The 74LVC257A is a quad 2-input multiplexer with 3-state outputs, which select 4 bits of data from two sources and are controlled by a common data select input (pin S). The data inputs from source 0 (pins 1I0 to 4I0) are selected when pin S is LOW and the data inputs from source 1 (pins 1I1 to 4I1) are selected when pin S is HIGH. Data appears at the outputs (pins 1Y to 4Y) in true (non-inverting) form from the selected inputs. The device is the logic implementation of a 4-pole, 2-position switch, where the position of the switch is determined by the logic levels applied to pin S. The outputs are forced to a high-impedance OFF-state when pin OE is HIGH.
Inputs can be driven from either 3.3 V or 5.0 V devices. When disabled, up to 5.5 V can be applied to the outputs. These features allow the use of these devices as translators in mixed 3.3 V and 5 V applications.