I have an application where I am reading product data from a UDT into a Transaction Group that loads a stored procedure. The group runs periodically at 500ms and looks for a Boolean trigger inside the UDT to be =1.
I have a Direct Scan Class with a slow rate of 350ms, that I have setup in Read mode.
I run into issues when I add other similar transaction groups that pull similar data from other PLC’s, if that PLC happens to be offline. Whether I use the same scan class, or create a unique scan class for the other machine, if either machine happens to be offline, then the tags within the scan class for the online machine will not update for 20-30 seconds.
I had hoped that having separate scan classes would protect against this issue. If I set the two scan classes at different, non-overlapping rates, then the problem disappears. This is not ideal, because I may have up to 10 production lines running on this same application.
Is there some way to avoid having to use prime numbers in my scan class rates to keep from running into this issue?
If I switch to Subscribed mode in the scan class, then having PLC’s offline has no effect on the other systems. I am concerned about not having current data in the transaction group using this method though.
Just looking for tips and/or advice.