UVM Plusargs

Common UVM plusargs

Put these arguments after the simulator command. The examples use one option at a time so you can see what each one changes.

Verbosity levels

UVM_NONE, UVM_LOW, UVM_MEDIUM, UVM_HIGH, UVM_FULL, and UVM_DEBUG go from fewer messages to more detail. Start with UVM_MEDIUM; raise it when you need more logging.

Run a test with plusargs

For example, a VCS simulation executable can be started like this. Keep the plusargs after the executable; compile options belong to the earlier compile step.

./simv \
  +UVM_TESTNAME=smoke_test \
  +UVM_VERBOSITY=UVM_HIGH \
  +UVM_MAX_QUIT_COUNT=1

Simulator executable names and random-seed switches vary by tool. Check your simulator's documentation before copying a command to a different simulator.

Read a custom plusarg

Use $value$plusargs when your testbench needs a run-time value that is not one of UVM's built-in options. This small example defaults to 10 transactions and replaces that value when +NUM_TXN is supplied.

module tb;
  int num_txn = 10;

  initial begin
    if ($value$plusargs("NUM_TXN=%d", num_txn))
      $display("NUM_TXN set from command line");

    $display("NUM_TXN=%0d", num_txn);
  end
endmodule

Run it and check the output

Append +NUM_TXN=100 to the simulator command. The %d format reads a decimal integer into num_txn.

Without the plusarg, the initial value remains in place and the output is NUM_TXN=10.

Debugging and random seeds

Use trace options only for the failing run because they can produce large logs. For example, combine +UVM_OBJECTION_TRACE with a short test to find an objection that was never dropped.