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DS12887A

Dallas
Part Number DS12887A
Manufacturer Dallas
Description Real Time Clock
Published Jul 21, 2014
Detailed Description DS12887A Real Time Clock www.dalsemi.com FEATURES § Drop–in replacement for IBM AT computer clock/calendar § Pin compat...
Datasheet PDF File DS12887A PDF File

DS12887A
DS12887A

Overview
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 identical in form, fit, and function to the DS1287A, and 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.
The RCLR pin is used to clear (set to logic 1) all 114 bytes of general purpose RAM but does not affect the RAM associated with the real time clock.
In order 1 of 2 031899 DS12887A to clear the RAM, RCLR must be forced to an input logic “0” (–0.
3 to +0.
8 volt...


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