FTS64K datasheet(37/44 Pages) FREESCALE

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FTS64K Block User Guide — Version V01.00

5. If any of the four 16-bit words does not match the Flash content the MCU remains secured.

After the Backdoor Access Sequence has been correctly matched, the microcontroller will be unsecured.

The Flash security byte can be programmed to the unsecure state, if desired.

In the unsecured state the user has full control of the contents of the four word Backdoor Key by

programming it in bytes $FF00 - $FF07 of the Flash Protection/Options Field.

The security of the Flash module as defined in the Flash Security/Options byte ($FF0F) is not changed by

unsecuring the flash module using the back door access scheme. The Back Door Comparison Key stored

in words $FF00 - $FF07 is unaffected by the Back Door Access sequence. After the next reset sequence,

the security state of the Flash module is determined by the Flash Security/Options byte ($FF0F)}. The

back door access method of unsecuring the microcontroller has no effect on the program and erase

protections defined in the Flash Protection Register FPROT.

It is not possible to unsecure the microcontroller in Special Single Chip mode by the Backdoor Access Key

sequence via the Background Debug Mode.

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FTS64K Datasheet(PDF) 37 Page - Freescale Semiconductor, Inc