DM74LS251 Datasheet | National Semiconductor

Description These data selectors multiplexers contain full on-chip binary decoding to select one-of-eight data sources and feature a strobe-controlled TRI-STATE output The strobe must be at a low logic level to enable these devices The TRI-STATE outputs permit direct connection to a mon 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 totempole outputs To minimize the possibility that two outputs will attempt to take a mon 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 Y Y Y Y Y Y TRI-STATE version of LS151 Interface directly with system bus Perform parallel-to-serial conversion Permit multiplexing from N-lines to one line plementary outputs provide true and inverted data Maximum number of mon outputs 54LS 49 74LS 129 Typical propagation delay time (D to Y) 54LS 17 ns 74LS 17 ns Typical power dissipation 54LS 35 m W 74LS 35 m W Connection Diagram Dual-In-Line Package Function Table Inputs Select C X L L L L H H H H B X L L H H L L H H A X L H L H L H L H Strobe S H L L L L L L L L Outputs Y Z D0 D1 D2 D3 D4 D5 D6 D7 W Z D0 D1 D2 D3 D4 D5 D6 D7 H e High Logic Level L e Low Logic Level X e Don’t Care Z e High Impedance (Off) D0 D1 D7 e The level of the respective D input TL F 6415 - 1 Order Number DM54LS251J DM54LS251W DM74LS251M or DM74LS251N See NS Package Number J16A M16A N16E or W16A TRI-STATE is a registered trademark of National Semiconductor Corporation C1995 National Semiconductor Corporation TL F 6415 RRD-B30M105 Printed in U S A Absolute Maximum Ratings (Note) If Military Aerospace specified devices are required please contact the National Semiconductor Sales Office Distributors for...