Atmel Evaluation Kit AT91SAM9G25-EK AT91SAM9G25-EK Data Sheet

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SAM9G25 [DATASHEET]

11032C–ATARM–25-Jan-13

A USB device has several possible states. Refer to Chapter 9 (USB Device Framework) of the Universal Serial Bus
Specification, Rev 2.0. 

Movement from one state to another depends on the USB bus state or on standard requests sent through control
transactions via the default endpoint (endpoint 0).

After a period of bus inactivity, the USB device enters Suspend Mode. Accepting Suspend/Resume requests from the
USB host is mandatory. Constraints in Suspend Mode are very strict for bus-powered applications; devices may not
consume more than 500 µA on the USB bus.

While in Suspend Mode, the host may wake up a device by sending a resume signal (bus activity) or a USB device may
send a wake-up request to the host, e.g., waking up a PC by moving a USB mouse.

The wake-up feature is not mandatory for all devices and must be negotiated with the host. 

Attached

Suspended

Suspended

Suspended

Suspended

Hub Reset

or

Deconfigured

Hub

Configured

Bus Inactive

Bus Activity

Bus Inactive

Bus Activity

Bus Inactive

Bus Activity

Bus Inactive

Bus Activity

Reset

Reset

Address

Assigned

Device

Deconfigured

Device

Configured

Powered

Default

Address

Configured

Power

Interruption