General description
The 74HC257; 74HCT257 are high-speed Si-gate CMOS devices and are pin compatible with Low-power Schottky TTL (LSTTL).
The 74HC257 and 74HCT257 have four identical 2-input multiplexers with 3-state outputs, which select 4 bits of data from two sources and are controlled by a common data select input (S).
The data inputs from source 0 (1I0 to 4I0) are selected when input S is LOW and the data inputs from source 1 (1I1 to 4I1) are selected when S is HIGH. Data appears at the outputs (1Y to 4Y) in true (non-inverting) form from the selected inputs.
The 74HC257 and 74HCT257 are the logic implementation of a 4-pole, 2-position switch, where the position of the switch is determined by the logic levels applied to S. The outputs are forced to a high-impedance OFF-state when OE is HIGH.

Features
■ Non-inverting data path
■ 3-state outputs interface directly with system bus
■ Complies with JEDEC standard no. 7A
■ ESD protection:
   ♦ HBM JESD22-A114E exceeds 2000 V
   ♦ MM JESD22-A115-A exceeds 200 V
■ Multiple package options
■ Specified from −40 °C to +85 °C and from −40 °C to +125 °C