![](http://datasheet.mmic.net.cn/200000/MT41J128M16HA-107-D_datasheet_15084792/MT41J128M16HA-107-D_141.png)
Mode Register 2 (MR2)
The mode register 2 (MR2) controls additional functions and features not available in
the other mode registers. These additional functions are CAS WRITE latency (CWL), AU-
TO SELF REFRESH (ASR), SELF REFRESH TEMPERATURE (SRT), and DYNAMIC ODT
(RTT(WR)). These functions are controlled via the bits shown in Figure 56. The MR2 is programmed via the MRS command and will retain the stored information until it is
programmed again or until the device loses power. Reprogramming the MR2 register
will not alter the contents of the memory array, provided it is performed correctly. The
MR2 register must be loaded when all banks are idle and no data bursts are in progress,
and the controller must wait the specified time tMRD and tMOD before initiating a sub-
sequent operation.
Figure 56: Mode Register 2 (MR2) Definition
M15
0
1
0
1
M16
0
1
Mode Register
Mode register set 0 (MR0)
Mode register set 1 (MR1)
Mode register set 2 (MR2)
Mode register set 3 (MR3)
A9
A7 A6 A5 A4 A3
A8
A2 A1 A0
Mode register 2 (MR2)
Address bus
9
7
6
5 4
3
8
2
1
0
A10
A12 A11
BA0
BA1
10
11
12
13
14
15
0
CWL
0
1
0
1
BA2
ASR
2
16
17
1
0
1
A13
A14
0
1
0
1
0
1 01 01
0
1
SRT
RTT(WR)
M6
0
1
Auto Self Refresh
(Optional)
Disabled: Manual
Enabled: Automatic
M7
0
1
Self Refresh Temperature
Normal (0°C to 85°C)
Extended (0°C to 95°C)
CAS Write Latency (CWL)
5 CK (tCK ≥ 2.5ns)
6 CK (2.5ns > tCK ≥ 1.875ns)
7 CK (1.875ns > tCK ≥ 1.5ns)
8 CK (1.5ns > tCK ≥ 1.25ns)
9 CK (1.25ns > tCK ≥ 1.07ns)
Reserved
M3
0
1
0
1
0
1
0
1
M4
0
1
0
1
M5
0
1
M9
0
1
0
1
M10
0
1
Dynamic ODT
(RTT(WR))
RTT(WR) disabled
RZQ/4
RZQ/2
Reserved
Notes: 1. MR2[17, 14:11, 8, and 2:0] are reserved for future use and must all be programmed to 0.
2. On die revision A, ASR is not available; MR2[6] must be programmed to a "0," and if
operating self refresh mode above 85°C, use SRT, MR2[7].
CAS Write Latency (CWL)
CWL is defined by MR2[5:3] and is the delay, in clock cycles, from the releasing of the
internal write to the latching of the first data in. CWL must be correctly set to the corre-
sponding operating clock frequency (see
Figure 56). The overall WRITE latency (WL) is
2Gb: x4, x8, x16 DDR3 SDRAM
Mode Register 2 (MR2)
PDF: 09005aef826aaadc
2Gb_DDR3_SDRAM.pdf – Rev. K 04/10 EN
141
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