# Overview

Welcome to Verilator!

The Verilator package converts Verilog [1] and SystemVerilog [2] hardware description language (HDL) designs into a C++ or SystemC model that, after compiling, can be executed. Verilator is not a traditional simulator but a compiler.

Verilator is typically used as follows:

1. The verilator executable is invoked with parameters similar to GCC or other simulators such as Cadence Verilog-XL/NC-Verilog, or Synopsys VCS. Verilator reads the specified SystemVerilog code, lints it, optionally adds coverage and waveform tracing support, and compiles the design into a source-level multithreaded C++ or SystemC “model”. The resulting model’s C++ or SystemC code is output as .cpp and .h files. This is referred to as “Verilating”, and the process is “to Verilate”; the output is a “Verilated” model.

2. For simulation, a small-user written C++ wrapper file is required, the “wrapper”. This wrapper defines the C++ standard function “main()”, which instantiates the Verilated model as a C++/SystemC object.

3. The user C++ wrapper, the files created by Verilator, a “runtime library” provided by Verilator, and, if applicable SystemC libraries are then compiled using a C++ compiler to create a simulation executable.

4. The resulting executable will perform the actual simulation during “simulation runtime”.

5. If appropriately enabled, the executable may also generate waveform traces of the design that may be viewed. It may also create coverage analysis data for post-analysis.

The best place to get started is to try the Examples.

[1]

Verilog is defined by the Institute of Electrical and Electronics Engineers (IEEE) Standard for Verilog Hardware Description Language, Std. 1364, released in 1995, 2001, and 2005. The Verilator documentation uses the shorthand, e.g., “IEEE 1364-2005”, to refer to the, e.g., 2005 version of this standard.

[2]

SystemVerilog is defined by the Institute of Electrical and Electronics Engineers (IEEE) Standard for SystemVerilog - Unified Hardware Design, Specification, and Verification Language, Standard 1800, released in 2005, 2009, 2012, and 2017. The Verilator documentation uses the shorthand e.g., “IEEE 1800-2017”, to refer to the, e.g., 2017 version of this standard.