Universal Serial Bus (USB)

Résumé du document

With increasing use of the Internet, cellular telephones, communications and media in general, interconnectivity has been growing at a rate that no one could have imagined ten years ago. As a result, problems have arisen in the wireless industry related to limited bandwidth as well as connections to "wired" devices. Of the many new serial protocols that have popped up in response to these problems, the USB (Universal Serial Bus) currently seems to be reigning supreme. One of the reasons that USB was implemented was to replace existing serial and parallel ports on computers. This document throws light on the basic aspects for those who are not too familiar with the serial bus technology, accompanied by a short summary of USB history followed by the basis of USB working. This will be followed by the strengths and weaknesses of the USB.

Extraits

[...] An example of this would be USB audio speakers. Strengths 1 Specification flexibility One of the interesting traits of USB is that it offers standardization of the mechanical form of ports, their electrical qualities, and the protocol used for them. The parallel port standard defines signaling and physical structures, but still doesn't say much about what data will pass over the port. Specifications normally run the range from complete-but-specialized to incomplete-but-generic. USB offers some fairly complete, specified instruction, such as the mass storage specifications or the human interface device specifications, but also leaves room for developer expansion and development. [...]

[...] USB has four types of communication transfer modes: Control mode. Interrupt mode. Bulk mode. Isochronous mode. Control mode is initiated by the host. In this mode, every data transfer must send data in both directions, but only in one direction at a time. The control mode is used mainly for initialization of devices, but it can also be used to transfer small amounts of data. In interrupt mode, interrupts do not occur in the usual sense. As in control mode, the host has to initiate the transfer of data. [...]

[...] In some cases, a device will use only part of the USB spec. Nintendo Gameboy SP is rechargeable and a third party sells a USB charging cable for it. This uses the physical spec and power, but doesn't even show up as a device. The protocol is ignored entirely. This is common enough that some car and airplane AC adapters now offer a "dumb" USB port which just provides power for rechargeable devices. On the other side of the same coin, not all USB devices have recognizable cables. [...]

[...] Universal Serial Bus ( USB ) Table of contents I. Introduction 4 II. History 4 III. How does USB works 4 IV. Strengths 5 a. Specification flexibility 5 b. Revisiting the cable 6 c. Documentation 6 V. Weaknesses 6 VI. Conclusion 7 VII. Sources 7 Introduction With increasing use of the Internet, cellular telephones, communications and media in general, communications interconnectivity has been growing at a rate that no one could have imagined ten years ago. As a result, problems have arisen in the wireless industry related to limited bandwidth as well as connections to "wired" devices. [...]

[...] Windows 95 (and earlier versions of Windows) has no USB support. A sub- release of Windows 95 (OEM Service Release was issued to computer manufacturers only and it added somewhat limited support for the USB protocol. Windows 98 added additional support and fixed some problems that were in the 95 OEM Service Release 2. Windows 98se (98 second edition) released in early June of 1999 had more robust support for USB. Both Windows 2000 and Windows Me released in early 2000 added additional features. [...]