There is no direct solution to execute a transition at a rising edge of an input, without impacting the general execution of the Stateflow chart.
As a workaround you could try one of the following:
1) Implement the edge detection in Simulink with a "Detect Rise" block, and use the output of the "Detect Rise" as a regular Stateflow input.
2) Implement the edge detection inside the Stateflow chart with local variables.
3) Use another event input to trigger the Stateflow chart at different time steps. This event should not be reused in a transition. I should only make sure that the Stateflow chart executes at the correct rate.
