Automatic Switching Of Communication Path - Mitsubishi Electric MELSEC SW1DNC-CCIEF-B User Manual

Error occurrence
The following example gives a flowchart for error occurrence at batch write.
Start
Write processing
(mdSend instruction), etc.
Did an error occur?
NO
Execute normal processing.
End
*1 For details and corrective action of the error code, refer to the following manual.
 QCPU User's Manual (Hardware Design, Maintenance and Inspection)
*2 Execute retry processing as required depending on the system specifications.

Automatic switching of communication path

When a communication error occurs during access to the Redundant CPU connected via MELSECNET/H, the
communication path is automatically switched to continue access to the control system.
Hereinafter, this automatic switching of the communication path is referred to as path switching.
The following describes the path switching conditions, checking method of path switching occurrence, and access examples
of path switching.
Path switching conditions
When access is being processed under the following conditions, access to the Redundant CPU is continued by path switching
even though a communication error occurs.
Conditions for continued access
Operation mode
Redundant CPU specification
Note, however, that if a tracking error
continued by path switching even if tracking is recovered after that.
*1 Includes the status in which either Redundant CPU is powered OFF or reset.
APPX
178
Appendix 1 Precautions for Accessing Redundant CPU System
YES
Check the error code.
Does the error require retry
processing?
NO
Process the error.
Backup mode, Separate mode
Control system, Standby system, System A, System B
*1
has already occurred at the start of communication, access to the control system is not
*1
YES Retry processing
*2
Execute wait processing.