Endpoint Reset

An endpoint can be reset at any time by writing a one to the Endpoint x Reset bit USBHS_DEVEPT.EPRSTx. This is recommended before using an endpoint upon hardware reset or when a USB bus reset has been received. This resets:

• the internal state machine of the endpoint,
• the receive and transmit bank FIFO counters,
• all registers of this endpoint (USBHS_DEVEPTCFGx, USBHS_DEVEPTISRx, the Endpoint x Control (USBHS_DEVEPTIMRx) register), except its configuration (USBHS_DEVEPTCFGx.ALLOC, USBHS_DEVEPTCFGx.EPBK, USBHS_DEVEPTCFGx.EPSIZE, USBHS_DEVEPTCFGx.EPDIR, USBHS_DEVEPTCFGx.EPTYPE) and the Data Toggle Sequence (USBHS_DEVEPTISRx.DTSEQ) field.

  Note: The interrupt sources located in USBHS_DEVEPTISRx are not cleared when a USB bus reset has been received.

The endpoint configuration remains active and the endpoint is still enabled.

The endpoint reset may be associated with a clear of the data toggle sequence as an answer to the CLEAR_FEATURE USB request. This can be achieved by writing a one to the Reset Data Toggle Set bit (RSTDTS) in the Device Endpoint x Control Set register (this sets the Reset Data Toggle bit USBHS_DEVEPTIMRx.RSTDT).

In the end, the user has to write a zero to the USBHS_DEVEPT.EPRSTx bit to complete the reset operation and to start using the FIFO.