--- On Thu, 18/3/10, Matias Vidoni <matiasvidoni@gmail.com> wrote:

> @Peter
> The 16F877 has 2 pairs of voltage inputs. I mean, there are
> two pins
> labeled VDD and 2 pins VSS.
> Should I connect both pairs? Now they are connected. But in
> first
> place they not.

YES, both sets of Vdd and Vss pins MUST be connected to the supply and to ground.  Both Vdd pins need decoupling capacitors connected close to the pins and going to a to a good low impedance ground point.

Not connecting and decoupling the second set of supply pins was most likely the thing that caused your resetting problems.

PeterO




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