The illusive ALU. next stop optimization

Activity 21:

Going to try to get the ALU working now with my custom chips and see if it works the way I want it to.

I think figuring out how to add overflow detection is very important when creating the ALU. Because when I go to create it in real hardware I will need to know when I get an overflow. I did create overflow detection in my adder but for the time being I am using the one the book made. Then if need be I will switch to mine.

This ALU does not do multiplication or division also it cannot do floating point math.

After reading the chapter I am not sure I understand what needs to happen. I first thought I would use a bunch of Mux’s but it doesn’t seem like it’s going to work out.

After working it out I figured most of it out but I still have to figure out how to check if the output is zero or negative.

My issue was the syntax of splitting up the pins. I think the book should cover this more clearly.

You can split the output pin as many times as you want when outputting but can not split the out put and use it for input if that makes since.

Here’s an example

    Mux16(a=AddAnd,b=NEgOut,sel=no,out[0..7]=out3,out[8..15]=out4,out[15]=out5,out=out);

Or8Way(in=out3,out=out1);

Or8Way(in=out4,out=out2);

But you cant

Or8Way(in=out[8..15],out=out);

This blog led me in the right direction.

http://justaguyinphilly.wordpress.com/2011/09/07/chapter-2-activity-5-build-an-alu/#comment-122

With only one Mux input switched around I got it working and now to see on optimization.

This is the one that took the longest by far.