Description:
When running simulation on the Lattice Simulation tool, the tool may encounter an error relating to the design unit. This is encountered when the needed libraries are not added in the simulation project.
Solution:
1) Go to Modelsim Simulate Menu, then select Start Simulation
2) Select your test bench on the design Tab
3) Select or Add the following libraries: ovi_lifcl , pmi_work , lifclm work
4) Then Select Okay