Usb c is an interface technology widely used on PC. its full English name is universal serial bus and its Chinese name is universal serial bus. It was first introduced in 1995, together with Pentium machine. Since Microsoft introduced USB technology into Windows 98, usb c has become popular, including digital cameras, cameras, scanners, joysticks, printers, keyboards, mice, etc., while cameras and USB drives are the most widely used.
Usb c has four lines, two serial ports for data, and the other two for downstream device power supply; USB can transmit 1.5 Mbps data in low speed external devices. Usb c bus can automatically switch dynamically according to different external devices in two different transmission modes. USB is a tag based bus. Similar to the token ring network or FDDI based bus. The USB host controller will send a signal, and the bus device will detect whether the address in the beacon matches, and respond by receiving or transmitting data to the host. USB manages the power supply of USB bus and supports suspension / recovery operation. The structure of usb c system is composed of host, center and functional device.
The USB interface includes an old USB1.1 and a very popular USB2.0. USB1.1 in the ordinary USB1.1, the maximum speed can reach 12 Mbps, and the usual manufacturers call it "full speed USB". The maximum transmission speed of USB2.0 is 240 Mbps, and then the USB2.0 expansion team increased its speed to 480 Mbps in October 1999, 40 times that of conventional USB1.1. USB2.0 is downward compatible with USB1.1 interface. Of course, USB1.1 interface is also "upward compatible" with USB2.0, but it cannot reach the speed of USB2.0, and will transmit at a slower speed. The maximum length of USB2.0 interface is 5 m, but using five USB interfaces can reach 30 m.
The product icon of USB1.1 certification is composed of black, blue, "USB" and "certified", while the USB2.0 certification mark is composed of blue, white and red, marked with "certified" and "hi speed" respectively. The product logo of this certification is part of the USB promotion group trademark plan, which aims to ensure the quality of USB products.
The data transmission rate of USB1.1 is 12 Mbps, but in practical applications, it is usually only 1 mb/s, which is only applicable to low-speed devices such as printers and scanners. The actual transmission speed of USB2.0 can exceed 20 MB / s, which can well support high-speed devices such as mobile hard disks. However, the downward compatibility of USB2.0 may also adopt the low-end transmission mode of USB1.1 without the following requirements! All interfaces of USB2.0 interface, including USB2.0 interface control card, USB2.0 driver and USB2.0 interface.
