Set the following:
Scan Class Name: Leased
Mode: Leased
Slow Rate: 0
Fast Rate: 1000
-
Click OK to save.
-
Set the scan class on the tags to use this new Leased scan class.
The tags are only polled when a component that is bound to it is showing in a Client. -
To verify that Ignition is working the way it should, go to the Status tab of the Ignition Gateway and click on the OPC Connections link on the left side.
If nothing is active, the list is empty for the Leased scan class.
As tags are needed, the list will fill in with only the tags that are currently being looked at.
