Atmel Xplained Evaluation Board AT32UC3A3-XPLD AT32UC3A3-XPLD Data Sheet

32072H–AVR32–10/2012

After writing a one to USBCON.USBE, the USBB enters the Device or the Host mode (according
to the ID detection) in idle state.

The USBB can be disabled at any time by writing a zero to USBCON.USBE. In fact, writing a
zero to USBCON.USBE acts as a hardware reset, except that the OTGPADE, VBUSPO,
FRZCLK, UIDE, UIMOD and, LS bits are not reset.

One interrupt vector is assigned to the USB interface. 

 shows the struc-

ture of the USB interrupt system.