DS12887A

DS12887A Real Time Clock www.dalsemi.com FEATURES § Drop–in replacement for IBM AT computer clock/calendar § Pin compatible with the MC146818B and DS1287A § 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– 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 ) § 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 PIN ASSIGNMENT PIN DESCRIPTION AD0-AD7 NC MOT CS AS R/ W DS RESET IRQ SQW VCC RCLR GND - Multiplexed Address/Data Bus - No Connection - Bus Type Selection - Chip Select - Address Strobe - Read/Write Input - Data Strobe - Reset Input - Interrupt Request Output - Square Wave Output - +5 Volt Supply - RAM Clear - Ground DESCRIPTION The DS12887A Real Time Clock plus RAM is designed to be a direct replacement for the DS1287A. The DS12887A is id...