DigicoolThings Forum

I've been working through the design of a 6502 based MECB CPU Card.

I intend to support both old recovered MOS 6502 chips, as well as the modern currently in-production WDC W65C02S chips.

This requires a couple of jumpers, due to pin-out changes on the newer 65C02. But it is definately worth supporting both on a single 6502 CPU Card design (for flexibility).

I recently made a post and video on building and using a 6502 NOP tester, where I tested some newly received MOS 6502 chips, and a newly purchased WDC W65C02S chip, all in preparation for testing the first CPU Card PCB (when I finally have some prototype PCBs!).

You'll find the 6502 NOP Tester topic here: Building a 6502 (and W65C02) NOP Tester

The Schematic and PCB layout was completed, and v1.0 gerbers sent off for prototype PCB manufacture in Nov 2023.

Finally, the first v1.0 PCB was assembled and tested. You can follow along here: Minimalist Europe Card Bus (MECB) - MOS 6502 or WDC W65C02 CPU Card

Subsequent Version Updates:

• v1.1 - Minor correction to a ROM Write Enable Jumper oversight. The ROM /WE pin (on v1.0), was permanently pulled high.
• v1.2 - Minor change to the PLD (U1) and ROM (U4) footprints, to accomodate ZIF socket pins (1mm instead of 0.8mm pad holes) - Thank you goes to Michael for pointing this out.
• v1.3 - Adds support for NMI via onboard debounced push-button and NMI push-button header, replicating the existing Reset push-button and header.

Looking forward to it.

So, ahead of myself to be sure, but if memory serves me, when you get to your Z80 board, will that be a dual socket setup to suit both the original DIP and the newer PLCC I've seen around? That's not so easily solved with a jumper there... right?

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 1:53 amSo, ahead of myself to be sure, but if memory serves me, when you get to your Z80 board, will that be a dual socket setup to suit both the original DIP and the newer PLCC I've seen around? That's not so easily solved with a jumper there... right?

Heh, this is the 6502 topic!

But, to answer you Z80 question, I haven't really put much thought into the Z80 Card yet. It's just at the initial planning ("I know I'd like one soon") stage at the moment, while I try and focus on progressing the 6502 (and ROM Expansion) Cards, at the moment.

One thing though, I have a desire to keep to the MECB Retro theme via TH components only, for easy assembly by anyone. So, as long as the PLCC version of the Z80 supports a PLCC TH socket, it's possible (I haven't recently looked up Z80 package types).

Of course, if someone else wants to implement a MECB Z80 CPU Card design first, then that might also satisfy my Z80 desires?

So, is there anything I ought to be looking for if I were to start sourcing 6502 CPUs?

bugeyedcreepy wrote: ↑Thu Nov 23, 2023 7:12 am So, is there anything I ought to be looking for if I were to start sourcing 6502 CPUs?

Well, the five MOS 6502 chips shown on my recent 6502 NOP Tester video, I got from AliExpress. Only 3 or the 5 appeared to work though.

The current WDC W65C02S chip (that I also showed being successfully NOP tested), I bought new from Mouser.

It really depends what you want to experiment with. i.e. Original old school MOS 6502s, or currently in production 65C02s.

Topic has been updated with the release (finally) of my first 6502 CPU Card assemby and testing Blog post & YouTube video: Minimalist Europe Card Bus (MECB) - MOS 6502 or WDC W65C02 CPU Card

Editor wrote: ↑Fri Jun 07, 2024 7:01 pm Topic has been updated with the release (finally) of my first 6502 CPU Card assemby and testing Blog post & YouTube video: Minimalist Europe Card Bus (MECB) - MOS 6502 or WDC W65C02 CPU Card

Awesome!! Any info on a tindie listing coming up?

EDIT: Never mind, Found it!

bugeyedcreepy wrote: ↑Fri Jun 07, 2024 11:35 pm Awesome!! Any info on a tindie listing coming up? EDIT: Never mind, Found it!

Thanks greatly for your support! Certainly helps with further prompting me to get on with my many projects, that I seem to have in progress.

Editor wrote: ↑Sat Jun 08, 2024 2:45 am

bugeyedcreepy wrote: ↑Fri Jun 07, 2024 11:35 pm Awesome!! Any info on a tindie listing coming up? EDIT: Never mind, Found it!

Thanks greatly for your support! Certainly helps with further prompting me to get on with my many projects, that I seem to have in progress.

My own goal to create a case & keyboard and end-user cartridge setup is coming along the best of all my projects - so far it should be capable of mounting all the standard cards you have in various configurations, and then of course I have my own backplane specifically to cater for the MECB standard, but enclosed internally, and I'm even redesigning to include the extended backplane that lenzjo designed - surprisingly it fits in just fine, even with a connected side card!

bugeyedcreepy wrote: ↑Sun Jun 09, 2024 11:27 am My own goal to create a case & keyboard and end-user cartridge setup is coming along the best of all my projects...

Can't wait to see the finished project! But take your time. These things are always an evolution. Well, at least for me. I think it's my perfectionist tendancies, which mean I seem to always modify and go back on my design path a few times, before I end up where I'm happy with the fiinal direction. Of course, it also means I end up with surplus parts in my parts inventory, due to the design tweaking journey!