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The USB story

Mah din Mahboob
MANY of us have recently seen the Intel's TV advertisement which shows Ajay Bhatt, the co-inventor of the USB, aptly termed as our rockstars aren 't like your rockstars walking and moving like a celebrity would. Interesting advertisement, to say the least. To those of you are thinking that this article is about Intel or the advertisement industry in general, behold! It's about neither and is about the Universal Serial Bus or USB in short.
For most of us using personal computers in our day-to-day lives, whether it be for office or college work or simply checking emails and facebooking, the USB port is a common device about which we barely ever think about.
Initially designed to replace the many varieties of serial and parallel ports that were jumbling up our PCs with every new gadget, and thus making the production of standard devices increasingly difficult, it has today become the quintessential bridge to connect computer peripherals like mice, keyboards, PDAs, gamepads and joysticks, scanners, digital cameras, printers, personal media players, flash drives, and external hard drives.
Although it was designed to be used for personal computers, USB has today become commonplace on other devices such as PDAs and video game consoles, and as a power cord between a device and an AC adapter plugged into a wall plug for charging. According to a PC World report published in 2008, there are about 2 billion USB devices sold every year with total about 6 billion sold to date!
The history of the USB dates back to 1594 when the specifications for the first generation of USB or USB 1.0 were introduced. The intention was to replace the multitude of connectors at the back of PCs, as well as to simplify software configuration of communication devices. The original USB 1.0 specification had a data transfer rate of 12 Mbit/s.
The creation of USB was a result of research conducted by a core group of companies that consisted oi Intel, Compaq, Microsoft, Digital, IBM, and Northern Telecom. Intel produced the UHCI (Universal Host Controller Interface) host controller and open software stack; Microsoft produced a USB software stack for Windows and coauthored the OHCI host controller specification with National Semiconductor and Compaq; Philips produced early USB-Audio; and T1 produced the most widely used hub chips.
Six years later, the USB 2.0 specification was released in April 2000 and was standardized at the end of 2001. Hewlett-Packard. Intel, I ucent Technologies (now Alcatel-Lucent following its merger with Alcatel in 2006), Microsoft, NEC, and Philips jointly led the initiative to develop a higher data
transfer rate, 480 Mbit/s, than the 1.0 specification of 12 Mbit/s.
The latest in line, the third generation of USB, or USB 3.0 specification was released on November 17, 2008 by the USB 3.0 Promoter Group. It has a transfer rate of up to 10 times faster than the USB 2.0 version and has been dubbed the SuperSpeed USB.
The benefit of USB is equipment conforming with any version of the standard will also work with devices designed to any previous specification (a property known as backiuard compatibility).
Every USB system has an asymmetric design, consisting of a host, a multitude of downstream USB ports, and multiple peripheral devices connected in a tiered-star topology. A USB host may have multiple host controllers and each host controller may provide one or more USB ports. Up to 127 devices, including the hub devices may be connected to a single host controller.
USB devices are linked in series through hubs and there always exists one hub known as the root hub, which is built into the host controller. I his sharing hubs, as they are popularly know to be, allow multiple computers to access the same peripheral device(s), also exist and work by switching access between PCs, either automatically or manually. They are popular in small-office environments.
A physical USB device may consist of several logical sub-devices that are referred to as device functions. A single device may provide several functions, for example, a webcam (video device function) with a built-in microphone (audio device function).
When a USB device is first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a reset signal to the USB device. The speed of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host, then the device is assigned a unique 7-bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices.
The host controller directs traffic flow to devices, so no USB device can transfer any data on the bus without an explicit request from the host controller. In USB 2.0, host controller polls the bus for traffic, usually in a round-robin fashion. In SuperSpeed USB, connected devices can request service from host.
Technical jargon aside, the Universal Serial Bus or USB has come as a blessing for PC users all over the world and in the coming days, it is all set to become even more faster and convenient for the users.
Information Source:The Internet.