Intentional Electromagnetic Irradiation of a Microcontroller

Using a state-of-the-art automated testing system called SALVO, pulsed RF signals were direct-injected into the clock line pin of a 8051 style Microcontroller (MCU) using careful timing. The MCU was programmed in assembly language to execute a simple binary counter operation, which counts from 0 to 7. The MCU's output lines were monitored to establish the count and determine whether the injected RF caused any deviation in the output lines of the MCU, referred to as an upset or effect. Since the timing of the MCU program was well understood, an RF pulse could be injected at specific locations relative to the rise and fall of the clock signal. Experiments to determine the variation in the probability of effect (PoE) during various software instructions were performed. In early experiments it was determined that injection of the RF pulse at different locations relative to the rise and fall of the clock had a significant impact on the PoE. Pulses which overlapped the rise and fall time locations had high probabilities, pulses overlapping the low state of the clock showed nearly zero probability, and pulses overlapping the high state of the clock varied greatly depending on the power amplitude of the pulse. This trend was observed to be consistent in each of the tested instructions suggesting that the effect mechanism is not a function of software instruction.