Datasheet

450
6120F–ATARM–03-Oct-06
AT91SAM7X512/256/128 Preliminary
34.5.3 Controlling Device States
A USB device has several possible states. Refer to Chapter 9 of the Universal Serial Bus Speci-
fication, Rev 2.0.
Figure 34-14. USB Device State Diagram
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 Sus-
pend/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 activ-
ity) 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