MECB Roadmap / Index

[Editor]

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?

I think I've discovered why this is happening. It appears to be due to your web browser not allowing mixed content (unsecure links within a SSL secured page), therefore the http image link is shown as a broken link.

This issue is pretty common these days, with web browsers being more secure.

If you have a look at your later post (preceding this post), I uploaded an image of yours to imgbly.com (free image hosting), and then (via admin) I changed the photo link in your post to the imgbly hosted raw image https link. i.e.:

Code: Select all

[img]https://www.imgbly.com/ib/PPqjuUXrGe.jpg[/img]

Then the image appears inline okay (well, at least to me now, using chrome), as below. The difference being that imgbly.com is a SSL enabled image host.



You might want to edit your post and try the same with the secoind image?

[Editor]

Were you intending it to do something like CPU personalities as proposed last time we discussed it?

Not at this stage. I think the added complexity this would likely require goes beyond my current Minimalist intent.

The ROM Expansion Card, as currently designed, will allow either a manual Bank Switch select of 1 of 16 ROM banks, or, alternatively via bus A16 - A19 addressing (from a CPU Card that supports 1MB addressing).

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!

I think I'll wait to see where you get to with this. It does sound like an interesting concept, to enable getting a system in a keyboard wedge case.

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...

With spike / noise filtering on the Backplane, pretty much just ensure you spread the capacitors out to get good power feed coverge across the slots. Short of some more indepth analysis and testing, this is always a good rule of thumb that has worked well for me.

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?

The current Backplane connectors are 0.8" spaced, which equates to 20.32mm. So, working on a less than 20mm thickness should give you enough clearance, as long as you have allowed enough clearance for the taller component side of boards.

[bugeyedcreepy]

I think I'll wait to see where you get to with this. It does sound like an interesting concept, to enable getting a system in a keyboard wedge case.

Okay, here it is! I bit the bullet - yet to test since I'm still to put together my MECB system, but I couldn't wait to see it come together - so here it is:

So, this is the two optional builds of this slimline backplane as described:


...when flipped vertically to show the underside:


...so flipping one on its long edge to back-to-back with the other:


...would see one rearward facing, three vertical bus connectors to the back, while the other now upside-down backplane with two forward-facing and one vertical backplane connector facing upward to act as a "cartridge" bus connector that would serve as the exposed system cartridge connector while the rest of the backplane and cards would be neatly tucked inside the wedge case I've designed:




and as suggested, I've sourced numerous 244 and 245 data and address ICs just in case my backplane extender (pictured pretending to be a cartridge at the end) doesn't work as it stands...



(p.s. I'm sure I conformed to all the image rules as far as I know them - not sure what the issue is with images this time... -_-)

[Editor]

(p.s. I'm sure I conformed to all the image rules as far as I know them - not sure what the issue is with images this time... -_-)

I took a quick look, and the image links were missing the file extension ".jpg"

I've edited your post and added the extensions, so all are now visible.

I've been a bit tied up with family during the holiday break, so I'll come back to your post and comment when I have some time to digest it.


EDIT: All looks really interesting. I imagine eventually seeing it integrated into a suitably designed wedge style case with a top cartridge slot, will bring it all together.

So, I’m assuming the pair of IDC style connectors are effectively making the same connections (i.e. duplicating the connections) between the boards, when you have them back-to-back sandwiched together?

As you also have a standard backplane, at least you can first prove everything is working in standard configuration, before migrating the cards over to your backplane design to confirm all is still working. Then, adding an extension backplane, and peripheral card, and then testing at various speeds will then determine if all is working as planned (or if drivers are going to be required).

[bugeyedcreepy]

I took a quick look, and the image links were missing the file extension ".jpg"

...I'm such a n00b...

So, I’m assuming the pair of IDC style connectors are effectively making the same connections (i.e. duplicating the connections) between the boards, when you have them back-to-back sandwiched together?

Exactly! and why one connector had to be a mirror image of the other. I've also set it up so the ribbon cable could be used to connect the two backplanes if they weren't directly connected too - allows for some extra extensibility for odd installs or unique case uses - not sure it'd be that useful, but that's how I set it up all the same... it'll even be possible to use my cartridge version of my slimline with my bus extender connecting your standard backplane to it - providing the ribbon connector doesn't introduce too many issues for its length and extra interconnects, that is...

As you also have a standard backplane, at least you can first prove everything is working in standard configuration, before migrating the cards over to your backplane design to confirm all is still working. Then, adding an extension backplane, and peripheral card, and then testing at various speeds will then determine if all is working as planned (or if drivers are going to be required).

Seems to be a legit course of action, I'll get to doing that & see how it goes. I'm c&c'ing a bracket to hold these backplanes in place within said case, and it'll be done in such a way that it can still take your full backplane laid flat where my slimline backplane would normally have taken an inserted card (plus a mount for a side connected card off your backplane's right angle connector) - but probably best I just show the concept once done, so it makes more sense...

[Editor]

... - but probably best I just show the concept once done, so it makes more sense...

Yes. I seem to be a bit challenged trying to visualise the final outcome. But, as they say, a picture is worth a thousand words! So, I'll wait to see what you come up with.

[epaell]

BTW, love the roadmap ... while I imagine you'll only have a single CPU card installed at a time, with all those cards in the works you may still need a bus expander at some point

[Editor]

BTW, love the roadmap ... while I imagine you'll only have a single CPU card installed at a time, with all those cards in the works you may still need a bus expander at some point

Yes, the thought of possibly needing a bus expander does arise from time-to-time.

But, it also serves to remind me of my core intention for defining MECB. That is, “Minimalist”.

Specifically, it’s about returning to my (our?) original roots of experimenting with early CPU’s and peripheral chips.

i.e. An updated platform, replacing the early (and time consuming), 70’s & 80’s wire-wrap experimenting / prototyping solutions, to allow for very easily mixing & matching different cards, to more easily experiment with different CPU’s with different Peripheral chips.

In some way, the existing 4 socket (plus 1 horizontal) Backplane design serves to reinforce this Minimalist idea, by limiting system size.
As in, all you really actually need for having some fun exploring different CPU’s and Peripheral chips of the 8-bit era.

Of course, who knows where I’ll eventually end up, but for now I have plenty of plans that fit my core Minimalist intention.

[epaell]

That is true. In fact, it was the simple and clean design that attracted me to this project (and the potential to play with other CPUs in future).

[Editor]

I've added a section: Address Decoding Glue Logic (ATF16V8), to the initial pinned post on this topic

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 now added to the MECB GitHub repository, compiled PLD .jed files for most of the standard memory map options included in the source .PLD files.

The idea is that this should make life a lot easier for those who don't have WinCupl installed, or have no prior experience with PLD programming, as you now just need a USB programmer (that supports programming ATF16V8 chips with .jed files).