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W9725G6KB25A Datasheet(HTML) 10 Page - Winbond

Part No. W9725G6KB25A
Description  DLL aligns DQ and DQS transitions with clock, Data masks (DM) for write data, Write Data Mask
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Maker  WINBOND [Winbond]
Homepage  http://www.winbond.com
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W9725G6KB25A Datasheet(HTML) 10 Page - Winbond

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W9725G6KB
Publication Release Date: Sep. 03, 2012
- 10 -
Revision A03
Notes:
1. To guarantee ODT off, VREF must be valid and a LOW level must be applied to the ODT pin.
2. VREF must be within
 300 mV with respect to VDDQ/2 during supply ramp time.
3. VDD/VDDL voltage ramp time must be no greater than 200 mS from when VDD ramps from 300 mV to VDD min.
4. The VDDQ voltage ramp time from when VDD min is achieved on VDD to when VDDQ min is achieved on VDDQ must be no
greater than 500 mS
tCH tCL
tIS
tIS
400nS
NOP
PRE
ALL
EMRS
MRS
PRE
ALL
REF
MRS
REF
EMRS
EMRS
ANY
CMD
tRP
tMRD
tMRD
tRP
tRFC
tRFC
tOIT
Follow OCD
Flow chart
OCD
CAL. Mode
Exit
OCD
Default
min 200 Cycle
DLL
Reset
DLL
Enable
CLK
CLK
CKE
Command
ODT
tMRD
Figure 1
– Initialization sequence after power-up
8.2
Mode Register and Extended Mode Registers Operation
For application flexibility, burst length, burst type, CAS Latency, DLL reset function, write recovery
time (WR) are user defined variables and must be programmed with a Mode Register Set (MRS)
command. Additionally, DLL disable function, driver impedance, additive CAS Latency, ODT (On Die
Termination), single-ended strobe and OCD (off chip driver impedance adjustment) are also user
defined variables and must be programmed with an Extended Mode Register Set (EMRS) command.
Contents of the Mode Register (MR) or Extended Mode Registers EMR (1), EMR (2) and EMR (3) can
be altered by re-executing the MRS or EMRS Commands. Even if the user chooses to modify only a
subset of the MR or EMR (1), EMR (2) and EMR (3) variables, all variables within the addressed
register must be redefined when the MRS or EMRS commands are issued.
MRS, EMRS and Reset DLL do not affect array contents, which mean re-initialization including those
can be executed at any time after power-up without affecting array contents.
8.2.1
Mode Register Set Command (MRS)
( CS = "L", RAS = "L", CAS = "L", WE = "L", BA0 = "L", BA1 = "L", A0 to A12 = Register Data)
The mode register stores the data for controlling the various operating modes of DDR2 SDRAM. It
programs CAS Latency, burst length, burst sequence, test mode, DLL reset, Write Recovery (WR) and
various vendor specific options to make DDR2 SDRAM useful for various applications. The default
value in the Mode Register after power-up is not defined, therefore the Mode Register must be
programmed during initialization for proper operation.
The DDR2 SDRAM should be in all bank precharge state with CKE already HIGH prior to writing into
the mode register. The mode register set command cycle time (tMRD) is required to complete the write
operation to the mode register. The mode register contents can be changed using the same command
and clock cycle requirements during normal operation as long as all banks are in the precharge state.
The mode register is divided into various fields depending on functionality. Burst length is defined by
A[2:0] with options of 4 and 8 bit burst lengths. The burst length decodes are compatible with DDR


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