參數(shù)資料
型號: MT46V64M4TG-75E
元件分類: DRAM
英文描述: 64M X 4 DDR DRAM, 0.75 ns, PDSO66
封裝: 0.400 INCH, PLASTIC, TSOP-66
文件頁數(shù): 13/83頁
文件大?。?/td> 2343K
代理商: MT46V64M4TG-75E
256Mb: x4, x8, x16
DDR SDRAM
09005aef8076894f
Micron Technology, Inc., reserves the right to change products or specifications without notice.
256MBDDRx4x8x16_2.fm - Rev. K 9/04 EN
20
2003 Micron Technology, Inc. All rights reserved.
READs
READ bursts are initiated with a READ command, as
shown in Figure 12 on page 21.
The starting column and bank addresses are pro-
vided with the READ command and auto precharge is
either enabled or disabled for that burst access. If auto
precharge is enabled, the row being accessed is pre-
charged at the completion of the burst.
NOTE:
For the READ commands used in the follow-
ing illustrations, auto precharge is disabled.
During READ bursts, the valid data-out element
from the starting column address will be available fol-
lowing the CAS latency after the READ command.
Each subsequent data-out element will be valid nomi-
nally at the next positive or negative clock edge (i.e., at
the next crossing of CK and CK#). Figure 13 on page 22
shows general timing for each possible CAS latency
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 DQs will go High-
Z. A detailed explanation of tDQSQ (valid data-out
skew), tQH (data-out window hold), and the valid data
window are depicted in Figure 40 on page 68 and
Figure 41 on page 69. A detailed explanation of
tDQSCK (DQS transition skew to CK) and tAC (data-out
transition skew to CK) is depicted in Figure 42 on
page 70.
Data from any READ burst may be concatenated
with or truncated with data from a subsequent 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 com-
pleted burst or the last desired data element of a longer
burst which is being truncated. The new READ com-
mand 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 14 on page 23. A
READ command can be initiated on any clock cycle
following a previous READ command. Nonconsecutive
read data is illustrated in Figure 15, Nonconsecutive
READ Bursts, on page 24. Full-speed random read
accesses within a page (or pages) can be performed as
shown in Figure 16, Random READ Accesses, on
page 25.
Data from any READ burst may be truncated with a
BURST TERMINATE command, as shown in Figure 17
on page 26. The BURST TERMINATE latency is equal
to the read (CAS) latency; i.e., the BURST TERMINATE
command should be issued x cycles after the READ
command, where x equals the number of desired data
element pairs (pairs are required by the 2n-prefetch
architecture).
Data from any READ burst must be completed or
truncated before a subsequent WRITE command can
be issued. If truncation is necessary, the BURST TER-
MINATE command must be used, as shown in
Figure 18 on page 27. The tDQSS (NOM) case is shown;
the tDQSS (MAX) case has a longer bus idle time.
(tDQSS [MIN] and tDQSS [MAX] are defined in the sec-
tion on WRITEs.)
A READ burst may be followed by, or truncated with,
a PRECHARGE command to the same bank provided
that auto precharge was not activated.
The PRECHARGE command should be issued x
cycles after the 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 28. Following the PRE-
CHARGE command, a subsequent command to the
same bank cannot be issued until both tRAS and tRP
have been met. Note that part of the row precharge
time is hidden during the access of the last data ele-
ments.
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相關代理商/技術參數(shù)
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