<p>Accuracy, speed and scalability are the basic requirements of sensor network simulation. To comprehend the accurate behavior of resource constrained embedded systems such as sensor nodes it is important in simulations to model the time-dependent behavior of the system. In this paper we present our extensions of TOSSIM – a widely used event-driven simulation environment for sensor networks – to enable its simulation models to capture the time-accurate behavior of sensor networks by exhibiting timing and interrupt properties of the platform dependent source-code. By mapping the device specific code with the simulation model, we can derive the timing of functional code blocks. As result of such a mapping it is possible to determine the time when a certain code block gets executed and the time the execution takes, eliminating the need of expensive cycle-accurate instruction level simulators with limited speed and restricted scalability.</p>