> If you use manual switches, sooner or later someone will forget
> one way or the other

Yeah, I'm not too keen on that idea either

It's not so much the powering up of the DB, it's about connecting
PIC DB pins to the data buss, especially if they connect before Vcc
is up. Current could go in the pin and out through the top diode.
That's why I thought the 74HC573 idea might be a goer

Good tip about the I2C BTW, that'll have to be taken care of in
the DB initialisation. The newly-insert DB will be functionally on
hold until the MB assigns it an ID. The MB will know via the PNP
system that it's there and will communicate with it when the I2C
is free. The whole I2C buss is on a 2 second timer base so there
should be no problem with priority or conflicts between devices

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