56F8014 datasheet(83/124 Pages) FREESCALE

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Flash Access Lock and Unlock Mechanisms

56F8014 Technical Data, Rev. 3

Freescale Semiconductor

Preliminary

To start the lockout recovery sequence, the JTAG public instruction (LOCKOUT_RECOVERY) must

first

shifted

into

the

chip-level

TAP

controller’s

instruction

Once

the

LOCKOUT_RECOVERY instruction has been shifted into the instruction register, the clock divider value

must be shifted into the corresponding 7-bit data register. After the data register has been updated, the user

must transition the TAP controller into the RUN-TEST/IDLE state for the lockout sequence to commence.

The controller must remain in this state until the erase sequence has completed. Refer to the 56F8000

Peripheral Reference Manual for more details, or contact Freescale.

Note:

Once the lockout recovery sequence has completed, the user must reset both the JTAG TAP controller

(by advancing the TAP state machine to the reset state) and the 56F8014 (by asserting external chip

reset) to return to normal unsecured operation.

7.2.3

Flash Lockout Recovery using CodeWarrior

CodeWarrior can unlock a device using the command sequence described in Section 7.2.2 by selecting the

Debug menu, then selecting DSP56800E, followed by Unlock Flash.

Another mechanism is also built into CodeWarrior using the device’s memory configuration file. The

command “Unlock_Flash_on_Connect1” in the .cfg file accomplishes the same task as using the Debug

menu.

7.2.4

Product Analysis

The recommended method of unsecuring a programmed 56F8014 for product analysis of field failures is

via the backdoor key access. The customer would need to supply Technical Support with the backdoor key

and the protocol to access the backdoor routine in the Flash. Additionally, the KEYEN bit that allows

backdoor key access must be set.

An alternative method for performing analysis on a secured microcontroller would be to mass-erase and

reprogram the Flash with the original code, but modify the security bytes.

To insure that a customer does not inadvertently lock himself out of the 56F8014 during programming, it

is recommended that the user program the backdoor access key first, the application code second and the

security bytes within the FM configuration field last.

56F8014 Datasheet(PDF) 83 Page - Freescale Semiconductor, Inc

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