The KK74AC158 is identical in pinout to the LS/ALS158, HC/HCT158. The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LS/ALS outputs. This device routes 2 nibbles (A or B) to a single port (Y) as determined by the Select input. The data is presented at the outputs in invertered form. A high level on the Output Enable input sets all four Y outputs to a high level.