USB Specification Introduction

EVS1
Wu, TJ
IEC961063
2014/01/13
Inventec Confidential 2
USB Products
USB Products
- Why USB?
• Ease of use.
• Various application are implemented via the common protocol
channel.
• Support Hot plug-in/out.
• Lower cost of implementation.
• Port Expansion :
– Max. support up to 127 devices for a host.
• Backward compatible.
What’s USB
- End user ‘s view

PC side Device side

USB
interface

End user ‘s view of USB is direct and simple as

a lot of and various applications.
What’s USB
- Engineering ‘s view
Job management

Function execution :
Ex: Word file, video file, MP3…
etc.

USB device configuration :

Ex: Device attach/remove
detection ,
Device type(1.0/1.1/2.0/3.0/3.1)
USB physical Transaction
interface:
Ex: Cable, Connector
*USB 2.0 and USB 3.x have the
same communication structure
concept except different HW
implementation and protocol.
 What’s USB
- Engineering ‘s view
• The composition of USB :
– Host side:
• Client Software
– Ex: MS Office, Windows Media Player…etc.
• USB System Software
– Configure the device and handle data transmission.
• Host Controller
– Arrange the attachment/Removal of USB device,

– Device side:
• Function
– Ex: Office document, MP3,..etc.
• USB Logical Device
• USB Bus Interface
– Signal transaction interface.

• The communication between USB system software & USB logical Device is independen
t with which between Client Software and Functions.
– That is why USB have various application in real.
 What’s USB
- Engineering ‘s view
USB Topology (I) : Physical topology
1. Tiered star topology with
Max. Support 127 devices.
(7bits Device Address)

2.Tier 7 can’t be attached

with Hub.

3. Red line connection

is forbidden.

4.When Hub is removed,

all function(device) on the Hub
will be removed, too.
 What’s USB
- Engineering ‘s view
USB Topology (II) :
-HW / Logical / Function topology of USB.

USB Bus interface L USB Device Layer Function Lay

ayer er
What’s USB
- Engineering ‘s view
• Current Summary:
– USB is a “common communication bridge” between different client
software and USB device function.

– Function logically communicate with client software directly, but it uses USB
bus to transfer data in physical.

– Similar example : Win RAR or Win Zip

USB 2.0
USB 2.0
- Introduction

USB 2.0(High Speed) is

backward compatible with
USB 1.0(Low speed) and
USB 1.1(Full Speed).
 USB 2.0
- Mechanical Structure
• USB 2.0 uses 4-wire cable for data transfering. D+/D- have 90Ohm differential
impedance.

• USB 2.0 connector types:

at
rec
ep
D ed
USB 2.0
- Coding
• NRZI coding :
– SE0: Both D+/D- are at low level state.
– 0 : J/K state reverse
– 1 : J/K state keep as-is.
– SE1: Both D+/D- are at high level state.
USB 2.0
- Detection
• 8bits (00000001) sequence is used for USB 1.1/1.0 device detection &
synchronization.
– Pull high D+ 1st : Full speed device
– Pull high D- 1st : Low speed device
USB 2.0
- Detection
• Chirping : Negotiate high speed device
– A device that is HS capable first connects as an FS device (D+ pulled high), but upon
receiving a USB RESET (both D+ and D− driven LOW by host for 10 to 20 ms) it pulls
the D− line high (800mV), known as chirp K.
– The device has to receive at least three sets of KJ chirps before it changes to high
bandwidth terminations and begins high bandwidth signaling.
 USB 2.0
- Data transaction
• USB 2.0 is polled bus, token-based transaction :
– If USB device has information need pass to host, it has to wait host controller polls it.
– Host possesses the right to arrange all USB device’s transaction.
• Transaction Flow : 1. Token Packet

2. data Packet

3. Hand-shake Packet

Write Operation Read Operation

USB 2.0
- Data transaction
Transfer type of USB
• 4 main type of data transfer type of USB
– Control transfer
• USB definition data format.
• Use by USB system SW(host side) to configure the USB device.
• Lossless Data Delivery.
• EX : USB device initialization

– Bulk transfer
• Non-USB definition data format
• Support devices that need to communicate relatively large amounts of data at highly variable
times where the transfer can use any available bandwidth.
• Larger amount of data transfer, without limited-latency assurance.
• Ex: Scanner, printer, file transaction.
Transfer type of USB
• 4 main type of data transfer type of USB (cont’d)
– Interrupt Transfer
• Non USB definition data format
• Support those devices that need to send or receive data infrequently but with bounded
service periods.
• Allow a limited-latency data transfer.
• Ex: Joystick, Keyboard, Mouse
– Isochronous Transfer
• Non USB definition data format
• Support isochronous sources and destinations
• Continuous, Real time data transfer
• Ex: Voice con-call, webcam, video…etc.

• Additional data transfer type :

– Split transaction
• Support the transaction of USB 1.0/1.1 device which are attached to high USB 2.0 Hub.
USB 3.X
USB 3.x
- Introduction
• Basically, USB 3.x has similar communication
structure and concept with USB2.0.

• USB3.x utilize Dual Bus Architecture and

Mechanical connector to both backward and
forward compatibility with USB 2.0.
– Backward compatibility:
• USB 3.x connector is capable of being attached with USB 2.0
device.
– Forward Compatibility:
• USB 2.0 connector is capable of being attached with USB 3.x
device.
• Implemented by Connector Mechanical structure

• USB 2.0 and 3.x Data transaction are

independent.
 USB 3.x
- Mechanical Structure
• USB 3.x use 8 wire cable to transfer data.
• D+/D- are used for non-USB 3.x transaction, SSRX+/SSRX- and SSTX+/SSTX- are used
for USB 3.x transaction.
USB 3.x
- Mechanical Structure

Type A

Type B

Micro
Super speed

Non-Super speed
USB 3.x
-Synchronization (detection)
• Rx Detection for USB 3.x device detection.
– USB 3.0 uses LFPS (Low Frequency Periodic Signaling) for device detection.

– USB 3.1 uses SCD1/SCD2 (SS+ Capacity Declaration) for device detection.
USB 3.x
- Super speed Data transaction
• USB 3.x Separate data transfer with IN/OUT
• Host still own the right to arrange the transaction.
• IN means Data To Host (Read Data)
• OUT means Data From Host (Write Data)
 USB 3.x
- Super speed Data transaction
IN transfer

2. Device immediately
1. Host sends handshake- transfer the data to host
packet to device (contain
token packet content) to
inform device sent the
data.

3. Host sends a ACK-packet

to device for next
transaction.
USB 3.x
- Super speed Data transaction
OUT Transfer
2.Device receive the
data and return a ACK
packet to host.

1. Host sent data

packet directly, and
token packet was
incorporated into
data packet already.
USB 3.0
- Super speed Data transaction
• Difference between USB2.0 and 3.x in data transaction:
– USB 2.0 use “Token”, “Data” & ”Handshake” packet to accomplish a transaction, USB 3.x
simplify the Token packet during transaction.

– USB 2.0 is half-duplex transaction; USB 3.x is dual-simplex uni-cast transaction, which
allow concurrent IN/OUT transaction.

– Because Super speed and non-super speed bus are parallel, so they can active
simultaneously.
Comparison of USB 2.0 & 3.x
USB 3.x
- Type C connector
• 24-pin double side reversible-plug connector
• Alternative mode (compatible with Display Port, MHL3.0, PCI-E…..)
• Support Power Delivery 2.0
USB 3.x
- Type C connector
• Compatible with Display Port, MHL3.0, PCI-E

DP signals are fully compatible to USB type C

connector
USB 3.x
- Type C connector
• Compatible with Display Port, MHL3.0, PCI-E
– Example of USB 3.1 / DP 1.2 ( Full feature )
USB 3.x
- Type C connector
• Compatible with Display Port, MHL3.0, PCI-E
– Example of USB 3.1 / DP 1.2 ( Alternative Mode)
USB 3.x
- Type C connector
• Compatible with Display Port, MHL3.0, PCI-E
– Example of USB 3.1 / PCI-E (x1) Docking ( Alternative Mode)
USB 3.x
- Type C connector
• Support Power Delivery 2.0 :
USB Battery Charge 1.2
• Battery Charge 1.2 :
– SDP (Standard Downstream Port):
• Current limitation and low voltage charging protection
• 500mA max
– CDP (Charging Downstream Port):
• Charging current < 900mA while data transferring
• 500mA ~ 1.5A_max
– DCP (Dedicate Downstream Port): 1.5A max
• 500mA ~ 1.5A max
• Data transferring is not available in DCP mode.
• Charging mode detection :
Device set D+
D- = 0.25 ~ 0.4 V
SDP
= 0.5 ~ 0.7 V

D- > 0.4 V Set D -= 0.5~ 0.7V D+ = 0.25 ~ 0.4V CDP

D+ > 0.4V
DCP
Primary Detection Secondary Detection
USB Power Delivery
• Multiple Profiles from 5V/2A (10W) ~ 20V/5A (100W)
• Using 24MHz BPSK coded transmission on Vbus for power configuration protocol.
 USB test items
Test Items Test Equipment EVS1 Test capability Note
SCD1/SCD2
1. For Type C connector USB test, new test fixture(e.g. C
LFBS
There is not test to A Adaptor) is required.
SSC 16GHz Scope(min) with test software package
Electrical software package 2. For Type C compatible PCI-E/DP test, New test fixture(
Eye Diagram
e.g. Spliter) is required.
TP1
USB 3.1
Rx test Pert/ J-bert/ AWG 12.5GHz J-bert need upgrade
CV Test USB-IF test fixture N/A
IOP USB-IF SS+ IOP Golden device N/A
Waiting USB-IF release test standard
B.C. USB-IF SS+ BC Golden device N/A
Link Layer USB Analyzer N/A
LFPS
SSC
13GHz Scope (min) with test software package V
Electrical Eye Diagram
TP1
USB 3.0 Rx test Pert/ J-bert/ AWG 6.5GHz V
CV Test USB-IF test fixture X
IOP USB-IF SS IOP Golden devices X
B.C. USB-IF SS BC Golden devices X
Link Layer USB Analyzer ( Lecroy & Ellesys) X
Eye Diagram 4GHz Scope (min) with test software package V
Chirp USB-IF test fixture V
Electrical Droop USB-IF test fixture V
USB 2.0
Inrush current
USB-IF test fixture V
(device only)
USB 2.0 IOP USB-IF USB 2.0 IOP Golden devices V
Chargin mode detection
V
B.C 1.2 (Protocol) test Allion USB Charging/Protocol/Electrical Tester(UCPET)
Chargin current test V
P.D. 2.0 unknown N/A N/A Waiting USB-IF release test standard
USB IOP
Interoperabili
ty

Inventec Confidential 40
Question and
Answer
Thank You
Reference
• USB Specification
• USB B.C 1.2
• USB Type C Specification
• USB Power Delivery Specification
• VESA DP-USB Type C Alternative mode overview
• Wiki – USB