ST10F272M-4Q3 STMICROELECTRONICS [STMicroelectronics], ST10F272M-4Q3 Datasheet - Page 38

• Manufacturer Part Number: ST10F272M-4Q3
• Description: 16-bit MCU with 256 Kbyte Flash memory and 20 Kbyte RAM
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

Internal Flash memory
5.5.8
5.5.9
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To enable Access Protection, the following sequence of operations is recommended:
●
●
●
●
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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 temporarily unprotected (see
Trying to write into the access protected Flash from internal RAM or external memories will
be unsuccessful. Trying to read into the access protected Flash from internal RAM or
external memories will output dummy data (software trap 0x009Bh).
When the Flash module is protected in access, data access through PEC of a peripheral is
also forbidden. To read/write data in PEC mode from/to a protected Bank, it is necessary to
first temporarily unprotect the Flash module.
The following table summarizes all possible Access Protection levels: In particular, it shows
what is possible and not possible to do when fetching from a memory (see fetch location
column) supposing all possible access protections are enabled.
Table 24.
When the Access Protection is enabled, Flash registers can not be written, so no
program/erase operation can be run on IFlash. To enable the access to registers again, the
Temporary Access Unprotection procedure has to be followed (see
Write protection
The Flash modules have one level of Write Protections: each Sector of each Bank of each
Flash Module can be Software Write Protected by programming at 0 the related bit W0Px in
FNVWPIRL register.
Temporary unprotection
Bits W0Px of FNVWPIRL can be temporarily unprotected by executing the Set Protection
operation and by writing 1 into these bits.
Fetching from IFlash
Fetching from IRAM
Fetching from XRAM
Fetching from External
Memory
Fetch location
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.
Summary of access protection level
Jump to IFlash
Read IFlash /
Yes / Yes
No / Yes
No / Yes
No / Yes
External Memory /
Jump to XRAM or
External Memory
Read XRAM or
Yes / Yes
Yes / Yes
Yes / Yes
Yes / Yes
Section 5.5.9: Temporary
Read Flash
registers
Yes
No
No
No
Section
unprotection).
5.5.9).
Write Flash
ST10F272M
registers
No
No
No
No