Depending on the design phase, flight time can be accessed from two different sources.
Case 1 - NCD File Available:
The Timing Analyzer / Trce reports (.twx or .twr files) generated by ISE (post-PAR), incorporate the flight times information in the I/O path analysis.
However, it is only used for flip-chip packages.
Note: To disable this feature set the following environment variable: XIL_NO_FLIGHT to 1
Case 2 - No NCD file Available:For pre-design situations or for performing rough estimates on total IO path delays, the package trace lengths for each I/O through the Flip-Chip package are provided in the readable ASCII package files (.pkg file generated by
partgen). The package files can be generated for all Flip-Chip packages for specific devices by running the following command from a ISE Design Suite Command prompt, Linux, or Solaris GNU prompt sourcing the Xilinx install. Note that the TRACE length data is available only for Flip-Chip packages. The first version of ISE to carry this data is 7.1i s3.
Example:
> partgen -v xc4vlx15sf656
Estimating Flight Time using Trace Length
The above is an example for the xc4vlx15sf363 package. The output of this command is the ".pkg" file written to the directory that you run the command from. To convert the TRACE lengths to flight times, you can use a factor of 6.0 ps/mm (best case) or 7.1 ps/mm (worst case).
NoteIf the latest version ISE (partgen) reports ZERO flight time for a device-package combination, it is likely that the data is not yet fully characterized. A future version of ISE software is likely to have this data updated.
For further assistance, open a WebCase at:
http://support.xilinx.com/support/clearexpress/websupport.htm