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Interview Question

ASIC Design Engineer Interview(Student Candidate) Austin, TX

design a full adder with 2-1 mux


Interview Answer

7 Answers


Full Adder can be implemented by two half adder; a half adder can be implemented by a XOR and AND gate. XOR and AND gate can be implemented by 2:1 MUX.

freedeluge on Oct 5, 2010

full adder can be got by 2 half adders and one OR gate; one half adder can be got by XOR, AND. Therefore, we need only OR, AND, XOR. All these three gates can be got by using MUX.?

2 on Nov 9, 2010

Can be implemented using 8 Muxes.

Veronica on Feb 5, 2012

Just need 6 2-to-1 mux. First draw the truth table and try to implement using two 4-to-1 mux, AB as select and Cin/~Cin as input. It should be quite easy. Then break each 4-to-1 mux to three 2-to-1 mux.

jamesly on Nov 6, 2012

sum = a xor b xor cin
carry = (a xor b) cin + ab

You can easiy make XOR, OR AND, NOT using 2:1 mux. So 8 mux ?!?

pp on Jan 30, 2013

if Mux(I1,I2,S) is a 2x1 mux module, then
Sum = Mux( (Mux(C,C',B), Mux(C',C,B), A) which requires 3 2x1 mux.
Carry = Mux( (Mux(0,C,B), Mux(C,1,B), A) which requires 3 2x1 mux.

Ravi on Feb 11, 2018

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