The standard enhanced PCI-to-USB host controller is a standard enhanced PCI-to-USB host controller called EHCI.
The standard openhcd USB host controller is a standard OpenHCD USB host controller, which stands for extensible USB interface.
EHCI is a universal serial bus (USB) version 2.0 register-level interface of the host controller. The purpose is to design hardware components, develop system integrators and device drivers (software).
Computer motherboards often provide multiple USB interfaces, which are often developed through USB hub chips on the motherboard. Common devices that can connect multiple USB interfaces can be used as USB hubs.
In the device manager of the computer, you can find the USB root hub in the universal serial bus controller. As shown in the figure below:
Extended data:
USB identification:
When a USB device is connected, the USB system can automatically detect the connection and identify the data transmission rate it uses. USB identifies low-speed and full-speed devices by adding pull-up resistors on D+ or D- lines. USB supports three transmission rates: 1.5Mb/s low-speed transmission, 12Mb/s full-speed transmission and 480 MB/s high-speed transmission. ..
When there is no USB device connected to the downstream port of the main controller or hub, the pull-down resistors on the D+ and D- lines make the voltage of these two data lines close to ground (0V); When full/low speed equipment is connected, the current flows through the voltage divider composed of the pull-down resistor of the hub and the pull-up resistor of the equipment at D+/D-.
Because the resistance of the pull-down resistor is15kΩ and the resistance of the pull-up resistor is1.5kΩ, a DC high level of (VCC *15/(15+1.5)) will appear on the D+/D line. When the USB host detects that the voltage of the D+/D- line is close to the high level, while the other lines remain grounded, it knows that the full/low speed device has been connected.
The two sockets on the PC motherboard are root hubs. The root hub is the main control port of USB system. It can connect peripherals directly, or control more peripherals through the hub.
The structure of USB hub is similar to the common network hub, with an uplink and many sub-ports. One peripheral can be connected to each sub-port, or more peripherals can be connected through a hub until all peripherals add up to 127.
When a USB device is connected to a hub or root hub, the host controller and host software (host controller &; Host software) can automatically detect the access of devices.
Then the host software reads a series of data to confirm the device characteristics, such as manufacturer ID, product ID, interface working mode, power consumption and other parameters.
Then, the host assigns a separate address to the peripheral. Addresses are dynamically assigned and may be different every time. Initialize the device after assigning the address, and IO operation can be performed on the device after initialization.
Before unplugging the USB device, you need to delete the hardware device in the computer. Do not unplug it directly, otherwise it will lead to unexpected situations such as abnormal operation of the equipment or data loss. Don't insert flash devices such as USB flash drive and mobile hard disk for a long time, which may lead to unexpected situations when the system starts and shuts down. Just insert it when it is used.
References:
Baidu encyclopedia -usb
References:
Baidu encyclopedia -EHCI
References:
People's Network-Do you really understand? On USB interface of notebook computer
References:
People's Network -USB encounters the biggest security hole in history: billions of devices around the world are affected.