SpritesMind.Net

I would like to know if exist a documentation describing when vdp registers are taked in account during the rendering line process (line cycle or slot).
For example, if horizontal scroll register is taked in account at x cycle / slot x so modifying register after this time has no effect on the current line.

Reading the forum i understand that the vdp have a pixel buffer (16 pixel width / 1 column)? So it means that the vdp render the column anf fill the buffer one column before the effective pixel are outputed to the screen?

Thanks for your help.