Precautions when connecting a GOT directly to a PLC CPU in the redundant
system without making Q redundant setting
(1) As the GOT monitors exclusively the PLC CPU that is directly connected to, the monitor target cannot be
changed in response to the system switching of the redundant system.
To change the target monitor in response to the system switching, change the target of the connection cable
between the GOT and PLC CPU to the other PLC CPU, or configure the system using GOTs connected to each
(2) In CPU direct connection, when monitoring a PLC CPU in the redundant system, only the PLC CPU that is
directly connected to the GOT can be monitored.
(3) When connected to the standby system PLC CPU, the writing of the GOT to a device in the connected PLC
CPU is not reflected. Design a monitor screen that disables writing to the standby system.
In the redundant system, the tracking function transfers device data from control system to standby system.
When the tracking function is enabled, the device value of the standby system PLC CPU is overwritten by the
device value transferred from the control system to the standby system even if the GOT writes to the standby
system PLC CPU (Numerical input, Ascii input, Script, Recipe, or others).
As countermeasures to the above, perform the following.
• Display a monitor screen which indicates that "the connected PLC CPU is the standby system" on a GOT
when connecting the GOT to the standby system PLC CPU.
• To display the specified monitor screen when connecting the GOT to the standby system PLC CPU, use the
special relay SM1515 (Control status identification flag) of the PLC CPU.
(When the SM1515 is OFF, the connected PLC CPU is the standby system)
• Control the operation of each object by the SM1515, which is set for the operation condition.
• For the screen switching device, use a GOT internal device.
If a device of the PLC CPU is used, the Status Observation operation of the GOT may be disabled since the
device data of the PLC CPU will is overwritten by the device value transferred with the redundant system
CPU direct connection
2) Tracks D100=5 from control
system to standby system.
MELSECNET/H remote I/O network
4. HOW TO MONITOR REDUNTANT SYSTEM
CPU direct connection
1) Numerically input D100=100
from the GOT.
4.2 Direct CPU Connection
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