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What is Flash memory and its uses
Flash memory is a form of EEPROM (Electrically-Erasable Programmable Read-Only Memory) that allows multiple memory locations to be erased or written in one programming operation. In layman's terms, it is a form of rewritable memory chip that, unlike a Random Access Memory chip, holds its content without the need of a power supply. It is also an example of a Non-Volatile Read Write Memory (NVRWM). The memory is commonly used in memory cards, USB flash drives, MP3 players, digital cameras and mobile phones.
Flash memory is non-volatile, which means that it does not need power to maintain the information stored in the chip. In addition, flash memory offers fast read access times (though not as fast as volatile DRAM memory used for main memory in PCs) and better shock resistance than hard disk. These characteristics explain the popularity of flash memory for applications such as storage on battery-powered devices like mobile phones and personal digital assistants.
Normal EEPROM only allows one location at a time to be erased or written. For that reason, flash memory can operate at higher effective speeds when the system architecture allows simultaneous multiple reads to take place during a single write (to different locations).
Flash memory is made in two forms: NOR flash and NAND flash. The names refer to the type of logic gate used in each storage cell. Both types of flash memory and EEPROM wear out after many erase operations, due to wear on the insulating oxide layer around the charge storage mechanism used to store data. A typical NOR flash memory unit wears out after 10,000-100,000 erase/write operations, a typical NAND flash memory after 1,000,000.
Flash memory is essentially an NMOS transistor with an additional conductor suspended between the gate and source/drain terminals. This variation is called the Floating-Gate Avalanche-Injection Metal Oxide Semiconductor (FAMOS) transistor.