− The ability to understand and predict the effects on electronic systems that might result from an intentional EMI attack is of great importance in defending critical electronic systems against such a threat. In this paper we focus on predicting the response of a microcontroller to a high-power electromagnetic waveform. We will describe our approach and present results from experimental investigations as well as modeling of the response of different microcontrollers to direct injection of an RF signal into clock and signal lines. In addition, we will discuss how these results may be extended to the case of free-field illumination. Finally, we will describe how our results shed light on the broader problem of predicting the response of a general digital system to a high-power electromagnetic waveform.