The CMOS bq3285E/L is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. The bq3285L supports 3V systems. Other bq3285E/L features include three maskable interrupt sources, square-wave output, and 242 bytes of general nonvolatile storage. A 32.768kHz output is available for sustaining power-management activities. Wake-up capability is provided by an alarm interrupt, which is active in battery-backup mode. The bq3285E/L write-protects the clock, calendar, and storage registers during power failure. A backup battery then maintains data and operates the clock and calendar. The bq3285E/L is a fully compatible real-time clock for IBM AT-compatible computers and other applications. The only external components are a 32.768kHz crystal and a backup battery.