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Re: leave unconnected pins open?
It is possible to leave inputs unconnected, but it is not recommended
since it may increase the susceptibility for ESD, and it may lead to
marginally higher power consumption too. Plain inputs that are not used
can be connected directly to GND or to Vdd (GND is recommended over Vdd
if you don't care about the value on the input). They can alternatively be
connected via pull-up or pull-down resistors. Suitable values for pull-up
and pull-down are between 2 kOhm and 40 kOhm.
If you connect directly to Vdd, use the same Vdd as for the ETRAX 100LX
itself for maximum reliability. With pull up resistors this is less
For the bidirectional signals I think the best idea is to leave them
open and to try to set them as outputs via SW. The other alternative
is to use pull-up or pull-down resistors. Never connect bidirectional
pins directly to Vdd of GND even if they are inputs in your configuration.
You can never be really sure there aren't SW bugs that will turn them on.
On Tue, 3 Dec 2002, Alex Raimondi wrote:
> What should I do with unused pins such as gXX_in, rxd1(T17), cts1 (V19) and
> other gXX (shared in-/output) ports? Can we leave them unconnected or should
> we pull them up by external pullup resistor?