Flash memory gets its name due to its microchip arrangement in such a way that its section of memory cells is erased in a single action or "Flash".
Both NOR and NAND Flash memory were invented by Dr. Fujio Masuoka Toshiba 'Flash' 1984.The name was suggested by the process of erasing the memory contents reminds a flash of a camera, and his name was coined to express how much faster could be erased "in a moment." Dr. Masuoka presented the invention at the International Meeting on Electron Devices (IEDM) held in San Jose, California in 1984 and Intel recognizes the potentiality of the invention and introduced the NOR flash chip first commercial in 1988, to wipe long and writing.
Flash memory is a form of nonvolatile memory that can be electrically erased and rewrite, which means no power to maintain the data stored on 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 storage in applications such as battery-powered devices.
Flash memory is in advance of EEPROM (electrically erasable programmable read only memory) that allows multiple memory locations to be erased or written in the programming operation. Unlike an EPROM (electrically programmable read only memory) an 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 effectively at higher speeds when the systems they use, but read and write in different places at the same time.
In reference to the type of logic gate used in each storage cell, Flash memory is based on two varieties and named as, NOR flash and NAND flash.
The flash memory stores one bit of information in an array of transistors, called "cells", however, recent flash memory devices is referred to as devices in the multi-level cell can store more than 1 bit per cell depending on placed the number of electrons in the floating gate of a cell. NOR flash cell is similar to a semiconductor device like transistors, but has two doors. The first is the control gate (CG) and the second is a floating gate (FG), which is the shield and isolated from everything with a layer of oxide. Because the FG is isolated by the protective oxide layer, electrons placed on it get trapped and the data is stored inside. On the other hand NAND Flash uses tunnel injection for writing and tunnel release for erasing.
NOR flash that was developed by Intel in 1988 with the sole function of erasing and writing over and endurance of erase cycles ranges from 10,000 to 100,000 makes it suitable for storing program code that needs to be updated only Often, as in digital cameras and PDAs. However, later cards demand toward the cheaper NAND flash, NOR flash based so far is the source of all removable media.
Followed in 1989 Samsung and Toshiba NAND flash memory as higher density, lower cost per bit then NOR Flash with faster erase and write times, but only allows sequence data access, not random like NOR Flash, NAND Flash makes it suitable for mass storage device such as memory cards. SmartMedia was the first NAND-based removable media and many others are behind like MMC, Secure Digital, xD-Picture Card and Memory Stick. Flash memory is commonly used to maintain control code, such as basic input / output system (BIOS) on a computer. When BIOS needs to be changed (re) flash memory can be written in the block rather than byte size, which facilitates the upgrade.
On the other hand, flash memory is not practical to random access memory (RAM) RAM memory must be byte addressable (no block) level. Therefore, it is used more as a hard drive as a RAM. Due to this particular uniqueness, it is used specially designed file systems which extend writes about the media and dealing with long times to erase NOR flash blocks. Jffs file system was first superseded by JFFS2. Then YAFFS was released in 2003, dealing specifically with NAND flash, and JFFS2 was updated to support NAND flash too. However, in practice most follows old FAT file system for compatibility reasons.
Although you can read or write a byte at a time in a random access memory limitation of flash is, it must be erased a "block" at a time. From a freshly erased block, any byte within that block can be programmed. However, once a byte has been programmed, you can not change again until the entire block is erased. In other words, flash memory (specifically NOR flash) offers random access read and programming operations, but can not offer random-access rewrite or erase operations.
This effect is partially offset by some chip firmware or file system drivers by counting the writes and dynamically remapping the blocks in order to spread write operations between sectors, or by write verification and remapping to spare sectors in case of typing error.
Due to wear of the insulating layer of oxide on the charge storage mechanism, all types of flash memory erode after a certain number of erase functions ranging from 100,000 to 1,000,000, but you can read an unlimited number of times. Flash Memory Card is easily rewritable and overwrites without warning with a high probability of the data is overwritten and lost so much.
Despite all these clear advantages, worse may occur due to system failure, battery failure, accidental deletion, reformatting, power surges, faulty electronics and corruption caused by hardware failure or software As a result, data can be lost and damaged.
Flash memory data recovery is the process of recovering data from primary storage media when it can not be accessed normally. Flash memory data recovery is a flash memory file recovery service that restores all corrupted pictures and deleted, even if a memory card is reformatted. This may be due to physical or logical damage to the storage device. Data even flash memory can be recovered damages and more than 90% loss of data can be restored.
Topic: Compact Flash Memory and Data Recovery (Read 1217 times)
