EDE1108AFBG
Extended Mode Register Set for OCD Impedance Adjustment
OCD impedance adjustment can be done using the following EMRS mode. In drive mode all outputs are driven out
by DDR2 SDRAM and drive of RDQS is dependent on EMRS bit enabling RDQS operation. In Drive (1) mode, all
DQ, DQS (and RDQS) signals are driven high and all /DQS signals are driven low. In drive (0) mode, all DQ, DQS
(and RDQS) signals are driven low and all /DQS signals are driven high.
In adjust mode, BL = 4 of operation code data must be used. In case of OCD calibration default, output driver
characteristics follow approximate nominal V/I curve for 18Ω output drivers, but are not guaranteed. If tighter control
is required, which is controlled within 18Ω ± 3Ω driver impedance range, OCD must be used.
OCD applies only to normal full strength output drive setting defined by EMRS (1) and if reduced strength is set,
OCD default output driver characteristics are not applicable. When OCD calibration adjust mode is used, OCD
default output driver characteristics are not applicable.
[OCD Mode Set Program]
A9
0
A8
0
A7
0
Operation
OCD calibration mode exit
Drive (1) DQ, DQS, (RDQS) high and /DQS low
Drive (0) DQ, DQS, (RDQS) low and /DQS high
Adjust mode
0
0
1
0
1
0
1
0
0
1
1
1
OCD calibration default
OCD Impedance Adjustment
To adjust output driver impedance, controllers must issue the ADJUST EMRS command along with a 4bit burst code
to DDR2 SDRAM as in OCD Adjustment Program table. For this operation, burst length has to be set to BL = 4 via
MRS command before activating OCD and controllers must drive this burst code to all DQs at the same time. DT0 in
OCD Adjustment Program table means all DQ bits at bit time 0, DT1 at bit time 1, and so forth. The driver output
impedance is adjusted for all DDR2 SDRAM DQs simultaneously and after OCD calibration, all DQs and DQS's of a
given DDR2 SDRAM will be adjusted to the same driver strength setting. The maximum step count for adjustment is
16 and when the limit is reached, further increment or decrement code has no effect. The default setting may be any
step within the 16-step range. When Adjust mode command is issued, AL from previously set value must be
applied.
[OCD Adjustment Program]
4bits burst data inputs to all DQs
Operation
DT0
0
DT1
0
DT2
0
DT3
0
Pull-up driver strength
NOP
Pull-down driver strength
NOP
0
0
0
1
Increase by 1 step
Decrease by 1 step
NOP
NOP
0
0
1
0
NOP
0
1
0
0
Increase by 1 step
Decrease by 1 step
Increase by 1 step
Increase by 1 step
Decrease by 1 step
Decrease by 1 step
1
0
0
0
NOP
0
1
0
1
Increase by 1 step
Decrease by 1 step
Increase by 1 step
Decrease by 1 step
Reserved
0
1
1
0
1
0
0
1
1
0
1
0
Other combinations
Preliminary Data Sheet E1430E20 (Ver. 2.0)
43
ELPIDA [ ELPIDA MEMORY ]
