Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual page 612

Automatic system switching
A system judges whether system switching is required or not, and automatically switches the systems between the control
system and the standby system as required.
■System switching due to power-off, reset, or hardware failure of the CPU module
The standby system CPU module monitors the control system status. If the current control system is unable to control the
system in the following situations, the standby system CPU module is switched to the control system and the new control
system CPU module continues the control over the system.
• The control system CPU module has been turned off.
• The control system CPU module has been reset.
• A hardware failure has occurred on the control system CPU module.
*1 The control system CPU module is switched to the standby system even when the existing standby system CPU module is not ready to
switch. ( Page 616 Execution availability of system switching)
Ex.
Operation of when the control system (system A) CPU module is turned off
Program executed
Control system
System A
System B
When a network is established using the CC-Link IE Field Network module, the systems can be switched even
when a redundant function module is removed from the base unit or a failure has occurred in the base unit.
■Stop error of the CPU module
When a stop error occurs on the control system CPU module, the standby system is notified of a system switching due to the
stop error, and the standby system CPU module is switched to the control system. The control system CPU module where the
stop error has occurred is switched to the standby system.
*1 If a WDT error has occurred, the control system CPU module is switched to the standby system even when the existing standby system
CPU module is not ready to switch. ( Page 616 Execution availability of system switching)
Ex.
Operation of when a stop error occurs on the control system (system A) CPU module
Program executed
Control system
System A
System B
37 FUNCTIONS
610
37.1 System Switching
Power-off
System switching
Standby system
Program stopped
Program executed
Stop error occurrence
Standby system
System switching
Standby system
Program stopped Program executed
*1
Control system
*1
Stop error
Control system