The paper describes an approach for semi-symbolic analysis of mixed-signal systems that contain discontinuous functions, e.g. due to modeling comparators. For modeling and semisymbolic simulation, we use extended Affine Arithmetic. Affine Arithmetic is currently limited to accurate analysis of linear functions and mild non-linear functions, but not yet discontinuities. In this paper we extend the approach to also handle discontinuities. For demonstration, we symbolically analyze a Σ∆-modulator.