19 DATA LOGGING FUNCTION
19.6 Steps Until the Collected Data Is Saved
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19
Switching to a storage file
The data collected by data logging is temporarily stored in a stack file that resides in the SD memory card. The stack file can
be switched to a storage file to free the space in the SD memory card.
How file switching (log rotation) works
File switching works as follows:
1. The CPU module writes collected data into a stack file (such as LOG01.BIN).
2. It changes the file name when the storage file switching condition is met.
*1
3. It creates a new stack file.
4. It continues to write collected data into the newly created stack file.
*1 The file name format can be customized. (Page 467 Save)
The file number of the most recent storage file is stored in the special register (Latest storage file number).
File switching condition
The following table lists the setting items that can be used to specify the file switching condition.
*1 File switching occurs before the file grows beyond the specified size.
However, file switching occurs regardless of the setting when:
• The number of records has reached 65500;
• The file size has reached 16M bytes;
• The CPU module is stopped or suspended/resumed.
• Data logging is started and there is an existing stack file.
Trigger logging does not require the configuration of these settings because the stack file is automatically
switched to a storage file after as much data as the specified number of records is written into the stack file.
Special relay (logging data storage file switching in progress) can be used to check if storage file switching is
in progress.
Setting item Description
Number of records Specify the number of records within the range of 1 to 65500.
File size
*1
Specify the number of kilobytes within the range of 10 to 16384K bytes.
CPU module
CPU module
LOG01.BIN
Stored file
Rename
LOG01.BIN
Stored file
(New file)
LOG01_00000001.BIN
Saved file
Device data sampling
Device data sampling
File switching
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