The DS12C887 Real Time Clock plus RAM is designed as a direct upgrade replacement for the DS12887 in existing IBM compatible personal computers to add hardware year 2000 compliance. A century byte was added to memory location 50, 32h, as called out by the PC AT specification. A lithium energy source, quartz crystal, and write-protection circuitry are contained within a 24pin dual in-line package. As such, the DS12C887 is a complete subsystem replacing 16 components in a typical application. The functions include a nonvolatile time-of-day clock, an alarm, a one-hundred-year calendar, programmable interrupt, square wave generator, and 113 bytes of nonvolatile static RAM. The real time clock is distinctive in that time-of-day and memory are maintained even in the absence of power. 1 of 19