MC9S12A128 Datasheet, PDF (47/92 Pages) Motorola, Inc – Microcontroller unit (MCU)

4.3.3 Unsecuring the Microcontroller
MC9S12A128 Device Guide — V01.01
In order to unsecure the microcontroller, the internal FLASH and EEPROM must be erased. This can be
done through an external program in expanded mode.
Once the user has erased the FLASH and EEPROM, the part can be reset into special single chip mode.
This invokes a program that verifies the erasure of the internal FLASH and EEPROM. Once this program
completes, the user can erase and program the FLASH security bits to the unsecured state. This is generally
done through the BDM, but the user could also change to expanded mode (by writing the mode bits
through the BDM) and jumping to an external program (again through BDM commands). Note that if the
part goes through a reset before the security bits are reprogrammed to the unsecure state, the part will be
secured again.
4.4 Low Power Modes
Consult the respective Block Guide for information on the module behavior in Stop, Pseudo Stop, and
Wait Mode.
47