Posted By
bubis
on 2019-08-27
10:58:51
|  Re: TED Hacks
Avoiding badlines is easy. If yshift is the lower 3 bits of $FF06, you get badlines at raster lines
yshift, yshift+1
yshift+8, yshift+9
yshift+16, yshift+17
...
until the bottom of the visible window.
To avoid badlines you either have to amend $FF06 or $FF1D, so that you never run on a rasterline where a badline should happen.
If you update $FF1D, you should avoid changing the lowest bit, otherwise you screw the PAL signal.
Also, if you update $FF1D you have to make sure you restore it's normal value after all the manipulations, otherwise you will not have a standard 312 lines screen.
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