osaboh / Tizzy

Graphviz dot to Verilog Finite State Machine (FSM) generator written in Python

Copyright (c) RTLCores LLC. 2010

Intro

Tizzy is a Finite State Machine generator for Verilog. It accepts a subset of the Graphviz dot syntax as input and generates synthesizable Verilog RTL.

Why Graphviz dot format?

1. Graphviz viewers are open source
2. The input is just a text file
3. Automatic documentation

The name:

Tizzy = A state of agitation. (That sounds like a state machine to me.)

Transition Syntax

The basic syntax used to describe state transitions:

STATE -> STATE_NEXT [label='affector_signal'];

Usage

$ ./tizzy.py --help
Usage: tizzy.py <options> [filename]

Options:
  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -d DEBUG, --debug=DEBUG
                        Run in special debug mode. Valid options are debug,
                        info, warning, error, critical
  -n, --nochecks        Do not run error checking routines
  -l, --long_messages   Print out extra help messages on warnings and errors
  -o OUTPUT_FILE, --output=OUTPUT_FILE
                        Write output to a file instead of stdout

Example

The file example_fsm.dot contains the following directed graph representation of a state machine:

digraph example_fsm
{
    label = "Example Finite State Machine";
    stIDLE -> stIDLE;
    stIDLE -> stPIPE1 [label = "din_rdy"];
    stPIPE1 -> stPIPE2;
    stPIPE2 -> stLOAD_NEXT;
    stLOAD_NEXT -> stLOAD_DOUT [label = "done"];
    stLOAD_NEXT -> stPIPE1
    stLOAD_DOUT -> stIDLE;
}

To convert this to verilog you would issue the following commands:

$ ./tizzy.py -o example_fsm.v example_fsm.dot 
Found 5 Unique States:
    stIDLE
    stPIPE1
    stPIPE2
    stLOAD_NEXT
    stLOAD_DOUT
Writing Verilog: example_fsm.v

Without the -o option the Verilog output would go to stdout. All the other messages all go to stderr.