Quote from SEGGER - Alex: “Hi, Quote: “ I believe, the "Erase chip" command from J-Link puts 0x00 instead of 0xFF at address 0x400. Hence, J-Link does write in this region!” Does not make sense... If you do a chip erase, all bytes in the internal flash will be set to 0xFF. Please note that the readout protection at 0x40C is defined as: 0xFF == device is read protected. This is a specification that comes from the Kinetis device. However, J-Link is able to recover a device that has all bytes (incl…