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7.2 Cautions on Fixed-Scan Clocks and Fixed Scan Execution Type Programs
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PROGRAMMING CAUTIONS
(5) Interrupt from Network module
Execution of the interrupt program that corresponds to the interrupt factor sent from a
network module varies according to the following conditions.
(a) When the Operation Mode is Backup Mode
1) When System Switching Occurs before Execution of the Interrupt
Program
The control system CPU module holds the received interrupt factor, even
when it becomes the standby system CPU module through system switching
before the interrupted program is executed.
When switching is done again and the standby system CPU module returns to
the control system CPU module, it executes the interrupt program for the held
interrupt factor.
Since the interrupt factor accepted by the control system CPU module is not
taken over by the new control system CPU module, the new control system
CPU module does not execute the interrupt program of the interrupt factor
accepted by the control system CPU module.
2) When the Standby System CPU Module receives an interrupt
The standby system CPU module holds the interrupt factor received from an
intelligent function module.
When the standby system CPU module becomes the new control system CPU
module through system switching, it executes the interrupt program for the
held interrupt factor.
POINT
The interrupt program corresponding to the held interrupt factor is executed when
the standby system CPU module becomes the control system CPU module
through system switching.
If multiple interrupt factors are held in the standby system CPU module, the scan
time is widely extended.
(b) When the Operation Mode is Separate Mode
Both control system CPU module and standby system CPU module execute
interrupt programs for the interrupt factors sent from a network module.
(c) When the Operation Mode is Debug Mode
The control system CPU module executes an interrupt program for the interrupt
factor sent from a network module.