A USB compound device contains an embedded
USB hub
Universal Serial Bus (USB) is an industry standard that establishes specifications for cables, connectors and protocols for connection, communication and power supply (interfacing) between computers, peripherals and other computers. A broad ...
and one or more non-removable USB devices.
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). Compound devices have separate device addresses assigned to the hub and each downstream function, while composite devices have a single address. The hub's
descriptors indicate whether it is part of a compound device or a regular hub with only removable devices.
This arrangement is used by wireless receivers for
cordless keyboards and
mice (where the mouse and keyboard are separate devices connected to the compound device) and sometimes for
printer
Printer may refer to:
Technology
* Printer (publishing), a person or a company
* Printer (computing), a hardware device
* Optical printer for motion picture films
People
* Nariman Printer (fl. c. 1940), Indian journalist and activist
* James ...
s which have
memory card
A memory card is an electronic data storage device used for storing digital information, typically using flash memory. These are commonly used in digital portable electronic devices. They allow adding memory to such devices using a card in a so ...
slots.
References
{{DEFAULTSORT:Compound device
USB