Compact Flash Memory and Data Recovery
Flash memory gets its name because the microchip arrangement in such a way, that part of the memory cells are erased in a single action or "Flash".
Both NOR and NAND Flash memory was invented by Dr. Fujio Masuoka from Toshiba in 1984.The name 'Flash' is suggested because of the removal process memory contents reminds a flash of the camera, and the name was created to express how much faster it could be removed "in a flash".
Flash memory is a form of non-volatile memory that can be electrically erased and rewrite, which means that it does not require power to retain 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 face of EEPROM (electrically-Erasable Programmable Read-Only Memory) that allows multiple memory locations to be deleted or written in one programming operation. Unlike a (Memory electrically Programmable Read-Only) EPROM EEPROM can be programmed and erased multiple times electrically. Normal EEPROM only allows one location at the time to be erased or written, meaning that flash can operate at higher effective speeds when the system uses, it reads and writes to different locations at the same time.
Referring to the type of logic gate used in each storage cell, Flash memory built in two varieties and named as, NOR flash and NAND flash.
Flash memory stores one bit of information in an array of transistors, called "cells", Flash memory devices, but recently referred to as multi-level cell devices, can store more than 1 bit per cell depending on the number of electrons placed in the cell Floating Gate . NOR flash cell looks similar to semiconductor devices such as transistors, but it has two gates. The first is the control gate (CG) and the second is a floating gate (FG) a shield or insulated by the oxide layer. Because the FG is secluded by its shield oxide layer, electrons placed on it are trapped and stored in the data. On the other hand NAND Flash uses tunnel injection for writing and tunnel release to remove.
NOR flash that was developed by Intel in 1988 with the unique features of the erase and write times and long endurance erase cycles ranges from 10,000 to 100,000 makes it suitable for storage of program code that needs to be updated infrequently, such as digital cameras and PDAs. Though, later cards demand moved towards the cheaper NAND flash; NOR-based flash until recently the source of all removable media.
Followed in 1989 Samsung and Toshiba form NAND flash with higher density, lower cost per bit then NOR Flash with faster erase and write times, but it only allows sequence data access, not random like NOR Flash, which makes NAND Flash suitable for mass storage devices like memory cards. SmartMedia 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 store control code such as system input / output base (BIOS) on the computer. When BIOS needs to be changed (rewritten), flash memory can be written in blocks rather than byte sizes, making it easy to update.
On the other hand, flash memory is not practical to random access memory (RAM) as RAM needs to be addressed in bytes (not block) level. So, more widely used as a hard drive than as RAM. Therefore a certain uniqueness, is used with the file system specifically designed to extend writes over the media and dealing with long blocks of time erase NOR flash. JFFS is the first file systems, outdated 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 purposes.
Although it can read or write a byte at a time in random access mode, the flash memory limitations, it should be removed "block" at a time. Starting with a new erased block, any byte within that block can be programmed. However, after a byte has been programmed, can not be changed again until the entire block will be removed. 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 was 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 mapping to spare sectors in case of write failure.
Due to wear and tear on the insulating oxide layer around 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 can be read in a limited number of times. Flash cards easily rewritable memory and overwrites without warning with a high probability of data being overwritten and hence lost.
Apart from all the obvious advantages, worse may occur due to system failure, battery failure, accidental deletion, reformatting, power surges, faulty electronics and corruption caused by damage to hardware or software malfunctions, as a result your data could be lost and damaged .
Flash Memory Data Recovery is the process of restoring the data from primary storage media when it can not be accessed normally. Flash memory is a data recovery flash memory file recovery restore services that the photographs of all damaged and removed even if the memory card is reformatted. This could be due to physical damage or logical damage to storage devices. Data even from damaged flash memory can be recovered, and more than 90% of lost data can be restored.