Universal Serial Bus is... An industry-wide cable bus standard (developed in 1995) that allows up to 127 plug-and-play serial devices to be daisy chai

Transcription

1 Lab 6-3 The Universal Serial Bus Copyright 2006 Heathkit Company, Inc. All Rights Reserved 1

2 Universal Serial Bus is... An industry-wide cable bus standard (developed in 1995) that allows up to 127 plug-and-play serial devices to be daisy chained to one port on a PC. It allows for fast, bi-directional communication between a host computer and hot-pluggable peripherals. It makes adding peripherals to a PC as easy as plugging headphones into a stereo. 2

3 USB Features and Advantages 3

4 Feature... It s an external expansion bus using cables (completely outside the PC). Users and computer technicians do not have to open the computer to add peripherals. Peripherals are daisy-chained using cables. Heathkit PC Tools 4

5 Advantage... Computer expansion up to this point has been limited by the number of serial or parallel ports or expansion cards. Not any more. Users can daisy chain up to 127 peripherals to a single port. 5

6 Advantages... Simple Installation Simply plug it in Peripheral is automatically configured for immediate use. This makes sharing peripherals easy. 6

7 Advantage... USB peripherals transfer data at a relatively fast 12 megabits per second. The typical serial port transfers data at about 100 kilobits per second. USB is 120 times faster than the standard Serial Port. 7

8 Advantage... Host quizzes peripheral How much power is needed? Supply the power or generates a message Often eliminates a separate power supply for the peripheral. 8

9 Advantage... The user can t plug the USB peripheral in wrong. The USB bus uses standardized connectors to prevent plugging devices in wrong. It cannot be done. 9

10 Advantage... USB allows for five meter (15 foot) cables between peripherals. That should make it easy to reach that printer across the room. 10

11 USB Peripherals 11

12 USB Peripherals The Ordinary... Storage Drives and Devices Printers, Scanners Modems NICs Input devices such as Mice, Joysticks, Keyboards, Graphics Tablets Multimedia Game Equipment 12

13 USB Peripherals The Not So Ordinary... Digital Cameras Biometric Security Devices Multi-User Games Digital Audio Devices Hubs CTI Devices Telephony (PBX, Digital Telephones) 13

14 The USB Flash Drive 14

15 USB Hard Drive 15

16 16

17 USB Card Reader 17

18 USB Components Host The Computer is the Host 18

19 USB Components - Host Data traffic cop for the USB bus. Controls the movement of data Responsible for the USB bus control functions Only one Host in a USB system Host may have a couple USB ports 19

20 USB Components - Function A Function is a device that provides capabilities to the Host. A Function might be a keyboard, a mouse, or some other device... A bus-powered device gets all its power from the USB cable. Self-powered devices have their own power supply. 20

21 Hub Plugs into Host or other Upstream Device USB Devices plug into Ports 21

22 Component Examples Function (with built-in Hub) Host Function Hub Function Scanner Function 22

23 Types of Data Transfers Control - Configuration, status, commands... How much power do you need? 23

24 Isochronous Types of Data Transfers Interrupt - For HIDs (Human Interface Devices) that need to transfer data infrequently in small amounts (like a mouse, joystick...) Bulk 24

25 USB Cable has Four Wires Vbus D+ :Data D- Gnd :+5 Volts DC to power USB devices :Data :Ground 25

26 Outer Jacket USB Cable Shield Vbus (+5VDC) Gnd D- D+ Twisted Pair 26

27 Low-Speed Cable Does not require D+ and D- to be a twisted pair. Does not require the shield. 27

28 USB Connector Shapes (Plugs and Sockets) Rectangular Connectors Square Connectors 28

29 Mini-USB Connectors 29

30 Mini-USB 2 30

31 What s the main difference between the USB 1.1 Spec and the USB 2.0 Spec? 31

32 Speed! 12 Mbits/sec x 10 = 120 Mbits/sec 12 Mbits/sec x 40 = 480 Mbits/sec...and the good news for users is that USB 2.0 is backwards compatible with USB

33 USB versus FireWire 33

34 USB versus FireWire (IEEE-1394) Both are cable expansion buses. Both use a small cable with peripherals that are hot-pluggable. Both use daisy chaining to connect peripherals. USB s top speed is 480 megabits/second while FireWire runs at 100, 200, and 400, and 800 megabits/second. 34

35 USB versus FireWire (IEEE-1394) continued... FireWire cable has 6 conductors (4 data/clocks and 2 power) while USB has 4 conductors (2 power and 2 data). USB 2.0 is aimed primarily at the PC peripheral market while FireWire is used for computer interfaces to consumer electronic products like digital camcorders, VCRs, digital televisions, and other audio visual products. 35

36 USB Devices 36

37 Where to Find More USB Information 37

38 38

39 Now, it s your turn. 39