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AR# 8272

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Virtex/-E/-II, Spartan-II - What happens to unused I/O pins after configuration?

Description


General Description:

What happens to the unused I/O pins on Virtex, Virtex-E, Virtex-II, and Spartan-II devices after configuration?

Solution


The unused pins are pulled down via an internal weak pull-down. The value of the pull-down is in the range of 50k-150k ohms.



If you require documentation, information is available in the Virtex data sheet under "Configuration."

http://www.xilinx.com/xlnx/xweb/xil_publications_index.jsp


The state of unused I/O can be set via the BitGen option:



bitgen -g Unusedpin:Pullup



For a list of BitGen options available for Virtex devices, type "bitgen -h virtex."



NOTES:

- Replace "virtex" with the appropriate device architecture if necessary.

- The first value listed is the default value. For example, "Pulldown" is the default value of "UnusedPin option: UnusedPin Pulldown, Pullup, Pullnone."

- 3.1i design tools do not list this option for "bitgen -h virtex" command. The option works for this device, but was missing from the command help information.



This is fixed in the 4.1i design tools release.



Unused PWRDNW or JTAG pins can be given an internal pull-up by setting the option in BitGen.
AR# 8272
Date 10/17/2011
Status Archive
Type General Article
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