Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual page 444

■System switching due to power-off, reset, or hardware failure of the CPU module
In a redundant system, the standby system CPU module monitors the control system status. If the control system is unable to
control the redundant system in the following cases, the standby system CPU module is switched to the control system CPU
module and the new control system CPU continues the control over the redundant 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 CPU module even when the existing standby system CPU module is
not ready to switch. ( Page 447 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 CPU module. The control system CPU
module where the stop error has occurred is switched to the standby system CPU module.
*1 If a WDT error has occurred, the control system CPU module is switched to the standby system CPU module even when the existing
standby system CPU module is not ready to switch. ( Page 447 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
28 FUNCTIONS
442
28.2 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
Stop error
Control system
* 1