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参数资料
| 型号： | S71PL254JC0BAITU3 |
| 厂商： | SPANSION LLC |
| 元件分类： | 存储器 |
| 英文描述： | SPECIALTY MEMORY CIRCUIT, PBGA84 |
| 封装： | 8 X 11.60 MM, 1.40 MM HEIGHT, FBGA-84 |
| 文件页数： | 136/188页 |
| 文件大小： | 5078K |
| 代理商： | S71PL254JC0BAITU3 |
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50
S29PL127J/S29PL064J/S29PL032J for MCP
S29PL127_064_032J_00_A1 May 21, 2004
Prelimin ary
erwise, a previously erased sector PPBs can potentially be over-erased. The Flash
device does not have a built-in means of preventing sector PPBs over-erasure.
Persistent Protection Bit Lock (PPB Lock)
The Persistent Protection Bit Lock (PPB Lock) is a global volatile bit. When set to
“1”, the PPBs cannot be changed. When cleared (“0”), the PPBs are changeable.
There is only one PPB Lock bit per device. The PPB Lock is cleared after power-
up or hardware reset. There is no command sequence to unlock the PPB Lock.
Dynamic Protection Bit (DYB)
A volatile protection bit is assigned for each sector. After power-up or hardware
reset, the contents of all DYBs is “0”. Each DYB is individually modifiable through
the DYB Write Command.
When the parts are first shipped, the PPBs are cleared, the DYBs are cleared, and
PPB Lock is defaulted to power up in the cleared state – meaning the PPBs are
changeable.
When the device is first powered on the DYBs power up cleared (sectors not pro-
tected). The Protection State for each sector is determined by the logical OR of
the PPB and the DYB related to that sector. For the sectors that have the PPBs
cleared, the DYBs control whether or not the sector is protected or unprotected.
By issuing the DYB Write command sequences, the DYBs will be set or cleared,
thus placing each sector in the protected or unprotected state. These are the so-
called Dynamic Locked or Unlocked states. They are called dynamic states be-
cause it is very easy to switch back and forth between the protected and
unprotected conditions. This allows software to easily protect sectors against in-
advertent changes yet does not prevent the easy removal of protection when
changes are needed. The DYBs maybe set or cleared as often as needed.
The PPBs allow for a more static, and difficult to change, level of protection. The
PPBs retain their state across power cycles because they are non-volatile. Indi-
vidual PPBs are set with a command but must all be cleared as a group through
a complex sequence of program and erasing commands. The PPBs are also lim-
ited to 100 erase cycles.
The PPB Lock bit adds an additional level of protection. Once all PPBs are pro-
grammed to the desired settings, the PPB Lock may be set to “1”. Setting the PPB
Lock disables all program and erase commands to the non-volatile PPBs. In ef-
fect, the PPB Lock Bit locks the PPBs into their current state. The only way to clear
the PPB Lock is to go through a power cycle. System boot code can determine if
any changes to the PPB are needed; for example, 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#/ACC write protect pin adds a final level of hardware protection to sec-
tors SA1-133, SA1-134, SA2-0 and SA2-1. When this pin is low it is not possible
to change the contents of these sectors. These sectors generally hold system
boot code. The WP#/ACC pin can prevent any changes to the boot code that could
override the choices made while setting up sector protection during system
initialization.
For customers who are concerned about malicious viruses there is another level
of security - the persistently locked state. To persistently protect a given sector
or sector group, the PPBs associated with that sector need to be set to “1”. Once
all PPBs are programmed to the desired settings, the PPB Lock should be set to
“1”. Setting the PPB Lock automatically disables all program and erase commands
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