MC9S12NE64_06 Datasheet, PDF (60/554 Pages) Freescale Semiconductor, Inc – Microcontrollers

Chapter 1 MC9S12NE64 Device Overview
Table 1-6. Mode Selection
BKGD = PE6 =
MODC MODB
0
0
0
0
0
1
0
1
1
0
1
0
1
1
1
1
PE5 =
MODA
0
1
0
1
0
1
0
1
PP6 =
ROMCTL
X
0
1
X
0
1
X
0
1
X
0
1
ROMON
Bit
1
1
0
0
1
0
1
0
1
1
0
1
Mode Description
Special Single Chip, BDM allowed and ACTIVE. BDM
is allowed in all other modes but a serial command is
required to make BDM active.
Emulation Expanded Narrow, BDM allowed.
Special Test (Expanded Wide), BDM allowed.
Emulation Expanded Wide, BDM allowed.
Normal Single Chip, BDM allowed.
Normal Expanded Narrow, BDM allowed.
Peripheral; BDM allowed but bus operations would
cause bus conflicts (must not be used).
Normal Expanded Wide, BDM allowed.
For further explanation on the modes, see the MEBI block description chapter.
1.4.2 Security
The MC9S12NE64 provides a security feature that prevents the unauthorized read and write of the
memory contents¹. This feature allows:
• Protection of the contents of FLASH
• Operation in single-chip mode
• Operation from external memory with internal FLASH disabled
On-chip security can be compromised by user code. An extreme example would be user code that dumps
the contents of the internal program. This code would defeat the purpose of security. At the same time the
user may also wish to put a back door in the user program. An example of this would be the user
downloading a key through the SCI, which would allow access to a programming routine that could update
parameters.
1.4.2.1 Securing the Microcontroller
After the user has programmed the FLASH, the MCU can be secured by programming the security bits
located in the FLASH module. These nonvolatile bits will keep the MCU secured through resetting the
MCU and through powering down the MCU.
The security byte resides in a portion of the FLASH array.
See the FLASH block description chapter for more details on the security configuration.
1.No security feature is absolutely secure. However, Freescale Semiconductor’s strategy is to make reading or copying
the FLASH difficult for unauthorized users.
MC9S12NE64 Data Sheet, Rev 1.0
60
Freescale Semiconductor