Flash MemoryFlash Memory

Points of DiscussionPoints of Discussion Flash Memory GeneralitiesFlash Memory Generalities

Construction & PropertiesConstruction & Properties

History of Flash MemoryHistory of Flash Memory NOR & NAND ArchitecturesNOR & NAND Architectures OptimizationsOptimizations StandardizationStandardization New Developments & Future of FlashNew Developments & Future of Flash Closing StatementsClosing Statements

Flash MemoryFlash Memory

A type of EEPROM (Electrically-Erasable A type of EEPROM (Electrically-Erasable Programmable Read-Only Memory)Programmable Read-Only Memory)

Non-volatile, solid state technologyNon-volatile, solid state technology Relatively limited lifespanRelatively limited lifespan Information is stored in an array of Information is stored in an array of

memory cells made from floating-gate memory cells made from floating-gate (FG) transistors(FG) transistors

Flash MemoryFlash Memory

Packaged inside a memory card:Packaged inside a memory card: Extremely durableExtremely durable Can withstand intense pressureCan withstand intense pressure Immersion in waterImmersion in water

Better kinetic shock resistance than hard Better kinetic shock resistance than hard disksdisks

Average power requirements range from Average power requirements range from 5V-12V5V-12V

Flash Memory CellFlash Memory Cell

History of Flash MemoryHistory of Flash Memory

Invented by Fujio Masuoka while he was Invented by Fujio Masuoka while he was working for Toshiba in the early 1980s working for Toshiba in the early 1980s

First introduced at the 1984 International First introduced at the 1984 International Electron Devices Meeting in San Electron Devices Meeting in San Francisco Francisco

Manufacturers of FlashManufacturers of Flash

NOR Flash MemoryNOR Flash Memory

Developed to replace read only memoryDeveloped to replace read only memory Full address and data buses allow random Full address and data buses allow random

access to any memory locationaccess to any memory location Can access any memory cellCan access any memory cell Slow sequential accessSlow sequential access

NAND Flash MemoryNAND Flash Memory

Developed to replace hard disks Sequential-accessed command and data

registers replace the external bus of NOR Decreases chip real estateDecreases chip real estate Can only access pagesCan only access pages Faster sequential accessFaster sequential access

OptimizationsOptimizations

Wear levellingWear levelling Counting writes & dynamically remapping Counting writes & dynamically remapping

blocksblocks

Bad block managementBad block management Write verification and remapping bad sectorsWrite verification and remapping bad sectors

Multi-Level Cell technologyMulti-Level Cell technology Memory cells store more than one bitMemory cells store more than one bit

StandardizationStandardization

Part of the reason for the success of Flash Part of the reason for the success of Flash memorymemory

Open NAND Flash Interface Working Open NAND Flash Interface Working Group developed standard low-level Group developed standard low-level interfaceinterface Standard pinoutStandard pinout Standard command set for reading, writing, Standard command set for reading, writing,

and erasing NAND flash chips and erasing NAND flash chips Mechanism for self-identification Mechanism for self-identification

New DevelopmentsNew Developments AND FlashAND Flash

Bit line replaced with embedded diffusion line Bit line replaced with embedded diffusion line to reduce cell sizeto reduce cell size

Low power dissipation (3V)Low power dissipation (3V)

DINOR (DIvided bit-line NOR) FlashDINOR (DIvided bit-line NOR) Flash Attempts to reduce the chip real estate Attempts to reduce the chip real estate

compared to conventional NORcompared to conventional NOR Low power dissipation (3V), sector erase, Low power dissipation (3V), sector erase,

high data transfer ratehigh data transfer rate

Future of Flash MemoryFuture of Flash Memory

Continues to be among the most Continues to be among the most aggressively scaled electronic aggressively scaled electronic technologiestechnologies

Memory cell size minimum of 20 nm Memory cell size minimum of 20 nm expected to be met in 2010expected to be met in 2010

May be replaced by Phase-Change RAM May be replaced by Phase-Change RAM or other emerging technologiesor other emerging technologies

In Closing…In Closing…

One of the most popular alternatives for One of the most popular alternatives for portable device storageportable device storage

Aggressive advances are still being madeAggressive advances are still being made

ReferencesReferencesWikipedia - Flash MemoryWikipedia - Flash Memory

How Stuff Works - Flash How Stuff Works - Flash MemoryMemory

http://smithsonianchips.si.eduhttp://smithsonianchips.si.edu

Questions?Questions?