ADSP-214xx SHARC Processor Hardware Reference
3-79
External Port
Listing 3-6. EPDMA With Read Optimization
ustat1=dm(DDR2CTL0);
bit set ustat1 DDROPT|DDRMODIFY2;
dm(SDCTL)=ustat1;
nop;
r0=DFLSH;
dm(DMAC1)=r0;
r0=intmem; dm(IIEP1)=r0;
r0=2; dm(IMEP1)=r0;
r0=N; dm(ICEP1)=r0;
r0=2; dm(EMEP1)=r0;
r0=extmem; dm(EIEP1)=r0;
r0=DEN;
dm(DMAC1)=r0;
Notes on Read Optimization
The core and the DMA engine take advantage of the major improvements
during reads using read optimization. However, in situations where both
the core and DMA need to read from different internal memory banks
with different modifiers at the same time, programs need to choose
whether or not to use optimization. Note that from a throughput prospec-
tive, external port arbitration also is a factor. A good rule is that the
requester with the higher priority should have the same modifier as
DDR2MODIFY
. In other words, if DMA has a higher priority over the core,
then the DMA modifier should match the
DDR2MODIFY
setting.
Self-Refresh Mode
This mode causes refresh operations to be performed internally by the
DDR2, without any external control. This means that the SDC does not
generate any auto-refresh cycles while the DDR2 is in self-refresh mode.
Self-refresh entry
—Self-refresh mode is enabled by writing a 1 to the
DDR2SRF
bit of the DDR2 memory control register (
DDR2CTL0
). This deas-
serts the
DDR2CKE
pin and puts the DDR2 in self-refresh mode if no access
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Содержание SHARC ADSP-214 Series
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Страница 616: ...Debug Features 14 22 ADSP 214xx SHARC Processor Hardware Reference www BDTIC com ADI...
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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...