Re: Vertical BLanking (VBL) for Apple II

From	mmphosis <mmphosis@macgui.com>
Newsgroups	comp.sys.apple2
Subject	Re: Vertical BLanking (VBL) for Apple II
Date	2015-02-01 18:56 +0000
Organization	Mac GUI
Message-ID	<mmphosis-1422817036@macgui.com> (permalink)
References	<mmphosis-1420157056@macgui.com> <c4c09601-5fda-4f1b-bfb4-4c75a76dc5a9@googlegroups.com>

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I've updated the VBL detection routine.  Reading Understanding the Apple II
by Jim Sather helped.

The routine is much more elaborate than I would have liked, but I think that
it works now.  There is probably a simpler method using a different graphics
mode, but those methods may have their own problems in scanning memory.  An
added feature of this updated routine is that it restores the HGR screen. 
This may be more useful than ending up with a cleared HGR screen as was done
in the original routine.

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Vertical BLanking (VBL) for Apple II mmphosis <mmphosis@macgui.com> - 2015-01-02 00:03 +0000
  Re: Vertical BLanking (VBL) for Apple II "Bill Buckels" <bbuckels@mts.net> - 2015-01-01 18:10 -0600
    Re: Vertical BLanking (VBL) for Apple II doug.dingus@gmail.com - 2015-01-01 18:32 -0800
      Re: Vertical BLanking (VBL) for Apple II Michael Black <et472@ncf.ca> - 2015-01-02 00:07 -0500
        Re: Vertical BLanking (VBL) for Apple II Michael J. Mahon <mjmahon@aol.com> - 2015-01-02 02:43 -0600
  Re: Vertical BLanking (VBL) for Apple II David Schmenk <dschmenk@gmail.com> - 2015-01-02 17:40 -0800
    Re: Vertical BLanking (VBL) for Apple II D Finnigan <dog_cow@macgui.com> - 2015-01-03 07:34 +0000
    Re: Vertical BLanking (VBL) for Apple II mmphosis <mmphosis@macgui.com> - 2015-02-01 18:56 +0000

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