A data processing method may include counting one of a plurality of clock signals with a first mode, counting clock signals based on a predetermined number of the plurality of clock signals with the first mode, to output a first clock signal every time a counter value becomes a first predetermined value, counting the first clock signal with the first mode, counting one of the clock signals with a second mode while the counted value is considered as a first initial value, counting clock signals based on the predetermined number of the plurality of clock signals with the second mode, to output a second clock signal every time the counter value becomes a second predetermined value while the counted value is considered as a second initial value, counting the second clock signal with the second mode, and outputting the counter values with the second mode as difference data between a first data signal and a second data signal.