can the Modbus plus proxy TCSEGDB23F24FA talk to more than one master?

Issue

can the Modbus plus proxy TCSEGDB23F24FA talk to more than one master?

Product Line

M340, M580

Resolution

A Modbus plus proxy TCSEGDB23F24FA can only talk to one master on the Ethernet side; however, a Master on Ethernet side can scan multiple Modbus plus proxy TCSEGDB23F24FA.

Two points are to consider:

1. Each MB+ proxy creates 5 Modbus TCP connections to the PLC. If you overload the number of sockets used on the PLC or NOC, the proxies will keep trying to establish new ones. The PLC behavior by design is to close the longest unused socket that is open. This will cause sockets to be opened and closed causing modbus messages to be dropped and errors to accrue . If a PLC or NOC can only handle 32 MBTCP sockets at a time, there should be no more than 6 MB+ proxies configured to use them as master.

2. Offsets for peer cop, global data, and 1x/3x registers need to be planed and managed by the customer to maintain data integrity in the PLC. Each proxy should have its own defined range for offsets. This is covered in the user manual.

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