The following error occurs when I load a design in ModelSim (VSIM):
"# ** Fatal: ERROR: Obsolete library format for design unit (see above)
# Time: 0 ps Iteration: 0 Region: /
# FATAL ERROR while loading design."
This error occurs if the simulation libraries or your design files are compiled with an older version of ModelSim and are now being loaded into a newer version. For example, if your design was compiled using ModelSim 5.4e and is then loaded (VSIM) using ModelSim 5.5, this error occurs.
To prevent this error, recompile the files using the latest version of ModelSim. Please refer to (Xilinx Answer 2561) on how to compile libraries for ModelSim.
This problem can also be fixed by finding the library that is obsolete and right-clicking that library from the left-hand window (library pane). When right-clicking the selected library, you will find that one of the options is to refresh.
Click the refresh option. This should start to refresh the library, and this error should not occur.
NOTE: You will need write permission to the folder where this library resides, or the refresh will error out, stating that it could not write to there.