The Watchdog Timer provides an independent protection system for microcontrollers. During a system failure, the X25043/45 watchdog will respond with a RESET/ RESET signal after a selectable time-out interval. The user selects the interval from three preset values. Once selected, the interval does not change, even after cycling the power. The system is protected from low voltage conditions by the X25043/45 low VCC detection circuits. When VCC drops below the minimum VCC trip point, the system is reset. Reset is asserted until VCC returns and stabilizes. The memory portion of the X25043/45 is a CMOS 4096bit serial E2PROM, internally organized as 512 X 8. The X25043/45 features a Serial Peripheral Interface (SPI) and software protocol allowing operation on a simple three-wire bus.