Mitsubishi Electric MELSEC iQ-R Series User Manual page 433

When an extension cable error occurs during system operation
When an error occurs in the extension cable on the active side (the side with the ACTIVE LED lit) between the extension base
units during system operation, an extension cable error occurs in the CPU module of the control system and the systems are
switched.
If "Tracking communication error at startup" is set to "Automatically recover" for the automatic recovery setting, when a stop
error occurs in the CPU module of the new standby system due to an extension cable error after system switching, the new
standby system is automatically recovered.
When redundant extension cables are used (when redundant extension base units are connected in the
second and later extension levels), automatic recovery is performed only when a cable error occurs between
extension base units. Therefore, automatic recovery is not performed when any of the following errors occur.
Take action according to the procedures for a stop error that has occurred, and then restore the standby
system manually.
• Extension cable error between the main base unit and the extension base unit
• Extension cable error when the extension cable is not redundant
If the extension cable is redundant, automatic recovery is performed even if there are both a level with one
extension cable and a level with two extension cables between the extension base units and an extension
cable error occurs in the level with two cables.
Cause of failure of automatic recovery
Automatic recovery may fail due to the following causes. If automatic recovery fails, recover the standby system by manual
operation (turning off and on or resetting the system).
• Tracking communications disabled (cable disconnection or control system power-off)
• A file on the CPU module of the standby system being accessed
• Stop error in the CPU module of the control system
• Memory copy being executed
• Online change being executed
• System switching being executed
*1 Only external file access is disabled. (Access to files by a system such as event history or data logging is reset after the completion of
the access.)
*2 If any cause of automatic recovery occurs during backup, it is not handled as automatic recovery failure, and automatic recovery is
executed after the completion of backup.
Precautions
The following describes the precautions for automatic recovery.
• If automatic recovery is performed by this function during writing to the programmable controller on the CPU module of the
standby system, the writing may fail and a file invalid error may occur at the time of recovery. In this case, write the data to
the programmable controller again.
*2
26.9 Settings for Redundant System with Redundant Extension Base Unit
*1
26 REDUNDANT FUNCTION
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