Why does Control Expert display a CPU load 90% when the PLC is configured in Cyclic mode?
Issue:
Starting with Control Expert V16.4, a CPU load indicator is displayed in the status bar when connected to a PLC. When the MAST task is configured in Cyclic mode, the CPU load indicator is displayed in orange at 90%, even for a simple or empty application. This behavior may be interpreted as a controller overload, although it is expected.
Environnement:
- Control Expert V16.4 and later
- PLC configured with a Cyclic MAST task
Resolution:
This behavior is expected and does not indicate a controller overload.
The CPU load indicator displayed in the Control Expert status bar reflects the value of%SW116 (Total System CPU Load). When the MAST task is configured in Cyclic mode, the controller continuously executes the application without any idle time between scans. Consequently,%SW116 reports a CPU load of approximately 90%, even for simple or empty applications.
In Periodic mode, the CPU load is generally more representative of the actual processing margin because task execution is based on a configured period.