In the Quartus® II software release version 14.0 update 2, manual assignment of PLLCLKOUT pin for the MAX® 10 device generates the following errors in the Fitter:
Error (176138): Can't place differential I/O pins and/or
associated SERDES transmitters or receivers -- location assignments
Error (176150): Pin "<pin name
with LVDS I/O standard must be driven by the external clock output
of an enhanced PLL
The PLLCLKOUT pin can be used as general purpose I/O pins for MAX 10 devices, but this option is currently not automatically supported by the Fitter.
There is no workaround. This issue will be fixed in a future release of the Quartus II software.