ST10F276Z5 datasheet(38/239 Pages) STMICROELECTRONICS

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Internal Flash memory

ST10F276Z5

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4.5

Protection strategy

The protection bits are stored in Non Volatile Flash cells inside XFLASH module, that are

read once at reset and stored in 7 Volatile registers. Before they are read from the Non

Volatile cells, all the available protections are forced active during reset.

The protections can be programmed using the Set Protection operation (see Flash Control

Registers paragraph), that can be executed from all the internal or external memories

except from the Flash Bank B2.

Two kind of protections are available: write protections to avoid unwanted writings and

access protections to avoid piracy. In next paragraphs all different level of protections are

shown, and architecture limitations are highlighted as well.

4.5.1

Protection registers

The 7 Non Volatile Protection Registers are one time programmable for the user.

Four registers (FNVWPXRL/H-FNVWPIRL/H) are used to store the Write Protection fuses

respectively for each sector of the XFLASH Module (see X) and IFLASH module (see I). The

other three Registers (FNVAPR0 and FNVAPR1L/H) are used to store the Access

Protection fuses (common to both Flash modules even though with some limitations).

4.5.2

Flash non volatile write protection X register low

FNVWPXRL (0x0E DFB0)

NVR

Delivery value: FFFFh

987

65432

W2PPR

reserved

W2P2W2P1W2P0

Table 20.

Flash non volatile write protection X register low

Bit

Function

W2P(2:0)

Write Protection Bank 2 sectors 2-0 (XFLASH)

These bits, if programmed at 0, disable any write access to the sectors of Bank 2

(XFLASH).

W2PPR

Write Protection Bank 2 Non Volatile cells

This bit, if programmed at 0, disables any write access to the Non Volatile cells of Bank

2. Since these Non Volatile cells are dedicated to Protection registers, once W2PPR

bit is set, the configuration of protection setting is frozen, and can only be modified

executing a Temporary Write Unprotection operation.

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