Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!mcsun!ukc!slxsys!stevem
From: stevem@specialix.co.uk (Steven Murray)
Newsgroups: sci.electronics
Subject: Pseudo-random numbers
Keywords: PRBS,m-sequence,random
Message-ID: <1991Mar27.101754.5326@specialix.co.uk>
Date: 27 Mar 91 10:17:54 GMT
Distribution: sci
Organization: Specialix International, London
Lines: 25


     'Pseudo-Random Binary Sequences', sometimes known as 
'm-sequences' and the basis for random number generation in some
electronic and software products, are produced by a 'shift-register'
where the input to the shift-register is an X-OR of some of the
shift-register outputs (usually called taps).  At each clock of
the shift-register, a new bit of 'pseudo-random' sequence is
generated at the XOR outupt.  The only danger is that the S/R
must not be allowed to power up in the 'all-zero's' condition -
because it will never change - and that the correct Taps are used.

There's the rub, has anyone got a definitive list of PRBS taps?
I saw one in a book once - a reference text - but didn't copy it.
The length of the PRBS sequence with proper taps ('maximal length')
is normally (2^n)-1, where n is the number of S/R bits - without
getting greedy, I saw taps for a 33 bit SR once - has anyone got
the taps for anything longer?

Regards,
Steven Murray
-- 
Steven Murray
uunet!slxsys!stevem  stevem@specialix.co.uk
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