A power-on reset (POR) circuit that initially asserts the POR signal when the supply voltage is turned on. As the supply voltage increases the POR signal is deasserted when it is determined that the supply voltage is sufficiently high to make storage elements in a circuit being controlled by the POR signal fully operational. The POR signal is kept deasserted until the power supply voltage level drops to a level low enough to render the storage elements in the controlled circuit incapable of holding accurate data. The POR signal is then reasserted at this low power supply voltage level. The low power supply voltage level that triggers the reassertion of the POR signal is lower than the sufficiently high power supply voltage level that triggers the deassertion of the POR signal, thus allowing the power supply voltage level to drop significantly before the POR signal is reasserted. A control signal allows the POR signal to be generated in response to different power supply voltage levels. Another control signal allows the POR signal to be forcibly generated.