Stratus

Name

Stratus - Procedural design language based upon Python

Description

Stratus is a set of Python methods/functions dedicated to procedural generation purposes. From a user point of view, Stratus is a circuit's description language that allows Python programming flow control, variable use, and specialized functions in order to handle vlsi objects.

Based upon the Hurricane data structures, the Stratus language gives the user the ability to describe netlist and layout views.

Configuration

A configuration file can be used to direct the generation process of Stratus. With this file, the user can choose the output format (vst, vhdl...), the simulator (asimut, ghdl...), the standard cell library... This configuration file named .st_config.py must be placed either in the HOME directory or in the current directory. This file contains a set of variables used in the process generation of Stratus, as for example :

 
format = 'vhdl'
simulator = 'ghdl'

The default configuration of Stratus uses the Alliance CAD system, ie 'vst' as format and 'asimut' as simulator.

Description of a cell

A cell is a hierachical structural description of a circuit in terms of ports (I/Os), signals (nets) and instances.

The description of a cell is done by creating a new class, derivating for class Model, with different methods :

• Method Interface : Description of the external ports of the cell :
  • SignalIn, SignalOut, ...
• Method Netlist : Description of the netlist of the cell :
  • Inst, Signal
• Method Layout : Description of the layout of the cell :
  • Place, PlaceTop, PlaceBottom, PlaceRight, PlaceLeft ...
• Method Stimuli : Description of the simulation stimuli of the cell :
  • affect, addd ...

Creation of the cell

After the description of a cell as a sub-class of Model, the cell has to be instantiated. The different methods described before have to be called.

Then different methods are provided :

• Method View : Opens/Refreshes the editor in order to see the created layout
• Method Save : Saves the created cell in the desired format thanks to the configuration file
  • no argument : creation of a netlist file
  • PHYSICAL : creation of a netlist file AND a layout file
  • STRATUS : creation of a python/stratus file
    • FileName : optionnal argument when using Save(STRATUS) in order to choose the name of the file to be generated
    • Be careful : if one wants to create a stratus file AND a netlist, always use Save(STRATUS) before Save() !
• Method Testbench : Creates the testbench of the cell using the Stimuli method to compute the stimuli. The output format depends of the format variable given in the configuration file
• Method Simul : Runs the simulation using the simulator named in the configuration file

Syntax

A Stratus file must have a .py extension and must begin as follow :

#!/usr/bin/env python

from stratus import *

The description of a cell as a sub-class of Model is done as follow :

class myClass ( Model ) :
    ...

The creation of the cell is done by instantiating the previous class as follow :

exemple = myClass ( name, param )

After the different methods can be called as follow :

exemple.Interface()
exemple.Netlist()
exemple.Save()
    ...

In order to execute a Stratus file (named file for example), one has two choices :

python file.py

Or :

chmod u+x file.py
./file.py

The names used in Stratus, as arguments to Stratus functions, should be alphanumerical, including the underscore. The arguments of Stratus are case sensitive, so VDD is not equivalent to VDD.

Vectorized connectors or signal can be used using the [N:M] construct.

Syntax highlighting

When using vi, it's possible to have the right syntax highlighting :

• Commands to do when you want to change once the coloration of your file :

:syntax off
:source /asim/coriolis/share/etc/stratus.vim

• Modification of your .vimrc in order to have the syntax highlighting each time you open a file :

syntax off
autocmd BufRead,BufNewfile *.py so /asim/coriolis/share/etc/stratus.vim
syntax on

Example

You can see a concrete example at : Example

See Also

Netlist Layout Stimuli Place and Route Virtual librayy Instanciation facilities