Datasheet

ST7LITE0xY0, ST7LITESxY0
15/124
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 E
2
memory are protected.
In flash devices, this protection is removed by re-
programming the option. In this case, both pro-
gram and data E
2
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 E
2
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 Related Documentation
For details on Flash programming and ICC proto-
col, refer to the ST7 Flash Programming Refer-
ence Manual and to the ST7 ICC Protocol Refer-
ence Manual
.
4.7 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)
Note: This register is reserved for programming
using ICP, IAP or other programming methods. It
controls the XFlash programming and erasing op-
erations.
When an EPB or another programming tool is
used (in socket or ICP mode), the RASS keys are
sent automatically.
Table 3. FLASH Register Map and Reset Values
70
00000OPTLATPGM
Address
(Hex.)
Register
Label
76543210
002Fh
FCSR
Reset Value
00000
OPT
0
LAT
0
PGM
0
1