Texas Instruments TMS320C6745 DSP - Transmit Descriptors and Queue Status Configuration

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
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SPRUH91D–March 2013–Revised September 2016
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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)
31.2.8.12.1 Transmit USB Data Flow Using DMA
The transmit descriptors and queue status configuration prior to the transfer taking place is shown in
Figure 31-21. An example of initialization for a transmit USB data flow is shown in Figure 31-22.
Figure 31-21. Transmit Descriptors and Queue Status Configuration