# Homework Help: Sklansky adder algorithm

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1. Dec 12, 2015

### Narkon

Hello. I am unsure if this subforum is the right place for this question, but without any alternatives, I will dare to post it here.

A few days ago I received an assignment which is about the creation in VHDL of a Sklansky adder. However, before I move to the coding part, I have trouble understanding the exact mechanics of the algorithm. Below you can see a pi is a picture I have found which shows the tree of a 16-bit Sklansky adder. I have already found the circuits that are represented by the black and grey boxes and I know that the triangles are just buffers.

Assuming we add the 16-bit A and B, I know that I have to find the generate and propagate values for each pair of bits A(i) and B(i) which are produced from the following equations
and
I also know that at some point I will have to calculate carry values with the equation:

but I can't find a detailed explanation about how all that ties together. I don't know which are the steps that take place after I get to the final "level" in the picture, which is depicted by the bottom most box (the one with the numbering 0:0, ... 15:0), and the professor who assign this has been less than helpful so far with cryptic explanations and confusing clarifications. I have no idea what happens after I am through with the black/grey components and the buffers. If someone can help me understand the basics and the flow of the algorithm, I will be grateful, even if it's only a link that offers the explanation I seek. Thank you

http://i1140.photobucket.com/albums/n575/artdevil27/2015-12-12_183428_zpsvkvhsjvq.png?t=1449862983 [Broken]

Last edited by a moderator: May 7, 2017
2. Dec 17, 2015