in reply to: First bit of preamble posted by Anirudh on 12 December 2009 at 17:02:33.
Carrier startup (1200Hz) comes first. Since HART is asynchronous, there is no definition of when a character should begin. So I suppose the carrier might be at any phase at the instant you choose to start a message.
See, for example, figure 2 in the Maxim DS8500 data sheet at datasheets.maxim-ic.com/en/ds/DS8500.pdf .