Waveform Generation

Usage

When using the Picker tool to encapsulate the DUT, use the -w [wave_file] option to specify the waveform file to be saved. Different waveform file types are supported for different backend simulators, as follows:

1. Verilator
   • .vcd format waveform file.
   • .fst format waveform file, a more efficient compressed file.
2. VCS
   • .fsdb format waveform file, a more efficient compressed file.

Note that if you choose to generate the libDPI_____.so file yourself, the waveform file format is not restricted by the above constraints. The waveform file format is determined when the simulator constructs libDPI.so, so if you generate it yourself, you need to specify the waveform file format using the corresponding simulator’s configuration.

Python Example

Normally, the DUT needs to be explicitly declared complete to notify the simulator to perform post-processing tasks (writing waveform, coverage files, etc.). In Python, after completing all tests, call the .finalize() method of the DUT to notify the simulator that the task is complete, and then flush the files to disk.

Using the Adder Example, the test program is as follows:

from UT_Adder import *

if __name__ == "__main__":
    dut = DUTAdder()

    for i in range(10):
        dut.a.value = i * 2
        dut.b.value = int(i / 4)
        dut.Step(1)
        print(dut.sum.value, dut.cout.value)

    dut.finalize() # flush the wave file to disk

After the run is completed, the waveform file with the specified name will be generated.

Viewing Results

GTKWave

Use GTKWave to open fst or vcd waveform files to view the waveform.

Verdi

Use Verdi to open fsdb or vcd waveform files to view the waveform.