K26 locked

[karimakelainen]

Hi, I have in our production series some issues on MK26FN2M0 being locked.

Seems like the chip can not be unlocked permanetly.

We are using J-link commander V6.34c to unlock the chip and then J-Flash v6.34c to erase chip.

After power cycle, the chip is locked again and needs to be unlocked to get connected.

We have pcba:s coming to us from assembly house and there seems to be no physical faults in the board.

By replacing the cpu in rework station, gets the board working ok.

Any ideas what elese than faulty chip could cause this ?

[mjbcswitzerland]

Hi

Beware that a chip erase and a reset/power cycle will LOCK a Kinetis part.

An unlock (unsecure) sequence is not just a mass erase, but a mass erase "followed by a write of 0xfe to the Flash address 0x40c". Without the write it will never unlock...

Regards

Mark

[FelipeGarcia]

Hi Kari,

You don't need to use two different tools to unlock the device.

On the J-Link commander execute the unlock kinetis command.

unlock kinetis command triggers a mass erase to the device so I think your issue is that unlock the board with the J-Link commander but then you lock it again with the J-Flash.

Please let me know if this helps you.

Best regards,

Felipe