M29DW128F60NF1 STMICROELECTRONICS [STMicroelectronics], M29DW128F60NF1 Datasheet - Page 24

• Manufacturer Part Number: M29DW128F60NF1
• Description: 128 Mbit (16Mb x8 or 8Mb x16, Multiple Bank, Page, Boot Block) 3V Supply, Flash Memory
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

5 Software Protection
5.2
5.2.1
5.2.2
24/93
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
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
mode is then activated by programming the 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).
Block Lock/Unlock Protection
The Block Lock/Unlock Protection operates exactly in the same way as in the Standard
Protection mode.
Non-Volatile Protection
The Non-Volatile Protection is more advanced in the Password Protection mode.
In this mode, the Lock-Down bit cannot be cleared through a hardware reset or a power-down/
power-up sequence.
The Lock-Down bit is cleared by issuing the Password Protection Unlock command along with
the correct password.
Password Program command
Table 10: Block Protection Status
and
Password Verify
and
Figure 7: Software Protection Scheme
ID
or at V
command). The Password Protection
IH
.
M29DW128F
for details