参数资料
型号: 256MBDDRSDRAM
厂商: SAMSUNG SEMICONDUCTOR CO. LTD.
英文描述: DDR SDRAM Specification Version 0.3
中文描述: DDR SDRAM的规格版本0.3
文件页数: 17/51页
文件大小: 658K
代理商: 256MBDDRSDRAM
- 17 -
REV. 0.3 November 2. 2000
256Mb DDR SDRAM
Preliminary
3.2.3 Precharge
3.2.4 No Operation(NOP) & Device Deselect
The precharge command is used to precharge or close a bank that has been activated. The precharge com-
mand is issued when CS, RAS and WE are low and CAS is high at the rising edge of the clock. The precharge
command can be used to precharge each bank respectively or all banks simultaneously. The bank select
addresses(BA0, BA1) are used to define which bank is precharged when the command is initiated. For write
cycle, tWR(min.) must be satisfied until the precharge command can be issued. After tRP from the precharge,
an active command to the same bank can be initiated.
A10/AP
0
0
0
0
1
BA1
0
0
1
1
X
BA0
0
1
0
1
X
Precharge
Bank A Only
Bank B Only
Bank C Only
Bank D Only
All Banks
The device should be deselected by deactivating the CS signal. In this mode DDR SDRAM should ignore
all the control inputs. The DDR SDRAMs are put in NOP mode when CS is active and by deactivating RAS,
CAS and WE. For both Deselect and NOP the device should finish the current operation when this com-
mand is issued.
Bank Selection for Precharge by Bank address bits
Table 5. Bank selection for precharge by Bank address bits
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