Analog Devices ADSP-BF506F Hardware Reference Manual page 270

Functional Description
peripheral are granted as soon as new prefetched data is available in
the DMA FIFO. The peripheral can thus use the Restart command
to re-attempt a failed transmission of a work unit.
If a channel programmed for receive (memory write) receives a
Restart command, the channel stops writing to memory, discards
any data held in its DMA FIFO, and resets its counters and FIFO.
As soon as this initialization is complete, the channel again grants
DMA write requests from the peripheral. The peripheral can thus
use the Restart command to abort transfer of received data into a
work unit and re-use the memory buffer for a later data transfer.
• Finish
The Finish command causes the current work unit to terminate
and move on to the next work unit. An interrupt is signalled as
usual, if selected by the DI_EN bit. The peripheral can thus use the
Finish command to partition the DMA stream into work units on
its own, perhaps as a result of parsing the data currently passing
though its supported communication channel, without direct
real-time control by the processor.
If a channel programmed for transmit (memory read) receives a
Finish command, the channel momentarily pauses while any pend-
ing memory reads initiated prior to the Finish command are
completed. During this period of time, the channel does not grant
DMA requests. Once all pending reads have been flushed from the
channel's pipelines, the channel signals an interrupt (if enabled),
and begins fetching the next descriptor (if any). DMA data requests
from the peripheral are granted as soon as new prefetched data is
available in the DMA FIFO.
If a channel programmed for receive (memory write) receives a Fin-
ish command, the channel stops granting new DMA requests while
it drains its FIFO. Any DMA data received by the DMA controller
prior to the Finish command is written to memory. When the
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