USB - Wikipedia. Universal Serial Bus (USB)Certified USB logo. Type. Bus. Production history. Designer. Compaq, DEC, IBM, Intel, Microsoft, NEC and Nortel. Designed. January 1. Produced. Since May 1. It has largely replaced a variety of earlier interfaces, such as serial ports and parallel ports, as well as separate power chargers for portable devices – and has become commonplace on a wide range of devices. Also, there are 5 modes of USB data transfer, in order of increasing bandwidth: Low Speed (from 1.
Full Speed (from 1. High Speed (from 2. Super. Speed (from 3.
Super. Speed+ (from 3. USB devices have some choice of implemented modes, and USB version is not a reliable statement of implemented modes. Modes are identified by their names and icons, and the specifications suggests that plugs and receptacles be colour- coded (Super. Speed is identified by blue). Unlike other data buses (e. Ethernet, HDMI), USB connections are directed, with both upstream and downstream ports emanating from a single host.
This applies to electrical power, with only downstream facing ports providing power; this topology was chosen to easily prevent electrical overloads and damaged equipment. Thus, USB cables have different ends: A and B, with different physical connectors for each. Therefore, in general, each different format requires four different connectors: a plug and receptacle for each of the A and B ends.
USB cables have the plugs, and the corresponding receptacles are on the computers or electronic devices. In common practice, the A end is usually the standard format, and the B side varies over standard, mini, and micro. The mini and micro formats also provide for USB On- The- Go with a hermaphroditic AB receptacle, which accepts either an A or a B plug. On- the- Go allows USB between peers without discarding the directed topology by choosing the host at connection time; it also allows one receptacle to perform double duty in space- constrained applications. There are cables with A plugs on both ends, which may be valid if the cable includes, for example, a USB host- to- host transfer device with 2 ports, but they could also be non- standard and erroneous and should be used carefully.
The standard and mini connectors have a design lifetime of 1,5. The micro connectors were designed with frequent charging of portable devices in mind, so have a design life of 1. Likewise, the springy component of the retention mechanism, parts that provide required gripping force, were also moved into plugs on the cable side. A team including Ajay Bhatt worked on the standard at Intel. The first widely used version of USB was 1. September 1. 99. 8.
The 1. 2 Mbit/s data rate was intended for higher- speed devices such as disk drives, and the lower 1. Mbit/s rate for low data rate devices such as joysticks.
Hewlett- Packard, Intel, Lucent Technologies (now Nokia), NEC, and Philips jointly led the initiative to develop a higher data transfer rate, with the resulting specification achieving 4. Mbit/s, 4. 0 times as fast as the original USB 1. The USB 3. 0 specification was published on 1. Was Ist Ein Core Keygen Cs5. November 2. 00. 8. Its main goals were to increase the data transfer rate (up to 5 Gbit/s), decrease power consumption, increase power output, and be backward compatible with USB 2. It did not allow for extension cables or pass- through monitors, due to timing and power limitations. Few USB devices made it to the market until USB 1.
August 1. 99. 8, which introduced the speed of 1. Mbit/s (full speed).
Though many designs for a miniaturised type B connector appeared on many peripheral devices, conformance to the USB 1. There was no known miniature type A connector until USB 2. USB 2. 0. Due to bus access constraints, the effective throughput of the High Speed signaling rate is limited to 2. Mbit/s or 3. 5 MB/s. The most important of these ECNs are included into the USB 2.
USB. org. Also receptacle that accepts both plugs for On- The- Go. These should not be confused with Micro- B plug and receptacle. Pull- up/Pull- down Resistors ECN: Released in May 2. Interface Associations ECN: Released in May 2. New standard descriptor was added that allows associating multiple interfaces with a single device function. Rounded Chamfer ECN: Released in October 2.
Several alternatives exist for networking two computers in this manner: Ethernet crossover cable; Null modem serial cable or parallel peripheral cable.
A recommended, backward compatible change to Mini- B plugs that results in longer lasting connectors. Unicode ECN: Released in February 2. This ECN specifies that strings are encoded using UTF- 1. LE. USB 2. 0 specified Unicode, but did not specify the encoding. Inter- Chip USB Supplement: Released in March 2. On- The- Go Supplement 1. Released in December 2. Best Software For Flash Presentations.
USB On- The- Go makes it possible for two USB devices to communicate with each other without requiring a separate USB host. In practice, one of the USB devices acts as a host for the other device. Battery Charging Specification 1. Released in March 2. April 2. 00. 9. Adds support for dedicated chargers (power supplies with USB connectors), host chargers (USB hosts that can act as chargers) and the No Dead Battery provision, which allows devices to temporarily draw 1.
A current after they have been attached. If a USB device is connected to a dedicated charger, maximum current drawn by the device may be as high as 1. A. Device in this state is not required to reduce its power consumption. However, switching between enabled and sleep states is much faster than switching between enabled and suspended states, which allows devices to sleep while idle.
Battery Charging Specification 1. Super. Speed plugs and receptacles are identified with a distinct logo and blue inserts in standard format receptacles. The new Super. Speed mode provides a data signaling rate of 5. Gbit/s. However, due to the overhead incurred by 8b/1.
Gbit/s, and the specification considers it reasonable to achieve only around 3. Gbit/s (0. 4 GB/s or 4. MB/s). However, this should increase with future hardware advances. Communication is full- duplex in Super. Speed transfer mode; earlier modes are half- duplex, arbitrated by the host. The USB 3. 1 specification takes over the existing USB 3. Super. Speed USB transfer rate, also referred to as USB 3.
Gen 1, and introduces a faster transfer rate called Super. Speed USB 1. 0 Gbps, also referred to as USB 3.
Gen 2. The new mode's logo features a caption stylized as SUPERSPEED+. The USB 3. 1 Gen 2 standard increases the data signaling rate to 1.
Gbit/s, double that of Super. Speed USB, and reduces line encoding overhead to just 3% by changing the encoding scheme to 1. Additional USB hubs may be included in the tiers, allowing branching into a tree structure with up to five tier levels. A USB host may implement multiple host controllers and each host controller may provide one or more USB ports. Up to 1. 27 devices, including hub devices if present, may be connected to a single host controller. One hub—built into the host controller—is the root hub. A physical USB device may consist of several logical sub- devices that are referred to as device functions.
A single device may provide several functions, for example, a webcam (video device function) with a built- in microphone (audio device function). This kind of device is called a composite device.
An alternative to this is compound device, in which the host assigns each logical device a distinctive address and all logical devices connect to a built- in hub that connects to the physical USB cable. A pipe is a connection from the host controller to a logical entity, found on a device, and named an endpoint. Because pipes correspond 1- to- 1 to endpoints, the terms are sometimes used interchangeably.
A USB device could have up to 3. IN, 1. 6 OUT), though it is rare to have so many. An endpoint is defined and numbered by the device during initialization (the period after physical connection called . A message pipe is bi- directional and is used for control transfers. Message pipes are typically used for short, simple commands to the device, and a status response, used, for example, by the bus control pipe number 0.
A stream pipe is a uni- directional pipe connected to a uni- directional endpoint that transfers data using an isochronous. If the direction of the data transfer is from the host to the endpoint, an OUT packet (a specialization of a TOKEN packet) having the desired device address and endpoint number is sent by the host. If the direction of the data transfer is from the device to the host, the host sends an IN packet instead. If the destination endpoint is a uni- directional endpoint whose manufacturer's designated direction does not match the TOKEN packet (e. Otherwise, it is accepted and the data transaction can start.
A bi- directional endpoint, on the other hand, accepts both IN and OUT packets. An exception to this is endpoint zero, which is used for device configuration and is not associated with any interface. A single device function composed of independently controlled interfaces is called a composite device. A composite device only has a single device address because the host only assigns a device address to a function. When a USB device is first connected to a USB host, the USB device enumeration process is started. The enumeration starts by sending a reset signal to the USB device.
The data rate of the USB device is determined during the reset signaling. After reset, the USB device's information is read by the host and the device is assigned a unique 7- bit address. If the device is supported by the host, the device drivers needed for communicating with the device are loaded and the device is set to a configured state. If the USB host is restarted, the enumeration process is repeated for all connected devices. The host controller directs traffic flow to devices, so no USB device can transfer any data on the bus without an explicit request from the host controller. In USB 2. 0, the host controller polls the bus for traffic, usually in a round- robin fashion. The throughput of each USB port is determined by the slower speed of either the USB port or the USB device connected to the port.
High- speed USB 2.