If you give each unit a serial number in ROM you can use that to delay
the start.  Dallas makes tiny one wire interfaced chips that have serial
numbers in them that are guaranteed to be unique.

Sherpa Doug

> -----Original Message-----
> From: Nikolai Golovchenko [mailto:golovchenko@MAIL.RU]
> Sent: Thursday, August 16, 2001 1:45 PM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [PIC]: Generating a "truly" random number on the
> application of power
>
>
> Tony,
>
> You could try to use a few unitialized RAM locations. On power-up,
> they would probably contain random values. But the problem is that
> the compiler clears all registers on power-up, so the start-up
> routine should be modified, which might be tricky though...
>
>  Nikolai
>
> Tuesday, August 14, 2001, 10:17:59 AM, Tony Pan wrote:
> > Hi,
>
> > In our project, several identical boards are connected
> together. Normally,
> > on the application of power, they will be turned on at the
> same time and
> > starting running at the same time. But we don't want that
> to happen. If all
> > boards are running at the same time, they will consume too
> much power and
> > cause a problem.
>
> > So, we want to impose a lockout time at the beginning of
> the software; the
> > lockout time should be random for each board (though they
> use the same
> > software). Only after the lockout time expires would the
> program start
> > running. Thus the boards will start at different time and
> won't cause a
> > power shortage.
>
> > My question is: how to generate a "truly" random number on
> the application
> > of power. The number should not be determined upon the
> compilation of the
> > software, but should be upon the initial powerup of the
> chip. (Or, it should
> > be determine by each individual chip.)
>
> > Help?
>
> > (By the way, I write my program in C and use PICC compiler.)
>
> > Thanks in advance.
>
> > Tony Pan
>
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