MT48H16M16LFB5-8L 데이터 시트보기 (PDF) - Micron Technology
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MT48H16M16LFB5-8L Datasheet PDF : 71 Pages
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BURST TERMINATE
AUTO REFRESH
SELF REFRESH
Auto Precharge
256Mb: 16 Meg x 16, 8 Meg x 32 Mobile SDRAM
Commands
The BURST TERMINATE command is used to truncate fixed-length bursts. The most
recently registered READ or WRITE command prior to the BURST TERMINATE
command will be truncated, as shown in “Operations” on page 23.
AUTO REFRESH is used during normal operation of the SDRAM and is analogous to
CAS#-BEFORE-RAS# (CBR) refresh in conventional DRAM. This command is non persis-
tent, so it must be issued each time a refresh is required. All active banks must be
PRECHARGED prior to issuing an AUTO REFRESH command. The AUTO REFRESH
command should not be issued until the minimum tRP has been met after the
PRECHARGE command, as shown in “Operations” on page 23.
The addressing is generated by the internal refresh controller. This makes the address
bits “Don’t Care” during an AUTO REFRESH command. The 256Mb SDRAM requires
8,192 AUTO REFRESH cycles every 64ms (tREF). Providing a distributed AUTO REFRESH
command every 7.8125µs will meet the refresh requirement and ensure that each row is
refreshed. Alternatively, 8,192 AUTO REFRESH commands can be issued in a burst at the
minimum cycle rate (tRFC), once every 64ms.
The SELF REFRESH command can be used to retain data in the SDRAM, even if the rest
of the system is powered down. When in the self refresh mode, the SDRAM retains data
without external clocking. The SELF REFRESH command is initiated like an AUTO
REFRESH command, except CKE is disabled (LOW). Once the SELF REFRESH command
is registered, all the inputs to the SDRAM become “Don’t Care” with the exception of
CKE, which must remain LOW.
Once self refresh mode is engaged, the SDRAM provides its own internal clocking,
causing it to perform its own auto refresh cycles. The SDRAM must remain in self refresh
mode for a minimum period equal to tRAS and may remain in self refresh mode for an
indefinite period beyond that.
The procedure for exiting self refresh requires a sequence of commands. First, CLK must
be stable (stable clock is defined as a signal cycling within timing constraints specified
for the clock ball) prior to CKE going back HIGH. Once CKE is HIGH, the SDRAM must
have NOP commands issued (a minimum of two clocks) for tXSR because time is
required for the completion of any internal refresh in progress.
Upon exiting the self refresh mode, AUTO REFRESH commands must be issued every
7.8125µs or less as both SELF REFRESH and AUTO REFRESH utilize the row refresh
counter.
Auto precharge is a feature which performs the same individual-bank precharge func-
tion described above, without requiring an explicit command. This is accomplished by
using A10 to enable auto precharge in conjunction with a specific READ or WRITE
command. A precharge of the bank/row that is addressed with the READ or WRITE
command is automatically performed upon completion of the READ or WRITE burst.
Auto precharge is non persistent in that it is either enabled or disabled for each indi-
vidual READ or WRITE command.
PDF:09005aef8219eeeb/Source: 09005aef8219eedd
MT48H16M16LF_2.fm - Rev F 4/07 EN
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©2006 Micron Technology, Inc. All rights reserved.
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