The CMOS bq3287E/bq3287EA is a low-power microprocessor peripheral providing a time-of-day clock and 100-year calendar with alarm features and battery operation. Other 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 bq3287EA version is identical to the bq3287E, with the addition of the RAM clear input. The bq3287E is a fully compatible real-time clock for IBM AT-compatible computers and other applications. The bq3287E write-protects the clock, calendar, and storage registers during power failure. The integral backup energy source then maintains data and operates the clock and calendar. As shipped, the real time clock is turned off to maximize battery capacity for in-system operation. The bq3287E is functionally equivalent to the bq3285E, except the battery (16,20) and crystal pins (2,3) are not accessible. These pins are connected internally to a coin cell and quartz crystal. The coin cell is sized to provide 10 years of data retention and clock operation in the absence of power. For a complete description of features, operating conditions, electrical characteristics, bus timing, and pin descriptions, see the bq3285E data sheet.