U disk Storage principle

U disk, as we live, the work of essential mobile storage equipment, for us can be said to be indispensable to help us store some important data files, but such an important device we know how much it? Now let's go through the storage principle of u disk, let us more familiar with its working principle.

Flash Memory disk is a miniature high-capacity Removable Storage product that uses a USB interface without a physical drive. We all call him a U disk, nonvolatile storage, with the advantage of switching off the power to save data, while also being able to read and write faster, and can store the maximum amount of data per unit volume. , as well as the advantages of low power consumption characteristics. Its storage physical mechanism is actually a new type of EEPROM (electrically erasable programmable read-only storage). is a kind of SCM (semiconductor memory).

The early SCM uses typical transistor triggers as storage bits, plus a selection, reading and writing circuits to form the memory. Modern SCM uses the VLSI technology to make the memory chip, each chip contains a considerable number of storage bits, and then a number of chips constitute the memory. At present, the main material used in SCM is metal oxide field effect transistor (MOS), including PMOs, NMOS, CMOS, especially NMOS and CMOS applications most widely.

RAM (random access storage) is a kind of semiconductor memory. You must work with power on, or you will lose storage information. RAM is divided into dram (dynamic) and SRAM (static) Two, we now commonly used in the PC memory is SDRAM (synchronous dynamic RAM), which in the course of the operation needs to be charged at a certain frequency (refresh) to maintain information. DDR DDR2 memory also belongs to SDRAM. But the SRAM does not need to refresh frequently, the cost is higher than the DRAM, mainly uses in the CPU integrated caching (cache).

PROM (programmable ROM) can be written only once and cannot be changed after writing.

EPROM (erasable Prom) This eprom can only read information when working normally, but it is possible to erase existing information with ultraviolet light and write information on the high voltage of a dedicated device.

EEPROM (electric erasable Prom), the user can read and write through the control of the program.

Flash memory is actually a kind of EEPROM. The gap between the General MOS Gate (GATE) and the channel is the insulation of the oxide layer (gate oxide), while the flash memory is characterized by an extra layer of material called the "Floating Gate" (floating gate) between the control gate and the channel. Thanks to this layer of floating gates, so that flash memory can quickly complete the reading, writing, Erasure and other three basic modes of operation; Even in the environment that does not provide the power supply to the storage, it is possible to preserve the integrity of the data through this floating gate.

The electrons in the cell in the Flash memory chip can be reduced to a normal 1 by the electronic region with a higher voltage. The Flash memory uses an internal circuit, which not only enables the electronic area to function on the entire chip, but also can preset "block". The target area in the chip is wiped clean at the same time the block is set to be rewritten. The traditional EEPROM chip can erase only one byte at a time, and flash memory can erase a piece or whole chip at a time. Flash Memory's work speed is significantly ahead of the traditional EEPROM chip.

MSM (Magnetic surface storage) is a non-magnetic metal or plastic as a substrate, the magnetic surface of a very thin high permeability and hard moment magnetic material is coated, plated, deposited or sputtered on its SU * CE, and the information "0" and "1" are recorded with two kinds of residual magnetism of the magnetic layer. The matrix and the magnetosphere are collectively known as magnetic recording media. The shape of the recording medium can be called magnetic card memory, tape memory, drum memory and disk memory, respectively. The current widely used MSM in computers is disk and tape storage. Hard drives belong to MSM devices.

The ODM (CD-ROM storage) is similar to MSM, and is used for recording thin layer coating on the substrate to form a recording medium. The difference is that the circular sheet of the matrix is made of plexiglass with very low heat conductivity and strong heat resistance. coating or depositing the protective layer on the surface of the recording thin layer to protect the recording surface. There are two kinds of nonmagnetic and magnetic materials in the recording thin layer, the former form the optical disc medium, the latter form the magnetic disc medium.

The ODM is the memory with the highest record density at present, and the storage capacity is very large and the disc is easy to replace. The disadvantage is that the storage speed is one order of magnitude lower than the hard drive. has produced a similar speed with the hard drive ODM. CD-ROM, DVD-ROM, etc. are common ODM.