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Next Descriptor Pointer
Buffer Pointer
Buffer Size (256)
Buffer Descriptor
Packet Size (608)
Packet Descriptor
Buffer Pointer
Buffer Size (256)
Next Descriptor Pointer
0
Buffer Pointer
Buffer Size (96)
Buffer Descriptor
Data Buffer
(Valid Data)
PPD
PBD(1)
PBD(2)
Data Buffer
(Valid Data)
Data Buffer
(Valid Data)
CPPI Packet
PBD(1)
PBD(2)
PPD
Head
Tail
Queue 16: TXSQ
Head
Tail
Queue 24: TXCQ
Architecture
1666
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
Universal Serial Bus 2.0 (USB) Controller
PPD—
Pointer to Host Packet Descriptor
RXCQ—
Receive Completion Queue or Receive Return Queue (for all Rx EPs, use 26 or 27)
RXSQ—
Receive Free Packet/Buffer Descriptor Queue or Receive Submit Queue. (for all Rx EPs, use 0
to 15)
TXCQ—
Transmit Completion Queue or Transmit Return Queue (for all Tx EPs, use 24 or 25)
TXSQ—
Transmit Queue or Transmit Submit Queue (for EP1, use 16 or 17)
34.2.8.12.1 Transmit USB Data Flow Using DMA
The transmit descriptors and queue status configuration prior to the transfer taking place is shown in
. An example of initialization for a transmit USB data flow is shown in
.
Figure 34-21. Transmit Descriptors and Queue Status Configuration