EDJ1108BABG, EDJ1116BABG
Programming the Mode Register
For application flexibility, various functions, features and modes are programmable in four mode registers, provided
by the DDR3 SDRAM, as user defined variables, and they must be programmed via a Mode Register Set (MRS)
command. As the default values of the Mode Registers (MR#) are not defined, content of mode registers must be
fully initialized and/or re-initialized, i.e. written, after Power-up and/or reset for proper operation. Also the contents of
the mode registers can be altered by re-executing the MRS command during normal operation. When programming
the mode registers, even if the user chooses to modify only a sub-set of the MRS fields, all address fields within the
accessed mode register must be redefined when the MRS command is issued. MRS command and DLL Reset
does not affect array contents, which means these commands can be executed any time after power-up without
affecting the array contents.
The mode register set command cycle time, tMRD is required to complete the write operation to the mode register
and is the minimum time required between two MRS commands. The MRS command to non-MRS command delay,
tMOD, is required for the DRAM to update the features except DLL reset and is the minimum time required from an
MRS command to a non-MRS command excluding NOP and DESL. The mode register contents can be changed
using the same command and timing requirements during normal operation as long as the DRAM is in idle state, i.e.
all banks are in the precharged state with tRP satisfied, all data bursts are completed and CKE is already high prior
to writing into the mode register. The mode registers are divided into various fields depending on the functionality
and/or modes.
Mode Register Set Command Cycle Time (tMRD)
tMRD is the minimum time required from an MRS command to the next MRS command. As DLL enable and DLL
reset are both MRS commands, tMRD is applicable between MRS to MR1 for DLL enable and MRS to MR0 for DLL
reset, and not tMOD.
/CK
CK
Command
MRS
NOP
MRS
NOP
tMRD
tMRD Timing
MRS Command to Non-MRS Command Delay (tMOD)
tMOD is the minimum time required from an MRS command to a non-MRS command excluding NOP and DESL.
Note that additional restrictions may apply, for example, MRS to MR0 for DLL reset followed by read.
/CK
CK
Command
MRS
NOP
non-MRS
NOP
tMOD
Old
setting
Updating
New Setting
tMOD Timing
Data Sheet E1248E40 (Ver. 4.0)
74
ELPIDA [ ELPIDA MEMORY ]
