Determination Of Control System/Standby System; When Starting Up Both Systems Simultaneously - Mitsubishi Electric MELSEC iQ-R-R00CPU User Manual

35.8

Determination of Control System/Standby System

This section describes how to determine which system is the control system and the other is the standby system.

When starting up both systems simultaneously

The following describes the method of determining the system types of when both systems are started up simultaneously.
How to determine the system types
Whether each system is the control system or standby system is determined when the both systems are started up by
powering off and on or reset of the CPU module and then ready for tracking communications. The safety operation mode
(TEST MODE or SAFETY MODE) of the system does not affect the determination of the system types.
■When both systems are started up simultaneously
The system A operates as the control system and the system B as the standby system.
"Simultaneously" here means that one system is started up within three seconds after the other system is started.
■When one of the system A and system B is started up first
The system will wait for the start-up of the other system in three seconds. ( Page 571 The system waiting for the start-up
of the other system)
When communications for both systems are established, system A operates as the control system and system B as the
standby system.
Checking method
Check the LED of each redundant function module to check the status of the control system/standby system.
System status
Control system
Standby system
Users can check the status of the control system/standby system with the engineering tool. ( GX Works3
Operating Manual)
• System monitor
• Monitor status bar
Precautions
■If the system A/B settings have not been set for both systems or the same system setting has
been set for both systems
A stop error occurs. To determine the control system and standby system, properly set the system A/B settings for both
systems.
■If both systems are restarted when a stop error has occurred on the standby system (system
A)
If both systems are restarted simultaneously in a system where the system A operates as the standby system due to a stop
error and the system B normally operates as the control system, a stop error may occur on both systems.
If the stop error cause of the system A is a program error, a stop error occurs on the system A again after the systems are
restarted. Even if the system B normally operates as the control system before the restart, a stop error also occurs on the
system B if a mismatch between files is detected in the system consistency check after the restart. As a result, a stop error
occurs on both systems.
In this case, eliminate the cause of the error that has occurred on the system A and restart and restore both systems.
LED of the redundant function module
35.8 Determination of Control System/Standby System
35 BASIC CONCEPT
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