D a t a S h e e t ( P r e l i m i n a r y )
8.2.1
Dynamic Protection Bits
Dynamic Protection Bits are volatile and unique for each sector and can be individually modified. DYBs only
control the protection scheme for unprotected sectors that have their PPBs cleared (erased to “1”). By issuing
the DYB Set or Clear command sequences, the DYBs are set (programmed to “0”) or cleared (erased to “1”),
thus placing each sector in the protected or unprotected state respectively. This feature allows software to
easily protect sectors against inadvertent changes yet does not prevent the easy removal of protection when
changes are needed.
Notes
1. The DYBs can be set (programmed to “0”) or cleared (erased to “1”) as often as needed. When the
parts are first shipped, the PPBs are cleared (erased to “1”) and upon power up or reset, the
DYBs can be set or cleared depending upon the ordering option chosen.
2. If the option to clear the DYBs after power up is chosen, (erased to “1”), then the sectorsmay be
modified depending upon the PPB state of that sector (see Table 8.2).
3. The sectors would be in the protected state If the option to set the DYBs after power up is chosen
(programmed to “0”).
4. It is possible to have sectors that are persistently locked with sectors that are left in the dynamic
state.
5. The DYB Set or Clear commands for the dynamic sectors signify protected or unprotectedstate of
the sectors respectively. However, if there is a need to change the status of the persistently locked
sectors, a few more steps are required. First, the PPB Lock Bit must be cleared by either putting
the device through a power-cycle, or hardware reset. The PPBs can then be changed to reflect the
desired settings. Setting the PPB Lock Bit once again locks the PPBs, and the device operates
normally again.
6. To achieve the best protection, it is recommended to execute the PPB Lock Bit Set command early
in the boot code and protect the boot code by holding WP#/ACC = VIL. Note that the PPB and DYB
bits have the same function when WP#/ACC = VHH as they do when ACC =VIH.
8.3
Persistent Protection Bit Lock Bit
The Persistent Protection Bit Lock Bit is a global volatile bit for all sectors. When set (programmed to “0”), it
locks all PPBs and when cleared (programmed to “1”), allows the PPBs to be changed. There is only one
PPB Lock Bit per device.
Notes
1. No software command sequence unlocks this bit unless the device is in the password protection
mode; only a hardware reset or a power-up clears this bit.
2. The PPB Lock Bit must be set (programmed to “0”) only after all PPBs are configured to the
desired settings.
8.4
Password Protection Method
The Password Protection Method allows an even higher level of security than the Persistent Sector Protection
Mode by requiring a 64-bit password for unlocking the device PPB Lock Bit. In addition to this password
requirement, after power up and reset, the PPB Lock Bit is set “0” to maintain the password mode of
operation. Successful execution of the Password Unlock command by entering the entire password clears the
PPB Lock Bit, allowing for sector PPBs modifications.
Notes
1. There is no special addressing order required for programming the password. Once the Password
is written and verified, the Password Mode Locking Bit must be set in order to prevent access.
2. The Password Program Command is only capable of programming “0”s. Programming a “1” after a
cell is programmed as a “0” results in a time-out with the cell as a “0”.
3. The password is all “1”s when shipped from the factory.
4. All 64-bit password combinations are valid as a password.
November 8, 2007 S29GL-P_00_A7
S29GL-P MirrorBit® Flash Family
45
SPANSION [ SPANSION ]
