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PLC to modbus Communication (RS485)
I am trying to find a modbus ASCII protocol so i can write the PLC code, with the specific request for coils and register, and a break down of responses so i can pick out the data i need.
Does anyone have an idea of where i could get the protocol from, or have a protocol document?
Thanks
Does anyone have an idea of where i could get the protocol from, or have a protocol document?
Thanks
Hi Lewis,
www.modbus.org have all the info. I have in front of me 'Modbus over Serial Line Specification and Implementation Guide' dated Dec 20 2006 which was downloaded from the site. It contains all you need including algorithms/look-up tables for generating LRC/CRC.
Regards,
TommyB
www.modbus.org have all the info. I have in front of me 'Modbus over Serial Line Specification and Implementation Guide' dated Dec 20 2006 which was downloaded from the site. It contains all you need including algorithms/look-up tables for generating LRC/CRC.
Regards,
TommyB
Hi, I assume that you are writing the software in a PLC, only ask as most PLC's have modbus functions. There is a lot of stuff written about modbus serial and ethernet, if you want I can email you a manual.
Kevin
Kevin
"http://www.modbus.org/tech.php" The link to the download area is at the top of the page. There isn't a dedicated document for Modbus ASCII. I think you are expected to put the general Modbus spec and the serial spec together to understand it.
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