The KK74AC258 is identical in pinout to the LS/ALS258, HC/HCT258. The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LS/ALS outputs. This device selects a (4-bit) nibble from either the A or B inputs as determined by the Select input. The nibble is presented at the outputs in inverted from when the Output Enable pin is at a low level. A high level on the Output Enable pin switches the outputs into the high-impedance state.