Digital Logic Made Easy

Question

Consider the following circuit:

• A. It outputs x+y
• B. It outputs y-x
• C. It outputs x+1
• D. It outputs y+1

Comments

y-x

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@Devwritt @Abhisek Tiwari 4 Please explain your solutions.

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A xor 1=A'

so Y==>one's complement of Y i.e -Y thus X-Y

Answer 1

See, given is 4 bit adder,

And, X⊕1= ~X   //  1⊕1=0  or 0⊕1=1

So, X3X2X1X0 ⊕ operation with 1 will give 1's complement of it.

And as we know , 2's complement = 1's complement +1   // here, Gn =1

So, Here, Y-X= Y+(2's complement of X)

Option B

 

Comments

What is the significance of Gn=1 here?