USB3.0中英文翻译 (2)

USB3.0中英文翻译 (2)

USB3.0

1 Introduction 1.1 Motivation

The original motivation for the Universal Serial Bus (USB) came from several considerations, two of the most important being:

? Ease-of-use

The lack of flexibility in reconfiguring the PC had been acknowledged as the Achilles’ heel to

its further deployment. The combination of user-friendly graphical interfaces and the hardware and software mechanisms associated with new-generation bus architectures have made computers less confrontational and easier to reconfigure. However, from the end user’s point of view, the PC’s I/O interfaces, such as serial/parallel ports, keyboard/mouse/joystick

interfaces, etc., did not have the attributes of plug-and-play.

? Port Expansion

The addition of external peripherals continued to be constrained by port availability. The lack

of a bidirectional, low-cost, low-to-mid speed peripheral bus held back the creative proliferation of peripherals such as storage devices, answering machines, scanners, PDA’s,

keyboards, and mice. Existing interconnects were optimized for one or two point products. As each new function or capability was added to the PC, a new interface had been defined to address this need.

Initially, USB provided two speeds (12 Mb/s and 1.5 Mb/s) that peripherals could use. As PCs became

increasingly powerful and able to process larger amounts of data, users needed to get more and more data into and out of their PCs. This led to the definition of the USB 2.0 specification in 2000 to provide a third transfer rate of 480 Mb/s while retaining backward compatibility. In 2005, with wireless technologies becoming more and more capable, Wireless USB was introduced to provide a new cable free capability to USB.

USB is the most successful PC peripheral interconnect ever defined and it has migrated heavily into the CE and Mobile segments. In 2006 alone over 2 billion USB devices were shipped and there are over 6 billion USB products in the installed base today. End users “know” what USB is. Product developers understand the infrastructure and interfaces necessary to build a successful product.

USB has gone beyond just being a way to connect peripherals to PCs. Printers use USB to

interface directly to cameras. PDAs use USB connected keyboards and mice. The USB On-The-Go definition provides a way for two dual role capable devices to be connected and negotiate which one will operate as the “host.” USB, as a protocol, is also being picked up and used in many nontraditional applications such as industrial automation.

Now, as technology innovation marches forward, new kinds of devices, media formats, and large inexpensive storage are converging. They require significantly more bus bandwidth to maintain the interactive experience users have come to expect. HD Camcorders will have tens of gigabytes of storage that the user will want to move to their PC for editing, viewing, and archiving. Furthermore existing devices like still image cameras continue to evolve and are increasing their storage capacity to hold even more uncompressed images. Downloading hundreds or even thousands of 10 MB, or larger, raw images from a digital camera will be a time consuming process unless the transfer rate is increased. In addition, user applications demand a higher performance connection between the PC and these increasingly sophisticated peripherals. USB 3.0 addresses this need by adding an even higher transfer rate to match these new usages and devices.

Thus, USB (wired or wireless) continues to be the answer to connectivity for PC, Consumer

Electronics, and Mobile architectures. It is a fast, bidirectional, low-cost, dynamically attachable interface that is consistent with the requirements of the PC platforms of today and tomorrow.

1.2 Objective of the Specification

This document defines the next generation USB industry-standard, USB 3.0. The specification describes the protocol definition, types of transactions, bus management, and the programming interface required to design and build systems and peripherals that are compliant with this specification

USB 3.0’s goal remains to enable devices from different vendors to interoperate in an open

architecture, while maintaining and leveraging the existing USB infrastructure (device drivers, software interfaces, etc.). The specification is intended as an enhancement to the PC architecture, spanning portable,

business desktop, and home environments, as well as simple device-to-device communications. It is intended that the specification allow system OEMs and peripheral developers adequate room for product versatility and market differentiation without the burden of carrying obsolete interfaces or losing compatibility.

1.3 Scope of the Document

The specification is primarily targeted at peripheral developers and platform/adapter developers, but provides valuable information for platform operating system/ BIOS/ device driver, adapter IHVs/ISVs, and system OEMs. This specification can be used for developing new products and associated software.

Product developers using this specification are expected to know and understand the USB 2.0

Specification. Specifically, USB 3.0 devices must implement device framework commands and descriptors as defined in the USB 2.0 Specification.

1.4 USB Product Compliance

Adopters of the USB 3.0 specification have signed the USB 3.0 Adopters Agreement, which

provides them access to a reasonable and nondiscriminatory (RANDZ) license from the Promoters and other Adopters to certain intellectual property contained in products that are compliant with the USB 3.0 specification. Adopters can demonstrate compliance with the specification through the testing program as defined by the USB Implementers Forum. Products that demonstrate compliance with the specification will be granted certain rights to use the USB Implementers Forum logos as defined in the logo license.

1.5 Document Organization

Chapters 1 through 4 provide an overview for all readers, while Chapters 5 through 11 contain detailed technical information defining USB 3.0.

Readers should contact operating system vendors for operating system bindings specific to USB 3.0.

1.6 Design Goals

USB 3.0 is the next evolutionary step for wired USB. The goal is that end users view it as the same as USB 2.0, just faster. Several key design areas to meet this goal are listed below: ? Preserve the USB model of smart host and simple device.

? Leverage the existing USB infrastructure. There are a vast number of USB products in use today. A large part of their success can be traced to the existence of stable software interfaces, easily developed software device

drivers, and a number of generic standard device class drivers (HID, mass storage, audio, etc.). SuperSpeed USB devices are designed to keep this software infrastructure intact so that developers of peripherals can continue to use the same interfaces and leverage all of their existing development work.

? Significantly improve power management. Reduce the active power when sending data and reduce idle power by providing a richer set of power management mechanisms to allow devices to drive the bus into lower power