Chapter 3USB Inside Your Computer

What Does a USB Host Do?

In a system built with the Universal Serial Bus, the host computer is the single most important element present—it acts as the hardware liaison between each of the separate components of the USB. It is the responsibility of the host to maintain the state of bus and all peripherals attached to it. In short, the host manages the whole thing. There is only one host in each system.

Within the host computer, there are a number of components (as is illustrated in Figure 3–1). The piece of hardware within the host computer that manages the physical part of the Universal Serial Bus is called the host controller. There is software on the USB host that is written to talk to the host controller, ...

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