The answer of Mark is right.
Also note that the port pins of MK64FN1M0VLQ12 are only 5V tolerant as inputs. The outputs are not 5V tolerant, and that includes pins configured as open-drain outputs. In output mode, if the pin is pulled above VDD, it will cause the output buffer to drive the output at VDD, which will pull-down the pin voltage to near VDD.
Best Regards,
Robin
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