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AS4DDR264M64PBG1R-38/ET 参数 Datasheet PDF下载

AS4DDR264M64PBG1R-38/ET图片预览
型号: AS4DDR264M64PBG1R-38/ET
PDF下载: 下载PDF文件 查看货源
内容描述: 64Mx64 DDR2 SDRAM W /共享控制总线集成塑封微电路 [64Mx64 DDR2 SDRAM w/ SHARED CONTROL BUS iNTEGRATED Plastic Encapsulated Microcircuit]
分类和应用: 动态存储器双倍数据速率
文件页数/大小: 28 页 / 243 K
品牌: AUSTIN [ AUSTIN SEMICONDUCTOR ]
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iPEM  
4.2 Gb SDRAM-DDR2  
Austin Semiconductor, Inc.  
AS4DDR264M64PBG1  
POSTED CAS ADDITIVE LATENCY (AL)  
Posted CAS additive latency (AL) is supported to make the  
command and data bus efficient for sustainable bandwidths  
in DDR2 SDRAM. Bits E3–E5 define the value of AL, as  
shown in Figure 7. Bits E3–E5 allow the user to program  
the DDR2 SDRAM with an inverse AL of 0, 1, 2, 3, 4, 5 or 6  
clocks. Reserved states should not be used as unknown  
operation or incompatibility with future versions may result.  
In this operation, the DDR2 SDRAM allows a READ or WRITE  
command to be issued prior to tRCD (MIN) with the  
requirement that AL = tRCD (MIN). A typical application using  
this feature would set AL = tRCD (MIN) - 1x tCK. The READ or  
WRITE command is held for the time of the AL before it is  
issued internally to the DDR2 SDRAM device. RL is controlled  
by the sum of AL and CL; RL = AL+CL. Write latency (WL) is  
equal to RL minus one clock; WL = AL + CL - 1 x t  
.
CK  
FIGURE 8 - EXTENDED MODE REGISTER 2 (EMR2) DEFINITION  
1
BA1 BA0 An1 A12 A11 A10 A9 A8 A7 A6 A5 A4 A3 A2 A1 A0  
Address bus  
BA2  
Extended mode  
register (Ex)  
16 15 14  
n
12 11 10  
9
8
7
6
0
5
4
3
2
1
0
0
0
0
0
0
0
0
0
0
0
0
SRT  
MRS  
0
0
E7  
0
SRT Enable  
E15 E14  
Mode Register Set  
Mode register (MR)  
1X refresh rate (0°C to 85°C)  
2X refresh rate (>85°C)  
0
0
1
1
0
1
0
1
1
Extended mode register (EMR)  
Extended mode register (EMR2)  
Extended mode register (EMR3)  
Notes:  
1.E16 bit (BA2) must be programmed to “0” and is reserved for future use.  
2.Mode bits (En) with corresponding address balls (An) greater than A12 are reserved for future use and must be programmed to “0.”  
Austin Semiconductor, Inc.  
Austin, Texas 512.339.1188 www.austinsemiconductor.com  
AS4DDR264M64PBG1  
Rev. 0.5 06/08  
12  
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