A d v a n c e I n f o r m a t i o n
Table 11. Sector Protection Schemes
DYB
0
PPB
0
PPB Lock
Sector State
0
1
0
0
0
1
1
1
Unprotected—PPB and DYB are changeable
0
0
Unprotected—PPB not changeable, DYB is changeable
0
1
1
0
Protected—PPB and DYB are changeable
1
1
0
1
1
0
Protected—PPB not changeable, DYB is changeable
1
1
Table 11 contains all possible combinations of the DYB, PPB, and PPB lock relating
to the status of the sector.
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 dynamically locked or unlocked. The DYB
then controls whether or not the sector is protected or unprotected.
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 sec-
tor enables status polling for approximately 1 µs before the device returns to read
mode without having modified the contents of the protected sector. An erase
command to a protected sector enables status polling for approximately 50 µs
after which the device returns to read mode without having erased the protected
sector.
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 Sector Protection mode locking
bit exists to guarantee that the device remain in software sector protection. Once
set, the Persistent Sector Protection locking bit prevents programming of the
password protection mode locking bit. This guarantees that an unauthorized user
could not place the device in password protection mode.
Password Protection Mode
The Password Sector Protection Mode method allows an even higher level of se-
curity than the Persistent Sector Protection Mode. There are two main differences
between the Persistent Sector Protection and the Password Sector Protection
Mode:
When the device is first powered on, or comes out of a reset cycle, the PPB
Lock bit set to the locked state, rather than cleared to the unlocked state.
The only means to clear the PPB Lock bit is by writing a unique 64-bit Pass-
word to the device.
The Password Sector Protection method is otherwise identical to the Persistent
Sector Protection method.
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S29CD032G
30606B0 March 22, 2004
SPANSION [ SPANSION ]
