DESCRIPTION
The DS1642 is a 2K x 8 nonvolatile static RAM and a full-function real time clock which are both accessible in a bytewide format. The nonvolatile time keeping RAM is pin- and function-equivalent to any JEDEC standard 2K x 8 SRAM. The device can also be easily substituted in ROM, EPROM and EEPROM sockets, providing read/write nonvolatility and the addition of the real time clock function.

FEATURES
● Integrated NV SRAM, real time clock, crystal, power fail control circuit and lithium energy source
● Standard JEDEC bytewide 2K x 8 static RAM pinout
● 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 times of 70 ns and 100 ns
● Quartz accuracy ±1 minute a month @ 25°C, factory calibrated
● 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
● Lithium energy source is electrically disconnected to retain freshness until power is applied for the first time