Copyright © Romilly Bowden 2007.
I receive many requests for the specifications for HART, usually asking for PDF files. I am sorry, I cannot supply this.
The only place to get the full specifications is the HART Communication Foundation. Do not be surprised that non-members have to pay - this is a significant source of income for the not-for-profit HCF.
Of course, there are other sources of information on HART, but none offering the complete specifications. See, for example, the rest this website, and the links listed here.
If you have other questions about HART, or need help understanding the specifications, by all means try my HART Discussion Forum / Message Board. Please make your questions as clear as possible, and use an explicit subject title.