VHDL compiler and simulator
C VHDL Makefile Other Shell Ruby CSS
Pull request Compare This branch is 191 commits behind nickg:master.
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Failed to load latest commit information.



NVC is a GPLv3 VHDL compiler and simulator aiming for IEEE 1076-1993 compliance. See these blog posts for background information. NVC should not be considered a production quality tool and language support is lacking in many areas. However it has been successfully used to simulate several real-world designs.

Brief usage example:

$ nvc -a my_design.vhd my_tb.vhd
$ nvc -e my_tb
$ nvc -r my_tb

Or more succinctly, as a single command:

$ nvc -a my_design.vhd my_tb.vhd -e my_tb -r

The full manual can be read after installing NVC using man nvc or online.

Report bugs using the GitHub issue tracker.


NVC is developed on Debian Linux and has been reported to work on OS X and Windows under Cygwin. Ports to other Unix-like systems are welcome.

To build from a Git clone:

mkdir build && cd build
make install

Generating the configure script requires autoconf and automake version 1.11 or later.

To use a specific version of LLVM add --with-llvm=/path/to/llvm-config to the configure command. LLVM 3.0 or later is required.

NVC also depends GNU Flex to generate the lexical analyser.

If a readline-compatible library is installed it will be used to provide line editing in the interactive mode.

GtkWave can be used to view simulation waveforms. Version 3.3.53 or later is reqiured for the default FST format.

Debian and Ubuntu

On a Debian derivative the following should be sufficient to install all required dependencies:

sudo apt-get install build-essential automake autoconf autoconf-archive flex \
    libreadline-dev tcl-dev check llvm-dev pkg-config zlib1g-dev curl

Mac OS X

This covers recent releases of OS X (10.9.X).

Install the Developer Command Line Tools. Either by installing Xcode and menu pull down to install Command Line Tools or by Developer download of the Developer Command Line Tools. This is essential for getting the include tree and making libraries, etc. available.

Get LLVM from llvm.org. Executable images found at http://llvm.org/releases/download.html. The most recent version will likely work, need at least LLVM 3.3. The target name would be for example Clang_for_x86_64_Darwin_10.9.

Install autotools. Either via Macports, Homebrew or directly. Insure these are in your path.

NVC installation is as described above with narrow exceptions.

Consider passing --with-llvm=<absolute_path_to_llvm_bin_directory> as a command line argument to configure. Apple provides clang and clang++ as well as gcc and g++ linked to them but no llvm-config, etc.

This also implies you could manipulate your execution search path to use clang and clang++ from your added LLVM distribution to use as CC and CXX:

configure CXX=clang++ CC=clang

The consequence of this is that LLVM is more strictly C99/C10/C11 compliant while development of NVC is generally done with GNU GCC with more relaxed compliance constraints.


Windows support is via Cygwin. Use setup.exe to install either gcc or clang and the following dependencies: automake, autoconf, pkg-config, llvm, libllvm-devel, flex, tcl, libreadline-devel, libffi-devel, libcurses-devel, curl, and make. Then follow the standard installation instructions above.



IEEE Libraries

Due to copyright restrictions the IEEE library source files cannot be freely redistributed and must be downloaded from an external source prior to building. See lib/ieee/README for details.

To recompile the standard libraries:

make bootstrap

Note this happens automatically when installing.


To run the regression tests:

make check

The unit tests require the check library.

You may need to install additional Ruby libraries:

gem install colorize getopt


NVC supports a small subset of VHDL-2008 which can be enabled with the --std=2008 option. If you require library functions from the 2008 standard you can use the VHDL-2008 Support Library which provides backwards-compatible implementations for VHDL-1993. Run ./tools/build-2008-support.rb to download and install this.

Vendor Libraries

NVC provides scripts to compile the simulation libraries of common FPGA vendors.

  • For Xilinx ISE use ./tools/build-xilinx.rb
  • For Altera Quartus use ./tools/build-altera.rb
  • For Lattice iCEcube2 use ./tools/build-lattice.rb

The libraries will be installed under ~/.nvc/lib.