ADSP-214xx SHARC Processor Hardware Reference
3-55
External Port
Each subsequent data-out appears on the
DDR2_DATA
pin in phase with the
DDR2_DQS
signal in a source synchronous manner.
The RL is equal to an additive latency (AL) plus CAS latency (CL). The
CL is defined by the mode register (MR), similar to the existing SDRAM.
The AL is defined by the
EMR1
register.
Burst Write
The burst write command, shown in
DDR2_CS
,
DDR2_CAS
and
DDR2_WE
pins low while holding
DDR2_RAS
high at
the rising edge of the clock. The address inputs determine the starting col-
umn address. Write latency (WL) is defined by a read latency (RL) minus
one and is equal to (AL + CL – 1) and is the number of clocks of delay
that are required from the time the write command is registered to the
clock edge associated to the first
DDR2_DQS
strobe.
A data strobe signal (
DDR2_DQS
) should be driven low (preamble) nomi-
nally a 1/2 clock prior to the WL. The first data bit of the burst cycle must
be applied to the
DDR2_DATA
pins at the first rising edge of
DDR2_DQS
fol-
lowing the preamble.
Figure 3-12. Burst Read
T0
T1
T4
T5
T2
T3
T7
T6
CMD
RL - 5
DQ
AL - 2
CL - 3
DDR2_DQS/
DDR2_DQS
DDR2_CLKx/
DDR2_CLKx
READ
N
NOP
NOP
NOP
NOP
NOP
NOP
ACTIVE
N
CAS Latency (CL) = 3
Additive Latence (AL) = 2
READ latency = RL - AL + CL - 5
t
AC,
t
DQSCK,
t
DQSQ = NOMINAL
Dout
n+1
Dout
n+2
Dout
n
Dout
n+3
T8
t
RCD (MIN)
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Содержание SHARC ADSP-214 Series
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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...
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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...
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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...