Designing an EMI Immune Software for a Microprocessor-Based Traffic Control System

Uncontrolled Electromagnetic Interference (EMI) like Electrostatic Discharge (ESD), Electrical Fast Transients (EFTs), Lightning Electromagnetic Pulse (LEMP) and Nuclear Electromagnetic Pulse (NEMP) has become a hazard to the electronic industry. The types malfunctions noticed in microprocessor-based system like a Traffic Control System, caused by EMI potential, are memory corruption, system hanging and damage of !Cs. As devices become smaller and faster, their susceptibility to EMI/Noises will increase. The interface connector body, bottom plate, enclosure area, keyboard etc., show their repetitive vulnerability for short duration pulses/EMI. Un grounded metal parts are found to be vulnerable points for ES-0. There are many well-known hardware-based solutions for controlling EMI potential. All the conventional methods of fixing hardware, involve proper grounding of all the exposed metal, careful design of keyboard & control panels, multipoint grounding, secondary shielding between sensitive circuits and the chasis, cable bypassing, separating 1/0 ground, minimising loop areas on printed wiring boards etc. However, a properly designed software/firmware plays an important role in reduction of the EMI/ESD potential of microprocessor-based systems without increasing weight, size and cost. Software/firmware fixes are more cost effective than hardware. This paper describes how to design an EMI immune software for any kind of microprocessor-based system like a Microprocessor-based Traffic Control System.