Now some manufacturer like Mercedes leave out this EEprom and simulate this function in the flash eprom. Therefore a special memory area is defined, which is much larger than the EEprom space. At first the EEprom contents is programmed at the start of this area. If something changes, the new contents is programmed behind the first one. This is done until the whole space is filled. Then the whole area is erased and the new contents is programmed at the beginning again.
For the tuner the problem appears, that a readout original file is possibly not valid any more after the next starting of the engine, because the data in the flash eprom has changed.
Valid is always the last file, which has successfully started the engine !