Injection of transient faults as a way to attack cryptographic implementations has been largely studied in the last decade. Several attacks that use electromagnetic fault injection against hardware or software architectures have already been presented. On microcontrollers, electromagnetic fault injection has mostly been seen as a way to skip assembly instructions or subroutine calls. However, to the best of our knowledge, no precise study about the impact of an electromagnetic glitch fault injection on a microcontroller has been proposed yet. The aim of this paper is twofold: providing a more in-depth study of the effects of electromagnetic glitch fault injection on a state-of-the-art microcontroller and building an associated register-transfer level fault model.