In the paper,a case of MCU failure under electromagnetic interference is introduced.Through demonstrating step-by-step debugging analysis and completing multiple comparative demonstration experiments,we can finally find a variety of solutions,and also deeply experience the gap between chips from different manufacturers.The impact of the Flash waiting period is discussed and discussed in a large space in the article.Because the manufacturers have not explained too much about the principle and function of this in their user manuals,many users have a half-understanding of it and apply it mechanically,and the understanding and use of this concept in various interference scenarios plays a very important role.