Groups > comp.sys.apple2.programmer > #4805

Reading the state of VBL on a IIc,IIc+.

From	Brian Patrie <bpatrie@bellsouth.spamisicky.net>
Newsgroups	comp.sys.apple2.programmer
Subject	Reading the state of VBL on a IIc,IIc+.
Date	2018-10-06 09:02 -0500
Organization	an elaborate system of piles and accidents
Message-ID	<ppaf98$6jt$1@gioia.aioe.org> (permalink)

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The Apple IIc Technical Reference Second Edition tells me: "Reading 
$C019 checks the current state of vertical blanking (VBL) on the Apple 
IIe, but it reads and then resets the vertical blanking interrupt flag 
in the Apple IIc family."

How, then, do we read the state of VBL on a IIc,IIc+?
(And, for that matter, WTF did they do this?)

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Reading the state of VBL on a IIc,IIc+. Brian Patrie <bpatrie@bellsouth.spamisicky.net> - 2018-10-06 09:02 -0500
  Re: Reading the state of VBL on a IIc,IIc+. Antoine Vignau <antoine.vignau@laposte.net> - 2018-10-06 07:30 -0700
  Re: Reading the state of VBL on a IIc,IIc+. "Frank M." <frank_o_rama@hotmail.com> - 2018-10-06 07:43 -0700
    Re: Reading the state of VBL on a IIc,IIc+. Brian Patrie <bpatrie@bellsouth.spamisicky.net> - 2018-10-07 17:29 -0500
      Re: Reading the state of VBL on a IIc,IIc+. Michael J. Mahon <mjmahon@aol.com> - 2018-10-08 15:18 -0500
        Re: Reading the state of VBL on a IIc,IIc+. kegs@provalid.com (Kent Dickey) - 2018-10-08 19:32 -0500
        Re: Reading the state of VBL on a IIc,IIc+. Brian Patrie <bpatrie@bellsouth.spamisicky.net> - 2018-10-09 13:19 -0500
          Re: Reading the state of VBL on a IIc,IIc+. Michael J. Mahon <mjmahon@aol.com> - 2018-10-09 15:48 -0500
            Re: Reading the state of VBL on a IIc,IIc+. TomCh <tomcharlesworth26@gmail.com> - 2018-10-10 14:32 -0700
              Re: Reading the state of VBL on a IIc,IIc+. Michael J. Mahon <mjmahon@aol.com> - 2018-10-11 00:19 -0500

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