DS12887 Просмотр технического описания (PDF) - Dallas Semiconductor -> Maxim Integrated

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DS12887

Real Time Clock

Dallas Semiconductor -> Maxim Integrated 

www.dalsemi.com

DS12887

Real Time Clock

FEATURES

§ 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– 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 ms to 500 ms

– End of clock update cycle

PIN ASSIGNMENT

NC

PIN DESCRIPTION

AD0–AD7 – Multiplexed Address/Data Bus

NC

– No Connection

MOT

– Bus Type Selection

CS

– Chip Select

AS

– Address Strobe

R/ W

– Read/Write Input

DS

– Data Strobe

RESET

– Reset Input

IRQ

SQW

VCC

GND

– Interrupt Request Output

– Square Wave Output

– +5 Volt Supply

– Ground

DESCRIPTION

The DS12887 Real Time Clock plus RAM is designed to be a direct replacement for the DS1287. The

DS12887 is identical in form, fit, and function to the DS1287, 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. 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 one-hundred–year calendar, programmable interrupt, square wave

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