ADSP-214xx SHARC Processor Hardware Reference
3-77
External Port
For SIMD accesses, if optimization is enabled and the modifier is
set to 2 (even if the modifier is changed, it remains at 2). The
throughput is at maximum if optimization is enabled for sequential
accesses. But in the case of non sequential accesses, throughput is
affected by enabling optimization.
DDR2 Read Optimization
The predictive address given to the memory depends on the
DDR2MODIFY
bit values. For example, if the DAG modifier = 2, the
DDR2MODIFY
value
should also be 2, in which case the a 2 is the predictive value pro-
vided to the DDR2 address pins. Programs may choose to determine
whether read optimization is used or not. If read optimization is disabled,
then each read takes 7 cycles for a CAS latency of 3, even for sequential
reads.
With read optimization enabled, 32 sequential reads, with offsets ranging
from 0 to 15, take only 40
DDR2CLK
cycles. Read optimization should not
be enabled while reading at the external bank boundaries. For example, if
DDR2MODIFY
= 1, then 32 locations in the boundary of the external banks
should not be used. These locations can be used without optimization
enabled. If
DDR2MODIFY
= 2, then 64 locations cannot be used at the
boundaries of the external bank (if it is fully populated).
By default, the read optimization is enabled (
SDROPT
= 1) with a
modifier of 1 (
DDR2MODIFY
= 1). Read optimization assumes that
the DDR2 pointer has a constant modifier. For non-sequential
accesses, turning off optimization provides better results.
Core Accesses
Any break of sequential reads of full page accesses can cause a throughput
loss due to a maximum of eight extra reads.
achieve maximum throughput using core accesses. Any cycle between con-
secutive reads to an DDR2 address results in non-sequential reads.
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Содержание SHARC ADSP-214 Series
Страница 60: ...Contents lx ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 72: ...Notation Conventions lxxii ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 130: ...Programming Model 2 52 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 264: ...Programming Models 3 134 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 290: ...Programming Model 4 26 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 296: ...Programming Model 5 6 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 396: ...Effect Latency 7 28 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 520: ...Programming Model 10 62 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 656: ...Programming Model 15 40 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 714: ...Programming Model 19 10 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1132: ...Register Listing A 306 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
Страница 1192: ...Index I 34 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...