mt48lc4m32b2tg-7-it Micron Semiconductor Products, mt48lc4m32b2tg-7-it Datasheet - Page 18

• Manufacturer Part Number: mt48lc4m32b2tg-7-it
• Description: 128mb X32 Sdram
• Manufacturer: Micron Semiconductor Products

BURST TERMINATE
AUTO REFRESH
SELF REFRESH
PDF: 09005aef80872800/Source: 09005aef80863355
128MbSDRAMx32_2.fm - Rev. K 9/07 EN
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,
except in the full-page burst mode, where auto precharge does not apply. Auto precharge
is nonpersistent in that it is either enabled or disabled for each individual Read or Write
command.
auto precharge ensures that the precharge is initiated at the earliest valid stage within a
burst. The user must not issue another command to the same bank until the precharge
time (
issued at the earliest possible time, as described for each burst type in the “Operation”
section of this data sheet.
The BURST TERMINATE command is used to truncate either fixed-length or full-page
bursts. The most recently registered READ or WRITE command prior to the BURST
TERMINATE command will be truncated, as shown in the “Operation” section.
The BURST TERMINATE command does not precharge the row; the row will remain
open until a PRECHARGE command is issued.
AUTO REFRESH is used during normal operation of the SDRAM and is analogous to
CAS#-BEFORE-RAS# (CBR) refresh in conventional DRAMs. This command is nonper-
sistent, so it must be issued each time a refresh is required.
The addressing is generated by the internal refresh controller. This makes the address
bits “Don’t Care” during an AUTO REFRESH command. The 128Mb SDRAM requires
4,096 AUTO REFRESH cycles every 64ms (
distributed AUTO REFRESH command every 15.625µs will meet the refresh requirement
and ensure that each row is refreshed. Alternatively, 4,096 AUTO REFRESH commands
can be issued in a burst at the minimum cycle rate (
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
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 pin) prior to CKE going back HIGH. Once CKE is HIGH, the SDRAM must
have NOP commands issued (a minimum of two clocks) for
required for the completion of any internal refresh in progress.
Upon exiting SELF REFRESH mode, AUTO REFRESH commands must be issued every
15.625µs or less as both SELF REFRESH and AUTO REFRESH utilize the row refresh
counter.
t
RP) is completed. This is determined as if an explicit PRECHARGE command was
18
t
RAS and may remain in self refresh mode for an
Micron Technology, Inc., reserves the right to change products or specifications without notice.
t
REF), regardless of width option. Providing a
t
RFC), once every 64ms.
t
XSR because time is
©2001 Micron Technology, Inc. All rights reserved.
128Mb: x32 SDRAM
Register Definition