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Author Topic: Maximum PLC ID for Modbus RTU  (Read 12506 times)

ccdubs

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Maximum PLC ID for Modbus RTU
« on: August 01, 2014, 04:42:34 PM »
I remember reading before that the PLC ID's were only valid up to a limit when using MODBUS RTU. I can't find this reference anymore, could you please confirm what this?

Thanks
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support

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Re:Maximum PLC ID for Modbus RTU
« Reply #1 on: August 01, 2014, 11:57:49 PM »
According to Modbus specifications the ID for a Modbus slave may only be between 1 and 247.
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EDGAR

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Re:Maximum PLC ID for Modbus RTU
« Reply #2 on: August 02, 2014, 08:00:25 AM »
Hi, and agreed!

You might be able to handle that many devices. However, if you are using RS-485 network,  the RS-485 transceivers may not be capable of driving that many devices in the same network. See http://www.modbus.org/ also see http://en.wikipedia.org/wiki/RS-485 for bias network termination and other details.

Ed
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