Datasheet

Figure 32-8. Pad Events

Suspend detected

Cleared on Wakeup

Wakeup detected Cleared by software to acknowledge the interrupt

Active

Idle

Active

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 (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.

32.6.2.14 Remote Wakeup

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.

First, the USB must have detected a “Suspend” state on the bus, i.e. the remote wakeup request can only

be sent after INTFLAG.SUSPEND has been set.

The user may then write a one to the Remote Wakeup bit (CTRLB.UPRSM) to send an Upstream

Resume to the host initiating the wakeup. This will automatically be done by the controller after 5 ms of

inactivity on the USB bus.

When the controller sends the Upstream Resume INTFLAG.WAKEUP is set and INTFLAG.SUSPEND is

cleared.

The CTRLB.UPRSM is cleared at the end of the transmitting Upstream Resume.

In case of a rebroadcast resume initiated by the host, the End of Resume bit (INTFLAG.EORSM) flag is

set when the rebroadcast resume is completed.

SAM D21 Family

USB – Universal Serial Bus

Datasheet Complete

DS40001882D-page 804