Description
You might encounter this error message in the Intel® Quartus® Prime Software, if you are using Cyclone® IV devices and your output pin uses the LVDS_E_3R I/O standard and is located on a CLKOUT pin.
Resolution
There is no plan to modify the Intel Quartus Prime Software to fix this problem.
You should not assign an output pin with the LVDS_E_3R I/O standard to a CLKOUT pin when using Cyclone® IV devices.