USB - Wikipedia
`
`WIKIPEDIA
`
`Page i of}:
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`USB
`
`USB, short for Universal Serial Bus, is an giggstman‘dflard that was developed to define cables, connmtors and protocols for
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`connection, communication, and power supply between personal computers and their peripheral devices.
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`Universal Serial Bus (USB)
`you.
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`USB was designed to standardize the connection of compote; EtePQEFQJE (including keyboards, pointiggmd‘eliges, digital cameras,
`printers, portable media £13355, giggggjyes and network adapters) to gersoflcomputerns, both to communicate and to supply ejegtn'c
`
` and
`pwg. it has largely replaced interfaces such as s
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`LEW-» and has become commonplace on a wide range of devices.
`
`USB connectors have replaced other types for ‘oatterxglfirgefi ofportable devices.
`
`CEBT’VIEB
`
`Certified USB logo
`Bus
`
`Type
`
`Released in 1996, the USE standard is currently maintained by the y§_B__l_nlglementer§_,EQ§pg_l (USE IF).
`
` Contents
`Overview
`Objectives
`Limitations
`History
`Version history
`Release versions
`Power related specifications
`USB 1.x
`USB 2.0
`USE 3.x
`System design
`Device classes
`Media Transfer Protocol
`058 mass storage 1 USB drive
`Human interface devices
`Device Firmware Upgrade
`
`Production history
`Designer
`Compaq. DEC. iBM,
`Intel. Microsoft. NEC.
`and NM“
`January 1996
`
`Designed
`3
`Since May 1996“]
`: Produced
`liSuperseded Serial port, parallel
`I
`port, game port,
`Apple Desktop Bus,
`i
`Fig/2 port and
`i
`MagSafe
`.
`!
`.
`9
`General specrficatlons
`4 Length
`2—5 m (5 ft 7 in—‘lfi ft
`i
`5 in) (by category)
`i Width
`12 mm (type-AW
`8 45 mm (type-E)
`6.8 mm (mini/micro)
`8.25 mm (type—C)
`
`4.5 mm (type—mm
`735 mm (Wpe'Bl
`10.44 mm (type~B
`SuperSpeed)
`1.8-3 mm
`.
`.
`.
`(mlnllrnlcro)
`2.4 mm (type-C)
`Yes
`
`Yes
`4 wires plus shield
`9 wires plus shield
`(SuperSpeed)
`4: 1 power, 2 data. 1
`ground
`
`11(P
`
`5 (On-The-Go)
`9 (SuperSpeed)
`were -
`SuperSpeed)
`24 (type-C)
`Unique
`Electrical
`5 v Dc
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`+0.25
`5.00 —O.60 \li
`+0 25
`5.00 -0.55 V (USE
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`3 0)
`20.00 V (PD)
`
`0.5 A (USB 2.0)
`0.9
`_
`A (USB 3 0)
`1.5 A (BC 1.2)
`
`Height
`
`Hot
`pluggable
`External
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`Connector
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`Connectors
`Connector properties
`Durability
`Compatibility
`Connector types
`t
`S Iandard connectors
`Mini connectors
`Micro connectors
`OMTP standard
`USB 3.0 connectors and backward compatibility
`USB—C
`USB On-The-Go connectors
`Host and device interface receptacles
`Pinouts
`c I Proprietary connectors and ionnats
`o are
`Cabling
`Power
`USB Battery Charging
`Accessory charging adaptors (ACA)
`Power Delivery (PD)
`Mobile device charger standards
`in China
`OMTP/GSMA Universal Charging Solution
`EU smartphone power supply standard
`Nan-standard devices
`PcweredUSB
`Signaling (use PHY)
`
`Sleep-and—chargeports
`
`Signaling rate (transmission rate}
`Transaction latency
`
`Electrical specification
`Line transition s13te
`Signaling state
`Line state (covering USB 1.x and 2.x)
`.
`-
`Transmissmn
`Transmission example on a USB 1.1 full-speed device
`USB 2.0 speed negotiation
`use 3.0
`
`https ://en.wikipedia.org/Wiki/USB
`
`HTC EXHIBIT 1033
`HTC America. Inc. v. Virginia-Innovation l/7/2018
`Selences, Inc.
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`IPR2017-000874
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`Protocol layer
`Hardshaw oackets
`Tcken caskets
`CJT, lN, SET-JP, and Dlit-3 token packets
`SOF: Start-ot-f-‘a'ne
`SSPLIT and CSDLIT: start-salt trarsaczie't and ccc‘p'ete scl‘: transaction
`Data oaeKers
`PRE packet (tells hubs te temperarily switch to low speed mode)
`Transaction
`OUT transaction
`lN transaction
`SETUP transaction
`Setup packet
`Control transfer exchange
`Audio streaming
`Comparisons with other connection methods
`FireVWe
`Ethernet
`MIDI
`eSATAIeSATAp
`Thunderbolt
`_
`_
`interoperability
`t d
`Rela a standards
`See also
`f r noes
`Re e e
`Further reading
`External links
`
`Pin 1
`Pin 2
`
`Pin 3
`
`2g
`
`Spin 4
`
`USB—A 3,‘ Gen
`
`ports
`
`Overview
`
`Objectives
`The Universal Serial Bus was developed to simplify and improve the interface be:ween personal computers and peripheral devices, when compared with previously existing standard
`or ad-hoc proprietary inter-faces. M
`
`From the computer user's perspective, the USB interface improved ease of use in several ways. The USB interface is self—configuring, so the user need not adjust settings on the
`device and interface ’c: speed or da:a format, or configure interrupts, input/output addresses, or direct memory access channels. ’5] USB connectors are standardized at the host, so
`any peripheral can use any available socket. USB takes full advantage of the additional processing power that can be economically put into peripheral devices so that they can
`manage themselves; USB devices often do not have user-adjustable interface settings. The USB interface is "hot pluggable", meaning devices can be exchanged without rebooting the
`host compuler. Small devices can be powered directly from the USB interface, displacing extra power supply cablesl Because use of the USB logos is only permitted after compliance
`testing, the user can have confidence that a USB device will work as expected without extensive interaction with settings and configuration; the USB interface defines protocols for
`recovery from common errors, improving reliability over previous interfaces. :4] Installation of a device relying on the USB standard requires minimal operator action. When a device
`is plugged into a port on a running personal computer system, it is either entirely automatically configured using existing device drivers, or the system prompts the user to locate a
`driver which is then installed and configured automatically,
`
`For hardware manufacturers and snfcvare developers, the USB standard eliminates the requirement to develop proprietary interfaces to new peripherals. The wide range of transfer
`speeds available from a USB interface suits devices ranging from keyboards and mice up to streaming video interfaces. A USB interface can be designed to provide the best available
`latency [or time-critical functions, or can be set up to do background transfers of bulk data with little impact on system resources. The USB interface is generalized with no signal
`lines dedicated to only one function of one device. I"
`
`Limitations
`USB cables are limited in length, as the standard was meant to connect to peripherals on the same table—top, not beaveen rooms or between buildings. However, a USB port can be
`connected to a gateway that accesses distant devices, USB has a strict "tree" topology and "master-slave" protocol for addressing peripheral devices; peripheral devices cannot
`interact with one another except via the host, and two hosts cannot communicate over their USB ports directly. Some extension to this limitation is possible through "USB On The
`Go". A host cannot "broadcast" signals to all peripherals at once, each must be addressed individually. Some very high speed peripheral devices require sustained speeds not
`available in the USB standard. 14' While converters exist between certain "legacy" interfaces and USB, they may not provide full implementation of the legacy hardware; for example,
`a USB to parallel port convert r may work well with a printer, but not with a scanner that requires bi—directional use :5 the data pinsl
`
`https://en.wikipedia.org/Wiki/ U SB
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`3 A {type-C}
`Up to 5 A tPD‘i
`_
`.
`Data
`Packet data, defined
`by specifications
`
`‘l hlt
`1.5; 12; 480; 5,000;
`10,000; 20,000 Mhitls
`(depending on mode)
`
`127
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`The type—A plug (left) and type-8
`plug (right)
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`USB - Wikipedia
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`Page 3 of 30
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`For a product developer, use of USE requires implementation of a complex protocol and implies an "intelligent" controller in the peripheral device. Developers of USB devices
`intended for public sale generally must obtain a USB ID which requirs a fee paid to the Implementers' Forum. Developers of products that use the USB specification must sign an
`agreement with Implementer's Forum. Use of the USE logos on the product require annual fees and membership in the organization. "1
`
`History
`
`
`
`
`
`USB logo on the head of a standard
`A plug
`
`.
`.
`The has}: USE indent [09°
`
`la]
`
`A group of seven companies began the development of USB in 1994: £95an, DEG, IBM;
`Intel, 1
`’grgsflgft, NEE, and Mtg!” The goal was to make it fundamentally easier to connect
`external devices to PCs by replacing the multitude of connectors at the back of PCs, addressing
`the usability issues of existing interfaces, and simplifying software configuration of all devices
`connected to USB, as well as permitting greater data rates for external devices. A team
`including Malian worked on the standard at
`IntelWe} the first integratedmglguhs
`supporting USE were produced by Intel in 1995.110]
`The original USB 1.0 specification, which was introduced in January 1996. defined data
`transfer rates of 1.5 ways Low Speed and 12 Mbit/s Full Speed)“:I Microsoft Windows Q5&SR 2.1 provided OEM support for the
`devices. The first widely used version of USB was 1.1, which was released in September 1998. The 12 Mbit/s data rate was intended for higher—speed devices such as disk drives, and
`the lower 1.5 Mbit/s rate for low data rate devices such asjpystiplts." I] Applelgg's iMac was the first mainstream product with USB and the iMac'S success popularized USB itself‘m‘
`Following Apple's design decision to remove all lflgflrtg from the iMac. many PC manufacturers began building mgjrgeflligs, which led to the broader PC market using USB
`as a standard.“3[‘"[‘5‘
`
`The USB 2.0 specification was released in April 2000 and was ratified by the y§§mllnplemgptgrgl§grpn1 (USE—IF) at the end of 2001. gewlett—Packargl, Intel. Lpggtjlfgghnologies
`[now Nokia), NEC, and 2.13119; jointly led the initiative to develop a higher data transfer rate, with the resulting specification achieving 480 Mbit/s, 40 times as fast as the original
`L'SE 1.1 specification.
`
`The USE 3gp specification was published on 12 November 2008. Its main goals were to increase the data transfer rate (up to 5 Ghit/s), decrease power consumption, increase power
`
`version is also called Supchpecdl‘al The first USE 3.0 equipped devices were presented in January 2010.['a][‘9’
`
`As of 2008, approximatelyo billion USB ports and interfaces were in the global marketplace. and about 2 billion were being sold each year.“
`The USB 3.1 specification was published in July 2013.
`
`In December 2014, USE-IF submitted USB 3.1, USB Power Delivery 2.0 and Uglfl'ype—C specifications to the LE; (19‘1ng — Audio, video and multimedia systems and equipment)
`for inclusion in the international standard IEC 62680 Universal Serial Bus interfacesfor data and power, which is currei
`lybased on USB 2.0.9”
`
`https://en.wikipedia.org/wiki/USB
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`USB - Wikipedia
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`
`
`The USB 3.2 spa- cation was published in September 2017'.
`
`Version history
`
`Release versions
`
`
`Note
`
`- ”W V M » W" W m V
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`mmmmmm
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`; Release Candidate
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`
`
`
`;
`‘ UéEC.é9
`; USE ECRC
`USB 1.0
`
`
`
`
`
`
`
`
`
`
`
`
`isoreer :1: as uses Cer1l231 and usaszeemx
`.’ SuperSpees- (10 Gbitls)
` Aisc referred to as use 3.1 Gen 2 ”3' and use 3.2 Gen 2x1
`SuperSseed+ (23 suit/s)
`< Includes new USB 32 Gen 1x2 and use a.2ae'i 21a multi-Iink modes ”“1
`
`Note
`
`"
`
`'” ”
`
`'
`
`.
`
`‘
`
`'"
`
`’”
`
`Power related specifications
`
`
`
`20 \j E A
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`‘
`
`Release name
`use Battery Charging r o
`usnfleauerywcmrgirig1:,"
`.JSB Battery Charging? A
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`"‘
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`l;
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`2 Release date
`IuMax.power
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`5 New connectorand cable specification
`
`
`
`
`USB 1.x
`
`Released in January 1996, USB 1.0 specified data rates at" 1.5 Mbit/s (Low Bundwidih or Low Speed) and 12 Mbit/s (Full Speediua] It did not allow for extension cables or pass—
`thruugh monitors, due to timing and power limitations. Few USB devices made it to the market until USB 1.1 was released in August 1998. USB 1.1 was the earliest revision that was
`widely adopted and led to what Microsoft designated the "Legacy-free POEM“13111 41“”
`Neither USB 1.0 nor 1.1 specified a design for any connector smaller than the standard type A or type B. Though many designs for a miniaturised type B connector appeared on many
`peripherals, conformance to the USB 1.1: standard was fudged by treating peripherals that had miniature connectors as though they had a tethered connection (that is: no plug or
`socket a: :he peripheral «311:1. There was no known miniature type A connector until USB 2.0 (rev 1.01) introduced on a.
`
`USB 2.0
`
`USB 2.0 was released in April 2000, adding a higher maximum signaling rate of 480 Mbit/s (High Speed or High Bandwidth}, in
`addition to the USB 1.x Full Speed signaling rate of 12 Mbit/s. Due to bus access constraints, the effective throughput of the High Speed
`signaling rate is limited to 280>Mbit/s or 35 MB/s.‘25'
`
`included into the USB 2.0 specification package available from USB.org:W]
`
`Modifications to the USB Specification have been made via Engineering Qhang§_Nptices (ECN). The most important of these ECNs are
`
`CHI ”1‘15 9
`
`,
`The H:—Speec i "- :'
`
`..\._;.--
`
`Some ofthe most significant items included in the change notices include:
`
`
`
`A [.88 2.0 PC] expansion card
`
`https://en.wikipedia.orgi’wiki/‘U SB
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`USB - Wikipcdia
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`- Mini-A and Mini-B Connector
`- Micro-USE Cables and Connectors Specification 1.01
`- 51ng USB Supplement
`I On-The-Ga Supplement 1.3 USB On-The-gg makes it possible for two USB devices to communicate with each other without requiring a separate USB host,
`- Battery Charging Specification 1.1 Added support for dedicated chargers , host chargers behavior for devices with dead batteries.
`- Battery Charging Specification 1.21pm with increased current of 1.5 A on charging ports for unconfigured devices, allowing High Speed communication while having a currentup
`to 1.5 A and allowing a maximum current of 5 A.
`I Link Power Management Addendum ECN which adds a sleep power state.
`
`USB 3.x
`
`The USB 3.0 specification was released on 12 November 2008, with its management transferring from USB 3.0 Promoter Group to the
`S PERS PEED
`USE lmplementersForum (USE-IF), and announcedon 17November 2008 attheSuperSpeedUSB Developers Conferenceps] fl
`USB 3.0 adds a Super-Speed transfer mode, with associated backward compatible plugs, receptacles, and cables. StiperSpeed plugs and
`Gamma u
`receptacles areidentifiedwith a distinctlogoandblueinsertsin standardformatreceptacles. H
`The SuperSpeed mode provides a d“
` The SuperSpead USB logo
`payload throughput is actually 4 Gbit/s, and the specification considers it reasonable to achieve about 3.2 Gbit/s (0.4 Gil/s or 400 MB/s).
`Communication is fvuyll-dupleg in SuperSpeed transfer mode; earlier modes are half—duplex, arbitrated by the host.”III
`
`Low-power and high—power devices remain operational with this standard, but devims using SuperSpeed can take advantage of increased available current of between 150 mA and
`900 mA, respectively.“
`
`‘, released in July 2013, preserves the existing SuperSpeed transfer rate under a new label USB 3.1 Gen 1PM] and introduces a new SuperSpeed+ transfer mode, USB 3.1
`Gen 2 with the maxi mum dagaflsggalipgpatg to 10 Gbit/s (1250 MB/s, twice the rate of USB 3.0), which reduces line encoding overhead to just 3% by changing the gnpodipg scheme
`to 128b/1 2b‘321MI35'
`
`
`[151333, released in September 2017, preserves existing USB 3.1 SuperSpeed and SuperSpeed+ data modes but introduces two new SuperSpeed+ transfer modes ovcr the US “a
`connector with data rates of 10 and 20 Gbit/s (1250 and 2500 MB/s). The increase in bandwidth is a result of multi—lane operation over existing wires that were intended for flipeflop
`capabilities of the Type—C connectori‘fil
`
`
`System design
`
`AUSB system consists of a host with one or more downstream ports, and multiple peripherals, forming a fiered—flampolngy. Additional ySB hubs may be included, allowing up to
`five tiers. A USB host may have multiple controllers, each with one or more ports. Up to 127 devices may be connected to a single host controllerimps' USB devices are linked in
`series through hubs. The hub built into the host controller is the root hub.
`
`A USB device may consist of several logical sub-devices that are referred to as devicefunctions. A composite device may provide several functions, for example, a weggayrn (video
`
`device function] with a built-in microphone (audio device function). An alternative to this is 99.723915;
`3, in which the host assigns each logical device a distinctive address and
`all logical devices connect to a built—in hub that connects to the physical USB cable.
`
`
`
`
`logical vices
`
`‘~
`
`. endpoints m
`the devlce
`
`USB device communication is based on pipes (logical channels). A pipe is a connection from the host controller to a logical entity, found
`on a device, and named an gripping. Because pipes correspond to endpoints, the terms are sometimes used interchangeably. A USB
`device could have up to 32 endpoints (16 IN, 16 OUT), though it is rare to have so many. An endpoint is defined and numbered by the
`device during initiali7ation (the period after physical connection called "enumeraiion") and so is relatively permanent, whereas a pipe
`may be opened and Closed.
`
`There are two types of pipe: stream and message. A message pipe is bi—directional and is used for control transfers. Message pipes are
`typically used for short, simple commands to the device, and a status response, used, for example, by the bus control pipe number 0. A
`stream pipe is a uni-directional pipe connected to a uni-directional endpoint that transfers data using an isochrono‘uslagl interrupt, or
`bulk transfer:
`
`Isochronous transfers
`At some guaranteed data rate (often, but not necessarily, as fast as possible) but with possible data loss
`(e.g., realtime audio or video)
`Interrupt transfers
`Devices that need guaranteed quick responses (bounded latency) such as pointing devices, r_n' e, and keyboards
`Bulk transfers
`
`USB endpotnts reside on the
`connected device: the channels to
`the host are referred to as pipes
`
`Large sporadic transfers using all remaining available bandwidth, but with no guarantees on bandwidth or latency (e.g., file transfers)
`When a host starts a data transfer, it sends a TOKEN packet containing an endpoint specified with a tug]; of (devicciaddr‘ess, endpoint_nun-rbzr). If the transfer is front the host to
`the endpoint, the host sends an OUT packet (a specialimtion of a TOKEN packet) with the desired device address and endpoint numberr If the data transfer is from the device to the
`host, the host sends an [N packet instead. If the destinaljon endpoint is a uni—directional endpoint whose manufacturer's designated direction does not match the TOKEN packet
`(e.g. the manufacturer's designated direction is IN while the TOKEN packet is an OUT packet), the TOKEN packet is ignored. Otherwise, it is accepted and the data transaction can
`start. A biedirec’donal endpoint, on the other hand, accepts both IN and OUT packets.
`
`Endpoints are grouped into interfaces and each interface is associated with a single device function. An exception to this is endpoint zero, which is used for device configuration and
`is not associated with any interface. A single device function composed of independently controlled interfaces is called a composite device. A composite device only has a single
`device address because the host only assigns a device address to a function.
`
`https ://en.Wikipedia.0rg/wiki/USB
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`USB — Wikipcdia
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`When a USB dev'ceIs first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a
`reset signal to the USB device. The data rate of the USB deviceIs determined during the reset signaling. After reset, the USE device's
`information is read by the host and the device is assigned a unique 7-bit address. If the device is supported by the host. the dovicchivers
`needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the
`enumeration process is repeated for all connected devices.
`
`The host controller directs traffic flow to devices, so no USB device can transfer any data on the bus without an arplicit request from the
`X
`N
`'
`
`host controller. In USB 2.0, the host controller polls the bus for traffic, usually in a re
`'n fashion. The throughput of each USB port
`is determined by the slower speed of either the 1.33 port or the USE deviceconnected to the port.
`High-speed USB 2.0 hubs contain devices called transaction translators that convert between high—speed USB 2.0 buses and full and low
`speed buses. There may be one translator per hub or per port.
`
`
`
`TWO USE 3-0 standard A SOCketS
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`Because there are two separate controllers in each USB 3.0 host, USB 3.0 devices transmit and receive at USB 3.0 data rates regardless of USB 2.0 or earlier devices connected to
`that host. Operating data rates for earlier devices are set in the legacy manner.
`
`Device classes
`___—__—_.—__——————————-—-————
`
`Tl“...5functionality of a USB device15 defined by a class code sent to a USB host. This allows the host to load software modules for the device and to support new devices from different
`manufacturers.
`
`Device classes includetlw]
`
`;
`
`Examples, or exception
`
`
`
`Usage
`
`‘ Class
`
`f DeVlCE
`interface
`
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`=Unspecifiedw
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`, USB smart card reader
`
`=:'sccal r-ealr‘ce'e device class [PHDQ 2 Pulse monrtor (watch)
`
`
`Device
`
`Billboard
`
`. Diagnostic DeVIce
`.Both
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`: Describes USE T e-C alternate modes supported by device.
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`-
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`’ USE compliance testing deVIoe
`
`'Bluetooth adapter. Microsoft RNDlS
`:ActiveSync deVIce
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`indicates that a device needs vendor--specific drivers
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`
`
`USB mass storage I USB drive
`QSBJEQSS storage devicegayss (MSC or U'MS) standardizes connections to storage devices. At first intended for magnetic and optical
`drives, it has been extended in support flash dgiyes. It has also been extended to support a wide variety of novel devices as many systems
`can be controlled with the familiar metaphor of file manipulation within directories. The process of making a novel device look like a
`familiar device is also known as extension. The ability to boot a write-looked “SDttard with a USB adapter is particularly advantageous for
`maintaining the integrity and non-corruptible, pristine state of the booting medium.
`Though most personal computers since mid--2004 can boot from USB mass storage devices, USB is not intended as a primary bus for a
`computer's internal storage. How,ever USE has the advantage of allowing hot-swapping, making it useful for mobile peripherals,
`including drives of various kinds.
`First conceived and still used today for optical storage devices (CD-Riv! drives, DVD drives, etc), several manufacturers offer external
`portable USB hard disk drives, or empty enclosures for disk drives. Thcso offcr performance comparable to internal drives, limited by the current number and types of attached USB
`devices. and?"y the upper limit‘f the USB interface. Other competing standards for external drive connectivitynclude eSATA, Frressf‘arl, FireWir’e (IEEE 1394), and most
`recentlylhJn’del‘bgli.
`
`A flash drive, a tyolcel USB mass-
`storage Comes
`
`'1 '2;
`
`https://cn.vvikipedia.org/wiki/USB
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`USB — Wikipedia
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`Another use for USB mass storage devices is the portable execution of software applications (such as web browsers and VoIP clients) with
`no need to install them on the host computer.[“"‘5'
`
`Media Transfer Protocol
`
`ft to give highcrelcvcl access to a device's filcsystcm than USB mass storage, at
`Media Transfer:253399.91 (MTP) was designed by Micro
`the level of files rather than disk blocks. It also has optional 13311311: features. MTP was designed for use with portable mediaplagerg, but it
`has since been adopted as the primary storage access protocol of the An
`peratipgjystgrn trom the version 4.1 Jelly Bean as well as
`
`Windows Phone 8 (Windows Phone 7 devices had used the Zune protocol—an evolution of MTP). The primary reason for this is that MTP
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`operating systems.
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`Human Interface devices
`
`Joysticks, keypads, tablem and other human-interface devices (HIDs) are also progressively migrating from MIDI, and PC garnep‘oi: connectors to USB.
`
`USB mice and keyboards can usually be used with older computers that have 3%wnnectors with the aid of a small USB—to—PS/2 adapter. For mice and keyboards with dual—
`protocol support, an adaptor that contains no logic circuitgy may be used; the hardware in the USB keyboard or mouse is designed to detect whether it is connected to a USB or PS/z
`port, and communicate using the appropriate protocol. Converters also exist that connect PS/2 keyboards and mice (usually one of each) to a USB port.“ These devices present two
`
`troller to perform bidirectional data translation between the two standards.
`HID endpoints to the system and use a tn;
`
`Device Firmware Upgrade
`Device Finnware Upgrade (DFU) is a vendor— and device—independent mechanism for upgrading the Err-33511;; of USB devices with improved versions provided by their
`manufacturers, oflering (for example) a way to deploy firmware bug fixes. During the firmware upgrade operation, USB devices change their operating mode effectively becoming a
`23.0.3.1. programmer. Any class ofUSB device can implement this capability by following the official DFU specificationswflmp’a’
`
`In addition to its intended legitimate purposes, DFU can also be exploited by uploading maliciously crafted firmware that causes USB devices to spoof various other device types; one
`such exploiting approach is known as EQQ‘QSQJM
`
`Connectors
`The three sizes of USB connectors are the default or standard format intended for desktop or portable equipment, the mini intended for mobile equipment , and the thinner micro
`size, for low—profile mobile equipment such as mobile phones and tablets. There are five speeds for USB data transfer: Low Speed, Full Speed, High Speed (from version 2.0 of the
`specification), §yperSpeed [from version 3.0], and SuperSpced+ (from version 3.1). The modes have differing hardware and cabling requirements. USB devices have some choice of
`implemented nioda, and USB version Is not a reliable statement ofimplemented modes. Modes are identified by their names and icons, and the specifications suggests that plugs
`and receptacles be colour-coded (Super-Speed is identified by blue).
`
`Unlike other data buses (such as Ethernet), USB connections are directed; a host device has "downstream" facing ports that connect to the "upstream" ports of devices. Only
`downstream facing ports provide power; this topology was chosen to easily prevent electrical overloads and. damaged equipment. Thus, USB cables have different ends: A and B,
`with different physical connectors for each. Each format has a plug and receptacle defined for each of the A and B ends. USB cables have plugs, and the corresponding receptacles are
`on the computers or electronic devices. in common practice, the A and is usually the standard format, and the B side varies over standard, mini, and micro. The mini and micro
`formats also provide for Esggpfligg with a hermaphroditicAB receptacle, which accepts either an A or a B plug. On-The—Go allows USB between peers without discarding the
`directed topology by choosing the host at connection time; it also allows one receptacle to perform double duty in space-constrained applications.
`
`Connector properties
`The connectors the USB committee specifies support a number of L'SB's underlying goals, and reflect lessons learned from the many
`connectors the computer industry has used. The female connector mounted on the host or device is called the receptacle, and the male
`connector attached to the cable is called the plug!” T5”
`
`By design, it is difficult to insert a USB plug into its rcccptaclc incorrectly. The USB spccification rcquircs that the cable plug and
`receptacle be marked so the user can recognize the proper orientation. [5”] The type-C plug is reversible. USB cables and small USB
`devices are held in place by the gripping force from the receptacle, with no screws, clips, or thumb—turns as other connectors use.
`
`
`
`The different A and B plugs prevent accidentally connecting two power sources. However, some of this directed topology is lost with the
`advent of multi-purpose USB connections (such as fibgnflhggo” in smanphones, and USE-powered Wi-Fi routers), which require
`A-tfl-A, 340-3, and sometimes Y/splitter cables. See the 15”]; QniIJLe-Gp connectors section below for a more detailed summary
`description. There are cables with A plugs on both ends, which may be valid if the cable includes, for example, a USB host-tc-host transfer
`dcvicc with 2 portslszl
`
`Type-A plug and, 55 part Of :- non-
`standard cable. receptacle
`
`Durability
`The standard connectors were designed to be more robust than many past connectors. This is because USB is hot—Emmi; and the connectors
`would be used more frequently, and perhaps with less care, than previous connectors.
`
`Standard USE has a minimum rated lifetime of 1,500 cydes of insertion and removal,“ the mini-USE receptacle increases this to 5,000 cycles,”1
`and the newer Micro-USES” and USE-C receptacles are both designed for a minimum rated lifetime of 10,000 cycles of insertion and removalls‘]
`To accomplish this, a locking device was added and the leaf-spring was moved from the jack to the plug, so that the most-stressed part is on the
`cable side of the connection. This change was made so that the connector on the less arpensive cable would bear the mostyeggfssusal
`
`
`
`USE extension cable
`
`https://en.wikipedia.0rg/wiki/USB
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`In standard USE, the electrical contacts in a USB connector are protected hy an adjacent plastic tongue, and THE entire connecting assembly is usually protected by an enclosing
`metal shel
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`
`The shell on the plug makes contact with the receptacle before any of the internal pins. The shell is typically grounded, to dissipate static electricity and to shield the wires within the
`connector.
`
`The micro format has the highest designed insertion lifetime. The standard and mini connectors have a design lifetime of 1,500 insertion-removal cycles,“ the improved Mini-B
`connectors increased this to 5,000. The micro connectors were designed with frequent charging of portable devices in mind, so have a daign life of 10,000 cycleslss] and also place
`the flexible contacts, which wear out sooner, on the easily replaced cable, while the more durable rigid contacts are located in the receptacles. Likewise, the springy component of the
`retention mechanism. parts that provide required gripping force, were also moved into plugs on the Cable sidedfifii
`
`Compatibility
`
`‘13:
`or compliant USE connectors to mmimzze physical incompatibilities it: cc:nectc-rs trcrr ”
`also cet‘nes
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`cent ports are not block ‘. Compliant ie .395 II:
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`
`Con nector types
`USB connector types multiplied as the specification progressed The original USB specification detailed
`standard-A and standard—B plugs and reoeptaclesfl‘he connectors were different so that users could not
`connect one computer receptacle to another. The data pins in the standard plugs are recessed compared to
`the power pins,so that the device can power up before estab