bq3287

The CMOS bq3287/bq3287A 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,  quare- wave output, and 114 bytes of gen-eral nonvolatile storage. Thebq3287A version is identical to the bq3287,with the addition of the RAM clearinput.


The bq3287 is a fully compatible real-time clock for IBM AT-compatible computers and other applications. The bq3287 write-protects the clock, calendar, and storage registers during power fail-ure. The integral backup energy source then maintains data and operatestheclockandcalendar.


As shipped from Benchmarq, the real time clock of bq3287 is turned off to maxi-mize battery capacity for in-system operation.


The bq3287 is functionally equivalent to the bq3285, except that the battery (16, 20) and crystal (2, 3) pins 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 bq3285 data sheet.