DDR2 DRAM Controller (ADSP-2146x)
3-68
ADSP-214xx SHARC Processor Hardware Reference
t
RAS
= 9 cycles
t
RP
= 3 cycles
The equation for
RDIV
yields:
RDIV
= (200
×
10
6
×
7.8
×
10
–6
) – (9 + 3) = 1548 clock cycles.
This means
RDIV
is 0x614 and the
DDR2RRC
register bits 13–0 should be
written with 0x60C.
Note that the
RDIV
bit must be programmed to a non-zero value if the
DDR2 controller is enabled. When
RDIV
= 0, operation of the controller is
not supported and can produce undesirable behavior. Values for
RDIV
can
range from 0x001 to 0x3FFF.
Data Mask
The DDR2 controller provides two
DDR2_DM1-0
pins. Both pins (for each
byte) should be connected to the DDR2 DM pins.
The meaning of this pin is significant, based on the fact that the minimum
burst length is 4 and a burst is not divisible. The
DDR2_DM1-0
pins are used
to mask the data on both edges of the
DQS
signal during writes in cases less
than 4 sequential writes, for example a single write need to mask the data
for the next sequential 3 writes.
The
DDR2_DM1-0
pins are useful for performance monitoring during
write commands. Every time these signals are asserted indicates the
controller masks unwanted data writes causing performance penal-
ties. For reads, the controller simply does not latch the data from
the burst.
Resetting the Controller
Like any other peripheral, the DDR2 controller can be reset by hard- or a
soft reset. Both reset modes pull the
DDR2_CKE
pin asynchronously low.
Since
DDR2_CKE
drops asynchronously and the PLL goes into bypass mode
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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...