Computing Dictionary
Universal Serial Bus definition
hardware, standard (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)
