美信电子推出非易失时钟RAM-DS1642

The DS1642 is a 2k x 8 nonvolatile static RAM and a full-function real-time clock (RTC), both of which are 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. 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 DS1642 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.

关键特性

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 85ns and 100ns

Quartz Accuracy ±1 Minute a Month at +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% V_CC Power Supply Tolerance

Lithium Energy Source is Electrically Disconnected to Retain Freshness Until Power is Applied for the First Time

原理框图