ADSP-BF50x Blackfin Processor Hardware Reference
7-27
Direct Memory Access
If
SYNC
= 0 (continuous transition) on a transmit (memory read)
descriptor, the next descriptor must have the same data word size,
read/write direction, and source memory (internal vs. external) as
the current descriptor.
SYNC
= 0 selects continuous transition on a work unit in
FLOW
= 0 mode
with interrupt enabled. The interrupt service routine may begin execution
while the final data is still draining from the FIFO to the peripheral. This
is indicated by the
DMA_RUN
bit in the
DMAx_IRQ_STATUS
register; if it is 1,
the FIFO is not empty yet. Do not start a new work unit with different
word size or direction while
DMA_RUN
= 1. Further, if the channel is dis-
abled (by writing
DMAEN
= 0), the data in the FIFO is lost.
SYNC
= 1 selects a synchronized transition in which the DMA FIFO is first
drained to the destination memory or peripheral before any interrupt is
signalled and before any subsequent descriptor or data is fetched. This
incurs greater latency, but provides direct synchronization between the
DMA interrupt and the state of the data at the peripheral.
For example, if
SYNC
= 1 and
DI_EN
= 1 on the last descriptor in a work
unit, the interrupt occurs when the final data has been transferred to the
peripheral, allowing the service routine to properly switch to non-DMA
transmit operation. When the interrupt service routine is invoked, the
DMA_DONE
bit is set and the
DMA_RUN
bit is cleared.
A synchronized transition also allows greater flexibility in the format of
the DMA descriptor chain. If
SYNC
= 1, the next descriptor may have any
word size or read/write direction supported by the peripheral and may
come from either memory space (internal or external). This can be useful
in managing MDMA work unit queues, since it is no longer necessary to
interrupt the queue between dissimilar work units.
DMA Receive
In DMA receive (memory write) channels, the
SYNC
bit controls the han-
dling of the DMA FIFO between descriptor chains (not individual
Содержание EZ-KIT Lite ADSP-BF506F
Страница 50: ...Contents l ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 92: ...Development Tools 1 30 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 110: ...Interface Overview 3 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 132: ...Unique Information for the ADSP BF50x Processor 4 22 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 236: ...Internal Flash Memory Control Registers 6 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 342: ...Unique Information for the ADSP BF50x Processor 7 106 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 484: ...Unique Information for the ADSP BF50x Processor 10 60 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 493: ...ADSP BF50x Blackfin Processor Hardware Reference 11 9 Core Timer Unique Information for the ADSP BF50x Processor None ...
Страница 494: ...Unique Information for the ADSP BF50x Processor 11 10 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 506: ...Unique Information for the ADSP BF50x Processor 12 12 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 544: ...Unique Information for the ADSP BF50x Processor 13 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 650: ...Programming Examples 15 56 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 712: ...Unique Information for the ADSP BF50x Processor 16 62 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 804: ...Programming Examples 17 92 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 972: ...Unique Information for the ADSP BF50x Processor 20 38 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1194: ...Programming Examples 24 90 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1256: ...ACM Registers A 50 ADSP BF50x Blackfin Processor Hardware Reference ...
Страница 1264: ...Boundary Scan Architecture B 8 ADSP BF50x Blackfin Processor Hardware Reference ...