This paper studies the problem of estimating the region of attraction of linear discrete-time systems with asymmetric input saturation. Using a Piecewise Quadratic Lyapunov function, we propose conditions for the local stability of the equilibrium. The asymmetric bounds of the saturation are considered in these conditions. Estimates of the region of attraction, possibly asymmetric with respect to the origin, are computed by solving convex optimization problems. Numerical results illustrate the effectiveness of the proposed method.