A d v a n c e I n f o r m a t i o n
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 “un-
freeze 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
Unprotect
Unprotect
Unfreeze
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 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 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 bit, PPB bit, and PPB Lock Bit for a given sec-
tor 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 Persistent Protection Mode Lock Bit prevents programming of
May 13, 2004 27631A4
S29GLxxxN MirrorBitTM Flash Family
49
SPANSION [ SPANSION ]
