Hi all,

Thank you so much for all the inputs and good suggestions!

Our products are used in motel environments to control ACs. The reason we
need to stagger the startup is that if we don't, in case of power loss and
resume, all the AC will start at the same time and that will cause a
problem. As you know each board is situated in its room and working
independently so there is no way one board knows what the other's doing.

After I read all the replies, I think I will try this:

In my hardware we use RC oscillator. Now I use the initial TMR0 value upon
powerup to get a random number. I also add the initial values of FSR, ADRES,
PORTB and some ADC reads of the board into the number. I guess that would
give me nearly "unique" number for each board. I then use the last few bits
of this number to determine the startup time.

I haven't got the chance to test it yet. For we have other features to
implement at the moment. If you see any potential problems with this
approach, please let me know.

Thanks alot!

Tony



----- Original Message -----
From: "Douglas Butler" <dbutler@IMETRIX.COM>
To: <PICLIST@MITVMA.MIT.EDU>
Sent: Tuesday, August 21, 2001 8:58 AM
Subject: Re: [PIC]: Generating a "truly" random number on the application of
power


> I believe at the beginning of the thread it was mentioned that he
> doesn't have any extra lines running between boards.
>
> Sherpa Doug
>
> > -----Original Message-----
> > From: Thomas McGahee [mailto:tom_mcgahee@SIGMAIS.COM]
> > Sent: Monday, August 20, 2001 7:43 PM
> > To: PICLIST@MITVMA.MIT.EDU
> > Subject: Re: [PIC]: Generating a "truly" random number on the
> > application of power
> >
> >
> > You don't really need a random number generator to accomplish
> > what you want, which is to prevent all pics from coming
> > up at once. What you DO need is two free i/o lines per pic.
> > Let's call these line IN and OUT. The IN of the first PIC is
> > connected to Ground. The OUT of the first pic connects to the
> > IN of the second pic. The OUT of the second pic connects to
> > the IN of the third pic. Continue this procedure of connecting
> > the IN and OUT connections for each succeeding pic.
>
> --
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>
>

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