I/O Interface

Discuss the CreatiVision hardware: models, revisions, fixing, hacking and modding.
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Scouter3d
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Re: I/O Interface

Post by Scouter3d » Sun May 26, 2024 7:20 am

Hi @username@,

sadly i did not reverse engineer the interface while i owned one...

from the picture i took, i think there are only (buffered) datalines and demuxed addresslines on the big connector and no PIA Portbits
I guess it should be possible to connect a ram expansion there, or a secont pia or other another I/O chip...

Cheers, TOM:0)
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Mobsie
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Re: I/O Interface

Post by Mobsie » Thu May 30, 2024 9:02 pm

Yes Tom is right, i played a lot with the interface in the past.
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@username@
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Re: I/O Interface

Post by @username@ » Fri May 31, 2024 8:40 am

If you look at the advances with Pi Pico (only 14.00 GBP!) - so one chip gives a whole OS and simulated RAM/ROM etc.

https://github.com/FreddyVRetro/ISA-PicoMEM

Could be fun!
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Scouter3d
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Re: I/O Interface

Post by Scouter3d » Thu Jun 06, 2024 4:53 pm

Hi @username@,

would it be possible to build a Creativision-Pi-Colecovision Adapter? Or even a Creativision-Pi-MSX Adapter?
(i recently repaired a few MSX computers and found them very nice :0))

I guess it would mean "rewriting" a lot of the respective BIOS (if one wants to use the hardware in the Creativision)
The official Salora Colecovision Adpter is nearly a complete Colecovision incl. different controllers, soundchip, RAM, ROM, CPU...

I a dreaming of a solution, where most of the Creativision hardware would be used... I/O, Controllers, Sound, ...
I guess it would be hard to do, as the I/O and sound surely are at different address-locations (and in the Creativision these are "hardwired")

And yes, it would only be possible to use on an MKII Creativision

Cheers, TOM:0)
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Re: I/O Interface

Post by @username@ » Thu Jun 06, 2024 6:55 pm

I would imagine you would need to rely on at least Pico doing the Z80 emulation - that way no BIOS to play with :)

Z80 I/O is to port addresses - which the emulation could pick up OUT, then forward to creatiVision memory address - reading likewise for IN.

Unfortunately MSX uses an AY-3-8910 - so somewhat incompatible.

One of the challenges would be to maintain a state machine for the SN76489 - and do a lookup table for speed X to 2Mhz, to correct frequencies etc.

This may not get the noise channel correctly - and further tweaking almost certainly would be required.

The base machine I would start with would be the Sega SG1000 / SC3000 - as there's no BIOS to care about.

Assuming it can be achieved - you can then do Colecovision, Sord M5, MTX512 and so on.

There is already (only one month old!) a ZX spectrum complete Pico system https://hackaday.com/2024/04/27/pi-pico ... -emulator/ and a RetroROM emulator https://hackaday.io/project/181419-picorom

The latter does make me think hammer to crack a nut approach - but hey, it's progress :D
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MADrigal
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Re: I/O Interface

Post by MADrigal » Fri Jun 07, 2024 12:13 am

Guys a few months ago I seeked assistance from the local Australian Museum's staff to unsolder the BIOS of the Salora Manager Colecovision converter so I could then dump it. I haven't got that done yet. That is my plan: get it unsoldered, dumped and then shared with the world.
Considering the BIOS is a derivative from the originally planned Creativision-Colecovision converter, it would be an excellent starting point.
Would this help the project?
I can touch base with the Museum again if this helps. Pls advise
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Re: I/O Interface

Post by @username@ » Fri Jun 07, 2024 8:42 am

I think any information is good - even when it's not what you expect :shock:

Can you remember how the Colecovision adapter boots on the Salora? Does it hook into the boot sequence as a CV cart, or is it more like a disc interface, where Solara BIOS jumps to the vector?

From the pictures, I assume the Salora is used really as a TV adapter - so you have the whole colecovision hardware within the adapter -and it just passes the video and sound through to the TV?

Does anyone know if the VBLANK interrupt is passed out through the Salora connector, or is there a stub ROM handling updates?

Is there a video which shows the boot sequence?
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MADrigal
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Re: I/O Interface

Post by MADrigal » Fri Jun 07, 2024 9:11 am

I took two videos and posted them on Youtube a few years ago - have a look. I hope this helps!

https://www.youtube.com/watch?v=-ym43K9wmeY
https://www.youtube.com/watch?v=CHMQWWGs_XY
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Scouter3d
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Re: I/O Interface

Post by Scouter3d » Sat Jun 08, 2024 5:35 am

The Salora Colecovision Adapter completly disables the 6502 and the BIOS just by beeing attached to the computer, so yes - it only uses the TMS9929 + the TV-Modulator circuit and the 16k Videoram, everything else is built into the Coleco Adapter (which is nearly a complete Colecovision).
My guess for the Coleco Adpter BIOS is, that it is a patched Colecovision BIOS with only a different Bootmessage...
Cheers, TOM:0)
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Re: I/O Interface

Post by @username@ » Sat Jun 08, 2024 11:35 am

Looking at the colecovision adapter - it appears that the sound solution is just decode at correct speed then output the sound wave to the Salora.
It would be interesting to see how non-BIOS colecovision ROMs would do - for example any of the SpectraVideo ports like Spectron.

Colecovision BIOS is vector driven - so call OS 10 would jump to the correct routine regardless of where / which BIOS version is in use.

I suspect they have just fixed OUT and IN for TMS9929 to re-route to $2000/$3000 - which would be a better solution for games that don't use BIOS.

For creativision, is the sound passthrough on the cassette interface always active? Can the ROM connector detect INT (TMS9929 vblank IRQ)?

Without these, some fancy 6502->Cortex M0 control would be needed :(
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