m29dw641f STMicroelectronics, m29dw641f Datasheet - Page 23

• Manufacturer Part Number: m29dw641f
• Description: 64 Mbit 4mb X16, Multiple Bank, Boot Block 3v Supply Flash Memory
• Manufacturer: STMicroelectronics

M29DW641F
5.2.2
The Non-Volatile Protection is more advanced in the Password Protection mode.
In this mode, the Lock-Down bit is non-volatile and 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.
Once the correct Password has been provided, the Lock-Down bit is cleared and the Non-Volatile Modify
Protection bits can be set or reset using the appropriate commands (the Set Non-Volatile Modify
Protection bit command or the Clear Non-Volatile Modify Protection bits command, respectively).
If the Password provided is not correct, the Lock-Down bit remains locked and the state of the Non-
Volatile Modify Protection bits cannot be modified.
The Password is a 64-bit code located in the memory space. It must be programmed by the user prior to
selecting the Password Protection mode. The Password is programmed by issuing a Password Program
command and checked by issuing a Password Verify command. The Password should be unique for each
part.
Once the device is in Password Protection mode, the Password can no longer be read or retrieved.
Moreover, all commands to the address where the password is stored, are disabled. Refer to
Figure 6: Software Protection scheme
Table 7.
1. The Lock bit can always be modified by issuing a Clear Lock bit command or by taking the device through a Power-up or
Lock bit
Volatile
Hardware Reset.
0
0
0
1
1
0
1
1
Modify Protection
Non-volatile Protection
Block Protection status
Non-volatile
bit
0
0
1
0
1
1
0
1
Lock-Down
bit
0
1
0
0
0
1
1
1
for details on the block protection scheme.
Protection
status
0000h
0001h
Block
Program/Erase
Unprotected
Protected
Block
Block
Block Protection status
Non-volatile Modify Protection bit
can be modified
Non-volatile Modify Protection bit
cannot be modified
Non-volatile Modify Protection bit
can be modified
Non-volatile Modify Protection bit
cannot be modified
Software Protection
(1)
(1)
(1)
(1)
Table 7
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and