A multiplexer can implement a truth table by using variables as select inputs and wiring its data inputs to constants or remaining variables. For each select pattern, ask what the function becomes. This turns an abstract Boolean rule into a practical selection problem.
Worked example
Implement F = A XOR B using a 2-to-1 multiplexer with A as select. When A = 0, F = B, so connect D0 to B. When A = 1, F = NOT B, so connect D1 to an inverted B. The selected input reproduces all four XOR rows.
What to watch for
Use the actual select convention of the chosen multiplexer. Swapping D0 and D1 changes the implemented function.
Try it yourself
Implement F = A AND B with A as a 2-to-1 select. What are D0 and D1?
Answer: D0 = 0 because A = 0 forces F low. D1 = B because A = 1 makes F equal B.
How to study this topic
Name each input and define its active level before drawing gates. Follow one data path at a time, then check the other combinations. A complete specification is the best starting point for a reliable circuit.
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Digital Electronics