Between this topic, and the others asking for ports of Sega Saturn and all other kinds of Resident Evil games ported to the Dreamcast, I just get the impression you don't have the slightest idea what you are talking about the majority of the time when it comes to technical things is all. No offense intended, I just thing you don't know a lot of basic technical terms, or have any understanding about how source code is needed for porting games. We were all there at one point trust me, so we have all been there before. Like I said no offense.
As for this topic, that SD adapter that you see floating around on the internet is a specially hand made serial adapter which started life as a USB device. It was heavily modified and rewired to function from the serial port on the Dreamcast in concert with Dreamshell.
I even made a review of mine when I got one around 2011. It was up on Racketboy. Even wrote up a detailed Q and A. Check it out and if there is anything else you don't understand about it let me know here and I will do my best to explain.
http://www.racketboy.com/forum/viewtopi ... 05&start=0