FM33256 pdf datasheet (3V Inte

The FM33256 and FM3316 are devices that integrate
FRAM memory with the most commonly needed
functions for processor-based systems. Major
features include nonvolatile memory, real-time clock,
low-VDD reset, watchdog timer, nonvolatile event
counter, lockable 64-bit serial number area, and
general purpose comparator that can be used for a
power-fail (NMI) interrupt or other purpose. The
devices operate from 2.7 to 3.6V.
Each FM33xx provides nonvolatile RAM available in
memory capacity of 16Kb and 256Kb. Fast write
speed and unlimited endurance allow the memory to
serve as extra RAM or conventional nonvolatile
storage. This memory is truly nonvolatile rather than
battery backed.
The real-time clock (RTC) provides time and date
information in BCD format. It can be permanently
powered from external backup voltage source, either
a battery or a capacitor. The timekeeper uses a
common external 32.768 kHz crystal and provides a
calibration mode that allows software adjustment of
timekeeping accuracy.