Consider the following multiplexer where I0, I1, I2, I3 are four data input…
2002
Consider the following multiplexer where I0, I1, I2, I3 are four data input lines selected by the address-line combinations A1A0 = 00, 01, 10, 11 respectively, and f is the output of the multiplexer. EN is the enable input.
The function f(x, y, z) implemented by the above circuit is:
- A.
xyz'
- B.
xy + z
- C.
x + z
- D.
None of these
Attempted by 18 students.
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Correct answer: A
From the diagram: I0 = x and I1 = x. Also, I2 = y and I3 = y'. The select inputs are A1 = y' and A0 = z, while the enable input is EN = z'.
For an active-high enable, the mux can produce a non-zero output only when z = 0. Then A0 = 0.
If y = 0, then A1 = 1 and A1A0 = 10, so the selected input is I2 = y = 0. If y = 1, then A1 = 0 and A1A0 = 00, so the selected input is I0 = x.
Therefore the output is x only when y = 1 and z = 0. Hence f(x, y, z) = x y z'.