Mitsubishi Electric MELSEC iQ-R Series Programming Manual page 1443

Processing details
• 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.
System A
SP.CONTSW instruction
System B
• 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.
Program executed
Execution of the instruction
Control system
Standby system
Program stopped
END Program stopped
Standby system
System
switching
Control system
Program executed
14 REDUNDANT SYSTEM INSTRUCTIONS
END
1441
14.1 System Switching
14