Comtrol eCos - Manual (Page 793)

SA11X0 USB Device Driver
The exact DMA engines that will be used are determined by the configuration options
CYGNUM_DEVS_USB_SA11X0_EP1_DMA_CHANNEL and CYGNUM_DEVS_USB_SA11X0_EP2_DMA_CHANNEL . These
options have the booldata flavor, allowing the use of DMA to be disabled completely in addition to controlling
which DMA engines are used. If DMA is disabled then the device driver will attempt to work purely using the
fifos, and the packet size will be limited to only 16 bytes. This limit should be reflected in the appropriate endpoint
descriptors in the enumeration data. The code for driving the endpoints without DMA should be considered
experimental. At best it will be suitable only for applications where the amount of data transferred is relatively
small, because four times as many interrupts will be raised and performance will suffer accordingly.
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