>> Pullups on Vdd and Vss are either pointless or not recommended.
>> Other pins depend on the application.

> I'd have to slightly disagree there Olin. I used a pull-up on Vss
> just a couple of days ago. Short of the usual 8V plug-pack for
> my CD's mains adapter, I had to use an unregulated 9V plug-
> pack (which floats unloaded at 14V) with a 47R pull-up from
> Vss to Vdd

You're hopelessly wrong there !!!

When measured relative to earth (local or terra firma varieties) odds 
are that Vss essentially didn't budge when you applied the resistor*. 
But, in the same reference frame,  the Vdd voltage fell, which was 
what you desired it to do. So clearly what you had was a pulldown on 
Vdd. Olin was (commendably) mute on the subject of pulldowns.

How can you expect the beginners to get it right when you use such 
sloppy descriptions ?


        R




And just in case anyone has any doubt:


                :-)



* Kelvin sensing assumed, naturally. 

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