Interrupt From Modules - Mitsubishi Electric MELSEC iQ-R Series User Manual

Interrupt from modules

This section describes the precautions for interrupts from modules.
System switching when redundant system is in backup mode
■When the old control system is switched to the new standby system
The old control system retains the interrupt factors that have occurred even after the system is switched to the new standby
system by system switching before execution of an interrupt program. After the systems are switched again, the interrupt
program of an interrupt factor that the old control system has retained will be executed.
Since the interrupt factor that has occurred on the old control system is not inherited to the new control system, the interrupt
program of an interrupt factor that has occurred on the old control system will not be executed on the new control system.
■When the old standby system is switched to the new control system
The old standby system retains the interrupt factors that have occurred. After the old standby system is switched to the new
control system by system switching, the interrupt program of an interrupt factor that the old standby system has retained will
be executed on the new control system.
When the old standby system has retained multiple interrupt factors, the scan time may greatly increase.
System switching when redundant system is in separate mode
■When the old control system is switched to the new standby system
The old control system executes the interrupt program of an interrupt factor that the old control system has retained even after
the system is switched to the new standby system by system switching before execution of an interrupt program.
■When the old standby system is switched to the new control system
The old standby system retains the interrupt factors that have occurred. The new control system executes the interrupt
program of an interrupt factor that the old standby system has retained regardless of the system switching operation.
When operation mode is changed to separate mode
■For the control system
The control system retains the interrupt factors before operation mode change to the separate mode. After operation mode
change to the separate mode, the control system executes the interrupt programs of the interrupt factors that have occurred
when the redundant system was in backup mode.
■For the standby system
The interrupt factors that the standby system has retained before operation mode change to the separate mode will be
discarded. Therefore, after operation mode change to the separate mode, the interrupt programs of the interrupt factors that
have occurred before operation mode change will not be executed.
When operation mode is changed to backup mode
■For the control system
When the interrupt programs of the interrupt factors before operation mode change to the backup mode have not been
executed yet, the control system will execute the programs retained when the redundant system is in separate mode.
■For the standby system
When the interrupt programs of the interrupt factors before operation mode change to the backup mode have not been
executed yet, the interrupt factors retained when the redundant system is in separate mode will remain retained. Interrupt
programs will not be executed.
26 REDUNDANT FUNCTION
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26.11 Precautions on Programming