I have a subject called computer architecture in university but I don't get a clue of it. We get assignments like: make a 2-bit two’s complement carry lookahead adder using 3 4-bit adder.

This is a circuit I have to make in Logisim, however, it's like you need an already deep insight in the subject to be able to make this; insights I don't have (because it's totally new for me).

Is there a kind of method to solve and make these circuits? Using truth tables or anything?

Note: I'm not asking for the solution for this specific problem, only for a method or steps-to-take in general, to be able to make any (basic) circuit.

This is the full exercise: http://msdl.cs.mcgil...A_Project_2.pdf (Ex5 if you want more explanation of the problem).

I was able to solve the other 4 by trying very hard and using Google but without actually knowing what I was doing.

So again, I'm not asking for this specific solution, only if there is a general way to solve these kind of assignments using a specific method or steps, eventually explained by using this one example-exercise.

# General method to solve circuits?

Page 1 of 1## 3 Replies - 483 Views - Last Post: 27 October 2017 - 06:57 PM

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**Replies To:** General method to solve circuits?

### #2

## Re: General method to solve circuits?

Posted 27 October 2017 - 01:35 AM

I'm confused, are you attending classes/lectures in the subject?

### #3

## Re: General method to solve circuits?

Posted 27 October 2017 - 06:34 AM

Quote

only for a method or steps-to-take in general, to be able to make any (basic) circuit.

No such algorithm exists. Combinatorial circuits are (polynomial-time) equivalent to algorithms (Turing Machines), and there is no algorithm to design an algorithm.

### #4

## Re: General method to solve circuits?

Posted 27 October 2017 - 06:57 PM

Essentially the project is acting you to build a 4-bit addr block. You create the 4 bit adder by utilizing 4 of the 1 bit adder blocks, that you have already created, then create than into it's own 4-bit adder block.

After you finish that, then you need to create a 12 bit adder which utilizes 3 of the 4-bit adder blocks which you created prior.

After you finish that, then you need to create a 12 bit adder which utilizes 3 of the 4-bit adder blocks which you created prior.

This post has been edited by **jjl**: 27 October 2017 - 06:58 PM

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