USB3.0协议规范 (完整版)

USB3.0协议规范 (完整版)

Revision History
Revision Comments Issue Date
0.7 First consolidated review draft. October 19, 2007
0.75 Updates to Chapters 6, 7, 8, 10, and 11. November 9, 2007
0.78 Added Chapters 1, 3, and 12 and Appendixes A, B, and C. Updated
Chapters 4, 5, 6, 7, 8, 10, and 11.
December 26, 2007
0.85 Moved content into Chapter 2 and Appendix C. Updated all other
chapters except Appendixes A and B.
April 4, 2008
0.9RC1 Updated all chapters except Chapter 1 and Appendixes A and B. June 19, 2008
0.9 Incorporated all approved SCRs July 30, 2008

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 bi-directional, 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, mice, etc. 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 are 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 host-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.

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