Cypress Semiconductor /psoc63 /USBFS0 /USBDEV /EP0_CNT

These bits indicate the number of data bytes in a transaction. For IN transactions firmware loads the count with the number of bytes to be transmitted to the host from the endpoint FIFO. Valid values are 0 to 8. For OUT or SETUP transactions the count is updated by hardware to the number of data bytes received plus two for the CRC bytes. Valid values are 2 to 10.

This bit is used for OUT/SETUP transactions only and is read only. It is cleared to ‘0’ if CRC bit stuffing errors or PID errors occur. This bit does not update for some endpoint mode settings.

0 (DATA_ERROR): No ACK’d transactions since bit was last cleared.

1 (DATA_VALID): Indicates a transaction ended with an ACK.

This bit selects the DATA packet’s toggle state. For IN transactions firmware must set this bit to the expected state. For OUT transactions the hardware sets this bit to the state of the received Data Toggle bit.