U disk isUSB disk(USB flash disk , the abbreviation of UFD), also known as "USB flash drive" according to the homophony. U disk is a type of flash memory, so it is sometimes called flash disk . The biggest difference between a USB flash drive and a hard disk is that itdoes not require a physical drive and is plug-and-play. Its storage capacity far exceeds that of a floppy disk, making it extremely easy to carry.
U disk integratesdisk storage technology, flash memory technology and universal serial bus technology into one. The USB port is connected to the computer and is the channel for data input/output; The main control chip enables the computer to recognize the U disk as a removable disk, which is the "Brain";U disk Flash (flash memory) chip saves data, which is different from the computer's memory, even if it is disconnected Data will not be lost after power-on; the PCB base board connects the components together and provides a platform for data processing.
Introduction
U disk
U disk, the full name is USB flash drive, and its English name is "USB flash disk". It is a micro high-capacity mobile storage productthat uses a USB interface and does not require a physical drive. It is connected to the computer through the USB interface to achieve plug-and-play. The name U disk originally came from a new type of storage device produced by Netac Technology, called "U disk", which is connected using a USB interface. After the U disk is connected to the USB interface of the computer, the data in the U disk can be exchanged with the computer. Since Netac has registered patents for equipment with similar technology produced later, it can no longer be called "U disk" and is renamed the homophonic "U disk". Later, the name USB flash drive became widely known because of its simplicity and ease of remembering, and it was one of the mobile storage devices.
Compared with other portable storage devices, flash USB flash drives have many advantages:It takes up less space and usually operates faster (USB1.1, 2.0, 3.0 standards) , can store more data, and has more reliable performance (because there is no mechanical equipment). It can be disconnected during reading and writing without damaging the hardware (the floppy disk will be damaged immediately when disconnected during reading and writing), and only data will be lost< a i=2>. This type of disk uses the USB mass storage device standard and has built-in support in operating systems such as Linux, Mac OS X, Unix and Windows.
U disks usually useABS plastic or metal casing, which contains a small printed circuit board, making the flash drive as small as Keychain accessories can also be placed in pockets or strung on a neck cord. Only the USB connector protrudes from the case and is usually covered by a small cover. Most USB flash drives use a standard Type-A USB connector, which allows them to be plugged directly into a USB port on a PC.
To access the data on the USB flash drive, you must connect the USB flash drive to the computer; whether it is directly connected tothe built-in USB controller of the computer Or aUSB hub will work. The flash drive only powers up when plugged into a USB port, and the required power is supplied by the USB connection.
Development History
Since 1998~2000, many companies have claimed to be the first to invent the USB flash drive. Including China's Netac Technology, Israel's M-Systems and Singapore's Trek. Butit was China Netac Corporation that actually obtained the basic invention patent for USB flash drives. In July 2002, Netac's "Fast Lightning External Storage Method and Device for Data Processing Systems" (Patent No.: ZL 99 1 17225.7) was officially authorized by the State Intellectual Property Office. This patent filled the field of computer storage in China. There has been a blank slate of invention patents in the past 20 years. The acquisition of this patent caused great shock in the entire storage industry, including Israel's M-Systems, which immediately filed an invalidation review with the State Intellectual Property Office of China. It once became a patent dispute that shocked both China and foreign countries in the global flash memory field. However, on December 7, 2004, Netac received the basic invention patent for flash disks officially authorized by the U.S. National Patent Office, U.S. Patent No. US6829672. The acquisition of this patent finally ended the competition. China Netac is the world's first inventor of USB flash drives. On February 10, 2006, U.S. time, Netac entrusted Morgan Lewis Law Firm to submit a complaint to the U.S. Federal Court for the Eastern District of Texas, accusing the U.S. company PNY of infringing Netac's U.S. patents. In February 2008, Netac and PNY reached an out-of-court settlement. Netac signed a patent licensing agreement with PNY, and PNY paid a patent licensing fee of US$10 million to Netac. This is the first time that a Chinese company has received huge patent licensing fees in the United States, and it further proves that Netac is the global inventor of USB flash drives.
Currently USB flash drives support the USB2.0 standard. However, due to technical limitations of NAND flash memory, their read and write speeds cannot reach the maximum transmission speed of 480Mb/s supported by the standard.. The fastest flash drives have used dual-channel controllers, but they are still far behind the maximum transfer rate provided by hard drives or USB2.0. The highest transfer rate is about 20~40 MB/s, while the general file transfer speed is about 10 MB/s.
U disk composition
The composition of a USB flash drive is very simple, mainly composed of shell + movement, among which:
1. Movement: The movement includes a PCB+USB main control chip+crystal oscillator+ Chip resistor, capacitor + USB interface + SMD LED (not all U disks have it) + FLASH (flash memory) chip.
U disk movement
2. Shell: classified by material, including ABS plastic, bamboo, metal, leather case, silicone, PVC software, etc.; classified by style, including card, pen, mini, cartoon, business, simulation, etc.; classified by function, Encryption, anti-virus, waterproof, smart, etc.
Storage principle
The computer converts the binary digital signal intocomposite binary digital signal (adding instructions such as allocation, checking, stacking, etc.), and reads and writes to the USB chip Adaptation interface, through chip processing signals, is assigned to the corresponding addressEEPROM memory chip 6> Store binary data to realize data storage. The control principle of EEPROM data memory is that the voltage controls the voltage of the gate transistor. The junction capacitance of the gate transistor can store the voltage value for a long time. The main reason why the data can be saved after power outage is in the original Floating gates and select gates are added to the transistors. A floating gate that stores electrons is formed on a semiconductor where current is conducted in one direction between the source and drain. The floating gate is wrapped with a silicon oxide film insulator. Above it is the select/control gate that controls the flow of current between source and drain. The data is 0 or 1 depending on whether there are electrons in the floating gate formed on the silicon substrate. If there are electrons, it is 0, if there are no electrons, it is 1.
Flash memory, as its name suggests, is initialized by deleting data before writing. Specifically, it is to export electrons from all floating gates. All data will be returned to "1". When writing, only write when the data is 0, and do nothing when the data is 1. When writing 0, a high voltage is applied to the gate and drain electrodes, increasing the electron energy conducted between the source and drain electrodes. In this way, electrons will break through the oxide film insulator and enter the floating gate. When reading data, a certain voltage is applied to the gate electrode. A large current is 1, and a small current is 0. When the floating gate has no electrons (data is 1), and a voltage is applied to the drain while a voltage is applied to the gate electrode, a current is generated due to the movement of a large number of electrons between the source and drain. In the state where the floating gate has electrons (data is 0), the number of electrons conducted in the channel will decrease. Because after the voltage applied to the gate electrode is absorbed by the floating gate electrons, it is difficult to affect the channel.
Functional classification
The main purpose of U disk is to store data. Through the efforts of enthusiasts and businesses, U disk has developed more functions: encrypted U disk, boot U disk, anti-virus U disk, temperature measurement U disk and music U disk, etc.
No drive type
Driverless products can be used on Windows 98/Me/2000/XP and Linux, Mac OS and other systems that supportUSB Mass Storage protocol It can be used normally under Windows 98 system and only needs to install the driver under Windows 98 system. In the operating system above Windows Me, there is no need to install the driver program to be correctly recognized and used by the system, which truly embodies the "plug and play" of USB devices. convenience. Most U disks on the market are driverless, so users have a lot of choice. U disks from Patriot, Lenovo, Jinbang, Netac and other companies are good choices.
Encrypted
In addition to encrypting the stored content, the encrypted USB flash drive can also be used as an ordinary USB flash drive. There are generally two types: one ishardware encryption, such asfingerprint recognition encrypted USB disk< a i=4>, this kind of U disk is more expensive, and is aimed at users in special departments. Generally speaking, hardware encryption is more secure; the other issoftware encryption a>, software encryption can specially divide a hidden partition (encrypted partition) in the U disk to store the files to be encrypted, or you can only encrypt a single file without dividing the partition. , the encrypted partition or an encrypted single file cannot be opened without a password, thereby maintaining confidentiality.
Start-up
The emergence of bootable USB flash drives has made people look at this portable product with admiration. As the name suggests, the bootable USB flash drive adds the function of booting the system, which makes up for the shortcomings of encrypted and driverless USB flash drives that cannot boot the system. It is the emergence of this product that accelerated the process of floppy drives being eliminated. To boot the system, the USB flash drive must simulate a USB peripheral. For example, the bootable USB disks on the market mainly rely on the simulation USB_HDD method to achieve system booting. There is an advantage to booting the system by simulating the USB_HDD method:After the system starts, the U disk is recognized as a hard disk, and the user can maximize the use of the U disk space. This also fully reflects the large capacity characteristics of U disk. In addition to being used in desktop computers, this kind of USB flash drive with multi-boot function can also be widely used in laptops with external USB floppy drives. With this kind of USB flash drive, laptops can completely eliminate floppy drives or even optical drives. .
There are bootable USB flash drives available on 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. There are generally two methods:
1. Download the USboot production tool for free from the Internet. It can be successfully produced in a few minutes, but it will have a pure DOS interface after startup.
2. Download the UltraISO production tool and WinPE.iso file for free from the Internet, and make the USB disk into a WinPE (a streamlined Windows XP operating system) boot disk. The production time is a little longer, and the Windows graphical interface will appear after startup.
advantage
1. The use of USB flash drive is very simple and convenient
There are many kinds of U disk interfaces. Strictly speakingOnly flash disks with USB interfaces can be called U disks. This means that most modern operating systems can read and write to flash drives without the need to install additional drivers.
The USB flash drive is displayed as ablock-style logical unit in the operating system, hiding the complex details required for the internal flash memory. The operating system can use any file system or block addressing method. You can also make a bootable USB flash drive to boot the computer. Current operating systems such as Linux, MacOSX, Unix, Windows2000, XP, and win7 all have built-in support.
When in use, no driver is required, no external power supply is required, plug and play, plug and unplug when powered. After connecting to the computer host through the USB interface, you can format, copy, delete and other operations on it like an ordinary hard disk. The data on the USB flash drive can be transferred to the computer, and the data on the computer can also be easily transferred to the USB flash drive. Can be removed or attached at any time. Portable mobile storage is realized. The access speed is fast (about 15 times the speed of floppy disk).
2. The biggest feature of U disk is that it is compact and easy to carry.
General U disk capacities include 1G, 2G, 4G, 8G, 16G, etc. Compared with traditional storage devices such as floppy disks, CD-RW, and Zip disks, "U disks" have very obvious advantages. The main features are: very small size (only about the size of a thumb) and weight of only about 20 grams; large capacity (8MB~256MB, even up to 2GB); can be used to store photos, information, and images, with an area of only 1 cm square and easy to carry Convenient and suitable for wireless computing fields and mobile offices, it greatly improves efficiency and makes human life more convenient.
3. U disk has good security
It barely allows water or dust to penetrate, and it won't get scratched, which were serious problems with older portable storage devices (such as compact discs, floppy disks). The solid-state storage design used in flash drives makes them resistant to inadvertent external impacts. These advantages make flash drives ideal for carrying personal data or work files from one place to another, such as from home to school or the office, or generally to various locations where personal data needs to be carried and accessed. . Since USB is almost ubiquitous in today's personal computers, flash drives can be used everywhere. However, the small size of flash drives also means that they are often misplaced, forgotten or lost.
4. Large storage capacity
Although flash drives are small, they have relatively large storage capacity. Most USB flash drives can store more data than a CD (700MB), and advanced ones can store more data than a double-sided double-layer DVD (17GB).
Instructions
The USB flash drive has a USB interface and is a USB device. If the operating system is WindowsXP/Vista/Win7/Linux/PrayayaQ3 or Apple system, insert the USB flash drive directly into the USB interface on the front panel or back of the chassis, and the system will automatically recognize it. If the system is Windows 98, you need to install the USB disk driver to use it. Drivers can be found on the included CD or on the manufacturer's website.
The first time you use a USB flash drive on a computer (when you plug the USB flash drive into the USB interface) the system will make a beep and then report "New hardware found". After a while, a message will appear: "The new hardware has been installed and is ready for use." (Sometimes you may need to restart.) At this time, open "My Computer" and you can see an extra hard disk icon. The name is usually the brand name of the USB flash drive. For example, Kingston is named KINGSTON. After this step, if you use the U disk again in the future, plug it in directly, and then open "My Computer" to find the removable disk. At this time, note that there will be a small icon on the far right side of the taskbar, which looks like a gray There is a green arrow next to the thing, which means safe removal of USB hardware devices. (U disk is one of the USB devices). Next, you can save and delete files on the U disk as you usually do with files, or send files directly to the U disk by right-clicking.
However, please note that after using the U disk, you must close all windows related to the U disk. Before unplugging the U disk, double-click the Safely Remove USB Hardware Device icon in the lower right corner with the left button, select "Stop" and then left-click "OK" ". When the prompt "The USB device can now be safely removed from the system" appears in the lower right corner, you can unplug the USB flash drive from the chassis, or click the icon directly and click "Safely Remove USB Device", and then When prompted, you can unplug the USB flash drive from the chassis.
Precautions
1. U disks generally have a write-protect switch, but it should be switched before the U disk is inserted into the computer interface. Do not switch it while the U disk is working.
2. The U disk has a working status indicator light. If it is an indicator light, when it is inserted into the host interface, the light will turn on to indicate that the power is on. When the light flashes, it means that data is being read and written. If there are two indicator lights, usually two colors, one lights up when the power is turned on, and the other lights up when the USB flash drive is reading and writing data. It is strictly prohibited to unplug the USB flash drive when the read/write status light is on. Be sure to wait until the read/write status indicator light stops flashing or goes out before unplugging the USB flash drive.
3.The storage principle of U disk is very different from that of hard disk. Do not defragment it, otherwise the service life will be affected.
future development
Semiconductor manufacturers strive to integrate various flash drive functions into a single chip to reduce the cost of flash drive components, thereby also reducing the overall cost.
In an effort to increase capacity, 1GB and smaller flash drives are no longer being manufactured. Kingston has released a 512GB USB3.0 flash drive and claims it can 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. (completed)
SanDisk has unveiled new technology that controls the use of copyrighted data on flash drives. The main users of this technology are students. This technology is called FlashCP.
Reprinted from:U disk (USB flash drive)_Baidu Encyclopedia