DMA Programming Model
MSC8144E Reference Manual, Rev. 3
Freescale Semiconductor
14-43
Figure 14-15 shows the structure of a multi-dimensional BD, which is a 256-bit entry.
Figure 14-15. DMA Channel Multi-Dimensional Buffer Descriptor
Table 14-16 shows an example structure for a BD table that holds multi-dimensional read and
one-dimensional DMA write tasks. The read channel uses 512 BDs of multi-dimensional BDs,
which is the maximum available for multiple dimensions. The write channel uses 1024
one-dimensional BDs, which is the maximum available for one dimension. For details on BD
address calculation.
Figure 14-16. Example BD Table with a Mixed Dimensional Structure
The BDs are either one-dimensional or multi-dimensional. One-dimensional BDs are chained
only to one-dimensional BDs and multi-dimensional BDs are chained only to multi-dimensional
BDs. The types of source and destination BDs are defined in the DMACHCR (see page 14-25).
Table 14-28 lists the channel parameters for a one-dimensional BD.
255
0
BD_MD_ADDR
BD_MD_BSIZE
BD_MD_SIZE
BD_MD_ATTR
BD_MD_3D
BD_MD_4D
32 Bits
16 Bits
16 Bits
48 Bits
52 Bits
52 Bits
40 Bits
BD_MD_2D
40
92
144
192
208
224
Multi-Dimensional BD 0
One-Dimensional BD 0
Multi-Dimensional BD 1
Multi-Dimensional BD 511
One-Dimensional BD 1
One-Dimensional BD 1023
BDT_BASE Address
Содержание MSC8144E
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