Stateflow User's Guide

Simulating a Stateflow Diagram

Stateflow allows you to observe the behavior of Stateflow diagrams in Simulink models during simulation of the model. Before you simulate a Stateflow diagram, you make sure that simulation is enabled for your model as you did in Setting Up Diagram Simulation.

When you simulate a Simulink model containing Stateflow blocks, Stateflow builds an application for each Stateflow block that graphically executes its Stateflow diagram by highlighting the active state and the executing transition. By simulating your Stateflow diagrams, you understand the behavior that you specify for them, and find out if they are behaving as you expect them to.

Simulate the SFcontrol1 model as described in the following steps:

1. Before you begin simulating the SFcontrol1 model, position the Simulink model window and the Controller Stateflow diagram window so that they can both be seen at once with no overlap.
2. From the Stateflow diagram editor Simulation menu, select Start to start simulation of the model and notice the following:
• Stateflow temporarily sets the model to read-only to prevent accidental modification while the model is simulating.

• This is displayed as "Ready (ICED)" at the bottom of the Stateflow diagram window, where "ICED" is an internal Stateflow designation.

• Stateflow parses the Controller Stateflow diagram for errors.

• Parsing the Stateflow diagram ensures that the notations you specified are valid and correct. If any critical errors are found, they are displayed in a Stateflow Builder window and simulation is halted. If no errors are found, the window does not appear, and simulation continues.

  The following example window results from an error introduced into the Controller diagram by removing the name of the On state.

  

  Critical error messages are displayed with a red button. You can display the full text of an error message in the bottom pane by clicking on it in the top pane. If you double-click an error message in the top pane, the Stateflow diagram editor appears with the error-causing object highlighted.

• Stateflow displays status messages in the MATLAB Command Window while it builds the simulation application.

• The simulation application that Stateflow generates for simulation is referred to as an sfun target. Stateflow creates a directory called sfprj in the current MATLAB directory if the directory does not already exist. Stateflow uses this directory to store the generated files that make up the sfun target.

1. Simulation commences when the Stateflow diagram editor background becomes shaded as shown.
   
   

   Stateflow begins in simulation mode. The Controller diagram is active, but nothing in it is.

3. In the Simulink window, double-click the Manual Switch.

1. This causes the Manual Switch to switch between its inputs, -1 and 1. Because the trigger event for the Controller block is set to Either, changing the switch in either direction (1 to -1 or -1 to 1) sends a falling edge or rising edge signal to the Controller block that recognizes it as the event event.

   The event causes the Stateflow diagram to execute and look for the first available transition, which is the default transition into the state Off. You see the following simulation sequence:
   
   

   The only available transition, the default transition, is taken.
   The destination state of the default transition, the state Off, is entered, becomes active, and stays active until another event occurs.

4. In the Simulink window, double-click the Manual Switch.

1. This sends another event event that causes the Stateflow diagram to look for an available transition. You see the following continued simulation behavior:
   
   

   The only available transition from the active state Off to another state is the transition to the state On. The transition to On is taken.
   The Off state is exited and the destination state On is entered, becomes active, and stays active.

5. In the Simulink window, double-click the Manual Switch.

1. This sends another event event that causes the Stateflow diagram to look for an available transition. You see the following continued simulation behavior:
   
   

   The only available transition from the active state On is the transition to the Off state. The transition to the state Off is taken.
   The On state is exited and the destination state Off, is entered, becomes active, and stays active.

6. Continue sending events by double-clicking the Manual Switch in the Simulink window to repeat the sequence in the preceding steps 4 and 5.
7. Choose Stop from the graphics editor Simulation menu to stop the simulation.

1. Once the simulation stops, Stateflow resets the model to be editable.

Setting Up Diagram Simulation

Using the Debug Tool During Simulation

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