39
GLOSSARY
Compound USB device
A compound USB device is a piece of equipment that
includes more than one USB Device or a combination of
USB Device(s) and USB Hub(s). For example, a USB
keyboard that includes a built-in USB Hub is a
compound USB device. Note that compound USB
devices are always full speed on the “upstream” side.
Upstream
Toward the host. Data passed from a device to a host
travels “upstream.”
Downstream
Toward a device. Data passed from a host to a device
travels “downstream.”
Full-speed
Describes a device that communicates with the host at
the full speed of the Universal Serial Bus, up to a
maximum of 12 Megabits per second (12 Mbps).
Low-speed
Describes a device that communicates with the host
using a special low-speed protocol, up to a maximum of
only 1.2 Megabits per second (1.2 Mbps).
