V_DD = 1.2
V_TN = 0.29
V_TP = -0.27
V_sw = 0.61

delta_V = V_DD + V_TP - V_TN

V_OH_min = V_DD - delta_V/8
V_IL_max = V_sw - delta_V/8
V_OL_max = delta_V/8
V_IH_min = V_sw + delta_V/8