Document Number: 002-00948 Rev. *C
S29CD032J
S29CD016J
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8.1
Advanced Sector Protection Overview
As shipped from the factory, all devices default to the persistent mode when power is applied, and all sector groups are unprotected.
The device programmer or host system must then choose which sector group protection method to use. Programming (setting to “0”)
any one of the following two one-time programmable, non-volatile bits locks the device permanently in that mode:
Persistent Protection Mode Lock Bit
Password Protection Mode Lock Bit
After selecting a sector group protection method, each sector group can operate in any of the following three states:
1. Persistently Locked. A sector group is protected and cannot be changed.
2. Dynamically locked. The selected sector groups are protected and can be altered via software commands.
3. Unlocked. The sector groups are unprotected and can be erased and/or programmed.
These states are controlled by the bit types described in sections
Persistent Protection Bits on page 39
to
Notes
1. If the password mode is chosen, the password must be programmed before setting the corresponding lock register bit.
The user must be sure that the password is correct when the Password Mode Locking Bit is set, as there is no means to
verify the password afterwards.
2. If both lock bits are selected to be programmed (to zeros) at the same time, the operation aborts.
3. Once the Password Mode Lock Bit is programmed, the Persistent Mode Lock Bit is permanently disabled, and no
changes to the protection scheme are allowed. Similarly, if the Persistent Mode Lock Bit is programmed, the Password
Mode is permanently disabled.
4. It is important that the mode is explicitly selected when the device is first programmed, rather than relying on the default
mode alone. This is so that it is impossible for a system program or virus to later set the Password Mode Locking Bit,
which would cause an unexpected shift from the default Persistent Sector Protection Mode into the Password Protection
Mode.
5. 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 modifying 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.
6. For the command sequence required for programming the lock register bits, refer to
Command Definitions on page 67
.
