ST10F272M datasheet(37/175 Pages) STMICROELECTRONICS

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ST10F272M

Internal Flash memory

37/176

5.5.5

Flash non-volatile access protection register 1 high (FNVAPR1H)

5.5.6

XBus Flash volatile temporary access unprotection register

(XFVTAUR0)

5.5.7

Access protection

The IFlash module has one level of access protection (access to data both in Reading and

Writing).

When bit ACCP of FNVAPR0 is programmed at 0 and bit TAUB in XFVTAUR0 is set at 0, the

IFlash module becomes access protected (data in the IFlash module can be read only if the

current execution is from the IFlash module itself).

Trying to read into the access protected Flash from internal RAM or external memories will

output a dummy data (software trap 009Bh).

When the Flash module is protected in access, data access through PEC transfers is also

forbidden. To read/write data through PEC in a protected Bank, first it is necessary to

temporarily unprotect the Flash module.

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

Name

Function

15:0 PEN[15:0]

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

Reserved

TAUB

-RW

Table 23.

XBus Flash volatile temporary access unprotection register

Bit

Name

Function

0TAUB

Temporary Access Unprotection bit

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

The fact that this bit can be written only while executing from IFlash guarantees that

only a code executed in IFlash can unprotect the IFlash when it is Access

Protected.

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