mc9s12q128 Freescale Semiconductor, Inc, mc9s12q128 Datasheet - Page 58

• Manufacturer Part Number: mc9s12q128
• Description: Hcs12 Microcontrollers
• Manufacturer: Freescale Semiconductor, Inc

Chapter 1 MC9S12Q Device Overview (MC9S12Q128-Family)
For further explanation on the modes refer to the S12_MEBI block guide.
1.5.2
The device will make available a security feature preventing the unauthorized read and write of the
memory contents. This feature allows:
The user must be reminded that part of the security must lie with the user’s code. An extreme example
would be user’s 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’s program. An example
of this is the user downloads a key through the SCI which allows access to a programming routine that
updates parameters.
1.5.2.1
Once the user has programmed the FLASH, the part can be secured by programming the security bits
located in the FLASH module. These non-volatile bits will keep the part secured through resetting the part
and through powering down the part.
58
BKGD =
MODC
•
•
•
0
0
0
0
1
1
1
1
Protection of the contents of FLASH,
Operation in single-chip mode,
Operation from external memory with internal FLASH disabled.
MODB
PE6 =
Security
0
0
1
1
0
0
1
1
Securing the Microcontroller
MODA
PE5 =
0
1
0
1
0
1
0
1
PE7 = XCLKS
ROMCTL
PP6 =
1
0
X
X
X
X
0
1
0
1
0
1
0
1
Table 1-8. Clock Selection Based on PE7
Colpitts Oscillator selected
Pierce Oscillator/external clock selected
ROMON
Table 1-7. Mode Selection
Bit
1
1
0
0
1
0
1
0
1
1
0
1
MC9S12Q128
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
Rev 1.09
Description
Mode Description
Freescale Semiconductor