Little-known U disk common sense

what is a USB flash drive

u disk, full name "USB flash drive", English "USB flash disk". It is a USB interface with no physical drive micro high-capacity mobile storage products, can be connected via USB interface to the computer for Plug and play. The name of the USB flash drive originated from NETAC Company, a new type of storage equipment, known as "USB", using USB interface to connect. USB interface connected to the computer's host, the data can be exchanged with the computer USB. And then the production of similar technology equipment because the NETAC has been patented, and can not be called "USB", and renamed the "U Disk" homophonic. Later, the name of the USB flash drive is widely known for its simplicity and ease of use, and until now the two have been common and are no longer distinguishable from one of the mobile storage devices.

　　Brief introduction

　　Basic information

USB flash drive, also known as USB flash drive, Chinese name "USB (Universal Serial Bus) interface of the memory disk", the English title "USB Disk", is a small hard disk. Flash disk interface has RS-232, USB, SCSI, IEEE-1394, E-sata, and so on, strictly speaking only USB interface Flash disk can be called U disk. Used to store photos, materials, images, only 1 centimeters square, realize portable mobile storage, greatly improve the office efficiency, make human life more convenient.

　　The composition of U disk

The composition of the USB stick is simple: Shell + movement + Flash + packaging

1. Movement: The movement includes a PCB board + main CONTROL + crystal oscillator + capacitive capacitance +usb head +led head +flash (Flash) chip

2. Shell: There are a variety of plastic, wood, metal, leather jacket, silicone

3. Packing: Carton packaging, plastic box packaging and metal box packaging, generally in cartons and iron box packaging mostly.

Compared to other portable storage devices (especially floppy discs), the flash drive has many advantages: less space, usually faster operation (USB1.1, 2.0, 3.0 standard), can store more data, and may be more reliable (because there is no mechanical equipment), when read and write disconnected without damaging the hardware ( The floppy disk is broken immediately when read and write, and only data is lost. This type of disk uses the USB mass storage device standard, which has built-in support in modern operating systems such as Linux, Mac os X, UNIX and Windows2000, XP, and Win7.

A flash drive typically uses a plastic or metal casing with a small printed circuit board that is small enough to fit in a pocket like a key ring, or strung on a neck string. Only the USB connector is highlighted outside the case and is usually covered with a small lid. Most of the drives use standard TYPE-A USB connectors, which allows them to be plugged directly into a USB port on the PC.

To access the data on the drive, the drive must be connected to the computer, either directly to the computer's built-in USB controller or to a USB hub. The drive will not start until the USB port is plugged in, and the required power is also supplied by the USB connection. However, some flash drives (especially high-speed flash drives with USB 2.0 standard) may require more power, so if they are connected to a USB hub that is built into a keyboard or screen, these drives will not work unless they are plugged directly into the controller (the USB port provided by the computer itself) or a USB hub with an external power supply. Some USB drives are composed of a drive and a USB stick, so be clear at the end (Dos/win32 environment).

　　Advantages

The biggest advantage of the U disk is: Small and easy to carry, large storage capacity, cheap, reliable performance. The volume of the flash drive is small, thumb-like size, very light weight, generally around 15 grams, especially suitable for carry-on, we can hang it on the chest, hanging on the keychain, or even put into the purse. The general U disk capacity of 1G, 2G, 4G, 8G, 16G, 32G, 64G, etc., the most common price of 4GB for example, about 50 yuan can be bought. There is no mechanical device in the disk, the anti-seismic performance is very strong. In addition, the flash disk also has moisture-proof, anti-magnetic, high and low temperature characteristics, safety and reliability is very good.

* The flash drive does not allow water or dust to penetrate or scratch, and these are serious problems in legacy portable storage devices such as CDs and floppy discs. The solid-state storage design used by the drives allows them to withstand unintentional external shocks. These advantages make the drive ideal for carrying personal data or working documents from one place to another, such as from home to school or office, or in a variety of locations where personal data is generally required to be carried and accessed. Because USB is almost ubiquitous in today's PCs, flash drives can be used everywhere. However, the small size of the drive also makes them often misplaced, forgotten or lost.

* Although the flash drive is small, it has a relatively large storage capacity. Most of the current commercially available flash drives can store more data than a piece of CD (700MB), advanced can store more than a double-sided double-layer DVD (17GB) more data.

* Flash drives use the category of USB mass storage devices, which means that most modern operating systems can read and write to a flash drive without having to install additional drivers. The flash drive displays a block-like logical unit inside the operating system, hiding the complex details required for internal flash memory. The operating system can use any file system or block addressing method. You can also make a bootable USB drive to boot the computer.

* As with other flash devices, the drive has a limit on the total number of reads and writes. The middle-level drive can read and write hundreds of thousands of times in normal use, but when the flash drive becomes old, the write action is more time-consuming. When we use a flash drive to run an application or an operating system, we cannot fail to consider this. Some program developers specifically target this feature and capacity limits, writing a special version of the operating system (such as Linux) or applications (such as Mozilla Firefox) for the flash drive. They typically optimize the use of space and store the scratch disk in the main memory of the computer, rather than the flash drive.

* Many flash drives support write-protection mechanisms. This switch on the shell prevents the computer from writing to or modifying the data on the disk. Write protection prevents a computer virus file from being written to the flash drive to prevent the virus from spreading. Without the write protection function of the flash disk, it becomes a variety of viruses with the function of automatic operation and other means of transmission.

* The flash drive is more tolerant of external shocks than mechanical disks, but can still fail or lose data due to serious physical damage. In an assembled computer, the faulty USB connection port wiring may also damage the drive's circuitry. Storage principle the computer turns the binary digital signal into the compound binary digital signal (add assignment, check, stack and so on) to read and write to the USB chip adapter interface, through the chip processing signal allocated to the EEPROM memory chip corresponding address store binary data, realizes the data storage. EEPROM data memory, the control principle is voltage control gate transistor voltage high and low value, the junction capacitance of the gate transistor can hold the voltage value for a long time, the reason why the data can be saved after power failure is to add the floating gate and the selection grating on the original transistor. A floating shed for storing electrons is formed on a semiconductor that conducts unidirectional currents between the source and drain poles. The floating grille is encased in a layer of silicon oxide film insulator. Above it is the selection/control grille that controls conduction currents between the source and the drain poles. The data is 0 or 1 depending on whether there is an electron in the floating grille formed on the silicon baseplate. There are electrons for 0, no electrons for 1. Flash memory, like its name, deletes data before it is written to initialize. In particular, the electrons are exported from all floating grids. There will be some data for "1". Write only when the data is 0 o'clock, and when the data is 1, nothing is done. At 0 o'clock, a high voltage is applied to the gate electrode and drain, which increases the electrical energy conduction between the source and drain poles. In this way, the electrons will break through the oxide film insulator and enter the floating gate. When the data is read, a certain voltage is applied to the gate electrode, the current is 1, and the current is set to 0. The floating gate does not have the state of the electrons (data 1), the voltage is applied to the drain when the gate electrode is applying a voltage, and the current is generated between the source and the drain due to the large amount of electrons moving between the poles. In the case of a floating gate having an electronic state (data 0), the electrons in the channel are reduced. Because the voltage applied to the gate electrode is absorbed by the floating gate electrons, it is difficult to influence the channel.

　　History of Inventions

From 1998 to 2000, many companies claimed that they were the first to invent a USB flash drive. Including China Netac Technology, Israel M-systems, Singapore Trek Company. But the real U. S basic invention patent is China Netac Company. In July 2002, NETAC Company "Fast Flash sub-storage method and its device for data processing System" (Patent No.: ZL 99 1 17225.6) was duly authorized by the State Intellectual Property Office. The patent fills the gap in the 20-year invention patent of the Chinese computer storage field. The acquisition of this patent has caused a great shock to the entire storage community. Including the Israeli m-systems immediately to the state Intellectual Property Office of China's invalidation review, once became the global flash industry shocked China and foreign patent dispute. However, December 7, 2004, NETAC obtained the U.S. National Patent Office officially authorized Flash Disk Basic invention patent, the United States patent number US6829672. The acquisition of this franchise ultimately ended the scramble. China Netac Company is the world's first inventor of u disk. U.S. time February 10, 2006, NETAC commissioned US Morgan Louis lawyer to the U.S. Texas Eastern Federal Court filed a petition, accusing the United States PNY Company violated the NETAC U.S. patent (U.S. Patent number US6829672). In February 2008, Netac and Pny reached an out-of-court settlement. NETAC signed a patent license agreement with PNY, and PNY paid a patent license fee of $10 million to NETAC company. This is the first time that Chinese companies have received huge patent licensing fees in the United States. It is further proved that NETAC is the global inventor of the U disk.

Today's flash drives support the USB2.0 standard; however, because of the limitations of NAND flash technology, their read and write speeds are currently not up to the maximum transfer speed supported by the standard 480mbit/s. The fastest flash drive now uses a dual-channel controller, but it is still a bit worse than the current-era hard drive, or the maximum transmission rate that USB2.0 can offer. The current highest transfer rate is approximately 20-40mb/s, while the average file transfer speed is approximately 10mb/s. The older type of 12mbit/s device has a transfer rate of about 1mb/s. One of the industry's leading companies are Shenzhen Netac Company, M-systems Company, Singapore Trek Company.

　　Future development

Semiconductor manufacturers are working hard to integrate the functions of various flash drives into a single chip to reduce the cost of the drive components, thus reducing the overall cost.

In the effort to increase capacity, 1GB and smaller flash drives are no longer being manufactured. Kanguru recently published a 16GB USB2.0 flash drive and claimed to be able to save data for 10 years.

Lexar is trying to introduce a USB flash memory card. It is compatible with USB flash drives and is expected to replace various flash memory cards. SanDisk has published new technologies that can control the use of copyrighted data on a flash drive. The main users of this technology are students. This technology is called FLASHCP.

Kingston Technology has developed the world's largest storage capacity of the flash disk, up to 512GB. USB drive, USB interface and plug-and-play in layman's words, a peripheral device is one of the interface types connected to the host computer. In addition to the USB interface, there are interfaces such as parallel buses.

However, the USB interface has a great advantage to make it very popular in this field, that is, the device with this interface can be Plug and Play on the computer (Plug and Play is sometimes called Hot plug). When the computer is turned on the peripheral equipment to open the host power, and the order of the shutdown is the opposite. The reason to follow this boot order is because all peripheral devices must be ready to be powered on before the computer starts, and then wait for the host to check each of these devices and install the appropriate software. Only in this way can the computer function properly, otherwise the peripheral device may not be available or the computer will not be able to recognize the peripheral device. The appearance of the USB interface has changed this situation, if a device is a USB interface, then it can be inserted at any time the computer host regardless of the state of the computer at this time, and if you want to take away this device, just follow the standard operation can be safe to remove the device from the computer. This undoubtedly provides people with great convenience in their study and life.

From the name of the USB flash drive, we can see that this storage disk is a USB interface, because this storage disk is a USB interface, so this storage disk can be Plug and Play on the computer, that is, the storage disk is Removable Storage disk, it can carry. Therefore, the generalized USB stick is actually refers to the mobile storage device.

　　Classification of USB devices

USB devices are divided into 5 categories, namely, monitors, communication devices, audio devices, human-computer inputs, and mass storage. The most commonly used USB drives, mobile hard disks are mass storage classes.

　　Detection and initialization of USB devices

When a USB device is plugged into the host, it causes the USB bus's data signal line to change, and the host often scans the USB bus, due to the USB device hardware itself. When a level change is found, it knows that a device is plugged in. When the USB device is just plugged into the host, the USB device itself initializes and considers the address to be 0. That is, there is no assigned address, which is a bit like the college students who have just entered the school did not study number.

　　USB Descriptor

USB descriptors mainly include: Device descriptor, configuration descriptor, interface descriptor, endpoint descriptor, and so on.

　　(1) Device descriptor

When the USB device is plugged into the host, the host will first ask the other party to nginx its device description back, which includes the device type and manufacturer information.

　　(2) Configuration descriptor

Configuration descriptors are used to define the capabilities of the device.

　　(3) Interface descriptor

The protocol used by the transport is determined by the interface descriptor.

　　(4) Endpoint Descriptor

The method of transmission is included in the endpoint descriptor.

　　USB interface and Endpoint

An interface is what hardware in the device wants to exchange information with the USB. The mass memory supports an interface (data interface) that contains three ports. The endpoint is a hardware device that switches information to and from USB. An interface is a collection of endpoints. USB Transmission type USB (Universal Serial Bus) is used to connect the peripheral devices of USB interface (device) to the host, the external bus structure for data transmission between the two, is a fast and flexible bus interface, the USB transmission type has control, batch ( Bulk), interrupt (interrupt) and synchronous (synchronous) transmission 4 kinds, its biggest feature is easy to use, Plug and Play, mainly used in medium and low speed peripherals.

　　USB Drive Storage Specification

The USB flash drive belongs to the mass storage class, and its storage specification includes 4 independent sub-specifications, namely CBI transfer, BULK-ONLY transmission, ATA command block, UFI Command specification. The first two protocols define the data/command/State transfer method on the USB bus, the BULK-ONLY transport protocol uses only the BULK endpoint to transmit the data/command/state, and the CBI transport protocol uses control/bulk/interrupt three types of endpoints for data/command/ The delivery of the state. The latter two protocols define the operational commands for the storage media, the ATA protocol for the hard disk, the UFI protocol for USB Removable Storage, and the design of the USB drive reader to follow the Bulk-only transport protocol and UFI Command specification. The UFI command block specification is designed for USB Removable Storage, which defines a total of 19 12-byte operation commands.

　　Security

Some flash drives provide data encryption capabilities. This is usually achieved by using full-disk encryption on the lower level of the file system. Encryption prevents unauthorized people from accessing data on the drive, and the disadvantage is that the drive can only be used on computers with a small number of compatible encryption software installed, because there is no uniform standard.

Some encryption software can be run without the need for installation. The executable files of these software can be stored on the flash drive along with the encrypted files. Encrypted files can be accessed on a computer running Microsoft Windows. Other flash drives allow users to set different sizes of encryption and public partitions. Cryptographic software executables designed for Windows, Macintosh, and Linux can be placed in the public partition area. Some poor encryption software may require administrator privileges to run and access data.

The new flash drive supports biometric fingerprint functionality to confirm the identity of the user. In the 2005, the ability to support fingerprint on a flash drive was more expensive than a standard password protection option. Most fingerprint scanning devices must rely on drivers in the operating system to verify fingerprints, so these drives can only be used on computers running the Microsoft Windows operating system.

Some manufacturers use flash drives as one of the devices that run the certification. The approach is to control access to sensitive systems by using cryptographic keys in the drive or communicating with software within the target system. These systems are designed to not function unless the flash drive is connected to the host. Some "computer locks" are plugged into a computer and behave like a flash drive.

All data protection methods also increase the risk that legitimate users (data owners) cannot access data.

Flash drives are a big security challenge for large organizations. Because of their small size and convenience, privileged visitors or malicious employees can steal confidential data in the unlikely event of discovery. In 2008, a number of hospitals in Hong Kong and Macau had lost and stolen flash drives, causing a crisis in patient privacy. Similarly, shared or public computers are vulnerable to attackers using flash drives to put malware, such as rootkits or packet interception software. To prevent these issues, some organizations prohibit the use of flash drives, while others prohibit a general user from mounting USB mass storage devices (this is a feature of Windows XP Service Pack 2). There are also computers that use third-party software to control the use of USB. There are also organizations that use non-technical solutions: Unplug the connector from the internal USB port of the host or simply plug the USB port with a resin.

　　U Disk Chip Classification Introduction

You know, u disk chip is graded, there is a-level, black, white and other claims. So, what kind of chip is a-class chip, what kind of chip is black chip, white chip?

The structure of the chip has a relatively core part called Wafer. The level of the USB chip is divided according to the size of the wafer capacity. A-class chip general wafer capacity is higher than 93%, mostly factory packaging products, usually we also call the original chip or a chip. Most of these chips are used on well-known brands of flash drives and are generally provided with a warranty. Less than 93% capacity of the wafer is called downgrade Flash, no longer hit the original logo, by a number of small packaging factory processing. The relatively sufficient amount, the use of stable commonly known as white film. The price is generally 70%-80% of a-class product. Black film: To be packaged in a chip in a serious shortage of capacity, quality is difficult to protect the black film. In addition, some of the bad business recovery of the old flash chip grinding flash memory chip is generally known as black film.

　　Encryption of U disk

With the rapid development of portable media today, the U disk is easily lost or stolen. USB sticks can be encrypted using encryption software, such as ZIP and RAR encryption software. Some of them are green software and do not have to be installed. Executable files can be stored on a USB flash drive and then encrypted files or pictures will be made. An encrypted partition on a computer that is running a healthy operating system can be accessed, but it requires the user's administrative privileges on the host computer to access the data. Some manufacturers of USB drives designed to be part of hardware-based encryption, thereby eliminating the need for third-party encryption software.

Other USB drives allow users to configure different sizes of security and public partitions, and provide hardware encryption.

The new USB flash drive now supports biometric fingerprints to confirm the identity of the user. But the sale price is too high, make this kind of USB stick cannot popularize.

　　Type of USB flash drive Gift

USB flash drive: Best gift.

Liquid U disk: crystal clear, water fish beauty, ornamental strong.

Metal u disk: Housing to take stainless steel.

Wooden U-Disk: solid wood shell.

Bottle Opener: Can be used as a beer bottle to open the lid.

Translucent U disk: the appearance of translucent, u disk inside the structure of the faint, so that you have endless reverie of the United States.

Mini U disk: the appearance of thin, small, light weight and other characteristics.

Leather cover U disk: The appearance uses the leather cover as the U disk Shell, uses the seal.

Card: Looks like a card, can be placed in a purse and other places. Easy to carry, compact features.

Open mode U disk: Can be customized according to your design drawings. Also called custom u disk, Shape u disk.

Pill u disk: looks like pills.

Pen u disk: Looks like a pen.

　　Various functions of USB flash drive

　　AD flash Drive

First Category: Advertising USB flash drive is a reader pre-storage of a business website URL, with ordinary U disk any function, when the website USB reader inserted into the computer interface, the computer will immediately automatically enter the business website URL.

The second type: can be the customer's logo for digital color printing processing, the formation of a variety of color effects, but also can be processed sub-bright light effect. It's very beautiful!

　　Start USB Drive

The first type: specifically used to do the system to start the function of the U disk, when the computer can not be opened at a normal time to enter the system for related operations, the function is relatively single.

The second type: a powerful USB flash drive specially made by computer city or computer technician to maintain the computer, in addition to starting the computer. Also can be disk partition, System antivirus, system repair, file backup, password modification and other functions. More suitable for a certain technical personnel to use, you can also add some of their own functions such as key installation system.

　　illuminated U Disk

The first type: This USB flash drive can be added to the shell of a special light-emitting material, similar to the effect of luminescent rods. It's simple but practical.

The second type: this u disk is through the U disk's PCB board traction a group of power supply circuit for the light emitting device power supply, light emitting device has many kinds of LED lights, there are led screens, there are small light cannon (but this is very rare). This USB stick can only be inserted into the computer to give a brilliant glow.

　　Encrypt USB Drive

The first type: Hardware encryption technology, this technology is generally through the shell of a U disk device cryptography device, like our daily use of the cipher box, generally this type of u disk is used abs or metal material, play a certain protective role.

The second type: Software encryption technology, this technology mainly relies on programming technical personnel to write a variety of encryption software to encrypt the U disk, generally through the production tools to write the program to the U disk, prevent formatting, delete and other operations, only enter the correct password to operate.

　　Waterproof U disk

Waterproof u disk: This kind of you, there are few selling on the market. Generally, luxury goods, business people dedicated. Generally on the process of waterproof treatment: The shell waterproof, USB and PCB isolation.

　　Temperature measurement U Disk

First class: This kind of temperature display is installed on the computer a software through a USB flash drive in a test temperature, and through the software, the flash drive to get the temperature. This method relies on computer software to test the temperature.

The second type: this way directly to the test temperature of the hardware encapsulated in a USB flash drive, and directly displayed in the U disk output LED screen. The software has been packaged into hardware.

　　Music usb

Music u disk, is a USB flash drive all the storage functions, but also has the music file playback function. General music U disk appearance and ordinary U disk is not strange, the difference is that it has built-in battery, and more than one jack, used to access equipped with headphones, plug in to listen to MP3, WMA and other common format music, support up and down song playback selection, can set the random play function.

The advantage of Music u disk is that: compared to the ordinary U disk it has a music playback function, and compared to MP3 and has the advantage of low cost, is the function of the U disk to extend and develop a new generation of mobile storage products.

　　Anti-Virus USB

Antivirus disk is a variety of anti-virus software u disk version embedded in the U disk, so that anti-virus software easy to use, safe, easy to operate. When connected to a computer's USB interface, it is recognized by the host and does not require cumbersome installation. And in the "My Computer" automatically appear a new drive letter, anti-virus disk version automatically run. Anti-virus disk from the performance of the written, embedded two. Write anti-virus program to be installed in the computer can play the role of anti-virus, and embedded anti-virus program written in the U disk control chip, do not need to install, at any time can be anti-virus.