ADSP-BF537 Blackfin Processor Hardware Reference
5-19
Direct Memory Access
All the other registers not loaded from the descriptor retain their prior val-
ues, although the
DMAx_CURR_ADDR
,
DMAx_CURR_X_COUNT
, and
DMAx_CURR_Y_
COUNT
registers are reloaded between the descriptor fetch and the start of
DMA operation.
shows the offsets for descriptor elements in the three modes
described above. Note the names in the table describe the descriptor ele-
ments in memory, not the actual MMRs into which they are eventually
loaded.
Note that every descriptor fetch steals bandwidth from either the DCB
bus or DEB bus and the external memory interface, so it is best to keep
the size of descriptors as small as possible.
Mixing Flow Modes
The
FLOW
mode of a DMA is not a global setting. If the DMA configura-
tion word is reloaded with a descriptor fetch, the
FLOW
and
NDSIZE
bit
fields can also be altered. A small descriptor might be used to loop back to
Table 5-2. Parameter Registers and Descriptor Offsets
Descriptor
Offset
Descriptor Array
Mode
Small Descriptor List
Mode
Large Descriptor List
Mode
0x0
SAL
NDPL
NDPL
0x2
SAH
SAL
NDPH
0x4
DMACFG
SAH
SAL
0x6
XCNT
DMACFG
SAH
0x8
XMOD
XCNT
DMACFG
0xA
YCNT
XMOD
XCNT
0xC
YMOD
YCNT
XMOD
0xE
YMOD
YCNT
0x10
YMOD
Summary of Contents for Blackfin ADSP-BF537
Page 42: ...Contents xlii ADSP BF537 Blackfin Processor Hardware Reference ...
Page 90: ...Development Tools 1 32 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 138: ...Programming Examples 4 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 340: ...SDC Programming Examples 6 84 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 606: ...Programming Examples 9 94 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 660: ...Programming Examples 10 54 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 720: ...Electrical Specifications 11 60 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 840: ...Programming Examples 13 42 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 876: ...Programming Examples 14 36 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 938: ...Programming Examples 15 62 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 958: ...Programming Examples 17 12 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 986: ...Programming Examples 18 28 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1162: ...G 26 ADSP BF537 Blackfin Processor Hardware Reference ...
Page 1218: ...Index I 56 ADSP BF537 Blackfin Processor Hardware Reference ...