Mitsubishi Electric MELSEC-Q/L Programming Manual page 884

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Operation error

• In any of the following cases, an operation error occurs, the error flag (SM0) turns ON, and an error code is stored into SD0.

Error details

The value specified at (S) is 0 at execution of the SP.CONTSW instruction.

The manual switching enable flag (SM1592) is OFF (disabled) at the

execution of the SP.CONTSW instruction.

The SP.CONTSW instruction was executed by the standby system CPU

module in the separate mode.

The SP.CONTSW instruction was executed in the debug mode.

• If system switching was unsuccessful, the error flag (SM0) is turned ON and an error code is stored into SD0.

Error details

The tracking cable is disconnected or faulty.

Hardware fault, power-off, reset or watchdog timer error occurred in the

standby system.

Watchdog timer error occurred in the control system.

Preparations are being made for tracking transfer.

Communication time-out occurred.

A stop error, excluding watchdog timer error, occurred in the standby system.

The operating status differs between the control system and standby system.

Memory copy is being executed from the control system to the standby

Writing during RUN

Network fault was detected by the standby system.

Program example

• The following program executes system switching on the rising edge of the system switching command (M100). If the

system switching command (M100) remains ON, the SP.CONTSW instruction is also executed by the new control system

CPU module after system switching. Therefore, M101 is added to the execution conditions as a consecutive switching

prevention flag.

[Ladder Mode]

11 REDUNDANT SYSTEM INSTRUCTIONS (FOR REDUNDANT CPU)

11.1 System Switching