DESCRIPTION
The DS1287A is identical to the DS1287 with the addition of the RAM clear pin. For a complete description of
operating conditions, electrical and mechanical characteristics, bus timing, and pin descriptions see the DS12887A data sheet.

FEATURES
•Drop-in replacement for IBM AT computer clock/calendar
•Pin compatible with the MC146818A
•Totally nonvolatile with over 10 years of operation in the absence of power
•Self-contained subsystem includes lithium, quartz, and support circuitry
•Counts seconds, minutes, hours, 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
•Selectable between Motorola and Intel bus timing
•Multiplex bus for pin efficiency
•Interfaced with software as 64 RAM locations
– 14 bytes of clock and control registers
– 50 bytes of general purpose RAM
•Programmable square wave output signal
•Bus-compatible interrupt signals (IRQ)
•Three interrupts are separately software-maskable and testable
– Time-of-day alarm once/second to once/day
– Periodic rates from 122
sto 500 ms
– End of clock update cycle