In addition to the actual event binning, this step includes the energy bin definition (through the spibounds software), the derivation of the GTI and of the dead time (GTI and DEAD tasks). So far no real GTI filter has been implemented at this stage and the complete time intervals of all pointings are considered as ``good'' (remember that bad pointing can be eliminated during the pointing step using a list of known bad pointings). The actual dead times are provided by the SPI electronics.
Dead time ratio and live time are defined by LIVETIME = DEADC * ONTIME, where the ontime is the net observing time, excluding any gaps in the data taking period, such as gaps due to slews or data loses, and the LIVETIME is the time corrected from the dead time. For more info on the definition of the exposure times, see
http://heasarc.gsfc.nasa.gov/docs/heasarc/ofwg/docs/ofwg_recomm/r11.html