08-23-2018 02:21 AM
In our Spartan 6 LX45 based design, we have one IO pin that is physically routed on the board but was never used.
Since it was never used (though physically routed or you can say in a "floating" condition), this pin was not defined in the UCF file.
I'm just wandering if this setup can cause problems in the long run. If so, what is the proper way to handle this unused pin.
I'm asking because the board in question was initially working since last year.
But now suddenly the board started failing and we traced the cause to a short between this unused pin and another pin located some distance apart with this unused pin in the package. We don't know what caused the short between these pins and how it happened.
But I'm just wandering if the cause of the issue could be this unused pin left "floating". Please advise.
08-23-2018 02:35 AM
In addition to the above, we have a 20K pull-up to 3.3V on this unused IO pin (not declared in UCF file).
08-27-2018 02:47 AM
if you have a pull up to 3.3V then i would leave this pin floating as the pull up will handle it.