About

Yosys is a framework for Verilog RTL synthesis. It currently has extensive Verilog-2005 support and provides a basic set of synthesis algorithms for various application domains. Selected features and typical applications:

Process almost any synthesizable Verilog-2005 design

Converting Verilog to BLIF / EDIF/ BTOR / SMT-LIB / simple RTL Verilog / etc.

Built-in formal methods for checking properties and equivalence

Mapping to ASIC standard cell libraries (in Liberty File Format)

Mapping to Xilinx 7-Series and Lattice iCE40 FPGAs

Foundation and/or front-end for custom flows

Yosys can be adapted to perform any synthesis job by combining the existing passes (algorithms) using synthesis scripts and adding additional passes as needed by extending the Yosys C++ code base.

Yosys is free software licensed under the ISC license (a GPL compatible license that is similar in terms to the MIT license or the 2-clause BSD license).

Example Usage

Yosys is controlled using synthesis scripts. For example, the following Yosys synthesis script reads a design (with the top module mytop ) from the verilog file mydesign.v , synthesizes it to a gate-level netlist using the cell library in the Liberty file mycells.lib and writes the synthesized results as Verilog netlist to synth.v :

# read design read_verilog mydesign.v # elaborate design hierarchy hierarchy -check -top mytop # the high-level stuff proc; opt; fsm; opt; memory; opt # mapping to internal cell library techmap; opt # mapping flip-flops to mycells.lib dfflibmap -liberty mycells.lib # mapping logic to mycells.lib abc -liberty mycells.lib # cleanup clean # write synthesized design write_verilog synth.v

The synth command provides a good default script that can be used as basis for simple synthesis scripts:

# read design read_verilog mydesign.v # generic synthesis synth -top mytop # mapping to mycells.lib dfflibmap -liberty mycells.lib abc -liberty mycells.lib clean # write synthesized design write_verilog synth.v