Precautions For Dedicated Instructions - Mitsubishi Electric MELSEC iQ-R Series User Manual

Precautions for dedicated instructions

This section describes precautions when using dedicated instructions.
Precautions for dedicated instructions (common)
■When changing data specified by dedicated instructions
Do not change any data (such as control data) until execution of the dedicated instruction is completed.
■When the dedicated instruction is not completed
Check whether the module operation mode setting of the RJ71LP21-25 is online mode.
The instruction cannot be executed when the module operation mode setting is set to a mode other than online mode.
■When executing multiple link dedicated instructions simultaneously
When executing multiple link dedicated instructions simultaneously, check that the channels for the instructions are not
duplicated.
Precautions for dedicated instructions (when used in a redundant system)
■System switching during execution of a dedicated instruction
When systems are switched during execution of a dedicated instruction, the dedicated instruction may not be completed.
Execute the dedicated instruction again from the control system CPU module after system switching.
■Processing at abnormal end of a dedicated instruction
When the dedicated instruction is executed by specifying the access destination CPU module, it may be completed with an
error if systems are switched in the target station. If the dedicated instruction was completed with an error, execute it again.
■SEND instruction
• When the target station is in a redundant system, the communication request source station must identify that the target
station is the control system to execute the SEND instruction. When the target station is the standby system, the RECV
instruction is not executed at the target station after data is sent by the SEND instruction, and the target station storage
channel becomes occupied and unable to be used.
• When a redundant system exists in a network where broadcast communications are performed, the RECV instruction is not
executed at the standby system, and the storage channel becomes occupied and unable to be used.
■RECV and RECVS instructions
• When the SEND instruction is executed for the control system, if the systems are switched before execution of the RECV
instruction and interrupt program, the control system retains RECV execution request flag (SB00A0 to SB00A7) and the
interrupt program interrupt factor (interrupt pointer). If system switching occurs again, and the standby system is switched
to the control system, the RECV instruction and interrupt program will be executed by the RECV execution request flag
(SB00A0 to SB00A7) and the retained interrupt program interrupt factor.
• When the SEND instruction is executed for the standby system, and the standby system receives data from the sending
station, the standby system retains RECV execution request flag (SB00A0 to SB00A7) and the interrupt program interrupt
factor (interrupt pointer). Therefore, when the standby system is switched to the control system due to system switching,
the RECV instruction and interrupt program will be executed by the RECV execution request flag (SB00A0 to SB00A7) and
the retained interrupt program interrupt factor.
■REQ, RRUN, and RSTOP instructions
When performing remote STOP or remote RUN on a redundant system, do as follows: Perform STOP on the standby system
 STOP on the control system  RUN on the control system  RUN on the standby system.
APPX
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Appendix 5 Dedicated Instruction