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From: Tom Moran <tmoran@bix.com>
Subject: Re: High Precision timing
Date: 1997/04/08
Message-ID: <334AAD2E.3641@bix.com>#1/1
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References: <5iddnc$57u@news.mel.aone.net.au>
Organization: InterNex Information Services 1-800-595-3333
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Newsgroups: comp.lang.ada
Date: 1997-04-08T00:00:00+00:00
List-Id: <comp.lang.ada>


It's been a while, but doesn't counter 2 of the PC's 8253 control
dynamic RAM refresh?  If so, I'd suggest you not fiddle with it.
  If you need high resolution timing, but not frequent, time consuming
interrupts, how about just reading, but not resetting, channel 1? 
That's what I did in my replacement Calendar body for RR's Ada 83
(available on their BBS).
  If you need frequent interrupts with pretty good timing properties,
output (junk) characters on a serial port at 115 Kbaud, with the
Transmit interrupt ISR merely stuffing another character out the port. 
That will give interrupts at just under 100 microseconds.  I've posted
code for a background speaker driver using this technique on Compuserve.