Kinetis Security - Backdoor usage - Please explain

[JHinkle]

I currently have a K64 which uses a bootloader and Application.

The K64 has security enabled but allows bulk erase and NXP access.

In another post, I noted a glitch in the VCC line has caused the App to hardfault and NOT recover after a reset or power cycle.

My only recourse, as I see it is to bulk erase, reflash with a debugger, and hope it faults again so I can understand what issue the VCC glitch caused.

Moving forward, I would like to be able to debug the faulted application - even with security set.

I understand that my app, prior to faulting, can use the backdoor key and release security temporarily.  If I do this, will I be able to attach a debugger to the target (jlink + Crossworks) and step thru the application or break when the hardfault occurs?

Thanks.

Joe

[Hui_Ma]

Hi

There is an useful application note AN4507 about Kinetis product security.

When using the debugger connect the K64 chip, which will reset the K64 and caused the K64 be re-secured again. Then debugger tool could not connect with K64 chip.

So, customer need to modify the Flash address 0x40C with unsecure value (0xFE) in backdoor key access application/firmware.

Wish it helps.

Have a great day,
Ma Hui
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