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.
Feature
- 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
