USB connector is a serial bus standard to connect the computer system and the external device, but also a technical specification input and output interfaces, and are widely used in personal computers and mobile devices and other information and communications products, and extend to photographic equipment, digital other related areas TV (STB), game consoles.
USB on faster than parallel port (for example, EPP, LPT) and serial interfaces (such as RS-232) and other traditional PC with a standard bus much faster. USB 1.1’s maximum transfer bandwidth of 12Mbps, USB 2.0’s maximum bandwidth of 480Mbps. USB 3.0 is 5Gbps.
USB is designed for non-symmetrical, which consists of a host controller and a number of devices in a tree through a hub connected devices. A step-down controller up to 5 Hub, including Hub included, can connect up to 128 devices, because the design is to use 7-bit addressing field, two of the seven parties is equal to 128, most people say that 127 is a USB connection refers to deduct connection (a device) a connection to the host USB connector, and a computer can have multiple controllers. And various other standard SPI-SCSI, USB hub does not require a terminator.
USB can connect peripherals have a mouse, keyboard, game pad, joystick, scanner, digital cameras, printers, hard drives and network components. For multimedia peripherals such as digital cameras, USB is already the default interface; as greatly simplifying the connection to a computer, USB has become the mainstream gradually replace parallel interface printer connection. 2004 has more than 100 million USB devices; to 2007, the high-definition digital video peripherals is the only not to meddle USB peripherals category, because he needs a higher transfer rate.
Version history overview:
|release name||speed and max signalling rate|
|usb 1.0||Low Speed (1.5 Mbit/s), Full Speed (12 Mbit/s)|
|usb 2.0||High Speed (480 Mbit/s)|
|usb 3.0||SuperSpeed (5 Gbit/s)|
|usb 3.1||SuperSpeed+ (10 Gbit/s)|