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
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