Do you know what you are talking about ?
Yes, I know perfectly well what...
Why do you need this for ?
Do you intend to sell/provide this info to some WD tool maker so they can implement reading/writing of ROM code by TTL ?
Autor Sediv needs this informations because working on Repairing internal flash on WDek, and repair Flash on all Wdeks using serial TTL, All Marvels using Cortex R4 core, ARM architecture, Loader just work but Autor needs UART protocol how work, examples.
People who have this info will not tell you how to do it as they would be able to implement it themselfs and make $$$ out of it !
I do not do this to reap the profits I want to help my friend.