ADSP-214xx SHARC Processor Hardware Reference
3-59
External Port
meeting the required timing specifications, pulls down the
DDR2CKE
signal.
If an internal access is pending, the controller delays entering the
power-down mode until it completes the pending DDR2 access and any
subsequent pending access requests.
•
DIS_DDR2CKE
= 0 No effect.
•
DIS_DDR2CKE
= 1 Enter precharge power down.
Once the DDR device enters into power-down mode, the DDR controller
asserts the
DDR2PD
bit in the DDR control status register (
DDR2STAT0
).
Unlike self-refresh mode, precharge power-down entry mode does
not refresh the DDR2 device. Therefore, careful software control is
required so as not to violate refresh conditions which leads to data
corruption. The typical refresh interval of t
REFI
can be extended up
to 8
×
t
REFI
. Consult the DDR2 data sheet for complete
information.
This mode is useful if the DDR2 operation is idling only for a
short
period
of time. This time is limited by the JEDEC spec and is typically 9 × t
REFI
.
If for example t
REFI
= 7.8µs the maximum power-down time is 9 × 7.8µs =
70µs.
When DDR2 memory pauses for a short period of time, systems should
evaluate on a case by case basis whether or not self-refresh or precharge
power-down should be used. This consideration will take into account
that precharge power-down is limited to a timing window of approxi-
mately 70 µs (9 × t
REFI
), and that self-refresh release requires 200 DDR2
cycles for the DLL to lock again.
Precharge Power-down Exit
The DDR2 device exits power-down mode only when the
DIS_DDRCKE
bit
in the control register is cleared. The controller takes care of the
power-down exit timing specifications t
XP
, t
XARD
, t
XARDS
and t
CKE
min.
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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...