When The Previous Control System Is Started Up As The Control System - Mitsubishi Electric MELSEC iQ-R Series User Manual

When the previous control system is started up as the control
system
In a redundant system, when both systems are simultaneously started up, the system A always will be the control system.
Even when both systems are temporarily powered off due to a power failure or other causes while the system B is operating
as the control system, the system A will start up as the control system when both systems are powered on.
To start up the system B, which was operating as the control system before power-off, as the control system again, use
SM1636 (Previous control system identification flag) in the program.
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Note that if a network module is included in the system, wait until the network module of the other system starts up, and
execute the SP.CONTSW instruction.
When network modules are not mounted on the main base units
■Program example
The following program switches the system B from the standby system to the control system by executing a system switching
instruction when the operating status of the CPU module in the system A is changed to RUN for the first time. Turn on
SM1646 (System switching by a user) in advance.
11 BASIC CONCEPT OF REDUNDANT SYSTEM
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11.6 System Determination