Not sure how to implement this using logism.

 

Ah, yes. It's crystal clear what you are talking about since everyone knows exactly what the ALU of the 2-bus CPU from Homework #3 is, including what function it is supposed to perform for each of the eight possible control input combinations.

Sheesh!

 

Ah, yes. It's crystal clear what you are talking about since everyone knows exactly what the ALU of the 2-bus CPU from Homework #3 is, including what function it is supposed to perform for each of the eight possible control input combinations.

Sheesh!

I've attached another file, does this help?

 

I've attached another file, does this help?

That certainly provided some rather critical information. Thanks.

The next thing that is needed is YOUR best attempt to work YOUR homework problem. It doesn't have to be complete or even correct. But we need a starting point to help guide you from where you are to where you need to get to. Note that we will NOT just work your homework for you are tell you exactly what you need to do -- doing so robs you of nearly all learning potential from the assignment (as well as being academically dishonest).

First go for the low hanging fruit. What if your ALU just included the first two functions on the list. Could you make an ALU that did just that much? Show your best attempt.

 

That certainly provided some rather critical information. Thanks.

The next thing that is needed is YOUR best attempt to work YOUR homework problem. It doesn't have to be complete or even correct. But we need a starting point to help guide you from where you are to where you need to get to. Note that we will NOT just work your homework for you are tell you exactly what you need to do -- doing so robs you of nearly all learning potential from the assignment (as well as being academically dishonest).

First go for the low hanging fruit. What if your ALU just included the first two functions on the list. Could you make an ALU that did just that much? Show your best attempt.

I understand, this is what I have so far

 

I understand, this is what I have so far

I think we are making progress.

Your schematic has a bunch of unlabeled symbols that have unlabeled and unconnected ports. While YOU know what these parts are supposed to do and which ports mean what, since you chose them from some library of components, WE don't know that information. You are forcing us to guess and, in some instance, those guesses are going to be just that -- a flip-a-coin-because-it-could-be-either-way guess.

How do these parts behave if an input is left unconnected? It actually shouldn't matter because you should never leave inputs unconnected -- it is a very bad habit to get into just because a particular simulator behaves in a way that is to your liking; real world parts to NOT generally behave in a well-defined manner under these conditions.

You should describe each one of the parts you use, including all the inputs and all the outputs. This wouldn't take long at all. For instance:



4-bit adder. A,B,Y are 4-bit signals; Cin and Cout are 1-bit signals.
Y = lower four bits of (A + B + Cin)
Cout = fifth bit of (A + B + Cin)

It is particularly relevant that you define whether the subtractor is A-B or B-A. If you force us to guess based upon how you are using it, then if you are using it wrong we can't detect that because our guess is based on the assumption that you are using it correctly.