M25PE16-VMP6TP datasheet(15/56 Pages) STMICROELECTRONICS

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M25PE16

Operating features

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4.8.2

Specific Hardware and Software protections

There are two Software Protected modes, SPM1 and SPM2, that can be combined to

protect the memory array as required. The SPM2 can be Hardware protected with the help

of the W input pin.

SPM1 and SPM2

●

The first Software Protected mode (SPM1) is managed by specific Lock Registers

assigned to each 64 Kbyte sector.

The Lock Registers can be read and written using the Read Lock Register (RDLR) and

Write to Lock Register (WRLR) instructions.

In each Lock Register two bits control the protection of each sector: the Write Lock Bit

and the Lock Down Bit.

–

Write Lock Bit:

The Write Lock Bit determines whether the contents of the sector can be modified

(using the Write, Program or Erase instructions). When the Write Lock Bit is set,

‘1’, the sector is write protected – any operations that attempt to change the data

in the sector will fail. When the Write Lock Bit is reset to ‘0’, the sector is not write

protected by the Lock Register, and may be modified.

–

Lock Down Bit:

The Lock Down Bit provides a mechanism for protecting software data from simple

hacking and malicious attack. When the Lock Down Bit is set, ‘1’, further

modification to the Write Lock and Lock Down Bits cannot be performed. A reset,

or power-up, is required before changes to these bits can be made. When the

Lock Down Bit is reset, ‘0’, the Write Lock and Lock Down Bits can be changed.

The Write Lock Bit and the Lock Down Bit are volatile and their value is reset to ‘0’ after

a Power-Down or a Reset (see Table 12: Device status after a RESET Low pulse).

The definition of the Lock Register bits is given in Table 9: Lock Register out.

Table 2.

Software protection truth table (Sectors 0 to 31, 64 Kbyte granularity)

Sector Lock

Protection Status

Lock

Down Bit

Write

Lock Bit

Sector Unprotected from Program/Erase/Write operations, Protection Status

Reversible

Sector Protected from Program/Erase/Write operations, Protection Status

Reversible

Sector Unprotected from Program/Erase/Write operations,

Sector Protection Status cannot be changed except by a Reset or Power-up.

Sector Protected from Program/Erase/Write operations,

Sector Protection Status cannot be changed except by a Reset or Power-up.

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