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 V_CC supply is in an out of tolerance condition. This feature prevents loss of data from unpredictable system operation brought on by low V_CC as errant access and update cycles are avoided.

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% V_CC 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 Connection to PowerCap Containing Battery and Crystal
  • Replaceable Battery (PowerCap)
  • Power-Fail Output
  • Pin-for-Pin Compatible with Other Densities of DS164XP Timekeeping RAM

原理框圖