This model shows triggered subsystems and describes the different trigger types. A triggered subsystem is executed for a single time step whenever the trigger port transitions in a specified direction. The transition of the trigger port may occur when the direction of the transition is rising, falling, or either rising or falling. A rising transition occurs when the trigger signal transitions from zero or below to a positive value. A falling transition occurs when the trigger signal transitions from zero or above to a negative value.
After running the simulation, look closely at the top plot in the scope. This shows a sine wave, a waveform, and the grounded value of zero. As the waveform transitions through zero, each of the subsystems is triggered appropriately. The output of each subsystem is equal to the current value of the sine wave at that time.