MC9S12T64 Datasheet, PDF (119/608 Pages) Motorola, Inc – Specification

Freescale Semiconductor, Inc.
Operating Modes
Secured Mode of Operation
Operation of the
Secured
Microcontroller
Normal Single
Chip Mode
This will be the most common usage of the secured part. Everything will
appear the same as if the part was not secured with the exception of
BDM operation. The BDM operation will be blocked.
Executing from
External Memory
The user may wish to execute from external space with a secured
microcontroller. This is accomplished by resetting directly into expanded
mode. The internal FLASH and The CALRAM will be disabled. BDM
operations will be blocked.
Unsecuring the
Microcontroller
In order to unsecure the microcontroller, the internal FLASH must be
erased. This can be done through an external program in expanded
mode.
Once the user has erased the FLASH, the part can be reset into special
single chip mode. This invokes a program that verifies the erasure of the
internal FLASH. 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.
Operating Modes
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MC9S12T64Revision 1.1.1