The MC74F353N has two identical 4-input multiplexers with 3-State outputs which select two bits from four sources selected by common Select inputs (S0, S1). When the individual Output Enable (OEa, OEb) inputs of the 4-input multiplexers are High, the outputs are forced to a high impedance (Hi-Z) state. The MC74F353N is the logic implementation of a 2-pole, 4-position switch; the position of the switch being determined by the logic levels supplied to the two common Select inputs. To avoid exceeding the maximum current ratings when the outputs of the 3-State devices are tied together, all but one device must be in the high-impedance state. Therefore, only one Output Enable must be active at a time.
Inverting version of 74F253
3-State outputs for bus interface and multiplex expansion
Common select inputs
Separate Output Enable Inputs
16 pin DIP. Manufactured by Motorola.