Recovery From An Overload - Honeywell C300 User Manual

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CPU Free Low
Threshold defaults to 20% and is user configurable
Alarm is generated when CPU Free is less than the threshold.
CPU Free Low Low
Threshold is fixed at 10% and is not user configurable.
Alarm is generated when CPU Free is less than 10%.
Alarms and parameters that are associated with monitoring CPU use in the C300
Controller are CPUFREEAVG and CPUFREEMIN. These parameters are displayed on
the C300 Detail Display in Station and on the C300 properties form, (the Statistics tab of
the C300 block configuration form).
Parameters that measure the ability of the controller to execute loaded control strategies
are CPUCYCLEAVG and CRCYCLEOVRN. These and other related parameters are
displayed of the CPU Loading tab and the CPU Overruns tab of the CEEC300 block
configuration form.

Recovery from an overload

Recovery from a controller overload condition depends upon whether the overload is due
to a control processing (CEE Overrun - slipped cycle) or non-control processing
(degraded or loss of view) overload condition.
ATTENTION
When attempting recovery from an overload condition, you should determine
the endpoint of this recovery process. Use these following guidelines:
The controller should operate in the steady state without persistent
overload alarms of any type.
The controller should operate in the steady state without CPULMLOLO
alarms.
The controller should operate in the steady state with an average
CPUFREEAVG of at least 20%.
Control processing overloads indicated by CEE Cycle Overruns and 'control cycle slips'
make enough processing time available so that adequate view of the controller is
maintained. Consider the following actions to lessen control processing overloads:
R500
April 2017
7.14. C300 Controller processing overload behavior
Series 8 C300 Controller User's Guide
Honeywell
7. C300 Controller Operation
205

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