Stateflow User's Guide

Introducing Stateflow Semantics

The behavior applied to the outgoing transition from a junction in the example in Simulating Junction Behavior also applies to states. For outgoing transitions of equal validity from a state or a junction, Stateflow makes the decision based on clock position.

Stateflow follows a rule like this to make sure your Stateflow diagrams are deterministic. If Stateflow does not have this kind of rule, it could get stuck determining the right thing to do. Instead, Stateflow has a set of rules called semantics that it uses to make sure your model always runs and never gets stuck.

Here are some of the semantics that you have learned in this Getting Started guide to this point:

• Stateflow updates only in response to a broadcast event.
• Transitions can be guarded to take place only in response to the specified event under the specified condition.
• States can have entry actions: actions that are performed when the state is entered.
• In testing for outgoing transitions or transition segments from a junction or a state, Stateflow gives preference to transitions with conditions.
• If two or more outgoing transitions test equal in validity, Stateflow prefers the transition with the smallest clock position.

Stateflow has other semantics to make your diagrams behave deterministically. This subject is dealt with in much greater detail in the "Stateflow Semantics" chapter of Stateflow documentation. This is a good place to go to further your education on Stateflow after you have completed this Getting Started guide.

Simulating Junction Behavior

Using Junctions in Flow Diagrams

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