In ModelSim 6.6c, X's are seen in functional or timing simulation, and simulation fails to complete successfully.
There is a known issue in ModelSim 6.6c that is scheduled to be fixed in ModelSim 6.6e.
This issue can be worked around in ModelSim 6.6c in the following ways:
- When all the signals are dumped in the waveform (add list -r *)
- When all signals are logged by the simulator without displaying any extra signals in the waveform window (add log -r *)