The DS1302 trickle-charge timekeeping chip contains a real-time clock/calendar and 31 bytes of static RAM. It communicates with a microprocessor via a simple serial interface. The real-time clock/calendar provides seconds, minutes, hours, day, date, month, and year information. The end of the month date is automatically adjusted for months with fewer than 31 days, including corrections for leap year. The clock operates in either the 24-hour or 12-hour format with an AM/PM indicator.

Interfacing the DS1302 with a microprocessor is simplified by using synchronous serial communication. Only three wires are required to communicate with the clock/RAM: CE, I/O (data line), and SCLK (serial clock). Data can be transferred to and from the clock/RAM 1 byte at a time or in a burst of up to 31 bytes. The DS1302 is designed to operate on very low power and retain data and clock information on less than 1µW.

The DS1302 is the successor to the DS1202. In addition to the basic timekeeping functions of the DS1202, the DS1302 has the additional features of dual power pins for primary and backup power supplies, programmable trickle charger for VCC1, and seven additional bytes of scratchpad memory.
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  • Completely Manages All Timekeeping Functions
    • Real-Time Clock Counts Seconds, Minutes, Hours, Date of the Month, Month, Day of the Week, and Year with Leap-Year Compensation Valid Up to 2100
    • 31 x 8 Battery-Backed General-Purpose RAM
  • Simple Serial Port Interfaces to Most Microcontrollers
    • Simple 3-Wire Interface
    • TTL-Compatible (VCC = 5V)
    • Single-Byte or Multiple-Byte (Burst Mode) Data Transfer for Read or Write of Clock or RAM Data
  • Low Power Operation Extends Battery Backup Run Time
    • 2.0V to 5.5V Full Operation
    • Uses Less Than 300nA at 2.0V
  • 8-Pin DIP and 8-Pin SO Minimizes Required Space
  • Optional Industrial Temperature Range: -40°C to +85°C Supports Operation in a Wide Range of Applications
  • Underwriters Laboratories® (UL) Recognized
Part Number Interface VSUPPLY
Time Keeping Current
Memory Type Memory Size
Time of Day Alarms Functions Package/Pins Budgetary
typ See Notes
DS1302  3-Wire
200 6 NV SRAM 31 0 RTC
$1.46 @1k
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