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#1 Atarigmr OFFLINE  

Atarigmr

    Star Raider

  • 81 posts

Posted Tue Feb 28, 2012 9:48 AM

Hi

I have started to play with some ataru 8 bit coding and I have ran into a problem, I am trying to have a widescreen with 240 lines (30 lines of which are mode 2 and the others mode 4), but it flickers, it only works with 232 lines, my dlist is:

dlist dta $42,a(vram),2,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,$41,a(dlist)

What am I doing wrong?

thx

#2 phaeron OFFLINE  

phaeron

    Stargunner

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Posted Tue Feb 28, 2012 10:31 AM

Your display list is actually 241 scanlines tall -- the JVB instruction ($41) occupies a blank line. If you aren't rewriting DLISTL/DLISTH every frame, you're alternating between what you wanted to see and a completely blank frame.

#3 Atarigmr OFFLINE  

Atarigmr

    Star Raider

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  • 81 posts

Posted Tue Feb 28, 2012 10:45 AM

Thank you a lot phaeron, it is working fine now :)

#4 Atarigmr OFFLINE  

Atarigmr

    Star Raider

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  • 81 posts

Posted Mon Apr 9, 2012 3:51 AM

I have found that I need two more lines :( , is it possible to have a 40x32 chars mode? If so would it be tricky to set up?

#5 Rybags OFFLINE  

Rybags

    Quadrunner

  • 12,816 posts
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Posted Mon Apr 9, 2012 4:41 AM

40 x 30 is normally the max - but you can get problems if the 240th scanline is in hires. There's a fix for it, involves using a DLI to play about with DMACTL at the right times.

You can create shortened characters using DLIs and VSCROL register changes.

So, e.g. if you have 6 pixel high chrs instead of 8 that means possibly 40x40.

My interlaced demo raises the usable resolution to 480 pixels instead of 240. 8 pixel high chrs could be done at 40 x 60 although they're half normal height and might be a bit hard to read.

Easist fix for you would be just use VSCROL tricks. You could get away without needing custom character sets by doing 7 pixel high characters.

240 / 7 gives 34 character rows with a few scanlines left over.

#6 Atarigmr OFFLINE  

Atarigmr

    Star Raider

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Posted Mon Apr 9, 2012 5:54 AM

Thank you for clarifying things Rybags.

Shorter chars are not an option but I have come with an idea but I don't know if it will look ok - the extra lines were to be top and bottom game stats but I can have the game area a bit smaller(horizontally) and then have some columns on the sides free where I would have the score and other stats displayed vertically but this might be impractical as it might be hard to read also if I want to have some displaylist interrupts to get more color this will affect the stats too... hmmm

#7 Rybags OFFLINE  

Rybags

    Quadrunner

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Posted Mon Apr 9, 2012 6:05 AM

You don't have to do it for the whole screen.

You could make a special font and just have short chars for a few lines top/bottom.
Or you could just use bitmap and render chars by software.

#8 Atarigmr OFFLINE  

Atarigmr

    Star Raider

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  • 81 posts

Posted Mon Apr 9, 2012 10:29 AM

Thx Rybags,

I have chosen char mode because I can have the 5th color.

The 30 lines of the play area must be 8 pixels high each.




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