The most relevant files for scientific analysis of a pn observation are (depending on the observing mode) the imaging mode, the timing mode or the burst mode event list files together with the auxiliary file providing a detailed description of each frame recorded during the exposure. One imaging mode event list file is produced per CCD by the ``Full Frame'' and ``Large Window'' instrumental modes. Only CCD 4 is active in ``Small Window'', ``Timing'' or ``Burst'' mode. Hence these modes produce event list data only for a single chip. The other chips do not collect any data. In timing and burst mode, CCD 4 collects spatial info only in one dimension (the X axis) whereas the Y axis is a measure of the detection time.