ITPEC FE Subject A October 2024 Question 16
Source exam: ITPEC FE Subject A October 2024Topic: Computer Systems & Hardware
ITPEC FE Subject A October 2024 — Question 16 of 60
MUX-based XOR gate — a 2-to-1 MUX can implement XOR.
Given a 2-to-1 MUX with inputs I₀ = X₂, I₁ = NOT(X₂), and select S = X₁:
- •When
S = 0→ outputZ = I₀ = X₂ - •When
S = 1→ outputZ = I₁ = NOT(X₂)
Truth table:
| X₁ | X₂ | S | Selected | Y |
|---|---|---|---|---|
| 0 | 0 | 0 | I₀ = 0 | 0 |
| 0 | 1 | 0 | I₀ = 1 | 1 |
| 1 | 0 | 1 | I₁ = 1 | 1 |
| 1 | 1 | 1 | I₁ = 0 | 0 |
Result 0, 1, 1, 0 matches XOR.
Why not others:
- (a) AND — output 0, 0, 0, 1
- (b) NAND — output 1, 1, 1, 0
- (c) OR — output 0, 1, 1, 1
Key rule: A MUX acts as a programmable gate. Feeding X and NOT(X) as data inputs with a second variable as select produces XOR.
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