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AR# 15122

5.1i ISE - The default value for "Unused IOB pins" is "Pull-up" (It should be "Pull-down")


Keywords: 4.2i, 5.1i, ISE, default, pull-up, pullup, pull-down, pulldown, unused, IOB, pin, I/O, IO, GUI, UnusedPIN

Urgency: Standard

General Description:
The default value for "Unused IOB pins" under Configuration Options in the 4.2i and 5.1i ISE software GUI is "Pull-up". However, the Xilinx online software manuals state that "the default setting for unused pins is Pull-down."

(This information is presented in the BitGen chapter (Chapter 13) of the Development System Reference Guide, available at:


If BitGen is run from a command line, the default value for "Unused IOB pins" (-g UnusedPin) is "Pull-down". The default value for "Unused IOB pins" in the 4.2i and 5.1i ISE GUIs should be changed to "Pull-down".

This will be changed in the 6.1i software release; until then, manually change the property to the desired value for your current project.
AR# 15122
Date Created 07/12/2002
Last Updated 01/08/2003
Status Archive
Type General Article