Mitsubishi Electric MELSEC Q Series Reference Manual page 158

*1 When the redundant system is in separate mode, power OFF and ON only system B or reset the CPU module of system
B.
*2 When the redundant system is in separate mode,
1) Set online mode for the system B and write data to the system B CPU module.
2) Power OFF and ON only system B or reset the CPU module of system B.
3) Connect the programming tool to the control system CPU module, and change the operation mode of the
redundant system to the backup mode.
The hardware test result can be confirmed with the link special relay (SB0090, SB0091). (
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Page 568, Appendix 1)