The DS1557WP-120+ is a 4meg, non-volatile, Y2K-compliant timekeeping RAM in 34 pin PWRCP package. This is full function, year-2000-compliant (Y2KC), real-time clock/calendar (RTC) with an RTC alarm, watchdog timer, power-on reset, battery monitor and 512k x 8 non-volatile static RAM. User access to all registers within the IC is accomplished with a byte-wide interface. The RTC registers contain century, year, month, date, day, hours, minutes and seconds data in 24-hour BCD format and corrections for day of month and leap year are made automatically. The RTC registers are double-buffered into an internal and external set. The user has direct access to the external set. Clock/calendar updates to the external set of registers can be disabled and enabled to allow the user to access static data.
- Supply voltage range is 2.97V to 3.63V, precision power-on reset
- Operating temperature range from 0°C to 70°C
- Integrated NV SRAM, real-time clock, crystal, power-fail control circuit and lithium energy source
- Clock registers are accessed identically to static RAM, registers reside in 16 top RAM locations
- Totally non-volatile with over 10 years of operation in the absence of power
- Programmable watchdog timer and RTC alarm, 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
- Active supply current is 20mA(typ), TTL standby current is 2mA(typ)
- Write protection voltage range from 2.75V to 2.97V
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