Stateflow

Chapter 8
Semantics

Overview

Semantics describe how the notation is interpreted and implemented. A completed Stateflow diagram communicates how the system will behave. A Stateflow diagram contains actions associated with transitions and states. The semantics describe in what sequence these actions take place during Stateflow diagram execution.

Knowledge of the semantics is important to make sound Stateflow diagram design decisions for code generation. Different use of notations results in different ordering of simulation and generated code execution.

Stateflow semantics consist of rules for:

• Event broadcasting
• Processing states
• Processing transitions
• Taking transition paths

The details of Stateflow semantics are described largely by examples in this chapter. The examples cover a range of various notations and combinations of state and transition actions.

See Semantic Rules Summary for a summary of the semantics.

List of Semantic Examples

This is a list of the semantic examples provided in this chapter.

Transitions to and from Exclusive (OR) States

• Example: Processing of One Event
• Example: Processing of a Second Event
• Example: Processing of a Third Event
• Example: Transition from a Substate to a Substate

Condition Actions

• Example: Actions Specified as Condition Actions
• Example: Actions Specified as Condition and Transition Actions
• Example: Using Condition Actions in For Loop Construct
• Example: Using Condition Actions to Broadcast Events to Parallel (AND) States
• Example: Cyclic Behavior to Avoid When Using Condition Actions

Default Transitions

• Example: Default Transition in an Exclusive (OR) Decomposition
• Example: Default Transition to a Junction
• Example: Default Transition and a History Junction
• Example: Labeled Default Transitions

Inner Transitions

• Example: Processing One Event Within an Exclusive (OR) State
• Example: Processing a Second Event Within an Exclusive (OR) State
• Example: Processing a Third Event Within an Exclusive (OR) State
• Example: Processing One Event with an Inner Transition to a Connective Junction
• Example: Processing a Second Event with an Inner Transition to a Connective Junction
• Example: Inner Transition to a History Junction

Connective Junctions

• Example: If-Then-Else Decision Construct
• Example: Self Loop
• Example: For Loop Construct
• Example: Flow Diagram Notation
• Example: Transitions from a Common Source to Multiple Destinations
• Example: Transitions from Multiple Sources to a Common Destination
• Example: Transitions from a Source to a Destination Based on a Common Event

Event Actions

• Example: Event Actions and Superstates

Parallel (AND) States

• Example: Event Broadcast State Action
• Example: Event Broadcast Transition Action (Nested Event Broadcast)
• Example: Event Broadcast Condition Action

Directed Event Broadcasting

• Example: Directed Event Broadcast Using send
• Example: Directed Event Broadcasting Using Qualified Event Names

Temporal Logic Events

Event-Driven Effects on Semantics