Patent ID: 8468187

Claim:
A digital filter device for filtering a binary input digital signal and outputting a binary output digital signal, comprising: a toggle flip-flop which switches a signal level of the output digital signal each time a predetermined trigger signal is input; a level judgment portion configured to output a predetermined first enable signal in either of a period during which a signal level of the input digital signal and the signal level of the output digital signal match and a period during which they do not match; a first counter configured to count predetermined clock signals while the first enable signal is being input so as to calculate a first count, suspend counting and hold a value counted hitherto when the input of the first enable signal is stopped, restart counting from the value held when the input of the first enable signal is restated, and reset the first count to a predetermined first initial value and output the trigger signal to the toggle flip-flop when the first count has reached a predetermined first reference value.