GENERAL DESCRIPTION
The DS1500 is a full-function, year 2000-compliant real-time clock/calendar(RTC) with an alarm, watchdog timer, power-on reset, battery monitors, 256 bytes of on-board nonvolatile (NV) SRAM, NV control for backing up an external SRAM, and a 32.768kHz output. User access to all registers within the DS1500 is accomplished with a byte-wide interface, as shown in Figure 7. The RTC registers contain century, year, month, date, day, hours, minutes, and seconds data in 24-hour binary-coded decimal (BCD) format. Corrections for day of month and leap year are made automatically.

FEATURES
BCD-Coded Century, Year, Month, Date, Day, Hours, Minutes, and Seconds with Automatic Leap-Year Compensation Valid Up to the Year 2100
Programmable Watchdog Timer and RTC Alarm
Century Register; Y2K-Compliant RTC
Automatic Battery Backup and Write Protection to External SRAM
+5V Operation
Precision Power-On Reset
Power-Control Circuitry Supports System Power-On from Date/Day/Time Alarm or Key Closure
256 Bytes User NV RAM
Auxiliary Battery Input
Accuracy Better than ±1 Minute/Month at +25°C
Day-of-Week/Date Alarm Register
Battery Voltage-Level Indicator Flags
Industrial Temperature Range: -40°C to +85°C