General Description

The DS12885, DS12887, and DS12C887 real-time

clocks (RTCs) are designed to be direct replacements

for the DS1285 and DS1287. The devices provide a

real-time clock/calendar, one time-of-day alarm, three

maskable interrupts with a common interrupt output, a

programmable square wave, and 114 bytes of battery-

backed static RAM (113 bytes in the DS12C887 and

DS12C887A). The DS12887 integrates a quartz crystal

and lithium energy source into a 24-pin encapsulated

DIP package. The DS12C887 adds a century byte at

address 32h. For all devices, the date at the end of the

month is automatically adjusted for months with fewer

than 31 days, including correction for leap years. The

devices

also

operate

in

either

24-hour

or

12-hour format with an AM/PM indicator. A precision

temperature-compensated circuit monitors the status of

automatically switches to a backup supply. A lithium

pin on the DS12885 to maintain time and date operation

when primary power is absent. The device is accessed

through a multiplexed byte-wide interface, which sup-

ports both Intel and Motorola modes.

Applications

Embedded Systems

Utility Meters

Security Systems

Network Hubs, Bridges, and Routers

Features

♦ Drop-In Replacement for IBM AT Computer

Clock/Calendar

♦ RTC Counts Seconds, Minutes, Hours, Day, Date,

Month, and Year with Leap Year Compensation

Through 2099

♦ Binary or BCD Time Representation

♦ 12-Hour or 24-Hour Clock with AM and PM in

12-Hour Mode

♦ Daylight Saving Time Option

♦ Selectable Intel or Motorola Bus Timing

♦ Interfaced with Software as 128 RAM Locations

♦ 14 Bytes of Clock and Control Registers

♦ 114 Bytes of General-Purpose, Battery-Backed

RAM (113 Bytes in the DS12C887 and

DS12C887A)

♦ RAM Clear Function (DS12885, DS12887A, and

DS12C887A)

♦ Interrupt Output with Three Independently

Maskable Interrupt Flags

♦ Time-of-Day Alarm Once Per Second to Once

Per Day

♦ Periodic Rates from 122μs to 500ms

♦ End-of-Clock Update Cycle Flag

♦ Programmable Square-Wave Output

♦ Automatic Power-Fail Detect and Switch Circuitry

♦ Optional 28-Pin PLCC Surface Mount Package or

32-Pin TQFP (DS12885)

♦ Optional Encapsulated DIP (EDIP) Package with

Integrated Crystal and Battery (DS12887,

DS12887A, DS12C887, DS12C887A)

♦ Optional Industrial Temperature Range Available

♦ Underwriters Laboratory (UL) Recognized

Real-Time Clock

______________________________________________

Maxim Integrated Products

1

DS12885

DS83C520

R/W

AS

GND

X2

X1

CRYSTAL

DS

AD(0–7)

SQW

RESET

IRQ

RCLR

CS

MOT

Typical Operating Circuit

Rev 3; 2/07

For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at

1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.

Pin Configurations and Ordering Information appear at end of data sheet.