DDR2 DRAM Controller (ADSP-2146x)
3-76
ADSP-214xx SHARC Processor Hardware Reference
• 2 x 8-bit/page 1k words
• 4 x 4-bit/page 2k words
The DDR2’s page size is used to determine the system you select. All three
systems have the same external bank size, but different page sizes. Note
that larger page sizes, allow higher performance but larger page sizes
require more complex hardware layouts.
Even if connecting DDR2s in parallel, the DDR2C always consid-
ers the cluster as one external DDR2 bank because all address and
control lines feed the parallel parts.
Buffering Controller for Multiple DDR2s
If using multiples DDR2s or modules, the capacitive load will exceed the
controller’s output drive strength. In order to bypass this problem an
external register (SSTL18 class) can be used for decoupling by setting bit
24 in
DDR2CTL0
register. This adds a cycle of data buffering to read and
write accesses.
Read Optimization
The best throughput numbers for reads are achievable only when the
DDR2OPT
bit in the
DDR2CTL0
register is set. To achieve better performance
for reads, predictive addresses need to be given to the DDR memory. The
predictive address given to the memory depends on the
DDR2MODIFY
bit
setting. If the
DDR2MODIFY
value is 2 then the a 2 is given
predictively on the DDR address pins. Programs have the option whether
to use read optimization or not.
It is advisable to use read optimization for core and DMA transfers, with a
constant modifier to achieve better performance. With multiple channels
running with ping-pong accesses, use arbitration freezing to get better
throughput.
www.BDTIC.com/ADI
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...