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On Wed, 19 Mar 2008, Wappler Marcel wrote: > Bodo Eggert wrote: > >> I have found this requirement in the SD host controller spec: > >> "The card detect is active regardless of the SD Bus Power." > >> > >> I wonder how the card should be able to pull up the CD/DAT3 Pad to > >> VCC if its only VCC pad is not connected to VCC due to the fact that > >> the host controller has switched off the cards power - any idea how > >> this could be managed? > > > If the VCC pin is connected to 0 V, the "pullup" will pull > > down to 0V. > > If the controller reverses it's logic while VCC=0, it might work. > > I am concerned that in this case there would be neither a pull > up nor a pull down at this signal. Due to floating gates that input > could lead to millions of "card detection" events a second, if As long as no card is inserted, the pin on the controller would be floating and generating the same amount of interrupts, unless there is a (weak) internal pulldown. You can do the same for the reversed logic, using an internal pullup and abusing the card's pullup as a pulldown. -- Never forget that your weapon is made by the lowest bidder. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | |||||||||
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