This paper presents a design methodology for a hybrid Hardwarein-the-Loop (HIL) tester tool, based on both discrete event system theory, given by timed automata, and continuous systems theory, given by difference equations. It is implemented using an FPGA platform that guarantees speed enhancement, time accuracy and extensibility with no performance loss. We have focused on the implementation of a discrete event system, specifically timed automata into FPGA, and we have linked them with continuous systems implemented as filters in fixed point arithmetic. The paper shows a methodology, which employs widely used tools (Matlab, UPPAAL) as a user interface, and which implements the FPGA based tester tool. keyword Hardware-in-the-Loop, Real-Time System Testing, Model checking, Timed Automata, FPGA, Hybrid System, System Control