523:
upstream port is broadcast to all devices attached to its downstream ports (pictorially described in the USB 2.0 specification in Figure 11-2, Hub
Signalling Connectivity). Data received from a downstream port is generally forwarded to the upstream port only. This way, what is sent by the host is received by all hubs and devices, and what is sent by a device is received by the host but not by the other devices (an exception is resume signaling). Downstream routing has been changed in USB 3.0 with the addition of Point to Point routing: A route string sent in the packet header allows a USB 3.0 host to only send a downstream packet to a single destination port, decreasing congestion and power consumption.
397:
335:
348:
231:
25:
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363:. It does not need a separate power connection. However, many devices require more power than this method can provide and will not work in this type of hub. It may be desirable to use a bus-powered hub with self-powered external hard-disks, as the hard-disk may not spin down when the computer turns off or enters sleep mode while using a self-powered hub since the hard disk controller would continue to see a power source on the USB ports.
126:
206: A, plus power for the hub itself. Designers assume the user will most likely connect many low-power devices and only one or two requiring a full 500 mA. On the other hand, the packaging for some self-powered hubs states explicitly how many of the ports can drive a 500 mA full load at once. For example, the packaging on a seven-port hub might claim to support a maximum of four full-load devices.
531:
endpoint. When the host polls this interrupt endpoint, it learns that the new device is present. It then instructs the hub (via the default control pipe) to reset the port where the new device was plugged in. This reset makes the new device assume address 0, and the host can then interact with it directly; this interaction will result in the host assigning a new (non-zero) address to the device.
64:
426:. Each transaction translator segregates lower speed traffic into its own pool, essentially creating a virtual full-speed bus. Some designs use a single transaction translator (STT), while other designs have multiple translators (MTT). Having multiple translators is a significant benefit when one connects multiple high-bandwidth full-speed devices.
543:(TT). For example, if a USB 1.1 device is connected to a port on a USB 2.0 hub, then the TT would automatically recognize and translate the USB 1.1 signals to USB 2.0 on the uplink. However, the default design is that all lower-standard devices share the same transaction translator and thus create a bottleneck, a configuration known as the
378:
is allocated in units of 100 mA up to a maximum total of 500 mA per port. Therefore, a compliant bus powered hub can have no more than four downstream ports and cannot offer more than four 100 mA units of current in total to downstream devices (since the hub needs one unit for itself).
429:
It is an important consideration that in common language (and often product marketing), USB 2.0 is used as synonymous with high-speed. However, because the USB 2.0 specification, which introduced high-speed, incorporates the USB 1.1 specification such that a USB 2.0 device is not required to operate
197:
There are many non-compliant hubs on the market which announce themselves to the host as self-powered despite really being bus-powered. Equally, there are plenty of non-compliant devices that use more than 100 mA without announcing this fact. These hubs and devices do allow more flexibility in
559:
Most USB hubs use one or more integrated controllers (ICs), of which several designs are available from various manufacturers. Most support a four-port hub system, but hubs using 16-port hub controllers are also available in the industry. The USB bus allows seven cascading tiers of ports. The root
530:
To this aim, each hub has a single interrupt endpoint "1 IN" (endpoint address 1, hub-to-host direction) used to signal changes in the status of the downstream ports. When someone plugs in a device, the hub detects voltage on either D+ or D− and signals the insertion to the host via this interrupt
526:
Hubs are not transparent when dealing with changes in the status of downstream ports, such as insertion or removal of devices. In particular, if a downstream port of a hub changes status, this change is dealt with in an interaction between the host and this hub; with any hubs between the host and
522:
Each hub has exactly one upstream port and a number of downstream ports. The upstream port connects the hub (directly or via other hubs) to the host. Other hubs or devices can be attached to the downstream ports. During normal transmission, hubs are essentially transparent: data received from its
387:
Dynamic-powered hubs are hubs which can work as bus-powered as well as self-powered hubs. They can automatically switch between modes depending on whether a separate power supply is available or not. While switching from bus-powered to self-powered operation does not necessarily require immediate
145:
Port arrays in which the port orientation is perpendicular to the array orientation generally have fewer blockage problems. External "Octopus" or "Squid" hubs (with each socket at the end of a very short cable, often around 2 inches (5 cm) long), or "star" hubs (with each port facing in a
133:
A USB network is built from USB hubs connected downstream to USB ports, which themselves may stem from USB hubs. USB hubs can extend a USB network to a maximum of 127 ports. The USB specification requires that bus-powered (passive) hubs are not connected in series to other bus-powered hubs.
94:), to small designs that can be directly plugged into a USB port (see the "compact design" picture). "Short cable" hubs typically use an integral 6-inch (15 cm) cable to slightly distance a small hub away from physical port congestion and increase the number of available ports.
56:
551:(Multi-TT) were created, which provide more transaction translators such that bottlenecks are avoided. Note that due to the nature of USB 3.0 hubs have separate logic for the USB 3.0 and 2.0 data and therefore report a HUB device for both protocols.
422:(USB 1.1) when plugged into a full-speed hub (or connected to an older full-speed computer port). While high-speed hubs can communicate at all device speeds, low- and full-speed traffic is combined and segregated from high-speed traffic through a
254:
137:
Depending on vendor and design, USB ports are often closely spaced. Consequently, plugging a device into one port may physically block an adjacent port, particularly when the plug is not part of a cable but is integral to a device such as a
560:
hub is the first tier, and the last devices are on the seventh tier, allowing five tiers worth of hubs between them. The maximum number of user devices is reduced by the number of hubs. With 50 hubs attached, the maximum number is
198:
the use of power (in particular, many devices use far less than 100 mA and many USB ports can supply more than 500 mA before going into overload shut-off), but they are likely to make power problems harder to diagnose.
101:
computers are equipped with USB ports, but an external USB hub can consolidate several everyday devices (like a mouse, keyboard or printer) into a single hub to enable one-step attachment and removal of all the devices.
388:
renegotiations with the host, switching from self-powered to bus-powered operation may cause USB connections to be reset if connected devices previously requested more power than available in bus-powered mode.
732:
Most PC manufacturers label each USB port using the logo for USB type the USB 2.0 logo is a trident, while the USB 3.0 logo is a similar trident with the letters 'SS' (which stands for SuperSpeed) attached.
201:
Some self-powered hubs do not supply enough power to drive a 500 mA load on every port. For example, many seven port hubs have a 1 A power supply, when in fact seven ports could draw a maximum of
456:
standard. It is recommended that manufacturers distinguish USB 3.0 connectors from their USB 2.0 counterparts by using blue (Pantone 300C) for the
Standard-A receptacles and plugs, and by the initials
158:(specialized connector-embedded one-port hubs) perform the same function, but since they are strictly bus-powered, externally powered USB hubs would likely be required for some of the segments.
230:
154:
USB cables are limited to 3 metres (10 feet) for low-speed USB 1.1 devices. A hub can be used as an active USB repeater to extend cable length for up to 5 metre (16 feet) lengths at a time.
302:
Smartphone charging: The USB Multiport adapter integrated 100 W USB cable connected to the phone, and the USB-C cable connected to the USB multiport hub PD port, and the wall charger.
189:
Self-powered hubs can power high-voltage devices such as speakers, printers, and scanners. Self-powered USB hubs are usually more bulky, and more expensive than bus-powered USB hubs.
113:
due to the similar nature of only needing one connection to charge the battery and connect peripherals. Hubs may feature power switches for individual ports to allow conveniently
794:
744:
260:
To power a USB multiport adapter and charge a connected mobile device that is connected to it at the same time, a 100 W USB-C PD wall charger is typically sufficient.
539:
Any USB 2.0 hub that supports a higher standard than USB 1.1 (12 Mbit/s) will translate between the lower standard and the higher standard using what is called a
170:
powered or self powered hubs. Power equals voltage times current. A USB port that draws 500 mA (0.5 A) at 5 volts is drawing 2.5 watts of power.
416:(USB 2.0) devices to operate in their fastest mode, all hubs between the devices and the computer must be high-speed. High-speed devices should fall back to
430:
at high speed, any compliant full-speed or low-speed device may still be labelled as a USB 2.0 device. Thus, not all USB 2.0 hubs operate at high speed.
379:
If a device requires more units of current than the port it is plugged into is able to supply, the operating system usually reports this to the user.
142:. A horizontal array of horizontal sockets may be easy to fabricate, but may cause only two out of four ports to be usable (depending on plug width).
703:
268:
Example how to calculate wattage consumption for a USB multiport hub with a USB PD port, and an HDMI port, connected to a smartphone and HDMI:
440:(USB) standard for interfacing computers and electronic devices. Among other improvements, USB 3.0 adds the new transfer rate referred to as
925:
173:
In Bus-powered USB hubs, each USB port can supply power as well as transfer data. A self-powered hub takes its power from an external
291:
100 W wall charger, 100 W USB-C cable. USB Multiport adapter: 100 W USB-C PD port, integrated 100 W USB cable.
898:
852:
801:
751:
670:
961:
719:
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466:, released in July 2013, is the successor standard that replaces the USB 3.0 standard. USB 3.1 preserves the existing
884:
1151:
1161:
79:(USB) port into several so that there are more ports available to connect devices to a host system, similar to a
405:
648:
1122:
1006:
109:(PD) to charge a laptop battery, if self-powered and certified to do so, but may be referred to as a simple
604:
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connector using two-lane operation, with data rates of 10 and 20 Gbps (1250 and 2500 MB/s).
418:
412:
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366:
All USB ports operate at 5 volts, but may draw or supply differing amounts of electric current.
1156:
1027:
631:
1228:
492:, released in September 2017, replaces the USB 3.1 standard. It preserves existing USB 3.1
437:
87:
76:
8:
38:
Please help update this article to reflect recent events or newly available information.
895:
860:
776:
708:
678:
106:
1041:
926:"Single TT Or Multi TT: USB Technology: Multi-TT Hub Goes Head-to-Head With Single-TT"
396:
1213:
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83:. All devices connected through a USB hub share the bandwidth available to that hub.
913:
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to every port. Self-powered hubs are usually more expensive than unpowered USB hubs
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which can transfer data at up to 10 Gbps over the existing USB-type-A and
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A four-port "compact design" USB hub: upstream and downstream ports shown
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with data rates of 80 and 120 Gbps (10,000 and 15,000 MB/s).
511:
826:
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463:
125:
245:
129:
A "star" "short cable" external USB with the plastic casing removed
710:
PCs for Grown-Ups: Getting the Most Out of Your
Windows 8 Computer
593:
What Is the
Difference Between Powered & Non-Powered USB Hubs?
1089:
1084:
1079:
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453:
338:
This self-powered USB hub gets power from a wall electrical plug.
146:
different direction, as pictured) avoid this problem completely.
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445:
237:
98:
400:
Hub Demo Board from VIA shows all internal components of a hub
1094:
949:
795:"USB 3.1 Specification Language Usage Guidelines from USB-IF"
745:"USB 3.1 Specification Language Usage Guidelines from USB-IF"
632:
USB Technology: Multi-TT Hub Goes Head-to-Head With Single-TT
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connectors (1250 MB/s, twice the rate of USB 3.0).
313:
8k HDMI cable connected: USB multiport adapter, and TV.
86:
Physically separate USB hubs come in a wide variety of
984:
943:
885:
What's The
Difference Between USB 2.0 And 3.0 Hubs?
707:
16:Device that expands a single USB port into several
853:"Universal Serial Bus Revision 3.1 Specification"
671:"Universal Serial Bus Revision 3.1 Specification"
177:unit and can therefore provide full power (up to
1251:
342:
184:
406:USB (Communications) § Signaling (USB PHY)
59:A four-port "long cable" "external box" USB hub
950:Atul P. Godse; Deepali A. Godse (2009-01-01).
928:. tomshardware.com. 2003-09-09. Archived from
1000:
236:USB multiport adapter: USB-C alt mode cable,
90:: from external boxes (looking similar to an
452:), which is about 10 times faster than the
1007:
993:
702:
534:
395:
346:
333:
124:
62:
54:
470:transfer rate, giving it the new label
444:(SS) that can transfer data at up to 5
382:
1252:
956:. Technical Publications. p. 16.
988:
918:
777:"USB 3.1 Gen 1 & Gen 2 explained"
651:. USB Implementers Forum. 1 June 2011
527:"changed hub" acting as transparent.
351:A 4-port USB hub that is bus-powered.
149:
554:
18:
605:"Sabrent 7-Port USB 3.0 Hub Review"
13:
706:(2013). "Connecting USB Devices".
500:data modes and introduces two new
436:is the third major version of the
329:
120:
75:is a device that expands a single
14:
1271:
980:
714:. Indianapolis: Que Publishing.
355:A bus-powered hub draws all its
253:
229:
192:
166:Many hubs can operate as either
23:
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889:
878:
845:
819:
677:. pp. 5–20. Archived from
209:
787:
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696:
663:
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625:
620:individual port power switches
597:
586:
369:
244:port, three USB 3.2 ports, an
1:
833:. USB Implementers Forum, Inc
636:Tom's Hardware UK and Ireland
579:
549:multi transaction translators
545:single transaction translator
359:from the host computer's USB
343:Bus-powered hub (passive hub)
185:Self-powered hub (active hub)
318:Remaining available wattage
7:
649:"USB-IF Compliance Updates"
567:
517:
221:USB multiport adapter setup
10:
1276:
403:
105:Some USB hubs may support
1201:
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1113:
1067:
1022:
214:
32:This article needs to be
1188:USB flash drive security
504:transfer modes over the
391:
161:
1014:
953:Advance Microprocessors
827:"USB 3.2 Specification"
638:. Retrieved 2006-08-24.
474:, while defining a new
92:Ethernet or network hub
1028:USB Implementers Forum
541:transaction translator
535:Transaction translator
478:transfer mode, called
424:transaction translator
401:
352:
339:
130:
117:unresponsive devices.
68:
60:
896:USB 2.0 specification
399:
350:
337:
128:
66:
58:
438:Universal Serial Bus
383:Dynamic-powered hubs
77:Universal Serial Bus
866:on 21 November 2014
914:USB in a nutshell
901:2012-02-07 at the
402:
353:
340:
150:Length limitations
131:
97:Almost all modern
69:
61:
1247:
1246:
1214:Ethernet over USB
1209:Enhanced mini-USB
963:978-81-8431-560-8
721:978-0-13-303501-8
555:Electronic design
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859:. Archived from
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807:on 12 March 2016
806:
800:. Archived from
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757:on 12 March 2016
756:
750:. Archived from
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684:on 12 April 2016
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376:electric current
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240:(USB-C) port, a
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903:Wayback Machine
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704:McFedries, Paul
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111:docking station
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932:on 2014-02-02
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204:7 * 0.5 = 3.5
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193:Compatibility
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1123:Mass storage
967:. Retrieved
952:
945:
934:. Retrieved
930:the original
920:
909:
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868:. Retrieved
861:the original
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847:
835:. Retrieved
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802:the original
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759:. Retrieved
752:the original
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725:. Retrieved
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686:. Retrieved
679:the original
674:
665:
653:. Retrieved
643:
635:
627:
619:
612:. Retrieved
608:
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386:
373:
365:
354:
321:58.5 W
310:-1.5 W
288:+100 W
267:
210:Power source
200:
196:
188:
175:power supply
172:
165:
153:
144:
136:
132:
104:
96:
88:form factors
85:
72:
70:
41:
33:
1128:Flash drive
870:19 November
502:SuperSpeed+
498:SuperSpeed+
476:SuperSpeed+
370:Limitations
299:-30 W
81:power strip
1234:PoweredUSB
1219:Decoration
1193:USB killer
1042:connectors
969:2013-01-03
936:2013-05-01
727:2016-02-18
580:References
512:USB4 Gen 4
494:SuperSpeed
468:SuperSpeed
419:full-speed
413:high-speed
404:See also:
1133:FlashCard
837:30 August
655:14 August
410:To allow
361:interface
1254:Category
1171:Security
1068:Versions
1035:Hardware
899:Archived
811:10 March
761:10 March
688:12 April
614:26 March
568:See also
518:Protocol
374:A USB's
277:Wattage
246:Ethernet
44:May 2017
1049:cabling
857:usb.org
831:usb.org
781:msi.com
675:usb.org
490:USB 3.2
464:USB 3.1
454:USB 2.0
434:USB 3.0
307:Output
296:Output
179:500 mA)
73:USB hub
34:updated
1239:WebUSB
1183:BadUSB
960:
718:
446:Gbit/s
285:Input
238:USB PD
215:USB PD
99:laptop
1202:Other
1157:Video
1095:USB-C
1056:power
864:(ZIP)
805:(PDF)
798:(PDF)
755:(PDF)
748:(PDF)
682:(ZIP)
609:Slant
506:USB-C
484:USB-C
448:(625
392:Speed
357:power
248:port.
162:Power
1140:UASP
1100:USB4
958:ISBN
872:2014
839:2018
813:2016
763:2016
716:ISBN
690:2016
657:2020
616:2022
496:and
450:MB/s
242:HDMI
1260:USB
1224:Hub
1145:SSD
1090:3.0
1085:2.0
1080:1.1
1075:1.0
1016:USB
168:bus
1256::
855:.
829:.
779:.
730:.
673:.
634:.
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607:.
564:.
460:.
458:SS
71:A
1008:e
1001:t
994:v
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46:)
42:(
36:.
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