Modes of Operation
5-18
ADSP-BF537 Blackfin Processor Hardware Reference
descriptor must reside in the same 64 KB address space as the first one,
because the upper 16 bits of the
DMAx_NEXT_DESC_PTR
register are not
updated.
Descriptor list modes are started by writing first to the
DMAx_NEXT_DESC_
PTR
register and then to the
DMAx_CONFIG
register.
Descriptor Array Mode
Descriptor array mode is selected by setting the
FLOW
bit field in the DMA
channel’s
DMAx_CONFIG
register to 0x4. In this mode, the descriptors do
not contain further descriptor pointers. The initial
DMAx_CURR_DESC_PTR
value is written by software. It points to an array of descriptors. The indi-
vidual descriptors are assumed to reside next to each other and, therefore,
their address is known.
Variable Descriptor Size
In any descriptor-based mode the
NDSIZE
field in the configuration word
specifies how many 16-bit words of the next descriptor need to be loaded
on the next fetch. In descriptor-based operation,
NDSIZE
must be
non-zero. The descriptor size can be any value from 1 entry (the lower 16
bits of
DMAx_START_ADDR
only) to 9 entries (all the DMA parameters).
illustrates how a descriptor must be structured in memory. The
values have the same order as the corresponding MMR addresses.
If, for example, a descriptor is fetched in array mode with
NDSIZE
=
0x5
,
the DMA controller fetches the 32-bit start address, the DMA configura-
tion word and the
XCNT
and
XMOD
values. However, it does not load
YCNT
and
YMOD
. This might be the case if the DMA operates in one-dimensional
mode or if the DMA is in two-dimensional mode, but the
YCNT
and
YMOD
values do not need to change.
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 ...