To keep continuity of a count value when switching a count mode in an asynchronous counter circuit which is capable of switching the count mode.
3-input and 1-output type three values switching parts 420 (422, 424, 426) for switching three values of a non-inverted output Q, an inverted output NQ and a power source (Vdd) level of each flip-flop 410 are provided between the flip-flops 410. Each of the three values switching parts 420 switches three input signals according to control signals SW1, SW2 of 2 bits and inputs one selected signal to a clock terminal CK of a flip-flop 410 on a post-stage. When switching a count mode, a count value just before mode switching is initially set and count processing after mode switching is then started by the control signals SW1, SW2.
FUKUSHIMA NORIYUKI
NITTA YOSHIKAZU
YASUI YUKIHIRO
