Principles of operationįlash memory stores information in an array of memory cells made from floating-gate transistors. For example, the microSD card has an area of just over 1.5 cm², with a thickness of less than 1 mm microSD capacities range from 64 MB to 16 GB, as of August 2009. A new generation of memory card formats, including RS-MMC, miniSD and microSD, and Intelligent Stick, feature extremely small form factors. The first NAND-based removable media format was SmartMedia in 1995, and many others have followed, including MultiMediaCard, Secure Digital, Memory Stick and xD-Picture Card. In this regard NAND flash is similar to other secondary storage devices such as hard disks and optical media, and is thus very suitable for use in mass-storage devices such as memory cards. This made NAND flash unsuitable as a drop-in replacement for program ROM since most microprocessors and microcontrollers required byte-level random access. ![]() Rather, data must be read on a block-wise basis, with typical block sizes of hundreds to thousands of bits. However, the I/O interface of NAND flash does not provide a random-access external address bus. It has faster erase and write times, and requires a smaller chip area per cell, thus allowing greater storage densities and lower costs per bit than NOR flash it also has up to ten times the endurance of NOR flash. Toshiba announced NAND flash at the 1987 International Electron Devices Meeting. NOR-based flash was the basis of early flash-based removable media CompactFlash was originally based on it, though later cards moved to less expensive NAND flash. Its endurance is 10,000 to 1,000,000 erase cycles. This makes it a suitable replacement for older Read-only memory (ROM) chips, which are used to store program code that rarely needs to be updated, such as a computer's BIOS or the firmware of set-top boxes. NOR-based flash has long erase and write times, but provides full address and data buses, allowing random access to any memory location. Intel Corporation saw the massive potential of the invention and introduced the first commercial NOR type flash chip in 1988. Masuoka presented the invention at the IEEE 1984 International Electron Devices Meeting (IEDM) held in San Francisco, California. Shoji Ariizumi, because the erasure process of the memory contents reminded him of the flash of a camera. According to Toshiba, the name "flash" was suggested by Dr. Fujio Masuoka while working for Toshiba circa 1980. įlash memory (both NOR and NAND types) was invented by Dr. Because erase cycles are slow, the large block sizes used in flash memory erasing give it a significant speed advantage over old-style EEPROM when writing large amounts of data. Īlthough technically a type of EEPROM, the term "EEPROM" is generally used to refer specifically to non-flash EEPROM which is erasable in small blocks, typically bytes. A trawlerman attempted to trace the owner of a digital camera after it was hauled from the Atlantic seabed in his nets with the photos still intact. Another feature of flash memory is that when packaged in a "memory card," it is extremely durable, being able to withstand intense pressure, extremes of temperature, and even immersion in water. These characteristics explain the popularity of flash memory in portable devices. In addition, flash memory offers fast read access times (although not as fast as volatile DRAM memory used for main memory in PCs) and better kinetic shock resistance than hard disks. Since flash memory is non-volatile, no power is needed to maintain the information stored in the chip. ![]() It has also gained popularity in console video game hardware, where it is often used instead of EEPROMs or battery-powered static RAM (SRAM) for game save data. Example applications include PDAs (personal digital assistants), laptop computers, digital audio players, digital cameras and mobile phones. Flash memory costs far less than byte-programmable EEPROM and therefore has become the dominant technology wherever a significant amount of non-volatile, solid state storage is needed. It is a specific type of EEPROM (Electrically Erasable Programmable Read-Only Memory) that is erased and programmed in large blocks in early flash the entire chip had to be erased at once. It is a technology that is primarily used in memory cards and USB flash drives for general storage and transfer of data between computers and other digital products. Flash memory is a non-volatile computer storage that can be electrically erased and reprogrammed.
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