pcornier/ucom43

A Verilog implementation of the Nec uCom-43 4-bit microcontroller from 1978.

Nec uCom-43 MCU

A Verilog implementation of the Nec uCom-43 4-bit microcontroller from 1978.

I was able to synthesize it on a Spartan-6 board without too much trouble: the compiler complained about 8 unconnected signals but those are the output signals for the two A & B ports that are inputs only, and I didn't want to complicate things. The core was also tested with Verilator and connected to an emulated VFD to play Tomy Scramble (D553C192) and Epoch Galaxy II.

About the ALU, I'm still not sure how it is possible to increment a 4-bit register while the ALU is XORing the two lower bits of DPH. I think there is an independant XOR circuitry for DPH only.

Use make scramble to create the Tomy Scramble simulation or make galaxy to generate Epoch Galaxy II. Then ./obj_dir/Vmcu to play the game!