ST10F272M datasheet(35/175 Pages) STMICROELECTRONICS

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ST10F272M

Internal Flash memory

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5.5

Protection strategy

The protection bits are stored in Non-Volatile Flash cells inside IFlash module, that are read

once at reset and stored in four 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 itself.

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.

5.5.1

Protection registers

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

One register (FNVWPIR) is used to store the Write Protection fuses respectively for each

sector IFlash module. The other three Registers (FNVAPR0 and FNVAPR1L/H) are used to

store the Access Protection fuses.

5.5.2

Flash non-volatile write protection I register (FNVWPIR)

SEQER

Sequence Error

This bit is automatically set when the control registers (FCR1H/L-FCR0H/L,

FARH/L, FDR1H/L-FDR0H/L) are not correctly filled to execute a valid Write

Operation. In this case no Write Operation is executed. This bit has to be software

reset.

RESER

Resume Error

This bit is automatically set when a suspended Program or Erase operation is not

resumed correctly due to a protocol error. In this case the suspended operation is

aborted. This bit has to be software reset.

8WPF

Write Protection Flag

This bit is automatically set when trying to program or erase in a sector write

protected. In case of multiple Sector Erase, the not protected sectors are erased,

while the protected sectors are not erased and bit WPF is set. This bit has to be

software reset.

Table 18.

Flash error register (continued)

Bit

Name

Function

FNVWPIR (0x08 DFB0)

NVR

Reset value: FFFFh

987

65432

Reserved

W0P7W0P6W0P5W0P4W0P3W0P2W0P1W0P0

RWRWRWRWRWRW

RWRW

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