1. PC Peripherals for Technicians
Mar 1998
PC Peripherals for Technicians
Chapter 1.3 -
Interfaces: USB
(Universal Serial Bus)
Systems Manufacturing Training and Employee Development
Copyright © 1998 Intel Corp.
Rev. 2.0 Sys MFG Training/Employee Development

2. PC Peripherals for Technicians
Mar 1998
USB Overview
OBJECTIVES: At the end of this section, the student will be able to do the following:
List features & applications of the Universal Serial Bus
Explain the Topology of the USB
Describe USB Cables and Connections
Discuss USB Bus transactions
Rev. 2.0 Sys MFG Training/Employee Development

3. Why Universal Serial Bus?
PC Peripherals for Technicians
Mar 1998
Why Universal Serial Bus?
Historically adding functionality to the PC has been problematic for the user:
Limited external standard ports:
Serial; Parallel
Add-in card configuration:
Dip switches; jumper cables; IRQ settings; DMA channels; I/O addresses; software drivers.
PC User Experience:
Time consuming; high-risk; fear of system crashing
USB allows simpler addition of peripherals to PC's.
Projected to replace many existing peripheral-to-host protocols (e.g. RS-232), allowing many peripherals to connect to PC through the same type of port.
Rev. 2.0 Sys MFG Training/Employee Development

4. Why Universal Serial Bus?
PC Peripherals for Technicians
Mar 1998
Why Universal Serial Bus?
Initially, USB is an addition to existing interfaces.
BEFORE AFTER ...
Gradual Transition
USB Connectors
Graphics
Port
LAN
USB
Keyboard
Mouse
Serial
Parallel
SCSI
Sound
/Game
Modem
Rev. 2.0 Sys MFG Training/Employee Development

5. Universal Serial Bus - Overview
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Overview
USB is a bi-directional, dynamically attachable, host-driven serial interface for adding peripheral devices on a single bus.
USB uses a single connector for keyboards, mice, serial devices, digital audio, printers, etc.
The USB provides a new serial protocol for sending data between a PC and peripherals.
USB enables low & medium speed I/O devices to be connected without card insertions or reconfiguration.
USB was jointly developed by Compaq, Digital Equipment, IBM, Intel, Microsoft, NEC, and Nortel.
The USB specification is royalty-free and openly available.
Rev. 2.0 Sys MFG Training/Employee Development

6. Universal Serial Bus - Features
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Features
USB Features Summary:
Plug & play “outside the box”
Supports hot-plugging
Supports up to 127 devices
Single connector across all devices
Up to 5 meters per cable segment
Built-in power distribution
12 Mb/s throughput--for highest performance
Low-speed option (1.5 Mb/s)--for lowest cost
2-wire differential signaling
Asynchronous and isochronous support
Rev. 2.0 Sys MFG Training/Employee Development

7. Universal Serial Bus - Features
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Features
Allows virtually unlimited expansion “outside the box.”
Can connect up to 127 daisy-chained devices.
Breaks the traditional log jam associated with the limited number of serial and parallel expansion connectors or PC card slots available for port expansion.
Supports hot-plugging:
Enables devices to be connected to the PC without card insertions, reconfiguration or powering down the computer.
Dynamic insertion-removal and autoconfiguration on change.
If the devices and the OS support Plug and Play, the appropriate device drivers can automatically load and unload without user intervention.
Rev. 2.0 Sys MFG Training/Employee Development

8. Universal Serial Bus - Features
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Features
USB employs a “one-size-fits-all” industry-standard connector and socket interface
Cables have only 4 wires, allowing compact connectors.
USB cable +5-volt power distribution eliminates the need for AC power supply boxes for low/bus-powered devices.
Data transfer rate of 12Mbits/second supports a wide variety of desktop peripherals:
Low-speed 1.5 Mbit/second option supports low-end, low-speed devices such as key-boards and mice for further cost reduction.
Isochronous transfers (such as audio), get top priority, assuring that time-sensitive data streams are not interrupted.
Rev. 2.0 Sys MFG Training/Employee Development

9. Universal Serial Bus - Applications
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Applications
USB eliminates need for mouse port, keyboard port, and eventually for serial and parallel ports
Keyboard, mouse, trackball
Printers and scanners
Game peripherals (Joystick)
Modem or ISDN/PBX interface
4x & 6x CD ROM drives and floppy drives
Digital audio interface - Eliminates need for an analog audio connection for speakers and microphones.
Speakers and microphones could be built into monitor.
Monitor - Control Only (Contrast, Brightness, Colors, etc.)
Video Signals are not managed (uses separate connection)
Rev. 2.0 Sys MFG Training/Employee Development

10. Universal Serial Bus - Applications
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Applications
USB in 1997:
An incremental Connector for new applications
1394.x Optional Add-in Card
Keyboard
Mouse
Serial
Port
Parallel
1394.x
Sound/Game
Ports
Graphics
LAN
Modem
USB
1394.x Card
Telephony, Modem,
Kyb, Mouse, Joystick,
Still/ Motion Camera,
Digital Audio,
Backup Store,
Printer, Scanner,
Wireless Adapters
Digital
Video,
Consumer
Electronics,
Storage
USB Future:
The PC evolves into a simpler, easier to use appliance.
Rev. 2.0 Sys MFG Training/Employee Development

11. Universal Serial Bus - Applications
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Applications
USB and IEEE1394 Are
Complementary Technologies
Digital VCR
DVD-RAM
DV Camcorder
“NIC”
DSS
Keyboard
Mouse
Joystick
Phone
1394 Domain
Video Conf
Camera
Audio
Personal Printers
Tape Backup
Floppy
USB Domain
Rev. 2.0 Sys MFG Training/Employee Development

12. Universal Serial Bus - Applications
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Applications
USB Focus on Low Cost, High Volume Applications
USB is targeted at devices requiring relatively low bandwidth (10Mb/s or less).
The USB, tiered star approach is cheap for downstream nodes, but requires a central host.
IEEE 1394 is more expensive and has a different design focus.
IEEE 1394 (FireWire) has no central host, and therefore requires a complete controller at each node.
IEEE 1394 is targeted at applications requiring 100Mb/s+ bandwidth which is not needed for most PC peripherals.
Digital VCRs and other consumer electronics require the bandwidth provided by IEEE 1394.
Rev. 2.0 Sys MFG Training/Employee Development

13. Universal Serial Bus - Topology
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Topology
The Universal Host Controller is integrated into the PIIX3 (and later) PCI-ISA Expansion Bridge chips. S C I B U
LAN
Adapter
SCSI
Host Bus
PCI Bus
Graphic
CPU
CPU Local Bus
Host
/PCI
Bridge
Memory Bus
Keyboard
(Hub)
Monitor
USB Host
Ctlr (e.g PIIX3)
(Root Hub)
Tape
Disk CD
ROM
Mouse
Speakers
USB
Port
Main
Memory
Rev. 2.0 Sys MFG Training/Employee Development

14. Universal Serial Bus - Topology
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Topology
Host: Initiates all transactions under software control.
Hub: Provides connecting ports and power.
Device: A Peripheral that attaches to the USB. 5m
Host
Hub
Device
Rev. 2.0 Sys MFG Training/Employee Development

15. Universal Serial Bus - Topology
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Topology
The USB physical interconnect is a tiered star topology.
Each segment is a point-to-point connection between the host and a hub/device, or a hub connected to another hub or device.
A hub is at the center of each star.
Up to 5 meters per segment
Up to 127 devices
Up to 6 tiers
Host (Root Tier)
Tier 1
Tier 2
Tier 3
Tier 4
Hub 1
Hub 2
Port
Host
Hub 3
Hub 4
RootHub
USB has the concept of a HUB: A device whose purpose is to allow the connection of additional devices.
Rev. 2.0 Sys MFG Training/Employee Development

16. Universal Serial Bus - Topology
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Topology
Each USB Hub converts a single attachment point into multiple attachment points (ports).
A USB Hub expands a single connection, or port (termed the upstream port), to two or more downstream ports.
Peripherals can act as Hub devices so only 1 peripheral device must be plugged directly into the host PC.
A Hub may have integrated device(s)--the combination is known as a compound device.
A Hub provides attach/detach detection.
A Hub also provides electrical safety services.
Automatically reports to the host every over-current event.
Shuts down the downstream power to all four ports when total load exceeds 400mA.
Rev. 2.0 Sys MFG Training/Employee Development

17. Universal Serial Bus - Topology
PC Peripherals for Technicians
Mar 1998
Universal Serial Bus - Topology
USB supports 100mA and 500 mA current levels.
Max current available is 500mA for bus powered devices.
Minimum current available at a port is 100mA (1 load).
Hubs may be self-powered or bus-powered
Unpowered devices (e.g. mice) can be attached to powered hubs--power distributed over the USB cabling.
A bus-powered hub draws electrical current (500ma) directly from its upstream connection to the USB.
It delivers 100ma to each of its 4 downstream connections, using the remaining power for its own operation.
Note: The USB spec. does not permit the connection of an additional bus-powered hub to one of the downstream ports of a bus-powered hub; the downstream hub must be self-powered (i.e., have its own power supply).
Rev. 2.0 Sys MFG Training/Employee Development

18. USB Cables and Connections
PC Peripherals for Technicians
Mar 1998
USB Cables and Connections
Physical Layer
4 pin connector, 4 wire cable
Supply Sourcing +5V
2-wire differential signaling
CMOS signal 3.3V
In most cases a USB cable should be captive (molded in) to it's peripheral.
The series "A" connector is a plug for a peripheral and a socket for a PC platform.
The series "B" connector (detachable) was created for applications where a captive cable is prohibitive.
Power pair
Differential Signal pair
Rev. 2.0 Sys MFG Training/Employee Development

19. USB Cables and Connections
PC Peripherals for Technicians
Mar 1998
USB Cables and Connections
Connectors
4-Position with shielded housing
Positive Retention
Blind Mating Capabilities
Staggered power/data pins in plug
Insures power will not flow through data lines
Cables have only four wires, allowing compact connectors roughly as wide as a staple.
Small size is important for notebooks & downsized desktop PCs.
Plug
~9.7 mm
~ 8.65 mm +5 D- D+
Gnd
Rev. 2.0 Sys MFG Training/Employee Development

20. USB Cables and Connections
PC Peripherals for Technicians
Mar 1998
USB Cables and Connections
Bi-directional, half-duplex link
The Differential Receiver amplifies the difference between the incoming data lines.
Communication toward the host PC is called upstream
Communication toward the devices is called downstream. - + D+ D-
Rcv Data
Differential Receiver
Xmt Data
Differential Driver
USB Cable
Upstream Port (HUB)
e.g. PC
Downstream Port
e.g. Digital Video Camera
Rev. 2.0 Sys MFG Training/Employee Development

21. USB Cables and Connections
PC Peripherals for Technicians
Mar 1998
USB Cables and Connections
5 meters max
...
+5V
GND D+ D-
Cables: AWG for power; 28 AWG for signaling
Full-Speed--Twisted & Shielded cable
USB runs at 12 Mbit / sec Full Speed (F.S.) bit rate
Low-Speed Mode--Unshielded & Untwisted cable
1.5 Mbit / sec Low Speed (L.S.) bit rate (1.5Mbps sub-channel)
Saves EMI suppression costs and allows very-low-cost devices to be built without compromising data rate for faster devices.
Mice, keyboards, and most other user interface peripherals don’t need fast data rate.
Rev. 2.0 Sys MFG Training/Employee Development

22. USB Cables and Connections
PC Peripherals for Technicians
Mar 1998
USB Cables and Connections
Device Connect Detection D- D+ R1
R1 = 15KW ±5%
R2 = 1.5KW ±5%
Twisted Pair, Shielded
Untwisted, Unshielded
F.S./L.S. USB
Transceiver
(45W Outputs)
Host or
Hub Port
ZO = 90 W
5 Meters Max.
F.S. USB
Hub Port 0 or
Full Speed Function R2
3 Meters Max.
Low Speed Function
Differential signal pair
Rev. 2.0 Sys MFG Training/Employee Development

23. USB Cables and Connections
PC Peripherals for Technicians
Mar 1998
USB Cables and Connections
Pull-down resistors on the D+ and D- lines ensure that both data lines are near ground when no device is attached.
USB devices have a pull-up resistor on either D+ or D-
When D+ (Full Speed) or D- (Low Speed) rise above 2VDC for longer than 2.5 us, the HUB recognizes device attachment.
Host software periodically polls each HUB to check for device attachment and detachment
Full Speed Device Connect Detection
Device
Connected D- D+
Connect
Detected
VOH (min)
VIH (max)
VIL (min)
VOL (max)
VSS
³ 2.5 ms
Rev. 2.0 Sys MFG Training/Employee Development

24. PC Peripherals for Technicians
Mar 1998
USB Bus Transactions
USB uses 7 bits to address each device on the bus.
The USB Host Controller broadcasts tokens on the bus and a device that detects a match on the address in the token responds by either accepting data or sending data to the host.
HUB
HOST/HUB
Monitor
Speaker
Pen
Mouse
Kbd
Mic
Phone PC
USB has automatic address selection, no terminators, and locations on the bus are arbitrary.
Rev. 2.0 Sys MFG Training/Employee Development

25. PC Peripherals for Technicians
Mar 1998
USB Bus Transactions
USB transfers data at regular intervals called frames.
All bus activity is controlled and directed by the host.
Four transfer types (Control, Interrupt, Bulk, Isochronous) enable a variety of peripherals:
Control (e.g.: Configuration, Messages)
Bi-directional; Used for bus management, configuration, device control, & status information.
Interrupt (e.g.: Keyboard, Mouse, Joystick)
Designed to support Human Input Devices (HID) such as joysticks, mice, & keyboards.
Used to poll devices to see if they have data to transfer.
Asynchronous, non periodic, low bandwidth, response time sensitive.
Rev. 2.0 Sys MFG Training/Employee Development

26. PC Peripherals for Technicians
Mar 1998
USB Bus Transactions
Bulk (e.g.: Printer, Scanner, Still camera)
Enables devices like printers to communicate large amounts of data as bus bandwidth becomes available.
Stream, NO guaranteed bandwidth.
Asynchronous, non periodic, high bandwidth utilization.
Used for data that may be bursty, less time-sensitive.
Isochronous (e.g.: Audio, Telephony)
Isochronous transfers get top priority, assuring that time-sensitive data streams are not interrupted.
Unidirectional, no handshake, no guaranteed delivery.
Based on time slices rather than handshaking.
No retry in the event of delivery failure or error.
Media access controlled by host.
Rev. 2.0 Sys MFG Training/Employee Development

27. PC Peripherals for Technicians
Mar 1998
REVIEW & SUMMARY
USB Features
Plug & play “outside the box”
Up to127 devices; Hot-plugging; Autoconfig. on change
Single connector across all devices
Built-in power distribution; 2-wire differential signaling
12 Mb/s throughput--for highest performance
Low-speed option (1.5 Mb/s)--for lowest cost
Asynchronous and isochronous support
USB Applications
Telephony, Modem, Kyb, Mouse, Joystick, Still/ Motion Camera, Digital Audio, Printer, Scanner, 4x/6x CD ROM, Floppy drives, & Monitor (control only).
Rev. 2.0 Sys MFG Training/Employee Development

28. PC Peripherals for Technicians
Mar 1998
REVIEW & SUMMARY
USB Topology
Tiered Star (Distributes Connectivity Points)
127 devices + host
Up to 6 tiers (up to 5 meters per segment)
USB Cables and Connections
2-wire differential signaling
Supply Sourcing +5V
4 pin connector, 4 wire cable
Power pair
Differential Signal pair
Rev. 2.0 Sys MFG Training/Employee Development

29. PC Peripherals for Technicians
Mar 1998
REVIEW & SUMMARY
USB Bus transactions
Media access controlled by host
Speed: 12Mbps full speed; 1.5Mbps sub-channel
Four transfer types enable a variety of peripherals:
Control (e.g.: Configuration, Messages)
Interrupt (e.g.: Keyboard, Mouse, Joystick)
Bulk (e.g.: Printer, Scanner, Still camera)
Isochronous (e.g.: Audio, Telephony)
BEFORE AFTER ...
End of Chapter 1-3
Rev. 2.0 Sys MFG Training/Employee Development