i want to know every minute details about how a usb port works......??

Question

that means how usb devices interact with the port, how port sends data to computer and how computer access that data from port(software as well as hardware knowledge).

Answer 1

Check this out:
http://en.wikipedia.org/wiki/Usb

Answer 2

Universal Serial Bus (USB) is a serial bus standard to interface devices. It was designed for computers such as PCs and the Apple Macintosh, but its popularity has prompted it to also become commonplace on video game consoles, PDAs, cellphones; and even devices such as televisions and home stereo equipment (e.g., mp3 players), and portable memory devices.

The radio spectrum-based USB implementation is known as Wireless USB.

A USB system has an asymmetric design, consisting of a host controller and multiple daisy-chained devices. Additional USB hubs may be included in the chain, allowing branching into a tree structure, subject to a limit of 5 levels of branching per controller. No more than 127 devices, including the bus devices, may be connected to a single host controller. Modern computers often have several host controllers, allowing a very large number of USB devices to be connected. USB cables do not need to be terminated.

Because of the capability of daisy-chaining USB devices, early USB announcements predicted that each USB device would include a USB port to allow for long chains of devices. In this model, computers would not need many USB ports, and computers shipped at this time typically had only two. However, for economical and technical reasons, daisy chaining never became widespread. To reduce the necessity of USB hubs, computers now come with a large number of USB ports, typically six. Most modern desktop computers have up to half of their total complement of USB ports on the front panel, to facilitate connection of small portable devices that are usually connected only long enough to do what needs to be done.

USB was designed to allow peripherals to be connected without the need to plug expansion cards into the computer's ISA, EISA, or PCI bus, and to improve plug-and-play capabilities by allowing devices to be hot-swapped (connected or disconnected without powering down or rebooting the computer). When a device is first connected, the host enumerates and recognises it, and loads the device driver it needs.
A USB hub
A USB hub

USB can connect peripherals such as mouse devices, keyboards, gamepads and joysticks, scanners, digital cameras, printers, external storage, networking components, etc. For many devices such as scanners and digital cameras, USB has become the standard connection method. USB is also used extensively to connect non-networked printers, replacing the parallel ports which were widely used; USB simplifies connecting several printers to one computer. As of 2004 there were about 1 billion USB devices in the world. As of 2005, the only large classes of peripherals that cannot use USB, because they need a higher data rate than USB can provide, are displays and monitors, and high-quality digital video components.

The design of USB is standardized by the USB Implementers Forum (USB-IF), an industry standards body incorporating leading companies from the computer and electronics industries. Notable members have included Apple Computer, Hewlett-Packard, NEC, Microsoft, Intel, and Agere.

As of 2006 the USB specification is at version 2.0 (with revisions). Hewlett-Packard, Intel, Lucent, Microsoft, NEC, and Philips jointly led the initiative to develop a higher data transfer rate than the 1.1 specification. The USB 2.0 specification was released in April 2000 and was standardized by the USB-IF at the end of 2001. Previous notable releases of the specification were 0.9, 1.0, and 1.1. Equipment conforming with any version of the standard will also work with devices designed to any previous specification (known as: backwards compatibility).

Smaller USB plugs and receptacles, called Mini-A and Mini-B, are also available, as specified by the On-The-Go Supplement to the USB 2.0 Specification. As of 2006-08-02, the specification is at revision 1.2.

http://en.wikipedia.org/wiki/USB_port

Answer 3

The USB Process


When the host powers up, it queries all of the devices connected to the bus and assigns each one an address. This process is called enumeration -- devices are also enumerated when they connect to the bus. The host also finds out from each device what type of data transfer it wishes to perform:
Interrupt - A device like a mouse or a keyboard, which will be sending very little data, would choose the interrupt mode.

Bulk - A device like a printer, which receives data in one big packet, uses the bulk transfer mode. A block of data is sent to the printer (in 64-byte chunks) and verified to make sure it is correct.

Isochronous - A streaming device (such as speakers) uses the isochronous mode. Data streams between the device and the host in real-time, and there is no error correction.
The host can also send commands or query parameters with control packets.
As devices are enumerated, the host is keeping track of the total bandwidth that all of the isochronous and interrupt devices are requesting. They can consume up to 90 percent of the 480 Mbps of bandwidth that is available. After 90 percent is used up, the host denies access to any other isochronous or interrupt devices. Control packets and packets for bulk transfers use any bandwidth left over (at least 10 percent).

The Universal Serial Bus divides the available bandwidth into frames, and the host controls the frames. Frames contain 1,500 bytes, and a new frame starts every millisecond. During a frame, isochronous and interrupt devices get a slot so they are guaranteed the bandwidth they need. Bulk and control transfers use whatever space is left. The technical links at the end of the article contain lots of detail if you would like to learn more.

USB Features
The Universal Serial Bus has the following features:

The computer acts as the host.

Up to 127 devices can connect to the host, either directly or by way of USB hubs.

Individual USB cables can run as long as 5 meters; with hubs, devices can be up to 30 meters (six cables' worth) away from the host.

With USB 2.,the bus has a maximum data rate of 480 megabits per second.

A USB cable has two wires for power (+5 volts and ground) and a twisted pair of wires to carry the data.

On the power wires, the computer can supply up to 500 milliamps of power at 5 volts.

Low-power devices (such as mice) can draw their power directly from the bus. High-power devices (such as printers) have their own power supplies and draw minimal power from the bus. Hubs can have their own power supplies to provide power to devices connected to the hub.

USB devices are hot-swappable, meaning you can plug them into the bus and unplug them any time.

Many USB devices can be put to sleep by the host computer when the computer enters a power-saving mode.
The devices connected to a USB port rely on the USB cable to carry power and data.

Inside a USB cable: There are two wires for power -- +5 volts (red) and ground (brown) -- and a twisted pair (yellow and blue) of wires to carry the data. The cable is also shielded.



USB 2.0
The standard for USB version 2.0 was released in April 2000 and serves as an upgrade for USB 1.1.

USB 2.0 (High-speed USB) provides additional bandwidth for multimedia and storage applications and has a data transmission speed 40 times faster than USB 1.1. To allow a smooth transition for both consumers and manufacturers, USB 2.0 has full forward and backward compatibility with original USB devices and works with cables and connectors made for original USB, too.

Supporting three speed modes (1.5, 12 and 480 megabits per second), USB 2.0 supports low-bandwidth devices such as keyboards and mice, as well as high-bandwidth ones like high-resolution Webcams, scanners, printers and high-capacity storage systems. The deployment of USB 2.0 has allowed PC industry leaders to forge ahead with the development of next-generation PC peripherals to complement existing high-performance PCs. The transmission speed of USB 2.0 also facilitates the development of next-generation PCs and applications. In addition to improving functionality and encouraging innovation, USB 2.0 increases the productivity of user applications and allows the user to run multiple PC applications at once or several high-performance peripherals simultaneously.

Answer 4

i think it works by send a pulse to the computer, awaitin a result with a command. once it recieves the first pulse it will run its autoplay automatically, unless option changed. it will continue send and recieving pulses untill removed from a computer or disabled through hardware manager

Answer 5

everything you ever wanted to know about usb 2.0
http://www.usb.org/developers/docs/

Answer 6

I do not know. sry