at91sam9260-cj ATMEL Corporation, at91sam9260-cj Datasheet - Page 647

• Manufacturer Part Number: at91sam9260-cj
• Description: At91 Arm Thumb Microcontrollers
• Manufacturer: ATMEL Corporation

37.5.3
Figure 37-14. USB Device State Diagram
647
AT91SAM9260
Controlling Device States
A USB device has several possible states. Refer to Chapter 9 of the Universal Serial Bus Speci-
fication, 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 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.
Reset
Interruption
Power
Deconfigured
Deconfigured
Hub Reset
Device
or
Configured
Attached
Powered
Address
Default
Configured
Configured
Assigned
Address
Hub
Device
Reset
Bus Inactive
Bus Inactive
Bus Inactive
Bus Inactive
Bus Activity
Bus Activity
Bus Activity
Bus Activity
Suspended
Suspended
Suspended
Suspended
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