USB 2.0

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VinChip Systems
Chennai
mail id : vinoth.ks@vinchip.com

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USB 2.0

  1. 1. USB 2.0 BasicsVinchip Systems(a Design and Verification Company)Chennai.
  2. 2. Universal Serial Bus History of USB Why We Need USB ? Architectural Overview USB communication flow Protocol Layer Conclusion
  3. 3. History of USB Universal Serial Bus (USB) is an industry standard developed in the mid-1990 USB was designed to standardize the connection of computer peripherals Keyboard Mouse Digital cameras Printers Portable media players HD drives Mobile devices PDA
  4. 4. Overview Key features of USB: Low cost Single connector type Hot pluggable Device handling Cable power
  5. 5. USBThree generations of USB USB 1.0 USB 2.0 USB 3.0 and WUSB
  6. 6. Version History Prereleases The USB standard evolved through several versions before its officialrelease in 1995: 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. USB 2.0: Released in April 2000 USB 3.0 was released in November 2008.
  7. 7. Speed Specifications
  8. 8. Why We Need USB ? Connection of the PC to the telephone :=>In order to transmit data Ease-of-use :  =>Support plug and play Port expansion :=>Up to 127 devices  =>Can add lots of device to a XX The logical topology of the USB is a star structure It is similar to computer network
  9. 9. USB Can Do Combines low speed and high speed bus activity , USB enablesshared access for both speed Automatic configuring of devices and a serial bus which issimplified and easy to plug into Attach / detach easily without restarting system
  10. 10. USB 2.0 Specs USB 2.0: Released in April 2000 maximum signaling rate of 480 Mbit/s effective throughput up to 35 MB/s Mini-A Mini-B Connector
  11. 11. Architectural Overview USB System Member - 1 USB System Member - 2 USB System Member - 3
  12. 12. USB System Member - 1 Host : only one The smartest element in the USB system Responsible to the complexity of the protocol to makedevices design simple and low cost Control the media access ( no one can Access the bus unless it get an approval requiredfrom the host )
  13. 13. USB System Member - 2 Hub : one or more=>Like the hubs used for computer network=>Enables many devices to connect to a singleUSB port
  14. 14. USB System Member - 3 Device : one or more=>Everything in the USB system , which is not a host , is adevice ( include hubs)=>A device may provides one or more USB functions=>Has an unique address at the end of the enumerationprocess
  15. 15. Communication Flow
  16. 16. Pipes (1) The logic communication between the client software on thehost and the function on the device is done through pipes It is a association between a specific endpoint on the deviceand the appropriate software in the host
  17. 17. Pipes (2) An endpoint is the source or destination of the data thattransmitted on the USB cable Two direction=>OUT :data flows from the host to the device=>IN :data flows from the device to the host
  18. 18. Signaling On The Bus The USB cable is 4 wire cable Signal on the bus is done by signaling over tow wires ( D+andD_ ) 1 : D_ low , D+high 0 : D_ high , D+low Data encoding and decoding is done using NRZI ( Non Returnto Zero Inverted )
  19. 19. SIE - Serial Interface Engine SIE : Serial Interface Engine It is part of both the host’s and the device’s physical layer Serialization and Deserialization Encoding and Decoding Generate (for out) and Verify (for in) CRC
  20. 20. HC -Host Controller It is an additional hardware to ensure that everything which istransmitted on the bus is correct It serves both the USB and the host and has the samefunctionality in ever USB system
  21. 21. Transaction USB transactions are done through packets include threephases Token phase : host initiates token indicating the future transfer type Data phase : Actual data transmitted Handshake phase : Indicate the success or failure of the transaction
  22. 22. Transfer Types (1) Control Transfer=>Used to configure a device (enumeration)=>Compose of three phases (setup, data, status) Isochronous Transfer=>Used for multimedia devices=>It is guarantee the required bandwidth=>No handshake phase
  23. 23. Transfer Types (2) Bulk Transfer=>Used for large burst data=>Guarantee of delivery , no guarantee ofbandwidth or minimum latency Interrupt Transfer=>If there is a pending interrupt , the functionwill send details to host after host poll it
  24. 24. Packet (1) PID : Packet Identifier Field Address Field=>So , there are up to 127 devices in USB
  25. 25. Packet Data Packet  Handshake Packet=>Such as ACK 、NAK 、 STALL…etc.
  26. 26. Conclusion USB is powerful and easy to use The complex host make the device easy to design
  27. 27. Cable
  28. 28. NRZI (1) Want to transmit :=>1 : without changing the level of thelevel of the signaling=>0 : flip the value of the differential pairexample :
  29. 29. NRZI (2) Problem :When we send “1” stream , the transmissionline will stay static ( no change period ) Solution :“Bit stuffing” , performed before the NRZIexample :data : 010111111101send : 0101111110101

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