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Modbus tcp master to rtu slaves through modbus tcp gateway
https://forum.codesys.com/viewtopic.php?f=11&t=6037
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Author:  rbragason [ Mon Feb 02, 2015 9:40 pm ]
Post subject:  Modbus tcp master to rtu slaves through modbus tcp gateway

I am using a Festo PLC w. Codesys v3. I am trying to connect to two temperature controllers that are Modbus RTU by using a Modbus TCP gateway (Antaira STM-501c). I set the PLC up as Modbus tcp master and attached two Modbus tcp slaves to it, each slave is set up with the gateway ip and the corresponding slave id. When doing this the bus becomes unstable and the connection to the slaves is lost. If I remove one slave from the configuration I have no problem connecting to either slave. It seems that the problem lies in the slaves both having the same ip. Although from what I have read it should not be a problem having to slaves with the same ip and different id's in the modbus standard. Has anyone encountered this and/or found a solution or workaround to this?

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