Mitsubishi Electric MELSEC iQ-R Series User Manual page 37

Storing the event history
This section describes storing of the event history.
■Modules from which event history information is collected
Event history information is collected from the remote head module and other modules installed on the same base unit (the
main base unit and extension base units). In the case of the Q series module mounted on the RQ extension base unit, only an
event history with the event type being "System" and the classification being "Warning" is stored.
Events that have occurred in equipment on the network are not collected as event history.
■Events stored in the remote head module
Information stored in the event history includes operation initiator and other detailed information for troubleshooting purposes.
For events that are stored in the event history on the remote head module, refer to the event list. ( Page 129 Event List)
■Event history file
• Storage destination memory: Data memory
• File size: The storage size of an event history file is 128K bytes. If the size exceeds 128K bytes, records are deleted from
the oldest one to store the latest one. An event history file size is obtained from the following calculation formula.
Event history file size = File header size + Event history management information size + (Number of records  Size per event
history record)
Element
File header size
Event history management information size
Size per event history record
*1 Because the contents of detailed information may differ depending on the event to be stored or the detailed information may include a
variable-length file name, the size per event history record is variable.
The number of events to be saved in the event history file differs depending on the event type to be stored. 3276 events can
be registered for the RUN, STOP, and switch operation of the remote head module. (The size of an event such as changing
the operating status to RUN or STOP is 40 bytes.)
[Calculation formula]
128 bytes  1024 = 131072 bytes
131072 bytes - (20 bytes + 12 bytes) = 131040 bytes
131040 bytes  40 bytes = 3276 events
• File creation timing: File is created when power is turned off and on (when there is no event history file), at the time of reset
(when there is no event history file), and at the time of parameter writing (when there is no event history file).
When a new event history file is created, that operation is logged into the event file as an event history.
The following table shows how the event history is treated depending on operation.
Operation
Memory initialization
Event history creation
■Loss of event history information
If events are detected frequently, or the power is turned off or reset immediately after event detection, some event histories
may be lost without being collected. When event history loss occurs, "*HST LOSS*" is displayed in the "Event Code" field of
the engineering tool.
Size
20 bytes
12 bytes
40 bytes minimum
Operation for the event history
When this event occurs, the event history is stored into the data memory. If the maximum number of event history files
storable into the data memory is exceeded, all subsequent event histories will be lost. ( Page 35 Storing the event
history)
The event history stored in the data memory before the creation of the event history file is saved in the data memory. (If
any event was lost, it is logged as "*HST LOSS*").
*1
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1 FUNCTIONS
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1.5 RAS Function