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'Two or more PICS sharing one memory'
1998\11\28@141309 by Spk41q

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Hello,

Is it possible that 2 or more PIC share one memory?

Perhaps using I2C ?

I think about an aplication needing that :
-one pic is master - rights to write and read and have priority
-others PICS are slave just read. no priority

Every things on this subject (pointers, code, opinion...) will be useful.

Have a nice day
Dan

1998\11\28@141935 by Goovaerts

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face
Hi, I have to do the same thing. I have to use a PIC16C63 to communicate
between a PC and a fully implemented I2C-bus with many slaves. It all comes
down on : protocolconvertor RS232-I2C. So if you know anything or get
something could you forward it to me please. I'll do the same.

Greetings from Glenn Goovaerts

Let me know something !!!

{Original Message removed}

1998\11\28@165516 by Mark Willis

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face
Spk41q@AOL.COM wrote:
>
> Hello,
>
> Is it possible that 2 or more PIC share one memory?
>
> Perhaps using I2C ?
>
> I think about an aplication needing that :
> -one pic is master - rights to write and read and have priority
> -others PICS are slave just read. no priority
>
> Every things on this subject (pointers, code, opinion...) will be useful.
>
> Have a nice day
> Dan

 There's such a thing as dual ported RAM (usually used with dual
processor micros), doubt you want to play with that here though <G>  It
involves a lot more pins than the 24C series SEEProms!

 What I'm doing on our current project is a redesign for 3 PICs, 1
handles keyboard tasks, 1 handles memory processing, 1 handles interface
to the rest of the world.  You just issue a command to the PIC that
handles the memory, "Look this up", and wait for results.  We chose to
just use 16F84's for ease of re-programming for now (Could do it all
with 1 16C66 but costs are about the same, either way, this way lets me
use the exact same core later for another project - just re-program the
keyboard tasks PIC to handle a different keyboard, everything else is
the same.  And easier for others to program 16F84's - this'll be GPL'ed
once it's done.)

 Just in the start of complete re-design (Lost one PCMCIA hard drive,
so I'll just re-do with what I know now!) - Should find the HD later.
Frustrating, though.  Sure slows me down!

 Mark, spam_OUTmwillisTakeThisOuTspamnwlink.com

1998\11\28@184627 by Gerhard Fiedler

picon face
Spk41q@AOL.COM wrote:
> Is it possible that 2 or more PIC share one memory?
>
> Perhaps using I2C ?
>
> I think about an aplication needing that :
> -one pic is master - rights to write and read and have priority
> -others PICS are slave just read. no priority

with i2c ram (or eeprom, if you're writing relatively rarely) that's
possible -- i don't know any i2c rams off the top of my head, though. but
in order to read from (or write to) the i2c memory, each pic has to be the
master for that instance. bus arbitration between different masters on i2c
is not according to some priority, it is according to whoever happens to be
first, or, if concurrent, to be high on sda when another master goes low
(the high one looses).

ge

1998\11\29@144809 by uter van ooijen / floortje hanneman

picon face
> Is it possible that 2 or more PIC share one memory?
NO

At least not for any PIC I known off.
But you could program each PIC to adhere to some master-slave protocol.
I2C seems a bad choice because implementing i2c slave behaviour is very
difficult.

regards,
Wouter.

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