Mitsubishi Electric MELSEC iQ-R Series User Manual page 217

Loss of event history information
If events are detected frequently, or the CPU module is powered off or reset immediately after the detection of events, some
events may not be collected and lost. When event loss occurs, "*HST LOSS*" appears in the "Event Code" field of the
engineering tool.
Event history logging restriction
When the number of minor events from the CPU module or intelligent function module such as link-up and link-down exceeds
the upper limit value, event history logging is restricted (stopped).
When the number of events for which logging is restricted decreases to the lower limit value or below, event history logging is
restarted.
The error codes of moderate and major errors that occur in the CPU module are logged in the event history.
Item
Upper limit value
Lower limit value
*1 For models and firmware versions that support the event history logging restriction, refer to the following.
Page 747 Added and Enhanced Functions
*2 Event history logging is not restricted (stopped) for CPU modules with firmware version earlier than "22".
In a redundant system, the CPU module of the control system monitors the logging of events that occur in a module on an
extension base unit and restricts the amount of events to save.
When systems are switched, the event history logging restriction state is cleared. Therefore, even if the old control system is
in the logging restriction state before system switching, the new control system is in the state of no event history logging
restriction.
■Events not supported by the logging restriction
The following events are not subject to the logging restriction.
• Events of the self-diagnostics for major errors from the intelligent function module
*1 For CPU modules with firmware version earlier than "22", CPU module events are not subjected to the logging restriction, either.
■How to check whether event history logging is restricted
When event history logging is restricted, SM1464 (Event history logging restriction status) turns on. SM1466 turns on when
the event history logging of the CPU module is restricted and the event category is error (minor error), and SM1467 turns on
when the event history logging of the CPU module is restricted and the event category is information or warning.
Modules on which event history logging is restricted can be identified in SD1464 to SD1467 (Module information on event
history logging restriction).
Modules from which event history information is collected
Event history information is collected from the CPU module and other modules installed on the same base unit (i.e., the main
base unit plus any additional extension base units). Event history information may or may not be collected from devices on the
network depending on the specifications of the network modules used to connect to them. Refer to the manuals of the
respective modules for more information including the coverage of event history collection regarding devices on the network.
For a multi-CPU system, note that each CPU module logs only events detected on the modules under its control. On Q series
modules, only errors of which even type is "System" are stored. (The above applies only to Q series modules that support the
module error collection (function).)
Events logged by the CPU module
Information logged in the event history includes operation initiator and other detailed information for troubleshooting purposes.
For events that are logged in the event history on the CPU module, refer to the event history. ( Page 633 Event List)
* 1*2
Condition
600 events/minute
300 events/minute
* 1
15 RAS FUNCTIONS
15.4 Event History Function
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