Programming Model
5-60
ADSP-BF537 Blackfin Processor Hardware Reference
DMAx_Y_COUNT = 4
for four sub-buffers
DMAx_Y_MODIFY = 4
, same as
DMAx_X_MODIFY
for contiguous
sub-buffers
The synchronization core might read
DMAx_Y_COUNT
to determine
which sub-buffer is currently being transferred, and then allow one
full sub-buffer to account for pipelining. For example, if a read of
DMAx_Y_COUNT
shows a value of 3, then the software should assume
that sub-buffer 3 is being transferred, but some portion of
sub-buffer 2 may not yet be received. The software could, however,
safely proceed with processing sub-buffers 1 or 0.
• 1D unsynchronized FIFO—if a system’s design guarantees that
the processing of a peripheral’s data and the DMA rate of the data
will remain correlated in the steady state, but that short-term
latency variations must be tolerated, it may be appropriate to build
a simple FIFO. Here, the DMA channel may be programmed using
1D Autobuffer mode addressing without any interrupts or polling.
Descriptor Structures
DMA descriptors may be used to transfer data to or from memory data
structures that are not simple 1D or 2D arrays. For example, if a packet
of data is to be transmitted from several different locations in memory (a
header from one location, a payload from a list of several blocks of mem-
ory managed by a memory pool allocator, and a small trailer containing a
checksum), a separate DMA descriptor can be prepared for each memory
area, and the descriptors can be grouped in either an array or list as desired
by selecting the appropriate
FLOW
setting in
DMAx_CONFIG
.
The software can synchronize with the progress of the structure’s transfer
by selecting interrupt notification for one or more of the descriptors. For
example, the software might select interrupt notification for the header’s
descriptor and for the trailer’s descriptor, but not for the payload blocks’
descriptors.
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 ...