A supervisory circuit for use in an integrated circuit to supervise the program execution of a processing unit is disclosed. The processing unit generates a restart signal at a particular duty cycle under proper program execution conditions and at an undesirable duty cycle under improper program execution conditions. The supervising circuit includes a capacitive or like circuit element for converting the restart signal into a signal representative of the duty cycle thereof and compares the generated signal to a reference window comprising upper and lower reference values. Should the generated signal exceed the boundaries of the window reference, a corresponding control signal is generated to change the circuit conditions and generate a reset signal to the processing unit to govern the program execution thereof to a prespecified point from which point program execution may continue upon removal of the reset signal.