The Dallas DS12887+ Real Time Clock (RTC) plus RAM is a direct replacement for the DS1287. The DS12887 is identical in form, fit, and function to the DS1287. It also has an additional 64 bytes of general-purpose RAM. Access to this additional RAM space is determined by the logic level presented on AD6 during the address portion of an access cycle. A lithium energy source, quartz crystal, and write-protection circuitry are contained within a 24-pin dual in-line package. As such, the DS12887 is a complete subsystem replacing 16 components in a typical application. The functions include a nonvolatile time-of-day clock, an alarm, a 100-year calendar, a programmable interrupt, a square-wave generator, and 114 bytes of NV SRAM. The RTC is unique in that time of day and memory are maintained even in the absence of power.