How to unlock the chip

[cychen88]

When I enable the chip security function.0x400-0x40F will be change  Flash security byte = 1, JTAG/SWD will closed. If the product has problems and returns to the factory, I want to remove JTAG restrictions. What methods can I use to temporarily unlock or permanently unlock, so as to read flash. FSLACC:Factory Failure Analysis Access Code How to use this function.

[kef2]

Temporary access is possible by the means of FW running on chip. Verify Backdoor Access Key flash command should be used for that. You can't trigger it via JTAG, only FW can do that. You communicate over some interface to FW "let me unsecure it" and FW should issue Verify Backdoor Access Key command. Of course not possible when FW is dead. 

Mass erase is another option. S32DS debugger should ask you automatically to unsecure (mass erase) on attempt to connect to unsecured chip. Unfortunately if CSEc is used you won't be able to recover this way chip with dead FW:

[cychen88]

Thank 。To reuse the JTAG interface, the chip must be restored to the unsecure mode through mass erase  before it can be reused. Is that right？

[petervlna]

Hello,

About which device are you asking?

Best regards,

Peter

[cychen88]

S32K148