restricting JTAG's access to flash

[ABC1024]

Hi,

I have a few questions about restricting JTAG's access to flash:

1.When MEAN is disabled and KEYEN is enabled, the MCU cannot connect to the jlink after resetting. After entering the backdoor key, the serial port displays unsecure, and JLINK can connect at this time. Is this the correct process?

2.According to 1, when I try to read and write(e.g. program or read back) with jlink after temporary unsecure, it still reports an error. I guess it is 'connect' that causes the MCU to reset again. If so, how can I read and write to the flash after inputting the key to temporarily unlock it?

3. When both MEEN and KEYEN are enabled, it can be erased without entering the backdoor key. So in order to use the backdoor key secure, it is necessary to disable MEEN, right?

4.Is it possible to configure unique backdoor keys for each device

Best Regards

[danielmartynek]

Hi @ABC1024,

1.

Yes, correct.

2.

The J-link must not reset the MCU, this would lock the MCU again.

A special J-link script is necessary

https://wiki.segger.com/S32Kxxx#Attach_to_debug_session

J-Link commander has to be called in the following way:
C:\Programme\SEGGER\JLink\JLink.exe -JLinkScriptFile NXP_Kinetis_S32_Attach.JLinkScript

Then, the MCU is not reset, and access to all the memory and registers is possible.

Please contact SEGGER support if you need more information.

3.

It is not necessary to disabled the mass erase (MEEN). The mass erase removes all the code and data from the MCU.

4.

This is up to the user.