Digital supervisory and diagnostic circuitry to provide a watchdog function and a low voltage detect function and diagnostics for those functions. The watchdog function has a high immunity to EMI and RFI disturbances and may be enabled or disabled as necessary. An indication is provided of the cause of the last reset so that a reset due to EMI can be distinguished from a reset due to a power failure. The low voltage detect circuitry is implementable in an integrated circuit chip. The low voltage detect circuitry eliminates oscillations from the reset signal and provides a delay which is programmable by the user. The circuitry is designed so that the length of the delay can never be zero.