> Another thing - are RB6 and RB7 both low when MCLR is raised to VPP.
> This must occur for the chip to enter programming mode.

I believe so.  I checked this with my POS scope, and it sure looks like
they are both held low while MCLR is raised to VPP.

(The pattern I get on my scope shows the state of RB6/RB7 starting about 5
uSec AFTER MCLR is raised to VPP.  At this point onward  (for at least a
few hundred uSec) RB6/RB7 are both low...Since the scope doesn't display
what happens until after the trigger condition (MCLR being raised to
VPP) it's hard to be *absolutely* certain that RB6 and RB7 stay low the
entire time (before, during, and slightly after MCLR is raised to Vpp))

Having said all that, I thin it's pretty darned likey.  They are low
before Vpp is applied, and they are low shortly after Vpp is applied, so
unless they are raised very briefly before Vpp is applied, and then
brought back low immediately afterwards....well, you get the point.


> As another simple test, you can tie RB6/7 to GND, apply 5V while MCLR is
> tied low via a 22K resistor. See if the chip gets hot after awhile. If
> it does, I would say the chip is faulty.
>
> If not, apply 12~13V to MCLR and now see if the chip gets hot. Better
> yet, use a multimeter to measure the current going into MCLR. It should
> be in the order of microamps. If you measure a high current which would
> be causing the heating, then the chip is faulty.

I will try this.

> If the high voltage caused the problem, then the chips are most likely
> dead by now anyway.

Yes, that's one thing I'm afraid of.  I can't be certian about my chips at
this point.  Hard to test.

Thanks again for the help.

-Steve

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