| Flash memory gets its name due to its microchip | | | | Followed in 1989 Samsung and Toshiba form NAND |
| arrangement in such a way, that its section of memory | | | | flash with higher density, lower cost per bit then NOR |
| cells gets erased in a single action or "Flash". | | | | Flash with faster erase and write times, but it only |
| Both NOR and NAND Flash memory were invented | | | | allows sequence data access, not random like NOR |
| by Dr. Fujio Masuoka from Toshiba in 1984.The name | | | | Flash, which makes NAND Flash suitable for mass |
| 'Flash' was suggested because the erasure process | | | | storage device such as memory cards. |
| of the memory contents reminds a flash of a camera, | | | | SmartMedia was first NAND-based removable media |
| and it's name was coined to express how much | | | | and numerous others are behind like MMC, Secure |
| faster it could be erased "in a flash". Dr. Masuoka | | | | Digital, xD-Picture Cards and Memory Stick. Flash |
| presented the invention at the International Electron | | | | memory is frequently used to hold control code such |
| Devices Meeting (IEDM) held in San Jose, California | | | | as the basic input/output system (BIOS) in a computer. |
| in1984 and Intel recognizes the potentiality of the | | | | When BIOS needs to be changed (rewritten), the flash |
| invention and introduced the first commercial NOR | | | | memory can be written to in block rather than byte |
| type flash chip in 1988, with long erase and write times. | | | | sizes, making it simple to update. On the other hand, |
| Flash memory is a form of non-volatile memory that | | | | flash memory is not practical to random access |
| can be electrically erased and rewrite, which means | | | | memory (RAM) as RAM needs to be addressable at |
| that it does not need power to maintain the data | | | | the byte (not the block) level. Thus, it is used more as |
| stored in the chip. In addition, flash memory offers fast | | | | a hard drive than as a RAM. |
| read access times and better shock resistance than | | | | Because of this particular uniqueness, it is utilized with |
| hard disks. These characteristics explain the popularity | | | | specifically-designed file systems which extend writes |
| of flash memory for applications such as storage on | | | | over the media and deal with the long erase times of |
| battery-powered devices. | | | | NOR flash blocks. JFFS was the first file systems, |
| Flash memory is advance from of EEPROM | | | | outdated by JFFS2. Then YAFFS was released in |
| (Electrically-Erasable Programmable Read-Only | | | | 2003, dealing specifically with NAND flash, and JFFS2 |
| Memory) that allows multiple memory locations to be | | | | was updated to support NAND flash too. Still, in |
| erased or written in one programming operation. Unlike | | | | practice most follows old FAT file system for |
| an EPROM (Electrically Programmable Read-Only | | | | compatibility purposes. |
| Memory) an EEPROM can be programmed and | | | | Although it can be read or write a byte at a time in a |
| erased multiple times electrically. Normal EEPROM only | | | | random access fashion, limitation of flash memory is, it |
| allows one location at a time to be erased or written, | | | | must be erased a "block" at a time. Starting with a |
| meaning that flash can operate at higher effective | | | | freshly erased block, any byte within that block can be |
| speeds when the systems using; it read and write to | | | | programmed. However, once a byte has been |
| different locations at the same time. Referring to the | | | | programmed, it cannot be changed again until the entire |
| type of logic gate used in each storage cell, Flash | | | | block is erased. In other words, flash memory |
| memory is built in two varieties and named as, NOR | | | | (specifically NOR flash) offers random-access read |
| flash and NAND flash. | | | | and programming operations, but cannot offer |
| Flash memory stores one bit of information in an array | | | | random-access rewrite or erase operations. |
| of transistors, called "cells", however recent flash | | | | This effect is partially offset by some chip firmware or |
| memory devices referred as multi-level cell devices, | | | | file system drivers by counting the writes and |
| can store more than 1 bit per cell depending on amount | | | | dynamically remapping the blocks in order to spread |
| of electrons placed on the Floating Gate of a cell. NOR | | | | the write operations between the sectors, or by write |
| flash cell looks similar to semiconductor device like | | | | verification and remapping to spare sectors in case of |
| transistors, but it has two gates. First one is the control | | | | write failure. |
| gate (CG) and the second one is a floating gate (FG) | | | | Due to wear and tear on the insulating oxide layer |
| that is shield or insulated all around by an oxide layer. | | | | around the charge storage mechanism, all types of |
| Because the FG is secluded by its shield oxide layer, | | | | flash memory erode after a certain number of erase |
| electrons placed on it get trapped and data is stored | | | | functions ranging from 100,000 to 1,000,000, but it can |
| within. On the other hand NAND Flash uses tunnel | | | | be read an unlimited number of times. |
| injection for writing and tunnel release for erasing. | | | | Flash Card is easily rewritable memory and overwrites |
| NOR flash that was developed by Intel in 1988 with | | | | without warning with a high probability of data being |
| unique feature of long erase and write times and its | | | | overwritten and hence lost. |
| endurance of erase cycles ranges from 10,000 to | | | | In spite of all these clear advantages, worse may |
| 100,000 makes it suitable for storage of program code | | | | occur due to system failure, battery failure, accidental |
| that needs to be infrequently updated, like in digital | | | | erasure, re-format, power surges, faulty electronics |
| camera and PDAs. Though, later cards demand | | | | and corruption caused by hardware breakdown or |
| moved towards the cheaper NAND flash; NOR-based | | | | software malfunctions; as a result your data could be |
| flash is hitherto the source of all the removable media. | | | | lost and damaged. |