On 6/16/2012 3:27 PM, Eloy Paris wrote: > Hi Phil, > > On 06/16/2012 07:43 AM, Phil White wrote: > >> On 13 June 2012 02:01, Eloy Paris<[email protected]> wrote: >> >>> All 1-Wire devices have this "presence pulse" feature that you mention >>> -- that's a fundamental part of the protocol, and all slave devices need >>> to generate a presence pulse right after they detect a reset pulse >>> generated by the master. >> My belief is that this statement is not correct - and it is this that >> has caused the confusion and prompted the original question. > I have no experience with the DS1990A and DS1990R, but after seeing your > comment that my statement above is incorrect, I read the datasheets for > both and I still see no indication of a slave that can act on its own, > i.e. without the master initiating communication first. A slave that can > do that (initiate communication on its own) would be speaking a protocol > different than 1-Wire, or a 1-Wire protocol extension that I have never > heard of. 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.
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