--- Eckhard Stolberg
<Eckhard_Stolberg@xxxxxxxxxxxxxxxxxxxxx> wrote:
> If you hit RESxx during the horizontal blank, the
> object will be
> positioned as if RESxx was hit at cycle 22. If you
> use a zero in
> your delay loop, RESP0 will be hit at cycle 21. So
> there will be
> a differnce of three pixels when the delay table
> values change
> from 0 to 1, which you will have to make up for with
> the fine coarse
> positioning.
Thank you. I will have to think about what to do in
the case of writing 0 to RESPx, since that's what is
causing the problem with the delay table.
> Another problem with your demo is that the code,
> that determines if
> the sprite should be drawn or not, takes too many
> cycles. If you
> want to display a sprite from pixel 5, you have to
> change the
> sprite's graphics and colour register within 24
> cycles after the
> WSYNC.
How'd you figure that out? I've read about leaving
fine coarse positioning registers alone until 24
cycles after an HMOVE, but never anything about
writing to GRPx within 24 cycles of a WSYNC.
Interesing.
>In your demo the graphics register gets
> changed at cycle
> 29 and the colour register gets changed at cycle 36.
> So during
> the leftmost part of the screen the sprite will
> display the graphics
> and/or colour from the scanline before.
Okay.....uh, sort of.
> BTW you are doing the sprite positioning not only
> during the VBLANK
> but also during the VSYNC. Doing anything during the
> three lines of
> VSYNC might result in your game not syncronizing
> properly on badly
> tuned TV sets.
Okay, gotcha. Will never do anything during Vertical
Sync again... Guess I got lucky this time!
> And finally, if you want us to find a problem in
> your code, it would
> be helpfull, if you could send the source code along
> with the binary,
> so that we don't have to disassemble it first. ;-)
For now on, I will post the source. You figured all
this out by using DiStella on the .bin? Wow...thanks, man!
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