No idea, actually! Wouldn't make sense for it to be a buffer, though, since the buffer is the '245

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BB816 Computer YouTube series

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

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http://WilsonMinesCo.com/ lots of 6502 resources
The "second front page" is http://wilsonminesco.com/links.html .
What's an additional VIA among friends, anyhow?

Maybe not, but for me, it does other stuff too. e.g. I also have BE going into it, so it pulls the upper address lines low when I pull BE low. It also manages the "wire-or" for IRQs and blocks IRQs when Rdy is low, and does address decoding for a 2nd 512KB RAM IC and generates a separate signal for the 2nd GAL to use as part of the address decoding for the VIA.

-Gordon

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Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

Can you implement a transparent latch with a GAL? I thought they only had D flip flops and you had to upgrade to a CPLDs to do that

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BB816 Computer YouTube series

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

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x86?  We ain't got no x86.  We don't NEED no stinking x86!

I think you can do things like D = D & PHI2 # Q & !PHI2 but I seem to remember having trouble with the cupl simulator if I took this too far. This is using combinatorial pins, not registered ones, as it's asynchronous.

No. I gave up on the open source thing after the open source "community" gave up on me.

I also use a tool that no-one else uses - GALasm, although it's a fairly trivial text file.

I sometimes publish things under a "source available" thing, but it's rare these days. Also the reality is that no-one else is going to build one of my boards so it's a bit moot.

Gordon

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Gordon Henderson.
See my Ruby 6502 and 65816 SBC projects here: https://projects.drogon.net/ruby/

eh, i'm not a fan of that mentality.

i made my 65816 SBC's schematics, CPLD logic, and BIOS ROM public. because having more resources and working examples online is always a good thing.
I don't expect anyone to ever actually build my SBC, and i'm perfectly ok with that.
but if someone is looking for some examples of how to make a 65816 SBC, they can use my design as a base or use it to look at how i did specific things like the latching circuit to then design their own.

that's why i would always recommend publishing details (schematics, code, etc) about larger projects (even if it has it's own thread where you can follow along the development), so that others might use it as learning resource in the future.
if you don't, then once you leave the community all your knowledge will be pretty much lost except for the few snippets thrown around in forum posts (which might be difficult to find).

that also applies for anything being sold, once you stop selling something there is no reason to not publish it, so others can make their own.
i still hate that about the kipper2k Amiga RAM expansion, which was a very simple design with some DRAM and a CPLD that plugs into the CPU socket to give an A500/600 4-8MB of RAM. but he stopped selling it without ever making the design public. the design was popular enough that it was remade from scratch and open sourced, but that extra work could've been easily avoided.

I use it, too - it's my favorite assember for GAL/ATF PLDs. I also find its source syntax easier to read than WinCUPL.



This. I'm often very happy to find someone's SBC with all the sources, since it really helps understand how the thing is supposed to work. I've learned a lot from other people's projects.
I think that's the true spirit of the Open Source, and I've always been trying to make all my works open - not for fame or commendations, but just in case it helps someone as much as similar projects used to help me.

EDIT: Sometimes, the most obscure projects with only few Github stars are the most valuable ones due to their rarity: I recently played with Intel 8008, and I found someone's SBC on Github. That was the only project with a great documentation, schematics and all the sources included, even PLD sources for GAL. Needless to say, it helped me tremendously to understand 8008's internals and usecases.

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/Andrew

deck65 - 6502 slab with screen and keyboard | ПК-88 - SBC based on KM1810VM88 (Ukrainian i8088 clone) | leo80 - simple Z80 SBC
nice65 - 6502 assembly linter | My parts, footprints & 3D models for KiCad/FreeCAD

(Just to say, I like to open source my own works, and I much prefer when published works have open source licenses, failing which I prefer published code to private code, but finally I also respect the decision of anyone who feels they need to do otherwise. Ideally we can still share our project stories and share ideas.)

All my 70+ designs except two are sufficiently documented to be replicated by others. They are stored in retrobrewcomputers under plasmo. Ultimately the documentations are for myself because it is where I can find the most current designs snap shots. If you are interested in any of my designs but couldn’t find certain document, let me know and I’ll upload the missing document. The two exception are Ultrawarp and IOU for Apple IIe implemented in CPLD; I am working in a team on these projects and agreed not to release the design files.
Bill