Path: 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


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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 "...I hate the white	JANET unpowell@uk.ac.liv.csvax
  man, and the man	UUCP  {backbone}!mcvax!ukc!mupsy!liv-cs!unpowell
  who turned you all	ARPA  unpowell%csvax.liv.ac.uk@nss.cs.ucl.ac.uk
  loose..." R. Harper

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