Multiplexers, expressions

Thread Starter

power13

Joined Oct 23, 2018
8
Hello everyone,

I am trying to design a circuit.

F(a,b,c) = ab +c (if a=0,2,5,7,8)
F(a,b,c) = b +c (if a≠0,2,5,7,8)
a,c are 4bit binary numbers, b: 2bit number

I have to use multiplexers 2by1, full adders and logic gates.

I am trying to find a solution for the first part.
f1 = ab (if a...)..
f1: 6 bits
Karnaugh map for 6 bits I think is overkill. Is there any way to check the "a" with multiplexers?

Thank you.
 

Thread Starter

power13

Joined Oct 23, 2018
8
It's arithmetic expression. It produces a number from multiplication and adder (using full adders, multiplexers 2by1 and logic gates).
 

WBahn

Joined Mar 31, 2012
25,918
So forget, for the moment, about the conditional component, how would you implement

f = a·b + c

using full adders and knowing that 'b' is a 2-bit value?
 

Thread Starter

power13

Joined Oct 23, 2018
8
I think that I need 4 full adders for a·b and 6 full adders for the "+".

I don't know how to handle the conditional component.
 

WBahn

Joined Mar 31, 2012
25,918
I think that I need 4 full adders for a·b and 6 full adders for the "+".

I don't know how to handle the conditional component.
Draw out your circuit for the a·b+c circuit. You need a starting point, so start with that.

Can you make a logic function that is a 1 when the condition is met and a 0 otherwise?
 

WBahn

Joined Mar 31, 2012
25,918
a·b+c, a cursory circuit: https://i.postimg.cc/hjDQgW4f/2akalo.jpg

For the condition, I can use Karnaugh map to have a logic function. But I'm trying to find a way to use multiplexers 2by1 for this.
Why do you want to use multiplexers for this part of the logic?

However you implement it, once you have a logic signal for the conditional part, how could you use a multiplexer to choose between the value of 'a' and '0001'? Would a mux really be the best choice here? Is there a simpler way?
 
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