深圳市中立信电子科技有限公司

DS1744W-120+

Y2K-Compliant, Nonvolatile Timekeeping RAMs

实时时钟 Timekeeping NV RAM

DESCRIPTION DS1744W-120+

The DS1744W-120+ DS1744 is a full-function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) and 32k x 8 NV SRAM. User access to all registers within the DS1744 is accomplished with a byte-wide interface as shown in Figure 1. The RTC information and control bits reside in the eight uppermost RAM locations. The RTC registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for the date of each 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 DS1744 also contains its own power-fail circuitry that 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.

FEATURES DS1744W-120+

 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 are Resident

in the Eight Top RAM Locations.

 Century Byte Register (i.e., Y2K Compliant)

 Totally Nonvolatile with Over 10 Years of

Operation in the Absence of Power

 BCD-Coded Century, Year, Month, Date,

Day, Hours, Minutes, and Seconds with

Automatic Leap-Year Compensation Valid

Up to the Year 2100

 Battery Voltage-Level Indicator Flag

 Power-Fail Write Protection Allows for ±10%

VCC Power-Supply Tolerance