[sdiy] Simplest random source

[Scott Gravenhorst]

See

http://home1.gte.net/res0658s/xapp052.pdf

A Xylinx PDF detailing much of this.  On page 5 you will see a chart that has feedback points for
shift registers up to 168 bits.

Get it while it's there, I can't leave it there permanently.

Seb Francis <seb at is-uk.com> wrote:
>Hi Magnus,
>
>I couldn't find too much in the archives ..
>http://www.buchi.de/sdiy/Search1.ASP?914
>
>And a search on google for PRBS didn't help me too much either. 
>But I am interested if you can give me a link to a schematic or 
>algorithm. Magnus Danielson wrote: > If you look way back in 
>time, you will be able to find a thread about random > generators 
>and there I posted PRBS generator polynoms all the way up to 64 
>bits > of length. You will also find me arguing for the use of 
>longer polynomial > lengths. Inside a PIC, AVR or anything like 
>it, there is no excuse not to use > up the hardware better and go 
>for a long polynomial. The question for me would be how many 
>instructions does it take to get a 16bit 'random-enough' number. 
>> You get both cycletimes > beyond lifetime of the apparatous and 
>thick noise-spectrum, which you do want > That comes hand-in-hand 
>when you go for the longer polynoms. a 64 bit polynom > requires 
>only 8 byte of storage and we're still only talking one or two 
>XOR > gates, so processing is still fairly simple. > The 
>previously posted algorithm should be an exact replica of this 
>circuit: 
>http://www.analog-synth.de/synths/mod2/trigdiv/dig_noise.gif Now 
>this looks very much to me like a long shift register with some 

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