ST10F272 datasheet(39/179 Pages) STMICROELECTRONICS

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ST10F272

Internal Flash memory

39/179

5.5.5

Flash non volatile access protection register 1 high

5.5.6

XBus flash volatile temporary access unprotection register (XFVTAUR0)

5.5.7

Access protection

The I-Flash module has one level of access protection (access to data both in Reading and

Writing): if bit ACCP of FNVAPR0 is programmed at 0 and bit TAUB in XFVTAUR0 is set at

0, the I-Flash module becomes access protected: data in the I-Flash module can be read

only if the current execution is from the I-Flash module itself.

To enable Access Protection, the following sequence of operations is recommended:

●

execution from external memory or internal Rams

●

program TAUB bit at 1 in XFVTAUR0 register

●

program ACCP bit in FNVAPR0 to 0 using Set Protection operation

●

program TAUB bit at 0 in XFVTAUR0 register

●

Access Protection is active when both ACCP bit and TAUB bit are set to 0.

Protection can be permanently disabled by programming bit PDS0 of FNVAPR1H, in order

to analyze rejects. Protection can be permanently enabled again by programming bit PEN0

of FNVAPR1L. The action to disable and enable again Access Protections in a permanent

way can be executed a maximum of 16 times. To execute the above described operations,

the Flash has to be temporary unprotected (See Section 5.5.9: Temporary unprotection)

FNVAPR1H (0x08 DFBE)

NVR

Delivery value: FFFFh

987

65432

PEN15PEN14PEN13PEN12PEN11PEN10 PEN9 PEN8 PEN7 PEN6 PEN5 PEN4 PEN3 PEN2 PEN1 PEN0

Table 22.

Flash non volatile access protection register 1 high

Bit

Function

PEN15-0

Protections Enable 15-0

If bit PENx is programmed at 0 and bit PDSx+1 is erased at 1, the action of bit

ACCP is enabled again. Bit PENx can be programmed at 0 only if bit PDSx has

already been programmed at 0.

XFVTAUR0 (0x00 EB50)

NVR

Reset value: 0000h

987

65432

TAUB

reserved

Table 23.

XBus flash volatile temporary access unprotection register

Bit

Function

TAUB

Temporary Access Unprotection bit

If this bit is set to 1, the Access Protection is temporary disabled.

This bit can be written only executing from IFlash.This fact guarantees that only a

code executed in IFlash, can unprotect the IFlash, when it is Access Protected.

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