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M29W400DT70ZA1 参数 Datasheet PDF下载

M29W400DT70ZA1图片预览
型号: M29W400DT70ZA1
PDF下载: 下载PDF文件 查看货源
内容描述: 4兆位( 512 KB ×8或256 KB ×16 ,引导块) 3 V电源闪存 [4 Mbit (512 Kb x 8 or 256 Kb x 16, boot block) 3 V supply Flash memory]
分类和应用: 闪存
文件页数/大小: 48 页 / 1025 K
品牌: NUMONYX [ NUMONYX B.V ]
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M29W400DT, M29W400DB  
Block protection  
Appendix B  
Block protection  
Block protection can be used to prevent any operation from modifying the data stored in the  
Flash. Each block can be protected individually. Once protected, Program and Erase  
operations on the block fail to change the data.  
There are three techniques that can be used to control block protection, these are the  
programmer technique, the in-system technique and temporary unprotection. temporary  
unprotection is controlled by the Reset/Block Temporary Unprotection pin, RP; this is  
described in the Section 2: Signal descriptions.  
Unlike the command interface of the Program/Erase controller, the techniques for protecting  
and unprotecting blocks change between different Flash memory suppliers. For example,  
the techniques for AMD parts will not work on Numonyx parts. Care should be taken when  
changing drivers for one part to work on another.  
B.1  
Programmer technique  
The programmer technique uses high (V ) voltage levels on some of the bus pins. These  
ID  
cannot be achieved using a standard microprocessor bus, therefore the technique is  
recommended only for use in programming equipment.  
To protect a block follow the flowchart in Figure 19: Programmer equipment block protect  
flowchart. To unprotect the whole chip it is necessary to protect all of the blocks first, then all  
blocks can be unprotected at the same time. To unprotect the chip follow Figure 20:  
Programmer equipment chip unprotect flowchart. Table 23: Programmer technique bus  
operations, BYTE = V or V , gives a summary of each operation.  
IH  
IL  
The timing on these flowcharts is critical. Care should be taken to ensure that, where a  
pause is specified, it is followed as closely as possible. Do not abort the procedure before  
reaching the end. Chip Unprotect can take several seconds and a user message should be  
provided to show that the operation is progressing.  
B.2  
In-system technique  
The in-system technique requires a high voltage level on the Reset/Blocks Temporary  
Unprotect pin, RP. This can be achieved without violating the maximum ratings of the  
components on the microprocessor bus, therefore this technique is suitable for use after the  
Flash has been fitted to the system.  
To protect a block follow the flowchart in Figure 21: In-system equipment block protect  
flowchart. To unprotect the whole chip it is necessary to protect all of the blocks first, then all  
the blocks can be unprotected at the same time. To unprotect the chip follow Figure 22: In-  
system equipment chip unprotect flowchart.  
The timing on these flowcharts is critical. Care should be taken to ensure that, where a  
pause is specified, it is followed as closely as possible. Do not allow the microprocessor to  
service interrupts that will upset the timing and do not abort the procedure before reaching  
the end. Chip Unprotect can take several seconds and a user message should be provided  
to show that the operation is progressing.  
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