D a t a S h e e t
Persistent Protection Bit Lock (PPB Lock Bit)
A global volatile bit. When set to the “freeze state”, the PPB bits cannot be changed. When
cleared to the “unfreeze state”, the PPB bits are changeable. There is only one PPB Lock Bit
per device. The PPB Lock Bit is cleared to the “unfreeze state” after power-up or hardware
reset. There is no command sequence to unlock or “unfreeze” the PPB Lock Bit.
Configuring the PPB Lock Bit to the freeze state requires approximately 100ns. Reading the
PPB Lock Status bit requires the initial access time of the device.
Table 7. Sector Protection Schemes
Protection States
Sector State
DYB Bit
PPB Bit
PPB Lock Bit
Unfreeze
Unprotect
Unprotect
Unprotected – PPB and DYB are changeable
Unprotected – PPB not changeable, DYB is
changeable
Unprotect
Unprotect
Freeze
Unprotect
Unprotect
Protect
Protect
Protect
Unfreeze
Freeze
Protected – PPB and DYB are changeable
Protected – PPB not changeable, DYB is changeable
Protected – PPB and DYB are changeable
Unprotect
Unprotect
Protect
Unfreeze
Freeze
Protect
Protected – PPB not changeable, DYB is changeable
Protected – PPB and DYB are changeable
Protect
Unfreeze
Freeze
Protect
Protect
Protected – PPB not changeable, DYB is changeable
Table 7 contains all possible combinations of the DYB bit, PPB bit, and PPB Lock Bit relating
to the status of the sector. In summary, if the PPB bit is set, and the PPB Lock Bit is set, the
sector is protected and the protection cannot be removed until the next power cycle or hard-
ware reset clears the PPB Lock Bit to “unfreeze state”. If the PPB bit is cleared, the sector can
be dynamically locked or unlocked. The DYB bit 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
sector 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 pro-
tected 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 bit, PPB
bit, and PPB Lock Bit for a given sector can be verified by writing a DYB Status Read, PPB
Status Read, and PPB Lock Status Read commands to the device.
The Autoselect Sector Protection Verification outputs the OR function of the DYB bit and PPB
bit per sector basis. When the OR function of the DYB bit and PPB bit is a 1, the sector is either
protected by DYB or PPB or both. When the OR function of the DYB bit and PPB bit is a 0, the
sector is unprotected through both the DYB and PPB.
Persistent Protection Mode Lock Bit
Like the Password Protection Mode Lock Bit, a Persistent Protection Mode Lock Bit exists to
guarantee that the device remain in software sector protection. Once programmed, the Per-
sistent Protection Mode Lock Bit prevents programming of the Password Protection Mode Lock
Bit. This guarantees that a hacker could not place the device in Password Protection Mode.
The Password Protection Mode Lock Bit resides in the “Lock Register”.
S29GL-N_00_B3 October 13, 2006
S29GL-N MirrorBit™ Flash Family
41
SPANSION [ SPANSION ]
