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Programming the flash config field after a SWD mass erase.

Question asked by Andrew Parlane on Mar 16, 2017
Latest reply on Mar 17, 2017 by Kerry Zhou

I'm looking specifically at a K66F.


When you use the MDM-AP to mass erase the chip. It erases flash to all 1s, except for the security bit in the flash config field. This is what I see in practice, and what I read in the Production Flash Programming Best Practices for Kinetis K- and L-series MCUs PDF here: 


However in the K66 reference manual in "Program Section command", it states:


A flash memory location must be in the erased state before
being programmed. Cumulative programming of bits (back-to-
back program operations without an intervening erase) within a
flash memory location is not allowed. Re-programming of
existing 0s to 0 is not allowed as this overstresses the device.


So how does this work for the flash config field where the security bit is set to 0 during a mass erase.


Do I just ignore this caution for this bit, and issue a program section command as normal? Or is it better to run a sector erase first to actually erase that bit?


When it says reprogramming of existing 0s to 0 is not allowed. Does that mean the program section command will fail (it doesn't in the FCF case, and I haven't tried it in any other cases).