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V9990

28 bytes added, 15:45, 14 October 2018
* In terms of physical addresses, if you consider physical address 0-&3ffff to be VRAM0 and physical address &40000-&7ffff to be VRAM1, then in P1 mode, the physical address equals logical address and in bitmap modes, every even address maps to &0-&3ffff (ever even is VRAM0) and every odd address maps to &40000-&7ffff (VRAM 1). This is described in the PDF.
* When reading 2bpp and 4bpp data with the POINT command the data appears to have undergone a circular shift so that in bitmap modes the pixel you are interested in has it's is moved into the topmost bits. The value in of the top 2 remaining bitsis unknown at this time.  
e.g.
X if byte in vram is aabbccdd x = 0 aabbccddaaxxxxx
x = 1
bbccddaabbxxxxx x = 2 ccddaabbccxxxxx
x = 3
ddaabbccddxxxxx
[[Category:Hardware]]
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