The IIR resonator digital filter which is the subject of this patent invention comprises a first register having a plurality of inputs and outputs, a multiplexer/demultiplexer having a plurality of inputs and outputs, a first multiplier having a plurality of inputs and an output, a second multiplier having a plurality of inputs and an output, a third multiplier having a plurality of inputs and an output, an adder having a plurality of inputs and an output, a subtractor having a plurality of inputs and an output, and a second register having an input and a plurality of outputs. The IIR resonator digital filter features a multiplexer/demultiplexer that has five logical states.