USB stick isUSBUSB flash disk is also called "USB flash disk".USB flash disk is a kind of flash memory, so it is sometimes calledflash disc。The biggest difference between a USB stick and a hard disk is that it does not require physicalDriver, plug and play, and its storage capacity far exceedsfloppy disk, extremely portable[1]。
USB set diskStorage technology、Flash MemoryTechnology and universal serial bus technology.USBThe port of is connected to the computer. Yesdata input/Output channel;Main control chipMake the computer recognize the USB flash disk as a removable disk, which is the "brain" of the USB flash disk;USB driveFlash(Flash memory) The chip stores data, which is different from the computer memory, and the data will not be lost even after power failure;The PCB backplane connects the components together and provides a platform for data processing[1]。
USB stick, full nameUSB flash drive, the English name is "USB flash disk".It is a way of usingUSB interfaceNo physics required forDriverOfHigh capacityRemovable StorageProduct, connected to computer through USB interfacePlug and Play。The name of USB flash disk comes fromLongcoA new type of scientific and technological productionstorage device, called "USB flash disk", and connected with USB interface.After the USB stick is connected to the USB interface of the computer, the data of the USB stick can be exchanged with the computer.However, the equipment of similar technology produced later can no longer be called "USB flash disk", but "USB flash disk" because of the patent registration of Lucco.Later, the term "U disk" was widely known because it was easy to rememberportable storage deviceone of[2]。
Compared with other portable storage devices, flash memory USB flash drives have many advantages: small space consumption, and generally fast operation speed（USB1.1, 2.0, 3.0), can store more data, and has reliable performance (because there is nomechanical equipment）, which can be disconnected during reading and writing without damaging the hardware（floppy diskIf it is disconnected during reading and writing, it will be damaged immediately.) Only data will be lost.This type of disk uses the USB mass storage device standard, and the operating system is as followsLinux、 Mac OS X、UnixAndWindowsBuilt in support in both[2]。
USB stick is usually usedABS plasticOr metal housing with a small print insideCircuit board, make the size of the flash disk as small asKey ringThe ornaments can also be put in the pocket or strung on the neck rope.Only the USB connector protrudes out of the protective housing and is usually covered by a small cover.Most USB flash drives use the standard Type-A USB connector, which allows them to be inserted directlypersonal computerIn the USB port on the[2]。
To access the data of the USB stick, you must connect the USB stick to the computer;WhetherDirect connectionTo the built-in USB controller or aUSB HubFine.The flash drive will start only when it is plugged into the USB port, and the required power is also supplied by the USB connection[2]。
Development history
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From 1998 to 2000, many companies claimed that they were the first to inventUSBFlash drive.Including ChinaLongcoTechnologyIsraelM-Systems andSingaporeTrek.But we really get the basics of USB flash driveInvention patentIt is China Lonco.In July 2002, Lucco "useddata processing systemFlash ofElectronicExternal storage method and device "（Patent No: ZL 99 1 17225.7)State Intellectual Property OfficeOfficially authorized, the patent fills the gap between ChinaComputer storageThe blank of invention patents in the past 20 years.Thispatent rightThe acquisition of has caused a great shock to the entire storage industry, including Israel M-Systems immediately filed an invalid review with the State Intellectual Property Office of China, which once became a shocking patent dispute in the global flash memory field at home and abroad.But on December 7, 2004, Ronco won the title ofState Patent OfficeOfficially authorized flash disk basic invention patent, US patent No. US6829672.The acquisition of this patent finally ended the fight.China Lonco is the first inventor of U disk in the world.US TimeOn February 10, 2006, Lonco entrustedMorgan Lewis Law FirmtowardsTexas, USAEastern FederationcourtsubmitPetition, accusing PNY of violating the US patent of Lucco.In February 2008, Lonco and PNY reached an out of court settlement.Lonco signs with PNYPatent licenseAccording to the agreement, PNY will pay the patent license fee of US $10 million to Lucco.This is the first time that a Chinese enterprise has received a huge patent license fee in the United States, which further proves that Lance is the global inventor of USB flash drives[3]。
The current USB flash disk supports the USB2.0 standard, but becauseNANDDue to the technical limitation of flash memory, their read/write speed cannot reach the maximum supported by the standardtransmission speed 480Mb/s。The fastest flash drive is in useDual channelBut compared with hard disk or USB2.0transmission speed For example, there is still a gap.The highest transfer rate is about 20-40 MB/s, while the general file transfer speed is about 10 MB/s[3]。
USB flash disk composition
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The USB flash disk is very simple, mainly composed of shell+movement, in which[4]：
2. Housing: pressMaterial classification, YesABS plastic, bamboo, wood, metal, leathersilica gel、PVCSoftware, etc;Sort by style, including card, pen, miniCartoon, commerce, simulation, etc;Classified by function, including encryption, anti-virus, waterproof, intelligent, etc[4]。
Storage principle
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Computer handleBinary digitThe signal is converted into a composite binary digital signal (add distribution, checkstackAnd other commands), read and write to the USB chip adapter interface, and distribute the signal toEEPROMMemory chipCorresponding address storage ofbinary dataTo store data.EEPROM datastorageIts control principle isvoltage control GridtransistorVoltage of gate transistorJunction capacitanceThe voltage value can be saved for a long time. The main reason why the data can be saved after power failure is that floating gate and selection gate are added to the original transistor.staySource poleandDrain electrodeA floating gate for storing electrons is formed on the semiconductor with unidirectional current conduction between them.The floating gate is wrapped with a layer of siliconOxide filminsulator。Above it is a selection/control gate that controls the transmission current between the source and drain.The data is 0 or 1 depending on whether there are electrons in the floating gate formed on the silicon backplane.0 with electron, 1 without electron[5]。
Just like its name, flash memory is initialized by deleting data before writing.Specifically, electrons are derived from all floating grids.Some data will be classified as "1".When writing, only the data is 0, and when the data is 1, nothing is done.When writing 0, applyhigh voltage, increase the electronic energy conducted between the source and drain.In this way, electrons will break through the oxide film insulator and enter the floating gate.When reading data, apply a certain voltage to the gate electrode, and the current is greater than 1, and the current is smaller than 0.When the floating gate has no electrons (the data is 1), voltage is applied to the drain when the gate electrode is applied with voltage, and current will be generated due to the movement of a large number of electrons between the source and drain.When the floating gate has electrons (the data is 0),ChannelThere will be fewer electrons conducting in.Because the voltage applied to the gate electrode is absorbed by the floating gate electrons, it is difficult to affect the channel[5]。
Function classification
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The main purpose of the USB stick is toStore dataWith the efforts of enthusiasts and businesses, we have developed more functions of USB flash disk:Encrypted USB flash disk, startup USB flash diskAntivirus U-disk, temperature measurement U disk, music U disk, etc[4]。
Driverless type
The driverless product can be used in Windows 98/Me/2000/XP andLinux、Mac OSIt can be used normally under other systems, and only needs to install drivers under Windows 98. In operating systems above Windows Me, it can be correctly recognized and used by the system without installing drivers, which truly reflects the convenience of "plug and play" of USB devices.Most USB flash drives in the market are driverless, and users have a wide choice,patriot、association、JinbangUSB flash drives from companies such as Lucco are good choices[6]。
Encrypted
In addition to encrypting the stored contents, the encrypted USB flash disk can also be used as an ordinary USB flash disk.There are generally two types: one isHardware encryption, such asfingerprint identificationEncryption USB stickThe price of this USB flash disk is high. For users in special departments, generally speaking, hardware encryption is more secure;The other isSoftware encryption, software encryption can be divided intoHide Section(Encrypted partition) to store the files to be encrypted, or it can only be used for a singleFile encryptionWithout a password, you cannot open an encrypted partition or an encrypted single file, thus playing the role of confidentiality[6]。
Startup
The appearance of startup USB flash disk makes people look at this portable product with new eyes.As the name implies, the startup USB stick is addedBoot systemThe function of USB flash disk can make up for the defects of encrypted and non drive USB flash disk non bootable systems.It is the emergence of this product that has acceleratedfloppy disk driveThe process of being eliminated.To proceedsystem bootThe USB flash disk must be realized by simulating a USB peripheral.For example, the bootable USB stick in the market mainly relies on analog USB_HDDTo realize system boot.One advantage of booting the system by simulating USB_HDD is that after the system starts, the USB flash disk is regarded as a hard disk, and users can use the space of the USB flash disk as much as possible.This also fully reflects the large capacity of the USB flash disk.This kind of USB flash disk with multiple startup function can be used not only in desktop computers, but also in those with external USB floppy drivesNotebook computerWith this kind of USB flash disk, the laptop can completely eliminate the floppy disk drive and even the optical disk drive[6]。
There are bootable USB flash drives available in the market, but they are more expensive than ordinary driveless USB flash drives. Users can actually make ordinary driveless USB flash drives into bootable USB flash drives in two ways[6]：
1. Download the USboot production tool from the Internet for free, and it can be produced successfully in a few minutes, but it is pureDOSInterface[6]。
2. Free download from the InternetUltraISOMake tools and WinPE.iso files to make the u disk WinPE (a simplifiedWindows XPOperating system)Startup Disk, the production time is a little longer, and Windows is startedGraphical interface[6]。
advantage
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1. The use of USB disk is very simple and convenient
There are many kinds of USB disk interfaces. Strictly speaking, only the flash disk with USB interface can be called a USB disk.This means that most modern operating systems can read and write to flash disks without installing additional drivers[7]。
The USB flash disk is displayed as a block in the operating systemLogical unitTo hide the complex details required for internal flash memory.The operating system can use anyfile systemOr block addressing.You can also make a startup USB flash disk to boot the computer.Current operating systems such as Linux, MacOSX, Unix andWindows2000、XP、win7Built in support in both[7]。
When in use, no drive is required, noneExternal power supply, plug and play, live plug and pull.After connecting to the host computer through USB interfaceLike pairFormat, copy, delete and other operations on ordinary hard disks.The data on the USB stick can be transferred to the computer, and the data on the computer can also be easily transferred to the USB stick.It can be removed or connected at any time.The portable mobile storage is realized.Access speedFast (about 15 times the speed of a floppy disk).
2. The biggest feature of the USB stick is its small size and portability
General U disk capacity includes 1G, 2G, 4G, 8G, 16G, and floppy diskCD-RWCompared with traditional storage devices such as, and Zip disk, "USB disk" has obvious advantages.It is mainly manifested in: the volume is very small (only the size of the thumb), and the weight is only about 20g;Large capacity (8MB~256MB, even 2GB);It can be used to store photos, data and images, with an area of only 1 cm square. It is convenient to carry and suitable for wireless computing andMobile office, greatly improving efficiency and making human life more convenient[7]。
3. USB flash disk is safe
It is almost impervious to water or dust and will not beScratches, and these are in the old portable storage devices (such as optical disksfloppy diskFilm) and so on are serious problems.The flash drive usesSolid state storageThey are designed to resist unintentional impact from external forces.These advantages make flash drives very suitable for transferring personal data orworking paperCarry to another place, such as from home to school or office, or various places where personal data needs to be carried and accessed generally.Because USB is almost ubiquitous in today's personal computers, flash drives can be used everywhere.However, small flash drives also make them often misplaced, forgotten or lost[7]。
4. Large storage capacity
Although the flash disk is small, it is relatively largestorage capacity 。Most USB flash drives can store more data than a CD (700MB). Advanced USB flash drives can store more data than a double-sided double-layerDVD(17GB) More data[7]。
usage method
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USB stick hasUSB interface, YesUSB device。If the operating system isWindowsXP/Vista/Win7/Linux/In the case of PrayayaQ3 or Apple, insert the USB stick directly into theCase front panelOr the USB interface at the back, the system willautomatic recognition 。If the system isWindows 98You need to install a USB stickDriverCan be used.The driver can be found on the attached CD or on the manufacturer's website[8]。
The first time you use a USB stick on a computer (when you plug the USB stick into the USB interface), the system will give a prompt tone, and then report "FoundNew Hardware”。Later, you will be prompted: "The new hardware has been installed and can be used".(Sometimes it may need to be restarted) At this time, open "My Computer", and you can see an icon of the hard disk. The name is generally the brand name of the USB flash disk, such asKingston, the name is KINGSTON.After this step, if you want to use the USB flash drive in the future, plug it in directly, and then you can open "My Computer" to findRemovable diskAt this time, notice thattaskbarOn the far right, there will be a small icon, which looks like a green arrow beside a gray object, meaning to safely delete the USB hardware device.(USB disk is one of USB devices). Next, you can saveDelete File, or right click to directly send the file to the USB flash drive[8]。
However, it should be noted that after the use of the USB flash disk, all the windows about the USB flash disk should be closed. Before unplugging the USB flash disk, you should double click the right button with the left buttonLower cornerSafely delete the USB hardware device icon, then select "Stop" and left click "OK".When the prompt "USB device can now be safely removed from the system" appears in the lower right corner, you can unplug the USB disk from the chassis, or click the icon directly, click "Safely remove USB device", and then unplug the USB disk from the chassis after the prompt appears[8]。
matters needing attention
1. The USB stick usually has a write protection switch, but it should be inserted in the USB stickcomputer interfaceSwitch before, not on the USB stickworking condition Switch under[9]。
2. All USB flash disks are in working statusindicator light, if it is an indicator light, when insertedHost interfaceWhen the light is on, it meansturn on electricity, when the light flashes, it indicates that data is being read or written.If there are two indicators, they usually have two colors. One is on when the power is turned on, and the other is on when the USB flash disk is reading or writing data.It is forbidden to unplug the USB stick when the read/write status light is on.Do not unplug the USB stick until the read-write status indicator stops flashing or is off[9]。
3. The storage principle of the USB flash disk is quite different from that of the hard disk. Do not defragment it, or its service life will be affected[9]。
Future development
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Semiconductor manufacturers strive toFunction integrationIn a single chip, to reduce the cost of flash disk components, thus also reducing the overall cost[10]。
In the effort to increase capacity, 1GB and smaller flash disks are no longer manufactured.KingstonA 512GBUSB3.0Flash disk, and claimed to be able to store data for 10 years[10]。
LexarAttempting to introduce aUSBflash Memory card。It is compatible with USB flash drives and is expected to replace various flash memory cards[10]。(Completed)
SandiPublished new technology that can control the use of copyrighted data on flash drives.The main users of this technology are students.This technology is calledFlashCP[10]。
