Introduction
In many of the more recent computers, little slot-like ports started to come
included. Of course, the manual never said anything about the ports, and there
were no devices back then with connectors that actually fit those slots. This
slot is called a Universal Serial Bus (USB) port. Though this technology is
fairly new, more and more manufacturers are beginning to sell USB-compatible
peripherals and equipment. Almost 100 per cent of PC shipments are USB compatible,
and the base of USB-installed PCs exceeds 500 million.
What the heck is USB?
USB stands for Universal Serial Bus. USB was developed by the computer industry
leaders including Microsoft, Compaq, Intel, and NEC to increase the
ease-of-use, performance and speed of peripherals by standardizing the way
they attach to the PC. It is the easiest way to attach devices to your PC.
The aim is on peripherals that connect to the outside of the computer. With
USB, users won't have to open up the computer to install new peripherals. USB
consists of a host, hub, and function. The host is the exchange point
between USB peripherals, which is linked to a host controller, integrated
into either the motherboard or PCI USB addon solutions. The hub allows multiple
devices connect to the host. There is a USB hub already in USB-compatible compatible
computers, that branches out to usually two connectors on the back of the computer.
A function is a device that attached to the USB port.
So what? Why should I use USB?
- Plug and Play(PnP) - USB was designed to meet to Microsoft's
Plug-and-Play specification, meaning that devices can be plugged in, installed,
and hot-swapped (removed and replaced with another device) without long
installation procedures and reboots. That means devices will automatically
detected as soon as you plug them in and will install without having to turn
off the computer at all. Once you have a USB device's drivers installed, then
you can remove it when you don't need it (even when the computer is on) and
replace it when you do need it. Even better, you can even take it with you
to other computers and connect it without installing permanent software, and
after you are done using it, you can remove it without worry. No need for
fiddling with the IRQ settings, no need to attach jumper cables. In fact,
the best thing about USB is that it only requires one interrupt in the computer
for all of the devices.
- Hot Swapping and Multiple Device Support - Some people like to
attach lots of devices to their computers at one time, but normally Windows
can't handle it, and often people worry about their computers crashing or
failing to work as they attach more and more devices to their PCs. The most
often scenario is when a user has no place to plug in the device. USB gets
rid of the problem by allowing up to 127 devices to be connected to it simultaneously.
In order to connect more devices, however, you have to get a USB hub. Hubs
allow multiple devices to plug into a single USB port. The reason you need
one is to supply power to the additional ports and control the flow of information
between the hub and the USB ports on the back of the computer. Still, with
USB hubs you can attach and remove devices without restarting your computer.
- High Speed and Electricity - USB ports have dual-speed transfer rates,
1.5 Megabits/second and 12 Megabits/second. Regular serial ports have
a data transfer speed of only 230 kilobytes/second. It can also provide
limited power, maximum 500mA of current, to devices attached to the USB
bus. That means that most USB devices will not require a power supply like
an AC adapter.
- One size fits all - There is only one standard connection type for
USB. There are two types of connectors, however. The series "A"
connector is intended for all USB devices, is a plug for a peripheral and
a socket for a PC platform. In most cases a USB cable should be captive
(molded in) to it's peripheral. This saves connector cost, eliminates incompatibilities
due to power drop in a cable and simplifies the user connection task. There
are some cases where a captive cable is prohibitive. A very large heavy
device may not be able to tolerate dangling cables that cannot be removed
and some devices that are only occasionally connected, but have a useful function
when not connected are good examples. The series "B" connector was
created for such applications. The 2 connector series are different to prevent
connections that violate the USB architecture topology.
What kind of peripherals can connect to USB?
There are thousands of USB peripherals on the market, from USB hubs, to scanners
and printers, to digital video cameras. There are even USB
modems and ISDN solutions on the market. Today, the USB logo appears all
over the place, indicating peripherals that have USB support.