M29DW128F datasheet(25/93 Pages) STMICROELECTRONICS

25 / 93 page

M29DW128F

5 Software Protection

25/93

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 Table 10: Block Protection Status and Figure 7: Software Protection Scheme for details

on the block protection scheme.

Table 10.

Block Protection Status

Figure 6.

Block Protection State Diagram

Volatile

Lock

Bit

Non-

Volatile

Modify

Protection

Bit

Lock-

Down bit

Block

Protectio

n Status

Block Protection Status

00h

Block

Unprotected

Non-Volatile Modify Protection bit can be

modified(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

Hardware Reset.

Non-Volatile Modify Protection bit cannot be

modified(1)

01h

Block

Program/

Erase

Protected

Non-Volatile Modify Protection bit can be

modified(1)

Non-Volatile Modify Protection bit cannot be

modified(1)

ai11503

Set Standard Protection

Mode

Default:

Standard

Protection

Password

Protection

Standard

Protection

Set Password Protection

Mode

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