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Old 27 August 2017, 21:26   #1
Tigerskunk
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Sprites on lowest area of PAL Screen

Hello fellow EAB coders,

I found some kind of weird problem, where I wonder if there is any solution for...

writing a sprite data structure word, the highest byte I can write for the vertical stop of a sprite is "FF".

Problem is, that doesn't go to the very lowest part of a PAL screen (with positions 0 to 44 being in the vertical blank, it seems. Which leaves 211 visible scanlines for sprites), so the Sprite won't get displayed down there (or just garbled)...

Any solution for this? Or do I need to work around this with displaying everything from scanline 1 to 200, and not below, so my sprites can use the whole play area that I blit into..

Just want to know, before I start rebuilding my blit and scroll engine to avoid this problem..

Thanks,
greets,
Steril707
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Old 27 August 2017, 21:49   #2
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The high bits of VSTART and VSTOP, and the low bit of HSTART are in bits [2:0] of the second sprite control word. See http://amigadev.elowar.com/read/ADCD.../node00BB.html
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Old 27 August 2017, 22:04   #3
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Ah, great....

Thank you, Mark....
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Old 27 August 2017, 22:16   #4
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Okay, one more question with a similar problem..

The highest ("lowest" in screen terms) I can go with a copper list entry is $ffdf.
That's leaving a big stripe on the lower part of the screen where i can't do any copper stuff.

Any idea if it is possible to do anything down there with the copper?
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Old 27 August 2017, 22:35   #5
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That should be explained at http://amigadev.elowar.com/read/ADCD.../node004D.html
Basically wait for position (0,255) when the copper vertical counter wraps around to 0, then another wait for the beam to reach the position you want.
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Old 28 August 2017, 06:30   #6
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Ah, nice to know...
Thanks again, Mark...
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Old 02 December 2017, 20:34   #7
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But what exactly is this position (0,255) as a value?

If I use
dc.w $00ff,$fffe

and then, to skip a further 8 lines,

dc.w $080f,$fffe


, I get a jump to some weird position in the center of the screen...

Doesn't make sense to me at the moment... :/


Edit: Okay, found it. It's $ffe1...

Last edited by Tigerskunk; 02 December 2017 at 20:40.
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