Qfsm is a graphical editor for finite state machines written in C++ using Qt the graphical Toolkit fromTrolltech.

Finite state machines are models to describe complex objects or systems in terms of the states they may be in. In practice they can be used to create regular expressions, scanners or other program code as well as for integrated curcuit design.

Current features of Qfsm are:

Copyright (C) 2000-2015 Stefan Duffner, Rainer Strobel

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 3 of the License, or (at your option) any later version.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

When you want to modify the properties of an existing FSM you can select Machine->Edit from the main menu and the same dialog box displays. As soon as you click OK the changes take effect.

The working area denotes the area of the Qfsm window that shows the state diagram. Once you have created a new FSM you see a blank working area and you are in the selectmode.

There are six different modes you can be in and which determine what happens when you click or drag the mouse inside the working area of Qfsm.

Only one mode can be activated at a time. To change the mode, click on one of the icons in the middle of the toolbar.

When a diagram is larger the working area, you have the possibility to move the view of a diagram. To move the view of a diagram, click on the middle mouse button and drag the mouse pointer. As soon as you release the middle mouse button the application reverts to the selected mode.

Alternatively, you can select the respective menu entry or press the respective short cut. The active mode is indicated by a highlighted toolbar button. In some modes, the form of the mouse cursor also changes, e.g. a magnifier for the zoom mode.

Using the Pan mode

In this mode, you can move the view to a different part of your diagram when your diagram is larger than the working area of the window.

To move the view, drag the mouse pointer.

Using the Zoom mode

In this mode you can zoom in the view.

To zoom in the view, click with the left mouse button on the working area.

To zoom out, keep the CTRL key pressed at the same time you click.

Using the Add State mode

In this mode you can add states and specify their properties.

To create a new state, click with the left mouse button and fill the dialog with the properties. For more details, see the section called “Adding and modifying states”

Using the Add Transition mode

In this mode you can add transitions and specify their properties.

To add a transition:

1) click on a state and drag the mouse pointer to another state.

2) fill the dialog with the properties of the transition.

For more details, see the section called “Adding and modifying transitions”

Using the Simulate mode

In the simulate mode, you can test the behaviour of your state machine with respect to external input.

When you enter this state, the simulator dialog opens and all interaction with the state diagram is disabled until you close the dialog. For more details, see the section called “Simulating a FSM”

To create a state:

1) first you need to:

- create a new FSM or;

- open an existing file.

To create a new FSM, select File->New (see the section called “Creating and modifying a Finite State Machine”)

To open an existing file, select File->Open

2) Switch to the "add state" mode (see the section called “Using the Add State mode”).

3) Click at the position of the working area where you want the new state to be.

The following dialog opens.

To specify or modify the properties of the state, fill the "State properties" dialog:

To modify an existing state:

1) switch to the "select mode" (see the section called “Using the Select mode”).

2) double-click on the respective state

Or

2) select one state and select State->Edit from the main menu.

To create a new transition:

1) you need first to:

- create a FSM or

- open an existing file.

To create a FSM, select File->New (see the section called “Creating and modifying a Finite State Machine”)

To open an existing file, select File->Open from the main menu and choose the desired file.

2) create at least one state (see the section called “Adding and modifying states”).

3) switch to the "add transition" mode (see the section called “Using the Add Transition mode”).

To create a transition from state A to state B, press and hold the left mouse button on state A and release it on state B.

To draw loops, i.e. transitions that go from one state to itself, press and release the mouse button on the same state.

The "Transition properties" dialog opens.To specify or modify the properties of the state, fill the dialog.

To modify the properties of an existing transition:

1) switch to the "select mode" (see the section called “Using the Select mode”).

2) double-click on the respective transition

Or

2) select one transition and selectTransition->Editfrom the main menu.

To change the bend of the transition as well as its start state and end state:

1) switch to the “Select mode”

2) click on the transition.

Four control points appear. You can drag them around with the left mouse button.

The green ones allow you to change the start and end state. With the red ones you can change the bend of the transition.

When you create a transition of FSM that processes ASCII characters you have to enter an input condition. This condition can be a simple character, e.g. 'a', or several characters that are expressed by a special notation explained in the following.

To check the integrity of a FSM, select Machine->Integrity Check from the main menu.

The following tests are performed:

A log of the checks that have been performed is printed in the protocol field at the bottom of the window.

Once you have created a FSM with some states and transitions you can simulate its behaviour with respect to varying input signals.

To start the simulation of an FSM, select Machine->Simulate from the main menu.

The "simulator" dialog opens allowing you to input data to the machine while displaying its current state and output.

There are two modes to send input data:

- click on the Send button or, press the Enter key)

- click on the Clock button.

In the clock mode, Qfsm periodically sends the data in the input text field on the top of the dialog to the FSM.

You can specify the frequency of the clock in the input field at the bottom right. For ASCII input, the input text field is cleared after each clock signal, which allows to simulate the behaviour of ASCII FSMs in real-time by pressing different keys.

To exit the Clock Mode, click once again on the Clock button.

To reset the FSM, click on the Reset Button.

This sets the FSM to its initial state.

There are several export functions in Qfsm.

To export, select File->Export in the main menu.

They can be divided into the following categories:

Here are some explanations about the different export functions:

public class FSM1
{
  private final FSM1Context fsm;
  public int a;

  FSM1()
  {
    fsm = new FSM1Context(this);
  }

  public void action1() { System.out.println("executing action1()"); }
  public void do1() { System.out.println("executing do1()"); }
  public void do2() { System.out.println("executing do2()"); }
  public void entering() { System.out.println("entering State"); }
  public void exiting() { System.out.println("exiting State"); }
  public void aa() { System.out.println("executing aa()"); }
  public void bb() { System.out.println("executing bb()"); }
  public void default_action() 
    { System.out.println("executing default_action()"); }

  public void testit()
  {
    a=1;
    fsm.init();
    fsm.run();
    fsm.init();
  }

  public static void main(String[] args)
  {
    FSM1 f = new FSM1();
    f.testit();
  }
}

	   Base_directory
	   |
	   +-src
	   |   fsmname.fsm
	   |   e_fsmname.vhd
	   |   a_fsmname_architecturename.vhd
	   |   t_fsmname.vhd
	   |   p_fsmname.vhd
	   |
	   +-stimuli
	   |   fsmname_stimuli.vec
	   |
	   +-log
	      fsmname_result.log
	  

Qfsm can import files written in the DOT language using Graphviz.

To import a DOT file (with extension .gv), select File->Import->Graphviz... in the main menu.

Qfsm uses Graphviz to transform the textual description of the FSM into a graphical layout of the state diagram.

When writing a DOT file make sure you respect the following syntax rules:

Here is an example of a dot file describing a binary FSM. The file is included in the Qfsm package in the examples folder.

digraph binary_finite_state_machine {
	rankdir=LR;
	size="8,5"
	node [shape = doublecircle]; LR_0 LR_3;
	node [shape = circle];
	LR_0 [ label = "State_1" moore = "01"];
	LR_0 -> LR_1 [ label = "0000|0001###11" ];
	LR_1 -> LR_2 [ label = "NOT 0000###00" ];
	LR_1 -> LR_3 [ label = "DEF###01" ];
	LR_0 -> LR_2 [ label = "ANY###10" ];
	LR_2 -> LR_3 [ label = "1111###11" ];
}
	

Qfsm automatically determines the type of FSM: binary, ASCII, or Free Text. In the above example, "LR_0", "LR_1", … denote the states. It can be given any name by specifying the label attribute. If you don't do this, the node name (here: "LR_1", …) is used as the state name. The moore attribute is used to specify the Moore outputs of a state.

Transitions are written as

State1 -> State2;

or

State1 -> State2 [ label = "00###11" ];

where the label attribute specifies the Mealy inputs, and optionally the Moore outputs separated by the string ###. NOT denotes negation, DEF a default transition, and ANY transitions that accept any input.

To define end states, use the shape = doublecircle node attribute as illustrated in the above example.