The X4283/85 combines four popular functions, Power-on Reset Control, Watchdog Timer, Supply Voltage Supervision, and Block Lock protect serial EEPROM memory in one package. This combination lowers system cost, reduces board space requirements, and increases reliability. Applying power to the device activates the power on reset circuit which holds RESET/RESET active for a period of time. This allows the power supply and oscillator to stabilize before the processor can execute code. The Watchdog Timer provides an independent protection mechanism for microcontrollers. When the microcontroller fails to restart a timer within a selectable time out interval, the device activates the RESET/ RESET signal. The user selects the interval from three preset values. Once selected, the interval does not change, even after cycling the power. The device's low VCC detection circuitry protects the user's system from low voltage conditions, resetting the system when VCC falls below the set minimum VCC trip point. RESET/RESET is asserted until VCC returns to proper operating level and stabilizes. Four industry