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Reviews the approaches to improve the noise immunity at the semiconductor level and system level through the analysis of the effect of EFT (electrical fast transient) pulse input into the system on the semiconductor and the coupling path. A thermometer evaluation board applying a microcontroller device KS57P2308 was used and the failure phenomenon happening at the time of the EFT pulse application was the halt status of the system due to the malfunctioning of the micom device. Two approaches were presented to prevent such a malfunction by improving the immunity against the EFT noise. It was confirmed that the first way was to divert the noise input into the semiconductor toward the reset pin and then the second way was to properly control the conditions for activation of reset by adjusting the minimum input low width of a noise filter inside the reset pin, thereby preventing the halt status of the system due to the malfunction of the semiconductor device. An accurate analysis of the amplitude of the input noise level and duration is required for the adjustment of minimum input low width of the noise filter and the new noise filler design is required accordingly. Also, it is required to review again the bulk capacitor applied to almost all boards inside the system. The existing reset circuit failed to properly function due to reduction of the noise input from the outside because of the bulk capacitor. However, this application is only possible in the case where the system is not greatly affected even if peripherals rather than main system are reset and if the system is seriously affected by such reset, this application is not appropriate.