CS355 Sylabus

Switching registers to ALU

The multiplexor that you have just seen can be used to connect the registers to the ALU.
Back in CS255, you should have learned about the internal organization of the ALU, not in a lot of details, but enough to know that there are general purpose registers that hold operands and results from operations, and an "Arithmetic and Logic Unit" (ALU) that does the *, /, +, - and other computations.
My CS255 webpage on the CPU architecture can be found here: click here
In CS355, you will learn exactly how the CPU works. The following is a taste of what's coming....
The following circuit diagram shows how the registers are connected to the ALU (I will explain or have explained in class exactly how and why these connection are made):
You can see how it works with the following logic-sim circuit program: click here
This circuit shows how you use 2 set of the Mux-circuits to bring 2 registers and I have added circuit to add the values together: