The pipe is maintained inactive and reset (see "Pipe Reset" for more details) as long as it is disabled (USBHS_HSTPIP.PENx = 0). The Data Toggle Sequence field (USBHS_HSTPIPISRx.DTSEQ) is also reset.
The algorithm represented in the following figure must be followed to activate a pipe.
As long as the pipe is not correctly configured (USBHS_HSTPIPISRx.CFGOK = 0), the controller cannot send packets to the device through this pipe.
The USBHS_HSTPIPISRx.CFGOK bit is only set if the configured size and number of banks are correct as compared to their maximal allowed values for the pipe (see the Description of USB Pipes/Endpoints table) and to the maximal FIFO size (i.e., the DPRAM size).
See "DPRAM Management" for additional information.
Once the pipe is correctly configured (USBHS_HSTPIPISRx.CFGOK = 1), only the USBHS_HSTPIPCFGx.PTOKEN and USBHS_HSTPIPCFGx.INTFRQ fields can be written by software. USBHS_HSTPIPCFGx.INTFRQ is meaningless for non-interrupt pipes.
When starting an enumeration, the user gets the device descriptor by sending a GET_DESCRIPTOR USB request. This descriptor contains the maximal packet size of the device default control endpoint (bMaxPacketSize0) and the user reconfigures the size of the default control pipe with this size parameter.