> However, just how robust is this?  I know, someplace I've seen and used dual voltage translators where you can have two independant Vcc and thus go
> from 5V to 3V (not 3.3) 
I have used one in the past too but I don't remember the part number 
offhand (and I don't have access to the machine with the designs on 
right now) sorry.

If your lines aren't bidirectional you can also use ordinary logic of 
certain families (this is a particularlly usefull trick if you already 
need a bit of glue logic). 74HCT chips work well for upconverting and 
any 3.3V family with 5V tollerant inputs will work for downconverting.
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