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Data Protection and Security
8.3 Flash Programmer and Self-Programming
Serial programming
Self-programming
Protection flags
(1)
(2)
(3)
Protection
In general, illegal read-out and re-programming of the flash memory contents
is possible via the flash writer interface and the self-programming feature.The
available flash memory protection methods are as follows.
It is possible to prohibit any access from external via the serial programming
interface,e.g. by an external flash programmer. With maximum protection the
internal flash memory can not be erased, read-out or written at all, neither in
block units nor the entire flash memory.
During self-programming all operations to erase, read or program the flash
memory is under control of the user's program. Thus no further protection
functions in self-programming mode are considered. One exception is the boot
block protection, which applies also in self-programming mode.
The protection flags can be set respectively reset by an external flash
programmer, provided the effective protection level allows to do so.
In self-programming mode the effective protection flags can not be reset, but
other ones can be set to enhance the protection level.
The protection flags are stored in the flash memory extra area.
Each protection function can be used in combination with the others at the
same time.
Write protection flag
Set this flag to disable the programming function via external flash programmer
interfaces.
No flash memory content can be written from external, if this flag is set.
Erasure of single blocks is prohibited as well.
This flag does not affect the self-programming interface.
In self-programming mode writing of the flash memory is further on possible.
Chip erase protection flag
Set this flag to disable the chip erase function via external flash programmer
interfaces.
No flash memory content can be erased - neither in single blocks nor the entire
flash memory - from external, if this flag is set.
Chip erase is not available in self-programming mode, though it is possible to
erase the entire flash memory content by block erase of all blocks all together.
Note that the contents of the extra area is not erased by this means. I.e.
protection flags, variable reset vector, etc. are still valid.
Block erase protection flag
Set this flag to disable the feature to erase single blocks via external flash
programmer interfaces.
Single blocks can not be erased. Chip erase is still possible, provided the chip
erase protection flag is not set.
This flag does not affect the self-programming interface.
In self-programming mode erasure of single blocks or sets of contiguous
blocks of the flash memory is further on possible.
User's Manual U18743EE1V2UM00
Chapter 8
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