Atmel Xplained Pro Evaluation Kit for the ATSAMD21J18A Microcontroller ATSAMD21-XPRO ATSAMD21-XPRO Data Sheet

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Atmel | SMART SAM D21 [DATASHEET]

Atmel-42181C–SAM-D21_Datasheet–07/2014

Endpoint n / IN: EPCFG.EPTYPE1 = Interrupt IN, PCKSIZE.SIZE = 64.

Endpoint n / OUT: EPCFG.EPTYPE0= Isochronous OUT, PCKSIZE.SIZE = 512.

 illustrates the behavior of the USB pad in device mode.

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

In Active state, the pad is active.

 illustrates the pad events leading to a PAD state change.

The Suspend Interrupt bit in the Device Interrupt Flag register (INTFLAG.SUSPEND) is set when a USB Suspend state 
has been detected on the USB bus. The USB pad is then automatically put in the Idle state. The detection of a non-idle 
state sets the Wake Up Interrupt bit in INTFLAG(INTFLAG.WAKEUP) and wakes the USB pad.

The pad goes to the Idle state if the USB module is disabled or if CTRLB.DETACH is written to one. It returns to the 
Active state when CTRLA.ENABLE is written to one and CTRLB.DETACH is written to zero.

The remote wakeup request (also known as upstream resume) is the only request the device may send on its own 
initiative. This should be preceded by a DEVICE_REMOTE_WAKEUP request from the host.

CTRLA.ENABLE = 0

|       CTRLB.DETACH = 1
| INTFLAG.SUSPEND = 1

CTRLA.ENABLE = 1

|        CTRLB.DETACH = 0

|   INTFLAG.SUSPEND = 0

SUSPEND

Suspend detected

Cleared on Wakeup

Wakeup detected

Cleared by software to acknowledge the interrupt

WAKEUP

PAD state

Active

Idle

Active