Document Number: 002-00948 Rev. *C
S29CD032J
S29CD016J
S29CL032J
S29CL016J
8.3
Persistent Protection Bit Lock Bit
The Persistent Protection Bit Lock Bit is a global volatile bit for all sectors. When set to “1”, it locks all PPBs; when set to “0”, it 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 only after all PPBs are configured to the desired settings.
8.4
Dynamic Protection Bits
A Dynamic Protection Bit (DYB) is volatile and unique for each sector group and can be individually modified. DYBs only control the
protection scheme for unprotected sector groups that have their PPBs set to “0”. By issuing the DYB Set or Clear command
sequences, the DYBS are set or cleared, thus placing each sector group in the protected or unprotected state respectively. This
feature allows software to easily protect sector groups against inadvertent changes, yet does not prevent the easy removal of
protection when changes are needed.
Notes
1. The DYBs can be set or cleared as often as needed with the DYB Write Command.
2. When the parts are first shipped, the PPBs are cleared, the DYBs are cleared, and PPB Lock is defaulted to power up in
the cleared state – meaning the PPBs are changeable. The DYB are also always cleared after a power-up or reset.
3. It is possible to have sector groups that are persistently locked with sector groups that are left in the dynamic state.
4. The DYB Set or Clear commands for the dynamic sector groups signify the protected or unprotected state of the sector
groups respectively. However, if there is a need to change the status of the persistently locked sector groups, 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.
Table 15. Sector Protection Schemes
DYB
PPB
PPB Lock
Sector State
0
0
0
Unprotected—PPB and DYB are changeable
0
0
1
Unprotected—PPB not changeable, DYB is changeable
0
1
0
Protected—PPB and DYB are changeable
1
0
0
1
1
0
0
1
1
Protected—PPB not changeable, DYB is changeable
1
0
1
1
1
1