Product manual

Spinpoint M9TU-USB 3.0 Product Manual REV 1.0
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USB INTERFACE AND USB COMMANDS
Table 6-4: Visible Device States
6.3.6.1.1 Attached
A USB device may be attached or detached from the USB. The state of a USB device when it is detached from
the USB is not defined by this specification. This specification only addresses required operations and attributes
once the device is attached.
6.3.6.1.2 Powered
USB devices may obtain power from an external source and/or from the USB through the hub to which they are
attached. Externally powered USB devices are termed self-powered. Although self-powered devices may already
be powered before they are attached to the USB, they are not considered to be in the Powered state until they are
attached to the USB and V
BUS is applied to the device.
A device may support both self-powered and bus-powered configurations. Some device configurations support
either power source. Other device configurations may be available only if the device is self powered. Devices
report their power source capability through the configuration descriptor. The current power source is reported as
part of a device’s status. Devices may change their power source at any time, e.g., from self- to bus-powered. If a
configuration is capable of supporting both power modes, the power maximum reported for that configuration is
the maximum the device will draw from V
BUS in either mode.
The device must observe this maximum, regardless of its mode. If a configuration supports only one power
mode and the power source of the device changes, the device will lose its current configuration and address and
return to the Powered state. If a device is self-powered and its current configuration requires more than