before
Execute chart before event broadcast or specified time
Description
before( returns
n,E)true if the event E has occurred fewer than
n times since the associated state became active. Otherwise, the
operator returns false.
before( returns
n,tick)true if the chart has woken up fewer than 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.
before(
returns n,time_unit)true if fewer than n units of time have
elapsed since the associated state became active. Otherwise, the operator returns
false.
Specify time_unit as seconds (sec), milliseconds
(msec), or microseconds (usec). If you specify
n as an expression, the chart adjusts the temporal delay as the
expression changes value during the simulation.
Note
The temporal logic operator before is supported only in Stateflow charts in Simulink models.
Examples
Execute State Action on Event Broadcast
Display a status message when the chart processes the first and
second broadcasts of the event E after the state became active.
on before(3,E):
disp('ON');
Trigger Transition on Event Broadcast
Transition out of the associated state when the chart processes a
broadcast of the event E, but only if the state has been active for
fewer than five broadcasts of E.
before(5,E)
Guard Transition with Temporal Condition
Transition out of the associated state if the state has been active
for fewer than five broadcasts of the event E.
[before(5,E)]
Trigger Transition on Chart Execution
Transition out of the associated state when the chart wakes up, but
only if the variable temp is greater than 98.6 and the chart has woken
up fewer than seven times since the state became active.
before(7,tick)[temp > 98.6]
Execute State Action Before Specified Time
Set the temp variable to MED
every time that the chart wakes up, but only if the associated state has been active for
fewer 12.3 seconds.
on before(12.3,sec):
temp = MED;
Tips
You can use quotation marks to enclose the keywords
'tick','sec','msec', and'usec'. For example,before(5,'tick')is equivalent tobefore(5,tick).The Stateflow chart resets the counter used by the
beforeoperator each time the associated state reactivates.