USB
Universal Serial Bus

The current connector for USB, Thunderbolt, and other protocols, USB-C (plug and receptacle shown)
Type	Bus
Production history
Designer	Compaq DEC IBM Intel Microsoft NEC Nortel
Designed	January 1996; 28 years ago (1996-01)
Produced	Since May 1996[1]
Superseded	Serial port, parallel port, game port, Apple Desktop Bus, PS/2 port, and FireWire (IEEE 1394)

Universal Serial Bus (USB) is an industry standard that allows data exchange and delivery of power between many types of electronics. It specifies its architecture, in particular its physical interface, and communication protocols for data transfer and power delivery to and from hosts, such as personal computers, to and from peripheral devices, e.g. displays, keyboards, and mass storage devices, and to and from intermediate hubs, which multiply the number of a host's ports.^[2]

USB was originally designed to standardize the connection of peripherals to computers, replacing various interfaces such as serial ports, parallel ports, game ports, and ADB ports.^[3] Prior versions of USB became commonplace on a wide range of devices, such as keyboards, mice, cameras, printers, scanners, flash drives, smartphones, game consoles, and power banks.^[4] It has evolved into a standard to replace virtually all common ports on computers, mobile devices, peripherals, power supplies, and manifold other small electronics.

In the current standard, the USB-C connector replaces the many various connectors for power (up to 240 W), displays (e.g. DisplayPort, HDMI), and many other uses, as well as all previous USB connectors.

As of 2024,^[update] USB consists of four generations of specifications: USB 1.x, USB 2.0, USB 3.x, and USB4. USB4 enhances the data transfer and power delivery functionality with

a connection-oriented, tunneling architecture designed to combine multiple protocols onto a single physical interface so that the total speed and performance of the USB4 Fabric can be dynamically shared.^[2]

USB4 particularly supports the tunneling of the Thunderbolt 3 protocols, namely PCI Express (PCIe, load/store interface) and DisplayPort (display interface). USB4 also adds host-to-host interfaces.^[2]

Each specification sub-version supports different signaling rates from 1.5 and 12 Mbit/s total in USB 1.0 to 80 Gbit/s (in each direction) in USB4.^[5][6][7][2] USB also provides power to peripheral devices; the latest versions of the standard extend the power delivery limits for battery charging and devices requiring up to 240 watts (USB Power Delivery (USB-PD)).^[8] Over the years USB(-PD) has been adopted as the standard power supply and charging format for many mobile devices, such as mobile phones, reducing the need for proprietary chargers.^[9]

Overview

USB was designed to standardize the connection of peripherals to personal computers, both to exchange data and to supply electric power. It has largely replaced interfaces such as serial ports and parallel ports and has become commonplace on a wide range of devices. Examples of peripherals that are connected via USB include computer keyboards and mice, video cameras, printers, portable media players, mobile (portable) digital telephones, disk drives, and network adapters.

USB connectors have been increasingly replacing other types as charging cables of portable devices.

USB connector interfaces are classified into three types: the many various legacy Type-A (upstream) and Type-B (downstream) connectors, found on hosts, hubs, and peripheral devices; and the modern Type-C (USB-C) connector (which as of 2014 starts to replace all of the many legacy connectors and is the only applicable connector for USB4).

The Type-A and Type-B connectors came in Standard, Mini, and Micro sizes. The standard format was the largest and was mainly used for desktop and larger peripheral equipment. The Mini-USB connectors (Mini-A, Mini-B, Mini-AB) were introduced for mobile devices, but they were quickly replaced by the thinner Micro-USB connectors (Micro-A, Micro-B, Micro-AB). The Type-C connector, also known as USB-C, is not exclusive to USB, is the only current standard for USB, is required for USB4, and is required by other standards as well, including modern DisplayPort and Thunderbolt. It is reversible and can support various functionalities and protocols including USB; some are mandatory, many optional, depending on the type of the hardware: host, peripheral device, or hub.^[10][11]

USB specifications provide backward compatibility, but this usually results in a decrease in signalling rates, maximal power offered, and other provided capabilities. The USB 1.1 specification replaces USB 1.0. The USB 2.0 specification is backward-compatible with USB 1.0/1.1. The USB 3.2 specification replaces USB 3.1 (and USB 3.0) while also including the USB 2.0 specification. USB4 "functionally replaces" USB 3.2 while retaining USB 2.0 bus operating in parallel.^[5][6][7][2]

The USB 3.0 specification defined a new architecture and protocol, named SuperSpeed (aka SuperSpeed USB, marketed as SS), which included a new lane for a new signal coding scheme (8b/10b symbols, 5 Gbps; also known as Gen 1) providing full-duplex data transfers that physically required five additional wires and pins, while preserving the USB 2.0 architecture and protocols and therefore keeping the original 4 pins/wires for the USB 2.0 backward-compatibility resulting in 9 wires (with 9 or 10 pins at connector interfaces; ID-pin is not wired) in total.

The USB 3.1 specification introduced an Enhanced SuperSpeed System – while preserving the SuperSpeed architecture and protocol (SuperSpeed USB) – with an additional SuperSpeedPlus architecture and protocol (aka SuperSpeedPlus USB) adding a new coding schema (128b/132b symbols, 10 Gbps; also known as Gen 2); for some time period marketed as SuperSpeed+ (SS+).

The USB 3.2 specification ^[7] added a second lane to the Enhanced SuperSpeed System besides other enhancements, so that the SuperSpeedPlus USB system part implements the Gen 1×2, Gen 2×1 and Gen 2×2 operation modes. The SuperSpeed USB part of the system however still implements the one-lane Gen 1×1 operation mode. Therefore, two-lane operations, namely USB 3.2 Gen 1×2 (10 Gbit/s) and Gen 2×2 (20 Gbit/s), are only possible with Full-Featured USB-C. As of 2023, they are somewhat rarely implemented; Intel, however, starts to include them in its 11th generation SoC processor models, but Apple never provided them. On the other hand, USB 3.2 Gen 1(×1) (5 Gbit/s) and Gen 2(×1) (10 Gbit/s) has been quite common for some years.

Connector type quick reference

Each USB connection is made using two connectors: a receptacle and a plug. Pictures show only receptacles:

Available connectors by USB standard

Standard		USB 1.0 1996	USB 1.1 1998	USB 2.0 2000	USB 2.0 Revised	USB 3.0 2008	USB 3.1 2013	USB 3.2 2017	USB4 2019	USB4 v2.0 2022
Max Speed	Marketing name (operation mode)	Low-Speed & Full-Speed		High-Speed		SuperSpeed USB 5Gbps, original: SuperSpeed (Gen 1)	SuperSpeed USB 10 Gbps, original: SuperSpeed+ (Gen 2)	SuperSpeed USB 20 Gbps (USB 3.2 Gen 2×2)	USB4 40 Gbps (USB4 Gen 3×2)	USB4 80 Gbps (USB4 Gen 4)
	Signaling rate	1.5 Mbit/s & 12 Mbit/s		480 Mbit/s		5 Gbit/s	10 Gbit/s	20 Gbit/s	40 Gbit/s	80 Gbit/s
Connector	Standard-A							[rem 1]	—
	Standard-B							[rem 1]	—
	Mini-A	[rem 2]				—
	Mini-AB[rem 3][rem 4]					—
	Mini-B					—
	Micro-A[rem 5]	[rem 2] [rem 6]						[rem 1]	—
	Micro-AB[rem 3][rem 7]							[rem 1]	—
	Micro-B							[rem 1]	—
	Type-C (USB-C)	[rem 6]			(Enlarged to show detail)
Remarks:	^ a b c d e Limited to max speed at 10 Gbit/s, since only one-lane (Gen ×1) operation mode is possible. ^ a b Backward compatibility given. ^ a b Only as receptacle. ^ Accepts both Mini-A and Mini-B plugs. ^ Only as plug. ^ a b Backward compatibility given by USB 2.0 implementation. ^ Accepts both Micro-A and Micro-B plugs.

Objectives

The Universal Serial Bus was developed to simplify and improve the interface between personal computers and peripheral devices, such as cell phones, computer accessories, and monitors, when compared with previously existing standard or ad hoc proprietary interfaces.^[12]

From the computer user's perspective, the USB interface improves ease of use in several ways:

• The USB interface is self-configuring, eliminating the need for the user to adjust the device's settings for speed or data format, or configure interrupts, input/output addresses, or direct memory access channels.^[13]
• USB connectors are standardized at the host, so any peripheral can use most available receptacles.
• USB takes full advantage of the additional processing power that can be economically put into peripheral devices so that they can manage themselves. As such, USB devices often do not have user-adjustable interface settings.
• The USB interface is hot-swappable (devices can be exchanged without shutting the host computer down).
• Small devices can be powered directly from the USB interface, eliminating the need for additional power supply cables.
Zdroj:https://en.wikipedia.org?pojem=USB_1.1
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