# Verilog: Instantiation of lpm_dff failed. The design unit was not found

I want to use lpm_dff components in my design. I can compile the code without problem in modelsim, But when i try to simulate my test bench i receive this error. I also add lpm library when i simulate the test bench.

Can someone help me fix the problem?

• That sounds like a vendor-specific library part. Which vendor's tools are you using? Do you really need that part, or can you use something more generic? – Dave Tweed May 18 '17 at 0:41
• Ensure you included this module's file into the project. While Quartus (you do not state which vendor you use) searches for appropriate modules if they are not in project, Modelsim may have difficulties finding it. – Anonymous May 18 '17 at 8:03

• For general cores, they are all in the altera_mf_ver library (for Verilog) or altera_mf library (VHDL versions).
• For device specific parts like PLLs you would use the library for your device as well (e.g. cyclonev_ver is the Verilog library for Cyclone V devices).
• For the LPM cores I believe they are in the lpm_ver library (for Verilog) or lpm library (for VHDL), but may also be in altera_mf_ver as well..
• If you are running it using the GUI (Simulate -> Start Simulation), simply select the required libraries in the Search Libraries (-L) box on the library tab of the start simulation screen.
• If you are using command line, you can append the switch -L altera_mf_ver -L lpm_ver to the end of your vlog command.