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20 DATA LOGGING FUNCTION
20.16 Precautions to Take When Using the Data Logging Function
About remote operation
When remote RUN is performed while the data logging function is in the following execution status, the remote RUN may fail.
In that case, wait for a while and retry remote RUN. If remote RUN still cannot be executed, check whether remote RUN is
acceptable and retry remote RUN.
RUN operation through switching operation or the RUN contact
During execution of data logging, when the status of the CPU module is switched from STOP to RUN with the RUN/STOP/
RESET switch, or when the RUN contact that is specified in the RUN-PAUSE contact setting turns off, it may take time to
return to the RUN state.
Using together with interrupt programs
When occurrence of an interrupt is specified as the data collection condition of data logging, the processing time of the
interrupt program increases because the processing time of the data logging function is added.
For this reason, a WDT error may occur if an interrupt interval of I49 set in the parameter of "Interrupt Setting from Internal
Timer" under "Fixed Scan Interval Setting" is too short (such as 0.05ms) and occurrence of I49 is specified as the data
collection condition, since the processing time of the interrupt program becomes longer than the set interrupt period and the
END instruction cannot be executed due to the continuous execution of the interrupt program. For how to reduce processing
time of interrupt programs, refer to Saving/restoring of the file register (R) block number. ( Page 126 Saving/restoring of
the file register (R) block number)
In redundant mode
When the data logging setting is written, please note the following.
• While the data logging setting is being written, do not perform the following operations on both of the control system and
standby system.
• In the following cases, the setting is written only to own system.
Execution state of data logging function The situation to accept remote RUN
Saving data in the internal buffer into a storage location in progress No special relay (Data logging data saving in progress) is on.
After the start operation of data logging by CPU Module Logging
Configuration Tool (Registration of the data logging setting in progress)
The special relay (data logging preparation) and the special relay (data logging
start) corresponding to the setting number of the data logging setting, which is
being registered in the way shown in the left column, are on.
After data logging is started by auto logging (Registration of the auto logging
setting in progress)
SM1200 (Auto logging setting file and registration status) is on.
• Turning off or resetting the CPU modules
• Connecting/disconnecting the tracking cable
• Online module change of redundant function modules
• The CPU module of the other system is off or reset.
• A hardware failure (a failure of the CPU module or redundant function module) has occurred on the other system.
• A tracking cable is disconnected or incorrectly connected, or failed.
• Tracking communications stop due to an error in the CPU module.
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