> I am trying to avoing the adding of a pull-up.  Till now, the pin had no
> purpose.  It is not connected to any circuitry except for a header.  Now I
> want to use that pin as an input to allow the user to select a setting (by
> shorting or not shorting the header to power or ground.
>

Shawn,
one thing i frequently use in such situations, even in greater volumes and
without any problems is the following. If the port is totally tristate and
can only be shorted to ground by a jumper, i use the pin and pcb capacity to
examine the jumpers position with this few steps:

1. Have the pin configured as an output and leave it cleared all the time.
2. To read the pin set it to high and configure it as an input within two
consecutive steps.
    Usually you drive current out of the pin for just 2 cycles that way.
3. If open, the pin reads high for AT LEAST 10 to 20 cycles at 4MHz., if
shorted it reads low     just the very next instruction.
You can use a scope to examine the decay time when open. Its pretty slow.

This method is not an idea, it is actually in use on lots of different
series production boards.

Germain Morbe

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