* When the vram address is calculated from dx and dy, dx and dy are masked before use.
This means that transfer wraps within the same line and column. i.e. if drawing in reverse and overlapping x=0, then pixels will wrap to 256-x on the same line and if overlapping x=256 then pixels will wrap to 0.
=== ADVN ===
* The use of internal x,y coordinates and when they are updated is the same as PSET.
=== PSET ===