The CMOS bq3285 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 114 bytes of general nonvolatile storage.
●The bq3285 write-protects the clock, calendar, and storage registers during power failure. A backup battery then maintains data and operates the clock and calendar.
●The bq3285 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.
● Direct clock/calendar replacement for IBM® AT-compatible computers and other applications
● Functionally compatible with the DS1285
● Closely matches MC146818A pin configuration
● 114 bytes of general nonvolatile storage
● 160ns cycle time allows fast bus operation
● Selectable Intel or Motorola bus timing
● Less than 0.5µA load under battery operation
● 14 bytes for clock/calendar and control
● BCD or binary format for clock and calendar data
● Calendar in day of the week, day of the month, months, and years, with automatic leap-year adjustment
● Time of day in seconds, minutes, and hours
● 12- or 24-hour format
● Optional daylight saving adjustment
● Programmable square wave output
● Three individually maskable interrupt event flags:
● Periodic rates from 122us to 500ms
● Time-of-day alarm once per second to once per day
● End-of-clock update cycle
● 24-pin plastic DIP or SOIC
