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USB Device Controller
Figure 45.
ISO TX DMA Start Routine
Important Note on DMA Requests
Note on DMA Channels Deconfiguration
190
Universal Serial Bus (USB)
ISO TXDMA[0,1, 2]
start routine
EP number −−>
TXDMA_CFG.
TXDMAn_EP
Application-specific
action to initialize the
main system DMA
controller
Start DMA transfer:
TXDMAn._TSC = FTZ,
TXDMAn.TXn_EOT = 1,
TXDMAn.TXn_START = 1.
End of ISO TXDMA
[0,1, 2]
start routine
For each direction, only one DMA request can be active at any time. A request
must then be serviced to allow the next pending request on the same direction
to be asserted. In particular, a TX DMA request is asserted at each
start-of-frame if a TX DMA channel is configured for an isochronous endpoint;
this
request must be serviced imperatively.
It is recommended that the MPU wait for an EOT (RX) or a DONE (TX) interrupt
before disabling the channel by writing a value 0 in the TX/RXDMA_CFG
Assign ISO endpoint number
to DMA channel n.
LH DMA write access
must point to
TXDCHn.TXDATn in
response to DMA
channel n request.
EOT bit is don't care for ISO
endpoints.
If no interrupt is signaled to
the LH (except SOF if
enabled), the Device DMA
sends a new request to the LH
DMA controller every frame.
SPRU761A
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