On Mon, 2 Jun 2003, Olin Lathrop wrote:

> >> Because it's a special pin that can also be MCLR, but more importantly
> >> Vpp.
> >
> > Yes, exactly like the 12CE67x and a few others, many of which are
> > equipped with WPU.  So my question still stands...
>
> But do these, or any PIC for that matter, have a passive pullup that can
> be enabled on the Vpp pin?  I rather doubt it because these passive
> pullups are really P channel FETs with deliberately high on resistance.
> These would have to be connected between Vdd and the pin, which presents
> problems if the pin could be raised to 8V above Vdd.

The 12CE67x chips have a GP3/MCLR/Vpp pin just like the 12F629/675, and
yes they do have an internal active weak pull-up exactly like the others.
It's disabled if you have the pin configured as MCLR.  Page 28 of the
12C67X data sheet shows the equivalent circuit for the pin.  And I've used
them, so yes, the WPU does work for GP3 on those devices.  That's why I
can't figure out why they'd leave it off the '629/675.

Dale
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