38.6.1.6 Pad Suspend

Figure 38-5 shows the pad behavior.

Figure 38-5. Pad Behavior
  • In Idle state, the pad is put in Low-power mode, i.e., the differential receiver of the USB pad is off, and internal pull-downs with a strong value (15 K) are set in HSDP/D and HSDM/DM to avoid floating lines.
  • In Active state, the pad is working.

Figure 38-6 illustrates the pad events leading to a PAD state change.

Figure 38-6. Pad Events

The USBHS_DEVISR.SUSP bit is set and the Wakeup Interrupt (USBHS_DEVISR.WAKEUP) bit is cleared when a USB “Suspend” state has been detected on the USB bus. This event automatically puts the USB pad in Idle state. The detection of a non-idle event sets USBHS_DEVISR.WAKEUP, clears USBHS_DEVISR.SUSP and wakes up the USB pad.

The pad goes to the Idle state if the USBHS is disabled or if the USBHS_DEVCTRL.DETACH bit = 1. It returns to the Active state when USBHS_CTRL.USBE = 1 and USBHS_DEVCTRL.DETACH = 0.