General Description: The .veo file for the NCO core incorrectly specifies the path to NCO behavioral model in XilinxCoreLib as $XILINX\XilinxCoreLib\ncovht.v, but there is no such file.
There are two problems:
1. The path delimiters should be forward slashes, not backslashes 2. The model name is ncoiqvht.v instead of nco_v1_0.v
ソリューション
Edit the .veo and correct the reference manually to point to <path_to_Xilinx_installation>/verilog/src/XilinxCoreLib/nco_v1_0.v.