Check Method Of System Switching Information - Mitsubishi Electric MELSEC iQ-R Series User Manual

Check method of system switching information

The following table lists the check methods of system switching information at system switching (automatic system switching
and manual system switching).
Check method
Event history
Special relay (SM)/Special register (SD)
CTRL LED and SBY LED of the redundant
function module
When the systems have been switched, check the switching cause or detailed information and take corrective action to
restore the system to a normal state as required.
Event history
The information related to system switching results, system switching cause, and control system/standby system transitions
can be checked with the event history of the engineering tool.
When the systems are switched, the following items are stored in the event history of both systems.
• Automatic system switching: "System switching (system)" (event code: 00F00)
• Manual system switching: "System switching (user)" (event code: 2B000)
When the systems are switched by the SP.CONTSW instruction, the system switching instruction ID number specified with
the SP.CONTSW instruction is also stored.
Special relay/Special register
System switching results and detailed information can be checked with the special relay and special register.
• Whether the systems have been switched or not can be checked by checking SD1649 (System switching cause (when the
systems are successfully switched)). When the systems have been switched, the system switching cause is stored in
SD1649 of the control system and standby system.
• If the systems have not been switched even after a system switching cause is generated, the cause why the systems have
not been switched can be checked by checking SD1644 (Cause of system switching failure). The switching cause is stored
in SD1643 (System switching cause) of the control system.
For the values stored in the special relay and special register, refer to the following.
• Special relay ( Page 665 Redundant function)
• Special register ( Page 701 Redundant function)
■Special relay
The following table shows the special relay numbers for system switching and the storage status of the CPU modules in the
control system and standby system.
: Stored, : Not stored
SM No. Name
SM1637 System switching detection (standby system to control system)
SM1643 ON for only one scan after system switching (standby system to control system)
SM1644 ON for only one scan after system switching (control system to standby system)
SM1645 System switching request from a network module
SM1646 System switching by a user
Information
System switching result, system switching cause, and
control system/standby system transition
System switching result and detailed information
System switching result
Reference
Page 383 Event history
Page 383 Special relay/Special register
Page 384 CTRL LED and SBY LED of the
redundant function module
Storage status at system switching
CPU module of the new CPU module of the new
control system standby system
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26 REDUNDANT FUNCTION
26.2 System Switching
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