Systems on chip are more and more heterogeneous and include software, analog/RF and digital hardware, and non-electronic components such as sensors or actuators. The design and the verification of such systems require appropriate modeling means to deal with the increasing complexity and to achieve efficient simulation. SystemC is providing a modeling and simulation framework that supports digital (discrete) hardware and software systems from abstract specifications to register transfer level models. In the paper, we are proposing a way to extend the capabilities of SystemC to support mixed discrete-continuous systems by implementing a synchronous dataflow (SDF) model of computation (MoC). The SDF MoC is used to embed continuous-time behavior in SDF modules and to support the synchronization with the existing SystemC kernel. The paper presents an overview of the architecture and the syntax of the proposed extensions and gives modeling examples with simulation results.