I have managed to get the basic “cpu” operational after a bit of debugging and rewiring. I have also added some status leds for the A register (top of the picture) and a manual clock button so that I can program the instructions in peace and send a clock pulse to the registers when I am ready.
Now all I have to do is to decide what to do next, I have several things that needs to be done.
- Add bitwise negation for a,b inputs and output to ALU.
- Decide a bit length for the instructions and design the instruction set. I will go with either 8-bit or 16-bit instructions. It would be nice if all instructions could be done in one clock cycle as that would simplify the design.
- Hook up rom and ram. I will have to purchase some premade sram, probably in the size of 8-16kb. Addressing will probably use A and B registers, Addr = A | (B << 8). And maybe some kind of direct addressing encoded in the instructions.
- Instruction counter, either a dedicated circuit or program my Arduino to act as one.
- Create a data bus for reading/writing to registers/ram.
- Add status leds for the B register.










