M29DW128F60NF1F datasheet(82/93 Pages) STMICROELECTRONICS

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M29DW128F

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Appendix C Extended Memory Block

The M29DW128F has an extra block, the Extended Block, that can be accessed using a

dedicated command.

This Extended Block is 128 Words in x16 mode and 256 Bytes in x8 mode. It is used as a

security block (to provide a permanent security identification number) or to store additional

information.

The Extended Block is divided into two memory areas of 64 Words each:

●

The first one is Factory Locked.

●

The second one is Customer Lockable. It is up to the customer to protect it from program

operations. Its status is indicated by bit DQ6 and DQ7. When DQ7 is set to ‘1’ and DQ6 to

‘0’, it indicates that this second memory area is Customer Lockable. When DQ7 and DQ6

are both set to ‘1’, it indicates that the second part of the Extended Block is Customer

Locked and protected from program operations. Bit DQ7 being permanently locked to

either ‘1’ or ‘0’ is another security feature which ensures that a customer lockable device

cannot be used instead of a factory locked one.

Bits DQ6 and DQ7 are the most significant bits in the Extended Block Protection Indicator and

a specific procedure must be followed to read it. See “Section 3.6.2: Verify Extended Block

Protection Indicator” and Table 5 and Table 8, Block Protection, for details of how to read bit

DQ7.

The Extended Block can only be accessed when the device is in Extended Block mode. For

details of how the Extended Block mode is entered and exited, refer to the Program command

and Exit Extended Block command paragraphs, and to Table 15 and Table 16, Block Protection

Commands.

C.1

Factory Locked Section of the Extended Block

The first section of The Extended Block is permanently protected from program operations and

cannot be unprotected. The Random Number, Electronic Serial Number (ESN) and Security

Identification Number (see Table 41: Extended Block Address and Data) are written in this

section in the factory.

C.2

Customer Lockable Section of the Extended Block

The device is delivered with the second section of the Extended Block "Customer Lockable":

bits DQ7 and DQ6 are set to '1' and '0' respectively. It is up to the customer to program and

protect this section of the Extended Block but care must be taken because the protection is not

reversible.

There are three ways of protecting this section:

●

Issue the Enter Extended Block command to place the device in Extended Block mode,

then use the In-System Technique with RP either at VIH or at VID. Refer to In-System

Technique in Appendix D: High Voltage Block Protection, and to the corresponding

flowcharts Figure 25 and Figure 26 for a detailed explanation of the technique).

●

Issue the Enter Extended Block command to place the device in Extended Block mode,

then use the Programmer Technique. Refer to Programmer Technique in Appendix D: High

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