GENERAL DESCRIPTION
The DS1553 is a full-function, year-2000-compliant (Y2KC) real-time clock/calendar (RTC) with an RTC alarm, watchdog timer, power-on reset, battery monitor, and 8k x 8 nonvolatile static RAM. User access to all registers within the DS1553 is accomplished with a byte-wide interface as shown in Figure 1. The RTC registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour BCD format. Corrections for day of month and leap year are made automatically.

FEATURES
■ Integrated NV SRAM, RTC, Crystal, Power-Fail Control Circuit, and Lithium Energy Source
■ Clock Registers are Accessed Identically to the Static RAM; These Registers are Resident in the 16 Top RAM Locations
■ Totally Nonvolatile with Over 10 Years of Operation in the Absence of Power
■ Precision Power-On Reset
■ Programmable Watchdog Timer and RTC Alarm
■ BCD-Coded 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
■ Lithium Energy Source is Electrically Disconnected to Retain Freshness Until Power is Applied for the First Time