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A four-port "long cable" "external box" USB hub A four-port "compact design" USB hub: upstream and downstream ports shown. A USB hub is a device that expands a single Universal Serial Bus (USB) port into several so that there are more ports available to connect devices to a host system, similar to a power strip. All devices connected through a ...
During USB communication, data is transmitted as packets. Initially, all packets are sent from the host via the root hub, and possibly more hubs, to devices. Some of those packets direct a device to send some packets in reply. After the sync field, all packets are made of 8-bit bytes, transmitted least-significant bit first. The first byte is a ...
USB up to 2.0 allows a host or hub to provide up to 2.5 W to each device, in five discrete steps of 100 mA, and SuperSpeed devices (USB 3.x) allows a host or a hub to provide up to 4.5 W in six steps of 150 mA. USB-C allows for dual-lane operation of USB 3.x with larger unit load (250 mA; up to 7.5 W) [96]. USB-C also allows for Type-C Current ...
Such a cable is non-standard, with the USB compliance specification stating that "use of a 'Y' cable (a cable with two A-plugs) is prohibited on any USB peripheral", meaning that "if a USB peripheral requires more power than allowed by the USB specification to which it is designed, then it must be self-powered." [51
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.
A USB compound device contains an embedded USB hub and one or more non-removable USB devices. [1] It may or may not have exposed downstream ports. The internal USB hub may be a physical IC that connects to other ICs, or the hub and all functions may be implemented in software on a single IC (though it is more common to integrate them as a composite device in this case).
In computing, a docking station, port replicator (hub), or dock provides a simplified way to plug-in a mobile device, such as connect common peripherals to a laptop, or charge a smartphone. Because a wide range of dockable devices—from mobile phones to wireless mouse —have different connectors, power signaling, and uses, docks are ...
USB 3.0 port provided by an ExpressCard-to-USB 3.0 adapter may be connected to a separately-powered USB 3.0 hub, with external devices connected to that USB 3.0 hub. On the motherboards of desktop PCs which have PCI Express (PCIe) slots (or the older PCI standard), USB 3.0 support can be added as a PCI Express expansion card .