Mitsubishi Electric MELSEC Q Series Reference Manual page 329

(c) Using the service processing setting (For Universal model QCPUs)
In the service processing setting of the PLC parameter (PLC system) in the programming tool, secure time of
2ms to 3ms for service processing.
Remark
For details on the COM instruction, refer to the following.
Programming Manual (Common Instructions) for the CPU module used
(4) Executing a dedicated instruction from a redundant system
If a system switching occurs during instruction execution, execution of the instruction is stopped and its
processing is not completed.
To re-execute such an uncompleted instruction in the new control system after system switching, provide an
interlock using One scan ON after system switching (SM1518) and Completion device.
Note that the same instruction may be executed twice.
• Program example: Page 361, Section 9.5 (5)
CHAPTER 9 DEDICATED INSTRUCTIONS
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