Full Adder

Thread Starter

aj88

Joined Sep 17, 2012
27
So here is the diagram I made. If you want to edit it, download edit.txt, copy the words, go on www.falstad.com/circuit click on the file tab, hit import, and paste! Edit it and copy it to me if you see any problems! Thanks!
 

Attachments

Austin Clark

Joined Dec 28, 2011
412
So here is the diagram I made. If you want to edit it, download edit.txt, copy the words, go on www.falstad.com/circuit click on the file tab, hit import, and paste! Edit it and copy it to me if you see any problems! Thanks!
Ok, this is as simple as I could get it with your on-hand gates. Surprisingly, little was sacrificed in terms of simplicity, I only had to use an extra inverter to get it to work :)
 

Attachments

Austin Clark

Joined Dec 28, 2011
412
The weird thing is, 1+1+1+1 (all switches on) equals 3 in the circuit and in my circuit. Why?
I just did a quick test, and it all seems to be in working order. I think you might be making a mistake in reading the binary inputs/outputs.

in binary,

11 (3)
+11 (3)
110 (6)

I think you're accidentally ignoring the 0 in the 1's place in the sum.
 

Thread Starter

aj88

Joined Sep 17, 2012
27
This is wrong... unless I am thinking wrong. Here is what I understood from you on this attachment, but it doesn't add up right.
 

Attachments

Last edited:

Austin Clark

Joined Dec 28, 2011
412
This is wrong... unless I am thinking wrong. Here is what I understood from you on this attachment, but it doesn't add up right.
You're not reading the labels correctly, look at the colors on that older post.

What you're actually doing there is:

11
+
10
=
101


A + B = S

The first half-adder takes care of the least significant bit on both numbers being added together, the second full-adder takes care of the next significant bits. That is, the first adder takes care of the first bits, the second adder takes care of the second bits, etc;
 

Thread Starter

aj88

Joined Sep 17, 2012
27
11
+
10
=
101


A + B = S

The first half-adder takes care of the least significant bit on both numbers being added together, the second full-adder takes care of the next significant bits. That is, the first adder takes care of the first bits, the second adder takes care of the second bits, etc;
So you can't add 11+01?
 
Top