14 REDUNDANT SYSTEM INSTRUCTIONS
14.1 System Switching
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• This instruction switches the systems (control system and standby system) during END processing of the scan where the
instruction is executed. The instruction must be executed in the control system. If it is executed in the standby system, no
processing is performed.
The following figure shows the system switching operation by using the instruction.
• To switch the systems by using the instruction, turn on SM1646 (System switching by a user) in advance. If the system
switching operation is disabled by using the DCONTSW instruction, execute the ECONTSW instruction in the standby
system before executing the SP.CONTSW instruction.
• The value specified by (s) is stored in SD1650 (System switching instruction ID number) of both CPU modules when the
systems are switched successfully. When multiple SP.CONTSW instructions are executed in a program, the instruction
used can be identified by reading data stored in SD1650. If two or more SP.CONTSW instructions are executed in one
scan, only the data (argument) of the first instruction is stored.
END
END
System A
System B
Program executed
Program stopped
Execution of the instruction
Control system Standby system
System
switching
SP.CONTSW instruction
Standby system
Program executed
Control system
Program stopped
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