VT82885 Datasheet PDF - ETC

[VIA Technologies, Inc.]

DESCRIPTION
The VT82885 Real Time Clock is designed to be a direct replacement for the DS12885. The VT82885 is identical in form, fit and function to the DS12885. It has 114 bytes of general purpose RAM. Access to this RAM space is determined by the logic level presented on AD6 during the address portion of an access cycle. An external crystal and battery are the only components required to maintain time-of-day and memory status in the absence of power.

FEATURES
• Drop-in replacement for IBM AT computer
   clock/calendar.
• Pin configuration closely matches the
   DS12887, DS12885and DS12885Q
• Counts seconds, minutes, hours, days,
   day of the week, date, month, and year
   with leap year compensation
• Binary or BCD representation of time,
   calendar and alarm
• 12- or 24-hour clock with AM and PM in
   12-hour mode
• Daylight Savings Time option
• Intel bus timing
• Multiplex bus for pin efficiency
• Interfaced with software as 128 RAM
   locations
   - 14 bytes of clock and control registers
   - 114 bytes of general purpose RAM
• Programmable square wave output signal
• Bus-compatible interrupt signals (IRQ#)
• Three interrpts are separately softwaremaskable and testable
   - Times-of-day alarm once/second to
      once/day
   - Periodic rates from 122 µs to 500 ms
   - End of clock update cycle
• Optional 28-pin PLCC surface mount
   package