M29DW128F datasheet(23/94 Pages) STMICROELECTRONICS

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M29DW128F

Software Protection

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Software Protection

The M29DW128F has two different Software Protection modes: the Standard Protection

mode and the Password Protection mode.

On first use all parts default to the Standard Protection mode and the customer is free to

activate the Standard or the Password Protection mode.

The desired protection mode is activated by setting one of two one-time programmable bits,

the Standard Protection Mode Lock bit or the Password Protection Mode Lock bit.

Programming the Standard and the Password Protection Mode Lock bit to ‘1’ will

permanently activate the Standard Protection mode and the Password Protection mode,

respectively. These two bits are one-time programmable and non-volatile, once the

Protection mode has been programmed, it cannot be changed and the device will

permanently operate in the selected Protection mode. It is recommended to activate the

desired Software Protection mode when first programming the device.

The device is shipped with all blocks unprotected. The Block Protection Status can be read

by issuing the Auto Select command (see Table 10: Block Protection status).

The Standard and Password Protection modes offer two levels of protection, a Block

Lock/Unlock protection and a Non-Volatile protection.

For the four outermost parameter blocks, an even higher level of block protection can be

achieved by locking the blocks using the Non-Volatile Protection and then by holding the

VPP/WP pin Low.

5.1

Standard Protection mode

5.1.1

Block Lock/Unlock Protection

It is a flexible mechanism to protect/unprotect a block or a group of blocks from program or

erase operations.

A volatile Lock bit is assigned to each block or group of blocks. When the lock bit is set to ‘1’

the associated block or group of blocks is protected from program/erase operations, when

the Lock bit is set to ‘0’ the associated block or group of blocks is unprotected and can be

programmed or erased.

The Lock bits can be set (‘1’) and cleared (‘0’) individually as often as required by issuing a

Set Lock Bit command and Clear Lock bit command, respectively.

After a Power-up or Hardware Reset, all the Lock bits are cleared to ‘0’ (block unlocked).

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