Modelsim - work (empty) problem

Step 1 Make Sure the Work Library Exists

Without the work folder, all compiled files may go to the wrong places. Check ModelSim’s preferences to ensure that the working folder is set correctly. To examine the log screen, look at the bottom of the interface; type the following command.

vlib work

If the library already exists, ModelSim will say so. If it does not, this command will create it.

At the bottom of the interface, there is a window named transcript. Let's open ModelSim first to verify if the library exists.

Type the command vlib work.

Now let’s check to see if “work” appears.

Step 2: Compile Your Verilog Files into the Work Library

Now that we know the work library is there, let's make sure your Verilog files are compiled correctly.

Method 1: Using the GUI

1. Go to the "Compile" menu → Click "Compile".
2. Select your .v files from where they are saved.
3. Look at the "Library" column in the compile window.

• It should say "work" (if not, select "work").

1. Click "Compile", then "Done".

Method 2: Using Commands

Alternatively, you can compile manually by typing:

vlog -work work myfile.v

(Replace myfile.v with your actual file name.)

Step 3: Verify the Work Library is Not Empty

After compiling, check if files were added to work:

1. Open "Library" tab on the left.
2. Click the "+" next to "work".
3. You should see your compiled modules listed.

If the work library is still empty, your files might not be compiled correctly.

Step 4: Check Your File Paths

If files are getting created outside of work, it may be due to incorrect paths.

1. Look at the path where your .v files are saved.

• Make sure they are in your ModelSim project folder.

1. Check where ModelSim is compiling to:

• Open Compile → Compile Options.
• Ensure the "Library" is set to "work".

Step 5: Load Simulation Properly

If your files are compiled correctly but still not appearing in simulation:

1. Go to "Simulate" → "Start Simulation".
2. Expand the "work" library.
3. Select your top module.
4. Click "OK".

Checking the understanding:

When you create a project, ModelSim automatically generates a work library, but in your case, it shows as empty even though you expect it to contain compiled files.

However, when you manually save and compile a source file into work, ModelSim recognizes it and allows simulation.

This means the library exists, but ModelSim’s project system isn’t linking to it properly.

If the understanding is correct, here are some possible Causes and Fixes

1. Your Work Library Is Not Set as the Active Library

Even though the work directory exists, ModelSim might not be treating it as the active library. Try setting it manually:

Command:

vmap work work

This explicitly tells ModelSim to map the work library to the correct folder.

2. The Project Is Using a Different Work Library Path

Your project might be looking at the wrong work directory.

Open Project Settings and check where the "work" library is mapped.

Also, check the Compile Options to ensure compiled files are going into work.

Instead of manually placing source files into work, try moving them to the project folder and compiling from there.

3. Your Project Might Have Corrupted or Misconfigured Settings

Sometimes, ModelSim's internal settings can become misconfigured. Try these steps:

Close ModelSim and delete the modelsim.ini file in your project directory.

Restart ModelSim, and it will regenerate modelsim.ini with default settings.

Run:

vlib work

vmap work work

Then try recompiling.

4. ModelSim Might Be Using a Different Default Library

In the Library tab, right-click and check the library settings.

Ensure that work is the default library for compilation.

Is there any update for the above?

Hi,

Is there any further update or concern?

Thanks,

Regards,

Sheng

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