When Only One System Is Started Up - Mitsubishi Electric MELSEC iQ-R Series User Manual

When only one system is started up

• In a redundant system without extension base units, only one system, system A or system B, can be started up as the
control system by the start-up methods described below.
• In a redundant system with redundant extension base unit, when the systems are powered on or reset one by one, the
system that is started up first will be the control system and the other system will be the standby system. Settings for the
state that waits for the other system to start in the CPU parameter (Control/Standby System Start-up Setting) become
invalid.
Start-up method
To start up one system as the control system, perform one of the following operations to the CPU module that is waiting for the
other system to start.
■Online operation
Perform the following operation on the engineering tool.
[Online]  [Redundant PLC Operation]  [Redundant Operation]
Select "Forced Start of Control System while Waiting for Other System to Start" and click the [Execute] button.
■Switch operation
Set the RUN/STOP/RESET switch of the CPU module to RUN  STOP  RUN.
Set "Control System Start-up Setting (Switch Operation)" to "Enable" in the CPU parameter in advance. ( Page 425
Redundant System Operation Setting)
■Operation with the input (X)
Turn on the input (X) set in the parameter.
Set "Control System Start-up Setting (Input (X))" to "Enable" in the CPU parameter in advance. ( Page 425 Redundant
System Operation Setting)
State that waits for the other system to start
In a redundant system without extension base units, if tracking communications are not established after the CPU module of
the own system has started up, the own system will enter the state that waits for the other system to start in three seconds.
The CTRL LED and the SBY LED of the redundant function module turn off because the control system cannot be determined
at this point. In addition, the BACKUP LED of the redundant function module flashes because a system switching disable
cause exists.
After tracking communications with the other system are established, the control system is determined and the system
switching disable cause is eliminated.
■Operation of the CPU module in the state that waits for the other system to start
Even when the RUN/STOP/RESET switch of the CPU module is set to the RUN position, the CPU module will be in the STOP
state while it is in the state that waits for the other system to start because the control system has not been determined yet.
The CPU module does not execute programs.
The following table lists the refresh operations to be performed while the CPU module is in the state that waits for the other
system to start.
Type
I/O refresh
Network module link refresh
Intelligent function module refresh
■Timeout of the state that waits for the other system to start
Time measurement starts for the state that waits for the other system to start upon completion of the initial processing.
Set the timeout time in "Other system Start-up Timeout Setting" of "CPU Parameter". ( Page 425 Redundant System
Operation Setting)
When a timeout is detected, a stop error occurs. To not to generate a stop error, set "Other system Start-up Timeout Setting"
of "CPU Parameter" to "Not Set".
Operation
Only the input refresh is performed. The output refresh is not performed.
Between the network module and the CPU module, SB/SW is refreshed but other link devices are not.
Data is refreshed between the intelligent function module and the CPU module.
11 BASIC CONCEPT OF REDUNDANT SYSTEM
11.6 System Determination
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