Ruigu Electronic

USB Root Hub
PC hosts typically contain one or more root hubs. When the host boots up, it searches for this root hub on its internal bus.

USB host controllers are typically discovered through PCI/E enumeration. The PCI/E configuration space of the host controller is accessed and configured with appropriate values. The controller’s registers are mapped via I/O or memory. All USB host controllers, like other physical devices, utilize the system bus for data transmission.

The PC directly communicates with the root hub in the USB host controller for enumeration, and the root hub then communicates with connected USB devices or USB hubs for enumeration.

A USB root hub constitutes a single USB bus. If the system has two root hubs, the system treats them as two separate USB buses.