0
CPPI Packet
Packet Descriptor
Buffer pointer
Buffer size (256)
Next descriptor pointer
Buffer Descriptor
Buffer pointer
Buffer size (256)
Next descriptor pointer
Buffer Descriptor
Buffer size (96)
Packet size (608)
Data
Buffer
(Valid
data)
Data
Buffer
(Valid
data)
Data
Buffer
(Valid
data)
PBD(1)
PBD(2)
PPD
PPD PBD(1) PBD(2)
. . .
Tail
Head
Queue 93: USB0 EP1 TXCQ
. . .
. . .
. . .
. . .
Tail
Head
Queue 32: USB0 EP1 TXSQ
Preliminary
Communications Port Programming Interface (CPPI) 4.1 DMA
www.ti.com
Figure 20-17. Transmit Descriptors and Queue Status Configuration
20.4.9.1.1 Transmit Initialization (Step 1)
The CPU performs the following steps for transmit initialization:
1. Initializes Memory Region 0 base address and Memory Region 0 size, Link RAM0 Base address,
Link RAM0 data size, and Link RAM1 Base address.
2. Creates PD, BDs, and DBs in main memory and link as indicated in
3. Initializes and configures the Queue Manager, Channel Setup, DMA Scheduler, and Mentor USB
2.0 Core.
4. Adds (pushes) the PPD and the two PBDs to the TXSQ by writing the Packet Descriptor address to
the TXSQ CTRL D Register.
captures the BD/DB pair in main memory and later submitted within the TXSQ.
1814
Universal Serial Bus (USB)
SPRUGX9 – 15 April 2011
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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