Path: utzoo!attcan!uunet!lll-winken!ames!oliveb!sun!pepper!cmcmanis
From: cmcmanis%pepper@Sun.COM (Chuck McManis)
Newsgroups: comp.sys.amiga
Subject: Re: Amiga Oscilloscope
Message-ID: <87296@sun.uucp>
Date: 27 Jan 89 20:15:58 GMT
References: <8914@bloom-beacon.MIT.EDU> <8947@bloom-beacon.MIT.EDU>
Sender: news@sun.uucp
Reply-To: cmcmanis@sun.UUCP (Chuck McManis)
Organization: Sun Microsystems, Mountain View
Lines: 31

In article <8947@bloom-beacon.MIT.EDU> (Jim Reich) writes:
>Just out of curiosity, does anyone out there know how to make a reasonably
>fast computer 'oscilloscope'?  Even with an immensely fast DAC, I wonder what
>a 7Mhz computer can do as for as processing nanosecond data, which would
>be necessary to debug something like, say, a 7MHz computer...  Can even the
>mighty blitter sling around data that fast?
>
>						-- Jim

Yes, the way you build one is similar to the way you build Image processing
cards :-). Get a good 12bit flash ADC (maybe two) and mount them with the
front end circuitry (impedence matchers and isolation circuits) on a board
with a nice signal processor such as an 56001 or 34010. Now, the sample 
circuit runs at say 50Mhz for good samples in the 25Mhz range and good
viewing of periodic waves up to about 100Mhz.You buffer the sample memory. 
With each buffer being roughly 1K X 12 since that would cover a screen 
left to right in samples even with a A2024 monitor. Now the sample speed 
is on the order of 20ns per sample so you know the front end of this this 
will either be Cypress CMOS or 10K ECL. You can get 1K x 4 Static RAMs
that will take data this fast. Actually with a decent signal processor
you can run the whole system of the 50Mhz clock. Now the signal processors
job is to scale the samples and in the pulse case dump them into display
ram, when reading periodic samples it would probably be averaging them as
well. The Amiga program would open a screen, pass a point to it's bitmap
to the Digital oscilloscope board which would then dump it's data into 
that memory area. The rest is all fancy software. Adjusting the sample
frequency, setting up trigger's versus continuous samples etc. 

--Chuck McManis
uucp: {anywhere}!sun!cmcmanis   BIX: cmcmanis  ARPAnet: cmcmanis@sun.com
These opinions are my own and no one elses, but you knew that didn't you.