DESCRIPTION
The DS1647 is a 512k 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 512k 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.

FEATURES
● Integrates 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
● Access time of 120 ns and 150 ns
● 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
● DS1647 only (DIP Module)
    - Upward compatible with the DS1643 Timekeeping RAM to achieve higher RAM density
    - Standard JEDEC byte-wide 128k x 8 RAM pinout
● DS1647P 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