Dallas Maxim DS12885 Manual
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General DescriptionThe DS12885, DS12887, and DS12C887 real-timeclocks (RTCs) are designed to be direct replacementsfor the DS1285 and DS1287. The devices provide areal-time clock/calendar, one time-of-day alarm, threemaskable interrupts with a common interrupt output, aprogrammable square wave, and 114 bytes of battery-backed static RAM (113 bytes in the DS12C887 andDS12C887A). The DS12887 integrates a quartz crystaland lithium energy source into a 24-pin encapsulatedDIP package. The DS12C887 adds a century byte ataddress 32h. For all devices, the date at the end of themonth is automatically adjusted for months with fewerthan 31 days, including correction for leap years. Thedevices also operate in either 24-hour or12-hour format with an AM/PM indicator. A precisiontemperature-compensated circuit monitors the status ofVCC . If a primary power failure is detected, the deviceautomatically switches to a backup supply. A lithiumcoin-cell battery can be connected to the V BAT inputpin on the DS12885 to maintain time and date operationwhen primary power is absent. The device is accessedthrough a multiplexed byte-wide interface, which sup-ports both Intel and Motorola modes.ApplicationsEmbedded SystemsUtility MetersSecurity SystemsNetwork Hubs, Bridges, and RoutersFeatures♦ Drop-In Replacement for IBM AT ComputerClock/Calendar♦ RTC Counts Seconds, Minutes, Hours, Day, Date,Month, and Year with Leap Year CompensationThrough 2099♦ Binary or BCD Time Representation♦ 12-Hour or 24-Hour Clock with AM and PM in12-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-BackedRAM (113 Bytes in the DS12C887 andDS12C887A)♦ RAM Clear Function (DS12885, DS12887A, andDS12C887A)♦ Interrupt Output with Three IndependentlyMaskable Interrupt Flags♦ Time-of-Day Alarm Once Per Second to OncePer 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 or32-Pin TQFP (DS12885)♦ Optional Encapsulated DIP (EDIP) Package withIntegrated Crystal and Battery (DS12887,DS12887A, DS12C887, DS12C887A)♦ Optional Industrial Temperature Range Available♦ Underwriters Laboratory (UL) RecognizedDS12885/DS12887/DS12887A/DS12C887/DS12C887AReal-Time Clock______________________________________________Maxim Integrated Products 1DS12885DS83C520R/WASGNDX2X1VCCVCCCRYSTALDSV BATAD(0–7) SQWRESETIRQRCLRCSMOTTypical Operating CircuitRev 3; 2/07For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.Pin Configurations and Ordering Information appear at end of data sheet. |
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