Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!srhqla!demott!kdq
From: kdq@demott.COM (Kevin D. Quitt)
Newsgroups: comp.sys.ibm.pc.hardware
Subject: Re: Hardware random bit generator needed
Message-ID: <682@demott.COM>
Date: 5 Oct 90 23:36:02 GMT
References: <1234@manta.NOSC.MIL>
Reply-To: kdq@demott.COM (Kevin D. Quitt)
Distribution: na
Organization: DeMott Electronics Co., Van Nuys CA
Lines: 26

In article <1234@manta.NOSC.MIL> psm@manta.NOSC.MIL (Scot Mcintosh) writes:
>I need a circuit to produce a random or pseudorandom
>bit stream that doesn't repeat until at least 2^32
>bits have gone by.

    If you need bytes, use a schmidt buffer with its output tied to its
input (makes a pretty good very-high speed unstable oscillator), and run
the output to the clock of a counter chip.  Since the counter will be
wrapping around so many times more often than you sample, and your
sampling is asynchronous to the oscillator, the output will effectively
random. 

    If you need a bit stream, you can feed the output into a flip-flop's
D, and issue a CLK whenever you want a bit.  Also pretty good.

    Another possibility is to use a cheap (i.e. noisy) transistor that's
forward biased, and let it amplify its own noise to act as the clock for
either of the above.

-- 
 _
Kevin D. Quitt         demott!kdq   kdq@demott.com
DeMott Electronics Co. 14707 Keswick St.   Van Nuys, CA 91405-1266
VOICE (818) 988-4975   FAX (818) 997-1190  MODEM (818) 997-4496 PEP last

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