Flash Memory

Points of Discussion  Flash Memory Generalities  Construction & Properties  History of Flash Memory  NOR & NAND Architectures  Optimizations  Standardization  New Developments & Future of Flash  Closing Statements

Flash Memory  A type of EEPROM (Electrically-Erasable Programmable Read-Only Memory)  Non-volatile, solid state technology  Relatively limited lifespan  Information is stored in an array of memory cells made from floating-gate (FG) transistors

Flash Memory  Packaged inside a memory card:  Extremely durable  Can withstand intense pressure  Immersion in water  Better kinetic shock resistance than hard disks  Average power requirements range from 5V-12V

Flash Memory Cell

History of Flash Memory  Invented by Fujio Masuoka while he was working for Toshiba in the early 1980s  First introduced at the 1984 International Electron Devices Meeting in San Francisco

Manufacturers of Flash

NOR Flash Memory  Developed to replace read only memory  Full address and data buses allow random access to any memory location  Can access any memory cell  Slow sequential access

NAND Flash Memory   Developed to replace hard disks   Sequential-accessed command and data registers replace the external bus of NOR  Decreases chip real estate  Can only access pages  Faster sequential access

Optimizations  Wear levelling  Counting writes & dynamically remapping blocks  Bad block management  Write verification and remapping bad sectors  Multi-Level Cell technology  Memory cells store more than one bit

Standardization  Part of the reason for the success of Flash memory  Open NAND Flash Interface Working Group developed standard low-level interface  Standard pinout  Standard command set for reading, writing, and erasing NAND flash chips  Mechanism for self-identification

New Developments  AND Flash  Bit line replaced with embedded diffusion line to reduce cell size  Low power dissipation (3V)  DINOR (DIvided bit-line NOR) Flash  Attempts to reduce the chip real estate compared to conventional NOR  Low power dissipation (3V), sector erase, high data transfer rate

Future of Flash Memory  Continues to be among the most aggressively scaled electronic technologies  Memory cell size minimum of 20 nm expected to be met in 2010  May be replaced by Phase-Change RAM or other emerging technologies

In Closing…  One of the most popular alternatives for portable device storage  Aggressive advances are still being made

References Wikipedia - Flash Memory Wikipedia - Flash Memory How Stuff Works - Flash Memory How Stuff Works - Flash Memory

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