DS12885:Real-Time Clocks

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 VCC. If a primary power failure is detected, the device automatically switches to a backup supply. A lithium coin-cell battery can be connected to the VBAT input 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 supports both Intel and Motorola modes.

Key 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
DS12885, DS12887, DS12887A, DS12C887, DS12C887A: Typical Operating Circuit
DS12885, DS12887, DS12887A, DS12C887, DS12C887A: Typical Operating Circuit
  • Embedded Systems
  • Network Hubs, Bridges, and Routers
  • Security Systems
  • Utility Meters
titleDownload file
DS12885-DS12C887A Data SheetDS12885-DS12C887A.pdf
Part NumberInterfaceVSUPPLY
Time Keeping Current
Memory TypeMemory Size
Time of Day AlarmsFunctionsPackage/PinsBudgetary
typSee Notes
DS12885Multiplexed52256NV SRAM1141RTCPDIP(W)/24
$3.50 @1k
DS12887--114EDIP/24$5.20 @1k
DS12887A--114EDIP/24$5.20 @1k
DS12C887--113EDIP/24$5.04 @1k
DS12C887A--113EDIP/24$5.04 @1k
Quality and Environmental Data
Ordering Information
Part NumberStatusRecommended ReplacementPackageTempRoHS
DS12885No Longer AvailableDS12885+PDIP(W),;24 pin;520.4 mm²0°C to +70°CNo
DS12885+ActivePDIP(W),;24 pin;520.4 mm²0°C to +70°CLead Free
DS12885NNo Longer AvailableDS12885N+PDIP(W),;24 pin;520.4 mm²-40°C to +85°CNo
DS12885N+ActivePDIP(W),;24 pin;520.4 mm²-40°C to +85°CLead Free
DS12885QNo Longer AvailableDS12885Q+PLCC,;28 pin;158 mm²0°C to +70°CNo
DS12885Q+ActivePLCC,;28 pin;158 mm²0°C to +70°CLead Free
DS12885Q+T&RActivePLCC,;28 pin;158 mm²0°C to +70°CLead Free
DS12885Q/T&RNo Longer AvailableDS12885Q+T&RPLCC,;28 pin;158 mm²0°C to +70°CNo
DS12885QNNo Longer AvailableDS12885QN+PLCC,;28 pin;158 mm²-40°C to +85°CNo
DS12885QN+ActivePLCC,;28 pin;158 mm²-40°C to +85°CLead Free
Part NumberStatusRecommended ReplacementPackageTempRoHS
DS12885QN+T&RActivePLCC,;28 pin;158 mm²-40°C to +85°CLead Free
DS12885SNo Longer AvailableDS12885S+SOIC(W),;24 pin;166.1 mm²0°C to +70°CNo
DS12885S+ActiveSOIC(W),;24 pin;166.1 mm²0°C to +70°CLead Free
DS12885S+T&RActiveSOIC(W),;24 pin;166.1 mm²0°C to +70°CLead Free
DS12885SNNo Longer AvailableDS12885SN+SOIC(W),;24 pin;166.1 mm²-40°C to +85°CNo
DS12885SN+ActiveSOIC(W),;24 pin;166.1 mm²-40°C to +85°CLead Free
DS12885SN+T&RActiveSOIC(W),;24 pin;166.1 mm²-40°C to +85°CLead Free
DS12885TNo Longer AvailableDS12885T+TQFP,;32 pin;84.6 mm²0°C to +70°CNo
DS12885T+ActiveTQFP,;32 pin;84.6 mm²0°C to +70°CLead Free
DS12885TN+No Longer AvailableTQFP,;32 pin;84.6 mm²-40°C to +85°CLead Free
DS12885-DS12C887A.pdf DS12C887A
Tips for Writing Bulletproof Real-Time Clock Control Code DS3234
State Machine Logic in Binary-Coded Decimal (BCD)-Formatted Real-Time Clocks DS3234
Oscillator Design Considerations for Low-Current Applications DS17885
Selecting a Backup Source for Real-Time Clocks DS3234
Problems and Solutions for Adjusting to Changes in Daylight Saving Time DS17887
Interface a Multiplexed-Bus Real-Time Clock to a µP With Separate Address and Data Buses DS17887
Using the DS32kHz with Maxim Real-Time Clocks DS17885
Using Multiplexed Bus Clocks with a Microcontroller DS17887
Lithium Coin-Cell Batteries: Predicting an Application Lifetime DS9034PCX
Design Considerations for Maxim Real-Time Clocks DS3234
Crystal Considerations with Maxim Real-Time Clocks (RTCs) DS3234
DS12885.pdf DS12885
DS12885-DS12C887A.pdf DS12C887A