The old Modbus Serial Line spec contained requirements for the serial Media Access and Link layers. They are beyond the scope of the current (version 1.0) Application layer spec and do not appear elsewhere in the Modbus Standard Library.

The FAQ contains a link to the old spec, but it is broken.

Is this information publicly available?

 

The Modbus serial specifications are being added to the Specifications section of the site. They should be available by the end of today.
The broken links to the specifications will also be updated.

Thank you for your feedback.

 

All public information about Modbus protocol is available at "www.modbus.org":http://www.modbus.org .

 

This is a good question to ask modbus.org - they also include a subheading on the spec page for serial Modbus but it empty at the moment. I suspect someone has it on their "todo" list to create a serial "Appendix" to the Open-Modbus spec for MB/TCP.

Best Regards

Lynn August Linse, alist (at) linse.org
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