CompactLogix L35E

Hi all,

I am having a problem with the CPU utilization running anywhere from 70 to 100 percent on a couple of L35E controllers. I have several L32E's which are running larger programs than the L35's and they all run in the 20's. I have unscheduled every program in one of the L35E controllers and the CPU utilization did not change (suspected the continuos task). Also, I had to change the overhead time slice to %10 just to get it down to where it is now. Before that, it stayed at %100 continuosly. Any help will be greatly appreciated.

The size of the application file is not the only determining factor when establishing the CPU's burden; a couple of the most important (and overlooked) factors are the number of the established and the "quality" of the connections a controller is expected to handle at any time.
Also, the RSL5K application's "modules" RPI settings could drastically "load" the CPU when set next to the lowest accepted ranges.
The firmware level could be a factor too if the 32Es carry a higher (newer) one than the 35Es, since, of course, the latest revisions increase the hardware's capabilities.
If none of the above are determined to be real issues, then maybe upgrading to the newest CompactLogix class (5370 L3 -L33ERM) is the solution to your problem.

Connect to the controllers with the RSLogix 5000 Task Monitor, and you'll see a much more detailed picture of what tasks, routines, and services are using up the controller bandwidth.

It's hard to really put a number on "CPU Utilization" in a ControlLogix controller because the Continuous Task by definition runs as fast as it can, so in a sense it's meant to use up all the available CPU resources it can, to run as fast as it can. This has been a matter of some debate and discussion even inside RA, and is reflected in the various changes to the task and housekeeping priority settings over the course of the Logix OS evolution.

If you want to make this a Forum thread, provide some more information about how many I/O connections you're running, as well as info like the Firmware Revision of the controller.