Mode Register 1 (MR1)
The mode register 1 (MR1) controls additional functions and features not available in
the other mode registers: Q OFF (OUTPUT DISABLE), TDQS (for the x8 configuration
only), DLL ENABLE/DLL DISABLE, RTT,nom value (ODT), WRITE LEVELING, POSTED
CAS ADDITIVE latency, and OUTPUT DRIVE STRENGTH. These functions are control-
MRS command and retains the stored information until it is reprogrammed, until RE-
SET# goes LOW, or until the device loses power. Reprogramming the MR1 register will
not alter the contents of the memory array, provided it is performed correctly.
The MR1 register must be loaded when all banks are idle and no bursts are in progress.
The controller must satisfy the specified timing parameters tMRD and tMOD before ini-
tiating a subsequent operation.
Figure 54: Mode Register 1 (MR1) Definition
AL
RTT
Q Off
A9
A7 A6 A5 A4 A3
A8
A2 A1 A0
Mode register 1 (MR1)
Address bus
9
7
6
5
4
3
8
2
1
0
A10
A12 A11
BA0
BA1
10
11
12
13
M0
0
1
DLL Enable
Enable (normal)
Disable
M5
0
1
Output Drive Strength
RZQ/6 (40Ω [NOM])
RZQ/7 (34Ω [NOM])
Reserved
14
WL
0
1
ODS DLL
RTT
TDQS
M12
0
1
Q Off
Enabled
Disabled
BA2
15
0
1
M7
0
1
Write Levelization
Disable (normal)
Enable
Additive Latency (AL)
Disabled (AL = 0)
AL = CL - 1
AL = CL - 2
Reserved
M3
0
1
0
1
M4
0
1
RTT
ODS
M1
0
1
0
1
A13
A14
16
17
0
1
M11
0
1
TDQS
Disabled
Enabled
0
1
0
1
RTT,nom (ODT)
2
Non-Writes
RTT,nom disabled
RZQ/4 (60Ω [NOM])
RZQ/2 (120Ω [NOM])
RZQ/6 (40Ω [NOM])
RZQ/12 (20Ω [NOM])
RZQ/8 (30Ω [NOM])
Reserved
RTT,nom (ODT)
3
Writes
RTT,nom disabled
RZQ/4 (60Ω [NOM])
RZQ/2 (120Ω [NOM])
RZQ/6 (40Ω [NOM])
n/a
Reserved
M2
0
1
0
1
0
1
0
1
M6
0
1
0
1
M9
0
1
Mode Register
Mode register set 0 (MR0)
Mode register set 1 (MR1)
Mode register set 2 (MR2)
Mode register set 3 (MR3)
M15
0
1
0
1
M16
0
1
Notes: 1. MR1[17, 14, 13, 10, 8] are reserved for future use and must be programmed to 0.
2. During write leveling, if MR1[7] and MR1[12] are 1, then all RTT,nom values are available
for use.
3. During write leveling, if MR1[7] is a 1, but MR1[12] is a 0, then only RTT,nom write values
are available for use.
DLL Enable/DLL Disable
The DLL may be enabled or disabled by programming MR1[0] during the LOAD MODE
ation. DLL enable is required during power-up initialization and upon returning to
normal operation after having disabled the DLL for the purpose of debugging or evalua-
tion. Enabling the DLL should always be followed by resetting the DLL using the
appropriate LOAD MODE command.
2Gb: x4, x8, x16 DDR3 SDRAM
Mode Register 1 (MR1)
PDF: 09005aef826aaadc
2Gb_DDR3_SDRAM.pdf – Rev. K 04/10 EN
137
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2006 Micron Technology, Inc. All rights reserved.