They are called eproms or eeproms

Usually memory banks made up of SRAMs or DRAMs or EPROMs consist of the storage area provided on a microprocessor. For understanding how the address space of a 20 bit address line microprocessor is organised, read about address decoding for even and odd memory addressing through SRAMs and EPROMs.

Processors have registers that store only a few bytes while the processor is working with them.

Information the system needs to start booting is stored on electronically programmable read-only memory chips (EPROMs).

Read Only Memory or ROM. There are also Erasable ROMs called EPROMs, EAROMS, EEROMS, and Flash Memory. The erasable ROMS will only be erased under special circumstances, and when in use they act the same as a normal ROM.

EPROM (Erasable Programmable Read-Only Memory) chips can be erased by exposing them to ultraviolet (UV) light after they have been removed from the main circuit. This exposure helps clear the programming on the chip, making it ready for reprogramming.

They cannot usually be modified.

There are special ROMs called EAROMs (Electrically Alterable Read Only Memories ) or EPROMs (Electrically Programmable Read Only Memories).

The BIOS ROMs in computers are of this type and can be reprogrammed.

Most other standard ROMs, are recorded once by burning links internally at the point of manufacture. This process is non reversible.

Programmable Read Only Memory is a hard programmed(non-writable) calibration module used in early engine control modules. Later ECMs used EPROMS which were writable, meaning they could be programmed by the installer to work with various engine combinations. Vehicles today have EEPROMS which can be written and rewritten, allowing them to be reprogrammed as needed for software updates and program corrections.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 7 words with the pattern E-RO--. That is, six letter words with 1st letter E and 3rd letter R and 4th letter O. In alphabetical order, they are:

enrobe

enroll

enrols

enroot

eproms

errors

euroky

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern E-ROM-. That is, six letter words with 1st letter E and 3rd letter R and 4th letter O and 5th letter M. In alphabetical order, they are:

eproms

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern EPRO--. That is, six letter words with 1st letter E and 2nd letter P and 3rd letter R and 4th letter O. In alphabetical order, they are:

eproms

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern E-R-MS. That is, six letter words with 1st letter E and 3rd letter R and 5th letter M and 6th letter S. In alphabetical order, they are:

eproms

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 3 words with the pattern EP-O-S. That is, six letter words with 1st letter E and 2nd letter P and 4th letter O and 6th letter S. In alphabetical order, they are:

ephods

ephors

eproms

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 3 words with the pattern E-RO-S. That is, six letter words with 1st letter E and 3rd letter R and 4th letter O and 6th letter S. In alphabetical order, they are:

enrols

eproms

errors

illegally? yes, of course, but for legal free games originally for consoles, google something like, "n64 emulator" or "ps1 emulator" download the software, and you'll be free gaming in no time

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Technically speaking copies of cartridges and eproms for now defunct video gameing machine run under emulation is also ilegal. However there is a number of companies who have released the copyright into the public domain. This is true of a few games on the mame32 emulator.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern E-ROMS. That is, six letter words with 1st letter E and 3rd letter R and 4th letter O and 5th letter M and 6th letter S. In alphabetical order, they are:

eproms

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 1 words with the pattern EPR-MS. That is, six letter words with 1st letter E and 2nd letter P and 3rd letter R and 5th letter M and 6th letter S. In alphabetical order, they are:

eproms

it converts the request into binary digits ............... and its stores the data in a database. as a table format.

The binary data can then be written onto a magnetic disc or tape. The data can also be held in a silicon chip, arranged with a grid of memory locations, called a memory chip.

Some chips need power applied in order to hold data. RAM

Others can hold data permanently, ROM

Others can hold data semi-permanently, power is used to change the data and then it will hold it without. EPROMS. (Electrically Programmable Read Only Memory.

Here ya go found this on the Internet for you: Acronym for erasable programmable read-only memory, and pronounced ee-prom, EPROM is a special type of memory that retains its contents until it is exposed to ultraviolet light. The ultraviolet light clears its contents, making it possible to reprogram the memory. To write to and erase an EPROM, you need a special device called a PROMprogrammer or PROM burner. An EPROM differs from a PROM in that a PROM can be written to only once and cannot be erased. EPROMs are used widely in personal computers because they enable the manufacturer to change the contents of the PROM before the computer is actually shipped. This means that bugs can be removed and new versions installed shortly before delivery.

Basically, anything. RAM stands for Random Access Memory, and it can contain programs, data, an operating system, pictures, videos, you name it. It's the main working area or scratchpad of your computer. It stays there until you turn the power off. This varies from ROM (Read-Only Memory) in that ROM may be read from, but not written to, and the contents remains unchanged. Examples of ROMs are a BIOS chip (allowing booting of a computer), a or video card ROM (containing a small program to make the card work). Once you boot your computer, the BIOS tells the computer where to find the operating system on disk, then it is loaded into the RAM, and execution continues in RAM, and everything starts up. See also: PROMs (Programmable Read-Only Memory), EPROMS (Erasable Programmable Read-Only Memory; uses a UV light to erase and re-program), and EEPROMs (Electrically Erasable Programmable Read-Only Memory; also called non-volatile memory).

The advantages of read only memory are its permanence and security. However, the only disadvantage is that a system will require more time as twice in reading the data stored in ROM than in RAM.

According to SOWPODS (the combination of Scrabble dictionaries used around the world) there are 673 words with the pattern E-----. That is, six letter words with 1st letter E. In alphabetical order, they are:

eadish

eagers

eagled

eagles

eaglet

eagres

eaning

earbob

earbud

earcon

earded

earful

earing

earlap

earned

earner

earths

earthy

earwax

earwig

easels

easers

easied

easier

easies

easily

easing

easles

eassel

eassil

easted

easter

eatage

eatche

eaters

eatery

eathly

eating

ebayer

ebbets

ebbing

ebooks

ecarte

ecbole

ecesic

ecesis

echard

eching

echini

echium

echoed

echoer

echoes

echoey

echoic

eclair

eclats

eclose

econut

ectopy

ectype

ecurie

eczema

eddied

eddies

eddish

eddoes

edemas

edenic

edgers

edgier

edgily

edging

edible

edicts

ediles

edited

editor

educed

educes

educts

eeched

eeches

eejits

eelier

eerier

eerily

eevens

efface

effect

effeir

effere

effete

effigy

effing

efflux

effort

effray

effuse

eftest

egally

egence

egency

egesta

egests

eggars

eggcup

eggers

eggery

eggier

egging

eggler

eggnog

egises

egoism

egoist

egoity

egress

egrets

eident

eiders

eidola

eighth

eights

eighty

eiking

eikons

eirack

eisell

eisels

either

ejecta

ejects

ekuele

elains

elance

elands

elanet

elapid

elapse

elated

elater

elates

elbows

elchee

elchis

elders

eldest

elding

eldins

elects

elegit

elemis

elench

eleven

elevon

elfing

elfins

elfish

eliads

eliche

elicit

elided

elides

elints

elites

elixir

ellops

elmier

elodea

eloges

eloign

eloins

eloped

eloper

elopes

elpees

elshin

elsins

eltchi

eluant

eluate

eluded

eluder

eludes

eluent

eluted

elutes

elutor

eluvia

elvans

elvers

elvish

elytra

emails

embace

embail

embale

emball

embalm

embank

embark

embars

embase

embays

embeds

embers

emblem

emblic

embody

embogs

emboil

emboli

emboly

embosk

emboss

embost

embows

embrue

embryo

embusy

emceed

emcees

emdash

emeers

emends

emerge

emerod

emeses

emesis

emetic

emetin

emeute

emigre

emlets

emmers

emmesh

emmets

emmews

emmove

emodin

emoted

emoter

emotes

emoved

emoves

empale

empare

emparl

empart

empery

empire

employ

empted

empusa

empuse

emuled

emules

emulge

emunge

emured

emures

emydes

enable

enacts

enamel

enamor

enarch

enarms

enates

enatic

encage

encalm

encamp

encase

encash

encave

encina

encode

encore

encyst

endart

endash

endear

enders

endews

ending

endite

endive

endoss

endows

endrin

endued

endues

endure

enduro

enemas

energy

enerve

enewed

enface

enfant

enfire

enfold

enform

enfree

engage

engaol

engild

engilt

engine

engird

engirt

englut

engobe

engore

engram

engulf

enhalo

eniacs

enigma

enisle

enjamb

enjoin

enjoys

enlace

enlard

enleve

enlink

enlist

enlock

enmesh

enmews

enmity

enmove

ennage

ennead

ennogs

ennuis

ennuye

enodal

enokis

enolic

enoses

enosis

enough

enrace

enrage

enrank

enrapt

enrich

enring

enrobe

enroll

enrols

enroot

ensate

enseal

enseam

ensear

enserf

ensews

ensign

ensile

ensoul

ensued

ensues

ensure

entail

entame

entera

enters

entete

entice

entire

entity

entoil

entomb

entrap

entree

entrez

enured

enures

envied

envier

envies

enviro

envois

envoys

enwall

enwind

enwomb

enwrap

enzian

enzone

enzyme

enzyms

eocene

eolian

eolith

eonian

eonism

eosine

eosins

eothen

epacts

eparch

epaule

epeira

eperdu

ephahs

ephebe

ephebi

ephods

ephori

ephors

epical

epigon

epilog

epimer

epizoa

epocha

epochs

epodes

epodic

eponym

epopee

epopts

eposes

eprise

eproms

epuise

epulis

equali

equals

equant

equate

equids

equine

equipe

equips

equity

erased

eraser

erases

erbias

erbium

erects

eremic

erenow

ergate

ergons

ergots

eriach

ericas

ericks

eringo

erinus

erlang

ermine

erning

eroded

erodes

eroses

erotic

errand

errant

errata

erring

errors

ersatz

erucic

eructs

erugos

erupts

eruvim

eruvin

ervils

eryngo

escape

escarp

escars

eschar

eschew

escort

escots

escroc

escrol

escrow

escudo

esiles

eskars

eskers

eskies

esloin

esnecy

espada

espial

espied

espier

espies

esprit

essays

essive

essoin

estate

esteem

esters

estocs

estops

estral

estray

estrin

estros

estrum

estrus

etages

etalon

etamin

etapes

etched

etcher

etches

eterne

ethals

ethane

ethene

ethers

ethics

ethion

ethnic

ethnos

ethoxy

ethyls

ethyne

etoile

etrier

ettins

ettled

ettles

etudes

etwees

etymic

etymon

etypic

eucain

euchre

eughen

euking

eulogy

eumong

eumung

eunuch

euouae

eupads

euphon

eupnea

eureka

euripi

euroky

eusols

eutaxy

evaded

evader

evades

evejar

evened

evener

evenly

events

everts

evicts

eviler

evilly

evince

evited

evites

evoked

evoker

evokes

evolue

evolve

evovae

evulse

evzone

ewftes

ewghen

ewking

exacta

exacts

exacum

exalts

examen

exarch

excamb

exceed

excels

except

excess

excide

excise

excite

excuse

exeats

exedra

exeems

exemed

exemes

exempt

exequy

exerts

exeunt

exhale

exhort

exhume

exiled

exiler

exiles

exilic

exines

exists

exited

exodes

exodic

exodoi

exodos

exodus

exogen

exomis

exonic

exonym

exopod

exotic

expand

expats

expect

expels

expend

expert

expire

expiry

export

expose

expugn

exsect

exsert

extant

extasy

extend

extent

extern

extine

extirp

extold

extoll

extols

extort

extras

exuded

exudes

exults

exurbs

exuvia

eyalet

eyases

eyebar

eyecup

eyeful

eyeing

eyelet

eyelid

eyliad

eyries

Computer systems typically employ a central processing unit (CPU), a display device, input devices, and memory for data storage. Memory devices are typically provided as internal storage areas in the computer. Memory for data storage generally comes in the form of integrated circuit chips. Memory for a computer system is technically any form of electronic, magnetic or optical storage. It is generally divided up into different categories based in part upon speed and functionality. In general, memory types can be categorized according to the storage state into volatile memory and non-volatile memory according to storage type. The primary difference between volatile memory and non-volatile memory is that a volatile memory needs to be supplied with external power in order to hold and refresh data while a non-volatile memory can maintain data for extended periods of time without any power being supplied to the device. Data intended for high-speed short-term access is typically stored in volatile memory. Data intended for long term future access is typically stored in non-volatile memory. Volatile memory currently has faster access times and higher data transfer rates than non-volatile memory. This makes it an appealing alternative for systems requiring very high-speed access to data typically stored in long term, non-volatile storage devices. Most computer systems utilize both volatile and non-volatile memory in the same system or device. In a typical computer system, data intended for high-speed short-term access, such as on-chip memory for the CPU, and often first and second level off-chip memory, are typically stored in volatile memory devices such as a cache or random access memory (RAM, DRAM, SRAM) which typically have nanosecond to microsecond access times. Data intended for long-term storage or mass storage are typically stored in non-volatile storage devices such as magnetic disks, hard disk drives, zip drives, floppy disk drives, tape drives and optical storage media which typically have access times on the order of milliseconds or seconds.

Random access memory (RAM) is the main memory of a computer system used for storing programs and data. RAM provides temporary read/write storage while hard disks offer semi-permanent storage. All programs must be run through RAM before they can be used. The term random derives from the fact that the CPU can retrieve data from any individual location, or address, within RAM. Most RAM is volatile, which means that it requires a steady flow of electricity to maintain its contents. As soon as the power is turned off, whatever data was in RAM is lost. The volatile memory typically comprises random access memory (RAM) and is considered the main memory for the computer system. To facilitate quick access for processing, a typical modern computer has a main memory connected by a memory bus directly to the processor. Random access memory is much faster to read from and write to than the other kinds of storage devices in a computer such as the hard disk, floppy disk, and CD-ROM. In contrast to the relatively slow storage memory, the main memory is generally comprised of fast, expensive volatile random access memory (RAM) with access times generally less than 100 nanoseconds. Volatile random access memory (RAM) devices may be further divided into two categories, including static random access memory (SRAM) and dynamic random access memory (DRAM). Static random access memory (SRAM) consists of flip-flop latches, which each retain one bit of data for as long as power is maintained. In dynamic random access memory (DRAM), each memory cell is made up from one transistor and a capacitor. Random access memory is usually used to designate a data memory having a multiplicity of memory cells, each of which can store a datum and which can be accessed selectively and directly to selectively write in or read out data. Random access memories, such as static random access memories or dynamic random access memories, generally comprise a multiplicity of addresses for writing therein data. Data in the addresses may be accessed, for example, through data latches for performing operations, e.g., programming, on a memory cell array, e.g., a non-volatile memory cell array. As a computer system may be used in a variety of ways the amount of RAM deemed appropriate in one instance may be insufficient or superfluous in another. For example, an image processing and manipulation application may not only be time consuming to initialize for use, but also may require the majority of available main memory RAM resources, while a simple text editor may hardly be noticeable to the system.

Static random access memory (SRAM) devices have been employed for decades to store electronic data. An SRAM device includes an array of memory cells organized into rows and columns of memory cells. An SRAM cell includes a pair of inverters with the outputs of the inverters cross-coupled to form a flip-flop. The typical SRAM cell includes four transistors for storing data and two transistors for selection of a particular cell. An addressable word line is coupled to the memory cells in a distinct row of memory cells. The memory cells of an SRAM typically have first and second inverters whose inputs and outputs are connected to each other, and first and second transfer transistors that connect the output ends of the first and second inverters to a bit line pair. The first and second inverters include a load transistor and a driver transistor. The memory cells in a column of memory cells are coupled to an addressable pair of bit lines. Data is written to and read from a memory cell in the memory cell array by selecting a row of memory cells and accessing memory cells therein that are coupled to selected bit line pairs. Static random access memory cells typically provide memory storage for bits that can be rapidly read from and written to. Unlike dynamic random access memory (DRAM) cells, because of the flip-flop feedback effect, SRAM cells typically enable storage of static data even without refresh operations. The static random access memory is the main stream of the on-chip memories to be mounted on an LSI together with other parts. In spite of this, the SRAM, since it is composed of six transistors, requires a large space for disposing memory cells, encountering a problem of mounting space when it employed to be mounted on an LSI together with other parts. Due to its larger memory cell size, an SRAM is typically more expensive to manufacture than a DRAM. An SRAM typically has a smaller read access time and lower power consumption than a DRAM. Therefore, where fast access to data or low power is needed, SRAMs are often used to store the data.

A dynamic random access memory (DRAM) device is a typical volatile memory device constructed from an array of memory cells. Each memory cell comprises an active device and a capacitor. Furthermore, each memory cell is electrically connected to a word line (WL) and a bit line (BL). A dynamic random access memory includes a large number of memory cells, each of which can store at least one bit of data. In typical DRAM, the coupling of memory cells results in a differential voltage appearing on a bit line (or bit line pair). The differential voltage is amplified by a sense amplifier, resulting in amplified data signals on the bit lines. The applied memory address also activates column decoder circuits, which connect a given group of bit lines to input/output circuits. The memory cells are arranged in an array having a number of rows and columns. Memory cells within the same row are commonly coupled to a word line and memory cells within the same column are commonly coupled to a bit line. The memory cells within the array are accessed according to various memory device operations. Such operations include read operations, write operations and refresh operations. DRAM memory cell stores data by placing charge on, or removing charge from, a storage capacitor. According to the type of capacitor used in each memory cell, dynamic random access memory can be further sub-divided into a stack capacitor DRAM and a deep trench capacitor DRAM. Computer systems and other electronic devices containing a microprocessor or similar device typically include system memory, which is generally implemented using dynamic random access memory. The primary advantage of DRAM is that it uses relatively few components to store each bit of data, and is thus relatively inexpensive to provide relatively high capacity system memory. A disadvantage of DRAM is that their memory cells must be periodically refreshed. Pseudo static random access memory (PSRAM) is another type of DRAM. PSRAM is a low power DRAM having a static random access memory interface for wireless applications.

DRAM uses a main clock signal and a data strobe signal (DQS) for addressing the array of memory cells and for executing commands within the memory. The clock signal is used as a reference for the timing of commands such as read and writes operations, including address and control signals. The DQS signal is used as a reference to latch input data into the memory and output data into an external device. Dynamic random access memory uses an interface with address lines that are typically multiplexed in time. DRAM memory devices generally employ a row decoder circuit comprising a decoding unit and a wordline driver to drive a voltage level of a wordline high or low in order to "open" or "close" access to an associated row of memory cells. Such circuits operate to drive the wordline voltage level between a range of a positive voltage, which is greater than a maximum available power supply voltage and a negative voltage, which is less than a reference voltage, such as a ground reference. A synchronous DRAM (SDRAM) is a type of DRAM that can run at much higher clock speeds than conventional DRAM memory. A synchronous DRAM can perform various functions in synchronism with a clock signal that is supplied from an external source. The synchronous DRAM can refresh itself independently of the computer system which incorporates the synchronous DRAM, by generating refresh addresses inside of the memory using internal addresses. While the synchronous DRAM is being refreshed, word lines are selected to satisfy a refresh period required by the refresh characteristics of cells and a refresh rate required by the computer system. When the synchronous DRAM is in normal operation, a common output word line is provided for a plurality of banks in an interleaved configuration, and only one of the banks is selected at a time. The SDRAM has internal logic used to advance the data address. In addition to the timing signals, certain control registers of the internal logic of the SDRAM must be loaded with timing control parameters before the sequential access mode may be used.

Recent advances in memory technology have included the development of magnetic RAM (MRAM). The MRAM is a memory device for reading and writing information wherein multi-layer ferromagnetic thin films is used by sensing current variations according to a magnetization direction of the respective thin films. MRAM uses a ferromagnetic material as one of the next generation memory devices. The MRAM embodies a memory device by using a giant magneto resistive (GMR) or spin-polarized magneto-transmission (SPMT) phenomenon generated when the spin influences electron transmission. MRAM stores information magnetically, so it does not require a constant power supply. This quality is known as non-volatility. A magnetic random access memory (MRAM) element typically has a structure that includes first and second magnetic layers which are separated by a non-magnetic layer. A magnetic vector in one of the two magnetic layers is magnetically fixed or pinned, while the magnetic vector of the other of the two magnetic layers is not fixed and thus its magnetization direction is free to be controlled and switched. Information is written to and read from the element as a logic "1" or a logic "0" by changing the direction of the non-fixed magnetization vector in the other of the two magnetic layers. The differences in magnetization vector direction cause resistance variations within the element which can be measured. MRAM can offer all the advantages in speed and size that volatile memory offers and brings the added advantage of being non-volatile and, in some architectural configurations, cheaper to manufacture. MRAM can operate at speeds similar to either SRAM or DRAM, thus allowing it to be utilized within main memory. The MRAM has a high speed and low power consumption, and allows high integration density due to its unique properties of the magnetic thin film, and also performs a nonvolatile memory operation such as a flash memory.

A cache memory and a main memory are used for a large scale integration circuit having a central processing unit. Memory caching is a widespread technique used to improve data access speed in computers and other digital systems. The speed at which processors can execute instructions has typically outpaced the speed at which memory systems can supply the instructions and data to the processors. Due to this discrepancy in the operating speeds of the processors and system memory, the system memory architecture plays a major role in determining the actual performance of the system. Most current memory hierarchies utilize cache memory in an attempt to minimize memory access latencies. A cache is a small, fast memory that acts as a buffer between a device that uses a large amount of memory and a large, slower main memory. The cache's purpose is to reduce average memory-access time. Caches are effective because of two properties of software programs: spatial and temporal locality. Cache memory is used to provide faster access to frequently used instructions and data, which helps improve the overall performance of the system. Caching relies on a property of memory access known as temporal locality. Temporal locality states that information recently accessed from memory is likely to be accessed again soon. Information in cache RAM may be stored based upon two principles, namely spatial locality and temporal locality. The principle of spatial locality is based upon the fact that when data is accessed at an address, there is an above average likelihood that the data which is next required will have an address close to that of the data which has just been accessed. By contrast, temporal locality is based upon the fact that there is an above average probability that data which has just been accessed will be accessed again shortly. Cache memory is typically implemented using static random access memory (SRAM) because such memory need not be refreshed and is thus always accessible for a write or a read memory access.

Computers almost always contain a small amount of read-only memory (ROM) that holds instructions for starting up the computer. Read only memory (ROM) is a non-volatile memory commonly used in electronic equipment such as microprocessor-based digital electronic equipment and portable electronic devices. Read only memory is a type of non-volatile data storage device that can retain stored data even when the power is cut off. Among the memory products, non-volatile memory is one type of memory device having the capacity for writing data into, reading data from and erasing stored data multiples of times. Moreover, data will be retained even if the power to the device is cut off. With these advantages, it has become one of the most widely adopted memory devices in personal computer and electronic equipment. Most standard electrical products are equipped with some read only memory for holding a normal operation. ROM devices typically include multiple memory cell arrays. Each memory cell array may be visualized as including intersecting word lines and bit lines. Each word and bit line intersection can correspond to one bit of memory. In mask programmable metal oxide semiconductor (MOS) ROM devices, the presence or absence of a MOS transistor at word and bit line intersections distinguishes between a stored logic `0` and logic `1`. A ROM array of memory cells is defined by a number of transistors generally arranged in a grid pattern having a plurality of rows and columns. Each individual transistor of each memory cell of the ROM array is placed between a column of the series of columns and a voltage bus. The column is supplied with power at a first predetermined voltage level, and the voltage bus is supplied with power at a second, different predetermined voltage level. A gate of each transistor of a ROM array is connected to a particular row of the series of rows. ROM memories may be included in any type of integrated circuit (IC). In general, ROM memory is used to hold and make available data or code that will not be altered after IC manufacture. Data or code is programmed into ROM memory during fabrication.

According to data storage format, read only memory (ROM) can be further sub-divided into mask ROM, one-time programmable ROM (OTPROM), erasable programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) and so on. The one-time electrically programmable read only memory (OTEPROM) permits the writing of data into the memory after leaving the factory. The data can be written by the user to fit a particular memory environment, which is more convenient to a user. Since data can be programmed into a one-time programmable ROM outside the factory according to the particular environment the memory is supposed to be working in, one-time programmable ROM is more convenient to work with than the mask ROM. A mask read only memory (Mask ROM) is a semiconductor memory device in which data required is coded during a manufacturing process. There are two types of Mask ROMs: an embedded diffusion-programmable ROM and an embedded metal programmable ROM. Mask ROM is able to write quaternary data into each memory cell transistor. A large amount of information can be stored in small circuits using this mask ROM. A programmable read only memory (PROM) is similar to the mask programmable ROM except that a user may store data values using a PROM programmer. A PROM device is typically manufactured with fusible links at all word and bit line intersections. An erasable programmable read only memory (EPROM) is programmable like a PROM, but can also be erased by exposing it to ultraviolet light. An EPROM integrated circuit is normally housed in a package having a quartz lid, and the EPROM is erased by exposing the EPROM integrated circuit to ultraviolet light passed through the quartz lid. Most PROMs can only be programmed once, typically by blowing open an appropriate word-to-bit connection path. Conversely, EPROMs can be programmed and reprogrammed multiple times. EPROMs are programmed by injecting hot electrons into, for example, a floating gate dielectrically spaced above the transistor channel. The injected electrons can thereafter be removed by irradiating the floating gate with ultraviolet light.

Electrically erasable programmable read-only memory (EEPROM) is a non-volatile memory device that allows multiple data writing, reading, and erasing operations. The structure of EEPROMs is similar to that of erasable programmable read-only memories (EPROMS) since both of them have a floating gate for storing charges and a control gate for controlling data access. EEPROM comprise a large number of memory cells having electrically isolated gates (floating gates). Data is stored in the memory cells in the form of charge on the floating gates. The electrical charge modifies the electrical characteristics of the EEPROM cell so that the information can be later read back using the modified electrical characteristics. The electrical charge is typically blocked in a trapping layer that gives to the EEPROM cell its memory capability. A typical EPROM device has a floating gate MOS transistor at all word and bit line intersections. Each MOS transistor has two gates: a floating gate and a non-floating gate. The floating gate is not electrically connected to any conductor, and is surrounded by a high impedance insulating material. The floating gates in the EEPROM device are surrounded by a much thinner insulating layer, and accumulated negative charges on the floating gates can be dissipated by applying a voltage having a polarity opposite that of the programming voltage to the non-floating gates. To program the EPROM device, a high voltage is applied to the non-floating gate at each bit location where a logic value is to be stored. This causes a breakdown in the insulating material and allows a negative charge to accumulate on the floating gate. When the high voltage is removed, the negative charge remains on the floating gate. An electrically erasable programmable read-only memory allows multiple data writing, reading and erasing operations. In addition, the stored data will be retained even after power to the device is removed. The EEPROM is very suitable to be used in an embedded function, such as an address book in cell phones, because of its byte program/erase feature. In addition, EEPROM products usually have good high reliability performance, which increases applicability in application fields requiring repetitive programming, reading, and erasing. With these advantages, it has been broadly applied in personal computer and other electronic equipment.

A flash memory is a type of flash EEPROM device that can be erased and reprogrammed in blocks instead of one byte at a time. Flash memory devices are different from EEPROM devices in that electrical erasure involves large sections of, or the entire contents of, a flash memory device. A flash memory cell includes a field effect transistor (FET) having a selection gate, a floating gate, a source and a drain. Data is stored in the flash memory cell by variations in the amount of charge stored in the floating gate, which causes a variation in a threshold voltage (Vt) of the flash memory cell. The data stored in the flash memory cell is read out by applying a selection voltage to a word line connected to the selection gate. The flash memory electrically deletes the data using a same method as that of an electrically erasable and programmable ROM (EEPROM), and the memory may be entirely deleted in one second or several seconds. The data stored in the flash memory is deleted throughout the chip in a block unit, but it is impossible to delete the data in a byte unit. The flash memory stores a correctable control program, which is used instead of an auxiliary memory. The flash memory is divided into a NAND flash memory and a NOR type flash memory. The NOR type flash memory uses an interface method as an SRAM or a ROM to easily construct a circuit with a processor. The NOR flash memory employs memory cell arrays that suppress the parasitic resistance. The NOR flash memory lowers the resistance by providing one through-hole to bit line for two cells connected in parallel. A NAND flash memory device is comprised of memory cells serially connected between a drain selection transistor and a source selection transistor in the unit of 16 or 32 in number. The flash memory cells of the NAND flash memory device include a current path formed between the source and drain on a semiconductor substrate, and a floating gate and a control gate that are connected over the semiconductor substrate with an insulator intervened between them. NAND flash memory devices are typically used as mass data storage devices, and NOR flash memory devices are typically used as information storage devices for high speed data processing.

Flash memory devices have achieved a commercial success in an electronic industry because they are able to store data for a relatively long time even without a power supply. Flash memory devices are applicable for multiple operations of data writing, reading and erasing, and have the advantage that stored data will not been vanished even after power supply is cut off. Thus, flash memory devices are widely used as non-volatile memory devices for personal computers and other electronic products. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Common uses for flash memory include portable computers, personal digital assistants (PDA), digital cameras, and cellular phones. Program code, system data such as a basic input/output system (BIOS), and other firmware can typically be stored in flash memory devices. Most electronic devices are designed with a single flash memory device. Flash memory devices are finding increasing applications in smart cards for recording, storing and transporting digital information. Flash memory cards are currently used in digital cameras for recording and storing pictures that can be later displayed on personal computers, TVs or printed. Flash memories in smart cards are being used not only for storing data but also for storing application programs such as fingerprint identification, identification cards, health records, transportation programs and many more applications which include encryption for personal security, and also applications such as e-passport, credit card, JAVA card subscriber identity module (SIM).