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USB ( U niversal S erial B us)

USB ( U niversal S erial B us). What is USB?. Universal Serial Bus ( USB ) is a serial bus standard to interface devices to a host computer It was designed to allow many peripherals to be connected using a single standardized interface socket

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USB ( U niversal S erial B us)

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  1. USB (Universal Serial Bus)

  2. What is USB? • Universal Serial Bus (USB) is a serial bus standard to interface devices to a host computer • It was designed to allow many peripherals to be connected using a single standardized interface socket • and to improve the Plug and play capabilities by allowing hot swapping or hot plugging

  3. Why? • Ease of adding peripherals to PC • Low cost, supporting transfer rates of up to 480 Mbps • Support for many configurations of OS and PC’s • Standard interface for peripherals in general • Plug and Play technology • No need for external power

  4. Overview • Multiple peripheral devices connected in a tiered-star topology up to 5 levels • Up to 127 devices, including the hub device • USB 1.0, 1.1 and 2.0 use a "speak-when-spoken-to“ protocol • Offers limited power

  5. How was it created? • USB was developed by a consortium of large companies, such as: • Microsoft; • IBM; • Apple; • Hewlett-Packard; • NEC; • Intel; • Compaq; • Digital; • Northern Telecom; • Philips; • ...

  6. Curiosity about the consortium • Obviously it was very difficult for these companies enter into agreement • Intel - UHCI - Universal Host Controller Interface (transfer part of the protocol processing for the software (driver), simplifying the electronic controller) • Compaq, Microsoft, National Semiconductor – OHCI - Open Host Controller Interface (transfer most of the effort to the electronic controller, simplifying the driver software (driver)) • 2.0 – EHCI - Enhanced Host Controller Interface (combines quality of the two models with a greater bandwidth)

  7. Device Classes • USB defines class codes used to identify a device’s functionality and to load a device driver based on that functionality

  8. USB Connectors

  9. Cable • The maximum length of a standard USB cable is 3.0 meters (1.1) or 5.0 meters (2.0) • Maximum hubs connected in series is 5 • Maximum distance of 30 meters between host and device • - because of the delay • The data cables are a Twisted pair to reduce noise and crosstalk

  10. USB Versions • USB 0.7: Released in November 1994 • USB 0.8: Released in December 1994 • USB 0.9: Released in April 1995 • USB 0.99: Released in August 1995 • USB 1.0: Released in January 1996, with data transfer rates of 1.5 Mbit / s • USB 1.1: Released in 1998 • USB 2.0: Released in April 2000

  11. USB 1.1 • Specified data rates of 1.5 Mbit/s (Low-Speed) and 12 Mbit/s (Full-Speed) • Standard interface • Fixed problems identified in 1.0, mostly relating to hubs • Used for small peripherals

  12. USB 2.0 • Added higher maximum speed of 480 Mbit/s (now called Hi-Speed) • Uses the same standart connector • Compatible with 1.1 devices but with reduced speed • Manufacturers could adopt the standard into their products without the obligation to pay a license to use the technology • There was an increase in the range of possibilities because of the hi-speed

  13. USB 3.0 • A SuperSpeed rate of 5.0 Gbit/s, 10 times faster than 2.0 • Products using the 3.0 specification are likely to arrive in 2009 or 2010 • The trade name will be SuperSpeed USB • The technology is similar to PCI Express 2.0 (5-Gbit/s) - comparing the cables

  14. Applications and Utilities

  15. hugo.baldioti@engenharia.ufjf.br

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