This is a very long term project to try to build a computer out of transistors.
The method chosen will be to have each individual module do as much of the work as possible to keep the control module as simple as possible.
For instance, the most efficient ALU would have inputs for individual selects, carry gating and control ect, and have the control module supply these signals, however I have chosen to provide a simple Operation select (3 bits), Carry in, Carry out and Zero out, with the details of the gating and selection of these signals performed by an extra board on the ALU dedicated to this purpose.
Doing it this way outsources the complexity to the ALU rather than to the Control unit and any microprogramming that may be required. However, it does mean its a lot easier to test as a unit.
|Arithmatic and Logic Unit (ALU)||Nearly done. All modules complete. Needs backplane finishing.|
|ALU A latch|
|Program counter High byte|
|Program counter Low byte|
|Address latch High byte|
|Address latch Low byte|