ESMT
M14D5121632A (2H)
Operation Temperature Condition (TC) -40°C~95°C
EMRS(1) for OCD Impedance Adjustment
OCD impedance adjustment can be done using the following EMRS(1) mode. In drive mode, all outputs are driven out by DDR2
SDRAM. In Drive-1mode, all DQ, DQS signals are driven HIGH and all DQS signals are driven LOW. In Drive-0 mode, all DQ,
DQS signals are driven LOW and all DQS signals are driven HIGH. In adjustable mode, BL = 4 of operation code data must be
used. In case of OCD default state, output driver characteristics have a nominal impedance value of 18 Ω during nominal
temperature and voltage conditions. Output driver characteristics for OCD default state are specified in OCD default characteristics
table. OCD applies only to normal full strength output drive setting defined by EMRS(1) and if weak strength is set or adjustable
mode is used, OCD default output driver characteristics are not applicable. After OCD calibration is completed or driver strength is
set to default, subsequent EMRS(1) commands not intended to adjust OCD characteristics must specify A9-A7 as '000' in order to
maintain the default or calibrated value.
Driver Impedance Adjustment Mode
A9
0
A8
0
A7
0
Operation
OCD calibration mode exit
0
0
1
Device-1: DQ,DQS High and DQS Low
0
1
0
Device-0: DQ,DQS Low and DQS High
Adjustable mode
OCD default state
1
1
0
1
0
1
Adjust OCD Impedance
To adjust output driver impedance, controllers must issue EMRS(1) command for adjustable mode along with a 4bit burst code to
DDR2 SDRAM as in the following 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 the following 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 DQs simultaneously and after OCD
calibration, all DQs of a given device 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 Adjustable mode command is issued, AL from previously set
value must be applied.
OCD Adjustment Table
DT0
0
DT1
0
DT2
0
DT3
0
Pull-up driver strength
NOP
Pull-down driver strength
NOP
0
0
0
0
0
1
0
1
0
1
0
0
Increase by 1 step
Decrease by 1 step
NOP
NOP
NOP
Increase by 1 step
Decrease by 1 step
Increase by 1 step
Increase by 1 step
Decrease by 1 step
Decrease by 1 step
Reserve
1
0
0
1
0
1
1
0
0
0
1
0
0
1
0
1
NOP
Increase by 1 step
Decrease by 1 step
Increase by 1 step
Decrease by 1 step
Reserve
1
0
1
0
Others
Elite Semiconductor Memory Technology Inc.
Publication Date : Aug. 2011
Revision : 1.1 31/62
ESMT [ ELITE SEMICONDUCTOR MEMORY TECHNOLOGY INC. ]
