In this paper, a compact model for PCM cells with a physical approach, which evaluates the state of the cell during and after a programming operation, is described. The model is able to simulate the state of the active material of the cell during the whole programming operation. It takes into account the dynamic of the amorphous cap growth during a RESET operation, as well as the crystallization process, expressed in terms of Crystal Fraction (CF) during a SET operation. The model was validated through comparison with experimental data.