There is a way for slaves to announce their presence on the bus by providing a 
presence pulse when
they are powered up. I'm not sure if all slaves to this or just some (or all) 
of the iButtons. Also
I don't know which masters or software supports this, it is mainly used for 
things like door lock
systems where the iButton is used as the security FOB.

> That's pretty weird. That'd kill any communication initiated by the
> master that is taking place when the iButton is powered up.
>
> Not saying I don't believe you, especially since I have no experience
> with these devices, but I'm tempted to order a sample just to further my
> knowledge of the protocol (and a possible extension to it like the one
> being discussed) ;-)
>
> Cheers,
>
> Eloy Paris.-
>
Yes it is rather strange that they allow it. After this thread started the 
other day I did a Google 
search and found a few references in some Maxim documents and they talked about 
a communication 
failure because of a presence pulse arriving at the wrong time.

Eric

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