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Path: utzoo!watmath!clyde!burl!geoff
From: geoff@burl.UUCP (geoff)
Newsgroups: net.micro,net.micro.apple
Subject: head noise in apple IIe
Message-ID: <740@burl.UUCP>
Date: Tue, 11-Jun-85 15:01:35 EDT
Article-I.D.: burl.740
Posted: Tue Jun 11 15:01:35 1985
Date-Received: Wed, 12-Jun-85 02:15:27 EDT
Reply-To: geoff@burl.UUCP (geoff)
Organization: AT&T Technologies, Burlington NC
Lines: 26
Xref: watmath net.micro:10733 net.micro.apple:1959
Summary: 

References:

I have a set of print routines for the apple IIe which write directly to
the display page (both 40 and 80 column pages).  I have a lot of trouble
with dos getting lost and having to resync the head.  While my routines
work ok (they are part of an editor) and dos works fine (files are read
and written without errors), I would like to eliminate the resync clatter.
I understand that dos (3.3) keeps some of its variables in the display pages
in the left-over space between the visible lines, and I suppose I am
trashing at least one of them.

The problem usually happens on long (200-400 line) files, and is decidedly
more prevalent on writing files than reading them.  However, sometimes even
very long files are written without problems, and sometimes even very short
files have problems.  I am using the Manx open, read, and write routines,
but I am sure their editor uses them and it never screws dos up.  A very
common place to get lost is between opening and writing the files.

Does anyone out there have any ideas about specific places to look?  I don't
have an assembly language debugger (all of the display routines are in assembly
language) so debugging is more by inference than a step-by-step process.
Again, the display works *perfectly* (so far as I can see, anyway).  It doesn't
lose characters, so I don't see how it could be writing them in non-visible
(i.e., dos) locations.  I don't know of anything else that could be causing
the problems.

	??help??
		geoff sherwood