Topic: Digital Electronics
The logic function implemented by following 4:1 MUX is
(The diagram shows a MUX with inputs $I_0=X$, $I_1=Y$, $I_2=X$, $I_3=0$ and select lines $S_1=X$ (MSB), $S_0=Y$ (LSB). The output is Z.)
- A. Z=X and Y
- B. Z=X or Y
- C. Z=X XOR Y
- D. Z=X XNOR Y
Answer: C. Z=X XOR Y
Explanation: The logical expression for Z is given by evaluating the MUX logic:
$Z = \overline{X}\overline{Y}I_0 + \overline{X}Y I_1 + X\overline{Y}I_2 + XY I_3$
$Z = \overline{X}\overline{Y}(X) + \overline{X}Y(Y) + X\overline{Y}(X) + XY(0)$
$Z = 0 + \overline{X}Y + X\overline{Y} + 0 = X \oplus Y = X \text{ XOR } Y$.