Universal Serial Bus InterfaceMCF5253 Reference Manual, Rev. 124-136 Freescale Semiconductor• All packets described dTD were successfully transmitted. *** Total bytes in dTD will equal zerowhen this occurs.RX-dTD is complete when:• All packets described in dTD were successfully received. *** Total bytes in dTD will equal zerowhen this occurs.• A short packet (number of bytes < maximum packet length) was received. *** This is a successfultransfer completion; DCD must check Total Bytes in dTD to determine the number of bytes thatare remaining. From the total bytes remaining in the dTD, the DCD can compute the actual bytesreceived.• A long packet was received (number of bytes > maximum packet size) OR (total bytes received >total bytes specified). *** This is an error condition. The device controller will discard theremaining packet, and set the Buffer Error bit in the dTD. In addition, the endpoint will be flushedand the USBERR interrupt will become active.On the successful completion of the packet(s) described by the dTD, the active bit in the dTD will becleared and the next pointer will be followed when the Terminate bit is clear. When the Terminate bit isset, the USB_DR will flush the endpoint/direction and cease operations for that endpoint/direction.On the unsuccessful completion of a packet (see long packet above), the dQH will be left pointing to thedTD that was in error. In order to recover from this error condition, the DCD must properly re-initializethe dQH by clearing the active bit and update the nextTD pointer before attempting to re-prime theendpoint.NOTEAll packet level errors such as a missing handshake or CRC error will beretried automatically by the device controller.There is no required interaction with the DCD for handling such errors.24.11.3.4.1 Interrupt/Bulk Endpoint Bus Response MatrixTable 24-85. Interrupt/Bulk Endpoint Bus Response MatrixStall Not Primed Primed Underflow OverflowSetup Ignore Ignore Ignore N/A N/AIn STALL NAK Transmit BS Error 11 Force Bit Stuff Error.N/AOut STALL NAK Receive + NYET/ACK 22 NYET/ACK— NYET unless the Transfer Descriptor has packets remaining according tothe USB variable length protocol then ACK.SYSERR—System error should never occur when the latency FIFOs are correctly sizedand the DCD is responsive.N/A NAKPing STALL NAK ACK N/A N/AInvalid Ignore Ignore Ignore Ignore Ignore
