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I have a 2:1 MUX. It would be designed by using NOR gates. Inputs are X and Y. S, which is data select. When S is 0 F=X , S is 1 F=Y. Until here, okey. I've found $$ F = S'X + SY $$ to make NOR, I've rewritten as $$ F = [(S + X') (S' + Y')]' $$ At this point , I'm stuck how I can make(draw) the expression by using just NOR gates. Actually, It can be drawn via softwares.But, I wonder that how I should think to draw. I need its logic.

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  • A=input 1, B=input 2, S=switch
  • from A create A' (nor port with 2 times A as input)
  • from B create B' (nor port with 2 times B as input)
  • from S create S' (nor port with 2 times S as input)
  • create X=(S+A')' (nor port with A' as input and S as input)
  • create Y=(S'+B')' (nor port with B' as input and S' as input)
  • create Z=(X+Y)'=((S+A')'+(S'+B')')'
  • create W=Z' (nor port with 2 times Z as input)
  • then W=(((S+A')'+(S'+B')')')'=((S'.A)+(S.B))''=S'.A+S.B
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  • \$\begingroup\$ is it right ? i.imgur.com/uoBXXtU.png \$\endgroup\$
    – NewCoder
    Commented Apr 12, 2015 at 22:18
  • \$\begingroup\$ NewCoder's answer needs only 4 NOR gates. Nice. \$\endgroup\$ Commented Apr 13, 2015 at 2:16

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