DESCRIPTION
The DS1644 is a 32k x 8 nonvolatile static RAM with a full function real time clock, which are both accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to any JEDEC standard 32k x 8 SRAM. The device can also be easily substituted for ROM, EPROM and EEPROM, providing read/write nonvolatility and the addition of the real time clock function. The real time clock information resides in the eight uppermost RAM locations.

FEATURES
■ Integrated NV SRAM, Real-Time Clock, Crystal, Power-Fail Control Circuit and Lithium Energy Source
■ Clock Registers are Accessed Identically to the Static RAM. These Registers are Resident in the Eight Top RAM Locations.
■ Totally Nonvolatile with Over 10 Years of Operation in the Absence of Power
■ BCD-Coded Year, Month, Date, Day, Hours, Minutes, and Seconds with Leap Year Compensation Valid Up to 2100
■ Power-Fail Write Protection Allows for ±10% VCC Power Supply Tolerance ■ DS1644 Only (DIP Module)
    Upward Compatible with the DS1643 Timekeeping RAM to Achieve Higher RAM Density
    Standard JEDEC Bytewide 32k x 8 Static RAM Pinout
■ DS1644P Only (PowerCap Module Board)
    Surface Mountable Package for Direct Connection to PowerCap Containing Battery and crystal
    Replaceable Battery (PowerCap)
    Power-Fail Output
    Pin-for-Pin Compatible with Other Densities of DS164XP Timekeeping RAM
    Underwriters Laboratory (UL) Recognized