[SOLVED] J-Flash Programming of NXP kinetis MK02FN128VLF10

shaw · Oct 5th 2017, 6:20pm

Hello,

Just wanted to double check how Segger handles the Flash Security field / Flash security register when erasing device Flash. As long as I selected Target MK02FN128VLF10 and I don't select MK02FN128VLF10( allow security), I believe the bits should stay in the default state, and I will be able to reconnect debugger after erase/program cycle (as long as my program doesn't change them).

Backdoor security key enable bits (10)
Mass Erase bits (00, 01, 11)
Flash Security bits (10)

Thanks,
Ed

SEGGER - Niklas · Oct 6th 2017, 9:49am

Hi Ed,

As long as I selected Target MK02FN128VLF10 and I don't select MK02FN128VLF10( allow security), I believe the bits should stay in the default state, and I will be able to reconnect debugger after erase/program cycle (as long as my program doesn't change them).

Yes and no.
It only checks for the Flash Security bits. Since the Mass Erase Enable Bits do not have any effect if the Flash security bits are set to unsecure.
Therefore, it should not be possible to enable security when downloading a data file with J-Link and "MK02FN128VLF10" (w/o security) selected as target device.

On mass erase, to complete flash is left 0xFF, which causes the device to be secured after a power-cylce, however the J-Link software unsecures the target device automatically in this case, which must be possible since mass erase is enables (Mass Erase Enable Bits = 11 = Mass erase is enabled)

Best regards,
Niklas

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