
ADSP-BF59x Blackfin Processor Hardware Reference
5-27
Direct Memory Access
items written to memory in the new work unit. This mode of operation
provides lower latency at work unit transitions and ensures that no data
items are dropped during a DMA pause, at the cost of certain restrictions
on the DMA descriptors.
If the
SYNC
bit is 0 on the first descriptor of a descriptor chain after
a DMA pause, the DMA word size of the new chain must not
change from the word size of the previous descriptor chain active
before the pause, unless the DMA channel is reset between chains
by writing the
DMAEN
bit to 0 and then to 1 again.
If the
SYNC
bit is 1 in the new work unit’s
DMAx_CONFIG
value, a synchro-
nized transition is selected. In this mode, only the data received from the
peripheral by the DMA channel after the write to the
DMAx_CONFIG
register
are delivered to memory. Any prior data items transferred from the
peripheral to the DMA FIFO before this register write are discarded. This
provides direct synchronization between the data stream received from the
peripheral and the timing of the channel restart (when the
DMAx_CONFIG
register is written).
For receive DMAs, the
SYNC
bit has no effect in transitions between work
units in the same descriptor chain (that is, when the previous descriptor’s
FLOW
mode was not 0, so that DMA channel did not pause.)
If a descriptor chain begins with a
SYNC
bit of 1, there is no restriction on
DMA word size of the new chain in comparison to the previous chain.
The DMA word size must not change between one descriptor and
the next in any DMA receive (memory write) channel within a sin-
gle descriptor chain, regardless of the
SYNC
bit setting. In other
words, if a descriptor has
WNR
= 1 and
FLOW
= 4, 6, or 7, then the
next descriptor must have the same word size. For any DMA
receive (memory write) channel, there is no restriction on changes
of memory space (internal vs. external) between descriptors or
Содержание ADSP-BF59x Blackfin
Страница 64: ...Development Tools 1 22 ADSP BF59x Blackfin Processor Hardware Reference...
Страница 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
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Страница 244: ...Programming Examples 6 40 ADSP BF59x Blackfin Processor Hardware Reference...
Страница 345: ...ADSP BF59x Blackfin Processor Hardware Reference 9 9 Core Timer Unique Information for the ADSP BF59x Processor None...
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Страница 398: ...Unique Information for the ADSP BF59x Processor 11 42 ADSP BF59x Blackfin Processor Hardware Reference...
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Страница 700: ...Programming Examples 16 78 ADSP BF59x Blackfin Processor Hardware Reference...
Страница 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...