State Transition Tables in Stateflow

A state transition table is an alternative way of expressing sequential modal logic. Instead of drawing states and transitions graphically in a Stateflow^® chart, use state transition tables to express the modal logic in tabular format. State transition tables are supported only as blocks in a Simulink^® model.

Benefits of using state transition tables include:

• Ease of modeling train-like state machines, where the modal logic involves transitions from one state to its neighbor

• Concise, compact format for a state machine

• Reduced maintenance of graphical objects

  When you add or remove states from a chart, you have to rearrange states, transitions, and junctions. When you add or remove states from a state transition table, you do not have to rearrange any graphical objects.

State transition tables support using MATLAB^® and C as the action language. For more information about the differences between these action languages, see Differences Between MATLAB and C as Action Language Syntax.

The following state transition table contains the modal logic for maintaining the temperature of a boiler between two set points:

This Stateflow chart represents the same modal logic:

Rules for Using State Transition Tables

• If you specify an action in a transition cell, it must be a condition action.

• State transition tables must have at least one state row and one transition column.

Differences Between State Transition Tables and Charts

State transition tables support a subset of the most commonly used elements in Stateflow charts. Elements that state transition tables do not support include:

• Supertransitions

• Parallel (AND) decomposition

• Local events

• Flow charts

• Use of chart-level functions (graphical, truth table, MATLAB, and Simulink)

Anatomy of a State Transition Table

A state transition table contains the following components:

Each transition column contains the following state-to-state transition information:

• Condition

• Condition action

• Destination state

Create State Transition Table and Specify Properties

How to Create a New State Transition Table

At the MATLAB command prompt, enter:

sfnew('-STT')

From the Simulink Library Browser:

1. Select the Stateflow library.

2. Drag a state transition table into your model.

   

Properties for State Transition Tables

To access properties, in the Stateflow editor, select Chart > Properties.

These properties are the same as those for charts that use MATLAB as the action language. For a description of each property, see Specify Properties for Stateflow Charts.

Generate Diagrams from State Transition Tables

Stateflow software automatically generates a read-only state transition diagram from the state transition table you create. As you enter changes to a state transition table, Stateflow incrementally updates the diagram as well. To see the most up-to-date version of the underlying diagram, select Chart > View auto-generated diagram.