BACKDOOR KEY Verify Failed if request multiple times in a power on cycle

[Asher]

Hi:

   I met a question about backdoor access function Based on S32K144/S32K146 chip.

  The situation is that the first time of unlocking by backdoor access key always pass at a power-on cycle of MCU. but if I retry to unlock several times, the result will generate MCU CORE LOCK reset cause sometimes. Blows figure is the backdoor access function code. Do you have any idea for this situation?

[danielmartynek]

Hello @Asher,

I'm not able to replicate it.

What is the purpose of launching the command several times?

If the command passes successfully, the MCU is unlocked untill it is reset.

Please read FSEC[SEC] and launch the command only if SEC = Secure.

BR, Daniel

[Asher]

Hi @danielmartynek :

 Thanks for your information.

For your question: 

What is the purpose of launching the command several times?

 In our project, software verify backdoor key by a CAN communication request,  the software should ensure that sending communication requests does not result in a software reset. So, Sending multiple unlock request is a test situation.

The failure frequency is not fixed. It may occur once every five times or once every ten or more times.

By the way, the flash command code is running at PFLASH memory area, are you replicate it at the same situation? or I have to program the code at RAM memory area?

Looking forward to your reply!

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Best regards

Asher

[danielmartynek]

Hi @Asher,

I used a modified version of this example.

https://community.nxp.com/t5/S32K-Knowledge-Base/Example-S32K144-Verify-Backdoor-Access-Key-S32DS1-3...

I can reproduce the issue only when the command is launched from PFlash, where it fails with an FTFC Read Collision Error (RDCOLERR). Previously, I tested it with the code in SRAM only.

I don't see this requirement mentioned in the documentation anywhere, so I reported it.

Best regards,

Daniel

[Asher]

Hi @danielmartynek :

    I catch your point,  I will try run flash command code in RAM.

    Thanks for all your support!

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Best Regards

Asher