In this model a merged signal serves as the input to a function-call subsystem. Latching is necessary if one of the signals entering the Merge block forms a feedback loop with the function-call subsystem. In this example, one of the output signals from FCSS2 combines with the output of an Enabled Subsystem block and then feeds back into an inport of FCSS2.
Digital Clock | Enabled Subsystem | Function-Call Feedback Latch | Function-Call Generator | Function-Call Subsystem | Merge | Pulse Generator