RTflow is a free, lightweight dataflow modelling tool for real-time systems. In RTflow, you build your system in a graphical language that is both parallel and deterministic, so that threading and timing problems are completely avoided. You verify your model in a simulator that produces graphs of every variable in the system, which allows you to spot bugs and their causes effortlessly. Finally, you generate software (C, C++ or Java) or hardware (VHDL) code from the model, allowing for immediate implementation on your target platform.
Download and use it now: RTflow