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What is a root hub

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Update time : 2023-09-23 11:08:06
  A hub is a specific component of the USB architecture, and a root hub is the hub on the motherboard that controls the bus.
  USB uses a four-wire cable, two of which are serial channels used to transmit data, and the other two provide power for downstream devices. For any peripherals that have been successfully connected and recognized each other, they will be used at the highest rate that both devices can support. transfer data. The USB bus will automatically and dynamically convert from high speed to low speed in the compatible transmission mode according to the peripheral conditions and match and lock at the appropriate rate.
root hub
  USB is a token-based bus. Similar to Token Ring network or FDDI token based bus. The USB host controller broadcasts the token, and the device on the bus detects whether the address in the token matches itself and responds by receiving or sending data to the host. USB manages USB bus power by supporting suspend/resume operations. The USB system adopts a cascade star topology, which consists of three basic parts: Host, Hub and functional devices.
  The host, also called the root, root node or root Hub, is built on the motherboard or installed on the computer as an adapter card. The host contains the main controller and the root hub (Root Hub), which controls the data and data on the USB bus. To control the flow of information, each USB system can only have one root hub, which is connected to the main controller. A computer may have multiple root hubs.
  The hub is a specific component in the USB structure. It provides a point called a port to connect devices to the USB bus. It also detects the devices connected to the bus, provides power management for these devices, and is responsible for bus fault detection and recovery.