Method of and device for determining pulse width

Abstract

A pulse width determining device includes a down counter for counting down from a first initial count value reloaded thereinto. If the down counter underflows, it can start counting down from a second initial count value reloaded thereinto as needed. Every time the device receives an input pulse, a count clock control circuit can set a period of time during which it can generate and furnish count clock pulses to the down counter, according to the pulse width of the input pulse. The device can determine whether or not the pulse width of the input pulse is in a predetermined range of pulse widths according to a relation between timing with which the down counter underflows and the time period during which the count clock pulses are generated. To be more specific, after the down counter, which started at the first initial count value, has underflowed, the device determines that the pulse width of the pulse lies in the predetermined range if the time period set by the count clock control circuit is finished before the down counter, which started counting down from the second initial count value, underflows.