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Old 09 May 2018, 01:49   #1
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320x256 on OCS?

I can't figure out how to setup 320x256 display resolution. I currently have 320x200 running but how should I modify it to show 320x256 pixels?

BTW: I'm targeting my code for OCS. Is the 256 Y-resolution even possible on OCS?

Actually I think I can see 211 vertical pixels on screen at the moment :-/

OK, I get 216 Y pixels if I do this:
DIWSTRT = 0x2781

Everywhere I've read that I should do this:
DIWSTRT = 0x2C81

Is there a reason I should always go with the latter instead of the first one?

Last edited by Crank; 09 May 2018 at 01:58.
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Old 09 May 2018, 08:18   #2
move.l #$c0ff33,throat

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Originally Posted by Crank View Post
Is the 256 Y-resolution even possible on OCS?
Of course it is. Default DIWSTRT/STOP values are $2c81/$2cc1.
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Old 09 May 2018, 10:25   #3
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Now it works, just by changing one line of code

And by reading carefully the Hardware Reference Manual page about DIWSTRT/STOP I now see that both registers assume that there are some extra bits in play which make the values written in them different. I.e. in DIWSTOP the V8 is automatically different than V7, but in DIWSTRT V8 is always 0. My ignorance about these details explains why I couldn't figure out how to use these registers properly.
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Old 19 May 2018, 19:47   #4
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H.R.M. is - a reference. Exact and complete*, but abstract. For concrete "how-to" explanations with examples, you could try System Programmer's Guide, link.

Under Denise in the menu, there is also a thought on centering.

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