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ST72F340S4T6 查看數據表(PDF) - STMicroelectronics

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ST72F340S4T6 Datasheet PDF : 191 Pages
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ST72340, ST72344, ST72345
FLASH PROGRAM MEMORY (Cont’d)
4.5 Memory Protection
There are two different types of memory protec-
tion: Read Out Protection and Write/Erase Protec-
tion which can be applied individually.
4.5.1 Read out Protection
Readout protection, when selected provides a pro-
tection against program memory content extrac-
tion and against write access to Flash memory.
Even if no protection can be considered as totally
unbreakable, the feature provides a very high level
of protection for a general purpose microcontroller.
Both program and data E2 memory are protected.
In flash devices, this protection is removed by re-
programming the option. In this case, both pro-
gram and data E2 memory are automatically
erased, and the device can be reprogrammed.
Read-out protection selection depends on the de-
vice type:
– In Flash devices it is enabled and removed
through the FMP_R bit in the option byte.
– In ROM devices it is enabled by mask option
specified in the Option List.
4.5.2 Flash Write/Erase Protection
Write/erase protection, when set, makes it impos-
sible to both overwrite and erase program memo-
ry. It does not apply to E2 data. Its purpose is to
provide advanced security to applications and pre-
vent any change being made to the memory con-
tent.
Warning: Once set, Write/erase protection can
never be removed. A write-protected flash device
is no longer reprogrammable.
Write/erase protection is enabled through the
FMP_W bit in the option byte.
4.6 Register Description
FLASH CONTROL/STATUS REGISTER (FCSR)
Read / Write
Reset Value: 000 0000 (00h)
1st RASS Key: 0101 0110 (56h)
2nd RASS Key: 1010 1110 (AEh)
7
0
0
0
0
0
0 OPT LAT PGM
Note: This register is reserved for programming
using ICP, IAP or other programming methods. It
controls the XFlash programming and erasing op-
erations. For details on XFlash programming, refer
to the ST7 Flash Programming Reference Manual.
When an EPB or another programming tool is
used (in socket or ICP mode), the RASS keys are
sent automatically.
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