usb's full name is "Universal Serial Bus", which means "Universal Serial Bus" in Chinese. It is an external bus standard used to standardize the connection and communication between computers and external devices; it is used in the PC field interface technology.
The operating environment of this tutorial: Windows 7 system, Dell G3 computer.
Universal Serial Bus (USB) is an emerging data communication method that gradually replaces other interface standards. It is used by computers such as Intel, Compaq, Digital, IBM, Microsoft, NEC and Northern Telecom. The company and communications companies jointly formulated it in 1995 and gradually formed an industry standard.
As a high-speed serial bus, the USB bus has extremely high transmission speed that can meet the application environment requirements of high-speed data transmission. The bus also has simple power supply (can be bus powered) and convenient installation and configuration ( Supports plug-and-play and hot-swap), simple expansion ports (up to 127 peripherals can be expanded through a hub), diversified transmission methods (4 transmission modes), and good compatibility (downward compatibility after product upgrades), etc. .
Since its launch, the universal serial bus (USB) has successfully replaced serial ports and parallel ports and has become the standard for a large number of computers and smart devices in the 21st century. One of the expansion interfaces and essential interfaces has now been developed to USB 4.0 version. USB has the advantages of fast transmission speed, easy use, hot-swappable support, flexible connection, and independent power supply. It can be connected to a variety of peripherals such as keyboards, mice, and large-capacity storage devices. This interface is also widely used in smartphones. The interaction between smart devices such as computers and external data is mainly through network and USB interfaces.
Hardware structure
USB uses a four-wire cable, two of which are serial channels used to transmit data, and the other two provide power for downstream (Downstream) devices , for any peripherals that have successfully connected and recognized each other, data will be transmitted at the highest rate that both devices can support. The USB bus will automatically and dynamically convert from high speed to low speed in the compatible transmission mode according to the peripheral conditions and match and lock at the appropriate rate. USB is a token-based bus. Similar to Token Ring network or FDDI token based bus. The USB host controller broadcasts the token, and the device on the bus detects whether the address in the token matches itself and responds by receiving or sending data to the host. USB manages USB bus power by supporting suspend/resume operations. The USB system adopts a cascade star topology, which consists of three basic parts: Host, Hub and functional devices.
The host, also called the root, root node or root Hub, is built on the motherboard or installed on the computer as an adapter card. The host contains the main controller and the root hub (Root Hub), which controls The flow of data and control information on the USB bus. Each USB system can only have one root hub, which is connected to the main controller. A computer may have multiple root hubs.
The hub is a specific component in the USB structure. It provides a point called a port to connect devices to the USB bus. It also detects the devices connected to the bus and provides power management for these devices. It is responsible for Bus fault detection and recovery. The hub can provide energy for the bus, or it can provide energy for itself (receiving power from the outside).
Functional devices are connected to the bus through ports. USB can be used as a hub at the same time.
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