Precautions On Starting Up The System When The Data Logging Function Is Used - Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual

5.
Clearing errors
When the ERROR LED of the CPU module of the control system is on, clear the error with the engineering tool. ( Page
133 Error Clear)
When "Watching Standby System Setting" of the CPU parameter has been set to "Disable" in the procedure
for starting up the control system, the ERROR LED may be off. ( Page 485 Redundant System Operation
Setting)
6.
Monitoring the program
Check that the program is normally running on the engineering tool. ( Page 434 Monitoring the Program)
Precautions on starting up the system when the data logging
function is used
If the systems are switched after data logging has failed (processing overflow) due to frequent and continuous data logging
collection, data logging continues frequently and continuously in the new control system, and thus the scan time of the new
control system increases considerably. Therefore, a WDT error may occur in the new control system and both systems may
stop. To avoid the above problem, check the following at system start-up.
• After the redundant system is started, the control system does not fail in data logging collection (processing overflow).
• The new control system does not fail in data logging collection (processing overflow) and the CPU module operates without
errors after system switching.
*1 Whether a processing overflow has occurred or not can be checked with the special register (Number of processing overflow
occurrences) corresponding to the data logging No. ( Page 833 List of Special Register Areas)
To prevent both systems from stopping, review the following settings.
• Collection interval and data to be collected in the data logging setting ( Page 967 Sampling,  Page 969 Data)
• "Scan Time Monitoring Time (WDT) Setting" of the CPU parameter ( Page 125 Scan time monitoring time setting)
When using the data logging function, note that the number of writings to the SD memory card is limited.
*1
27 PROCEDURE FOR STARTING UP A REDUNDANT SYSTEM
27
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427
27.1 Overview