i use a MK64FN1M0VLL12 processor on 2 applications, a FRDM-K64f board and a custom application. I noticed that the processor would not boot after longer power failures (> than 20 seconds) and only a manual reset makes the processor boot again. Shorter periods do not lead to this behaviour.
The ethernet phy does not seem to fail because it provides a stable 50MHz clock output.
Does anyone have an idea, what may cause this problem ?