universal serial bus
(foldoc) | Universal Serial Bus
USB 2.0
(USB) An external peripheral interface
standard for communication between a computer and external
peripherals over an inexpensive cable using biserial
transmission.
USB is intended to replace existing serial ports, {parallel
ports}, keyboard, and monitor connectors and be used with
keyboards, mice, monitors, printers, and possibly some
low-speed scanners and removable hard drives. For faster
devices existing IDE, SCSI, or emerging FC-AL or
FireWire interfaces can be used.
USB works at 12 Mbps with specific consideration for low cost
peripherals. It supports up to 127 devices and both
isochronous and asynchronous data transfers. Cables can
be up to five metres long and it includes built-in power
distribution for low power devices. It supports {daisy
chaining} through a tiered star multidrop topology. A USB
cable has a rectangular "Type A" plug at the computer end and
a square "Type B" plug at the peripheral end.
Before March 1996 Intel started to integrate the necessary
logic into PC chip sets and encourage other manufacturers
to do likewise. It was widely available by 1997. Later
versions of Windows 95 included support for it. It was
standard on Macintosh computers in 1999.
The USB 2.0 specification was released in 2000 to allow USB to
compete with Firewire etc. USB 2.0 is backward compatible
with USB 1.1 but works at 480 Mbps.
usb.org (http://usb.org/).
(2004-01-31)
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