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From: rond@pro-grouch.cts.com (Ron Dippold)
Newsgroups: comp.sys.apple2
Subject: Re: Timing problem
Message-ID: <3380.apple.net2@pro-grouch>
Date: 26 Jul 90 00:46:08 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 30

In-Reply-To: message from dat33228@uxa.cso.uiuc.edu

Got to thinking about my comment re: your timing problem again...  I had
thought you wanted a continuous pulse, but then I reread it and realized you
only want a one-shot...

My suggestion would be to go to normal mode, do your thing, then return to
whatever mode you were in.  That way you can get an exactly 2 microsecond
(well, 2.046 microsecond) timer.  All you need is:
 
  lda ($e0),y    ; y has zero, $e0 has $5r, $e1 has $c0 (annunciator 3)
  lda ($e2),y    ; $e2 has $5e       $5F^^^  , $e3 has $c0

if you don't want to get into any IIgs stuff.  If you do, then
  phd           ; save direct page
  pea $c000     ; make $c000 direct page
  pld
  lda $5F       ; turn it on
  lda $5E       ; turn it off
  pld           ; restore old direct page
 
 
I still think the best way to do it would be a one-shot timer, where you could
turn off the annunciator to prime it, then turn it on for a 2 msec pulse.  You
wouldn't need to worry about what speed you were running at.
 

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