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參數(shù)資料
| 型號： | HB52R168DB |
| 廠商： | Hitachi,Ltd. |
| 英文描述： | 128 MB Unbuffered SDRAM S.O.DIMM(128 MB 未緩沖同步DRAM S.O.DIMM) |
| 中文描述： | 128 MB的無緩沖內(nèi)存的SODIMM（128 MB的未緩沖同步內(nèi)存的SODIMM） |
| 文件頁數(shù)： | 43/57頁 |
| 文件大?。?/td> | 860K |
| 代理商： | HB52R168DB |
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HB52R168DB-F
43
Refresh
Auto-refresh:
All the banks must be precharged before executing an auto-refresh command. Since the auto-
refresh command updates the internal counter every time it is executed and determines the banks and the
ROW addresses to be refreshed, external address specification is not required. The refresh cycle is 4096
cycles/64 ms. (4096 cycles are required to refresh all the ROW addresses.) The output buffer becomes High-
Z after auto-refresh start. In addition, since a precharge has been completed by an internal operation after the
auto-refresh, an additional precharge operation by the precharge command is not required.
Self-refresh:
After executing a self-refresh command, the self-refresh operation continues while CKE is held
Low. During self-refresh operation, all ROW addresses are refreshed by the internal refresh timer. A self-
refresh is terminated by a self-refresh exit command. Before and after self-refresh mode, execute auto-refresh
to all refresh addresses in or within 64 ms period on the condition (1) and (2) below.
(1) Enter self-refresh mode within 15.6
μ
s after either burst refresh or distributed refresh at equal interval to
all refresh addresses are completed.
(2) Start burst refresh or distributed refresh at equal interval to all refresh addresses within 15.6
μ
s after
exiting from self-refresh mode.
Others
Power-down mode:
The SDRAM module enters power-down mode when CKE goes Low in the IDLE state.
In power down mode, power consumption is suppressed by deactivating the input initial circuit. Power down
mode continues while CKE is held Low. In addition, by setting CKE to High, the SDRAM module exits from
the power down mode, and command input is enabled from the next clock. In this mode, internal refresh is
not performed.
Clock suspend mode:
By driving CKE to Low during a bank-active or read/write operation, the SDRAM
module enters clock suspend mode. During clock suspend mode, external input signals are ignored and the
internal state is maintained. When CKE is driven High, the SDRAM module terminates clock suspend mode,
and command input is enabled from the next clock. For details, refer to the “CKE Truth Table”.
Power-up sequence:
The SDRAM module should be initialized by the following sequence with power up.
The CK, CKE,
S
, DQMB and DQ pins keep low till power stabilizes.
The CK pin is stabilized within 100
μ
s after power stabilizes before the following initialization sequence.
The CKE and DQMB is driven to high between power stabilizes and the initialization sequence.
This SDRAM module has V
CC
clamp diodes for CK, CKE,
S
DQMB and DQ pins. If these pins go high
before power up, the large current flows from these pins to V
CC
through the diodes.
Initialization sequence:
When 200
μ
s or more has past after the above power on, all banks must be
precharged using the precharge command (PALL). After t
RP
delay, set 8 or more auto refresh commands
(REF). Set the mode register set command (MRS) to initialize the mode register. We recommend that by
keeping DQM, DQMU/DQML to High, the output buffer becomes High-Z during Initialization sequence, to
avoid DQ bus contention on memory system formed with a number of device.
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