usb30中英文翻译

usb30中英文翻译内容摘要：

chapter presents an overview of Universal Serial Bus architecture and key concepts. USB is similar to earlier versions of USB in that it is a cable bus supporting data exchange between a host puter and a wide range of simultaneously accessible peripherals. The attached peripherals share bandwidth through a hostscheduled protocol. The bus allows peripherals to be attached, configured, used, and detached while the host and other peripherals are in operation.USB utilizes a dualbus architecture that provides backward patibility with USB . It provides for simultaneous operation of SuperSpeed and nonSuperSpeed (USB speeds)information exchanges. This chapter is organized into two focus areas. The first focuses onarchitecture and concepts related to elements which span the dual buses. The second focuses on SuperSpeed specific architecture and concepts.Later chapters describe the various ponents and specific requirements of SuperSpeed USB in greater detail. The reader is expected to have a fundamental understanding of the architectural concepts of USB . Refer to the Universal Serial Bus Specification, Revision for plete details. USB System DescriptionUSB is a physical SuperSpeed bus bined in parallel with a physical USB bus (seeFigure 31). It has similar architectural ponents as USB , namely:• USB interconnect• USB devices• USB hostThe USB interconnect is the manner inwhich USB and USB devicesconnect to and municate with theUSB host. The USB interconnectinherits core architectural elements fromUSB , although several are augmented toacmodate the dual bus architecture.The baseline structural topology is the sameas USB . It consists of a tiered startopology with a single host at tier 1 andhubs at lower tiers to provide busconnectivity to devices.The USB connection modelacmodates backwards and forwardpatibility for connecting USB orUSB devices into a USB bus.Similarly, USB devices can be attachedto a USB bus. The mechanical andelectrical backward/forwards patibility for USB is acplished via a posite cable and associated connector assemblies that form the dualbus architecture. USB devices acplish backward patibility by including both SuperSpeed and nonSuperSpeed bus interfaces. USB hosts also include both SuperSpeed and nonSuperSpeed bus interfaces, which are essentially parallel buses that may be active simultaneously.The USB connection model allows for the discovery and configuration of USB devices at the highest signaling speed supported by the device, the highest signaling speed supported by all hubs between the host and device, and the current host capability and configuration.USB hubs are a specific class of USB device whose purpose is to provide additional connection points to the bus beyond those provided by the host. In this specification, nonhub devices are referred to as peripheral devices in order to differentiate them from hub devices. In addition, in USB the term “function” was sometimes used interchangeably with device. In this specification a function is a logical entity within a device, see Figure 33.The architectural implications of SuperSpeed on hosts and devices are described in detail inSection . USB Physical InterfaceThe physical interface of USB is prised of USB electrical (Chapter 7 of the USB specification), mechanical (Chapter 5), and SuperSpeed physical (Chapter 6) specifications for the buses. The SuperSpeed physical layer is described in Section . USB MechanicalThe mechanical specifications for USB cables and connector assemblies are provided inChapter 5. All USB devices have an upstream connection. Hosts and hubs (defined below) have one or more downstream connections. Upstream and downstream connectors are not mechanically interchangeable, thus eliminating illegal loopback connections at hubs.USB cables have eight primary conductors: three twisted signal pairs for USB data paths and a power pair. Figure 32 illustrates the basic signal arrangement for the USB cable. In addition to the twisted signal pair for USB data path, two t。