s32k144 Backdoor Key Access

[kmh48301]

Hello.

I need to block debug interface.

So I have studied FSEC, Backdoor key access in RM, nxp community.

It seems when the muc is secured and Mass Erase is disabled,

the backdoor key FTFC command is the only way to reprogram the mcu.

But that way is also able when the flash have the code to run that backdoor key FTFC command.

Is it correct? 

what if the flash have to code to reprogram the flash configuration field to make unsecured?

I need to make sure the ways and condition how to change from secured state to unsecured state.

Thanks

Best regards

Phillip

[kmh48301]

I got it. Thank you so much Daniel !!!

[danielmartynek]

Hi Phillip,

I'm not sure if I understand this:

what if the flash have to code to reprogram the flash configuration field to make unsecured?

The MCU can be unlocked by erasing the first sector (0x0000-0x1000) and programming it to an unlocked state, the MCU is then unlocked once it is reset.

But this is not recommended.

BR, Daniel

[kmh48301]

Hi, Daniel.

Thanks for replying.

===========================================================================

what if the flash have to code to reprogram the flash configuration field to make unsecured?

: If I unsecure the chip by reprogramming flash configuration field, any problem can be occurred?

I think if that doesn't have any problem, the backdoor command is useless.

============================================================================

compare please.

"backdoor command" vs "reprogram flash configuration field"  [Unsecuring Method]

Thanks

Best Regards

Phillip

[danielmartynek · Accepted solution]

The Backdoor key command is recommended, it unlocks the MCU without a need to reprogram anything, The MCU is then secure again after a reset.

Reprogramming the Flash configuration field is not recommended.

You would need to

1. Save the first sector somewhere

2. Erase the first sector (including the vector table)

3. Program the Flash configuration field (to unsecure) and put all the erased data back.

4. Reset the MCU

There is a risk that something goes wrong during the re-programming (e.g. the MCU gets reset during the process).

Also, to secure the MCU, you would need to do all the steps again.

Regards,

Daniel