System Switching Operation - Mitsubishi Electric MELSEC iQ-R Series User Manual

System switching operation

In a redundant system, if the control system fails, the control system and the standby system are switched.
In the RJ71LP21-25, send data is transferred to the new control system after system switching to continue data link.
The following shows system switching operation when a communication error occurs in the control system.
(1)
1.
A communication error occurs in control system (1).
2.
The RJ71LP21-25 of control system (1) issues a system switching request to the CPU module.
3.
System switching occurs in the redundant system.
4.
Standby system (2) starts operating as the new control system to continue network control.
In the RJ71LP21-25, settings can be made from "System Switching Monitoring Time" under "Supplementary
Cyclic Settings" in "Application Settings", or by directly rewriting 'System switching monitoring time setting'
(SW0018).
Setting method
When using the module in a redundant system, select "RJ71LP21-25(R)" for the module model name in the "Add New
Module" window.
In addition, pairing setting is required for the RJ71LP21-25 of both systems.
Pairing is set under "Network Range Assignment" in "Required Settings" of the control station. (Page 55 Network Range
Assignment)
Precautions
• If system switching is performed by any reason other than a communication error, control station switching is not
performed.
• While the control is switched to a station of the new control system, the cyclic data output is held. For cyclic data holding
time (output holding time) when system switching occurs, refer to the following.
Page 181 Cyclic data holding time when system switching occurs
1 FUNCTIONS
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1.5 Redundant System Function
(2)