At the bottom find the majority of my (and Jan-Erik's) previous
postings on this matter, for context.

As promised, I did a few experiments with a half-built
micropower board.  All that's on it right now is a PIC18F2320,
a micropower LDO regulator (TPS77001), necessary bypass
capactiors for other ICs yet to be populated, and a few other
passives which are not connected to anything yet.

In its "natural" state, i.e., as it is intended to operate, it pulls
(per my meter; I don't know how good the accuracy really is)
25 uA.  This is with PORTB all made into outputs and held
low.  With PORTB all as outputs and held high, the current
draw is 825 uA.  The only connection to any of these pins is
between RC7 and RB1, but RC7 is configured as an input,
so there SHOULD be no conflict.

With PORTB as inputs, and the internal pullups enabled,
the current draw is, you guessed it, 825 uA.  That value
doesn't change with respect to whether LATB is all high
or all low.

The datasheet tells me that at 5V, I should expect Ipu to
be not more than 400 uA.  Strange that it should be 800.
Perhaps it's due to the RC.7->RB.1 connection, but I 
don't see why, since the datasheet also tells me that
input leakage current is < 1uA.

Comments?

Mike H.

> > > > Not as I understood it.  As I understand it, the act of
> > > > flipping the
> > > > NOT_RBPU bit is to activate a circuit which connects a
> > > > weak resistor
> > > > between each pin of PORTB and the positive supply rail.  At
> > > > that point, the current the device is drawing goes up by ~200 uA.
> > >
> > > And where should the current go if the pin is unconnected (or held
> > > high) ?
> >
> > The same place current goes if you tie any other pin high through
> > an external pullup- through the logic.
> 
> Yes, **IF** that pin is an OUTPUT so it can source
> or sink any current !
> 
> But, for the weak pull-up to be enabled *at all*,
> the PIC pin must be an input, so there is noware for
> the current to go, is there ?
> 
> > There just isn't any current through the external pin.
> 
> And noware else either, AFAIK.
> 
> Jan-Erik.
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