Flash Memory Store

Both NOR and NAND Flash memory were invented by Dr. Fujio Masuoka of Toshiba in 1984.The name 'Flash' was suggested because the process of erasing the contents of memory like a flash of a camera and his name has been coined to express how much faster it could be erased "in a flash." Dr. Masuoka presented the invention at the International Electron Devices Meeting (IEDM), held in San Jose in California in 1984 and Intel recognizes the potential of the invention and introduced the first commercial chip NOR Flash type in 1988, with long time writing and erasing.

Flash memory is a form of nonvolatile memory that can be electrically erased and rewrite, which means it does not need power to maintain data stored in the chip. In addition, flash memory offers fast read access times and better shock resistance than hard disks. These characteristics explain the popularity of flash memory for applications such as storage on battery-powered devices.

Flash memory is the advance of EEPROM (electrically erasable programmable read-only memory) that allows multiple memory locations must be erased or written in one programming operation. Unlike an EPROM (Electrically Programmable Read-Only Memory) EEPROM can be programmed and erased multiple times electrically. Normal EEPROM only allows one location at a time to be erased or written, which means that the flash can operate at higher speeds in force when the systems using it read and write in different places at the same time .

Referring to the type of logic gate used in each storage cell, Flash memory is built in two varieties and named, NOR flash and NAND flash. Flash memory stores one bit of information in an array of transistors, called "cells", but these flash memory devices referred to as multi-level cell devices can store more than one bit per cell depending on the amount electron placed on the floating gate of a cell. NOR flash memory cell is like a semiconductor device like transistors, but it has two doors.

The first is the control gate (CG) and the second is a floating gate (FG) that is shield or insulated all around by an oxide layer. Because the FG is isolated by its shield oxide layer, electrons placed on it get trapped and the data are stored inside. Moreover NAND Flash uses tunnel injection for writing and tunnel exit for deletion.

NOR flash that was developed by Intel in 1988 with the unique ability to erase and write times along the lines of his endurance and erase cycles from 10,000 to 100,000 makes it suitable for storing program code that must be updated frequently, as in a digital camera and PDA. Although maps later, demand is directed towards the cheaper NAND flash, NOR Flash-based is hitherto the source of all removable media.

Followed in 1989 by Samsung and Toshiba form NAND flash, high density, low cost per bit then NOR Flash with faster erase and write, but it only allows sequence data access, not random as NOR Flash, NAND Flash, which is suitable for the mass storage device such as memory cards. SmartMedia was first NAND removable media and many others are at the origin as MMC, Secure Digital, xD-Picture Card and Memory Stick. Flash memory is commonly used to hold control code such as the Basic Input / Output System (BIOS) in a computer. When the BIOS must be changed (rewritten), flash memory can be written in the block rather than byte sizes, making it easier to update.

On the other hand, flash memory is not practical to random access memory (RAM) as RAM needs to be addressable at the byte (not the block) level. Thus, it is used more as a hard drive as a ram. Because of this unique individual, it is used with specifically designed file systems which extend writes over the media and cope with long periods of erasing blocks of NOR flash. JFFS was the file system first.