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| 型号： | MT46H256M32L4CM-54IT:A |
| 元件分类： | DRAM |
| 英文描述： | 256M X 32 DDR DRAM, 5 ns, PBGA90 |
| 封装： | 10 X 13 MM, GREEN, PLASTIC, VFBGA-90 |
| 文件页数： | 105/106页 |
| 文件大小： | 3431K |
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AUTO REFRESH Operation
Auto refresh mode is used during normal operation of the device and is analogous to
CAS#-BEFORE-RAS# (CBR) REFRESH in FPM/EDO DRAM. The AUTO REFRESH com-
mand is nonpersistent and must be issued each time a refresh is required.
The addressing is generated by the internal refresh controller. This makes the address
bits a “Don’t Care” during an AUTO REFRESH command.
For improved efficiency in scheduling and switching between tasks, some flexibility in
the absolute refresh interval is provided. The auto refresh period begins when the AU-
TO REFRESH command is registered and ends tRFC later.
Figure 57: Auto Refresh Mode
CK
CKE
CK#
Command1
NOP2
Valid
NOP2
NOP2
PRE
Row
A10
BA0, BA1
Bank(s)5
Bank
AR
NOP2, 3
AR4
NOP2, 3
ACTIVE
NOP2
One bank
All banks
tCK
tCH
tCL
tIS
tIH
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tRFC4
tRP
tRFC
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T1
T2
T3
T4
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Ta1
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Tb2
Don’t Care
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Notes: 1. PRE = PRECHARGE; AR = AUTO REFRESH.
2. NOP commands are shown for ease of illustration; other commands may be valid during
this time. CKE must be active during clock positive transitions.
3. NOP or COMMAND INHIBIT are the only commands supported until after tRFC time; CKE
must be active during clock positive transitions.
4. The second AUTO REFRESH is not required and is only shown as an example of two back-
to-back AUTO REFRESH commands.
5. Bank x at T1 is “Don’t Care” if A10 is HIGH at this point; A10 must be HIGH if more than
one bank is active (for example, must precharge all active banks).
6. DM, DQ, and DQS signals are all “Don’t Care”/High-Z for operations shown.
Although it is not a JEDEC requirement, CKE must be active (HIGH) during the auto
refresh period to provide support for future functional features. The auto refresh period
begins when the AUTO REFRESH command is registered and ends tRFC later.
2Gb: x16, x32 Mobile LPDDR SDRAM
AUTO REFRESH Operation
PDF: 09005aef83a73286
2gb_ddr_mobile_sdram_t69m.pdf - Rev. M 11/10 EN
98
Micron Technology, Inc. reserves the right to change products or specifications without notice.
2009 Micron Technology, Inc. All rights reserved.
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