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Broadcast Events to Synchronize States

Directed Event Broadcasting

You can broadcast events directly from one state to another to synchronize parallel (AND) states in the same chart. The following rules apply:

  • The receiving state must be active during the event broadcast.

  • An action in one chart cannot broadcast events to states in another chart.

Using a directed local event broadcast provides the following benefits over an undirected broadcast:

  • Prevents unwanted recursion during simulation.

  • Improves the efficiency of generated code.

For information about avoiding unwanted recursion, see Guidelines for Avoiding Unwanted Recursion in a Chart.

Directed Local Event Broadcast Using send

The format of a directed local event broadcast with send is:

send(event_name,state_name)

where event_name is broadcast to state_name and any offspring of that state in the hierarchy. The event you send must be visible to both the sending state and the receiving state (state_name).

The state_name argument can include a full hierarchy path to the state. For example, if the state A contains the state A1, send an event e to state A1 with the following broadcast:

send(e, A.A1)

    Tip   Do not include the chart name in the full hierarchy path to a state.

The following example of a directed local event broadcast uses the send(event_name,state_name) syntax.

In this example, event E_one belongs to the chart and is visible to both A and B. See Directed Event Broadcast Using Send for more information on the semantics of this notation.

Directed Local Event Broadcast Using Qualified Event Names

The format of a directed local event broadcast using qualified event names is:

send(state_name.event_name)

where event_name is broadcast to its owning state (state_name) and any offspring of that state in the hierarchy. The event you send is visible only to the receiving state (state_name).

The state_name argument can also include a full hierarchy path to the receiving state. Do not use the chart name in the full path name of the state.

The following example shows the use of a qualified event name in a directed local event broadcast.

In this example, event E_one belongs to state B and is visible only to that state. See Directed Event Broadcast Using Qualified Event Name for more information on the semantics of this notation.

Diagnostic for Detecting Undirected Local Event Broadcasts

If you have undirected local event broadcasts in state actions or condition actions in your chart, a warning appears by default during simulation. Examples of state actions with undirected local event broadcasts include:

  • entry: send(E1), where E1 is a local event in the chart

  • exit: E2, where E2 is a local event in the chart

You can control the level of diagnostic action for undirected local event broadcasts in the Diagnostics > Stateflow pane of the Model Configuration Parameters dialog box. Set the Undirected event broadcasts diagnostic to none, warning, or error. For more information, see the documentation for the Undirected event broadcasts diagnostic.

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