SC9S12XS256J1MAA FREESCALE [Freescale Semiconductor, Inc], SC9S12XS256J1MAA Datasheet - Page 227

• Manufacturer Part Number: SC9S12XS256J1MAA
• Description: HCS12 Microcontrollers
• Manufacturer: FREESCALE [Freescale Semiconductor, Inc]

Chapter 7
Security (S12XS9SECV2)
7.1
This specification describes the function of the security mechanism in the S12XS chip family (9SEC).
7.1.1
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 S12XS chip family (in secure mode) are:
Table 7-2
Freescale Semiconductor
Number
Version
02.00
02.01
02.02
•
•
•
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)
Flash Array Access
Introduction
gives an overview over availability of security relevant features in unsecure and secure modes.
Revision
27 Aug
21 Feb
19 Apr
2004
2007
2007
Date
Features
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.
Table 7-2. Feature Availability in Unsecure and Secure Modes on S12XS
Effective
08 Sep
21 Feb
19 Apr
2004
2007
2007
Date
NS
✔
S12XS Family Reference Manual, Rev. 1.09
Author
SS
✔
Table 7-1. Revision History
Unsecure Mode
NX
ES
NOTE
reviewed and updated for S12XD architecture
added S12XE, S12XF and S12XS architectures
corrected statement about Backdoor key access via BDM on XE, XF,
XS
EX
ST
NS
Description of Changes
✔
SS
✔
Secure Mode
NX
ES
EX
ST
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