Mitsubishi Electric MELSEC iQ-R Series User Manual page 378

■Stop error of the CPU module
When a stop error occurs in the CPU module of the control system, the CPU module of the standby system is notified of a
system switching due to the stop error, and the CPU module of the standby system is switched to the control system. The
CPU module of the control system where the stop error has occurred is switched to the standby system.
*1 If a WDT error has occurred, the CPU module of the control system is switched to the standby system even when the current standby
system is not ready to switch. ( Page 381 Execution availability of system switching)
Ex.
Operation when a stop error occurs in the CPU module of the control system (system A)
Program executed
Control system
System A
System B
26 REDUNDANT FUNCTION
376
26.2 System Switching
Stop error occurrence
Standby system
System switching
Standby system
Program stopped
Program executed
Stop error
Control system
* 1