1Gb DDR3 SDRAM A-Die
NT5CB256M4AN / NT5CB128M8AN / NT5CB64M16AP
30
REV 1.2
01 / 2009
Timing details of Write Leveling sequence [DQS -
is capturing CK - low at T1 and CK -
high at T2
NO P
N OP
NO P
N OP
NO P
N OP
CK
CMD
O DT
Di ff_ DQ S
Prime D Q
Late
Re ma ini ng
DQs
tMO D
tWLMR D
tWLO
tWLS
t WLH
tWLOE
tWLS
t WLH
t WLO
N OP
M RS
tD QSH
tDQ SL
tD QSH
t DQ SL
T1
T2
Time
break
Do not
Care
On e Pri me DQ:
Earl y
Re ma ini ng
DQs
tWLO
t WLO
Undefined
Driving Mode
tWLOE
tWLO
t WLO
A ll DQ s are Prime :
Late
Re ma ini ng
DQs
Earl y
Re ma ini ng
DQs
tWLMRD
tWLO
t WLO
t WLO E
tWLDQ SEN
NO P
Note:
1. DRAM has the option to drive leveling feedback on a prime DQ or all DQs. If feedback is driven only on
one DQ, the remaining DQs must be driven low as shown in above Figure, and maintained at this state
through out the leveling procedure.
2. MRS: Load MR1 to enter write leveling mode
3. NOP: NOP or deselect
4. diff_DQS is the differential data strobe (DQS,
). Timing reference points are the zero crossings. DQS
is shown with solid line,
is shown with dotted line.
6. DQS/
needs to fulfill minimum pulse width requirements tDQSH(min) and tDQSL(min) as defined for
regular Writes; the max pulse width is system dependent.
Write Leveling Mode Exit
The following sequence describes how Write Leveling Mode should be exited:
1.
After the last rising strobe edge (see ~T0), stop driving the strobe signals (see ~Tc0). Note: From now on, DQ pins are in
undefined driving mode, and will remain undefined, until tMOD after the respective MR command (Te1).
2.
Drive ODT pin low (tIS must be satisfied) and keep it low (see Tb0).
3.
After the RTT is switched off, disable Write Level Mode via MRS command (see Tc2).
4.
After tMOD is satisfied (Te1), any valid command may be registered. (MR commands may be issued after tMRD (Td1).
Timing detail of Write Leveling exit
CK
T0
T1
Ta0
Tc0
Tc1
Tc2
Td1
Te1
CMD
BA
tIS
tMOD
tMRD
ODT
RTT_DQS_DQS
DQS_DQS
Result = 1
tWLO
DQ
RTT_Nom
Td0
Te0
T2
Tb0
tAOFmin
tAOFmax
Transitioning
Time Break
Do not Care
Undefined
Driving Mode
NOP
MRS
NOP
Valid
NOP
Valid
MR1
Valid
tODTLoff