| 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 valid up to 2100 Binary or BCD representation of time, calendar, and alarm 12-hour 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 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-bar) Three interrupts are separately software-maskable and testable Time-of-day alarm once/second to once/day Periodic rates from 122ms to 500ms End-of-clock update cycle Underwriters Laboratory (UL) recognized |