Rockwell Automation GMLC Reference Manual - Manual (Page 889)

Publication GMLC-5.2 - November 1999
852 CPU Utilization
Effects of Excessive CPU Utilization
If CPU Utilization in your application exceeds the thresholds set forth
above, program execution speed slows drastically, and external
communications can fail.
Also, when the CPU_utilization variable value reaches 90%, the motion
controller (using firmware version 3.5 or higher) executes a Kill System
command, and generate a CPU Utilization Overrun fault (Global Fault
15), which in turn triggers the following events:
• The CPU Watchdog is disabled, with the result that the green System
OK LED turns off (or turns red, depending on the version of your
controller).
• Feedback for all axes is disabled.
• Motion on all axes is disabled.
• All servo outputs are set to zero.
• The drive enable outputs are disconnected.
As a result, CPU utilization is lowered to an acceptable rate, and serial
port communication is restored. The CPU_utilization_peak variable
retains and displays the highest value reached by the CPU_utilization
variable.
See Connecting the CPU Watchdog in the Installation and Hookup section
of your controller’s Installation and Setup Manual.
To clear the CPU_utilization_peak variable, execute an Equation function
block using the Online Toolbar:
1. Select Type: Configured.
2. Select General System Variables.
3. Set the CPU_utilization_peak variable equal to zero.