Since I read you posts ( and mail archive ) regarding to NES scrolling, I'm completly lost ..
What I did before was, writting to VRAM regarding to the value of $2006 and scrolling between NT when CPU was writting to $2005. This was working well for most demos.
After reading the different docs, here is what I understood ( maybe I did understand completely wrong ) ...
In Vblank :
When CPU accesses $2007, we use $2006 as a reference of where to write.
Does that mean that we can not access VRAM this way out of VBlank ???
When CPU writes to $2005, what happens is that $2006 is updated and so there is no real scrolling but an update of where we read/write data in VRAM. Is that true ?
Out of VBlank :
We can not use the $2006 / $ 2007 method to access VRAM because when writting to 2006 there are some updates made to $2005 as described in Loopy's doc.
Vertical scrolling values are ignored out of Vblank ?
As you can see, it is not clear at all for me
Can someone explain ?