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Multiple Modbus Connection Problem


cmcdonald
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I have a clipper set up successfully as a Modbus Client to a Siemens S7-1200 (Server). Once I introduce another device (pc software)on the network it cannot connect unless i unplug the Ethernet connection to the Clipper.

 

It seems that the clipper is holding the connection to the PLC. I have tried to increase the Timer in the MODBUS command setup but it seems to stay connected to the PLC all the time thus blocking any connections to the PLC.

 

Is there a way to have the Clipper disconnect so that other devices can connect to the server?

 

Thanks

 

Chris

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Hi Chris,

Does your S7 Modbus gateway accept multiple simultaneous Modbus clients?

If yes - What happens if you connect the PC software first, then try to connect with the Clipper?

 

Regards,

Steve

 

Yes it does. But it has to use a different port.

 

The S7 requires another Modbus Server Rung. We are still having random Modbus disconnects (1-2 a day) and are in the process of using the PC software to check if the Modbus server is working on port 502 but we cant access 502 because the clipper is connected constantly. I would like to connect get data then disconnect from the server but Im not sure if that is possible.

 

Chris

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Try the following:

M89->X:$FFFFC2,4

I67=0

M89=1

M89=0

You should then be able to connect with your software.

I don't know if you can restart the Modbus by setting I67 to a non-zero value or not - I think so, but if not, you will need to reset PMAC to restart the Modbus.

Regards,

Steve

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