Do your boards have serial numbers, and (if so) does the software have
knowledge of that serial number?  If so you could base a startup-delay
on, say, the last digit of the serial number, giving you ten different
delays (just for example).

Tony Pan wrote:
>
> Mike,
>
> I guess it's more economic to do it in software rather than in hardware.
> (It's a commercial product.)
>
> It 's OK to allow a handful of boards to start at the same time. What we
> want to avoid is that all the boards (20, 30 or more) to start at the same
> time.
>
> Tony
>
> ----- Original Message -----
> From: "Dipperstein, Michael" <mdippers@HARRIS.COM>
> To: <PICLIST@MITVMA.MIT.EDU>
> Sent: Thursday, August 16, 2001 1:26 PM
> Subject: Re: [PIC]: Generating a "truly" random number on the application of
> power
>
> > Why not just delay the application of power to each board?  If you have a
> > control pin to spare, you can build a system that where it's the job of
> each
> > board to allow power to flow to the next.
> >
> > In any random number scheme, you still have the possibility that all
> generators
> > will generate the same number and come up at the same time.  This can't
> happen
> > when it's the job of one board to apply power to the next.
> >
> > -Mike
> >
> >
> > -----Original Message-----
> > From: Tony Pan [mailto:weidong.pan@verizon.net]
> > Sent: Tuesday, August 14, 2001 10:18 AM
> > To: PICLIST@mitvma.mit.edu
> > Subject: [PIC]: Generating a "truly" random number on the application of
> > power
> >
> >
> > 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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