Article View: comp.sys.atari.st
Article #32097Re: ST hardware scrolling (It works!)
From: unpowell
Date: Fri, 22 Apr 1988 09:46
Date: Fri, 22 Apr 1988 09:46
30 lines
1558 bytes
1558 bytes
In article <4484@batcomputer.tn.cornell.edu>, braner@batcomputer.tn.cornell.edu (braner) writes:
> []
>
> Two problems with the suggestion for "hardware scrolling":
>
> (1) The ST's video pointer must be on a 512-byte boundary, NOT 256.
> Thus, incrementing it by $500 (1280) (to scroll by one text line)
> is NOT feasible.
The video pointer goes on a 256 byte boundary. You must have a pretty
weird ST there. I've had the hardware scrolling working fine.
The screen memory location is held in addresses $ff8201 (high byte)
and $ff8203 (mid byte). The low byte is always taken as 0 by the ST. Thus,
as you can see, this allows the screen to be put on 256 byte boundaries.
> (I tried it: the screen goes crazy!)
Maybe it's just you thats crazy?
Mark Powell
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Path: arc1-ca.pugleaf.net!utzoo!mnetor!uunet!mcvax!ukc!mupsy!liv-cs!unpowell From: unpowell@csvax.liv.ac.uk Newsgroups: comp.sys.atari.st Subject: Re: ST hardware scrolling (It works!) Message-ID: <787@csvax.liv.ac.uk> Date: 22 Apr 88 09:46:22 GMT References: <544@csvax.liv.ac.uk> <4484@batcomputer.tn.cornell.edu> Lines: 29 Organisation: Computer Science CSVAX (VAX1), Liverpool University