Fujitsu F2MC-16LX Hardware Manual page 315

CHAPTER 13 USB FUNCTION
Getting descriptor
The device receives a request from the host PC and sends data to the host.
In more detail, communications are performed in the following three stages:
Figure 13.4-3 Communication Stage
→ → status stage
Setup stage data stage
The setup stage ensures that the device receives normal packets from the host PC and identify the command
by decoding it. In addition, the next data stage prepares information on a descriptor to be sent back in a
transmission buffer. The data stage simply confirms that normal data is sent from the host PC. The status
stage performs end processing when the host PC sends a packet without data.
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