Changing a task from continuous to periodic L61?

[Bob O]

I've inherited a L61 that was installed last year and the memory usage is well into the red. There is only one continuous task with a scan time of 8-9 ms and from what I can see, default rate on a continuous task is 10 ms so I don't have any room of communications which I believe is one of my issues with some of my tag communications in Ignition.
I read on the Inductive Automation forum that I should change the continuous task to a periodic task to improve my tag loading factor. Can the change from continuous to periodic be done while online?




Thanks for any shoves in the right direction.
Bob

 

[kekrahulik]

You will need to do that offline and download. After that, you will be be able to change your scan rate while online.

That should help with your issues

 

[cardosocea]

Do you know why the fast update rate on that task and whether "slowing" it down will cause trouble?

Not the same, but I experienced some issues with a PLC upgrade where the cycle time went from 30 to 4 ms and a couple of maths stopped working properly due to the intervals at stake. This is the opposite, but it may happen as well.

 

[TheWaterboy]

Also bear in mind that if you are getting your CPU times from the task manager utility, that there was a bug in a version that made it lie. make sure you have the latest version of that utility.

 

[Ken Roach]

Bob, I think you might be chasing the wrong rabbits.

Good HMI performance requires sufficient network bandwidth, processing bandwidth, and free RAM.

If your RAM use is into the red, then you might not be able to get good performance with your HMI communications even if you have plenty of bandwidth on the network and the CPU.

You can read extensively on how the Continuous Task and the Communications Timeslice interact. A system with a Continuous Task and the Timeslice set to a healthy amount (30%) can generally get good HMI comms.

You mentioned a "10 ms default rate" for the Continuous Task. I'm not sure where you're getting that. Continuous Tasks work a lot like classic PLC/SLC scans, where the task just runs and when it's over, the controller spends a little time doing housekeeping and communications. As the Continuous Task execution time gets longer, the overall "scantime" of the controller gets longer. 9 ms on a Continuous Task is middle-of-the-road for machine control.

You can't change a Task's execution type online, but you can move Programs from the Continuous Task to a newly-created Periodic Task.

I would focus on the Communications Timeslice and the available RAM more than I would the scantime of the sole Continuous Task.

 

[Bob O]

Thanks all! My ignorance is on display.
I monitored two different programs written by others and the rate of 10 was displayed in both. This was using the task monitoring tool in V 20.04 and I'm probably misunderstanding what that 10 meant.

I assumed this was the fixed rate of the cont. task since one had a scan of 8-9 ms and the other 1.5 ms. My bad!
I have a date to RTFM and continue after that.


Thanks!