Atmel SAM4L-EK Atmel ATSAM4L-EK ATSAM4L-EK Data Sheet

42023E–SAM–07/2013

 illustrates the behavior of the USB pad in device mode.

Figure 17-4. Pad Behavior

• In Idle state, the pad is in low power consumption mode.

• In Active state, the pad is working.

 illustrates the pad events leading to a PAD state change.

Figure 17-5. Pad events

The Suspend Interrupt bit in the Device Global Interrupt register (UDINT.SUSP) is set when a
USB Suspend state has been detected on the USB bus. This event automatically puts the USB
pad in the Idle state. The detection of a non-idle event sets WAKEUP and wakes the USB pad.

The pad goes to the Idle state if the module is disabled or if UDCON.DETACH is written to one.
It returns to the Active state when USBCON.USBE is written to one and DETACH is written to
zero.

Idle

Active

   USBE = 1
& DETACH = 0
& Suspend

  USBE = 0
| DETACH = 1
| Suspend

SUSP

Suspend detected

Cleared on Wakeup

Wakeup detected

Cleared by software to acknowledge the interrupt

WAKEUP

PAD state

Active

Idle

Active