Non Volatile Memory1

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Introduction Non-volatile memory is computer memory that

can retain the stored information even thesystem is not powered.

It is typically used for the task of secondarystorage, or long-term persistent storage.

It either costs more or performs worse thanvolatile random access memory.

IBM is currently developing MRAM (Magnetoresistive RAM)

Its data storage, classified as, electricallyaddressed and mechanically addressedsystems.



Types of Non VolatileMemory

ROM

FLASHMEMORY

EEPROMPROM

PROM



ROMRead only Memory

Permanently or semi-permanently holdsdata

Special program required to write data Ideal place to put the computer’s start-up

instruction

3 types of ROM:PROMEPROMEEPROM



PROMProgrammable Read Only Memory

Originally contained silicon or metalfuses which would be blown in orderto change 0s and 1s.

Once the bits are changed, theycannot be restored

Widely used in consumer andautomotive electronics, RFID, HDMI



EPROMErasable Programmable Read Only Memory

Invented by Engineer Dov Frohman

Can hold data from 10-20 years

Erasing EPROM ProgrammingErasure is accomplished by using UV light

UV light belongs to UVC range

Frequency of 253.7

Shouldn’t remain under EPROM erasure for toolong, may lead to “over-erasure”

Over-charging of UV light makes the EPROM’s

floating gates unstable



TYPES OF EPROM

UV Erase EPROM OTP EPROM

Data erased by UV light

To remove charge,place chip under UV lampfor 20-30 minutes

Its electrically anEPROM, but with aquartz windowmissing

First 2716 EPROMlaunched in October

1977 in Texas



EEPROMElectrically Erasable Programmable Read-Only Memory

The only user-modifiable ROM that can be erased& reprogrammed

EEPROM IC SERIAL, 32K x 8 64K chip

HISTORY Designed by George Perlegos at Intel

Seeq Technology designed 1st

fully functionalEEPROM

To configure an EEPROM chip, an electric fieldproduced by the charge pump is applied locally

to cells marked for modification.



EEPROM EEPROM Structure

Physically similar to EPROM but also composedof cells with two transistors

Floating gate - separated from the control gate by athin oxide layer

Insulating layer - around 1nanometer voltagerequirements to initiate changes in cell

Floating gate and control gate’s bit value is from 1-0

LimitationsCan be re-programmed but only limited times

Hence, used as computer’s BIOS code

Modern day EEPROM can be rewritten upto amillion times



FLASH MEMORY A type of constantly powered non-volatile memory that can

be erased and reprogrammed

A close relative to EEPROM

Information stored in cells in the chip

Data gets erased off in a flash

Advantages (over traditional hard-drive) Non-volatile

Smaller in size

Highly portable Faster Access Time

Low Price & High Capacity

Maintains Storage even

without Power Supply



FLASH MEMORY Uses

Digital Cellular Phones

Digital Cameras

LAN switches

PC Cards for Notebooks Digital Set-top Boxes

Your Computer’s BIOS

Memory Sticks

Video Game Cards

Modems

MP3 Players

Pen Drives



Summary From all of these, we conclude that non volatile

memory has 5 basic types which have helped instoring data, using effective techniques evenwhen there is no power supply connected to the

storage device

We still have the hope that non-volatile memorymay one day eliminate the need for

comparatively slow forms of secondary storagesystems, which include hard disks.

Non Volatile Memory1

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