At 05:46 PM 8/30/01 +0100, you wrote:

>I think it has more to do with driving the programming circuitry when it
>should not. Consider that under programming conditions you have 13V on this
>pin, i.e. 8V higher than Vcc. Now if you have 5V on this pin due to large
>capacitor, and no other supply to the chip, what is happening inside the
>programming enable circuitry? I suspect some large currents can flow because
>devices are not biased correctly and things get destroyed in the manner
>described by someone else.

They don't say anything about a capacitor.. here's the exact quote:

>Voltage spikes below VSS at the MCLR pin, inducing currents greater than
>80 mA, may cause latch-up. Thus, a series resistor of 50-100 should be used
>when applying a  low  level to the MCLR pin, rather than pulling this pin
>directly to VSS.

They are concerned about undershoot. Why /MCLR, since every pin should be
similarly sensitive to latchup due to undershoot? Maybe that's your
programming circuitry - connected by long wires to the in-circuit
programmer. It still doesn't explain it completely, because the other
pins should be similarly sensitive and require similar resistors.

Best regards,

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