We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 22993

8.1i CPLDFit - Using the "Preserve unused I/O" option does not keep placeholder I/O from being removed from the design


My design contains several I/O that are unconnected. Since they are not used in the design, the CPLDFit tools optimize them out. I use the "Preserve Unused I/O" option, but these I/O continue to be optimized away. How do I keep these I/O from being removed from the design?


To work around this problem, place pin location constraints on these unused I/O. This, in combination with the "Preserve Unused I/O" option, will allow these I/O to be retained through implementation.

This application of the pin location constraints should not be required, and it will be corrected in a future software version.

AR# 22993
Date Created 09/04/2007
Last Updated 12/15/2012
Status Active
Type General Article