EMI Response of Microcontroller I/O Ports under Different Input Modes

To investigate the response pattern of embedded microcontrollers to conducted electromagnetic interference (EMI), EMI response experiments were performed using the direct power injection (DPI) method. By injecting singlefrequency continuous signals, the microcontroller's ability to identify and respond to signals above the power frequency was tested. The results indicate that in pull-up input mode, for singlefrequency signals greater than 100 MHz, the probability of the microcontroller recognizing a low logic level can significantly exceed 50%, even reaching 100%. The responses are asymmetric between pull-up and pull-down input modes. Significant waveform distortion is observed in the pull-up input mode, whereas no such distortion is found in the pull-down input mode. These findings are significant for analyzing the EMI response of circuit systems centered around embedded microcontrollers.