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    Date: Mon, 18 Oct 1999  20:17:26
    From: "Nikolai Golovchenko" <golovchenko@mail.ru>
      To: "pic microcontroller discussion list" <PICLIST@MITVMA.MIT.EDU>
 Subject: Re:      12c508 "random delay"
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Hi Kev.

>I need to generate a "random" delay between 0.5 and 10 second using 12c508
>int osc, prescaled at whatever!


I think that you need an n-bit random number generator that would satisfy
the number of steps in the interval. Here is an 8-bit example (sorry, no
code). I came across it somewhere in TI's MSP430 application notes some time
ago.

rnd(n) = rnd(n-1)*mult+inc

n - iteration number
rnd(0)= 123 - seed number
mult = 221 - multiplier
inc = 53 - prime number


(I modeled this in MATLAB. Looks ok)

Note, that result may be greater than 8 bit. Just leave only lower 8 bits.

This will generate pseudo-random sequence. Addition is not a problem.
Multiplication too can be found in Microchip's apps.

Bye.