The input threshold voltage for switching between 'H' and 'L' is approx. VDD/2 with respect to the supply voltage VDD. VIL becomes 'L' when below 30% of VDD (VIL<VDD×0.3) and VIH becomes 'H' when above 70% of VDD (VIH>VDD×0.7). For example, with VDD=3.3V, VIH>2.31V、VIL<0.99V.