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7/29/2019 USB Good Info1

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USBUniversal Serial Bus

Basic Protocol

&

Verification Methodolgy of USB block


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USB

USB COMMUNICATION LAYERS

1. PHYISICAL LAYER

2. PROTOCOL ENGINE LAYER

3. APPLICATION LAYER

USB PROTOCOL

1. TRANSFER TYPE

2. PACKET FORMAT


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FRAMES

What is a Frame ?


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Frames


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The Fundamental Packet

All communications on the USB are organized into small packets.

Four types of packets:

Token, Data, Handshake, and Special.

Each packets consists of 3 parts:

Start (SYNC), information and end.


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Packet Types

NYET (No Response Yet)0110

STALL Handshake1110

NAK Handshake1010

ACK Handshake0010

Handshake

MDATA1111

DATA20111

DATA11011

DATA00011

Data

SETUP Token1101

SOF Token0101

IN Token1001

OUT Token0001

Token

Packet IdentifierPID ValueGroup


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Four Data flow Types

ExamplesMax size

HS

Max size

FS

Max size

LS

Importantattributes

Type

Systemcontrol

64648Quality +time

Control

Audio, video30721023-timeIsochronous

Printer,scanner

51264-QualityBulk

Mouse,keyboard

3072648Quality +time

Interrupt


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USB Data Transfer Types

Interrupt - A device like a mouse or a keyboard, which will be sending very

little data, would choose the interrupt mode.

Bulk - A device like a printer, which receives data in one big packet, uses t

bulk transfer mode. A block of data is sent to the printer (in 64-byte chunks)

and verified to make sure it is correct.

Isochronous - A streaming device (such as speakers) uses the isochronou

mode. Data streams between the device and the host in real-time, and ther

is no error correction.

As devices are enumerated, the host is keeping track of the total bandwidththat all of the isochronous and interrupt devices are requesting. They can

consume up to 90% of the 480 Mbps of bandwidth that is available. After 90

is used up, the host denies access to any other isochronous or interrupt

devices. Control packets for bulk transfers use any bandwidth left over.


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Control Transfer


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Bulk Transfer

IN transfer - in which the host asks for data from the device - data

flow direction is from the device into the host.

OUT transfer - in which the host whishes to send data to the device -

data flows from the host out to the device.


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Bulk Transfer - OUT


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Bulk IN transfer


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Interrupt Transfer


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Isochronous Transfer


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Enumeration

When a device is attached, the OS enumerates the device, identifiesits driver, and assigns an address to it.

In the numeration process, data structures (transfer descriptors)contain information needed by the host to generate transactions. Thisinformation includes:

USB device address.

Type of transfer.

Direction of transfer (write or read).

Transfer size (# of bytes).

Speed.

Address of the device drivers memory buffer.


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Enumeration Steps

Getting the device descriptor.

Setting an address.

Getting the device descriptor again.

Getting the configuration descriptor.

Selecting the device driver.

Setting the configuration.


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Transaction Format

Control Transfer

SET_ADDRESS : setting a permanent address to afunction.

GET_DEVICE_DESCRIPTOR: the host wishes to get thedevice descriptor, which contains details concerning the

device - how many configurations, interfaces it has, isthe device is self/ bus powered etc.

GET_CONFIGURATION_DESCRIPTOR: the host wishes tolearn about a specific configuration of a device.

GET_CONFIGURATION: the host detects whichconfiguration is active at the moment in the device.

SET_CONFIGURATION: the host sets a specificconfiguration on the device.


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USB Verification Diagram

DUT

USB_SLM

Denali

Testcase.in

USB IO

Flash Cache 8051

PHUB DMA

PFSUB

Testcase.c

tst.v

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