BQ4802YDW Clock/Timing - Real Time Clocks by Texas Instruments

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The CMOS bq4285 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.
Features➤ 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➤ Automatic backup and writeprotect control to external SRAM➤ 160 ns cycle time allows fast bus operation➤ Selectable Intel or Motorola bus timing (PLCC), Intel bus timing (DIP and SOIC)➤ Less than 0.5 µA load under battery operation➤ 14 bytes for clock/calendar and control➤ 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➤ BCD or binary format for clock and calendar data➤ Programmable square wave output➤ Three individually maskable interrupt event flags: - Periodic rates from 122 µs to 500 ms - Time-of-day alarm once per second to once per day - End-of-clock update cycle➤ 24-pin plastic DIP or SOIC