Functional Description
5-30
ADSP-BF537 Blackfin Processor Hardware Reference
DMA Receive
In DMA receive (memory write) channels, the
SYNC
bit controls the han-
dling of the DMA FIFO between descriptor chains (not individual
descriptors), when the DMA channel is paused. The DMA channel pauses
after descriptors with
FLOW = STOP
mode, and may be restarted (for exam-
ple, after an interrupt) by writing the channel’s
DMAx_CONFIG
register with
DMAEN = 1
.
If the
SYNC
bit is 0 in the new work unit’s
DMAx_CONFIG
value, a continuous
transition is selected. In this mode, any data items received into the DMA
FIFO while the channel was paused are retained, and they are the first
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.
L
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 1.
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
STOP
, so that DMA channel did not pause.)
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 ...