Datasheet

262
7766F–AVR–11/10
ATmega16/32U4
Figure 21-12. Pad behaviour
The SUSPI flag indicated that a suspend state has been detected on the USB bus. This flag
automatically put the USB pad in Idle. The detection of a non-idle event sets the WAKEUPI flag
and wakes-up the USB pad.
Moreover, the pad can also be put in the “idle” mode if the DETACH bit is set. It come back in
the active mode when the DETACH bit is cleared.
21.11 Plug-in detection
The USB connection is detected by the VBUS pad, thanks to the following architecture:
Idle mode
Active mode
USBE=1
& DETACH=0
& suspend
USBE=0
| DETACH=1
| suspend
SUSPI
Suspend detected = USB pad power down
Clear Suspend by software
Resume = USB pad wake-up
Clear Resume by software
WAKEUPI
PAD status
Active
Power Down
Active