# Drawing graphs of logic gates

1. Mar 17, 2012

### Femme_physics

1. The problem statement, all variables and given/known data

Graphs A and B are entries to a NOR gate with 2 inputs. Draw the output C.

Graphs X and are entries to a XOR gate. Draw the output Z.

2. Relevant equations

3. The attempt at a solution

2. Mar 17, 2012

### Max.Planck

Looks good.

3. Mar 17, 2012

### I like Serena

I'm afraid you've slipped at $\overline{x} \cdot y$.

Tip: XOR means "either the one, or the other (but not both)".

4. Mar 21, 2012

### Femme_physics

I'm confused...if XOR mean either this or that, how can u draw it on a single graph?

EDIT: nevermind, I think I figured it out

Last edited: Mar 21, 2012
5. Mar 21, 2012

### Femme_physics

Last edited by a moderator: May 5, 2017
6. Mar 21, 2012

### Staff: Mentor

You are making heavy work of this, Femme_physics. Would you like to start again?

All you need are 3 graphs: x and y, and a blank one for your answer. https://www.physicsforums.com/images/icons/icon3.gif [Broken]

Now graph the answer following this EXCLUSIVE-OR rule: where x differs from y, draw
logic level 1. (And if x equals y, draw level 0.)

That's all there is to it. Too easy!

I'm not sure why your output trails off to the right at logic 1, where x and y are both at 0 https://www.physicsforums.com/images/icons/icon5.gif [Broken]

Last edited by a moderator: May 5, 2017
7. Mar 22, 2012

### Femme_physics

Oops, you're right, but I think this is my only mistake right?

As far as "heavy work" -- well, I think it has an added value, being more thorough allows you to see the whole picture and revise the issue better.

8. Mar 22, 2012

### Staff: Mentor

You have made another careless mistake, which will reveal itself.
Exactly right, there is much to be gained by doing it the rigorous way, if only to confirm that the formula jives with the common sense approach. Unfortunately, the more steps you go through, the greater the opportunity to make mistakes. If this were an exam question, I'm sure the time allocation would be for the simple route. It is good to know how to do the task both ways.

If you solve a problem two ways, agreement of answers usually confirms you as being correct. Disagreement can often highlight the error.

9. Mar 22, 2012

### Femme_physics

Oh yes, I forgot to include that little block in the middle. Thank you

Completely agree

10. Mar 22, 2012

### Staff: Mentor

Congratulations on your 2000th post to physicsforums, Femme_physics!

11. Mar 22, 2012

### Femme_physics

Last edited by a moderator: May 5, 2017
12. Mar 22, 2012

### Staff: Mentor

Finally looks right.

13. Mar 23, 2012

### Femme_physics

Thanks :)

14. Apr 11, 2012

### Femme_physics

Last edited by a moderator: May 5, 2017
15. Apr 11, 2012

### Staff: Mentor

Good idea. Don't forget exclusive-OR, too.
yes​

Last edited by a moderator: Apr 19, 2017
16. Apr 13, 2012

### Femme_physics

Thanks NascentOx :)