Functional Description
5-34
ADSP-BF59x Blackfin Processor Hardware Reference
the FIFO reaches an empty state, the channel signals an interrupt
(if enabled) and begins fetching the next descriptor (if any). Once
the next descriptor has been fetched, the channel initializes its
FIFO and then resumes granting DMA requests from the
peripheral.
•
Request Data
The
Request Data
command is identical to the DMA request oper-
ation of peripherals that are not DMA-management-capable.
•
Request Data Urgent
The
Request Data Urgent
command behaves identically to the
DMA
Request
command, except that the DMA channel performs
its memory accesses with urgent priority while it is asserted. This
includes both data and descriptor-fetch memory accesses. A
DMA-management-capable peripheral might use this command if
an internal FIFO is approaching a critical condition.
Restrictions
The proper operation of the 4-location DMA channel FIFO leads to cer-
tain restrictions in the sequence of DMA control commands.
Transmit Restart or Finish
No
Restart
or
Finish
command may be issued by a peripheral to a chan-
nel configured for memory read unless the peripheral has already
performed at least one DMA transfer in the current work unit and the cur-
rent work unit has more than four items remaining in
DMAx_CURR_X_COUNT
/
DMAx_CURR_Y_COUNT
(thus not yet read from mem-
ory). Otherwise, the current work unit may already have completed
memory operations and can no longer be restarted or finished properly.
If the
DMAx_CURR_X_COUNT
/
DMAx_CURR_Y_COUNT
value of the current work
unit is sufficiently large that it is always at least five more than the
Summary of Contents for ADSP-BF59x Blackfin
Page 64: ...Development Tools 1 22 ADSP BF59x Blackfin Processor Hardware Reference...
Page 74: ...Processor Specific MMRs 2 10 ADSP BF59x Blackfin Processor Hardware Reference...
Page 244: ...Programming Examples 6 40 ADSP BF59x Blackfin Processor Hardware Reference...
Page 700: ...Programming Examples 16 78 ADSP BF59x Blackfin Processor Hardware Reference...
Page 738: ...Boundary Scan Architecture B 8 ADSP BF59x Blackfin Processor Hardware Reference...