K4N56163QF Datasheet, PDF (39/73 Pages) Samsung semiconductor – 256Mbit gDDR2 SDRAM

K4N56163QF-GC
256M gDDR2 SDRAM
Burst Read Command
The Burst Read command is initiated by having CS and CAS low while holding RAS and WE high at the rising edge of the
clock. The address inputs determine the starting column address for the burst. The delay from the start of the command to
when the data from the first cell appears on the outputs is equal to the value of the read latency (RL). The data strobe out-
put (DQS) is driven low 1 clock cycle before valid data (DQ) is driven onto the data bus. The first bit of the burst is synchro-
nized with the rising edge of the data strobe (DQS). Each subsequent data-out appears on the DQ pin in phase with the
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 Set (MRS), similar to the existing SDR and DDR SDRAMs. The AL is defined by the
Extended Mode Register Set (1)(EMRS(1)).
gDDR2 SDRAM pin timings are specified for either single ended mode or differen-tial mode depending on the setting of
the EMRS “Enable DQS” mode bit; timing advantages of differential mode are realized in system design. The method by
which the gDDR2 SDRAM pin timings are measured is mode dependent. In single
ended mode, timing relationships are measured relative to the rising or falling edges of DQS crossing at VREF. In differen-
tial mode, these timing relationships are measured relative to the crosspoint of DQS and its complement, DQS. This dis-
tinction in timing methods is guaranteed by design and characterization. Note that when differential data strobe mode is
disabled via the EMRS, the complementary pin, DQS, must be tied externally to VSS through a 20 ohm to 10 Kohm resis-
tor to insure proper operation.
t_CH
t_CL
CK
CK
CK
DQS
DQ
DQS
DQS
t_RPRE
t_DQSQmax
Q
t_QH
t_RPST
Q
Q
Q
t_DQSQmax
t_QH
Burst Read Operation: RL = 5 (AL = 2, CL = 3, BL = 4)
T0
T1
T2
T3
T4
T5
T6
T7
T8
CK/CK
CMD ^{Posted CAS}
READ A
NOP
DQS
DQs
AL = 2
NOP
NOP
NOP
RL = 5
CL =3
NOP
=< t_DQSCK
NOP
NOP
DOUT A₀ DOUT A₁ DOUT A₂ DOUT A₃
NOP
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Rev 1.6 (Apr. 2005)