usb application

With the rapid development of computer hardware and peripheral equipment have increased, keyboards, mice, modems, printers, scanners has long been well known, digital cameras, MP3 players one after another, so much equipment, how to access personal computers » USB is based on the purpose of this. USB is a computer peripheral devices connected to standardization, a single interface, its specifications by Intel, NEC, Compaq, DEC, IBM, Microsoft, Northern Telecom established contact.

USB1.1 standard interface transfer rate of 12 Mbps, but a USB device can only receive up to 6 Mbps of bandwidth. So if an external drive, then up to six speed drive, can not be high. To play immediately and MPEG-1 VCD of the film, at least 1.5 Mbps of bandwidth, this USB to do so, but the large amount of data to be completed four times in the MPEG-2 DVD video player, USB may be very difficult for the , If coupled with AC-3 audio data, USB devices it will be difficult to achieve real-time broadcast.

A USB interface in theory can support 127 devices, but is still unable to meet this figure. In fact, for a computer, the next few surrounding peripherals over 10, so this figure is enough we used.

USB there is a significant advantage is hot-swappable, meaning that the start-up situation, you can safely connect or disconnect the USB devices, to achieve true plug-and-play.

However, not all of the Windows system support USB. Currently, Windows system has many different versions, in these versions, only the above version of the Windows98 system to better USB support, while the other version of Windows and can not complete support USB. Windows95 such as the retail version does not support USB, and only later bundled with the PC version of the Windows95 only support USB.

Although the current USB devices are widely used, but generally it is the USB1.1 interface, it is only the transmission speed of 12 Mbps. For example, when you use USB1.1 So a scanner the size of the picture for the 40 M, 4 minutes long. Such a speed, so that users find it very inconvenient, if there are few images to sweep the case, you must have good patience to wait.

The needs of users, is the driving force of science and technology development, manufacturers are also aware of this bottleneck. At this time, COMPAQ, Hewlett Packard, Intel, Lucent, Microsoft, NEC and PHILIPS this seven companies jointly developed a USB 2.0 interface standard. USB 2.0 devices will be between the data transmission speed increased to 480 Mbps, faster than the USB 1.1 standard 40 times, the speed of the user's greatest advantage is that means users can use to more efficient external equipment, but also has a variety of speed Peripheral devices can be connected to the USB 2.0 line, but without worrying about data transmission bottleneck effect when.

So, if you use a USB 2.0 scanner, completely different, sweeping a 40 M Ban Fenzhong the picture just about the time, Yi Zhayan to have passed, and greatly improve efficiency.

Moreover, USB2.0 can use the original definition of the same standard USB cables, connectors also identical to the specifications, under the premise of the high-speed, like a USB 1.1 to maintain the outstanding characteristics and, USB 2.0 devices will not USB 1.X Equipment in common use of any conflict.

USB2.0 compatible with USB1.1, that is to say USB1.1 devices and equipment USB2.0 Universal, but then USB2.0 equipment can only work in full swing state (12 Mbit / s). USB2.0 high-speed, full-speed and low-speed three working speed, high-speed is 480 Mbit / s, at full speed is 12 Mbit / s, low-speed is 1.5 Mbit / s. One full-speed and low-speed USB1.1 and is compatible with the design, optional USB products not only heard businessmen publicity USB2.0, but also make clear that high-speed, full-speed or low-speed equipment. USB bus is a one-way bus, the main controller on a PC, USB devices can not take the initiative and PC communications. USB devices to address the communication problems among the manufacturers also developed a USB OTG standard, allowing embedded systems communicate with each other through the USB interface to get rid of the PC.

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