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(5)
Status Stage (Control-Out)
0-byte transmission to host
Set EP0i transmission
End of control transfer
The control-out status stage starts with an IN token from the host. When an IN-token is received at
the start of the status stage, there is not yet any data in the EP0i FIFO, and so an EP0i transfer
request interrupt is generated. The application recognizes from this interrupt that the status stage
has started. Next, in order to transmit 0-byte data to the host, 1 is written to the EP0i packet enable
bit but no data is written to the EP0i FIFO. As a result, the next IN token causes 0-byte data to be
transmitted to the host, and control transfer ends.
After the application has finished all processing relating to the data stage, 1 should be written to
the EP0i packet enable bit.
USB function
IN token reception
No
Valid data
in EP0i FIFO?
NAK
Yes
ACK
complete flag
(IFR0.EP0i TS = 1)
Figure 22.14 Status Stage (Control-Out) Operation
Section 22 USB Function Module (USB)
Clear EP0i transfer
Interrupt request
(IFR0.EP0i TR = 0)
Write 1 to EP0i packet
(TRG.EP0i PKTE = 1)
Clear EP0i transmission
Interrupt request
(IFR0.EP0i TS = 0)
End of control transfer
Rev. 1.00 Mar. 12, 2008 Page 877 of 1178
Application
request flag
enable bit
complete flag
REJ09B0403-0100
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