USB Transaction
When the USB transmits or receives data:
1.The USB uses the address generation in Table
2.After reading the BDT, if the OWN bit equals 1, the SIE DMAs the data to or from the buffer indicated by the BD’s ADDR field.
3.When the TOKEN is complete, the USB updates the BDT and changes the OWN bit to 0 if KEEP is 0.
4.The USB updates the STAT register and sets the TOK_DNE interrupt.
5.When the microprocessor processes the TOK_DNE interrupt:
6.The microprocessor reads the status register for the information it needs to process the endpoint
7.The microprocessor allocates a new BD, so the endpoint can transmit or receive additional USB data, then processes the last BD.
Figure
Figure 4-2. USB Token Transaction
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