D a t a S h e e t
8.12.3
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 8.11 Sector Protection Schemes
Protection States
DYB Bit
Unprotect
Unprotect
Unprotect
Unprotect
Protect
PPB Bit
Unprotect
Unprotect
Protect
PPB Lock Bit
Unfreeze
Freeze
Sector State
Unprotected – PPB and DYB are changeable
Unprotected – PPB not changeable, DYB is changeable
Protected – PPB and DYB are changeable
Unfreeze
Freeze
Protect
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 8.11 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 hardware 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 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 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.
8.13 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 Persistent 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”.
November 16, 2007 S29GL-N_01_09
S29GL-N MirrorBit® Flash Family
33
SPANSION [ SPANSION ]
