DMA Operation
13-119
USB Function Module
13.7.3 Isochronous OUT (USB HOST
−>
LH) DMA Transactions
During isochronous transfers to a DMA-operated OUT endpoint, a request to
the local host DMA controller is generated every 1-ms frame when an isochro-
nous data packet is received with no error. There is no interrupt associated with
DMA transfer to isochronous OUT endpoints.
Figure 13–39. Isochronous RX DMA Transaction
1ms
1
1
2
3
4
Host message
FIFO content
System DMA read
Dma_request
1
2
2
3
3
4
4
Error
6
6
6
Figure 13–40. Isochronous RX DMA Start Routine
ISO RXDMA[0,1, 2]
start routine
Assign ISO endpoint number
to DMA channel n.
End of
ISO RXDMA [0,1, 2]
start routine
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.
Application-Specific
action to intialize the
main system DMA
controller
LH DMA read access
must point to
DATA_DMA register in
response to DMA
channel n request.
EP number
−−>
RXDMA_CFG.
RXDMAn_EP.