MT41J64M16JT-15E AIT:G Micron, MT41J64M16JT-15E AIT:G Datasheet - Page 115

• Manufacturer Part Number: MT41J64M16JT-15E AIT:G
• Description: DRAM Chip DDR3 SDRAM 1G-Bit 64Mx16 1.5V 96-Pin FBGA
• Manufacturer: Micron

Write Leveling
Figure 42: Write Leveling Concept
PDF: 09005aef84491df3
1Gb_AIT_AAT_DDR3_SDRAM.pdf – Rev. C 8/11 EN
Destination
Source
Destination
Differential DQS
Differential DQS
Differential DQS
CK#
CK#
CK#
DQ
DQ
CK
CK
CK
Tn
Tn
T0
For better signal integrity, DDR3 SDRAM memory modules have adopted fly-by topolo-
gy for the commands, addresses, control signals, and clocks. Write leveling is a scheme
for the memory controller to adjust or de-skew the DQS strobe (DQS, DQS#) to CK rela-
tionship at the DRAM with a simple feedback feature provided by the DRAM. Write lev-
eling is generally used as part of the initialization process, if required. For normal
DRAM operation, this feature must be disabled. This is the only DRAM operation where
the DQS functions as an input (to capture the incoming clock) and the DQ function as
outputs (to report the state of the clock). Note that nonstandard ODT schemes are re-
quired.
The memory controller using the write leveling procedure must have adjustable delay
settings on its DQS strobe to align the rising edge of DQS to the clock at the DRAM pins.
This is accomplished when the DRAM asynchronously feeds back the CK status via the
DQ bus and samples with the rising edge of DQS. The controller repeatedly delays the
DQS strobe until a CK transition from 0 to 1 is detected. The DQS delay established by
this procedure helps ensure
fly-by topology by de-skewing the trace length mismatch. A conceptual timing of this
procedure is shown in Figure 42.
Push DQS to capture
0–1 transition
T0
T0
T1
T1
T1
T2
0
t
DQSS,
115
T2
T2
1
T3
1Gb: x8, x16 Automotive DDR3 SDRAM
t
DSS, and
Micron Technology, Inc. reserves the right to change products or specifications without notice.
T3
T3
T4
t
DSH specifications in systems that use
0
T4
T4
1
T5
‹ 2010 Micron Technology, Inc. All rights reserved.
T5
T5
T6
Write Leveling
Don’t Care
T6
T6
T7