Oric -on-a-chip

This is the right place to discuss on how to implement hardware vsync, adding a VIA or AY chipset, puting multiple roms, or how to design a new flash expansion card.
Torlus
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Oric -on-a-chip

Post by Torlus »

My work, started some months ago, then started again since the Alchimie party until now, is now showing first good results :)

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As you can see there are some issues here, yet to be solved ;)

More info to come on my site : http://torlus.com/

If you have any idea on the reason why it looks like the * key is pressed forever, please let me know ;)
About the display glitches, I guess my ULA code needs some rework.
Any tip/suggestion welcome.
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Dbug
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Post by Dbug »

Do you emulate correctly the VIA and the small chip in the keyboard ?
Perhaps you just have non initialized states, and the keyboard polling routine detects you have the '*' key pressed.
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G Squad
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Post by G Squad »

Torlus you nutter! :D

Looks like you are getting close with that, well done!

I have some questions...

I guess you are using third party 6502 VHDL source code, which/who's version is it?

Also, what about your ULA emulation? Did you base that on the document by Mike Brown, or is there VHDL out there for it already? Because I noticed some errors in Mike Brown's document...

Your screen problem seems like it might be related to the generation of the composite video signal, looks like a carrier problem. Are you able to directly test the RGB output of the 'ULA' instead? You may find this is working and therefore be able to isolate the problem.

Are you putting the ROM image in the Flash of the S3 board? I guess you have plenty spare for a nice filing system in the future!

What about the RAM? Are you using the SRAM on the S3 board? An ORIC with 1 MegaByte of RAM!!!

The keyboard issue....

8 and SHIFT (i.e. '*') both correspond to input 7 of the '4051' (as dbug said, make sure you included this part in your FPGA design?!). So, it looks like the row select lines (ABC) could all be stuck high - this points to a problem in your '6522' emulation.

Another thing to note. As the Oric uses a 4051 ANALOG switch to read the key matrix, the tri-stated condition passes through the 4051 chip.

It won't if you have coded the 4051 as a DIGITAL mux! So, you'll need to pull up (or down, don't know which way without doing some reading)) ALL of it's inputs.

If you would like me to collaborate with you on this project I would be happy to do so.

Well done mate, and the best of luck, you nutter :D
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Post by Torlus »

Hi, G Squad

My ULA had some issues, that I've been able to fix this night. It still has a pixel off on the end of an horizontal frame, but well it's not much of an issue now...

The 6522 code comes from fpga-arcade's VIC-20 stuff.
What's really weird in this case, is that the issue doesn't show up in simulation, and I still haven't figured out why.
Anyway, I will release my code soon, so if you want to help, I'll be glad ;)
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Post by Torlus »

I managed to fix the ULA, and I found out what that caused the "key pressed forever" issue.
See http://torlus.com/index.php?2007/11/18/ ... a-bugfixes.
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G Squad
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Post by G Squad »

Well done Torlus, keep up the good work!
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Post by Torlus »

Some progress, i.e PS/2 keyboard interface and USB loading of .TAP files, with the help of Fabrice Frances and Dbug :)

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tingo
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Post by tingo »

Hello, how is progress with this project?

I have just got an Altera DE1 board, and would love to test / play with Oric in an FPGA, if something is available for testing.
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Post by ibisum »

I also would love to play with this project, I wish there was some updates on it .. maybe he's moved on to other more interesting things, but it sure seems to me that we Oric fans could do a *lot* with an Oric-on-a-chip .. :)
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Post by Torlus »

Well I haven't worked on it since what is shown on these photos.
However, I also have an Altera DE1 board, and it features all the required interfaces, so it won't need an additional board, like I added for the Spartan-3 board.
Someday, I will "port" it over this board (as well as many others of my projects), but I seriously lack time for now...
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