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A library for constructing a Verilog HDL source code in Python

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A library for constructing a Verilog HDL source code in Python

Copyright (C) 2015, Shinya Takamaeda-Yamazaki



Apache License 2.0 (


If you use Veriloggen in your research, please cite my paper about
Pyverilog. (Veriloggen is constructed on Pyverilog.)

- Shinya Takamaeda-Yamazaki: Pyverilog: A Python-based Hardware Design
Processing Toolkit for Verilog HDL, 11th International Symposium on
Applied Reconfigurable Computing (ARC 2015) (Poster), Lecture Notes
in Computer Science, Vol.9040/2015, pp.451-460, April 2015.
`Paper <>`__


title={Pyverilog: A Python-Based Hardware Design Processing Toolkit for Verilog HDL},
author={Takamaeda-Yamazaki, Shinya},
booktitle={Applied Reconfigurable Computing},
series={Lecture Notes in Computer Science},
publisher={Springer International Publishing},

What’s Veriloggen?

Veriloggen is an open-sourced library for constructing a Verilog HDL
source code in Python.

Veriloggen is not a behavior synthesis (or high level synthesis).
Veriloggen provides a lightweight abstraction of Verilog HDL AST. You
can build up a hardware design written in Verilog HDL very easily by
using the AST abstraction and the entire functionality of Python.

Veriloggen is not designed for designing a hardware by programmer
directly, but is for providing an efficient abstraction to develop a
more efficient domain specific language and tools.



- Python3: 3.6 or later

- Icarus Verilog: 10.1 or later


sudo apt install iverilog

- Jinja2: 2.10 or later
- pytest: 3.2 or later
- pytest-pythonpath: 0.7 or later
- Pyverilog: 1.1.2 or later
- IPgen: 1.0.0 or later


pip3 install jinja2 pytest pytest-pythonpath pyverilog ipgen


- Graphviz: 2.38.0 or later
- Pygraphviz: 1.3.1 or later

These softwares are required for graph visualization by


sudo apt install graphviz
pip3 install pygraphviz

- NumPy: 1.14 or later

This is required for the memory image generation function of
types.axi.AxiMemoryModel from Python list or numpy.ndarray:


pip3 install numpy


Install Veriloggen:


python3 install

On Docker

Dockerfile is available, so that you can try Veriloggen on Docker
without any installation on your host platform.


cd docker
sudo docker build -t user/veriloggen .
sudo docker run --name veriloggen -i -t user/veriloggen /bin/bash
cd veriloggen/examples/led/

Getting Started

You can find some examples in ‘veriloggen/examples/’ and

Let’s begin veriloggen by an example. Create a example Python script in
Python as below. A blinking LED hardware is modeled in Python. Open
‘’ in the root directory.

.. code:: python

from __future__ import absolute_import
from __future__ import print_function
import sys
import os
from veriloggen import *

def mkLed():
m = Module('blinkled')
width = m.Parameter('WIDTH', 8)
clk = m.Input('CLK')
rst = m.Input('RST')
led = m.OutputReg('LED', width, initval=0)
count = m.Reg('count', 32, initval=0)

seq = Seq(m, 'seq', clk, rst)

seq.If(count == 1024 - 1)(

seq.If(count == 1024 - 1)(

Systask('display', "LED:%d count:%d", led, count)

return m

def mkTest():
m = Module('test')

# target instance
led = mkLed()

uut = Submodule(m, led, name='uut')
clk = uut['CLK']
rst = uut['RST']

simulation.setup_waveform(m, uut, m.get_vars())
simulation.setup_clock(m, clk, hperiod=5)
init = simulation.setup_reset(m, rst, m.make_reset(), period=100)

Delay(1000 * 100),

return m

if __name__ == '__main__':
test = mkTest()
verilog = test.to_verilog(filename='tmp.v')
#verilog = test.to_verilog()

sim = simulation.Simulator(test)
rslt =

# sim.view_waveform()

Run the script.



You will have a complete Verilog HDL source code named ‘tmp.v’ as below,
which is generated by the source code generator.

.. code:: verilog

module test


localparam uut_WIDTH = 8;
reg uut_CLK;
reg uut_RST;
wire [uut_WIDTH-1:0] uut_LED;


initial begin
$dumpvars(0, uut, uut_CLK, uut_RST, uut_LED);

initial begin
uut_CLK = 0;
forever begin
#5 uut_CLK = !uut_CLK;

initial begin
uut_RST = 0;
uut_RST = 1;
uut_RST = 0;


module blinkled #
parameter WIDTH = 8
input CLK,
input RST,
output reg [WIDTH-1:0] LED

reg [32-1:0] count;

always @(posedge CLK) begin
if(RST) begin
count <= 0;
LED <= 0;
end else begin
if(count == 1023) begin
count <= 0;
end else begin
count <= count + 1;
if(count == 1023) begin
LED <= LED + 1;
$display("LED:%d count:%d", LED, count);


You will also see the simulation result of the generated Verilog code on
Icarus Verilog.


VCD info: dumpfile uut.vcd opened for output.
LED: x count: x
LED: x count: x
LED: x count: x
LED: x count: x
LED: x count: x
LED: x count: x
LED: x count: x
LED: x count: x
LED: x count: x
LED: x count: x
LED: 0 count: 0
LED: 0 count: 1
LED: 0 count: 2
LED: 0 count: 3
LED: 0 count: 4
LED: 9 count: 777
LED: 9 count: 778
LED: 9 count: 779
LED: 9 count: 780
LED: 9 count: 781
LED: 9 count: 782
LED: 9 count: 783

If you installed GTKwave and enable ‘sim.view_waveform()’ in
‘’, you can see the waveform the simulation result.

.. figure:: img/waveform.png
:alt: waveform.png


Veriloggen Extension Libraries

Mixed-Paradigm High-Level Synthesis

- veriloggen.thread.Thread: Procedural high-level synthesis for DMA and
I/O controls
- veriloggen.thread.Stream: Dataflow-based high-level synthesis for
high-performance stream processing

Frequently-used Abstractions

- veriloggen.verilog: Verilog HDL source code synthesis and import APIs
- veriloggen.simulation: Simulation APIs via Verilog simulators
- veriloggen.seq: Synchronous circuit builder (Seq)
- veriloggen.fsm: Finite state machine builder (FSM)

Please see examples and tests directories for many examples.

Related Project

`Pyverilog <>`__ - Python-based
Hardware Design Processing Toolkit for Verilog HDL

`IPgen <>`__ - IP-core package generator
for AXI4/Avalon

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