The DS1554-70IND+ is a 256K, Non-volatile, Y2K-compliant timekeeping RAM in 32 pin EDIP package. It has RTC alarm, watchdog timer, power-on reset, battery monitor and 32K x 8 non-volatile static RAM, user access to all registers within the DS1554 is accomplished with a byte wide interface. 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. The RTC registers are double buffered into an internal and external set. The user has direct access to external set. Clock/calendar updates to external set of registers can be disabled and enabled to allow user to access static data. Assuming internal oscillator is turned on, internal set of registers is continuously updated, this occurs regardless of external registers settings that accurate RTC information is always maintained.
- Supply voltage range is 4.5V to 5.5V
- Operating temperature range from -40°C to 85°C
- Integrated NV SRAM, RTC, crystal, power fail control circuit and lithium energy source
- Clock registers are accessed identically to static RAM, registers reside in the 16 top RAM locations
- Totally non-volatile with over 10 years of operation in absence of power
- Precision power-on reset, 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
时钟与计时
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