M29DW128F60NF1F datasheet(84/93 Pages) STMICROELECTRONICS

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M29DW128F

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Appendix D High Voltage Block Protection

The High Voltage Block Protection can be used to prevent any operation from modifying the

data stored in the memory. The blocks are protected in groups, refer to Appendix A, Table 34 for

details of the Protection Groups. Once protected, Program and Erase operations within the

protected group fail to change the data.

There are three techniques that can be used to control Block Protection, these are the

Programmer technique, the In-System technique and Temporary Unprotection. Temporary

Unprotection is controlled by the Reset/Block Temporary Unprotection pin, RP; this is described

in the Signal Descriptions section.

To protect the Extended Block issue the Enter Extended Block command and then use either

the Programmer or In-System technique. Once protected issue the Exit Extended Block

command to return to read mode. The Extended Block protection is irreversible, once protected

the protection cannot be undone.

D.1

Programmer Technique

The Programmer technique uses high (VID) voltage levels on some of the bus pins. These

cannot be achieved using a standard microprocessor bus, therefore the technique is

recommended only for use in Programming Equipment.

To protect a group of blocks follow the flowchart in Figure 23: Programmer Equipment Group

Protect Flowchart. To unprotect the whole chip it is necessary to protect all of the groups first,

then all groups can be unprotected at the same time. To unprotect the chip follow Figure 24:

Programmer Equipment Chip Unprotect Flowchart. Table 42: Programmer Technique Bus

Operations, 8-bit or 16-bit Mode, gives a summary of each operation.

The timing on these flowcharts is critical. Care should be taken to ensure that, where a pause is

specified, it is followed as closely as possible. Do not abort the procedure before reaching the

end. Chip Unprotect can take several seconds and a user message should be provided to show

that the operation is progressing.

D.2

In-System Technique

The In-System technique requires a high voltage level on the Reset/Blocks Temporary

Unprotect pin, RP (1). This can be achieved without violating the maximum ratings of the

components on the microprocessor bus, therefore this technique is suitable for use after the

memory has been fitted to the system.

To protect a group of blocks follow the flowchart in Figure 25: In-System Equipment Group

Protect Flowchart. To unprotect the whole chip it is necessary to protect all of the groups first,

then all the groups can be unprotected at the same time. To unprotect the chip follow Figure 26:

In-System Equipment Chip Unprotect Flowchart.

The timing on these flowcharts is critical. Care should be taken to ensure that, where a pause is

specified, it is followed as closely as possible. Do not allow the microprocessor to service

interrupts that will upset the timing and do not abort the procedure before reaching the end.

Chip Unprotect can take several seconds and a user message should be provided to show that

the operation is progressing.

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