"MTX Plus⁺" CPU Board V 1.1 (Draft)

Superseded by Version 2.0

(Version 1 didn't even make it to prototype build stage)

The "draft" design for the CPU board is shown below, I think that all components and connections are there now but I need to clean up some floating logic inputs and add decoupling capacitors for the ICs. So far, the footprint indicates that I can fit everything that I plan onto a Eurocard board - although whether I can built it on a Eurocard form factor prototype board is another question . . .

My original plan was to build a prototype to check the functionality of the boards before getting them professionally made. However, the board is looking like it will require more effort than I had anticipated and I can get boards professionally made by iteadstudio for a very reasonable price. The minimum quantity is 5, but at $38 for the 5, it may not be worth the effort of trying to make a prototype first. I am probably just going to spend a lot of time checking the electronic and physical design before sending it off for manufacture.

"To-do" List

• Optimise the logic gates

• Add De-coupling capacitors

Potential Design Changes Identified

• Add a an additional ROM board to allow the flexibility to have 7 (1 to 7) additional ROMs installed - in progress

Provisional schematic for the CPU board, drawn in Eeschema, the KiCad schematic editor. The board holds the major components associated with the CPU, the CPU itself, CTC, ROM, Static RAM, clock generation, buffers for the address and data buses, DIN 41612 connector for the backplane bus and a "local" I/O connector for initial testing. It does require a good dose of checking before finalising though.
The components laid out on a Eurocard sized PCB using  Pcbnew, the KiCad printed circuit board editor and the signals routed using the web based FreeROUTE Java application that interfaces to KiCad.
Pcbnew 3D visualisation of the placed and routed components