The DS1643 is an 8K x 8 nonvolatile static RAM with a full function Real Time Clock (RTC) that are
both accessible in a byte-wide format. The nonvolatile timekeeping RAM is functionally equivalent to
any JEDEC standard 8K 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. The
real time clock information resides in the eight uppermost RAM locations. The RTC registers contain
year, month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the day
of the month and leap year are made automatically. The RTC clock registers are double-buffered to
avoid access of incorrect data that can occur during clock update cycles. The double-buffered system also
prevents time loss as the timekeeping countdown continues unabated by access to time register data. The
DS1643 also contains its own power-fail circuitry, which deselects the device when the VCC supply is in
an out of tolerance condition. This feature prevents loss of data from unpredictable system operation
brought on by low VCC as errant access and update cycles are avoided.
Key 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 Reside in the
Eight Top RAM Locations.
Totally Nonvolatile with Over 10 Years of
Operation in the Absence of Power
Access Times of 70ns and 100ns
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
DS1643 Only (DIP Module)
Standard JEDEC Byte-Wide 8K x 8 RAM
Pinout
DS1643P Only (PowerCap Module Board) Surface Mountable Package for Direct
Notes: **This pricing is BUDGETARY, for comparing similar parts. Prices are in
U.S. dollars and subject to change. Quantity pricing may vary
substantially and international prices may differ due to local
duties, taxes, fees, and exchange rates. For volume-specific prices
and delivery, please see the price and availability page
or contact an authorized distributor.
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