Mitsubishi Electric MELSEC iQ-R Series User Manual page 438

Instructions whose operations vary depending on tracking of the signal flow memory
The following describes the instructions whose operations after system switching vary depending on whether the signal flow
memory is tracked or not when the redundant system is in backup mode. The operations vary when one of the following
instructions is executed among program organization units that have the signal flow memory, memory to which tracking can
be performed.
Classification/type of special relay
Rising instruction
Falling instruction
SCJ instruction
Data processing instructions
TIMCHK instruction
XCALL instruction
Rising instruction using SM1643 as an execution
condition
■Rising instruction
If the system switching is performed without the signal flow memory being tracked, the signal flow memory of the new control
system turns on. Thus, a rising instruction whose execution condition turned on during system switching will not be executed.
■Falling instruction
If the system switching is performed without the signal flow memory being tracked, the signal flow memory of the new control
system turns on. Thus, a falling instruction whose execution condition turned off before the system switching will be executed.
■SCJ instruction
• When the signal flow memory is not tracked
Once the system switching is performed, the execution condition of the SCJ instruction turns on after the signal flow memory
of the new control system turns on. In the new control system, processing jumps to the pointer specified by the SCJ
instruction in the first scan.
Execution condition of the SCJ
instruction
Jump by using the SCJ instruction
(old control system)
Jump by using the SCJ instruction
(new control system)
(1) After system switching, the processing jumps in the first and later scans.
26 REDUNDANT FUNCTION
436
26.11 Precautions on Programming
Instruction symbol
LDP, ANDP, ORP, LDPI, ANDPI, ORPI, PLS, MEP, EGP, SET F, RST F, FF, LEDR, DUTY,
LOGTRG, LOGTRGR, P (including MOVP and INCP), SP., JP., GP., ZP.
LDF, ANDF, ORF, LDFI, ANDFI, ORFI, PLF, MEF, EGF
SCJ
SORTD(_U), DSORTD(_U)
TIMCHK
XCALL

System switching start
ON
OFF
Jump
No jump
Jump
No jump
Systems are being switched.
System switching completion
(1)