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F272-BAR-P View Datasheet(PDF) - STMicroelectronics

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F272-BAR-P Datasheet PDF : 188 Pages
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ST10F272B/ST10F272E
Internal Flash memory
5.5.5
Flash non volatile access protection register 1 high
FNVAPR1H (0x08 DFBE)
NVR
Delivery value: FFFFh
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
PEN15PEN14PEN13PEN12PEN11PEN10 PEN9 PEN8 PEN7 PEN6 PEN5 PEN4 PEN3 PEN2 PEN1 PEN0
RW RW RW RW RW RW RW RW RW RW RW RW RW RW RW RW
Table 22.
Bit
PEN15-0
Flash non volatile access protection register 1 high
Function
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.
5.5.6
XBus flash volatile temporary access unprotection register (XFVTAUR0)
XFVTAUR0 (0x00 EB50)
NVR
Reset value: 0000h
15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
TAUB
reserved
RW
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.
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
Doc ID 11917 Rev 3
41/188
 

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