DESCRIPTION
The DS12B887 Real Time Clock plus RAM is designed to be a direct replacement for the DS1287A or DS12887A. The DS12B887 is identical in form, fit, and function to the DS1287A or DS12887A, with the exception of RCLR, and has an additional 64 bytes of general purpose RAM.

FEATURES
• Drop-in replacement for IBM AT computer clock/calendar
• Pin compatible with the MC146818B and DS1287
• 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, 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
• 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 interrupts are separately software-maskable and testable
    – Time-of-day alarm once/second to once/day
    – Periodic rates from 122 µs to 500 ms
    – End of clock update cycle