Like any successful standard, USB, Universal Serial Bus has kept pace with technology and the standard has been updated seeing USB 1, USB 1.1, USB2, USB 3 and then USB 3.1.Each successive USB standard has added more to the technology, improving and refining the performance.With the use of USB being so widespread, backwards compatibility as far as is possible is very important, along with a future upgrade path.
USB Implementers Forum
In order to ensure that USB is an industry standard and not one that is a standard for a particular manufacturer, the USB standard is developed and maintained by the USB Implementers Forum, USB-IF.
This is a non-profit corporation that has been founded by the companies that developed the USB standard and now want to sue and develop it.
Some of the member companies for the USB-IF include companies such as Hewlett Packard, Intel, LSI Corporation, Renesas, Microsoft, etc..
The USB Implementers Forum develops and maintains the USB standards, including Wireless USB and runs a compliance programme to maintain the quality of USB products and ensure compatibility between devices.
Wired USB standards
- USB1.1: This was the original version of the USB, Universal Serial Bus and was released in September 1998 after a few problems with the USB 1.0 specification released in January 1996 were resolved.. It provided a Master / Slave interface and a tiered star topology which was capable of supporting up to 127 devices and a maximum of six tiers or hubs. The master or "Host" device is normally a PC with the slaves or "Devices" linked via the cable.
One of the aims of the USB standard was to minimise the complexity within the Device by enabling the Host to perform the processing. This meant that devices would be cheap and readily accessible.
The data transfer rates of USB 1.1 are defined as:
- Low speed: 1.5 Mbps
- Full speed: 12 Mbps
USB 1.1 does not allow extension cables or the inclusion of pass-through monitors (due to timing and power limitations).
- USB 2.0: The USB 2.0 standard is a development of USB 1.1 which was released in April 2000. The main difference when compared to USB 1.1 was the data transfer speed increase up to a "High Speed" rate of 480 Mbps. However it should be noted that even though devices are labelled USB 2.0, they may not be able to meet the full transfer speed.
- USB 3.0: This improved USB standard which was first demonstrated at the Intel Developer Forum in September 2007. The major feature is what is termed the SuperSpeed bus, which provides a fourth transfer mode which gives data transfer rates of 4.8 Gbit/s. Although the raw throughput is 4 Gbit/s, data transfer rates of 3.2 Gbit/s, i.e.0.4 GByte/s more after protocol overhead are deemed acceptable within the standard. The standard is also backwards compatible with USB 2.0.
Often USB ports on computers, etc. may have the USB symbol with 'SS' added, i.e. SS USB. SS USB denotes USB 3, i.e. Super Speed USB.
Since its first introduction, USB, Universal Serial Bus has maintained its position in the market and its use has become very widespread. Further updates and improvements will be introduced in the future to ensure the functionality meets the on-going needs of the industry.
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