
S29GL-N_00_B3  October 13, 2006
S29GL-N MirrorBit Flash Family
41
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
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”.
Protection States
Sector State
DYB Bit
PPB Bit
PPB Lock Bit
Unprotect
Unprotect
Unfreeze
Unprotected – PPB and DYB are changeable
Unprotect
Unprotect
Freeze
Unprotected – PPB not changeable, DYB is 
changeable
Unprotect
Protect
Unfreeze
Protected – PPB and DYB are changeable
Unprotect
Protect
Freeze
Protected – PPB not changeable, DYB is changeable
Protect
Unprotect
Unfreeze
Protected – PPB and DYB are changeable
Protect
Unprotect
Freeze
Protected – PPB not changeable, DYB is changeable
Protect
Protect
Unfreeze
Protected – PPB and DYB are changeable
Protect
Protect
Freeze
Protected – PPB not changeable, DYB is changeable