EtronTech
Extended Mode Register Set (EMRS )
EM68916DVAA
The Extended Mode Register is designed to support Partial Array Self Refresh and Driver Strength. The
EMRS cycle is not mandatory, and the EMRS command needs to be issued only when either PASR or DS is
used. The Extended Mode Register is written by asserting Low on
CS
,
RAS
,
CAS
,
WE
, and BA0 and High
on BA1 (the device should have all banks idle with no bursts in progress prior to writing into the Extended
Mode Register, and CKE should be High). Values stored in the register will be retained until the register is
reprogrammed, the device enters Deep Power Down mode, or power is removed from the device. The state
of address pins A0~A11 and BA0, BA1 in the same cycle in which
CS
,
RAS
,
CAS
and
WE
are asserted
Low is written into the Extended Mode Register. Two clock cycles, t
MRD
, are required to complete the write
operation in the Extended Mode Register. A0~A2 are used for Partial Array Self Refresh and A5~A6 are used
for Driver Strength. An automatic Temperature Compensated Self Refresh function is included with a
temperature sensor embedded into this device. A3~A4 are no longer used to control this function; any inputs
applied to A3~A4 during EMRS are ignored. All the other address pins, A7~A11 and BA0, must be set to Low
for proper EMRS operation. Refer to the tables below for specific codes. If the user does not write values to
the Extended Mode Register, DS defaults to Full Strength; and PASR defaults to the Full Array.
Table 6. Extend Mode Register Bitmap
BA1 BA0 A11 A10 A9
A8
A7
A6
A5
A4
A3
A2
A1
A0
Address Field
1
0
0
0
0
DS
0
0
PASR
Extended Mode Register
A6
0
0
1
1
A5
0
1
0
1
Drive Strength
Full Strength
1/2 Strength
1/4 Strength
1/8 Strength
A2 A1 A0 Partial Array Self Refresh Coverage
0 0 0
Full Array (All Banks)
0 0 1
Half of Full Array (BA1=0)
0 1 0 Quarter of Full Array (BA1=BA0=0)
0 1 1
Reserved
1 0 0
Reserved
1 0 1
Reserved
1 1 0
Reserved
1 1 1
Reserved
TEMPERATURE COMPENSATED SELF REFRESH
In order to reduce power consumption, a Mobile DDR SDRAM includes the internal temperature sensor and
other circuitry to control Self Refresh operation automatically according to two temperature ranges: max. 40°C
and max. 85°C
Table 7. IDD6 Specifications and Conditions
Temperature Range
Max. 40°C
Max. 85°C
Self Refresh Current (I
DD6
)
Full Array
200
160
1/2 of Full Array
150
110
1/4 of Full Array
120
90
Unit
µA
µA
PARTIAL ARRAY SELF REFRESH
For further power savings during Self Refresh, the PASR feature allows the controller to select the amount of
memory that will be refreshed during Self Refresh. The refresh options are all banks (banks 0, 1, 2 and 3);
two banks (bank 0 and 1); and one bank (bank 0). Write and Read commands can still affect any bank during
standard operations, but only the selected banks will be refreshed during Self Refresh. Data in unselected
banks will be lost.
Etron Confidential
9
Rev. 1.0
Apr. 2009
ETRON [ ETRON TECHNOLOGY, INC. ]
