Into the world of USB

With the development of PC, especially peripherals, more and more interfaces are available. For example, the printer uses a parallel port and the keyboard has PS/2 ports. PC interfaces are often insufficient. In this case, a new interface standard emerged, namely, USB (Universal Serial Bus ). It is a computer interface standard developed by Microsoft, Intel, HP, NEC, and other companies. There is also a tendency to replace the serial port and parallel port.

At present, the maximum communication rate of USB 480 is Mbps, and USB has started to appear. The maximum communication rate can reach 5 Gbps.

Basic USB frame:

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

USB mainly includes the master controller and USB hub. The CPU sends commands to the master controller, then the master controller executes the commands, and the CPU then performs other tasks. USB hub is similar to the hub in our dormitory. When there is only one computer in the dormitory, a network cable can access the Internet. However, when there are multiple computers, a hub is needed. There are many arrangement interfaces on the hub, and other computers can connect them here. Allows multiple computers to access the Internet.

 

The USB hub function is similar. By connecting to a hub, You can cascade many devices, up to 127. There are two USB interfaces in front of the hosts box of our computer, and four USB interfaces are usually behind the chassis. They are all on a USB hub.

 

USB specifications mainly include:

 

1. USB controller and driver

 

2. USB chip and driver

 

3. USB device driver

 

USB devices support hot dial. When we connect a USB device to a computer, the host controller and host software can automatically detect the device,

 

The host software starts to read information about the USB device, such as the product ID vendor ID interface, and then dynamically allocates an address to it.

After necessary initialization, you can perform Io operations.