Product manual

Spinpoint M9TU-USB 3.0 Product Manual REV 1.0
47
USB INTERFACE AND USB COMMANDS
Figure 6-24: Data Stage
Status Stage reports the status of the overall request and this once again varies due to direction of transfer.
Status reporting is always performed by the function.
• IN (Figure 6-25): If the host sent IN token(s) during the data stage to receive data, then the host must
acknowledge the successful receipt of this data. This is done by the host sending an OUT token followed by a
zero length data packet. The function can now report its status in the handshaking stage. An ACK indicates the
function has completed the command is now ready to accept another command. If an error occurred during the
processing of this command, then the function will issue a STALL. However if the function is still processing, it
returns a NAK indicating to the host to repeat the status stage later.
Figure 6-25: Status In Stage
• OUT (Figure 6-26): If the host sent OUT token(s) during the data stage to transmit data, the function will
acknowledge the successful receipt of data by sending a zero length packet in response to an IN token.
However if an error occurred, it should issue a STALL or if it is still busy processing data, it should issue a
NAK asking the host to retry the status phase later.
Figure 6-26: Status Out Stage