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From: mykes@3comvax.UUCP
Newsgroups: net.micro.amiga
Subject: Re: Clarifications for the Ultra Fast Timer
Message-ID: <525@3comvax.UUCP>
Date: Mon, 2-Jun-86 14:51:16 EDT
Article-I.D.: 3comvax.525
Posted: Mon Jun  2 14:51:16 1986
Date-Received: Thu, 5-Jun-86 06:45:53 EDT
References: <724@watcgl.UUCP> <1177@well.UUCP>
Reply-To: mykes@3comvax.UUCP (Mike Schwartz)
Distribution: net
Organization: 3Com Corp; Mountain View, CA
Lines: 25

In article <1177@well.UUCP> rab@well.UUCP (Bob Bickford) writes:
>(WHAT line ea
>
>   One microsecond accuracy?  In a psychology experiment?  Be real.
>You'll be measuring times in the range of several hundred milleseconds
>at least; ask the prof. why the hell he needs five-digit accuracy.
>I bet he doesn't.   Probably you'd do just fine with one MILLISECOND
>accuracy...!
>
>
I worked with EEG devices for a while, and from the sounds of the experiment,
1 microsecond is appropriate time slices for acquiring such data.  For
example, the brain scanner that I worked on (NeuroScience Inc. see the PBS
show called the Brain) showed that there were two responses from the brain
to a light or pattern shown to a patient.  The first response was at the
Occipital (sp?) lobe at the base of the skull, and the second was in the
cognitive part of the brain.  All of this action took place within 120
microseconds (first reponse to second response).  This is what makes EEGs
work.

I do agree that you need external hardware to get that degree of accuracy.
The NeuroScience machine had 32 A/D converters monitored by over a half
dozen 6809s, which reported the samples back to a master 68000 controller.
It took a lot of clock cycle counting and all, but it took only 10 micro-
seconds/byte to do a PIA type transfer between a 6809 and a 68000.