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Compacta Uniboard - A 6809 SBC cicrca 1982

intabits

Experienced Member
Joined
Jan 22, 2019
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148
Location
Melbourne, Australia
A while ago, I posted this stuff in the retro section of the EEVBlog forum, and just realized I should have put it here also.

Some time in the 1980's (judging by the latest date code, about 1985) I bought and assembled this "Uniboard" by "Compacta Incorporated". They supplied just the PCB and a couple of pre-programmed PALs, and the user had to source all the other parts and assemble it.

It's been sitting in my junk room since then, and I'm struggling to remember if I even ever got it going. I think I did, but I can't picture it actually running, so maybe not. I do remember that U15, the ceramic chip with the badly corroded lid, an MC6844 DMA controller, was hard to get and expensive. The board has some corrosion and general scum, but it does look a little worse in the photo than it actually is.


6809-single-board-computer-project


I've also found and scanned the documentation (there is some duplication):-

https://www.filehosting.org/file/details/829492/Manuals.rar

https://www.filehosting.org/file/details/829493/Page Scans.rar

https://www.filehosting.org/file/details/829494/Schematics.rar

https://www.filehosting.org/file/details/829495/ROMs n stuff.rar

I managed to read the monitor ROM (U14, a 2732), and the video character generator ROM (U59, a 2716).
But the two PALs (U29 PAL12L60J) and U40 (PAL10L8CN), both from MMI are unknown to my programmer. Looks like a job for Arduino...
(update: U29 might be a PAL12L6CN)

The only ASCII in the ROM is a few error messages:-
https://www.eevblog.com/forum/proje...-project/?action=dlattach;attach=520706;image


More images added to imgur:-
https://imgur.com/gallery/lgEpyMm

This stuff has also been made available to someone who has created a web page for the UNIBOARD:- (not sure how complete/ready it is)
http://www.sardis-technologies.com/oth6809/uniboard.htm
 
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The "Compacta Uniboard" 6809 based Single Board Computer that I have been working on came as a bare kit with just the PCB and 4 pre-programmed parts.

Two of those were ROMs for the monitor program and the video character generator, which I was able to read with my device programmer and so was able to save their contents for posterity, and also to help with understanding, testing, debugging, and eventually using and possibly modifying the board.

But the other two parts were Programmable Array Logic (PAL) chips - a PAL12L6 and a PAL10L8, which my programmer could not read.
To save their programming in case it were ever lost, to check that they were still good, and to help understand the Uniboard, I needed to read them somehow.

I used an Arduino Nano to to that, and in the process realized that there were considerations that were not apparent to me at first.

Going from setting port bits inside the Arduino's AVR chip, then through several sets of pins, and finally to signals on the Uniboard, needed to be accounted for in the process, and I show how my PAL reader software dealt with these "mappings" (4 of them).

But the sequence of bit patterns presented to the PAL also needs some thought, as that is critical to getting meaningful results.
The reader software also has a mechanism for helping with that.

Finally, I found a piece of software called "Logic Friday" that can also help with understanding the results of reading these PALs.

https://www.youtube.com/watch?v=LgENrWFcL3E
 
Thanks for that, interesting stuff.
The part about programming a GAL will be useful if I ever need to replace the PAL or want to modify its programming.
 
I've run out of steam on this thing for now, so this project will probably move to the back burner.

But I would be very interested in any thoughts, suggestions or insights you nay have as to what to check for next, or what approach to take in getting this board working.

I suspect the problem is in the RAM, and that the random junk showing on the screen:-

iKc3ahO.png


Is because the monitor initialization is not getting to the section where it clears the Video RAM.
It appears to set up the CRT controller, so that the display format is correct, but does not return from that (very first) subroutine call because the RAM is not remembering the return address from the stack (and so it never goes on to clear the display RAM).

I have:-
* Read out the Monitor and Character Generator ROMS, and they are good.
* Checked that the RAM RAS and CAS signals appear to match the timing diagrams in the manual.
* Fixed a couple of issues that were causing false interrupt request signals.
* Read out the contents of the 2 PALs (which look sensible. One I'm sure is correct, the other is hard to tell)
* Replaced all the chips involved in the RAM and video interface (basically all the core, non-I/O device stuff).
* Tested the 4116 RAM chips, and found 3 duds (but they were in lower memory, and not needed for initial testing)
* Modified the board to use 4164 RAM chips. Which changed the random display:-

kSPiFOh.png


But not much else.

Any ideas on where to go with this?


Front & back of PCB:-
lspdff3.jpg

AuyLgqa.jpg


The schematic is shown earlier in this thread, and all documentation is at:-
http://www.sardis-technologies.com/oth6809/uniboard.htm

My partial disassembly of the Monitor ROM:-
https://pastebin.com/yNnw5Fuh

Video of my latest blunderings:-
https://www.youtube.com/watch?v=6dtMcu93KDA

Thanks in advance for any bright ideas!
 
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