DMA Controller Overview
5-10
ADSP-BF537 Blackfin Processor Hardware Reference
A memory-to-memory transfer always requires the source and the destina-
tion channel to be enabled. The four channels are hardwired for DMA
priorities 12 through 15. Each source/destination channel forms a
“stream,” and these two streams are hardwired for DMA priorities 8
through 11.
• Priority 12: MDMA0 destination
• Priority 13: MDMA0 source
• Priority 14: MDMA1 destination
• Priority 15: MDMA1 source
MDMA0 takes precedence over MDMA1, unless round robin scheduling
is used or priorities become urgent as programmed by the
DRQ
bit field in
the
HMDMA_CONTROL
register. Note it is illegal to program a source channel
for memory write or a destination channel for memory read.
The channels support 8-, 16-, and 32-bit memory DMA transfers, but
both ends of the MDMA connect to 16-bit buses. Source and destination
channel must be programmed to the same word size. In other words, the
MDMA transfer does not perform packing or unpacking of data; each
read results in one write. Both ends of the MDMA FIFO for a given
stream are granted priority at the same time. Each pair shares an
8-word-deep 16-bit FIFO. The source DMA engine fills the FIFO, while
the destination DMA engine empties it. The FIFO depth allows the burst
transfers of the External Access Bus (EAB) and DMA Access Bus (DAB) to
overlap, significantly improving throughput on block transfers between
internal and external memory. Two separate descriptor blocks are required
to supply the operating parameters for each MDMA pair, one for the
source channel and one for the destination channel.
Because the source and destination DMA engines share a single FIFO
buffer, the descriptor blocks must be configured to have the same data
size. It is possible to have a different mix of descriptors on both ends as
long as the total transfer count is the same.
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 ...