> > Anyone considered their solution would employ more
> > than one PIC, and as a result have any observations
> > to offer ?
> >
>
> I considered it in a recent project, but ended up with
> a single PIC.
>
> The application would have needed some transfer of
> data between the 2 PICs. It soon became apparent that
> they were going to spend more time handing the data
> transfer than they were on their primary task.
>
> So instead of 2 C84s, I went for a single C73.
>
> Synergy does not apply to multi-processor systems. You
> always end up with less than the sum of the parts
> because of the overhead of sharing data.

>  I've also been toying with the idea. At the moment all
> the IO routines take up a hefty chunk of ROM space. I
> already have some E2 memory hooked up, so by writing
> I2C slave routines for a 12000, I should be able to
> move all the I/O out of the main chip.

>  Of course, adding more I/O would be rather simple then.
>  Has anybody tried this?

Hey, I do it all the time!  I'm not shy about throwing in more than
one PIC at a project... especially if it is a one-off product.   I've
used this technique in a piece some testgear where I had to log the
timing sequences of 200 inputs from mine detonators.  I have also
used it in another product where a separate PIC would drive my seven
segment LED display and handle the BCD to 7segment conversion and
another product where I controlled my LCD, keypad, RF modem and I/O
all with different PICS and connected uo through a custom serial
protocol.  This nicely isolates each part of the design as a separate
project, and makes designing much simpler.

I also used the technique in another product which I designed for a
company that installs security doors for banks.  The wanted a
constroller that would allow only one person in or out at a time and
also had some remote control as well.  A total of about 36 I/O pins
was required, so  I used two PIC16C55's in this design which is
currently still being used in the doors of a major bank group all
over South Africa.

Even my latest product, a variometer and thermal snooper combination
also uses two PICS.  This allows my to build three models of the same
product on the same PCB.  A Variometer only, a Snooper only and a
Vario/Snooper combination.  I would not have had enough RAM in only
one PIC to implement both funtions in just one.

With the low price of PICS it certainly makes sense to use more than
one of them in a design if space permits.   You can even share a
common clock between them if you want, but I usually don't.

Rgds
Werner









--
Werner Terreblanche     http://www.aztec.co.za/users/werner
wterreb@plessey.co.za (work)  OR  werner@aztec.co.za  (home)
Plessey SA, PO Box 30451,Tokai 7966, Cape Town, South Africa
or at home : Suite 251, PostNet X5061, Stellenbosch, 7599
Tel +27 21 7102251  Fax +27 21 7102886  Home +27 21 8872196
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