MC9S12XE-Family Reference Manual , Rev. 1.19
Freescale Semiconductor
345
Chapter 9
Security (S12XE9SECV2)
9.1
Introduction
This specification describes the function of the security mechanism in the S12XE chip family (9SEC).
NOTE
No security feature is absolutely secure. However, Freescale’s strategy is to
make reading or copying the FLASH and/or EEPROM difficult for
unauthorized users.
9.1.1
Features
The user must be reminded that part of the security must lie with the application code. An extreme example
would be application code that dumps the contents of the internal memory. This would defeat the purpose
of security. At the same time, the user may also wish to put a backdoor in the application program. An
example of this is the user downloads a security key through the SCI, which allows access to a
programming routine that updates parameters stored in another section of the Flash memory.
The security features of the S12XE chip family (in secure mode) are:
•
Protect the content of non-volatile memories (Flash, EEPROM)
•
Execution of NVM commands is restricted
•
Disable access to internal memory via background debug module (BDM)
•
Disable access to internal Flash/EEPROM in expanded modes
•
Disable debugging features for the CPU and XGATE
Table 9-1. Revision History
Revision
Number
Revision Date
Sections
Affected
Description of Changes
V02.00
27 Aug 2004
- Reviewed and updated for S12XD architecture
V02.01
21 Feb 2007
- Added S12XE, S12XF and S12XS architectures
V02.02
19 Apr 2007
- Corrected statement about Backdoor key access via BDM on XE, XF, XS
Because
of
an
order
from
the
United
States
International
Trade
Commission,
BGA-packaged
product
lines
and
part
numbers
indicated
here
currently
are
not
available
from
Freescale
for
import
or
sale
in
the
United
States
prior
to
September
2010:
S12XE
products
in
208
MAPBGA
packages