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AM29BDS64HE9VKI 参数 Datasheet PDF下载

AM29BDS64HE9VKI图片预览
型号: AM29BDS64HE9VKI
PDF下载: 下载PDF文件 查看货源
内容描述: 128或64兆比特( 8 M或4米×16位) CMOS 1.8伏只同步读/写,突发模式闪存 [128 or 64 Megabit (8 M or 4 M x 16-Bit) CMOS 1.8 Volt-only Simultaneous Read/Write, Burst Mode Flash Memory]
分类和应用: 闪存
文件页数/大小: 89 页 / 1587 K
品牌: SPANSION [ SPANSION ]
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D A T A S H E E T  
System boot code can determine if any changes to the  
In summary, if the PPB is set, and the PPB lock is set,  
the sector is protected and the protection can not be  
removed until the next power cycle clears the PPB  
lock. If the PPB is cleared, the sector can be dynami-  
cally locked or unlocked. The DYB then controls  
whether or not the sector is protected or unprotected.  
PPB are needed e.g. to allow new system code to be  
downloaded. If no changes are needed then the boot  
code can set the PPB Lock to disable any further  
changes to the PPBs during system operation.  
The WP# write protect pin adds a final level of hard-  
ware protection to the four highest and four lowest 4  
Kbyte sectors. When this pin is low it is not possible to  
change the contents of these four sectors. These sec-  
tors generally hold system boot code. So, the WP# pin  
can prevent any changes to the boot code that could  
override the choices made while setting up sector pro-  
tection during system initialization.  
If the user attempts to program or erase a protected  
sector, the device ignores the command and returns to  
read mode. A program command to a protected sector  
enables status polling for approximately t  
before  
PSP  
the device returns to read mode without having modi-  
fied the contents of the protected sector. An erase  
command to a protected sector enables status polling  
for approximately t  
to read mode without having erased the protected sec-  
tor.  
after which the device returns  
SEA  
It is possible to have sectors that have been persis-  
tently locked, and sectors that are left in the dynamic  
state. The sectors in the dynamic state are all unpro-  
tected. If there is a need to protect some of them, a  
simple DYB Write command sequence is all that is  
necessary. The DYB write command for the dynamic  
sectors switch the DYBs to signify protected and un-  
protected, respectively. If there is a need to change the  
status of the persistently locked sectors, a few more  
steps are required. First, the PPB Lock bit must be dis-  
abled by either putting the device through a power-cy-  
cle, or hardware reset. The PPBs can then be  
changed to reflect the desired settings. Setting the  
PPB lock bit once again will lock the PPBs, and the de-  
vice operates normally again.  
The programming of the DYB, PPB, and PPB lock for a  
given sector can be verified by writing a  
DYB/PPB/PPB lock verify command to the device.  
Persistent Sector Protection Mode  
Locking Bit  
Like the password mode locking bit, a Persistent Sec-  
tor Protection mode locking bit exists to guarantee that  
the device remain in software sector protection. Once  
set, the Persistent Sector Protection locking bit pre-  
vents programming of the password protection mode  
locking bit. This guarantees that a hacker could not  
place the device in password protection mode.  
Note: to achieve the best protection, it’s recommended  
to execute the PPB lock bit set command early in the  
boot code, and protect the boot code by holding WP#  
Password Protection Mode  
= V .  
IL  
The Password Sector Protection Mode method allows  
an even higher level of security than the Persistent  
Sector Protection Mode. There are two main differ-  
ences between the Persistent Sector Protection and  
the Password Sector Protection Mode:  
Table 6. Sector Protection Schemes  
PPB  
When the device is first powered on, or comes out  
of a reset cycle, the PPB Lock bit is set to the  
locked state, rather than cleared to the unlocked  
state.  
DYB  
PPB  
Lock  
Sector State  
Unprotected—PPB and DYB are  
changeable  
0
0
0
The only means to clear the PPB Lock bit is by writ-  
ing a unique 64-bit Password to the device.  
Unprotected—PPB not  
changeable, DYB is changeable  
0
0
1
The Password Sector Protection method is otherwise  
identical to the Persistent Sector Protection method.  
0
1
1
0
1
1
1
0
1
1
0
1
0
0
0
1
1
1
Protected—PPB and DYB are  
changeable  
A 64-bit password is the only additional tool utilized in  
this method.  
The password is stored in a one-time programmable  
(OTP) region of the flash memory. Once the Password  
Mode Locking Bit is set, the password is permanently  
set with no means to read, program, or erase it. The  
password is used to clear the PPB Lock bit. The Pass-  
word Unlock command must be written to the flash,  
along with a password. The flash device internally  
compares the given password with the pre-pro-  
Protected—PPB not  
changeable, DYB is changeable  
Table 6 contains all possible combinations of the DYB,  
PPB, and PPB lock relating to the status of the sector.  
May 10, 2006 27024B3  
Am29BDS128H/Am29BDS640H  
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