MT46V16M16CV-6ITK Datasheet, PDF (60/91 Pages) Micron Technology – 256Mb: x4, x8, x16 DDR SDRAM Features

256Mb: x4, x8, x16 DDR SDRAM
Operations
Figure 17: Example: Meeting ^tRCD (^tRRD) MIN When 2 < ^tRCD (^tRRD) MIN/^tCK 3
T0
T1
T2
T3
T4
T5
T6
T7
CK#
CK
Command
ACT
NOP
NOP
ACT
NOP
NOP
RD/WR
NOP
Address
Row
Row
Col
BA0, BA1
Bank x
Bank y
Bank y
tRRD
tR_CD
Don’t Care
READ
Note:
During the READ command, the value on input A10 determines whether or not auto
precharge is used. If auto precharge is selected, the row being accessed will be
precharged at the end of the READ burst; if auto precharge is not selected, the row will
remain open for subsequent accesses.
For the READ commands used in the following illustrations, auto precharge is dis-
abled.
During READ bursts, the valid data-out element from the starting column address will
be available following the CL after the READ command. Each subsequent data-out
element will be valid nominally at the next positive or negative clock edge (that is, at the
next crossing of CK and CK#). Figure 18 on page 62 shows the general timing for each
possible CL setting. DQS is driven by the DDR SDRAM along with output data. The
initial LOW state on DQS is known as the read preamble; the LOW state coincident with
the last data-out element is known as the read postamble.
Upon completion of a burst, assuming no other commands have been initiated, the DQ
will go High-Z. Detailed explanations of ^tDQSQ (valid data-out skew), ^tQH (data-out
window hold), and the valid data window are depicted in Figure 26 on page 70 and
Figure 27 on page 71. Detailed explanations of ^tDQSCK (DQS transition skew to CK) and
t_{AC (data-out transition skew to CK) are depicted in Figure 28 on page 72.}
Data from any READ burst may be concatenated or truncated with data from a subse-
quent READ command. In either case, a continuous flow of data can be maintained. The
first data element from the new burst follows either the last element of a completed
burst or the last desired data element of a longer burst which is being truncated. The
new READ command should be issued x cycles after the first READ command, where x
equals the number of desired data element pairs (pairs are required by the 2n-prefetch
architecture). This is shown in Figure 19 on page 63. A READ command can be initiated
on any clock cycle following a previous READ command. Nonconsecutive read data is
illustrated in Figure 20 on page 64. Full-speed random read accesses within a page (or
pages) can be performed, as shown in Figure 21 on page 65.
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DDR_x4x8x16_Core2.fm - 256Mb DDR: Rev. S, Core DDR: Rev. E 9/12 EN
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