RAMified Watchdog Timekeeper

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The DS1486 is a nonvolatile Static RAM with a full function real-time clock (RTC), alarm, watchdog timer, and interval timer which are all accessible in a bytewide format. The DS1486 contains a lithium energy source and a quartz crystal which eliminate the need for any external circuitry. Data contained within 128K by 8-bit memory and the timekeeping registers can be read or written in the same manner as bytewide static RAM. The timekeeping registers are located in the first 14 bytes of memory space. Data is maintained in the RAMified Timekeeper by intelligent control circuitry which detects the status of VCC and write-protects memory when VCC is out of tolerance. The lithium energy source can maintain data and real time for over 10 years in the absence of VCC. Timekeeper information includes hundredths of seconds, seconds, minutes, hours, day, date, month, and year. The date at the end of the month is automatically adjusted for months with less than 31 days, including correction for leap year. The RAMified Timekeeper operates in either 24-hour or 12-hour format with an AM/PM indicator. The watchdog timer provides alarm interrupts and interval timing between 0.01 seconds and 99.99 seconds. The real time alarm provides for preset times of up to one week. Interrupts for both watchdog and RTC will operate when system is powered down. Either can provide system “wake-up” signals.

Key Features

  • 128 kbytes of user NV RAM
  • Integrated NV SRAM, real-time clock, crystal, power-fail control circuit and lithium energy source
  • Totally nonvolatile with over 10 years of operation in the absence of power
  • Watchdog timer restarts an out-of-control processor
  • Alarm function schedules real-time related activities such as system wakeup
  • Programmable interrupts and square wave output
  • All registers are individually addressable via the address and data bus
  • Interrupt signals active in power-down mode
Product Reliability Reports: DS1486P.pdf 
Device   Fab Process   Technology   Sample size   Rejects   FIT at 25°C   FIT at 55°C   Material Composition  

Note : The failure rates are summarized by technology and mapped to the associated material part numbers. The failure rates are highly dependent on the number of units tested.

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