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Chapter 10 Code Protection and Security
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10.1 Overview
The microcontroller supports various methods for protecting the program code
in the flash memory from undesired access, such as illegal read-out or illegal
reprogramming.
Some interfaces offer in general access to the internal flash memory: N-Wire
debug interface, external flash programmer interface, self-programming
facilities and test interfaces.
In the following the security relevant items are listed. The features to protect
the internal flash memory data from being read by unauthorized persons are
described.
For more information on the flash memory, see "Flash Memory" on page 229.
The following sections give an overview about supported code protection
methods.
10.2 Boot ROM
Undesired access to the flash memory via the boot ROM is not possible.
10.3 N-Wire Debug Interface
In general, illegal read-out of the flash memory contents is possible via the
N-Wire debug interface. For protection of the flash memory, the usage of the
debug interface can be protected and it can be disabled. The debug interface is
protected via a 10-byte ID code and an internal flag (N-Wire use enable flag).
When the debugger is started, the status of a flag is queried (N-Wire use
enable flag). Set this flag to zero to disable the use of the N-Wire in-circuit
emulator.
When debugging is enabled (N-Wire use enable flag is set), you have to enter
a 10-byte ID code via the debugger. The code is compared with the ID code
stored in the internal flash memory. If the codes do not match, debugging is not
possible.
The N-Wire use enable flag can be set or reset while reprogramming the flash
by an external flash writer or with the self-programming feature. The flag is
located at bit 7 at address 0000 0079
You can specify your own 10-byte ID code and program it to the internal flash
memory by an external flash writer or with the self-programming feature. The
ID code is located in the address range 0000 0070
The protection levels are summarized in Table 10-1
Preliminary User's Manual U17566EE1V2UM00
.
H
to 0000 0079
H
.
H
339
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