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This post follows on from my earlier Minimalist Europe Card Bus posts and videos. For MECB, to date, I’ve designed and built a Backplane, a Prototype card, and a TMS9929A Video card. The next logical step is to create my first CPU card.

My journey designing my ideal 6809 CPU card was a longer than expected journey. Finaly resolved at v2.2, with a flexible design that allows either Internally clocked or Externally clocked MC6809 or HD6309 CPUs.

The journey starts here: Minimalist Europe Card Bus (MECB ) – MC6809 (or HD6309) CPU Card

Next was a follow-up Part 2 - Testing, whihc can be found here: Minimalist Europe Card Bus (MECB) – MC6809 CPU Card (Part 2 – Testing)

Then I designed v2.x of the CPU card here: Minimalist Europe Card Bus (MECB) – 6809 / 6809E CPU Card v2.x

Finally, we arived at v2.2 here: Minimalist Europe Card Bus (MECB) – 6809 / 6809E CPU Card – v2.2 Update!

Version v2.3, attended to a minor oversight in the v2.2 design, and also added a reset header to allow easily connecting an external reset button. The v2.3 update is detailed here: Minimalist Europe Card Bus (MECB) - 6809 or 6309 CPU Card - v2.3 Update!

Related: In another post we pushed the speed of our 6809 CPU Card based system to twice the manufacturers speed rating!
You can find this post here: Minimalist Europe Card Bus (MECB) – Let’s push our 6809 speed!

For some more 6809 related fun, I also received some PLCC packaged HD63C09 CPU's which I then created an adapter board to enable testing them in the 6809 CPU Card. It's also inspired me to think about a PLCC version of the CPU Card, combining some ROM Expansion with the space saved.
You can find this post here: HD63C09 PLCC Packaged CPUs Received & Tested!

You'll also find some additional posts in the 6809 Software Forum, where we further tested the 6809 CPU Card based system.

Subsequent Version Updates:

• v2.4 - Minor correction to a ROM Write Enable Jumper oversight. The ROM /WE pin (on v2.3 and prior), was permanently pulled high.
• v2.5 - 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.

I've just updated this topic (and the above post) to reflect v2.3 as the current version.

v2.3 update fixes a minor oversight in the v2.2 design, and also adds a Reset header to allow easily connecting an external reset button.

The v2.3 update is detailed here: Minimalist Europe Card Bus (MECB) - 6809 or 6309 CPU Card - v2.3 Update!

Editor wrote: ↑Fri Apr 12, 2024 7:00 pm I've just updated this topic (and the above post) to reflect v2.3 as the current version.

v2.3 update fixes a minor oversight in the v2.2 design, and also adds a Reset header to allow easily connecting an external reset button.

The v2.3 update is detailed here: Minimalist Europe Card Bus (MECB) - 6809 or 6309 CPU Card - v2.3 Update!

Nice! I think I might have to grab myself one of those updated designs - the reset header is indeed a handy feature I can use in my case design!

bugeyedcreepy wrote: ↑Sun Apr 21, 2024 11:24 am Nice! I think I might have to grab myself one of those updated designs - the reset header is indeed a handy feature I can use in my case design!

and... I'm pretty sure it was you who inspired me to add reset headers to my CPU Cards.

Editor wrote: ↑Wed Apr 24, 2024 7:15 am

bugeyedcreepy wrote: ↑Sun Apr 21, 2024 11:24 am Nice! I think I might have to grab myself one of those updated designs - the reset header is indeed a handy feature I can use in my case design!

and... I'm pretty sure it was you who inspired me to add reset headers to my CPU Cards.

lol!! I'm totally gonna take that as a WIN!!

I recently received some PLCC packaged HD63C09 CPU's, which I then created an adapter board for, to enable me to test them on the 6809 CPU Card.

This has also inspired me to think about a PLCC version of the CPU Card, combining some ROM Expansion by using the PCB space saved.

You can find this post here: HD63C09 PLCC Packaged CPUs Received & Tested!

Editor wrote: ↑Sat Jun 15, 2024 8:09 pm This has also inspired me to think about a PLCC version of the CPU Card, combining some ROM Expansion by using the PCB space saved.

That sure does save a lot of space. Could also use the extra space for jumper settings, headers and any other imaginative thing I have no idea about right now... like an all-in-one "space saver" cpu/video/keyboard combo card - but now I'm going way off-topic again. Would make for a dense card - or maybe some kind of dual cpu card could even be the go, I remember seeing something about a dual 8-bit cpu system recently, where one cpu did regular cpu-ey things, while the other operated as a gpu of sorts, doing full-time duties rendering video and graphics

...See? My imagination only gets me in trouble...

bugeyedcreepy wrote: ↑Tue Jun 18, 2024 7:21 am ...See? My imagination only gets me in trouble...

Imagination is a good thing. Many great things have come to be, from great imaginative thoughts!

For now, a single combination CPU Card, catering for DIP / PLCC / 1MB ROM Expansion, will keep me busy routing traces for a while.
I decided to try going this more difficult route, instead of just making a seperate PLCC only CPU Card.

It remains a CPU & Memory Card, which still aligns with the MECB Card logical segmentation of function, but interestingly will expand nicely on the capabilities & function of the existing CPU Card.

Effectively, enhancing it with the ability to now either choose a DIP or PLCC packaged CPU, and either the existing 32KB DIL EEPROM or faster 512KB FLASH ROM chips (in PLCC package), and, also either 1 or 2 ROM’s for up to 1MB of switched bank-selected ROM (just like the existing seperate ROM Expansion card).

In addition, you could also continue to use a DIP40 CPU and simply just swap out the existing 150ns 32KB DIP28 ROM for a single faster 70ns 64KB of PLCC32 FLASH ROM (without adding the bank-switching components). Thus, giving you full 64K Memory Map freedom, to mix up to 64KB RAM with up to 64KB ROM, and also potentially allowing faster overclock speeds (on the basis that the existing 150ns ROM is possibly the main speed limiting factor at the moment).

My vision for this new enhanced Card would then be a MECB 6809 CPU Card v3.0.

The only issue is that it is quite crowded, and will require me to go to a 4 layer PCB, which is more expensive.
So far, I have settled on the layout, I’m now just in the process of trying to route this busy creation!

Once done, I will have to decide whether to retire the existing CPU Card (as the enhanced v3.0 CPU Card will be backward compatible), or, to offer both (on the basis that new 4 layer PCB will be a little more expensive than the original 2 layer PCB).

But, lots of routing challenges to solve first, before this vision becomes a reality (or I revert to the idea of a seperate PLCC only Card).

EDIT (3 days later)...

Life is a learning curve... So, after 2 days of PCB routing, when I was about 90% finished with my 4-layer all-in-one combination PCB creation, I took a moment to check the ordering process for the first prototype PCB manufacture.

It was only then that I realised that the "little more expensive" 4 layer PCB, was actually going to cost me 4x (four times!) the price of my usual 2-layer PCB's. Even at a higher production quantity, I was looking at 3x the PCB cost!

So, it then dawned on me that anybody obtaining the PCB (for their own build), would either be building a DIP CPU based system, or a PLCC CPU based system. Obviously not both!
So, from an end-user perspective there is no real advantage to a "all-in-one combination PCB" (to justify the increased cost!).

My desire to make one was purely from a simplified stocking / inventory point of view (and of course... The Challenge!).
I'd then have just one PCB, to suit both DIP and PLCC build desires.

So, roll on the next day, and I've started-out again on a 2-layer PLCC only CPU Card. Still enabling the combination of CPU Card and ROM Expansion Cards, but no longer supporting a choice of either DIP or PLCC packages (for CPU & ROM).

This will mean a seperate 6309 PLCC CPU Card being added to the available MECB Cards (and the existing 6809 CPU Card will remain).

But, as I said, this does actually make more sense (from a user perspective), and the additional PCB option will be the same usual 2-layer PCB price.

So, I must now get back to my PCB Layout & Routing (starting again from square one).

In the meantime, I'll share below a 3D PCB render of what my 90% complete 4-layer all-in-one combination PCB looks like!
Pretty nice (a work of art, if I do say so myself). But, for now, it will remain as a 90% complete project (on hold for now).


So, hopefully, in another couple of days, I'll eventually have a 2-layer PLCC PCB ready to submit for manufacture!
Then I can eventually get back to one of my other in-waiting projects!

I just edited the above post... after several days of PCB trace routing work. Well, everything below the EDIT in the above post explains it all...