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9 RAS FUNCTIONS
9.3 Event History Function
Event history file
The storage memory and file size for event history files can be changed in event history setting. Refer to CPU parameter for
details of the event history setting. (Page 55 CPU parameter)
■Storage memory
Choose either the standard ROM or SD memory card. If the storage memory is the SD memory card, when the write protect
switch of the SD memory card is enabled, an event history will not be stored. (It is still possible to read the event history file in
the SD memory card using MT Developer2.)
Therefore, if the write protect switch of the SD memory card is changed from disabled to enabled during operation, a write
error to the SD memory card occurs when an event for storing in the event history occurs (SD memory card available event is
registered) after the write protect switch is enabled. (At the time immediately after an error has occurred, the module
diagnostics of GX Works3 can detect it, however, after the Multiple CPU system power supply is turned OFF to ON or after
resetting operation, the error that occurred will not be stored in the event history.)
For a system where file writes occur frequently or the communication conditions are unstable and frequently
change, the event history file size should be made large enough to accommodate a greater number of events.
If this is the case, the SD memory card is highly recommended as the storage memory.
■File size
The size for event history files can be changed in event history setting. (Page 55 CPU parameter) If the specified size is
exceeded, the records are deleted from the oldest one and the latest one is stored. 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)
*1 Because the contents of detailed information may differ depending on the event to be saved 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 saved. An example for
when the event history file size is 128K bytes (default) is shown below.
Minor error (error code: 1901H)
Because one record is 64 bytes, approximately 2040 events can be registered.
Element Size
File header size 20 bytes
Event history management information size 12 bytes
Size per event history record At least 40 bytes
*1
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