TECHNICAL DATA IN74AC251 8-Input Data Selector/Multiplexer with 3-State Outputs High-Speed Silicon-Gate CMOS The IN74AC251 is identical in pinout to the LS/ALS251, HC/HCT251.
The device inputs are compatible with standard CMOS outputs; with pullup resistors, they are compatible with LS/ALS outputs.
The device selects one of the eight binary Data Inputs, as determined by the Address Inputs.
The Output Enable pin must be at a low level for the selected data to appear at the outputs.
If Output En