Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!umd5!hans
From: hans@umd5.umd.edu (Hans Breitenlohner)
Newsgroups: comp.sys.atari.8bit
Subject: Re: Finding the HSYNC signal
Message-ID: <4777@umd5.umd.edu>
Date: 28 Apr 89 19:39:07 GMT
References: <773@sunkisd.CS.Concordia.CA>
Reply-To: hans@umd5.umd.edu (Hans Breitenlohner)
Organization: University of Maryland, College Park
Lines: 10

In article <773@sunkisd.CS.Concordia.CA> jean@maxwell.Concordia.Ca ( JEAN GOULET | DCKS004 |              | ) writes:
>Hello.  I've been looking into making a light pen for my computer, and I think
>the design is complete, except for one important detail.  My circuit needs
>to be restarted every time the electron beam starts a new horizontal line, so
>I figure the HSYNC signal is what I need.  Unfortunately I don't have the
>...

The sync signal appears on pin 25 of the GTIA chip.  I believe it is combined
horizontal and vertical sync, scope it if you need to know for sure.
From there it goes through a CD4050 into a summing network.