CAT1161/2 is a complete memory and supervisory solution for microcontroller-based systems. A 16K serial EEPROM memory with hardware memory write protection, a system power supervisor with brown out protection and a watchdog timer are integrated together in low power CMOS technology. Memory interface is via an I2C bus. The 1.6-second watchdog circuit returns a system to a known good state if a software or hardware glitch halts or “hangs” the system. The CAT1161 watchdog monitors the SDA line, making an additional PC board trace unnecessary. The lower cost CAT1162 does not have a watchdog timer. The power supply monitor and reset circuit protects memory and system controllers during power up/down and against brownout conditions. Five reset threshold voltages support 5V, 3.3V and 3V systems. If power supply voltage drops below the threshold, the system will reset.