What is USB

USB Basics


USB port or Universal Serial Bus according to ABBREVIATIONFINDER.ORG, is a universal serial bus or Universal Serial CUS Driver, it is a port that is used to connect peripherals to a computer. An important feature is that it allows devices to work at higher speeds, on average about 12 Mbps, this is more or less 3 to 5 times faster than a parallel port device and 20 to 40 times faster than a device of serial port.


Created in 1996 by seven companies (which currently form the board of directors): IBM, Intel,

NorthernTelecom, Compaq, Microsoft, Digital Equipment Corporation, and NEC.

In the beginning there was the serial and parallel interface, but it was necessary to unify all the connectors creating a simpler and higher performance one. Thus was born the USB (Universal Serial Bus) with a speed of 12Mb / sec. and like its evolution, USB 2.0, nicknamed Hi-Speed ​​USB, with speeds at this time of up to 480Mb / sec., that is, 40 times faster than connections via USB 1.1 cables. A USB port can transmit at speeds between 1.5 Mb / second and 12 Mbps; a parallel port between 600 Kb / s to 1.5 Mb / s and a serial port can reach up to 112 Kb / s.

Characteristics in data transfer.

USB devices are classified into four types based on their data transfer speed:

Low speed (1.0)

Transfer rate of up to 1.5 Mbps (192 KB / s). Used for the most part by

Human interface devices such as keyboards, mice, webcams, etc.

Full speed (1.1)

Transfer rate of up to 12 Mbps (1.5 MB / s), according to this standard but it is said in independent sources that the measurements would have to be carried out again. This was the fastest before the USB 2.0 specification, and many devices manufactured today work at this speed. These devices divide the bandwidth of the USB connection between them, based on an algorithm of LIFO impedances.

High speed (2.0)

Transfer rate up to 480 Mbps (60 MB / s) but typically up to 125Mbps (16MB / s). It is present in almost 99% of today’s computers. The USB 2.0 cable has four lines, one pair for data, one for power and one for ground.

Super high speed (3.0)

It has a transfer rate of up to 4.8 Gbps (600 MB / s). This specification is ten times faster than the previous 2.0 and was released in mid- 2009 by Intel, according to estimates, or perhaps by another hardware company, according to information gathered from the Internet. Although currently any GNU / Linux distribution is capable of supporting the new standard, however, there is no hardware available yet. The bus speed is ten times faster than USB 2.0, because they have included 5 extra connectors, discarding the fiber optic connectorinitially proposed, and will be compatible with previous standards. Products made with this technology are expected to reach the consumer between 2009 and 2015.

USB 3.0.

File: USB Adapter, USB 2.0 – Parallel, 1,50M.gif

USB Adapter, USB 2.0 – Parallel, 1,50M.

The main characteristic is the multiplication by 10 of the speed of

transfer, which goes from 480 Mbps to 4.8 Gbps (600 MB / s). Another of the characteristics of this port is its “intelligence rule”: devices that are plugged in and after a while are in disuse, immediately go to a low-power state. At the same time, the intensity of the current rises from 500 to 900 milliamps, which is used to supply a mobile phone or a portable audiovisual player in less time.
On the other hand, it increases the speed in data transmission, since instead of working with three lines, it does so with five. In this way, two lines are used to send, another two to receive, and a fifth is in charge of supplying the current. Thus, the traffic is bidirectional (full duplex).

At the end of 2009, manufacturers such as Asus or Gigabyte presented motherboards with this new revision of the bus. Version 3.0 of this universal connector is 10 times faster than the previous one. Those who have a keyboard or a mouse of the previous version will not have compatibility problems, since the system will recognize it instantly, although they will not be able to benefit from the new advances of this usb serial bus port.

Connectors and compatibility.

The USB 1.0, 1.1, and 2.0 specifications define two types of connectors for connecting devices to the server: A and B. However, the mechanical layer has changed on some connectors. For example, the IBM UltraPort is a private USB connector located on top of the LCD of laptops from IBM. It uses a different mechanical connector while maintaining the characteristic USB signals and protocols. Other manufacturers of small items have also developed their small connecting means, and a great variety of them have appeared, some of low quality.

An extension of the USB called ” USB-On-The-Go ” (on the fly) allows a port to act as a server or as a device – this determines which side of the cable is connected to the device. Even after the cable is connected and the units are communicating, the 2 units can “switch roles” under the control of a program. This facility is specifically designed for devices such as PDAs, where the USB link could be connected to a PC as a device, and connected as a server to a keyboard or mouse. The “USB-On-The-Go” has also designed 2 small connectors, the mini-A and the mini-B, so this should stop the proliferation of miniaturized input connectors.

USB mass storage.

USB implements connections to storage devices using a group of standards called USB mass storage device class (“MSC” or “UMS” for short). This was originally designed for optical and magnetic memories, but now it also supports a wide variety of devices, particularly USB memories.

Wireless USB.

Wireless USB (commonly abbreviated W-USB or WUSB) is a high-bandwidth wireless radio communication protocol that combines the ease of use of USB with the versatility of wireless networking. It uses as a radio base the Ultra-WideBand platform developed by WiMedia Alliance, which can achieve transmission rates of up to 480 Mbps (same as USB 2.0) in ranges of three meters and 110 in ranges of ten meters and operates in the frequency ranges 3.1 to 10.6 GHz. Currently it is in full transition and there are still not many devices that incorporate this protocol, both clients and hosts. While this process lasts, using the appropriate adapters and / or cables, a WUSB device can be converted into a USB one and vice versa.


USB was born as a medium-high speed input / output standard that will allow connecting devices that until now required a special card to get all the performance, which caused an increase in the price of the product in addition to being proprietary products since they forced purchase a card for each device.

In addition, USB provides us with a single connector to solve almost all communication problems with the outside, being able to form a real peripheral network of up to 127 elements.

Through a pair of USB connectors that are already standard on all motherboards today, and in the space that today occupies a single 9-pin serial connector, it will allow us to connect all the devices we have, from the keyboard to the modem, through mice, printers, speakers, monitors, scanners, digital cameras, video cameras, plotters, etc… without the need for our PC to have a dedicated connector for each of these elements, saving space and money.

As you can see, it really is a standard that is necessary to make our lives easier, since it also has the famous PnP (Plug and Play) feature and the “hot” connection facility, that is, they can be connected and disconnected. peripherals without restarting your computer.

Just as ISA cards tend to disappear, all the aforementioned connectors will also disappear from our computer, also eliminating the need to have the corresponding drivers for serial, parallel, PS / 2 mouse devices on the motherboard or on an expansion card., joystick, etc…

What is USB