DDR2 DRAM Controller (ADSP-2146x)
3-50
ADSP-214xx SHARC Processor Hardware Reference
and falling edges of the
DDR2_DQS
signal. The read data is captured by the
DDR2 DLL using a delayed
DQS
that is phase shifted by approximately 90
degrees for the positive edge data and by approximately 90 degrees for the
negative edge data. These delays are precisely generated using the internal
DDR2 DLL circuit.
The captured data is sent out, corresponding to the data launched by the
DRAM with the positive edge and negative edge of
DDR2_DQS
respectively.
Both data buses are internally retimed such that they can be captured
directly by the controller on the positive edge of
DDR2_CLK
, irrespective of
the arbitrary phase relation that may exist between
DDR2_CLK
and the
DDR2_DQS
. During initial operation (external bank calibration), the DLL
determines the phase difference between the
DDR2_CLK
and
DDR2_DQS
and
retimes the data captured accordingly.
During a DRAM write, the DDR2 controller performs the multiplexing
of positive and negative edge data. This in turn is driven onto
DQ
as write
data when the write path in the memory I/O buffers is activated. The cor-
responding write
DDR2_DQS
is also driven through the memory I/O, but
after a phase shift of 90 degrees (controlled by the DLL).
The configuration is programmed in the
DDR2CTL5-0
registers. The DDR2
controller can hold off the processor core or DMA controller with an
internally connected acknowledge signal, as controlled by refresh, or page
miss latency overhead. A programmable refresh counter is provided which
generates background auto-refresh cycles at the required refresh rate based
on the clock frequency used. The refresh counter period is specified using
the
RDIV
field in the DDR2 refresh rate control register (
Control Register (DDR2RRC)” on page A-36
The DDR2C uses burst length 4 (BL = 4) for read and write operations.
This requires the DDR2C to post only the first read or write address on
the bus, all subsequent sequential address are posted by the DDR2 inter-
nal burst counter.
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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...