What happens to the unused I/O pins on Spartan-3/-3E devices after configuration?
By default, unused I/O pins exhibit high impedance with an internal pull-down enabled. The value of the pull-down depends on VCCO. The pull-down range is denoted by the IRPD parameter in the Spartan-3/-3E Data Sheet.
The Spartan-3 DC and Swtiching Characteristic Data Sheet is located at:
The Spartan-3E DC and Swtiching Characteristic Data Sheet is located at:
You can use the following BitGen option to set the state of unused I/O:
bitgen -g Unusedpin:Pullup
For a list of BitGen options available for Spartan devices, enter the following:
bitgen -h spartan3
bitgen -h spartan3e
- The first value listed is the default value. For example, "Pulldown" is the default value of "UnusedPin option: UnusedPin Pulldown, Pullup, Pullnone."
- Replace "spartan3" with appropriate device architecture if necessary.
- You can also specify the Unused IOB Pins value in the Generate Programming File Properties -> Configuration Options inside of Project Navigator.