On Thu, 29 Aug 2002 17:37:21 -0300, you wrote:

>Hi,
>
>> 4 Input tied to ground.supply
>
>> 4 Is free BUT can cause bad problems if software is changed.
>
>    I would NEVER do that ! I have seen a product ( Thanks God it was =
not
>mine ! ) from a client that just blew 200 boards in a cold month because=
 of
>that !!!! It was poorly designed in every way I can think of and was =
very
>sensitive to EMI. The ports changed state from input to output and the =
chips
>just blew apart. I agree that if the other aspects of the design were =
better
>thought that should not happen often but I can't see any advantages of =
tying
>the pin to ground !!
>
>    Pull-ups or down are the best if you can afford it, if not just =
leave
>the ports as outputs. There is nothing to be gained by relying on the
>internal pullups or tying the pin to ground or VCC.

Have you ever designed complex single-layer PCBs ?=20

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