EM47EM1688MBB
Mode Register MR1
The Mode Register MR1 stores the data for enabling or disabling the DLL, output driver strength, RTT_Nom
impedance, additive latency, write leveling enable and Qoff. The Mode Register 1 is written by asserting low on
/CS, /RAS, /CAS, /WE, high on BA0, low on BA1 and BA2, while controlling the states of address pins
according to the table below.
A13 A12 A11
A10
A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
A14
BA2 BA1 BA0
01
Level
0
Qoff
0
0
Rtt
0
Rtt
D.I.C
AL
Rtt
D.I.C
DLL
0
0
Output Driver
Impedance Control
A5
A1
DLL Enable
Enable
A0
0
RZQ/6
0
0
1
1
0
1
0
1
Disable
1
RZQ/7
A8
Reserved
Reserved
0
1
Qoff
A12
0
Write leveling enable
Disabled
Output buffer enabled
Output buffer disabled
1
Enabled
MRS Mode
BA1
0
BA0
0
Rtt_Nom
ODT disabled
RZQ/4
A9
0
A6
0
A2
0
Additive Latency
A4
0
A3
0
MR0
MR1
MR2
MR3
0
0
1
0
0
1
CL- 1
0
1
1
0
RZQ/2
0
1
0
CL- 2
1
0
1
1
RZQ/6
0
1
1
Reserved
1
1
RZQ/12
1
0
0
RZQ/8
1
0
1
Reserved
Reserved
1
1
0
1
1
1
Note1. BA2, A8, A10, A13 & A14 are reserved for future use (RFU) and must be programmed to 0 during MRS.
Note2. Qoff: Outputs disabled - DQs, DQSs, /DQSs.
Note3. In Write leveling Mode (MR1[bit7] = 1) with MR1[bit12] = 1, all RTT_Nom settings are allowed; in Write
Leveling Mode (MR1[bit7] = 1) with MR1[bit12] = 0, only RTT_Nom settings of RZQ/2, RZQ/4 and
RZQ/6 are allowed.
DLL Enable
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. During normal operation (DLL-on) with MR1 (A0 =
0), 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, tDLLK clock cycles must
occur before a read or synchronous ODT 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
tDQSCK, tAON or tAOF parameters. During tDLLK, CKE must continuously be registered high. DDR3 SDRAM
does not require DLL for any Write operation, except when RTT_WR is enabled and the DLL is required for
proper ODT operation. For more detailed information on DLL Disable operation refers to “DLL-off Mode”.
Oct. 2013
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