at91rm3400 ATMEL Corporation, at91rm3400 Datasheet - Page 412

• Manufacturer Part Number: at91rm3400
• Description: Atmel Advanced At91 Arm Microcontroller
• Manufacturer: ATMEL Corporation

Controlling Device
States
412
AT91RM3400
A USB device has several possible states. Please refer to Chapter 9 of the Universal Serial
Bus Specification, Rev 2.0.
Figure 176. 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 UDP 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 uA 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.
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
1790A–ATARM–11/03