FM31256/FM3164
Integrated Processor Companion with Memory
Features
High Integration Device Replaces Multiple Parts
• Serial Nonvolatile Memory
• Real-time Clock (RTC)
• Low Voltage Reset
• Watchdog Timer
• Early Power-Fail Warning/NMI
• Two 16-bit Event Counters
• Serial Number with Write-lock for Security
Processor Companion
• Active-low Reset Output for VDD and Watchdog
• Programmable VDD Reset Trip Point
• Manual Reset Filtered and Debounced
• Programmable Watchdog Timer
• Dual Battery-backed Event Counter Tracks
System Intrusions or other Events
• Comparator for Early Power-Fail Interrupt
• 64-bit Programmable Serial Number with Lock
Ferroelectric Nonvolatile RAM
• 64Kb, and 256Kb versions
• Virtually Unlimited Read/Write Endurance
• 38 year Data Retention (+75°C)
• NoDelay™ Writes
Fast Two-wire Serial Interface
• Up to 1 MHz Maximum Bus Frequency
• Supports Legacy Timing for 100 kHz & 400 kHz
• Device Select Pins for up to 4 Memory Devices
• RTC, Supervisor Controlled via 2-wire Interface
Real-time Clock/Calendar
• Backup Current at 2V, 1.15 μA (max.) at +25C
• Seconds through Centuries in BCD format
• Tracks Leap Years through 2099
• Uses Standard 32.768 kHz Crystal (6pF)
• Software Calibration
• Supports Battery or Capacitor Backup
Easy to Use Configurations
• Operates from 2.7 to 5.5V
• Small Footprint 14-pin “Green” SOIC (-G)
• Low Operating Current
• -40°C to +85°C Operation
Description
The FM31xx is a family of integrated devices that
includes the most commonly needed functions for
processor-based systems. Major features include
nonvolatile memory available in various sizes, realtime clock, low-VDD reset, watchdog timer,
nonvolatile event counter, lockable 64-bit serial
number area, and general purpose comparator that
can be used for an early power-fail (NMI) interruptor
other purpose. The family operates from 2.7 to 5.5V.
Each FM31xx provides nonvolatile RAM available
in sizes including 64Kb and 256Kb versions. 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.
This product conforms to specifications per the terms of the Ramtron
standard warranty. The product has completed Ramtron’s internal
qualification testing and has reached production status.
The processor companion includes commonly
needed CPU support functions. Supervisory
functions include a reset output signal controlled by
either a low VDD condition or a watchdog timeout.
/RST goes active when VDD drops below a
programmable threshold and remains active for 100
ms after VDD rises above the trip point. A
programmable watchdog timer runs from 100 ms to
3 seconds. The watchdog timer is optional, but if
enabled it will assert the reset signal for 100 ms if
not restarted by the host before the timeout. A flagbit indicates the source of the reset.
A general-purpose comparator compares an external
input pin to the onboard 1.2V reference. This is
useful for generating a power-fail interrupt (NMI)
but can be used for any purpose. The family also
includes a programmable 64-bit serial number that
can be locked making it unalterable. Additionally it
offers a dual battery-backed event counter that tracks
the number of rising or falling edges detected on
dedicated input pins.
Ramtron International Corporation
1850 Ramtron Drive, Colorado Springs, CO 80921
(800) 545-FRAM, (719) 481-7000
www.ramtron.com
Rev. 3.0
Aug. 2012
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