David VanHorn <PICLIST@mitvma.mit.edu> wrote:

> this borders on a religious flamewar, ....

    Yeah, but I'm going to jump in and stir the pot, anyway.

> I would generally agree, set [unused IO pins] as outputs, and leave
> them untied, or add a series resistor to ground, and make them
> output low.

    The problem with making them open outputs is that they'll be
    FLOATING INPUTS during power-on reset and before your firmware
    configures them as outputs.

    Anyone who refuses to tie unused pins to ground should be even more
    worried about leaving the pins open; it seems much more likely that a
    floating input pin will latchup than a tied-low input pin will
    magically become a high-driving output.

    The safest way, of course -- and the most expensive -- is the
    other one you suggested:  Tie the unused pins to ground through
    a resistor.

    -Andy

=== Andrew Warren -- aiw@cypress.com
=== Principal Design Engineer
=== Cypress Semiconductor Corporation
===
=== Opinions expressed above do not
=== necessarily represent those of
=== Cypress Semiconductor Corporation

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