DigicoolThings Forum

The purpose of this topic is to provide a Roadmap of intended MECB product developments, as well as Index links to the individual MECB product discussion topics.

Please also use this topic to raise new product suggestions, and to advise us of a product you are creating, that you’d like us to add to the lists below together with the link to the main discussion Topic for your product.
This will help avoid re-inventing the wheel, if multiple users are planning on creating similar products.

Individual MECB Product - Topic Subject Naming Standard

Each topic created to discuss a specific MECB product should have the Subject prefixed with either [P], to indicate an in Planning or in-Progress product, or [version number] (e.g. [v1.0]), to indicate a product that's now in-Production (i.e. realised / available).

Roadmap

Status	Product	Who
Planning	MECB Mass Storage and/or Keyboard Interface Card	DigicoolThings
Planning	MECB 68008 CPU Card	DigicoolThings
Planning	MECB WDC I/O Card	DigicoolThings
Planning	MECB Z80 CPU Card	DigicoolThings

In-Production

Version	Product	Who
v1.2	MECB Backplane	DigicoolThings
v2.0	MECB Prototype Card	DigicoolThings
v1.0	MECB Prototype PLD Card	DigicoolThings
v2.0	MECB TMS9918 / TMS992x VDP Video Card	DigicoolThings
v2.5	MECB MC6809 (or HD6309) CPU Card	DigicoolThings
v1.1	MECB Motorola I/O + Sound Card	DigicoolThings
v1.1	MECB 1MB ROM Expansion Card	DigicoolThings
v1.3	MECB 6502 or 65C02 CPU Card	DigicoolThings
v1.0	MECB 6309 CPU PLCC Card	DigicoolThings

Be sure to also first review the MECB Background & Introduction topic.

Address Decoding Glue Logic (ATF16V8)

For MECB, I standardised on the ATF16V8 as a good "retro friendly" solution for providing simplified & flexible Address Decoding Glue Logic.

The MECB GitHub repository contains a folder for each MECB Card, containing the source file for the card's PLD. Each source file contains commented-out sections for various different standard memory maps.

To allow easily re-programming of your PLD chip with a simple USB programmer (e.g. TL866), without the need to install WinCupl (to compile the .PLD source), I've also included in the GitHub folders, compiled .jed files, for most of the standard memory maps included in the source.

This should make life a lot easier for those who don't have WinCupl installed, or have no prior experience with PLD programming (but do have a USB programmer for your ROMs).

Last Updated: 15-Nov-2024

So, my astutely keen eye has noticed the MECB bus has extra address lines that would allow up to 16Mb of addressing, and I imagine there's a chance that my bad habit of recovering electronics from old photocopiers, could mean I can use some of the numerous fancy CPUs I've pulled out of them, like this one:



which I imagine should be relatively straight forward? I notice there is a fair bit of homebrew software for the 68000 series, so perhaps another stretch objective after the current array of possibilities has been explored?

tbh, I wouldn't mind getting this going as it is and perhaps rewrite the rom to allow doing something else with it - but I don't have the knowhow, let alone an oscilloscope & all the other electronic goodies to make it go - it's attached to a touchscreen & keypad out of that photocopier, so my only hope of getting any interesting use out of it, would be to try building my own MECB CPU card for it in lieu...

p.s. - not sure why, but the image doesn't seem to open when I look at it here - but it opens fine if I right-click and open in new tab, so is there something I'm not doing here that I should be?

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 2:28 amSo, my astutely keen eye has noticed the MECB bus has extra address lines that would allow up to 16Mb of addressing

Note that MECB uses the original Kontron ECB 64-pin (A&C row) DIN connector. Within rows A&C there is support for A0 - A19, or 20 bits, which allows for 1MB of addressing. Still pretty good for any 8-bit system, or even for a 68000 system.

But, only 8-bit data bus is allowed for on rows A&C, so a full 68000 would be ruled out (in a Minimalist 64-pin MECB bus). D8 - D15 is implement on the middle "B" row of the full 96-pin 3-row DIN connector.

However, a 68008 MECB CPU Card wouldn't be out of the question!

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 2:28 amI notice there is a fair bit of homebrew software for the 68000 series, so perhaps another stretch objective after the current array of possibilities has been explored?

Being a Motorola fan, I also have a fondness for the 68K processor. But as noted above, the 8-bit data bus would limit us to a 68008 Card.

This would certainly interest me as something to play with, so it certainly may be something I'd like to make, eventually.

To be honest, a 68008 card would probably be of more "fun to program" interest to me personally, than the Z80.

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 2:28 amp.s. - not sure why, but the image doesn't seem to open when I look at it here - but it opens fine if I right-click and open in new tab, so is there something I'm not doing here that I should be?

Hmm. I noticed that also. I have checked the phpBB settings, and enabled the "Create Thumbnail" option, in case that helps.

I also noted that the maximum image attachment size defaults to 256KB (seems reasonable), however the image you've linked to is 301KB in size.

Perhaps try editing your post to see if phpBB now creates a thumbnail, or alternatively see if you can resize your image to be < 256KB?

Editor wrote: ↑Mon Nov 20, 2023 3:08 am Note that MECB uses the original Kontron ECB 64-pin (A&C row) DIN connector. Within rows A&C there is support for A0 - A19, or 20 bits, which allows for 1MB of addressing. Still pretty good for any 8-bit system, or even for a 68000 system.

But, only 8-bit data bus is allowed for on rows A&C, so a full 68000 would be ruled out (in a Minimalist 64-pin MECB bus). D8 - D15 is implement on the middle "B" row of the full 96-pin 3-row DIN connector.

....bugger. I think I read the datasheet for this particular one, and it has an "8-bit mode ", though entirely out of my depth for confidence on that point - am I right about this one I have?

Editor wrote: ↑Mon Nov 20, 2023 3:08 amBeing a Motorola fan, I also have a fondness for the 68K processor. But as noted above, the 8-bit data bus would limit us to a 68008 Card.

This would certainly interest me as something to play with, so it certainly may be something I'd like to make, eventually.

To be honest, a 68008 card would probably be of more "fun to program" interest to me personally, than the Z80.

I'm IN!! - now not to muddy the waters, but what if I were to happen across some 96 pin connectors and say a design that implemented a couple of those relevant B-row lines to enable a 24 bit address and 16 bit data bus, would that be possible to achieve while still maintaining backward compatibility with MECB standards and cards working within the 8-bit bus limitation?

Alternatively, how hard would it be to put several meg onto the CPU card itself, and if only some (512k-1Mb), would it be doable to prioritise addressable ram on the bus into & up to the first 1Mb to allow onboard ram to extend "in-house" to whatever could fit? That might be a challenge too far, but I agree, a lot can be done in 1Mb anyway - look at the early Amigas!

Editor wrote: ↑Mon Nov 20, 2023 3:08 amHmm. I noticed that also. I have checked the phpBB settings, and enabled the "Create Thumbnail" option, in case that helps.

I also noted that the maximum image attachment size defaults to 256KB (seems reasonable), however the image you've linked to is 301KB in size.

Perhaps try editing your post to see if phpBB now creates a thumbnail, or alternatively see if you can resize your image to be < 256KB?

I reduced it to 239k (243,976 bytes) and made out like I made editing changes to my post that should register as an update, but alas, no dice. No biggie of course, don't let it distract you from your mission!!

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 5:56 am I think I read the datasheet for this particular one, and it has an "8-bit mode ", though entirely out of my depth for confidence on that point - am I right about this one I have?

The 8-bit mode only applies to the MC68HC001 variant of the 68K.

To be honest, the MC68008 version, with it's 8-bit Data bus and 20-bit Address bus and smaller 48-pin DIL package, looks to be actually a perfect "high end" match for the MECB bus design capabilities (and also the "Minimalist" intention).

The MC68008 is still a full MC68000 32-bit register processor internally, only that it communicates externally via an 8-bit Data bus and is limited to 1MB 20-bit Address bus. These were cost saving measures to allow the MC68008 to be used in a world where existing system and memory designs were pre-dominatly 8-bit. Again, this actually fits quite nicely with the MECB "Minimalist" design intention.

The MC68008 runs the same code that the MC68000 does (it is basically identical internally).

If you want to explore a full MC68000 16/32-bit processor, then you'd be best to look at bigger ECB designs that are intended for supporting the larger 16/32-bit processors.

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 5:56 am... now not to muddy the waters, but what if I were to happen across some 96 pin connectors and say a design that implemented a couple of those relevant B-row lines to enable a 24 bit address and 16 bit data bus, would that be possible to achieve while still maintaining backward compatibility with MECB standards and cards working within the 8-bit bus limitation?

As above, I think for this you'd be better advised to explore full ECB designs. This is really beyond the intent of the MECB design.

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 5:56 amI reduced it to 239k (243,976 bytes) and made out like I made editing changes to my post that should register as an update, but alas, no dice. No biggie of course, don't let it distract you from your mission!!

Hmm, I will have to explore this a lottle more. It would be good to resolve this so we can have images appearing in-line!

Editor wrote: ↑Mon Nov 20, 2023 7:06 amTo be honest, the MC68008 version, with it's 8-bit Data bus and 20-bit Address bus and smaller 48-pin DIL package, looks to be actually a perfect "high end" match for the MECB bus design capabilities (and also the "Minimalist" intention).

I'm In!! Let's Do it!

Next feature request would be an MECB mass storage card, like an SD card, or preferably one that could do compact flash cards for all the recovered cf receptacles and compact flash cards I found with them when I pulled apart all my old cisco gear - I have so many of them - so let me know if you need some to be sent to you - I have Heaps of 32/64/128Mb and even a few 256/512Mb compact flash cards, I would Love to use them to house all my various versions of 6809/6502/Z80 and even 68008 (:P) software that will no doubt become available in your planned software repository somewhere... if I don't set one up myself first... and that MECB card would ideally be able to have the cf receptacle attached on either side of the card given I have numerous receptacles that suit either (I recently saw a Youtuber design & order their CF PCB only to find their CF receptacle took the card the other way around, so shorted out his homebrew, preventing it from booting!!) - I'm not proud, certainly not ashamed to use second-hand parts I recovered - that's half the fun imho!! I also get that SDcards are much more cost effective, so even a combo mass storage MECB would be Awesome! Also, a stretch objective might be a dual mass storage MECB card, or a configurable feature that would allow multiple mass storage MECB cards on the same bus would be the Ultimate Achievement Unlock!!

Yet another feature request, would be an RTC, but maybe something like a CMOS - i.e. an RTC with on board ram for any future configuration, such as pre-defined I/O or standard boot options, or even that multi-cart style CPU rom I think I mentioned earlier that could set the appropriate bank to boot into on startup - I ask because I've also recovered some Hitachi HD146818 ICs, which would suit such a thing...

That's all for now, but don't get complacent, I'm sure I'll be back with more suggestions and my "hurry along" whip!!

bugeyedcreepy wrote: ↑Mon Nov 20, 2023 10:46 amNext feature request would be...

All good ideas. We almost need a 3rd list on this topic. i.e. a "Wishlist".
But, I think for now we'll leave the wishlist items as simply discussion posts. Mainly, as I need to focus my available time on progressing my immediate In-Progress projects.
Ideally, there will eventually be more Retro enthusiasts contributing to the project, both discussing and creating more MECB Card designs.

Editor wrote: ↑Mon Nov 20, 2023 8:20 pm All good ideas. We almost need a 3rd list on this topic. i.e. a "Wishlist".
But, I think for now we'll leave the wishlist items as simply discussion posts. Mainly, as I need to focus my available time on progressing my immediate In-Progress projects.
Ideally, there will eventually be more Retro enthusiasts contributing to the project, both discussing and creating more MECB Card designs.

Agreed - you're doing great stuff. I can't remember where, but we did discuss the idea of a cartridge, and even a multi-cart style EPROM/logic/hardware features MECB card, and as much as I've got my slimline backplane idea going on, I've reached a point where I'd wonder if having a cartridge just use the MECB bus connector just like any other MECB card, because I have my slimline backplane idea sorted in such a way that I can have my cake and eat it too - essentially it would just be a reduced bus connector count (three) where the third slot at the bottom could either be a vertical connector or a right angle connector, and two single-row connectors yet to be decided that would be spaced apart from each other (male and female) on the flip-side to allow two of these slimline backplanes to be connected back to back - then the upside-down one could have a right-angle MECB connector at Slot 3 that would essentially give that up-side down backplane an exposed upward facing connector that would operate as just such a cartridge slot - and if we all keep to the MECB standard you have here for card design, a standard cartridge style enclosure could be designed to wrap any MECB card into a sealed cartridge package...

How's that for an idea?

I'll naturally send some KiCAD images and editable projects for you to look over and see what you think in your limited spare time before embarking on any PCB manufacturing, I am NOT savvy with electronics, and I don't understand the capacitor thing around the MECB connectors, and hate to get any cards done to find out they don't work...

bugeyedcreepy wrote: ↑Wed Nov 22, 2023 1:24 pmI can't remember where, but we did discuss the idea of a cartridge, and even a multi-cart style EPROM/logic/hardware features MECB card

Yes, I do remember the discussion, as I mentioned I'd already made plans for a "Cartridge" style ROM Card, related to my original intent to eventually mimic the CreatiVision game console (on completion of my 6502 CPU Card).

Your comment about also using the ROM Card to facilitate easier switching between 6809 sytem personalities (ASSIST09, BASIC etc.), actually prompted me to raise the priority of my ROM Card design and to also make it more flexible / versatile (also optionally using the Bus A16 - A19 signals).

In fact, I'm currently routing an initial v1.0 PCB, so I can get it on it's way to PCB prototype manufacture.

The topic for this can be found here: MECB 1MB ROM Expansion Card

bugeyedcreepy wrote: ↑Wed Nov 22, 2023 1:24 pm... - essentially it would just be a reduced bus connector count (three) where the third slot at the bottom could either be a vertical connector or a right angle connector, and two single-row connectors yet to be decided that would be spaced apart from each other (male and female) on the flip-side to allow two of these slimline backplanes to be connected back to back - then the upside-down one could have a right-angle MECB connector at Slot 3 that would essentially give that up-side down backplane an exposed upward facing connector that would operate as just such a cartridge slot ...

Unfortunatly I'm having difficulty visualising this from your description. Probably needs a diagram to better convey your vision?

bugeyedcreepy wrote: ↑Wed Nov 22, 2023 1:24 pmI am NOT savvy with electronics, and I don't understand the capacitor thing around the MECB connectors, and hate to get any cards done to find out they don't work...

The capacitors are simply power line bypass / filter capactors. Digital electronics (especially old school more power hungry devices), can generate significant power line noise (i.e. spikes), as gates switch on & off, particularly bus drivers etc. which cause spikes of higher current drain.

Filtering on the MECB system is achieved via a mix of 100µf / 10µf / 0.1µf, with the 0.1µf capacitors located on each card, close to each IC's power pins.

Editor wrote: ↑Wed Nov 22, 2023 8:05 pm Your comment about also using the ROM Card to facilitate easier switching between 6809 sytem personalities (ASSIST09, BASIC etc.), actually prompted me to raise the priority of my ROM Card design and to also make it more flexible / versatile (also optionally using the Bus A16 - A19 signals).

In fact, I'm currently routing an initial v1.0 PCB, so I can get it on it's way to PCB prototype manufacture.

That is Fr3akin' Awesome!! I'm hanging!!

Were you intending it to do something like CPU personalities as proposed last time we discussed it? As in a ROM Cartridge connects and would identify and switch to an appropriate bank in ROM to run the CPU specific code based on the A16-A19 line signals (though would you envision having as many as 16 different CPU cards)? If you're using A16 - A19, I guess it could be possible to simply pass those lines through to an appropriately sized ROM address lines, and then there's still up to 64k of banking within a 1Mb ROM again, so 4 to 16 banks of usable ROM per CPU profile if you sectioned off all 4 address lines for CPU identification - and in the short term, your 6809 CPU card would identify as CPUID 0 given it has no access to those lines anyway in its current version... though I suppose there has to be a way for the CPU card to yield to a cartridge ROM instead of its own on-board ROM - so that's a signal line right there that the 6809 v2.2 likely doesn't have to the bus right now...

Editor wrote: ↑Wed Nov 22, 2023 8:05 pm Unfortunatly I'm having difficulty visualising this from your description. Probably needs a diagram to better convey your vision?

Okay, This is what it looks like on the topside:


and then this is how the underside would look:


Now, imagine two of these cards with both of them having one male connector closest to the power end, and another female connector at the other, so you could back-to-back them upside-down and their connectors would connect the two busses allowing one "ring" bus across both boards. You'll also note that slot 3 is a dual fitment connector, so could fit either vertical or right-angle connector, and if you could imagine this backplane in a system where three vertical connectors would be mounted facing rearward to allow three cards to be connected, then the upside down backplane facing forward under the keyboard of the case I'm designing for this, would have a right-angle connector at Slot 3 offering an upward facing connector that could literally be a bus cartridge connector, again, I'd design the case to have a "cartridge recess" to fit this combination of backplanes!

Editor wrote: ↑Wed Nov 22, 2023 8:05 pm The capacitors are simply power line bypass / filter capactors. Digital electronics (especially old school more power hungry devices), can generate significant power line noise (i.e. spikes), as gates switch on & off, particularly bus drivers etc. which cause spikes of higher current drain.

Filtering on the MECB system is achieved via a mix of 100µf / 10µf / 0.1µf, with the 0.1µf capacitors located on each card, close to each IC's power pins.

Bugger, I might get your opinion on the remaining caps on that board above then, maybe I should add in two 100µf caps on the flip side (space is at a premium with all that crushing down I'm doing...), and reposition the 10µf cap somewhere better suited? Once I've tortured myself getting everything laid out on this board, I'll send you the project to look at for your opinion/correction, if you have the time, that is...

Also, I'm assuming the connectors are at least 20mm apart, appropriate for standard board displacement, and that would also mean any cartridge shell might be wise to stay within 20mm thickness, or should we assume it wouldn't be connected on the main bus, but to the side bus (on your MECB backplane, or my topside edge connector on my slimline backplane), so it ought to be at least 20mm inside space to accommodate the electronics?