Digital ICs in all microprocessor based systems get digital inputs from the external world such as from a keyboard, serial port, shaft encoders, A to D converters, programmable ports, switches, contacts etc. These inputs contain noise from a variety of sources such as RFI, EMI, contact noise, transmission line effects, ground and/or supply rail loading, capacitive coupling of hi frequency signals on adjacent tracks or layers, of a PCB etc. If this noise is not removed it may cause the system to malfunction. Application of a conventional RC or opamp based low pass filter on the pin, may not be effective as it may filter out the signal itself or reduce its slew rate.Debouncing logic which acts only on posi tive or negative edge (not both) or only synchronises the signal with a clock, may actually worsen the situation under certain circumstances.This VHDL core reliably removes noise from the input signal

PREREQUISITES

        Course-A1. Introduction to VHDL and VLSI design (I)

CONTENTS

        1. Identification of cutoff frequency.
        2. Designing the cutoff frequency waveforms
        3. Designing the positive and negative edge filteration logic