Precautions - Mitsubishi Electric GOT2000 Series Connection Manual

4.2.10

Precautions

■1. System switching
(1) When system is switched by user program
• The communication path does not change, and the GOT follows the monitor.
• The system alarm is not displayed.
(2) When system switches because of a dislocated cable, etc.
• The communication path changes, and the GOT follows the monitor.
• "450 Path has changed or timeout occurred in redundant system." appears as the system alarm.
■2. Redundant system configuration and operation mode
(1) System alarm display
With the following system configuration "451: MELSEC Redundant setting and actual system configuration do not
match" will appear as the system alarm, and the GOT will not be able to correctly monitor the redundant system's
CPU.
<System configuration>
• System configuration with MELSEC redundant settings that do not match the actual redundant system
• System configuration in which the redundant system operation mode is not the backup mode
(2) Changing the MELSEC redundant settings
Always reset the GOT after changing the MELSEC redundant settings. If not reset, the changed MELSEC redundant
settings will not be applied on the GOT.
■3. When non-redundant system is monitored after setting MELSEC redundant settings
If the MELSEC redundant settings were set for a non-redundant system, the GOT will operate normally. In this case, if
an abnormality (such as powering OFF, or communication timeout error) occurs at the PLC CPU for which the
MELSEC redundant setting has been made, the PLC CPU may operate in a different way from the monitoring target
change mode that was set in the MELSEC redundant setting.
■4. When redundant system is monitored without making MELSEC redundant setting
When the MELSEC redundant setting is not made, the GOT does not automatically change the monitoring target even
if system switching occurs in the redundant system. When the GOT is connected to the standby system, data written to
a device are overwritten by the data of the control system, failing to be reflected.
In this case, when data are written to a device in the standby system normally, the system alarm "315 Device writing
error. Correct device." is not detected.
■5. CC-Link(ID) connection
When system switching is occurred by the following factors, data link control of CC-Link(ID) does not move from the
master station of the new standby system to the standby master station of the new control system and the GOT cannot
follow the monitor.
Make sure that the standby master station of the new control system should control data link.
For details of the ladder program for data link control, refer to the following manuals.
• MELSEC Q Series
➠
QnPRHCPU User's Manual (Redundant System)
<Factors of system switching>
• Execution of the system switching instruction at the PLC side
• Execution of system switching operation using the engineering tool
• Execution of system switching request from other network modules.
<Why the GOT cannot follow the monitor>
When system switching is occurred by the above factors, data link control does not move to the standby master station
because the master station of the new standby system can communicate with the GOT.
Also, the new control system is the standby master station without changing. Therefore, the GOT monitors the master
station without following the new control system/new standby system and cannot monitor the redundant system.
4.2 MELSEC Q Series
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