f4pga/docs/how.rst

How it works
############

EDA Tooling Ecosystem
=====================

For both ASIC- and FPGA-oriented EDA tooling, there are three major areas that
the workflow needs to cover: hardware description, frontend and backend.

Hardware description languages are generally open, with both established HDLs
such as Verilog and VHDL and emerging software-inspired paradigms like
`Chisel <https://chisel.eecs.berkeley.edu/>`_,
`SpinalHDL <https://spinalhdl.github.io/SpinalDoc-RTD/>`_ or
`Migen <https://m-labs.hk/gateware/migen/>`_.
The major problem lies however in the front- and backend, where previously
there was no established standard, vendor-neutral tooling that would cover
all the necessary components for an end-to-end flow.

This pertains both to ASIC and FPGA workflows, although F4PGA focuses
on the latter (some parts of F4PGA will also be useful in the former).

.. figure:: _static/images/EDA.svg

Project structure
=================

To achieve F4PGA's goal of a complete FOSS FPGA toolchain, a number of tools and projects are necessary to provide all
the needed components of an end-to-end flow.
Thus, F4PGA serves as an umbrella project for several activities, the central of which pertains to the creation of
so-called FPGA "architecture definitions", i.e. documentation of how specific FPGAs work internally.
More information can be found in the :doc:`F4PGA Architecture Definitions <arch-defs:index>` project.

Those definitions and serve as input to backend tools like
`nextpnr <https://github.com/YosysHQ/nextpnr>`_ and
`Verilog to Routing <https://verilogtorouting.org/>`_, and frontend tools
like `Yosys <http://www.clifford.at/yosys/>`_. They are created within separate
collaborating projects targeting different FPGAs - :doc:`Project X-Ray
<prjxray:index>` for Xilinx 7-Series, `Project IceStorm
<http://www.clifford.at/icestorm/>`_ for Lattice iCE40 and :doc:`Project Trellis
<prjtrellis:index>` for Lattice ECP5 FPGAs.

.. figure:: _static/images/parts.svg