Functional Description
5-46
ADSP-BF59x Blackfin Processor Hardware Reference
When one or more DMA channels express an urgent memory request, two
events occur:
• All non-urgent memory requests are decreased in priority by 32,
guaranteeing that only an urgent request will be granted. The
urgent requests compete with each other, if there is more than one,
and directional preference among urgent requests is observed.
• The resulting memory transfer is marked for expedited processing
in the targeted memory system (L1 or external). All prior incom-
plete memory transfers ahead of it in that memory system are also
marked for expedited processing. This may cause a series of exter-
nal memory core accesses to be delayed for a few cycles so that a
peripheral’s urgent request may be accommodated.
The preferential handling of urgent DMA transfers is completely auto-
matic. No user controls are required for this function to operate.
Memory DMA Priority and Scheduling
All MDMA operations have lower precedence than any peripheral DMA
operations. MDMA thus makes effective use of any memory bandwidth
unused by peripheral DMA traffic.
By default, when more than one MDMA stream is enabled and ready,
only the highest priority MDMA stream is granted. If it is desirable for the
MDMA streams to share the available bandwidth, the
MDMA_ROUND_ROBIN_PERIOD
may be programmed to select each stream in
turn for a fixed number of transfers.
If two MDMA streams are used (S0-D0 and S1-D1), the user may choose
to allocate bandwidth either by fixed stream priority or by a round-robin
scheme. This is selected by programming the
MDMA_ROUND_ROBIN_PERIOD
field in the
DMA_TC_PER
register (see
“Static Channel Prioritization” on
page 5-44
).
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...