# sfbuild module "synth"

##### _Category: Common_

-------------------------------

The _synth_ module is meant to be used to execute YOSYS synthesis.

The module should guarantee the following outputs:
 * `eblif`
 * `fasm_extra` (can be empty)
 * `json`
 * `synth_json`
 * `synth_log` (on demand)

For detailed information about these targets, please refer to
`docs/common targets and variables.md`

## Setup

What files and how are they generated is dependendent on TCL scripts executed
withing YOSYS and the script vary depending on the target platform. Due to this
design choice it is required for the author of the flow defnition to parametrize
the `synth` module in a way that will **GUARANTEE** the targets mentioned above
will be generated upon a successful YOSYS run.

The setup of the synth module follows the following specifications:

### 1. Module parameters:

The `params` section of a stage configuration may contain a `produces` list.
The list should specify additional targets that will be generated
(`?` qualifier is allowedd).

### 2. Values:

The `synth` module requires the following values:

* `tcl_scripts` (string, required ): A path to a directory containing `synth.tcl`
  and `conv.tcl` scripts that wiull be used by YOSYS.
* `read_verilog_args` (list[string | number], optional) - If specified, the verilog
  sources will be read using the `read_verilog` procedure with options contained in
  this value.
* `yosys_tcl_env` (dict[string -> string | list[string], required) - A mapping that
  defines environmental variables that will be used within the TCL scripts. This
  should contain the references to module's inputs and outputs in order to gurantee
  the generation of the desired targets.