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From: dr@ski.UUCP (David Robins)
Newsgroups: net.micro.apple
Subject: Re: Apple IIe and IIc raster scan synchronization.
Message-ID: <327@ski.UUCP>
Date: Mon, 29-Sep-86 16:07:22 EDT
Article-I.D.: ski.327
Posted: Mon Sep 29 16:07:22 1986
Date-Received: Wed, 1-Oct-86 01:43:34 EDT
Reply-To: dr@unix.UUCP (David Robins)
Organization: Smith-Kettlewell Institute, S.F., CA.
Lines: 28

I neglected to mention, in the article I just posted, that the FIELD
SYNC enhancement was updated in the second printing of Enhancing Your
Apple ][, Volume I.  

The one-wire addition was for the old ]['s.  In the update section, it
is pointed out that the //e has the VBL signal available at $C019.
The appropriate software corrections for the assembly program are
given.  Since $C019 is used for a different purpose on the //c, the
//e routines were not applicable.

However, since the other software solution in Vol.2  works on all
Apples, the above problems can be ignored.  The software solution
takes advantage of the Apple common data bus, reading a floating value
from the video cycle that is still present.  (The stray capacitance
holds the last value.)

				-Dave

-- 
====================================================================
David Robins, M.D. 
Smith-Kettlewell Eye Research Foundation
(previously known as: Smith-Kettlewell Institute of Visual Sciences)
2232 Webster St; San Francisco CA 94115
415/561-1705 (voice)
			{ihnp4,qantel,dual}!ptsfa!ski!dr

The opinions expressed herein do not reflect the opinion of the Institute!