Real Time Clock Multiplexed 242Byte 24-Pin SSOP T/R

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