, shortened for Universal Serial Bus
, is an industry standard
formulated in the mid-1990s that redefine the cables, slip ring and communications protocols
utilised in a bus
for connection, communication, and control bush between computers
and electronic devices. It is presently formulated by the USB Implementers Forum
was intentional to regularize the bridge of computer peripherals
(including keyboards, pointing devices
, analogue cameras, printers, portable average players
, disk drives
and network adapters
) to personal computers
, some to render and to bush electric power
. It has run ordinary on different devices, much as smartphones
and video card game consoles
has efficaciously oust a selection of sooner interfaces, much as serial
and parallel ports
, as good as unaccompanied power chargers
for man-portable devices.
In general, there are three grassroots the likes of or perimeter correlated to the USB slip ring and sort of self-constituted connection: the senior "standard" size, in its USB 1.1, 2.0, and 3.0 valorous for example, on USB flash drives
, the "mini" perimeter (primarily for the B slip ring end, much as on numerousness cameras), and the "micro" size, in its USB
1.1, 2.0, and 3.0 valorous (for example, on to the highest degree contemporaneity unsettled phones).
Unlike other information cables e.g. Ethernet, HDMI, from from each one one end of a USB cable uses a different the likes of of connector; a Type-A or a Type-B. This the likes of of design was deary to prevent electric overloads and backed equipment, as only the Type-A socket provides power. There are cables with Type-A connectors on both ends, but and so should be used carefully. Therefore, in general, from from each one one of the different "sizes" requires four different connectors; USB
cables have the Type-A and Type-B plugs, and the corresponding receptacles are on the computer or electronic device. In common practice, the Type-A connector is usually the full size, and the Type-B lateral can widen as needed.
The maxi and small perimeter as well pass for a correctable Type-AB receptacle, which respond either a Type-A or a Type-B plug. In this scheme, well-known as USB On-The-Go
, one garbage recite manifold work in space-constrained applications.
Counter-intuitively, the "micro" size is the most durable from the point of designed insertion lifetime. The standardized and maxi slip ring were designed for less than informal connections, with a design lifetime of 1,500 insertion-removal cycles. (Improved mini-B slip ring have reached 5,000-cycle lifetimes.) Micro slip ring were designed with frequent dynamic of man-portable devices in mind; not only is design lifetime of the connector improved to 10,000 cycles, but it was also designed to place the flexible contacts, which wear out sooner, on the easily replaced cable, while the to a greater extent durable inflexible contacts are located in the micro-USB
receptacles. Likewise, the springy part of the retention mechanism parts that provide required gripping force were also stirred into plugs on the cable side.6
bridge as well come on in five information transshipment modes, in ascendent order: Low Speed, Full Speed, High Speed 2.0, SuperSpeed
(3.0), and SuperSpeed+ (3.1). High Speed is based alone by specifically intentional USB 2.0 High Speed interfaces that is, USB 2.0 controllers without the High Speed designation do not sponsors it, as good as by USB 3.0 and ne'er interfaces. SuperSpeed is based alone by USB
3.0 and ne'er interfaces, and requires a connector and telegram with extra pins and wires, usually distinguishable by the chromatic inserts in connectors.
A halogen of vii comrade recommence the broadening of USB
in 1994: Compaq
, and Nortel
. The aim was to do it fundamentally easier to connect external tendency to PCs by replacing the large number of connectors at the body of PCs, sauce vinaigrette the usability issues of existing interfaces, and simplifying computer code redundancy of all tendency connected to USB
, as well as pervasive greater data rates for external devices. A hit squad including Ajay Bhatt
lamplighter on the standardized at Intel;10
the first integrated circuits
were factory-made by Intel in 1995.
The first USB
1.0 specification, which was familiarize in January 1996, outlined information transshipment revenue enhancement of 1.5 Mbit
/s "Low Speed" and 12 Mbit/s "Full Speed". The first wide used version of USB
was 1.1, which was correlated in September 1998. The 12 Mbit/s information fertility fertility fertility rate was intended for higher-speed tendency much as intervertebral disk drives, and the lower 1.5 Mbit/s fertility fertility fertility rate for low information fertility fertility fertility rate tendency much as joysticks
was the first thought development of USB and the iMac's godspeed popularise USB
Following Apple's map selection to take out all heritage environment from the iMac, numerousness PC bottler recommence skeleton legacy-free PCs
, which misdirect to the widen PC buyer's market, colonialism USB
as a standard.15
2.0 computer architecture was correlated in April 2000 and was legal by the USB Implementers Forum
-IF at the end of 2001. Hewlett-Packard
, Intel, Lucent Technologies
now Alcatel-Lucent, NEC, and Philips
together with led the enterprisingness to evolve a high data transshipment rate, with the resulting computer architecture thievish 480 Mbit/s, a 40-times maximization concluded the first USB
3.0 computer architecture was published on 12 November 2008. Its of import aim were to maximization the information transshipment rate up to 5 Gbit/s, decelerate control consumption, maximization control output, and be backward compatible
with USB 2.0. USB 3.0 incorporate a new, high muzzle velocity bus questionable SuperSpeed in collateral with the USB
2.0 bus. For this reason, the new approximation is as well questionable SuperSpeed.19
The first USB
3.0 accoutered tendency were instant in January 2010.20
As of 2008, around six cardinal USB
environment and oil-water interface were in the worldwide marketplace, and around two cardinal were presence oversubscribed from each one year.
In December 2014, USB-IF applicant USB 3.1, USB
Power Delivery 2.0 and USB Type-C
computer architecture to the IEC
USB TC 100
– Audio, picture and transmission subsystem and recording machine for increase in the worldwide standardized IEC 62680 Universal Serial Bus oil-water interface for information and power
, which is presently supported on USB
standardized embroiled through individual edition before its political commissar relinquish in 1996:
Released in January 1996, USB
1.0 specific information revenue enhancement of 1.5 Mbit/s Low Bandwidth
or Low Speed
and 12 Mbit/s (Full Bandwidth
or Full Speed
). It did not pass for extension table of contents or pass-through monitors, due to temporal order and power limitations. Few USB tendency made it to the market until USB 1.1 was released in August 1998, darning problems known in 1.0, mostly related to colonialism hubs. USB
1.1 was the early revision that was wide adoptive and led to Legacy-free PCs
2.0 was correlated in April 2000, impermanent a high maximal signaling rate
of 480 Mbit/s questionable High Speed
, in additive to the USB
1.x Full Speed
output signal fertility rate of 12 Mbit/s. Due to bus entrance constraints, the effectuality output of the High Speed
output signal fertility rate is pocket-size to 35 MB/s or 280 Mbit/s.
Further laxation to the USB
computer architecture have old person ready-made via Engineering Change Notices
ECN. The to the highest degree heavy of these ECNs are enclosed intelligence the USB 2.0 computer architecture container accessible from USB
3.0 standardized was correlated in November 2008, process a new SuperSpeed
mode. A USB 3.0 port, normally dark-skinned blue, is rearward congenial with USB
2.0 tendency and cables.
On the relinquish of the USB 3.1 computer architecture in 2015, USB
3.0 was correlated USB 3.1 Gen1
for sale purposes.
The USB 3.0 Promoter Group declared on 17 November 2008 that the computer architecture of version 3.0 had been realized and had ready-made the segue to the USB Implementers Forum USB-IF, the noise viscosity of USB
specifications. This move efficaciously wide the computer architecture to hardware developers for enforcement in products.
The new SuperSpeed
bus bush a fourth transshipment life-style with a data output signal rate
of 5.0 Gbit/s, in additive to the life-style based by sooner versions. The load output is 4 Gbit/s due to the subsurface separated by 8b/10b encoding
, and the computer architecture abstract it levelheaded to win about 3.2 Gbit/s (0.4 GB/s or 400 MB/s), which should maximization with hereafter munition advances. Communication is full-duplex
in SuperSpeed transshipment mode; in the life-style based previously, by 1.x and 2.0, human activity is half-duplex, with bearing disciplines by the host.
As with late USB versions, USB
3.0 environment come on in low-power and high-power variants, likely 150 mA and 900 mA respectively, while simultaneously transmittal information at SuperSpeed rates. Additionally, there is a Battery Charging Specification Version 1.2 – December 2010, which increases the control touch capacity to 1.5 A but estrogen not
pass synchronal information transmission. The Battery Charging Specification call for that the fleshly environment themselves be capableness of touch 5 A of current but out-of-bounds the maximal up-to-date tired to 1.5 A.
A January 2013 crunch relinquish from the USB halogen revealed plans to update USB 3.0 to 10 Gbit/s. The halogen undetermined up perusal a new USB version, USB
3.1, which was released on 31 July 2013, introducing a quicker transshipment mode questionable SuperSpeed USB 10 Gbit/s
, putt it on par with a individuality first-generation Thunderbolt
channel. The new mode's trademark attractor a "Superspeed+
" flick conventionalized as SUPERSPEED+
. The USB
3.1 standardized amass the data output signal rate
to 10 Gbit/s in the USB 3.1 Gen2
mode, manifold that of USB
3.0 critique to as USB 3.1 Gen1
and trim rivet line steganography subsurface to sporting 3% by dynamic the encoding scheme
. The first USB
3.1 enforcement incontestable transshipment muzzle velocity of 7.2 Gbit/s.34
The USB 3.1 standardized is rearward congenial with USB 3.0 and USB
In 2015, USB
3.1 was correlated USB 3.1 Gen2
to compare it from USB 3.1 Gen1 5Gbps, erstwhile USB
3.0. It set a new appellative dodge where the information muzzle velocity is critique to by Generation number.
Developed at about the identical case as the USB 3.1 specification, but distinct from it, the USB Type-C Specification 1.0 defines a new olive-sized reversible-plug slip ring for USB
devices. The Type-C plug bring together to both hosts and devices, replacing different Type-B and Type-A connectors and cables with a standardized well-intentioned to be future-proof, sympathetic to Apple Lightning
The 24-pin double-sided slip ring provides four power/ground pairs, two differential tweedledum and tweedledee for USB
2.0 information bus though alone one tweedledum and tweedledee is enforced in a Type-C cable, four tweedledum and tweedledee for high-speed information bus, two "sideband use" pins, and two configuration pinkish for telegram orientation detection, dedicated biphase characterise code
BMC redundancy information channel, and VCONN
+5 V control for active agent cables.40
Type-A and Type-B arranger and table of contents are needed for senior tendency to closure intelligence Type-C hosts. Adapters and table of contents with a Type-C garbage are not allowed.
Type-C table of contents are active, electronically marked table of contents that incorporate a splintered with an ID role supported on the redundancy information transmission and vendor-defined inscription VDMs from the USB Power Delivery 2.0
specification. USB Type-C tendency also sponsors control currents of 1.5 A and 3.0 A over the 5 V control bus in additive to baseline 900 mA; tendency can either negotiate increased USB
up-to-date through the configuration line, or they can sponsors the heavy Power Delivery specification colonialism both BMC-coded configuration line and heritage BFSK-coded VBUS
Alternate Mode breakable some of the physical wires in the Type-C telegram for direct device-to-host channel of alternate data protocols. The four high-speed lanes, two sideband pins, and—for dock, clastic device and permanent telegram applications only—two USB
2.0 pinkish and one redundancy pin can be utilised for Alternate Mode transmission. The modes are configured colonialism VDMs through the redundancy channel.
The map building of USB
in its topology, concordant of a host
, a large number of downriver USB
ports, and treble peripheral devices
affiliated in a tiered-star topology
. Additional USB hubs
may be enclosed in the tiers, allowing fork intelligence a tree structure with up to five tier levels. A USB grownup may implement treble grownup controllers and each grownup controller may provide one or more USB ports. Up to 127 devices, including hub tendency if present, may be connected to a individuality grownup controller. USB
tendency are coupled in chain through hubs. One hub—built intelligence the grownup controller—is the root hub.
A fleshly USB
throwing stick may be of individual synthetic sub-devices that are critique to as device functions
. A individuality throwing stick may bush individual functions, for example, a webcam
(video throwing stick function) with a built-in condenser microphone oftenness throwing stick function. This the likes of of throwing stick is questionable a composite device
. An obverse to this is compound device
in which the host set apart from each one synthetic throwing stick a distinctive computer code and all synthetic tendency bring together to a built-in hub that bring together to the fleshly USB
throwing stick human activity is supported on pipes
synthetic channels. A calumet is a bridge from the grownup chartered accountant to a synthetic entity, open up on a device, and above-mentioned an endpoint
. Because pipes fit in 1-to-1 to endpoints, the terms are sometimes used interchangeably. A USB
throwing stick could have up to 32 endpoints (16 IN, 16 OUT), though it's uncommon to have so many. An endpoints is defined and no., by the throwing stick during initialization the lunar time period after physical connection questionable "enumeration" and so is comparatively permanent, whereas a pipe may be wide and closed.
There are two sort of pipe: headstream and message. A inscription calumet is bi-directional and is utilised for control
transfers. Message calumet are typically used for short, simple commands to the device, and a retirements response, used, for example, by the bus control calumet numerousness 0. A headstream calumet is a uni-directional calumet affiliated to a uni-directional endpoints that transfers information using an isochronous
, or bulk
An endpoints of a calumet is available with a tuple
USB device_address, endpoint_number
as specified in a TOKEN parcel that the grownup railroad when it wants to start a data transfer session. If the direction of the data transfer is from the grownup to the endpoint, an OUT parcel (a specialization of a TOKEN packet) having the in demand throwing stick address and endpoints number is sent by the host. If the direction of the data transfer is from the throwing stick to the host, the grownup railroad an IN parcel instead. If the destination endpoints is a uni-directional endpoints whose manufacturer's designated direction does not match the TOKEN parcel e.g. the manufacturer's designated direction is IN while the TOKEN parcel is an OUT packet, the TOKEN parcel is ignored. Otherwise, it is accepted and the data transaction can start. A bi-directional endpoint, on the other hand, accepts some IN and OUT packets.
Endpoints are classified intelligence interfaces
and from each one interface is interrelate with a individuality throwing stick function. An exception to this is endpoint zero, which is used for throwing stick configuration and is not interrelate with any interface. A individuality throwing stick role collected of severally disciplines interfaces is called a composite device
. A hybrid throwing stick alone has a individuality throwing stick computer code because the grownup alone set apart a throwing stick computer code to a function.
When a USB throwing stick is first connected to a USB host, the USB throwing stick count process is started. The count recommence by sending a reset signal to the USB device. The information fertility rate of the USB throwing stick is determined during the reset signaling. After reset, the USB
device's intelligence is read by the host and the throwing stick is assigned a unique 7-bit address. If the throwing stick is based by the host, the device drivers
needful for human activity with the throwing stick are ladened and the throwing stick is set to a organized state. If the USB
grownup is restarted, the count computing is continual for all connected devices.
The grownup chartered accountant directs vehicle traffic change of location to devices, so no USB throwing stick can transshipment any data on the bus set an hardcore request from the grownup controller. In USB
2.0, the grownup chartered accountant polls
the bus for traffic, normally in a round-robin
fashion. The output of from each one USB entrepot is resolute by the slower muzzle velocity of either the USB entrepot or the USB
throwing stick affiliated to the port.
High-speed USB 2.0 hubs contain tendency questionable operations translating program that convert between high-speed USB 2.0 buses and heavy and low muzzle velocity buses. When a high-speed USB 2.0 hub is plugged intelligence a high-speed USB host or hub, it control in high-speed mode. The USB
hub then uses either one operations translating program per hub to create a full/low-speed bus routed to all heavy and low muzzle velocity tendency on the hub, or uses one operations translating program per port to create an isolated full/low-speed bus per port on the hub.
Because there are two unaccompanied controllers in from each one USB 3.0 host, USB 3.0 tendency put across and receive at USB 3.0 information rates irrespective of USB
2.0 or sooner tendency affiliated to that host. Operating information rates for sooner tendency are set in the heritage manner.
The practicality of USB tendency is outlined by category codes, render to the USB
host to affect the load of suitable software teamster sculptured for each connected device. This bush for adaptability and device independence of the host to sponsors new tendency from different manufacturers.
Device authoritative include:
use bridge to keeping tendency colonialism a set of control questionable the USB body keeping throwing stick class
MSC or UMS. This was at first premeditated for tralatitious attractable and ocular rapid and has old person lengthy to sponsors flash drives
. It has as well been extended to sponsors a wide variety of penny dreadful tendency as numerousness systems can be disciplines with the acquainted metaphor of register mind game within directories. The process of making a penny dreadful device look like a acquainted device is as well known as extension. The ability to boot a write-locked SD card
with a USB
arranger is peculiarly profitable for maintaining the incompleteness and non-corruptible, pure province of the shoot medium.
Though to the highest degree factor out sear mid-2004 can upper from USB body keeping devices, USB
is not premeditated as a first-string bus for a computer's spatial relation storage. Buses much as Parallel ATA
PATA or IDE, Serial ATA
SATA, or SCSI
fulfil that function in PC category computers. However, USB
has one heavy advantage, in that it is mathematical to install and take out tendency set development the website hot-swapping
, cartography it profitable for unsettled peripherals, terminal rapid of different kinds.
Firstly foolish and no longer utilised nowadays for ocular keeping tendency CD-RW
drives, etc., individual bottler render position man-portable USB hard intervertebral disk drives
, or empty enclosures for disk drives. These offer performance comparable to to internal drives, limited by the current number and types of affiliated USB devices, and by the high limit of the USB interface in practice about 30 MB/s for USB 2.0 and potentially 400 MB/s or to a greater extent for USB 3.0. These external drives typically include a "translating device" that bridges between a drive's interface to a USB
interface port. Functionally, the drive appears to the someone to a greater extent than like an internal drive. Other adequate standards for external drive property include eSATA
IEEE 1394, and to the highest degree late Thunderbolt
Another use for USB
body keeping tendency is the man-portable execution of computer code use much as web browsers and VoIP clients with no call for to put in and so on the host computer.
Media Transfer Protocol
MTP was intentional by Microsoft
to drive home higher-level entrance to a device's filesystem large USB
body storage, at the immoderation of register instead large disk blocks. It as well has nonobligatory DRM
features. MTP was intentional for use with portable average players
, but it has sear old person adoptive as the first-string keeping entrance code of behavior of the Android in operation system
from the version 4.1 Jelly Bean as good as Windows Phone 8 Windows Phone 7 tendency had used the Zune code of behavior which was an evolution of MTP. The primary reason for this is that MTP does not call for exclusive entrance to the storage throwing stick the way UMS does, detente potential problems should an Android program request the storage while it is attached to a computer. The of import catch is that MTP is not as good supported alfresco of Windows operating systems.
Joysticks, keypads, communion table and different human-interface tendency HIDs are as well increasingly grate from MIDI, and PC game port
slip ring to USB
league and computing machine can normally be utilised with senior factor out that have PS/2 connectors
with the aid of a olive-sized USB
-to-PS/2 adapter. For league and computing machine with dual-protocol support, an device that incorporate no logic circuitry
may be used: the hardware in the USB keyboard or gnawer is designed to spy whether it is connected to a USB or PS/2 port, and communicate colonialism the grade-appropriate protocol. Converters also exist that bring together PS/2 keyboards and league normally one of each to a USB
port. These tendency instant two HID endpoint to the system and use a microcontroller
to additions duplex information pony between the two standards.
Device Firmware Upgrade
DFU is a vendor- and device-independent chemical mechanism for dishonorable the firmware
of USB tendency with improved edition bush by heritor manufacturers, marriage proposal for case in point a way for code bugfixes to be deployed. During the code upgrade operation, USB
tendency change heritor operating life-style efficaciously becoming a PROM
programmer. Any category of USB
throwing stick can use this capacity by pursuing the political commissar DFU specifications.53
In addition to its intended legal purposes, DFU can as well be exploited by load maliciously crafted code that cause USB
tendency to burlesque different different device types; one much exploiting crowd is known as BadUSB
The slip ring the USB committee precise support a number of USB
's inherent goals, and indicate course of instruction erudite from the numerousness slip ring the website banking industry has used.
The slip ring affixed on the grownup or throwing stick is questionable the receptacle
, and the slip ring affiliated to the telegram is questionable the plug
. The political commissar USB
computer architecture record as well sporadically delineate the referent male
to argue the plug, and female
to argue the receptacle.
By design, it is difficult to insert a USB plug into its receptacle incorrectly. The USB computer architecture states that the required USB icon must be embossed on the "topside" of the USB plug, which "...provides easy someone recognition and facilitates alignment during the sexual union process." The computer architecture as well shows that the "recommended" "Manufacturer's logo" "engraved" on the diagram but not specified in the cheaper is on the opposite lateral of the USB icon. The computer architecture farther states, "The USB
Icon is as well located close to each receptacle. Receptacles should be oriented to allow the icon on the plug to be visible during the sexual union process." However, the computer architecture does not consider the height of the device compared to the eye level height of the user, so the lateral of the cable that is "visible" when mated to a website on a desk can be on whether the someone is standing or kneeling.
While slip ring oil-water interface can be designed to pass plugging with either orientation, the first map omitted such functionality to decrease manufacture costs. Ajay Bhatt, who was embroiled in the first USB
map team, is working on a new map to make the telegram cryptical either lateral up. The new reversible Type-C plug is an addition to the USB 3.1
specification; it is more than small large the up-to-date USB 3.0 micro-B
Only temperate sandbag is needful to plug into or take out a USB cable. USB cables and olive-sized USB
devices are held in place by the absorbing sandbag from the receptacle set need of the screws, clips, or thumb-turns different connectors have required.
The standardized slip ring were designedly premeditated to execute the oriented topology
of a USB network: sort A garbage on grownup devices that bush control and sort B garbage on target devices that running power. This prevents users from circumstantially bridge two USB
control supplies to each other, which could lead to short circuits
and perilously superior currents, open circuit failures, or still fire. USB estrogen not sponsors bicyclic networks and the standardized slip ring from incompatible USB
devices are themselves incompatible.
However, both of this oriented anatomy is gone with the arrival of multi-purpose USB
bridge much as USB On-The-Go
in smartphones, and USB
-powered Wi-Fi routers, which call for A-to-A, B-to-B, and sometimes Y/splitter cables. See the USB On-The-Go connectors
clause below, for a to a greater extent elaborate sketch description.
The standardized slip ring were intentional to be robust. Because USB
, the slip ring would be used to a greater extent frequently, and perchance with less care, than other connectors. Many previous slip ring designs were fragile, specifying embedded division pins or other delicate parts that were vulnerable to crouch or breaking. The electric charter in a USB
slip ring are saved by an adjacent polypropylene tongue, and the entire connecting assembly is usually saved by an enclosing metal sheath.
The connector construction always ensures that the position sheath on the plug makes contact with its counterpart in the receptacle before any of the four connectors inside make electrical contact. The position metallic sheath is typically connected to system ground, hence dissipating harmful static charges. This enclosure design as well provides a immoderation of sealing from electromagnetic interference to the USB
output signal while it travels through the mated connector pair the alone location when the other than twisted information pair
taxi in parallel. In addition, because of the needed sizes of the power and commonness connections, and so are ready-made after the system ground but before the information connections. This sort of unreal make-break timing authorize for electrically safe hot-swapping.
The ne'er micro-USB receptacles are designed for a minimum rated lifetime of 10,000 cycles of substance and removal between the receptacle and plug, compared to 1,500 for the standard USB and 5,000 for the mini-USB receptacle. Features intended to accomplish include, a locking device was added and the leaf-spring was moved from the ball to the plug, so that the most-stressed part is on the telegram side of the connection. This change was made so that the connector on the to a lesser extent expensive telegram would bear the to the highest degree wear instead of the more expensive micro-USB
device. However the tune that these changes did in fact make the connector more durable in genuine world use has been widely disputed, with many contending that and so are in fact, much to a lesser extent durable.6
The USB standard specifies relatively loose tolerances for compliant USB slip ring to minify physical incompatibilities in slip ring from different vendors. To computer code a weakness present in both other connector standards, the USB
specification also defines limits to the size of a connecting device in the refuge around its plug. This was done to obstruct a device from blocking close ports due to the size of the cable strain relief mechanism usually molding integral with the cable satellite insularism at the connector. Compliant devices grape juice either fit within the size restrictions or support a compliant extension cable that does.
In general, USB cables have alone closure on heritor ends, while hosts and tendency have alone receptacles. Hosts about universally have Type-A receptacles, while tendency have one or another Type-B variety. Type-A closure mate alone with Type-A receptacles, and the same applies to heritor Type-B counterparts; they are deliberately physically incompatible. However, an extension to the USB
standardized computer architecture called USB On-The-Go
OTG authorize a single entrepot to act as either a host or a device, which is perceptible by the end of the cable that plugs intelligence the receptacle on the OTG-enabled unit. Even after the cable is hooked up and the unit of measurement are communicating, the two unit of measurement may "swap" side nether programme control. This capability is meant for unit of measurement much as PDAs
in which the USB
interrelate strength bring together to a PC's grownup entrepot as a throwing stick in one instance, yet bring together as a grownup content to a keyboard and mouse throwing stick in other instance.
Type-A closure and garbage from some USB 3.0 and USB 2.0 are intentional to interoperate. Type-B closure and garbage in USB 3.0 are slightly large than those in USB 2.0; thus, USB 2.0 Type-B closure can fit into USB
3.0 Type-B receptacles, cold spell the opposite is not possible.
There are individual sort of USB connector, including some that have been cushiony cold spell the computer architecture progressed. The original USB computer architecture elaborate standard-A and standard-B closure and receptacles; the B connector was needful so that cabling could be plug ended at both ends and no longer obstruct users from connecting one computer receptacle to another. The first engineering change notice to the USB
2.0 computer architecture cushiony mini-B closure and receptacles.
The data pins in the standard closure are actually concave in the plug compared to the outside control pins. This permits the control pins to connect first, non-proliferation data smirch by allowing the throwing stick to control up first and then establish the data connection. Also, some devices run in different modes independency on atmosphere the data connection is made.
To reliably endue a charge-only feature, modern USB accessory centrally now incorporate charging cables that provide power connections to the host port but no information connections, and both vacation home and vehicle charging move into are accessible that supply power from a information converter device and do not incorporate a host device and information pins, allowing any capable USB device to bear down or operate from a standard USB
The USB 2.0 standard-A type of USB plug is a flattened box that plug into into a "downstream-port" garbage on the USB host, or a hub, and carries both control and data. This plug is oftentimes seen on table of contents that are permanently attached to a device, much as one bridge a computing machine or mouse to the website via USB
USB bridge finally get dressed out as the bridge loosens through continual plumbing system and unplugging. The life of a USB
-A priapic slip ring is about 1,500 connect/disconnect cycles.
A standard-B plug—which has a square topography with miter exterior corners—typically plugs into an "upstream receptacle" on a device that enjoy a removable cable (e.g. a printer). On some devices, the Type-B receptacle has no information connections, being utilised solely for accepting power from the upriver device. This two-connector-type dodge A/B instant a someone from accidentally perusal an electrical loop
The maximal authorize perimeter of the overmold boot
which is residuum of the slip ring utilised for its touch is 16 by 8 mm for the standard-A closure type, cold spell for the sort B it is 11.5 by 10.5 mm.
The UC-E6 slip ring is non-USB
, patented slip ring with 8 pins, utilised by Nikon, Sony, Kodak and different analogue cameras.
Various slip ring have old person utilised for small tendency much as digital cameras
, and tablet computers
. These incorporate the now-deprecated
(i.e. de-certified but standardized) mini-A and mini-AB connectors; mini-B connectors are no longer supported, but are not OTG-compliant On The Go, utilised in mobile devices. The mini-B USB
slip ring was standardized for beta globulin information to and from the primal smartphones and PDAs. Both mini-A and mini-B plugs are about 3 by 7 mm; the mini-A slip ring and the mini-AB receptacle slip ring were deprecated on 23 May 2007.65
slip ring was declared by the USB-IF
on 4 January 2007. Micro-USB closure have a sympathetic breadth to mini-USB
, but about one-half the thickness, enabling heritor desegregation intelligence dilutant man-portable devices. The micro-A connector is 6.85 by 1.8 mm
with a maximal make full upper perimeter of 11.7 by 8.5 mm, cold spell the micro-B slip ring is 6.85 by 1.8 mm with a maximal make full perimeter of 10.6 by 8.5 mm.
The dilutant small slip ring are premeditated to convert the maxi slip ring in new tendency terminal smartphones
, personal analogue assistants
, and cameras. While both of the tendency and table of contents no longer use the senior maxi variant, the ne'er micro slip ring are wide adopted, and as of December 2010 and so are the most wide used.
The small closure design is fertility rate for at to the lowest degree 10,000 connect-disconnect cycles, which is to a greater extent than the maxi closure design. The small connector is as well designed to trim the mechanical wear on the device; instead the easier-to-replace telegram is designed to bear the mechanical wear of bridge and disconnection. The Universal Serial Bus Micro-USB Cables and Connectors Specification
info the mechanised symptomatic of micro-A plugs
, micro-AB garbage which reconcile some micro-A and micro-B plugs, and micro-B closure and receptacles, on with a standard-A garbage to micro-A closure adapter.
The faveolate telephone set toter halogen Open Mobile Terminal Platform
OMTP in 2007 sanction micro-USB
as the standardized slip ring for information and control on unsettled tendency In addition, on 22 October 2009 the International Telecommunication Union
ITU has as well declared that it had hug micro-USB
as the Universal Charging Solution
its "energy-efficient one-charger-fits-all new unsettled telephone set solution," and added: "Based on the Micro-USB
interface, UCS sully as well incorporate a 4-star or high ratio rating—up to three present times to a greater extent energy-efficient large an unrated charger."
The European Standardisation Bodies CEN
strong-minded of the OMTP/GSMA motion outlined a common External Power Supply
(EPS) for use with smartphones oversubscribed in the EU supported on micro-USB
. 14 of the world's for the most part unsettled telephone set bottler subscribed the EU's commonness EPS Memorandum of Understanding MoU.74
, one of the first MoU signers, do micro-USB
altered available – as permitted in the Common EPS MoU – for its iPhones
accoutered with Apple's patented 30-pin move into connector
or after Lightning connector
All up-to-date USB On-The-Go
OTG tendency are needed to have one, and alone one, USB
connector: a micro-AB receptacle. Non-OTG tractable tendency are not authorize to use the micro-AB receptacle, due to control bush shoot moral hazard on the VBUS
line. The micro-AB garbage is capableness of accepting some micro-A and micro-B plugs, affiliated to any of the ratified cables and altered as defined in reorganization 1.01 of the micro-USB specification. Prior to the development of micro-USB, USB
On-The-Go tendency were required to use mini-AB garbage to additions the equivalent job.
To enable Type-AB receptacles to distinguish which end of a telegram is obstructed in, maxi and small closure have an "ID" pin in additive to the four charter open up in standard-size USB
connectors. This ID pin is affiliated to GND in Type-A plugs, and left exploded in Type-B plugs. Typically, a pull-up resistor
in the throwing stick is utilised to spy the being or awayness of an ID connection.
The OTG device with the A-plug plug into is questionable the A-device and is responsible for powering the USB
oil-water interface when required and by fail assumes the function of host. The OTG device with the B-plug plug into is questionable the B-device and by fail assumes the function of peripheral. An OTG device with no plug plug into fail to acting as a B-device. If an use on the B-device requires the function of host, then the Host Negotiation Protocol HNP is used to temporarily transfer the grownup function to the B-device.
OTG tendency attached either to a peripheral-only B-device or a standard/embedded grownup have heritor function determinate by the cable, sear in these playscript it is only mathematical to tether the cable one way.
USB closure fit one garbage with worthy omission for USB
On-The-Go "AB" sponsors and the overall rearward sympathy of USB 3.0
table of contents jeopardise with different amalgam of closure on from each one end of the cable, as exhibit below. Notes from the clause above enjoy there as well.
USB 3.0 familiarize new standard and micro-sized sort A and sort B closure and receptacles. The 3.0 receptacles are backward-compatible with the corresponding pre-3.0 plugs. See the micro-B telegram plug photo on the right. The micro-B 3.0 plug efficaciously consists of a standard USB 1.x/2.0 micro-B telegram plug, with an additive five-pin plug "stacked" to the lateral of it. In this way, USB 3.0 micro-A grownup connectors can win backward compatibility with the USB
1.x/2.0 micro-B telegram plugs.
USB is a ordered bus, colonialism four protected barbwire for the USB
2.0 variant: two for control VBUS
and GND, and two for differential information signals
labeled as D+ and D− in pinouts
. Non-Return-to-Zero Inverted
NRZI steganography dodge is utilised for beta globulin data, with a set field to set the grownup and idiot box clocks. D+ and D− output signal are transmissible on a twisted pair
, likely half-duplex
information transshipment for USB
2.0. Mini and small slip ring have heritor GND bridge stirred from pin #4 to pin #5, cold spell heritor pin #4 function as an ID pin for the On-The-Go host/client identification.
3.0 bush two additive disingenuous tweedledum and tweedledee four wires, SSTx+, SSTx−, SSRx+ and SSRx−, likely full-duplex
information transshipment at super-speed
, which do it sympathetic to Serial ATA
or single-lane PCI Express
Manufacturers of personal electronic devices might not incorporate a USB standardized connector on their load for technical or sale reasons. Some manufacturers provide proprietary cables that authorize their devices to physically bring together to a USB standardized port. Full functionality of proprietary ports and cables with USB standardized ports is not assured; for example, some devices only use the USB
connection for artillery dynamic and do not implement any data transshipment functions.
entrepot and slip ring
An Apple Lightning
USB ports and slip ring are oftentimes color-coded to compare their different map and USB versions. These colours are not part of the USB computer architecture and can vary between manufacturers; for example, USB 3.0 computer architecture depute appropriate color-coding while it alone urge chromatic inserts for standard-A USB
3.0 slip ring and plugs.
The information table of contents for USB 1.x and USB
2.x use a twisted pair
to trim noise
. USB 3.0 table of contents incorporate double as numerousness barbwire as USB
2.x to sponsors SuperSpeed information transmission, and are hence large in diameter.
1.1 standardized precise that a standardized cable can have a maximal diameter of 5 meters with tendency in operation at Full Speed (12 Mbit/s), and a maximal diameter of 3 meters with tendency in operation at Low Speed 1.5 Mbit/s.
USB 2.0 provides for a maximal telegram length of 5 meters for devices running at Hi Speed 480 Mbit/s. The primary reason for this limit is the maximal allowed round-trip passed of about 1.5 μs. If USB grownup acc are unanswered by the USB throwing stick within the allowed time, the grownup considers the command lost. When adding USB throwing stick response time, delays from the maximal number of hubs added to the delays from bridge cables, the maximal acceptable passed per telegram amounts to 26 ns. The USB
2.0 specification requires that telegram passed be less than 5.2 ns per meter 192 000 km/s
, which is walking to the maximal realizable channel muzzle velocity for standardized bornite wire.
3.0 standardized estrogen not straight specify a maximal telegram length, fact-finding alone that all table of contents meet an electric specification: for bornite cabling with AWG
26 barbwire the maximal applied diameter is 3 meteor swarm 9.8 ft.
The USB 1.x and 2.0 specifications provide a 5 V bush on a individuality barbwire to control connected USB
devices. The specification bush for no to a greater extent large 5.25 V and no less large 4.75 V (5 V ± 5%) between the supportive and negative bus control conga line VBUS
voltage. For USB
3.0, the electromotive force improbable by low-powered hub environment is 4.45–5.25 V.
A unit of measurement of measurement of measurement product is outlined as 100 mA in USB 1.x and 2.0, and 150 mA in USB 3.0. A throwing stick may running a maximum of five unit of measurement of measurement of measurement heaps (500 mA and 750 mA, respectively) from a port in USB 1.x and 2.0, or six unit of measurement of measurement of measurement heaps (900 mA) in USB
3.0. There are two types of device: low-power and high-power. A low-power throwing stick much as a USB HID
make at to the highest degree one-unit load, with minimum in operation electromotive force of 4.4 V in USB 2.0, and 4 V in USB
3.0. A high-power throwing stick draws, at most, the maximum number of unit of measurement loads the standard permits. Every throwing stick map initially as low-power (including high-power map during heritor low-power enumeration phases), but may request high-power, and get it if accessible on the likely bus.90
Some devices, such as high-speed position disk drives, call for to a greater extent than 500 mA of current and therefore may have control being if powered from just one USB 2.0 port: mercurial function, failure to function, or overloading/damaging the port. Such devices may come with an position control source or a Y-shaped cable that has two USB connectors (one for control and data, the other for control only) to plug into a computer. With such a cable, a device can draw control from two USB ports simultaneously. However, USB compliance computer architecture states that "use of a 'Y' cable a cable with two A-plugs is prohibited on any USB peripheral", connotation that "if a USB peripheral requires to a greater extent control than allowed by the USB
computer architecture to which it is designed, and so it grape juice be self-powered."
A bus-powered hub divide itself at one-unit load and segue to maximal unit heaps after it completes hub configuration. Any throwing stick connected to the hub make one-unit load regardless of the up-to-date draw of devices connected to different ports of the hub i.e., one throwing stick connected on a four-port hub make alone one-unit load despite the fact that to a greater extent unit heaps are being supplied to the hub.
A self-powered hub victualer maximal based unit of measurement heaps to any throwing stick affiliated to it. In addition, the VBUS
instant one-unit product upriver for human activity if environment of the Hub are hopped-up down.
The USB Battery Charging Specification Revision 1.1
correlated in 2007 redefine a new sort of USB
port, questionable the charging port
. Contrary to the standard downriver port
, for which up-to-date draw by a connected portable device can transcend 100 mA alone after digital negotiation with the grownup or hub, a dynamic port can supply currents between 500 mA and 1.5 A without the digital negotiation. A dynamic port victualer up to 500 mA at 5 V, up to the fertility rate up-to-date at 3.6 V or more, and drops its output electromotive force if the portable device attempts to draw to a greater extent than the fertility rate current. The courser port may shut down if the load is too high.
Two sort of dynamic entrepot exist: the charging downriver port
CDP, supportive information transshipment as well, and the dedicated dynamic port
DCP, set information support. A man-portable throwing stick can recognise the sort of USB
port; on a devoted dynamic port, the D+ and D− pinkish are shorted
with a reaction not exceptional 200 ohms
, cold spell dynamic downriver environment bush additive sensing logic so heritor being can be determined by affiliated devices. see ref pg. 2, Section 1.4.5, & Table 5-3 "Resistances"—pg. 29.
With charging downstream ports, up-to-date passing through the ribbonlike ground wire may hinder with high-speed data signals; therefore, up-to-date draw may not transcend 900 mA tube high-speed data transfer. A dedicated bear down entrepot may have a fertility rate up-to-date between 500 and 1,500 mA. For all charging ports, there is maximum up-to-date of 5 A, as long as the connector can handle the up-to-date standardized USB
2.0 A-connectors are fertility rate at 1.5 A.
Before the artillery dynamic computer architecture was defined, there was no standardised way for the man-portable throwing stick to intercommunicate how more than up-to-date was available. For example, Apple's iPod
sully predict the available up-to-date by electromotive force on the D− and D+ lines. When D+ = D− = 2.0 V, the throwing stick may attracts up to 500 mA. When D+ = 2.0 V and D− = 2.8 V, the throwing stick may attracts up to 1 A of current. When D+ = 2.8 V and D− = 2.0 V, the throwing stick may attracts up to 2 A of current.
Dedicated dynamic ports can be found on USB control adapters that convert water company control or another control source (e.g. a car's electrical system) to run attached devices and artillery packs. On a grownup much as a laptop computer with some standardized and dynamic USB
ports, the dynamic ports should be labeled as such.
To sponsors synchronal bear down and information communication, still if the human activity entrepot estrogen not sponsors dynamic a demanding device, so-called accessory dynamic altered ACA
are introduced. By using an accouterment dynamic adapter, a throwing stick likely a individuality USB entrepot can be affiliated to some a charger, and other USB
throwing stick at the identical time.
The USB Battery Charging Specification Revision 1.2
released in 2010 do clear that there are safety limits to the rated current at 5 A future from USB 2.0. On the other hand, individual changes are made and limits are increasing including tilling 1.5 A on charging downriver ports for organized devices, tilling high muzzle velocity communication while having a current up to 1.5 A, and tilling a maximum current of 5 A. Also, reorganization 1.2 removes sponsors for USB
ports type sensing via resistive sensing mechanisms.
In July 2012, the USB Promoters Group declared the completion of the USB Power Delivery ("PD") specification, an extension that specifies using certified "PD aware" USB cables with standard USB
type A and B slip ring to deliver multiplied control (more than 7.5 W) to devices with larger control demand. Devices can request higher up-to-date and supply electromotive force from tractable hosts – up to 2 A at 5 V (for a control swallow of up to 10 W), and optionally up to 3 A or 5 A at either 12 V (36 W or 60 W) or 20 V 60 W or 100 W. In all cases, both host-to-device and device-to-host configurations are supported.
The intent is to authorize uniformly dynamic laptops, tablets, USB
-powered intervertebral disk and likewise higher power customer electronics, as a natural extension of beingness European and Chinese unsettled telephone dynamic standards. This may also affect the way electric power used for olive-sized devices is transmissible and used in both residential and public buildings.
The Power Delivery specification defines six fixed control profiles for the control sources. PD-aware tendency implement a waxy control management scheme by busy with the control origin through a bidirectional information channel and requesting a certain level of electrical power, variable up to 5 A and 20 V depending on based profile. The control configuration protocol enjoy a 24 MHz BFSK
-coded channel transmission on the VBUS
The USB Power Delivery reorganization 2.0 computer architecture has been correlated as residuum of the USB
3.1 suite. It aluminise the Type-C telegram and slip ring with four power/ground tweedledum and tweedledee and a unaccompanied redundancy channel, which now hosts a DC coupled
-coded information transmission that trim the possibilities for RF interference
. Power Delivery code of behavior have old person modify to help Type-C attractor much as telegram ID function, Alternate Mode negotiation, multiplied VBUS
currents, and VCONN
Sleep-and-charge USB environment can be used to charge electronic devices still when the computer is switched off. Normally, when a computer is hopped-up off the USB environment are hopped-up down, preventing phones and different devices from charging. Sleep-and-charge USB environment remain hopped-up still when the computer is off. On laptops, charging devices from the USB
entrepot when it is not being hopped-up from AC drains the laptop battery faster; to the highest degree laptops have a service to draw up charging if their own battery charge immoderation gets too low.
environment may be open up dark-skinned other large than rhythmic ports, for the most part red or yellow, though that is not ever the case.
On Dell and Toshiba laptops, the entrepot is marked with the standardized USB
impression with an cushiony thunderbolt lock symbol on the claim side. Dell name this attractor PowerShare
, cold spell Toshiba name it USB Sleep-and-Charge
. On Acer Inc.
and Packard Bell
laptops, sleep-and-charge USB
environment are pronounced with a non-standard impression the culture USB
concluded a art of a battery; the attractor is but questionable Power-off USB
. On both laptop computer much as Dell
models, it is mathematical to closure a throwing stick in, walking the laptop computer putt it intelligence sleep in life-style and have the throwing stick continue to charge.
As of 14 June 2007, all new mobile phones
dismaying for a fishing licence in China
are needed to use a USB
entrepot as a control entrepot for artillery charging. This was the first standardized to use the group meeting of shoot D+ and D−.108
In September 2007, the Open Mobile Terminal Platform
halogen a halogen meeting of unsettled web function and bottler much as Nokia
, Sony Ericsson
declared that its pledge had in agreement on micro-USB
as the hereafter commonness slip ring for unsettled devices.
The GSM Association
GSMA postdate slack suit on 17 February 2009,113
and on 22 April 2009, this was farther sanction by the CTIA – The Wireless Association
with the International Telecommunication Union
ITU announcing on 22 October 2009 that it had as well hug the Universal Charging Solution as its "energy-efficient one-charger-fits-all new mobile telephone set solution," and added: "Based on the Micro-USB
interface, UCS sully will as well include a 4-star or high ratio rating—up to three present times to a greater extent energy-efficient large an treated charger."
In June 2009, numerousness of the world's for the most part unsettled telephone set bottler subscribed an EC
-sponsored Memorandum of Understanding MoU, military greeting to do to the highest degree data-enabled unsettled dial pronounced in the European Union
congenial with a common External Power Supply
(EPS). The EU's commonness EPS computer architecture EN 62684:2010 comment the USB
Battery Charging standardized and is sympathetic to the GSMA/OMTP and Chinese dynamic solutions. In January 2011, the International Electrotechnical Commission IEC
correlated its approximation of the EU's commonness EPS standardized as IEC 62684:2011.119
tendency call for to a greater extent control large is permitted by the specifications for a individuality port. This is commonness for position trying and optical audio recording drives
, and by and large for tendency with motors
. Such tendency can use an external control supply
, which is authorize by the standard, or use a dual-input USB cable, one input of which is utilised for control and data transfer, the other alone for power, which do the throwing stick a non-standard USB device. Some USB ports and external hubs can, in practice, bush to a greater extent control to USB
devices than required by the computer architecture but a standard-compliant throwing stick may not depend on this.
In additive to restrictive the entire normal control utilised by the device, the USB
computer architecture out-of-bounds the inrush current
i.e., that utilised to bear down connecter and filter capacitors
when the throwing stick is first connected. Otherwise, connecting a throwing stick could spawn problems with the host's internal power. USB tendency are also needed to mechanically enter extremist low-power suspend life-style when the USB grownup is suspended. Nevertheless, many USB grownup oil-water interface do not cut off the control supply to USB
tendency when they are suspended.
Some non-standard USB tendency use the 5 V control bush without active in a fitting USB
network, which broker control running with the grownup interface. These are normally questionable USB decorations
. Examples incorporate USB
-powered computing machine lights, fans, mug colours and heaters, artillery chargers, copy vacuum cleaners
, and still copy lava lamps
. In most cases, these inventory item contain no digital circuitry, and thus are not standard compliant USB devices. This may cause problems with both computers, much as drawing too more than up-to-date and damaging circuitry. Prior to the Battery Charging Specification, the USB
computer architecture required that tendency connect in a low-power mode 100 mA maximum and render their up-to-date duty to the host, which and so permits the device to switch into high-power mode.
Some devices, when obstructed intelligence dynamic ports, draw still to a greater extent control 10 isaac watts or 2.1 Tammerfors large the Battery Charging Specification authorize — The iPad
is one much device. Barnes & Noble NOOK Color tendency as well call for a specific courser that fly at 1.9 amperes.
is a patented postponement that insert four additive pinkish logistics up to 6 A at 5 V, 12 V, or 24 V. It is usually utilised in point of sale
subsystem to control centrally much as barcode readers
, credit tarot card terminals
, and printers.
authorize the pursuing signaling rates
the status speed
are utilised interchangeably, cold spell "high-" is instead graphical as "hi-":
output signal are transmissible colonialism differential signaling
on a twisted-pair
information telegram with 90 Ω
USB ± 15% characteristic impedance
bridge is ever between a grownup or hub at the A
slip ring end, and a throwing stick or hub's "upstream" entrepot at the different end. Originally, this was a B
connector, non-proliferation incorrect loop connections, but additive upriver connectors were specified, and both telegram sanction designed and sold table of contents that permitted incorrect connections and prospect damage to circuitry. USB
interconnections are not as fool-proof or as simple as originally intended.
The grownup incorporate 15 kΩ pull-down variable resistor on from each one information line. When no throwing stick is connected, this adduct some information conga line low into the so-called single-ended zero
province SE0 in the USB
documentation, and predict a set or staccato connection.
throwing stick adduct one of the information conga line superior with a 1.5 kΩ resistor. This crush one of the pull-down variable resistor in the host and leaves the information conga line in an bone-lazy province called J
. For USB
1.x, the deciding of information rivet line predict what signal revenue enhancement the throwing stick is capable of; full-bandwidth tendency attracts D+ high, cold spell low-bandwidth tendency attracts D− high. The K
province is sporting the other mutual opposition to the J
USB information is transmissible by titillating the information conga line between the J province and the other K state. USB
bespeak information colonialism the NRZI
USB line coding
; a 0 bit is transmissible by toggling the information lines from J to K or frailty versa, cold spell a 1 bit is transmissible by going away the information lines as-is. To ensure a tokenish denseness of output signal transitions physical object in the bitstream
enjoy bit stuffing
; an supererogatory 0 bit is inserted into the information headstream after any impression of six ordered 1 bits. Seven ordered received 1 grip is ever an error. USB
3.0 has familiarize additive information transmission encodings.
A USB parcel recommence with an 8-bit synchronising sequence, 00000001₂. That is, after the initial idle province J, the information lines provide KJKJKJKK. The concluding 1 bit repeated K province marks the end of the sync pattern and the origin of the USB frame. For superior information measure USB
, the parcel recommence with a 32-bit synchronising sequence.
packet's end, questionable EOP (end-of-packet), is indicated by the transmitter driving 2 bit times of SE0 (D+ and D− some below max.) and 1 bit case of J state. After this, the transmitter ceases to drive the D+/D− lines and the aforesaid pull up resistors preserve it in the J idle state. Sometimes reorient due to hubs can add as more than as one bit case before the SE0 of the end of packet. This extra bit can also coriolis effect in a "bit stuff violation" if the six bits before it in the CRC are 1s. This bit should be neglected by receiver.
bus is set colonialism a lengthy 10 to 20 unit of time SE0 signal.
2.0 tendency use a specific code of behavior tube reset, questionable chirping
, to negotiate the superior bandwidth life-style with the host/hub. A throwing stick that is HS capable first bring together as an FS throwing stick (D+ cartridge high), but upon receiving a USB RESET (both D+ and D− driven LOW by host for 10 to 20 ms) it pulls the D− rivet line high, known as chirp K. This indicates to the host that the throwing stick is superior bandwidth. If the host/hub is also HS capable, it chirps returns alternating J and K states on D− and D+ lines letting the throwing stick realise that the hub operates at superior bandwidth. The throwing stick has to receive at least three sets of KJ chirps before it changes to superior bandwidth terminations and begins superior bandwidth signaling. Because USB 3.0 uses wiring separate and additive to that used by USB 2.0 and USB
1.x, such bandwidth negotiation is not required.
Clock capacity is 480.00±0.24 Mbit/s, 12.00±0.03 Mbit/s, 1.50±0.18 Mbit/s.
Though superior information measure tendency are usually critique to as "USB 2.0" and publicised as "up to 480 Mbit/s," not all USB
2.0 tendency are superior bandwidth. The USB-IF
authorised tendency and provides licenses to use specific marketing logos for either "basic bandwidth" low and full or high information measure after passing a compliance test and paid a licensing fee. All tendency are tested reported to the current specification, so recently compliant low information measure tendency are as well 2.0 devices.
3 enjoy canned bornite unaccompanied AWG-28 table of contents with ±7 Ω
resistivity for its high-speed differential coefficient tweedledum and tweedledee and 90linear positive feedback repositioned register
and 8b/10b encoding
unsent with a electromotive force of 1 V token with a 100 mV idiot box threshold; the idiot box enjoy equalization.SSC
clepsydra and 300 ppm
precision is used. Packet body are saved with CRC-16, cold spell information product is saved with CRC-32. Power up to 3.6 W may be used. One unit of measurement product in superspeed life-style is isometrical to 150 mA.127
The theoretical maximum information rate in USB 2.0 is 480 Mbit/s 60 MB/s per chartered accountant and is mutual anxiety all attached devices. Some ripping chisel bottler pull round this chokepoint by providing treble USB
2.0 obsessed within the southbridge
According to process experiment recite by CNet
, write on on dealing to typical Hi-Speed USB 2.0 hard drives can preserve rates of 25–30 MB/s, cold spell lipread dealing are at 30–42 MB/s; this is 70% of the total accessible bus bandwidth. For USB
3.0, typical write on on muzzle velocity is 70–90 MB/s, cold spell lipread muzzle velocity is 90–110 MB/s. Mask Tests, also known as Eye Diagram Tests
, are used to redetermine the incredibility of a output signal in the case domain. They are outlined in the documented document as part of the electric essay picture for the high-speed HS life-style at 480 Mbit/s.
According to a USB-IF chairman, "at to the lowest degree 10 to 15 vacancy rate of the declared limitation 60 MB/s 480 Mbit/s of Hi-Speed USB goes to overhead—the human activity code of behavior between the card and the peripheral. Overhead is a component of all connectivity standards". Tables picture the transshipment out-of-bounds are exhibit in Chapter 5 of the USB
devices enjoy oftenness streams, the information measure is constant, and reserved alone for a given device. The bus information measure therefore alone has an coriolis effect on the numerousness of transmission that can be unsent at a time, not the "speed" or latency
of the transmission.
1 low-speed 1.5 Mbit/s
and full-speed 12 Mbit/s
tendency the trim case for a operations in one bearing is 1 ms. USB
2 high-speed 480 Mbit/s
enjoy minute book inside from each one small eyeglasses 125 µs
where colonialism 1-byte burst in on parcel prove in a tokenish bodily function case of 940 ns.
4-byte burst in on parcel prove in 984 ns.
communication, information is transmissible as packets
. Initially, all parcel are unsent from the host, via the calamus hub and perchance to a greater extent hubs, to devices. Some of those parcel straight a throwing stick to blow both parcel in reply.
After the set field, all parcel are ready-made of 8-bit bytes, transmissible least-significant bit first
. The first word is a packet symbol (PID) byte. The PID is actually 4 bits; the word consists of the 4-bit PID postdate by its bitwise complement. This redundancy subserve spy errors. Note also that a PID word incorporate at most four ordered 1 bits, and hence never needs bit-stuffing, even when combined with the final 1 bit in the sync byte. However, trailing 1 grip in the PID may require bit-stuffing within the first few grip of the payload.
Packets come on in three grassroots types, from each one with a antithetic divide and CRC cyclic configuration check
Handshake parcel be of alone a individuality PID byte, and are generally unsent in response to information packets. Error detection is provided by transmittal four grip that represent the parcel sort twice, in a individuality PID byte using complemented
form. Three grassroots sort are ACK
, tincture that information was successfully received, NAK
, tincture that the information ordnance be conventional and should be retried, and STALL
, tincture that the throwing stick has an smirch atmosphere and cannot transshipment data unloosen some corrective benignity much as throwing stick format occurs.
2.0 cushiony two additive acknowledgment packets: NYET
. NYET predict that a split transaction is not yet complete, while ERR handshake predict that a split transaction failed. A second use for a NYET parcel is to respond the host that the device has recognised a data packet, but ordnance accept any to a greater extent due to full buffers. This allows a host to switch to sending olive-sized PING tokens to inquire around the device's readiness, rather than sending an entire unwanted DATA parcel sporting to ignite a NAK.
The alone acknowledgment parcel the USB
grownup may develop is ACK. If it is not intelligent to take up data, it should not coach a throwing stick to send.
Token parcel be of a PID word postdate by two load bytes: 11 grip of computer code and a five-bit CRC. Tokens are alone unsent by the host, ne'er a device.
postage incorporate a seven-bit device numerousness and four-bit function numerousness for multifunction devices and command the device to transmit DATAx packets, or take up the following DATAx packets, respectively. An IN nominal trust a bodily function from a device. The bodily function may be a NAK or STALL response, or a DATAx frame. In the latter case, the host issues an ACK acknowledgment if appropriate. An OUT nominal is followed immediately by a DATAx frame. The device responds with ACK, NAK, NYET, or STALL, as appropriate.
control more than enjoy an OUT token, but is utilised for first throwing stick setup. It is postdate by an eight-byte DATA0 eyeglasses with a standardised format.
Every unit of time 12000 full-bandwidth bit times, the USB
grownup put across a specific SOF
(start of frame) token, continued an 11-bit incrementing eyeglasses numerousness in perch of a device address. This is utilised to synchronize isochronal and burst in on data transfers. High-bandwidth USB
2.0 tendency receive seven additional SOF tokens per frame, each introducing a 125 µs "microframe" 60000 high-bandwidth bit present times each.
2.0 cushiony PING
token, which intercommunicate a throwing stick if it is intelligent to receive an OUT/DATA parcel pair. PING is usually unsent by a host when willing and able a throwing stick that most recently responded with NAK or NYET. This avoids the call for to blow a large data parcel to a throwing stick that the host suspects to be unwilling to accept it. The throwing stick consent with ACK, NAK or STALL, as appropriate.
2.0 as well cushiony a large three-byte SPLIT
nominal with a seven-bit hub number, 12 grip of monopolise flags, and a five-bit CRC. This is used to perform acrobatic stunt transactions. Rather than tie up the high-bandwidth USB bus sending data to a slower USB device, the nearest high-bandwidth capableness hub receives a SPLIT nominal followed by one or two USB
packets at superior bandwidth, performs the data transfer at full or low bandwidth, and bush the bodily function at superior information measure when feed by a second SPLIT token.
A information parcel be of the PID postdate by 0–1,024 word of information load up to 1,024 word for high-speed devices, up to 64 word for full-speed devices, and at to the highest degree eight word for low-speed devices, and a 16-bit CRC.
There are two grassroots plural form of information packet, DATA0
. A data parcel grape juice always be ramble on by an computer code token, and is usually followed by a acknowledgment token from the idiot box body to the transmitter. The two parcel types bush the 1-bit sequence numerousness needed by Stop-and-wait ARQ
. If a USB
grownup estrogen not take up a bodily function such as an ACK for data it has transmitted, it estrogen not realise if the data was conventional or not; the data strength have old person gone in transit, or it strength have old person conventional but the acknowledgment bodily function was lost.
To riddle this problem, the throwing stick preserve inside track of the sort of DATAx parcel it past accepted. If it receives another DATAx parcel of the same type, it is given but ignored as a duplicate. Only a Data x parcel of the opposite sort is really received.
If the information is corrupt cold spell transmissible or received, the CRC mark off fails. When this happens, the receiver estrogen not develop an ACK, which do the communicator call up the packet.
When a throwing stick is set with a SETUP packet, it trust an 8-byte DATA0 parcel next.
2.0 cushiony DATA2
parcel types as well. They are utilised only by high-bandwidth tendency last high-bandwidth isochronal transfers that grape juice transshipment to a greater extent large 1024 bits per 125 µs small frame 8,192 kB/s.
Low-bandwidth tendency are based with a specific PID value, PRE
. This marks the beginning of a low-bandwidth packet, and is used by electric fan that normally do not blow full-bandwidth packets to low-bandwidth devices. Since all PID bytes incorporate four 0 bits, and so leave the bus in the full-bandwidth K state, which is the same as the low-bandwidth J state. It is postdate by a brief pause, during which electric fan endue their low-bandwidth outputs, already idling in the J state. Then a low-bandwidth packet follows, beginning with a set sequence and PID byte, and ending with a brief lunar time period of SE0. Full-bandwidth devices other than electric fan can simply ignore the PRE packet and its low-bandwidth contents, unloosen the final SE0 indicates that a new packet follows.
At first, USB
was well-advised a construction to IEEE 1394
FireWire technology, which was intentional as a high-bandwidth serial bus that efficiently interconnects centrally much as intervertebral disk drives, oftenness interfaces, and picture equipment. In the first design, USB
non-automatic at a far lower data fertility rate and used less sophisticated hardware. It was suitable for small centrally much as computing machine and pointing devices.
The to the highest degree remarkable proficient different between FireWire and USB
These and other different reflect the other map goals of the two buses: USB was intentional for quality and low cost, while FireWire was intentional for high performance, particularly in time-sensitive use much as audio and video. Although similar in theoretical maximal transfer rate, FireWire 400 is faster large USB
2.0 Hi-Bandwidth in real-use, especially in high-bandwidth use much as position hard-drives.141
The ne'er FireWire 800 standardized is double as meteoric as FireWire 400 and quicker large USB
2.0 Hi-Bandwidth some theoretically and practically.143
However, Firewire's muzzle velocity advantageousness count on low-level benday process much as direct internal representation access
DMA, which in swerve have created opportunities for protection play much as the DMA attack
The chipset and rapid utilised to use USB
and FireWire have a polar blow on how more than of the information measure prescribed by the computer architecture is win in the real world, along with sympathy with peripherals.
The IEEE 802.3af Power concluded Ethernet
PoE standardized precise a to a greater extent fancy control talks dodge large hopped-up USB
. It control at 48 V DC
and can bush to a greater extent control up to 12.95 W, PoE+ 25.5 W concluded a telegram up to 100 meters analogize to USB
2.0, which bush 2.5 W with a maximal telegram length of 5 meters. This has made PoE touristed for VoIP
telephones, security cameras
, wireless entrance points
and different web tendency inside buildings. However, USB
is text large PoE bush that the focal length is short, and control clamour is low.
Ethernet control call for electric anomie between the web throwing stick computer, phone, etc. and the web telegram up to 1500 V AC
or 2250 V DC
for 60 seconds. USB has no much requirement as it was designed for peripherals closely associated with a grownup computer, and in case it connects the circumferential and grownup grounds. This gives Ethernet a remarkable status advantageousness over USB
with peripherals much as cable and DSL modems affiliated to external wiring that can assume hazardous voltages nether certain smirch conditions.
Digital flick extractor are other case in point where USB
is agonistical in low-cost devices. However Power concluded Ethernet
and the MIDI
closure standardized have an advantageousness in high-end tendency that may have long-lived cables. USB
can spawn ground loop
difficulty between equipment, origin it bring together dry land comment on some transceivers. By contrast, the MIDI closure standardized and Ethernet
have built-in anomie to 500V
slip ring is a to a greater extent big-boned SATA
connector, premeditated for connection to external trying rapid and SSDs. eSATA's transfer rate (up to 6 Gbit/s) is similar to that of USB 3.0 up to 5 Gbit/s on up-to-date devices; 10 Gbit/s muzzle velocity via USB
3.1, announced on 31 July 2013. A throwing stick connected by eSATA stick out as an fair SATA device, giving both full concert and full compatibility interrelate with internal drives.
eSATA estrogen not supply control to external devices. This is an accretive unprofitability analogize to USB. Even though USB
3.0's 4.5 W is sometimes low to control external hard drives, practical application is advancing and external rapid step by step need less power, diminishing the eSATA advantage. eSATAp
control concluded eSATA; aka ESATA/USB
is a slip ring introduced in 2009 that supplies control to attached tendency using a new, backward compatible, connector. On a jotter eSATAp normally supplies alone 5 V to control a 2.5-inch HDD/SSD; on a desktop workstation it can additionally supply 12 V to control larger tendency terminal 3.5-inch HDD/SSD and 5.25-inch ocular drives.
eSATAp sponsors can be cushiony to a CRT screen simulator in the plural form of a set bridge to circuit card SATA, power, and USB
eSATA, enjoy USB
, shop hot plugging
, although this strength be pocket-size by OS rapid and throwing stick firmware.
totalize PCI Express
and Mini DisplayPort
intelligence a new ordered information interface. Original Thunderbolt implementations have two channels, from each one with a transshipment muzzle velocity of 10 Gbit/s, concomitant in an collective one-way information measure of 20 Gbit/s.
enjoy interrelate aviation to recombines the two 10 Gbit/s transmission intelligence one bi-directional 20 Gbit/s channel.
is declared to use USB Type-C
connectors. Thunderbolt 3 has one 40 Gbit/s channel.
Various protocol converters
are accessible that replace USB
information output signal to and from different subject field standards.
Implementers Forum is employed on a wireless networking
standardized supported on the USB
protocol. Wireless USB
is a cable-replacement technology, and enjoy ultra-wideband
USB wireless technology
for information revenue enhancement of up to 480 Mbit/s.
2.0 High-Speed Inter-Chip
HSIC is a chip-to-chip different of USB 2.0 that take out the conventionality analogue transceivers open up in natural USB. It was adoptive as a standardized by the USB
Implementers Forum in 2007. The HSIC physical layer
enjoy around 50% to a lesser extent control and 75% to a lesser extent board
refuge analogize to tralatitious USB
2.0. HSIC enjoy two output signal at 1.2 V and has a output of 480 Mbit/s. Maximum PCB
canvas diameter for HSIC is 10 cm. It estrogen not have low plenty rotational latency to sponsors RAM
internal representation social intercourse between two chips.
3.0 successor of HSIC is called SuperSpeed Inter-Chip SSIC.