Undesired FLASH protection on MC9S08QB4

[benthie]

Hey everybody,

my current application uses the flash programming routines from AN3942. At some point my program writes data to the flash (0xFFC0 - 0xFFFF). Everything works fine so far, the data is where I want it to be and when I debug the controller, the FOPT register tells me, that the flash is unsecured (FOPT = 0xC2).

If I stop my program and debug it again, then the "device is secured"-dialog pops up.

Does anybody has an idea, at which point the securing happens?

Regards,

Ben

[benthie · Accepted solution]

I found the problem. I erased the NVOPT bits due to a page erase and did not set the SEC00 bit back to 0. Ref.Manual p.55.

Thank you anyway.

Ben