On Mon, Dec 11, 2000 at 01:18:42PM +0000, Maarten ter Huurne wrote:
> On Monday 11 December 2000 11:46, you wrote:
> > > SCREEN7 reorder is more difficult to implement than SCREEN8, because what
> > > appears to be a byte to the programmer is actually spread over two VRAM
> > > locations. For example, when a byte is written through port #98, it must
> > > be split into two nibbles which end up in different VRAM locations.
> >
> > In the define above, (X&2) is unused; I assume this determines whether the
> > high or the low nibble is used. Probably if (X&2) is set, it is the low
> > nibble (bit 3 - bit 0) and if it's not set, it's the high nibble (bit 7 -
> > bit 4).
> >
> > Is that correct Maarten?
>
> I have some doubts about the way I described SCREEN7. I can't get the pixel
> reorder working, which could be an implementation error, but could also mean
> I got the algorithm wrong.
Last night I tried to figure it out on the MSX, but failed. :( My monitor
it terrible which doesn't help. :( Using POINT (X,Y) it can be checked of
course. I'll try again tonight.
Sean
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