SUMMARY DESCRIPTION
The M41T256Y Serial TIMEKEEPER® SRAM is a low power 256 Kbit static CMOS SRAM organized as 32K words by 8 bits. A built-in 32.768kHz oscillator (external crystal controlled) and 8 bytes of the SRAM (see Table 3., page 14) are used for the clock/calendar function and are configured in binary coded decimal (BCD) format.

FEATURES SUMMARY
■ 5V OPERATING VOLTAGE
■ SERIAL INTERFACE SUPPORTS EXTENDED I2C BUS ADDRESSING (400kHz)
■ AUTOMATIC SWITCH-OVER AND DESELECT CIRCUITRY
■ POWER-FAIL DESELECT VOLTAGES:
   – M41T256Y: VCC = 4.5 to 5.5V;
      VPFD = 4.2 < VPFD < 4.5V
■ COUNTERS FOR TENTHS/HUNDREDTHS OF SECONDS, SECONDS, MINUTES, HOURS, DAY, DATE, MONTH, and YEAR
■ PROGRAMMABLE SOFTWARE CLOCK CALIBRATION
■ 32,752 BYTES OF GENERAL PURPOSE RAM
■ MICROPROCESSOR POWER-ON RESET
■ HOLDS MICROPROCESSOR IN RESET UNTIL SUPPLY VOLTAGE REACHES STABLE OPERATING LEVEL
■ AUTOMATIC ADDRESS-INCREMENTING
■ TAMPER INDICATION CIRCUIT WITH TIMESTAMP
■ SLEEP MODE FUNCTION
■ PACKAGING INCLUDES A 44-LEAD SOIC AND SNAPHAT® TOP (to be ordered separately)
■ SOIC PACKAGE PROVIDES DIRECT CONNECTION FOR A SNAPHAT® TOP WHICH CONTAINS THE BATTERY AND CRYSTAL