38.6.2.9 Remote Wakeup

The Remote Wakeup request (also known as Upstream Resume) is the only one the device may send without a host invitation, assuming a host command allowing the device to send such a request was previously issued. The sequence is the following:

  1. The USBHS must have detected a “Suspend” state on the bus, i.e., the Remote Wakeup request can only be sent after a USBHS_DEVISR.SUSP interrupt has been set.
  2. The user writes a one to the Remote Wakeup (USBHS_DEVCTRL.RMWKUP) bit to send an upstream resume to the host for a remote wakeup. This will automatically be done by the controller after 5 ms of inactivity on the USB bus.
  3. When the controller sends the upstream resume, the Upstream Resume (USBHS_DEVISR.UPRSM) interrupt is set and USBHS_DEVISR.SUSP is cleared.
  4. USBHS_DEVCTRL.RMWKUP is cleared at the end of the upstream resume.
  5. When the controller detects a valid “End of Resume” signal from the host, the End of Resume (USBHS_DEVISR.EORSM) interrupt is set.