Analog Devices VisualDSP++ 5.0 Service Manual page 258

Theory of Operation
can pass in the address of the descriptor union
(
ADI_DMA_DESCRIPTOR_UNION
itself (
ADI_DMA_DESCRIPTOR_LARGE
data type. This descriptor can be a single descriptor or the first descriptor
in a chain of descriptors.
Large model descriptors contain all the information necessary for the
DMA manager to control the operation of the DMA controller. This
information includes:
• A pointer to the next large descriptor in the chain. If this field is
NULL, the given descriptor is the only descriptor the client is
submitting to the channel.
• The starting address of the buffer. This value is the address in
memory where data is initially read from (when the transfer is for
outbound data), or the address in memory where data is initially
stored (when the transfer is for inbound data).
• The configuration word for the transfer. This 16-bit value
represents the DMA configuration register for the channel. The
DMA manager include file provides macros that allow the client to
quickly and easily create a configuration word. The client provides
the following values to fields within the configuration word.
WNR
(Transfer Direction)
WDSIZE
(Transfer Element Size)
DMA2D
(Dimension Select)
6-18
) or alternatively, the address of the descriptor
) to the
ADI_DMA_WNR_READ
ADI_DMA_WNR_WRITE
ADI_DMA_WD_SIZE_8BIT
ADI_DMA_WD_SIZE_16BIT
ADI_DMA_WD_SIZE_32BIT
ADI_DMA_DMA2D_LINEAR
ADI_DMA_DMA2D_2D
VisualDSP++ 5.0 Device Drivers and System
Services Manual for Blackfin Processors
ADI_DMA_DESCRIPTOR_HANDLE
Transfer is for outbound data.
Transfer is for inbound data.
Elements are 1 byte wide (8 bits).
Elements are 2 bytes wide (16 bits).
Elements are 4 bytes wide (32 bits).
One-dimensional (linear) transfer
Two-dimensional transfer