Datasheet

265
ATmega16U4/32U4 [DATASHEET]
Atmel-7766J-USB-ATmega16U4/32U4-Datasheet_04/2016
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:
Figure 21-13. Plug-in Detection Input Block Diagram
The control logic of the VBUS pad outputs a signal regarding the VBUS voltage level:
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
VBUSTI
USBINT.0
VBUS
VBUS
USBSTA.0
VSS
VDD
Pad logic
Session_valid
R
PU
R
PU