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M29W256GL 参数 Datasheet PDF下载

M29W256GL图片预览
型号: M29W256GL
PDF下载: 下载PDF文件 查看货源
内容描述: 并行NOR闪存的嵌入式存储器 [Parallel NOR Flash Embedded Memory]
分类和应用: 闪存存储
文件页数/大小: 89 页 / 1158 K
品牌: MICRON [ MICRON TECHNOLOGY ]
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256Mb: 3V Embedded Parallel NOR Flash  
Device Protection  
Blocks with volatile protection and nonvolatile protection can coexist within the memo-  
ry array. If the user attempts to program or erase a protected block, the device ignores  
the command and returns to read mode.  
The block protection status can be read by performing a read electronic signature or by  
issuing an AUTO SELECT command (see the Block Protection table).  
Refer to the Block Protection Status table and the Software Protection Scheme figure for  
details on the block protection scheme. Refer to the Protection Operations section for a  
description of the command sets.  
Volatile Protection Mode  
Volatile protection enables the software application to protect blocks against inadver-  
tent change and can be disabled when changes are needed. Volatile protection bits are  
unique for each block and can be individually modified. Volatile protection bits control  
the protection scheme only for unprotected blocks whose nonvolatile protection bits  
are cleared to 1. Issuing a PROGRAM VOLATILE PROTECTION BIT or CLEAR VOLATILE  
PROTECTION BIT command sets to 0 or clears to 1 the volatile protection bits and pla-  
ces the associated blocks in the protected (0) or unprotected (1) state, respectively. The  
volatile protection bit can be set or cleared as often as needed.  
When the device is first shipped, or after a power-up or hardware reset, the volatile pro-  
tection bits default to 1 (unprotected).  
Nonvolatile Protection Mode  
A nonvolatile protection bit is assigned to each block. Each of these bits can be set for  
protection individually by issuing a PROGRAM NONVOLATILE PROTECTION BIT com-  
mand. Also, each device has one global volatile bit called the nonvolatile protection bit  
lock bit; it can be set to protect all nonvolatile protection bits at once. This global bit  
must be set to 0 only after all nonvolatile protection bits are configured to the desired  
settings. When set to 0, the nonvolatile protection bit lock bit prevents changes to the  
state of the nonvolatile protection bits. When cleared to 1, the nonvolatile protection  
bits can be set and cleared using the PROGRAM NONVOLATILE PROTECTION BIT and  
CLEAR ALL NONVOLATILE PROTECTION BITS commands, respectively.  
No software command unlocks the nonvolatile protection bit lock bit unless the device  
is in password protection mode; in nonvolatile protection mode, the nonvolatile protec-  
tion bit lock bit can be cleared only by taking the device through a hardware reset or  
power-up.  
Nonvolatile protection bits cannot be cleared individually; they must be cleared all at  
once using a CLEAR ALL NONVOLATILE PROTECTION BITS command. They will re-  
main set through a hardware reset or a power-down/power-up sequence.  
If one of the nonvolatile protection bits needs to be cleared (unprotected), additional  
steps are required: First, the nonvolatile protection bit lock bit must be cleared to 1, us-  
ing either a power-cycle or hardware reset. Then, the nonvolatile protection bits can be  
changed to reflect the desired settings. Finally, the nonvolatile protection bit lock bit  
must be set to 0 to lock the nonvolatile protection bits. The device now will operate nor-  
mally.  
To achieve the best protection, the PROGRAM NONVOLATILE PROTECTION LOCK BIT  
command should be executed early in the boot code, and the boot code should be pro-  
tected by holding VPP/WP# LOW.  
PDF: 09005aef84bd3b68  
m29w_256mb.pdf - Rev. B 5/13 EN  
Micron Technology, Inc. reserves the right to change products or specifications without notice.  
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© 2013 Micron Technology, Inc. All rights reserved.