Description
Due to a problem in the Quartus® II software version 11.1 and later, you may see this internal error if you have assigned an I/O an invalid value for the OUTPUT_IO_TIMING_NEAR_END_VMEAS or OUTPUT_IO_TIMING_FAR_END_VMEAS settings.
Resolution
To work around this problem, correct the assignment. Legal values for these settings are "HALF VCCIO", "HALF SIGNAL SWING", or numeric value.
Future releases of the Quartus II software are scheduled to report an explanatory message for this illegal assignment.