S71GL256NB0 SPANSION [SPANSION], S71GL256NB0 Datasheet - Page 39

• Manufacturer Part Number: S71GL256NB0
• Description: Stacked Multi-chip Product (MCP)
• Manufacturer: SPANSION [SPANSION]

June 14, 2004 S29GLxxxN_00_A4
Persistent Sector Protection
The Persistent Sector Protection method replaces the old 12 V controlled protec-
tion method while at the same time enhancing flexibility by providing three
different sector protection states:
In order to achieve these states, three types of “bits” are going to be used:
Dynamic Protection Bit (DYB)
A volatile protection bit is assigned for each sector. After power-up or hardware
reset, the contents of all DYB bits are in the “unprotected state” if the DYB Lock
Bit of the “Lock Register” is not programmed. If the DYB Lock Bit of the “Lock
Register” is programmed, all DYB bits will power-up or hardware reset to the
“protected state”. Each DYB is individually modifiable through the DYB Set Com-
mand and DYB Clear Command. When the parts are first shipped, all of the
Persistent Protect Bits (PPB) are cleared into the unprotected state. The DYB bits
and PPB Lock bit are defaulted to power up in the cleared state or unprotected
state - meaning the all PPB bits are changeable.
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 PPB bits cleared,
the DYB bits control whether or not the sector is protected or unprotected. By is-
suing the DYB Set and DYB Clear command sequences, the DYB bits will be
protected or unprotected, thus placing each sector in the protected or unpro-
tected state. These are the so-called Dynamic Locked or Unlocked states. They
are called dynamic states because it is very easy to switch back and forth be-
tween the protected and un-protected conditions. This allows software to easily
protect sectors against inadvertent changes yet does not prevent the easy re-
moval of protection when changes are needed.
The DYB bits maybe set or cleared as often as needed. The PPB bits allow for a
more static, and difficult to change, level of protection. The PPB bits retain their
state across power cycles because they are Non-Volatile. Individual PPB bits are
set with a program command but must all be cleared as a group through an erase
command.
The PPB Lock Bit adds an additional level of protection. Once all PPB bits are pro-
grammed to the desired settings, the PPB Lock Bit may be set to the “freeze
Persistent Protection Mode Lock Bit allows the user to set the device perma-
nently to operate in the Persistent Protection Mode
Password Protection Mode Lock Bit allows the user to set the device perma-
nently to operate in the Password Protection Mode
Dynamically Locked-The sector is protected and can be changed by a sim-
ple command
Persistently Locked-A sector is protected and cannot be changed
Unlocked-The sector is unprotected and can be changed by a simple com-
mand
Don’t Care
DQ15-3
A d v a n c e
Password Protection
S29GLxxxN MirrorBit
Mode Lock Bit
I n f o r m a t i o n
Table 4. Lock Register
DQ2
Persistent Protection
TM
Mode Lock Bit
Flash Family
DQ1
Sector Protection
Secured Silicon
DQ0
Bit
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