The DS1286 Watchdog Timekeeper is a self-contained real time clock, alarm, watchdog timer, and interval timer in a 28-pin JEDEC DIP package. The DS1286 contains an embedded lithium energy source and a quartz crystal which eliminates the need for any external circuitry. Data contained within 64 eightbit registers can be read or written in the same manner as bytewide static RAM. Data is maintained in the Watchdog Timekeeper by intelligent control circuitry which detects the status of VCC and write protects memory when VCC is out of tolerance. The lithium energy source can maintain data and real time for over 10 years in the absence of VCC. Watchdog Timekeeper information includes hundredths of seconds, seconds, minutes, hours, day, date, month, and year. The date at the end of the month is automatically 1 of 13