1. Data Communications (E&T2760): USB and IEEE 1394 1 USB and IEEE 1394

2. Data Communications (E&T2760): USB and IEEE 1394 2 Introduction Serial interface standards of PCs which –define the hardware and software interfaces for connecting a variety of computer peripherals and consumer electronics devices with their standard sets of cables and connectors –benefits eliminate the use of different interfaces (e.g. KBD, PS/2, COM, PRN, SCSI) for different types of devices hot-plugged

3. Data Communications (E&T2760): USB and IEEE 1394 3 Agenda USB –topology –connectors, hub and cables –addresses and endpoints –data transfer IEEE 1394 –topologies –cable and connector –data transfer

4. Data Communications (E&T2760): USB and IEEE 1394 4 Vocabulary Isochronous –uniform in time; having equal duration; and recurring at regular intervals

5. Data Communications (E&T2760): USB and IEEE 1394 5 USB Universal Serial Bus Designed to handle slow to medium speed applications –e.g. mouse, keyboard, joystick, printer, scanner –connect up to 127 devices in tiered star topology Data rates: –USB 1.0 – 1.5Mbps or 12Mbps –USB 2.0 – 480Mbps (target)

6. Data Communications (E&T2760): USB and IEEE 1394 6 USB Topology: Tree

7. Data Communications (E&T2760): USB and IEEE 1394 7 USB Connectors Downstream ports –rectangular (Type A) –going away from the computer Upstream ports –square (Type B) –going towards the computer

8. Data Communications (E&T2760): USB and IEEE 1394 8 USB Connectors

9. Data Communications (E&T2760): USB and IEEE 1394 9 USB Hub Provide branching with one upstream port and a number of downstream ports Bus-powered hub –can supply each downstream device with 10mA Self-powered hub –can supply each downstream device with 500mA

10. Data Communications (E&T2760): USB and IEEE 1394 10 USB Cable A square upstream connector at one end and a rectangular downstream connector at the other end Up to 5m long Four wires: Vcc, Ground, D + and D- – D + and D- are twisted pair Un-shielded –connect low speed (1.5Mbps) devices Shielded (D + and D-) –connect high speed (12Mbps) devices

11. Data Communications (E&T2760): USB and IEEE 1394 11 USB Addresses and Endpoints Each device has a 7-bit address Inside each device, there are a number of Endpoints (up to 16) –an endpoint is an internal address within the device which is responsible for a particular function of the device –e.g. for a combined scanner/printer: Endpoint 0: set up the device Endpoint 1: scanner function Endpoint 2: printer function

12. Data Communications (E&T2760): USB and IEEE 1394 12 USB Data Packet USB host divides time into 1ms frames Each frame contains data packets of up to 8K bits long (i.e. around 700  s at 12MHz data rate) CRC is applied to each packet for error checking

13. Data Communications (E&T2760): USB and IEEE 1394 13 USB Data Transfers Line Coding: NRZI –bit stuffing is employed to help clock recovery Initiated by host and carried out between host and an device endpoint Four types: 1)Control used for setting up the device 2)Interrupt a device’s interrupt endpoint is polled regularly by host

14. Data Communications (E&T2760): USB and IEEE 1394 14 USB Data Transfers 3)Bulk variable bandwidth, determined by host used for devices like printers and scanners where the delivery of data is not time critical 4)Isochronous fixed bandwidth that is pre-negotiated between host and the device used for devices that must have a certain bandwidth throughout the transfer, e.g. digitized audio/video

15. Data Communications (E&T2760): USB and IEEE 1394 15 IEEE 1394 Derived from Apple Computer’s FireWire design Also called iLink by Japanese manufacturers Designed to handle high speed applications –e.g. digitized video, hard disk –connect up to 65 devices Data rates: –100, 200 and 400 Mbps –required data rate for uncompressed digitized video: 320 x 240, 24-bit color, 30 frames/second: 55Mbps 640 x 480, 24-bit color, 30 frames/second: 221Mbps

16. Data Communications (E&T2760): USB and IEEE 1394 16 IEEE 1394 –compared with the data rates of other interfaces: Serial Port: 230Kbps USB: 12Mbps SCSI-2: 80Mbps (10MBps) Ultra-Wide SCSI: 320Mbps (40MBps) Ultra-Wide-2 SCSI: 640Mbps (80MBps)

17. Data Communications (E&T2760): USB and IEEE 1394 17 1394 Topologies: daisy-chain and tree

18. Data Communications (E&T2760): USB and IEEE 1394 18 1394 Cable Up to 4.5m long Six wires: –two power conductors plus two shielded twisted pairs for: Data (Signal Pair A) Strobe (Signal Pair B, = data XOR clock) –iLink: only 4 wires. The two power conductors are not included. –the entire cable is also shielded

19. Data Communications (E&T2760): USB and IEEE 1394 19 1394 Cable and Connector

20. Data Communications (E&T2760): USB and IEEE 1394 20 1394 Data Transfers Line coding: NRZ –at the receiver, the data and strobe signals are XORed to regenerate the clock signal Two types: 1)Asynchronous one way, low bit-rate asynchronous stream used for control purposes 2)Isochronous high bit-rate synchronous stream guarantees the pre- determined data transfer rate

21. Data Communications (E&T2760): USB and IEEE 1394 21 Where to Get More Information USB –www.usb.orgwww.usb.org –http://www.cypress.com/usb/index.htmlhttp://www.cypress.com/usb/index.html IEEE 1394 –www.1394ta.org/Technology/Links/index.htmwww.1394ta.org/Technology/Links/index.htm