What is USB?

Universal Serial Bus

     USB is an abbreviation of Universal Serial Bus. USB is a standard port that enables you to connect external devices (such as digital cameras, scanners, and mice) to Windows 98 and Macintosh computers. The Universal Serial Bus standard supports data transfer rates of 12Mbps (million bits per second), a vast improvement over the serial port standard it is beginning to replace. Aside from speed advantages, Universal Serial Bus devices can be connected or disconnected without the need to restart the computer. Many Universal Serial Bus devices can work on either a Windows 98 PC or a Mac, provided the device manufacturer offers connectivity software for both computer systems. Many of the latest digital cameras offer Universal Serial Bus as well as serial connections.
     Probably a cool idea, basicly, a high-speed, multi-device serial interface. Actually, closer perhaps to a simplistic network system for peripherals. Crams a lot of devices into a single interupt, which is something we REALLY need on the PC archetecture. Claims to be "plug-and-play", and comes closer than other things describing themselves that way. Currently being used for keyboards, mice, scanners, printers, digital cameras, etc. One port on the computer can be "split" into multiple ports using hubs. Universal Serial Bus ports actually also provide a 5v power supply, so many devices can be powered directly from your computer (or the hub), so the device may connect to the outside world with only one cable.
     There are several different editions of the USB standard that have been released:

Universal Serial Bus 1.0, the first edition, was released in January 1996. It supported 1.5 Mbps (low speed) and 12 Mbps (high speed) transfer rates. Note that this is Megabits per second and not MegaBytes per second -- a common misunderstanding. A percentage of this data rate is reserved for USB protocol overhead, so the actual data transfer is less than the indicated speed. How much less depends on the transfer type and the packet sizes.
USB 1.1 was released in September 1998. This edition fixed many of the problems in release 1.0.
USB 2.0 was released in early 2000 and has increased the maximum transfer speed by a factor of 14 up to 480 Mbps! USB 2.0 is backwards compatible with USB 1.x. Although the USB 2.0 specification has been released, operating programs for personal computers are not expected to have USB 2.0 support until about the fourth quarter of 2001. A few peripherals supporting USB 2.0 have already begun to show up on the market in late 2000.

Pin Number	Wire Colors	Function
1	Red	V_BUS (5 volts)
2	White	D-
3	Green	D+
4	Black	Ground

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