System Switching; System Switching Method - Mitsubishi Electric MELSEC iQ-R Series User Manual

Process cpu module

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System Switching

This function switches the systems between the control system and the standby system to continue operation of the

redundant system when a failure or an error occurs in the control system. For debugging and maintenance purpose, users

can switch the systems at any desired timing.

The following two methods are available for system switching: automatic system switching (performed by a redundant

system) and manual system switching (performed by a user).

The following table lists the system switching types, causes, execution availability by operation mode of the redundant

system, and priority of when multiple causes are simultaneously generated.

: Operation possible, : Operation not possible

System switching type

Automatic system switching

Manual system switching

• When multiple system switching causes are simultaneously generated, the systems are switched according to the cause

with higher priority. The switching cause determined according to the priority is stored in the event history and SD1643

(System switching cause).

• A manual system switching request is executed for the CPU module of the control system.

The systems are not switched even when the CPU module is set to the STOP state. They are switched when

any of the above system switching causes is generated.

26 REDUNDANT FUNCTION

26.2 System Switching

System switching cause

Power-off, reset, hardware failure of the CPU module

Stop error of the CPU module

System switching request from a network module

System switching request by the SP.CONTSW instruction

System switching request from the engineering tool

Operation mode

Separate mode