The physical processes in an Ar/N-2 magnetron discharge used for the reactive sputter deposition of TiNx thin films were simulated with a 2d3v particle-in-cell/Monte Carlo collisions (PIC)/MCC) model. Cathode currents and voltages were calculated self-consistently and compared with experiments. Also, ion fractions were calculated and validated with mass spectrometric measurements. With this PIC/MCC model, the influence of N-2/Ar gas ratio on the particle densities and fluxes was investigated, taking into account the effect of the poisoned state of the target.