Description

74LS251 – 3-STATE 1-of-8 Line Data Selector/Multiplexer

General Description
These data selectors/multiplexers contain full on-chip binary decoding to select one-of-eight data sources, and feature a strobe-controlled 3-STATE output. The strobe must be at a low logic level to enable these devices. The 3-STATE outputs permit direct connection to a common bus. When the strobe input is HIGH, both outputs are in a high impedance state in which both the upper and lower transistors of each totem-pole output are OFF, and the output neither drives nor loads the bus significantly. When the strobe is LOW, the outputs are activated and operate as standard TTL totem-pole outputs.
To minimize the possibility that two outputs will attempt to take a common bus to opposite logic levels, the output control circuitry is designed so that the average output disable time is shorter than the average output enable time

Features
■ 3-STATE version of DM74LS151
■ Interface directly with system bus
■ Perform parallel-to-serial conversion
■ Permit multiplexing from N-lines to one line
■ Complementary outputs provide true and inverted data
■ Maximum number of common outputs: 129
■ Typical propagation delay time (D to Y): 17 ns
■ Typical power dissipation: 35 mW