In the example above, the 8.2i version of the project is backed up before migration to the 9.1i project file format. This backup file can be used to open the project in 8.2i or can be migrated again to the 9.1i file format by opening in Project Navigator 8.2i However, project changes made after project file migration are not recoverable from the backed-up version of the 8.2i project file.
To avoid unintentionally opening ISE 9.1i projects in ISE 8.2i, the "Always Open Last Project" project option should be turned off in ISE 8.2i (Edit -> Preferences -> ISE General).
A fix added in ISE 9.1i SP1 prevents ISE 9.1.01i project files from being corrupted by previous software versions. With the fix, if an older version attempts to open the 9.1.01i project, the .ise file becomes READ ONLY to prevent corruption by the older version. The READ ONLY permission needs to be manually changed before the project can be opened again with a valid software version (i.e. ISE 9.1.01i).
This problem has been fixed in the latest 9.1i Service Pack available at:
http://www.xilinx.com/xlnx/xil_sw_updates_home.jspThe first service pack containing the fix is 9.1i Service Pack 1.