USB, is the English Universal Serial BUS (Universal Serial Bus) abbreviation, and its Chinese referred to as "through the line, is an external bus standard, used to regulate the computer and external equipment connection and communication. Is used in the PC field interface Technology. USB interface to support the device plug and play and hot swap function.

With the rapid development of computer hardware, the increasing number of peripherals, keyboards, mice, modems, printers, scanners have long been known, digital cameras, MP3 players followed, so many devices, how to access personal computers? USB is based on this purpose. USB is a standardized, modular interface for computer peripherals, and specifications are developed by Intel, NEC, Compaq, DEC, IBM, Microsoft, and Northern Telecom. The same time as

USB1.1 standard interface transfer rate of 12Mbps, but a USB device can only get up to 6Mbps transmission bandwidth. So to external optical drive, up to six times the speed of the drive can not be high. And to instantly play MPEG-1 VCD movie, at least 1.5Mbps transmission bandwidth, which USB do, but to complete the data volume four times the MPEG-2 DVD movie playback, USB may be very difficult , If coupled with AC-3 audio data, USB device is difficult to achieve real-time playback. The same time as

A USB interface can theoretically support 127 devices, but it is not yet possible to reach that number. In fact, for a computer, the surrounding peripheral peripherals rarely have more than 10, so this figure is enough for us to use. USB also has a significant advantage is to support hot-swappable, that is to say in the case of boot, you can also safely connect or disconnect the USB device to achieve real plug and play. The same time as

However, not all Windows systems support USB. At present, Windows systems have many different versions, in these versions, only Windows98 version of the system support for USB better, and other versions of Windows and can not fully support USB. For example, Windows95 retail version does not support USB, only later bundled with the PC version of Windows95 support USB. The same time as

Although the current USB device has been widely used, but it is more common is USB1.1 interface, its transmission speed is only 12Mbps. For example, when you use the USB1.1 scanner to sweep a 4M picture size, it takes four seconds. This speed, so that users feel very inconvenient, if there are several pictures to sweep, you have to have a good patience to wait. The needs of users, is to promote the development of science and technology, manufacturers are also aware of this bottleneck. At this time, COMPAQ, Hewlett Packard, Intel, Lucent, Microsoft, NEC and PHILIPS 7 manufacturers jointly developed a USB 2.0 interface standard. USB 2.0 will increase the data transfer speed between devices to 480Mbps, 40 times faster than the USB 1.1 standard, the speed increase for the user's biggest advantage is that users can use more efficient external devices, and has a variety of speed Peripheral devices can be connected to USB 2.0 lines, and there is no need to worry about the bottleneck of data transmission. The same time as

So, if you use the USB 2.0 scanner, it is completely different, and sweep a 4M picture only half a second or so, blink of an eye on the past, the efficiency greatly improved. The same time as

Moreover, USB2.0 can use the original USB definition of the same specifications of the cable, the connector specifications are exactly the same, under the premise of high speed to maintain the excellent features of USB 1.1, and USB 2.0 devices and USB 1.X Equipment in the common use of any conflict. The same time as

USB2.0 compatible USB1.1, which means USB1.1 devices and USB2.0 devices can be used, but then USB2.0 devices can only work in full speed (12Mbit / s). USB2.0 has high speed, full speed and low speed three working speed, high speed is 480Mbit / s, full speed is 12Mbit / s, low speed is 1.5Mbit / s. Which is full speed and low speed is compatible with USB1.1 and USB1.0 and designed, so buy USB products can not listen to business promotion USB2.0, but also clear out whether it is high speed, full speed or low speed equipment. USB bus is a one-way bus, the main controller on the PC, USB devices can not take the initiative to communicate with the PC. In order to solve the problem of mutual communication between USB devices, the manufacturers have developed a USB OTG standard, allowing embedded systems through the USB interface to communicate with each other, and thus get rid of the PC. The same time as

New USB 2.0 specification re-named the USB standard will be the original USB 1.1 into a USB 2.0 Full Speed (full speed version), while the original USB 2.0 into a USB 2.0High-Speed (high-speed version), and announced A new logo. It goes without saying that the high speed version of USB 2.0 speed certainly exceeds the full speed version of USB 2.0.