Internal Error: Sub-system: FTITAN, File: /quartus/fitter/ftitan/ftitan_expert.cpp, Line: 4431 - Internal Error: Sub-system: FTITAN, File: /quartus/fitter/ftitan/ftitan_expert.cpp, Line: 4431 Description Due to a problem in the Quartus® II software version 13.1 and earlier, you may see this error in designs that implement the altlvds_rx megafunction with the Use External PLL option enabled. Resolution To work around this problem, in your design implement and open a PLL megafunction. For the output clock that drives the rx_inclock of the altlvds_rx megafunction, enable the option Use these clock settings for the DPA clock . This problem is scheduled to be fixed in a future release of the Quartus II software. Custom Fields values: ['novalue'] Troubleshooting novalue False ['novalue'] ['FPGA Dev Tools Quartus II Software'] novalue 12.1 ['Programmable Logic Devices'] ['novalue'] ['novalue'] ['novalue']