Hello,
there is an information on wiki (
http://prizm.cemetech.net/index.php?title=Technical_Info ), that Prizm has probably different LCD resolution than 384×216. Does somebody have any additional information ?
All my Prizm programs count with this resolution and everything works. I mean if I access VRAM[384], I access the first pixel of the second row, in the case of different HW resolution this would not work (I think).
The Prizm operating system abstracts out a central display area of 384x216 using the LCD commands to create a window. We also have a syscall that lets us change the border of the screen outside of that 384x216 area, so we have always known that the screen has more than 384 by 216 pixels. Calc84maniac definitively played around with the registers last night and figured out the actual resolution.
The LCD controller supports defining a "window" into which pixels are sent to the Graphics RAM. The PRIZM OS defines this window as [6,389] horizontally and [4,219] vertically, which is a 384x216 window. The actual screen resolution is 396x224.
MPoupe wrote:
I mean if I access VRAM[384], I access the first pixel of the second row, in the case of different HW resolution this would not work (I think).
Well, from the discussion held last night, Video RAM is simply a chunk of memory 384*2*214 bytes large at address 0x08000000 (physical address), in P2, non-cacheable memory. Since the Video RAM given by casio has no effect on the actual hardware LCD GRAM, the Hardware may actually support -4-0-0-*-2-3-2- -o-r- -s-o- -p-i-x-e-l-s-. (ignore that last bit, I didn't get to hear the information above, I left earlier in the discussion.)
Ashbad wrote:
Well, from the discussion held last night, Video RAM is simply a chunk of memory 384*2*214 bytes large at address 0x08000000 (physical address), in P2, non-cacheable memory.
I know that, I meant that the structure in LCD RAM must be the same. Otherwise the DMA transfer (VRAM-DD) would need to be restarted after each line.
Interesting, why Casio does limit screen size ?
It could be that they like having an exact 16:9 ratio
MPoupe wrote:
I know that, I meant that the structure in LCD RAM must be the same. Otherwise the DMA transfer (VRAM-DD) would need to be restarted after each line.
No, it wouldn't, because a window is defined for the LCD in the LCD's control registers that make the LCD act as if it is actually a smaller LCD as far as its buffer and DMA are concerned.
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