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Connecting more than one device over RS485 port


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When I checked my project I notice error on my RS485 CPU COM port it says "Both Slaves have been set to the same communication protocol. Slave1 may be set to TCP/IP, while Slave2 is set to RS485."

Does it mean UniLogic RS485 can access only one slave device ?? So if I have more than one modbus slave I have to connect second slave through TCP/IP connection ?? What happens when I have 21 devices ?? I am really screwed if there are this kind of limitation.

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  • MVP 2023

I was able to create two RS485 slaves under the Master tree without a problem.


You may have master and slave reversed in your mind where you are defining "slaves" under the Slave tree, in which case you are telling the UniStream that it has to be a slave with more than one personality.  Which will not work.  


I think your configuration needs to be fixed.  Upload your program so we can see the rest of the story.

Joe T.

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  • 1 month later...

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