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USB Implementers Forum, Inc. (USB-IF) is a nonprofit organization created to promote and maintain USB (Universal Serial Bus), a set of specifications and transmission procedures for a type of cable connection that has since become used widely for electronic equipment.
The USB HID class keyboard is normally designed with an IN endpoint that communicates keystrokes to the computer and an OUT endpoint that communicates the status of the keyboard's LEDs from the computer to the keyboard. The PC 97 standard requires that a computer's BIOS must detect and work with USB HID class keyboards that are designed to be ...
USB bridge cables, or data transfer cables can be found within the market, offering direct PC to PC connections. A bridge cable is a special cable with a chip and active electronics in the middle of the cable.
USB communications device class (or USB CDC) is a composite Universal Serial Bus device class. The communications device class is used for computer networking devices akin to a network card , providing an interface for transmitting Ethernet or ATM frames onto some physical media.
Thus, USB cables have different ends: A and B, with different physical connectors for each. Each format has a plug and receptacle defined for each of the A and B ends. A USB cable, by definition, has a plug on each end—one A (or C) and one B (or C)—and the corresponding receptacle is usually on a computer or electronic device.
For example, a USB 2 PCIe host controller card that presents 4 USB "Standard A" connectors typically presents one 4-port EHCI and two 2-port OHCI controllers to system software. When a high-speed USB device is attached to any of the 4 connectors, the device is managed through one of the 4 root hub ports of the EHCI controller.
Some other computer architectures use different modules with a different bus width. In a single-channel configuration, only one module at a time can transfer information to the CPU. In multi-channel configurations, multiple modules can transfer information to the CPU at the same time, in parallel.
The OHCI standard for USB is similar to the OHCI standard for IEEE 1394, but supports USB 1.1 (full and low speeds) only; so as a result its register interface looks completely different. Compared with UHCI, it moves more intelligence into the controller, and thus is accordingly much more efficient; this was part of the motivation for defining it.