M29DW128F60NF1E STMICROELECTRONICS [STMicroelectronics], M29DW128F60NF1E Datasheet - Page 24

• Manufacturer Part Number: M29DW128F60NF1E
• Description: 128 Mbit (16Mb x8 or 8Mb x16, Multiple Bank, Page, Boot Block) 3V supply Flash memory
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Software Protection
5.1.2
5.2
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Non-Volatile Protection
A Non-Volatile Modify Protection bit is assigned to each block or group of blocks.
When a Non-Volatile Modify Protection bit is set to ‘1’ the associated block or group of
blocks is protected, preventing any program or erase operations in this block or group of
blocks.
The Non-Volatile Modify Protection bits are set individually by issuing a Set Non-Volatile
Modify Protection bit command. They are non-volatile and will remain set through a
hardware reset or a power-down/power-up sequence.
The Non-Volatile Modify Protection bits cannot be cleared individually, they can only be
cleared all at the same time by issuing a Clear Non-Volatile Modify Protection bits
command.
However if any one of the Non-Volatile Modify Protection bits has to be cleared, care should
be taken to preprogram to ‘1’ all the Non-Volatile Modify Protection bits prior to issuing the
Clear Non-Volatile Modify Protection bits in order to prevent the over-erasure of previously
cleared Non Volatile Modify Protection bits. It is crucial to prevent over-erasure because the
process may lead to permanent damage to the Non-Volatile Modify Protection bits and the
device does not have any built-in means of preventing over-erasure.
The device features a volatile Lock-Down bit which can be used to prevent changing the
state of the Non-Volatile Modify Protection bits. When set to ‘1’, the Non-Volatile Modify
Protection bits can no longer be modified; when set to ‘0’, the Non-Volatile Modify Protection
bits can be set and reset using the Set Non-Volatile Modify Protection bit command and the
Clear Non-Volatile Modify Protection bits command, respectively.
The Lock-Down bit is set by issuing the Set Lock-Down bit Command. It is not cleared using
a command, but through a hardware reset or a power-down/power-up sequence.
The parts are shipped with the Non-Volatile Modify Protection bits set to ‘0’.
Locked blocks and Non-Volatile Locked blocks can co-exist in the same memory array.
Refer to
details on the block protection mechanism.
Password Protection mode
The Password Protection mode provides a more advanced level of software protection than
the Standard Protection mode.
Prior to entering the Password Protection mode, it is necessary to set a password and to
verify it (see
Verify
Password Protection Mode Lock bit to ‘1’. The Reset/Block Temporary Unprotect pin, RP,
can be at V
This operation is not reversible and once the bit is programmed the device will permanently
remain in the Password Protection mode.
The Password Protection mode uses the same protection mechanisms as the Standard
Protection mode (Block Lock/Unlock, Non-Volatile Protection).
command). The Password Protection mode is then activated by programming the
Table 10: Block Protection status
ID
Section 6.3.5: Password Program command
or at V
IH
.
and
Figure 7: Software Protection scheme
and
Section 6.3.6: Password
M29DW128F
for