Internal Error: Sub-system: GIOQ, File: /quartus/edt/gioq/gioq_port.cpp, Line: 696

Description

Due to a problem in the Quartus® II software version 13.1 and earlier, you may see this error when you double click on any port connection wire in a Block Design File (.bdf).

Resolution

To work around this problem, edit the port by double clicking on the port text to rather than the wire. 

This problem is scheduled to be fixed in a future release of the Quartus II software.