> I got 30 slaves and 1 master if 2 slaves try to
> Communicate with master at the same time then what will happen?

This will cause a runaway nuclear reaction in the driver chips and all life
as we know it will cease to exist.  Seriously, the data will all be mush and
none of it will get thru.  You have to guarantee this won't happen with the
higher levels of the protocol.  For example, a slave only sends when
requested to do so by the master, and the master makes sure only one slave
at a time is supposed to send.  You still have to deal with things screwing
up and getting out of sync.  I've done this on RS-485 by wrapping everything
into checksummed packets, timeout rules, etc.  I had such a system with an
embedded Pentium master controlling 15 PIC slaves.  Worked very nicely.


********************************************************************
Olin Lathrop, embedded systems consultant in Littleton Massachusetts
(978) 742-9014, olin@embedinc.com, http://www.embedinc.com

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