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16 RAS FUNCTIONS
16.2 Event History Function
Event history file
The storage memory and file size for event history files can be changed in event history setting. (Page 139 Event history
settings)
■Storage memory
The following storage memory can be used.
• Data memory
• Built-in RAM battery keeping
*1
• Memory card (SD memory card)
*1 Only FX5U/FX5UC CPU module is supported.
For a system where 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.
• If the storage memory is the built-in RAM battery keep: when the battery is not loaded or the battery voltage is low, if an
operation such as power is turned OFF ON or RESET operation is made, the generated error will not be stored into the
event history.
• If the storage memory is a memory card (SD memory card), the event history will not be stored when the SD memory card's
write protect switch is enabled. (The event history file in the SD memory card can be read with the engineering tool.) Thus,
if the SD memory card's write protect switch is changed from disabled to enabled during operation, and an event that saves
to the event history occurs, a write to SD memory card error will occur. (Immediately after the error occurs, it can be
checked with the engineering tool's module diagnosis. However, the occurring error will not be saved in the event history
after the power has been turned OFF and ON or the module reset, etc.)
• If the storage memory is the memory card (SD memory card): when the SD memory card is not loaded, after power is
turned OFF ON or after resetting operation, errors will not be stored into the event history.
■File size
The size for event history files can be changed in event history setting (Page 139 Event history settings). If the storage
size exceeds the specified size, records are deleted in order 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.
Element Size
File header size 20 bytes
Event history management information size 12 bytes
Size per event history record
*1
40 to 1112 bytes (variable)
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