> On Fri, Feb 22, 2002 at 10:31:32PM -0800, andre abelian wrote:
> > Sherpa,
> >
> > Thanks for your replay,
> > I have max1482 chips that I can use.
> > A few things are not clear for me lets assume
> > I got 30 slaves and 1 master if 2 slaves try to
> > Communicate with master at the same time then what will happen?
>
> That doesn't happen by definition. The primary node directs the
secondaries
> as to when they may communicate. So if one secondary has been granted
> access to the line, the others will not communcate on that line until
directed
> to do so.

By who's definition? There is nothing in the RS-485 spec that prevents that.
The spec says that multiple transmitters will not destroy each other by
attempting to send at the same time, it does not say you can't do it. It's
up to your implementation to watch out for that happening, usually by
monitoring the output and comparing with the input, then retrying after a
random delay, as in Ethernet collision detection or else by assigning a
transmit window to each node.

/\/\/\/*=Martin

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