in the KL27 series user guide page 858. for program flash protection register FTFA_FPROTn, it says, In NVM Normal mode FPROT can only goes 1 to 0. ... In the NVM Special mode, FPORTn can be changed.
I don't know where is the NVM mode setup?
Thus, only the debugger uses the special mode.
See also the following video for more details: https://www.youtube.com/watch?v=c9GRYXFs9LU&list=PLWKlVb_MqDQFZAulrUywU30v869JBYi9Q&index=4
Complete Solutions and technical support for professional Kinetis developments: http://www.utasker.com/kinetis.html
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