What value is your pot?  The port pins can only source 20ma, and sink 25ma.
 They are much better at sinking than sourcing as can be seen by the given
 current spec.  Is there any particular reason why they need to be driven
 from the port pins?  ie couldnt you tie one end to vcc and have the other
 end connected to a port pin.  Then make the port pin an output and drive
 it low.  And with the other two pins set as outputs, I'm not sure that the
 device would see that as HiZ.  If it were me, I'd make the other two pins
 inputs.  Then the other pot would definitely see HiZ.

 Anyway, these are the questions and suggestions I have.

                                                Good Luck and Regards,

                                                        Jim



> Ran into a strange problem, that might be explained away, but not sure
> yet since I am still investigating it.
>
> 16F877 is the chip, using 4 bits of a port, each pair tied to a pot,
> and the centertap of each pot tied togeher and then to the analog input
> port.
>
> I measured the voltage on a port with the bit set, and it was about
> 4.95 volts. Problem is across the pot it only measures 4.75 when its
> attached to the two pins (bsf on one, bcf on the other).  I have the
> other two bits for the other pot set as outputs so should be hi-Z as
> seen by the device.
>
> I haven't yet isolated the other pot, but wonder if there is some
> leakage currents going on that cause the current output to exceed the
> limits of the chip and thus limit the output voltage?  Or what can
> cause the voltage to change like this.  Seems to be load dependant, but
> not sure yet...
>
>
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