I have a similar task to complete shortly - with a 'Memory Controller' that is connected to Mirrors, Seat and Pedals. The Mirror in particular has a sub-module that is responsible for mirror control but is connected to the Memory Module by a single data line.
The only way I know how to see this is with an oscilloscope, and it sounds like you might be in the same situation my friend. I am suspecting that the Memory Module has to send a 'position number' to the mirror controller - Position 1,2, 3, and Reverse - and the Mirror module is responsible for remembering it's direction for each of the memory 'positions'.
The question for me is, how did you even get that information for the frame format?