Copyright © Romilly Bowden 2006, 2007, 2015.
I receive many requests for details of the Profibus and Modbus protocols. Before you ask for more information, please look carefully at the material listed here.
If these don't help, by all means try my HART Discussion Forum / Message Board. But, especially for Profibus, you may do better elsewhere.
From the Profibus International website:/p>
From the modbus.org website: