O'Reilly logo

OS X and iOS Kernel Programming by Douglas Clarke, Ole Henry Halvorsen

Stay ahead with the world's most comprehensive technology and business learning platform.

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, tutorials, and more.

Start Free Trial

No credit card required

USB Architecture

In a USB system, the host controller is the master and the USB devices are the subordinates. The USB topology is organized in a tree-like structure, which forms a bus, with the host controller being the root and the controller of the subordinated device. The host controller is responsible for coordinating activities on the bus, and a device is not able to perform I/O, or any other activity on the bus, without first being asked to do so by the host.

The tree structure branches out with the help of hubs, which allow connected devices to become part of the bus, and thus extend it, as a new branch. The subordinate devices of a hub can have other hubs connected to them— up to four levels deep is possible. The root hub is usually embedded ...

With Safari, you learn the way you learn best. Get unlimited access to videos, live online training, learning paths, books, interactive tutorials, and more.

Start Free Trial

No credit card required