MK60F12 - Unable to lock JTAG by securing flash through FSEC

[LRawlyk]

I'm trying to lock the JTAG on the MK60F12 by through the Flash Configuration loaded from program flash at 0x400 at startup.

However, no matter what I put in the SEC field of flash configuration FSEC (0b00, 0b01 or 0b11), the FTFL_FSEC register always loads with 0b10 (unsecured).

I tried changing other fields of FSEC (KEYEN, MEEN, etc.) and that works, but FSEC is always 0b10.

I'm using the SEGGER J-Link JTAG programmer.

Would anybody have any clue to why I'm not able to secure FSEC?

[diego_charles · Accepted solution]

Hi @LRawlyk 

Thank you for reaching out!

Let me provide my first recommendation, so you could double check. 

In the device selection, please try to select the Allow security option option for your part. Here is an example for the Segger J-Link commander. I do not know about the tools that you are using, but please ensure to select that option, per my experience, with this it will allow you to manipulate FSEC. 

Just beware of the MEEN, the if the mass erase is not enabled, you won't be able to write a new image with the FSEC enabled again.

I hope this could help you! 

Diego