Mitsubishi Electric MELSEC iQ-R Series User Manual page 311

In redundant mode
The internal data of the CPU module in each own system is backed up and is restored only to the CPU module in the own
system.
In the CPU module of both systems, when the data which is backed up in the different system is restored, a
system mismatch is detected. Restore the data that is backed up in the same system.
■Differences in usage from the memory copy function
When combining the data in the CPU module of the standby system with the data in the CPU module of the control system,
use the memory copy function. When changing the data of both systems at the same time, use the CPU module data backup/
restoration function.
Function
CPU module data backup/restoration function
Memory copy function ( Page 405 Memory
Copy from Control System to Standby System)
Application
When adding the same system as the redundant system that has already operated
When restoring programs and parameters of both systems to the data before change due to trouble
occurrence
When replacing only the CPU module of the standby system due to a failure and others
When recovering the data due to error occurrence in the system consistency check
22 CPU MODULE DATA BACKUP/RESTORATION FUNCTION
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