MT46V16M8TG-8 データシートの表示（PDF） - Micron Technology
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MT46V16M8TG-8 Datasheet PDF : 68 Pages
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Operations
BANK/ROW ACTIVATION
Before any READ or WRITE commands can be
issued to a bank within the DDR SDRAM, a row in that
bank must be “opened.” This is accomplished via the
ACTIVE command, which selects both the bank and
the row to be activated, as shown in Figure 4.
After a row is opened with an ACTIVE command,
a READ or WRITE command may be issued to that
row, subject to the tRCD specification. tRCD (MIN)
should be divided by the clock period and rounded up
to the next whole number to determine the earliest
clock edge after the ACTIVE command on which a
READ or WRITE command can be entered. For ex-
ample, a tRCD specification of 20ns with a 133 MHz
clock (7.5ns period) results in 2.7 clocks rounded to 3.
This is reflected in Figure 5, which covers any case where
2 < tRCD (MIN)/tCK ≤ 3. (Figure 5 also shows the same
case for tRCD; the same procedure is used to convert
other specification limits from time units to clock
cycles).
A subsequent ACTIVE command to a different row
in the same bank can only be issued after the previous
active row has been “closed” (precharged). The mini-
mum time interval between successive ACTIVE com-
mands to the same bank is defined by tRC.
A subsequent ACTIVE command to another bank
can be issued while the first bank is being accessed,
which results in a reduction of total row-access over-
head. The minimum time interval between successive
ACTIVE commands to different banks is defined by
tRRD.
PRELIMINARY
128Mb: x4, x8, x16
DDR SDRAM
CK#
CK
CKE HIGH
CS#
RAS#
CAS#
WE#
A0-A11
RA
BA0,1
BA
RA = Row Address
BA = Bank Address
Figure 4
Activating a Specific Row in
a Specific Bank
T0
T1
T2
T3
T4
T5
T6
T7
CK#
CK
COMMAND
ACT
NOP
NOP
ACT
NOP
NOP
RD/WR
NOP
A0-A11
Row
Row
Col
BA0, BA1
Bank x
tRRD
Bank y
tRCD
Bank y
DON’T CARE
Figure 5
Example: Meeting tRCD (tRRD) MIN When 2 < tRCD (tRRD) MIN/tCK < 3
128Mb: x4, x8, x16 DDR SDRAM
128Mx4x8x16DDR_C.p65 – Rev. C; Pub. 4/01
16
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2001, Micron Technology, Inc.
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