at

Execute chart at event broadcast or specified time

Syntax

at(n,E)

at(n,tick)

at(n,sec)

Description

at(n,E) returns true if the event E has occurred exactly n times since the associated state became active. Otherwise, the operator returns false.

at(n,tick) returns true if the chart has woken up exactly n times since the associated state became active. Otherwise, the operator returns false.

The implicit event tick is not supported when a Stateflow^® chart in a Simulink^® model has input events.

at(n,sec) returns true if exactly n seconds have elapsed since the associated state became active. Otherwise, the operator returns false.

In standalone charts in MATLAB^®, specify n with a value greater than or equal to 0.001. The operator creates a MATLAB timer object that generates an implicit event to wake up the chart. MATLAB timer objects are limited to 1 millisecond precision. For more information, see Events in Standalone Charts.

• The timer object is created when the chart finishes executing the entry actions of the associated state and its substates. If you specify n as an expression whose value changes during chart execution, the chart does not adjust the temporal delay of the timer object.

• The timer object starts running at the end of the chart step when the associated state becomes active. This step can include the execution of other parallel states in the chart.

• If the chart is processing another operation when it receives the implicit event from the timer object, the chart queues the event. When the current step is completed, the chart processes the event.

• If the state associated with the temporal logic operator becomes inactive before the chart processes the implicit event, the event does not wake up the chart.

Note

This syntax is supported only in standalone charts in MATLAB. For charts in Simulink models, use the after operator instead. For more information, see Do Not Use at for Absolute-Time Temporal Logic in Charts in Simulink Models.

Examples

Execute State Action on Event Broadcast

Display a status message when the chart processes the third broadcast of the event E after the state became active.

on at(3,E):
   disp("ON");

Trigger Transition on Event Broadcast

Transition out of the associated state when the chart processes the fifth broadcast of the event E after the state became active.

at(5,E)

Guard Transition with Temporal Condition

Transition out of the associated state if the state has been active for exactly five broadcasts of the event E.

In charts in a Simulink model, enter:

[at(5,E)]

Conditional notation for temporal logic operators is not supported in standalone charts in MATLAB.

Trigger Transition on Chart Execution

Transition out of the associated state when the chart wakes up for the seventh time since the state became active, but only if the variable temp is greater than 98.6.

at(7,tick)[temp > 98.6]

Execute State Action at Specified Time

Set the temp variable to HIGH if the state has been active for exactly 12.3 seconds.

In standalone charts in MATLAB, enter:

on at(12.3,sec):
   temp = HIGH;

Using every as an absolute-time temporal logic operator is not supported in charts in Simulink models.

Tips

• You can use quotation marks to enclose the keywords 'tick' and 'sec'. For example, at(5,'tick') is equivalent to at(5,tick).

• The Stateflow chart resets the counter used by the at operator each time the associated state reactivates.

• Standalone charts in MATLAB define absolute-time temporal logic in terms of wall-clock time, which is limited to 1 millisecond precision.

Version History

Introduced in R2014b