Hi Richard,


On Fri, 14 Aug 1998, Richard A. Smith wrote:

> >circuits, it might cause problems, but I have been an electronics hobbist
> >in earnest for about 6 years, have played with lots of chips from many
> >logic families, and I have never had any problem with a circuit that was
> >cured by tieing an unused input! Have I just had good luck? Or, is this
> >similar to other's experience as well?
>
> I have had a 68HC11 that this was exactly the problem.  Pullups on the unused
ports fixed it.

Was the CPU watching the state of these inputs in any way? Is it capable
of causing an interrupt depending on the state of these pins?  I could
see how a floating input could cause a metastable state, but if the rest
of the circuitry on the IC is not dependent on the state of the pin, I
don't see how it could cause major problems.

Sean


>
> --
> Richard A. Smith                         Bitworks, Inc.
> rsmith@bitworks.com               501.521.3908
> Sr. Design Engineer        http://www.bitworks.com
>