ISE 下的IP核使用问题 ISE

driver2008

IP核例如FIR, 可以综合及实现,  但不能功能仿真和后仿真.功能仿真会出现如下错误:

ERROR:HDLParsers:3482 - Could not resolve instantiated unit fir_df in Verilog module work/t in any library
ERROR:Simulator:198 - Failed when handling dependencies for module b

各位大虾帮个忙,小弟不胜感激!!