Datasheet
Extended Mode Register Set (EMRS)
EMR(1)
The extended mode register(1) stores the data for enabling or disabling the DLL, output driver strength, ODT value
selection and additive latency. The default value of the extended mode register is not defined, therefore the
extended mode register must be written after power-up for proper operation. The extended mode register is written
by asserting LOW on CS#, RAS#, CAS#, WE#, BA1 and HIGH on BA0, while controlling the states of address pins
A0 ~ A12. The DDR2 SDRAM should be in all bank precharge with CKE already HIGH prior to writing into the
extended mode register. The mode register set command cycle time (t
MRD
) must be satisfied to complete the write
operation to the extended mode register. 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. A0 is used for DLL
enable or disable. A1 is used for enabling a half strength data-output driver. A3~A5 determine the additive latency,
A2 and A6 are used for ODT value selection, A7~A9 are used for OCD control, A10 is used for DQS# disable.
- DLL Enable/Disable: The DLL must be enabled for normal operation. DLL enable is required during power up
initialization, and upon returning to normal operation after having the DLL disabled. The DLL
is automatically disabled when entering self refresh operation and is automatically re-enabled
upon exit of self refresh operation. Any time the DLL is enabled (and subsequently reset), 200
clock cycles must occur before a Read command can be issued to allow time for the internal
clock to be synchronized with the external clock. Failing to wait for synchronization to occur
may result in a violation of the t
AC
or t
DQSCK
parameters.
Table 6. Extended Mode Register EMR (1) Bitmap
BA2
BA1
BA0
A12
A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Address Field
0
*3
0
1
Qoff
0
*3
DQS#
OCD program
Rtt
Additive Latency
Rtt
D.I.C
DLL
Extended Mode Register
BA1
BA0
MRS mode
A6
A2
Rtt
(NOMINAL)
0
0
MR
0
0
ODT Disable
A0
DLL Enable
0
1
EMR(1)
0
1
75
Ω
0
Enable
1
0
EMR(2)
1
0
150
Ω
1
Disable
1
1
EMR(3)
1
1
50
Ω
A9
A8
A7
OCD Calibration Program
A1
Output Driver
Impedance Control
0
0
0
OCD Calibration mode exit; maintain setting
0
0
1
Drive(1)
0
Full strength
0
1
0
Drive(0)
1
Reduced strength
1
0
0
Adjust mode
*1
1
1
1
OCD Calibration default
*2
A5
A4
A3
Additive Latency
0
0
0
0
A12
Qoff
*3
0
0
1
1
0
Output buffer enabled
0
1
0
2
A10
DQS#
1
Output buffer disabled
0
1
1
3
0
Enable
1
0
0
4
1
Disable
1
0
1
5
1
1
0
6
1
1
1
Reserved
NOTE 1: When Adjust mode is issued, AL from previously set value must be applied.
NOTE 2: After setting to default, OCD calibration mode needs to be exited by setting A9-A7 to 000.
NOTE 3: Output disabled – DQs, DQSs, DQSs#.This feature is intended to be used during I
DD
characterization of read current.
NOTE 4: A11 and BA2 are reserved for future use and must be set to 0 when programming the MR.
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Rev.1.1 October 2017