Last two or three weeks I spent on designing registers module. I decided to make all the registers 8 bit width. I decided to extend 4-bit upper halves of the address registers to increase number of full 8-bit registers that could be used as ALU inputs/outputs.

All registers will be able to be connected to the both data buses. M and LR registers will also include relays for connecting them to the address bus.

Now I almost made the board, cut the cabinet, and got the relays for the registers module.