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Figure 42.
ISO RX DMA Start Routine
Transmit DMA Channels Overview
SPRU761A
ISO RXDMA[0,1, 2]
start routine
EP number −−>
RXDMA_CFG.
RXDMAn_EP.
Application-Specific
action to intialize the
main system DMA
controller
End of
ISO RXDMA [0,1, 2]
start routine
Transmit DMA channels are programmed via the three TXDMA control
registers. Each channel can be assigned to a given endpoint number by
assigning a non-zero value in TXDMA_CFG.TXDMAn_EP (a 0 value means
the DMA channel is deselected). The other three control registers (TXDMA0,
TXDMA1, and TXDMA2) operate in a different manner for ISO and non-ISO
endpoints. Transmitted data must be written into the DATA_DMA when a TX
DMA request is active. They are written into the TX FIFO of the endpoint
associated with active request (only one TX DMA request active at a given
time).
The USB device controller transmit DMA channels 0 through 2 are connected
to OMAP5912 DMA controller requests DMA_REQ_29, DMA_REQ_30, and
DMA_REQ_31, respectively.
USB Device Controller
Assign ISO endpoint number
to DMA channel n.
LH DMA read access
must point to
DATA_DMA register in
response to DMA
channel n request.
If no interrupt is signaled to
the LH (except SOF if
enabled), the Device DMA
sends a new DMA request to the LH
DMA controller every frame till
the HOST stops sending ISO
packets to the endpoint.
Universal Serial Bus (USB)
185
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