Fatal Error: Segment Violation faulting address=(nil), PC=(nil): 0: - Fatal Error: Segment Violation faulting address=(nil), PC=(nil): 0: Description Due to an illegal RTL construct, you may see the above error message in the Intel® Quartus® Prime Pro Edition Software version 20.3 and later. This error happens during Synthesis when a System Verilog interface contains a localparam that is dependent on one of its parameters. For example: // Parameterized interface interface intf #( int unsigned WIDTH ) ( input logic data ); // localparam that depends on a parameter localparam DWIDTH = WIDTH; // modports that allow access to localparam modport mst ( input data, import DWIDTH ); modport slv ( input data, import DWIDTH ); Resolution Avoid "import" of "interface localparams" in " modport " description of System Verilog Interfaces. This RTL construct will display an error message beginning with version 22.1 of the Intel® Quartus® Prime Pro Edition Software. Custom Fields values: ['novalue'] Troubleshooting 14015499505 False ['novalue'] ['FPGA Dev Tools Quartus® Prime Software Pro'] 22.1 20.3 ['Programmable Logic Devices'] ['novalue'] ['novalue'] ['novalue']